Diagnosis system for vane-type variable valve timing controller

Abstract

One-way valves are provided in a hydraulic pressure supply passage in an advance hydraulic chamber and a hydraulic pressure supply passage in a retard hydraulic chamber respectively. A drain oil passage bypassing each of the one-way valves is provided in the hydraulic pressure supply passage in the each hydraulic chamber to be in parallel therewith. A drain switching valve is provided in the each drain oil passage. A drain switching control function for switching the hydraulic pressure driving the each drain switching valve is integral with a function of the hydraulic control valve for controlling the hydraulic pressure supplied to the advance hydraulic chamber and the retard hydraulic chamber. It is determined whether the responsiveness of an advance/retard operation is in a normal range based upon a changing rate of the VTC displacement angle during advance/retard operating, thereby determining presence/absence of abnormality in the advance/retard operation.

1 . A diagnosis device for a vane-type variable valve timing controller in which each of a plurality of vane accommodating chambers formed in a housing of the vane-type variable valve timing controller is divided into an advance hydraulic chamber and a retard hydraulic chamber by a vane comprising: 
 a one-way valve disposed in each of a hydraulic supply passage of the advance hydraulic chamber and a hydraulic supply passage of the retard hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the each hydraulic chamber;    a drain oil passage disposed in parallel to the hydraulic supply passage of the each hydraulic chamber for bypassing the one-way valve;    a drain switching valve disposed in the each drain oil passage and driven by hydraulic pressure; and    a hydraulic switching valve for switching the hydraulic pressure driving the each drain switching valve, wherein:    during hold operating of holding a displacement angle of the variable valve timing controller (hereinafter, referred to as VTC displacement angle) to a target displacement angle, both the drain switching valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber are closed to effectively function both the one-way valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber;    the hydraulic switching valve is controlled to prevent reverse flow of the operating oil from the each hydraulic chamber and also a control current of a hydraulic control valve controlling the hydraulic pressure in the each hydraulic chamber is controlled to a predetermined holding current;    during advance/retard operating of displacing the VTC displacement angle to the advance direction or the retard direction, either one of the drain switching valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber is opened in accordance with the displacement direction to control the hydraulic switching valve so that either one of the one-way valves does not operate; and    the control current of the hydraulic control valve is controlled to vary the hydraulic pressure in the each hydraulic chamber, displacing the VTC displacement angle toward the target displacement angle, further comprising:    abnormality diagnosis means adapted to determine presence/absence of abnormality in the advance/retard operation based upon a changing rate of the VTC displacement angle when a predetermined abnormality diagnosis execution condition is met during the advance/retard operating.    
   
   
       2 . A diagnosis device for a vane-type variable valve timing controller according to  claim 1 , wherein: 
 at least one of abnormality diagnosis execution conditions is a condition that an engine rotational speed is in a low rotational region less than a predetermined rotational speed.    
   
   
       3 . A diagnosis device for a vane-type variable valve timing controller according to  claim 1 , wherein: 
 at least one of abnormality diagnosis execution conditions is a condition that a deviation between the VTC displacement angle and the target displacement angle is more than a predetermined value.    
   
   
       4 . A diagnosis device for a vane-type variable valve timing controller according to  claim 1 , wherein: 
 at least one of abnormality diagnosis execution conditions is a condition that a predetermined time elapses after the target displacement angle has changed.    
   
   
       5 . A diagnosis device for a vane-type variable valve timing controller according to  claim 1 , wherein: 
 the abnormality diagnosis means determines presence/absence of the abnormality in the advance/retard operation in consideration of continuing time of a state where a changing rate of the VTC displacement angle is less than a predetermined value.    
   
   
       6 . A diagnosis device for a vane-type variable valve timing controller according to  claim 1 , wherein: 
 the abnormality diagnosis means includes means for determining presence/absence of abnormality regarding the hydraulic control value and the hydraulic switching valve, wherein when the abnormality of the advance operation is detected, if it is determined that the hydraulic control valve and the hydraulic switching valve are normal, the means determines occurrence of a closed abnormality state where at least one of the drain switching valve in the side of the retard hydraulic chamber and the one-way valve in the side of the advance hydraulic chamber remains to be closed or an open abnormality state where at least one of the drain switching valve in the side of the advance hydraulic chamber and the one-way valve in the side of the advance hydraulic chamber remains to be opened; and wherein when the abnormality of the retard operation is detected, if it is determined that the hydraulic control valve and the hydraulic switching valve are normal, the means determines occurrence of a closed abnormality state where at least one of the drain switching valve in the side of the advance hydraulic chamber and the one-way valve in the side of the retard hydraulic chamber remains to be closed or an open abnormality state where at least one of the drain switching valve in the side of the retard hydraulic chamber and the one-way valve in the side of the retard hydraulic chamber remains to be opened.    
   
   
       7 . A diagnosis device for a vane-type variable valve timing controller according to  claim 1 , wherein: 
 the hydraulic switching valve is integral with the hydraulic control valve.    
   
   
       8 . A diagnosis device for a vane-type variable valve timing controller in which each of a plurality of vane accommodating chambers formed in a housing of the vane-type variable valve timing controller is divided into an advance hydraulic chamber and a retard hydraulic chamber by a vane comprising: 
 a first one-way valve disposed in a hydraulic supply passage of the advance hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the advance hydraulic chamber;    a first drain control valve disposed in a first drain oil passage bypassing the first one-way valve and driven by hydraulic pressure;    a second one-way valve disposed in a hydraulic supply passage of the retard hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the retard hydraulic chamber;    a second drain control valve disposed in a second drain oil passage bypassing the second one-way valve and driven by the hydraulic pressure;    a first hydraulic control valve for controlling the hydraulic pressure supplied to the variable valve timing controller;    a second hydraulic control valve for controlling the hydraulic pressure driving the first and second drain control valves, wherein:    during hold operating of holding a displacement angle of the variable valve timing controller (hereinafter, referred to as VTC displacement angle) to a target displacement angle, both the drain control valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber are closed to effectively function both the one-way valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber;    the second hydraulic control valve is controlled to prevent reverse flow of the operating oil from the advance hydraulic chamber and the retard hydraulic chamber and also a control current of the first hydraulic control valve controlling the hydraulic pressure supplied to the variable valve timing controller is controlled to a predetermined holding current;    during advance/retard operating of displacing the VTC displacement angle to the advance direction or the retard direction, either one of the drain control valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber is opened in accordance with the displacement direction to control the second hydraulic control valve so that either one of the one-way valves does not operate; and    the control current of the first hydraulic control valve is controlled to vary the hydraulic pressure supplied to the variable valve timing controller, displacing the VTC displacement angle toward the target displacement angle, further comprising:    abnormality diagnosis means adapted to determine presence/absence of abnormality in the advance/retard operation based upon a changing rate of the VTC displacement angle when a predetermined abnormality diagnosis execution condition is met during the advance/retard operating.    
   
   
       9 . A diagnosis device for a vane-type variable valve timing controller according to  claim 8 , wherein: 
 at least one of abnormality diagnosis execution conditions is a condition that an engine rotational speed is in a low rotational region less than a predetermined rotational speed.    
   
   
       10 . A diagnosis device for a vane-type variable valve timing controller according to  claim 8 , wherein: 
 at least one of abnormality diagnosis execution conditions is a condition that a deviation between the VTC displacement angle and the target displacement angle is more than a predetermined value.    
   
   
       11 . A diagnosis device for a vane-type variable valve timing controller according to  claim 8 , wherein: 
 at least one of abnormality diagnosis execution conditions is a condition that a predetermined time elapses after the target displacement angle has changed.    
   
   
       12 . A diagnosis device for a vane-type variable valve timing controller according to  claim 8 , wherein: 
 the abnormality diagnosis means determines presence/absence of the abnormality in the advance/retard operation in consideration of continuing time of a state where a changing rate of the VTC displacement angle is less than a predetermined value.    
   
   
       13 . A diagnosis device for a vane-type variable valve timing controller according to  claim 8 , wherein: 
 the abnormality diagnosis means includes means for determining presence/absence of the abnormality regarding the first hydraulic control value and the second hydraulic control valve, wherein when the abnormality of the advance operation is detected, if it is determined that the first hydraulic control valve and the second hydraulic control valve are normal, the means determines occurrence of a closed abnormality state where at least one of the drain switching valve in the side of the retard hydraulic chamber and the one-way valve in the side of the advance hydraulic chamber remains to be closed or an open abnormality state where at least one of the drain switching valve in the side of the advance hydraulic chamber and the one-way valve in the side of the advance hydraulic chamber remains to be opened; and wherein when the abnormality of the retard operation is detected, if it is determined that the first hydraulic control valve and the second hydraulic control valve are normal, the means determines occurrence of a closed abnormality state where at least one of the drain control valve in the side of the advance hydraulic chamber and the one-way valve in the side of the retard hydraulic chamber remains to be closed or an open abnormality state where at least one of the drain control valve in the side of the retard hydraulic chamber and the one-way valve in the side of the retard hydraulic chamber remains to be opened.    
   
   
       14 . A diagnosis device for a vane-type variable valve timing controller according to  claim 8 , wherein: 
 a shaft for driving the first hydraulic control valve is integral with a shaft for driving the second hydraulic control valve.    
   
   
       15 . A diagnosis device for a vane-type variable valve timing controller in which each of a plurality of vane accommodating chambers formed in a housing of the vane-type variable valve timing controller is divided into an advance hydraulic chamber and a retard hydraulic chamber by a vane comprising: 
 a first one-way valve disposed in a hydraulic supply passage of the advance hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the advance hydraulic chamber;    a first drain control valve disposed in a first drain oil passage bypassing the first one-way valve and driven by hydraulic pressure;    a second one-way valve disposed in a hydraulic supply passage of the retard hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the retard hydraulic chamber;    a second drain control valve disposed in a second drain oil passage bypassing the second one-way valve and driven by the hydraulic pressure;    a single first hydraulic control valve for controlling the hydraulic pressure supplied to the first and second drain control valves and the variable valve timing controller; wherein:    during hold operating of holding a displacement angle of the variable valve timing controller (hereinafter, referred to as VTC displacement angle) to a target displacement angle, a control current of the hydraulic control valve is controlled to a predetermined holding current to close both the drain control valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber to effectively function both the one-way valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber; thereby preventing reverse flow of the operating oil from the advance hydraulic chamber and the retard hydraulic chamber and also controlling the hydraulic pressure supplied to the variable valve timing controller;    during advance/retard operating of displacing the VTC displacement angle to the advance direction or the retard direction, the control current of the hydraulic control valve is controlled to open either one of the drain control valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber in accordance with the displacement direction so that either one of the one-way valves does not operate; and    further, the hydraulic pressure supplied to the variable valve timing controller is varied, thereby displacing the VTC displacement angle toward the target displacement angle, further comprising:    abnormality diagnosis means adapted to determine presence/absence of abnormality in the advance/retard operation based upon a changing rate of the VTC displacement angle when a predetermined abnormality diagnosis execution condition is met during the advance/retard operating.    
   
   
       16 . A diagnosis device for a vane-type variable valve timing controller according to  claim 15 , wherein: 
 at least one of abnormality diagnosis execution conditions is a condition that an engine rotational speed is in a low rotational region less than a predetermined rotational speed.    
   
   
       17 . A diagnosis device for a vane-type variable valve timing controller according to  claim 15 , wherein: 
 at least one of abnormality diagnosis execution conditions is a condition that a deviation between the VTC displacement angle and the target displacement angle is more than a predetermined value.    
   
   
       18 . A diagnosis device for a vane-type variable valve timing controller according to  claim 15 , wherein: 
 at least one of abnormality diagnosis execution conditions is a condition that a predetermined time elapses after the target displacement angle has changed.    
   
   
       19 . A diagnosis device for a vane-type variable valve timing controller according to  claim 15 , wherein: 
 the abnormality diagnosis means determines presence/absence of the abnormality in the advance/retard operation in consideration of continuing time of a state where a changing rate of the VTC displacement angle is less than a predetermined value.    
   
   
       20 . A diagnosis device for a vane-type variable valve timing controller according to  claim 15 , wherein: 
 the abnormality diagnosis means includes means for determining presence/absence of the abnormality regarding the hydraulic control value, wherein when the abnormality of the advance operation is detected, if it is determined that the hydraulic control valve is normal, the means determines occurrence of a closed abnormality state where at least one of the drain control valve in the side of the retard hydraulic chamber and the one-way valve in the side of the advance hydraulic chamber remains to be closed or an open abnormality state where at least one of the drain control valve in the side of the advance hydraulic chamber and the one-way valve in the side of the advance hydraulic chamber remains to be opened; and wherein when the abnormality of the retard operation is detected, if it is determined that the hydraulic control valve is normal, the means determines occurrence of a closed abnormality state where at least one of the drain control valve in the side of the advance hydraulic chamber and the one-way valve in the side of the retard hydraulic chamber remains to be closed or an open abnormality state where at least one of the drain control valve in the side of the retard hydraulic chamber and the one-way valve in the side of the retard hydraulic chamber remains to be opened.    
   
   
       21 . A diagnosis device for a vane-type variable valve timing controller in which each of a plurality of vane accommodating chambers formed in a housing of the vane-type variable valve timing controller is divided into an advance hydraulic chamber and a retard hydraulic chamber by a vane comprising: 
 a one-way valve disposed in each of a hydraulic supply passage of the advance hydraulic chamber and a hydraulic supply passage of the retard hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the each hydraulic chamber;    a drain oil passage disposed in parallel to the hydraulic supply passage of the each hydraulic chamber for bypassing the one-way valve;    a drain switching valve disposed in the each drain oil passage and driven by hydraulic pressure; and    a hydraulic switching valve for switching the hydraulic pressure driving the each drain switching valve, wherein:    during hold operating of holding a displacement angle of the variable valve timing controller (hereinafter, referred to as VTC displacement angle) to a target displacement angle, both the drain switching valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber are closed to effectively function both the one-way valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber;    thereby, the hydraulic switching valve is controlled to prevent reverse flow of the operating oil from both the hydraulic chambers and also a control current of the hydraulic control valve controlling the hydraulic pressure in the each hydraulic chamber is controlled to a predetermined holding current;    during advance/retard operating of displacing the VTC displacement angle to the advance direction or the retard direction, either one of the drain switching valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber is opened in accordance with the displacement direction to control the hydraulic switching valve so that either one of the one-way valves does not operate; and    the control current of the hydraulic control valve is controlled to vary the hydraulic pressure in the each hydraulic chamber, displacing the VTC displacement angle toward the target displacement angle, further comprising:    when at the time of meeting a predetermined abnormality diagnosis execution condition during the advance/retard operating, the holding current is vibrated in a predetermined amplitude, abnormality diagnosis means adapted to determine presence/absence of the abnormality in at least one of the drain switching valve and the one-way valve based upon a changing degree of the VTC displacement angle due to the vibration of the holding current.    
   
   
       22 . A diagnosis device for a vane-type variable valve timing controller according to  claim 21 , wherein: 
 the hydraulic switching valve is integral with the hydraulic control valve.    
   
   
       23 . A diagnosis device for a vane-type variable valve timing controller according to  claim 21 , wherein: 
 the abnormality diagnosis means sets an amplitude and a cycle in the vibration of the holding current so that a changing degree of the VTC displacement angle at a normal operation is within a range of an allowance changing amount in the VTC displacement angle during a usual holding operating.    
   
   
       24 . A diagnosis device for a vane-type variable valve timing controller according to  claim 21 , wherein: 
 the abnormality diagnosis means sets an amplitude in the vibration of the holding current so that a changing amount of the VTC displacement angle due to an increasing direction amplitude of the holding current is substantially equal to a changing amount in the VTC displacement angle due to a decreasing direction amplitude thereof.    
   
   
       25 . A diagnosis device for a vane-type variable valve timing controller according to  claim 21 , wherein: 
 the abnormality diagnosis means sets a cycle in the vibration of the holding current close to the minimum time of being capable of transmitting the hydraulic pressure to the each hydraulic chamber in an increasing direction amplitude and a decreasing direction amplitude of the holding current in consideration of a delay of a hydraulic transmission system to the each hydraulic chamber.    
   
   
       26 . A diagnosis device for a vane-type variable valve timing controller according to  claim 21 , wherein: 
 the abnormality diagnosis means starts the vibration of the holding current after a predetermined time elapses from start of the holding operation and determines presence/absence of the abnormality by performing the vibration of the holding current for a predetermine time.    
   
   
       27 . A diagnosis device for a vane-type variable valve timing controller according to  claim 21 , further comprising: 
 holding current learning means for learning the holding current, wherein:    the abnormality diagnosis means vibrates the holding current centered at a holding current learning value learned by the holding current learning means.    
   
   
       28 . A diagnosis device for a vane-type variable valve timing controller according to  claim 21 , wherein: 
 the each drain switching valve is structured in such a manner as to be all the time opened in a region of a high rotational side where an engine generated hydraulic pressure is high; and    in a region of a low rotational side where both of the drain switching valves are closed, the abnormality diagnosis means determines whether or not there occurs an open abnormality state where at least one of the drain switching valve and the one-way valve in the side of the advance hydraulic chamber or the retard hydraulic chamber remains to be opened, based upon whether or not a changing degree of the VTC displacement angle exceeds a predetermined abnormality determination threshold value to increase in an advance or a retard direction, and    in a region of a high rotational side where both of the drain switching valves are opened, the abnormality diagnosis means determines whether or not there occurs a closed abnormality state where the drain switching valve in the side of the advance hydraulic chamber or the retard hydraulic chamber remains to be closed, based upon whether or not a changing degree of the VTC displacement angle exceeds a predetermined abnormality determination threshold value to increase in an advance or a retard direction.    
   
   
       29 . A diagnosis device for a vane-type variable valve timing controller in which each of a plurality of vane accommodating chambers formed in a housing of the vane-type variable valve timing controller is divided into an advance hydraulic chamber and a retard hydraulic chamber by a vane comprising: 
 a first one-way valve disposed in a hydraulic supply passage of the advance hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the advance hydraulic chamber;    a first drain control valve disposed in a first drain oil passage bypassing the first one-way valve and driven by hydraulic pressure;    a second one-way valve disposed in a hydraulic supply passage of the retard hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the retard hydraulic chamber;    a second drain control valve disposed in a second drain oil passage bypassing the second one-way valve and driven by the hydraulic pressure;    a first hydraulic control valve for controlling the hydraulic pressure supplied to the variable valve timing controller;    a second hydraulic control valve for controlling the hydraulic pressure driving the first and second drain control valves, wherein:    during hold operating of holding a displacement angle of the variable valve timing controller (hereinafter, referred to as VTC displacement angle) to a target displacement angle, both the drain control valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber are closed to effectively function both the one-way valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber;    thereby, the second hydraulic control valve is controlled to prevent reverse flow of the operating oil from the advance hydraulic chamber and the retard hydraulic chamber and also a control current of the first hydraulic control valve controlling the hydraulic pressure supplied to the variable valve timing controller is controlled to a predetermined holding current;    during advance/retard operating of displacing the VTC displacement angle to the advance direction or the retard direction, either one of the drain control valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber is opened in accordance with the displacement direction to control the second hydraulic control valve so that either one of the one-way valves does not operate; and    the control current of the first hydraulic control valve is controlled to vary the hydraulic pressure supplied to the variable valve timing controller, displacing the VTC displacement angle toward the target displacement angle, further comprising:    when at the time of meeting a predetermined abnormality diagnosis execution condition during the advance/retard operating, the holding current is vibrated in a predetermined amplitude, abnormality diagnosis means adapted to determine presence/absence of abnormality in at least one of the drain control valve and the one-way valve based upon a changing rate of the VTC displacement angle due to the vibration of the holding current.    
   
   
       30 . A diagnosis device for a vane-type variable valve timing controller according to  claim 29 , wherein: 
 a shaft for driving the first hydraulic control valve is integral with a shaft for driving the second hydraulic control valve.    
   
   
       31 . A diagnosis device for a vane-type variable valve timing controller according to  claim 29 , wherein: 
 the abnormality diagnosis means sets an amplitude and a cycle in the vibration of the holding current so that a changing degree of the VTC displacement angle at a normal operation is within a range of an allowance changing amount in the VTC displacement angle during a usual holding operating.    
   
   
       32 . A diagnosis device for a vane-type variable valve timing controller according to  claim 29 , wherein: 
 the abnormality diagnosis means sets an amplitude in the vibration of the holding current so that a changing amount of the VTC displacement angle due to an increasing direction amplitude of the holding current is substantially equal to a changing amount in the VTC displacement angle due to a decreasing direction amplitude thereof    
   
   
       33 . A diagnosis device for a vane-type variable valve timing controller according to  claim 29 , wherein: 
 the abnormality diagnosis means sets a cycle in the vibration of the holding current close to the minimum time of being capable of transmitting the hydraulic pressure to the each hydraulic chamber in an increasing direction amplitude and a decreasing direction amplitude of the holding current in consideration of a delay of a hydraulic transmission system supplying the hydraulic pressure to the variable valve timing controller.    
   
   
       34 . A diagnosis device for a vane-type variable valve timing controller according to  claim 29 , wherein: 
 the abnormality diagnosis means starts the vibration of the holding current after a predetermined time elapses from start of the holding operation and determines presence/absence of the abnormality by performing the vibration of the holding current for a predetermine time.    
   
   
       35 . A diagnosis device for a vane-type variable valve timing controller according to  claim 29 , further comprising: 
 holding current learning means for learning the holding current, wherein:    the abnormality diagnosis means vibrates the holding current centered at a holding current learning value learned by the holding current learning means.    
   
   
       36 . A diagnosis device for a vane-type variable valve timing controller according to  claim 29 , wherein: 
 the each drain control valve is structured in such a manner as to be all the time opened in a region of a high rotational side where an engine generated hydraulic pressure is high; and    in a region of a low rotational side where both of the drain control valves are closed at a normal operation, the abnormality diagnosis means determines whether or not there occurs an open abnormality state where at least one of the drain control valve and the one-way valve in the side of the advance hydraulic chamber or the retard hydraulic chamber remains to be opened, based upon whether or not a changing degree of the VTC displacement angle exceeds a predetermined abnormality determination threshold value to increase in an advance or a retard direction, and    in a region of a high rotational side where both of the drain control valves are opened at a normal operation, the abnormality diagnosis means determines whether or not there occurs a closed abnormality state where the drain control valve in the side of the advance hydraulic chamber or the retard hydraulic chamber remains to be closed, based upon whether or not a changing degree of the VTC displacement angle exceeds a predetermined abnormality determination threshold value to increase in an advance or a retard direction.    
   
   
       37 . A diagnosis device for a vane-type variable valve timing controller in which each of a plurality of vane accommodating chambers formed in a housing of the vane-type variable valve timing controller is divided into an advance hydraulic chamber and a retard hydraulic chamber by a vane comprising: 
 a first one-way valve disposed in a hydraulic supply passage of the advance hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the advance hydraulic chamber;    a first drain control valve disposed in a first drain oil passage bypassing the first one-way valve and driven by hydraulic pressure;    a second one-way valve disposed in a hydraulic supply passage of the retard hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the retard hydraulic chamber;    a second drain control valve disposed in a second drain oil passage bypassing the second one-way valve and driven by the hydraulic pressure;    a single first hydraulic control valve for controlling the hydraulic pressure supplied to the first and second drain control valves and the variable valve timing controller; wherein:    during holding operating of holding a displacement angle of the variable valve timing controller (hereinafter, referred to as VTC displacement angle) to a target displacement angle, a control current of the hydraulic control valve is controlled to a predetermined holding current to close both the drain control valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber to effectively function both the one-way valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber; thereby preventing reverse flow of the operating oil from the advance hydraulic chamber and the retard hydraulic chamber and also controlling the hydraulic pressure supplied to the variable valve timing controller;    during advance/retard operating of displacing the VTC displacement angle to the advance direction or the retard direction, the control current of the hydraulic control valve is controlled to open either one of the drain control valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber in accordance with the displacement direction so that either one of the one-way valves does not operate; and    further, the hydraulic pressure supplied to the variable valve timing controller is varied, thereby displacing the VTC displacement angle toward the target displacement angle, further comprising:    when at the time of meeting a predetermined abnormality diagnosis execution condition during the advance/retard operating, the holding current is vibrated in a predetermined amplitude, abnormality diagnosis means adapted to determine presence/absence of abnormality in at least one of the drain control valve and the one-way valve based upon a changing degree of the VTC displacement angle due to the vibration of the holding current.    
   
   
       38 . A diagnosis device for a vane-type variable valve timing controller according to  claim 37 , wherein: 
 the abnormality diagnosis means sets an amplitude and a cycle in the vibration of the holding current so that a changing degree of the VTC displacement angle at a normal operation is within a range of an allowance changing amount in the VTC displacement angle during a usual holding operating.    
   
   
       39 . A diagnosis device for a vane-type variable valve timing controller according to  claim 37 , wherein: 
 the abnormality diagnosis means sets an amplitude in the vibration of the holding current so that a changing amount of the VTC displacement angle due to an increasing direction amplitude of the holding current is substantially equal to a changing amount in the VTC displacement angle due to a decreasing direction amplitude thereof    
   
   
       40 . A diagnosis device for a vane-type variable valve timing controller according to  claim 37 , wherein: 
 the abnormality diagnosis means sets a cycle in the vibration of the holding current close to the minimum time of being capable of transmitting the hydraulic pressure to the each hydraulic chamber in an increasing direction amplitude and a decreasing direction amplitude of the holding current in consideration of a delay of a hydraulic transmission system supplying the hydraulic pressure to the variable valve timing controller.    
   
   
       41 . A diagnosis device for a vane-type variable valve timing controller according to  claim 37 , wherein: 
 the abnormality diagnosis means starts the vibration of the holding current after a predetermined time elapses from start of the holding operation and determines presence/absence of the abnormality by performing the vibration of the holding current for a predetermine time.    
   
   
       42 . A diagnosis device for a vane-type variable valve timing controller according to  claim 37 , further comprising: 
 holding current learning means for learning the holding current, wherein:    the abnormality diagnosis means vibrates the holding current centered at a holding current learning value learned by the holding current learning means.    
   
   
       43 . A diagnosis device for a vane-type variable valve timing controller according to  claim 37 , wherein: 
 the each drain control valve is structured in such a manner as to be all the time opened in a region of a high rotational side where an engine generated hydraulic pressure is high; and    in a region of a low rotational side where both of the drain control valves are closed at a normal operation, the abnormality diagnosis means determines whether or not there occurs an open abnormality state where at least one of the drain control valve and the one-way valve in the side of the advance hydraulic chamber or the retard hydraulic chamber remains to be opened based upon whether or not a changing degree of the VTC displacement angle exceeds a predetermined abnormality determination threshold value to increase in an advance or a retard direction, and    in a region of a high rotational side where both of the drain control valves are opened at a normal operation, the abnormality diagnosis means determines whether or not there occurs a closed abnormality state where the drain control valve in the side of the advance hydraulic chamber or the retard hydraulic chamber remains to be closed based upon whether or not a changing degree of the VTC displacement angle exceeds a predetermined abnormality determination threshold value to increase in an advance or retard direction.    
   
   
       44 . A diagnosis device for a vane-type variable valve timing controller in which each of a plurality of vane accommodating chambers formed in a housing of the vane-type variable valve timing controller is divided into an advance hydraulic chamber and a retard hydraulic chamber by a vane comprising: 
 a one-way valve disposed in each of a hydraulic supply passage of the advance hydraulic chamber and a hydraulic supply passage of the retard hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the each hydraulic chamber;    a drain oil passage disposed in parallel to the hydraulic supply passage of the each hydraulic chamber for bypassing the one-way valve;    a drain switching valve disposed in the each drain oil passage and driven by hydraulic pressure; and    a hydraulic switching valve switching the hydraulic pressure driving the each drain switching valve, wherein:    during hold operating of holding a displacement angle of the variable valve timing controller (hereinafter, referred to as VTC displacement angle) to a target displacement angle, both the drain switching valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber are closed to effectively function both the one-way valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber;    thereby, the hydraulic switching valve is controlled to prevent reverse flow of the operating oil from both the hydraulic chambers and also a control current of the hydraulic control valve controlling the hydraulic pressure in the each hydraulic chamber is controlled to a predetermined holding current;    during advance/retard operating of displacing the VTC displacement angle to the advance direction or the retard direction, either one of the drain switching valves in the side of the advance hydraulic chamber and the of the retard hydraulic chamber side is opened in accordance with the displacement direction to control the hydraulic switching valve so that either one of the one-way valves does not operate; and    further, the control current of the hydraulic control valve is controlled to vary the hydraulic pressure in the each hydraulic chamber, displacing the VTC displacement angle toward the target displacement angle, further comprising:    abnormality diagnosis means adapted to determine whether or not there occurs an open abnormality state where at least one of the drain switching valve and the one-way valve remains to be opened, based upon a changing amount of the VTC displacement angle within a predetermined period during the holding operating.    
   
   
       45 . A diagnosis device for a vane-type variable valve timing controller according to  claim 44 , wherein: 
 the abnormality diagnosis means calculates a difference between a VTC displacement angle immediately after start of the holding operation and a VTC displacement angle at elapse of the predetermined period to determine presence/absence of the open abnormality state in at least one of the drain switching valve and the one-way valve based upon this difference.    
   
   
       46 . A diagnosis device for a vane-type variable valve timing controller according to  claim 44 , wherein: 
 the abnormality diagnosis means detects a maximum value and a minimum value of a VTC displacement angle from a point immediately after start of the holding operation until a point at elapse of the predetermined period to calculate a difference between the maximum value and the minimum value, determining presence/absence of the open abnormality state in at least one of the drain switching valve and the one-way valve based upon this difference.    
   
   
       47 . A diagnosis device for a vane-type variable valve timing controller according to  claim 44 , wherein: 
 the abnormality diagnosis means detects a maximum value and a minimum value of a VTC displacement angle from a point immediately after start of the holding operation until a point at elapse of the predetermined period to calculate a deviation between a target displacement angle during the holding operating and the maximum value and a deviation between the target displacement angle and the minimum value, determining presence/absence of the open abnormality state in at least one of the drain switching valve and the one-way valve based upon these two deviations.    
   
   
       48 . A diagnosis device for a vane-type variable valve timing controller in which each of a plurality of vane accommodating chambers formed in a housing of the vane-type variable valve timing controller is divided into an advance hydraulic chamber and a retard hydraulic chamber by a vane comprising: 
 a one-way valve disposed in each of a hydraulic supply passage of the advance hydraulic chamber and a hydraulic supply passage of the retard hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the each hydraulic chamber;    a drain oil passage disposed in parallel to the hydraulic supply passage of the each hydraulic chamber for bypassing the one-way valve;    a drain switching valve disposed in the each drain oil passage and driven by hydraulic pressure; and    a hydraulic switching valve for switching the hydraulic pressure driving the each drain switching valve, wherein:    during hold operating of holding a displacement angle of the variable valve timing controller (hereinafter, referred to as VTC displacement angle) to a target displacement angle, both the drain switching valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber are closed to effectively function both the one-way valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber;    thereby, the hydraulic switching valve is controlled to prevent reverse flow of the operating oil from both the hydraulic chambers and also a control current of the hydraulic control valve controlling the hydraulic pressure in the each hydraulic chamber is controlled to a predetermined holding current;    during advance/retard operating of displacing the VTC displacement angle to the advance direction or the retard direction, either one of the drain switching valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber side is opened in accordance with the displacement direction to control the hydraulic switching valve so that either one of the one-way valves does not operate; and    further, the control current of the hydraulic control valve is controlled to vary the hydraulic pressure in the each hydraulic chamber, displacing the VTC displacement angle toward the target displacement angle, further comprising:    abnormality diagnosis means determines a convergent state to the target displacement angle of the VTC displacement angle at changing the target displacement angle to determine whether or not there occurs a closed abnormality state where the drain switching valve remains to be closed, based upon the convergent state.    
   
   
       49 . A diagnosis device for a vane-type variable valve timing controller according to  claim 48 , wherein: 
 the abnormality diagnosis means measures, as data representing the convergent state, continuing time of a state where a deviation between the target displacement angle and the VTC displacement angle is more than a predetermined value to determine presence/absence of the closed abnormality state in the drain switching valve based upon this continuing time.    
   
   
       50 . A diagnosis device for a vane-type variable valve timing controller according to  claim 48 , wherein: 
 the abnormality diagnosis means measures, as data representing the convergent state, elapse time from a point where a deviation between the target displacement angle and the VTC displacement angle is more than a first predetermined value until a point where the deviation is less than a second predetermined value smaller than the first predetermined value to determine presence/absence of the closed abnormality state in the drain switching valve based upon this elapse time.    
   
   
       51 . A diagnosis device for a vane-type variable valve timing controller according to  claim 48 , wherein: 
 the abnormality diagnosis means determines the convergent state by setting as a precondition that a supply hydraulic pressure to the hydraulic control valve is more than a predetermined value.    
   
   
       52 . A diagnosis device for a vane-type variable valve timing controller according to  claim 51 , wherein: 
 the abnormality diagnosis means determines whether or not the supply hydraulic pressure to the hydraulic control valve is more than the predetermined value, based upon information regarding at least one of an engine rotational speed and an oil temperature.    
   
   
       53 . A diagnosis device for a vane-type variable valve timing controller according to  claim 44 , wherein: 
 the hydraulic switching valve is integral with the hydraulic control valve.    
   
   
       54 . A diagnosis device for a vane-type variable valve timing controller in which each of a plurality of vane accommodating chambers formed in a housing of the vane-type variable valve timing controller is divided into an advance hydraulic chamber and a retard hydraulic chamber by a vane comprising: 
 a first one-way valve disposed in a hydraulic supply passage of the advance hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the advance hydraulic chamber;    a first drain control valve disposed in a first drain oil passage bypassing the first one-way valve and driven by hydraulic pressure;    a second one-way valve disposed in a hydraulic supply passage of the retard hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the retard hydraulic chamber;    a second drain control valve disposed in a second drain oil passage bypassing the second one-way valve and driven by hydraulic pressure;    a first hydraulic control valve for controlling the hydraulic pressure supplied to the variable valve timing controller;    a second hydraulic control valve for controlling the hydraulic pressure driving the first and second drain control valves, wherein:    during hold operating of holding a displacement angle of the variable valve timing controller (hereinafter, referred to as VTC displacement angle) to a target displacement angle, both the drain control valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber are closed to effectively function both the one-way valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber;    thereby, the second hydraulic control valve is controlled to prevent reverse flow of the operating oil from the advance hydraulic chamber and the retard hydraulic chamber and also a control current of the first hydraulic control valve controlling the hydraulic pressure supplied to the variable valve timing controller is controlled to a predetermined holding current;    during advance/retard operating of displacing the VTC displacement angle to the advance direction or the retard direction, either one of the drain control valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber is opened in accordance with the displacement direction to control the second hydraulic control valve so that either one of the one-way valves does not operate; and    further, the control current of the first hydraulic control valve is controlled to vary the hydraulic pressure supplied to the variable valve timing controller, displacing the VTC displacement angle toward the target displacement angle, further comprising:    abnormality diagnosis means adapted to determine whether or not there occurs an open abnormality state where at least one of the drain control valve and the one-way valve remains to be opened, based upon a changing amount of the VTC displacement angle within a predetermined period during the holding operating.    
   
   
       55 . A diagnosis device for a vane-type variable valve timing controller according to  claim 54 , wherein: 
 the abnormality diagnosis means calculates a difference between a VTC displacement angle immediately after start of the holding operation and a VTC displacement angle at elapse of the predetermined period to determine presence/absence of the open abnormality state in at least one of the drain control valve and the one-way valve based upon this difference.    
   
   
       56 . A diagnosis device for a vane-type variable valve timing controller according to  claim 54 , wherein: 
 the abnormality diagnosis means detects a maximum value and a minimum value of a VTC displacement angle from a point immediately after start of the holding operation until a point at elapse of the predetermined period to calculate a difference between the maximum value and the minimum value, determining presence/absence of the open abnormality state in at least one of the drain control valve and the one-way valve based upon this difference.    
   
   
       57 . A diagnosis device for a vane-type variable valve timing controller according to  claim 54 , wherein: 
 the abnormality diagnosis means detects a maximum value and a minimum value of a VTC displacement angle from a point immediately after start of the holding operation until a point at elapse of the predetermined period to calculate a deviation between a target displacement angle during the holding operating and the maximum value and a deviation between the target displacement angle and the minimum value, determining presence/absence of the open abnormality state in at least one of the drain control valve and the one-way valve based upon these two deviations.    
   
   
       58 . A diagnosis device for a vane-type variable valve timing controller in which each of a plurality of vane accommodating chambers formed in a housing of the vane-type variable valve timing controller is divided into an advance hydraulic chamber and a retard hydraulic chamber by a vane comprising: 
 a first one-way valve disposed in a hydraulic supply passage of the advance hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the advance hydraulic chamber;    a first drain control valve disposed in a first drain oil passage bypassing the first one-way valve and driven by hydraulic pressure;    a second one-way valve disposed in a hydraulic supply passage of the retard hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the retard hydraulic chamber;    a second drain control valve disposed in a second drain oil passage bypassing the second one-way valve and driven by the hydraulic pressure;    a first hydraulic control valve for controlling the hydraulic pressure supplied to the variable valve timing controller;    a second hydraulic control valve for controlling the hydraulic pressure driving the first and second drain control valves, wherein:    during hold operating of holding a displacement angle of the variable valve timing controller (hereinafter, referred to as VTC displacement angle) to a target displacement angle, both the drain control valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber are closed to effectively function both the one-way valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber;    thereby, the second hydraulic control valve is controlled to prevent reverse flow of the operating oil from the advance hydraulic chamber and the retard hydraulic chamber and also a control current of the first hydraulic control valve controlling the hydraulic pressure supplied to the variable valve timing controller is controlled to a predetermined holding current;    during advance/retard operating of displacing the VTC displacement angle to the advance direction or the retard direction, either one of the drain control valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber is opened in accordance with the displacement direction to control the second hydraulic control valve so that either one of the one-way valves does not operate; and    further, the control current of the first hydraulic control valve is controlled to vary the hydraulic pressure supplied to the variable valve timing controller, displacing the VTC displacement angle toward the target displacement angle, further comprising:    abnormality diagnosis means determines a convergent state to the target displacement angle of the VTC displacement angle at changing the target displacement angle to determine whether or not there occurs a closed abnormality state where the drain control valve remains to be closed, based upon the convergent state.    
   
   
       59 . A diagnosis device for a vane-type variable valve timing controller according to  claim 58 , wherein: 
 the abnormality diagnosis means measures, as data representing the convergent state, continuing time of a state where a deviation between the target displacement angle and the VTC displacement angle is more than a predetermined value to determine presence/absence of the closed abnormality state in the drain control valve based upon this continuing time.    
   
   
       60 . A diagnosis device for a vane-type variable valve timing controller according to  claim 58 , wherein: 
 the abnormality diagnosis means measures, as data representing the convergent state, elapse time from a point where a deviation between the target displacement angle and the VTC displacement angle is more than a first predetermined value until a point where the deviation is less than a second predetermined value smaller than the first predetermined value to determine presence/absence of the closed abnormality state in the drain control valve based upon this elapse time.    
   
   
       61 . A diagnosis device for a vane-type variable valve timing controller according to  claim 58 , wherein: 
 the abnormality diagnosis means determines the convergent state by setting as a precondition that a supply hydraulic pressure to the hydraulic control valve is more than a predetermined value.    
   
   
       62 . A diagnosis device for a vane-type variable valve timing controller according to  claim 61 , wherein: 
 the abnormality diagnosis means determines whether or not the supply hydraulic pressure to the hydraulic control valve is more than the predetermined value, based upon information regarding at least one of an engine rotational speed and an oil temperature.    
   
   
       63 . A diagnosis device for a vane-type variable valve timing controller according to  claim 54 , wherein: 
 a shaft for driving the first hydraulic control valve is integral with a shaft for driving the second hydraulic control valve.    
   
   
       64 . A diagnosis device for a vane-type variable valve timing controller in which each of a plurality of vane accommodating chambers formed in a housing of the vane-type variable valve timing controller is divided into an advance hydraulic chamber and a retard hydraulic chamber by a vane comprising: 
 a first one-way valve disposed in a hydraulic supply passage of the advance hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the advance hydraulic chamber;    a first drain control valve disposed in a first drain oil passage bypassing the first one-way valve and driven by hydraulic pressure;    a second one-way valve disposed in a hydraulic supply passage of the retard hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the retard hydraulic chamber;    a second drain control valve disposed in a second drain oil passage bypassing the second one-way valve and driven by the hydraulic pressure;    a single first hydraulic control valve for controlling the hydraulic pressure supplied to the first and second drain control valves and the variable valve timing controller; wherein:    during hold operating of holding a displacement angle of the variable valve timing controller (hereinafter, referred to as VTC displacement angle) to a target displacement angle, a control current of the hydraulic control valve is controlled to a predetermined holding current to close both the drain control valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber to effectively function both the one-way valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber; thereby preventing reverse flow of the operating oil from the advance hydraulic chamber and the retard hydraulic chamber and also controlling the hydraulic pressure supplied to the variable valve timing controller;    during advance/retard operating of displacing the VTC displacement angle to the advance direction or the retard direction, the control current of the hydraulic control valve is controlled to open either one of the drain control valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber in accordance with the displacement direction so that either one of the one-way valves does not operate; and    further, the hydraulic pressure supplied to the variable valve timing controller is varied, thereby displacing the VTC displacement angle toward the target displacement angle, further comprising:    abnormality diagnosis means adapted to determine whether or not there occurs an open abnormality state where at least one of the drain control valve and the one-way valve remains to be opened, based upon a changing amount of the VTC displacement angle within a predetermined period during the holding operating.    
   
   
       65 . A diagnosis device for a vane-type variable valve timing controller according to  claim 64 , wherein: 
 the abnormality diagnosis means calculates a difference between a VTC displacement angle immediately after start of the holding operation and a VTC displacement angle at elapse of the predetermined period to determine presence/absence of the open abnormality state in at least one of the drain control valve and the one-way valve based upon this difference.    
   
   
       66 . A diagnosis device for a vane-type variable valve timing controller according to  claim 64 , wherein: 
 the abnormality diagnosis means detects a maximum value and a minimum value of a VTC displacement angle from a point immediately after start of the holding operation until a point at elapse of the predetermined period to calculate a difference between the maximum value and the minimum value, determining presence/absence of the open abnormality state in at least one of the drain control valve and the one-way valve based upon this difference.    
   
   
       67 . A diagnosis device for a vane-type variable valve timing controller according to  claim 64 , wherein: 
 the abnormality diagnosis means detects a maximum value and a minimum value of a VTC displacement angle from a point immediately after start of the holding operation until a point at elapse of the predetermined period to calculate a deviation between a target displacement angle during the holding operating and the maximum value and a deviation between the target displacement angle and the minimum value, determining presence/absence of the open abnormality state in at least one of the drain control valve and the one-way valve based upon these two deviations.    
   
   
       68 . A diagnosis device for a vane-type variable valve timing controller in which each of a plurality of vane accommodating chambers formed in a housing of the vane-type variable valve timing controller is divided into an advance hydraulic chamber and a retard hydraulic chamber by a vane comprising: 
 a first one-way valve disposed in a hydraulic supply passage of the advance hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the advance hydraulic chamber;    a first drain control valve disposed in a first drain oil passage bypassing the first one-way valve and driven by hydraulic pressure;    a second one-way valve disposed in a hydraulic supply passage of the retard hydraulic chamber in at least one of the vane accommodating chambers for preventing reverse flow of operating oil from the retard hydraulic chamber;    a second drain control valve disposed in a second drain oil passage bypassing the second one-way valve and driven by the hydraulic pressure;    a single first hydraulic control valve for controlling the hydraulic pressure supplied to the first and second drain control valves and the variable valve timing controller; wherein:    during hold operating of holding a displacement angle of the variable valve timing controller (hereinafter, referred to as VTC displacement angle) to a target displacement angle, both the drain switching valves in a side of the advance hydraulic chamber and a side of the retard hydraulic chamber are closed to effectively function both the one-way valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber;    thereby, the hydraulic switching valve is controlled to prevent reverse flow of the operating oil from both the hydraulic chambers and also a control current of the hydraulic control valve controlling the hydraulic pressure in the each hydraulic chamber is controlled to a predetermined holding current;    during advance/retard operating of displacing the VTC displacement angle to the advance direction or the retard direction, either one of the drain switching valves in the side of the advance hydraulic chamber and the side of the retard hydraulic chamber is opened in accordance with the displacement direction to control the hydraulic switching valve so that either one of the one-way valves does not operate; and    further, the control current of the hydraulic control valve is controlled to vary the hydraulic pressure in the each hydraulic chamber, displacing the VTC displacement angle toward the target displacement angle, further comprising:    abnormality diagnosis means determines a convergent state to the target displacement angle of the VTC displacement angle at changing the target displacement angle to determine whether or not there occurs a closed abnormality state where the drain switching valve remains to be closed, based upon the convergent state.    
   
   
       69 . A diagnosis device for a vane-type variable valve timing controller according to  claim 68 , wherein: 
 the abnormality diagnosis means measures, as data representing the convergent state, continuing time of a state where a deviation between the target displacement angle and the VTC displacement angle is more than a predetermined value to determine presence/absence of the closed abnormality state in the drain control valve based upon this continuing time.    
   
   
       70 . A diagnosis device for a vane-type variable valve timing controller according to  claim 68 , wherein: 
 the abnormality diagnosis means measures, as data representing the convergent state, elapse time from a point where a deviation between the target displacement angle and the VTC displacement angle is more than a first predetermined value until a point where the deviation is less than a second predetermined value smaller than the first predetermined value to determine presence/absence of the closed abnormality state in the drain control valve based upon this elapse time.    
   
   
       71 . A diagnosis device for a vane-type variable valve timing controller according to  claim 68 , wherein: 
 the abnormality diagnosis means determines the convergent state by setting as a precondition that a supply hydraulic pressure to the hydraulic control valve is more than a predetermined value.    
   
   
       72 . A diagnosis device for a vane-type variable valve timing controller according to  claim 51 , wherein: 
 the abnormality diagnosis means determines whether or not the supply hydraulic pressure to the hydraulic control valve is more than the predetermined value, based upon information regarding at least one of an engine rotational speed and an oil temperature.