Control apparatus for internal-combustion engine with variable valve mechanism

Abstract

An intake variable valve mechanism 34 is provided that allows closing timing of an air intake valve 30 to be varied. The intake variable valve mechanism 34 has a first control mode that controls IVC timing of the intake valve 30 at an angle-advancing side relative to a certain range including an air intake bottom dead center BDC, and a second control mode that controls the IVC timing of the intake valve 30 at an angle-retarding side relative to the certain range. IVC variable control (first control mode) for making the IVC timing of the intake valve 30 variable according to load is selected for operation in a region of relative low loads, and intake valve closing retardation control (second control mode) for controlling the intake valve 30 in fully retarded IVC timing is selected for operation in a region of relatively high loads.

1 - 3 . (canceled) 
   
   
       4 . A control apparatus for an internal-combustion engine having a variable valve mechanism which at least makes closing timing of an intake valve variable, the control apparatus comprising:
 intake valve control means with a first control mode for controlling the closing timing of the intake valve at an angle-advancing side relative to a certain range including an air intake bottom dead center, in which knock is more likely to occur, and with a second control mode for controlling the closing timing of the intake valve at an angle-retarding side relative to the certain range, wherein the intake valve control means controls the closing timing of the intake valve in either the first control mode or the second control mode; and   control mode selection means for selecting the first control mode for operation in a region of relatively low loads, and selecting the second control mode for operation in a region of relatively high loads;   wherein the first control mode is the control that determines the closing timing of the intake valve according to a load of the internal-combustion engine;   wherein the closing timing of the intake valve is retarded to an angle side nearer the air intake bottom dead center as the load of the internal-combustion engine increases;   wherein the control mode selection means changes the first control mode, if the load of the internal-combustion engine has become high until such an extent that the closing timing of the intake valve is likely to enter the certain range where knock is more likely to occur, to the second control mode that controls the closing timing of the intake valve at the angle-retarding side relative to the air intake bottom dead center and at the angle-retarding side relative to the certain range where knock is more likely to occur;   wherein the second control mode is the intake valve closing retardation control that determines the closing timing of the intake valve such that even under a steady state, blowback of intake air into an intake passage occurs;   wherein a load region in which the intake valve closing retardation control excels the first control mode in fuel efficiency is set, in a low engine speed region in which the engine runs at a speed equal to or smaller than a certain value, so as to extend down to a load side lower than a region in which knock is likely to occur; and   wherein the control mode selection means changes the first control mode to the second control mode, in the low engine speed region, when it is judged that the intake valve closing retardation control excels the first control mode in fuel efficiency.   
   
   
       5 . The control apparatus for an internal-combustion engine having a variable valve mechanism according to  claim 4 ,
 wherein the intake valve closing retardation control is used in an operating region in which the engine runs at a speed equal to or smaller than a certain value and under a load equal to or greater than a certain value.   
   
   
       6 . The control apparatus for an internal-combustion engine having a variable valve mechanism according to  claim 4 ,
 wherein the control mode selection means selects the first control mode until the load region of the internal-combustion engine has reached the higher region as engine speed increases.   
   
   
       7 . The control apparatus for an internal-combustion engine having a variable valve mechanism according to  claim 4 , the control apparatus further comprising:
 torque control means for controlling a torque of the internal-combustion engine in addition to controlling the closing timing control of the intake valve via the intake valve control means; and   torque control change means for, when the second control mode is selected by the control mode selection means, changing the torque control performed by the intake valve control means, to the torque control performed by the torque control means.   
   
   
       8 . The control apparatus for an internal-combustion engine having a variable valve mechanism according to  claim 7 ,
 wherein the torque control means is a throttle valve that controls an intake air amount,   wherein the torque control means adjusts an open position of the throttle valve in accordance with at least the closing timing of the intake valve, of the closing timing and operating angle of the intake valve existing when the first control mode is changed to the second control mode.   
   
   
       9 . The control apparatus for an internal-combustion engine having a variable valve mechanism according to  claim 4 , the control apparatus further comprising:
 ignition timing change means for changing ignition timing of the internal-combustion engine in synchronization with the control mode change between the first control mode and the second control mode.   
   
   
       10 . The control apparatus for an internal-combustion engine having a variable valve mechanism according to  claim 9 ,
 wherein the ignition timing change means determines an advancing amount of the ignition timing in accordance with a valve overlapping period existing when the control mode change between the first control mode and the second control mode is performed.   
   
   
       11 . A control apparatus for an internal-combustion engine having a variable valve mechanism which at least makes closing timing of an intake valve variable, the control apparatus comprising:
 an intake valve control device with a first control mode for controlling the closing timing of the intake valve at an angle-advancing side relative to a certain range including an air intake bottom dead center, in which knock is more likely to occur, and with a second control mode for controlling the closing timing of the intake valve at an angle-retarding side relative to the certain range, wherein the intake valve control device controls the closing timing of the intake valve in either the first control mode or the second control mode; and   a control mode selection device for selecting the first control mode for operation in a region of relatively low loads, and selecting the second control mode for operation in a region of relatively high loads;   wherein the first control mode is the control that determines the closing timing of the intake valve according to a load of the internal-combustion engine;   wherein the closing timing of the intake valve is retarded to an angle side nearer the air intake bottom dead center as the load of the internal-combustion engine increases;   wherein the control mode selection device changes the first control mode, if the load of the internal-combustion engine has become high until such an extent that the closing timing of the intake valve is likely to enter the certain range where knock is more likely to occur, to the second control mode that controls the closing timing of the intake valve at the angle-retarding side relative to the air intake bottom dead center and at the angle-retarding side relative to the certain range where knock is more likely to occur;   wherein the second control mode is the intake valve closing retardation control that determines the closing timing of the intake valve such that even under a steady state, blowback of intake air into an intake passage occurs;   wherein a load region in which the intake valve closing retardation control excels the first control mode in fuel efficiency is set, in a low engine speed region in which the engine runs at a speed equal to or smaller than a certain value, so as to extend down to a load side lower than a region in which knock is likely to occur; and   wherein the control mode selection device changes the first control mode to the second control mode, in the low engine speed region, when it is judged that the intake valve closing retardation control excels the first control mode in fuel efficiency.