Valve timing adjuster

Abstract

A control apparatus controls supply of working fluid to advancing chambers and retarding chambers. The control apparatus alternately and repeatedly implements an advancing supply period, during which the working fluid is supplied to the advancing chambers, and a retarding supply period, during which the working fluid is supplied to the retarding chambers, at time of limiting a phase of a camshaft relative to a crankshaft within a target phase range.

1 . A valve timing adjuster that adjusts opening and closing timing of at least one of an intake valve and an exhaust valve of an internal combustion engine and is placed in a drive force transmission system, which transmits a drive force from a drive shaft of the internal combustion engine to a driven shaft that drives the at least one of the intake valve and the exhaust valve to open and close the same, the valve timing adjuster comprising:
 a first rotatable body that is rotated together with the drive shaft;   a second rotatable body that is rotated together with the driven shaft, wherein the second rotatable body cooperates with the first rotatable body to form an advancing chamber and a retarding chamber, which are arranged one after another in a rotational direction between the first rotatable body and the second rotatable body, and the second rotatable body drives the driven shaft in an advancing direction or a retarding direction relative to the drive shaft upon supplying of working fluid to the advancing chamber or the retarding chamber; and   a supply control means for controlling supply of the working fluid to the advancing chamber and the retarding chamber, wherein the supply control means alternately and repeatedly implements an advancing supply period, during which the working fluid is supplied to the advancing chamber, and a retarding supply period, during which the working fluid is supplied to the retarding chamber, at time of limiting a phase of the driven shaft relative to the drive shaft within a target phase range.   
   
   
       2 . The valve timing adjuster according to  claim 1 , further comprising a resilient member that generates an urging torque to urge the driven shaft in a direction that is opposite from a direction of an average torque of a variable torque, which changes with time and is applied to the driven shaft. 
   
   
       3 . The valve timing adjuster according to  claim 2 , wherein the supply control means alternately and repeatedly implements the advancing supply period and the retarding supply period in a case where an actual phase of the driven shaft relative to the drive shaft reaches a corresponding one of an advancing end and a retarding end of the target phase range, which is opposite from the direction of the average torque upon satisfaction of a limiting condition for limiting the phase of the driven shaft relative to the drive shaft within the target phase range. 
   
   
       4 . The valve timing adjuster according to  claim 3 , wherein the supply control means alternately and repeatedly implements the advancing supply period and the retarding supply period after the supply control means returns the actual phase to an intermediate phase in the target phase range in the case where the actual phase reaches the corresponding one of the advancing end and the retarding end of the target phase range, which is opposite from the direction of the average torque, upon the satisfaction of the limiting condition for limiting the phase of the driven shaft relative to the drive shaft within the target phase range. 
   
   
       5 . The valve timing adjuster according to  claim 2 , wherein:
 the supply control means alternately and repeatedly implements the advancing supply period and the retarding supply period in a case where an actual rotational speed of the internal combustion engine becomes equal to or larger than a reference rotational speed of the internal combustion engine upon satisfaction of a limiting condition for limiting the phase of the driven shaft relative to the drive shaft within the target phase range; and   the reference rotational speed of the internal combustion engine is defined as a rotational speed of the internal combustion engine, at which the average torque that increases as the rotational speed of the internal combustion engine increases generally coincides with a minimum value of the urging torque.   
   
   
       6 . The valve timing adjuster according to  claim 1 , wherein the supply control means maintains the alternately and repeatedly implementing of the advancing supply period and the retarding supply period as long as the supply control means limits the phase of the driven shaft relative to the drive shaft within the target phase range. 
   
   
       7 . The valve timing adjuster according to  claim 1 , wherein:
 a rotational torque, which drives the driven shaft in an advancing direction or a retarding direction relative to the drive shaft, is generated by the supplying of the working fluid to the advancing chamber or the retarding chamber; and   the supply control means alternately and repeatedly implements the advancing supply period and the retarding supply period such that the rotational torque is generated with a different period of a cycle that is different from a period of a cycle of the variable torque.   
   
   
       8 . The valve timing adjuster according to  claim 1 , wherein:
 a rotational torque, which drives the driven shaft in an advancing direction or a retarding direction relative to the drive shaft, is generated by the supplying of the working fluid to the advancing chamber or the retarding chamber; and   the supply control means alternately and repeatedly implements the advancing supply period and the retarding supply period in a case where a pressure of the working fluid supplied to the advancing chamber and the retarding chamber becomes equal to or less than a preset value upon satisfaction of a limiting condition for limiting the phase of the driven shaft relative to the drive shaft within a target phase range.