Valve timing adjusting system of internal combustion engine

A valve timing adjusting system of an internal combustion engine for adjusting opening time and closing time of at least one of intake and exhaust valves, wherein the valve timing adjusting system is provided in a driving force transmission system that allows the internal combustion engine to be started at generally an intermediate phase of a driven shaft located in the middle of a variable phase range of the driven shaft, which is driven by a driving shaft of the internal combustion engine to open and close the at least one of the intake and exhaust valves, the valve timing adjusting system comprising:

• (a) a driving-side rotator, which is rotated synchronously with the driving shaft of the internal combustion engine;
• (b) a driven-side rotator, which is rotated together with the driven shaft and is capable of relative rotation relative to the driving-side rotator;
• (c) an advancing chamber, which applies hydraulic fluid pressure to the driven-side rotator to rotate the driven-side rotator in such a manner that a phase of the driven-side rotator is advanced relative to the driving-side rotator;
• (d) a retarding chamber, which applies hydraulic fluid pressure to the driven-side rotator to rotate the driven-side rotator in such a manner that the phase of the driven-side rotator is retarded relative to the driving-side rotator;
• (e) a hydraulic pressure supply/drain means, which supplies the hydraulic pressure to the advancing chamber and drains the hydraulic pressure from the retarding chamber when the internal combustion engine is turned off;
• (f) a phase restraining means, which restrains the relative rotation between the driving-side rotator and the driven-side rotator at generally an intermediate phase of the driven-side rotator after the engine is turned off or when the engine is started, wherein the intermediate phase of the driven-side rotator is located in the middle of a variable phase range of the driven-side rotator;
• and
• (g) an advance side urging means, which applies urging force to the driven-side rotator to advance the driven-side rotator on an advance side, wherein
• an effective range of the urging force of the advance side urging means is between a maximum retarded phase of the driven-side rotator and a predetermined phase of the driven-side rotator, which is located near an intermediate phase of the driven-side rotator on an advance side of the intermediate phase of the driven-side rotator.