In recent years, valve opening/closing timing control devices that make it possible to change the opening/closing timing of an intake valve and an exhaust valve in accordance with the operation status of an internal combustion engine (hereinafter referred to as an “engine” as well) have been put to practical use. These valve opening/closing timing control devices have a mechanism that, for example, by changing the relative rotation phase of the driven rotating body with respect to the rotation of the driving rotating body (hereinafter referred to as simply “relative rotation phase”) by means of an engine operation, changes the opening/closing timing of an intake/exhaust valve that is opened and closed accompanying the rotation of the driven rotating body.
In general, the optimal opening/closing timing of the intake/exhaust valve differs according to the operation state of the engine, such as the state in which the engine is started, and the state in which the vehicle is traveling. By constraining the relative rotation phase to an intermediate lock phase between the maximum retard phase and the maximum advance phase when starting the engine, the opening/closing timing of the intake/exhaust valve that is optimal for starting the engine is realized, and a case in which a knocking sound is generated due to a partition of a fluid pressure chamber formed by the driving rotating body and the driven rotating body swinging is suppressed. For this reason, it is desired that the relative rotation phase is constrained to the intermediate lock phase before the engine is stopped. The stopping of the engine also includes idling stops in which the engine is stopped for a short amount of time at an intersection or the like so as to suppress the discharge of exhaust gas or the consumption of gasoline.
Patent Document 1 discloses a valve timing adjustment device that can reliably perform locking when a lock pin is to be locked in an intermediate phase between the maximum advance phase and the maximum retard phase. With this valve timing adjustment device, a control valve is configured to connect an advancing port and a lock port to a main supply port and a discharge opening respectively by moving to a first region, and to connect both the advancing port and the lock port to the main supply port by moving to a second region that is shifted away from the first region in a second direction. The first region is a lock region for locking the rotation phase in a restricted phase using a first main restricting member. Furthermore, the first region has a reduction region in which an advance supply flow amount to be supplied to an advancing chamber by connecting the advancing port in communication with the advancing chamber to the main supply port is reduced to a flow amount that is smaller than the flow amount at the moving end in the first direction. Accordingly, in the constricted region, the speed at which a vane rotor rotates to the advance side is a slower speed that corresponds to the flow amount controlled to be a smaller amount. Furthermore, when the phase of the vane rotor gradually changes to the advance side in this way, the lock port and the discharge opening are connected so that working oil is discharged from the lock chamber. Accordingly, locking of the rotation phase that accompanies the flow of the working oil from the lock chamber can be performed reliably due to the phase of the vane rotor gradually changing to the advance side.