There is provided an engagement groove (31) which is formed in a first shoe (S1) of first to fourth shoes (S1), (S2), (S3), (S4) at a circumference position at which the engagement groove (31) is not overlapped an abutment surface (30) with a first vane (V1), which includes a pair of side surfaces (31a) and (31a) that are substantially parallel to the abutment surface (30), and with which a positioning pin (19) protruding from a sprocket (13) is engaged, so as to match phases of a housing main body (11) and the sprocket (13) in a rotation direction.

In a valve timing control system, a control command unit includes: a first stage setting block and a next stage setting block. The first stage setting block sets a retard holding command value as a control command value to introduce hydraulic fluid to each retard operation chamber under a state where a rotation phase is locked, to start applying an operation pressure more than or equal to an unlock pressure to a lock component. The next stage setting block sets an advance holding command value as a control command value to introduce hydraulic fluid to each advance operation chamber, after setting the retard holding command value, to maintain the applying of the operation pressure more than or equal to the unlock pressure to the lock component.

A retard supply check valve is installed in a retard supply passage and is located on a side of a hydraulic oil controller where a hydraulic oil supply source is placed. The retard supply check valve enables only a flow of hydraulic oil from the hydraulic oil supply source toward a retard chamber. An advance supply check valve is installed in an advance supply passage and is located on the side of the hydraulic oil controller where the hydraulic oil supply source is placed. The advance supply check valve enables only a flow of the hydraulic oil from the hydraulic oil supply source toward an advance chamber.

A valve timing adjustment device includes a vane rotor and a hydraulic oil control valve. The vane rotor is fixed to an end portion of one of a drive shaft and a driven shaft and defines a through hole. The hydraulic oil control valve includes a sleeve and a spool. The sleeve includes a body portion in the through hole and a fixing portion fixed into a shaft fixing hole defined in the one. At least a portion of the through hole is sealed by the body portion. A difference between a radial dimension of the shaft fixing hole and a radial dimension of the fixing portion is greater than a total of a predetermined coaxiality between the through hole and the shaft fixing portion and a predetermined coaxiality between the body portion and the fixing portion.

A camshaft phaser for an internal combustion engine includes a stator defining a receptacle therein. The stator includes a ring and a plurality of webs extending radially inward from the ring. The camshaft phaser also includes a rotor rotatable with respect to the stator and received inside the receptacle. The rotor includes a center section and a plurality of vanes extending radially outward from the center section. The center section abuts the webs to define chambers circumferentially between the webs. Each of the vanes is positioned in one of the chambers and sealingly engaging an inner circumferential surface of the ring. At least one of the chambers is a locking chamber and at least one the vanes is a locking vane positioned in the locking chamber. The camshaft phaser also includes a locking valve in the locking vane configured to allow fluid to enter into the locking chamber and to prevent fluid from flowing out of the locking chamber to lock the rotor with respect to the stator in a locked orientation.

Methods and systems are provided for estimating engine oil temperature during conditions when sensors used for engine oil temperature measurement are not functional or not reliable. A null duty cycle of a solenoid spool valve of a variable cam timing mechanism is estimated. Then, a calibrated relationship between the duty cycle, an angular velocity of the associated cam, and the engine oil temperature is used to estimate an engine oil temperature when existing sensors used in the calculation of engine oil temperature calculation become unreliable.

A switched cushion stop for a variable cam timing phaser of a variable cam timing system is disclosed. The cushion stop may be actively controlled by the spool valve or passively controlled.

A check valve part includes: a valve seat hole into which hydraulic oil flows; a valve seat formed around the valve seat hole; a lateral hole formed to have an axis intersecting an axis of the valve seat hole; and a valve body provided so as to be separated from the valve seat or abutted against the valve seat. The valve timing adjustment device further includes a back pressure oil passage that communicates a space opposite to the valve seat with respect to the valve body with the lateral hole.

A spool is configured to reciprocate at an inside space of a sleeve and includes: a spool tube; a spool cover, which closes an end portion of the spool tube located on a camshaft side; a pressure accumulation space, which is formed at an inside of the spool tube; a supply passage, which is configured to connect between the pressure accumulation space and a supply port; a control passage, which is configured to connect between the pressure accumulation space and a primary control port; and a control passage, which is configured to connect between the pressure accumulation space and a secondary control port. A variable volume space is formed between the spool cover and a sleeve bottom. The sleeve includes a breathing hole at an outside of the inside space while the breathing hole is a hole that communicates between the variable volume space and the atmosphere.

A variable valve timing control device includes a drive-side rotational body, a driven-side rotational body, a connecting bolt being coaxially disposed with a rotary axis and connecting the driven-side rotational body to a camshaft, a valve unit including a spool being disposed at an inner space of the connecting bolt and supplying and discharging a fluid to and from an advanced-angle chamber and a retarded-angle chamber, the valve unit discharging the fluid from an opening of a head portion of the connection bolt when the spool controls the fluid, and a reservoir being coaxially disposed with the rotary axis that is positioned laterally, the reservoir accumulating the fluid discharged from the opening of the head portion from which the fluid is configured to be sucked.