A camshaft phaser includes a stator having a plurality of lobes and a rotor coaxially disposed within the stator and having a plurality of vanes interspersed with the lobes defining a plurality of alternating advance chambers and retard chambers such that a phasing valve supplies and vents oil to and from the advance and retard chambers. A first check valve allows oil to flow from only one of the retard chambers to only one of the advance chambers when a first diverter valve permits communication between the one of the advance chambers and the first check valve and a second check valve allows oil to flow from the one of the advance chambers to the one of the retard chambers when a second diverter valve permits communication between the one of the retard chambers and the second check valve.

A bushing member includes: a large diameter portion which is inserted on a radially inner side of a coiled segment of an assist spring and includes a straight portion which extends in an axial direction; and a small diameter portion which is located on a radially inner side of a housing and has an outer diameter that is smaller than an outer diameter of the large diameter portion. The coiled segment includes a contact portion that contacts the straight portion at a radially inner surface of the contact portion. In an axial direction, a location of an end of the straight portion, which is located on one axial side where a driven shaft is placed, coincides with a location of an end of the contact portion located on the one axial side, or is on the one axial side of the location of the end of the contact portion.

A bushing member includes: a large diameter portion which is inserted on a radially inner side of a coiled segment of an assist spring and includes a straight portion which extends in an axial direction; and a small diameter portion which is located on a radially inner side of a housing and has an outer diameter that is smaller than an outer diameter of the large diameter portion. The coiled segment includes a contact portion that contacts the straight portion at a radially inner surface of the contact portion. In an axial direction, a location of an end of the straight portion, which is located on one axial side where a driven shaft is placed, coincides with a location of an end of the contact portion located on the one axial side, or is on the one axial side of the location of the end of the contact portion.

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 hydraulic oil control valve is coaxially disposed with a rotational axial of a valve timing adjustment device. The hydraulic oil control valve includes a sleeve, a spool slidably moving in an axial direction within the sleeve, and a filter member configured to capture foreign matters contained in the hydraulic oil. The sleeve includes an inner sleeve and an outer sleeve defining therein an axial hole extending in the axial direction. A space between the axial hole and the inner sleeve in a radial direction serves as a hydraulic oil supply passage. The filter member is disposed in the space to overlap with at least one of internal members in the inner sleeve when viewed in the radial direction.

A hydraulic oil control valve, which is placed along a rotational axis of a valve timing adjusting device, includes a sleeve and a spool configured to slide in an axial direction on an inner side of the sleeve in a radial direction. The sleeve includes: an inner sleeve that has an opening in which a distal end portion of the spool is inserted; and an outer sleeve. In a state where the spool is positioned farthest from an actuator, the distal end portion projects from the opening toward a side that is opposite to the actuator.

A hydraulic oil control valve is coaxially disposed with a rotational axis of a valve timing adjustment device for adjusting valve timing of a valve. The valve is selectively opened or dosed by a drive shaft receiving a driving force from a drive shaft. The hydraulic oil control valve includes a tubular sleeve and a spool that is slidably moved within the sleeve. The sleeve includes an inner sleeve and an outer sleeve that is fixed to an end portion of one of the drive shaft and the driven shaft with an axial force. When the axial force is not applied, a minimum clearance between the outer sleeve and the inner sleeve in a radial direction is larger than a minimum clearance between the inner sleeve and the spool in the radial direction.

A hydraulic oil control valve is coaxially disposed with a rotational axis of a valve timing adjustment device. The hydraulic oil control valve includes a sleeve, a spool, a movement restricting portion, a fixing member. The sleeve includes an inner sleeve and an outer sleeve. The fixing member is fixed to an end portion of the outer sleeve facing the actuator. The fixing member is configured to restrict the inner sleeve from moving in a circumferential direction relative to the outer sleeve and to restrict the inner sleeve and the spool from coming off from the outer sleeve toward the actuator in the axial direction.

A hydraulic oil control valve is coaxially disposed with a rotational axis of a valve timing adjustment device. The hydraulic oil control valve includes a sleeve and a spool that is slidably moved in an axial direction within the sleeve in a radial direction. The sleeve includes an inner sleeve disposed radially outside of the spool and an outer sleeve defining an axial hole extending in the axial direction. The inner sleeve is inserted into the axial hole. The outer sleeve is fixed to an end portion of one shaft when an axial force is applied to the outer sleeve in the axial direction. An inner sleeve end portion of the inner sleeve in the axial direction away from the actuator protrudes from the outer sleeve away from the actuator in the axial direction.

A hydraulic oil control valve is coaxially disposed with a rotational axis of a valve timing adjustment device. The hydraulic oil control valve includes a sleeve and a spool sliding in an axial direction within the sleeve. The spool has an inner space serving as a drain passage through which the hydraulic oil discharged from a phase shifting portion flows. The spool defines a drain inlet that guides the hydraulic oil discharged from the phase shifting portion into the drain passage. At least one of the sleeve or the spool defines an opening through which the hydraulic oil in the drain passage is discharged from the hydraulic oil control valve. A protrusion is formed between the drain inlet and the opening to extend radially inward beyond the drain inlet.