A cam plate is coupled to a driven-side shaft and is rotatable relative to a housing. A gear is placed on a side of the cam plate, which is opposite to the driven-side shaft. The housing has a contact surface that is configured to contact a wall surface of the cam plate, which is located on one side in an axial direction of the housing. Among two external toothed portions, one external toothed portion is located on an opposite side of the contact surface, which is opposite to the gear in the axial direction. The cam plate has a bearing portion that is located on a side of the contact surface, which is opposite to the gear, and the bearing portion has an outer peripheral surface configured to receive a radial load applied from an inner peripheral surface of the housing in a radially inward direction.

A sleeve includes: a supply port communicated with a hydraulic oil supply source; a primary control port communicated with a retard chamber, a secondary control port communicated with an advance chamber; and a drain port communicated with an outside of a valve timing adjustment device. A spool includes: a pressure accumulation space formed at an inside of the spool; a supply passage configured to connect between the pressure accumulation space and the supply port; a primary control passage configured to connect between the pressure accumulation space and the primary control port; a secondary control passage configured to connect between the pressure accumulation space and the secondary control port; and a recycle passage configured to connect between the primary control port or the secondary control port and the pressure accumulation space. The recycle passage and the drain port are connected with each other at the inside of the sleeve.

A sleeve includes: a supply port communicated with a hydraulic oil supply source; a primary control port communicated with a retard chamber, a secondary control port communicated with an advance chamber; and a drain port communicated with an outside of a valve timing adjustment device. A spool includes: a pressure accumulation space formed at an inside of the spool; a supply passage configured to connect between the pressure accumulation space and the supply port; a primary control passage configured to connect between the pressure accumulation space and the primary control port; a secondary control passage configured to connect between the pressure accumulation space and the secondary control port; and a recycle passage configured to connect between the primary control port or the secondary control port and the pressure accumulation space. The recycle passage and the drain port are connected with each other at the inside of the sleeve.

A system and method of controlling an angular position of a camshaft relative to an angular position of a crankshaft includes detecting rotational movement of an electric motor output shaft controlling a camshaft phaser; detecting rotational movement of the crankshaft; determining the relative difference between the rotational movement of the electric motor output shaft and the rotational movement of the crankshaft; and determining whether the angular position of the camshaft relative to the angular position of the crankshaft is advancing, retarding, or remaining constant.

A system and method of controlling an angular position of a camshaft relative to an angular position of a crankshaft includes detecting rotational movement of an electric motor output shaft controlling a camshaft phaser; detecting rotational movement of the crankshaft; determining the relative difference between the rotational movement of the electric motor output shaft and the rotational movement of the crankshaft; and determining whether the angular position of the camshaft relative to the angular position of the crankshaft is advancing, retarding, or remaining constant.

A variable camshaft timing (VCT) system includes an independent camshaft phaser, receiving input from a crankshaft of an internal combustion engine, having an output coupled to one of an inner concentric camshaft or an outer concentric camshaft; and a dependent camshaft phaser, coupled to the other of the inner concentric camshaft or the outer concentric camshaft, comprising a half-Oldham link configured to permit radial movement of the inner concentric camshaft relative to the outer concentric camshaft in one radial direction and at least one pivotable arm configured to permit radial movement of the inner concentric camshaft relative to the outer concentric camshaft in another, different radial direction.

A variable camshaft timing (VCT) system includes an independent camshaft phaser, receiving input from a crankshaft of an internal combustion engine, having an output coupled to one of an inner concentric camshaft or an outer concentric camshaft; and a dependent camshaft phaser, coupled to the other of the inner concentric camshaft or the outer concentric camshaft, comprising a half-Oldham link configured to permit radial movement of the inner concentric camshaft relative to the outer concentric camshaft in one radial direction and at least one pivotable arm configured to permit radial movement of the inner concentric camshaft relative to the outer concentric camshaft in another, different radial direction.

A case for rotating integrally with a crankshaft of an engine; a rotor housed in the case, to be rotated integrally with a camshaft of the engine by fastening the rotor coaxially to the camshaft with a center bolt; and a groove provided around an axis of the rotor on an opposite side of the rotor to the camshaft, and having an inner wall intersecting a rotation direction of the rotor are provided.

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 valve timing change device includes: a housing rotor (10); a vane rotor; a fastening bolt (40) for fastening the vane rotor to a cam shaft; and an advance angle oil passage that constitutes a ring-shaped groove communicating with an advance angle chamber and a delay angle oil passage that constitutes a ring-shaped groove communicating with a delay angle chamber, via oil passages which are open at intervals on an outer circumferential surface of the fastening bolt. The vane rotor includes: a rotor body (20) having a small-diameter inner circumferential portion (23) and a large-diameter inner circumferential portion (24); and a rotor sleeve (30) that is fitted into the large-diameter inner circumferential portion, is in tight contact with the outer circumferential surface (41a) of the fastening bolt, and demarcates the advance angle oil passage (23a) in cooperation with the small-diameter inner circumferential portion.