Valve timing control apparatus

A valve timing control apparatus that controls opening timing and closing timing of one of an intake valve and an exhaust valve of an internal combustion engine, which is driven by a driven-side shaft that is, in turn, driven by a driving-side shaft at the internal combustion engine, through changing of a rotational phase between the driving-side shaft and the driven-side shaft, the valve timing control apparatus comprising:

• a housing that is rotatable integrally with one of the driving-side shaft and the driven-side shaft;
• a boss that is placed in the housing and is configured into a tubular form, wherein the boss is rotatable integrally with the other one of the driving-side shaft and the driven-side shaft;
• a vane that radially extends from the boss and partitions a hydraulic pressure chamber, which is formed between the housing and the boss, into a first chamber and a second chamber, wherein the vane is rotatable together with the boss in an advancing direction or a retarding direction relative to the housing in response to a pressure of hydraulic oil in the first chamber and a pressure of the hydraulic oil in the second chamber;
• a sleeve that is configured into a bottomed tubular body and is fitted to an inner peripheral surface of the boss;
• an intake oil passage that radially extends through a tubular portion of the sleeve and guides the hydraulic oil from an outside into an inside of the sleeve;
• a supply oil passage that radially extends through the tubular portion of the sleeve and is communicated with the first chamber through the boss to guide the hydraulic oil from the inside of the sleeve to the first chamber;
• a discharge oil passage that radially extends through the tubular portion of the sleeve and is communicated with the first chamber through the boss to guide the hydraulic oil from the first chamber to the inside of the sleeve;
• a supply and discharge oil passage that radially extends through the tubular portion of the sleeve and is communicated with the second chamber through the boss to conduct the hydraulic oil between the inside of the sleeve and the second chamber;
• a spool that is configured to reciprocate in an axial direction in the sleeve, wherein the spool enables and disables communication between each corresponding two of the intake oil passage, the supply oil passage, the discharge oil passage and the supply and discharge oil passage depending on an axial position of the spool;
• and
• an isolator that is fixed to one end portion of the spool, which is located on a side where a bottom portion of the sleeve is placed, wherein the isolator isolates a space, which is formed between the one end portion of the spool and the bottom portion of the sleeve, from the intake oil passage, the supply oil passage, the discharge oil passage and the supply and discharge oil passage.