Valve timing adjuster

Abstract

A valve timing adjuster includes a first rotor, a second rotor, a spool valve, a connection passage, and a connection check valve. A spool of the spool valve is displaceable to a first position such that the first rotor is rotated relative to the second rotor. The spool is displaceable to a second position to hold the phase of a camshaft at a full phase. The connection passage connects a first output port with a second output port of the spool valve when the spool is positioned at the first position. The connection check valve of the connection passage allows working fluid to flow from the second output port toward the first output port.

1 . A valve timing adjuster for an internal combustion engine having a crankshaft, a valve, and a camshaft, wherein the adjuster adjusts valve timing of the valve, which is opened and closed by the camshaft through torque transmission from the crankshaft, the adjuster comprising:
 a first rotor that is rotatable synchronously with the crankshaft;   a second rotor that is rotatable synchronously with the camshaft, wherein:
 the first rotor and the second rotor define therebetween an advance chamber and a retard chamber, which are arranged circumferentially one after another; 
 the second rotor is adapted to drive the camshaft relative to the crankshaft in an advance direction when working fluid is supplied to the advance chamber; and 
 the second rotor is adapted to drive the camshaft relative to the crankshaft in a retard direction when working fluid is supplied to the retard chamber; 
   a spool valve that includes:
 an input port, through which working fluid is supplied to the spool valve from an external fluid supply source; 
 a drain port, through which working fluid is drained; 
 a first output port, through which working fluid is output to one of the advance chamber and the retard chamber; 
 a second output port, through which working fluid is output to the other one of the advance chamber and the retard chamber; and 
 a spool that is adapted to be displaceable to a first position, at which the first rotor is rotated relative to the second rotor in order to shift a phase of the camshaft relative to the crankshaft, wherein: 
 the spool is adapted to be displaceable to a second position, at which the second rotor is pressed against the first rotor in order to hold the phase of the camshaft at a full phase, at which the phase is fully shifted; 
 when the spool is positioned at the first position, the spool valve connects the first output port with the input port and disconnects the second output port from the drain port; and 
 when the spool is positioned at the second position, the spool valve connects the first output port with the input port and connects the second output port with the drain port; 
   a connection passage that is provided in the spool, wherein the connection passage connects the first output port with the second output port when the spool is positioned at the first position; and   a connection check valve that is provided in the connection passage, wherein:   the connection check valve opens to allow working fluid to flow from the second output port toward the first output port when the spool is positioned at the first position; and   the connection check valve closes to limit working fluid from flowing from the first output port toward the second output port when the spool is positioned at the first position.   
   
   
       2 . The valve timing adjuster according to  claim 1 , wherein:
 the second position is a full retard phase position;   the phase of the camshaft is held fully retarded when the spool is positioned at the full retard phase position; and   when the spool is positioned at the full retard phase position, the first output port acts as a retard output port, through which working fluid is output to the retard chamber, and the second output port acts as an advance output port, through which working fluid is output to the advance chamber.   
   
   
       3 . The valve timing adjuster according to  claim 1 , wherein:
 the second position is a full advance phase position;   the phase of the camshaft is held fully advanced when the spool is positioned at the full advance phase position; and   when the spool is positioned at the full advance phase position, the first output port acts as an advance output port, through which working fluid is output to the advance chamber, and the second output port acts as a retard output port, through which working fluid is output to the retard chamber.   
   
   
       4 . The valve timing adjuster according to  claim 1 , wherein:
 the drain port opens to atmosphere;   the first position and the second position are arranged adjacent to each other in a direction, in which the spool is displaceable;   the connection passage connects the first output port with the second output port also when the spool is positioned at the second position;   the connection check valve opens in a case, where pressure on one side of the connection passage toward the second output port is higher than pressure on the other side of the connection passage toward the first output port when the spool is positioned at the one of the first position and the second position; and   the connection check valve closes in another case, where pressure on the one side of the connection passage is lower than pressure on the other side of the connection passage when the spool is positioned at the one of the first position and the second position.   
   
   
       5 . The valve timing adjuster according to  claim 1 , further comprising:
 an input line that is communicated with the fluid supply source and the input port; and   an input check valve that is provided to the input line, wherein:   the input check valve is adapted to open to allow working fluid to flow from the fluid supply source toward the input port; and   the input check valve is adapted to close to limit working fluid from flowing from the input port toward the fluid supply source.   
   
   
       6 . The valve timing adjuster according to  claim 1 , further comprising:
 a controlling unit that controls displacement of the spool based on a reference phase of the camshaft relative to the crankshaft, wherein the controlling unit is adapted to learn an actual phase of the camshaft relative to the crankshaft as the reference phase under a condition, where the controlling unit controls the spool to be positioned at the second position.   
   
   
       7 . The valve timing adjuster according to  claim 6 , wherein the controlling unit learns the actual phase as the reference phase by controlling the spool to be positioned at the second position after the engine has started. 
   
   
       8 . The valve timing adjuster according to  claim 6 , wherein the controlling unit learns the actual phase as the reference phase by controlling the spool to be positioned at the second position in a case, where a condition for adjusting the phase of the camshaft to the full phase is satisfied while the engine rotates at a speed not higher than a set value.