Spool valve for VCT locking pin release mechanism
View Patent ↗A spool valve 10 for a variable camshaft timing (VCT) phaser for an internal combustion engine comprises a spool 11 slidable in a bore 12 in a valve sleeve 13 , the spool 11 having spaced apart lands 14 - 17 dividing the bore 12 into chambers 41, 42, 43 between adjacent lands. The valve sleeve 13 has fluid passages 22 - 27 including a lock passage 26 communicating with a lock pin 31 , a vent passage 27 communicating with a fluid sump 35 , and a lock pin oil feed passage 22 , with the spool 11 being slidable in the bore 12 to interconnect select passages via particular chambers, wherein the vent passage 27 and the lock pin passage 26 are connectable with different chambers 43 and 42 respectively. The arrangement avoids unnecessary operation of the lock pin 31.
1. A hydraulic control system for a variable camshaft timing (VCT) phaser for an internal combustion engine, comprising:
a spool valve having a spool slidably located within a bore in a valve sleeve, said spool comprising: first, second, third, and fourth lands spaced apart dividing said bore into first, second, and third chambers between adjacent lands, said valve sleeve having a plurality of fluid passages which open into said bore, said passages comprising:
a lock pin oil feed passage;
a lock pin passage communicating with a lock pin; and
a vent passage communicating with a fluid sump;
wherein spool valve is incapable of attaining a position where said lock pin passage is in communication with said vent passage.
2. The hydraulic control system of claim 1 wherein said second land is arranged between said first and third lands and said third land is arranged between said second and fourth lands.
3. The hydraulic control system of claim 1 wherein said first chamber is defined between said first land and said second land and said plurality of passages further comprises: an advance passage in communication with an advance chamber of the VCT, a common oil feed passage, and a retard passage in communication with a retard chamber of the VCT, said advance and retard passages selectively connectable through the first chamber.
4. The hydraulic control system of claim 3 , wherein when said spool is in a null position, said advance passage is blocked by said first land, said retard passage is blocked by said second land, and said lock pin passage is in fluid communication with a second chamber defined between said second land and said third land, such that the lock pin is in an unlocked position with said third land blocking communication between said lock pin oil feed passage and said lock pin passage.
5. The hydraulic control system of claim 3 wherein said second chamber is defined between said second land and said third land, said third chamber is defined between said third land and said fourth land, and said spool is capable of being displaced in a first position in which said lock pin oil feed passage is in communication with said lock pin passage and a second position in which said lock pin oil feed passage is in communication with said vent passage.
6. The hydraulic control system of claim 5 , further comprising:
a solenoid coupled to said spool; and
a spring coupled to said spool, wherein said spool is biased to a base position by said spring when no current is supplied to said solenoid, such base position comprising said third land interrupting fluid communication between said lock pin oil feed passage and said vent passage.
7. The hydraulic control system of claim 1 , further comprising:
a solenoid coupled to said spool; and
a spring coupled to said spool;
wherein all operational positions attainable under action of said solenoid and said spring causes said third land prevents communication between said vent passage and said lock pin passage.
8. The system of claim 1 , further comprising:
a spring coupled to said spool on a first end;
a solenoid coupled to said spool on a second end;
an electronic control unit coupled to said solenoid, said electronic control unit commanding a current to be supplied to said solenoid and said current supply determines a position that said spool attains.
9. The system of claim 8 wherein when no current is supplied to said spool, the spool attains a base position in which fluid communication between said lock pin oil feed passage and said vent passage is blocked.
10. The system of claim 8 wherein said second land is arranged between said first and third lands and said third land is arranged between said second and fourth lands and said spring is coupled to an end of said spool farthest said first land.
11. The system of claim 8 wherein said fluid passages further comprise an advance passage and a retard passage, said spool having an advance position in which said retard passage is occluded by the first land and a retard position in which said advance passage is occluded by the second land.