General Information
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| Illustration 1 | g02849224 |
(1) Valve (tilt section) (1a) Port (rackback) "A" (1b) Port (dump) "B" (1c) Relief and check valves (dump) (1d) Relief and check valves (rackback) (1e) Manifold (pilot valve) (2) Valve (lift section) (2a) Port (lower) "A" (2b) Port (lift) "B" (2c) Relief and check valves (lift) (2d) Check valve (lower) (2e) Manifold (pilot valve) (3) Manifold (3a) Port (test gauge) (3b) Valve (high flow solenoid) (4) Valve (auxiliary) (4a) Port (auxiliary "A1") "A" (4b) Port (auxiliary "A2") "B" (4c) Manifold (pilot valve) | |
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| Illustration 2 | g02851457 |
(1f) Solenoid (rackback) "C1" (1g) Solenoid (dump) "C2" (2f) Solenoid (lower) "C1" (2g) Solenoid (lift)"C2" (3e) Port (outlet) (tank return) (3f) Port (load sense) (3g) Port (pilot supply) (3h) Port (solenoid drain to tank) (3j) Port (inlet) (pump supply) (3k) Relief valve (4d) Solenoid (normal "A2" flow ) "C2" (4e) Solenoid (reverse "A1" flow) "C1" | |
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| Illustration 3 | g02921538 |
(1) Valve (tilt section) (1a) Port (rackback) "A" (1b) Port (dump) "B" (1c) Relief and check valves (dump) (1d) Relief and check valves (rackback) (1e) Manifold (pilot valve) (1f) Solenoid (rackback) "C1" (1g) Solenoid (dump) "C2" (1h) Spool (tilt circuit) (1j) Valve (compensator) (2) Valve (lift section) (2a) Port (lower) "A" (2b) Port (lift) "B" (2c) Relief and check valves (lift) (2d) Check valve (lower) (2e) Manifold (pilot valve) (2h) Spool (lift circuit) (2j) Valve (compensator) (2k) Valve (shuttle) (3) Manifold (3a) Port (test gauge) (3b) Valve (high flow solenoid) (3k) Valve (load sense relief) (3m) Valve (shuttle) (4) Valve (auxiliary) (4a) Port (auxiliary "A1") "A" (4b) Port (auxiliary "A2") "B" (4c) Manifold (pilot valve) (4d) Solenoid (normal "A2" flow ) "C2" (4e) Solenoid (reverse "A1" flow) "C1" (4f) Spool (auxiliary circuit) (4g) Check valve (auxiliary "A1") (4h) Relief and check valves (auxiliary "A2") (4j) Valve (compensator) | |
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| Illustration 4 | g02919138 |
Instruction decal for the right-hand joystick (5) Right-hand joystick | |
General Information
Note: All references to the joystick control are based on the standard Caterpillar Joystick Control Pattern. Refer to the machine Operation and Maintenance Manual , "Operator Controls". Refer to the section on "Selectable Control Pattern and Dedicated Control Pattern".
The control valve is an electrohydraulic controlled, closed center valve. Any movement of the right-hand joystick (5) will send a Pulse Width Modulation Signal (PWM signal) to the machine Electronic Control Module (ECM). The machine ECM will regulate electrical current to the corresponding solenoid in order to regulate pilot oil to the control valve spool.
If the right-hand joystick (5) is not moved, oil flows into the inlet and oil is blocked by the spools. The springs keep the spools centered because the pilot oil is not flowing to the spool. No movement of the implements occur.
The control valve contains three control valves and one manifold. Valve (4) controls the auxiliary function. The auxiliary valve (4) is controlled by solenoids (4d) and (4e) . Valve (2) controls the lift cylinder functions. Valve (2) is controlled by solenoids (2f) and (2g) . Valve (1) controls the tilt cylinder functions. Valve (1) is controlled by solenoids (1f) and (1g) .
Auxiliary Valve Section
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| Illustration 5 | g02849679 |
(4) Valve (auxiliary) (4a) Port (auxiliary "A1") "A" (4b) Port (auxiliary "A2") "B" (4c) Manifold (pilot valve) (4d) Solenoid (normal "A2" flow) "C2" (4e) Solenoid (reverse "A1" flow) "C1" (4f) Spool (auxiliary circuit) (4g) Check valve (auxiliary "A1") (4h) Relief and check valves (auxiliary "A2") (4j) Valve (compensator) (4k) Chamber (4m) Load sense port (4n) Spring (4p) Chamber (4r) Passage (4s) Chamber (4t) Passage (4u) Chamber (4v) Pump passage (4w) Passage (4x) Return (4y) Chamber (4z) Passage (4aa) Signal port | |
Auxiliary Valve - HOLD Position
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| Illustration 6 | g02928539 |
(4d) Solenoid (normal "A2" flow) "C2" (4e) Solenoid (reverse "A1" flow) "C1" (4f) Spool (auxiliary circuit) (4v) Pump passage | |
The "AUX 1" switch and the "AUX 2" switch are combined on the thumb-roller switch on the right-hand joystick (5) .
When the thumb-roller switch is not rolled forward or backwards, the spool (auxiliary circuit) (4f) is in the HOLD position. When the thumb-roller switch is not rolled forward or backwards, no PWM signal is sent to the machine ECM.
Springs keep auxiliary valve spool (4f) in the HOLD position when solenoids (4d) and (4e) have not been actuated. Implement pump oil flows to auxiliary control valve at port (4v) . Spool movement is controlled by actuation of solenoids (4d) and (4e) that allow oil to flow to either end of auxiliary valve spool (4f) .
The position of auxiliary valve spool (4f) blocks the oil in both ends of the auxiliary cylinder. The spool keeps the auxiliary cylinder from moving.
Auxiliary Valve - Reverse "A1" Flow Position
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| Illustration 7 | g02928697 |
(4) Valve (auxiliary) (4a) Port (auxiliary "A1") "A" (4b) Port (auxiliary "A2") "B" (4c) Manifold (pilot valve) (4d) Solenoid (normal "A2" flow) "C2" (4e) Solenoid (reverse "A1" flow) "C1" (4f) Spool (auxiliary circuit) (4g) Check valve (auxiliary "A1") (4j) Valve (compensator) (4k) Chamber (4m) Load sense port (4n) Spring (4p) Chamber (4r) Passage (4s) Chamber (4t) Passage (4u) Chamber (4v) Pump passage (4w) Passage (4x) Return (4y) Chamber (4z) Passage (4aa) Signal port | |
When the auxiliary thumb-roller on the right-hand joystick (5) is rolled back down, the ECM sends a signal to solenoid (4e) . Pilot oil is sent to chamber (4p) at the right end of auxiliary valve spool (4f) . Auxiliary valve spool (4f) moves to the left. Implement oil is sent from pump port (4v) to chamber (4u) . Oil flows around auxiliary valve spool (4f) to the bottom of compensation and load check valve (4j) . Compensation and load check valve (4j) is pushed up and flow goes through the openings in the load check valve to passages (4t) and (4w) . Oil flows around auxiliary valve spool (4f) to work port (4a) .
Solenoid valves (4e) and auxiliary valve spool (4f) respond in proportion to the signal that is received from the thumb-roller.
Oil returns from the work tool, enters through work port (4b) and exits through tank port (4x) to the hydraulic tank.
Auxiliary Valve - Forward "A2" Flow Position
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| Illustration 8 | g02928896 |
(4) Valve (auxiliary) (4a) Port (auxiliary "A1") "A" (4b) Port (auxiliary "A2") "B" (4c) Manifold (pilot valve) (4d) Solenoid (normal "A2" flow) "C2" (4f) Spool (auxiliary circuit) (4g) Check valve (auxiliary "A1") (4j) Valve (compensator) (4n) Spring (4s) Chamber (4t) Passage (4u) Chamber (4v) Pump passage (4w) Passage (4x) Return (4y) Chamber (4aa) Signal port | |
When the auxiliary thumb-roller on the right-hand joystick (5) is rolled forward (up), the ECM sends a signal ot solenoid (4d) . Pilot oil is sent to the left end of auxiliary valve spool (4f) . Auxiliary valve spool (4f) moves to the right. Implement oil is sent from pump port (4v) around auxiliary valve spool (4f) to the bottom of compensation and load check valve (4j) . Compensation and load check valve (4j) is pushed up and flow goes through the openings in the load check valve to passages (4t) and (4w) . Oil flow in chamber (4t) is blocked by the spool. Oil flows into chamber (4w) , around auxiliary valve spool (4f) to work port (4b) .
Oil flows to the rod end of the auxiliary cylinder. Solenoid valve (4d) and auxiliary valve spool (4f) respond in proportion to the movement of the thumb-roller.
Oil from the head end of the auxiliary cylinder enters through work port (4a) and exits through return (4x) to the hydraulic tank.
Lift Control Valve Section
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| Illustration 9 | g02850518 |
(2) Valve (lift section) (2a) Port (lower) "A" (2b) Port (lift) "B" (2c) Relief and check valves (lift) (2d) Check valve (lower) (2e) Manifold (pilot valve) (2f) Solenoid (lower) "C1" (2g) Solenoid (lift)"C2" (2h) Spool (lift circuit) (2j) Valve (compensator) (2k) Valve (shuttle) (2m) Spring (spool) (2n) Chamber (2p) Passage (pump) (2r) Chamber (2s) Spring (2t) Chamber (2u) Passage (2v) Passage (2w) Chamber (2x) Passage (2y) Chamber | |
Oil from the implement piston pump flows to raise control valve (2) at pump port (2p) . Pump oil flows from pump port (2p) through lift control valve (2) to the tilt control valve (3) . Lift valve spool (2h) is controlled by solenoids (2f) and (2g) . The lift valve spool is spring centered with a closed center. The lift valve spool has four positions: LIFT, HOLD, LOWER and FLOAT.
Lift Control Valve - HOLD Position
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| Illustration 10 | g02935315 |
(2c) Relief and check valves (lift) (2f) Solenoid (lower) "C1" (2g) Solenoid (lift)"C2" (2h) Spool (lift circuit) (2m) Spring (spool) | |
Spring (2m) keep raise valve spool (2h) in the HOLD position when solenoid valves (2g) and (2f) have not been actuated. Raise valve spool (2h) in the HOLD position blocks the oil in both ends of the raise cylinders. The spool (2h) keeps the raise cylinders from moving.
Check valve (2g) further limits raise cylinder drift toward the lower position if leakage occurs between raise valve spool (2h) and the valve body.
Spool movement is controlled by actuation of solenoids (2g) and (2f) , which allow oil to flow to either end of raise valve spool (2h) .
Lift Control Valve - Lift Position
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| Illustration 11 | g02935756 |
(2a) Port (lower) "A" (2c) Relief and check valves (lift) (2f) Solenoid (lower) "C1" (2h) Spool (lift circuit) (2j) Valve (compensator) (2m) Spring (spool) (2p) Passage (pump) (2u) Passage (2v) Passage (2w) Chamber (2y) Chamber | |
When the control joystick is moved to the RAISE position, the ECM sends a PWM signal to solenoid (2f) . Pilot oil is sent to chamber (2y) at the left end of the raise valve spool (2h) . When the oil pressure overcomes the spring (2m) , the tilt valve spool (2h) moves to the right. Implement pump oil is sent from pump port (2p) to chamber (2u) . Oil flows around raise valve spool (28) to the bottom of compensation and check valve (2j) . Compensation and check valve (2j) is pushed up and flow goes through the openings on to passages (2u) and (2v) . Oil in chamber (2u) is blocked by spool (2h) . Oil flows through passage (2v) , around spool (2h) and into chamber (2w) . The oil pressure in chamber (2w) overcomes the spring in check valve (2c) and flows to work port (2b) .
Oil is allowed to flow to the head end of the raise cylinders. The bucket will rise. Solenoid valves (2f) and raise valve spool (2h) respond in proportion to the movement of the joystick.
Oil from the rod end of the raise cylinders enters through work port (2a) and exits through tank port (2w) to the hydraulic tank.
Lift Control Valve - LOWER Position
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| Illustration 12 | g02936276 |
(2a) Port (lower) "A" (2b) Port (lift) "B" (2c) Relief and check valves (lift) (2g) Solenoid (lift)"C2" (2h) Spool (lift circuit) (2j) Valve (compensator) (2p) Passage (pump) (2u) Passage (2v) Passage (2y) Chamber | |
When the raise control joystick is moved to the LOWER position, the ECM sends a signal to solenoid (2g) . Pilot oil is sent to passage (2y) . Oil fills chamber (2y) at the right end of raise valve spool (2h) . Raise valve spool (2h) moves partially to the left. Implement oil is sent from pump port (2p) through chamber (2u) . Oil flows around raise valve spool (2h) to the bottom of compensation and load check valve (2j) . Compensation and load check valve (2j) is pushed up and flow goes through the openings in load check valve (2j) to passages (2v) and (2u) . Oil flow is blocked at chamber (2v) by the spool (2h) . Oil flows around raise valve spool (2h) , into chamber (2u) and to work port (2a) .
Oil is allowed to flow to the rod end of the raise cylinders. The bucket will lower. Solenoid valve (2g) and raise valve spool (2h) respond in proportion to the movement of the joystick.
Oil from the rod end of the raise cylinders enters work port (2b) but must get past check valve (2c) before flowing to tank. Check valve (2c) is piloted opened. Workport pressure on the spring chamber side of check valve (2c) is allowed to drain to tank and allows the check valve to open. The oil flows through chamber (2w) and exits to tank.
Lift Control Valve - FLOAT Position
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| Illustration 13 | g02936498 |
(2a) Port (lower) "A" (2b) Port (lift) "B" (2d) Check valve (lower) (2g) Solenoid (lift)"C2" (2h) Spool (lift circuit) (2p) Passage (pump) (2u) Passage (2v) Passage (2x) Passage (2y) Chamber | |
When the control joystick is moved to the FLOAT position, the ECM sends a signal to solenoid (2g) . Pilot oil is sent from passage (2x) , through passage (2y) to the right end of raise valve spool (2h) . Raise valve spool (2h) moves completely to the left. The control joystick FLOAT position is identified by a soft detent. The raise valve spool remains in the float position until the bucket reaches the preset kickout position. The ECM will then stop the signal to solenoid valve (2g) and the raise control valve will then return to the HOLD position.
When the spool moves to the FLOAT position, work port (2b) is connected to the tank at port (2v) through shifted raise valve spool (2h) . Complete movement of raise valve spool (2h) to the left closes off the flow of pump oil from port (2p) to passages (2u) and (2v) . Work port (2a) is also connected to the tank through shifted raise valve spool (2h) .
Oil from the rod end of the raise cylinder and the oil from the head end of the raise cylinder drains to the tank. The weight of the lift arm assembly lowers the lift arm assembly to the ground. The lift arm assembly will follow the contour of the ground. Neither the rod end of the raise cylinder or the head end of the raise cylinder are under hydraulic pressure. The raise cylinders can move freely in either direction according to the force on the bucket.
Tilt Control Section
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| Illustration 14 | g02977138 |
(1) Valve (tilt section) (1a) Port (rackback) "A" (1b) Port (dump) "B" (1c) Relief and check valves (dump) (1d) Relief and check valves (rackback) (1e) Manifold (pilot valve) (1f) Solenoid (rackback) "C1" (1g) Solenoid (dump) "C2" (1h) Spool (lift circuit) (1j) Valve (compensator) (1k) Valve (shuttle) (1m) Spring (spool) (1n) Chamber (1p) Passage (pump) (1r) Chamber (1s) Spring (1t) Chamber (1u) Passage (1v) Passage (1w) Chamber (1x) Passage (1y) Chamber | |
Oil from the implement piston pump flows to valve (1) at pump port (1p) . Pump oil flows from pump port (1p) through valve (2) to the tilt control valve (1) . Spool (1h) is controlled by solenoids (1f) and (1g) . The spool is spring centered with a closed center. The spool has three positions: HOLD, RACK BACK and DUMP.
Tilt Control - HOLD Position
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| Illustration 15 | g02938118 |
(1f) Solenoid (rackback) "C1" (1g) Solenoid (dump) "C2" (1h) Spool (tilt circuit) (1m) Spring (spool) | |
Spring (1m) keeps spool (1h) in the HOLD position when solenoids (1g) and (1f) have not been actuated. Spool movement is controlled by actuation of solenoids (1g) and (1f) that allow oil to flow to either end of tilt valve spool (1h) .
Spool (1h) in the hold position blocks the oil in both ends of the tilt cylinder. The spool prevents the tilt cylinder from moving.
Tilt Control - RACK BACK Position
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| Illustration 16 | g02938178 |
(1a) Port (rackback) "A" (1b) Port (dump) "B" (1c) Relief and check valves (dump) (1d) Relief and check valves (rackback) (1g) Solenoid (dump) "C2" (1h) Spool (tilt circuit) (1j) Valve (compensator) (1m) Spring (spool) (1n) Chamber (1p) Passage (pump) (1u) Passage (1v) Passage (1w) Chamber (1x) Passage (1z) Chamber | |
When the joystick is moved to the RACK BACK position, the ECM sends a signal to the rack back solenoid (1g) . Pilot oil is sent from passage (1x) through passage (1n) to chamber (1z) at the right end of spool (1h) . The oil pressure overcomes the pressure of spring (1m) . Spool (1h) moves to the left. Pump oil is sent through the tilt control valve from port (1p) to chamber (1u) . Oil flows around spool (1h) to the bottom of compensation and load check valve (1j) . Compensation and load check valve (1j) is pushed up and flow goes through the openings in the load check valve to passages (1u) and (1v) . Oil flow is blocked at passage (1v) by the spool (1h) . Oil flows through passage (1u) , around spool (1h) , through chamber (1u) to work port (1d) .
Oil flows from work port (1a) to the head end of the tilt cylinder forces the relief valve (1c) open. Oil flows to the work port (1b) . The cyclinder will be extended. The bucket will rack back. Solenoid valve (1g) and spool (1h) respond in proportion to the signal that is received from the joystick.
Oil from the rod end of the tilt cylinder enters through work port (1a) and exits to the hydraulic tank through passage (1u) .
Tilt Control - DUMP Position
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| Illustration 17 | g02938317 |
(1a) Port (rackback) "A" (1d) Relief and check valves (rackback) (1f) Solenoid (rackback) "C1" (1h) Spool (tilt circuit) (1j) Valve (compensator) (1m) Spring (spool) (1p) Passage (pump) (1u) Passage (1v) Passage (1w) Chamber (1y) Chamber | |
When the joystick is moved to the DUMP position, the ECM sends a signal to solenoid (1f) . Pilot oil is sent to chamber (1y) at the left end of spool (1h) . When the oil pressure overcomes the spring (1m) , the spool (1h) moves to the right. The implement oil flows from pump port (1p) around spool (1h) to the bottom of the compensation valve and check valve (1j) . Compensation valve and check valve (1j) is pushed up and flows to passages (1u) and (1v) . Oil in chamber (1u) is blocked by spool (1h) . Oil flows through passage (1v) , around spool (1h) , through chamber (1v) to work port (1a) .
Oil flows from work port (1a) to the rod end of the tilt cylinder. Return oil from the cylinder enters through port (1a) but most get past check valve (1d) . Check valve (1d) is a vented check held closed by workport pressure and a spring. When the spool (1h) is shifted in the DUMP direction, a connection is opened up. The connection opens between the back side of the check valve (1d) and the tank passage (1w) . Work port pressure opens the check valve. Oil will flow through to passage (1w) to the tank. The cylinder will retract. The bucket will dump. Solenoid valve (1f) and spool (1h) respond in proportion to the signal that is received from the joystick.
Oil from the head end of the tilt cylinder enters through work port (1a) and exits to the hydraulic tank through passage (1w) .