Hydraulic control system
1. clutch piston; 2. Belleville spring; 3. diaphragm; 4. front oil pump; 5. rear oil pump; 6. oil filter; 7. bypass valve; 8. thermal relay; 9. differential clutch assembly
Starting and accelerating in forward gear (4WD)
1. clutch piston; 2. diaphragm; 3. front oil pump; 4. rear oil pump
When starting off or accelerating in forward gear, the dual-pump system can engage four-wheel drive.
If the front wheels spin faster than the rears, the front oil pump spins faster than the rear. The front oil pump draws fluid through stop valve B and drains it. Part of the liquid at the outlet of the front oil pump is sucked in by the rear oil pump. The rest of the fluid passes through check valve E into the clutch piston, where the hydraulic pressure is controlled by two diaphragms.
Adjustable hydraulic pressure on the clutch piston compresses the clutch plates and discs together and forms a bond. At the same time, the included clutch transfers traction from the transfer case to the rear wheels and creates four-wheel drive (4WD).
Driving in forward gear at a constant speed (2WD)
1. front oil pump; 2. rear oil pump
When driving in forward gear at a constant speed, the dual-pump system operates in two-wheel drive mode.
The speed of rotation of the front and rear wheels is the same, so the speed of the front and rear pumps is the same. Fluid leaving the front oil pump is sucked in by the rear oil pump and circulated through the system. Since there is no pressure applied to the clutch piston, the clutch does not engage and the vehicle remains in 2WD mode (front wheel drive).
Deceleration in forward gear (2WD)
1. rear oil pump
When decelerating in forward gear, the dual-pump system operates in two-wheel drive mode.
Due to braking performance, when decelerating, the rear wheel speed may exceed the front wheel speed. In this case, the rear oil pump rotates faster than the front.
Fluid at the outlet of the rear oil pump is simply sucked up again by the rear oil pump and recirculated. Since there is no pressure applied to the clutch piston, the clutch piston does not engage and the vehicle remains in 2WD mode (front wheel drive).
Movement and acceleration in reverse gear (4WD)
; 1. diaphragm; 2. front oil pump
When starting off and accelerating in reverse gear, the dual-pump system can activate the four-wheel drive.
If the front wheels spin faster than the rears, the front oil pump spins faster than the rear. The front oil pump draws fluid through stop valve A and drains it. (It should be noted that in the case of reverse gear, the direction of operation of the pumps is opposite to the direction when driving in forward gear).
Part of the liquid at the outlet of the front oil pump is sucked in by the rear oil pump. The rest of the fluid passes through check valve F into the clutch piston cylinder, where the hydraulic pressure is controlled by two diaphragms.
Adjustable hydraulic pressure on the clutch piston can press the clutch plates and discs together and form a bond. At the same time, the included clutch transfers traction from the transfer case to the rear wheels and creates four-wheel drive (4WD).
Driving in reverse gear at a constant speed (2WD)
1. diaphragm; 2. front oil pump; 3. rear oil pump
When driving in reverse gear at a constant speed, the dual-pump system operates in two-wheel drive mode. The speed of rotation of the front and rear wheels is the same, so the speed of the front and rear pumps is the same. The fluid at the outlet of the front oil pump is sucked by the rear oil pump and circulates through the system, but because there is a difference in pump performance, the fluid flows through check valve E and further through the diaphragms. This fluid lubricates and cools the clutch assembly and bearings.
Under these conditions, only a small amount of pressure is applied to the clutch piston, so the clutch does not engage and the vehicle remains in 2WD mode (front wheel drive).
Deceleration in gear rear xofla (4WD)
1. diaphragm; 2. front oil pump; 3. rear oil pump
When decelerating in reverse gear, the dual-pump system can engage four-wheel drive.
When decelerating in reverse, the rear wheel speed may exceed the front wheel speed (due to engine braking). Under these conditions, the rear oil pump draws fluid through check valves B and C. Fluid at the rear oil pump outlet then flows through check valve E to the clutch piston, where pressure is controlled by two diaphragms. Adjustable hydraulic pressure on the clutch piston can press the clutch plates and discs together and form a bond. At the same time, the included clutch transfers traction from the transfer case to the rear wheels and creates four-wheel drive (4WD).
Thermal switch operation
1. thermal relay; 2. bypass valve
When operating in 4WD mode (four wheel drive) fluid under controlled pressure is in contact with the clutch piston and the thermal switch. When the temperature of the liquid in the differential rises, the thermal switch opens the bypass valve R. In this case, the pressure on the clutch piston decreases and the 4WD mode is exited.
Bypass valve operation
1. bypass valve
When the fluid pressure becomes greater than the resistance of the relief valve spring, stop valve R opens. The pressure applied to the clutch piston is kept constant. In this way, excessive torque is prevented in the rear-wheel drive system and operation stability is improved.