Hydraulic Control System

HYDRAULIC CONTROL SYSTEM

Oil Pump

Outline
A variable capacity trochoid oil pump is used for improved discharge efficiency and reduced fuel consumption. The former involute gear oil pump discharged oil in proportion to the engine speed. The variable capacity pump also outputs oil in proportion to engine speed but, when the engine reaches a certain rpm, the output of the pump is fixed at a maximum to minimize the drive torque losses caused by the pump.





Construction
An outer rotor, inner rotor, and oil pump flange are installed within the pump housing of the trochoid gear oil pump.
The oil pump flange and oil pump shaft are coupled to the inner rotor.
The other end of the oil pump shaft is coupled to the pump impeller side of the torque converter, and via the converter, to the engine.
As a result, the oil pump flange, the inner rotor, and the outer rotor rotate unitedly with the engine.
A spool and spring installed in the discharge section of the pump housing regulates the oil discharge.

Fig.A:

Fig.B:

Operation
1. When the speed of the engine is low the spool is as shown in Fig. A, and the amount of oil discharged increases in proportion to engine rpm.
2. When the engine rpm increases and the p-p' differential pressure becomes greater, the spool is pressed against the spring and compresses it as it moves to the right. When the spool is in the position shown in Fig. B, the oil is redirected through port A to port B and circulates back to the inlet side of the pump, with the result that the amount of oil discharged fixed.

Control Valve

Component location

Premain Control Valve Body:

Main Control Valve Body:

Upper Control Valve Body:

Accumulators

Accumulators:

Component descriptions

Component Descriptions:

Manual valve
The manual valve switches the hydraulic path for the line pressure generated by the oil pump.

P Position:

R Position:

N Position:

D Range:

2 Range:

1 Range:

When the selector lever is moved, the manual valve also moves until it is located in a position where line pressure (7) is distributed to each line pressure circuit for each P, R, N position, and D, 2 and 1 range.
Line pressures (1), (3), (5), and (6) are distributed to each valve. When line pressure (7) is not in a distribution position, the line pressures (1), (3), (5), and (6) are drained at the X position.
Line pressure (1)
^ 1-2 shift valve
^ 2-3 shift valve
^ 3-4 shift valve
^ N-D accumulator
^ Forward clutch
^ Torque converter clutch control valve
Line pressure (3)
^ 2-3 shift valve
Line pressure (5)
^ Low reducing valve
Line pressure (6)
^ 1-2 shift valve
^ N-R accumulator
^ Reverse clutch
^ Low and reverse brake

1-2 Shift valve

Outline
The 1-2 shift valve automatically shifts between first and second gear.
The 1-2 shift valve switches the paths for the line pressure applied to the 1-2 shift valve. The shift solenoid A ON-OFF signal is controlled by the powertrain control module.

Operation
With shift solenoid A OFF, line pressure (12) is applied to the right side of the valve.
This allows the valve to overcome line pressure (7) and the spring force, causing the valve to move to the left, shifting to first gear position.
Also, in 1 range, low reducing pressure (10) is transmitted to (11) in first gear, engaging the low and reverse brake.





When vehicle speed is high, the powertrain control module turns ON the shift solenoid A and line pressure (12) is drained from shift solenoid A.
Consequently, spring force and line pressure (7) working on the left end of the valve push the valve to the right, shifting to second gear position. Even when line pressure (12) is drained, line pressure (7) does not change, due to there being an orifice.
In second gear position, line pressure (1) is transmitted to (9), engaging the 2-4 brake band with a slow pressure increase by the orifice check valve and the 1-2 accumulator operation.
In second gear position, low reducing pressure (11) is drained, releasing the low and reverse brake.





2-3 shift valve

Outline
The 2-3 shift valve automatically shifts between second and third gear.
The 2-3 shift valve switches the paths for the line pressure applied to the 2-3 shift valve. The shift solenoid B ON-OFF signal is controlled by the powertrain control module.

Operation
With shift solenoid B ON, line pressure (14) is drained from shift solenoid B. Consequently, spring force and line pressure (7) push the valve to the right, shifting to second gear position. In second gear position, line pressure (3) is closed and line pressure (13) is drained.





When vehicle speed is high, the powertrain control module turns OFF the shift solenoid B. As a result, line pressure (14) is applied to the right side of the valve.
This allows the valve to overcome line pressure (7) and the spring force, causing the valve to move left, shifting to third gear position.
In third gear position, line pressure (3) is transmitted to (13), applying the 3-4 clutch with a slow pressure increase by the bypass valve and the 2-3 accumulator operation.
The line pressure (13) release the 2-4 brake band through the 3-4 shift valve.





3-4 shift valve Outline
The 3-4 shift valve automatically shifts between third and fourth gear.
The 3-4 shift valve switches paths for line pressure applied to the 3-4 shift valve. The shift solenoid C ON-OFF signal is controlled by the powertrain control module.

Operation
With shift solenoid C OFF, line pressure (17) is applied to the right side of the valve. This allows the valve to overcome line pressure (7) and the spring force, causing the valve to move left, shifting to third gear position. In third gear position, line pressure (1) is transmitted to (16) and line pressure (13) is transmitted to (15). The line pressure (16) engages the coasting clutch through the orifice check ball. The line pressure (15) releases the 2-4 brake band.





When vehicle speed is high, the powertrain control module turns ON the shift solenoid C, allowing line pressure (17) to be drained from shift solenoid C.
Consequently, the combination of spring force and line pressure (7) push the valve to the right side, shifting to fourth gear position. In fourth gear position, line pressure (15) and (16) are drained, engaging the 2-4 brake band and releasing the coasting clutch.





Torque converter clutch control valve

Outline
The torque converter clutch control valve controls torque converter clutch operation based on the torque converter clutch solenoid valve ON-OFF signal which is controlled by the powertrain control module.

Operation
With the torque converter clutch solenoid valve OFF, line pressure (7) is applied to the right side of the valve.
This allows the valve to overcome line pressure (1) and the spring force, causing the valve to move left. As a result, the hydraulic pressure (ATF) working on the torque converter front chamber passes from the torque converter clutch control valve, distributes the ATF, and inhibits torque converter clutch engagement.





With the torque converter clutch solenoid valve ON, line pressure (7) is drained through the torque converter clutch solenoid valve. The combination of spring force and line pressure (1) push the valve to the right side. Consequently, the hydraulic pressure applied to the torque converter front chamber is drained through the valve, engaging the torque converter clutch.





Pressure regulator valve

Outline
The pressure regulator valve adjusts the line pressure generated by the oil pump to match driving conditions.

Operation
Line pressure (7) that is generated in the oil pump works on chambers (A) and (B). The line pressure applied to chamber (A) moves the pressure regulator valves to the left side due to a difference between the surface areas of the two valves.
Line pressure is then drained from chamber (C).
As a result, the pressure regulator valve balances at the point which the (A) chamber line pressure acting toward the left balances with the spring force and modifier pressure (21) acting toward the right side. The line pressure (7) that works on chamber (A) becomes torque converter pressure (23) which is sent into the torque converter through the torque converter clutch control valve.





When the accelerator pedal is depressed, modifier pressure (21) rises and adds to the spring force which moves the pressure regulator valve to the right side.
This makes drainage of line pressure (7) from chamber (C) difficult. Therefore, the pressure regulator valve balances at a high level line pressure (7). In R position, line pressure (6) is applied to the pressure regulator valve, moving the valve to the right. This makes drainage of line pressure (7) in chamber (C) difficult. Therefore, the pressure regulator valve balances at a considerably high level line pressure (7).





Pressure modifier valve

Outline
The pressure modifier valve converts solenoid reducing pressure to modifier pressure that matches the throttle valve opening angle(engine load).

Operation
The solenoid reducing pressure generated by the solenoid reducing valve is constantly applied to the step in the right side of the pressure modifier valve.
When the throttle valve opening angle is small, the duty value of the pressure control solenoid is low.
The hydraulic pressure applied to the left side of the pressure modifier valve drops due to the pressure control solenoid action, moving the modifier valve to the left. the resulting modifier pressure is low.





When the throttle valve opening angle is large, the duty value of the pressure control solenoid is high.
The hydraulic pressure applied to the left side of the pressure modifier valve is not easily drained by the pressure control solenoid, moving the pressure modifier valve to the right. The resulting modifier pressure is high. Through this process, modifier pressure is controlled, depending on the throttle valve opening angle.





Pressure modifier accumulator

Outline
This valve stabilizes the modifier pressure adjusted by the pressure modifier valve to prevent modifier pressure pulsation.

Operation
The valve is pushed to the left by modifier pressure (21) and to the right by spring force. When modifier pressure (21) pulsates at high pressure, the valve moves to the left. When it pulsates at low pressure, the valve moves to the right. This operation stabilizes modifier pressure.





Converter relief valve

Outline
The converter relief valve prevents torque converter pressure from exceeding a specified level.

Operation
Torque converter pressure (23) generated by the pressure regulator valve is constantly applied to the left end of the converter relief valve. It is spring force, however, which moves the valve to the left side.





When torque converter pressure (23) increases, it overcomes spring force and pushes the converter relief valve to the right side. The pressure (23) is drained and maintained under a specified level.





Solenoid reducing valve

Outline
The solenoid reducing valve converts line pressure to solenoid reducing pressure which acts on the pressure control solenoid.

Operation
Solenoid reducing pressure (20) pushes the solenoid reducing valve to the right, while spring force pushes it to the left.
When solenoid reducing pressure (20) increases, the solenoid reducing valve moves to the right until pressure is drained.
This maintains a constant pressure to keep the spring force and line pressure (7) balanced. Solenoid reducing pressure becomes fixed.





Bypass valve

Outline
The bypass valve controls the 3-4 clutch engagement timing and shift shock to match the throttle valve opening.

Operation
The bypass valve is located parallel to the orifice check valve.
The bypass valve is held closed by the spring and throttle-modulated pressure (21), and line pressure (13) is transmitted to (18).





When line pressure (18) increases, it overcomes spring force and modifier pressure (21). The bypass valve moves to the left and closes line pressure (13).
Line pressure (13) passes through the orifice check valve and the 3-4 clutch engagement pressure is caused to gradually increase.





Low reducing valve

Outline
The low reducing valve reduces low and reverse brake engagement pressure and capacity, there by reducing shock when shifting from second gear to 1 range first gear.

Operation
The low reducing valve is normally pushed to the left side by spring force.
When 1 range is selected, line pressure (5) is transmitted to low reducing pressure (10).
Low reducing pressure (10) is then also applied to the left end of the valve, pushing it to the right side.
As a result, the valve closes the passage from line pressure (5) to (10) and opens the drain port for low reducing pressure (10).





Thus, low reducing pressure (10) is lowered.
If low reducing pressure (10) decreases, allowing the valve to move to the left side by spring force the valve will close the drain port.





N-D accumulator

Outline
The N-D accumulator moderates the rapid increase in hydraulic pressure during the forward clutch engagement. This reduces shift shock generated when D range is selected from N position.

Operation
In N position, line pressure (7) is applied to the right end of the piston, pushing it to the left side.





When D range is selected from the N position, line pressure (1), which engages the forward clutch, is applied to the left end of the piston.
As a result, the combination of line pressure (1) and spring force overcomes the combination of line pressure (7) and spring force, moving the piston gradually to the right side.
This movement of the piston moderates the rapid increase in line pressure (1).





N-R accumulator

Outline
The N-R accumulator moderates the rapid increase in the hydraulic pressure during the reverse clutch engagement. This reduces shift shock generated when R position is selected from N position.

Operation
In N position, spring force pushes the piston to the left side.





When R position is selected from N position, line pressure (6), which engages the reverse clutch, is applied to the left end of the piston.
As a result, line pressure (6) overcomes spring force, moving the piston gradually to the right side.
This movement of the piston moderates the rapid increase in line pressure (6).





1-2 accumulator

Outline
The 1-2 accumulator moderates the rapid increase in hydraulic pressure during 2-4 brake band engagement. This reduces shift shock generated when shifting to second and fourth gear.

Operation
In first gear, line pressure (7) is applied to the right end of the piston, pushing it to the left side.





When shift solenoid A turns ON to shift to second gear, line pressure (9), which engages the 2-4 brake band, is applied to the left of the piston by the 1-2 shift valve. As a result, the combination of line pressure (9) and spring force overcomes line pressure (7), moving the piston gradually to the right side.
This movement of the piston moderates the rapid increase in line pressure (9).
When shifting from third gear to fourth gear, line pressure (9) is temporarily drained while still in third gear, the 2-4 brake bard is newly applied, and then shifted to fourth gear. As a result, line pressure (7) and line pressure (18), which engages the 3-4 clutch, make the counteractive line pressure (9) shift high.
This provides optimal 2-4 brake band engagement timing during third to fourth gear shifting.





2-3 accumulator

Outline
The 2-3 accumulator moderates the rapid increase in hydraulic pressure during the 3-4 clutch engagement. This reduces shift shock generated when shifting to third gear.

Operation
In second gear, line pressure (7) is applied to the right end of the piston, pushing it to the left side.





When shift solenoid B turns OFF to shift to third gear, line pressure (18), which engages the 3-4 clutch, is applied to the left side of the piston by the 2-3 shift valve. As a result, the combination of line pressure (18) and spring force overcomes line pressure (7), moving the piston gradually to the right side. This movement of the piston moderates the rapid increase in pressure (18).