Fluid Pressure Control

The oil pressure control system fundamentally consists of three parts: (1) oil pressure producing system which consists of an oil pump to produce oil pressure and regulator valve to regulate the pressure, (2) oil circuit to feed fluid into the torque converter, the oil cooler and the transmission components to be lubricated, and (3) control system to shift the gear of the planetary gear unit by acting on each clutch and brake.

VALVE BODY





The valve body is installed in the oil pan and has valves to control oil pressure. In the valve body, oil passages connect valves.

OIL PUMP





The oil pump is of the internal gear type. It feeds fluid to the torque converter, lubricates each part of the transmission and delivers oil pressure to operate each clutch and brake. The oil pump is driven together with the pump impeller by the engine.

MANUAL VALVE





The manual valve is directly connected with the selector lever by wire. It opens and closes the oil passage mechanically so as to form respective oil pressure circuit for "L", "2", "D", "N", "R", or "P" range according to the selector lever movement.

THROTTLE VALVE





As the throttle valve is linked with the accelerator pedal by wire, it produces the throttle pressure corresponding to the extent to which the accelerator pedal is depressed which is, in other words, the engine output.
When the accelerator pedal is depressed, the throttle cam pushes the shift plug which then compresses two springs to move the throttle valve. Thus the line pressure passage is opened and the throttle pressure is produced.
The throttle pressure is also applied to the back of the throttle valve to push back the valve. The throttle pressure is determined by the tensile force of the springs (position of the shift plug) and applied to the primary and secondary regulator valves to regulate the line pressure.

PRIMARY REGULATOR VALVE





This valve regulates the oil pressure produced by the oil pump (line pressure) to correspond to each condition of use. It is operated by the throttle pressure, line pressure when in reverse and the springs.

SECONDARY REGULATOR VALVE





This valve regulates the oil pressure to the torque converter and lubricating oil pressure to each part of the transmission by means of the throttle pressure and the spring.

B2 CONTROL VALVE





When in "L" range, this valve controls the line pressure acting on the 1st-reverse brake to reduce a shock.

COOLER BY-PASS VALVE





This valve is provided to keep the oil pressure in the torque converter constant.

1 - 2 SHIFT VALVE





This valve carries out the gear shift between 1st and 2nd gears. When the 2nd brake solenoid valve operates, the line pressure is applied to the shift valve and the valve moves to allow the line pressure to be applied to the 2nd brake and thus the transmission is shifted into 2nd gear.
When the oil pressure to the 2nd brake solenoid valve is relieved, the shift valve returns by means of the spring force and the transmission is shifted to the 1st gear.
In "L" or "R" range, the fluid pressure is applied to the 1st-reverse brake when the 2nd brake solenoid valve operates.

2 - 3 SHIFT VALVE





This valve carries out the gear shift between 2nd and 3rd gears. When the direct clutch solenoid valve operates, the line pressure is applied to the shift valve and the valve moves to allow the line pressure to be applied to the direct clutch and thus the transmission is shifted from the 2nd to the 3rd gear. When the oil pressure to the solenoid valve is relieved, the shift valve returns by means of the spring force and the transmission is shifted to the 2nd gear.

ACCUMULATOR





This serves to reduce a shock in each gear shift. There are two accumulators, one for the forward clutch and the other for the 2nd brake.

DIRECT CLUTCH AND 2ND BRAKE SOLENOID VALVES





These solenoid valves turn ON and OFF by the electric signals from the transmission control module. They serve to control the gear shift by operating the 1 - 2 and 2 - 3 shift valves. Direct clutch solenoid valve operates the 2 - 3 shift valve, and 2nd brake solenoid valve does the 1 - 2 shift valve. When the solenoid valve is ON, the valve moves up to relieve the line pressure and when OFF, the valve moves down and therefore the line pressure is applied to the shift valve.

OIL CIRCUIT IN "N" RANGE





When the engine is started and the oil pump starts to operate, fluid in the oil pan passes through the oil pump, is regulated by the primary regulator valve and sent to the torque converter. Also, the fluid which is further regulated by the secondary regulator valve lubricates each part of the transmission. In this range, the oil pressure is not applied to any clutch or brake as the line pressure from the regulator valve is stopped by means of the manual valve.

OIL CIRCUIT IN "D" OR "2" RANGE (1ST GEAR)





The line pressure which has passed through the manual valve is applied directly to the forward clutch. As this causes the clutch to be engaged, the 1st gear is shifted. The line pressure is also applied to the accumulator to reduce shocks at the time of clutch engagement.
As the direct clutch and the 2nd brake solenoid valves receive the electric signal from the controller, that is, they are turned ON, they relieve the line pressure. Therefore, neither the 1 - 2 nor 2 - 3 shift valve operates due to no oil pressure.

OIL CIRCUIT IN "D" OR "2" RANGE (2ND GEAR)





As the vehicle speed is accelerated at the 1st gear and reaches the 2nd gear shift point, the 2nd brake solenoid valve turns OFF and closes the relief circuit. This causes the line pressure (1) to act on the 1 - 2 shift valve. Then the valve moves to allow the line pressure (3) to be applied to the 2nd brake and the 2nd gear is attained. At this time, the line pressure (3) is also applied to the accumulator to reduce a shock occurring when the 2nd brake works.
The same oil circuit acts in "D" when the vehicle speed is lowered to the shift down point from the 3rd to the 2nd gear.

OIL CIRCUIT IN "D" RANGE (3RD GEAR)





As the vehicle speed is further accelerated in the 2nd gear and reaches the 3rd gear shift point, the direct clutch solenoid valve turns OFF and closes the relief circuit. This causes the line pressure (4) to be applied to the 2 - 3 shift valve. Then the oil pressure is applied to the direct clutch to make it engaged. At the same time, the oil pressure acts, as a back pressure, on the 2nd brake piston.
Thus the 2nd brake piston is pushed back, the 2nd brake is released and the 3rd gear is attained. In this state, as the 2nd brake solenoid valve is OFF, the 1 - 2 shift valve is at work and opens the oil passage to the 2nd brake but the 2nd brake does not operate. It is because the oil pressure to the 2nd brake is balanced with the above mentioned back pressure and the return spring force pushes back the piston to prevent the 2nd brake from operating.

OIL CIRCUIT IN "L" RANGE





The line pressure (1), after passing through the manual valve, comes out as the line pressures (2) and (5). The line pressure (2) is applied to the forward clutch. In this state, as the 2nd brake solenoid valve is OFF because it is not electrically charged from the Transmission Control Module (TCM) (controller), the line pressure (1) is applied to the 1 - 2 shift valve. Then the line pressure is applied to the 1st-reverse brake. Consequently the 1st gear is attained.
When the selector lever is shifted to "L" at a speed higher than 53 km/h (33 mile/h), the 2nd brake solenoid valve is electrically actuated and the solenoid valve opens to allow the line pressure (1) to be relieved. Then the 1 - 2 shift valve is pushed back by its return spring and the passage of the line pressure (5) is switched from the 1st-reverse brake to the 2nd brake piston. Therefore, the 2nd gear is attained until the vehicle speed lowers.

OIL CIRCUIT "R" RANGE





The line pressure (1), after passing through the manual valve, comes out as the line pressure (5) and (6). In this state, as the 2nd brake solenoid valve is OFF, the line pressure (1) is applied to the 1 - 2 shift valve and the line pressure (5) is applied to the 1st-reverse brake after passing through the B2 control valve. On the other hand, the line pressure (6) is applied to the direct clutch via the 2 - 3 shift valve, thus resulting in the reverse gear. Also, a part of the line pressure (6) acts on the primary regulator valve to regulate the line pressure (1).

OIL COOLING SYSTEM





The oil cooler of dual pipe type is built in the lower tank of the engine cooling radiator and cools off the automatic transmission fluid.