Fluid Pump: Description and Operation

OIL PUMP AND INTERNAL VALVES

The oil pump is mounted in the transmission assembly situated between the torque converter and the transmission gears casing. The pump is a constant mesh spur gear type and the drive gear, being keyed to the torque converter hub, is driven at engine speed whenever the engine is running. The oil pump contains valves for pressure regulation, torque converter clutch (TCC) enable and shift, converter limiting, and reverse boost.


Pressure Regulator Valve Train

A pressure regulating valve maintains the transmission fluid at a constant pressure, to ensure correct operation of the transmission, directing fluid into the converter limit valve, and the pump suction circuit to regulate the pump output.


Reverse Boost Valve

The boost valve is moved towards the pressure regulating valve when activated by torque signal fluid pressure from the variable force motor, the regulating valve is then moved against the fluid supply from the pump, and so boosts the line pressures in relation to engine torque. When reverse gear has been selected, the reverse fluid pressure forces the reverse boost valve to move towards the pressure regulator valve to boost the line pressure.


Torque Converter Clutch Enable Valve

To retain the TCC in a released condition, the TCC shift valve is held by regulated converter feed fluid which passes through the enable valve to the TCC enable circuit.


Torque Converter Clutch Shift Valve

The TCC shift valve, being held in the release position by spring force and TCC enable fluid, permits regulated converter feed fluid to pass through the valve and enter the TCC release circuit. To apply the TCC, enable fluid exhausts and the valve is shifted by signal fluid pressure


Converter Limiting Valve

This valve permits converter feed pressure from the pressure regulator valve to enter the regulated converter feed circuit. Excess converter feed pressure causes the limit valve to move against its spring pressure, and so the converter feed fluid is opened to exhaust.