Line pressure control device for auto gearbox has sensor for engine speed with microprocessor calculating lubricating oil and clutch pressures and if engine speed threshold is exceeded

摘要

A line pressure control device for an auto gearbox (200) that contains a transmission ratio-changing mechanism (203) and a clutch mechanism (202) to transmit the torque of an IC engine (100) to an output shaft (215). The control device has: - an oil circuit (210) to change a line pressure supplied to the transmission ratio-changing mechanism and to the clutch mechanism - a sensor (68) to detect the speed of the engine and - a microprocessor (610 which is programmed so that it: - calculates a lubricating oil pressure to lubricate the transmission ratio-changing mechanism and a clutch pressure to operate the clutch mechanism with the aid of the operating state of the gearbox - determines whether the speed of the engine is higher or lower than a fixed threshold - sets a setpoint line pressure to the higher of the lubricating oil and clutch pressures when the speed of the engine is higher than the threshold - sets the clutch pressure as the setpoint line pressure when the speed of the engine is lower than the threshold and - controls the oil pressure circuit in the way that the line pressure converges towards the setpoint line pressure.