A transmission for a machine is disclosed. The transmission may comprise a torque path providing a path for transmission of torque from an input shaft to an output shaft, and a single clutch element along the torque path. The transmission may further comprise a clutch actuator configured to actuate engagement of the clutch element, and a clutch pressure control (CPC) valve configured to permit a flow of hydraulic fluid to the clutch actuator through a control pressure line when in an open position to cause the clutch actuator to actuate engagement of the clutch element. The transmission may further comprise a failure mode response (FMR) valve in the control pressure line between the CPC valve and the clutch actuator. The FMR valve may have a failure position obstructing flow of the hydraulic fluid from the CPC valve to the clutch actuator when the CPC valve is in the open position.

A method for operating a pneumatic actuating system of a transmission. The actuating system has an air reservoir at a first pressure. The reservoir couples an actuating space of the actuating system which is at a second pressure, and the actuating space couples, via control valves, shifting cylinders. When conducting a transmission gearshift, an air mass delivered to the active shifting cylinders via corresponding control valves, and an air mass sum including a nominal air mass in the active cylinders required for accomplishing the gearshift and an actual basic leakage from the activated shifting cylinder are determined. A defect leak in the pneumatic actuating system is recognized, if the air mass delivered to the active shifting cylinders is larger than the air mass sum. If a defect leak is recognized, the control valves coupling the actuating space and the shifting cylinders are shut off for a period of time.

The invention relates to a hydraulic circuit (100, 200, 300) having a first, hydraulically actuable clutch (K1) which is closed in a rest state and a second, hydraulically actuable clutch (K2) which is closed in the rest state, wherein the hydraulic circuit (100, 200, 300) is configured in such a way that a hydraulic medium which is present in a main pressure line (HD) can be loaded with a working pressure by means of a pressure generating device (DE) and/or by means of a pressure accumulator (DS), and the hydraulic medium can be discharged for pressure dissipation via a main return line (HR) into the return reservoir (T), and wherein the hydraulic circuit (100, 200, 300) has a first distributor pressure line (VD1) and a separate, first collector return line (SR1) for the hydraulic supply of a first part circuit (TK1) and at least one separate, second distributor pressure line (VD2) and at least one separate, second collector return line (SR2) for the hydraulic supply of a second part circuit (TK2), wherein the first clutch (K1) is assigned to the first part circuit (TK1) and the second clutch (K2) is assigned to the second part circuit (TK2), and wherein, in an operating state of the hydraulic circuit (100, 200, 300), either the first collector return line (SR1) or the second collector return line (SR2) is connected hydraulically to the main pressure line (HD).

A method for detecting an oil leakage of a main pump during a stopping process of an internal combustion engine, where the oil leakage is caused by a reversal of a direction of rotation of a crankshaft of a vehicle including an electric auxiliary pump and the main pump, where the main pump is driven by the internal combustion engine of the vehicle. The method includes determining whether a rotational speed of the electric auxiliary pump exceeds a predefined threshold value, and when the rotational speed of the electric auxiliary pump exceeds the predefined threshold value for the rotational speed, detecting that the main pump is leaking, recording an error in an error memory of the vehicle, and demanding an engine start.

A drive apparatus of a hybrid vehicle including an internal combustion engine, a first motor-generator, a power division mechanism, a second motor-generator and a mode switching unit. The mode switching unit includes a hydraulic pressure source, a planetary gear mechanism, a clutch actuator, a brake actuator, a parking lock actuator, control valves, a failure detecting part and an electronic control unit, A microprocessor of the electronic control unit is configured to perform controlling the control valves so that hydraulic oil is supplied to the clutch actuator, the brake actuator and the parking lock actuator, respectively, when a parking brake is operated in a state that the failure of the third control valve is detected by the failure detecting part.

A controller of a power transmission system for a vehicle includes an electronic control unit. When a difference between a secondary pressure set by use of a command pressure of the electromagnetic control valve for the secondary pulley, and an actual pressure obtained by a hydraulic pressure sensor, is larger than a predetermined pressure difference, the electronic control sets a primary pressure and the secondary pressure such that a speed ratio of a continuously variable transmission becomes substantially equal to a maximum value. The electronic control unit determines that there is an abnormality that an output pressure of the electromagnetic control valve for a secondary pulley is low, when the speed ratio is smaller than a predetermined first determination value, and determines that there is an abnormality in the hydraulic pressure sensor, when the speed ratio is larger than a predetermined second determination value.

First, the pressure of oil within an oil passage in a control valve device is measured. Then, an amplitude and period of pressure fluctuations are detected on the basis of an obtained measurement result, and an oil vibration state or an oil non-vibration state is diagnosed. In this case, when the amplitude is greater than a reference amplitude value and when the period is less than a reference period value, the oil vibration state is diagnosed. Further, a duration time of the oil vibration state is determined on the basis of a diagnostic result. Then, when the oil vibration state continues for a period greater than or equal to a reference time, warning information is output. In this way, warning information is output stepwise in accordance with occurrence or continuation of oil vibration.

In a transmission control device for controlling a transmission, a controller determines failure of a SOL corresponding to a hydraulic primary-pressure actuator. The controller variably controls line command pressure, and in a case where the failure is determined, continuously changes a speed ratio of a variator by variably controlling the line command pressure. The controller variably controls primary command pressure, and in a case where the failure is determined, fixes the primary command pressure to a primary pressure set value. The controller variably controls secondary command pressure, and in a case where the failure is determined, fixes the secondary command pressure to a secondary pressure set value.

Selection solenoid valve (75) controls engagement/disengagement of travel clutch (31, 32) in synchronization with a selecting operation of selector lever (90) that selects a range position of belt-type continuously variable transmission (CVT). Selection solenoid valve abnormality diagnosing unit (Sa) is configured to, when performing a selecting operation from no-drive range to drive range, if a time required for travel clutch (31, 32) to be judged to be engaged from a start of selection of the drive range is less than a predetermined time, judge selection solenoid valve (75) to be a maximum hydraulic pressure side abnormality. When performing the selecting operation of drive range.fwdarw.no-drive range.fwdarw.drive range, if a selecting operation speed condition indicating that a no-drive range selection time is shorter than a setting time (Tth) is satisfied, execution of abnormality diagnosis of selection solenoid valve (75) is not permitted. With this configuration, misjudgment is prevented.

Pressure regulation valve control device has line pressure regulation valve (4) having line pressure solenoid (41) and line pressure spool valve (42) and CVT control unit (8) controlling secondary pressure (Psec) by actuating the line pressure spool valve (42) by solenoid pressure (Psol) produced by controlling current command value (I) to the line pressure solenoid (41). CVT control unit (8) has abnormality control unit (81). The abnormality control unit (81) is configured to, when decrease in secondary pressure (Psec) is detected during travel, execute, during travel, abnormality control that increases solenoid pressure (Psol), supplied to line pressure spool valve (42) from line pressure solenoid (41), more than solenoid pressure (Psol) of a time when the decrease in secondary pressure (Psec) is detected. With this, even when the decrease in the pressure is detected during travel, the decrease in the pressure is suppressed during travel while reducing influence on vehicle travel.