A circle drive system with clutch protection in motor graders is disclosed. The circle drive system includes a hydraulic motor that is configured to receive a pressurized fluid and generate a torque for a rotation of a circle and a moldboard. The circle drive system also includes a gearbox to transfer the torque generated by the hydraulic motor to the circle. Further, the circle drive system includes a clutch connected to the hydraulic motor at one end and to the gearbox at another end. In addition, the circle drive system also includes a hydraulic circuit having a pressure relief valve to relieve the pressurized fluid supplied to the hydraulic motor when a pressure of the pressurized fluid exceeds a predefined threshold. The pressure relief valve thereby, limits the torque generated by the hydraulic motor to less than or equal to a torque capacity of the clutch.

The hydraulic circuitry of a factory installed automatic automotive transmission is modified to include a check ball and spring to limit balance oil to a predetermined pressure applied to first end of the clutch regulator valve. When the onboard automobile computer ramps up solenoid oil pressure applied to the clutch regulator valve through a gain valve that acts on a first end of the clutch regulator valve, this pressure is opposed by a spring as well as clutch balance oil pressure that is routed and applied to a second opposite end of the clutch regulator valve. The arrangement limits the balance oil pressure applied to the second end of the clutch regulator valve to a predetermined maximum value so the onboard computer regulates the clutch up to that predetermined value. When the pressure/force applied to the second end of the clutch regulator valve exceeds the predetermined maximum value, a check ball disposed at the second end of the clutch regulator valve, held in place by a spring, is displaced and unseated from a seat in a valve bore, resulting in the exhaust or leaking of the balance oil applied to the second end of the clutch regulator valve so that the oil pressure applied to the first end of the clutch regulator valve is no longer opposed by the balance oil applied to the second end of the clutch regulator valve, thereby enabling the clutch regulator valve to quickly move in a direction to complete the shift and to hold added engine power during the shift.

The present disclosure describes a hydraulic control system comprising a first pressure chamber and a second pressure chamber, each pressure chamber configured to receive a hydraulic fluid, a first movable member configured to assume a position depending on a hydraulic pressure of the hydraulic fluid in the first pressure chamber and a second movable member configured to assume a position depending on a hydraulic pressure of the hydraulic fluid in the second pressure chamber, a hydraulic command circuit configured to provide the hydraulic fluid and to control the hydraulic pressure of the hydraulic fluid in the first pressure chamber and/or the second pressure chamber, having a switchable valve in fluid communication with the first pressure chamber, wherein the switchable valve is configured to be pilotable depending on the hydraulic pressure of the hydraulic fluid in the second pressure chamber.

This clutch control device includes an engine (13), a transmission (21), a clutch device (26) configured to connect and disconnect motive power transmission between the engine (13) and the transmission (21), a clutch actuator (50) configured to drive the clutch device (26) and change a clutch capacity, a hydraulic circuit (63) provided between the clutch device (26) and the clutch actuator (50), an air bleeding device (64) configured to perform air bleeding of the hydraulic circuit (63), a control unit (60) configured to calculate a control target value of the clutch capacity, a control mode changeover switch (59) configured to enable a control mode of the control unit (60) to be switched to an air bleeding mode, and an air bleeding switch (65) configured to enable a hydraulic pressure of the hydraulic circuit (63) to increase in the air bleeding mode.

Systems and methods of controlling a clutch in a vehicle are provided. With the goal of enabling autonomous/assisted control of the clutch by an electronic control unit while preserving the familiar mechanical feeling at the clutch pedal that driving enthusiasts prefer, embodiments of the disclosed technology use a shuttle valve to blend control of clutch engagement between a driver and an ECU. In these embodiments, a clutch pedal in the vehicle may be mechanically connected to a piston in a first hydraulic cylinder (just like in a traditional mechanical/hydraulic clutch actuation system), and an ECU may actuate a second hydraulic cylinder. Accordingly, a shuttle valve may be used to route the fluid coming from the cylinder with the greater pressure (i.e. the driver actuated cylinder or the ECU actuated cylinder), to a third hydraulic cylinder which adjusts engagement of a clutch by a mechanical linkage.

The present disclosure describes a hydraulic control system comprising a first pressure chamber and a second pressure chamber, each pressure chamber configured to receive a hydraulic fluid, a first movable member configured to assume a position depending on a hydraulic pressure of the hydraulic fluid in the first pressure chamber and a second movable member configured to assume a position depending on a hydraulic pressure of the hydraulic fluid in the second pressure chamber, a hydraulic command circuit configured to provide the hydraulic fluid and to control the hydraulic pressure of the hydraulic fluid in the first pressure chamber and/or the second pressure chamber, having a switchable valve in fluid communication with the first pressure chamber, wherein the switchable valve is configured to be pilotable depending on the hydraulic pressure of the hydraulic fluid in the second pressure chamber.

A hydraulic actuation device for a motor vehicle friction clutch has a manually actuatable master cylinder, that has a master pressure chamber which, in a rest position, is fluidically connected to a reservoir. The master cylinder is connected to a slave arrangement that is functionally connected to the motor vehicle friction clutch. A pressure line connects the master pressure chamber to the slave arrangement and in which incorporates an electrically actuatable valve arrangement with an electrically actuatable proportional valve and, connected in parallel, a first check valve which blocks in the direction of the master pressure chamber. A motor pump is connected, on the input side, to the reservoir and can be connected, on the output side, to the pressure line between the valve arrangement and the slave pressure chamber through a second check valve that blocks in the direction of the motor pump.

In a hydraulic system with a dog clutch (23-25), a hydraulically operated dog clutch actuator is arranged to alternatively bring the dog clutch into a connect mode or a disconnect mode. The clutch actuator has a piston (27) reciprocally movable under hydraulic pressure between two end positions, corresponding to the two clutch modes. Pressurized hydraulic oil is supplied to the clutch actuator by a hydraulic power system comprising a pump (4) driven by an electric motor (3). Means are provided in the clutch actuator to decrease the hydraulic pressure acting on the piston (27) at the approaching by the piston of either of its end positions, so that a hydraulic signal is transmitted back to the hydraulic power system.

The present invention relates to a hydrostatic clutch actuator (1) for a clutch, in particular a wet clutch, of a motor vehicle, wherein the clutch actuator (1) has a drive unit (2, 3), a master cylinder-piston-cylinder unit (4, 5) driven thereby, a hydraulic reservoir (6) fluidically connected to the master cylinder-piston-cylinder unit, and a hydraulic system for actuating the clutch, wherein, by use of the master cylinder-piston-cylinder unit (4, 5), hydraulic medium can be conveyed out of the hydraulic reservoir (6) into the hydraulic system and the hydraulic system can be pressurized, and the hydraulic reservoir (6) has an overflow (10), via which hydraulic medium can be discharged from the hydraulic reservoir (6) and the hydraulic system.

A circle drive system with clutch protection in motor graders is disclosed. The circle drive system includes a hydraulic motor that is configured to receive a pressurized fluid and generate a torque for a rotation of a circle and a moldboard. The circle drive system also includes a gearbox to transfer the torque generated by the hydraulic motor to the circle. Further, the circle drive system includes a clutch connected to the hydraulic motor at one end and to the gearbox at another end. In addition, the circle drive system also includes a hydraulic circuit having a pressure relief valve to relieve the pressurized fluid supplied to the hydraulic motor when a pressure of the pressurized fluid exceeds a predefined threshold. The pressure relief valve thereby, limits the torque generated by the hydraulic motor to less than or equal to a torque capacity of the clutch.