In a method for controlling a clutch actuator for an automated manual transmission, when a driver's operation signal is input for operation of the clutch actuator, the hydraulic pressure of a hydraulic chamber of the clutch actuator forms pressure equilibrium with the atmospheric pressure through a pressure equilibrium control by standing by at a control-standby state before an actual stroke position of the clutch actuator enters a hydraulic pressure generation range from a hydraulic pressure release range. When the actual stroke position of the clutch actuator enters the hydraulic pressure generation range from the hydraulic pressure release range, the clutch actuator is moved to the predetermined stroke position by a predetermined operation speed, and then controlled to follow the driver's operation signal.

Braking systems and methods having above atmospheric pressure applied to the working hydraulic fluid of the braking system. In certain preferred arrangements, the braking system includes at least one source of pressure, which pressurizes a fluid. The pressurized fluid acts on respective pressure surfaces of the master plunger(s) and the slave piston(s) that are opposite the active or working surfaces of the master plunger(s) and the slave piston(s).

A clutch mechanism switches a clutch to one of an engaging state and a released state by a piston operated by an oil pressure. The piston includes a first side surface portion configured to press the clutch, and a second side surface portion on which the oil pressure acts. The second side surface portion has an uneven shape in a circumferential direction.

A clutch connecting/disconnecting device comprises: a clutch pedal; a clutch cylinder; a depression force transmission mechanism; and an actuator. The depression force transmission mechanism is configured to include a cylinder device. The cylinder device includes an input piston, an output piston, a first oil chamber, and a second oil chamber. A pressure receiving area on the first oil chamber side of the output piston is made equal to a pressure receiving area on the second oil chamber side of the output piston. The first oil chamber and the second oil chamber are connected via an electromagnetic valve connecting and disconnecting between the first oil chamber and the second oil chamber, and the actuator is connected to the output piston in a power transmitting manner.

Braking systems and methods having above atmospheric pressure applied to the working hydraulic fluid of the braking system. In certain preferred arrangements, the braking system includes at least one source of pressure, which pressurizes a fluid. The pressurized fluid acts on respective pressure surfaces of the master plunger(s) and the slave piston(s) that are opposite the active or working surfaces of the master plunger(s) and the slave piston(s).

A piston, comprising: a shaft side with a first circumferential groove, said first circumferential groove bounded by a continuous circumferential seal plateau, said seal plateau extending axially outward from said first circumferential groove, wherein a planar outboard surface extends radially outboard from said seal plateau; a clutch side having two grooves alternating with two lands; an inner circumferential surface having a seal groove formed therein; and an outer circumferential surface having a seal groove formed therein, wherein the sides and surfaces form a ring shape.

A seal includes an annular seal body formed of an elastomeric material and has opposing first and second circumferential surfaces and a sealing projection extending radially from the first circumferential surface. The projection has a frustoconical primary sealing surface with first and second axial ends and an axial length between the first and second ends. The projection is sealingly engageable with the inner surface of the outer member when the seal body is coupled with the inner member, such that substantially the entire axial length of the primary sealing surface is disposed against the inner surface of the outer member. Alternatively, the projection is sealingly engageable with the outer surface of the inner member when the seal body is coupled with the outer member, such that substantially the entire axial length of the primary sealing surface is disposed against the outer surface of the inner member.

An automatic transmission is provided, which includes a friction engaging element. The friction engaging element includes a plurality of friction plates disposed inside a transmission case, a piston configured to cause the plurality of friction plates to be engaged with each other, and a spring configured to bias the piston. The spring includes a first spring and a second spring with a longer free length than the first spring, and the first spring and the second spring are aligned in circumferential directions of the transmission case.

A piston (50), comprising: a shaft side (52) with a first circumferential groove, said first circumferential groove (90) bounded by a continuous circumferential seal plateau (88), said seal plateau extending axially outward from said first circumferential groove, wherein a planar outboard surface (96) extends radially outboard from said seal plateau; a clutch side (54) having two grooves alternating with two lands (102, 108); an inner circumferential surface (56) having a seal groove (62) formed therein; and an outer circumferential surface (58) with a having a seal groove (76) formed therein, wherein the sides and surfaces form a ring shape.

A clutch drive unit 220 includes a crank arm 221 configured to rotate by rotary driving of a clutch actuator 231. The crank arm 221 includes an output pin 222 configured to press a master cylinder 232, and a receiving pin 223 configured to receive pressing force P from an extendable body 228. The extendable body 228 includes a lock spring 228a with such strength that the pressing force P is generated. The pressing force P allows pressing moment PM greater than reactive force moment RM based on reactive force R acting on the crank arm 221 from a clutch 210 to act on the crank arm 221. The extendable body 228 is, by the stretching force of the lock spring 228a, provided in a stretched state between the receiving pin 223 and a holder receiving pin 229.