An electric booster may include: a motor part configured to be driven by power applied thereto; a body part mounted and fixed onto the motor part; a cylinder part coupled to the body part; a screw part connected to the motor part and rotated; a nut part embedded in the body part, and screwed to the screw part so as to linearly move; a first piston part constraining an end of the screw part, and moved to the cylinder part while being pressed by the nut part; a first elastic part supporting the first piston part; a second piston part supported by the first elastic part; and a second elastic part supporting the second piston part.

A clutch actuating device has an actuating cylinder with piston and rod-side chamber, a multiplier cylinder with piston-side and rod-side chambers separated by a piston, a rod(s) interconnecting the pistons, and a directional control valve. The valve has a pilot port, ports in fluid connection with piston-side and rod-side chambers of the multiplier cylinder, and a port in fluid connection with a secondary source. When a first fluid pressure (P1) from a first pressure source is applied to the pilot port and rod-side chamber of the actuating cylinder, a second fluid pressure (P2) is applied to the piston-side chamber of the multiplier cylinder by the secondary source. This results in the first and second fluid pressures (P1 and P2) acting on the piston of the actuating cylinder to produce a clutch actuation fluid pressure.

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).

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 silencer for a clutch air booster may include an exhaust retainer including a disk-shaped bottom portion seated on the upper side of an outlet body of the clutch air booster and a retainer hole formed in the center of the bottom portion, a valve seated on the exhaust retainer to cover the retainer hole, a valve housing coupled to an outer side of the exhaust retainer and forming an inner space configured to accommodate the valve, and a rubber cap coupled to an outer side of the valve housing to cover an upper side of the valve housing.

A silencer for a clutch air booster may include an exhaust retainer including a disk-shaped bottom portion seated on the upper side of an outlet body of the clutch air booster and a retainer hole formed in the center of the bottom portion, a valve seated on the exhaust retainer to cover the retainer hole, a valve housing coupled to an outer side of the exhaust retainer and forming an inner space configured to accommodate the valve, and a rubber cap coupled to an outer side of the valve housing to cover an upper side of the valve housing.

An electric booster may include: a motor part configured to be driven by power applied thereto; a body part mounted and fixed onto the motor part; a cylinder part coupled to the body part; a screw part connected to the motor part and rotated; a nut part embedded in the body part, and screwed to the screw part so as to linearly move; a first piston part constraining an end of the screw part, and moved to the cylinder part while being pressed by the nut part; a first elastic part supporting the first piston part; a second piston part supported by the first elastic part; and a second elastic part supporting the second piston part.

An electric booster may include: a motor part configured to be driven by power applied thereto; a body part mounted and fixed onto the motor part; a cylinder part coupled to the body part; a screw part connected to the motor part and rotated; a nut part embedded in the body part, and screwed to the screw part so as to linearly move; a first piston part constraining an end of the screw part, and moved to the cylinder part while being pressed by the nut part; a first elastic part supporting the first piston part; a second piston part supported by the first elastic part; and a second elastic part supporting the second piston part.

A clutch actuator structure provided for an internal combustion engine and a hydraulic clutch mechanism for transmitting a rotational driving force of a crankshaft of said engine includes a clutch actuator for controlling an oil pressure for engaging and disengaging the hydraulic clutch mechanism. The clutch actuator structure ensures that noises generated at the times of operation of the clutch actuator for actuating a hydraulic clutch are prevented from being transmitted to the exterior. The clutch actuator structure includes an oil sump part for reserving oil provided in the periphery of a clutch actuator. The clutch actuator is disposed in the oil sump part.

A clutch actuator structure provided for an internal combustion engine and a hydraulic clutch mechanism for transmitting a rotational driving force of a crankshaft of said engine includes a clutch actuator for controlling an oil pressure for engaging and disengaging the hydraulic clutch mechanism. The clutch actuator structure ensures that noises generated at the times of operation of the clutch actuator for actuating a hydraulic clutch are prevented from being transmitted to the exterior. The clutch actuator structure includes an oil sump part for reserving oil provided in the periphery of a clutch actuator. The clutch actuator is disposed in the oil sump part.