A brake device includes a master cylinder, a braking mechanism for braking a wheel of a vehicle, a hydraulic pressure circuit coupling the master cylinder to the braking mechanism, and a reservoir tank storing a hydraulic fluid of the master cylinder. The master cylinder includes a housing, a piston, and a seal member. The piston changes a hydraulic pressure of the hydraulic fluid in a hydraulic pressure chamber in the housing. The seal member is moved with the piston to seal a gap between the housing and the piston. First to third positions are positioned in sequence in a moving direction of the piston. A replenishing hole of the housing communicates with the hydraulic pressure chamber when the piston is at the first position. The seal member closes the replenishing hole when the piston is at the second position. The hydraulic pressure of the hydraulic fluid is made negative with the seal member closing the replenishing hole when the piston is at the third position.

A brake device includes a master cylinder, a braking mechanism for braking a wheel of a vehicle, a hydraulic pressure circuit coupling the master cylinder to the braking mechanism, and a reservoir tank storing a hydraulic fluid of the master cylinder. The master cylinder includes a housing, a piston, and a seal member. The piston changes a hydraulic pressure of the hydraulic fluid in a hydraulic pressure chamber in the housing. The seal member is moved with the piston to seal a gap between the housing and the piston. First to third positions are positioned in sequence in a moving direction of the piston. A replenishing hole of the housing communicates with the hydraulic pressure chamber when the piston is at the first position. The seal member closes the replenishing hole when the piston is at the second position. The hydraulic pressure of the hydraulic fluid is made negative with the seal member closing the replenishing hole when the piston is at the third position.

A piston-cylinder unit includes a piston delimiting at least one working chamber, in which a first seal for sealing at least one first working chamber is arranged either between the piston and cylinder or between a plunger connected to the piston and the cylinder. A second seal is arranged between the first seal and the first working chamber, and the piston-cylinder unit further includes a first channel arranged in the wall of the cylinder or in the piston, which joins the first seal and the second seal in the inner chamber of the cylinder. The first channel and/or a hydraulic line connected thereto may have a throttle device and/or a valve device. An electronic control and regulating device may have a diagnosis or monitoring function for a possible defect or failure of a seal. Multiple hydraulic devices may have such piston-cylinder units and respective control and such regulating devices.

A piston-cylinder unit includes a piston delimiting at least one working chamber, in which a first seal for sealing at least one first working chamber is arranged either between the piston and cylinder or between a plunger connected to the piston and the cylinder. A second seal is arranged between the first seal and the first working chamber, and the piston-cylinder unit further includes a first channel arranged in the wall of the cylinder or in the piston, which joins the first seal and the second seal in the inner chamber of the cylinder. The first channel and/or a hydraulic line connected thereto may have a throttle device and/or a valve device. An electronic control and regulating device may have a diagnosis or monitoring function for a possible defect or failure of a seal. Multiple hydraulic devices may have such piston-cylinder units and respective control and such regulating devices.

A sealing element for sealing a pressure chamber is provided in a master cylinder for a clutch or brake system. The sealing element has a sealing lip for sealing a feed of hydraulic fluid from a reservoir mounted on a housing of the master cylinder into the pressure chamber and has a sealing structure for sealing the pressure chamber from the surroundings of the pressure chamber.

A sealing element for sealing a pressure chamber is provided in a master cylinder for a clutch or brake system. The sealing element has a sealing lip for sealing a feed of hydraulic fluid from a reservoir mounted on a housing of the master cylinder into the pressure chamber and has a sealing structure for sealing the pressure chamber from the surroundings of the pressure chamber.

A brake pedal unit includes a housing defining a bore formed therein. An input piston is slidably disposed in the bore. The input piston is connected to a brake pedal such that engagement of the brake pedal causes movement of the input piston within the bore of the housing of the brake pedal unit. The brake pedal unit is defined to be in an at rest position when the brake pedal in not engaged causing movement of the input piston. A primary piston is slidably disposed in the bore for pressurizing a primary chamber. A primary passageway permits fluid communication between the primary chamber and the reservoir, wherein fluid flow through the primary passageway is blocked when the brake pedal unit is in the rest position. A secondary piston is slidably disposed in the bore for pressurizing a secondary chamber. A secondary passageway permits fluid communication between the secondary chamber and the reservoir, wherein fluid flow through the secondary passageway is blocked when the brake pedal unit is in the rest position.

A brake pedal unit includes a housing defining a bore formed therein. An input piston is slidably disposed in the bore. The input piston is connected to a brake pedal such that engagement of the brake pedal causes movement of the input piston within the bore of the housing of the brake pedal unit. The brake pedal unit is defined to be in an at rest position when the brake pedal in not engaged causing movement of the input piston. A primary piston is slidably disposed in the bore for pressurizing a primary chamber. A primary passageway permits fluid communication between the primary chamber and the reservoir, wherein fluid flow through the primary passageway is blocked when the brake pedal unit is in the rest position. A secondary piston is slidably disposed in the bore for pressurizing a secondary chamber. A secondary passageway permits fluid communication between the secondary chamber and the reservoir, wherein fluid flow through the secondary passageway is blocked when the brake pedal unit is in the rest position.

An electro-hydraulic control unit for a vehicle brake system includes a hydraulic control unit including an HCU block defining a motor bore containing an electric motor and an eccentric chamber containing a rotating eccentric driven by the electric motor. The HCU block also defines a pump bore containing a piston pump including a piston rod having a generally cylindrical shape with a smooth exterior surface extending substantially its entire length. An end cap is press fit around an end of the piston rod and includes a flange portion extending annularly outwardly for engaging a return spring. A piston guide includes a tubular portion guiding the piston rod and a shoulder for engaging the return spring. A throat of the piston guide holds a gland seal surrounding the piston rod. An outlet valve housing includes a tubular protrusion extending into the throat of the piston guide to hold the gland seal.

An electro-hydraulic control unit for a vehicle brake system includes a hydraulic control unit including an HCU block defining a motor bore containing an electric motor and an eccentric chamber containing a rotating eccentric driven by the electric motor. The HCU block also defines a pump bore containing a piston pump including a piston rod having a generally cylindrical shape with a smooth exterior surface extending substantially its entire length. An end cap is press fit around an end of the piston rod and includes a flange portion extending annularly outwardly for engaging a return spring. A piston guide includes a tubular portion guiding the piston rod and a shoulder for engaging the return spring. A throat of the piston guide holds a gland seal surrounding the piston rod. An outlet valve housing includes a tubular protrusion extending into the throat of the piston guide to hold the gland seal.