Abstract: A method for operating a brake system of a motor vehicle includes actuating a first actuating device of the brake system, exerting an electromechanical braking force to decelerate the motor vehicle in an event of a fault in the hydraulic braking device and when the first actuating device is actuated, and generating the electromechanical braking force after a start of the actuation of the first actuating device for a minimum generation period and/or generating the electromechanical braking force after an end of the actuation of the first actuating device for an additional continued generation period. The brake system includes a hydraulic braking device, an electromechanical braking device, and a first actuating device, in particular a brake pedal.

Abstract: A compressed air system for a motor vehicle with an air supply system includes an electric drive motor, which can be controlled for variable speed, an air compressor coupled to be driven by the electric drive motor, an electric power supply for supplying electric power to the electric drive motor, at least one air reservoir connected with the air compressor to receive air from the air compressor, an air utilization system connected to the air reservoir to receive air from the air reservoir, and a controller to control the speed of the electric drive motor.

Abstract: Disclosed is a rail braking system including a detection and storage device designed to receive first information representing the position of a device for locking a service brake piston, to receive second information representing the supply of a service brake pressure chamber with a pneumatic pressure agent, to deduce information representing the application of a parking brake from the first and second information, and to store the deduced information; as a result of which the information representing the application of the parking brake is kept even if the service brake pressure chamber is no longer supplied with the pneumatic pressure agent.

Abstract: A method is disclosed for the operation of an automated parking brake of a motor vehicle with a hydraulic operating brake and an automated parking brake. The parking brake can adopt at least a disengaged position, an engaged position, and an intermediate position between the disengaged position and the engaged position. The method includes determining a parking variable representing a parking process of the motor vehicle, and bringing the parking brake into the intermediate position in response to the determined parking variable.

Abstract: A bicycle hydraulic device comprises a base member and a cover member. The base member is configured to be mounted to a bicycle body. The base member comprises a hydraulic bore and an insertion portion. The hydraulic bore has a first end and a second end. The first end defines a first opening. The insertion portion is provided between the first end and the second end. The insertion portion includes an insertion opening different from the first opening. The cover member is provided at the insertion portion via the insertion opening to cover the hydraulic bore.

Abstract: A locking mechanism for a brake cylinder that has a tube surrounding the hollow shaft of the brake cylinder with a first set of teeth formed along an outer surface thereof. A gate having a second set of teeth corresponding to the first set of teeth is moveable in between a first position, wherein the first and second set of teeth are engaged to prevent movement of the brake cylinder piston, and a second position where the first and second set of teeth are disengaged to allow movement of the brake cylinder piston. A spring biases the gate into the locked position and a supplemental piston responsive to a source of brake pipe pressure can move the gate into the unlocked position so that the main piston is free to move.

Abstract: A method for releasing an automatic parking break includes estimating a release travel of the automatic parking brake based on a measured motor voltage and a motor current. The method further includes querying an additional switch-off criterion to obtain a minimum total release travel. The method further includes comparing the estimated release travel with the minimum total release travel. The automatic parking brake includes an electric motor brake device for producing an electromechanical clamping force.

Abstract: Disclosed herein is a brake system including a main brake applying braking force to a wheel of a vehicle when the vehicle travels, a parking brake applying braking force to the wheel of the vehicle when the vehicle is parked, and a parking brake controller operating the main brake when the parked vehicle is sensed to move above a predetermined reference value and stopping the operation of the main brake after increasing locking force of the parking brake when the movement of the vehicle is stopped according to the operation of the main brake.

Abstract: In a method for activating a driver assistance system in a vehicle, a check is performed after an activating request for a driver assistance system from a driver as to whether the driver of the vehicle is suitable for utilizing the requested driver assistance system, and the activation of the requested driver assistance system is carried out depending on the suitability of the driver.

Abstract: The invention relates to a method of managing parking braking in a braking system for a vehicle fitted with at least one electric brake including at least one electric actuator having a pusher actuated by an electric motor for selectively applying a force against friction elements of the brake, the method comprising the steps of: establishing a series of direct adjustment tables for parking braking, corresponding to braking situations at different energy levels; when applying parking braking, selecting a direct adjustment table corresponding to a braking situation preceding the application of parking braking; and directly adjusting a parking braking force in application with the selected direct adjustment table.

Abstract: A method of detecting a failure of a brake actuator is provided. The method includes monitoring an angular position of a motor controlling the brake actuator. Also included is monitoring a linear position of a linear translation arrangement of the brake actuator, wherein the linear position of the linear translation arrangement is controlled by a gear assembly in communication with the motor and the linear translation arrangement. Further included is comparing the linear position of the linear translation arrangement with the angular position of the motor. Yet further included is determining whether the linear position of the linear translation arrangement is within a predetermined range of linear positions corresponding to a plurality of angular positions.

Abstract: A brake cylinder for pneumatic vehicle brakes, especially for commercial vehicles, includes in addition to a pneumatic locking mechanism, a manual release mechanism for manually releasing the spring brake section, and a device designed to visually recognize the manual release condition of the spring brake section outside of the housing.

Abstract: The invention relates to a method for operating a brake device, in particular of a motor vehicle, wherein the brake device comprises a service brake and a mechanical parking brake, wherein the parking brake can be actuated by means of a mechanical actuating element, comprising at least the steps of establishing that the actuating element has been moved from an idle position into a position of use, simultaneously controlling a pressure-increasing element, so that a hydraulic pressure is generated, which hydraulic pressure acts on a brake element that is common with the holding element, blocking the common brake element of the service brake and the parking brake with a mechanical block of the mechanical parking brake.

Abstract: There is provided a disk brake that can hold a required thrust force and maintain a stop state of a vehicle without increasing complexity in the disk brake even if the disk brake is operated in a high temperature state of a brake pad and then a temperature of the brake pad is reduced. In the disk brake 1, an electric motor 8 is driven to thrust a piston 6, the piston 6 presses the brake pad 5 against a disk rotor 2, and the piston 6 is held in the pressed position, the electric motor 8 is re-driven after a predetermined time from a start of holding of the piston 6, and a driving condition of the electric motor 8 after re-driving is determined based on a change in value of a current supplied to the electric motor 8 by the re-driving.

Abstract: A brake cylinder having a parking brake function includes a cylinder housing, a piston, and a piston tube for actuating a brake. A threaded bolt protruding into the piston tube and fixed to the cylinder housing by its upper end is used to effect the parking brake function. A clamping nut displaceable by means of a forked, axially rotatable driving element extends over the threaded bolt. The driving element is rotated with the clamping nut while the cylinder is subjected to pressure by the parking brake until the clamping nut is supported against the piston in the parking position of the piston. The piston is mechanically locked when the cylinder housing is not subjected to pressure.

Abstract: A control device for work vehicle includes: a hydraulic brake device that generates a braking force according to operation of a brake pedal upon traveling; a brake lock device that hydraulically locks the hydraulic brake device and unlocks hydraulic lock of the hydraulic brake device; a brake pedal operation detection unit that detects the operation of the brake pedal; a hydraulic lock directing switch that is provided on a manual operating lever for operating a work device of the work vehicle; and a control unit that controls the brake lock device such that when the hydraulic lock directing switch is operated, the hydraulic brake device is hydraulically locked and when a predetermined depression operation of the brake pedal is detected by the brake pedal operation detection unit, the hydraulic lock of the hydraulic brake device is unlocked.

Abstract: A method for operating an electric vehicle, the electric vehicle having an electric motor and a brake device, and the electric motor and the brake device being capable of being influenced by a control device. When the electric vehicle is at a standstill, when there is an error of the control device, the brake device is actuated so that the electric vehicle cannot move, or at least can move only to a very limited extent.

Abstract: A device with an electronic brake system (EBS) and a brake assembly is provided for protecting against unauthorized removal of a trailer where a control device can activate and deactivate a protection state of the electronic brake system. When the electronic brake system is activated, protection can be provided by the brake assembly, which can brake the trailer if unauthorized removal is attempted.

Abstract: A vehicle hand control brake valve includes a piston, positioned based on an engagement of a vehicle parking brake, a service brake actuation valve, and a control mechanism. The control mechanism mechanically interacts with the service brake actuation valve to set a position of the service brake actuation valve. A level of actuation of vehicle service brakes is set based on the position of the service brake actuation valve. The service brake actuation valve is set to a position to actuate the service brakes when the control mechanism is set to a latch position. The control mechanism only is latched in the latch position when the vehicle parking brake is engaged.

Abstract: An apparatus and method for preventing parking brake-caused disabling of a vehicle is provided. In at least one of the vehicle's parking brake release actuators' supply lines there is provided a flow arrangement which allows parking brake release fluid to flow to and from the release actuator when its supply line is undamaged, and restricts flow from the release pressure source when the line between the flow arrangement and the actuator is damaged. The flow arrangement may be a pilot-operated, non-graduated control valve, a combination of a pressure protection valve and a check valve arranged in parallel, a velocity-sensing check valve, or any other device or combination of devices which provide the damaged line shutoff or metering functionality. Such an arrangement prevents automatic application of the parking brake by releasing pressure from all of the vehicle's parking brake actuators, thereby precluding automatic vehicle immobilization following damage at one wheel end.

Abstract: A locking apparatus for a parking brake includes a parking lever, a parking lever spring applying a restoring force to the parking lever, a cylinder of which an oil hole is formed thereto, a piston comprising a piston rod connected to the parking lever and a piston main body disposed within the cylinder, and the piston movable along length direction of the cylinder according to supplying or releasing of oil through the oil hole, a solenoid valve and a locking unit disposed within the cylinder for unlocking the piston when the solenoid valve is supplied electric power and for locking the piston when the solenoid valve is not supplied electric power.

Abstract: In a method for controlling an electronic parking brake system and an electronic parking brake system, a travel-optimized method is used to achieve the released state of the parking brake system. When the parking brake is applied, travel-force values are detected and a plausibility check is run, the values being used to arrive at a first optimized position when the brake is released. If the residual force applied to the brake exceeds a threshold value, the parking brake is released even more until the value remains just under the threshold value or until a maximum defined release travel is achieved.

Abstract: A pneumatic vehicle brake system includes first and second groups of wheel brakes belonging, respectively, to first and second brake circuits having first and second compressed air storage tanks for providing first and second stored pressures. At least one first circuit brake cylinder is a combined spring-store/diaphragm cylinder with a spring store part for providing a parking brake and a diaphragm part for providing a service brake. If the first circuit fails, the spring store part is deaerated to engage the parking brake. A pressure sensor for measuring the first stored pressure is connected to a control unit that controls a modulator for aerating and deaerating the spring store part. The control unit generates a signal for an electrically actuatable modulator solenoid valve if the value measured by the sensor falls below a minimum value, such that the spring store part can be aerated and deaerated via the valve.

Abstract: A method for monitoring that a vehicle on standby has been correctly immobilized for transport, the vehicle including a course control device, wheel speed sensors, a yaw speed sensor, a processing unit processing information managing operation modes of the vehicle, and a device for immobilizing the vehicle. The method includes detecting the vehicle is in a standby mode at a standstill following installing of the vehicle on a transport support, detecting a non-zero vehicle speed through the speed sensors of at least two wheels over a defined period, detecting a non-zero yaw speed through the yaw speed sensor, over a predefined period, and under these conditions determining a mode whereby immobilization of the vehicle for transport is monitored, in which mode information from at least the wheel speed sensors is filtered after a determined number of attempts at immobilizing the vehicle and allowing the vehicle to be fired up.

Abstract: A control device 10 of an industrial vehicle which performs the control of actuating a parking brake 7 during operator's absence in an industrial vehicle includes a seat switch 1, a vehicle speed sensor 2, and the parking brake 7 controlled by a parking brake solenoid 6, and a counter 11 which counts the elapsed time after the seat switch 1 detects the operator's absence. The control device sets the time corresponding to the time until the operator leaves the vehicle after the operator leaves the seat as a preset absence time. When the seat switch 1 has detected absence, a control signal which validates the parking brake 7 is output to the parking brake solenoid 6, thereby actuating the parking brake 7 if the vehicle speed shows a vehicle stopped state, and the elapsed time becomes equal to or more than the set absence time.

Abstract: A system and procedures for adjusting brake mechanisms for an aircraft having an electric brake system are disclosed. The brake actuator mechanisms are controlled to achieve different parking brake actuation states as a function of the current engine run status (e.g., engine off, engine idle, or engine above idle). Procedures for adjusting an aircraft parking brake as disclosed herein include setting the brake actuator mechanisms to achieve a relatively low clamping force when the aircraft engines are off or idling, and setting the brake mechanisms to achieve a relatively high clamping force when the aircraft engines are running above idle, and to maintain commanded brake force without active or battery power by engaging a mechanical clutch or latch to the brake actuator.

Abstract: A parking brake control device performs a releasing control with good precision by more precisely maintaining clearance between a friction-applying member and a friction-applied member. During a releasing control, a timing at which a braking force generated by an electric parking brake 2 drops to zero is detected based on a change in a motor current, and a second releasing operation time is set according to the magnitude of the motor current at the time the braking force drops to zero. This makes it possible for the second releasing operation time to be set in accordance with fluctuations in a motor load due to temperature changes or the like. Therefore, a clearance between a brake pad and a brake disc can be kept constant according to the motor load.

Abstract: An air brake locking device for a vehicle includes a main body having a pair of internal channels capable of connecting to a vehicle air line, a valve interposed between the internal channels for controlling the flow of air, and a control unit for regulating the operation of the valve.

Abstract: The invention relates to a motor vehicle brake system having a hydraulically actuatable service brake system and an electromechanically actuatable brake system, including an operating element HMI, in particular for activating a parking brake function, an electronic control device (EPB-ECU) for activating an electromechanical actuator of the electromechanically actuatable brake system, and an electrohydraulic control unit (HECU) associated with a service brake and serving to control or regulate hydraulically implemented service brake functions, driving stability functions and/or braking assistance functions. It is an aim of the invention to contribute to reducing the stress on parts or components of the brake system.

Abstract: The present invention includes a hydraulic brake device 4, 5 that generates a braking force corresponding to an operation of a brake pedal 1 performed while the vehicle is traveling, a brake lock means 6 for applying a hydraulic lock on the hydraulic brake device 4, 5 and releasing the hydraulic lock, a brake pedal operation detection means 22 for detecting an operation of the brake pedal 1, and a control means 10 for controlling the brake lock means 6 so as to apply the hydraulic lock on the hydraulic brake device 4, 5 upon detecting via the brake pedal operation detection means 22 a predetermined depressing operation of the brake pedal 1.

Abstract: Provided is an electric brake capable of accurately estimating the brake pad temperature and securing a sufficient braking force and response. An electric brake has a disc rotor rotating with a wheel, an actuator for rectilinearly actuating a piston in the axial direction of the disc rotor by using an electric motor, a drive controller for controlling the drive of the actuator, a brake pad pressed by the piston to give a frictional resistance to the disc rotor in the direction of rotation, and a braking start position detector for detecting a braking start position of the piston where the disc rotor is brought into contact with the brake pad. The drive controller stores the braking start position detected by the braking start position detector as the maximum braking start position. When the braking start position shifts in the pressing force-increasing direction, the drive controller updates the value stored as the maximum braking-start position.

Abstract: A brake cylinder for pneumatic vehicle brakes includes a spring brake section for parking brake actions and a service brake section for service brake actions combined in one housing. The housing is subdivided by a piston into two compartments, one compartment being used as the pressure compartment for the service brake, and the brake spring of the spring section being arranged in the other compartment on the opposite end of the piston. The brake spring acts upon an additional spring piston, which can be locked and released relative to the piston by a pneumatic locking mechanism. The spring piston is connected to a piston rod directly or via additional elements to actuate the brake. Once the locking mechanism is released, the brake spring displaces the pistons relative each other during a parking brake action. At least one pneumatic valve for controlling the brake cylinder are integrated into the brake cylinder.

Abstract: A brake cylinder for pneumatic vehicle brakes, especially for commercial vehicles, includes in addition to a pneumatic locking mechanism, a manual release mechanism for manually releasing the spring brake section, and a device designed to visually recognize the manual release condition of the spring brake section outside of the housing.

Abstract: An air brake locking device for a vehicle includes a main body having a pair of internal channels capable of connecting to a vehicle air line, a valve interposed between the internal channels for controlling the flow of air, and a control unit for regulating the operation of the valve.

Abstract: A brake cylinder for pneumatically actuated vehicle brakes, especially for commercial vehicles, includes a housing. The housing is divided into two chambers by a piston, one of the chambers being used as a pressure chamber for actuating an operating brake section, and a cylinder spring of a spring-loaded brake section being arranged in the other chamber on the opposite side of the piston. The cylinder spring acts on another spring-loaded piston in the chamber, which can be blocked in relation to the first piston by a pneumatically actuated locking mechanism. The other spring-loaded piston is released from the first piston by a releasing action of the blocking mechanism, and is connected to a piston rod for actuating the vehicle brake. Following release of the blocking mechanism, the cylinder spring acts between the two pistons and moves them in relation to each other during a parking braking operation.

Abstract: A housing has upper and lower faces, front and rear faces and side faces. A vertical bore extends through the housing between the upper and lower faces. A horizontal bore extends into the housing from the front face. The horizontal bore further extends to the vertical bore. A ball valve is positioned within the vertical bore laterally spaced from the horizontal bore. The ball valve is rotatable between open and closed orientations. A lock cylinder is located within the vertical bore. The lock cylinder has an exposed end with a keyway. The lock cylinder has an unexposed end with a connector clip. The connector clip couples the lock cylinder and the ball.

Abstract: The present invention includes a hydraulic brake device 4, 5 that generates a braking force corresponding to an operation of a brake pedal 1 performed while the vehicle is traveling, a brake lock means 6 for applying a hydraulic lock on the hydraulic brake device 4, 5 and releasing the hydraulic lock, a brake pedal operation detection means 22 for detecting an operation of the brake pedal 1, and a control means 10 for controlling the brake lock means 6 so as to apply the hydraulic lock on the hydraulic brake device 4, 5 upon detecting via the brake pedal operation detection means 22 a predetermined depressing operation of the brake pedal 1.

Abstract: A motor current detecting device is provided in a parking brake control system for detecting electric current flowing through an electric motor. And current supply to the electric motor is stopped in case of carrying out a parking brake releasing operation, when a time period in which a differentiated value of the electric current flowing through the electric motor is smaller than a predetermined threshold value exceeds a predetermined time. As a result, a partial braking condition, in which parking brake force partly remains even after the parking brake releasing operation, and which is caused by, for example, the elongation of the brake cable is prevented.

Abstract: A pneumatic brake system for a heavy duty vehicle is provided. The work brake system is operably dependent on a predetermined high trip brake system pressure and a predetermined reset brake system pressure. Upon actuation of the work brake system, when brake system pressure is greater than the predetermined high trip pressure, the work brake system is configured to deliver a pneumatic control signal to the second control valve to activate the service brake assembly. When brake system pressure is less than the predetermined high trip pressure, the work brake system is configured to deliver a pneumatic spring brake signal to the first control valve to activate the spring brake assembly and remove the pneumatic control signal to the second control valve. The delivery of the pneumatic control signal to the second control valve via the work brake system is prevented until brake system pressure exceeds the predetermined reset pressure.

Abstract: An electric parking brake system is equipped with a parking brake driven by an electric actuator for braking wheels of a vehicle, a vehicle condition sensing section for detecting vehicle conditions, a target braking force setting section for setting a target braking force on the basis of vehicle condition detected, compared and weighted by the vehicle condition sensing section so as to overcome a trouble of a part of sensing section, a parking condition detecting section for sensing a change of the vehicle condition from a stopping condition to a parking condition, and a control section for increasing a braking force according to the change in the vehicle condition so as to avoid a creep movement of the vehicle. Thereby, the electric parking brake system with a highly improved reliability can be provided.

Abstract: The parking brake control device sets a lock control target tension TTAR to a value which depends on the brake fluid pressure (i.e. M/C pressure), wherein the lock control target tension TTAR is used as a threshold determining whether the condition for terminating a lock control is satisfied or not. This operation is aimed for compensating the decrease of the tension applied to the brake cable which occurs caused by the service brake when the service brake is operating and does not occur when the service brake is not operating. Therefore, it is possible to prevent the service brake from causing a problem in which the lock control is terminated while a desired brake force is not achieved at the EPB.

Abstract: A cargo carrying vehicle has a towing unit and a storage unit defining a cargo space. The towing unit is operable to: a) advance the storage unit; and b) generate electrical power for operating at least one component on the vehicle. An input is provided for external power to be supplied to at least one of: a) charge; and b) operate the at least one component. A safety system has first and second states. With the safety system in the first state, with no external power supplied to the external power input, the towing unit can be operated to advance the storage unit. With the safety system in the second state, with external power supplied to the eternal power input, the towing unit cannot be operated to advance the storage unit.

Abstract: A brake cylinder for pneumatic vehicle brakes, especially for utility vehicles includes a spring brake section for carrying out parking brake actions by way of a brake spring, and a service brake section for carrying out pneumatic service brake actions. The spring brake section and the service brake section are combined in one housing as a structural unit. The housing is subdivided by a piston into two compartments, one compartment of the two being used as the pressure compartment for actuating the service brake section, and the brake spring of the spring section being arranged in the other compartment on the opposite end of the piston. The brake spring acts upon an additional spring piston in the compartment, which can be locked relative to the piston by a pneumatic locking mechanism and can be released therefrom by releasing the locking mechanism. The spring piston is connected to a piston rod directly or via additional elements to actuate the vehicle brake.

Abstract: The invention relates to a combination cylinder including a service brake cylinder as an active service brake with at least one pressure-medium-actuated service brake piston which actuates a brake mechanism via a service brake piston rod, and a spring store brake cylinder as a passive parking brake with a spring store brake piston which is actuated by pressure medium counter to the action of at least one store spring, with the spring store brake piston transmitting the force of the at least one store spring to the service brake piston rod by a force-transmitting gearing in the parking braking situation. The invention provides for the gearing to be designed such that the movements of the spring store brake piston and of the service brake piston rod are coaxial and the force transmission ratio becomes greater with progressive stroke of the spring store brake piston.

Abstract: A brake cylinder for pneumatically actuated vehicle brakes includes a parking brake spring-loaded brake section and a service brake section combined to form a structural unit in a housing. The housing is divided into two chambers by a piston. A cylinder spring of the spring-loaded brake section acts on another spring-loaded piston in the chamber, which can be blocked in relation to the first piston by a pneumatically actuated locking mechanism, and can be released from the first piston by the releasing action of the blocking mechanism. Following the release, the cylinder spring acts between the two pistons and moves the two pistons in relation to each other during a parking brake process. The pneumatically actuatable blocking mechanism acts only in an expansion direction of the spring.

Abstract: In a vehicle control apparatus, a hybrid ECU automatically stops and starts an engine if a predetermined condition is met while the vehicle is stopped. A brake ECU controls the braking force applied to wheels. A hybrid ECU controls the brake ECU so that braking force is applied to the wheels at the time of startup of the engine if while the vehicle is stopped, the vehicle run position is not selected as a shift position of the transmission. This restrains vibration of the vehicle at the time of startup of the engine.

Abstract: An hydraulically activated internal locking apparatus is disclosed including an hydraulic fluid reservoir, an hydraulically activated locking system and a electronic control system, where the electronic control system is in electrical communication with the locking system and the reservoir is in fluid communication with the locking system so that the locking system can be transitioned from a locked state to an unlocked state when the electronic control system receives a unlock or lock code or instruction.

Abstract: An exemplary embodiment of a Hill Start Aide system for a vehicle includes a brake system. The brake system including a brake actuator for manually actuating the brake system. The brake system is selectively configurable in a stopped configuration, where the brake system is manually maintained via the brake actuator such that a vehicle road wheel speed is about zero rpm, a released configuration, where the brake system will not generally inhibit rotation of at least one vehicle road wheel, and a control stop configuration, where the vehicle road wheel speed is about zero rpm. The Hill Start Aide system also includes a controller for at least partially controlling the brake system. The controller will selectively send a signal to maintain the brake system in the control stopped configuration when the brake actuator is manually released.

Abstract: A parking brake having an electromechanical and hydraulic device for gripping a pack of movable sectors connected mechanically to the wheels to exert the desired braking force on the wheels. The parking brake is characterized by having an oil flow regulating valve assembly, in turn having a first control solenoid valve and a second safety solenoid valve in series with each other.

Abstract: A locking mechanism for installing between a master cylinder and a brake line includes a housing having an internal bore, an inlet port, a passage, and an outlet port. A reciprocating piston is movable within the bore. A locking lever is coupled to the reciprocating piston for actuating the reciprocating piston. A fastener having an internal fluid passage for providing fluid communication between the passage and the master cylinder secures the housing to the master cylinder. The locking lever is moveable between a first position, wherein the hydraulic fluid can flow freely between the master cylinder and the brake line for engaging and disengaging the vehicle brake and a second position, wherein the hydraulic fluid is prevented from returning to the master cylinder for maintaining the vehicle brake in an engaged state.