Abstract: A parking brake device with at least one first connector line to a compressed air source and with at least one second connector line to a compressed air source, includes at least one electronically actuable bistable valve arrangement for the actuation of a spring brake cylinder and at least one further electronically actuable redundancy control valve arrangement for the actuation of a redundant brake system. At least one first control electronics module and at least one second control electronics module are provided which can be operated independently of one another. The bistable valve arrangement can be actuated via the first control electronics module, and, independently thereof, the redundancy control valve arrangement can be actuated via the second control electronics module.

Abstract: An electropneumatic trailer control module (1) for an electronically controllable pneumatic brake system (520) for a vehicle combination (500) with a tractor vehicle (502) and a trailer vehicle (504), has an electronic control unit (ECU), a pneumatic reservoir input (11), a trailer control valve unit (65) with electropneumatic valves (RV, IV, OV), a trailer brake pressure port (22), and a trailer supply pressure port (21). The electronic control unit (ECU) has a parking brake signal input (200) for receiving an electronic brake representation signal (SB1, SB2, SB3) for an immobilizing brake (6, 532a, 532b) of the tractor vehicle (502) and is configured to, on the basis of the brake representation signal (SB1, SB2, SB3), switch at least one of the one or more electropneumatic valves (RV, IV, OV) of the trailer control valve unit (65) in order to output a brake pressure.

Abstract: A redundant brake system (1) for an autonomously driven vehicle is provided. The redundant brake system (1) comprises an electro-pneumatic service brake system, wherein the redundant brake system (1) is provided with at least three control circuits for controlling the electro-pneumatic service brake system.

Abstract: A method for electronically controlling a pneumatic brake system in a vehicle includes determining that a failure or a defect has occurred in electronic actuation of wheel brakes of the pneumatic brake system, and electronically actuating a pilot valve via a redundancy signal in response to determining that the failure or the defect in the electronic actuation has occurred so as to actuate the wheel brakes in a redundant electropneumatic manner. The redundancy signal is specified in such a manner that the pilot valve alternately turns for a pulse time into a second switch position and for a pause time into a first switch position. The pilot valve outputs, as a pilot pressure, a low pressure level in the first switch position and a high pressure level in the second switch position. The wheel brakes are actuated using a service brake braking pressure that is dependent upon the pilot pressure.

Abstract: Method for operating an automated hand brake comprising at least one first actuator and one second actuator for a motor vehicle, wherein each of the actuators is activated for an operation using a defined amperage, is characterized in that, in a first phase, the actuators are operated essentially synchronously until a defined first amperage is reached and, in a subsequent phase, the actuators are sequentially operated until a defined second amperage is reached.

Abstract: A control system that controls a driveline of a motor vehicle to operate in a selected one of a plurality of configurations is configured to receive a brake signal responsive to the application of a braking system. The control system causes the driveline to operate in a second configuration and not a first configuration in dependence at least in part on the brake signal. In the first configuration a first group of one or more wheels and in addition a second group of one or more wheels are arranged to be driven by the driveline, and in the second configuration the first group of one or more wheels and not the second group are arranged to be driven by the driveline.

Abstract: An air management system and method are provided. The system includes a pressurized air source. A manifold block is coupled to the pressurized air source and includes a plurality of suspension valves in fluid communication with the pressurized air source and each defines a suspension orifice of a first diameter for controlling air flow to and from a plurality of air springs. A manifold pressurization valve is in fluid communication with the plurality of suspension valves and the pressurized air source and defines a manifold pressurization orifice of a second diameter that is less than the first diameter of the suspension orifice for opening under high pressure to allow pressurized air into the manifold block. An electronic control unit controls the manifold pressurization valve and the plurality of suspension valves to equalize a high pressure differential across the plurality of suspension valves from the plurality of air springs.

Abstract: System for reducing the brake wear of heavy vehicles, in particular for public transportation or for garbage collection, the vehicle comprising a pneumatic braking system for the actuation of the brakes, the wear reducing system being characterized in comprising limiting means, suitable to be activated, for limiting the air pressure within the pneumatic braking system.

Abstract: A valve device for brake control of a different pressure medium-operated vehicle brake systems comprises a housing that has pressure medium ducts. A relay valve provides a pneumatic control pressure, which is fed to the relay valve via at least one of the pressure medium ducts at a higher flow rate. At least one insert is pneumatically connected to at least two of the pressure medium ducts, which can be pneumatically connected to each other by the insert. The two pressure medium ducts define a pressure medium path, the profile of which differs based on the housing that is in each case selected and/or switched based on the selected insert. The housing is selected from a set of housings having different pressure medium ducts, in particular bores, but which are otherwise essentially similar. The insert is selected from a set of different inserts.

Abstract: A valve arrangement for controlling a brake system, comprising at least one spring brake cylinder and at least one service brake cylinder, of a trailer vehicle of a traction vehicle-trailer combination, characterized in that said valve arrangement includes a 3/2 way valve which, as a function of the control pressure present at its control inlet, connects either its connection, which is connected to an outlet of a control valve device in order to generate service brake pressure for the at least one service brake cylinder, or connects its connection, which is connected to a trailer-vehicle-side compressed air supply, to its further connection which is connected to the at least one spring brake cylinder.

Abstract: Various embodiments of a controller, system and method of preventing vehicle rollaway for a heavy vehicle are disclosed. The controller receives a service brake signal indicating an operator has engaged the service brakes, a parking brake signal indicating the operator intent to actuate the parking brake and a signal indicative of motion. The controller transmits a control signal to at least two braking system components in response the service brake signal, the parking brake signal, and the motion of the vehicle to maintain engagement of the vehicle service brakes after the service brake pressure signal begins to decrease.

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 vehicle air braking system having a source of fluid under pressure (1), an air dryer (A) downstream of the source (1), and an air consumer circuit (2) downstream of the air dryer (A), the system being operable to suspend the source (1) on demand to permit backflow of air under pressure from the air consumer circuit (2) through the air dryer (A) to a drain valve (B), the system including a regeneration valve (D), and a command valve (C) having an inlet connected to the air consumer circuit (2), and a supply outlet operably connected to the drain valve (B), wherein the regeneration valve (D) is operable to permit regeneration backflow in response to connection of the inlet and supply outlets of the command valve (C).

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: An air braking system for a vehicle blends regenerative and foundation braking during low deceleration conditions in an effective and controlled manner. The braking system also includes a mechanical override that bypasses system electronics in response to an aggressive brake request such that treadle circuit pressure is sent directly to a brake relay circuit to actuate vehicle brakes.

Abstract: An air braking system for a vehicle blends regenerative and foundation braking during low deceleration conditions in an effective and controlled manner. The braking system also includes a mechanical override that bypasses system electronics in response to an aggressive brake request such that treadle circuit pressure is sent directly to a brake relay circuit to actuate vehicle brakes.

Abstract: A brake device arrangement and auxiliary device arrangement of a pneumatic brake system of a vehicle include a pneumatic control valve and other pneumatic components for carrying out braking functions or auxiliary braking functions of the braking system. In order to produce a modular construction, a brake control module, which is pre-mounted on a support for producing a braking pressure, is arranged adjacent to a filter module, for treating the air on the input side, and at least one auxiliary module for fulfilling the auxiliary braking functions.

Abstract: A pneumatic brake system for a motor vehicle includes a compressed air system including a plurality of compressed air reservoirs containing compressed air. A service brake system in fluid communication with the compressed air system is operably engaged by application of the compressed air from the compressed air system. A parking brake system in fluid communication with the compressed air system is operably engaged upon the engagement of a spring brake component. A compressed air release system is coupled to the compressed air system and the parking brake system. The compressed air release system is configured to receive a command and in response to the command drain compressed air from the compressed air system if the parking brake system is engaged.

Abstract: A brake device of a rail vehicle includes at least one spring-loaded cylinder having a pressure port and at least one service brake cylinder having a pressure port configured to receive a service brake pressure. Further included is a control valve arrangement having at least three ports, wherein a first port is connected to the pressure port of the spring-loaded cylinder and the control valve arrangement is configured to connect the first port to one of the following: (1) a second port configured to receive a pressure derived from a first pressure reservoir; and (2) a third port.

Abstract: A braking system for vehicles, including at least one first brake circuit, and at least one second brake circuit, in which the at least one first brake circuit and the at least one second brake circuit each have an electrical control circuit, which respectively has an electronic control unit and its own power supply device, and brake actuating devices which are activatable by the electronic control units, at least one of the brake actuating devices being activatable by more than one of the electronic control units, in which the brake circuits are electrically activatable via a foot brake valve, and the foot brake valve has two electrical braking transmitter devices which are each connected to the electronic control units so that they are DC-isolated.

Abstract: For the assembly of a spring-type brake cylinder, a rear cylinder is provided with a preloaded spring, with a rear piston and with an intermediate flange. Then, a front cylinder, in which a front piston with an actuating rod for a brake element of the braking system is movably arranged, is fixed to the rear cylinder, so that the rear cylinder and the front cylinder are in contact with one another by means of a sliding rod passing through the intermediate flange. As a result, the front piston is displaceable by the rear piston.

Abstract: A magnetic levitation railways has at least one vehicle, a compressed air supply unit provided in the vehicle and at least one consumer connection line, the compressed air supply unit has at least two compressed air lines laid in the vehicle and connected to at least one compressed air source each, and the consumer connection line can be connected to one another of the compressed air lines.

Abstract: An air braking unit for use in an air braking system. The air braking unit is arranged to be positioned, in use, at a vehicle wheel, and comprises an inlet for receiving, in use, compressed air from a central source. At least one first valve is arranged to selectively allow compressed air from the inlet to enter a wheel brake chamber in use. At least one second valve is arranged to selectively allow air from the brake chamber to be released via an outlet to the atmosphere in use and control means controls the first and second valves to operate to selectively control the air pressure in the brake chamber in use.

Abstract: A control device and a method for a brake system of a utility vehicle are provided. The brake system includes service brake cylinders and spring brake cylinders for braking the utility vehicle, an electronic control device, sensors for detecting the state of motion of the utility vehicle, a foot brake valve for actuating the service brake, a manual control unit, a module encompassing electrically controllable valves for an anti-blocking system, and a module encompassing electrically controllable valves for an electrically controlled parking brake. The electronic control device influences both the anti-lock system and the electrically controlled parking brake.

Abstract: The invention relates to a parking brake module (10) for a pressure medium-operated brake system of a vehicle having a parking brake function by means of at least one spring brake cylinder (12). Said parking brake module (10) comprises a first valve device (44) which increases the amount of pressure medium and is fitted with an inlet (46) that can be connected to a pressure medium reservoir (24), an outlet (50) that can be connected to at least one spring-loaded part (14) of a spring brake cylinder (12), and a control input (58) that is connected to a control line (60). The parking brake module (10) further comprises a second valve device (76) encompassing at least one first connection (78) which is used as a trailer control valve connection and can be connected to a trailer control valve (22) in order to control a trailer brake.

Abstract: The invention relates to a method for operating a brake device of a motor vehicle, comprising a service brake (16) and a parking brake (14). Upon activation of a rolling brake function (S1), and achieving a full stop of the vehicle, monitoring (S2) of an actuating element occurs with regard as to whether a driver has contact with an actuating element. In order to improve the safety of the rolling brake function, the invention provides that, if the monitoring (S2) finds that the driver has no contact with the actuating element, the parking brake (14) is applied (S3), or a braking pressure (14) is controlled using the service brake (16), the braking pressure corresponding to the maximum braking pressure (S10) that can be generated by the parking brake (14), by means of an electric or electronic brake device (26) for controlling the service brake (16) and the parking brake (14).

Abstract: A pneumatic emergency brake assurance module comprises a high capacity transfer valve connected in a first position to the output of the variable load relay valve and in a second position connected to a source of emergency braking air pressure. A timing reservoir is in communication with the pilot port of the high capacity transfer valve. A check valve/choke circuit provides parallel connections between a double check valve and the output of the variable load relay valve such that flow from the variable load relay valve passes through a charging choke and opposite flow to the variable load relay valves passes through a dissipation choke.

Abstract: The present invention includes a pneumatic system for an agro-industrial vehicle including an air compressor, a dual circuit foot valve connected to the air compressor, and at least two air storage tanks connected to said dual circuit foot valve. The operation of the dual circuit valve establishes an air pressure link from the storage tanks to a rear air chamber as well as to a front air chamber. Each storage tank fills the rear or front air chambers and the movement of the rear air chamber and the front air chamber activate a brake device.

Abstract: A valve for use in a pneumatic fluid system, such as an air brake system, is disclosed. The valve provides for fast release of pneumatic fluid from the delivery cavity through the exhaust port upon cessation of flow from the pneumatic fluid reservoir through the supply cavity. The valve includes a flow diverter that restricts fluid flow from the delivery cavity to the supply cavity when pneumatic fluid pressure in the supply cavity is less than that in the delivery cavity with minimal restriction of flow from the supply cavity to the delivery cavity when pressure in the supply cavity is greater than in the delivery cavity.

Abstract: A parking brake system uses a pneumatically controlled brake actuator to provide both service and parking brake functions. The parking brake system for a vehicle includes a hand control that is manually movable between a plurality of operational positions. A valve is responsive to movement of the hand control and controls air flow from a parking brake air supply to the pneumatically controlled brake actuator. The valve includes a gate that defines the plurality of operational positions, which include a park position, a release position, and an off position. When the hand control is moved out of the off position and into the park position, the pneumatically controlled brake actuator remains pressurized and a latching mechanism is activated to mechanically lock the vehicle brake. When the hand control is moved to the release position, the vehicle brakes are re-applied to unload the latching mechanism.

Abstract: An electronic brake system for a tractor-trailer vehicle includes a front electronic brake system for braking a front axle assembly and a rear electronic brake system for braking a rear axle assembly. During normal vehicle operation, front and rear air reservoirs supply air to actuate front and rear brake actuators, respectively. In response to a failure of the front electronic brake system, an electronic control unit automatically activates a trailer control valve to supply air to actuate the front brake actuator in addition to actuating the rear brake actuator from the rear air reservoir. The trailer control valve receives air supply from an independent reservoir.

Abstract: A valve arrangement is disclosed for controlling the pressure in first and second brake actuation outputs (9, 10). First and second air inlet valves (1,3) supply air to respective ones of the actuation outputs; first and second exhaust valves (2,4) are each associated with a respective one of the inlet valves; and a link valve (11) is between the actuation outputs. The arrangement is such that the pressure in each of the actuation outputs is controllable selectively either in mode a) jointly, with the link valve enabling air flow between the actuation outputs or in mode b) independently, with the link valve blocking air flow between the brake actuation outputs.

Abstract: The invention relates to a pneumatic operating unit for compressed air brakes including a housing having at least one exterior compressed air connection device and at least one air-carrying connection. The operating unit further includes at least one piston, at least one piston rod, at least one valve body, at least one valve seat and at least one cylinder body fitted into the housing. The at least one cylinder body has at least one transverse connection and includes one or more of the at least one piston, valve seat and body. The at least one cylinder body also includes a seal in an axial direction between two transverse connections with respect to the housing so that the transverse connections are sealed off with respect to one another.

Abstract: A compressed air treatment device is designed to be installed in an industrial vehicle consisting of a motor vehicle that can pull a trailer. The device comprises a set of electropneumatic components that are controlled by an electronic command/control unit which is interfaced with a computer communication bus and with various electrical components (sensors, switches, etc.). The device is used in particular to manage the compressed air in terms of supplying the service braking circuit(s).

Abstract: A vehicle air braking system having a source of fluid under pressure (1), an air dryer (A) downstream of said source (1), and an air consumer circuit (2) downstream of the air dryer (A), the system having control means to suspend the source (1) on demand to permit backflow of air under pressure from the air consumer circuit (2) through the air dryer (A) to a drain valve (B), the control means comprising a regeneration valve (D), and a command valve (C) having an inlet connected to the air consumer circuit (2), and a supply outlet operably connected to the drain valve (B), wherein the regeneration valve (D) is operable to permit regeneration backflow in response to connection of the inlet and supply outlets of the command valve (C).

Abstract: A pneumatic braking method and system for a vehicle is provided. The system includes a brake cylinder, a reservoir, a latching exhaust valve (LEV) movable between an open position and closed position and fluidly connected between the reservoir and the brake cylinder. The LEV includes a first solenoid having a first pilot fluidly connected to the reservoir and a second solenoid having a second pilot fluidly connected to the reservoir wherein the pilots are configured to be controlled electronically and pneumatically, said selectable between electronic and pneumatic control based on the vehicle operating requirements. The solenoids are configured to be piloted with pneumatic pressure from the reservoir and an electronic controller that includes a release on failure circuit. The release on failure circuit is configured to control the LEV during at least one of a loss of power to the braking system and a failure of the electronic controller.

Abstract: The invention relates to a control device for compressed-air brakes having a control valve, comprising a housing, a piston rod, a piston, a second piston, a double-seat valve, having a control element, having a supply air reservoir, having a control chamber, having a main air pipe; one side of the piston being connected in a compressed-air carrying manner with the main air pipe; the other side of the piston being connected in a compressed-air carrying manner with the control chamber; one side of the second piston having a compressed-air connection to a brake cylinder or a brake cylinder pilot chamber; the double-seat valve being connected between a compressed-air connection of the supply air reservoir and the compressed-air connection to the brake cylinder or to the brake cylinder pilot chamber.

Abstract: An integral intermodal train is provided for carrying standard over-the-highway semi-trailers. Each segment can have a plurality of platforms and may be loaded or unloaded independently of any other segment using a self contained, roll-on/roll-off system. Several sub-systems to speed performance and enhance reliability, such as an electronic assisted air brake, health monitoring, trailer tie-down and locomotive interface subsystems, can be provided on each segment. A spring applied parking brake is provided for the segments and operably connected to the train pneumatic brake systems. In a preferred embodiment the brake is automatically applied when brake pipe pressure falls below 40 psi nominal. The pneumatic valving for the parking brake prevents application of the valve in an emergency braking situation, until the pressure has bled off in normal system leakage, preventing wheel damage. A handle is provided for manual application and release of the parking brake when desired.

Abstract: An electronic vent valve for an electronically controlled pneumatic (ECP”) braking system having a plurality of braking sites at which a braking force can be applied. The ECP braking system includes a master controller processing circuit, individual braking control units located proximate each of the braking sites and a brake pipe supplying compressed air to the braking sites. The electronic vent valve is in fluid communication with the compressed air carried by the brake pipe and has an open position for substantially venting the compressed air from the brake pipe and a closed position for substantially retaining the compressed air within the brake pipe. The electronic vent valve includes a control circuit for causing the valve to open during emergency braking operations, thereby assuring a rapid decrease in the brake pipe pressure.

Abstract: A pneumatic system serves as a backup to the electronic system that normally provides load compensation on a railcar truck during both service and emergency applications of the brakes. The pneumatic system compensates for the load railcar bears during service and emergency brake applications whenever the electronic load compensation system fails due to a loss of power or other electrical failure. Ideal for railcar trucks equipped with brake pipe controlled brake equipment, the pneumatic system provides load compensation through use of a four-port variable load valve in combination with a low complexity MC-30A-1 control valve.

Abstract: The present invention is directed to the interface of various components of an automatic tire inflation system and an anti-locking braking system through the inside of a stationary axle of a vehicle.

Abstract: A snowmobile suspension that provides a substantially constant motion-ration (i.e. reduced falling rate) over the entire suspension stroke of the suspension system. The suspension system includes a suspension assembly that includes a lower arm assembly, a suspension arm, and a shock absorber. The lower arm assembly pivotally interconnects the lower portion of the suspension arm and the lower end of the shock absorber to the slide frame at a location relative to the chassis and within the endless track. The upper portion of the suspension arm and the upper end of the shock absorber pivot independently from each other, and the upper portion of the suspension arm is positioned lower and forward of the upper end of the shock absorber. The upper end of the shock absorber is positioned relative to the chassis and within the endless track.

Abstract: A two solenoid pressure modulated ABS relay valve incorporates a quick release valve in the control air circuit to allow a majority of the air in the control cavity to escape directly to ambient. The orifice through the exhaust solenoid need only handle a relatively small volume of air upstream of the quick release valve, i.e., between the quick release diaphragm and the inlet solenoid seat.

Abstract: An air braking system of a vehicle has a compressor, non-return valve, manifold, electrically actuable demand valve, an air consumer circuit. An auxiliary circuit connects the manifold to the consumer circuit via an electrically actuable valve and non-return valve. In the event of electrical failure air under pressure can be supplied to the consumer circuit via the auxiliary circuit. In another aspect a plurality of consumer circuits are provided. These circuits may be charged from the compressor via the manifold, or interconnected via the manifold independently of the compressor. This arrangement permits more flexible compressor operation and/or a greater reserve in the event of failure of the pressure source.

Abstract: A full-function value for the tractor-trailer vehicle is provided with a unitary valve body enveloping service brake, pressure-protection, at least one solenoid, modulator and delivery pistons actuatable to be displaced between respective rest and operative positions within the body to provide a regular braking and ABS braking modes of the full function valve.

Abstract: A modulator valve for an ABS system for heavy duty vehicles is disclosed. It uses non flow-through solenoid valve assemblies that simplify the machining and manufacturing costs associated with the present arrangement. This eliminates complex pilot passages and also achieves a quicker acting release of the brakes during normal service braking.

Abstract: A brake pressure control device is provided that includes a brake valve, an air master cylinder, and an air control valve. The air control valve is provided between the brake valve and the air master cylinder for selectively controlling the air pressure supplied from the brake valve to the air master cylinder. The air control valve includes an input port coupled to the brake valve for receiving air pressure provided from the brake valve; an exhaust port coupled to open air and to a back pressure chamber of the air master cylinder; an output port coupled to the air master cylinder; a pipe passageway coupled between the input port, the exhaust port, and the output port; at least one diaphragm provided within the pipe passageway; and a release valve connected between the exhaust port and the output port for releasing air pressure from the output port to the exhaust port during a brake releasing operation.

Abstract: A braking system comprising an anti-lock vehicle braking system for a vehicle having a pair of drive wheels (13, 14), the wheels of said pair being disposed on opposite sides of the vehicle, comprising a wheel speed sensor (17, 18) for each wheel (13, 14), a controller (19) responsive to wheel speed signals from said two wheel speed sensors (17, 18) for sensing skid conditions at said wheels (13, 14) and for generating skid control instructions, a wheel brake (23, 24) for each wheel (13, 14), responsive to fluid pressure, hereinafter referred to as brake pressure, supplied thereto, a common supply line (37), for supplying a common brake pressure for both of said brakes from a fluid pressure supply valve means (38) in accordance with a brake demand signal and a skid control means (40) controlled by said skid control instructions for modulating the common brake pressure, having a brake apply valve (51) to supply fluid under pressure to the common supply valve (39), in response to the controller detecting a whee

Abstract: A full function skid control valve assembly for use in an air brake system which provides for brake control utilizing a compact single assembly. The system provides for the maintenance of certain minimum operating pressures so that, when the air pressure within the vehicle brake system falls below predetermined levels, the valve assembly automatically partially or entirely exhausts the air pressure sometimes causing the spring parking brakes to engage. Once the air pressure within the brake system returns to predetermined levels, the valve assembly will allow a reservoir to be charged and the spring brakes to be deactuated. During operation, the assembly provides control of the service brakes while preventing undesired skid conditions.

Abstract: In a method of controlling an anti-skid brake system for a vehicle having one modulator and two wheel speed sensors for each axle, when the vehicle brakes during running, for example, on a split road where surface friction coefficients on the right and left surfaces of the road are greatly different from each other or on a curved road where torque values of the right and left wheels are quite different from each other, in case that one of the right and left wheels which is lower torque is set in a pressure reducing mode while the other wheel which is higher torque of the road is in a normal service braking state, a retaining mode or a slow pressure reducing mode is selected to the braking pressure of the right and left wheels. Therefore, when the conditions of the right and left wheel are quite different from each other as mentioned above, the braking pressure is retained or is intensified slowly so as to secure its braking force and thereby shorten the braking distance of the vehicle.