Abstract: An electrically controlled fluid displacement piston positioned in a bore modulates braking pressure at a wheel brake for antilock controlled braking by modulating the position of the piston in the bore. At a fully extended home position, a check valve is unseated by the piston to hydraulically couple the brake system master cylinder to the wheel brake. To minimize the occurrences of the condition where the check valve is opened during ABS controlled braking, the piston is initialized prior to entry into antilock controlled braking at a position away from the check valve resulting in a greater volume of fluid being trapped upon entry into antilock controlled braking when a hydraulic passage in parallel with the check valve is closed in response to a detected incipient wheel lock condition. This permits the antilock brake system to apply a controlled brake pressure greater than the pressure initially trapped in the closed system.

Abstract: A brake system for off-road vehicles of the type including an operator seat, a brake pedal and a hydraulic brake responsive to operator actuation on the brake pedal. The brake system includes a tank for hydraulic fluid, an electric pump hydraulically connected to the tank, a pressure modulating valve actuated by the brake pedal and a flow control valve for controlling the flow of pressurized hydraulic fluid between the pump, pressure modulating valve and brake. During normal braking operation, a switch responsive to operator actuation of the brake pedal causes to provide pressurized hydraulic fluid to the brake through the flow control valve. The return flow of pressurized fluid to the tank is modulated by the pressure modulating valve in response to operator actuation of the brake pedal to control the braking pressure. The flow control valve is responsive to the presence of an operator in the operator compartment, and is coupled to a switch.

Abstract: A pressure source for a pressure device includes a pump for pumping fluid from fluid tank, an accumulator connected to the pump and a pressure device, a device for detecting the pressure in the accumulator, and a controller for controlling the operation of the pump in an ON-OFF manner on the basis of a result of detection by the pressure detecting device. In this pressure source, the controller includes first and second drive signal generating circuits each capable of independently generating a drive signal for determining the on-off operation of the pump, and a judging circuit which has a calculating function therein and to which at least the pressure detecting device is connected. The judging circuit is connected to the first drive signal generating circuit, and the pressure detecting device is connected to the second drive signal generating circuit.

Abstract: An anti-skid brake control device has a control circuit 6 to which signals from a steering angle sensor 14, a yaw detector 7 and respective wheel velocity sensors 3a.about.3d of a motor vehicle are inputted, an oil pressure actuator 5 controls of the pressure of the braking fluid for respective wheel cylinders 2a.about.2d based upon target slip rates Sfrt. Sflt, Srrt and Srlt and measured slip rates Sfr, Sfl, Srr and Srl for the respective wheels calculated in the control circuit 6. The target slip rates for the respective wheels, which are principally determined dependent upon the deviation .beta. between compensated target yaw angular acceleration .omega.R and measured yaw angular acceleration .omega., are set independently and are modified dependent upon the motor vehicle body velocity, whereby the braking forces for the respective wheels are independently controlled .

Abstract: A parking brake circuit for a hydraulically driven vehicle which prevents the occurrence of an erroneous operation at the time when the vehicle travels on a downward slope. The parking brake circuit comprises first and second main circuits (2, 3) for supplying hydraulic operating fluid into a hydaulically driven motor (1) for traveling the vehicle. A counterbalance valve (4) provided between these main circuits for feeding hydraulic operating fluid on the side of high hydraulic pressure into a pressure receiving chamber (6a) of a parking brake actuating actuator (6). A conduit (5) for connecting an outlet port of the counterbalance valve to the pressure receiving chamber, and a slow return valve (12) are provided in the conduit so as to control a flow of hydraulic operating fluid directed from the pressure receiving chamber to the counterbalance valve.

Abstract: The present invention relates to a brake fluid pressure control apparatus in which a casing contains a pump communication port separately from a master cylinder communication port. A spool is also provided which limits the communication between the pump communication port and the master cylinder communication port in a manner such that the discharge pressure from the pump is not added directly to the master cylinder. Additionally, in the intake and discharge sides of the pump, a bypass channel is provided. In this bypass channel, a relief valve is provided which allows the escape of pressure force to the intake side of the pump in the case when the pressure force between the discharge side of the pump and the flow control increases to a high pressure.

Abstract: In one embodiment the invention comprises a system (50; 200) for controlling service brake and parking functions of at least one wheel of a vehicle comprising: an electric motor (64) drivingly connected to a hydraulic pump (66) for pressurizing hydraulic fluid; the output of the pump communicated to at least one service brake (58a,b), comprising a first hydraulic cylinder (62a,b), an electronics circuit for controlling the speed of the motor (64) to regulate hydraulic pressure in the first hydraulic cylinder in response to operator braking activity (56, 64, 62), the motor and pump providing the primary means of service brake activation.

Abstract: A system and method of controlling pressure in a wheel brake cylinder of a brake. The hydraulic cylinder is connected to an electrically driven pump and a flow control valve is connected between the pump and the wheel cylinder. The system and method operate to control the speed of a motor driven pump to generate a desired pressure in a cylinder of the brake; generate a differential pressure, in the flow control valve, proportional to pump flow and communication same to a spring biased valving element; cause the valving element to move, in response to pressure forces acting on the valving element, generated by the pressure differential, and the force of the bias spring, so as to selectively open and close an associated exhaust port, connected to a drain or sump, such that in the steady state an equilibrium condition is achieved where the pressure forces balance the spring force and the pressure in the hydraulic cylinder is constant.

Abstract: Circuit provides maximum current to an electric motor for a hydraulic pump in a brake system for a brief time interval after the motor is switched on, and thereafter limits the current to a lower value which corresponds to the torque necessary for generating the pressure required in the system.

Abstract: An anti-lock/traction modulator which includes a hydraulic pressure passage circuit for an anti-skid control and a hydraulic pressure source circuit for a traction control in which an accumulator disposed at an inlet side of a pump for accumulating a predetermined pressure and which circuit supplies a brake pressure to the hydraulic circuit for the anti-skid control merely during the traction control operation. These circuits are connected to each other through a piston so that brake pressure is supplied to brake cylinders of vehicle wheels from the piston during the traction control operation.

Abstract: In a braking pressure control apparatus for a vehicle, a first valve connected between a hydraulic pressure source and a wheel cylinder serves to permit and inhibit a supply of brake fluid to the wheel cylinder from the hydraulic pressure source. A second valve connected between the wheel cylinder and a reservoir serves to permit and inhibit an escape of the brake fluid from the wheel cylinder toward the reservoir. A control device serves to output control signals to the first and second valves respectively to control the braking pressure in the wheel cylinder in response to a detected running condition of the vehicle.

Abstract: A method of controlling the operation of a vehicle brake system, the brake system including a master cylinder controlled by the operator of the vehicle to vary applied brake pressure to various brake mechanisms during normal service brake operation and an antiskid brake subsystem, activated when one or more vehicle wheels are skidding, for controlling brake pressure in the various brake mechanisms to permit various wheels to operate in a nonskidding manner. The method comprising the steps of: 1) determining and storing a control relationship which relates changes in vehicle deceleration and changes in applied brake pressure, with none of the wheels of the vehicle skidding, 2) subsequently measuring at least two values (P.sub.1 P.sub.2) of applied brake pressure to determine changes in applied brake pressure .DELTA.P during a measurement interval and calculating the change in control deceleration .DELTA.D.sub.ci corresponding to the change .DELTA.

Abstract: The object is to shorten the installation length of the pump. The high-pressure pump has a pump housing with a bore, in which a pump element having a cylinder, a piston longitudinally movable therein and an outlet valve is received. The cylinder is screwed into the bore and axially fixed at a bore step. The outlet valve has a ball, received in a hollow-cylindrical extension of the cylinder and loaded on its end remote from the valve seat by a leaf spring secured to the cylinder. The hydraulic high-pressure pump is usable in particular in motor vehicle brake systems having an anti-lock and possibly traction control system.

Abstract: A hydraulic dual-circuit brake system with front/rear brake circuit distribution, an anti-skid system (ABS) and traction control (ASR) for motor vehicles including a four-channel hydraulic unit with control valves and with one return pump and a separate pump element for each brake circuit. An apparatus to supply brake pressure to the rear axle brake circuit in traction control has a reversing valve, which in traction control disconnects the rear-axle brake circuit from the master brake cylinder, and a pump feed apparatus, which upon activation feeds brake fluid into the pump element of the rear axle brake circuit.

Abstract: An anti-lock-controlled brake system with a auxiliary-force-assisted braking pressure generator accommodates a master cylinder in which at least one wheel brake is connected to a main pressure line, with an auxiliary hydraulic pressure pump connected to an auxiliary pressure line the system further includes wheel sensors and electronic circuits for detecting the rotational behavior of the wheels and for generating electric braking pressure control signals which, for the purpose of slip control, control the electromagnetically operable inlet valves and outlet valves inserted into the pressure medium lines. A pressure limiting valve is responsive to the pressure of the auxiliary pressure pump and to a pressure acting on the wheel brake to control the outlet pressure of the pump.

Abstract: A pressure supply system for a vehicle according to the invention incorporates a pump and an accumulator in which an output pressure of the pump is maintained within a prescribed range by controlling the on-off operation of the pump according to the inner pressure of the accumulator. By changing the prescribed range of pressure according to the actual pressure requirement, for instance according to the change in the travelling speed of the vehicle, the burden on the system is reduced. The prescribed range can be changed either by simply changing the upper and/or lower pressure limits at which the pump is deactivated and activated, respectively, or by operating the pump for a prescribed time period which is dependent on the pressure requirement after a certain reference pressure value is reached. Thus, the structure of the fluid pressure system is simplified, and the generation of unnecessary high pressure can be avoided.

Abstract: An anti-lock hydraulic brake system is described having a bypass line to a pump used to evacuate and pressurize the wheel brakes during antilock control. A pressure control valve in the bypass line regulates the pressure in the pressure line to the master cylinder pressure level. A low pressure accumulator absorbs recirculated fluid flow from the bypass line. A pressure operated valve opens only when a difference in pressure between the master cylinder pressure and the pump outlet pressure line pressure develops. The consequence is that a non-return valve a and pressure operated valve in combination bring about isolation of the master cylinder during antilock control to prevent brake pedal reaction to pump pressure developed during a braking pressure control operation. When the accumulator is fully charged, the bypass line is closed by means of a shut-off valve operated by an accumulator piston so that the pump delivers fluid via the pressure valve (18) back into the master cylinder (1).

Abstract: A brake hydraulic pressure generator is provided which employs a first booster piston which applies a brake pedal treading force to a brake piston and a second booster piston which selectively additively increases the braking pedal treading force applied to the brake piston. The second booster piston is operated by hydraulic fluid pressure supplied from an auxiliary hydraulic pressure source.

Abstract: The brake system comprises two hydraulic sub-circuits, each connecting a driving wheel and a free wheel to a working chamber of a master cylinder (1) connected to a general reservoir (20) of fluid under low pressure, and including a wheel anti-lock braking device comprising a three-way solenoid valve (51, 52, 53, 54) normally opening communication between an inlet of fluid under pressure and the brake motor, while, in the expansion phase of the anti-lock device, it closes this communication and connects the brake motor to a reservoir (21, 22) of fluid under low pressure to each sub-circuit. The device comprises a differential valve slide consisting of a valve of which one face receives the pressure prevailing in the associated brake motor (31, 32, 33, 34) and the other that as generated by a pump (45, 46) and, at rest, putting in communication the working chamber of the master cylinder (1) and the inlet of fluid under pressure.

Abstract: A hydraulic braking system having wheel cylinders, a tandem type master cylinder with first and second output ports, a hydraulic pressure transmitting device with a free piston slidably received in a housing with an input chamber located on one side of the free piston connected to the first output port in the master cylinder and an output chamber on the opposite side of said free piston leading to the wheel cylinders. An on-off valve is included, adapted to cut off the communication between a valve chest and the wheel cylinder in response to the hydraulic pressure in a pilot chamber leading to the first output port becoming larger than the hydraulic pressure in the valve chest by at least a given value. A differential pressure generating device is interposed between the second output port and the valve chest to reduce the output hydraulic pressure from the second output port in the master cylinder by a predetermined value to apply the reduced hydraulic pressure to the valve chest.

Abstract: An improved hydraulically actuated brake system for off-road heavy vehicles is disclosed that include a first accumulator, a second accumulator, a first manual and pilot actuated brake valve for controlling the flow from the first accumulator to the front brakes and to a first and a second pressure comparing devices and a second manual and pilot actuated brake valve for controlling the flow from the second accumulator to the first and second pressue comparing devices. The higher pressure from the first and second pressure comparing devices is output to the rear brakes so the front brakes are set by the pressure in the first accumulator while the rear brakes are set by the higher pressure of the first and second accumulators. A separate manually actuated brake valve controls the flow from the second accumulator to a third pressure comparing device which also is connected to receive the output of the first manual and pilot actuated brake valve.

Abstract: A brake system for automotive vehicles with a device for anti-lock control. A pump is provided which, in the control mode, delivers a reduced fluid volume for positioning a piston of the master cylinder. The reduction of the delivery volume is accomplished in that the non-return valve (64, 65) is kept open. Accordingly the movements of the piston (56) become ineffective with respect to the delivery of pressure fluid. The non-return valve (64, 65) is kept open by an electromagnetic actuating unit (62). This actuating unit is controlled by the electronic control unit of the anti-lock device. In this manner at least one piston of the master cylinder and thus the brake pedal are positioned during the control mode in a predefined manner.

Abstract: A hydraulic retarder has a control valve mechanism with a regulator valve for controlling the pressure of the fluid delivered to the retarder as a function of operator demand and an operating parameter of the retarder. The regulator valve has an opening pressure bias that is determined by a retarder signal valve which is responsive to an operator input and a closing pressure bias determined by the outlet pressure of the retarder.

Abstract: A vital pressure regulating system is constructed using an alternating current system, and the absolute value of an output signal is inversely proportional to the air pressure in the main air reservoir and therefore if some critical circuit component fails, the output of a comparator circuit becomes a direct current signal in the same way as the case in which the air pressure in the main air reservoir is higher than the predetermined upper limit value so that the switch shuts off the air compressor to achieve fail-safe operation.

Abstract: In a vehicular brake control system, a hydraulic braking operation starting from a master cylinder and ending at a wheel cylinder is divided into two systems, i.e., starting from the master cylinder and ending at a stroke absorber (master cylinder system) and starting from a hydraulic generator and ending at the wheel cylinder (wheel cylinder system). Since the master cylinder system is provided with the stroke absorber, a relationship between a depression force imposed on a brake pedal and a brake stroke can be fixed. Since the wheel cylinder system is provided with an output hydraulic control valve controlled so as to produce a braking deceleration rate according to the depression force, another relationship between the depression force and braking deceleration rate can also be fixed.

Abstract: A pressure supply system for the generation of the auxiliary pressure of a hydraulic brake system for motor vehicles comprises an accumulator, a hydraulic pump driven by electromotive force and a pressure switch (1) controlling the turning on and off of the hydraulic pump. The pressure switch (1) includes a switch piston (2) having a piston rod (5) mechanically actuating in a pressure-responsive manner, successively, two or three switches (8,9,10). The pump motor (26), by way of these switches, and by way of a relay, is turned on when a bottom pressure limit value (P.sub.U) is reached, and turned off when the upper pressure limit value (P.sub.O) is reached and exceeded. A holding circuit is connected in the electric circuit, in which are provided the switches (8,9,10) of the pressure switch (1), which holding circuit ensures an abrupt switch-over of the relay into the other switching position when a slow approach of a pressure (p) to the pressure limit values (p.sub.U, P.sub.

Abstract: A safety relay circuit for operating electric systems of automotive vehicles is disclosed. The circuit includes two series-connected change-over relays connecting the vehicle's electrical system to the operative voltage. The change-over relays are actuated by switches acted upon by a control circuit. The control circuit assures that the change-over relays are actuated alternatively.

Abstract: A hydraulic motor vehicle brake system with a master cylinder (61) and a hydraulic power booster (24) connected upstream of the master cylinder (61), in which a pressure medium pump (1) which may be driven by an electric motor is used for providing an auxiliary hydraulic energy. The drive of the pressure medium pump (1) may be switched on by a pressure accumulator (26) which in the unbraked operation of the automotive vehicle is permanently kept on a pressure level sufficient for an initial actuation of the brake. The pressure accumulator (26) is charged by means of a pressure control valve (7) in which a valve passage (15, 17) is operable by a hydraulic pressure in the booster chamber (23) of the power booster (24) such as to ensure that upon pressurization of the booster chamber (23) a connection will be locked between the pressure accumulator (26) and the power booster (24).

Abstract: In a brake system for automotive vehicles comprising a master cylinder, wheel cylinders and a device for anti-lock control, the piston of the master cylinder is positioned in its nominal position by the variable volume of delivery of a pressure fluid source, in particular, a pump. The actual position of the piston is determined by a sensing device which is mounted on axially movable parts of the tandem master cylinder, booster, pedal assembly or other elements. The volume of delivery of the pump is adjusted so as to cause the piston of the master cylinder and, thus, the brake pedal to assume the desired position. For this purpose, the pump is connected with the pressure chamber of the master cylinder. Advantageously, it will be accomplished thereby that the brake pedal will not depress through its full travel when, during the control mode, more pressure fluid is removed from the hydraulic system, in particular from the pressure chamber of the master cylinder than the pressure fluid pump is able to deliver.

Abstract: Disclosed is an electric switching device for monitoring the operation of a hydraulic brake system for automotive vehicles of the type including a brake slip control device. The electric switching device includes a first switch for switching the brake slip control device on and off, a second switch operating a warning lamp, a third switch for controlling a hydraulic pressure pump and a pressure responsive actuating element for actuating the switches dependent on the state of pressure on the brake system. Improved reliability is provided for by including functional redundancy of the first switch into the circuitry including a diode connecting a make type first switch to a break type second switch whereupon the brake slip controller circuit is grounded upon a fault condition in the controller circuit to prevent false signals from reaching the controller.

Abstract: An anti-skid apparatus for installation in a vehicle braking system having a master cylinder, a wheel brake cylinder and a primary fluid passage connecting the cylinders includes a changeover valve disposed in the primary passage to selectively communicate the wheel brake cylinder with the master cylinder or with a reservoir, and a fluid pump for pumping a brake fluid from the reservoir and returning it to a point of the primary passage between the master cylinder and the changeover valve, via a check valve. The anti-skid apparatus further includes a cut-off valve disposed in the primary passage between the master cylinder and the point where the pumped fluid is returned, and a regulator valve disposed in a recirculation passage for recirculating the pumped fluid to the reservoir. The cut-off valve normally allows a flow of the fluid and inhibits the flow of the fluid when the hydraulic pressure from the master cylinder exceeds the pressure from the wheel brake cylinder by at least a predetermined value.

Abstract: To monitor and control the pressure in the auxiliary pressure supply system of a hydraulic motor vehicle brake system, a circuit arrangement is employed which is provided with a door-contact switch (24) which closes when the driver's door of the motor car is opened and which at a pressure in the auxiliary pressure supply system (11-16) below the telltale threshold activates the hydraulic pump (11) irrespective of the activation of the ignition. Moreover, a holding circuit (25, 26, 30, D30) is provided through which, after closure of the driver's door, the hydraulic pump (11) continues to operate until the telltale pressure threshold or responding threshold is reached or exceeded.

Abstract: A system for supplying fluid under pressure for a motor vehicle brake system having a pressure supply system including which has a pump, a pressure reservoir, a reservoir pressure switch connected to the pressure reservoir for switching the pump on and off, and a check valve disposed following the pump, and a brake control valve connected to the pump and the pressure reservoir for directing fluid braking pressures into at least one brake circuit which has at least one wheel brake. Between the pressure reservoir and the brake control valve, there is a second check valve through which the pressure reservoir supplies the brake control valve with a pressure medium when the pump is not operating.

Abstract: A regulator valve for a hydraulic anti-skid apparatus, in which a first valve member in the form of a piston is reciprocable within a housing for the regulator valve and subdivides the interior of the housing into first and second chambers arranged to be respectively applied with a hydraulic power pressure from a fluid pump and a master cylinder pressure from a master cylinder, the first valve member being formed at its one end with a valve part exposed within the first chamber, and in which a second annular valve member is arranged in the first chamber coaxially with the first valve member and is formed at its one end with a first small diameter valve part cooperating with the valve part of the first valve member to form a first annular throttle for throttling the fluid flow from the pump to a fluid reservoir through the first chamber and at its other end with a second large diameter valve part cooperating with the inner end wall of the first chamber to form a second annular throttle for throttling the fluid

Abstract: A hydrodynamic brake is disclosed. It comprises a working chamber with a rotor and a stator in it. An inlet supplies fluid to the working chamber which tends to increase the braking torque. An outlet permits exit of fluid from the working chamber, which tends to decrease the braking torque. An overflow valve may be opened or closed to selectively permit or prohibit exit of working fluid from the working chamber outlet. A pressure source, such as the pressure in the working chamber, normally holds the overflow valve open. A regulating valve is connected by a pressurized connection with the overflow valve and the regulating valve selectively opens or closes the overflow valve. The regulating valve compares the desired braking torque, which is established by an operating lever for the brake, with the actual braking torque, and the regulating valve opens or closes the overflow valve for tending to bring the actual braking torque to the desired braking torque.

Abstract: To produce pulsating operation of vehicle wheel brakes in response to a continuous application of pressure to the brake pedal, a motor operated pressure switch controlled pulsating or pumping device is interposed between the brake master cylinder and the wheel brake cylinders of a hydraulic braking system. A ported piston within the pumping device is reciprocated and this action cyclically relieves pressure in the wheel brake cylinder lines and re-establishes braking pressure at a rapid rate of pulsation.

Abstract: A powered assist braking system having a pressurized fluid source which also supplies fluid to the steering system of a vehicle is disclosed herein. The braking system includes left and right-hand brake actuators that cooperate with a power brake valve and the actuators are designed so that, when actuated, hydraulic fluid is trapped in a chamber and this fluid is supplied to actuate the brake while the pressurized fluid source assists in pressurizing the trapped fluid. The power brake valve has a pressure release assembly incorporated therein which controls the maximum pressure of the inlet fluid and also controls the flow of fluid to the steering system. The system also is designed to equalize the pressure of the fluid when both brakes are simultaneously actuated.

Abstract: A control circuit for reducing the output cycle of a compressed air system of a rapid transit car during "lay-over" periods, when only a minimum of compressed air for a parking brake, for example, is needed by the car, by activating a secondary governor set for a low pressure operating range and connected in series with a primary governor, one or the other of the governors being activated by the control circuit responsively to control signals denoting the state of compressed air requirement of the car.