DE102020201083A1 - Pressure generator for a hydraulic brake system - Google Patents

Abstract

The invention relates to a pressure generator (10) for a hydraulic brake system, with a drive (11) and a cylinder-piston unit (14) which comprises at least one piston (17A, 17B) and at least one chamber (18A, 18B) into which at least two fluid connections (14.1, 14.2, 14.3, 14.4) open, the drive (11) moving the at least one piston (17A, 17B) starting from a zero position against the force of a corresponding return spring (19.1, 19.2) to build up pressure, the Cylinder-piston unit (14) for the at least one chamber (18A, 18B) for volume compensation has a volume compensation arrangement (20) which in the at least one chamber (18A, 18B) has a circumferential annular groove fluidically connected to a first fluid connection (14.1, 14.3) (22) and a piston position-dependent fluid connection between the chamber (18A, 18B) and the circumferential annular groove (22), via which brake fluid when the at least one piston (17A, 17B) retracts d can be derived from the at least one chamber (18A, 18B) to the corresponding fluid connection (14.1, 14.3), as well as a corresponding braking system (1) with such a pressure generator (10). The volume compensation arrangement (20) has compensation means (24) which are suitable as a function of a force ratio between a driving force of the drive (11) and a spring force of the return spring (19.1, 19.2) and a pressure in the at least one chamber (18A) , 18B) to continuously enlarge an effective flow cross section of the piston position-dependent fluid connection until an equilibrium of forces or the zero position is reached.

Description

The invention is based on a pressure generator for a hydraulic brake system according to the preamble of independent claim 1. The present invention also relates to a multi-circuit, hydraulically open brake system, in particular for a highly automated or autonomous vehicle, with such a pressure generator.

Brake systems for vehicles are known from the prior art, which have a master brake cylinder that can be actuated by the driver, and an ESP system, which can also build up pressure in the brake system without the driver's influence, to build up pressure in the brake system. In addition, vehicles with at least one highly automated or autonomous driving function are known which can at least partially take over an actual driving task. As a result, the vehicles can drive highly automated or autonomously, for example by the vehicles independently recognizing the course of the road, other road users or obstacles and calculating the corresponding control commands in the vehicle and forwarding them to the actuators in the vehicle, which correctly influences the course of the vehicle. In such a highly automated or autonomous vehicle, the driver is usually not involved in the driving process. This means that there is no provision for hydraulic access by the driver in such highly automated or autonomous vehicles.

If a pressure generator with a cylinder-piston unit is used as the main pressure generator in open brake systems, in the case of ABS this means that the pressure generator has to compensate for a loss of brake fluid by “pushing it further” or “sniffing it back”. If the ABS control is too long, the existing volume of the cylinder-piston unit is exhausted by the cyclical draining of brake fluid or hydraulic fluid via the outlet valves, so that no more volume is available for a subsequent pressure build-up. In order to enable a renewed build-up of pressure, the isolating valves of the associated wheel brakes are closed and the pressure generator is moved in the direction of its starting position in order to suck up a defined amount of liquid. After the reloading process has been completed, the isolating valves for the wheel brakes can be opened again and a renewed pressure build-up can be initiated by moving the dual-circuit pressure generator and brake fluid or hydraulic fluid. This reloading process can be repeated several times.

From the DE 10 2018 206 613 A1 Generic pressure generator for a multi-circuit hydraulic brake system and a multi-circuit hydraulically open brake system, in particular for a highly automated or autonomous vehicle, is known. The pressure generator is designed with two circuits and comprises a drive and a cylinder-piston unit, which comprises two pistons and two chambers. A first piston is firmly coupled to a drive rod of the drive, which moves the first piston to build up pressure in the first chamber against the force of a corresponding first return spring, the pressure built up in the first chamber via a floating second piston against the force of a corresponding second Return spring causes a pressure build-up in a second chamber. A coupling unit forcibly couples the second piston to the first piston in the retraction direction during the transition to a zero position, so that the two pistons assume a defined position in the zero position. For volume compensation for the two chambers, the cylinder-piston unit has in each case a volume compensation arrangement which, in the corresponding chamber, comprises a circumferential annular groove fluidly connected to a first fluid connection and a fluid connection between the chamber and the circumferential annular groove, which is dependent on the piston position and via which when the corresponding chamber retracts Piston brake fluid can be derived from the corresponding chamber to the corresponding fluid connection. The pistons each have an axial cavity connected to the corresponding chamber, into which radial bores of the respective volume compensation arrangement open, the radial bores being at the same distance from a control edge of the corresponding piston in the longitudinal direction of the piston. When the pistons reach a predetermined position, the radial bores overlap with the circumferential annular groove, so that brake fluid can flow off via the fluid connection that is created and the corresponding fluid connection.

Disclosure of the invention

The pressure generator for a hydraulic brake system with the features of independent claim 1 and the multi-circuit hydraulically open brake system with the features of independent claim 11 each have the advantage that the pressure generator is designed as a plunger system, with at least one piston of a corresponding cylinder-piston unit interacting with compensating means of a volume compensating arrangement acts as a controllable valve slide, which can drain volume from the at least one chamber of the cylinder-piston unit until the pressure in the at least one chamber is no longer sufficient to counteract the force of a drive of the cylinder-piston unit to keep open. Through the Constantly increasing effective flow cross-section of the piston position-dependent fluid connection until an equilibrium of forces or a zero position is reached, very good control of the volume compensation or the pressure compensation in the at least one chamber is possible, so that a pressure drop and the system oscillate between the states fluid connection open and fluid connection closed and the associated noises, such as rattling, humming or squeaking, can be prevented or at least reduced.

Embodiments of the present invention provide a pressure generator for a hydraulic brake system, with a drive and a cylinder-piston unit, which comprises at least one piston and at least one chamber into which at least two fluid connections open. To build up pressure, the drive moves the at least one piston, starting from a zero position, against the force of a corresponding return spring. The cylinder-piston unit has a volume compensation arrangement for the at least one chamber for volume compensation, which in the at least one chamber comprises a circumferential annular groove fluidically connected to a first fluid connection and a piston position-dependent fluid connection between the chamber and the circumferential annular groove, via which when the at least one piston of brake fluid can be diverted from the at least one chamber to the corresponding fluid connection. In this case, the volume compensation arrangement has compensation means which are suitable, depending on a force ratio between a driving force of the drive and a spring force of the return spring and a pressure in the at least one chamber, to steadily increase an effective flow cross-section of the piston position-dependent fluid connection until an equilibrium of forces is reached or the zero position enlarge. This means that the at least one piston, in interaction with the compensating means of the volume compensating arrangement, is designed as a controllable valve slide.

In addition, a multi-circuit hydraulically open brake system, in particular for a highly automated or autonomous vehicle, with at least two wheel brakes, which are each assigned to a brake circuit with a pressure release path, at least two pressure generators, which are arranged between at least one fluid container and the at least two wheel brakes, and one Modulation unit proposed, which hydraulically connects the first pressure generator and the second pressure generator with the at least two wheel brakes and performs an individual brake pressure modulation in the at least two wheel brakes in normal operation, with brake fluid drained from the at least one wheel brake via at least during the individual brake pressure modulation in the at least one wheel brake a pressure relief path can be returned to the at least one fluid container, a first of the at least two pressure generators as a plunger system and a second of the at least two pressure generators a Is designed as a pump system, and the second pressure generator is connected directly to the at least one fluid container via at least one suction path.

In the proposed hydraulically open brake system, the at least one piston of the first pressure generator, designed as a plunger system, acts as a controllable valve slide in interaction with the compensation means of the volume compensation arrangement. The compensation means are a central element for the function of the system according to the invention. When brake fluid is replenished by the second pressure generator, which is designed as a pump system, due to an inaccurate volume estimate and the fact that a pump delivers the same volume in both brake circuits, too much delivered volume flows off in a controlled manner via the compensating means. The subsequent delivery can completely fill up the at least one chamber of the first pressure generator. If the brake is released in a controlled manner at this point, for example because a critical driving situation has been overcome, then the brake pressure in the wheel brakes is reduced in a controlled manner via the compensation means or the corresponding fluid connection. Here, the driving force of the drive of the plunger system and the pressure in the at least one chamber and the spring force of the return spring form an equilibrium. If the drive torque is reduced due to a lower braking requirement, the at least one piston is displaced by the wheel brake pressure in the direction against the drive until the compensation means release or open the fluid connection. Volume is then released via the corresponding volume compensation arrangement until the pressure is no longer sufficient to keep the fluid connection open against the driving force. Therefore, the pressure reduction is no longer implemented in a path-controlled manner, as is customary in a plunger system, by pulling back the at least one piston, but is controlled by releasing the volume through the volume compensation arrangement and the force equilibrium.

A highly automated or autonomous vehicle is understood below to mean a vehicle that has at least one highly automated or autonomous driving function that can at least partially take over an actual driving task. Using this at least one highly automated or autonomous driving function, the vehicle recognizes, for example, the course of the road, other road users or Obstacles independently and calculates the corresponding control commands, which are passed on to the actuators in the vehicle, whereby the course of the vehicle is correctly influenced. In such a highly automated or autonomous vehicle, the driver is usually not involved in the driving process. Nevertheless, measures and means, for example in the form of electrical or electronic actuation elements, can be provided which enable the driver to intervene in the driving process himself at any time. The braking request generated by the driver by means of the actuating elements is then passed on to the braking system via electrical signals. However, there is no mechanical and / or hydraulic access by the driver.

The at least one driving function evaluates vehicle data recorded by internal sensor units such as ABS interventions, steering angle, position, direction, speed, acceleration, etc. and / or vehicle surroundings data, which are recorded, for example, via camera, radar, lidar and / or ultrasonic sensor units, for trajectory planning and controls the evaluation and control units of the main system and the secondary system accordingly in order to generate a desired brake pressure and / or to implement stabilization processes in the longitudinal and / or transverse direction through individual brake pressure modulation in the wheel brakes.

The measures and developments listed in the dependent claims make it possible to improve the pressure generator specified in independent claim 1 for a hydraulic brake system and the multi-circuit hydraulically open brake system specified in independent claim 10.

It is particularly advantageous that the at least one piston can have an axial cavity connected to the corresponding chamber, into which compensating means of the volume compensating arrangement, designed as radial through openings, can open. Here, the radial through-openings can each have elongated depressions, for example on an outer contour of the at least one piston, the width and / or depth of which decreases starting from the through-opening in the direction of the circumferential annular groove. The radial through-openings can, for example, simply be designed as radial bores, on the outer edge of which the elongated depressions can be made, for example by milling. Due to the elongated depressions, the steady increase in the effective flow cross-section of the fluid connection can be predefined and adjusted very well and adapted to various requirements. Alternatively, the radial through openings can be arranged offset in the longitudinal direction of the at least one piston. In addition, the radial through openings can have cross-sectional areas of different sizes. This enables a particularly simple implementation of the compensation means of the volume compensation arrangement. The constant increase in the effective flow cross-section of the fluid connection of the volume compensation arrangement can be specified and set and adapted to various requirements via the number and degree of overlap of the offset through openings.

Alternatively, the compensating means of the volume compensating arrangement can be designed as grooves made in the at least one piston, which run from a control edge of the piston in the direction of the circumferential annular groove. Here, the grooves can have different dimensions. The constant increase in the effective flow cross section of the fluid connection of the volume compensation arrangement can also be simply predetermined and set and adapted to various requirements through the grooves.

As a further alternative, the compensation means of the volume compensation arrangement can be designed as a tapering control edge of the at least one piston. For example, the tapering control edge can be designed as a spherical cap section, as a truncated cone or as a bevel. Of course, other suitable forms are also possible, by means of which the constant increase in the flow cross section of the fluid connection of the volume compensation arrangement can be specified and adjusted.

Of course, the various compensating means can be combined or used in isolation as required.

In a further advantageous embodiment of the pressure generator, the cylinder-piston unit can be designed with two circuits and comprise two pistons and two chambers and two volume compensation arrangements. A first of the two pistons can be permanently coupled to a drive rod of the drive and a second of the two pistons can be mounted in a floating manner. The drive can move the first piston to build up pressure in a first of the two chambers against the force of a first return spring, and the pressure built up in the first chamber can move the floating second of the two pistons to build up pressure in the second of the two chambers against the force of a second Move the return spring. Due to the two-circuit design of the piston-cylinder unit with only one drive, the pressure generator can can easily be built into a two-circuit braking system.

In an advantageous embodiment of the brake system, the first pressure generator and the second pressure generator can be arranged hydraulically in parallel between the at least one fluid container and the at least two wheel brakes. Due to the parallel arrangement, the two pressure generators can deliver brake fluid from the at least one fluid container independently of one another. In addition, the second pressure generator can compensate for the volume loss caused by the individual wheel pressure regulation via at least one suction path from the at least one fluid container. In embodiments of the hydraulically open brake system, the brake pressure for a main braking effect is built up by the first pressure generator, whereby a loss of volume in the brake circuits caused by ABS control processes (ABS: anti-lock braking system) can be compensated for by activating the second pressure generator designed as a pump system. In this way, what is known as “sniffing” can be dispensed with in an advantageous manner.

In a further advantageous embodiment of the brake system, the pressure generators can each be designed with two circuits, whereby the first chamber of the two-circuit first pressure generator, designed as a plunger system, can be connected to at least one fluid container via the first fluid opening and to at least one wheel brake of a first of the two brake circuits via a second fluid opening , and the second chamber of the two-circuit first pressure generator designed as a plunger system can be connected to at least one fluid container via the first fluid opening and to at least one wheel brake of a second of the two brake circuits via a second fluid opening. Here, the two-circuit second pressure generator designed as a pump system can include two pumps, a first of the two pumps being able to be assigned to the first brake circuit and a second of the two pumps being able to be assigned to the second brake circuit. Thus, when the pump system replenishes the volume after a loss of volume, the end position can be reached through individual wheel controls and the replenishment can be ended as soon as both pistons open the fluid connections. While the position of the first piston, which is also referred to as "rod piston", can be detected via a rotor position sensor of the drive, the position of the second piston, which is also referred to as "floating piston", cannot be measured and can only be estimated using a hydraulic model become. This hydraulic model corresponds approximately to the model of an ESP (ESP: electronic stability program) for a storage chamber position, which is known to be very imprecise. The control strategy for the system should therefore not rely on the accuracy of the position estimate for the floating piston. Instead, the corresponding pump should run long enough to safely compensate for the lost volume. Too much delivered volume can be drained via the volume compensation arrangements of the cylinder-piston unit. Due to the good controllability of the effective flow cross-section of the fluid connection of the volume compensation arrangement, problems that arise when the controllability is poor, such as a drop in wheel brake pressure, sudden deceleration fluctuations, oscillation of the system, interfering noises and impairment of the functionality of controllers due to superimposed vibrations, can be avoided or at least reduced.

In a further advantageous embodiment of the brake system, the first pressure generator can generate the brake pressure in the at least two wheel brakes during normal operation, the second pressure generator being able to generate the brake pressure in the at least two wheel brakes during emergency operation if the first pressure generator fails, with at least one switching valve the first Can disconnect pressure generator in emergency mode from the at least two wheel brakes.

Exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the following description. In the drawing, the same reference symbols designate components or elements that perform the same or analogous functions.

Figure list

• 1 shows a schematic hydraulic circuit diagram of an embodiment of a multi-circuit hydraulically open brake system according to the invention, in particular for a highly automated or autonomous vehicle.
• 2 shows a schematic sectional view of an exemplary embodiment of a pressure generator according to the invention of the brake system according to the invention 1 .
• 3 shows a schematic sectional illustration of a first embodiment a volume compensation arrangement for the pressure generator according to the invention 2 .
• 4th FIG. 11 shows a schematic sectional illustration of a second exemplary embodiment of a volume compensation arrangement for the pressure generator according to the invention from FIG 2 .
• 5 FIG. 10 shows a schematic sectional illustration of a third exemplary embodiment of a volume compensation arrangement for the pressure generator according to the invention from FIG 2 .
• 6th FIG. 11 shows a schematic sectional illustration of a fourth exemplary embodiment of a volume compensation arrangement for the pressure generator according to the invention from FIG 2 .

Embodiments of the invention

How out 1 until 6th As can be seen, the illustrated embodiment comprises a multi-circuit, hydraulically open brake system according to the invention 1 , especially for a highly automated or autonomous vehicle, at least two wheel brakes RB1 , RB2 , RB3 , RB4 which each have a brake circuit BK1 , BK2 with a pressure relief path 7.1 , 7.2 are assigned, at least two pressure generators 10 , 30th , which between at least one fluid container 5 and the at least two wheel brakes RB1 , RB2 , RB3 , RB4 are arranged, and a modulation unit 3 , which the first pressure generator 10 and the second pressure generator 30th with the at least two wheel brakes RB1 , RB2 , RB3 , RB4 hydraulically connects and, in normal operation, an individual brake pressure modulation in the at least two wheel brakes RB1 , RB2 , RB3 , RB4 performs. During the individual brake pressure modulation in the at least one wheel brake RB1 , RB2 , RB3 , RB4 is from the at least one wheel brake RB1 , RB2 , RB3 , RB4 drained brake fluid via at least one pressure relief path 7.1 , 7.2 in the at least one fluid container 5 traceable. In addition, a first 10 is the at least two pressure generators 10 , 30th as a plunger system and a second 30 of the at least two pressure generators 10 , 30th is designed as a pump system.

How out 1 until 6th It can also be seen that the first pressure generator according to the invention comprises 10 a drive 11 and a cylinder-piston unit 14th , which at least one piston 17A , 17B and at least one chamber 18A , 18B comprises, in which at least two fluid connections 14.1 , 14.2 , 14.3 , 14.4 flow out. The drive 11 moves the at least one piston to build up pressure 17A , 17B starting from a zero position against the force of a corresponding return spring 19.1 , 19.2 . In addition, the cylinder-piston unit 14th for the at least one chamber 18A , 18B a volume compensation arrangement for volume compensation 20th on which in the at least one chamber 18A , 18B one with a first fluid connection 14.1 , 14.3 fluidically connected circumferential annular groove 22nd and a piston position dependent fluid communication between the chamber 18A , 18B and the circumferential ring groove 22nd includes, via which during a retraction movement of the at least one piston 17A , 17B Brake fluid from the at least one chamber 18A , 18B to the corresponding fluid connection 14.1 , 14.3 can be derived. Here, the volume compensation arrangement 20th Compensatory means 24 which are suitable, depending on a force ratio between a driving force of the drive 11 and a spring force of the return spring 19.1 , 19.2 and a pressure in the at least one chamber 18A , 18B to steadily enlarge an effective flow cross-section of the fluid connection, which is dependent on the piston position, until an equilibrium of forces is reached or the zero position is reached.

How out 1 can also be seen are the first pressure generator 10 and the second pressure generator 30th hydraulically in parallel between the at least one fluid container 5 and the at least two wheel brakes RB1 , RB2 , RB3 , RB4 arranged. Here is the second pressure generator 30th via at least one suction path 36A , 36B directly to the at least one fluid container 5 connected. In addition, the second pressure generator is the same 30th the volume loss caused by the individual wheel pressure regulation via the at least one suction path 36A , 36B from the at least one fluid container 5 the end.

How out 1 can also be seen, comprises the braking system shown 1 two brake circuits BK1 , BK2 each with a pressure relief path 7.1 , 7.2 and four wheel brakes RB1 , RB2 , RB3 , RB4 , with a first wheel brake RB1 and a second wheel brake RB2 and a first depressurization path 7.1 a first brake circuit BK1 and a third wheel brake RB3 and a fourth wheel brake RB4 and a second pressure relief path 7.2 are assigned to a second brake circuit. Here is an X-division of the wheel brakes RB1 , RB2 , RB3 , RB4 on the two brake circuits BK1 , BK2 possible, ie the first wheel brake RB1 is on the left front wheel and the second wheel brake RB2 is on the right rear wheel and the third wheel brake RB2 is on the right front wheel and the fourth wheel brake RB4 is located on the left rear wheel. Alternatively, there is also a II division of the wheel brakes RB1 , RB2 , RB3 , RB4 on the two brake circuits BK1 , BK2 possible, ie the first wheel brake RB1 is on the left front wheel and the second wheel brake RB2 is on the left rear wheel and the third wheel brake RB2 is on the right front wheel and the fourth wheel brake RB4 is located on the right rear wheel.

How out 1 can also be seen, comprises the fluid container 5 in the illustrated embodiments of the braking system 1 a first fluid chamber 5.1 for supplying fluid to the first brake circuit BK1 and a second fluid chamber 5.2 for supplying fluid to the second brake circuit BK2 .

How out 1 and 2 can also be seen are the two pressure generators 10 , 30th each designed with two circuits. Therefore, the as First pressure generator implemented in a plunger system 10 a two-circuit cylinder-piston unit 14th which two pistons 17A , 17B and two chambers 18A , 18B and two volume balancing arrangements 20th includes. Here is a first 17A of the two pistons 17A , 17B via a fixed connection 12.1 fixed with a drive rod 12th of the drive 11 coupled, and a second 17B of the two pistons 17A , 17B is floating. The drive 11 moves the first piston 17A to build up pressure in a first 18A of the two chambers 18A , 18B against the force of a first return spring 19.1 . The pressure built up in the first chamber 18A moves the floating second 17B of the two pistons 17A , 17B to build up pressure in the second 18B of the two chambers 18A , 18B against the strength of a second 19.2 of the two return springs 19.1 , 19.2 . A coupling unit 13th forcibly couples the second piston 17B during the retraction movement with the transition to a zero position with the first piston 17A so that the two pistons 17A , 17B assume a defined position in the zero position. That means that the coupling unit 13th the second piston 17B in the pressure build-up direction, which is in 2 runs from right to left, from the first piston 17A decouples or releases, and the second piston 17B exclusively in the direction of retraction with the first piston, which is opposite to the direction of pressure build-up 17A couples.

How out 2 can also be seen, comprises the coupling unit 13th in the illustrated embodiment a coupling element designed as a bolt or pin 13.1 , which has a fixed connection at a first end 13.2 firmly with the second piston 17B connected is. The coupling element has a second end 13.1 a head 13.3 on, which is inside a cavity 17.1 of the first piston 17A is guided axially movably in a hat-shaped sleeve. The coupling element reaches through here 13.1 a guide opening 17.2 in the hat-shaped sleeve so that the head 13.3 of the coupling element 13.1 at the transition to the zero position at an edge of the guide opening 17.2 or rests on the bottom of the hat-shaped sleeve and the second piston 17B in the retraction direction with the first piston 17A forcibly coupled. 2 shows the two pistons 17A , 17B in their end position in the pressure build-up direction. The coupling unit 13th enables the pistons to be withdrawn quickly and safely 17A , 17B via the actuator stem 12.1 with a defined retraction speed in the retraction direction into the defined zero position. In the illustration, the direction of retraction runs from left to right. In an alternative exemplary embodiment, not shown, an additional travel sensor can determine the current position of the second piston 17B to capture.

How out 2 can also be seen are the two pistons 17A , 17B each with two circumferential seals 15th against a wall of the cylinder-piston unit 14th sealed. Here are the seals 15th in corresponding grooves in the wall of the cylinder-piston unit 14th inserted. In addition, the chambers are 18A , 18B each via a first fluid opening 14.1 , 14.3 with at least one fluid container 5 and via a second fluid port 14.2 , 14.4 with at least one wheel brake RB1 , RB2 , RB3 , RB4 connectable. Here are the first fluid openings 14.1 , 14.3 of the two chambers 18A , 18B each between associated seals 15th arranged. Furthermore, there are the two chambers 18A , 18B each via a suction path 16A , 16B with non-return valve in addition with at least one fluid container 5 hydraulically connected. The suction paths open here 16A , 16B each in a lower area of the chambers 18A , 18B .

In the illustrated embodiment of the brake system 1 is the first chamber 18A of the two-circuit first pressure generator 10 via the first fluid port 14.1 with a first fluid chamber 5.1 of the fluid container 5 connected, and through the second fluid port 14.2 and a first switch valve UPS1 with the wheel brakes RB1 , RB2 of the first brake circuit BK1 connectable. The second chamber 18A of the two-circuit first pressure generator 10 is via the first fluid port 14.3 with a second fluid chamber 5.2 of the fluid container 5 connected, and through the second fluid port 14.4 and a second switching valve UPS2 with the wheel brakes RB3 , RB4 of the second brake circuit BK2 connectable. The two switching valves UPS1 , UPS2 are each designed as normally open solenoid valves, so that the wheel brakes RB1 , RB2 , RB3 , RB4 in the de-energized state with the chambers 18A , 18B of the two-circuit first pressure generator 10 are connected. How out 1 It can also be seen that the two-circuit second pressure generator comprises 30th two pumps 32A , 32B with a common drive 34 , with a first 32A of the two pumps 32A , 32B the first brake circuit BK1 is assigned, and a second 32B of the two pumps 32A , 32B the second brake circuit BK2 assigned. The first pump 32A is on the input side via a first suction path 36A with the first fluid chamber 5.1 of the fluid container 5 connected and on the output side with the wheel brake RB1 , RB2 of the first brake circuit BK1 connectable. The second pump 32B is on the input side via a second suction path 36B with the second fluid chamber 5.2 of the fluid container 5 connected and on the output side with the wheel brakes RB3 , RB4 of the second brake circuit BK2 connectable.

How out 1 can also be seen, comprises the modulation unit 3 in the illustrated embodiment for each wheel brake RB1 , RB2 , RB3 , RB4 one inlet valve each EV1 , EV2 , EV3 , EV4 , which are designed as controllable normally open solenoid valves, and one outlet valve each AV1 , AV2 , AV3 , AV4 , which are designed as electromagnetic, normally closed switching valves. Here are a first inlet valve EV1 and a first exhaust valve AV1 the first wheel brake RB1 assigned. A second inlet valve EV2 and a second exhaust valve AV2 are the second wheel brake RB2 assigned. A third inlet valve EV3 and a third exhaust valve AV3 are the third wheel brake RB3 assigned, and a fourth inlet valve EV4 and a fourth exhaust valve AV4 are the fourth wheel brake RB4 assigned. In addition, during an individual brake pressure modulation in the at least one wheel brake RB1 , RB2 , RB3 , RB4 via an assigned outlet valve AV1 , AV2 , AV3 , AV4 drained brake fluid from the at least one wheel brake RB1 , RB2 , RB3 , RB4 via the pressure relief paths 7.1 , 7.2 into the fluid container 5 returned. In the illustrated embodiment, the brake fluid or hydraulic fluid is from the wheel brakes RB1 , RB2 of the first brake circuit BK1 into the first fluid chamber 5.1 of the fluid container 5 returned, and the brake fluid or hydraulic fluid from the wheel brakes RB3 , RB4 of the second brake circuit BK2 is in the second fluid chamber 5.2 of the fluid container 5 returned.

In the illustrated embodiment of the brake system 1 generated by the first pressure generator 10 the brake pressure in the at least two wheel brakes during normal operation RB1 , RB2 , RB3 , RB4 , the second pressure generator 30th if the first pressure generator fails 10 the brake pressure in the at least two wheel brakes during emergency operation RB1 , RB2 , RB3 , RB4 generated. The first switchover valve disconnects in emergency operation UPS1 the first chamber 18A of the first pressure generator 10 of the two wheel brakes RB1 , RB2 of the first brake circuit BK1 , and the second switching valve UPS2 separates the second chamber 18B of the first pressure generator 10 of the two wheel brakes RB3 , RB4 of the second brake circuit RB3 , RB4 .

How out 2 until 4th can also be seen, point the two pistons 17A , 17B of the first pressure generator 10 each one with the corresponding chamber 18A , 18B connected axial cavity 17.1 on, in which as radial through openings 24.1 executed compensatory means 24 the volume equalization arrangement 20th flow out.

How out 3 It can also be seen that the radial through-openings 24.1 in the illustrated first embodiment of the volume compensation arrangement 20A on an outer contour of the corresponding piston 17A , 17B in each case elongated depressions 24.2 on, the width of which is based on the through opening 24.1 in the direction of the circumferential ring groove 22nd decreases. About the number and dimensions of the radial through openings 24.1 as well as the shape and dimensions of the elongated depressions 24.2 can be the steady increase in the effective flow cross-section of the fluid connection of the volume compensation arrangement 20A specified and adapted to existing requirements.

How out 4th can also be seen are the radial through-openings 24.1 in the illustrated second embodiment of the volume compensation arrangement 20B in the longitudinal direction of the corresponding piston 17A , 17B staggered. About the number and dimensions of the radial through openings 24.1 as well as a degree of overlap of the offset arranged through openings 24.1 can be the steady increase in the effective flow cross-section of the fluid connection of the volume compensation arrangement 20B specified and adapted to existing requirements. In the two exemplary embodiments, the radial through openings 24.1 have cross-sectional areas of different sizes.

How out 5 can also be seen are the compensatory means 24 in the illustrated third embodiment of the volume compensation arrangement 20C than in the corresponding flask 17A , 17B introduced grooves 24.3 executed which from a control edge of the piston 17A , 17B in the direction of the circumferential ring groove 22nd get lost. How out 5 can also be seen, have the grooves 24.3 in the illustrated embodiment, different dimensions and are designed to be of different lengths and widths. About the number and dimensions of the grooves 24.3 as well as a degree of overlap of the grooves 24.3 can be the steady increase in the effective flow cross-section of the fluid connection of the volume compensation arrangement 20C specified and adapted to existing requirements.

How out 6th can also be seen are the compensatory means 24 in the illustrated fourth embodiment of the volume compensation arrangement 20D as a tapered control edge 24D of the corresponding piston 17A , 17B executed. About the shape and dimensions of the tapered control edge 24D can be the steady increase in the effective flow cross-section of the fluid connection of the volume compensation arrangement 20D specified and adapted to existing requirements. In the fourth embodiment shown, the tapering control edge is 24D designed as a spherical cap section. Of course, other suitable shapes, such as a truncated cone or a chamfer, are also possible, via which the constant increase in the flow cross section of the fluid connection of the volume compensation arrangement is possible 20D can be specified and set.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102018206613 A1 [0004]

Claims (14)

Pressure generator (10) for a hydraulic brake system (1), with a drive (11) and a cylinder-piston unit (14) which comprises at least one piston (17A, 17B) and at least one chamber (18A, 18B) into which at least two fluid connections (14.1, 14.2, 14.3, 14.4) open, the drive (11) moving the at least one piston (17A, 17B) starting from a zero position against the force of a corresponding return spring (19.1, 19.2), the cylinder Piston unit (14) for the at least one chamber (18A, 18B) for volume compensation has a volume compensation arrangement (20) which, in the at least one chamber (18A, 18B), has a circumferential annular groove ( 22) and a piston position-dependent fluid connection between the chamber (18A, 18B) and the circumferential annular groove (22), via which brake fluid from the at least one n chamber (18A, 18B) can be diverted to the corresponding fluid connection (14.1, 14.3), characterized in that the volume compensation arrangement (20) has compensation means (24) which are suitable as a function of a force ratio between a driving force of the drive (11 ) and a spring force of the return spring (19.1, 19.2) and a pressure in the at least one chamber (18A, 18B) to steadily increase an effective flow cross section of the piston position-dependent fluid connection until an equilibrium of forces or the zero position is reached. Pressure generator (10) Claim 1 , characterized in that the at least one piston (17A, 17B) has an axial cavity (17.1) connected to the corresponding chamber (18A, 18B), into which compensating means (24) designed as radial through openings (24.1) open. Pressure generator (10) Claim 2 , characterized in that the radial through openings (24.1) on an outer contour of the at least one piston (17A, 17B) each have elongated depressions (24.2), the width and / or depth of which, starting from the through opening (24.1), in the direction of the circumferential annular groove ( 22) decreases. Pressure generator (10) Claim 2 , characterized in that the radial through openings (24.1) are arranged offset in the longitudinal direction of the at least one piston (17A, 17B). Pressure generator (10) according to one of the Claims 2 until 4th , characterized in that the radial through-openings (24.1) have cross-sectional areas of different sizes. Pressure generator (10) Claim 1 , characterized in that the compensating means (24) are designed as grooves (24.3) introduced into the at least one piston (17A, 17B) which run from a control edge of the piston (17A, 17B) in the direction of the circumferential annular groove (22). Pressure generator (10) Claim 6 , characterized in that the grooves (24.3) have different dimensions. Pressure generator (10) Claim 1 , characterized in that the compensating means (24) are designed as a tapering control edge (24D) of the at least one piston (17A, 17B). Pressure generator (10) according to one of the Claims 1 until 8th , characterized in that the cylinder-piston unit (14) is designed with two circles and comprises two pistons (17A, 17B) and two chambers (18A, 18B) and two volume compensation arrangements (20), a first (17A) of the two pistons (17A , 17B) is fixedly coupled to a drive rod (12) of the drive (11) and a second (17B) of the two pistons (17A, 17B) is mounted in a floating manner, the drive (11) using the first piston (17A) to build up pressure in a first (18A) of the two chambers (18A, 18B) moves against the force of a first return spring (19.1), and the pressure built up in the first chamber (18A) causes the floating second (17B) of the two pistons (17A, 17B) to Pressure build-up in the second (18B) of the two chambers (18A, 18B) is moved against the force of a second return spring (19.2). Multi-circuit hydraulically open brake system (1), in particular for a highly automated or autonomous vehicle, with at least two wheel brakes (RB1, RB2, RB3, RB4), each of which is assigned to a brake circuit (BK1, BK2) with a pressure release path (7.1, 7.2), at least two pressure generators (10, 30), which are arranged between at least one fluid container (5) and the at least two wheel brakes (RB1, RB2, RB3, RB4), and a modulation unit (3), which the first pressure generator (10) and the second pressure generator (30) hydraulically connects to the at least two wheel brakes (RB1, RB2, RB3, RB4) and performs an individual brake pressure modulation in the at least two wheel brakes (RB1, RB2, RB3, RB4) during normal operation, whereby during the individual brake pressure modulation in the at least one wheel brake (RB1, RB2, RB3, RB4) from the at least one wheel brake (RB1, RB2, RB3, RB4) drained brake fluid via at least one pressure relief path (7.1, 7.2) into the at least e inen fluid container (5) can be returned, wherein a first (10) of the at least two pressure generators (10, 30) is designed as a plunger system and a second (30) of the at least two pressure generators (10, 30) is designed as a pump system, characterized in that the first pressure generator (10) according to one of the Claims 1 until 9 and the second pressure generator (30) is connected directly to the at least one fluid container (5) via at least one suction path (36A, 36B). Brake system (1) Claim 10 , characterized in that the first pressure generator (10) and the second pressure generator (30) are arranged hydraulically in parallel between the at least one fluid container (5) and the at least two wheel brakes (RB1, RB2, RB3, RB4). Brake system (1) Claim 10 or 11 , characterized in that the second pressure generator (30) compensates for the volume loss caused by the individual wheel pressure regulation via the at least one suction path (36A, 36B) from the at least one fluid container (5). Brake system (1) according to one of the Claims 10 until 12th , characterized in that the pressure generators (10, 30) are each designed with two circuits, the first chamber (18A) of the two-circuit first pressure generator (10) designed as a plunger system via the first fluid opening (14.1) with at least one fluid container (5) and via a second fluid opening (14.2) can be connected to at least one wheel brake (RB1, RB2) of a first (BK1) of the two brake circuits (BK1, BK2), and the second chamber (18A) of the two-circuit first pressure generator (10) designed as a plunger system via the first fluid opening (14.3) can be connected to at least one fluid container (5) and via a second fluid opening (14.4) to at least one wheel brake (RB3, RB4) of a second (BK2) of the two brake circuits (BK1, BK2), and the two-circuit as Pump system executed second pressure generator (30) comprises two pumps (32A, 32B), wherein a first (32A) of the two pumps (32A, 32B) is assigned to the first brake circuit (BK1), and a second (32B) of the two Pumps (32A, 32B) is assigned to the second brake circuit (BK2). Brake system (1) according to one of the Claims 10 until 13th , characterized in that the first pressure generator (10) generates the brake pressure in the at least two wheel brakes (RB1, RB2, RB3, RB4) during normal operation, the second pressure generator (30) in the event of failure of the first pressure generator (10) during emergency operation generates the brake pressure in the at least two wheel brakes (RB1, RB2, RB3, RB4), with at least one switching valve separating the first pressure generator (10) from the at least two wheel brakes (RB1, RB2, RB3, RB4) in emergency operation.

Images