Hydraulic braking system with a first and second hydraulic unit

Abstract

In a hydraulic brake system (22) for a vehicle (10) with a pressure medium reservoir (52) for compensating the storage of pressure medium (80) as well as a first hydraulic unit (24) and a second hydraulic unit (26), each of which hydraulic unit (24, 26) belongs to a wheel (12) of the vehicle (10), both the first hydraulic unit (24) and the second hydraulic unit (26) are fluidly connected to the same pressure medium reservoir (52).

Description

State of the art The invention relates to a hydraulic braking system for a vehicle with a pressure medium reservoir for compensating the storage of pressure medium and a first and a second hydraulic unit, each of which is assigned to a wheel of the vehicle. In vehicle braking systems, brake systems with hydraulic units are known, which, unlike a central hydraulic brake unit such as a hydraulic power unit, are decentralized and assigned to each individual wheel. Such decentralized brake units are installed in newer vehicles with increasing levels of automation. There are electromechanical brakes located at each wheel, in which a piston, axially movable by a motor, mechanically presses against a friction element that moves radially during travel. There are also decentralized electrohydraulic brake actuators, in which a braking force generated at each wheel by an electric motor is hydraulically transmitted to the friction element of the corresponding wheel brake. One of the aims of the invention is to create a force- and space-optimized braking system, especially for newer vehicle developments. Disclosure of the invention According to the invention, a hydraulic braking system for a motor vehicle is provided, comprising a hydraulic fluid reservoir for compensating the storage of hydraulic fluid, a first hydraulic unit, and a second hydraulic unit, each hydraulic unit belonging to one wheel of the vehicle. Each hydraulic unit is subsequently referred to as a unit. In particular, each unit is arranged at or near one wheel of the vehicle. The two units are thus spatially separated from each other within the vehicle and can be controlled individually for each wheel. According to the invention, the first and second units are fluidly connected to the same hydraulic fluid reservoir. It is also according to the invention that more than one second unit is present.With the design according to the invention, only one reservoir is sufficient to supply the brake system with enough hydraulic fluid. This saves on reservoirs and reduces the number of connections and plug contacts required. Furthermore, a more robust and compact design is achieved. The reservoir is preferably arranged externally, i.e., outside the units. This enables a modular, cost-saving design of the individual units. Each unit is a brake unit. Each unit comprises a corresponding first and second housing, preferably designed as a hydraulic block. These housings contain lines and receptacles for accommodating hydraulic components and for connecting these components. Each housing is located at or near a wheel of the vehicle. Advantageously, according to the invention, the reservoir belongs to the first unit, and the second unit is fluidly coupled to the reservoir by means of a hydraulic connection. The first unit, together with its associated reservoir, forms a main unit, and the second unit is a follower unit. This allows the main unit to be positioned in a space-optimized manner on the associated wheel, where more installation space is available than is required for the follower unit. In particular, the reservoir is arranged on the first unit, preferably on one side of the unit or its housing, and is thus stably and compactly supported there. Furthermore, it is preferred to provide one main unit and at least one follower unit, preferably three follower units for a four-wheeled vehicle. Preferably, the hydraulic connection is designed with a line, which is particularly preferably a fixed brake line that is highly pressure-resistant and expands only minimally under pressure. Brake pressure can be transmitted with exceptional precision. Furthermore, preferably, the first unit is arranged on a first wheel of a vehicle axle and the second unit on a second wheel of the same axle, which is preferably a front axle of the vehicle. This ensures a uniformly generated braking effect on a common axle. A correspondingly higher braking force is then achieved at the front axle. The described reservoir is advantageously the only reservoir in the brake system that is located externally, outside the housing. This saves a significant amount of installation space in the vehicle. Furthermore, according to the invention, the second unit advantageously does not have a reservoir. According to the invention, the reservoir advantageously has at least two chambers, a first chamber being fluidly connected to a first hydraulic system of the first unit and a second chamber being fluidly connected to the second unit and an associated second hydraulic system via the hydraulic connection. The two chambers are preferably designed to be fluid-separated. In particular, the second chamber provides a pressureless area that is connected to the second unit via the hydraulic connection. Furthermore, each hydraulic system comprises lines and fittings arranged in and on the respective housing. The chambers of the reservoir are defined, in particular, such that a separate chamber belongs to the second unit and is connected to the second unit via a brake line. Fluid separation is provided within the reservoir, allowing the hydraulic units to be supplied separately with hydraulic fluid from the reservoir.Furthermore, at least one of the two hydraulic systems is advantageously designed according to the invention such that a specific volume of hydraulic fluid is integrated into the hydraulic system itself. This specific volume is preferably integrated into a receptacle within the hydraulic system itself, which is particularly preferably designed as a blind hole or hollow cylinder in the respective housing. In particular, the specific volume corresponds to the volume of an associated pressure generator, which is preferably externally actuated. "Integrated" here means that the specific volume is contained within the respective unit or its housing itself, without an externally arranged container. In particular, the specific volume is a volume of hydraulic fluid required during operation.The volume required in this way corresponds in particular to a maximum volume that the pressure generator has in its working chamber as a preferred piston-cylinder unit with the piston retracted maximally into the cylinder. Preferably, at least one receptacle is provided for integrating the specified volume into the respective hydraulic system. This receptacle is located in the unit or its housing at the position of an actuator, such as a master brake cylinder, and / or a pedal feel simulator. Such positions are known in conventional hydraulic housings. Preferably, precisely these positions are also used in at least one of the units according to the invention. This allows for even better utilization of existing production facilities and production lines, resulting in significant cost savings. The at least one receptacle is sealed fluid-tight with a cover in the associated unit for the integration of the volume. Furthermore, according to the invention, the first unit advantageously comprises a first pressure generator connected to the reservoir via a fluid-conducting supply line, and the second unit comprises a second pressure generator connected to the reservoir via a hydraulic connection. In particular, both pressure generators are adapted to independently increase, maintain, or decrease the brake pressure at their respective wheel connections as required. Thus, the brake pressure can be modulated solely by means of the pressure generator. This modulation of the brake pressure is achieved without valves, which has proven to be very efficient in transmitting force. Force losses at valves are avoided. Preferably, each pressure generator is externally driven and preferably operated by an electrically controlled motor. In particular, the pressure generators are driven independently of one another. Together with the externally driven pressure generator, each unit is an electro-hydraulic brake actuator, each assigned to one of the wheel brakes of the corresponding wheel. Preferably, the first pressure generator is fluidly connected to the first chamber and the second pressure generator to the second chamber of the reservoir. This enables reliable and redundant pressure generation at each wheel. Advantageously, according to the invention, each unit has a system valve, which is preferably normally open (i.e., de-energized), arranged in a line connecting the reservoir to its respective wheel connection and which can be individually controlled. In particular, the system valve is designed to close when the associated pressure generator is activated. This ensures effective pressure generation at the wheel connection during normal operation. If pressure relief is required, the system valve can be reopened by means of a corresponding control signal. The system valve then acts as a pressure relief valve. Furthermore, in the event of a fault, the normally open system valve allows for the reduction of generated brake pressure and thus the release of the associated braking force. Advantageously, according to the invention, the first unit comprises a pressure transmitter or actuator that can be actuated by the driver and is fluidly connected to the second unit via a further hydraulic connection. This further hydraulic connection is in addition to the hydraulic connection already mentioned. By means of this further hydraulic connection, both units can be supplied with brake pressure at the respective wheel connections by only one pressure transmitter, which can be actuated by the driver, thus saving components and weight. This creates a reliable hydraulic backup system in both units, while both units are arranged individually for each wheel. Preferably, the pressure transmitter is designed as a master brake cylinder that can be actuated by a pedal. In particular, the first unit is mounted on a firewall of the vehicle, into which a pedal rod of a pedal located in a passenger compartment then engages compactly. Furthermore, according to the invention, at least one of the two units advantageously provides a control valve, preferably normally closed, in a pressure line between the respective pressure generator and the respective wheel connection in each of the two units. This isolates the pressure generator's volume from the wheel connection in the event of a pressure generator failure. In such a backup scenario, this prevents undesirable additional elasticity caused by the pressure generator's volume. Reliable and rapid braking can then be achieved via the hydraulic backup system using the pressure transmitter, which can be actuated by the driver. Further advantageous developments and benefits arise from further sub-claims or from the following character description. Exemplary embodiments of the solution according to the invention are explained in more detail below with reference to the accompanying schematic drawings. These show: Fig. 1 a highly simplified top view of a vehicle with a first embodiment of a braking system according to the invention, Fig. 2 a hydraulic diagram of a first unit according to Fig. 1, Fig. 3 a hydraulic diagram of a second unit according to Fig. 1, Fig. 4 an oblique view of the first unit according to Fig. 2, Fig. 5 an oblique view of the second unit according to Fig. 3, Fig. 6 detail VI in Fig. 2 and Fig. 3, Fig. 7 detail VII in Fig. 2 and Fig. 3, Fig. 8 the view according to Fig. 1 with a second embodiment of a braking system according to the invention, Fig. 9 a hydraulic diagram of a first unit according to Fig. 8, Fig. 10 a hydraulic diagram of a second unit according to Fig. 9, Fig. 11 a section of a hydraulic diagram of a third embodiment of a braking system according to the invention. Figure 1 shows a highly schematic representation of a passenger car, vehicle 10, with four wheels 12. Two wheels 12 are located on a front axle 14 and two wheels 12 on a rear axle 16. Both axles 14 and 16 are shown with dashed lines for clarity. An electromechanical brake (EMB) 18 is arranged on each wheel 12 of the rear axle 16. Each brake 18 has an electrically controlled electric motor 20, which, when needed, presses a pressure piston (not shown) against a friction element (not shown), such as a brake disc or brake drum. The two wheels 12 on the front axle 14 are to be braked by means of a hydraulic braking system 22. For this purpose, the braking system 22 comprises a first hydraulic unit 24 and a second hydraulic unit 26, which are hereinafter referred to as units 24 and 26, respectively. Each unit 24, 26 is arranged on one wheel 12. Here, the two units 24, 26 are arranged on the front axle 14. Other arrangements are also possible, such as a total of four units, each of which is arranged on one wheel 12 of the vehicle 10. The braking system 22, together with the two brakes 18, forms part of a vehicle braking system 28 of the vehicle 10. This also includes a pedal unit 30 with a pedal feel simulator (not shown), a control unit, and associated sensors. The pedal unit 30 is located on a firewall 32 of the vehicle 10 and projects into a passenger compartment 34, where it is operated by the driver of the vehicle 10. Depending on the driver's braking request or the automatically determined braking requirement, corresponding signals are sent to an associated control unit, which then causes the units 24, 26, and, if necessary, the brakes 18 to generate a braking effect. The braking system 22 according to Figs. 1, 2, 3, 4, 5, 6, 7, 8 to 9 is designed without hydraulic access by the driver to the associated wheel brakes 36, 38. There is no hydraulic connection between the pedal unit 30 and the first unit 24, thus no hydraulic backup system is formed. To ensure reliable braking in the event of a power supply failure, two batteries are provided as power sources 40, 42. For redundancy, the power sources 40, 42 are independently electrically connected to the braking system 22 and the units 24, 26 and the brakes 18, respectively, which is not shown in Fig. 1 for clarity. Preferably, the first unit 24 is arranged near the firewall 32 on a side facing away from the passenger compartment 34 in a space 44, which here serves as the engine compartment, on the associated wheel 12. This wheel 12 is positioned to the left in the direction of travel with respect to a longitudinal axis 45 of the vehicle 10. A parallel X-axis is defined with the longitudinal axis 45 in a forward direction of travel, from which a Y-axis 46 points to the left with respect to a forward direction of travel. The first unit 24 is formed with a first housing 48, which is preferably block-shaped. A pressure medium reservoir 52 belonging to the first unit 24 is arranged on the top of the first housing 48 in its installed position, i.e., along an upwardly directed Z-axis 50. The reservoir 52 is thus located externally on a reservoir side 53 of the housing 48. Furthermore, a first pressure line 54 leads from the first unit 24 to the associated wheel brake 36, which is designed with a brake caliper (not shown in detail). A hydraulic connection 56 leads from the first unit 24 to the second unit 26, which is arranged on the associated wheel 12 at the associated wheel brake 38. Furthermore, the second unit 26 has a second housing 58, which is preferably designed in the same block shape as the first housing 48. A second pressure line 60 leads from the second unit 24 to the wheel brake 38. However, the second unit 24 does not have a pressure medium reservoir externally arranged on the second housing 58. Both units 24, 26, with their housings 48, 58, are largely identical in design. Each housing 48, 58 has a broad side serving as the control unit side 62, to which a control unit 64 is attached. Opposite this is a motor side 66, to which a motor 68 is arranged, each of which is an electric motor. Each unit 24, 26 comprises a hydraulic system 70, 72, which is largely housed within the associated housing 48, 58. Fig. 2 shows a first hydraulic system 70 belonging to the first unit 24. It can be seen that the reservoir 52, arranged externally on the housing 48, has two chambers 76, 78 largely separated by a partition 74. These chambers contain brake fluid as a hydraulic fluid 80, the level of which is monitored by a level indicator 82. A first chamber 76 is connected to the hydraulic system 70 of the first unit 24 as the main unit. A second chamber 78 is connected without pressure, via the hydraulic connection 56, to a second hydraulic system 72 of the second unit 26 as a secondary unit, shown in Fig. 3. The hydraulic fluid 80 can flow from the reservoir 52 into the first unit 24 and the second unit 26, and in particular from the first unit 24 and / or the second unit 26 back into the reservoir 52. In the first unit 24, a supply line 84 leads from the first chamber 76 to a fluid inlet 86 of an externally driven first pressure generator 88, which is to be driven by means of the motor 68 belonging to the unit 24 in such a way as to achieve a pressure-building or pressure-reducing effect. For this purpose, the pressure generator 88 is preferably designed as a plunger or... A piston-cylinder unit is designed, comprising a piston 92 that is axially displaceable within a cylinder 90. The piston 92 divides the cylinder 90 into a working chamber 94 filled with pressurized fluid and a chamber 96 facing the motor 68. The chamber 96 is not filled with pressurized fluid and is connected to a vent volume 98 for pressure equalization. Furthermore, a transmission 100 projects through the chamber 96, by which a rotary motion of the motor 68 is converted into a translational motion of the piston 92. Preferably, the transmission 100 is a spindle or ball screw drive. The working chamber 94 serves to build up or reduce pressure by means of an axial displacement of the piston 92. During operation, the working chamber 94 has a changing volume 102, which reaches its maximum volume when the piston 92 is fully retracted. The volume 102 of the working chamber 94 decreases when the piston 92 is driven forward by the motor 68 in a pressure-building direction into the cylinder 90, and increases when the piston is driven backward by the motor in a pressure-reducing direction out of the cylinder 90 towards its retracted position. In the supply line 84, which runs through the housing 48, two receptacles 104 and 106, each serving as a volume reservoir, are arranged between the first chamber 76 and the fluid inlet 86. Receptacle 104 projects as a blind hole into the control unit side 62 and is sealed there by a fluid-tight cover 108 to function as a volume reservoir (Fig. 6). Receptacle 106 projects from a narrow side 110 lengthwise to the reservoir side 53 into the housing 48 and is sealed by a fluid-tight cover 112 to function as a volume reservoir (Fig. 7). With the intakes 104 and 106, a specific volume 114 is integrated into the first hydraulic system 70, representing their combined volume. Volume 114 specifically contains and stores a pressure medium required during operation within the hydraulic system 70 itself. Volume 114 corresponds to the maximum volume of the working chamber 94. The pressure generator 88 is directly connected to a wheel connection 116 of the wheel brake 36 via the working chamber 94 and the first pressure line 54. A line 120 leads from the wheel connection 116, or from a branch 118 off the pressure line 54, and is connected at a branch 122 to the supply line 84 and thus to the first chamber 76. A 2 / 2-way solenoid valve, configured as a system valve 124, is located in the line 120 and is normally open. The system valve 124 closes when the pressure generator 88 is activated, thereby directing the hydraulic fluid through the pressure line 54 to the wheel connection 116. This generates brake pressure at the wheel brake 36. To release the brake pressure, the piston 92 is moved in the opposite axial direction towards the motor 68 during normal operation.A suction effect is created in the expanding working chamber 94, which, when the system valve 124 is closed, relieves the pressure at the wheel connection 116. For thermal equalization, the system valve 124 is opened, thus establishing a connection between the wheel brake 36 and the chamber 76. Any residual pressure in the wheel brake 36 is then released via the reservoir 52, which is connected to atmospheric pressure. The system valve 124 acts as a pressure relief valve in this process. Because the system valve 124 is designed to be normally open (de-energized), this release of the braking force is always possible, even in the event of a fault, such as a power failure. A section of supply line 84 leading from storage tank 52 to branch 122, line 120, and a section of pressure line 54 leading from branch 118 to wheel connection 116 form a line 126, which connects storage tank 52 to wheel connection 116. Line 126 provides a pressure relief line without a pressure generator. The system valve 124 is also located within line 126. A pressure sensor 128 is provided on line 126, or, when system valve 124 is closed, on pressure line 54. This sensor is used to determine the pressure at pressure generator 88, particularly when system valve 124 is closed. Fig. 3 shows a second hydraulic system 72 belonging to the second unit 26. The hydraulic system 72 has a second pressure generator 130, which is connected to the second chamber 78 of the reservoir 52 arranged on the first unit 24 by means of the hydraulic connection 56. In the connection 56, which continues into the second housing 58, the receptacle 104 and then the receptacle 106 are arranged first, until the connection 56 leads into the fluid inlet 86 of the cylinder 90 of the second pressure generator 130. Thus, the connection 56 in the housing 58 also serves as a supply line, as is known from the first unit 24. The second pressure generator 130 is designed like the first pressure generator 88 and is accordingly provided with the same reference numerals in detail. Furthermore, the second hydraulic system 72 is designed largely like the first hydraulic system 70 in its receptacles 104, 106 and in its piping structure.The same applies to its function and circuitry. Therefore, further identical elements with the same reference numerals as in Fig. 2 are provided and are not described again here. With a circuitry and activation already described, a desired brake pressure can be generated by means of the pressure generator 130 and the system valve 124 via the pressure line 60 at the wheel connection 116 of the associated wheel brake 38. The two pressure generators 88, 130 and their respective system valves 124 can be controlled independently of each other. This allows different brake pressures to be set at the wheel brakes 36, 38. Likewise, a uniform brake pressure can also be provided if required. Thus, each unit 24, 26 is designed as an electro-hydraulic brake actuator, arranged as a decentralized and wheel-individual brake unit at the wheel brake 36, 38 of each associated wheel 12. With the two hydraulic systems 70, 72, which largely correspond, both housings 48, 58, including the lines and receptacles arranged therein, which are preferably manufactured as bores or milled recesses, are also largely identical in design. The sizes or external dimensions of the two housings 48, 58 are also preferably substantially the same. Particularly preferably, the housings 48, 58, with their lines and receptacles, are designed largely as in a known actuation unit of a two-box system of a decoupled power brake (DPB). This enables modular manufacturing according to a building block system, in which the units, as basic bodies, are designed as identically as possible and then, depending on the function, are only adapted to a small extent to the required function or to a specific vehicle model. This allows for considerable cost savings. For schematic illustration of largely identical housings 48, 58, Figures 2 and 3 are shown.3 and in Fig. 9 and Fig. 10, empty boxes outlined with dotted lines are shown, illustrating the positions of valves, whose associated receptacles are provided in the housing 48, 58 and, depending on the associated hydraulic system 70, 72, in the case of a dotted representation, serve only as dummies to standardize the manufacturing process. Furthermore, Fig. 4 shows an oblique view from the outside of the first unit 24 with its housing 48 and the reservoir 52 attached to it, and Fig. 5 shows an identical view of the second unit 26 with its housing 58. The same size and external dimensions of both housings 48 and 58, as well as the identical design of the respective motor side 66, can be seen. In addition, both units 24 and 26 each have a mounting element 132 for attaching them to the body of the vehicle 10. Furthermore, the first unit 24, as the main unit, can be mounted on the firewall 32 in both a regular and an inverted configuration. This means that by simply rotating it around the receptacle 106 along its longitudinal axis, space-saving arrangements can be achieved depending on the space requirements in the compartment 44. As shown in Fig. 4, a connection receptacle or receptacle 134 is provided on the motor side 66, arranged in the Z-direction 50 above between the motor 68 and the reservoir side 53, to which the hydraulic connection 56 from the first unit 24 to the second unit 26 is to be connected. Approximately in line below the receptacle 134, a receptacle 136 is provided, in which the wheel connection 116 for the wheel brake 36 is to be received. As shown in Fig. 5, a receptacle 138 is provided on the engine side 66 at the same position as the receptacle 134 located above, to which the hydraulic connection 56 of the second unit 26 is to be connected. Both receptacles 134 and 138 are thus positioned identically in their respective housings 48 and 58, and are also each located in an upper area to accommodate a possible idle position. Consequently, the hydraulic connection 56, which is connected to them via a brake line, is also located in the upper area of ​​the units 24 and 26. The receptacles 134 and 138 are preferably each designed with a thread for connecting the brake line. To achieve fluid flow from receptacle 134 to receptacle 138, the second unit 26 is positioned in the vehicle 10 in the Z-direction 50 below the first unit 24.Furthermore, a receptacle 140 is provided in the second housing 58 in the same position as the receptacle 136 of the first housing 48, in which the wheel connection 116 for the wheel brake 38 is to be received. Thus, with receptacles 134, 136 and receptacles 138, 140, two identically positioned port connections are created for each unit 24, 26. Fig. 6 shows a cross-section of the housing 48 and / or the housing 58, intersecting at right angles to the reservoir side 53 and motor side 66. The receptacle 104 is shown, extending from the control unit side 62 towards the motor side 66. Here, it is closed by a cup-shaped cover 108 and thus accommodates part of the volume 114. The receptacle 104 is designed and positioned like a receptacle for a pedal feel simulator, as is common in conventional hydraulic housings, e.g., in an actuation unit of a DPB system (see also Fig. 9). Fig. 7 shows a cross-section of the housing 48 and / or the housing 58, which intersects at right angles to the reservoir side 53 and parallel to the motor side 66. The receptacle 106 is shown, which extends as a blind hole into the narrow side 110, is closed there by the cover 112, is sealed by means of a sealing ring 142, and thus additionally accommodates the volume 114. The receptacle 106 is shaped and positioned like a hollow cylinder, which in known hydraulic housings serves as a receptacle for a master brake cylinder (see also Fig. 9). Figures 8, 9 to 10 show an embodiment of the braking system 22 which, unlike the first embodiment according to Figures 1, 2, 3, 4, 5, 6 to 7, allows the driver to apply the brakes hydraulically. This ensures that the driver can always brake in an emergency or in the event of a power failure. For the necessary redundancy, it is sufficient that the vehicle braking system 28 has only one power source 40. Elements already present in the first embodiment are designated with the same reference numerals. Fig. 8 shows that the first unit 24 is attached to the splash guard 32 in space 44, directly hydraulically coupled to the pedal unit 30, and located near the associated wheel 12. Furthermore, in addition to the hydraulic connection 56 between the reservoir 52 and the second unit 26, the first unit 24 has another hydraulic connection 144 from the first unit 24 to the second unit 26. There are two hydraulic connections 56 and 144 between the two units 24 and 26. As shown in Fig. 9, the first unit 24 has a pressure sensor 146, which is actuated by a pedal 148 of the pedal unit 30. The pedal 148 can be actuated by the driver, thereby moving a pedal rod 150 such that a piston 152 located in the receptacle 106 is pushed into the receptacle 106. A spring element 154 acts to return the piston 152 to its original position. The receptacle 106 here represents a cylinder for the piston 152, corresponding to a master brake cylinder, in this case a monomaster cylinder, as a pedal-actuated pressure generator 155. A pressure line 156 extends from the receptacle 106, is connected to the wheel connection 116, and a pressure sensor 157 is attached to it. The pressure sensor 157 monitors the availability of the hydraulic fallback system or backup.A normally open isolating valve 158 is provided in the pressure line 156. During normal operation of the brake system 22, this valve is closed when energized, thus isolating the pressure sensor 146 from the wheel connection 116 and also from the pressure generator 88. Pressure is then generated solely by the externally actuated pressure generator 88, from which the pressure line 54 leads to the wheel connection 116. In contrast to the first embodiment, a normally closed control valve 160 is arranged in the pressure line 54, which is open when energized during normal operation. In the event of a power failure, the isolation valve 158 is open and the control valve 160 is closed. This isolates the pressure generator 88, or rather its volume 102, from the wheel connection 116, thus preventing the brake system 22 from being elastically compressed by the volume 102 of the pressure generator 88. A rapid, targeted transfer of the pressure medium 80 from the receptacle 106 to the wheel connection 116 is achieved by means of the pressure transmitter 146. This ensures that brake pressure can be generated even in the event of a fault. Furthermore, the hydraulic system 70 of the first unit 24 preferably includes a simulator line 162 leading from the receptacle 106, to which a pedal feel simulator 164 is connected, the simulator having an axially displaceable piston 166. A normally closed control valve 168 is arranged in line 162 between the simulator 164 and the receptacle 106, upstream of the piston 166. In normal operation, the control valve 168 is open, and pressure generated by the driver when the pedal is actuated is routed to the simulator 164. A braking request from the driver is detected by a linear position sensor 170 arranged on the pedal rod 150, transmitted by the control unit 64 to the pressure generator 88, and a corresponding pressure is generated at the wheel connection 116. On the rear side of the piston 166, the simulator 164 is preferably connected by means of a line 172 to a third chamber 174 of the reservoir 52, which is fluid-separated from the first chamber 76 and the second chamber 78. The third chamber 174 is also connected to line 120, in which the system valve 124 is located, via a branch 176 from line 172 for pressure relief at the wheel connection 116. Thus, line 126, which connects the reservoir 52 to the wheel connection 116, is formed here by a portion of line 172 leading from the third chamber 174 to branch 176, by line 120, and by the portion of pressure line 54 leading from branch 118 to the wheel connection 116. Figures 9 and 10 show that the pressure sensor 146 is supplied with hydraulic fluid 80 from the first chamber 76 via the supply line 84 at its mounting 106. A line 178 extends from the mounting 106 parallel to the pressure line 156, from which line 162 branches off. Line 178 provides the additional hydraulic connection 144 between the first unit 24 and the second unit 26. Thus, the hydraulic connection 144 connects the pressure sensor 146 within its pressure range to the second unit 24. In the second unit 24, the associated second hydraulic system 72 is designed very similarly to the hydraulic system 70 of the first unit 24 described above. A normally open shut-off valve 180 is arranged in a section of the hydraulic connection 144 running within the housing 58. Furthermore, the hydraulic connection 144 extends to the wheel connection 116 of the wheel brake 38.Thus, when the isolating valve 180 is open, brake pressure can also be generated at the wheel brake 38 by means of the pressure sensor 146. A hydraulic backup is provided, whereby brake pressure can be generated at both wheel brakes 36 and 38 with only one pressure sensor 146. The availability of the backup is monitored separately in each unit 24 and 26 via the respective pressure sensor 157. Furthermore, the first unit 24 is designed with a total of four active valves 124, 158, 160, and 168, and the second unit with three active valves 124, 160, and 180, each in the same position in the housings 48 and 58. Fig. 11 shows an alternatively pedal-operated pressure transmitter 146, in which a tandem master brake cylinder with a first chamber 182 and a second chamber 184 is provided. The first chamber 182 is connected within the hydraulic system 70 of the first unit 24 to the wheel connection 116 of the wheel brake 36. The second chamber 184 is connected via the hydraulic connection 144 to the hydraulic system 72 of the second unit 26 and thus to the wheel connection 116 of the wheel brake 38.

Claims

Hydraulic brake system (22) for a vehicle (10) with a pressure medium reservoir (52) for compensating the storage of pressure medium (80) as well as a first hydraulic unit (24) and a second hydraulic unit (26), each of which hydraulic unit (24, 26) belongs to a wheel (12) of the vehicle (10), characterized in that both the first hydraulic unit (24) and the second hydraulic unit (26) are fluidly connected to the same pressure medium reservoir (52). Hydraulic brake system according to claim 1, characterized in that the pressure medium reservoir (52) belongs to the first hydraulic unit (24) and the second hydraulic unit (26) is fluidly coupled to the pressure medium reservoir (52) by means of a hydraulic connection (56), wherein in particular the pressure medium reservoir (52) is arranged on the first hydraulic unit (24). Hydraulic brake system according to claim 2, characterized in that no pressure medium reservoir (52) is arranged on the second hydraulic unit (26). Hydraulic brake system according to one of claims 1 to 3, characterized in that the pressure medium reservoir (52) has at least two chambers (76, 78, 174), of which a first chamber (76) is connected to a first hydraulic system (70) of the first hydraulic unit (24) and a second chamber (78) is connected by means of the hydraulic connection (56) to the second hydraulic unit (26) and an associated second hydraulic system (72) in a fluid-conducting manner. Hydraulic brake system according to claim 4, characterized in that at least one of the two hydraulic systems (70, 72) is designed such that a certain volume (114) of pressure medium (80) is integrated into the hydraulic system (70, 72) itself, wherein in particular the certain volume (114) corresponds to a volume (102) of a respective associated pressure generator (88, 130). Hydraulic brake system according to one of claims 1 to 5, characterized in that the first hydraulic unit (24) has a first pressure generator (88) connected to the pressure medium reservoir (52) by means of a supply line (84) in a fluid-conducting manner and the second hydraulic unit (26) has a second pressure generator (130) connected to the pressure medium reservoir (52) by means of the hydraulic connection (56), and in particular both pressure generators (88, 130) are adapted to independently increase, maintain or decrease a brake pressure at a respective associated wheel connection (116) as required. Hydraulic brake system according to one of claims 1 to 6, characterized in that at least one of the two hydraulic units (24, 26) each has a system valve (124) which is in particular open without current, which is arranged in a line (126) connecting the pressure medium reservoir (52) with a corresponding wheel connection (116) and which can each be controlled individually. Hydraulic brake system according to one of claims 1 to 7, characterized in that the first hydraulic unit (24) has a pressure transmitter (146) that can be actuated by a driver and which is fluidly connected to the second hydraulic unit (26) by means of a hydraulic connection (144), wherein in particular the first hydraulic unit (24) is to be attached to a firewall (32) of the vehicle (10). Hydraulic brake system according to claim 8, characterized in that the hydraulic connection (144) of the pressure transmitter (146) leads to a wheel connection (116) of the second hydraulic unit (26) and a separating valve (180) which is open in particular without current is arranged in the hydraulic connection (144) and the pressure transmitter (146) is connected to a wheel connection (116) of the first hydraulic unit (24) by means of a pressure line (156) and a separating valve (158) which is open in particular without current is arranged in the pressure line (156). Hydraulic brake system according to one of claims 6 to 9, characterized in that in at least one of the two hydraulic units (24, 26) a control valve (160) is provided in each pressure line (54, 60) between the respective associated pressure generator (88, 130) and the respective associated wheel connection (116), in particular a normally closed control valve (160).

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