External pressure device with cylinder chamber

Abstract

The invention relates to an external force pressure device (10), in particular for a hydraulic assembly (12) of a vehicle brake system (14), comprising a housing (18) having a motor side (26) for receiving a motor (16) driving the external force pressure device (10), and a controller side (28) opposite the motor side (26), the controller side is used for placing a controller (32) for regulating and controlling the motor (16); a cylinder (46) arranged in the housing (18), the cylinder extending with its cylinder axis (48) from the motor side (26) to the controller side (28); a piston (22) is guided in the cylinder (46) in an axially displaceable manner, a cylinder chamber (80) is delimited by a piston end face (76) of the piston, the cylinder chamber (80) is a first cylinder chamber (80), and an additional second cylinder chamber (84) is provided in the cylinder (46).

Description

Field of the Invention

[0001] The present invention relates to an external force pressure device, in particular for a hydraulic assembly of a vehicle braking system, the external force pressure device having: a housing having a motor side and a controller side opposite the motor side, the motor side being for accommodating a motor for driving the external force pressure device, and the controller side being for accommodating a controller for regulating the motor; a cylinder disposed in the housing, the cylinder extending from the motor side to the controller side with its cylinder axis; and a piston that is guided axially displaceably in the cylinder, and a cylinder chamber is defined by a piston end face of the piston. The present invention also relates to the use of such an external force pressure device in a hydraulic assembly of a vehicle braking system. Background Art

[0002] In motor vehicles, such as motorcycles, passenger vehicles or trucks, known vehicle braking systems are used to provide a regulated braking pressure at the associated wheel brakes, thereby enabling slip regulation. The core of such an adjustable braking system is a hydraulic assembly having hydraulic structural elements, which are usually connected to a master brake cylinder. The master brake cylinder is actuated by the driver via a pedal and is thus used to generate a braking pressure at the wheel brakes connected via brake lines. To regulate the braking pressure, there are provided hydraulic structural elements to be controlled by a controller, such as solenoid valves, sensors and usually electrically operated pressure devices.

[0003] In today's braking systems, especially in electronically controlled braking systems, an external force pressure device operated by an electric motor itself serves as an external force source for generating a braking pressure at the wheel brakes. The resulting braking pressure is in this case transmitted to the wheel brakes by means of a hydraulic or electromechanical actuator. In this normal braking situation, the master brake cylinder is decoupled from the wheel brakes and is used to detect the driver's braking request. In the event of a failure of the external force source, a hydraulic backup level is provided by the master brake cylinder, which the driver can operate via the pedal.

[0004] Recent vehicle developments have also enabled driving with an increasing degree of automation, which has placed new requirements on braking systems. In order to no longer require driver intervention, it must be possible in particular to generate pressure in a particularly reliable and operationally safe manner, especially by means of an external force source. Summary of the Invention

[0005] It is an object of the present invention to provide an external force pressure device that provides a particularly compact and cost-effective design for generating pressure, which is in addition particularly safe in operation.

[0006] According to the present invention, an external force pressure device is provided, which is particularly used for a vehicle braking system or a hydraulic assembly of a braking system. The external force pressure device has: a housing or a hydraulic housing, which has a motor side and a controller side opposite to the motor side. The motor side is used to place a motor for driving the external force pressure device, and the controller side is used to place a controller for regulating the motor; a cylinder block arranged in the housing, and the cylinder block extends from the motor side to the controller side along its cylinder axis; and a piston, which is guided axially movable in the cylinder block, and a cylinder chamber is defined by the piston end face of the piston. Herein, the cylinder chamber is the first cylinder chamber, and an additional second cylinder chamber is also provided in the cylinder block. Herein, the second cylinder chamber is particularly designed to be separated from the first cylinder chamber from each other, so that the pressure medium contained in the first cylinder chamber does not contact the pressure medium contained in the second cylinder chamber.

[0007] Thus, by means of the second cylinder chamber according to the present invention between the motor side and the controller side, an external force cylinder is formed, and the external force cylinder has two cylinder chambers that are particularly separated from each other in terms of the pressure medium. Therefore, braking pressure can be generated at at least one relevant wheel brake of the relevant braking circuit from each cylinder chamber. This means that the braking pressures generated by the external force pressure device can be separately guided into two braking circuits. A redundant operation mode can be achieved.

[0008] In addition, by arranging the two cylinder chambers between the motor side and the controller side, a particularly compact arrangement in the housing is achieved. Herein, the cylinder axis of the cylinder block extends perpendicular to the motor side or the controller side, thereby determining the Y axis or the Y direction. The housing thickness of the housing extends along the Y axis, and the housing thickness is preferably designed to be relatively narrow compared to the housing height extending along the Z axis or the housing length extending along the X axis. The cylinder block having two cylinder chambers protrudes beyond the preferably narrow housing thickness. Preferably, according to the volume requirement, the cylinder block is extended by means of a cup-shaped cylinder head, and the cylinder head closes the relevant cylinder opening on the controller side. For the same purpose, the cylinder block is preferably extended by means of a housing molding part protruding from the controller side. Particularly preferably, the cylinder block is completely accommodated in the housing along its cylinder axis, and if a larger volume is required, the housing thickness of the housing is adjusted or the diameter of the cylinder block is increased accordingly. For a larger volume, increasing the diameter requires less space and is more compact in the X direction and the Z direction compared to increasing the length in the Y direction.

[0009] In contrast, a traditional master brake cylinder, especially operated by a pedal, is arranged in the housing, and the axis of the housing is parallel to the motor side and thus parallel to the X axis or along the housing length. Preferably, in order to save space and components, such a master brake cylinder is not provided in the hydraulic assembly related to the external force pressure device according to the present invention.

[0010] In contrast, according to the present invention, the external force pressure device is advantageously arranged to be used only or solely for generating braking pressure at at least one wheel brake of the relevant braking system in the hydraulic assembly. Thus, the external force pressure device is advantageously the only braking pressure generator in the relevant hydraulic assembly and braking system. This enables a very compact arrangement in the housing with only a single braking pressure generator that extends axially from the motor side through the housing to the controller side. Moreover, the relevant braking system is then a true brake-by-wire system, namely a so-called True-Brake-By-Wire-Bremssystem. This significantly saves components, weight, and cost.

[0011] Advantageously, in the external force pressure device according to the present invention, the second cylinder chamber is arranged axially behind the first cylinder chamber in the compression direction of the piston. This axial arrangement of the two cylinder chambers is particularly compact and is particularly easy to implement in terms of structural technology. Alternatively, a more complex structural arrangement is also possible, which is very compact in terms of structure and can be applied as needed. Preferably, the two cylinder chambers are arranged radially, where in particular, one cylinder chamber surrounds the other cylinder chamber radially, or alternatively, the two cylinder chambers are preferably arranged adjacent to each other.

[0012] Furthermore, according to the present invention, it is advantageous that another piston coupled to the piston in a force-transmitting manner is arranged axially behind the piston in the compression direction of the piston. Thus, the piston is the primary piston, and the other piston is the secondary piston, with the secondary piston depending on the movement of the primary piston. In this case, it is preferred that the other piston is coupled to the piston in a force-transmitting manner by means of a spring, where the spring is particularly arranged axially between the two pistons and is preferably designed as a helical spring. Moreover, the other piston is supported on the cylinder by means of a return spring that is also preferably designed as a helical spring. This means that a piston and support system known from the traditional tandem master cylinder are selected, enabling the cost-effective use of known components.

[0013] Furthermore, according to the invention, it is advantageous that the piston is axially moved by means of a motor-driven threaded drive. Thereby, the rotational movement of the motor shaft assigned to the motor is mechanically converted into a translational movement of the piston. The reverse conversion is also easily achievable. For this purpose, the threaded drive has a screw with a thread and a nut that surrounds the screw in a hollow cylindrical manner and engages in the thread. Thus, the piston can be moved in a very finely adjustable manner. Preferably, the threaded drive or the screw drive is designed in a component-saving manner as a trapezoidal threaded drive, where the nut slides directly on the trapezoidal thread of the screw. Particularly preferably, the screw drive is designed as a ball screw drive with very little friction, where balls serving as rolling supports are provided between the screw and the nut.

[0014] According to the invention, it is advantageous that a first discharge line is led out from the first cylinder chamber, and the first discharge line is used to supply pressure medium to the first brake circuit, and a second discharge line is led out from the second cylinder chamber, and the second discharge line is used to supply pressure medium to the second brake circuit. Here, both brake circuits are assigned to an adjustment device, and the adjustment device is used to adjust the brake pressure generated at at least one wheel brake assigned to the corresponding brake circuit by means of an external force pressure device, and the brake pressure is used for slip control or an electronic stability program. Thereby, a connection from the adjustment device to the actuation device is established by means of these two discharge lines, and the external force pressure device is advantageously assigned to the actuation device as the sole brake pressure generator.

[0015] Furthermore, according to the invention, it is advantageous that a first input line is introduced into the first cylinder chamber, the first input line is connected to the first storage chamber of a two-part storage, and a second input line is introduced into the second cylinder chamber, the second input line is connected to the second storage chamber of the two-part storage, where, in particular, radial sealing elements are provided on both sides of each input line axially along the cylinder axis. Here, the sealing elements are in particular arranged in sealing grooves or recesses in the relevant cylinder wall and extend radially from the sealing grooves into the cylinder and radially surround the piston. With this sealing, separation of the pressure medium in the two cylinder chambers is achieved. Furthermore, with two separate storage chambers that exchange pressure medium with the relevant cylinder chambers respectively, a separate pressure medium supply is achieved. Thereby, even in case of a failure, for example, in case of a leak in one pressure medium supply, it is still always possible to build up brake pressure at at least one wheel brake relevant there in the assigned brake circuit by means of the other pressure medium supply. In particular, in combination with two discharge lines respectively led from the cylinder chambers to their respective assigned brake circuits, brake circuit separation is achieved, and a redundant brake system with two hydraulically separated brake circuits is provided by this brake circuit separation.

[0016] Advantageously, the motor is arranged on the motor side of the housing, the controller is arranged on the controller side of the housing, and a passage is arranged through the housing from the motor side to the controller side. The electrical connection between the motor and the controller is guided through this passage. Thereby, a compact and short control connection through the thickness of the housing is provided.

[0017] Furthermore, according to the invention, it is advantageous to provide a pressure detection device by which the pressure in the first cylinder chamber and / or the pressure in the second cylinder chamber can be detected. Here, the pressure is in particular the pressure of the pressure medium located in the respective cylinder chamber. By detecting this pressure, in particular pressure monitoring is achieved, by which the tightness of the corresponding relevant sealing element can be monitored simultaneously. For this purpose, the pressure detection device is preferably provided with a pressure sensor which can be easily installed in the housing and directly read by means of the electronics of the controller's circuit board. Thereby, an externally pressurized device which is particularly safe during operation is provided.

[0018] Furthermore, the invention also relates to an application of such an externally pressurized device in a hydraulic assembly of a vehicle braking system, wherein in the hydraulic assembly, advantageously, only by means of such an externally pressurized device and the motor driving the externally pressurized device, braking pressure is generated at at least one relevant wheel brake. In particular, in this case, the externally pressurized device belongs to an actuating device by which braking pressure is generated at at least one relevant wheel brake.

[0019] Advantageously, the hydraulic assembly further has a regulating device in addition to the actuating device, by which the braking pressure generated at at least one relevant wheel brake is regulated. Here, the regulating device includes a pump motor for driving at least one pump, by which the braking pressure generated by means of the externally pressurized device is regulated. In this case, the regulating device is a known electronic stability program system (ESP system).

[0020] Furthermore, the invention also relates to an application of such an externally pressurized device in a hydraulic assembly of a vehicle braking system having a first brake circuit and a second brake circuit, for generating hydraulic pressure at at least one relevant wheel brake respectively. Here, it is advantageous that braking pressure is generated at at least one first wheel brake and / or at least one second wheel brake only by means of the externally pressurized device.

[0021] Accordingly, the present invention also relates to a hydraulic assembly of a vehicle braking system and a vehicle braking system, wherein the hydraulic assembly and the vehicle braking system have an external force pressure device designed in such a way. In this case, the external force pressure device is advantageously only or solely used for generating braking pressure, so that no additional pressure generator is provided, and in particular, no pedal-operated master brake cylinder is provided. This provides a very compact hydraulic assembly and braking system, especially in the case of no driver intervention, which enables increasingly more highly safe autonomous driving.

[0022] Generally speaking, in the external force pressure device according to the present invention, the primary piston is preferably constructed, and advantageously the secondary piston, as well as an advantageous spring and, for example, an advantageous sealing element, are constructed in a manner similar to the known tandem master brake cylinder technology. In the best case, the components required for this are taken from traditional pressure generation schemes. By using known components and the resulting scale effect (Mengeneffekt), manufacturing costs can be saved to a large extent. Description of the Drawings

[0023] The embodiments of the solution according to the present invention will be explained in more detail below with reference to the attached schematic drawings. Among them:

[0024] Figure 1 A schematic longitudinal sectional view showing an embodiment of the external force pressure device according to the present invention is shown;

[0025] Figure 2 Shows a vehicle braking system provided with the external force pressure device according to Figure 1 A hydraulic wiring diagram of an embodiment variant of the vehicle braking system. Detailed Description of the Invention

[0026] Figure 1 The external force pressure device 10 or the pressure device 10 of the hydraulic assembly 12 shown partially is shown, and the hydraulic assembly is used for Figure 2 The electrohydraulic vehicle braking system 14 or the braking system 14 schematically shown in. The braking system 14 is provided for the vehicle braking equipment of a four-wheel vehicle not shown. The braking system is required to meet the functions of an anti-lock braking system (ABS), an electronic stability program (ESP), and / or a traction control system (ASR).

[0027] The pressure device 10 is designed as a plunger device and is driven by a motor 16 designed as an electric motor. The motor 16 itself is known and is shown only very schematically. The motor 16 represents the external force driver of the braking system and is thus part of the external force vehicle braking equipment. Here, the motor 16 is assigned to the pressure device 10, so that the pressure device serves as a brake pressure generator for generating brake pressure. Thus, the pressure device 10 is an external pressure source in the braking system 14, which is designed as a linear control braking system in the current case. In this case, the energy required for the brake pressure is provided only by the relevant external energy source.

[0028] In terms of structural technology, the hydraulic assembly 12 has a hydraulic housing 18 or housing 18, which is only partially shown and is designed as a hydraulic block. In the housing 18, a channel 20 is arranged, which is designed as a stepped hole. The channel 20 forms an external force cylinder receiving part, in which a piston 22 serving as an external force piston is received, and the piston is designed as a plunger or a plunger piston. In addition, the channel 20 extends axially perpendicular to the housing side serving as the motor side 26 to the opposite housing side serving as the controller side 28 with its channel axis 24 coinciding with the piston axis. The Y-axis of the virtual Cartesian coordinate system is defined by the channel axis 24, and the housing 18 with a housing thickness 29 extends along the Y-axis between the motor side 26 and the controller side 28. Here, the motor 16 is arranged with its motor housing 30 on the motor side 26, and the electronic controller 32 is arranged on the controller side 28. Parallel to the channel axis 24, another channel 34 extending completely through from the motor side 26 to the controller side 28 is provided, and this another channel has a significantly smaller cross-sectional diameter compared to the channel 20. The electrical connection 36 is guided through the another channel 34, and the controller 32 and the motor 16 are coupled to each other in a signal-transmitting manner by means of this electrical connection.

[0029] The channel 20 is designed to be open at its first end 38 facing the motor 16 and extends with its second end 40 facing the controller 32 to a distance 42 from the controller side 28. Thus, a rigid bottom 44 of the cylinder 46 formed by the channel 20 is provided by means of the distance 42, and the cylinder has a cylinder axis 48 coinciding with the channel axis 24. Here, the cylinder 46 is completely formed by the channel 20. Alternatively, the cylinder 46 is formed with the channel 20 and a cup-shaped cylinder head coaxial with the extension of the channel 20 or a housing forming structure coaxial with the extension of the channel 20 (both not shown).

[0030] The piston 22, designed as a first or primary piston, is cup-shaped and has a circular cross-section, and can be axially reciprocated by a motor 16 by means of a threaded drive 50. When the piston 22 moves into the cylinder block 46, a pressure is generated in the cylinder block 46 along the compression direction 52. In the compression direction 52 of the piston 22, another piston 56 is arranged axially behind the piston 22, and the other piston is coupled to the piston 22 in a force-transmitting manner by means of a coaxially arranged spring 54 and accordingly moves together with the first piston 22. The other piston 56, designed as a second or secondary piston, is supported on the bottom 44 of the cylinder block by means of a coaxially arranged return spring 58.

[0031] In addition, a screw 60 is accommodated inside the cup-shaped first piston 22, and the screw is surrounded by a hollow cylindrical thin-walled nut 62. The nut 62 engages in a form-fitting manner from the outside into a screw thread 64 formed on the screw 60. In addition, the nut 62 is surrounded on the end side facing the motor 16 by a rotary bearing 66, and the rotary bearing is fixedly held on the outside by a cup-shaped bearing cover 68 fixedly connected to the housing 18. The nut 62, rotatably supported by means of the rotary bearing 66, is rotated by means of the motor 16, and this rotary motion causes the screw 60 to move via the screw thread 64 and thus causes the piston 22 in the cylinder block 46 to move. For this purpose, a transmission 70, designed here as a planetary gear transmission, is used to drive the screw 60, and the transmission is coupled to a motor shaft 72 assigned to the motor 16 in a force-transmitting manner. The motor shaft 72, the transmission 70, the screw 60 and the nut 62 together with the motor 16 are assigned to an actuator 74, and by means of this actuator, the piston 22 can be optionally moved back and forth in the cylinder block 46 depending on the rotation direction of the motor 16.

[0032] To this end, the piston 22 has a piston end face 76 at its end facing the actuator 74. The first cylinder chamber 80 is defined by the piston end face together with the housing 18 surrounding the passage 20 and the piston end face 78 of the second piston 56 facing the piston 22. Here, the second piston 56 is designed such that its longitudinal section is double-T-shaped. Specifically, the piston end face 78 of the second piston 56 is designed to be cup-shaped and open in the direction of the first piston 22. The spring 54, designed as a helical spring here, is axially received in part with its outer circumference in this cup-shaped form and is supported axially and radially there. On the second piston 56, opposite the piston end face 78, there is another cup-shaped piston end face 82, which is designed to be open in the direction of the cylinder bottom 44. Correspondingly there, the return spring 58, also designed as a helical spring, is axially received in part with its outer circumference in the cup-shaped form and is supported axially and radially. The second cylinder chamber 84 is defined by the cylinder bottom 44, the housing 18, which usually surrounds the passage 20, and the piston end face 82. The second cylinder chamber is axially arranged behind the first cylinder chamber 80 in the compression direction 52. Thus, the two cylinder chambers 80 and 84 are designed to be axially movable and their axial extent variable depending on the positions of the two relevant pistons 22 and 56.

[0033] The first cylinder chamber 80 is connected to the first storage chamber 88 via a first input line 86 in a fluid-conducting or pressure-medium-conducting manner. The first storage chamber 88 belongs to a reservoir 90, which serves as a pressure-medium storage container for compensatingly storing the pressure medium or the brake fluid. A second storage chamber 92 is provided in the reservoir 90, which is separate from the first storage chamber 88 in terms of the pressure medium. The second storage chamber is connected to the second cylinder chamber 84 via a second input line 94 in a fluid-conducting manner. For this purpose, the two input lines 86 and 94 preferably each extend into a relatively narrow groove 96 arranged in the passage 20.

[0034] On both axial sides of the first input line 86, in each radially surrounding groove 98 arranged in the passage 20, an annular radially surrounding sealing element 100 is respectively arranged. Each sealing element 100 projects radially from the groove 98 into the passage 20 here and seals the first piston 22 radially. Similarly, on both axial sides of the second input line 94, in each radially surrounding groove 102, an annular radially surrounding sealing element 104 is respectively arranged, which seals the second piston 56 radially correspondingly. Thus, the two relevant cylinder chambers 80, 84 are each designed to be sealed relative to each other and thus separated from each other in terms of the pressure medium. To monitor the tightness of the sealing elements 100, 104, a pressure detection device 106 coupled to the first cylinder chamber 80 is provided. The pressure detection device 106 is designed as a pressure sensor and is connected to the controller 32 in a signal-transmitting manner.

[0035] Furthermore, a first discharge line 108, which is only shown here very schematically, is guided from the first cylinder chamber 80 at a location approaching the second piston 56 along the compression direction 52. The first discharge line 108 supplies a pressure medium from the first cylinder chamber 80 to a first brake circuit 110 of the brake system 14. Correspondingly, a second discharge line 112 is guided from the second cylinder chamber 84 at a location approaching the bottom 44 of the cylinder block, and this second discharge line supplies a pressure medium to a second brake circuit 114 of the brake system 14.

[0036] During operation, when the first piston 22 and the second piston 56 coupled thereto are moved out of the cylinder block 46, fluid is sucked into the two cylinder chambers 80, 84 through the input lines 86, 94 serving as suction lines. Here, the cylinder chambers 80, 84 serve as suction chambers. When the first piston 22 and the second piston 56 coupled thereto are moved into the cylinder block 46, the sucked fluid is pressurized, and in this case, the cylinder chambers 80, 84 serve as pressure chambers, and pressures are generated by these pressure chambers for the brake system 14. The fluid is transferred from the cylinder chambers 80, 84 to the respectively associated brake circuits 110, 114 through the discharge lines 108, 112 to generate a braking pressure at the respectively associated wheel brakes 116. Thereby, the pressure device 10 forms an actuating device 118 for generating a braking pressure accordingly.

[0037] Figure 2 It is shown that in the associated brake system 14, the pressure device 10 is the only brake pressure generator in the actuating device 118. To adjust the generated brake pressure, an ESP system serving as an adjustment device 120 is connected to the actuating device 118.

[0038] Specifically, for this purpose, the first discharge line 108 is fluid-conductively connected to a first supply line 122, or rather, the first discharge line corresponds to the first supply line 122 of the first brake circuit 110. Furthermore, a first control valve 124, or rather, a plunger control valve, is arranged in the first supply line 122, which is designed as a normally open 2 / 2-way solenoid valve and can be closed by applying an electric current when needed. The first supply line 122 extends, by means of a branched line bundle, through two first inlet valves 126 arranged in parallel connection, respectively, to the respectively associated wheel brakes 116. Here, the two wheel brakes 116 of the first brake circuit 110 are respectively connected to a common first return line 130 through the respective first discharge valves 128, and the first return line 130 is provided with a first pump 132 on the suction side. Here, the term "line" can also be understood as a branched or re-merged line bundle as necessary.

[0039] Correspondingly, in the second brake circuit 114, the second discharge line 112 is connected in a fluid-conducting manner to the second supply line 134, in which a normally open second control valve 136 is arranged. The second supply line 134 leads to two second inlet valves 138, at which wheel brakes 116 are respectively connected. The two wheel brakes 116 of the second brake circuit 114 are respectively connected to a common second return line 142 via associated second discharge valves 140 and are thus connected to the second pump 144 on the suction side. Furthermore, a pump motor 146 is provided between the two brake circuits 110 and 114, by means of which the two pumps 132 and 144 are driven. By means of the pumps 132, 144 and the pump motor 146 and by means of the corresponding, per se known connection relationships of the inlet valves 126, 138 and the discharge valves 128, 140, the brake pressure generated at the wheel brakes 116 by means of the pressure device 10 is adjusted as required.

[0040] Thus, the external force pressure device 10 for a brake-by-wire system according to the invention provides an optimized brake pressure generator, which is combined with a known standard regulating device 120 (ESP system) by means of two hydraulic discharge lines 108, 112 and thus forms a redundant brake system 14. In particular, a particularly cost-optimized design is thereby achieved, which uses components that are already available in large quantities, such as the motor 16, the pistons 22 and 56, the spring 54, the return spring 58 and the sealing elements 100, 104. Furthermore, the arrangement of the motor 16 on one side of the housing 18 and the controller 32 on the opposite controller side 28 enables assembly on a unified ESP assembly line. Since no special investment is required, this significantly reduces the manufacturing costs.

Claims

1. An external force pressure device (10), in particular an external force pressure device for a hydraulic assembly (12) of a vehicle brake system (14), the external force pressure device comprising: - a housing (18), the housing comprising a motor side (26) and a controller side (28) opposite to the motor side (26), the motor side being used to accommodate a motor (16) for driving the external force pressure device (10), and the controller side being used to accommodate a controller (32) for regulating the motor (16); a cylinder (46) arranged in the housing (18), which extends with its cylinder axis (48) from the motor side (26) to the controller side (28); and a piston (22) which is guided in the cylinder (46) so as to be axially displaceable and whose piston end face (76) delimits a cylinder chamber (80), It is characterized in that The cylinder chamber (80) is a first cylinder chamber (80), and an additional second cylinder chamber (84) is provided in the cylinder (46).

2. The external force pressure device according to claim 1, It is characterized in that The external force pressure device (10) is provided in the hydraulic assembly (12) for generating brake pressure only at at least one wheel brake (116) of an associated vehicle brake system (14).

3. The external force pressure device according to claim 1 or 2, It is characterized in that The second cylinder chamber (84) is arranged axially behind the first cylinder chamber (80) in the compression direction (52) of the piston (22).

4. The external force pressure device according to any one of claims 1 to 3, It is characterized in that A further piston (56) is arranged axially behind the piston (22) in the compression direction (52) of the piston (22), and is coupled to the piston (22) in a force-transmitting manner. It is characterized in that the further piston (56) is coupled to the piston (22) in a force-transmitting manner by means of a spring (54).

5. The external force pressure device according to any one of claims 1 to 4, It is characterized in that The piston (22) can be moved in the axial direction by means of a screw transmission (50) which can be driven by the motor (16).

6. The external force pressure device according to any one of claims 1 to 5, It is characterized in that A first discharge line (108) is led out from the first cylinder chamber (80) and is used to supply pressure medium to a first brake circuit (110), and a second discharge line (112) is led out from the second cylinder chamber (84) and is used to supply pressure medium to a second brake circuit (114).

7. The external force pressure device according to any one of claims 1 to 6, It is characterized in that A first supply line (86) is introduced into the first cylinder chamber (80), the first supply line being connected to a first storage chamber (88) of a two-part reservoir (90), and a second supply line (94) is introduced into the second cylinder chamber (84), the second supply line being connected to a second storage chamber (92) of the two-part reservoir (90), wherein radial sealing elements (100, 104) are provided on both sides of each supply line (86, 94), in particular axially along the cylinder axis (48).

8. The external force pressure device according to any one of claims 1 to 7, It is characterized in that A pressure detection device (106) is provided, by means of which the pressure in the first cylinder chamber (80) and / or the pressure in the second cylinder chamber (84) is detected.

9. Use of an external force pressure device (10) according to any one of claims 1 to 8 in a hydraulic assembly (12) of a vehicle brake system (14) having a first brake circuit (110) and a second brake circuit (114) for generating a hydraulic pressure at at least one associated wheel brake (116), in, the first brake circuit (110) comprises a first supply line (122) to which at least one first wheel brake (116) can be connected, and, the second brake circuit (114) comprises a second supply line (134) to which at least one second wheel brake (116) can be connected, as well as, - An electrically controllable external pressure device (10) is provided, wherein the external pressure device comprises: A housing (18), the housing having a motor side (26), on which a motor (16) for driving the external force pressure device (10) is arranged, and the housing also having a controller side (28) opposite to the motor side (26), on which a controller (32) for regulating the motor (16) is arranged; and a cylinder (46) arranged in the housing (18), the cylinder extending with its cylinder axis (48) from the motor side (26) to the controller side (28); as well as a piston (22) which is guided in the cylinder (46) so as to be axially displaceable and which, with its piston end face (76), delimits a cylinder chamber (80) filled with a pressure medium, It is characterized in that the cylinder chamber (80) is a first cylinder chamber (80) filled with a pressure medium, and an additional second cylinder chamber (84) filled with a pressure medium is provided in the cylinder (46), wherein the first cylinder chamber (80) is optionally connected to the first supply line (122) in a manner of conducting a pressure medium, and the second cylinder chamber (84) is optionally connected to the second supply line (134) in a manner of conducting a pressure medium.

10. Use of the external force pressure device according to claim 9, It is characterized in that Braking pressure is generated at at least one first wheel brake (116) and / or at least one second wheel brake (116) solely by means of the external force pressure device (10).

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