Brake system for motor vehicle having pressure supply device

Abstract

A brake system (2) for a motor vehicle, comprising an electrically controllable pressure supply (6) and a pressure modulator (10) to which hydraulic wheel brakes (88, 92, 124, 128) are connected, the brake system further comprising a reservoir (80) for brake fluid, the electrically controllable pressure supply device (6) has a control regulating unit (60) which is connected at a signal input to the brake request device (20), the electrically controllable pressure supply device (6) being connected to the reservoir (80) via at least one equalization port (164, 168) in a stationary state.

Description

[0001] The invention relates to a brake system for a motor vehicle, comprising an electrically controllable pressure supply and a pressure modulator to which hydraulic wheel brakes are connected, and a reservoir for a brake fluid.

[0002] The electrification of vehicles is increasing, and this trend is leading to brake systems that are no longer vacuum-dependent in terms of brake pressure generation. An example of a vacuum-independent brake system is a brake system with a brake master cylinder operated by a brake pedal and an electrically controllable pressure supply. Here, an electric motor moves the hydraulic piston of the pressure supply in order to provide the desired pressure. In normal operating mode (drive-by-wire operating mode), at least during braking, the brake pedal is decoupled from the two brake circuits and connected to a simulator that generates the pedal feel. However, these systems still have a mechanical / hydraulic connection from the brake pedal to the hydraulic wheel brakes or a hydraulic fallback stage in which the driver can generate braking forces on the wheels in an unamplified manner by muscle power and with the help of the hydraulic transmission ratio of the brake system.

[0003] In the case of semi-autonomous or fully autonomous vehicles, the driver is not always actively involved in the driving situation. Therefore, a second electrically controllable pressure regulator is required so that braking can still be achieved in the event of a failure of the main pressure regulator.

[0004] Brake-by-wire systems are also gaining in importance due to the development of modular vehicle construction systems or skateboard chassis. The need for greater flexibility and freedom in the arrangement of brake system components is becoming increasingly evident.

[0005] The components that generate the brake pressure are referred to below as pressure supply devices or pressure supply means. The brake pressure generated is the same for all wheels and is therefore referred to as central pressure. If the pressure at individual wheels is to be limited (for example because the wheels must be slip-controlled), the pressure modulator of the brake system takes on this task.

[0006] DE 10 2010 024 739 A1 discloses a vehicle brake system comprising an electrically operated brake force generator arranged between a brake pedal and a tandem brake master cylinder and a pneumatic pedal simulator connected to the brake pedal. The tandem brake master cylinder is actuated by the driver in a mechanical fallback stage via the brake pedal. The pneumatic pedal simulator comprises a housing with a compression chamber and comprises a device for reducing the volume of the compression chamber.

[0007] DE 10 2019 213 886 A1 describes a braking system for a motor vehicle, which comprises an ESC module and an electric brake booster, wherein a pedal simulator unit comprising a brake pedal with a mechanical gap is connected upstream of the electric brake booster so that the brake booster is mechanically actuated by the brake pedal once the mechanical gap has been closed.

[0008] A disadvantage of the above-described systems with a mechanical / hydraulic connection from the brake pedal to the hydraulic wheel brakes and a hydraulic backup stage is that they have severe restrictions regarding their installation in the vehicle. These mechanical components must be designed and positioned so that the driver can manipulate them from the driver's seat. This manipulation can be ensured purely mechanically by a linkage or by hydraulic transmission via a remote pedal actuation unit (remote PAU). However, the flexibility is also limited in this case. When an electronic brake pedal is used, this mechanical connection is omitted.

[0009] Purely electric brake systems are known, in which the driver's brake request is transmitted purely electrically. However, an electronic brake pedal for detecting the driver's request without a hydraulic connection to the brake system requires redundancy in the generation of the braking force, ideally with a very high degree of fail-safety.

[0010] If hydraulic brake calipers are used in brake systems which are still based entirely or only partially on hydraulic energy transmission, new types of brake force actuators are required which are intended to displace the volume of brake fluid and thereby generate pressure in the brake system.

[0011] The invention is based on the object of specifying a braking system with hydraulic wheel brakes which has a high level of fail-safety and high availability in the event of a fault, in which braking system a braking request can be generated or received electrically.

[0012] According to the invention, this object is achieved by a brake system as claimed in claim 1 .

[0013] The pressure supply device has a control and regulation unit which is connected at a signal input to the brake request device, wherein the pressure supply device is connected to the reservoir via at least one equalization port in the stationary state.

[0014] The dependent claims relate to advantageous developments of the invention.

[0015] The invention is based on the consideration that it is advantageous to provide brake pressure generation decoupled from the driver by means of a brake force regulator (pressure supply) which acts as a main pressure regulator and volume regulator. The system should work in conjunction with an electronic brake pedal which captures the driver's request or calculates its braking demand in an autonomous vehicle. The brake force regulator (pressure supply) should work in conjunction with an ESC system or a pressure modulator which can be used as a redundant pressure regulator and still be used for wheel control functions.

[0016] As a further requirement, such a system should have a high degree of fail-safety and high availability in the event of a fault. Problems with residual pressures, which occur, for example, when the integrated parking brake (IPB) is applied or in the event of component expansion, should be avoided. The system should have redundancy in terms of pressure regulation and optional redundancy for the integrated parking brake. The system should have few components and therefore be cost-effective to manufacture. In the event of wear, it should be possible to supply brake fluid to the brake system. Finally, the demand for a brake system with a purely electronic brake pedal should be met. Problems with residual pressures, which occur, for example, when the integrated parking brake (IPB) is applied or in the event of component expansion, should be avoided.

[0017] It has now been recognized that these requirements can be met by a brake force regulator (electrically controllable pressure supply) that works in conjunction with an ESC system or a pressure modulator that can be used as a redundant pressure regulator and still be used for wheel control functions.

[0018] The electrically controllable pressure supply device is connected to the reservoir via at least one equalization port in the rest state.

[0019] The rest state of the pressure supply device is preferably a non-actuated state of the pressure supply device.

[0020] The electrically controllable pressure supply device preferably cannot be actuated mechanically or hydraulically by the driver via the brake pedal.

[0021] The braking system preferably does not include a driver-operated mechanical and / or hydraulic fallback stage.

[0022] In an advantageous embodiment, the brake request device is in the form of an electronic brake pedal or in the form of an autonomous driver, in particular a controller or sensor receiving electrical information from a pressure regulator via CAN. The electronic brake pedal preferably comprises redundant pedal sensors for acquiring pedal position or pedal travel / pedal angle.

[0023] The pressure modulator is preferably electrically controllable and has at least one electrically actuatable inlet valve for each of the hydraulic wheel brakes.

[0024] The electrically controllable pressure supply device, the pressure modulator and the brake request device are preferably designed as three separate modules or components. In this case, it is particularly preferred that a hydraulic connection exists only between the electrically controllable pressure supply device and the pressure modulator.

[0025] The pressure supply device and the pressure modulator are preferably connected to one another via two hydraulic, pressure-resistant connecting lines. No additional hydraulic connecting lines are provided between the pressure supply device and the pressure modulator. No hydraulic connecting lines are provided between the pressure supply device and the brake request device, and no hydraulic connecting lines are provided between the pressure modulator and the brake request device.

[0026] The pressure modulator advantageously has a separate control and regulation unit which is connected to the brake request device at the signal input. In the event of a failure in the signal connection between the brake request device and the control and regulation unit, the brake request is still available in the other control and regulation unit, so that redundancy in terms of control and regulation is created. In an alternative advantageous embodiment, only one control and regulation unit is provided, which has two separate circuit boards, wherein the control and regulation routine for the pressure supply device is implemented by software and / or hardware on the first circuit board and the control and regulation routine for the pressure regulator is implemented by software and / or hardware on the second circuit board.

[0027] The pressure modulator advantageously has at least one electrically controllable pressure regulator. In this way, if a fault or failure occurs in the pressure supply device, the pressure modulator can still build up the brake pressure.

[0028] The corresponding pressure regulator is preferably in the form of a pump. If two different pumps (eg a plunger pump and a double piston pump) are used here, their respective disadvantages can be compensated. By using a double piston pump, costs can be saved.

[0029] In a preferred embodiment, the two control and regulation units are configured such that, in the event of a fault or failure of one of the two control and regulation units, the other control and regulation unit takes over the control and regulation tasks of the faulty or failed control and regulation unit.

[0030] The pressure supply device advantageously comprises a cylinder-piston device having a main chamber and a secondary chamber, and comprises a motor that can be controlled by a control and adjustment unit, and also comprises a main piston that can be moved into the main chamber by a rotation-translation mechanism. The main chamber and the secondary chamber are advantageously separated from each other by a secondary piston (floating piston). Both the main chamber and the secondary chamber are particularly preferably hydraulically connected or hydraulically connectable to the reservoir through an equalization port and a corresponding equalization line in a stationary state (i.e., in an unactuated state of the cylinder-piston device with a retracted (main) piston). The corresponding spring element is particularly preferably arranged in the main chamber and the secondary chamber, and when the motor is not actuated, the spring element moves the main piston and the floating piston to an unactuated state or keeps them in an unactuated state (e.g., at a rear stop).

[0031] Preferably, two brake circuits are formed in the pressure modulator, wherein each brake circuit is hydraulically connected to two wheel brakes, each wheel brake being assigned a corresponding inlet valve and a corresponding outlet valve.

[0032] The primary chamber is preferably connected to one brake circuit of the pressure modulator via a single first hydraulic connection line and the secondary chamber is preferably connected to the other brake circuit of the pressure modulator via a single second hydraulic connection line.

[0033] At least two wheel brakes are advantageously equipped with an integrated parking brake. In this way, a third electronic brake actuation unit is provided, which can be used to brake the vehicle or to safely park the vehicle. If these are assigned redundantly to the controller, the pressure regulator and the pressure regulator, parking can also be performed redundantly.

[0034] The brake system preferably has a pressure sensor in the pressure modulator, which is connected at a signal input to the at least one open-loop control unit.

[0035] The advantages of the invention are in particular that a pressure regulator (electrically controllable pressure supply device) and a pressure modulator (component of an ESC system) can be used together with an electronic brake pedal. Due to the signal redundancy of the wheel speed sensors, in addition to the normal wheel-specific ABS control by means of the pressure modulator in the event of a malfunction, an emergency ABS can furthermore be implemented with a central pressure by means of the pressure regulator. The system has redundancy in terms of pressure setting and optional redundancy for an integrated parking brake. The brake system has few components and is inexpensive to manufacture. In the event of wear, the brake system can still be supplied with brake fluid. The IPB function can be assigned to the ECUs of the pressure modulator and the pressure regulator in order to ensure redundancy for the integrated parking brake.

[0036] Exemplary embodiments of the invention will be explained in more detail below with reference to the accompanying drawings, in which, in a highly schematic view:

[0037] Figure 1 A first schematic diagram showing a braking system,

[0038] Figure 2 A second schematic diagram of a brake system is shown.

[0039] In both Figures, identical parts are provided with the same reference numerals.

[0040] Figure 1 The brake system 2 shown comprises an electrically controllable pressure supply 6, a (e.g. electrically controllable) pressure modulator 10, hydraulic wheel brakes 14, and a brake request device 20. As in the present case, the brake request device 20 can be in the form of a pedal unit with an electronic brake pedal 24 with redundant pedal sensors or alternatively in the form of an autonomous driver (level 5).

[0041] The pressure supply device 6 or pressure supply means cooperates with an electronic brake pedal 24, which determines the driver's braking request or the driver's manipulation and transmits it to the pressure supply device 6, which is indicated by the arrow 28. Similarly, the driver's braking request is redundantly forwarded to the pressure modulator 10, which is indicated by the arrow 30. The pressure supply device 6 generates the desired pressure in the brake system 2. If necessary, the pressure modulator 10 regulates the wheel brake pressure in the wheel brake 14, in particular based on a control function (such as a wheel slip controller).

[0042] The brake system 2 further comprises wheel speed sensors which are connected at their signal input to a control and regulation unit 60 (arrow 34) of the pressure supply 6 and to a control and regulation unit 64 (arrow 38) of the pressure modulator 10, see Figure 2 .

[0043] Figure 2 A further schematic diagram of a brake system 2 is shown. An electrically controllable pressure supply device 6 is in the form of a (dual-circuit) linear actuator comprising a cylinder-piston arrangement 40 with a primary piston 44 which can be moved back and forth into a hydraulic primary chamber 48 and a floatingly mounted secondary piston 52 which can be moved into a secondary chamber 54. The pressure supply device 6 comprises an electric motor 68 and an in particular redundant motor position sensor 72. By means of a rotation-translation mechanism 76, for example in the form of a ball screw drive, the rotation of the rotor of the electric motor 68 is converted into a translation of the primary piston 44. In the rest state (unactuated state) of the pressure supply device 6, the two chambers 48, 54 are connected to a reservoir 80 for brake fluid via equalization ports 164, 168 ("compensation holes") and equalization lines 170, 174.

[0044] The use of a cylinder-piston arrangement 40 with a compensating hole ensures communication with the atmosphere and thus a reduction in residual pressure in the system. It is also ensured that in the event of wear, brake fluid can continue to flow from the brake fluid container or reservoir 80 into the system. There is a double circuit, which is always ensured even if the supply energy fails.

[0045] The main chamber 48 of the cylinder-piston arrangement 40 is hydraulically connected to a first brake circuit 84 formed in the pressure regulator 10, to which two wheel brakes 88, 92 are connected. A corresponding electrically actuatable inlet valve 100, 104 and a corresponding electrically actuatable outlet valve 104, 108 are assigned to each wheel brake 88, 92. In addition, a pump 112 and a low-pressure accumulator 116 are arranged in the first brake circuit 84.

[0046] The secondary chamber 54 of the cylinder-piston arrangement 40 is hydraulically connected to a second brake circuit 120 formed in the pressure modulator 10, to which two wheel brakes 124, 128 are connected. A respective inlet valve 132, 134 and a respective outlet valve 140, 144 are assigned to each wheel brake 124, 128. In addition, a pump 148 and a low-pressure accumulator 152 are arranged in the first brake circuit 84.

[0047] For faults with a high FIT rate, it is necessary to be able to operate the pressure supply 6 independently of the pressure regulator 10. Therefore, the control and regulation functions are distributed between two different controllers or control and regulation units 60, 64, or alternatively at least between two different ECU circuit boards. In the event of an electrical fault in the control and regulation unit 60, 64 or circuit board, the remaining parts can further enable the generation of braking force.

[0048] Regardless of whether an electrical or mechanical fault occurs in the pressure supply 6, all four wheels are decelerated by the pressure modulator 10. The pressure build-up is produced by the corresponding pumps 112, 148 in the pressure modulator 10. In this case, the required brake fluid volume is obtained from the pressure supply 6.

[0049] In the event of a leak, the dual circuit of the brake system 2 ensures that at least 50% of the brake pressure of the hydraulic system can still be built up. In addition, this proportion can be increased by isolating the leak or by using the integrated parking brake as a brake force modulator. Leaks are identified with the aid of the brake fluid sensor 156 or are detected by increased volume absorption during pressure generation. The pressure sensor 160 in the pressure modulator 10 is used to ensure pressure generation.

[0050] The pressure supply device does not have any valves. The pressure supply device has only two sensors, specifically the motor position sensor 72 or the position sensor of the drive and the brake fluid level sensor 156. This enables simple operation with little requirement for operating software. Both the diagonal partitioning and the front-rear partitioning of the brake system 2 can be represented by the described combination of the pressure supply device 6 and the pressure modulator 10. Therefore, the brake system can be easily adapted to the vehicle.

[0051] List of Reference Numerals

[0052] 2 Braking system

[0053] 6 Pressure supply device

[0054] 10. Pressure regulator

[0055] 14 Wheel brakes

[0056] 20 Brake request device

[0057] 24 Brake pedal

[0058] 28 Arrow

[0059] 30 Arrow

[0060] 34 Arrow

[0061] 38 Arrow

[0062] 40 Cylinder Piston Assembly

[0063] 44 Main piston

[0064] 48 main chamber

[0065] 52 Auxiliary piston

[0066] 54 Sub-chamber

[0067] 60 Control and regulation unit

[0068] 64 Control and regulation unit

[0069] 68 Motor

[0070] 72 Motor position sensor

[0071] 76 Rotation-Translation Mechanism

[0072] 80 Storage

[0073] 84 First brake circuit

[0074] 88 Wheel brakes

[0075] 92 Wheel brakes

[0076] 96 Inlet valve

[0077] 100 Inlet valve

[0078] 104 Outlet valve

[0079] 108 Outlet valve

[0080] 112 Pumps

[0081] 116 Low pressure accumulator

[0082] 120 Second brake circuit

[0083] 124 Wheel brakes

[0084] 128 Wheel brakes

[0085] 132 Inlet valve

[0086] 134 Inlet valve

[0087] 140 Outlet valve

[0088] 144 Outlet valve

[0089] 148 Pump

[0090] 152 Low pressure accumulator

[0091] 156 Brake fluid sensor

[0092] 160 Pressure Sensor

[0093] 164 Balance port

[0094] 168 Balance port

[0095] 170 Balanced pipeline

[0096] 174 Balanced pipeline

Claims

1. A braking system (2) for a motor vehicle, the braking system comprising an electrically controllable pressure supply device (6) and a pressure modulator (10), to which hydraulic wheel brakes (88, 92, 124, 128) are connected, the braking system also comprising a reservoir (80) for brake fluid, the electrically controllable pressure supply device (6) having a control regulating unit (60) connected to a brake request device (20) at a signal input, the electrically controllable pressure supply device (6) being connected to the reservoir (80) via at least one equalization port (164, 168) in a stationary state.

2. The brake system (2) according to claim 1, wherein: The brake request device (20) is in the form of an electronic brake pedal (24) or in the form of an autonomous driver.

3. The braking system (2) according to claim 1 or 2, wherein: The pressure modulator (10) has a control and regulating unit (64) which is connected at a signal input to the brake request device (20).

4. The brake system (2) according to claim 3, wherein: The pressure modulator (10) includes at least one pressure regulator.

5. The brake system (2) according to claim 4, wherein: The respective pressure regulator is in the form of a pump (112, 148).

6. The brake system (2) according to any one of claims 3 to 5, wherein: The two control and regulation units (60, 64) are configured such that, in the event of a fault or failure of one of the two control and regulation units (60, 64), the other control and regulation unit (60, 64) takes over the control and regulation tasks of the faulty or failed control and regulation unit (60, 64).

7. A braking system (2) as claimed in any one of the preceding claims, wherein: The electrically controllable pressure supply device (6) comprises a cylinder piston device (40) having a main chamber (48) and a secondary chamber (54), and also comprises a motor controllable by a control and adjustment unit (60) and a main piston (44), which can be moved into the main chamber (48) under the action of a rotation and translation mechanism (76).

8. A braking system (2) as claimed in any one of the preceding claims, wherein: The electrically controllable pressure supply device (6) cannot be actuated mechanically or hydraulically by the driver using the brake pedal.

9. The brake system (2) as claimed in any one of the preceding claims, wherein: The braking system does not include a driver operated mechanical and / or hydraulic backup stage.

10. The brake system (2) as claimed in any one of the preceding claims, wherein: Two brake circuits (84, 120) are formed in a pressure modulator (10), wherein each brake circuit (84, 120) is hydraulically connected to two wheel brakes (88, 92; 124, 128), and each wheel brake (88, 92; 124, 128) is assigned a corresponding inlet valve (132, 134) and a corresponding outlet valve (140, 144).

11. The brake system (2) as claimed in any one of the preceding claims, wherein: At least two wheel brakes (88, 92; 124, 128) are equipped with integrated parking brakes.

12. The brake system (2) as claimed in claim 1, comprising a pressure sensor (160) in the pressure modulator (10), which is connected at a signal input to at least one control and regulation unit (60, 54).

13. The brake system (2) as claimed in any one of the preceding claims, wherein: The electrically controllable pressure supply device (6), the pressure modulator (10) and the brake request device (20) are designed as three separate modules or components, wherein, in particular, only a hydraulic connection exists between the electrically controllable pressure supply device (6) and the pressure modulator (10).

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