Electrohydraulic assisted vehicle braking system for autonomous land vehicles

Abstract

The present invention relates to an electro-hydraulic assisted vehicle brake system (1) for a motor vehicle that is driven autonomously on public roads. The present invention proposes that a assisted brake pressure generator (3) of the assisted vehicle brake system (1) is connected to the vehicle brake system (1) by means of two hydraulically parallel assisted valves (4, 31), and the two assisted valves (4, 31) are controlled by means of two redundant electronic controllers (10, 11).

Description

Technical Field

[0001] The present invention relates to an electrohydraulic power-assisted vehicle brake system according to the invention for a land vehicle capable of autonomous driving on public roads up to level 4 or level 5. The designation "autonomous driving" relates to the possibility of autonomous driving, but the vehicle brake system according to the invention can also be used for land vehicles that do not drive autonomously or for land vehicles with a lower level of autonomy. Background Art

[0002] In order to achieve autonomous driving levels 4 (driver intervention may be required) and 5 (the highest level, no driver required), a redundant power-assisted vehicle braking system is required that excludes complete failure of the vehicle braking system with a probability of near safety without the need for driver intervention.

[0003] Publication DE 10 2014 220 440 A1 discloses an electrohydraulic assisted vehicle brake system having two brake units, each of which includes a assisted brake pressure generator with an electrically controllable pressure source and a brake pressure regulating valve assembly for each wheel brake. A brake unit is connected to the other brake unit, and hydraulic wheel brakes are connected to the one brake unit, so that the wheel brakes can be actuated using the one brake unit and, through the one brake unit, the other brake unit. This allows the wheel brakes to be actuated using the other brake unit without driver intervention in the event of a fault or failure of one brake unit. The active brake unit regulates the wheel brake pressure in the wheel brakes. Summary of the Invention

[0004] The electrohydraulic assisted vehicle braking system according to the present invention is designed for autonomous driving on public roads up to levels 4 and 5. Level 4 is also known as highly automated driving and means that the electronic system permanently takes over vehicle control, and driver intervention is required only when the system is no longer capable of the driving task. Level 5 is also known as fully automated and does not require a driver. However, the vehicle braking system according to the present invention can also be used for lower levels and non-autonomous driving.

[0005] The electrohydraulic assisted vehicle brake system according to the present invention comprises a assisted brake pressure generator to which one or more hydraulic wheel brakes are connected via two assisted valves hydraulically connected in parallel. In a multi-circuit vehicle brake system, one brake circuit is connected to the assisted brake pressure generator via two assisted valves hydraulically connected in parallel. One or more additional brake circuits can each be connected to the assisted brake pressure generator via one or two assisted valves hydraulically connected in parallel. It is also conceivable to connect the wheel brakes and / or one or more brake circuits to the assisted brake pressure generator via more than two assisted valves hydraulically connected in parallel.

[0006] Alternatively or additionally, one or more power-assisted valves can have independent actuating devices, for example two electromagnets.

[0007] Furthermore, the electro-hydraulic assisted vehicle brake system according to the present invention has at least two electronic controllers for redundantly controlling the vehicle brake system. Control can also be understood as regulation. "Control" refers, in particular, to the control of electrical components of the vehicle brake system, such as the electric motor of the assisted brake pressure generator, and / or to the control of electro-hydraulic components, such as solenoid valves. "Redundant" means that the vehicle brake system can be operated using each of the two electronic controllers, even if only limited auxiliary braking can be achieved using one controller, for example, using only some of the wheel brakes of the vehicle brake system to build up brake pressure more slowly and / or to achieve a lower braking force. Assisted service braking can be achieved using one of the two controllers or using both controllers together. More than two controllers are also possible.

[0008] The present invention increases the availability of a power-assisted vehicle brake system with little effort. In particular, the present invention can be implemented with minimal modifications to known hydraulic power-assisted vehicle brake systems.

[0009] A power-assisted valve is in particular a solenoid valve which is referred to here as a power-assisted valve for the purpose of clarifying its designation.

[0010] The remainder of the disclosure has as its subject matter advantageous embodiments and developments of the invention specified in the claims.

[0011] The power-assisted vehicle brake system according to the invention preferably has two or more redundant power sources, in particular batteries, in order to ensure the power supply to the electronic control unit and the electrohydraulic and electrical components of the vehicle brake system. Each power source should be capable of operating at least one electronic control unit and at least a portion of the components of the vehicle brake system, thereby enabling the vehicle brake system to be actuated, even if only with limited auxiliary braking.

[0012] To increase the availability of the booster brake pressure generator, further sections of this disclosure provide for an electric motor having two or more windings or winding groups, with which the electric motor can be independently operated to drive the booster brake pressure generator. "Independently operable" means that the electric motor can be operated by energizing any of the windings or winding groups.

[0013] Another alternative is to provide a second booster brake pressure source, which can be used to actuate the vehicle brake system if the booster brake pressure generator fails. The second booster brake pressure source can, for example, comprise a pressure accumulator, which can be used to actuate the vehicle brake system once or, preferably, multiple times. The second booster brake pressure source can also, for example, comprise a booster brake pressure generator having, for example, a hydraulic pump driven by an electric motor or an electromechanically drivable piston-cylinder unit. The second booster brake pressure source does not exclude an electric motor having two or more windings or winding groups.

[0014] All features disclosed in the description and drawings can be realized in embodiments of the invention individually or in principle in any combination. In principle, embodiments of the invention are possible which do not have all but only one or more features of the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The hydraulic circuit diagram of the electrohydraulic assisted vehicle brake system 1 according to the invention is shown.

[0016] The invention is explained in detail below with reference to the embodiments shown in the accompanying drawings. Figure 1 A hydraulic circuit diagram of an electrohydraulic power-assisted vehicle brake system according to the present invention is shown. DETAILED DESCRIPTION

[0017] The electro-hydraulic assisted vehicle brake system 1 according to the present invention, shown in the accompanying drawings, is configured for autonomous driving of a land vehicle, i.e., a passenger car, on public roads up to Level 4 or Level 5. Level 4 represents autonomous driving in which driver intervention may be required, while Level 5 represents the highest level, i.e., autonomous driving in which no driver intervention is required. Lower levels and non-autonomous driving are also possible.

[0018] The vehicle brake system 1 according to the invention is designed as a dual-circuit vehicle brake system having four hydraulic wheel brakes 2 , two hydraulic wheel brakes each being connected to one of the two brake circuits I, II.

[0019] Vehicle brake system 1 includes a power-assisted brake pressure generator 3 to which two brake circuits I and II are connected via solenoid valves, referred to herein as power-assisted valves 4, 31, and 32. A first brake circuit I, which can also be understood as a primary circuit, is connected to power-assisted brake pressure generator 3 via a first power-assisted valve 4 and a second power-assisted valve 31 hydraulically connected in parallel with first power-assisted valve 4, so that first brake circuit I can selectively be acted upon by brake pressure from power-assisted brake pressure generator 3 via the first, second, or both power-assisted valves 4 and 31. Another second brake circuit II, which can also be understood as a secondary circuit, is connected to power-assisted brake pressure generator 3 via another power-assisted valve 32.

[0020] Alternatively, the first booster valve 4 (through which the first brake circuit 1 is connected to the booster brake pressure generator 3) has two electromagnets, so that if one electromagnet fails, the first booster valve can be switched using the other electromagnet. In this case, the second booster valve 31 can (but is not necessarily) be omitted.

[0021] In the embodiment of the invention shown and described, first booster brake pressure generator 3 has a piston-cylinder unit 5, whose piston 6 can be moved axially in a cylinder 9 by means of an electric motor 7 via a screw drive 8 or another rotation-translation conversion drive to generate brake pressure. The piston-cylinder unit 5 can also be referred to as a plunger unit, and the piston 6 can be referred to as a plunger.

[0022] Vehicle brake system 1 includes two electronic controllers 10 and 11 for redundantly controlling vehicle brake system 1, where control can also be understood as regulation. "Controlling vehicle brake system 1" refers to the control of electrohydraulic components, such as solenoid valves, electrical components, such as electric motor 7, and possibly other components of vehicle brake system 1. "Redundant" means that components are selectively controlled using one of the two controllers 10 and 11, so that if either controller 10 or 11 fails, the other controller 11 or 10 can control vehicle brake system 1. It is sufficient that, in the event of a failure of the first of the two controllers 10, limited auxiliary braking can be achieved using the second of the two controllers 11. For service braking, vehicle brake system 1 is controlled jointly by first controller 10 or both controllers 10 and 11. Limited auxiliary braking can, for example, mean that only one of the two brake circuits 1 is pressurized, thereby actuating only the wheel brakes connected to that brake circuit 1, or that brake pressure is built up more slowly.

[0023] For control and in particular for regulation, the two electronic controllers 10, 11 receive signals from sensors of the vehicle brake system 1, such as pressure sensors, wheel rotation sensors, rotation angle sensors and current sensors of the electric motor 7 of the power brake pressure generator 7, wherein the two controllers 10, 11 can receive signals from all sensors or signals from selected sensors.

[0024] In order to increase its availability, the vehicle brake system 1 has two batteries as redundant power sources 12 , wherein each control unit 10 , 11 is connected to one of the two power sources 12 .

[0025] The electric motor 7 of the booster brake pressure generator 3 has two windings 13, each of which is connected to one of the two power sources 12. The electric motor 7 can be operated with each of the two windings 13 independently of the other winding 13.

[0026] Electric motor 7 is selectively controlled by each of two controllers 10, 11. First controller 10 controls first and second booster valves 4, 32, via which both brake circuits I, II are connected to booster brake pressure generator 3. Second controller 10 controls second booster valve 31, hydraulically connected in parallel with first booster valve 4 (via which first brake circuit I is additionally connected to booster brake pressure generator 3), so that first brake circuit I can always be actuated in the event of failure of first controller 10 and / or one of booster valves 4, 31, 32. If first booster valve 4 has two electromagnets, one electromagnet is controlled by first controller 10 and the second electromagnet by second controller 11.

[0027] Via fourth booster valve 33, a brake circuit (in this embodiment, the first brake circuit 1) is connected to a hydraulic accumulator serving as a booster brake pressure source 14. This hydraulic accumulator contains pressurized brake fluid and can be pressurized, for example, by booster brake pressure generator 3. In the event of failure of booster brake pressure generator 3, multiple braking operations can preferably be performed using booster brake pressure source 14. Instead of a hydraulic accumulator, booster brake pressure source 14 can also comprise a hydraulic pump or piston-cylinder unit driven by an electric motor, such as booster brake pressure generator 3 (not shown). Booster brake pressure source 14 can therefore also be a booster brake pressure generator. This pressure source is referred to as a booster brake pressure source 14 because it is not actuated by muscle force but rather by external energy. In this embodiment, fourth booster valve 33 is controlled by second controller 11. Therefore, in the event of failure of first controller 10, wheel brakes 2 connected to first brake circuit 1 can be actuated in a controlled manner using brake pressure from booster brake pressure source 14 by second controller 11. The booster brake pressure source 14 makes the second winding 13 of the electric motor 7 of the booster brake pressure regulator 3 unnecessary.

[0028] Each wheel brake 2 has an inlet valve 15 and an outlet valve 16 , which are connected to the corresponding brake circuits I and II via the inlet valves. The wheel brakes 2 are connected to a pressureless brake fluid reservoir 17 via the outlet valves. The inlet valves 15 and outlet valves 16 form a brake pressure regulating valve assembly, which can be used to individually regulate the wheel brake pressure in each wheel brake 2 . Together with the booster brake pressure generator 3 , slip control, particularly anti-lock braking, drive slip, and / or driving dynamics control or an electronic stability program, is possible. The abbreviations ABS, ASR, and / or FDR, or ESP are commonly used for such slip control. Driving dynamics control and electronic stability programs are also colloquially referred to as anti-slip control systems. Such slip control is well known per se and will not be explained in detail here.

[0029] The vehicle brake system 1 according to the present invention has a dual-circuit master brake cylinder 19 that can be actuated using a brake pedal 18. Two brake circuits I and II are connected to the dual-circuit master brake cylinder via a respective isolating valve 20. Service braking is performed as power-assisted braking using power-assisted brake pressure generator 3, for which purpose the first and further power-assisted valves 4 and 32 are opened. Isolating valve 20 is closed, thereby hydraulically isolating master brake cylinder 19 from brake circuits I and II.

[0030] During non-autonomous driver operation, the master brake cylinder 19 serves as a setpoint value generator for the brake pressure to be generated or adjusted. To displace brake fluid from the master brake cylinder 19 and move the brake pedal 18 when the isolating valve 20 is closed, a pedal travel simulator 21 is connected to the master brake cylinder 19 via a simulator valve 22 in one of the two brake circuits—in this embodiment, the first brake circuit 1. The pedal travel simulator 21 is a spring-loaded hydraulic accumulator. Even in the event of failure of the booster brake pressure generator 3, the vehicle brake system 1 can be actuated using the master brake cylinder 19 during driver operation.

[0031] The master brake cylinder 19 is connected to a pressureless brake fluid reservoir 17 , wherein in one of the two brake circuits, in the present embodiment in the first brake circuit I, a reservoir valve 34 is arranged between the brake fluid reservoir 17 and the master brake cylinder 19 .

[0032] In the described and illustrated embodiment of the present invention, valves 4, 15, 16, 20, 21, 31, 32, 33, 34, etc., are provided as 2 / 2-way solenoid valves, wherein the inlet valve 15 and the outlet valve 16 can also be combined to form a 3 / 3-way solenoid valve (not shown). In this embodiment, the boost valves 4, 31, 32, 33, the outlet valve 16, the isolating valve 20, and the simulator valve 20 are closed in their de-energized initial positions, while the inlet valve 15, the isolating valve 20, and the storage container valve 34 are open in their de-energized initial positions.

[0033] The first and further power-assisted valves 4 , 32 , the inlet valve 15 , the outlet valve 16 , the separation valve 20 and the simulator valve 22 are controlled by the first electronic controller 10 , and the second and fourth power-assisted valves 31 , 33 and the reservoir valve 34 are controlled by the second electronic controller 11 .

[0034] The components of vehicle brake system 1, including brake fluid reservoir 17, wheel brakes 2, controllers 10 and 11, power supply 12, and booster brake pressure source 14, are housed in hydraulic assembly 23. Hydraulic assembly 23 is a rectangular metal block with holes that serve as receptacles for the components of vehicle brake system 1. These receptacles are connected to one another via holes drilled in hydraulic assembly 23 according to the hydraulic circuit diagram. With these components assembled, hydraulic assembly 23 forms the hydraulic unit of vehicle brake system 1. Wheel brakes 2 are connected to hydraulic assembly 23 via brake lines, and brake fluid reservoir 17 is mounted on hydraulic assembly 23. However, brake fluid reservoir 23 can also be located at a different location and connected to the hydraulic assembly via brake fluid lines. Booster brake pressure source 14 is also connected to hydraulic assembly 23 via brake lines. However, this booster brake pressure source can also be located on or within hydraulic assembly 23 (if space is available). The hydraulic assembly 23 only has to be modified to accommodate the second power-assisted valve 31 and, if present, the fourth power-assisted valve 33 and to connect the power-assisted brake pressure source 14 .

[0035] The two control units 10 , 11 are electrically insulated from one another, spatially and electrically separated from one another, and are arranged in a fluid-tight manner on different sides of the hydraulic assembly 23 .

Claims

1. An electro-hydraulic assisted vehicle brake system (1) for a land vehicle that is driven autonomously on public roads, comprising a assisted brake pressure generator (3) and a first electronic controller (10) for controlling the vehicle brake system (1), wherein: A hydraulic wheel brake (2) is connected to the booster brake pressure generator (3) via a first booster valve (4), characterized in that a second booster valve (31) is hydraulically connected in parallel with the first booster valve (4) and / or the first booster valve (4) has two independent operating devices, and the vehicle brake system (1) has a second electronic controller (11) for redundantly controlling the vehicle brake system (1), wherein a first brake circuit (I) is connected to the booster brake pressure generator (3) via the first booster valve (4) and the second booster valve (31), wherein one operating device is controlled by the first electronic controller (10) and the other operating device is controlled by the second electronic controller (11).

2. The electro-hydraulic power-assisted vehicle brake system according to claim 1, characterized in that: The vehicle brake system (1) has two redundant power supplies (12).

3. The electro-hydraulic power-assisted vehicle brake system according to claim 1, characterized in that: The first power-assisting valve (4) is controlled by the first electronic controller (10) and the second power-assisting valve (31) is controlled by the second electronic controller (11).

4. The electro-hydraulic power-assisted vehicle brake system according to any one of claims 1 to 3, characterized in that: The second booster valve (31) is controlled by the second electronic controller (11), all other electro-hydraulic structural elements (4, 20, 22, 31, 32, 33) of the vehicle brake system (1) are controlled by the first electronic controller (10), and the booster brake pressure generator (3) is selectively controlled by the first or second electronic controller (10, 11).

5. The electro-hydraulic power-assisted vehicle brake system according to any one of claims 1 to 3, characterized in that: The vehicle brake system (1) has a brake fluid storage container (17), which is connected to the vehicle brake system (1) via a storage container valve (34) controlled by the second electronic controller (11).

6. The electro-hydraulic power-assisted vehicle brake system according to any one of claims 1 to 3, characterized in that: The boost brake pressure generator (3) has an electric motor (7) with two windings (13), with which the electric motor (7) can be operated independently.

7. The electro-hydraulic power-assisted vehicle brake system according to any one of claims 1 to 3, characterized in that: The vehicle brake system (1) has, in addition to the booster brake pressure generator (3), a second booster brake pressure source (14).

8. The electro-hydraulic power-assisted vehicle brake system according to any one of claims 1 to 3, characterized in that: The two electronic controllers (10, 11) are electrically insulated from each other and / or electrically separated from each other and / or individually fluid-tight.

9. The electro-hydraulic power-assisted vehicle brake system according to any one of claims 1 to 3, characterized in that: The vehicle brake system (1) has a brake pressure regulating valve assembly for regulating the wheel brake pressure in the wheel brake (2).

10. The electro-hydraulic power-assisted vehicle brake system according to any one of claims 1 to 3, characterized in that: The vehicle brake system (1) has a master brake cylinder (19) by means of which the wheel brakes (2) can be actuated.

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