Service brake with hydraulic multi-circuit power assistance for a vehicle

Abstract

The invention proposes connecting the wheel brakes (2) of the vehicle axle of a hydraulic dual-circuit power-assisted vehicle brake system (1) for an electric or hybrid vehicle to the brake circuits (I, II) and loading the two brake circuits (I, II) with brake pressure by means of a power-assisted brake pressure generator (5) in time-offset fashion. As a result, the deceleration effect of the electric motor (23) of the vehicle, which operates as a generator during braking, can be compensated.

Description

Technical Field

[0001] This invention relates to a service braking method using a hydraulic multi-circuit power-assisted vehicle braking system, characterized by the features of this disclosure. Specifically, it involves operating the wheel brakes of the hydraulic multi-circuit power-assisted vehicle braking system by generating hydraulic braking pressure through power assistance. The service braking is the defined operation of the vehicle braking system or its wheel brakes. Other braking operations are possible. Background Technology

[0002] International patent application WO 2012 / 150 120 A1 discloses a hydraulic dual-circuit power-assisted vehicle braking device with an electro-hydraulic power-assisted braking pressure generator. The electro-hydraulic power-assisted braking pressure generator has a piston-cylinder unit, in which the piston is movable within the cylinder via a screw drive by means of an electric motor to generate braking pressure. Hydraulic wheel brakes are connected to the power-assisted braking pressure generator or to their cylinders via power-assisted valves for each braking circuit and inlet valves for each wheel brake. The wheel brakes are each connected to an unpressurized brake fluid reservoir via outlet valves. The wheel braking pressure in each wheel brake can be individually adjusted using the inlet and outlet valves. For auxiliary braking in the event of a power-assisted braking pressure generator failure, known vehicle braking devices have a manually operable master brake cylinder that is hydraulically separated from the braking circuit during service braking by the closure of a release valve. The master brake cylinder functions as a setter for braking pressure during service braking. Summary of the Invention

[0003] The vehicle braking device for implementing the service brake according to the invention is configured as a hydraulic multi-circuit-assisted vehicle braking device. It has an assist-brake pressure generator, with two or more brake circuits connected to the generator via an assist valve for each circuit. Each brake circuit has one or more hydraulic wheel brakes. Each wheel brake is connected to its respective brake circuit via an inlet valve, and each wheel brake has an outlet valve through which the wheel braking pressure can be reduced. The wheel braking pressure is the braking pressure in the wheel brake. The outlet valve connects the wheel brake, for example, to one or more hydraulic accumulators or one or more unpressurized brake fluid storage containers, thereby reducing the wheel braking pressure in the associated wheel brake by opening the outlet valve.

[0004] The booster-brake pressure generator can, for example, have a piston-cylinder unit, in which the piston can be moved within the cylinder of the piston-cylinder unit via a screw drive and an electric motor to generate braking pressure. Another feasible option is a hydraulic pump that can be driven by an electric motor as the booster-brake pressure generator. These examples are merely illustrative and not exhaustive.

[0005] To perform service braking according to the invention, the booster-brake pressure generator generates braking pressure in the brake circuit. The booster-brake pressure generator applies braking pressure, i.e., brake circuit pressure, to the wheel brakes of this brake circuit through an open inlet valve and when the outlet valve is closed, and operates accordingly. The booster valve of the pressure-loaded brake circuit is either open or closed, while the booster valves of other brake circuits are either closed or closed. The brake circuit pressure is the hydraulic pressure or braking pressure present in the brake circuit.

[0006] The brake circuit pressure can also be generated in multiple brake circuits together with the booster-brake pressure generator. Alternatively, the brake circuit pressure can be generated first in all brake circuits or in multiple brake circuits together using the booster-brake pressure generator, and after reaching a certain brake circuit pressure, the brake circuit pressure in one or more brake circuits can be further increased using the booster-brake pressure generator, and the other brake circuits can be separated from the booster-brake pressure generator by closing the booster valves of the other brake circuits, so that their brake circuit pressures do not increase further.

[0007] The other braking circuits may be pressureless and their wheel brakes may be unoperated, or they may be under pressure and their wheel brakes may be operated. While pressure is being generated in one or more braking circuits using the booster-brake pressure generator, the braking circuit pressure in the other braking circuits—whose booster valves are closed—cannot be changed by the booster-brake pressure generator. It is possible to reduce the braking circuit pressure or wheel brake pressure in the other braking circuits by opening the outlet valve of the wheel brake, thereby reducing the braking force of the wheel brake.

[0008] This disclosure also includes improvement plans and advantageous design solutions.

[0009] In each braking circuit, the braking circuit pressure can be reduced independently of each other by opening the outlet valve of at least one wheel brake connected to the corresponding braking circuit when the inlet valve is open. This disclosure specifies the use of the booster-brake pressure generator to reduce the braking circuit pressure in one or more braking circuits, for which the booster valve of the corresponding braking circuit has been opened or closed and the booster valves of the other braking circuits have been closed or closed. The braking circuit pressure can be increased, kept constant, and reduced using the booster-brake pressure generator.

[0010] According to the present invention, a booster-brake pressure generator is used to generate, increase, maintain a constant level, and / or decrease the brake circuit pressure in the brake circuit when the timing is staggered. It is possible to apply brake pressure to a brake circuit having the same brake circuit pressure, together with the booster-brake pressure generator.

[0011] Provided that the vehicle braking device has a master brake cylinder that can be manually operated, the master brake cylinder is preferably hydraulically separated from the braking circuit during the service braking according to the invention as explained above, by the closure of the release valve.

[0012] This disclosure specifies that the wheel brakes of an axle are connected to a braking circuit, thereby applying the same braking circuit pressure to the wheel brakes. By closing the inlet valves of one or more wheel brakes in the braking circuit and opening their outlet valves, the wheel braking pressure can be reduced below the braking circuit pressure. Slip adjustment can be performed, for example, using the inlet and outlet valves.

[0013] The vehicle brake according to the invention is particularly designed for electric or hybrid vehicles, where the electric motor operates as a generator to decelerate the vehicle. The braking force of the vehicle braking device is reduced based on the deceleration effect of the electric motor operating as a generator. The braking force of the wheel brakes, whose wheels are driven by electric motors to propel the vehicle, can be reduced, and the wheel brakes drive the electric motors operating as generators when the vehicle decelerates. The vehicle may also have one or more generators driven by one or more wheels. Generally speaking, a rotating motor can be referred to, which may be an electric motor operating as a generator to decelerate the vehicle or may be a generator.

[0014] All features disclosed in the specification and drawings can be implemented individually or in virtually any combination in embodiments of the invention. Embodiments of the invention having not all features of this disclosure, but only one or more of those features, are possible in principle. Attached Figure Description

[0015] The invention will now be explained in detail with the aid of embodiments shown in the accompanying drawings. The single drawing shows a hydraulic circuit diagram of a multi-circuit power-assisted vehicle braking system for implementing the hydraulic system of the service brake according to the invention. Detailed Implementation

[0016] The attached diagram illustrates a hydraulic multi-circuit, or dual-circuit, power-assisted vehicle braking system 1, which has two braking circuits I and II, each with two hydraulically operated wheel brakes 2. The vehicle braking system 1 has a dual-circuit master brake cylinder 4 that can be manually operated with a foot brake pedal and a power-assisted brake pressure generator 5. The two braking circuits I and II are hydraulically connected in parallel to the master brake cylinder 4 and the power-assisted brake pressure generator 5, wherein each braking circuit I and II is connected to the master brake cylinder 4 via a release valve 6 and to the power-assisted brake pressure generator 5 via a power assist valve 7.

[0017] The piston-cylinder-unit 9 with spring-loaded piston 10 is connected as a pedal stroke simulator 11 to one of the two braking circuits I, that is, to the chamber of the dual-circuit master brake cylinder 4, via simulator valve 8.

[0018] The master brake cylinder 4 has a pressureless brake fluid reservoir 12 with three chambers, wherein the two brake circuits I and II of the master brake cylinder 4 are connected to two of the three chambers of the brake fluid reservoir 12. One of the two chambers of the master brake cylinder 4 is connected to the brake fluid reservoir 12 via a test valve 13, and the other chamber is directly connected to the brake fluid reservoir 12.

[0019] The booster-brake pressure generator 5 has a piston-cylinder unit 14, in which the piston 15 can be moved within the cylinder 18 of the piston-cylinder unit 14 by an electric motor 16 via a lead screw drive 17 to generate braking pressure with assistance. The two braking circuits I and II of the vehicle braking device 1 are connected to the cylinder 18 of the booster-brake pressure generator 5 via two booster valves 7.

[0020] The cylinder 18 of the piston-cylinder unit 14 of the booster-brake pressure generator 5 is connected to one of the three chambers of the brake fluid reservoir 12 via a check valve 19 that allows flow toward the cylinder 18, and more specifically, to the chamber of the master brake cylinder 4 that is not connected thereto. Furthermore, the cylinder 18 of the piston-cylinder unit 14 of the booster-brake pressure generator 5 is directly connected to the brake fluid reservoir 12 via a brake line 20 without the insertion of a valve. The piston 10 of the booster-brake pressure generator 5 passes through the orifice of this brake line 20 into the cylinder 18 of the piston-cylinder unit 14 to initiate piston movement, thereby hydraulically separating the piston-cylinder unit 14 of the booster-brake pressure generator 5 from the brake fluid reservoir 12 when the booster-brake pressure generator 5 is operated.

[0021] Each wheel brake 2 is connected to one of the two brake circuits I and II via inlet valve 21 and to the unpressurized brake fluid reservoir 12 via outlet valve 22.

[0022] In the embodiments shown and described in this invention, the disconnect valve, booster valve 7, simulator valve 8, test valve 13, inlet valve 21, and outlet valve 22 are two-position two-way solenoid valves, wherein the disconnect valve 6, test valve 13, and inlet valve 21 are open in their un-energized initial position, and the booster valve 7, simulator valve 8, and outlet valve 22 are closed in their un-energized initial position. For better adjustability of the wheel braking pressure in the wheel brake 2, the inlet valve 21 is a continuous valve in the embodiments shown and described in this invention, and the other valves 6, 7, 8, 13, and 22 are simpler on / off valves. This invention does not exclude other valve configurations. Continuous valves have a continuous transition between closed and open positions and vice versa, while on / off valves only have two switching positions: open and closed. A continuous valve can also be understood as a throttling valve with a controllable flow cross-section or controllable flow resistance.

[0023] The wheel brakes 2 of one axle are respectively connected to the same brake circuits I and II.

[0024] The vehicle braking device 1 is configured for electric vehicles or hybrid vehicles, that is, for vehicles having one or more electric motors 23 for their own propulsion. Hybrid vehicles have an additional drive unit, such as an internal combustion engine. The vehicle can have electric motors 23 for single, multiple, or all wheels. In the accompanying drawings, electric motors 23 are shown for the wheels on each axle.

[0025] According to the present invention, the service brake is operated as a power-assisted braking system using a power-assisted braking pressure generator 5. For this purpose, the power-assisted braking pressure generator 5 generates braking pressure, and the braking pressure of the power-assisted braking pressure generator 5 is applied to the braking circuit, such as braking circuit I, by opening the power-assisted valve 7. The braking pressure present in the braking circuit I is also referred to as the braking circuit pressure. The inlet valve 21 remains open and the outlet valve 22 remains closed, thereby applying the braking circuit pressure to the wheel brake 2 connected to the braking circuit I and manipulating it in this way. The braking pressure present in the wheel brake 2 is also referred to as the wheel braking pressure. The braking circuit pressure and wheel braking pressure can be increased or decreased by the forward or backward movement of the piston 15 within the cylinder 18 of the piston-cylinder-unit 14 of the power-assisted braking pressure generator 5, and the braking circuit pressure and wheel braking pressure remain constant when the piston 15 stops.

[0026] In another braking circuit II, the brake circuit pressure is generated, increased, decreased, or maintained constantly using the booster-brake pressure generator 5 in the same manner, even when the timing is staggered. Therefore, the brake circuit pressure in braking circuits I and II is generated, increased, decreased, or maintained constantly using the booster-brake pressure generator 5, even when the timing is staggered. Alternatively, brake circuit pressure may be generated simultaneously in both braking circuits I and II initially, and then increased, decreased, or maintained constantly only afterward, even when the timing is staggered.

[0027] To decelerate the vehicle, the electric motors 23 are operated as generators for generating electricity. Therefore, they can generally be understood as rotating motors 24. Based on the deceleration effect of the electric motors 23 during generator operation, the braking force of the wheel brakes 2 is reduced; that is, a lower brake circuit pressure is generated than would be necessary without the deceleration effect of the electric motors 23 during generator operation. Because the wheels of the axles are driven by the electric motors 23 and their wheel brakes 2 are connected to the same brake circuits I and II, the deceleration effect of the electric motors 23 during generator operation can be well compensated for.

[0028] During service braking, the master brake cylinder 4 is hydraulically separated from brake circuits I and II by the closure of the release valve 6. The master brake cylinder serves as a setter for the brake circuit pressures that may differ in the two brake circuits I and II, generated by the standby booster-brake pressure generator 5. The simulator valve 8 is opened during service braking, allowing the master brake cylinder 4 to expel brake fluid into the pedal travel simulator 11 and to generate piston and pedal travel on the master brake cylinder 4.

[0029] When the booster-brake pressure generator 5 malfunctions or fails, auxiliary braking can be performed by manual operation of the master brake cylinder 4, wherein the release valve 6 remains open and the booster valve 7 remains closed.

[0030] The inlet valve 19 and outlet valve 20 form a wheel brake pressure regulating valve device, which enables individual adjustment of the wheel brake pressure in the wheel brakes 2 of the vehicle braking system 1. This allows for slip adjustment. Such slip adjustment includes anti-lock braking system (ABS), drive slip adjustment, and driving dynamics adjustment, or electronic stability program (ESP), the latter also colloquially known as anti-wheel slip adjustment. Common abbreviations for these slip adjustments are ABS, ASR, FDR, or ESP. Such slip adjustments are known and will not be explained in detail here. Slip adjustment can also be performed shaft-by-shaft using the power-assisted brake pressure generator 5.

[0031] By closing the inlet valve 21 and opening the outlet valve 22 of the wheel brake 2, the wheel braking pressure in the wheel brake 2 can be reduced to below the braking circuit pressure of the brake circuits I and II connected to the wheel brake 2.

[0032] During service braking according to the invention, the inlet valve 21 of the following brake circuits I and II—which are hydraulically separated from the booster-brake pressure generator 5 by the closure of their booster valve 7—can be closed to prevent an increase in wheel braking pressure in the wheel brakes 2 of these brake circuits I and II if the closed booster valve 7 is not closed in an absolutely sealed manner.

Claims

1. Method for operating a service brake in a hydraulic multi-circuit power-assisted vehicle brake system, wherein the vehicle brake system (1) has at least two brake circuits (I, II), including a first brake circuit and a second brake circuit, a power brake pressure generator (5), each brake circuit (I, II) being connected to the power brake pressure generator (5) via a power valve (7), and at least one hydraulic wheel brake (2) in each brake circuit (I, II), each wheel brake being connected to the brake circuit (I, II) via an inlet valve (21), wherein the wheel brake pressure in the wheel brake (2) can be reduced by opening of an outlet valve (22) connected to each wheel brake (2), characterized in that The brake circuit pressure in the first brake circuit is generated by the power-assisted brake pressure generator (5), for which the power-assisted valve (7) of the first brake circuit is opened and the power-assisted valve (7) of the second brake circuit is closed, and the outlet valve of each wheel brake connected to the first brake circuit is closed.

2. The method according to claim 1, characterized in that, The brake circuit pressure in the first brake circuit is reduced by using the boost-brake pressure generator (5), for which the boost valve (7) of the first brake circuit is opened and the boost valve (7) of the second brake circuit is closed.

3. The method according to claim 1 or 2, characterized in that, The brake circuit pressure in these brake circuits (I, II) is generated by the boost-brake pressure generator (5) when the timing is staggered.

4. The method according to claim 1 or 2, characterized in that, The inlet valve (21) is a continuous valve, and / or the outlet valve (22) and / or the power valve (7) are on / off valves.

5. The method according to claim 1 or 2, characterized in that, The vehicle braking device has a manually operable master brake cylinder (4) for auxiliary braking. The brake circuits (I, II) are connected to the master brake cylinder (4) via a separation valve (6), which is closed during service braking.

6. The method according to claim 1 or 2, characterized in that, The wheel brakes (2) of the axle are connected to the brake circuit (I, II), and / or the wheel brakes (2) of different axles are connected to different brake circuits (I, II).

7. The method according to claim 1 or 2, characterized in that, The vehicle equipped with the vehicle braking device (1) has a rotating motor (24) that can be driven by the wheels and that operates as a generator to slow down the vehicle.

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