Method for controlling a hydraulic volume

Abstract

The invention relates to a method for controlling a hydraulic volume in a system (1) consisting of a power brake (10) and a driving dynamics control system (14), wherein the power brake (10) is hydraulically coupled to the driving dynamics control system (14). The method comprises the steps of generating (A) a control signal by means of the driving dynamics control system (14), and providing a control signal for the power brake (10), in order to provide hydraulic volumes for the driving dynamics control system (14). The method further comprises the steps of performing (D) a control of the driving dynamics, returning (E) the hydraulic volume from the driving dynamics control system (14), after the control of the driving dynamics is ended, to a reservoir (50) via previously opened circuit isolating valves (38, 42), via which the driving dynamics control system (14) can be connected to the reservoir (50). In addition, the method comprises the step of closing (G) the circuit isolating valves (38, 42) and controlling (H) the brake pressure in the driving dynamics control system (14) using an external-power piston (54) arranged in an external-power cylinder (52), for the case where, before or during the return (E) of the hydraulic volume, an active braking manoeuvre is initiated.

Description

[0001] Description

[0002] Title:

[0003] Method for controlling a hydraulic volume

[0004] The present invention relates to a method for controlling a hydraulic volume in a system comprising a power brake and a vehicle dynamics control system. Furthermore, the invention relates to a system for controlling a hydraulic volume.

[0005] State of the art

[0006] In addition to stabilizing functions, for example in the form of a classic ESP / ABS function, current vehicle braking systems increasingly include extended functions, such as driver support, or force application to the brake pedal during brake actuation by an eBKV (electromechanical brake booster) or assisting or partially assisting functions by a unit for actively modulating the hydraulic brake pressure (e.g. ESP, eBKV, boost unit, etc.), without active participation of the driver.

[0007] Driver assistance systems are becoming increasingly widespread in today's motor vehicles in various forms. They intervene in a semi-automatic or automated manner in the drive, control (e.g. steering) or signaling systems of the vehicle, or warn the driver shortly before or during critical situations via suitable human-machine interfaces. Typically, a braking system features an electronic brake booster (eBKV) and an ESP system. In this combination, the majority of braking system functions can be implemented using an ESP system, and the brake booster is used as an external actuator to build up dynamic pressure. Braking systems can operate with closed hydraulics, i.e. a reservoir of hydraulic fluid in the braking system serves only to compensate for leaks and temperature, thus ensuring a constant available hydraulic volume.Examples of this are classic braking systems such as vacuum brake boosters, electromechanical brake boosters such as the iBooster or a Decoupled Power Brake (DPB) combined with an ESP system. Alternatively, braking systems can work with open hydraulics, such as IPB systems (IPB: integrated power brake). In this case, a reservoir of hydraulic fluid can be used to temporarily store hydraulic volume during normal operation. This means that the hydraulic volume used by the braking system can change during braking. Different braking systems have different disadvantages. For example, systems with closed hydraulics have the problem that, depending on operation, a suction effect from an ESP system can result in more hydraulic volume in the relevant area of ​​the braking system, i.e. from below the master brake cylinder up to the brake cylinders on the wheels, than should be available during normal operation.

[0008] The object underlying the invention is to provide a method for controlling a hydraulic volume in a system comprising a power brake and a vehicle dynamics control, in which no pressure remains in the brake system when the brake is released, despite a power cylinder without a compensation connection.

[0009] The object is achieved by a method for controlling a hydraulic volume having the features of claim 1. Furthermore, the invention provides a system having the features of claim 9. The respective dependent claims represent advantageous developments of the invention.

[0010] Disclosure of the invention

[0011] The invention provides a method for controlling a hydraulic volume in a system comprising a power brake and a vehicle dynamics control system, wherein the power brake is hydraulically coupled to the vehicle dynamics control system. The method comprises the steps of generating a control signal by means of the vehicle dynamics control system and providing a control signal for the power brake, for providing hydraulic volume for the vehicle dynamics control system and for regulating the vehicle dynamics. A further step comprises returning the hydraulic volume from the vehicle dynamics control system, after the vehicle dynamics control system has ended, to a reservoir via previously opened circuit isolation valves, via which the vehicle dynamics control system can be connected to the reservoir.

[0012] In the event that an active braking maneuver is initiated before or during the return of the hydraulic volume, the circuit isolation valves are closed and the brake pressure in the vehicle dynamics control is regulated with an external power piston arranged in an external power cylinder.

[0013] After the circuit isolation valves are closed, the hydraulic volume cannot be discharged due to the lack of compensation connections on the external power cylinder. In contrast to the state of the art, the external power cylinder does not add additional hydraulic volume; instead, the brake pressure in the vehicle dynamics control system is controlled via the external power piston. The external power piston is moved forwards or backwards for control purposes, so that the corresponding hydraulic volume can be added to or removed from the vehicle dynamics control system. To release the brakes, the hydraulic volume in the vehicle dynamics control system is reduced accordingly by moving the external power piston back. This means that the brakes can be released despite the lack of a compensation connection on the external power cylinder and the closed circuit isolation valves. Accordingly, no lines are required between the compensation connection and the reservoir, thus saving material and therefore costs.In addition, the installation space for such a system can be reduced.

[0014] In a preferred embodiment of the invention, the circuit isolation valves are opened after the end of the driving dynamics control. The circuit isolation valves are thus only opened after the end of the driving dynamics control, and if no active braking maneuver is initiated, in order to be able to return the hydraulic volume to the reservoir. During the driving dynamics control, the circuit isolation valves are therefore closed. If an active braking maneuver has to be carried out during the driving dynamics control, these valves do not have to be closed first, thus shortening the braking time. In addition, it can be determined before the active braking maneuver is carried out that a valve will not close in the event of a fault, so that this fault can be responded to early. This further increases safety.

[0015] In a further preferred embodiment of the invention, the circuit isolation valves are opened before the vehicle dynamics control is carried out. The circuit isolation valves are thus already open during the vehicle dynamics control. This allows the hydraulic volume to be quickly drained into the reservoir after the vehicle dynamics control.

[0016] Preferably, the external power piston is moved forward by a certain amount of travel before the vehicle dynamics control is implemented. This provides additional hydraulic volume to the vehicle dynamics control system from the external power cylinder. This allows the vehicle dynamics to be quickly supplied with the necessary hydraulic volume. It also ensures that the external power cylinder can absorb sufficient hydraulic volume from the vehicle dynamics control system to reduce the pressure there, if necessary, to release the brakes.

[0017] In an advantageous further development, the external power piston is moved rearward by a certain distance after the hydraulic volume has been returned. Advantageously, the external power piston is moved to a rear end position. By moving the piston rearward, the hydraulic braking volume in the external power cylinder is increased. After the process has been carried out, sufficient braking volume is available to perform safe active braking.

[0018] Advantageously, the hydraulic volume is controlled with a power cylinder without a compensation port. A power cylinder without a compensation port is distinguished by the fact that it does not have a compensation port through which the vehicle dynamics control system is connected to the reservoir for returning hydraulic volume, even when the circuit isolation valves are closed.

[0019] In a further advantageous embodiment, the vehicle dynamics control system transmits information about the required hydraulic volume along with the control signal. Advantageously, the travel distance to a forward position of the power piston is adjusted according to the required hydraulic volume. This information enables better pressure control in the vehicle dynamics control system. Accordingly, it is possible to control the power piston in such a way that this volume can be absorbed again by the power cylinder after active braking. The brake can then be released again.

[0020] The problem underlying the invention is additionally solved by a system for controlling a hydraulic volume in a system comprising a power brake and a vehicle dynamics control system. The system comprises a power brake, a vehicle dynamics control system hydraulically coupled to the power brake, a control unit for controlling the vehicle dynamics control system, the power brake being signal-coupled to the vehicle dynamics control system, and the system is configured to carry out the method according to the invention. Such a device essentially has the advantages mentioned for the method.

[0021] According to a further advantageous embodiment, the power brake has a power cylinder that is free of compensation connections. Such a power brake achieves the advantages described above.

[0022] Embodiments of the invention are illustrated in the drawing and explained in more detail in the following description. It shows:

[0023] Figure 1 shows a system comprising a power brake and a driving dynamics control system during the control of the driving dynamics, and Figure 2 shows an embodiment of a method for controlling a hydraulic volume in a system comprising a power brake and a driving dynamics control system.

[0024] Figure 1 shows a system 1 comprising a power brake 10 and a vehicle dynamics control system 14 during vehicle dynamics control. System 1 is configured to hydraulically couple the power brake 10 to the vehicle dynamics control system 14 by means of first and second coupling valves of the power brake 18 and 22 and first and second coupling valves of the vehicle dynamics control systems 26 and 30, thus forming a hydraulic coupling. Both the power brake 10 and the vehicle dynamics control system 14 are designed as dual-circuit systems.

[0025] A master cylinder 34 can be manually actuated by a pedal mechanically connected to the master cylinder 34 to hydraulically act on brake cylinders 46a, 46b, 46c, and 46d by means of a first and second circuit isolation valve 38 and 42, respectively, via respective associated circuits of the vehicle dynamics control system 14 to achieve an emergency braking effect. The master brake cylinder 34 is hydraulically connected to a reservoir 50 for hydraulic fluid.

[0026] During normal operation, the braking effect on the brake cylinders 46a, 46b, 46c, and 46d can be achieved by means of an external power cylinder 52, in which an external power piston 54 in the external power cylinder 52 displaces hydraulic volume via the coupling valves of the external power brake 18, 22 into the two circuits of the vehicle dynamics control system 14. The external power cylinder 52 can be hydraulically coupled to the hydraulic reservoir 50 via an external power cylinder valve 58. The external power cylinder 52 is coupled to an electric motor in order to be able to release or absorb hydraulic volume via the external power piston 54. The electric motor can be controlled by a controller coupled to a sensor system for determining the electric motor position 62. The pressure of the master cylinder 34 can be determined by means of a pressure sensor 66.The dual-circuit master cylinder 34 can be hydraulically coupled to a brake simulator 74 via a brake simulator valve 70 to simulate a hydraulic pressure buildup when a driver presses the brake pedal. During normal operation, the hydraulic volume is then provided to the vehicle dynamics control system 14 via the external power piston 54 to achieve a braking effect on the brake cylinders 46a, 46b, 46c, 46d, which are hydraulically coupled to the vehicle dynamics control system 14. A mechanical position of the brake pedal can be determined by a pedal travel sensor 78, which is mechanically coupled to the brake pedal, to control the external power piston 54.

[0027] The pressure generated by the external power piston 54 is determined by an external power piston pressure sensor 82. Hydraulic fluid can be supplied from the reservoir 50 to the hydraulic system comprising the external power brake 10 and the vehicle dynamics control system 14 by means of a first and second check valve 86, 90. The vehicle dynamics control system 14 is constructed in a known manner, so a detailed description thereof is omitted.

[0028] Figure 2 shows an embodiment of a method for controlling a hydraulic volume in a system 1 shown in Figure 1. In a first step of the method A, a control signal is generated in a control unit of the vehicle dynamics control system 14. This control signal is provided to the external power brake 10 so that hydraulic volume can be made available to the vehicle dynamics control system 14. In a second step B, the previously closed circuit isolation valves 38, 42 are opened. This allows the vehicle dynamics control system 14 to draw hydraulic fluid from the reservoir 50, additionally via check valves 86, 90. In a next step C, the external power piston 54 is displaced forward towards an outlet to the vehicle dynamics control system 14. This provides the vehicle dynamics control system 14 with additional hydraulic fluid through the external power cylinder 52.

[0029] In a subsequent step D, the driving dynamics are controlled in a known manner. After the driving dynamics have been controlled, in a next step E the hydraulic volume from the driving dynamics control system 14 is discharged via the open circuit isolation valves 38, 42 through the master cylinder 34 into the reservoir 50. When the return flow begins, it is monitored whether an active braking maneuver is initiated via the pedal. If this is not the case, after the hydraulic volume has been returned, the external power piston 54 is moved rearward again in a subsequent step F so that sufficient hydraulic fluid is available in the hydraulic cylinder 34 for an active braking maneuver. As a result, brake fluid is moved into the external power cylinder 52 either via the external power cylinder valve 58 or via the hydraulic path of the master cylinder 34, the circuit isolation valves 38, 42 and the coupling valves of the external power brake 18, 22.

[0030] In the event that an active braking maneuver Bs is to be initiated before or during the step of returning the hydraulic volume E, the circuit isolation valves 38, 42 are closed in a next step G. Subsequently, in a next step H, the brake pressure in the driving dynamics control is regulated using the external power piston 54. After the active braking maneuver has ended, the external power piston 54 is moved rearward so that the hydraulic volume of the driving dynamics control 14 is absorbed in the external power cylinder 52. As a result, after the active braking maneuver has ended, the brake cylinders 46a, 46b, 46c, 46d can be released without brake pressure remaining in the driving dynamics control 14.

Claims

Claims 1. A method for controlling a hydraulic volume in a system (1) comprising a power brake (10) and a vehicle dynamics control system (14), wherein the power brake (10) is hydraulically coupled to the vehicle dynamics control system (14), comprising the steps: Generating (A) a control signal by means of the driving dynamics control (14), and providing a control signal for the external power brake (10) to provide hydraulic volume for the driving dynamics control (14); Carrying out (D) a control of the driving dynamics, returning (E) the hydraulic volume from the driving dynamics control (14), after the control of the driving dynamics has ended, to a reservoir (50) via previously opened circuit isolation valves (38, 42), via which the driving dynamics control (14) can be connected to the reservoir (50), Closing (G) the circuit isolation valves (38, 42) and regulating (H) the brake pressure in the driving dynamics control (14) with an external power piston (54) arranged in an external power cylinder (52), in the event that an active braking maneuver is initiated before or during the return (E) of the hydraulic volume.

2. Method according to claim 1, characterized in that the circuit isolation valves (38, 42) are opened after the end of the control (H) of the driving dynamics.

3. Method according to claim 1, characterized in that the circuit isolation valves (38, 42) are opened (B) before carrying out the control of the driving dynamics (D). Method according to one of the preceding claims, characterized in that the external power piston (54) is displaced forwards (C) by a certain amount of travel before the control of the driving dynamics is carried out (D). Method according to one of the preceding claims, characterized in that the external power piston (54) is displaced rearwards (F) by a certain amount of travel after the hydraulic volume has been returned. Method according to one of the preceding claims, characterized in that the hydraulic volume is controlled using an external power cylinder (52) that has no compensation connection. Method according to one of the preceding claims, characterized in that the driving dynamics control (14) transmits information about the required hydraulic volume together with the control signal. Method according to one of the preceding claims, characterized in that the amount of travel to a forward position of the external power piston (54) is set according to the required hydraulic volume.System (1) for controlling a hydraulic volume in a system comprising a power brake (10) and a vehicle dynamics control system (14), comprising: a power brake (10), a vehicle dynamics control system (14) hydraulically coupled to the power brake (10), a control unit for controlling the vehicle dynamics control system (14), wherein the power brake (10) is signal-coupled to the vehicle dynamics control system (14); and wherein the system is configured to carry out the method according to one of claims 1 to 8. System (1) according to claim 9, characterized in that the power brake (10) has a power cylinder (52) which is free of compensation connections.

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