Brake system, vehicle, and method for operating a brake system

Abstract

The invention relates to a brake system comprising at least one actuating element, in particular a hand or foot lever, and a hydraulic system which has at least one fluid circuit, wherein the actuating element is operatively connected to the fluid circuit in order to directly or indirectly generate a brake pressure, the actuating element can be moved along a lever path in order to generate the brake pressure, and the brake system has a control device which is designed to adjust the fluid volume in the fluid circuit in such a way that the lever path-based brake pressure remains constant during operation.

Description

[0001] Braking system, vehicle and method for operating a braking system

[0002] The present invention relates to a braking system, a vehicle, and a method for operating a braking system.

[0003] During operation, braking systems, for example on motorcycles, and their components, in particular the brake pistons, the brake caliper and the brake fluid, become very hot. This causes the internal volume of the closed system in which the brake fluid is located to change relative to the volume of the brake fluid itself. At the same time, the behavior of the elastomer seal on the brake piston also changes with increasing system temperatures, etc. Due to these mechanisms, a different lever travel on the brake lever must be selected at high braking system temperatures than at low system temperatures to achieve the same braking effect. This change in lever travel is disadvantageous for the rider because it impairs the modulation of the brake. The impression of quality deteriorates and confidence in the braking system suffers.

[0004] It is therefore an object of the present invention to provide a braking system, a vehicle and a method for operating a braking system, wherein it is to be ensured that a uniform system behavior is ensured even at high and extremely high system temperatures.

[0005] This object is achieved by a braking system according to claim 1, by a vehicle according to claim 5 and by a method according to claim 6. Further advantages and features emerge from the subclaims as well as the description and the attached figure.

[0006] According to the invention, a braking system comprises at least one actuating element, in particular a hand or foot lever / foot pedal, and a hydraulic system having at least one fluid circuit, wherein the actuating element is operatively connected to the fluid circuit for directly or indirectly generating a braking pressure, wherein the actuating element can be moved along a lever travel to generate the braking pressure, and wherein the braking system has a control device designed to adjust or regulate the fluid volume in the fluid circuit such that the lever travel-dependent braking pressure remains constant during operation. During operation, the braking system or its components, in particular, for example, the brake pistons, the brake caliper, and the brake fluid (brake fluid or, hereinafter, also simply referred to as fluid), become very hot.This changes the internal volume of the closed system in which the fluid is located relative to the fluid's own volume. In addition, the behavior of the elastomer seal on the brake piston also changes with increasing system temperatures, etc. Due to these mechanisms, a different lever travel on the brake lever must typically be selected at high brake system temperatures than at low system temperatures to achieve the same braking performance or braking effect. In this case, this can be expediently compensated for by adjusting the fluid volume. The fluid volume is therefore expediently increased or decreased in such a way that any volume fluctuations in the fluid circuit or the entire hydraulic system can be compensated for. This ensures that the brake always behaves the same, even at high and extremely high system temperatures. The lever travel-dependent brake pressure therefore remains constant during operation.

[0007] The hydraulic system expediently comprises means for regulating the brake pressure, in particular for implementing ABS functionality (ABS - anti-lock braking system), and the control device is designed to operate the means for adjusting the fluid volume accordingly. Thus, the actuators already available via the anti-lock braking system are expediently used to change the fluid volume in the hydraulic system.

[0008] With regard to the at least one fluid circuit, it should be noted that the hydraulic system can also have multiple fluid circuits. For example, there are brake systems that have a control circuit and a wheel circuit. The control circuit is directly connected to the actuating element, while the wheel circuit is the fluid circuit that is operatively connected to the brake piston(s) and in which the actual brake pressure is built up. In addition, there are also brake systems that have only one fluid circuit and, for example, operate with a conventional brake booster, etc. Advantageously, the invention can be implemented for a wide variety of brake systems. The existing hydraulic system only needs to be examined to determine where a volume change occurs during operation that is responsible for the lever travel-dependent brake pressure change.Once this volume change has been determined and recorded, it can be compensated accordingly by means of the control device, which is designed to operate the aforementioned means.

[0009] According to one embodiment, the aforementioned means are selected, for example, from at least the following: control valve, solenoid valve, pump, buffer, etc. The ABS actuator is expediently used to adjust the fluid volume in such a way that any volume fluctuations of the hydraulic system are compensated.

[0010] According to a preferred embodiment, the control device comprises a temperature model which is designed to determine the brake caliper temperature based on a detected brake pressure, and wherein the brake caliper temperature is used according to one embodiment to calculate the relative volume change of the fluid circuit. The system temperature, which is decisive for the expansion of the hydraulic volume in the brake system, is expediently determined via a thermal model or via the aforementioned temperature model for the brake caliper. The brake caliper temperature therefore corresponds, for example, to a first approximation of the system temperature. According to one embodiment, the volume of the corresponding fluid circuit is divided into several sub-volumes since the temperature of the fluid will be lower the further it is from the brake caliper.The relationship between the system temperature and the volume expansion to be compensated can, for example, be determined empirically.

[0011] The aforementioned braking system is suitable for motor vehicles, such as passenger cars or, in particular, motorcycles, such as scooters or motorbikes, especially single- or multi-track tilting vehicles. The braking system is also suitable for bicycles, whether with or without an (electric) auxiliary motor. This braking system can be particularly useful for sports bicycles, such as mountain bikes, which are used for downhill riding. The braking system can be a braking system with one or more disc brakes. The braking system can also have one or more drum brakes. In the passenger car sector, especially for small cars, mixed systems are also common.

[0012] The invention also relates to a vehicle comprising at least one braking system according to the invention. Possible vehicles have already been mentioned. In particular, vehicles of the type in question are motorcycles, especially tilting vehicles, which include both single- and multi-track vehicles, in particular LMW (Leaning Multiwheel) vehicles, trikes, quads, etc. Motorcycles used for sport riding, in particular, but also touring motorcycles, which, for example, must tackle long mountain pass descents, can benefit from such a braking system.

[0013] The invention also relates to a method for operating a braking system, wherein the braking system comprises at least one actuating element, in particular a hand or foot lever (or a foot pedal), and a hydraulic system which has at least one fluid circuit, wherein the actuating element is operatively connected to the fluid circuit for directly or indirectly generating a braking pressure, and wherein the method comprises the steps:

[0014] - Determining a temperature-related relative volume change of the fluid circuit;

[0015] - Adjusting the fluid volume in the fluid circuit to compensate for the volume change, whereby the lever travel-dependent brake pressure can be kept constant during operation.

[0016] The advantages and features mentioned in connection with the braking system also apply analogously and accordingly to the process, and vice versa.

[0017] The procedure conveniently comprises the following steps:

[0018] - Determine the system temperature;

[0019] - Determine the volume change based on the system temperature;

[0020] - Adjusting the fluid volume.

[0021] A control unit of the braking system is expediently used to implement the method. Preferably, the control unit runs a software function that determines and influences the temperature-dependent internal volume of the hydraulic system or the corresponding fluid circuit in such a way that the change in the required lever travel is compensated for at different system temperatures.

[0022] According to one embodiment, the method comprises the steps:

[0023] - Detecting the brake pressure;

[0024] - Using brake pressure to determine a brake caliper temperature; - Using the brake caliper temperature to determine the relative volume change.

[0025] According to one embodiment, the system temperature, which is decisive for the relative volume change of the fluid circuit or, more generally, of the hydraulic system, is determined using a thermal model for the brake caliper. The relative volume change takes into account the change in the internal volume of the fluid circuit relative to the fluid volume. This means that the internal volume of the fluid circuit increases at higher temperatures, for example. At the same time, the fluid volume contained therein also expands, although perhaps not to the same extent. This leads to a change in the lever travel-dependent brake pressure. By adjusting the fluid volume or the fluid quantity, this can be compensated for in such a way that the lever travel-dependent brake pressure remains constant.

[0026] For this purpose, the already available actuators of the ABS system are used or employed.

[0027] In the case of a drum brake, the temperature of the wheel cylinder is used instead of the brake caliper temperature. This component is designed to spread the brake shoes and press them against the brake drum.

[0028] According to one embodiment, the method comprises the step:

[0029] - Providing a characteristic curve to depict the relative volume change as a function of the system temperature.

[0030] The expansion model of the temperature-dependent internal volume of the fluid circuit or the hydraulic system can, for example, consist of a simple characteristic curve in which the dependency between the determined system temperature / brake caliper temperature and the desired volume change is stored.

[0031] According to one embodiment, the method comprises the steps:

[0032] - Dividing the volume of the fluid circuit into sub-volumes;

[0033] - Determine the temperatures of the partial volumes;

[0034] - Determine the relative volume change based on the temperatures of the sub-volumes.

[0035] This takes into account that the fluid in the fluid circuit, or the fluid circuit itself, including the various components, does not have the same temperature everywhere. This allows for a better approximation of an "optimal" system temperature.

[0036] As already mentioned, the existing ABS actuator system is expediently used to adjust the fluid volume. To adjust the fluid volume or fluid quantity, a control valve, a solenoid valve, a pump, and / or an (intermediate) reservoir of the hydraulic system / fluid circuit are expediently operated accordingly.

[0037] Further advantages and features will become apparent from the following description of an embodiment of a braking system with reference to the attached figure.

[0038] It shows:

[0039] Fig. 1: a schematic view of an embodiment of a braking system according to the invention.

[0040] Fig. 1 schematically shows an embodiment of a braking system according to the invention (disc brake system), comprising an actuating element 10, which is operatively connected to a fluid circuit 22 of a hydraulic system 20 for generating a braking pressure. The braking pressure expediently acts on a brake caliper 40, in which the brake pads are mounted, which act on a brake disc 50. The hydraulic system 20 comprises means 30 which are necessary for operating the brake. In the present case, this particularly refers to components of the anti-lock braking system, such as control valves, solenoid valves, pumps, buffers, etc. The braking system expediently comprises a control device (not shown here), which is designed to adjust the fluid volume in the fluid circuit 22 such that the lever-travel-dependent braking pressure remains constant during operation.The temperature-dependent internal volume of the fluid circuit 22 is expediently determined and influenced in such a way that the change in the required hand lever travel is compensated for at different system temperatures. For this purpose, the system temperature, which is decisive for the volume change in the volume of the fluid circuit 22, is determined, for example, with the aid of a thermal model for the brake caliper 40. The necessary volume change is then determined using an expansion model of the temperature-dependent internal volume of the fluid circuit 22. In a final step, the actuators already available for the anti-lock braking system are expediently used to change the internal volume in the hydraulic system / fluid circuit in order to implement the required volume change. As a result, the lever travel-dependent brake pressure does not change even at high and extremely high system temperatures.

[0041] List of reference symbols

[0042] 10 Actuating element 20 Hydraulic system

[0043] 22 Fluid circuit

[0044] 30 remedies

[0045] 40 brake caliper

[0046] 50 brake disc

Claims

Claims 1. A braking system comprising at least one actuating element (10), in particular a hand or foot lever, and a hydraulic system (20) which has at least one fluid circuit (22), wherein the actuating element (10) is operatively connected to the fluid circuit (22) for directly or indirectly generating a braking pressure, wherein the actuating element (10) can be moved along a lever travel to generate the braking pressure, and wherein the braking system has a control device which is designed to adjust the fluid volume in the fluid circuit (22) such that the lever travel-dependent braking pressure remains constant during operation.

2. Brake system according to claim 1, wherein the hydraulic system (20) comprises means (30) for regulating the brake pressure, in particular for realizing an ABS functionality, and wherein the control device is designed to operate the means (30) for adjusting the fluid volume.

3. Braking system according to claim 2, wherein the means (30) are at least selected from the following: control valve, solenoid valve, pump, buffer.

4. Brake system according to one of the preceding claims, wherein the control device comprises a temperature model which is designed to determine the brake caliper temperature on the basis of a detected brake pressure, and wherein the brake caliper temperature is used to calculate the relative volume change of the fluid circuit (22).

5. A vehicle comprising a braking system according to any one of the preceding claims.

6. A method for operating a braking system, wherein the braking system has at least one actuating element (10), in particular a hand or foot lever, and a hydraulic system (20) which has at least one fluid circuit (22), wherein the actuating element (10) is operatively connected to the fluid circuit (22) for directly or indirectly generating a braking pressure, comprising the steps: - determining a temperature-related relative volume change of the fluid circuit (22); - Adjusting the fluid volume in the fluid circuit (22) to compensate for the volume change, whereby the lever travel-dependent brake pressure can be kept constant during operation.

7. The method according to claim 6, comprising the steps: - Determine the system temperature; - Determine the volume change based on the system temperature; - Adjusting the fluid volume.

8. Method according to claim 6 or 7, comprising the steps: - Detecting the brake pressure; - Using brake pressure to determine a brake caliper temperature; - Using the temperature of the caliper (40) to determine the relative volume change.

9. Method according to one of claims 6 to 8, comprising the step: - Providing a characteristic curve to depict the relative volume change as a function of the system temperature.

10. Method according to one of claims 6 to 9, comprising the steps: - Dividing the volume of the fluid circuit into sub-volumes; - Determine the temperatures of the subvolumes; - Determine the relative volume change based on the temperatures of the subvolumes.

11. Method according to one of claims 6 to 10, wherein a control valve, a solenoid valve, a pump and / or a reservoir of the hydraulic system are operated accordingly to adjust the fluid volume.

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