Method for distributing a braking load, and braking device

Abstract

The invention relates to a method for distributing a braking load, having the step of building up an initial first braking pressure (P1) in order to adjust a braking power (P) by means of a first braking device (11) and the step of building up a second braking pressure (P2) by activating a second braking device (12) in the event of a specified condition and simultaneously lowering the first braking pressure (P1) such that the braking power (P) remains substantially unchanged.

Description

[0001] Description

[0002] title

[0003] Method for distributing a braking load and braking device

[0004] State of the art

[0005] The present invention relates to a method for distributing a braking load and a related method.

[0006] Methods are known from the state of the art for motor vehicles which enable pressure to be maintained in the wheel brake cylinders in various automation levels.

[0007] On the one hand, a driver can, for example, keep the vehicle stationary and, if necessary, on an incline by continuously pressing the pedal.

[0008] Second, there are so-called hold functions, which usually run as a value-added feature on an electronic stability program. These are activated autonomously or by the driver and allow the vehicle to be braked to a standstill using hydraulic pressure. The primary benefit is increased comfort when stopping briefly on an incline.

[0009] If pressure maintenance is performed solely via the electronic stability program, switchover valves are used. If pressure maintenance is performed via the brake booster, the brake booster's pressure buildup capability is utilized, which is activated by the electronic stability program via the volume flow interface. Pressure maintenance when the pedal is depressed is also performed by the brake booster. Depending on the configuration, the long-term pressure maintenance requires the switchover valves in the electronic stability program or the electric motor in the brake booster to be continuously energized. This can lead to thermal overload of the respective device or to a restriction of functionality if deliberately deactivated.

[0010] The document DE 10 2006 042 930 A1 describes a previously known example of a braking device with several braking devices.

[0011] Disclosure of the invention

[0012] With the present invention, thermal overload of a braking device can be advantageously avoided.

[0013] According to the invention, a method for distributing a braking load having the features of patent claim 1 and a braking device having the features of patent claim 5 are therefore provided.

[0014] Accordingly, a method for distributing a braking load is provided. Initially, a first braking pressure is generated by a first braking device to adjust the braking power. Upon the occurrence of a predetermined condition, a second braking pressure is generated by activating a second braking device, while simultaneously reducing the first braking pressure such that the braking power remains substantially unchanged.

[0015] Furthermore, a braking device is provided. The braking device comprises a first braking device and a second braking device. The first braking device is designed to build up an initial first braking pressure for setting a braking power. The second braking device is designed to build up a second braking pressure. The first braking device is further designed to reduce the first braking pressure when the second braking device is activated such that the braking power remains essentially unchanged. One idea of ​​the invention lies in the distribution of the pressure load during stopping maneuvers when the vehicle is stationary between two braking devices. This advantageously keeps the heat output occurring in the respective braking devices low, whereby thermal overload can be avoided.

[0016] Advantageous embodiments and further developments emerge from the further subclaims and from the description with reference to the figures.

[0017] According to a preferred embodiment of the invention, the first braking device and the second braking device comprise a combination of at least one brake booster and an electronic stability program. In this case, the first braking device can comprise a brake booster and the second braking device an electronic stability program, or vice versa. The use of these braking devices, which are standard in many vehicles, allows for an advantageously simple implementation of the present invention.

[0018] According to a preferred embodiment of the invention, the predetermined condition comprises the expiration of a predetermined time after the initial first brake pressure has been built up, the reaching of a predetermined temperature of the first brake device, or a manual input by a user. Activating the second brake device after a predetermined time has elapsed is advantageously simple to implement technically. Activating the second brake device when a predetermined temperature of the first brake device is reached is particularly suitable for preventing thermal overload. Activating the second brake device by manual input advantageously allows a user to have a high degree of control over the process.

[0019] According to a preferred embodiment of the invention, the method is only carried out under certain conditions, in particular when the engine is stationary or running. This advantageously prevents the braking load from being applied in situations in which this is not desired. According to a preferred embodiment of the invention, the braking device comprises a control device designed to control the function of the first braking device and the second braking device. This control device can also be designed as a component of the first braking device or the second braking device. This advantageously allows the control of the braking device to be individually adapted to the braking device to be controlled.

[0020] The present invention is explained in more detail below with reference to the exemplary embodiments shown in the schematic figures. They show:

[0021] Fig. 1 is a schematic flow diagram of a method for distributing a braking load according to an embodiment of the present invention;

[0022] Fig. 2 is a schematic representation of a braking device according to an embodiment of the present invention;

[0023] Fig. 3 is a schematic representation of a braking device according to a further embodiment of the present invention; and

[0024] Fig. 4 is a time diagram of the curves of first brake pressure, second brake pressure, braking power and temperature of a first braking device in an embodiment of the present invention.

[0025] The accompanying figures are intended to provide a further understanding of embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention. Other embodiments and many of the noted advantages will become apparent upon review of the drawings. Elements of the drawings are not necessarily shown to scale relative to one another.

[0026] In the figures of the drawing, identical, functionally identical, and acting elements, features, and components are provided with the same reference numerals unless otherwise stated. Figure 1 shows a schematic flowchart of a method M for distributing a braking load according to an embodiment of the invention.

[0027] In a first method step M1, an initial first brake pressure is built up by means of a first brake device to adjust the braking power. In a method step M2a, a second brake pressure is built up by activating a second brake device when a predetermined condition occurs. In a simultaneous method step M2b, the first brake pressure is reduced such that the braking power remains essentially unchanged.

[0028] The method shown here is explained in more detail in the following figures using braking devices according to embodiments of the present invention.

[0029] Figure 2 shows a schematic representation of a braking device 10 according to an embodiment of the present invention.

[0030] The braking device 10 comprises a first braking device 11 and a second braking device 12. The first braking device 11 is designed to initially build up a first braking pressure P1 to set a braking power P. The second braking device 12 is designed to build up a second braking pressure P2. The first braking device 11 is further designed to reduce the first braking pressure P1 at the same time as building up the second braking pressure P2 such that the braking power P remains substantially unchanged.

[0031] In the following, an exemplary embodiment is explained in more detail, in which the first braking device 11 comprises a brake booster and the second braking device 12 comprises an electronic stability program. However, this exemplary embodiment serves only for explanatory purposes and is not intended to limit the subject matter of the present invention. Initially, a first brake pressure is initially built up in a master brake cylinder by means of the brake booster, which corresponds to the first method step M1 in Figure 1.

[0032] For example, if the vehicle is stationary and the pressures in the master brake cylinder and wheel brake cylinder are approximately static, further method steps of a method according to the invention can be performed. The execution can then be time-controlled, temperature-controlled, based on another sensor input, such as a manual actuation, or randomly.

[0033] The electronic stability program can use transfer valves to create a pressure difference between the wheel pressure and the master cylinder pressure. For example, the switchover valves can be closed, which corresponds to process step M2a in Figure 1. At the same time, the brake booster reduces its boosting force, which corresponds to process step M2b in Figure 1. Due to the high rigidity between the master cylinder and the switchover valves, the pressure drops suddenly.

[0034] Due to the reduced back pressure, less power is required in the brake booster, which allows temperature saturation to be achieved before a critical temperature threshold is exceeded.

[0035] Figure 3 shows a schematic representation of a braking device 10 according to a further embodiment of the present invention.

[0036] In addition to the features shown in Figure 2, the braking device 10 additionally comprises a control device 13 which is designed to control the function of the first braking device 11 and the second braking device 12.

[0037] The control device 13 can be configured, among other things, to control the first braking device 11 and the second braking device 12 only under certain conditions, in particular when the engine is stationary or running. The control device 13 can be a standalone component, as shown here with solid lines. However, the control device 13a, 13b can alternatively also be configured as a component of the first braking device 11 or the second braking device 12, as shown here with dashed lines.

[0038] If the control device 13a is arranged in the first brake device 11, the actuator position known internally in a brake booster can be used as a predetermined condition.

[0039] If the control device 13b is arranged in the second braking device 12, a pressure measured in an electronic stability program can be used as a predetermined condition.

[0040] It is also conceivable that several control devices are provided, either as independent components or components of the braking devices 11, 12, which communicate with each other in order to control the individual components of the braking device.

[0041] Figure 4 shows a time diagram of the curves of first brake pressure, second brake pressure, braking power and temperature of a first braking device in an embodiment of the present invention.

[0042] At an initial time t0, a brake signal is triggered, whereupon an initial first brake pressure P1 is built up by means of a first brake device. This also directly results in a braking power P to be achieved. It can also be seen that a temperature T in the first brake device increases over time. When a predetermined condition occurs at time t1, a second brake device is switched on, as a result of which a second brake pressure P2 is built up. At the same time, the first brake pressure P1 is reduced. The braking power P to be achieved does not change, however. By reducing the first brake pressure P1, the increase in temperature T in the first brake device is also flattened, as a result of which thermal overload of the first brake device can be avoided. In the present invention, several features have been designated "first" and "second".These designations serve only to clearly define the individual features. In particular, they are not intended to imply any spatial or functional arrangement or prioritization.

[0043] In the present application, “essentially unchanged” is to be understood as meaning that the corresponding value either remains absolutely unchanged or changes only so slightly that no functional difference is discernible.

[0044] When a list of alternatives in this application is marked with the designation “or”, this should be understood to mean both the listed alternatives taken individually and, where appropriate, a combination of several or all of the listed alternatives.

Claims

Claims 1. Method (M) for distributing braking load, comprising: Building up (M1) an initial first brake pressure (P1) to set a braking power (P) by means of a first braking device (11); and building up (M2a) a second brake pressure (P2) by engaging a second braking device (12) when a predetermined condition occurs, and simultaneously reducing (M2b) the first brake pressure (P1) such that the braking power (P) remains essentially unchanged.

2. Method (M) according to claim 1, wherein the first braking device (11) and the second braking device (12) comprise a combination of at least one brake booster and an electronic stability program.

3. Method (M) according to one of claims 1 or 2, wherein the predetermined condition comprises the elapse of a predetermined time after the initial first brake pressure (P1) has been built up, the attainment of a predetermined temperature (T) of the first brake device (11), or manual input by a user.

4. Method (M) according to one of the preceding claims, wherein the method (M) is carried out only under certain conditions, in particular when the engine is stationary or running.

5. Braking device (10) comprising: a first braking device (11) configured to build up an initial first braking pressure (P1) for setting a braking power (P); and a second braking device (12) configured to build up a second braking pressure (P2); wherein the first braking device (11) is further configured to reduce the first braking pressure (P1) when the second braking device (12) is engaged, such that the braking power (P) remains essentially unchanged. Braking device (10) according to claim 5, wherein the first braking device (11) and the second braking device (12) comprise a combination of at least one brake booster and an electronic stability program. Braking device (10) according to claim 5 or 6, wherein the predetermined condition comprises the elapse of a predetermined time after the initial first braking pressure (P1) has been built up, the attainment of a predetermined temperature (T) of the first braking device (11), or manual input by a user.A braking device (10) according to any one of claims 5 to 7, further comprising a control unit (13; 13a; 13b) configured to control the function of the first braking device (11) and the second braking device (12). A braking device (10) according to claim 8, wherein the control unit (13a; 13b) is configured as a component of the first braking device (11) or the second braking device (12). A braking device (10) according to any one of claims 8 or 9, wherein the control unit (13) is configured to control the first braking device (11) and the second braking device (12) only under certain conditions, in particular when stationary or with the engine running.

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