METHOD FOR DETERMINING OPERATING VARIABLES OF A DRUM BRAKE, ASSOCIATED DRUM BRAKE ASSEMBLY, ANALYSIS DEVICE AND STORAGE MEDIUM

Abstract

A method for ascertaining operating variables of a drum brake has the following steps: a) recording at least one supporting force of a brake shoe of the drum brake by means of a sensor, and b) ascertaining the operating variable based on the supporting force, the operating variable being selected from the brake lining friction value and the spreading force.

Claims

1. A method for ascertaining operating variables of a drum brake comprising: recording at least one supporting force of a brake shoe of the drum brake with a sensor, and ascertaining at least one operating variable based on the supporting force, the operating variable being selected from the brake lining friction value and the spreading force.

2. The method as claimed in claim 1, wherein the supporting forces of two brake shoes of a drum brake are measured.

3. The method as claimed in claim 1, wherein at least one further parameter of the brake is ascertained from the operating variable.

4. The method as claimed in claim 3, wherein the further parameter of the brake is a brake characteristic value.

5. The method as claimed in claim 1, further comprising carrying out a brake diagnosis or is used in the course of a brake diagnosis.

6. The method as claimed in claim 1, wherein at least one of the ascertained operating variable and an ascertained brake characteristic value is compared with a setpoint range stored in a memory.

7. The method as claimed in claim 6, wherein when at least one the ascertained operating variable and the ascertained brake characteristic value do not correspond to the stored setpoint range, at least one of either a countermeasure and an error message is initiated.

8. The method as claimed in claim 1, wherein an electromechanical drum brake is used as the drum brake.

9. The method as claimed in claim 1, wherein a hybridized brake system control comprises an evaluation device and at least one of: hydraulic wheel brake actuators, electromechanical wheel brake actuators, at least one recuperative brake wherein the at least the wheel brake actuators require different operating variables and/or actuating variables, and further comprising: feeding at least one hydraulic wheel brake pressure as an additional operating variable to the evaluation device, wherein the at least one hydraulic wheel brake pressure is measured in parallel by sensors for each wheel; ascertaining on the basis of this additional operating variable wheel-individual wheel brake setpoints with the evaluation device; and imparting the wheel brake setpoints to the wheel brakes in a coordinated manner for parallel open-loop and/or closed-loop control of all of the brakes.

10. A drum brake assembly comprising: at least one brake shoe; at least one supporting bearing; at least one force sensor on the supporting bearing for measuring a supporting force generated by the brake shoe in the supporting bearing; and an evaluation device, which is configured with instructions for; recording at least one supporting force of a brake shoe of the drum brake with a sensor, and ascertaining at least one operating variable based on the supporting force, the operating variable being selected from the brake lining friction value and the spreading force.

11. The drum brake assembly as claimed in claim 10, further comprising: at least one further brake shoe; at least one further supporting bearing; and at least one further force sensor on the further supporting bearing for measuring a further supporting force generated by the further brake shoe in the further supporting bearing.

12. The drum brake assembly as claimed in claim 10, further comprising: at least one brake pressure sensor for at least one hydraulically actuated wheel brake, wherein the brake pressure sensor is electrically connected to the evaluation device; at least one brake pressure control valve for hydraulic brake pressure control of the hydraulically actuated wheel brake actuated by the evaluation device; and wherein, the evaluation device controls a wheel brake pressure of the at least one hydraulically actuated wheel brake in one of an open-loop and a closed-loop manner.

13. (canceled)

14. A non-volatile computer-readable storage medium which contains program codes, during the execution of which a processor performs said program codes having instructions for: recording at least one supporting force of a brake shoe of the drum brake with a sensor; and ascertaining at least one operating variable based on the supporting force, the operating variable being selected from the brake lining friction value and the spreading force.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG. 1 schematically shows a component of an electromechanical drum brake;

[0056] FIG. 2 schematically shows a diagram showing the supporting forces in dependence on the spreading force;

[0057] FIG. 3 schematically shows a diagram showing the supporting forces in dependence on the brake lining friction value;

[0058] FIG. 4 schematically shows a diagram showing the supporting forces in dependence on the spreading force and the brake lining friction value;

[0059] FIG. 5 schematically shows a block diagram for a method; and

[0060] FIG. 6 schematically shows ascertained parameters for carrying out the method.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0061] FIG. 1 shows a drum brake assembly 10 with an electromechanical drum brake in a schematic illustration, although the drum is not shown.

[0062] The drum brake assembly 10 illustrated in FIG. 1 has a first brake shoe 12 and a second brake shoe 14. The drum (not shown) of a drum brake typically surrounds the brake shoes 12, 14. The first brake shoe 12 is supported in a first supporting bearing 16. This contains a first force sensor, which is not shown separately. The second brake shoe 14 is supported in a second supporting bearing 18. This contains a second force sensor, which is not shown separately. The supporting bearings 16, 18 may be arranged on a back plate of the drum not shown.

[0063] Between the two brake shoes 12, 14, a spreading unit 20 is arranged on the upper side of the drum brake. In the present case, this is an electromechanical spreading unit 20. This can push the two brake shoes 12, 14 apart, causing them to make contact with a surrounding drum and to brake the drum if it is rotating. If the drum is not rotating, the brake shoes 12, 14 may exert a holding force. Thus, the drum brake 10 can be used both as a service brake and as a parking brake.

[0064] When the spreading unit 20 presses the two brake shoes 12, 14 against the inside of the drum, they are supported by reaction forces on the supporting bearings 16, 20. There, the forces which arise as a result are measured.

[0065] According to one exemplary embodiment, the drum brake assembly 10 has an evaluation device 22. This is configured for performing a method according to an exemplary embodiment. During this process, the measured forces which have just been mentioned are processed further. The measurement of the forces on the supporting bearing is a prerequisite for a method, a device, components and software for determining the characteristic variables ascertained, that is in particular the brake lining friction value and the spreading force.

[0066] In the following, it is described with reference to FIG. 2 to FIG. 5 how the measured supporting forces can be evaluated in the course of a method. Thus, FIGS. 2 to 5 show a method for determining the brake lining friction value and the spreading force.

[0067] The measured supporting forces (F.sub.Abutment) show a dependence on variable boundary conditions, such as in particular temperature, speed, brake lining friction value, spreading force, etc. of the brake. To ascertain the brake lining friction value (.sub.Lining) and the spreading force (F.sub.Spread Unit) in the operational case of braking with a rotating drum, the calculation of the supporting forces is found to be a suitable criterion.

[0068] In this case, the amounts of both supporting forces clearly describe a brake lining friction value and a spreading force. FIGS. 2 and 3 show the dependences of the supporting forces, shown in each case on the Y-axis, on the spreading force, shown in FIG. 2 on the X-axis, and the brake lining friction value, shown in FIG. 3 on the X-axis, with in each case the solid line showing the leading side and the dashed line showing the trailing side of the brake shoes 12, 14.

[0069] Superposing the two diagrams produces a three-dimensional map in which the clear dependence of force pairs in the supporting bearing with respect to the brake lining friction value and the spreading force can be seen. This is shown in FIG. 4.

[0070] FIG. 5 relates to a block diagram for clarification of the process.

[0071] In detail, block 24 shows the sensor for measuring the supporting force of the first brake shoe 12, block 26 shows the sensor for measuring the supporting force of the second brake shoe 14 and block 28 shows further parameters that affect the brake lining friction value and the spreading force, such as for instance the temperature at the brake shoes and the wheel speed. These are preferably included as further input parameters in the calculation, which is intended to be represented as block 30. Subsequently obtained as output values are the brake lining friction value according to block 32 and the spreading force according to block 34.

[0072] The figures show that, for the reliable estimation, ascertainment, and calculation of the spreading force and the brake lining friction value, only measurement information on the basis of the measurement results of sensors concerning brake shoe supporting forces as well as geometric parameters of the brake are required as input information.

[0073] The specific calculation of the brake lining friction value or spreading force is indicated in FIG. 6, which shows a brake as described in FIG. 1, and can be performed as follows.

[0074] Shown in detail in FIG. 6 are the forces (F.sub.Spread Unit) on the spreading unit 20, the circumferential forces (F.sub.T), and the forces (F.sub.Abutment) on the supporting bearings 16, 18, respectively represented by the appropriately positioned arrows. This is the basis of the calculation. With reference to a circular shape based on the brake shoes 12, 14, the further parameters describe the distance (c) of the center of the drum brake from the spreading unit 20, the distance (d) of the center of the drum brake from the supporting bearings 16, 18 and the radius (r) of the circular shape of the drum brake at the outer points of the brake linings 12, 14 in the functional state and thus also the inner radius of the drum.

[0075] This results in the equation (1), which is known in principle to the skilled person and which represents the torque equilibrium around the center for the respective brake shoe 12, 14 and forms the starting point of the calculation, with the sign +/ applying as the upper sign (in equation (1) +) for the leading brake shoe and applying as the lower value (in equation (1) ) for the trailing brake shoe:

[00001]$\begin{array}{cc}{F}_{\mathrm{Spread}\mathrm{Unit}}.Math.c{F}_T.Math.r=F_{\mathrm{Abutment}}.Math.d& \left(1\right)\end{array}$

[0076] The following equations (2) and (3) are used to ascertain the spreading force and the brake lining friction value based on the information of the supporting forces and the geometric variables of the drum brake. Here, equation (2) represents the ascertainment of the brake characteristic value on the basis of the circumferential force and the spreading force and equation (3) represents the dependence of the brake characteristic value on the lining friction value and the parameters H.sub.1-H.sub.5, which are ascertained on the basis of geometric variables:

[00002]$\begin{array}{cc}{C}^{*}=\frac{F_T}{F_{\mathrm{Spread}\mathrm{Unit}}}& \left(2\right)\end{array}$$\begin{array}{cc}{C}^{*}=\frac{H_1{}_{Li}.Math.H_2}{H_3.Math.\left({}_{Li}+\frac{1}{{}_{Li}}\right)+{}_{Li}.Math.H_4{H}_5}& \left(3\right)\end{array}$

[0077] According to the embodiments, it is thus possible to determine the spreading force or the brake lining friction value by using equations (2) and (3), which are known in principle to the skilled person for determining the brake characteristic value C*, and equation 1. In equations (2) and (3) .sub.Li denotes the brake lining friction value and, as described above, F.sub.Spread Unit denotes the spreading force. H1 to H5 are geometric auxiliary variables known to the skilled person for these equations, relating to the specific brake.

[0078] By inserting equation (2) and (3) in equation (1) and a corresponding resolution toward the desired parameters, a calculation of the corresponding target variables is possible by a method according to the invention.

[0079] Since different motor vehicle manufacturers may demand completely different motor vehicle systems and/or motor vehicle concepts with different brake system interpretations, increased flexibility is sometimes required. In the present context, it may be made possible in addition to this that a brake system control developed in a correspondingly hybridized manner is defined. In this case, not only hydraulic wheel brake actuators but also electromechanical wheel brake actuators as well as possibly at least one recuperative brake are present side by side in a motor vehicle system and the wheel brake actuators may require correspondingly different operating variables and/or actuating variables. In order therefore also to allow a jointly performable method as well as a common evaluation device 22, this evaluation device 22 is to be fed in parallel, as an additional operating variable, at least one hydraulic wheel brake pressure p that is measured by sensors and wheel-individually, and with the common evaluation device 22 at the same time ascertaining on the basis of this additional operating variable wheel-individual wheel brake setpoints and imparting them to the wheel brakes in such a coordinated manner that simultaneously parallel open-loop and/or closed-loop control of all of the brakes in the hybridized motor vehicle system is made possible. Accordingly, the common evaluation device 22 may be assigned at least one brake pressure sensor S for at least one hydraulically actuated wheel brake, and with the brake pressure sensor S electrically connected to the common evaluation device 22, and the common evaluation device 22 may also be assigned at least one brake pressure control valve for hydraulic brake pressure control of the hydraulically actuated wheel brake, so that the common evaluation device 22 is thereby fundamentally and systematically enabled, for example separately or together with all of the other brakes (including the recuperative brake) in the hybridized system, additionally also to control a wheel brake pressure p of the hydraulically actuated wheel brake(s) in an open-loop and/or closed-loop manner.