GB2500777A - Monitoring of an electromechnical parking brake - Google Patents

Abstract

Monitoring the functioning of an electromechanical parking brake 1 having an electric brake motor 3, and an additional clamping force generated by an additional brake device, preferably a hydraulic service brake, as required. When the number of actuating requirements for the additional brake device exceeds a limit value, a fault signal is generated. The actuating requirements and/or the level of additional clamping force are preferably only used for monitoring when the characteristics of the electric motor and/or the temperature of the parking brake are in a defined value range.

Description

Method for monitoring the functioning of a parking brake The invention relates to a method for monitoring the functioning of a parking brake.

Prior art

Electromechanical parking brakes in vehicles, which are used to arrest the vehicle when stationary, are known. As described, for example, in DE 103 61 042 B3, the * parking brake can comprise an electric brake motor which subjects a brake piston with * 10 a brake lining to a force against a brake disc in order to generate the clamping force.

The brake disc may be that of the hydraulic vehicle brake. This allows the possibility of using the hydraulic vehicle brake as an additional brake device, in case the clamping force generated by means of the electric brake motor is not sufficient to arrest the vehicle securely, for example when parking the vehicle on roads with a relatively high incline. The brake force generated by means of the hydraulic vehicle brake is added to the clamping force generated by means of the electric brake motor.

Disclosure of the invention

The object of the invention is to be able to detect, with simple measures, the proper functioning of a parking brake for a vehicle, which brake is equipped with an electric brake motor for generating an electromechanical clamping force.

This object is achieved according to the invention by the features of Claim 1. The subclaims specify expedient developments.

The method according to the invention relates to a parking brake in a vehicle having an * eleotromechanical brake device, comprising an electric brake motor for generating an electromechanical target clamping force, The clamping force is provided by a rotational movement of the rotor of the brake motor, in that the rotational movement is converted to a positioning movement of an actuator, via which movement a brake piston, which carries a brake lining, is pressed axially against a brake disc.

The parking brake is equipped with an additional brake device, by means of which an additional clamping force can be generated, as required, which force is added to the electromechanical clamping force provided by the electric brake motor. In principle, various brake types are suitable as the additional brake device, for example additional electric brake motors, it being provided accorthng to an advantageous embodiment that the additional brake device is the hydraulic vehicle brake by means of which the vehicle is braked in regular braking. The hydraulic pressure of the hydraulic vehicle brake in this case acts upon the same brake piston which is also pressed against the brake disc by the electric brake motor.

In the method according to the invention, the number of actuating requirements for the additional brake device and/or the level of the additional clamping force required, and which is to be provided by the additional brake device, is related to an associated limit value. If the limit value is exceeded, then a fault signal is generated. In this case, owing to the high number of actuating requirements and/or the level of the additional clamping force, it is possible to infer a deteriorating efficiency of the electromechanical part of the parking brake, that is to say of the electric brake motor or the power supply or the control of the electric brake motor. In this way, even over a long operating period, a possibly slow deterioration of the efficiency of the electric brake motor or of the associated units can be detected. The deterioration is indicated in the form of a fault signal or the fault signal can be further processed in a suitable manner. In particular, it is possible to detect early a deteriorating brake performance of the brake motor.

Overall, the protection against failure of the parking brake is increased.

Suitable for the method according to the invention are, both operating modes in which an additional clamping force is required and also provided by means of the additional brake device, and procedures in which the additional clamping force, although required, in practice is not generated by means of the additional brake device owing, for example, to limitations on the use of the additional brake device. Such limitations may exist in particular where the additional brake device is formed by the regular hydraulic vehicle brake.

Furthermore, it is possible for the requirement for the additional brake device to occur merely in the form of a request to the driver to provide an additional clamping force by manual actuation of the brake pedal when the vehicle is stationary.

In all the aforementioned cases, even the requirement for the additional brake device to provide an additional clamping force is sufficient, regardless of the actual provision of the additional clamping force, to obtain information on the proper functioning or the decreasing efficiency of the electric brake motor with the aid of the method according to the invention.

Preferably, the number of actuating requirements for the additional brake device for providing an additional clamping force is evaluated. If the number of actuating requirements exceeds an asèociated limit value, a fault signal is generated. Additionally.

or alternatively, the level of the additional clamping force required may also be used for assessing the state of the electromechanical part of the parking brake, in that a fault signal is generated if the additional clamping force exceeds an associated limit valua Here, in particular also the number of actuating requirements is additionally taken into account.

Furthermore, other boundary conditions in the parking brake or environmental conditions may also be taken into account, in particular when defining the limit values.

Thus, for example, it is expedient that the additional clamping force required for assessing the state of the electromechanicl part of the parking brake is evaluated only in the case where one or more electrical state quantities or characteristic quantities of the electric brake motor or of the power supply or of the control of the electric brake motor lie in a defined value range. For example, the evaluation takes place only in the case where the actuator voltage or motor voltage exceeds a threshold value. In this * case, the number of events in which the motor voltage exceeds the threshold value is evaluated, where an actuating requirement for the additional brake device counts as an event.

As an additional or alternative condition for the evaluation, it may also be stipulated that the temperature in the parking brake must lie in a defined temperature range, in particular in the temperature range suitable for normal operational functioriing, which lies, for example, between -40°C and +60°C.

Various actuating patterns may be taken into account in the evaluation. Thus, for S example, it is advantageous to take into account only above-average accumulations of requirements for providing an additional clamping force, which is the case, for example, with a plurality of requirements for the additional brake device which immediately follow one another.

It is also possible to employ different evaluating algorithms in dependence on the events that occur. Thus, for example, with the exceeding of a defined number of requirements for providing additional clamping force, a progressive rating may take place, since in this case increased wear may be assumed. Conversely, the evaluation may be reset again and started from the beginning if, following a plurality of requirements for providing additional clamping force, over a defined number of actuations of the parking brake or over a defined period of time, no further requirement for the additional brake device takes place.

The method according to the invention proceeds in a closed-or open-loop control device in the vehicle, which may be a component part of the parking brake.

Further advantages and expedient embodiments can be gathered from the further claims, the description of the figures and the drawings, in which: Fig. 1 shows a section through an electromechanical parking brake for a vehicle, having an electric brake motor for generating a clamping force which arrests the vehicle, Fig. 2 shows a flow chart with method steps for monitoring the functioning of the parking brake, Fig. 3 shows a further flow chart with method steps for monitoring the functioning in a modified embodiment. .

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Fig. 1 shows an electromechanical parking brake 1 in a vehicle, in which a clamping force, which arrests the vehicle when stationary, can be generated by means of the parking brake. The parking brake 1 has a brake caliper 2 with a clasp 9 which reaches S over a brake disc 10:A brake motor 3, designed as an electric motor, serves as the actuator of the parking brake 1 and rotationally drives a spindle 4, on which a spindle component 5 is rotatably mounted. The spindle component 5 is axially displaced when the spindle 4 rotates. The spindle component 5 moves inside a brake piston 6, which carries a brake lining 7 which is pressed against the brake disc 10 by the brake piston 6. On the opposite side of the brake disc 10 there is arranged a further brake lining 8, which is held stationarily on the clasp 9..

The spindle component 5 can move inside the brake piston 6 axially forwards in the direction towards the brake disc in the case of one rotational movement Of the spindle 4 and axially rearwards until it reaches a stop 11 in the case of an opposite rotational movement of the spindle 4. In order to generate a desired target clamping force, the spindle component 5 acts upon the inner end side of the brake piston 6, so that the brake piston 6, mounted axially displaceably in the parking brake 1, with the brake lining 7 is pressed against the end face, directed towards it, of the brake disc 10.

The parking brake has an additional brake device, which is formed by the regular, hydraulic vehicle brake. If the target clamping force cannot be generated solely by the electric brake motor, the hydraulic vehicle brake is actuated in addition, so that the total clamping force is composed of an electric-motor portion and a hydraulic portion. With the hydraulic assistance, the rear side, directed towards the brake motor, of the brake piston 6 is acted upon by hydraulic fluid under pressure.

Fig. 2 illustrates a first procedure for monitoring the functioning of the parking brake. In the first methOd step 20, the application operation begins by actuation of the electric brake motor to generate a clamping force. In the next method step 21, it is queried whether hydraulic assistance by means of the vehicle brake is required. In this case, the clamping force is composed additively of the portion generated by the electric brake motor and the hydraulic portion of the parking brake. If no hydraulic assistance is required, the procedure is continued by following the No branch ("N") to the next method step 22, according to which no further action in performing the monitoring of the functioning takes place. The method for monitoring of the functioning is provisionally ended; renewed actuatibn of the parking brake is started again.

By contrast, if it is ascertained in the method step 21 that the provision of the required target clamping force cannot be provided solely by means of the electric brake motor, so that additional hydraulic assistance by means of the vehicle brake is required, the procedure is continued by following the Yes branch ("Y") to the next method step 23, in which two queries which must be cumulatively present for performing the monitoring of the functioning are carried out. Firstly, it is queried whether the motor voltage or actuator voltage exceeds an associated limit value. Furthermore, it is queried whether the temperature in the brake motor lies within a defined temperature range, which lies, for example, between -40°C and +60°C. If one of these conditions is not fulfilled, the procedure is continued by following the No branch to the method step 22, and the monitoring of the functioning is provisionally ended. Otherwise, the procedure is continued by following the Yes branch to the next step 24, in which the number of requirements for the hydraulic additional assistance is counted. A counter is incremented for this.

In the following method step 25, it is queried whether the current count of the counter, i.e. the total number of requirements for the hydraulic additional assistance, exceeds a threshold value or limit value. If this is not the case, the procedure is continued by following the No branch to the method step 22 again, and the action is ended, with the count of the counter being retained for a new run of the method which takes place subsequently. If, however, the limit value has been reached, then a defined number of requirements for providing hydraulic additional clamping force are present, indicating a deteriorating efficiency of the electromechanical. brake system, and the procedure is continued by following the Yes branch to the method step 26, according to which a fault signal is generated. The fault signal can be indicated to the driver by requesting the driver, for example, to visit a workshop for an inspection of the parking brake.

A further exemplary embodiment of a method for monitoring the functioning of the parking brake is illustrated in Fig. 3. Firstly, in the method step 30 the application operation is started by actuation of the electric brake motor to generate a clamping force. In the next method step 31, it is queried whether additional hydraulic assistance by means of the hydraulic vehicle brake is required. If this is not the case, the procedure is continued by following the No branch to the method step 32, in which it is queried whether the conditions for performing the method for monitoring of the functioning in one or more preceding runs were fulfilled or not. With this, it is intended to check whether the environmental conditions for the parking brake have normalised to such a degree that a correctly functioning state of the electric brake motor may be assumed. In this case, that is to say if the conditions for performing the method for monitoring of the functioning have not been present one or more times in succession, the procedure is continued by following the Yes branch to the method step 34 and the counter which shows the number of requirements for the hydraulic additional assistance is reset again. Then, the procedure is continued to the method step 33, according to which the entire action, that is to say the monitoring of the functioning, is ended. Only with the renewed actuation of the parking brake is the method for monitoring of the functioning restarted.

By contrast, if it is ascertained in the method step 32 that the query has a no" outcome, that is to say the conditions for performing the monitoring of the functioning have been fulfilled in one of the preceding runs, then the procedure is continued, directly and without resetting the counter representing the number of hydraulic clamping force requirement, to the method step 22 and the method is provisionally ended. However, the counter showing the number of hydraulic clamping force requirement remains as it is and may, if necessary, be further incremented upon a renewed run.

If the query in the method step 31 shows that hydraulic assistance is required, since the target clamping force cannot be provided solely by means of the electric brake motor, the procedure is continued by following the Yes branch to the next method step 35. In this method step, it is queried whether the actuator voltage or motor voltage exceeds an associated limit value, If this is not the case, the procedure is continued by

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following the No branch to the method step 32 again and the above-described sequence is carried out in this branch. By contrast, if the query is. satisfied, the procedure is continued by following the Yes branch to the next method step 36.

In the method step 36, the query is. carried out as to whether the conditions for performing the monitoring of the functioning were already present in the preceding actuation of the parking brake as well. By means of this additional condition, it is checked whether in a plurality of successive actuations of the parking brake the actuator voltage or motor voltage.!xceeds the associated limit value, indicating a deterioration of the efficiency of the electric brake motor. This procedure haá the advantage that no temperature information is required for the monitoring of the functioning.

If it is ascertained in the method step 36 that the voltage condition from the method step 35 did not apply in the preceding actuation of the parking brake, that is to say did not exceed the associated limit value, the procedure is continued by following the No branch to the method step 33, according to which the monitoring of the functioning for this actuation of the parking brake is ended, but the count of the counter is retained. By contrast, if it is ascertained in the method step 36 that the condition from method step 35 applies, that is to say in the preceding run the actuator voltage exceeded the associated limit value, the procedure is continued by following the Yes branch to the next method step 37, in which the counter indicating the number of actuations of the parking brake with hydraulic additional assistance under the stated condition is incremented. In the next method step 38, it is queried whether the count of the counter exceeds an associated limit value. If this is not the case, then no critical situation is present, and the procedure is continued by following the No branch to the method step 33. Otherwise, the procedure is continued by following the Yes branch to the next method step 39 and a fault signal is generated.

The limit value, which is associated with the couht of the counter by means of which the number of hydraulic additional requirement is counted, is set here such that overloading of the hydraulic components is precluded.

Claims (13)

1. CLAIMS1. Method for monitoring the functioning of a parking brake (1) comprising an electromechanical brake device having an electric brake motor (3) for generating an eleétromechanical target clamping force (Fi), it being possible for an additional clamping force to be generated by means of an additional brake device, as required, characterised in that, in the case where the number of actuating requirements for the additional brake device and/or the level of the additional clamping force required exceeds an associated limit value, a fault signal is generated.
2. 2. Method according to Claim 1, characterised in that the actuating requirements and/or the level of the additional clamping forc! required are taken into account for the monitoring of the functioning only in the case where electrical state quantities or characteristic quantities of the electric brake motor (3) lie in a defined value range.
3. 3. Method according to Claim 2, characterised in that the evaluation takes place only in the case where the motor voltage exceeds a threshold value.
4. 4. Method according to Claim 3, characterised in that the number of events where the motor voltage lies above the threshold value is evaluated.
5. 5. Method according to one of Claims 1 to 4, characterised in that the actuating requirements and/or the level of the additional clamping force required are taken into account only in the case where the temperature in the parking brake (1) lies in a defined temperature range.
6. 6. Method according to Claim 5, characterised in that the temperature range lies between -40°C and +60°C.
7. 7. Method according to one of Claims I to 6, characterised in that only actuating requirements immediately following one another are taken into account.
8. 8. Method according to one of Claims 1 to 7, characterised in that the additional brake device is a hydraulic vehicle brake.
9. 9. Closed-or open-loop control device for carrying out the method according to one of Claims 1 to8.
10. 10. Parking brake (1) in a vehicle having a closed-or open-loop control device according to Claim 9.
11. 11. Method for monitoring the functioning of a parking brake, substantially as hereinbefore described with reference to the accompanying drawings.
12. 12. Closed-or open-loop control device substantially as hereinbefore described with reference to the accompanying drawings.
13. 13. Parking brake substantially as hereinbefore described with reference to the accompanying drawings.