Brake device, electromechanical brake system and method for operating an electromechanical brake system - Patents.com

Abstract

In electromechanical braking systems, the power required for the braking process is provided by an asynchronous machine, the asynchronous machine, and in particular the torque delivered by this asynchronous machine, being regulated by means of a quasi-stationary rotor position for the rotor of the asynchronous machine.

Description

[Technical field]

[0001] The present invention relates to a braking device and to an electromechanical braking system comprising such a braking device.The present invention further relates to a method for operating an electromechanical braking system. [Background technology]

[0002] To brake or slow down a motor vehicle, the motor vehicle has a braking system capable of braking several wheels of the vehicle. Currently, hydraulic braking systems are used exclusively for this purpose. Electromechanical braking systems are also increasingly used.

[0003] For example, Patent Document 1 describes an electrically operable parking brake device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2000 / 29268 Summary of the Invention

[0005] The invention provides a braking device and an electromechanical braking system and a method for operating an electromechanical braking system having the features set forth in the independent claims. Further preferred embodiments are the subject of the dependent claims.

[0006] According to the present invention, A braking system is provided which comprises a braking element, a transmission, an asynchronous machine and a control device. The braking element is designed for applying a force to a brake shoe, which in particular can be pressed against a brake disc when a force is applied to the brake shoe. The transmission is designed for mechanically coupling a drive shaft of the asynchronous machine to the braking element. The control device is designed for controlling the asynchronous machine. In particular, the control device can control the asynchronous machine with a quasi-stationary rotor position. In other words, when controlling the asynchronous machine, the control device starts from at least approximately a stationary rotor position.

[0007] moreover, According to the invention, an electromechanical braking system is provided which comprises a braking device, a brake disc and at least one brake shoe, the at least one brake shoe being designed to be pressed against the brake disc by the braking device.

[0008] lastly, A method for operating an electromechanical brake system, in particular an electromechanical brake system controlled by an asynchronous machine, is provided, the method comprising a step of receiving a setpoint value for a braking force to be adjusted, and further comprising a step of controlling the asynchronous machine, in particular the asynchronous machine can be controlled using the received setpoint value for the braking force to be adjusted and a quasi-steady rotor position of the asynchronous machine. Effect of the Invention

[0009] The invention is based on the knowledge that an electric drive is necessary for the operation of electromechanical brakes.

[0010] In this case, preferably a brushless motor, in particular a permanently excited synchronous machine, is used for the electromechanical brake system.

[0011] However, in order to operate such a synchronous machine in a quasi-static state or at low speeds, it is necessary to compulsorily determine the rotor position, for example by means of an additional rotor position sensor.

[0012] In view of this knowledge, the idea of ​​the present invention is to provide a drive for an electromechanical brake system that is as simple and robust as possible. In particular, an electromechanical brake system must be provided that can be driven by a robust electric machine without a rotor position sensor.

[0013] For this purpose, the invention provides that an electromechanical brake system is driven by an asynchronous machine. Due to the relatively small movements of the brake elements, in particular the brake shoes, during the braking process, it can be assumed that the rotor of such an asynchronous machine only undergoes a very small rotational movement during the braking process. Correspondingly, for the drive control of the asynchronous machine, an at least approximately constant rotor position can be assumed. The drive control of the asynchronous machine can therefore be carried out without an additional rotor position sensor for determining the rotational movement of the rotor of the asynchronous machine.

[0014] For the drive control of an asynchronous machine, it is sufficient to set the frequency of the phase voltages in the asynchronous machine based on the so-called slip, i.e. the speed difference between the rotor and the rotating magnetic field, the torque generated being proportional to the magnetic flux and the slip.

[0015] As already mentioned above, only very small movements are required for the actuation of the electromechanical brake. Correspondingly, the rotational movement of the rotor of the electric machine is also very small. Therefore, the torque to be adjusted by the asynchronous machine used according to the invention can be adjusted based on the rotor being at least approximately stationary. Therefore, no rotor position sensor is required to determine the rotational movement of the rotor.

[0016] According to one embodiment, the control device of the brake device is designed to receive a setpoint value for the braking force to be adjusted. Correspondingly, the control device of the asynchronous machine can adjust the torque using the received setpoint value for the braking force to be adjusted. Since the torque provided by the asynchronous machine and thus also the force that the brake element exerts on the brake shoe is proportional to the magnetic flux and thus proportional to the slip in the asynchronous machine, the control device can adjust the braking force in a simple manner, assuming a quasi-stationary state for the rotor in the asynchronous machine, without requiring a rotor position sensor in the asynchronous machine for this purpose.

[0017] According to one embodiment, the control device is designed to receive a sensor value from a speed sensor. This speed sensor can in particular detect the speed of the wheel to be braked. The wheel to be braked can be mechanically connected, for example, to a brake disk, which is braked by one or more brake shoes actuated by a brake element of the brake device. Correspondingly, the control device can also be designed to receive a torque at the asynchronous machine using the sensor value received from the speed sensor. By evaluating the sensor value of the speed sensor, the rotational movement of the wheel or the brake disk can be calculated. This makes it possible to monitor the deceleration, i.e. the reduction in the speed, during the braking process. Correspondingly, the torque provided by the asynchronous machine can be adapted according to the calculated speed in order to apply a preset braking force, so that a locking of the wheel can be detected very quickly, for example by monitoring the sensor value of the speed sensor. The torque provided by the asynchronous machine can then be reduced, for example, in order to reduce the braking force and thus to prevent further locking of the wheel.

[0018] According to one embodiment, the control device is designed for regulating the electrical phase currents in an asynchronous machine by means of the torque to be regulated.

[0019] According to one embodiment of the electromechanical brake system, a speed sensor is provided in the electromechanical brake system. The speed sensor is designed to detect the speed of rotation of the brake disc or of a wheel mechanically connected to the brake disc. The control device is accordingly designed to drive the asynchronous machine using the detected speed. In this way, the deceleration of the wheel can be monitored. The braking force can then be adapted by adapting the torque delivered by the asynchronous machine. In particular, wheel locking can be detected very quickly and the braking force can then be reduced in order to release the locked wheel again.

[0020] The above-mentioned embodiments and developments can be combined with one another in any way, provided this is meaningful. Other embodiments, developments and realizations of the invention also include combinations not explicitly mentioned of the features of the invention described above or below in relation to the examples. In particular, those skilled in the art will add individual aspects as improvements or supplements to the respective basic forms of the invention. [Brief description of the drawings]

[0021] [Figure 1] 1 is a schematic diagram of an electromechanical braking system including a braking device according to an embodiment; [Diagram 2] 4 is a flow chart based on a method for operating an electromechanical braking system according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Other features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.

[0023] 1 shows a schematic diagram of an electromechanical brake system 1 according to an embodiment. The electromechanical brake system 1 has a brake disc 50, which is mechanically coupled to a wheel 60 via a friction-locking connection. A rotational speed sensor 61 can be provided on the wheel 60, or possibly on the brake disc 50, which can sensor-monitor the rotational movement of the wheel 60 and thus also of the brake disc 50 and provide a sensor signal D corresponding to the rotational speed.

[0024] To brake the rotating wheel 60, one or more brake shoes 41, 42 may be pressed against the brake disc 50. In this case, the rotation of the brake disc 50 is braked in response to the force applied by the brake shoes 41, 42.

[0025] Whereas in conventional braking systems the brake shoes 41, 42 are generally pressed against the brake disc 50 by a hydraulic system, in the electromechanical braking system shown in Figure 1 a braking device is provided which comprises an electric drive, the functioning principle of which is explained in more detail below.

[0026] To apply the braking force of the brake shoes 41, 42 to the brake disc 50, an asynchronous machine 10 is provided in the electromechanical brake system 1, which presses at least one brake shoe 41 against the brake disc 50 via a transmission 20. Optionally, a mechanical component 43 may be provided, which allows the force generated by the transmission 20 to be distributed evenly to the two brake shoes 41, 42, so that the brake disc 50 can be braked from both sides via the brake shoes 41, 42. For example, the force generated by the transmission 20 can first act on the brake element 30, to which the brake shoe 41 can be fixed.

[0027] In the non-operating state, i.e. when no braking force should be applied to the brake disc 50 by the brake shoes 41, 42, there is only a very small distance between the brake shoes 41, 42 and the brake disc 50. Therefore, in order to apply a braking force to the brake disc 50, the brake shoes 41 or 42 only need to be moved very slightly. As a result, the rotation shaft of the asynchronous machine 10 also needs to be rotated very slightly, i.e. by a very small angle, in order to press the brake shoe or shoes 41, 42 against the brake disc 50. Due to the very small distance of the brake shoes 41, 42 from the brake disc 50 in the non-operating state, even the gear ratio of the transmission 20 requires only a very small rotational movement of the drive shaft of the asynchronous machine 10. This makes it possible to start from at least approximately a steady state of the drive shaft of the asynchronous machine 10 and thus of the rotor for the drive control of the asynchronous machine 10 described below. This is referred to below as a quasi-steady rotor position.

[0028] To adjust the preset braking force, the brake shoes 41 and 42 must be pressed against the brake disc 50 with a force corresponding to the preset braking force. For this purpose, the asynchronous machine 10 must provide a corresponding torque at the input of the transmission 20. In this case, the torque provided by the asynchronous machine 10 is proportional to the magnetic flux and the slip, i.e. the speed difference between the rotor and the rotating magnetic field in the asynchronous machine. As mentioned above, the illustrated brake system 1 can be started from a quasi-stationary rotor position, so that the desired slip and thus the torque provided by the asynchronous machine 10 can be adjusted solely by the frequency of the phase voltages at the asynchronous machine. This allows the braking force to be controlled without the need for an additional rotor position sensor at the asynchronous machine 10.

[0029] The drive control of the asynchronous machine 10 can be effected, for example, by a control device 11. The control device 11 can provide the asynchronous machine 10 with electrical phase currents and phase voltages that are suitable for supplying the desired torque to the transmission 20 by the asynchronous machine 10.

[0030] For this purpose, for example, a setpoint value S for the braking force can be predefined in the control device 11. The control device 11 can use this setpoint value S to set a current and a voltage that are appropriate for the braking force to be set at the asynchronous machine 10. For example, a corresponding correspondence between the predefined braking force and the current or voltage to be set can be stored in the memory of the control device 11. Alternatively, it is also possible to define the relationship between the braking force to be set and the current or voltage as a functional relationship, and to calculate the respective current or voltage as a function of the predefined braking force using this functional relationship. Of course, any other method for calculating the current or voltage to be set as a function of the setpoint value S for the braking force to be set is also possible.

[0031] Furthermore, it is also possible to factor in the rotational speed of the wheels 60 or the brake discs 50 into the drive control of the asynchronous machine 10. For this purpose, for example, a sensor value D provided by the rotational speed sensor 61 can be evaluated by the control device 11. For example, from the change in the rotational speed, in particular the drop in the rotational speed during a braking process, inferences can be made about the actual deceleration caused by the electromechanical brake system 1. Correspondingly, further control of the torque provided by the asynchronous machine 10 or of the phase currents or phase voltages to be adjusted can also be carried out according to the actual change in the rotational speed and the deceleration derived from the rotational speed. In this way, a very rapid adaptation of the braking behavior is possible with the electromechanical brake system 1.

[0032] In particular, the locking of the wheel 60 can also be detected, for example by evaluation of the sensor signal D from the rotational speed sensor 61. In such a case, i.e. when the locking of the wheel 60 is detected, the torque provided by the asynchronous machine 10 can be reduced, and thus the force with which the brake shoes 41 and 42 act on the brake disc 50 can also be reduced. This allows the braking force to be reduced so that the wheel does not lock for longer. In this way, the braking behavior can be intervened very quickly, so that the vehicle can be better controlled with such a brake system 1.

[0033] 2 shows a flow chart according to a method for operating an electromechanical brake system 1 according to an embodiment, in this case in particular with an electromechanical brake system having an asynchronous machine 10. Correspondingly, the method may comprise any steps as already described above in connection with the electromechanical brake system 1. Similarly, the electromechanical brake system 1 may comprise the components required to carry out the method described below.

[0034] In step S1, a target value S for the braking force to be adjusted can be received.

[0035] Then, in step S2, the asynchronous machine 10 of the electromechanical braking system can be controlled using the received setpoint value S. The control of the asynchronous machine 10 is performed using the quasi-stationary rotor position of the asynchronous machine.

[0036] Furthermore, any suitable further parameters, such as the rotation speed of the wheel to be braked, may be taken into account in the drive control of the asynchronous machine.

[0037] In summary, the present invention relates to an electromechanical braking system, in which the force required for the braking process is provided by an asynchronous machine, and the asynchronous machine, and in particular the torque delivered by the asynchronous machine, is regulated by means of a quasi-stationary rotor position for the rotor of the asynchronous machine. [Explanation of symbols]

[0038] 1 Brake system 10 Asynchronous Machines 11 Control device 20 Transmission 30 Brake element 41,42 Brake shoes 43 Mechanical Components 50 Brake disc 60 Wheels 61 Rotational speed sensor D Sensor signal, sensor value S Target Value S1, S2 steps

Claims

1. In the braking device, a braking element (30) designed to apply a force to a brake shoe (41); An asynchronous machine (10); a transmission (20) designed to mechanically couple a drive shaft of said asynchronous machine (10) to said braking element (30); a control device (11) designed to drive and control said asynchronous machine (10) with a quasi-steady rotor position of said asynchronous machine (10); A brake device having

2. 2. The brake system according to claim 1, wherein the control device (11) is designed to receive a setpoint (S) for a braking force to be adjusted and to adjust the torque at the asynchronous machine (10) using the received setpoint (S) for the braking force to be adjusted.

3. said control device (11) being designed to receive a sensor value (D) from a rotational speed sensor (61) detecting the rotational speed of a wheel (60) to be braked, the control device (11) is designed to regulate the torque at the asynchronous machine (10) using the received sensor values ​​(D); 3. The brake device according to claim 1 or 2.

4. 4. A braking system according to claim 1, wherein the control device (11) is designed for regulating the phase currents in the asynchronous machine (10) with a preset torque.

5. In an electromechanical braking system (1), A brake device according to any one of claims 1 to 4, A brake disc (50); a brake shoe (41) designed to be pressed against the brake disc (50) by the braking device; An electromechanical brake system (1).

6. a rotational speed sensor (61) designed to detect the rotational speed of the brake disc (50) or the rotational speed of a wheel (60) mechanically connected to the brake disc (50), the control device (11) of the braking device is designed to drive and control the asynchronous machine (10) using the detected rotational speed. Electromechanical braking system (1) according to claim 5.

7. A method for operating an electromechanical braking system (1) driven and controlled by an asynchronous machine (10), comprising: The method comprises the steps of: receiving a target value (S) for the braking force to be adjusted (S1); A step (S2) of driving and controlling the asynchronous machine (10) using the target value (S) for the braking force to be adjusted and a quasi-steady rotor position of the asynchronous machine (10); 2. A method for operating an electromechanical brake system (1), comprising:

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