Brake device, electromechanical brake system and method for operating an electromechanical brake system

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 multiple wheels of the vehicle. Currently, hydraulic braking systems are used exclusively for this purpose, but electromechanical braking systems are also increasingly used.

[0003] Patent Document 1, for example, 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 present 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 brake system is proposed that includes a brake element, a transmission, an asynchronous machine, and a control device. The brake element is designed to apply a force to a brake shoe. In particular, applying a force to the brake shoe can press the brake shoe against a brake disc. The transmission is designed to mechanically couple a drive shaft of the asynchronous machine to the brake element. The control device is designed to drive and control the asynchronous machine. In particular, the control device can drive and control the asynchronous machine with a quasi-steady rotor position. In other words, when driving and controlling the asynchronous machine, the control device starts from at least approximately a steady rotor position.

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

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

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

[0010] In this case, the electromechanical braking system preferably uses a brushless motor, in particular a permanently excited synchronous machine.

[0011] However, in order to operate such a synchronous machine in a quasi-static state or at low speeds, it is necessary to calculate the rotor position compulsorily, 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 for an electromechanical brake system to be driven by an asynchronous machine. Due to the relatively small movement of the brake elements, particularly the brake shoes, during the braking process, it can be assumed that the rotor of such an asynchronous machine will only undergo a very small rotational movement during the braking process. Accordingly, an at least approximately constant rotor position can be assumed for the drive control of the asynchronous machine. Therefore, the drive control of the asynchronous machine can be performed 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, in which case the generated torque is proportional to the magnetic flux and the slip.

[0015] As already mentioned above, only a very small movement is required for the operation 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 in accordance with the present invention can be adjusted based on the rotor being at least approximately stationary. Therefore, a rotor position sensor is not required to calculate the rotational movement of the rotor.

[0016] According to one embodiment, the control device of the brake system is designed to receive a setpoint for the braking force to be adjusted. Correspondingly, the control device of the asynchronous machine can adjust the torque using the received setpoint for the braking force to be adjusted. Since the torque provided by the asynchronous machine, and thus the force that the brake elements apply to the brake shoes, is proportional to the magnetic flux and therefore proportional to the slip in the asynchronous machine, the control device can assume a quasi-steady state for the rotor in the asynchronous machine and adjust the braking force in a simple manner 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 sensor values ​​from a speed sensor. This speed sensor can detect, in particular, the speed of the wheel to be braked. The wheel to be braked can be, for example, mechanically coupled to a brake disc, which is braked by one or more brake shoes actuated by a braking element of the brake system. Correspondingly, the control device can also be designed to receive the torque at the asynchronous machine using the sensor values ​​received from the speed sensor. By evaluating the sensor values ​​of the speed sensor, the rotational movement of the wheel or brake disc can be calculated. This makes it possible to monitor deceleration, i.e., a drop in 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 predetermined braking force. Thus, wheel lock can be detected very quickly, for example, by monitoring the sensor values ​​of the speed sensor. The torque provided by the asynchronous machine can then be reduced, for example, to reduce the braking force and thus prevent further wheel lock.

[0018] According to one embodiment, the control device is designed to regulate the electrical phase currents in the asynchronous machine using the torque to be regulated.

[0019] According to one embodiment of the electromechanical braking system, a speed sensor is provided in the electromechanical braking system. The speed sensor is designed to detect the speed of the brake disc or the speed of a wheel mechanically coupled to the brake disc. A control device is accordingly designed to drive and control 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 supplied by the asynchronous machine. In particular, wheel lock can be detected very quickly, and the braking force can then be reduced in order to release the locked wheel again.

[0020] The above-described 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 connection with the examples. In particular, those skilled in the art will also add individual aspects as improvements or supplements to the respective basic forms of the invention. [Brief explanation of the drawings]

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

[0022] Other features and advantages of the present invention are explained below with reference to the accompanying drawings.

[0023] 1 shows a schematic diagram of an electromechanical brake system 1 according to one embodiment. The electromechanical brake system 1 has a brake disc 50, which is mechanically coupled to a wheel 60 via a friction-locked 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 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] While in conventional braking systems the brake shoes 41, 42 are typically pressed against the brake disc 50 by a hydraulic system, the electromechanical braking system shown in Figure 1 is provided with a braking device having 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 enables 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 may first act on the brake element 30, to which the brake shoe 41 may be fixed.

[0027] In the deactivated state, i.e., when no braking force should be applied to the brake disc 50 by the brake shoes 41, 42, only a very small distance exists between the brake shoes 41, 42 and the brake disc 50. Therefore, 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 rotational axis of the asynchronous machine 10 also needs to be rotated very slightly, i.e., only a very small angle, to press the brake shoe(s) 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 deactivated 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 allows the drive control of the asynchronous machine 10, as described below, to start from at least an approximately steady state of the drive shaft of the asynchronous machine 10, and thus of the rotor. This is hereinafter referred to as a quasi-steady rotor position.

[0028] To adjust a 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. To achieve this, the asynchronous machine 10 must provide a corresponding torque to the input of the transmission 20. 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 start from a quasi-steady 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 voltage at the asynchronous machine. This allows the braking force to be controlled without the need for an additional rotor position sensor on the asynchronous machine 10.

[0029] The drive control of the asynchronous machine 10 can be performed, 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 preset in the control device 11. The control device 11 can use this setpoint value S to set the current and voltage appropriate for the braking force to be set at the asynchronous machine 10. For example, a corresponding correspondence between the preset 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 function, and to calculate the respective current or voltage in accordance with the preset braking force using this function. Of course, any other method for calculating the current or voltage to be set in accordance with the setpoint value S for the braking force to be set is also possible.

[0031] Furthermore, the rotational speed of the wheels 60 or the brake discs 50 can also be taken into account in the drive control of the asynchronous machine 10. For this purpose, the sensor value D provided by the rotational speed sensor 61 can be evaluated by the control unit 11, for example. For example, from the change in the rotational speed, in particular the decrease in the rotational speed during a braking process, inferences can be made about the actual deceleration achieved by the electromechanical brake system 1. Correspondingly, further control of the torque provided by the asynchronous machine 10 or the phase current or phase voltage 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, locking of the wheel 60 can also be detected, for example, by evaluating the sensor signal D from the rotational speed sensor 61. In such a case, i.e., when 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 can reduce the braking force so that the wheel does not lock for longer. In this way, very rapid intervention in the braking behavior can be achieved, and 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 particularly relating to said electromechanical brake system with an asynchronous machine 10. Correspondingly, the method may comprise any of the steps already described above in connection with the electromechanical brake system 1. Likewise, said electromechanical brake system 1 may comprise the components necessary 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-steady rotor position of the asynchronous machine.

[0036] Furthermore, any suitable further parameters, such as the rotational 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 supplied by the asynchronous machine, is regulated by means of a quasi-steady 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 discs 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 the drive shaft of said asynchronous machine (10) to said braking element (30); a control device (11) designed to drive and control the asynchronous machine (10) using a quasi-steady rotor position of the asynchronous machine (10); A braking device having:

2. 2. The brake system according to claim 1, wherein the control device (11) is designed to receive a setpoint (S) for the 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. the control device (11) is designed to receive a sensor value (D) from a rotational speed sensor (61) that detects the rotational speed of the 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. 3. A braking device according to claim 1 or 2, 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), The brake device according to claim 1 or 2; A brake disc (50); a brake shoe (41) designed to be pressed against the brake disc (50) by the braking device; An electromechanical braking system (1) comprising:

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); 1. A method for operating an electromechanical braking system (1), comprising:

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