Sensor unit for determining the rotor position of an electric motor and an electric motor, preferably for a clutch actuator of a clutch actuation system of a motor vehicle.

Abstract

Sensor unit (16) for determining the rotor position of an electric motor (12), comprising at least one magnetic field sensor (19) which is mounted on a carrier element (20), wherein the carrier element (20) is positioned in a sensor housing (18) which is open on one side and has a sensitive surface of the at least one magnetic field sensor (19) facing the open side (23) of the sensor housing (18), characterized in that the sensor housing (18) has a step (25) in its axial extension by means of which the sensor housing (18) is divided into areas (26, 27) with two cross-sections, so that the distance of the sensitive surface of the magnetic field sensor (19) to a magnetic encoder ring (14) is adjustable.

Description

[0001] The invention relates to a sensor unit for determining the rotor position of an electric motor, comprising at least one magnetic field sensor positioned on a carrier element and an electric motor, preferably for a clutch actuator of a clutch actuation system of a motor vehicle.

[0002] In modern motor vehicles, especially passenger cars, automated clutches are increasingly being used, as described in DE 10 2011 014 936 A1. The use of such clutches offers the advantage of improved driving comfort and allows for more frequent use of gears with higher ratios. The clutches used are integrated into hydraulic clutch systems, in which a hydrostatic actuator, driven by an electrically commutated motor, is connected to the clutch via a hydraulic line.

[0003] To improve driving comfort, the position of the electric motor's rotor, measured by sensors, must be compared with the desired position of the rotor. Typically, the rotor position is detected using three Hall-effect magnetic field sensors positioned at different distances from each other. The edges of these sensors are used as the position signal.

[0004] Further relevant prior art is known from US 5 581 179 A. The technical background is also described in US 2013 / 0 200 884 A1 and US 2002 / 0 135 497 A1.

[0005] From DE 10 2013 213 948 A1, an electric motor is known in which the magnetic field sensors are arranged outside the axis of rotation of the electric motor on the stator. The three magnetic field sensors and possibly also further analog sensors are positioned on a circuit board and detect the magnetic field of a magnetic encoder ring, which is non-rotatably connected to the externally rotating rotor of the electric motor (DE 10 2013 208 986 A1).

[0006] The circuit board containing the magnetic field sensors is typically permanently installed between the stator and a stator support, meaning that once the stator is mounted, the sensor board cannot be replaced. Furthermore, sealing the sensor support presents another problem, as holes are required for contacting and screwing in the sensors. These holes reduce the rigidity of the actuator housing in which the electric motor is located.

[0007] The invention is therefore based on the objective of specifying a position for the circuit board carrying the magnetic field sensor in which it is easy to mount and at the same time prevents reductions in the stiffness of the actuator housing.

[0008] According to the invention, the problem is solved by a sensor unit according to the features of claim 1, in which the carrier element is positioned in a sensor housing which is open on one side and which has a sensitive surface of the at least one magnetic field sensor facing the open side of the sensor housing. Using such a separate sensor unit, the sensor can be easily replaced even after the stator has been mounted, so that the sensor remains easily accessible in the event of a fault. The rigidity of the actuator housing remains unchanged.

[0009] Advantageously, the carrier element is designed as a circuit board or as a stamped grid. In particular, using a stamped grid reduces the weight of the sensor unit and allows for a space-saving arrangement of the magnetic field sensors on the carrier element.

[0010] In one embodiment, the at least one magnetic field sensor, together with the mounting element, is encapsulated or overmolded with a plastic within the sensor housing. This encapsulation with a plastic ensures reliable retention of the sensor on the mounting element and simultaneously relative to the sensor housing without the need for additional components. This prevents vibrations acting on the sensor housing during the movement of a vehicle from affecting the sensor's positioning. Furthermore, the sensor housing is reliably protected against environmental influences such as moisture.

[0011] In one variant, the wiring for the carrier element and / or the magnetic field sensors is routed through a cable outlet extending outwards from the sensor housing, with the cable outlet preferably filled with a plastic material. Here, too, the plastic ensures a secure fit for the wiring. Simultaneously, the outward-facing cable outlet can be used for precise alignment of the sensor relative to the magnetic sensor ring. Depending on the available installation space, the cable outlet can be routed radially or tangentially away from the sensor housing.

[0012] According to the invention, the sensor housing has a step in its axial extension by means of which the sensor housing is divided into areas with two cross-sections. This step has, in particular, the function of correctly adjusting the distance of the sensitive surfaces of the magnetic field sensors to the magnetic encoder ring, so that the magnetic field generated by the magnetic encoder ring can be reliably detected by the magnetic field sensors.

[0013] Advantageously, the sensor housing is cylindrical and features at least one sealing ring on its outer circumference. This cylindrical design allows the housing to be easily adapted to the shape of the rotor housing. The sealing ring positioned on the outer circumference ensures a seal after the sensor housing is inserted into the rotor housing, thus protecting the inserted sensor from environmental influences.

[0014] In another embodiment, the carrier element is equipped on both sides with magnetic field sensors and / or evaluation and / or amplification electronics. This double-sided mounting of the carrier element is advantageously possible when the sensor housing is designed as a cylinder. The double-sided mounting with magnetic field sensors thus enables redundancy of the signals detected by the magnetic field sensors.

[0015] A further development of the invention relates to an electric motor, in particular for a clutch actuator of a clutch actuation system of a motor vehicle, comprising a rotor which is rotationally fixed to a magnetic sensor ring and a stator on which at least one magnetic field sensor for detecting the magnetic field generated by the magnetic sensor ring is arranged, wherein the magnetic field sensor is arranged outside the axis of rotation of the rotor. In an electric motor in which the sensor is easily replaceable, the at least one magnetic field sensor is arranged in a sensor unit which is configured according to at least one of the features described in this patent application.

[0016] Advantageously, the sensor unit is arranged on the stator, with one open side of the sensor housing facing the magnetic encoder ring. This ensures that the magnetic field sensors can reliably detect the magnetic field generated by the magnetic encoder ring and output a correspondingly accurate sensor signal.

[0017] In one embodiment, the sensor housing can be attached to the rotor housing. This makes the rotor housing particularly easy to mount and dismount.

[0018] The invention allows for numerous embodiments. One of these will be explained in more detail with reference to the figures shown in the drawing.

[0019] They show: Fig. 1. A schematic representation of a clutch actuation system for actuating an automated friction clutch, Fig. 2 an embodiment of an electric motor according to the invention Fig. 3 an embodiment of the sensor unit according to the invention.

[0020] In Fig. Figure 1 is a simplified representation of a clutch actuation system 1 for an automated clutch. The clutch actuation system 1 is associated with a friction clutch 2 in the drivetrain of a motor vehicle and comprises a master cylinder 3, which is connected to a slave cylinder 5 via a hydraulic line 4, also referred to as a pressure line. A slave piston 6 is axially movably mounted in the slave cylinder 5 and actuates the friction clutch 2 via a bearing 7. A master piston 8 is axially movably mounted in the master cylinder 3. A piston rod 9 extends from the master piston 8 and is translationally movable along the longitudinal extent of the master cylinder 3 together with the master piston 8. The piston rod 8 of the master cylinder 3 is coupled to an electric motor actuator 11 via a threaded spindle 10.The electromechanical actuator 11 comprises an electric motor 12 designed as a commutated DC motor and an evaluation unit 13. The threaded spindle 10 converts a rotary movement of the electric motor 12 into a longitudinal movement of the piston rod 9 or the encoder piston 8.

[0021] The electric motor 12 exhibits according to Fig. 2 a rotor 121 on which a magnetic encoder ring 14 is mounted in a rotationally fixed manner. Spatially spaced from the magnetic encoder ring 14 and outside the axis of rotation of the rotor 121, a sensor unit 16 is attached to a stator 15, wherein the position signal taken from a magnetic field sensor 19 is evaluated by an evaluation electronics 17, which is part of the sensor unit 16.

[0022] An embodiment of the sensor unit 16 is shown in Fig.Figure 3 shows the sensor unit 16. It consists of a cylindrical sensor housing 18 in which at least one magnetic field sensor 19 is positioned on a carrier element 20. The carrier element 20 can be designed as a flat circuit board or as a stamped grid. The sensitive surface of the at least one magnetic field sensor 19 faces an open side 23 of the sensor housing 18, which, in the installed state, faces the magnetic encoder ring 14.

[0023] Starting from the carrier element 20, a cable 21 of the circuit board or the die-cut grid is led to the outside in a cable outlet 22, the cable outlet 22 pointing radially away from the sensor housing 18 or being tangentially molded onto it. The interior of the sensor housing 18 and the cable outlet 22 are injection-molded with a plastic, so that the internal electronics in the form of the magnetic field sensor 19 and the evaluation electronics 17, as well as the electrical lines 24, are adequately protected from moisture and are simultaneously positioned immovably within the sensor unit 16.

[0024] The cylindrical sensor housing 16 has a step 25 that divides the sensor housing 18 into two sections 26 and 27. Section 26, which encompasses the open side 23 of the sensor housing 18, has a smaller diameter than the adjacent second section 27. This step 25 defines the distance between the open side 23 and the sensitive area of ​​the magnetic field sensors 19 to be detected. Furthermore, the larger-diameter section 27 of the sensor housing 18 has a locking mechanism 28 that holds the sensor housing 18 in a housing of the rotor 121 (not shown) when the rotor is positioned behind the stator 15. This second section 27 is also surrounded by a sealing ring 29 in the form of an O-ring, which seals the area of ​​the electric motor 12 housing against the inserted sensor unit 16.

[0025] Due to its cylindrical shape, the carrier element 20 can be equipped on both sides. This allows magnetic field sensors 19 to be arranged on both sides to provide redundancy in the detected magnetic field. Alternatively, the magnetic field sensors 19 can be mounted on one side of the carrier element 20, while the other side carries the evaluation and / or amplification circuitry 17. Various sensor types can be used as magnetic field sensors 19, such as switch Hall sensors, analog Hall sensors, 2D / 3D Hall sensors, inductive sensors, or GMR sensors. Reference symbol list 1 Clutch actuation system 2 friction clutch 3 master cylinders 4 Hydraulic lines 5 slave cylinders 6 slave pistons 7 warehouses 8 sensor pistons 9 Piston rod 10 threaded spindles 11 Electromotive actuator 12 Electric motor 121 Rotor 13 Evaluation unit 14 Magnetic sensor ring 15 Stator 16 sensor units 17 Evaluation electronics 18 sensor housings 19 Magnetic field sensor 20 support element 21 Cabling 22 Cable outlet 23 Open side of the sensor housing 24 Electrical line Level 25 26 First area of ​​the sensor housing 27 Second area of ​​the sensor housing 28 Locking mechanism 29 Sealing ring

Claims

[1] Sensor unit (16) for determining a rotor position of an electric motor (12), comprising at least one magnetic field sensor (19) which is mounted on a carrier element (20), wherein the carrier element (20) is positioned in a sensor housing (18) which is open on one side and has a sensitive surface of the at least one magnetic field sensor (19) facing the open side (23) of the sensor housing (18), characterized by , that the sensor housing (18) has a step (25) in its axial extension, by means of which the sensor housing (18) is divided into areas (26, 27) with two cross-sections, so that the distance of the sensitive surface of the magnetic field sensor (19) to a magnetic encoder ring (14) is adjustable. [2] Sensor unit (16) according to claim 1, characterized by , that the support element (20) is designed as a circuit board or as a stamped grid. [3] Sensor unit (16) according to claim 2, characterized by, that the carrier element (20) is encapsulated or overmolded with a plastic in the sensor housing (18). [4] Sensor unit (16) according to claim 1, 2 or 3, characterized by , that a wiring (21) of the carrier element (20) and / or a wiring (21) of the magnetic field sensor (19) are guided in a cable outlet (22) which protrudes from the sensor housing (18), wherein the cable outlet (22) is preferably filled with a plastic. [5] Sensor unit (16) according to at least one of the preceding claims, characterized by , that the sensor housing (18) is cylindrical in shape and has at least one sealing ring (29) on its outer circumference. [6] Sensor unit (16) according to at least one of the preceding claims, characterized by , that the carrier element (20) is equipped on both sides with magnetic field sensors (19) and / or evaluation or amplification electronics (17). [7] Electric motor (12), preferably for a clutch actuator of a clutch actuation system (1) of a motor vehicle, comprising a rotor (121) which is non-rotatably connected to a magnetic sensor ring (14) and a stator (15) on which at least one magnetic field sensor (19) for detecting the magnetic field spanned by the magnetic sensor ring (14) is arranged outside the axis of rotation of the rotor (121), characterized by , that the at least one magnetic field sensor (19) is arranged in a sensor unit (16) which is designed according to at least one of the preceding claims 1 to 6. [8] Electric motor (12) according to claim 7, characterized by , that the sensor unit (16) is arranged on the stator (15), wherein an open side (23) of a sensor housing (18) faces the magnetic encoder ring (14). [9] Electric motor (12) according to claim 7 or 8, characterized by , that the sensor housing (18) can be attached to a rotor housing.

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