Device for measuring the angular position of a machine shaft

Abstract

A device for measuring the angular position of a machine shaft is described herein. The following describes a device for measuring the angular position or rotational movement of a machine shaft. According to one embodiment, the device has a first housing part and a machine shaft arranged in the first housing part and rotatable about a rotation axis. The machine shaft has a hole, which extends from an end face of the machine shaft into the machine shaft along the rotation axis. The device also includes: a magnet unit with at least one permanent magnet, which is arranged in the hole and fixed to the machine shaft; a second housing part with a protrusion extending into the hole along the rotation axis; and a magnetic field sensor element arranged inside the protrusion of the second housing part.

Description

Technical Field

[0001] The present description relates to the field of angle measuring systems which can be used, for example, to measure the angular position of a machine shaft. Background Art

[0002] In order to control an electric motor, for example, a measuring system is required for measuring the angular position of the motor shaft. Such a measuring system is often based on detecting a rotating magnetic field and usually (in addition) comprises: one or more permanent magnets, which are connected to the machine shaft and thus rotate with the shaft; and one or more magnetic field sensors for detecting the generated magnetic field. It can be seen that one object on which the present invention is based is to make existing sensor systems more efficient (e.g. with regard to costs, installation, number of parts, reduction of installation space, etc.). Summary of the invention

[0003] The above object is achieved by the device according to the present invention. Various embodiments and improvements are as follows.

[0004] A device for measuring the angular position or rotational movement of a machine shaft is described below. A device for measuring the angular position or rotational movement of a machine shaft is described below. According to one embodiment, the device has a first housing part and a machine shaft arranged in the first housing part and rotatable about a rotation axis. The machine shaft has a hole, which extends from an end face of the machine shaft along the rotation axis into the machine shaft. In the case of a hollow shaft, the hole mentioned is a through hole. The device also includes: a magnet unit with at least one permanent magnet, which is arranged in the hole and fixed to the machine shaft; a second housing part with a protrusion extending into the hole along the rotation axis; and a magnetic field sensor element arranged inside the protrusion of the second housing part.

[0005] Furthermore, a drive device with an electric motor is described. According to one embodiment, the device has an electric motor, which is arranged in a first housing part and has a motor shaft rotatable about a rotation axis, and the motor shaft has a hole extending from an end face of the shaft along the rotation axis. The device also has: a magnet unit with at least one permanent magnet arranged inside the hole and fixed to the shaft; and a drive control unit, which is arranged in a housing, and the housing has a protrusion extending into the hole along the rotation axis. An electronic circuit for driving the electric motor is arranged in the drive control unit, and a magnetic field sensor element is arranged inside the protrusion, which is coupled to the electronic circuit for driving the electric motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Below, the embodiments are explained in more detail with the aid of the accompanying drawings. These illustrations are not necessarily drawn to scale, and the embodiments are not limited to the aspects shown. Instead, it is important to present the principles on which the embodiments are based. For the accompanying drawings:

[0007] Figure 1 An example of a magnetic sensor is shown, which is arranged in the central axial bore of the shaft at the end of the shaft; the sensor can be pushed into the central axial bore through an opening in the housing.

[0008] Figure 2 is a block diagram showing, by way of example, a control unit for an electric motor, for example, a converter for a brushless DC motor.

[0009] Figure 3 An exemplary embodiment is shown having a magnetic sensor integrated in the housing cover.

[0010] Figure 4 Shows something like Figure 3 However, in this case, the control unit for the electric motor serves as housing cover, which enables a more compact design.

[0011] Figure 5 Shows Figure 4 A modification of the example in . DETAILED DESCRIPTION

[0012] Figure 1 A sensor system coupled to a machine shaft is described for measuring the angular position and / or the rotational speed (angular velocity) of a machine shaft, in particular a motor shaft of an electric motor, which is arranged in a housing. The electric motor can be, for example, a permanent magnet synchronous motor (PMSM), which is also often referred to as a brushless DC motor. The design of such electric motors is known in principle and can therefore be used in the following manner: Figure 1 Not shown in order to simplify the diagram.

[0013] Figure 1 A shaft 10 is shown which is arranged in a housing and is rotatably mounted about a rotation axis R (for example, a motor shaft of an electric motor). The shaft 10 has an axial hole 11, i.e., the hole 11 extends from an end face of the shaft 11 into the shaft 11 along the rotation axis R. The hole 11 may be a blind hole or a through hole. In the case of a through hole, the shaft 10 is a hollow shaft. A magnet unit 20 is arranged in the hole 11, which is fixed to the shaft 10 and thus rotates together with the shaft. The magnet unit 20 has at least one permanent magnet. Figure 1 In the figure, only a part of the housing is shown, namely the housing cover 41, which is approximately located in a plane perpendicular to the axis of rotation. A narrow gap (gap width t) may exist between the end face of the shaft 10 and the inner side of the housing cover. Various designs of the magnet unit 20 are known per se. For the examples described here, the specific embodiments of the magnet unit 20 are known per se, so they are not repeated here.

[0014] The housing cover 41 has a central opening through which the sensor unit 30 can be inserted. A portion of the sensor unit 30 has an elongated shape (e.g., a cylindrical shape). The portion is approximately located on the rotation axis R, and is introduced into the hole 11 when the sensor unit 30 is inserted through the opening in the housing cover 41. The sensor unit 30 can be fixed to the housing cover 41. For example, the sensor unit is bonded to the housing cover 41 or fixed by screws.

[0015] Inside the sensor unit 30 there are one or more sensor elements 31 which are sensitive to the magnetic field generated by the magnet unit 21 which also rotates with the shaft 10. Furthermore, the sensor unit 30 can contain sensor electronics for controlling the sensor elements 31 and for (pre-processing) the sensor signals (however, this does not necessarily have to be the case). Figure 1 In the example shown, the sensor unit 30 has a socket with electrical contacts 33, which can be plugged into a plug 40. By means of the plug 40, a cable 41 can be connected to the sensor electronics inside the sensor unit 30. The sensor system comprising the sensor unit 30 and the magnet unit 20 rotating with the shaft 10 allows the angular position of the shaft 10 to be measured. The angular velocity and / or angular acceleration of the shaft can be derived from the measured angular position.

[0016] Figure 2 The block diagram in FIG. 1 schematically shows an electric motor M having a sensor unit 30 for measuring the angular position φ of the motor shaft. The sensor unit 30 is connected to a control unit 50 via a cable 41, which contains electronic components for controlling the electric motor M. The electronic components for controlling the electric motor M include, for example, a converter (e.g., a three-phase inverter), a gate driver circuit for controlling a power transistor contained in the converter, a microcontroller for generating a control signal for the gate driver circuit (especially based on information about the angular position φ of the motor shaft received from the sensor unit 30, etc.).

[0017] Figure 3 An embodiment of a sensor unit for measuring the angular position φ of the shaft 10 is shown which is integrated in the motor housing. Figure 3 The illustration is simple, and the crankshaft 10 is shown relatively large relative to the housing. Figure 3 Elements shown are not drawn to scale. Figure 1 In the example of the invention, the shaft 10 has an axial hole 11 along the rotation axis R, and the magnet unit 20 is installed inside the hole 11, and the magnet unit rotates with the shaft 10 and thus generates a magnetic field that rotates with the shaft. The magnet unit 20 includes at least one permanent magnet, which generates a magnetic field extending in the diameter direction (the direction of the magnetic field is in the direction of Figure 3 indicated by arrows).

[0018] The electric motor is arranged in a first housing part 40, which can be closed from the side by a second housing part 41. The second housing part 41 is referred to as the housing cover hereinafter. The housing cover can have a cavity 42 and, for example, an elongated, for example prismatic (or cylindrical) and hollow protrusion 43, which extends along the rotation axis into the hole 11 when the housing cover 41 is mounted to the housing part 40. The elongated protrusion 43 is also called a tower element or "sensor dome". A carrier 34 is arranged inside the hollow protrusion 43, on which one or more sensor elements 31 are mounted. The sensor elements 31 on the carrier 34 are sensitive to magnetic fields. The carrier 34 can be a printed circuit board (PCB), a lead frame, a punched grid, etc.

[0019] A circuit board 35 is arranged in a cavity 42 of the housing cover 41, on which the sensor electronics 32 are arranged. The carrier 34 is also connected to the circuit board 35 and thus enables an electrical connection between the sensor element 31 and the sensor electronics 32. The sensor electronics 32 are designed to control the sensor element 31 and to process the signals provided by the sensor element 31 in order to generate one or more measurement signals indicating the angular position or rotational movement of the machine shaft 10. Suitable sensor elements, such as Hall sensors or magnetoresistive sensors, and suitable sensor electronics are known per se and are therefore not described in detail here. The sensor electronics 32 can have a socket with plug-in contacts so that a cable 41 can be connected to the sensor electronics 32 via a connector 40. Cable 41 (see also Figure 2 ) connects the sensor electronics 32 to a drive control unit 50 for the electric motor.

[0020] The elongated protrusion 43 (sensor dome) can be an integral component of the housing cover 41. In one example, the elongated protrusion is fixedly connected, for example, by adhesive or screws, to the main part of the housing cover 41 (in which the cavity 43 is located). In addition, the elongated protrusion 43 and the housing cover 41 can be made of one component (for example as an injection molded part made of plastic).

[0021] Figure 4 A further embodiment is shown which makes it possible to omit the cable 41 and the associated plug connection between the sensor electronics 32 and the control unit 50 for the electric motor M. In this example, the electronic components for controlling the electric motor (see Figure 2 , the control unit 50) such as a converter (three-phase inverter) and the sensor electronic device 32 (see Figure 3 ) are integrated together in a housing part 41, which also serves as a housing cover.

[0022] Figure 5 The example shows Figure 4, in which the housing part 41 is a normal housing cover with a central opening. Alternatively, the housing part 41 can also be part of the housing part 40 (motor housing). The control unit 50 with the control electronics 51 for the electric motor and the sensor electronics is a module with a separate housing, which (as in the above example of a housing cover) has a hollow protrusion 43, which is also called a sensor dome. The protrusion 43 is a tower-shaped element, in which the sensor element 31 is arranged on a carrier (similar to Figure 3 In this example, the control electronics 51 and the sensor electronics for the electric motor are also arranged in the same module together with the sensor element 31, and no cables with plug connectors are required between the sensor electronics and the control electronics 51. The sensor element 31 is (electrically) coupled to the control electronics 51 within the control unit 50. The sensor element can be arranged, for example, on a carrier (for example, a carrier plate), as in Figure 3 as shown in the example.

[0023] Different from the previous example, according to Figure 5 A hollow shaft 10 ′ is used instead of a crankshaft with a hole. It goes without saying that in all other embodiments described here, a hollow shaft can be used instead of a solid crankshaft with an axial hole.

Claims

1. A device, comprising: a first housing portion (40), a crankshaft (10) arranged in the first housing part (40) and rotatable about a rotation axis, the crankshaft having a hole (11) extending from an end face of the crankshaft (10) along the rotation axis; a magnet unit (20), the magnet unit having at least one permanent magnet, the at least one permanent magnet being arranged in the hole (11) and fixed to the shaft (10); a second housing portion (41) having a protrusion extending into the hole (11) along the rotation axis; and a magnetic field sensor element (31) arranged inside the protrusion of the second housing part (41), The second housing portion (41) serves as an end cover to close an end surface of the first housing portion (40) to define a cavity for accommodating the shaft (10). The second housing part (41) has a central opening, and the magnetic field sensor element (31) is inserted into the hole through the central opening.

2. The device according to claim 1, wherein the projection is an integral component of the second housing part (41).

3. The device according to claim 1 or 2, wherein a carrier is arranged inside the projection of the second housing part (41), on which the magnetic field sensor element (31) is mounted. 4 . The device according to claim 3 , wherein a carrier circuit board with sensor electronics is arranged inside the second housing part ( 41 ).

5. The device according to claim 1 or 2, wherein the machine shaft (10) is a motor shaft of an electric motor.

6. The device according to claim 1 or 2, wherein the hole (11) is a through hole and the shaft (10) is a hollow shaft.

7. The device according to claim 5, wherein a control unit (50) for controlling the electric motor is arranged inside the second housing part (41).

8. A device, comprising: An electric motor, which is arranged in a first housing part (40) and has a shaft (10) rotatable about a rotation axis, the shaft having a hole (11) extending from an end face of the shaft (10) along the rotation axis; a magnet unit (20) having at least one permanent magnet, the at least one permanent magnet being arranged in the hole (11) and fixed to the shaft (10); A drive control unit (50), which is arranged in a drive control unit housing, the drive control unit housing having a protrusion (43) extending along the rotation axis into the hole (11); An electronic circuit (51) for controlling the electric motor is arranged in the control unit (50), and A magnetic field sensor element (31) is arranged inside the projection and is coupled to the electronic circuit (51) for driving the electric motor. The device also includes: The second housing part (41) serves as an end cover to close an end surface of the first housing part (40) to define a cavity for accommodating the shaft (10). The second housing part (41) has a central opening, and the magnetic field sensor element (31) is inserted into the hole through the central opening.

9. The device according to claim 8, wherein the hole (11) is a through hole, whereby the shaft (10) is a hollow shaft.

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