DEVICE FOR MEASURING THE ANGLE OF A SHAFT

Description

TECHNICAL FIELD

[0001] This description concerns the field of angle measuring systems, which can be used, for example, to measure the angular position of shafts. BACKGROUND

[0002] For example, the control of electric motors requires measuring systems for measuring the angular position of the motor shaft. Such measuring systems are often based on the detection of a rotating magnetic field and typically include (among other things) one or more permanent magnets connected to the shaft and thus rotating with it, as well as one or more magnetic field sensors for detecting the resulting magnetic field. One object underlying the invention can be seen in making existing sensor systems more efficient (e.g., with regard to cost, assembly, number of parts, reduction of installation space, or similar).

[0003] Angle measuring devices for electric motors are known, for example, from the publications DE 10 2017 104 206 A1, DE 10 2017 212 039 and DE 102 12 859A1 A1. SUMMARY

[0004] The above-mentioned object is achieved by a device according to claim 1. Various embodiments and further developments are the subject of the dependent claims.

[0005] The following describes a device for measuring the angular position or rotational movement of a shaft. According to one embodiment, the device comprises a first housing part and a shaft arranged in the first housing part and rotatable about a rotational axis. The shaft has a bore extending from an end face of the shaft into the shaft along the rotational axis. In the case of a hollow shaft, the aforementioned bore is a through-hole. The device further comprises a magnet unit with at least one permanent magnet arranged within the bore and fastened to the shaft, a second housing part with a projection extending into the bore along the rotational axis, and a sensor unit comprising a magnetic field sensor element arranged on a carrier, wherein the carrier is arranged inside the projection of the second housing part.The projection is an integral part of the second housing part. The projection is hollow, and the magnetic field sensor element is arranged in the hollow projection. The second housing part forms a housing cover for the first housing part and has a central opening through which the sensor unit can be inserted. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Below, exemplary embodiments are explained in more detail using illustrations. The illustrations are not necessarily to scale, and the exemplary embodiments are not limited to the aspects shown. Rather, emphasis is placed on illustrating the principles underlying the exemplary embodiments. Regarding the illustrations: Figure 1 illustrates an example of a magnetic sensor mounted at the end of a shaft in a central axial bore of the shaft; the sensor can be inserted into the central axial bore through an opening in the housing. Figure 2 is a block diagram showing an example of a control unit for an electric motor, for example a power converter for a brushless DC motor. Figure 3 illustrates an embodiment with a magnetic sensor integrated into a housing cover. Figure 4 illustrates an embodiment similar to Fig. 3 However, in this case the control unit for the electric motor serves as the housing cover, which enables an even more compact design. Figure 5 illustrates a modification of the example from Fig. 4 which is not covered by the claims. DETAILED DESCRIPTION

[0007] Fig. 1 describes a sensor system coupled to a shaft for measuring the angular position ( angular position ) and / or the rotation speed ( angular velocity) of a shaft mounted in a housing, in particular a motor shaft of an electric motor. The electric motor can, for example, be a permanent magnet synchronous motor (PMSM), which is often also called a brushless DC motor ( brushless DC motor ). The structure of such engines is basically known and therefore in Fig. 1 not shown to keep the presentation simple.

[0008] Fig. 1shows a shaft 10 arranged in a housing, which is mounted for rotation about a rotational axis R (for example, the motor shaft of an electric motor). The shaft 10 has an axial bore 11, i.e., the bore 11 extends along the rotational axis R from the end face of the shaft 11 into the shaft 11. The bore 11 can be a blind hole or a through hole. In the case of a through hole, the shaft 10 is a hollow shaft. Within the bore 11, a magnet unit 20 is arranged, which is attached to the shaft 10 and thus rotates therewith. The magnet unit 20 has at least one permanent magnet. In Fig. 1Only a portion of the housing is shown, namely a housing cover 41, which lies approximately in a plane perpendicular to the rotation axis. A small gap (gap width t) may exist between the end face of the shaft 10 and the inside of the housing cover. Various designs of the magnet unit 20 are known per se. For the examples described here, the specific implementation of the magnet unit 20 is known per se and will therefore not be discussed further here.

[0009] The housing cover 41 has a central opening through which a sensor unit 30 can be inserted. Part of the sensor unit 30 has an elongated shape (e.g., a cylindrical shape). This part lies approximately on the rotation axis. When the sensor unit 30 is inserted through the opening in the housing cover 41, it is inserted into the bore 11. The sensor unit 30 can be attached to the housing cover 41. For example, the sensor unit is glued to the housing cover 41 or fastened with screws.

[0010] Inside the sensor unit 30 are one or more sensor elements 31, which are sensitive to the magnetic field generated by the magnet unit 21, which 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 (which, however, does not necessarily have to be the case). Fig. 1In the example shown, the sensor unit 30 has a socket with electrical contacts 33, which enable a plug connection with a plug 402. With the help 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 a measurement of the angular position of the shaft 10. The angular velocity and / or the angular acceleration of the shaft can be derived from measured angular positions.

[0011] The block diagram in Fig. 2schematically illustrates an electric motor M with a sensor unit 30 for measuring the angular position φ of the motor shaft. The sensor unit 30 is connected via cable 41 to the control unit 50, which contains the electronics for controlling the electric motor M. The electronics for controlling the electric motor M include, for example, a power converter (e.g., a 3-phase inverter), gate driver circuits for controlling the power transistors contained in the power converter, a microcontroller for generating the control signals for the gate driver circuits (based, among other things, on the information about the angular position φ of the motor shaft received from the sensor unit 30), etc.

[0012] Fig. 3 illustrates an embodiment of a sensor unit integrated into the motor housing for measuring the angular position φ of a shaft 10. At this point it should be noted that for the sake of simplicity in Fig. 3The shaft 10 is drawn relatively large in relation to the housing. Fig. 3 The elements shown are not to scale. Similar to the example from Fig. 1 The shaft 10 has an axial bore 11 along the rotation axis R, and inside the bore 11, a magnet unit 20 is mounted, which rotates with the shaft 10 and consequently generates a magnetic field that rotates with the shaft. The magnet unit 20 comprises at least one permanent magnet, which generates, for example, a diametrically directed magnetic field (the direction of the field is in Fig. 3 indicated by the arrows).

[0013] The electric motor is arranged in a first housing part 40, which can be closed laterally by means of a second housing part 41. The second housing part 41 is referred to below as the housing cover. The housing cover can have a cavity 42 and has an elongated, e.g., prism-shaped (or cylindrical) and hollow projection 43, which, when the housing cover 41 is mounted on the housing part 40, extends along the rotation axis into the bore 11. The elongated projection 43 is also referred to as a tower-shaped element or a "sensor dome." Arranged inside the hollow projection 43 is a carrier 34, 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 circuit board ( printed circuit board, PCB ), a lead frame, a punched grid or similar.

[0014] A circuit board 35 is arranged in the cavity 42 of the housing cover 41, on which the sensor electronics 32 is arranged. The carrier 34 is also connected to the circuit board 35 and thus enables an electrical connection of the sensor elements 31 to the sensor electronics 32. The carrier 34 protrudes approximately at a right angle from the circuit board 35. The sensor electronics 32 is designed to control the sensor elements 31 and to process the signals supplied by the sensor elements 31 in order to generate one or more measurement signals which indicate the angular position or the rotational movement of the shaft 10. Suitable sensor elements such as Hall sensors or magnetoresistive sensors as well as suitable sensor electronics are known per se and will therefore not be discussed further here. The sensor electronics 32 can have a socket with plug contacts in order to be able to connect a cable 41 to the sensor electronics 32 by means of a plug 40. The cable 41 connects (see also Fig. 2 ) the sensor electronics 32 with a control unit 50 for the electric motor.

[0015] The elongated protrusion 43 (the sensor dome) may be an integral part of the housing cover 41. In one example, the elongated protrusion is firmly connected to the main part of the housing cover 41 (in which the cavity 43 is located), e.g., by means of an adhesive or screw connection. Furthermore, the elongated protrusion 43 and the housing cover 41 may be manufactured as a single piece (e.g., as an injection-molded plastic part).

[0016] Fig. 4 illustrates a further embodiment 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 electronics used to control the electric motor (cf. Fig. 2, control unit 50) such as a power converter (3-phase inverter) and the like together with the sensor electronics 32 (cf. Fig. 3 ) is integrated into the housing part 41, which also serves as the housing cover.

[0017] The example from Fig. 5 illustrates a modification of the example from Fig. 4 , in which the housing part 41 is a conventional 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 as well as the sensor electronics is a module with a separate housing, which (like the housing cover in the previous examples) has a hollow projection 43, which is also referred to as a sensor dome. The projection 43 is a tower-shaped element in which the sensor element 31 is arranged on a carrier (similar to Fig. 3). In this example, the control electronics 51 for the electric motor and the sensor electronics including the sensor element 31 are arranged in the same module, and a cable with a connector between the sensor electronics and the control electronics 51 is not required. The sensor element 31 is (electrically) coupled to the control electronics 51 inside the control unit 50. The sensor element can be arranged on a carrier (e.g., a carrier board), as in the example from Fig. 3 is shown.

[0018] Unlike the previous examples, according to Fig. 5 Instead of a shaft with a bore, a hollow shaft 10' is used. It is understood that in all other embodiments described here, a hollow shaft can also be used instead of a solid shaft with an axial bore.

Claims

1. Apparatus for measuring an angular position of a shaft, wherein the apparatus has: a housing which comprises a first housing part (40) and a second housing part (41), a shaft (10) which is arranged in the first housing part (40) and can rotate about a rotation axis and has a bore (11) which extends along the rotation axis from an end side of the shaft (10); a magnet unit (20) with at least one permanent magnet which is arranged within the bore (11) and is fastened to the shaft (10) ; wherein the second housing part (41) has a projection (43) which extends along the rotation axis into the bore (11); wherein the apparatus furthermore has a sensor unit (30) which comprises a magnetic field sensor element (31) which is arranged on a support (34), wherein the support (34) is arranged in the interior of the projection (43) of the second housing part (41), wherein the projection (43) is an integral constituent part of the second housing part (41), wherein the projection (43) is hollow and the magnetic field sensor element (31) is arranged in the hollow projection (43), wherein the second housing part (41) forms a housing cover for the first housing part (40), wherein the second housing part (41) has a central opening through which the sensor unit (30) can be inserted.

2. Apparatus according to Claim 1, wherein a mounting board (35) with sensor electronics is arranged in the interior of the second housing part (41).

3. Apparatus according to Claim 1 or 2, wherein the shaft (10) is the motor shaft of an electric motor.

4. Apparatus according to Claim 3, wherein an actuation unit (50) for actuating the electric motor is arranged in the interior of the second housing part (41) .

5. Apparatus according to one of Claims 1 to 4, wherein the bore (11) is a passage hole and consequently the shaft (10) is a hollow shaft.