Rotation angle detection device

Abstract

To provide a rotation angle detection device capable of accurately detecting angle.SOLUTION: A rotation angle detection device 21 includes a sensor magnet 41 and a sensor 51. The sensor magnet 41 is fixed to a shaft 15 at the outside in the radial direction that rotates together with the rotor 14. The sensor 51 has detector elements 511 and 512 capable of detecting the magnetic field of the sensor magnet 41. The sensor 51 is placed at a position radially outside of the shaft 15, where the sensor magnet 41 is displaced from the center line Ay in the axial direction, and is capable of detecting magnetic flux in two directions different from the main magnetic flux component of the sensor magnet 41.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a rotation angle detection device. [Background technology]

[0002] Conventionally, there is known a rotation angle detection device that detects a rotation angle by detecting a change in magnetic flux accompanying the rotation of a rotor. For example, in Patent Document 1, a radial Hall sensor and a circumferential Hall sensor are arranged so that the amplitude of the magnetic flux density component received by the radial Hall sensor and the amplitude of the magnetic flux density component received by the circumferential Hall sensor are the same. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-276261 A Summary of the Invention [Problem to be solved by the invention]

[0004] Because the magnetic flux density in the magnetization direction of the sensor magnet is greater than the magnetic flux density in other directions, the amplitude difference in the magnetic flux density components cannot be completely reduced by simply devising a layout as in Patent Document 1, and high installation precision is required.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a rotation angle detection device capable of detecting angles with high accuracy. [Means for solving the problem]

[0006] The rotation angle detection device of the present invention includes a sensor magnet (41-46) and a sensor unit (51-54). The sensor magnet is fixed to the radially outer side of a shaft (15) that rotates integrally with a rotor (14). The sensor unit has detection elements (511, 512, 521, 522) capable of detecting a magnetic field of the sensor magnet.

[0007] The sensor unit is disposed radially outward of the shaft and offset from the center line of the sensor magnet in the axial direction, and detects magnetic flux in two directions different from the main magnetic flux component of the sensor magnet, thereby enabling accurate angle detection. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a motor according to a first embodiment. [Diagram 2] 1 is a plan view showing a rotation angle detection device according to a first embodiment. [Diagram 3] 1 is a plan view showing a rotation angle detection device according to a first embodiment. [Figure 4] 1 is a side view of a rotation angle detection device according to a first embodiment. [Diagram 5] FIG. 2 is a perspective view showing the arrangement of a sensor magnet and a sensor unit according to the first embodiment. [Figure 6] FIG. 2 is a plan view of a sensor unit according to the first embodiment. [Figure 7] FIG. 2 is a side view of the sensor unit according to the first embodiment. [Figure 8] FIG. 2(a) is a diagram showing magnetization of the sensor magnet according to the first embodiment, and FIG. 2(b) is a diagram explaining magnetic flux density. [Figure 9] FIG. 1A is a diagram showing magnetic flux density in the radial and tangential directions, and FIG. 1B is a diagram showing magnetic flux density in the axial and tangential directions. [Figure 10] 5A and 5B are diagrams illustrating the axial position of a sensor unit. [Figure 11] 13A is a diagram showing the magnetic flux density when the sensor unit is disposed at position C3, and FIG. 13B is a diagram showing the magnetic flux density when the sensor unit is disposed at position C2. [Figure 12] 1A is a side view in which the sensor units are arranged on the same plane, and FIG. 1B is a side view in which the sensor units are arranged on different planes. [Figure 13]FIG. 11(a) is a diagram showing magnetization of a sensor magnet according to a second embodiment, and FIG. 11(b) is a diagram explaining magnetic flux density. [Figure 14] FIG. 11(a) is a diagram showing magnetization of a sensor magnet according to a third embodiment, and FIG. 11(b) is a diagram explaining magnetic flux density. [Figure 15] FIG. 11 is a plan view showing a rotation angle detection device according to a fourth embodiment. [Figure 16] FIG. 13 is a plan view showing a rotation angle detection device according to a fifth embodiment. [Figure 17] FIG. 13(a) is a diagram showing magnetization of a sensor magnet according to a fifth embodiment, and FIG. 13(b) is a diagram explaining magnetic flux density. [Figure 18] FIG. 13 is a plan view showing a rotation angle detection device according to a sixth embodiment. [Figure 19] FIG. 13 is a plan view showing a rotation angle detection device according to a seventh embodiment. [Figure 20] FIG. 13 is a side view showing a rotation angle detection device according to the seventh embodiment. [Figure 21] FIG. 13 is a plan view of a sensor unit according to the seventh embodiment. [Figure 22] FIG. 13 is a side view of a sensor unit according to the seventh embodiment. [Figure 23] FIG. 13 is a plan view showing a rotation angle detection device according to an eighth embodiment. [Figure 24] FIG. 13 is a side view showing a rotation angle detection device according to the eighth embodiment. [Diagram 25] FIG. 13 is a plan view showing a rotation angle detection device according to a ninth embodiment. [Figure 26] FIG. 23 is a plan view showing a rotation angle detection device according to a tenth embodiment. [Figure 27] FIG. 23 is a side view showing a rotation angle detection device according to a tenth embodiment. [Figure 28] FIG. 11 is a side view showing a rotation angle detection device according to another embodiment. [Figure 29] FIG. 11 is a plan view showing a rotation angle detection device according to another embodiment. [Diagram 30] FIG. 11 is a plan view showing a rotation angle detection device according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotation angle detection device according to the present invention will be described below with reference to the drawings. In the following, in a number of embodiments, substantially the same components are designated by the same reference numerals, and description thereof will be omitted.

[0010] (First embodiment) A first embodiment is shown in Figs. 1 to 12. As shown in Fig. 1, a rotation angle detection device 21 detects the rotation angle of a motor 10. The motor 10 includes a motor case 11, a stator 12, windings 13, a rotor 14, and a shaft 15. The motor case 11 is formed in a cylindrical shape. The stator 12 is formed, for example, from a laminated iron plate, and is fixed to the radially inner side of the motor case 11. The windings 13 are wound around the stator 12.

[0011] The rotor 14 has a rotor core 141 and a rotor magnet 145. The rotor core 141 is formed of, for example, laminated iron plates, and is provided radially inside the stator 12 so as to be rotatable relative to the stator 12. The rotor magnet 145 is provided radially outside the rotor 14. The shaft 15 is fixed to the axial center of the rotor core 141 by press-fitting or the like. The shaft 15 is rotatably supported by the motor case 11 by a bearing (not shown). As a result, when current is applied to the windings 13, the rotor 14 and the shaft 15 rotate together.

[0012] The rotation angle detection device 21 includes a sensor magnet 41, a circuit board 50 as a substrate, and a sensor unit 51. As shown in FIGS. 1 to 6, the sensor magnet 41 is an annular two-pole magnet, and is fixed to the shaft 15. This causes the sensor magnet 41 to rotate integrally with the shaft 15.

[0013] The circuit board 50 is provided radially outside the sensor magnet 41. The sensor unit 51 is mounted on the circuit board 50 and provided radially outside the sensor magnet 41 so as to be able to detect magnetic flux generated by the rotation of the sensor magnet 41. In this embodiment, the mounting surface of the circuit board 50 is provided in a direction perpendicular to the axis Ax, and the sensor unit 51 is disposed within a projection area of ​​the sensor magnet 41 projected in the radial direction. In other words, when the axial length of the sensor magnet 41 is defined as the height, the sensor unit 51 is provided within the height range of the sensor magnet 41.

[0014] This allows the axial size to be smaller than when the sensor unit 51 is disposed on the axial side of the sensor magnet 41. Here, "perpendicular" means that deviations are permitted to the extent that errors in assembly and angle calculation are permitted. The same applies to angles other than perpendicular, such as "parallel," "orthogonal," and "equal."

[0015] As shown in FIG. 2, the rotation angle detection device 21 has two sensor units 51. The two sensor units 51 are arranged on a concentric circle centered on the axis Ax of the sensor magnet 41, with an electrical angle of 60° between them. By taking the difference between the outputs of the two sensor units 51, the electric third-order distortion component can be cancelled. As in the rotation angle detection device 22 shown in FIG. 3, two sensor units 51 may be provided with an electrical angle of 120° between them. Regardless of the arrangement, by providing two sensor units 51, angle detection by the other unit can be continued even if one unit fails. In the drawings for explaining the arrangement of the sensor magnet 41 and the sensor units 51, such as FIG. 2, the circuit board 50 is omitted as appropriate.

[0016] 4 and 5, one sensor unit 51 is shown for simplification. As shown in Fig. 4 and 5, the sensor unit 51 is disposed radially outward of the sensor magnet 41. In the figures, the radial direction is the R direction, the tangential direction is the T direction, and the axial direction is the Z direction. In Fig. 4, the left-right direction on the paper is the R direction, the front-rear direction on the paper is the T direction, and the up-down direction on the paper is the Z direction. As shown in Fig. 5, the magnetization direction of the sensor magnet 41 is the radial direction, and the magnetic flux component in the radial direction is Br, the magnetic flux component in the tangential direction is Bt, and the magnetic flux component in the axial direction is Bz.

[0017] 6 and 7, the sensor unit 51 has an element pair 510, a sealing portion 515, and a sensor terminal 516. The element pair 510 includes detection elements 511 and 512 that detect magnetic flux in different directions. The detection elements 511 and 512 are sealed in the sealing portion 515. The sensor terminal 516 is provided to protrude from the sealing portion 515, and is electrically connected to the circuit board 50.

[0018] 6 and 7, the magnetic flux detection direction of detection element 511 is indicated by a thick arrow. Detection element 511 has a detection surface parallel to the mounting surface of circuit board 50 and detects tangential magnetic flux component Bt. Detection element 512 has a detection surface perpendicular to the mounting surface of circuit board 50 and detects axial magnetic flux component Bz. Rotation angle detection device 21 calculates the rotation angle of motor 10, for example, by Atan calculation, based on the detected tangential magnetic flux component Bt and axial magnetic flux component Bz. The detection value may be transmitted to an external calculation circuit or the like, and angle calculation may be performed outside the rotation angle detection device.

[0019] 8, (a) is a plan view of the sensor magnet 41, and (b) shows the magnetic flux density according to the electrical angle. The sensor magnet 41 of this embodiment is a radially anisotropic magnet that is magnetized parallel to the radial direction, and the magnetic flux density is sinusoidal with a period of 360 electrical degrees.

[0020] Since the sensor magnet 41 is magnetized in the radial direction, the radial magnetic flux component Br is the main magnetic flux. On the other hand, the tangential magnetic flux component Bt and the axial magnetic flux component Bz are leakage magnetic flux. Therefore, as shown in FIG. 9(a), the amplitude of the magnetic flux density in the radial direction is larger than that in the tangential direction. In other words, the radial direction can be regarded as the detection direction in which the amplitude of the magnetic flux density is maximum.

[0021] To perform angle calculations with high accuracy, it is desirable that the difference in amplitude between two magnetic flux densities with different phases is small. However, since the magnetic flux density in the magnetization direction is greater than the magnetic flux density in the other direction, the difference cannot be canceled out by simply devising the layout, and high assembly accuracy is required. In addition, when performing corrections using software calculations, the calculations become complicated.

[0022] Therefore, in this embodiment, the detection value of the main magnetic flux component having a larger amplitude than the other directional components is not used, and leakage magnetic flux components in two directions with different phases are detected. Specifically, as shown in Fig. 9(b), the sensor unit 51 detects the tangential magnetic flux component Bt and the axial magnetic flux component Bz.

[0023] The axial magnetic flux component Bz will now be described. As shown in Fig. 10, when the sensor unit 51 is disposed at a position indicated by C1 on the center line Ay of the axial length of the sensor magnet 41, the axial magnetic flux component Bz is not generated, and therefore angle calculation cannot be performed.

[0024] In addition, the axial magnetic flux component Bz increases with distance from the center line Ay. Therefore, if the sensor unit 51 is placed at the position indicated by C3, the difference in amplitude with the tangential magnetic flux component Bt increases as shown in FIG. 11(a), and the accuracy of angle calculation decreases. In this embodiment, the sensor unit 51 is placed at the position C2, which is shifted from the center line Ay and has the same amplitude as the tangential magnetic flux component Bt (see FIG. 11(b)). In this embodiment, the sensor unit 51 is placed at a position radially outside the sensor magnet 41, within a projection area obtained by projecting the sensor magnet 41 radially, and shifted from the center line Ay. This allows accurate angle calculation without complicated corrections on the software side.

[0025] 12(a), in the rotation angle detection device 21, the two sensor units 51 are arranged on the same plane so that their axial positions relative to the sensor magnet 41 are the same. Alternatively, as in the rotation angle detection device 23 shown in FIG. 11(b), the two sensor units 51 may be arranged on different planes and have different axial positions relative to the sensor magnet 41. When the axial positions of the sensor units 51 are different, it is desirable to arrange the sensor units 51 on both sides of the center line Ay of the axial length of the sensor magnet 41 at positions equidistant from the center line Ay.

[0026] As described above, the rotation angle detection device 21 includes the sensor magnet 41 and the sensor unit 51. The sensor magnet 41 is fixed to the radially outer side of the shaft 15 which rotates integrally with the rotor 14. The sensor unit 51 has detection elements 511, 512 capable of detecting the magnetic field of the sensor magnet 41.

[0027] The sensor unit 51 is provided radially outward of the shaft 15 and at a position offset from the center line Ay of the sensor magnet 41 in the axial direction, and detects magnetic flux in two directions different from the main magnetic flux component of the sensor magnet 41. In this embodiment, leakage magnetic flux in the tangential direction and the axial direction is detected. Since the main magnetic flux component has a larger amplitude of magnetic flux density than magnetic flux in other directions, detecting magnetic flux in two directions different from the main magnetic flux component can reduce angle calculation errors caused by amplitude differences.

[0028] The sensor magnet 41 is magnetized parallel to the radial direction. This makes it possible to reduce angle errors caused by magnetic flux distortion. The sensor unit 51 is disposed at a location where the amplitudes of the magnetic flux density in the two directions to be detected are equal. This makes it possible to reduce angle calculation errors.

[0029] The sensor unit 51 has an element pair 510, consisting of two detection elements 511, 512 that detect magnetic flux in different directions, sealed by a sealing portion 515, and is mounted on a circuit board 50 provided on a virtual plane perpendicular to the axis Ax of the shaft 15. The detection surface of one detection element 511 of the element pair is provided parallel to the mounting surface of the circuit board 50, and the detection surface of the other detection element 512 is provided perpendicular to the mounting surface of the circuit board 50. This allows the leakage magnetic flux component Bz in the axial direction to be properly detected.

[0030] A plurality of sensor units 51 are provided, and are arranged on a concentric circle centered on the axis line Ax at intervals of 60° or 120° electrical angle. By providing a plurality of sensor units 51, redundancy can be provided. Furthermore, by arranging the sensor units at intervals of 60° or 120° electrical angle, third-order electrical distortion can be cancelled.

[0031] (Second to fourth embodiments) In the second to sixth embodiments, the description will be centered mainly on variations of the sensor magnet. The sensor magnet described here may be combined with any of the first and seventh and subsequent embodiments. Figures 13, 14, and 17 correspond to Figure 8.

[0032] The sensor magnet 42 of the second embodiment shown in FIG. 13(a) is a radially anisotropic magnet, and when it is magnetized equally in all directions, the magnetic flux density has a trapezoidal wave shape as shown in FIG. 13(b).

[0033] The sensor magnet 43 of the third embodiment shown in FIG. 14(a) is a radially anisotropic magnet similar to that of the second embodiment, and is magnetized so that the magnetic flux becomes smaller closer to the neutral zone. As a result, as shown in FIG. 14(b), the magnetic flux density according to the electrical angle becomes sinusoidal, and angle calculation can be performed with relatively high accuracy. The shape of the sensor magnet may be designed so that the magnetic flux density according to the electrical angle becomes sinusoidal. Specifically, like the sensor magnet 44 of the rotation angle detection device 24 of the fourth embodiment shown in FIG. 15, the magnet shape may be designed to be elliptical in plan view, so that the magnetic flux density according to the electrical angle becomes sinusoidal.

[0034] (Fifth and Sixth Embodiments) A fifth embodiment is shown in Fig. 16 and Fig. 17, and a sixth embodiment is shown in Fig. 18. The sensor magnet 45 of the rotation angle detection device 25 of the fifth embodiment is a polar anisotropic magnet, and is a four-pole magnet. As shown in Fig. 17(b), the magnetic flux density forms a sine wave with a period of 180 electrical degrees.

[0035] The sensor magnet 46 of the rotation angle detection device 26 of the sixth embodiment is an eight-pole magnet. Although an increase in the number of poles results in space limitations for arranging a plurality of sensor units 51, the sensor magnet may be a multi-pole magnet as in the fifth and sixth embodiments. Even with this configuration, the same effects as the above embodiments can be achieved.

[0036] Seventh embodiment The seventh embodiment is shown in Fig. 19 to Fig. 22. As shown in Fig. 19 and Fig. 20, in a rotation angle detection device 27, a circuit board 50 is provided radially outside the sensor magnet 41, with the mounting surface being parallel to the axis Ax. A sensor unit 52 is mounted on the circuit board 50, with the top surface of the sensor unit 52 facing the sensor magnet 41 side.

[0037] 21 and 22, in sensor unit 52, detection surfaces of detection elements 521 and 522 constituting element pair 520 are provided parallel to the mounting surface of circuit board 50. Detection elements 521 and 522 are mounted on circuit board 50 so that their detection directions are perpendicular to each other. As a result, sensor unit 52 detects tangential magnetic flux component Bt and axial magnetic flux component Bz. Even with this configuration, the same effects as those of the above embodiment can be achieved.

[0038] Eighth embodiment An eighth embodiment is shown in Figures 23 and 24. A circuit board 50 of a rotation angle detection device 28 is disposed on one axial side of the sensor magnet 41, perpendicular to the axis Ax. A sensor unit 51 mounted on the circuit board 50 is provided such that its top surface faces the axial end side of the sensor magnet 41, and the outer edge of the sensor magnet 41 is included within a projection area projected in the axial direction. The sensor unit 51 of this embodiment detects a tangential magnetic flux component Bt and an axial magnetic flux component Bz, similar to the above embodiments.

[0039] By arranging the sensor magnet 41 and the sensor unit 51 so that they at least partially overlap in the radial direction, the size in the radial direction can be reduced. In addition, the same effects as those of the above embodiment can be achieved.

[0040] (Ninth and Tenth Embodiments) The ninth embodiment is shown in Fig. 25. In the sensor unit 53 of the rotation angle detection device 29, a plurality of element pairs 510 (three in this embodiment) are sealed in one sealing portion 535. The plurality of element pairs 510 are arranged side by side in the tangential direction of a circle centered on the axis Ax. When the center of the sensor unit 53 is taken as the reference position, the two sensor units 53 are arranged at an interval of an electrical angle of 120°.

[0041] A tenth embodiment is shown in Fig. 26 and Fig. 27. In a sensor unit 54 of a rotation angle detection device 30, a plurality of element pairs 510 (three in this embodiment) are stacked in the axial direction and sealed in a sealing portion 545. The two sensor units 54 are also arranged at an interval of an electrical angle of 120°. Even with this configuration, the same effects as the above embodiments can be achieved.

[0042] (Other embodiments) In the above-described embodiment, the sensor unit is provided perpendicular or parallel to the rotation axis of the sensor magnet. In another embodiment, the sensor unit 51 may be arranged at an angle with respect to the axis Ax of the sensor magnet 41, as in a rotation angle detection device 31 shown in Fig. 28. In another embodiment, the sensor unit 51 may be arranged at an angle with the detection direction rotated at an angle different from the tangential direction, as in a rotation angle detection device 32 shown in Fig. 29.

[0043] In the above embodiment, when two sensor units are provided, they are arranged at intervals of 60° or 120° electrical angle. In other embodiments, the number of sensor units is not limited to two, and may be one or three or more. In the rotation angle detection device 33 shown in FIG. 30, an example is shown in which four sensor units 51 are provided. Furthermore, the intervals between the multiple sensor units are not limited to 60° or 120° electrical angle, and they may be arranged at intervals of 30° electrical angle, for example, as shown in FIG. 30.

[0044] The rotation angle detection device may be configured as described in any one of aspects 1 to 3, wherein the sensor unit is mounted on a substrate (50) provided on a virtual plane perpendicular to the axis of the shaft, and an element pair (510) consisting of two detection elements that detect magnetic flux in different directions is sealed by a sealing portion (515), and the detection surface of one detection element (511) of the element pair is provided parallel to the mounting surface of the substrate, and the detection surface of the other detection element (512) is provided perpendicular to the mounting surface of the substrate.

[0045] The rotation angle detection device may be configured as described in any one of aspects 1 to 4, in which the sensor units are provided in plurality, arranged on a concentric circle centered on the axis of the shaft, and spaced at intervals of 60° or 120° electrical angle.

[0046] As described above, the present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. [Explanation of symbols]

[0047] 10. Motor 14 Rotor 15 Shaft 21~33 Rotation angle detection device 41~46 Sensor magnet 50 Circuit board (substrate) 51 to 54: Sensor section 510, 520... element pair 511, 512, 521, 522...Detection elements 515, 535, 545...Sealing part

Claims

1. a sensor magnet (41-46) fixed to the radially outer side of a shaft (15) that rotates integrally with the rotor (14); A sensor unit (51 to 54) having a detection element (511, 512, 521, 522) capable of detecting a magnetic field of the sensor magnet; Equipped with The sensor unit is provided radially outward of the shaft and at a position offset from the center line of the sensor magnet in the axial direction, and is a rotation angle detection device that detects magnetic flux in two directions different from the main magnetic flux component of the sensor magnet.

2. 2. The rotation angle detection device according to claim 1, wherein the sensor magnet is magnetized parallel to a radial direction.

3. 3. The rotation angle detection device according to claim 1, wherein the sensor unit is disposed at a position where amplitudes of magnetic flux density in two directions to be detected are equal.

4. The sensor unit is mounted on a substrate (50) provided on a virtual plane perpendicular to the axis of the shaft, and an element pair (510) consisting of two of the detection elements for detecting magnetic flux in different directions is sealed by a sealing portion (515).

2. The rotation angle detection device of claim 1, wherein a detection surface of one of the detection elements (511) of the element pair is arranged parallel to the mounting surface of the substrate, and a detection surface of the other detection element (512) is arranged perpendicular to the mounting surface of the substrate.

5. 2. The rotation angle detection device according to claim 1, wherein the sensor unit is provided in plurality, the sensor units being arranged on a concentric circle centered on the axis of the shaft and at intervals of 60 degrees or 120 degrees electrical angle.

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