JP6430043B2 - Rotation angle detection device and electric motor - Google Patents

Description

  The present invention relates to a rotation angle detection device and an electric motor that detect the rotation angle of a shaft by magnetism.

  Generally, in a servo motor that is an electric motor, a rotation angle detection device that detects a rotation angle of a shaft is divided into an optical type and a magnetic type. In a magnetic rotation angle detection device, the rotation angle of a shaft may be detected by detecting a magnetic field from a detection magnet attached to one end surface of a shaft that rotates about the shaft by a magnetic detection element. It is common.

  The servo motor may be used by being incorporated in a machine tool. Inside the machine tool, a cable for passing a large current and a large-capacity electric motor are provided. The magnetic field generated from the cable and the electric motor reaches the detection range of the magnetic detection element. Since the magnetic field from the cable and the motor is not the magnetic flux from the detection magnet, it becomes a noise component and becomes an error factor in detecting the rotation angle. In the following description, a magnetic field different from the magnetic field of the detector magnet, that is, a magnetic field that becomes a noise component is also simply referred to as an external magnetic field.

  As a countermeasure against the external magnetic field, Patent Document 1 discloses a configuration that suppresses the magnetic field that becomes a noise component from reaching the magnetic detection element by covering the periphery of the rotation angle detection device with a cover made of a magnetic material. .

Japanese Patent Laying-Open No. 2015-169439

  In the configuration disclosed in Patent Document 1, the entire rotation angle detection device is covered with a dome-shaped cover made of a magnetic material. The cover that covers the rotation angle detection device needs to prevent water and dust from entering the rotation angle detection device. For this reason, high dimensional accuracy is required for the seal structure portion of the cover. However, there is a problem that the price of the cover is increased and the manufacturing cost is increased in order to satisfy the necessary specifications in the condition of limiting the material composed of the magnetic material.

  The present invention has been made in view of the above, and it is an object of the present invention to obtain a rotation angle detection device capable of improving the rotation angle detection accuracy by suppressing the influence of an external magnetic field while suppressing the manufacturing cost. Objective.

  In order to solve the above-described problems and achieve the object, a rotation angle detection device according to the present invention includes a shaft, a magnet provided on one end side in a direction along the rotation axis of the shaft, and a shaft side from the magnet. A magnetic part made of a magnetic material, a magnetic detection element that is arranged at a position facing the magnet and detects a change in the magnetic field due to the rotation of the magnet, and a position facing the magnetic part across the magnet and the magnetic detection element And a plate portion made of a magnetic material. When viewed along the axis of rotation of the shaft, the outer diameter of the surface of the magnetic portion facing the plate portion and the outer diameter of the surface of the plate portion facing the magnetic portion are both the outer diameter of the magnet and the magnetic detection. It is larger than the outer diameter of the element. The distance between the magnetic part and the magnetic detection element in the direction along the rotation axis is smaller than the distance between the magnetic part and the plate part in the direction along the rotation axis.

  The rotation angle detection device according to the present invention has an effect that the detection accuracy of the rotation angle can be improved by suppressing the influence of an external magnetic field while suppressing the manufacturing cost.

Sectional drawing which shows typically the rotation angle detection apparatus concerning Embodiment 1 of this invention. Sectional drawing which shows typically the rotation angle detection apparatus concerning Embodiment 2 of this invention. Sectional drawing which shows typically the rotation angle detection apparatus concerning Embodiment 3 of this invention. Sectional drawing which shows typically the rotation angle detection apparatus concerning Embodiment 4 of this invention. Sectional drawing which shows typically the rotation angle detection apparatus concerning Embodiment 5 of this invention. Sectional drawing which shows typically the rotation angle detection apparatus concerning Embodiment 6 of this invention. Sectional drawing which shows typically the rotation angle detection apparatus concerning Embodiment 7 of this invention. Sectional drawing which shows typically the rotation angle detection apparatus concerning Embodiment 8 of this invention. The result of a three-dimensional magnetic field simulation of the effect of magnetic shielding by the rotation angle detection device according to the eighth embodiment, and the comparison rotation angle detection device in which the periphery of the magnetic detection element and the detection magnet is covered with a magnetic cover The figure which shows the result of three-dimensional magnetic field simulation about the effect of shielding Sectional drawing which shows schematic structure of an electric motor provided with the rotation angle detection apparatus concerning Embodiment 1. FIG.

  Hereinafter, a rotation angle detection device and an electric motor according to an embodiment of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment, In the range which does not deviate from the summary, it can change suitably. In the drawings shown below, the scale of each layer or each member may be different from the actual for easy understanding, and the same applies to the drawings. Further, even a cross-sectional view may not be hatched for easy viewing of the drawing.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view schematically showing a rotation angle detection device according to Embodiment 1 of the present invention. The rotation angle detection device 100 according to the first embodiment includes a magnetic shaft 10 and a bracket 20 that surrounds the shaft 10 and supports the shaft 10. The shaft 10 is rotatable about the rotation axis O. A mounting surface 10 </ b> T is formed at one end portion (magnetic portion) of the shaft 10 at a position intersecting with the rotation axis O. Since the mounting surface 10 </ b> T is formed on the shaft 10, it rotates in synchronization with the rotation of the shaft 10.

  The rotation angle detection device 100 further includes a detection magnet 30 placed at a position intersecting the rotation axis O on the placement surface 10T, and a magnetic detection element 40 arranged to face the detection magnet 30. . The magnetic detection element 40 is mounted on a substrate 50 that is a wiring substrate. The substrate 50 is disposed with the surface on which the magnetic detection element 40 is mounted facing the mounting surface 10T.

The rotation angle detection device 100 further includes a magnetic plate 60. The plate portion 60 is provided at a position facing the placement surface 10T with the detection magnet 30 and the magnetic detection element 40 interposed therebetween. The center of the shaft 10, the plate part 60, the magnetic detection element 40, and the detection magnet 30 is more preferably on the rotation axis O. The plate portion 60 does not have a portion that protrudes further toward the detection magnet 30 than the magnetic detection element 40. In the first embodiment, the lower surface portion 60B is a flat surface. When the shape of the plate portion 60 is described by the distance from one end portion of the shaft 10 that is a magnetic portion, than the distance X between the one end portion (magnetic portion) of the shaft 10 and the plate portion 60 in the direction along the rotation axis O, The distance Y between the one end portion (magnetic portion) of the shaft 10 and the magnetic detection element 40 in the direction along the rotation axis O is smaller. In the case of the first embodiment, the first magnetic shielding effective surface 10S is the mounting surface 10T facing the plate portion 60, and the second magnetic shielding effective surface 60S is the mounting surface 10T of the plate portion 60. It corresponds to the lower surface portion 60B which is the opposing surface on the plate portion side. The outer diameters of the first magnetic shielding effective surface 10 </ b> S and the second magnetic shielding effective surface 60 </ b> S are larger than the outer diameter of the detection magnet 30 and the outer diameter of the magnetic detection element 40. Thus, the magnetic flux region _RH connecting the detection magnet 30 and the magnetic detection element 40 is sandwiched between the first magnetic shielding effective surface 10S and the second magnetic shielding effective surface 60S. The detection magnet 30 is fixed to the mounting surface 10T of the shaft 10 with an adhesive.

In the rotation angle detection device 100, the detection magnet 30 placed on the placement surface 10 </ b> T also rotates as the shaft 10 rotates. Changes in the magnetic field H _M by the rotation of the detecting magnet 30 is detected in the magnetic detection element 40, the rotation angle of the shaft 10 is detected by a detection circuit (not shown) on the substrate 50.

The external magnetic field _HOT from the opposite side of the lower surface portion 60B with respect to the plate portion 60 propagates along the plate portion 60 that is a magnetic body and is induced in a direction away from the rotation axis O. Therefore, it is difficult for the external magnetic field _HOT to propagate to the magnetic detection element 40 disposed on the lower surface portion 60B side of the plate portion 60.

The external magnetic field H _OS to be intruding from the rotational axis O and perpendicular to the magnetic flux region R _H is guided to the plate portion 60 is a shaft 10 and the magnetic body is a magnetic body. Therefore, the external magnetic field _HOS is difficult to propagate to the detection magnet 30, the magnetic detection element 40, and the magnetic flux region _RH disposed between the plate portion 60 and the shaft 10 and on the rotation axis O.

The shaft 10 can efficiently guide the external magnetic field _HOS to the shaft 10 by sufficiently increasing the outer diameter of the first magnetic shielding effective surface 10S. For example, the outer diameter of the first magnetic shielding effective surface 10 </ b> S is set to the same outer diameter as that of the substrate 50 or larger than that. Thus, the propagation of the external magnetic field H _OS to detecting magnet 30 and the magnetic detection element 40 and the flux region R _H, can be more effectively prevented.

The plate part 60 can efficiently guide the external magnetic field _HOS to the plate part 60 by sufficiently increasing the outer diameter of the second magnetic shielding effective surface 60S. For example, the outer diameter of the second magnetic shielding effective surface 60S is set to the same outer diameter as the mounting surface 50T or an outer diameter larger than that. Thus, the propagation of the external magnetic field H _OS to detecting magnet 30 and the magnetic detection element 40 and the flux region R _H, can be more effectively prevented.

Moreover, the plate part 60 can induce the external magnetic field _HOT to the plate part 60 efficiently by making it sufficiently thick. For example, the thickness of the plate portion 60 is made thicker than that of the substrate 50. Thereby, the propagation of the external magnetic field _HOT to the detection magnet 30, the magnetic detection element 40, and the magnetic flux region _RH can be prevented more effectively.

Further, the shorter the distance between the first magnetic shielding effective surface 10S and the second magnetic shielding effective surface 60S, the better. At least the distance between the first magnetic shielding effective surface 10S and the second magnetic shielding effective surface 60S is the minimum value of the outer diameter of the second magnetic shielding effective surface 60S and the outer diameter of the first magnetic shielding effective surface 10S. It is preferable to be smaller than the minimum value. For example, the distance between the first magnetic shielding effective surface 10S and the second magnetic shielding effective surface 60S is made shorter than the thickness of the plate portion 60. By shortening the distance between the first magnetic shield effective surface 10S and the second magnetic shielding effective surface 60S, the propagation of the external magnetic field H _OS to the detecting magnet 30 and the magnetic detection element 40 a magnetic flux region R _H, It can prevent more effectively.

As described above, the detection magnet 30 and the magnetic detection element 40 arranged on the rotation axis O are composed of the placement surface 10T of the shaft 10 that is a magnetic body and the lower surface portion 60B of the plate portion 60 that is a magnetic body. The external magnetic fields H _OT and H _OS can be prevented from propagating to the magnetic detection element 40 with a simple structure of sandwiching. Therefore, in the rotation angle detection device 100, it is possible to improve the detection accuracy of the rotation angle while suppressing the manufacturing cost as compared with the case where the detection magnet 30 and the magnetic detection element 40 are covered with the magnetic cover.

Embodiment 2. FIG.
FIG. 2 is a cross-sectional view schematically showing the rotation angle detection device 100 according to the second embodiment of the present invention. In addition, about the structure similar to the said Embodiment 1, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

In the rotation angle detection device 100 according to the second embodiment, a boss portion (magnetic portion) 70 that is a magnetic body is attached to one end side of the shaft 10. A mounting surface 70 </ b> T on which the detection magnet 30 is mounted is formed on the boss portion 70. The mounting surface 70T formed on the boss portion 70 corresponds to the first magnetic shielding effective surface 70S. First magnetic shielding effective surface 70S is to induce external magnetic field H _OS to boss 70, it is formed by the larger outer diameter sufficiently. For example, the outer diameter of the first magnetic shielding effective surface 70 </ b> S is set to the same outer diameter as the outer diameter of the substrate 50 or an outer diameter larger than that. Note that the same outer diameter herein includes substantially the same outer diameter.

  When viewed along the rotation axis O, the outer diameter of the shaft 10 is smaller than the outer diameter of the mounting surface 70T.

Also with the above configuration, propagation of the external magnetic fields H _OT and H _OS to the magnetic detection element 40 can be prevented. That is, the external magnetic field _HOS can be efficiently guided to the boss portion 70 by sufficiently increasing the outer diameter of the first magnetic shielding effective surface 70S of the magnetic boss portion 70. Thus, the propagation of the external magnetic field H _OS to the detecting magnet 30 and the magnetic detection element 40 a magnetic flux region R _H, can be effectively prevented. According to the rotation angle detection device 100 according to the second embodiment, in addition to the effects of the rotation angle detection device 100 according to the first embodiment, the diameter of the shaft 10 can be reduced and the inertia of the shaft 10 can be reduced. it can.

  In addition, the fastening method of the boss | hub part 70 and the magnet 30 for a detection is not specifically limited, The fastening system represented by adhesion | attachment, integral molding, or screw fixation is employable. Moreover, the fastening method of the boss | hub part 70 and the shaft 10 is not specifically limited, The fastening system represented by the press fit, the set screw system, or the adhesion system is employable.

Embodiment 3 FIG.
FIG. 3 is a cross-sectional view schematically showing a rotation angle detection device 100 according to the third embodiment of the present invention. In addition, about the structure similar to the said Embodiment 1, 2, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. In the rotation angle detection device 100 according to the third embodiment, the wall portion 70 </ b> W protrudes toward the plate portion 60 on the mounting surface 70 </ b> T of the boss portion (magnetic portion) 70 and surrounds the detection magnet 30. Is formed. The wall portion 70 </ b> W is made of a magnetic material like the boss portion 70. The wall portion 70 </ b> W is formed around the detection magnet 30 over the entire circumference in the rotation direction.

Since the boss portion 70 has the wall portion 70W, the first magnetic shielding effective surface 70S corresponds to the tip surface 70U of the boss portion 70, and the first magnetic shielding effective surface 70S and the second magnetic shielding effective surface. The distance from 60S can be shortened. Thereby, the effect of preventing the propagation of the external magnetic field _HOS to the magnetic detection element 40 can be enhanced. Further, since the wall portion 70W is formed in the boss portion 70, the leakage magnetic field H _I from motor propagating through the shaft 10, can be guided to the wall 70W of the boss portion 70. Thus, leakage magnetic field H _I from the motor is less likely to propagate to the magnetic detection element 40.

As described above, according to the rotation angle detection device 100 according to the third embodiment, in addition to the effect obtained by the rotation angle detection device 100 according to the second embodiment, the external magnetic field H _{OS is obtained} by the effect of the wall portion 70W of the boss portion 70. it is possible to improve the propagation prevention effect on the magnetic detecting element 40, the leakage magnetic field H _I from the motor can be difficult to propagate to the magnetic detection element 40.

Embodiment 4 FIG.
FIG. 4 is a cross-sectional view schematically showing a rotation angle detection device 100 according to the fourth embodiment of the present invention. In addition, about the structure similar to the said Embodiment 1, 2, 3, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  In the rotation angle detection device 100 according to the fourth embodiment, the enlarged portion 11 is formed at one end portion (magnetic portion) of the shaft 10. When viewed along the rotation axis O, the outer diameter of the enlarged portion 11 of the shaft 10 is larger than the outer diameter of the portion on the other end side. The mounting surface 10 </ b> T on which the detection magnet 30 is mounted is formed in the enlarged portion 11.

  In addition, a wall 10 </ b> W is formed on the mounting surface 10 </ b> T so as to protrude toward the plate portion 60 and surround the detection magnet 30. The wall portion 10 </ b> W is made of a magnetic material like the shaft 10. The wall 10 </ b> W is formed around the detection magnet 30 over the entire circumference in the rotation direction. By forming the wall portion 10W, the front end surface 10U of the wall portion 10W becomes the first magnetic shielding effective surface 10S.

In the rotation angle detection device 100 according to the fourth embodiment, the effect of preventing the propagation of the external magnetic field _{HOS to} the magnetic detection element 40 can be improved as in the rotation angle detection device 100 according to the third embodiment. together, it can be difficult to propagate the leakage magnetic field H _I from the motor to the magnetic detection element 40.

  Further, in the rotation angle detection device 100 according to the fourth embodiment, it is not necessary to assemble a separately prepared boss as compared with the case where the boss portion is fixed to one end portion of the shaft 10, so that the manufacturing cost can be reduced. it can. As in the first embodiment, a wall portion may be formed on the shaft 10 whose thickness does not change.

Embodiment 5. FIG.
FIG. 5 is a cross-sectional view schematically showing a rotation angle detection device 100 according to the fifth embodiment of the present invention. In addition, about the structure similar to the said Embodiment 1, 2, 3, 4, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  In the rotation angle detection device 100 according to the fifth embodiment, the bracket 20 is made of a magnetic material. The bracket 20 has a wall portion 20 </ b> W that protrudes toward the plate portion 60 and surrounds the detection magnet 30.

In the rotation angle detection device 100 according to the fifth embodiment, the tip surface 20T of the wall 20W corresponds to the first magnetic shielding effective surface 20S. The external magnetic field _HOS can be efficiently guided to the bracket 20 by sufficiently increasing the outer diameter of the first magnetic shielding effective surface 20S. Thus, the propagation of the external magnetic field H _OS to the detecting magnet 30 and the magnetic detection element 40 a magnetic flux region R _H, can be effectively prevented.

  According to the rotation angle detection device 100 according to the fifth embodiment, in addition to the effect of the rotation angle detection device 100 according to the second embodiment, there is an effect that the number of parts can be reduced.

  Note that, as in the second embodiment or the third embodiment, a boss portion may be attached to one end portion of the shaft 10 and a mounting surface may be formed on the boss portion.

Embodiment 6 FIG.
FIG. 6 is a cross-sectional view schematically showing a rotation angle detection device 100 according to the sixth embodiment of the present invention. In addition, about the structure similar to the said Embodiment 1, 2, 3, 4, 5, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  In addition to the configuration of the rotation angle detection device 100 according to the third embodiment, the rotation angle detection device 100 according to the sixth embodiment has a cord disk that is a nonmagnetic rotating plate on the tip surface 70U of the wall 70W. 90. The code disk 90 is fixed to the distal end surface 70U of the wall portion 70W and rotates in synchronization with the shaft 10. With this configuration, the code disk 90 is provided closer to the magnetic detection element 40 than the placement surface 70T.

  A light receiving element 80 used for an optical detector is provided on the substrate 50, and a signal emitted from the code disk 90 is read by the light receiving element 80. Thus, the rotation angle detection device 100 according to the sixth embodiment has a configuration that also serves as an optical detector in addition to a magnetic detector.

In the above arrangement, since the code disc 90 is a non-magnetic material, a magnetic field H _M from detecting magnet 30 is propagated to the magnetic sensing element 40, it is possible to detect the rotation angle by the magnetic change. Further, similarly to the rotation angle detection apparatus 100 according to the third embodiment, the external magnetic field _{H OT} and _{H OS} to detecting magnet 30 and the magnetic detection element 40 and the flux region _{R H,} the propagation of the leakage magnetic field _{H I} of the motor Can be effectively prevented. Note that the code disk 90 may be provided for the rotation detection device 100 according to the fourth and fifth embodiments as in the sixth embodiment.

Embodiment 7 FIG.
FIG. 7 is a cross-sectional view schematically showing a rotation angle detection device 100 according to the seventh embodiment of the present invention. In addition, about the structure similar to the said Embodiment 1, 2, 3, 4, 5, 6, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

The rotation angle detection device 100 according to the seventh embodiment includes a code disk 91 as in the rotation angle detection device 100 according to the sixth embodiment. However, in the rotation angle detection device 100 according to the seventh embodiment, an opening 91 a is formed in a region of the code disk 91 that faces the detection magnet 30. In addition, the size of the opening 91a does not interfere with the magnetic flux region _RH .

Therefore, even when the material of the code disc 91 is of a magnetic material, a magnetic field H _M from detecting magnet 30 is propagated to the magnetic sensing element 40, possible to detect the rotation angle by the magnetic variation Can do. If the material of the code disk 91 is a magnetic material, the surface of the code disk 91 that faces the plate portion 60 is the first magnetic shielding effective surface 91S. Further, similarly to the rotation angle detection apparatus 100 according to the third embodiment, the external magnetic field _{H OT} and _{H OS} to detecting magnet 30 and the magnetic detection element 40 and the flux region _{R H,} the propagation of the leakage magnetic field _{H I} of the motor Can be effectively prevented. In addition, the cord disk 91, the boss portion 70, and the shaft 10 can be integrally formed of a magnetic material. In addition, the code disc 91 may be provided for the rotation detection device 100 according to the fourth and fifth embodiments as in the seventh embodiment.

Embodiment 8 FIG.
FIG. 8 is a cross-sectional view schematically showing a rotation angle detection device 100 according to the eighth embodiment of the present invention. In addition, about the structure similar to the said Embodiment 1,2,3,4,5,6,7, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  In the eighth embodiment, the placement surface 10T on which the detection magnet 31 is placed is formed at one end of the shaft 10 as in the first embodiment. However, the shaft 10 is a nonmagnetic material made of a nonmagnetic material. Part. That is, in the eighth embodiment, the detection magnet 31 is placed on the nonmagnetic portion. In addition, when providing a boss | hub part as demonstrated in the said embodiment, you may make a boss | hub part a nonmagnetic part.

  The magnetic detection element 41 responds only to a change in the magnetic field in the in-plane direction orthogonal to the rotation axis O of the magnet and outputs a detection signal. That is, there is sensitivity in the left-right direction and depth direction on the paper surface of FIG. 8, but no sensitivity in the vertical direction on the paper surface. The detection magnet 31 is magnetized so that the magnetic field changes in a direction in which the magnetic detection element 41 has sensitivity by rotating about the rotation axis O. Examples of magnetization in which the magnetic field changes in this way include single-sided double-pole magnetization, radial magnetization, or double-sided quadrupole magnetization in which each of the S and N poles is magnetized.

  The magnetic detection element 41 is attached to the substrate 50 by being soldered by surface mounting. The substrate 50 is fixed to the bracket 20 via, for example, a columnar fixing member 81. The bracket 20 rotatably supports the shaft 10, but the bracket 20 itself does not rotate. Therefore, even if the detection magnet 31 rotates, the substrate 50 and the magnetic detection element 41 do not rotate. In the first, second, third, fourth, fifth, sixth and seventh embodiments, the substrate 50 is fixed to the bracket 20 via a fixing member (not shown).

  The plate portion 60 is fixed to the substrate 50 via a columnar fixing member 82. Therefore, even if the detection magnet 31 rotates, the plate portion 60 does not rotate. Note that the plate portion 60 may be fixed to the bracket 20 similarly to the substrate 50. In the first, second, third, fourth, fifth, sixth and seventh embodiments, the plate portion 60 is fixed to the substrate 50 via a fixing member (not shown).

  The bracket 20 includes a bracket body 61 that rotatably supports the shaft 10, and a bracket side plate portion 62 that is fixed to the bracket body 61 and faces the plate portion 60. The bracket side plate portion 62 is made of a magnetic material and is fixed to the bracket body 61. Examples of the method for fixing the bracket side plate portion 62 to the bracket body 61 include screwing and adhesion. In the eighth embodiment, the bracket side plate portion 62 made of a magnetic material is a magnetic portion.

  The centers of the magnetic detection element 41, the detection magnet 31, the plate part 60, and the bracket side plate part 62 are preferably on the rotation axis O. If the bracket side plate portion 62 is not provided on the bracket 20, the bracket body 61 may be made of a magnetic material, and the bracket body 61 may be a magnetic portion. That is, the entire bracket 20 may be a magnetic part.

  In the eighth embodiment, by using the magnetic detection element 41 that is sensitive only to a magnetic field change in the in-plane direction orthogonal to the rotation axis O of the detection magnet 31, the direction of the external magnetic field to be shielded is the magnetic detection element. Limited to 41 sensitive directions. This further reduces the need to shield the external magnetic field in the direction parallel to the rotation axis O, so that the magnetic detection element 41 and the detection magnet 31 are not covered with the cover, and the plate portion 60 and the bracket that is the magnetic portion are provided. Even when a gap is provided between the side plate 62 and the side plate 62, the influence of the external magnetic field on the magnetic detection element 41 can be suppressed more reliably.

Specifically, external magnetic field H _OS from the left in FIG. 8 is absorbed by the plate portion 60 and the bracket side plate portion 62 of the arranged magnetic material vertically through the inside of the plate portion 60 and the bracket side plate portion 62 To the right. Thus, the influence of the external magnetic field H _OS for output signals of the magnetic detecting element 41 is extremely slight.

Further, a part of the external magnetic field _HOT from the upper direction in FIG. 8 is absorbed by the plate portion 60, but when the thickness of the plate portion 60 is thin, it cannot be absorbed and penetrates to reach the magnetic detection element 41. . However, since the magnetic detection element 41 is not sensitive to the magnetic field from the vertical direction in FIG. 8, the external magnetic field _HOT does not affect the output signal. That is, by using the magnetic detection element 41 that is sensitive only to a change in the magnetic field in the in-plane direction orthogonal to the rotation axis O of the detection magnet 31, the plate portion 60 can be thinned. The external magnetic field H _I extending from the lower direction to the magnetic detection element 41 in FIG. 8 through the shaft 10 also does not affect the output signal of the magnetic sensor 41. Therefore, it is not necessary to provide a magnetic part in a region facing the magnetic detection element 41 on the shaft 10 side with respect to the detection magnet 31.

  FIG. 9 shows a result of a three-dimensional magnetic field simulation of the effect of magnetic shielding by the rotation angle detection device 100 according to the eighth embodiment, and a comparison in which the periphery of the magnetic detection element 41 and the detection magnet 31 is covered with a magnetic cover. It is a figure which shows the result of having carried out the three-dimensional magnetic field simulation of the effect of a magnetic shielding with the rotation angle detection apparatus of FIG. Although the illustration of the cover of the magnetic body provided in the rotation angle detection device for comparison is omitted, the outer peripheral portion of the plate portion 60 shown in FIG. 8 protrudes toward the bracket 20, and the protruding portion is in contact with the bracket 20. ing. In FIG. 9, the result of the three-dimensional magnetic field simulation of the magnetic shielding effect by the rotation angle detection device 100 is shown by a solid line, and the result of the three-dimensional magnetic field simulation of the magnetic shielding effect by a comparative rotation angle detection device is shown by a broken line. Yes.

  In addition, in order to match the conditions of the rotation angle detection device 100 according to the eighth embodiment and the rotation angle detection device for comparison, the outer diameter of the plate portion 60 and the outer diameter of the cover made of a magnetic material are φ40 mm, the bracket 20 The height from the plate portion 60 to the plate portion or the height from the bracket to the cover is 6 mm, the thickness of the plate portion 60, the thickness of the bracket side plate portion 62, and the thickness of the cover are 0.5 mm. Analysis was performed with iron.

Further, in FIG. 9, the vertical axis represents the magnitude of the magnetic field in the horizontal direction in FIG. 8 of the external magnetic field H _OS, and magnitude of the magnetic field of the external magnetic field H _OS unmasked and absorb and 10. In FIG. 9, the horizontal axis indicates the position in the left-right direction in FIG. 8, and the position of 20 mm indicated on the horizontal axis is the center of the plate portion 60 or the center of the cover. That is, in the rotation angle detection device for comparison, the entire range of 0 mm to 40 mm shown on the horizontal axis is inside the cover.

According to the results shown in FIG. 9, in the comparative rotation angle detection device, the magnitude of the external magnetic field is about 1/100 in all the areas inside the cover. On the other hand, in the rotation angle detection device 100 according to the eighth embodiment, the shielding effect of the external magnetic field in the vicinity of the center of the plate portion 60 is large, and the influence of the external magnetic field increases as going outward. However, in the vicinity of the center of the plate portion 60, the same magnetic field shielding effect as that obtained when the cover is provided can be obtained. Therefore, by placing the magnetic detection element 41 near the center of the plate portion 60, the influence of the external magnetic field _{HOS on} the magnetic detection element 41 can be suppressed as in the case where the cover is provided. As described above, even if the gap is provided between the plate portion 60 and the bracket 20, the influence of the external magnetic field _{HOS on} the magnetic detection element 41 can be suppressed. Even if the magnetic flux region _RH is not sandwiched between the first magnetic shielding effective surface 10S and the second magnetic shielding effective surface 60S, the influence of the external magnetic field _{HOS on} the magnetic detection element 41 is affected. Can be suppressed.

  Further, the volume ratio between the cover and the plate portion 60 is 3: 2, and the material cost of the cover is 1.5 times higher. Further, from the viewpoint of workability, the cover needs to be bent or cut to form a side wall with respect to the plate portion 60 which is a flat plate, and the manufacturing cost increases.

  The detection magnet 31 and the magnetic detection element 41 described in the eighth embodiment may be used in the first, second, third, fourth, fifth, sixth, and seventh embodiments.

  FIG. 10 is a cross-sectional view illustrating a schematic configuration of the electric motor 110 including the rotation angle detection device 100 according to the first embodiment. The electric motor 110 includes a rotor 111 connected to the shaft 10 of the rotation angle detection device 100 and a stator 112 surrounding the rotor 111. Of course, the electric motor may be configured by providing the rotor 111 and the stator 112 with respect to the rotation angle detection device 100 according to the second, third, fourth, fifth, sixth, seventh, and eighth embodiments.

  The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

  10 shaft, 10T placement surface, 10W wall portion, 10U tip surface, 10S first magnetic shielding effective surface, 11 enlarged portion, 20 bracket, 20S first magnetic shielding effective surface, 20T tip surface, 20W wall portion, 30 , 31 detection magnet, 40, 41 magnetic detection element, 50 substrate, 50T mounting surface, 60 plate portion, 60B lower surface portion, 60S second magnetic shielding effective surface, 61 bracket body, 62 bracket side plate portion, 70 boss portion, 70T placement surface, 70U tip surface, 70W wall, 70S first magnetic shielding effective surface, 81, 82 fixing member, 90, 91 code disk, 91S first magnetic shielding effective surface, 91a opening, 100 rotation angle Detection device, 110 electric motor, 111 rotor, 112 stator.

Claims (14)

A shaft,
A magnet provided on one end side in a direction along the rotation axis of the shaft;
A magnetic part provided on the shaft side of the magnet and made of a magnetic material;
A magnetic detection element that is disposed at a position facing the magnet and detects a change in a magnetic field due to rotation of the magnet;
A plate portion made of a magnetic body provided at a position facing the magnetic portion across the magnet and the magnetic detection element,
When viewed along the rotation axis, the outer diameter of the surface of the magnetic portion facing the plate portion and the outer diameter of the surface of the plate portion facing the magnetic portion are both outside the magnet. Larger than the diameter and the outer diameter of the magnetic sensing element,
The distance between the magnetic part and the magnetic detection element in the direction along the rotation axis is smaller than the distance between the magnetic part and the plate part in the direction along the rotation axis.
The rotation angle detection device according to claim 1, wherein the plate portion is not formed with a convex portion that protrudes toward the magnet with respect to the magnetic detection element in a direction along the rotation axis.   The rotation angle detection device according to claim 1, wherein the magnetic part has a wall part that protrudes toward the plate part and surrounds the periphery of the magnet.   The rotation angle detecting device according to claim 1, wherein the magnetic part has an enlarged part having an outer diameter larger than an outer diameter of the shaft.   The rotation angle detecting device according to any one of claims 1 to 3, wherein the magnetic part is a boss part fixed to one end side of the shaft. A bracket made of a magnetic material that surrounds the periphery of the shaft when viewed along the rotation axis and rotatably supports the shaft;
The rotation angle detection device according to claim 1, wherein the bracket has a wall portion that protrudes toward the plate portion and surrounds the periphery of the magnet. A bracket made of a magnetic material that surrounds the periphery of the shaft when viewed along the rotation axis and rotatably supports the shaft;
The rotation angle detection device according to claim 1, wherein the bracket is the magnetic part.   The rotation angle detection device according to claim 1, wherein the magnetic detection element is sensitive only to a magnetic field change in an in-plane direction orthogonal to the rotation axis.   The rotation angle detection device according to claim 1, wherein a center of the plate portion, the magnetic detection element, the magnet, and the magnetic portion is on the rotation axis. The shaft is made of a magnetic material,
The shaft is the magnetic part;
The rotation angle detection device according to claim 1, wherein the magnet is placed on the shaft. A non-magnetic portion provided on the shaft side of the magnet and made of a non-magnetic material;
The rotation angle detection device according to claim 1, wherein the magnet is placed on the nonmagnetic portion.   The distance between the placement surface on which the magnet is placed and the plate portion is the minimum value of the outer diameter of the plate portion in the direction perpendicular to the rotation axis and the distance between the placement surface in the direction perpendicular to the rotation axis. The rotation angle detection device according to claim 1, wherein the rotation angle detection device is smaller than a minimum value of the outer diameter. A rotating plate that rotates with the shaft;
A substrate on which the magnetic detection element is mounted;
The rotation angle detection device according to claim 1, further comprising: a light receiving element that is mounted on the substrate and detects a rotation angle of the rotation plate.   The rotation angle detection device according to claim 12, wherein the rotation plate is provided on the magnetic detection element side of the magnet and is made of a magnetic material, and has an opening in a region facing the magnet. . The rotation angle detection device according to any one of claims 1 to 13,
A rotor coupled to the shaft;
And a stator surrounding the rotor.

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