Rotation position detection device

Abstract

A rotation position detection device comprising: a sensor magnet (30) configured to generate a magnetic flux; a holder (34) configured to hold the sensor magnet and comprising a pressure contact section (340) for attachment to a shaft (40, 40b1, 40b2) of a motor (1, 1b); and a magnetic sensor (32) configured to detect the magnetic flux generated by the sensor magnet, wherein the magnetic sensor is attached directly or indirectly to the motor and is arranged away from the sensor magnet in an axial direction of the shaft, wherein the shaft is configured with a contact section to receive a distal end section (341) of the pressure contact section (340) characterized by the fact that the support (34) has a shaft relief section (342) in a section located on an inner periphery of the sensor magnet (30), and the shaft relief section (342) is configured to reduce the stress generated on the sensor magnet (30) by thermal expansion of the shaft.

Description

Technical field

[0001] The present invention relates to a rotary position detection device, and in particular, a rotary position detection device comprising a sensor magnet attached to a rotating section, such as a shaft of an electric power steering drive motor, and a magnetic sensor attached to a non-rotating section, such as a motor housing. background

[0002] A prior art rotary position detection device configured to detect the rotational speed and position of a motor is known to include a position detection magnet as a sensor magnet and a sensor board as a magnetic sensor (see, for example, JP 2015 - 65 789 A). In this case, the sensor magnet is an element that is attached to a rotating section, such as a motor shaft, either directly or by means of an intermediate mounting element, such as a bracket, and is configured to generate a magnetic flux for detecting a rotational position. The sensor magnet has an annular shape and is arranged in a circumferential direction of a rotating shaft, or it has a circular shape and is arranged at one end of the rotating shaft.The magnetic sensor is a component attached to a non-rotating section, such as a motor housing, and is configured to detect a change in magnetic flux caused by rotation of the sensor magnet and output a signal corresponding to that change. This signal is used to determine the rotational position of the motor shaft or other component.

[0003] Furthermore, another rotation position detection device was previously known, comprising a rotation position detection magnet and a fixed element. The rotation position detection magnet is arranged in a region separated by a tubular first circumferential wall section and a lower wall section extending axially inward from an end section of the first circumferential wall section, and is configured to generate a magnetic flux for detecting the rotation position of a rotating body. The fixed element is made of a non-magnetic material and is attached to a rotating shaft of the rotating body. The fixed element has a plurality of inwardly projecting protrusions formed at intervals in a circumferential direction on an inner peripheral surface of the first circumferential wall section in the aforementioned region (see, for example, JP 2014 - 57 431 A).

[0004] The generic designation WO 2016 / 098 627 A1 discloses a rotation angle detection device comprising a first magnetic detection unit for detecting changes in the direction or magnitude of a magnetic field, provided on a rotating shaft; a second magnetic detection unit for detecting changes in the direction or magnitude of a magnetic field, provided on the rotating shaft and positioned at a location offset in the direction of rotation of the shaft relative to the first magnetic detection unit; and a magnet rotatable relative to the first and second magnetic detection units, provided on the outside of the first and second magnetic detection units in a radial direction relative to the rotating shaft and positioned such that the N and S poles are opposite each other, with the rotating shaft centered between them.

[0005] DE 10 2015 002 562 A1 discloses an electric machine, in particular an electric motor of a motor vehicle, with a rotor (34) rotatably mounted by means of a rotor shaft, as well as with a position encoder having a rotationally fixed sensor unit and with a shaft-fixed sensor encoder, which is designed as a plastic injection-molded part with an encoder head receiving a magnet, in particular a magnetic dipole, and with a connecting shaft, or is provided with a plastic overmolding together with the magnet on the encoder head side to form the connecting shaft, wherein the connecting shaft is joined to the rotor shaft at the end face of a shaft end in a form-fitting manner and forming a press fit or an interference fit.

[0006] US 2014 / 0070799 A1 discloses a rotary position sensing device comprising a rotary position sensing magnet and a fastening element. The fastening element is made of a non-magnetic material and is attached to a rotatable shaft of a rotor. The fastening element includes several projections that extend radially inward and are arranged sequentially in the circumferential direction on an inner circumferential surface of a first circumferential wall section within a space bounded by the first circumferential wall section and a bottom wall section, and which holds the rotary position sensor magnet. Summary of the invention: Technical problem

[0007] With the rotation position detection device described above, JP 2015-065 789 A, a "rotation position detection error" occurs when there is a change in the distance or inclination between the sensor magnet and the magnetic sensor. This "rotation position detection error" is caused by fluctuations in the magnetic flux required for detection by the magnetic sensor, due to changes in the distance between the sensor magnet and the magnetic sensor, or by magnetic flux fluctuations due to changes in the distance between the sensor magnet and the magnetic sensor during rotation due to the inclination between the sensor magnet and the magnetic sensor. As a result, the generated torque fluctuates, and performance deteriorates.

[0008] Furthermore, in JP 2015 - 65 789 A, a bracket configured to hold the sensor magnet is held by the shaft, and no element for regulating the distance to the magnetic sensor is provided. As a result, changes in the distance between the sensor magnet and the magnetic sensor can occur, necessitating positioning management during assembly. Moreover, the sensor, which has a ring shape and is arranged circumferentially around the rotating shaft, is positioned away from the rotating shaft. Consequently, the tilt of the bracket causes a large change in the distance between the sensor magnet and the magnetic sensor during rotation. This results in a significant "rotational position detection error."

[0009] Additionally, also in JP 2014-057431A, a bracket configured to hold a sensor magnet is held by a shaft, and an element for regulating a distance to a magnetic sensor is not provided, with the result that a change in the distance between the sensor magnet and the magnetic sensor may occur.

[0010] The present invention was made to solve the above-mentioned problem and has the objective of providing a rotary position detection device in which a rotary position detection error caused by a change in the distance between a sensor magnet and a magnetic sensor is reduced, as well as reducing the load on the sensor magnet due to thermal expansion of the shaft and preventing damage to the sensor magnet. Solution to the problem

[0011] This problem is solved by a rotation position detection device with the features of claim 1. Advantageous embodiments are set out in the dependent claims. Advantageous effects of the invention

[0012] According to the present invention, the shaft includes the mounting section configured to receive the distal end section of the pressure contact section of the holder, which is configured to hold the sensor magnet. The sensor magnet is positioned opposite the magnetic sensor attached to the motor shaft. This regulates the distance between the sensor magnet and the magnetic sensor, thereby preventing changes in distance and reducing rotational position detection errors. Furthermore, according to the invention, the stress on the sensor magnet caused by thermal expansion of the shaft is reduced, thus preventing damage to the sensor magnet 30. Brief description of the characters Fig. Figure 1 is a cross-section of a motor that includes a rotary position detection device according to a first embodiment of the present invention. Fig. Figure 2 is a cross-section of the rotary position detection device according to the first embodiment of the present invention. Fig. Figure 3 is a cross-section of a rotary position detection device according to a second embodiment of the present invention. Fig. Figure 4 is a cross-section of a rotation position detection device according to a third embodiment of the present invention. Fig. Figure 5 is a cross-section of a motor which includes a rotary position detection device according to another embodiment. Fig. Figure 6 is a cross-section of a motor that includes a rotary position detection device according to a fourth embodiment of the present invention. Description of the embodiments

[0013] Now, rotation position detection devices according to the embodiments of the present invention will be described in detail with reference to Fig. 1 to Fig. 6 described by a case example in which the rotary position detection device is applied to an electric power steering motor as an example. First embodiment

[0014] A in Fig. The motor 1 shown comprises a motor housing 10, a stator 11 attached to the motor housing 10, a rotating body 4 provided in the stator 11, a control 2 connected to the motor housing 10, a rotary position detection device 3 provided in the control 2, and a shaft 40 running through the rotating body 4 and the control 2 via intermediate bearings 5.

[0015] The stator 11 comprises a stator core 110 and windings 111. The stator core 110 has a cylindrical shape and is made of a magnetic material. The windings 111 wrap around the stator core 110. When the windings 111 are supplied with a predetermined electric current, a rotating magnetic field is generated in the stator core 110.

[0016] The rotating body 4 comprises a rotor 41, a shaft 40, and a hub 42, and is held in rotation by an interposed bearing 5. The rotor 41 is positioned opposite an inner peripheral surface of the stator 11 and includes a rotor core 411 and a magnet 412. The rotor core 411 is cylindrical and made of a magnetic material. The magnet 412 is located on an outer periphery of the rotor core 411. With this configuration, the rotating magnetic field generated in the stator core 111 imparts a rotational force to the rotating body 4. This rotational force is transmitted via the bearing 42 to an external steering mechanism (not shown).

[0017] The rotary position detection device 3 includes a sensor magnet 30, a holder 34, a magnetic sensor 32 and a magnetic sensor board 31. The sensor magnet 30 is made of a plastic magnetic material and is configured to generate a magnetic flux and to rotate in conjunction with the rotating body 4 by means of an intermediate shaft 40.

[0018] As in Fig. As shown in Figure 2, the shaft 40 has a stepped section 403 between a small-diameter section 401 and a large-diameter section 402. The small-diameter section 401 is located on a part of the shaft 40 corresponding to the sensor magnet 30, and the large-diameter section 402 is located on the side of the rotor 41. Furthermore, a bearing inner ring mounting section 404 of the shaft 40 forms another stepped section 404, which is configured to receive a bearing inner ring 50 of a bearing 5 in conjunction with the large-diameter section 402.

[0019] The holder 34 is made of a non-magnetic metallic material. The holder 34 is configured to hold, for example, the sensor magnet 30, which is a resin magnet, and is mounted and secured on the shaft 40 by a pressure contact section 340 with a cylindrical shape. A distal end section 341, formed on the side of the rotor 41 of the pressure contact section 340 and extending in an axial direction, is brought into contact with and positioned against the stepped section 403 between the small-diameter section 401 and the large-diameter section 402 of the shaft 40.

[0020] Furthermore, the holder 34 is integrated into the sensor magnet 30 by means of insert shapes. A sensor-side surface 300 of the sensor magnet 30 is formed such that it is parallel to the distal end section 341 of the holder 34 and perpendicular to a central axis of the pressure contact section 340, and has a cylindrical shape.

[0021] The magnetic sensor 32 is configured to detect a change in the magnetic flux of the rotary sensor magnet 30 and to output a signal corresponding to the change. Furthermore, the magnetic sensor 32 is arranged axially away from the sensor magnet 30, so that it faces the sensor-side surface 300. The magnetic sensor board 31 transmits the signal to the controller 2. The magnetic sensor board 31, with the magnetic sensor 32 mounted on it, is attached to a controller housing 21 by screws or other elements. An inner bearing ring 51 is installed in the controller housing 21 and is axially aligned against a bearing outer ring mounting section 210.

[0022] As in Fig. As shown in Figure 1, the control unit 2 comprises a control board 20, the control housing 21, and a control cover 22. The control board 20 receives a detection signal from the rotary position detection device 3 and controls electrical currents in the windings 111 of the stator 11 based on a control signal from, for example, a microcomputer. This rotates the rotating body 4 and supplies the required torque to the motor 1. Furthermore, if the

[0023] The rotary position detection device 3 is to be arranged on the side of the hub 42, which is configured to transmit rotational force from the shaft 40. The sensor magnet 30 has an annular shape and is arranged in an outer peripheral direction of the shaft 40. In this case, the bracket 34 has a shaft relief section 342 for the shaft 40 in a section located on an inner periphery of the sensor magnet 30. This arrangement is adopted to reduce the stress generated on the sensor magnet 30 by thermal expansion of the shaft 40 and to prevent damage to the sensor magnet 30.

[0024] Next, the procedure and effects of the first embodiment of the present invention will be described.

[0025] According to the first embodiment, the holder 34, which is configured to hold the sensor magnet 30, is configured such that the distal end section 341, which is arranged on the distal end of the cylindrical pressure contact section 340, is brought into contact with the step section 403 between the small diameter section 401 and the large diameter section 402 of the shaft 40.

[0026] The inner bearing ring 50 is additionally positioned by the other stepped section 404, which is formed in the shaft 40. Furthermore, the magnetic sensor board 31 with the magnetic sensor 32 mounted on it is attached to the control housing 21 by screws or other elements. The outer bearing ring 51 is installed in the control housing 21 and is brought into contact with the outer bearing ring mounting section 210 and the mounting section 404 in order to be positioned thereon.

[0027] Thus, the change in the distance between the sensor magnet 30 and the magnetic sensor 32 can be prevented by increasing the accuracy of components that include the bracket 34, the shaft 40, the bearing 5 and the control housing 21, which are arranged between the sensor magnet 30 and the magnetic sensor 32.

[0028] The accuracy of the components can be increased by the following procedure.

[0029] With reference to the bracket 34, dimensional accuracy between a mounting surface of the sensor magnet 30 and the pressure contact section 340, which extends in the axial direction, is increased by sheet metal drawing by compression forming.

[0030] Furthermore, with reference to shaft 40, dimensional accuracy between the bearing inner ring mounting section 404 and the step section 403, which is formed between the small diameter section 401 and the large diameter section 402, is increased by machining.

[0031] Additionally, with regard to the control housing 21, the accuracy is increased by injection molding the entire housing by die casting or another process and by partial machining on the bearing outer ring mounting section 210 and a substrate carrier section 211 of the magnetic sensor board 31. The accuracy of the bearing 5 can be ensured in advance by means of a finished product.

[0032] Thus, by increasing the accuracy of the components comprising the bracket 34, the shaft 40, the bearing 5, and the control housing 21, which are arranged between the sensor magnet 30 and the magnetic sensor 32, the distal end section 341 of the bracket 34, configured to hold the sensor magnet 30, can be brought into contact with the stepped section 403 between the small-diameter section 401 and the large-diameter section 402 of the shaft 40, and the inner bearing ring 50 is brought into contact with the large-diameter section 402 and the stepped section 404 for assembly. This facilitates assembly management and prevents changes in the distance between the sensor magnet 30 and the magnetic sensor 32.

[0033] Additionally, the holder 34 is integrated into the sensor magnet 30 by means of insert shapes. This ensures that the sensor-side surface 300 of the sensor magnet 30 is formed such that it is parallel to the distal end section 341 of the holder 34 and perpendicular to the central axis of the pressure contact section 340. Thus, by means of insert shapes of the sensor-side surface 30, so that it is parallel to the distal end section 341 and perpendicular to the central axis of the pressure contact section 340, regardless of profile irregularities of the holder 34, changes in the inclination between the sensor-side surface 300 and the magnetic sensor 32 can be prevented.

[0034] When a pre-formed sensor magnet 30 is attached to the holder 34 by gluing, sealing, or another method, the sensor-side surface 300 is unfavorably inclined unless irregularities in the connection profile between the holder 34 and the sensor magnet 30 are increased. Furthermore, to ensure adhesive strength, a large bonding area is required, thus making it more difficult to compensate for irregularities in the connection profile.

[0035] In contrast, in the case of insert forms of this structure, only molding is required to achieve the dimensional accuracy of the sensor-side surface 300 with reference to the distal end section 341 and the central axis of the pressure contact section 340, and thus it is easier to ensure the accuracy compared to attachment by gluing or another method.

[0036] If the rotary position detection device 3 is arranged on the side of the hub 42, which is configured to transmit the rotational force of the shaft 40, and the sensor magnet 30 has an annular shape and is arranged in the outer peripheral direction of the shaft 40, the degree of freedom in the design of the motor 1 can be increased and it is possible to obtain the rotary position detection device 3 in which the change in distance and inclination between the sensor magnet 30 and the magnetic sensor 32 is prevented. Second embodiment

[0037] In a second in Fig. In the embodiment of the present invention shown in Figure 3, the stepped section 403 between the small-diameter section 401 and the large-diameter section 402 is omitted in the first embodiment described above, and the large-diameter section 402 of the shaft 40 is in Fig. 2 is replaced by a shaft spacer 405 with an annular shape as a separate element. The shaft spacer 405 is arranged between the inner bearing ring 50 and the distal end section 341 of the holder 34. Thus, the holder 34, which is configured to hold the sensor magnet 30, is positioned axially by one dimension of the shaft spacer 405. The shaft spacer 405 can be held without contact with the inner bearing ring 50 and can be separated from it.

[0038] Next, the procedure and effects of the second embodiment of the present invention will be described.

[0039] According to the second embodiment, by ensuring the dimensional accuracy of the shaft spacer 405 in the axial direction, changes in the distance between the sensor magnet 30 and the magnetic sensor can be prevented. In contrast to the first embodiment described above, it is not necessary for the shaft 40 to achieve dimensional accuracy between the bearing inner ring contact section 404 and the stepped section 403, which is formed between the small-diameter section 401 and the large-diameter section 402.

[0040] This allows assembly management to be easily carried out with the distal end section 341 of the holder 34, which is configured to hold the sensor magnet 30, which rests against the shaft spacer 405, for assembly, and prevents changes in the distance between the sensor magnet 30 and the magnetic sensor 32. Third embodiment

[0041] In a third in Fig. In the embodiment of the present invention shown in section 4, in the first embodiment described above, the large-diameter section 402 of the holder 40 is Fig. 2 is replaced by a bearing 5, in particular by the inner bearing ring 50. This positions the holder 34, which is configured to hold the sensor magnet 30, in such a way that the pressure contact section 340, with a cylindrical shape, is brought into contact with the inner bearing ring 50 at the distal end section 341, which extends in the axial direction.

[0042] Next, the procedure and effects of the third embodiment of the present invention will be described.

[0043] According to the third embodiment, by increasing the accuracy between the mounting surface of the sensor magnet 30 to the holder 34 and the distal end section 341 of the pressure contact section 340, which extends in the axial direction, changes in the distance between the sensor magnet 30 and the magnetic sensor 32 can be prevented.

[0044] Therefore, in contrast to the first embodiment, it is not necessary for the shaft 40 to achieve the dimensional accuracy between the bearing inner ring contact section 404 and the stepped section 403, which is formed between the small-diameter section 401 and the large-diameter section 402. Furthermore, compared to the second embodiment described above, it is not necessary to achieve the dimensional accuracy of the shaft spacer 405 in the axial direction.

[0045] This means that, with the holder 34, which is configured to hold the sensor magnet 30, which rests against the inner bearing ring 50, for assembly, assembly management can be easily carried out and the change in the distance between the sensor magnet 30 and the magnetic sensor 32 can be prevented. Non-inventive embodiment

[0046] In a Fig. In the non-inventive embodiment shown in Figure 5, a motor 1a is configured such that a rotary position detection device 3a is arranged on one side opposite a side of a hub 42a, which is configured to transmit a rotational force to a shaft 40a. In this case, a sensor magnet 30a has a circular shape and is arranged at one end of the shaft 40a. Furthermore, a magnetic sensor 32a is moved in a direction of the extension of an axis with respect to the sensor magnet 30a and is arranged such that it faces a sensor-side surface 300a. The other configuration and functions are similar to those described above and are therefore omitted from this description.

[0047] The effects of this design will be described next.

[0048] According to this embodiment, with the above-mentioned arrangement and configuration, effects similar to those of the third embodiment described above can be achieved. Furthermore, the degree of freedom of the motor 1a can be increased, and the rotary position detection device 3a can be configured such that changes in the distance (including inclination) between the sensor magnet 30 and the magnetic sensor 32 are prevented. Fourth embodiment

[0049] In a fourth in Fig. In the embodiment of the present invention shown in Figure 6, the same configuration is used, except that the shaft 40 of the motor 1 is Fig. 4 includes a wave 40b1 and a wave 40b2 embedded within wave 40b1.

[0050] The shaft 40b1 of the rotating body 4 is in particular made of an S45C material or of another magnetic material and forms the rotor side, and the shaft 40b2 is made of a SUS304 material or of another non-magnetic material and forms a rotation position detection device 3. Alternatively, the entire shaft 40 of the motor 1 can be in Fig. 4. be made of a non-magnetic material.

[0051] During rotation in motor 1, magnetic field noise is generated by the rotating magnetic field produced in the stator core 110, the magnetic flux of the magnet 412 of the rotating rotor 41, and the like. If the shaft 40 is made of a magnetic material, the magnetic field noise propagates through the shaft 40 and affects the magnetic sensor 32.

[0052] Next, the procedure and effects of the fourth embodiment of the present invention will be described.

[0053] According to the fourth embodiment, the rotary position detection device 3 is easily affected by the magnetic field noise used for position detection with the magnetic sensor 32. Therefore, it is desirable that the rotary position detection device 3 be arranged such that it is separated from the magnet 412, the stator core 110, the rotor 41, and the motor 412.

[0054] The fourth embodiment was developed with this arrangement limitation in mind, and it is possible to provide the rotary position detection device 3a, which is reduced in the number of components, allows for simple assembly management and enables the prevention of changes in the distance (including inclination) between the sensor magnet 30a and the magnetic sensor 32a. List of reference symbols

[0055] 1, 1a, 1b Motor, 10 Motor housing, 2 Controller, 20 Control board, 21 Controller housing, 22 Controller cover, 3, 3a Rotary position detection device, 4 Rotating body, 41 Rotor, 411 Rotor core, 412 Magnet, 5 Bearing, 50 Inner bearing ring, 51 Outer bearing ring, 11 Stator, 110 Stator core, 111 Winding, 30, 30a Sensor magnet, 31 Magnetic sensor board, 32, 32a Magnetic sensor, 34 Mount, 40, 40a, 40b1, 40b2 Shaft, 42, 42a Hub, 210 Outer bearing ring mounting section, 211 Substrate carrier section, 300, 300a Sensor-side surface, 340 Pressure contact section, 341 Distal end section, 342 Shaft relief section, 401 small diameter section, 402 large diameter section, 403, 404 step section, 405 shaft spacer.

Claims

A rotary position detection device comprising: a sensor magnet (30) configured to generate a magnetic flux; a holder (34) configured to hold the sensor magnet and having a pressure contact section (340) for attachment to a shaft (40, 40b1, 40b2) of a motor (1, 1b);and a magnetic sensor (32) configured to detect the magnetic flux generated by the sensor magnet, wherein the magnetic sensor is attached directly or indirectly to the motor and is arranged away from the sensor magnet in an axial direction of the shaft, wherein the shaft is configured with a mounting section to receive a distal end section (341) of the pressure contact section (340), characterized in that the support (34) has a shaft relief section (342) in a section located on an inner periphery of the sensor magnet (30), and the shaft relief section (342) is configured to reduce the stress generated on the sensor magnet (30) by thermal expansion of the shaft. The rotary position detection device according to claim 1, wherein the system section comprises a step section (403, 404) formed by a diameter difference of the shaft. The rotary position detection device according to claim 1, wherein the system section comprises an annular shaft spacer (405) which is attached to an outer periphery of the shaft. The rotary position detection device according to claim 1, wherein the system section comprises a bearing (5) provided such that the shaft is rotatably mounted by a control (2) connected to the motor. The rotary position detection device according to claim 2, wherein the shaft comprises: a large diameter shaft (402) made of a magnetic material; and a small diameter shaft (401) made of a non-magnetic material, wherein the pressure contact section is attached to the small diameter shaft, wherein the small diameter shaft is inserted into the large diameter shaft to form the step section. The rotary position detection device according to one of claims 1 to 5, wherein the sensor magnet (30) comprises an annular sensor magnet arranged in an outer peripheral direction of the shaft when mounted on one side of a hub (42) mounted on the shaft. The rotary position detection device according to one of claims 1 to 6, wherein the holder (34) is made of a non-magnetic metallic material. The rotary position detection device according to one of claims 1 to 7, wherein the holder (34) is integrated into the sensor magnet (30) by means of insert forms.

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