Position detection device

Abstract

To provide a position detection device that can be easily carried while protecting a circuit board and a target.SOLUTION: A position detection device 1 comprises a circuit board 3, a target 4, and a case 5. The circuit board 3 includes a detection portion in which an exciting coil generates an induced electromotive force. The target 4 rotates around an axis AX according to the rotation of a rotary shaft 2 of an object, and changes the induced electromotive force generated in the detection portion by a non-magnetic metal portion. The case 5 includes a support 51 that supports the circuit board 3 and a cover 52 that is fixed to the support 51, and accommodates the circuit board 3 and the target 4. In the support 51, a support through hole H1, which is a hole smaller than the outer diameter of the target 4 and centered on the axis AX, is formed. In the cover 52, a cover through hole H2, which is a hole smaller than the outer diameter of the target 4 and centered on the axis AX, is formed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a position detection device. [Background technology]

[0002] For example, Patent Documents 1 and 2 describe a position detection device called an inductive position sensor. This position detection device includes a circuit board having an excitation coil and a detection unit in which an induced electromotive force is generated by the excitation coil, and the induced electromotive force generated in the detection unit changes depending on the displacement of a target having a non-magnetic metal part. The target displaces according to the displacement of the object. The device detects the position of the object based on this changing induced electromotive force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-76548 [Patent Document 2] Japanese Patent Publication No. 2023-159506 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Documents 1 and 2 do not disclose the details of the structure of the device, and there is room for improvement in the structure in which the circuit board and the target are mounted within the device.

[0005] The present disclosure has been made in consideration of the above-described circumstances, and aims to provide a position detection device that can be easily carried while protecting a circuit board and a target. [Means for solving the problem]

[0006] In order to achieve the above object, the position detection device according to the present disclosure includes: a circuit board having an excitation coil that is excited by application of a voltage and a detection unit that generates an induced electromotive force by the excited excitation coil; a target having a non-magnetic metal part facing the circuit board with a gap therebetween, which rotates about an axis in response to rotation of a rotation shaft of an object, and which changes the induced electromotive force generated in the detection unit by the non-magnetic metal part; a case having a support for supporting the circuit board and a cover fixed to the support, and accommodating the circuit board and the target; a support through-hole that is smaller than the outer diameter of the target and has the axis as its center is formed in the support; The cover has a cover through-hole formed therein, the cover through-hole being smaller than the outer diameter of the target and centered on the axis. [Effects of the Invention]

[0007] According to the present disclosure, the circuit board and the target can be easily carried while being protected. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view of a position detection device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic exploded view of the position detection device according to the embodiment. [Figure 3] 2 is a schematic cross-sectional view of the position detection device according to the embodiment taken along line II in FIG. 1; [Figure 4] FIG. 2 is a functional block diagram illustrating functions of the target and the circuit board according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present disclosure will be described with reference to the drawings.

[0010] 1 to 3 is attached to an object and detects the rotational position of a rotation shaft 2 (see FIG. 3) of the object. The object is, for example, a motor that rotates the rotation shaft 2 about an axis AX. The position detection device 1 includes a circuit board 3, a target 4 that rotates about the axis AX in response to the rotation of the rotation shaft 2, and a case 5.

[0011] The circuit board 3 is a printed circuit board, and is configured by providing various circuits and electronic components on an insulating substrate 30. In addition to the substrate 30, the circuit board 3 is equipped with an excitation coil 31, a detection unit 32 having a first detection coil 32a and a second detection coil 32b, and a control unit 33, which are shown as functional blocks in Fig. 4. The circuit board 3 also includes a group of EMC (Electromagnetic Compatibility) components and a connector, which are not shown in the figure.

[0012] The detection principle of the device and the configuration of the circuit board 3 are described in detail in Japanese Patent Application Laid-Open Nos. 2021-76548 and 2023-159506, both of which are filed by the same applicant as the present application. As long as the rotational position of the rotating shaft 2 can be detected, (i) the number of layers of the substrate 30 (for example, it may be a multi-layer substrate such as a four-layer substrate), and (ii) the formation pattern and number of the excitation coil 31, first detection coil 32a, and second detection coil 32b can be changed as desired. Below, the functions of the configuration mounted on the circuit board 3 will be mainly described.

[0013] The excitation coil 31 is excited by passing a current through it under the control of the control unit 33. The excitation coil 31 is a coil with a plurality of windings, and is formed, for example, by printing a conductor such as copper (Cu), aluminum (Al), silver-palladium (Ag / Pd), or gold (Au) on the substrate 30. A voltage is applied to the excitation coil 31 from a terminal (not shown).

[0014] An induced electromotive force is generated in the detection unit 32 by the magnetic field generated by the excited excitation coil 31. The detection unit 32 includes a pair of first and second detection coils 32a and 32b. The first and second detection coils 32a and 32b are not electrically connected to each other and are shaped such that one is shifted relative to the other in the rotation direction of the target 4. For example, the first and second detection coils 32a and 32b are formed on the substrate 30 so as to have a phase difference of 90° when the angle around the axis AX is considered. The first and second detection coils 32a and 32b are formed by printing a conductor such as copper (Cu), aluminum (Al), silver-palladium (Ag / Pd), or gold (Au) on the substrate 30. Next, before describing the control unit 33, the target 4 will be described.

[0015] The target 4 has a non-magnetic metal portion 4a (see FIG. 4), and rotates in accordance with the rotation of the rotating shaft 2, which is the object, causing the non-magnetic metal portion 4a to change the induced electromotive force generated in the detection portion 30. The non-magnetic metal portion 4a is made of a non-magnetic metal material, such as aluminum (Al) or copper (Cu), that is not magnetized by the magnetic field generated by the excitation coil 31.

[0016] As shown in FIG. 3, the target 4 includes a cylindrical portion 40 attached to the rotating shaft 2 and a flange 41 formed around the cylindrical portion 40. The cylindrical portion 40 is formed around the axis AX. The rotating shaft 2 of the motor is inserted into the cylindrical portion 40. As shown in FIG. 2, the flange 41 is composed of a plurality of blades (four blades in the illustrated example) arranged at equal intervals in the circumferential direction around the axis AX. At least the flange 41 of the target 4 has a non-magnetic metal portion 4a. For example, the target 4 may be configured such that the cylindrical portion 40 and the flange 41 are made of resin, and a plate-shaped or film-shaped non-magnetic metal portion 4a is provided on the surface of each blade constituting the flange 41 facing the circuit board 3. Note that a configuration in which at least the flange 41 of the target 4 is formed of the non-magnetic metal portion 4a may also be employed. In either configuration, the non-magnetic metal portion 4a faces the circuit board 3 with a gap therebetween. The detection unit 32 is provided on the circuit board 3 at a position facing the non-magnetic metal portion 4a. The flange 41 is located between a cover 52 (to be described later) and the circuit board 3 in the direction in which the axis AX extends.

[0017] The shapes of the flange 41 and the non-magnetic metal portion 4a can be changed as desired depending on the purpose. For example, the number of blades constituting the flange 41 may be determined according to the number of poles of the motor, which is the target object. The flange 41 may also be formed in a disk shape. The non-magnetic metal portion 4a may be provided partially on the disk-shaped flange 41.

[0018] The target 4 rotates about the axis AX together with the rotating shaft 2 relative to the detecting unit 32 formed on the circuit board 3. Excitation of the exciting coil 31 generates eddy currents in the non-magnetic metal part 4a, and the generated eddy currents act to reduce the electromagnetic coupling between the exciting coil 31 and the detecting unit 32. As the rotating shaft 2 rotates, the part of the detecting unit 32 covered by the non-magnetic metal part 4a changes, and the voltage induced in the detecting unit 32 (induced electromotive force) changes. Based on this change in the induced electromotive force, the controlling unit 33 calculates the rotational position of the rotating shaft 2.

[0019] The control unit 33 includes a DSP (Digital Signal Processor), an oscillator that converts DC voltage from a power supply (not shown) into AC voltage under the control of the DSP and applies the AC voltage to the excitation coil 31, and an ADC (Analog to Digital Converter) that converts a voltage (analog signal) output by induced electromotive force generated in each of the first detection coil 32a and the second detection coil 32b into a digital signal and supplies the digital signal to the DSP. The control unit 33 is configured, for example, by an IC (Integrated Circuit) mounted on the circuit board 3. Note that an amplifier may be provided between each of the first detection coil 32a and the second detection coil 32b and the ADC.

[0020] The DSP of the control unit 33 applies an AC voltage to the excitation coil 31 via an oscillator, exciting the excitation coil 31. A magnetic field formed by the excited excitation coil 31 induces an electromotive force in each of the first detection coil 32a and the second detection coil 32b. The DSP acquires the induced electromotive force in each of the first detection coil 32a and the second detection coil 32b as an output voltage converted into a digital signal via an ADC. The control unit 33 determines the rotational position of the rotation shaft 2 based on the output voltages from the first detection coil 32a and the second detection coil 32b. The control unit 33 outputs a signal indicating the determined rotational position of the rotation shaft 2 to an external device via a connector (not shown). The EMC parts group (not shown) is made up of ceramic capacitors, resistor elements, etc. for suppressing noise from the electronic circuits mounted on the circuit board 3.

[0021] As shown in FIG. 1, the case 5 has a disk-shaped exterior and accommodates the circuit board 3 and the target 4 inside. The case 5 has a support 51 that supports the circuit board 3 and a cover 52 fixed to the support 51. The cover 52 is fixed to the support 51 with bolts B. Note that the bolts B are not shown in FIG. 2. The case 5 is provided with a wiring insertion hole 5a through which wiring connected to the aforementioned connector provided on the circuit board 3 passes. The wiring passes through the wiring insertion hole 5a and is electrically connected to an external device. As shown in FIG. 3, the wiring insertion hole 5a is a hole formed between a notch formed in the support 51 and the cover 52.

[0022] The case 5 is provided with bolt insertion holes C through which target bolts D (see FIG. 3) are inserted to fix the case 5 to a motor case (not shown), which is the target object. As shown in FIG. 1, the bolt insertion holes C are arc-shaped holes provided on the outer edge of the case 5. In this embodiment, three bolt insertion holes C are provided at intervals in the circumferential direction around the axis AX. The bolt insertion holes C consist of a hole C2 formed in the cover 52 and a hole C1 formed in the support body 51 and communicating with the hole C2. The case 5 is fixed to the motor case (not shown) by the target bolts D inserted into each bolt insertion hole C as shown in FIG. 3. At this time, a washer W is provided between the head of the target bolt D and the cover 52. In this manner, the position detection device 1 is fixed to the motor case.

[0023] The support body 51 has a cover attachment portion 512 to which the cover 52 is attached, and a board accommodating portion 513 having a recessed shape corresponding to the outer shape of the circuit board 3 from the cover attachment portion 512 .

[0024] 2, a bolt hole 512a through which a bolt B is passed is formed in the cover mounting portion 512. A bolt hole 52a is also formed in the cover 52 corresponding to this bolt hole 512a. The bolt B is passed through the bolt hole 52a and the bolt hole 512a to connect the cover 52 and the support body 51. The bolt hole 512a in the cover mounting portion 512 communicates with the inside of a nut (not shown), and the bolt B is fastened to the nut.

[0025] A support through-hole H1, which is a hole that is smaller than the outer diameter of the target 4 and is centered on the axis line AX, is formed in the substrate accommodating portion 513 of the support 51. Here, the outer diameter of the target 4 refers to the diameter of the flange 41 centered on the axis line AX. As shown in FIG. 3 , the support 51 has a cylindrical first rib R1 that faces the flange 41 in the direction in which the axis line AX extends. The first rib R1 protrudes from the substrate accommodating portion 513 toward the flange 41. The support through-hole H1 is a hole that includes the interior of the cylindrical first rib R1.

[0026] The circuit board 3 is accommodated in the board accommodation portion 513 and fixed to the board accommodation portion 513 by a screw E shown in Fig. 2. The screw E is passed through a screw insertion hole 3a formed in the board 30 and fastened to a screw hole 513a formed in the board accommodation portion 513. Note that the screw E is not shown in Fig. 3.

[0027] A substrate through-hole H3, which is a hole centered on the axis line AX, is formed in the substrate 30 of the circuit board 3. As shown in FIG. 3, the first rib R1 is located inside the substrate through-hole H3. The tip of the first rib R1 (the left end in FIG. 3) is located closer to the flange 41 than the circuit board 3. This prevents the target 4 from becoming oblique with respect to the axis line AX and causing the flange 41 to come into contact with the circuit board 3 when the position detection device 1 is being transported or used. In other words, the first rib R1 prevents interference between the target 4 and the circuit board 3. The extent to which the tip of the first rib R1 protrudes beyond the circuit board 3 can be determined arbitrarily depending on the design.

[0028] The cover 52 has a cover through-hole H2, which is smaller than the outer diameter of the target 4 and is centered on the axis AX. As shown in FIG. 3 , the cover 52 has a cylindrical second rib R2 facing the flange 41 in the direction of extension of the axis AX. The cover through-hole H2 is a hole that includes the interior of the second rib R2. One end of the second rib R2 facing the flange 41 protrudes toward the flange 41. This, together with the first rib R1, can prevent the target 4 from being oblique with respect to the axis AX and the flange 41 from contacting the circuit board 3 during transportation or use of the position detection device 1. In other words, the first rib R1 and the second rib R2 can prevent interference between the target 4 and the circuit board 3. Note that the extent to which one end of the second rib R2 (the end facing the flange 41) protrudes toward the flange 41 can be determined arbitrarily depending on the design. Although Figure 3 shows an example in which the first rib R1 and the second rib R2 face each other in the direction in which the axis line AX extends, the first rib R1 and the second rib R2 do not have to face each other in the direction in which the axis line AX extends.

[0029] Here, as shown in Fig. 3, the rotating shaft 2 of the motor, which is the object, is inserted into the support through-hole H1 and the cylindrical portion 40 that communicates with the support through-hole H1. A threaded portion (not shown) is formed on the portion of the rotating shaft 2 that is exposed from the cylindrical portion 40. A nut N is fastened to this threaded portion, thereby attaching the rotating shaft 2 to the cylindrical portion 40. The rotating shaft 2 attached to the cylindrical portion 40 is positioned within the support through-hole H1, the substrate through-hole H3, and the cover through-hole H2.

[0030] The other end of the second rib R2 opposite to the one end (the end facing the flange 41) protrudes in a direction away from the flange 41. The other end of the second rib R2 protrudes as described above in order to prevent the nut N from interfering with the cover 52.

[0031] The present invention is not limited to the above-described embodiments and drawings. Appropriate modifications (including the deletion of components) can be made within the scope of the present invention. For example, the first rib R1 and the second rib R2 may be formed in a tubular shape other than a cylindrical shape. Furthermore, the method of fixing the cover 52 to the support body 51 is not limited to the bolt B and is arbitrary. Furthermore, the method of fixing the case 5 to the object is not limited to the object bolt D and is arbitrary.

[0032] The position detection device 1 described above can be described from the viewpoints set forth in Supplementary Notes 1 to 3 below.

[0033] (Appendix 1) (Appendix 1-1) a circuit board having an excitation coil that is excited by application of a voltage and a detection unit that generates an induced electromotive force by the excited excitation coil; a target having a non-magnetic metal part facing the circuit board with a gap therebetween, which rotates about an axis in response to rotation of a rotation shaft of an object, and which changes the induced electromotive force generated in the detection unit by the non-magnetic metal part; a case having a support for supporting the circuit board and a cover fixed to the support, and accommodating the circuit board and the target; Position detection device.

[0034] The position detection device described in Appendix 1-1 is provided with a case that houses the circuit board and the target, so that the circuit board and the target can be protected. Furthermore, the position detection device described in Appendix 1-1 is easy to carry and handle because each component is housed in the case.

[0035] (Appendix 1-2) the target has a cylindrical portion attached to the rotating shaft and a flange formed around the cylindrical portion and having the nonmagnetic metal portion; The flange is located between the cover and the circuit board in the direction in which the axis extends. 1. A position detection device according to claim 1-1.

[0036] According to the position detection device described in Supplementary Note 1-2, it is possible to appropriately protect the flange having the non-magnetic metal part that is one of the essential parts for position detection.

[0037] (Appendix 1-3) The support body has a support body through-hole that is a hole centered on the axis line, The rotating shaft is insertable into the support through-hole and the cylindrical portion communicating with the support through-hole. 3. The position detection device according to claim 1-2.

[0038] According to the position detection device described in Supplementary Note 1-3, the rotary shaft can be inserted into the cylindrical portion through the support through-hole and attached, making it easy to handle.

[0039] (Appendix 2) (Appendix 2-1) a circuit board having an excitation coil that is excited by application of a voltage and a detection unit that generates an induced electromotive force by the excited excitation coil; a target having a non-magnetic metal part facing the circuit board with a gap therebetween, which rotates about an axis in response to rotation of a rotation shaft of an object, and which changes the induced electromotive force generated in the detection unit by the non-magnetic metal part; a case having a support body that supports the circuit board and a cover that is fixed to the support body and that houses the circuit board and the target, a support through-hole that is smaller than the outer diameter of the target and has the axis as its center is formed in the support; a cover through-hole that is smaller than the outer diameter of the target and is centered on the axis is formed in the cover; Position detection device.

[0040] The position detection device described in Appendix 2-1 is provided with a case that houses the circuit board and the target, thereby protecting the circuit board and the target. Furthermore, the case configuration prevents the target from slipping out through the support through-hole and the cover through-hole, making the device easy to carry.

[0041] (Appendix 2-2) the target has a cylindrical portion attached to the rotating shaft and a flange formed around the cylindrical portion and having the nonmagnetic metal portion; The rotating shaft is insertable into the support through-hole and the cylindrical portion communicating with the support through-hole. 2. A position detection device according to claim 1.

[0042] According to the position detection device described in Supplementary Note 2-2, the rotary shaft can be inserted into the cylindrical portion through the support through-hole and attached, making it easy to handle.

[0043] (Appendix 2-3) a board through-hole that is a hole centered on the axis is formed in the circuit board; the rotation shaft attached to the cylindrical portion is positioned within the support through-hole, the substrate through-hole, and the cover through-hole; A position detection device as described in Appendix 2-2.

[0044] According to the position detection device described in Supplementary Note 2-3, the rotation axis attached to the target is disposed to pass through the case, so that the relative positions of the target and the rotation axis can be stabilized.

[0045] (Appendix 3) (Appendix 3-1) a circuit board having an excitation coil that is excited by application of a voltage and a detection unit that generates an induced electromotive force by the excited excitation coil; a target having a non-magnetic metal part facing the circuit board with a gap therebetween, which rotates about an axis in response to rotation of a rotation shaft of an object, and which changes the induced electromotive force generated in the detection unit by the non-magnetic metal part; a case having a support body that supports the circuit board and a cover that is fixed to the support body and that houses the circuit board and the target, the target has a cylindrical portion attached to the rotating shaft and a flange formed around the cylindrical portion and having the nonmagnetic metal portion; the support body has a cylindrical first rib that faces the flange in the direction in which the axis extends, The support body has a support body through-hole formed therein, the support body through-hole being a hole including the inside of the first rib and centered on the axis line. Position detection device.

[0046] The position detection device described in Appendix 3-1 includes a case that houses the circuit board and the target, so that the circuit board and the target can be protected. Also, as described above, the first rib can prevent interference between the target and the circuit board.

[0047] (Appendix 3-2) the cover has a cylindrical second rib facing the flange in the direction in which the axis extends, The cover has a cover through-hole that includes the inside of the second rib and is a hole centered on the axis. 3. A position detection device according to claim 1.

[0048] The position detection device described in Supplementary Note 3-2 has the second rib in addition to the first rib, and therefore, as described above, can more effectively prevent interference between the target and the circuit board.

[0049] (Appendix 3-3) a board through-hole that is a hole centered on the axis is formed in the circuit board; the first rib is located within the substrate through-hole; The tip of the first rib is located closer to the flange than the circuit board. A position detection device according to appendix 3-1 or 3-2.

[0050] According to the position detection device described in Supplementary Note 3-3, the tip of the first rib is located closer to the flange than the circuit board, so that interference of the target with the circuit board can be more effectively suppressed.

[0051] In the above description, in order to facilitate understanding of the present disclosure, descriptions of well-known technical matters have been omitted as appropriate. [Explanation of symbols]

[0052] 1...Position detection device 2...rotation axis, AX...axis 3...circuit board, 3a...screw insertion hole 30… Board, H3… Board through hole 31...Excitation coil 32...detection unit, 32a...first detection coil, 32b...second detection coil 33...Control unit 4...target, 4a...non-magnetic metal part 40...Cylindrical portion, 41...Flange 5...Case, 5a...Wiring insertion hole 51...support body, R1...first rib, H1...support body through hole 512...cover mounting portion, 512a...bolt hole 513...board receiving portion, 513a...screw hole 52...cover, 52a...bolt hole, R2...second rib, H2...cover through hole B...Bolt C...Bolt insertion hole, C1, C2...holes D...target bolt, W...washer E...Screw

Claims

1. a circuit board having an excitation coil that is excited by application of a voltage and a detection unit that generates an induced electromotive force by the excited excitation coil; a target having a non-magnetic metal part facing the circuit board with a gap therebetween, which rotates about an axis in response to rotation of a rotation shaft of an object, and which changes the induced electromotive force generated in the detection unit by the non-magnetic metal part; a case having a support for supporting the circuit board and a cover fixed to the support, and accommodating the circuit board and the target; a support through-hole that is smaller than the outer diameter of the target and has the axis as its center is formed in the support; a cover through-hole that is smaller than the outer diameter of the target and is centered on the axis is formed in the cover; Position detection device.

2. the target has a cylindrical portion attached to the rotating shaft and a flange formed around the cylindrical portion and having the nonmagnetic metal portion; The rotating shaft is insertable into the support through-hole and the cylindrical portion communicating with the support through-hole. The position detection device according to claim 1 .

3. a board through-hole that is a hole centered on the axis is formed in the circuit board; the rotation shaft attached to the cylindrical portion is positioned within the support through-hole, the substrate through-hole, and the cover through-hole; The position detection device according to claim 2 .

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