Rotation detection structure and motor

Abstract

The rotation detection structure comprises a sensor magnet (3) that rotates integrally with a rotating body (1), and a magnetic sensor (2) that detects the magnetic flux of the sensor magnet (3). The sensor magnet (3) has a first magnet (4) with alternating north poles and south poles in the circumferential direction, and a second magnet (5) that is positioned parallel to the first magnet (4) in the axial direction and offset by one magnetic pole from the first magnet (4) with alternating north poles and south poles in the circumferential direction. The sensor magnet (3) forms an interaxial magnetic flux region (Rd) on the radially outer side of the sensor magnet (3) that serves as a path for interaxial magnetic flux (Φd) traveling from one north pole of the first magnet (4) and the second magnet (5) to the other south pole of the first magnet (4) and the second magnet (5) in the axial direction. The magnetic sensor (2) has a sensor surface (2s) that receives the interaxial magnetic flux (Φd) located within the interaxial magnetic flux region (Rd), and the inclination of the sensor surface (2s) with respect to a plane (PL) perpendicular to the axis (C) is 45 degrees or less.

Description

Technical Field

[0001] This invention relates to a rotation detection structure for detecting the rotation angle of a rotating body that rotates around an axis, and a motor to which the rotation detection structure is applied.

Background Art

[0002] Conventionally, there is known a rotation detection structure including a cylindrical magnet (sensor magnet) fixed coaxially with a rotating body, and a Hall element (magnetic sensor) that outputs a signal according to the magnetic flux density generated by the magnet (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the rotation detection structure disclosed in Patent Document 1, the Hall element is disposed to face the circumferential surface of the magnet on the radially outer side of the magnet in order to detect the magnetic flux generated from the circumferential surface of the magnet toward the radially outer side. That is, the Hall element of Patent Document 1 is disposed such that the surface for detecting the magnetic flux extends in the axial direction. However, in a rotation detection structure including such a Hall element (magnetic sensor), the axial length (thickness) of the rotation detection structure tends to increase, and there is room for improvement in reducing the thickness of the rotation detection structure in the axial direction. Note that this problem is not limited to the case where the magnetic sensor is a Hall element.

[0005] This invention has been devised in view of such problems, and one of its objects is to reduce the thickness of the rotation detection structure in the axial direction. Note that this is not the only object, and another object of this invention is to achieve an operational effect that cannot be obtained by the conventional technology, which is an operational effect derived from each configuration shown in the embodiments for implementing the invention described below. [Means for solving the problem]

[0006] The disclosed rotation detection structure and motor can be implemented in the following embodiments (application examples) and solve at least some of the above problems.

[0007] Embodiment 1. The rotation detection structure disclosed is a rotation detection structure for detecting the rotation angle of a rotating body that rotates about an axis, and comprises a sensor magnet that rotates integrally with the rotating body, having a first magnet in which north poles and south poles are alternately arranged in the circumferential direction, and a second magnet that is arranged in parallel with the first magnet in the axial direction and offset by one magnetic pole from the first magnet in which north poles and south poles are alternately arranged in the circumferential direction, and a magnetic sensor for detecting the magnetic flux of the sensor magnet. The sensor magnet forms an interaxial magnetic flux region on the radially outer side of the sensor magnet, which is the path for the interaxial magnetic flux that travels from the north pole of one of the first magnet and the second magnet in the axial direction to the south pole of the other of the first magnet and the second magnet. The magnetic sensor has a sensor surface that receives the interaxial magnetic flux located within the interaxial magnetic flux region, and the inclination of the sensor surface with respect to a plane perpendicular to the axis is 45 degrees or less.

[0008] Embodiment 2. The disclosed motor comprises the rotation detection structure described in Embodiment 1, a shaft as the rotating body, a rotor that rotates integrally with the shaft, and a stator positioned opposite the rotor. [Effects of the Invention]

[0009] According to the disclosed rotation detection structure and motor, the rotation detection structure can be made thinner in the axial direction. [Brief explanation of the drawing]

[0010] [Figure 1] This is a view of the rotation detection structure according to the embodiment, seen from the radially outer side. [Figure 2] Figure 1 is a plan view of the rotation detection structure as seen from the first direction side. [Figure 3]This figure illustrates another example of the rotation detection structure according to the embodiment. [Figure 4] This is an axial cross-sectional view of a motor to which the rotation detection structure according to the embodiment is applied. [Modes for carrying out the invention]

[0011] The rotation detection structure and motor as embodiments will be described with reference to the drawings. The embodiments shown below are merely illustrative, and there is no intention to exclude various modifications and applications of technologies not explicitly shown in the embodiments below. Each component of these embodiments can be modified in various ways without departing from their spirit.

[0012] [1. Rotation detection structure] The rotation detection structure of this embodiment will be described with reference to Figures 1 to 3. The rotation detection structure detects the rotation angle of a rotating body 1 that rotates around axis C. As shown in Figure 1, the rotation detection structure comprises a sensor magnet 3 that rotates integrally with the rotating body 1, and a magnetic sensor 2 that detects the magnetic flux of the sensor magnet 3. The rotation detection structure detects the rotation angle of the rotating body 1 by having the magnetic sensor 2 detect the magnetic flux of the sensor magnet 3, which changes as it rotates integrally with the rotating body 1. The rotation detection structure of this embodiment further comprises a flat substrate 6 for fixing the magnetic sensor 2.

[0013] An example of a rotating body 1 whose rotation angle is detected by the rotation detection structure is a columnar (e.g., cylindrical) or tubular (e.g., cylindrical) shaft that extends in the direction of extension of axis C, centered on axis C. In this embodiment, a cylindrical shaft will be described as the rotating body 1. Hereinafter, the rotating body 1 will also be referred to as shaft 1. The sensor magnet 3 is fixed to one end of shaft 1, for example, and rotates integrally with shaft 1.

[0014] Hereinafter, the direction in which axis C extends will be referred to as the axial direction. Of the axial directions, the direction on the side where the sensor magnet 3 is fixed to shaft 1 (the "one end side of shaft 1" mentioned above) will be referred to as the first direction D1, and the opposite direction will be referred to as the second direction D2. The directions perpendicular to the axial direction that move away from axis C and the directions toward axis C will be referred to as the radial direction. Of the radial directions, the direction moving away from axis C will be referred to as the radially outward direction, and the direction toward axis C will be referred to as the radially inward direction. The directions perpendicular to the axial direction that circle around axis C will be referred to as the circumferential direction.

[0015] Figure 1 is a view of the rotation detection structure of this embodiment from the radially outer side, and for convenience, only the substrate 6 is shown in an axial cross-section. Figure 2 is a plan view of the rotation detection structure of Figure 1 from the first direction D1 side.

[0016] The magnetic sensor 2 is an electronic component that has a planar sensor surface 2s (sensing surface, detection surface) and outputs an electrical signal corresponding to the change (density) of magnetic flux passing through the sensor surface 2s in a direction perpendicular to the sensor surface 2s (indicated by the solid arrow in Figure 1, hereinafter referred to as the detection direction N). The magnetic sensor 2 has a Hall element as the sensor surface 2s that receives magnetic flux, which, for example, outputs a Hall voltage proportional to the magnetic flux density in a direction perpendicular to both the detection direction N and the direction of current flow (a so-called Hall effect occurs) when a current is passed in a direction perpendicular to the detection direction N.

[0017] In this embodiment, the magnetic sensor 2 is a chip-type Hall IC in which a Hall element as a sensor surface 2s and a signal processing circuit (not shown) are molded (coated) with resin and integrated. In FIGS. 1 to 3, the sensor surface 2s is shown as a thick solid line for clarity, but the sensor surface 2s is actually built-in and thus not visible from the outside. The Hall element forms, for example, a rectangular plane as the sensor surface 2s when viewed from the detection direction N as shown in FIG. 2. However, the sensor surface 2s formed by the Hall element only needs to be a plane orthogonal to the detection direction N, and the outer shape of the sensor surface 2s when viewed from the detection direction N does not have to be rectangular. The signal processing circuit includes, for example, an amplification circuit that amplifies the output voltage of the Hall element, a compensation circuit that corrects the error of the output voltage with respect to temperature changes, and the like.

[0018] As shown in FIG. 1, the covering portion 2a that covers the Hall element and the signal processing circuit has a bottom surface 2b that extends parallel to the sensor surface 2s. The covering portion 2a may be, for example, a substantially rectangular parallelepiped shape having a bottom surface 2b and a top surface 2c that extend parallel to the sensor surface 2s, and side surfaces 2d that connect the bottom surface 2b and the top surface 2c. The length (thickness) of the covering portion 2a (i.e., the magnetic sensor 2) in the detection direction N is set to be smaller than the length and width of the covering portion 2a in the direction orthogonal to the detection direction N, and preferably smaller than the length in the axial direction of the sensor magnet 3. That is, the outer shape of the magnetic sensor 2 is preferably a flat shape.

[0019] In addition, a plurality of lead terminals 2t (input terminals, output terminals, ground terminals, etc.) for electrically connecting the Hall element and the signal processing circuit to conductors outside the magnetic sensor 2 are implanted on the side surface 2d of the covering portion 2a. These lead terminals 2t extend from the side surface 2d of the covering portion 2a toward the bottom surface 2b side to a position substantially flush with the bottom surface 2b. The magnetic sensor 2 is fixed to the substrate 6 by joining the plurality of lead terminals 2t to conductors 6c (to be described later) of the substrate 6, for example, by soldering, with the bottom surface 2b of the covering portion 2a placed on a surface 6f (to be described later) of the substrate ⑥.

[0020] That is, the chip type Hall IC mentioned here means a Hall IC in which lead terminals 2t extend from the side surface 2d of the coating portion 2a to the bottom surface 2b side extending parallel to the sensor surface 2s, and the lead terminals 2t can be joined to this flat plate when the bottom surface 2b is placed on a flat plate (for example, a substrate 6). On the other hand, a Hall IC in which lead terminals extend from the side surface of the coating portion in a direction orthogonal to the detection direction is also called a footed Hall IC, distinguished from the chip type Hall IC. In such a footed Hall IC, generally, the lead terminals are joined to the flat plate in a state where the footed Hall IC floats from the flat plate in the plate thickness direction of the flat plate with respect to the flat plate on which the footed Hall IC is mounted.

[0021] The sensor magnet 3 is a permanent magnet that generates a magnetic flux (magnetic field) around it. The sensor magnet 3 has a first magnet 4 and a second magnet 5 arranged in parallel in the axial direction. The first magnet 4 and the second magnet 5 are arranged in parallel in this order, for example, from the first direction D1 to the second direction D2. In each of the first magnet 4 and the second magnet 5, N poles and S poles are alternately arranged in the circumferential direction. With respect to the first magnet 4, the second magnet 5 is shifted by one magnetic pole in the circumferential direction, and N poles and S poles are alternately arranged.

[0022] In the present embodiment, in each of the first magnet 4 and the second magnet 5, as shown in FIGS. 1 and 2, N poles and S poles are arranged such that one magnetic pole is arranged one by one in the circumferential direction, that is, one magnetic pole pair is formed over the entire circumferential direction. The first magnet 4 is configured such that, for example, the left portion of the paper surface of FIG. 1 (the 180-degree portion on the left when viewed from the axial direction) is the N pole, and the right portion of the paper surface of FIG. 1 (the 180-degree portion on the right when viewed from the axial direction) is the S pole. The second magnet 5 is shifted by one magnetic pole in the circumferential direction from the first magnet 4, and is configured such that the portions overlapping with the N-pole portion and the S-pole portion of the first magnet 4 when viewed from the axial direction are opposite poles to the magnetic poles of the first magnet 4. The second magnet 5 is configured such that, for example, in the case of the magnetic pole arrangement of the first magnet 4 described above, corresponding to this arrangement, the left portion of the paper surface of FIG. 1 is the S pole, and the right portion of the paper surface of FIG. 1 is the N pole.

[0023] Furthermore, in this embodiment, the first magnet 4 and the second magnet 5 are integrally connected in the axial direction, as shown in Figure 1. The sensor magnet 3 is formed by the first magnet 4 and the second magnet 5 in such a way that it is cylindrical, extending in the axial direction and having an inner hole through which the shaft 1 can be inserted, as shown in Figures 1 and 2. In Figure 1, the portion of the sensor magnet 3 that is the first magnet 4 and the portion that is the second magnet 5 are separated by a dashed line extending horizontally (left to right) on the page of Figure 1. Also, the dashed line extending vertically (up and down) on the page of Figure 1 of the sensor magnet 3 indicates the boundary between the south pole and the north pole. These dashed lines are imaginary lines and do not actually exist.

[0024] Such a sensor magnet 3 may be formed, for example, by magnetizing one half (semi-cylindrical portion) of a cylindrical magnetic material such that the first direction D1 side becomes the north pole and the second direction D2 side becomes the south pole, and then magnetizing the remaining half of the magnetic material such that the first direction D1 side becomes the south pole and the second direction D2 side becomes the north pole, in a so-called double-sided magnetization process. Note that the first magnet 4 and the second magnet 5 are not limited to being formed by magnetizing a magnetic material, but may also be formed by arranging (distributing) north-pole permanent magnets and south-pole permanent magnets alternately in the circumferential direction.

[0025] Magnetic flux from the north pole to the south pole of the first magnet 4 and the second magnet 5 is generated around the sensor magnet 3. More specifically, as shown by the long dashed arrow in Figure 1, around the corner 4c of the first magnet 4 on the first direction D1 side, magnetic flux Φc passes from the north pole to the south pole of the first magnet 4, via the space on the first direction D1 side of the first magnet 4. Similarly, around the corner 5c of the second magnet 5 on the second direction D2 side, magnetic flux Φc passes from the north pole to the south pole of the second magnet 5, via the space on the second direction D2 side of the second magnet 5. In addition, radially outward from the corner 4c of the first magnet 4 and the corner 5c of the second magnet 5 in the sensor magnet 3, magnetic flux Φd passes from one north pole of the first magnet 4 and the second magnet 5 to the other south pole of the first magnet 4 and the second magnet 5, which are arranged at the same position in the circumferential direction as this north pole.

[0026] Hereinafter, the magnetic flux passing around the corners 4c and 5c of the first magnet 4 and the second magnet 5 will be referred to as the angular magnetic flux Φc, and the magnetic flux from one N pole of the first magnet 4 and the second magnet 5 to the other S pole will be referred to as the interaxial magnetic flux Φd. Furthermore, in the radially outer region (space) of the sensor magnet 3, the region that serves as the path for the angular magnetic flux Φc will be referred to as the angular magnetic flux region Rc, and the region that serves as the path for the interaxial magnetic flux Φd will be referred to as the interaxial magnetic flux region Rd. In Figure 1, the angular magnetic flux Φc and the interaxial magnetic flux Φd are shown by long dashed arrows, the general shape of the angular magnetic flux region Rc is shown by dark dots, and the general shape of the interaxial magnetic flux region Rd is shown by light dots.

[0027] The angular flux region Rc and the interaxial flux region Rd are both cylindrical, three-dimensional spatial regions surrounding the sensor magnet 3 around axis C, and may be defined, for example, by experiment or simulation, as regions through which angular flux Φc and interaxial flux Φd of a density detectable by the magnetic sensor 2 pass. The radial width of the angular flux region Rc and the radial width of the interaxial flux region Rd do not have to be the same, as shown in the figure, and the axial cross-sectional shapes of the angular flux region Rc and the interaxial flux region Rd do not have to be rectangles as shown.

[0028] The radial width of the angular flux region Rc and the interaxial flux region Rd can be larger, for example, when a neodymium magnet is used as the sensor magnet 3 than when a ferrite magnet, which has a weaker magnetic force than a neodymium magnet, is used. The axial position and length of the interaxial flux region Rd may be predetermined, for example, as a region that is on the second direction D2 side of the axial center of the first magnet 4 and on the first direction D1 side of the axial center of the second magnet 5, rather than being determined by experiment or simulation.

[0029] The angular flux region Rc of the first magnet 4, the interaxial flux region Rd, and the angular flux region Rc of the second magnet 5 are formed in this order from the first direction D1 to the second direction D2 without overlapping. Therefore, the interaxial flux region Rd can also be described as the region formed in the axial direction between the angular flux region Rc of the first magnet 4 and the angular flux region Rc of the second magnet 5.

[0030] In the interaxial magnetic flux region Rd, the interaxial magnetic flux Φd from the north pole of the first magnet 4 to the south pole of the second magnet 5 proceeds radially outward from the north pole of the first magnet 4 towards the second direction D2, as shown on the left side of Figure 1. This interaxial magnetic flux Φd then folds back at the boundary position P between the two magnets 4 and 5 in the axial direction and proceeds radially inward towards the second direction D2. Conversely, the interaxial magnetic flux Φd from the north pole of the second magnet 5 to the south pole of the first magnet 4 proceeds radially outward from the north pole of the second magnet 5 towards the first direction D1, as shown on the right side of Figure 1, folds back at the boundary position P, and proceeds radially inward towards the first direction D1.

[0031] In other words, the interaxial magnetic flux Φd flows from the north pole to the south pole, tracing an arc (semicircular arc) that is convex radially outward. The interaxial magnetic flux Φd is furthest radially outward from the outer surface of the sensor magnet 3 at boundary position P, and flows from one of the two magnets 4 and 5 to the other so as to be parallel to the axis C at this boundary position P. Here, boundary position P refers to the position where the first magnet 4 and the second magnet 5 meet in the axial direction. Boundary position P coincides with the axial position of the line separating the first magnet 4 and the second magnet 5 (the horizontally extending dashed line in Figure 1).

[0032] In the rotation detection structure illustrated here, the boundary position P approximately coincides with the axial center of the sensor magnet 3. However, the boundary position P is not necessarily approximately coincident with the axial center of the sensor magnet 3. For example, if there is an imbalance in the magnetic force applied when magnetizing the magnetic material that forms the sensor magnet 3, the boundary position P may be a position shifted in either direction from the axial center of the sensor magnet 3.

[0033] In this invention, the magnetic sensor 2 detects the interaxial magnetic flux Φd of the sensor magnet 3. The magnetic sensor 2 is positioned such that its sensor surface 2s is located within the interaxial magnetic flux region Rd, and the inclination of the sensor surface 2s with respect to an orthogonal plane PL (plane) perpendicular to the axis C (the angle that the sensor surface 2s makes with respect to the orthogonal plane PL) is 45 degrees or less. The orthogonal plane PL is a hypothetical plane extending in a direction perpendicular to the axis C. In Figures 1 and 3, for convenience, the orthogonal plane PL perpendicular to the axis C at the boundary position P is shown.

[0034] Here, in a conventional rotation detection structure, such as the one disclosed in Patent Document 1, the magnetic sensor is positioned opposite the outer surface of the sensor magnet (i.e., the magnetic sensor is positioned vertically). In contrast to this configuration, the rotation detection structure of the present invention positions the magnetic sensor 2 horizontally instead of vertically. Specifically, the magnetic sensor 2 is positioned such that the inclination of the sensor surface 2s with respect to the orthogonal plane PL is 45 degrees or less, for example, when the sensor surface 2s coincides with (is parallel to) the orthogonal plane PL, or when the sensor surface 2s is aligned with (or roughly aligned with) the orthogonal plane PL. Focusing on the orientation of the sensor surface 2s, the magnetic sensor 2 is positioned so that the sensor surface 2s faces not only in the radial direction but also in the axial direction (or only in the axial direction). Furthermore, focusing on the detection direction N, the magnetic sensor 2 is positioned so that the inclination of the detection direction N with respect to the axial direction is 45 degrees or less. This makes it possible to reduce the axial length of the magnetic sensor 2 in the rotation detection structure.

[0035] Furthermore, the rotation detection structure is equipped with a first magnet 4 and a second magnet 5 on the sensor magnet 3, and the magnetic sensor 2 is positioned so that the sensor surface 2s is located within the interaxial magnetic flux region Rd formed by the sensor magnet 3. As a result, the magnetic sensor 2 detects the interaxial magnetic flux Φd rather than the angular magnetic flux Φc. The rotation detection structure, with this arrangement of the magnetic sensor 2 and sensor magnet 3, keeps the magnetic sensor 2 within the axial length range of the sensor magnet 3, in other words, prevents the magnetic sensor 2 from protruding axially beyond the sensor magnet 3, thereby making it possible to reduce the axial thickness of the rotation detection structure.

[0036] In this embodiment, the magnetic sensor 2 is positioned such that its sensor surface 2s is perpendicular to the axis C at a position that substantially coincides with the boundary position P in the axial direction. In other words, the magnetic sensor 2 is positioned such that the inclination of the sensor surface 2s with respect to the orthogonal plane PL is 0 degrees, that is, the sensor surface 2s is parallel to the orthogonal plane PL. Focusing on the detection direction N of the sensor surface 2s, this can also be rephrased as the magnetic sensor 2 being positioned such that the detection direction N is parallel to the axis C (coinciding with the axial direction).

[0037] As a result, the thickness of the roughly rectangular cover portion 2a (magnetic sensor 2) in the detection direction N becomes the axial length of the magnetic sensor 2, thus further reducing the axial length of the rotation detection structure (especially the axial length on the radially outer side of the sensor magnet 3). Furthermore, at the boundary position P, as described above, the interaxial magnetic flux Φd flows parallel to the axis C from one of the two magnets 4 and 5 towards the other. At the boundary position P, the direction in which the interaxial magnetic flux Φd passes coincides with the detection direction N of the sensor surface 2s, thus improving the detection accuracy of the magnetic flux of the magnetic sensor 2.

[0038] Furthermore, the position of the sensor surface 2s within the interaxial magnetic flux region Rd and the inclination of the sensor surface 2s with respect to the orthogonal plane PL are not limited to the position and inclination described above. From the viewpoint of ensuring magnetic flux detection accuracy, it is preferable that the sensor surface 2s be positioned such that the detection direction N of the sensor surface 2s coincides with the tangential direction of the interaxial magnetic flux Φd that passes through the interaxial magnetic flux region Rd in an arc, within a range where the inclination of the sensor surface 2s with respect to the orthogonal plane PL is 45 degrees or less.

[0039] As an example, the magnetic sensor 2 may be positioned inclined with respect to the orthogonal plane PL, as shown in Figure 3, such that the inner edge of the sensor surface 2s on the radial side approximately coincides with the boundary position P, and the inclination α of the sensor surface 2s with respect to the orthogonal plane PL is 45 degrees or less, with this inner edge as the base point. Note that Figure 3 is a diagram illustrating another example of the rotation detection structure of this embodiment, and corresponds to an enlarged view of the left half of the page, with the substrate 6 removed from the rotation detection structure shown in Figure 1. The sensor surface 2s only needs to be located within the interaxial magnetic flux region Rd, and the sensor surface 2s does not need to overlap with the boundary position P when viewed from the radial direction. Note that an inclination of 45 degrees or less means that, when viewed from the radial direction, the angle toward the first direction D1 side and the angle toward the second direction D2 side with respect to the orthogonal plane PL is 45 degrees or less. That is, the inclination of the sensor surface 2s is set within a range of 90 degrees centered on the orthogonal plane PL when viewed from the radial direction.

[0040] As shown in Figure 1, the substrate 6 is an electronic substrate in which conductors 6c (see Figure 2) are arranged on the end faces 6f and 6g in the thickness direction of a plate-shaped insulator 6b. The substrate 6 is fixed to the housing of the device equipped with the shaft 1 (for example, the housing 18 or cover 19 described later). The magnetic sensor 2 is mounted and fixed on the end face 6f of the substrate 6 so that it does not rotate together with the shaft 1. Hereinafter, of the end faces 6f and 6g of the substrate 6, the side on which the magnetic sensor 2 is mounted and fixed (first direction D1 side, first side) will be called the front surface 6f, and the end face 6g (see Figure 1) on the opposite side of the front surface 6f (second direction D2 side, second side) will be called the back surface 6g.

[0041] In this embodiment, the substrate 6 is located on the second direction D2 side of the magnetic sensor 2, and extends radially such that its front surface 6f and back surface 6g each face the first direction D1 and the second direction D2, respectively. The substrate 6 may be positioned and have a thickness such that its back surface 6g is located on the first direction D1 side of the end surface 5g of the second magnet 5, which is located on the second direction D2 side of the magnetic sensor 2. In other words, in the axial direction, the substrate 6 is located on the second direction D2 side of the boundary position P, and on the first direction D1 side of the end surface 5g of the second magnet 5.

[0042] The shape of the substrate 6 as viewed from the axial direction is, for example, an annular shape surrounding the sensor magnet 3, as shown in Figure 2. The outer shape of the substrate 6 as viewed from the axial direction may be, for example, rectangular, or it may be a rectangular shape with chamfered corners (approximately octagonal). Figure 2 shows a substrate 6 of the latter shape. In addition to the magnetic sensor 2, electronic components such as chip-type resistors and chip-type capacitors may be mounted and fixed on the surface 6f of the substrate 6.

[0043] In addition to the electronic components described above, terminals 7 may be attached to the circuit board 6. Terminals 7 are metal terminals that are electrically connected to electronic components located at a position separate from the periphery of the circuit board 6, and are fixed to the circuit board 6 by soldering. Terminals 7 may be, for example, power supply terminals (power lines) that are electrically connected to a connector of an external power supply device provided outside the device comprising the shaft 1.

[0044] Four terminals 7 may be attached to the substrate 6, for example, as shown in Figure 2. The four terminals 7 are arranged in parallel (approximately parallel to the edge) along the right edge of the substrate 6, which is rectangular (or has chamfered corners) when viewed from the axial direction, and which extends in the vertical direction of the paper in Figure 2. Hereinafter, the diameter line (a line parallel to the right edge in the figure) that passes through axis C and extends in the direction in which the terminals 7 are arranged will be conveniently referred to as the center line Lc. Figure 1 can be said to be a view of the rotation detection structure as seen from the direction of extension of the center line Lc.

[0045] In this embodiment, all four terminals 7 penetrate the substrate 6 from the first direction D1 to the second direction D2, as shown in Figure 1, and are soldered to the back surface 6g of the substrate 6. By soldering the terminals 7 to the back surface 6g rather than the surface 6f on which the magnetic sensor 2 is placed, the transfer of heat from the soldering iron to the magnetic sensor 2 during soldering of the terminals 7 is suppressed. Note that in Figure 1, the soldering locations of the terminals 7 are shown in black.

[0046] As described above, the back surface 6g to which terminal 7 is attached is located on the first direction D1 side of the end face 5g of the second magnet 5 of the sensor magnet 3. This ensures that there is space on the radially outer side of the sensor magnet 3 and on the second direction D2 side of the substrate 6 for soldering terminal 7 to the back surface 6g of the substrate 6, thereby suppressing an increase in the axial length of the rotation detection structure including the substrate 6 to which terminal 7 is attached.

[0047] Furthermore, in this embodiment, the four terminals 7 are positioned on the opposite side of the center line Lc from the magnetic sensor 2, as shown in Figure 2. That is, the magnetic sensor 2 is positioned to the left of the center line Lc in Figure 2, while the four terminals 7 are positioned to the right of the center line Lc in Figure 2. By positioning the magnetic sensor 2 and the terminals 7 on opposite sides of the axis C in this way, the magnetic sensor 2 can be separated from the terminals 7, thereby further suppressing the transfer of heat from the soldering iron to the magnetic sensor 2 when soldering the terminals 7.

[0048] Two of the four terminals 7 may be power supply terminals electrically connected to, for example, the lead terminals 2t of the magnetic sensor 2. The remaining two of the four terminals 7 may be power supply terminals electrically connected via, for example, a conductor 6c to an electrical element (for example, a brush 14 described later) that rotates the shaft 1. The substrate 6 may have mounting through holes 6h for attaching the above-mentioned terminals 7, engagement holes 6i for engaging with terminals electrically connected to the above-mentioned electrical element (for example, connection terminals 15 described later), and fixing holes 6j for fixing the substrate 6 to the housing described above, running axially through the substrate 6.

[0049] [2. Application Examples of Rotation Detection Structures] The following describes an example of the application of the rotation detection structure of this embodiment with reference to Figure 4. Figure 4 is an axial cross-sectional view of a motor 10 to which the rotation detection structure of this embodiment is applied, and corresponds to a view of the motor 10 from the direction of extension of the center line Lc mentioned above. For convenience, in Figure 4, the shaft 1 and the sensor magnet 3 are shown in side view rather than cross-section.

[0050] The motor 10 comprises a shaft 1 as an output shaft, a rotor 11 that rotates integrally with the shaft 1, and a stator 12 positioned opposite the rotor 11. The rotation detection structure detects the rotation angle of the shaft 1. With respect to the rotor 11 and stator 12, the direction in which the magnetic sensor 2, sensor magnet 3, and substrate 6 of the rotation detection structure are positioned corresponds to the first direction D1 described above, and the opposite direction corresponds to the second direction D2.

[0051] In this embodiment, the motor 10 is an inner rotor type brushed motor, and the stator 12 is positioned opposite the rotor 11 on the radially outer side. The motor 10 is provided with a commutator 13 that rotates integrally with the shaft 1, brushes 14 that slide against the commutator 13, connection terminals 15 electrically connected to the brushes 14, and a brush holder 16 that holds the brushes 14 and the connection terminals 15.

[0052] The motor 10 is further provided with a terminal 7 and a terminal holder 17 for holding the terminal 7. The motor 10 is constructed by housing at least some of the above-mentioned parts 1-3, 6, 7, 11-17 within a housing 18 and a cover 19.

[0053] The housing 18 is a bottomed cylindrical shape opening in the first direction D1. The cover 19 has a bottomed cylindrical cover body portion 19a opening in the second direction D2. The housing 18 and the cover 19 engage with each other through the opening of the housing 18 and the opening of the cover body portion 19a, forming a space that accommodates at least a portion of the above-mentioned parts 1-3, 6, 7, 11-17.

[0054] The stator 12 and the brush holder 16 are fixed in the housing 18 in the order from the second direction D2 to the first direction D1. The connection terminal 15 protrudes in the first direction D1 beyond the end face of the brush holder 16 on the first direction D1 side and engages with the engagement hole 6i (see Figure 2) of the substrate 6 within the housing space of the cover body 19a. The shaft 1 is rotatably supported by bearings provided at the bottom of the housing 18 and on the brush holder 16. The end of the shaft 1 on the first direction D1 side extends further in the first direction D1 than the brush holder 16 and is located within the housing space of the cover body 19a.

[0055] A terminal holder 17, holding the terminal 7, is positioned and fixed to the cover 19 in the housing space of the cover body 19a on the first direction D1 side. The terminal 7 may have a substantially crank shape, as shown in the figure, having an intermediate portion 7c extending in a direction perpendicular to the axis C and center line Lc (i.e., the left-right direction of the paper in Figure 4), a first portion 7a extending from the left end of the intermediate portion 7c toward the first direction D1, and a second portion 7b extending from the right end of the intermediate portion 7c toward the second direction D2. The second portion 7b of the terminal 7 is joined to the substrate 6. The first portion 7a of the terminal 7 penetrates the bottom of the cover body 19a and extends toward the first direction D1, as shown in the figure. A cylindrical portion 19b surrounding the first portion 7a of the terminal 7 exposed from the cover body 19a may be erected on the cover 19 from the bottom of the cover body 19a toward the first direction D1.

[0056] The magnetic sensor 2, sensor magnet 3, and substrate 6 of the rotation detection structure are all arranged within the housing space of the cover body 19a. The sensor magnet 3 is fixed to the end of the shaft 1 on the first direction D1 side. With the magnetic sensor 2 fixed to it, the substrate 6 is fixed to the cover 19 via the terminal holder 17 by fitting the projection of the terminal holder 17 protruding on the second direction D2 side into the fixing hole 6j of the substrate 6.

[0057] When the motor 10 is assembled, the terminal holder 17, which holds the terminal 7, is first fixed to the cover 19. Then, the circuit board 6, to which the magnetic sensor 2 is fixed, is fixed to the terminal holder 17, and the terminal 7 is soldered to the back surface 6g of the circuit board 6. In this way, the magnetic sensor 2, circuit board 6, terminal 7, terminal holder 17, and cover 19 are integrated as a cover-side unit.

[0058] In this configuration, the magnetic sensor 2, which is fixed to the surface 6f of the substrate 6 facing the first direction D1, is covered by the substrate 6 from the second direction D2, which is the opening side of the cover 19. This ensures that the magnetic sensor 2 is protected as an integrated unit with the cover. Furthermore, the terminal 7 is soldered to the back surface 6g, which is opposite to the surface 6f and faces the second direction D2, which is the opening side of the cover 19. This makes it easier to solder the terminal 7 to the back surface 6g while suppressing heat transfer to the magnetic sensor 2 during soldering.

[0059] [3. Action, Effects] (1) In the rotation detection structure described above, the magnetic sensor 2 is positioned such that the sensor surface 2s is located within the interaxial magnetic flux region Rd formed by the sensor magnet 3, and the inclination of the sensor surface 2s with respect to the orthogonal plane PL is 45 degrees or less. This reduces the axial length of the magnetic sensor 2 and makes it easier to install the magnetic sensor 2 within the range of the axial length of the sensor magnet 3, thus enabling the rotation detection structure to be made thinner in the axial direction. Furthermore, with the motor 10 described above, the axial length of the rotation detection structure is reduced because the rotation detection structure described above is applied, thus suppressing an increase in the axial dimensions of the motor 10.

[0060] (2) In the rotation detection structure described above, the first magnet 4 and the second magnet 5 of the sensor magnet 3 are connected in the axial direction and integrated. This makes it possible to reduce the axial length of the sensor magnet 3 compared to when the first magnet 4 and the second magnet 5 are separated in the axial direction, thus making the rotation detection structure thinner.

[0061] (3) In the rotation detection structure described above, the sensor surface 2s is perpendicular to the axis C at a position that approximately coincides with the boundary position P between the first magnet 4 and the second magnet 5. This arrangement of the sensor surface 2s allows the thickness of the magnetic sensor 2 in the detection direction N to be equal to the length of the magnetic sensor 2 in the axial direction, thus enabling the rotation detection structure (especially the radially outer side of the sensor magnet 3) to be made thinner in the axial direction. Furthermore, the detection direction N of the sensor surface 2s perpendicular to the axis C can be made to coincide with the direction through which the interaxial magnetic flux Φd passes parallel to the axis C at the boundary position P, thereby improving the detection accuracy of the magnetic flux of the magnetic sensor 2.

[0062] (4) In the rotation detection structure described above, the magnetic sensor 2 is fixed to the substrate 6 with the covering portion 2a of the magnetic sensor 2 resting on the substrate 6. In this way, the magnetic sensor 2 is fixed to the substrate 6 in a resting position on the substrate 6, rather than being fixed in a floating position, thereby stabilizing the mounting position of the magnetic sensor 2 on the substrate 6. Consequently, the sensing of the magnetic sensor 2 can be stabilized.

[0063] (5) If the magnetic sensor 2 is a chip-type Hole IC instead of a Hole IC with leads, the lead terminals 2t of the magnetic sensor 2 can be placed on the conductor 6c of the substrate 6 simply by placing the magnetic sensor 2 on the substrate 6. Therefore, the magnetic sensor 2 can be easily joined (fixed) to the substrate 6. In addition, the lead bending process required when mounting a Hole IC with leads is unnecessary with a chip-type Hole IC, which contributes to reducing the mounting time of the magnetic sensor 2 and suppresses the occurrence of defects in the magnetic sensor 2 caused by the lead bending process. Furthermore, by using a chip-type Hole IC which is less expensive than a Hole IC with leads, the cost of the rotation detection structure can be reduced.

[0064] (6) If the back surface 6g of the substrate 6 is located on the first direction D1 side of the end face 5g of the second magnet 5, a space can be secured on the back surface 6g of the substrate 6 for soldering components (e.g., terminal 7). In other words, it is no longer necessary to provide a space for soldering components on the back surface 6g of the substrate 6 on the second direction D2 side of the sensor magnet 3, so the rotation detection structure including the substrate 6 can be made thinner in the axial direction. Furthermore, since such a space for soldering is secured between the back surface 6g of the substrate 6 and the end face 5g of the sensor magnet 3, the axial gap between the sensor magnet 3 and the brush holder 16 located on the second direction D2 side of the motor 10 can be narrowed. Thus, the axial dimensions of the motor 10 can be reduced.

[0065] (7) When the terminal 7 is soldered to the back surface 6g of the circuit board 6, the heat from the soldering iron used to attach the terminal 7 to the circuit board 6 can be suppressed from being transmitted to the magnetic sensor 2, thereby suppressing the thermal effects on the magnetic sensor 2. Therefore, failure of the magnetic sensor 2 due to heat can be suppressed. (8) Furthermore, if the terminal 7 is located on the opposite side of the axis C from the magnetic sensor 2, the terminal 7 and the magnetic sensor 2 can be separated further, thereby further suppressing the thermal impact on the magnetic sensor 2 when the terminal 7 is installed.

[0066] (9) If the axial length of the magnetic sensor 2 is shorter than the axial length of the sensor magnet 3, the magnetic sensor 2 can be installed more easily within the range of the axial length of the sensor magnet 3, thereby enabling the rotation detection structure to be made thinner in the axial direction.

[0067] [4. Others] The rotation detection structure and motor 10 configuration described above are examples and are not limited to the above configuration. The motor 10 to which the rotation detection structure described above is applied does not have to be an inner rotor type brushed motor, but may also be an outer rotor type brushed motor. The motor 10 may also be a brushless motor. The device (object to which the rotation detection structure is applied) does not have to be a motor, and the rotating body that is the target of rotation detection by the rotation detection structure does not have to be the shaft 1.

[0068] The magnetic sensor 2 does not have to be a chip-type Hall IC; it may also be a Hall IC with leads. The magnetic sensor 2 only needs to be capable of detecting the magnetic flux of the sensor magnet 3, and does not have to be a Hall IC with a built-in signal processing circuit.

[0069] The sensor magnet 3 may consist of a first magnet 4 and a second magnet 5 that are spaced apart from each other in the axial direction. The number of magnetic pole pairs of the first magnet 4 and the second magnet 5 may be two or more. The shape of the sensor magnet 3 is not limited to a cylindrical shape; for example, it may be a rectangular tube, a cylindrical shape, or a rectangular prism shape.

[0070] The substrate 6 only needs to be at least flat, and its shape when viewed from the axial direction does not need to be rectangular, nor does it need to be annular that surrounds the sensor magnet 3. The number of terminals 7 attached to the substrate 6 is not limited to four. Also, components soldered to the back surface 6g of the substrate 6 do not have to be terminals 7. In the rotation detection structure, the substrate 6 and terminals 7 may be omitted. [Explanation of symbols]

[0071] 1. Shaft (rotating body) 2 Magnetic Sensor 2a Covered part 2s sensor surface 3 Sensor Magnet 4. First Magnet 5. Second Magnet 5g end face 6 circuit boards 6g Back side (end side, side) Terminal 7 10 motors 11 rotors 12 staters C axis N detection direction P boundary position PL Orthogonal plane (plane) Rd Inter-axis magnetic flux area Φd Interaxial magnetic flux

Claims

1. A rotation detection structure for detecting the rotation angle of a rotating body that rotates around an axis, A sensor magnet comprising a first magnet having alternating north and south poles arranged in the circumferential direction, and a second magnet positioned parallel to the first magnet in the axial direction and offset by one magnetic pole from the first magnet, with alternating north and south poles arranged in the circumferential direction, and which rotates integrally with the rotating body, The system includes a magnetic sensor that detects the magnetic flux of the aforementioned sensor magnet, The sensor magnet forms an interaxial magnetic flux region that is radially outside the sensor magnet and serves as a path for interaxial magnetic flux extending from the north pole of one of the first magnet and the second magnet in the axial direction to the south pole of the other of the first magnet and the second magnet. The magnetic sensor is configured such that the sensor surface receiving the interaxial magnetic flux is located within the interaxial magnetic flux region. A rotation detection structure characterized by the following features.

2. The inclination of the sensor surface with respect to a plane perpendicular to the axis is 45 degrees or less. The rotation detection structure according to claim 1, characterized in that

3. The first magnet and the second magnet are connected integrally in the axial direction. The rotation detection structure according to claim 2, characterized in that

4. The sensor surface is perpendicular to the axis at a position that substantially coincides with the boundary position between the first magnet and the second magnet in the axial direction. The rotation detection structure according to claim 3, characterized in that

5. It further comprises a flat substrate, The magnetic sensor has a covering portion that covers the sensor surface, and the covering portion is fixed to the substrate while it is placed on the substrate. The rotation detection structure according to claim 2, characterized in that

6. The magnetic sensor is a chip-type Hall IC. The rotation detection structure according to claim 5, characterized in that

7. The second side of the substrate, opposite to the first side on which the covering portion is placed, is located on the first side relative to the magnetic sensor, and is located on the second side relative to the end face of the first magnet or the second magnet. The rotation detection structure according to claim 5, characterized in that

8. The substrate has terminals soldered to the second side opposite to the first side on which the covering portion is placed. The rotation detection structure according to claim 5, characterized in that

9. The terminal is located on the opposite side of the axis from the magnetic sensor. The rotation detection structure according to claim 8, characterized in that

10. The axial length of the magnetic sensor is shorter than the axial length of the sensor magnet. The rotation detection structure according to claim 2, characterized in that

11. A rotation detection structure according to any one of claims 2 to 10, The shaft as the rotating body, A rotor that rotates integrally with the aforementioned shaft, The rotor is provided with a stator positioned opposite to it. A motor characterized by the following features.

Images