Rotation detection device

Abstract

This rotation detection device includes: a power generation sensor disposed in a first support body; and a magnetic field generation source fixed to a second support body which performs a relative rotary movement about the rotation axis. The power generation sensor includes a magnetic wire, a coil, and a pair of magnetic flux conductive pieces which have formed therein wire disposition parts comprising through-holes or grooves for fixing both end parts of the magnetic wire. The magnetic flux conductive pieces comprise axially orthogonal parts and axially parallel parts. The magnetic field generation source comprises a plurality of magnetic poles arranged in the circumferential direction about the rotation axis. The plurality of magnetic poles are alternately arranged such that the magnetic polarities are alternately different in the circumferential direction. The magnetization direction of each of the magnetic poles is parallel to the rotation axis.

Description

Rotation detection device

[0001] The present invention relates to a rotation detection device using a power generation sensor.

[0002] Magnetic wire with a large Barkhausen effect (large Barkhausen jump) is known as Wiegand wire or pulse wire. This magnetic wire has a core and a skin surrounding the core. One of the core and skin is a soft (soft magnetic) layer whose magnetization direction reverses even in a weak magnetic field, while the other is a hard (hard magnetic) layer whose magnetization direction does not reverse unless a strong magnetic field is applied. A power generating sensor can be constructed by winding a coil around such a magnetic wire.

[0003] When the hard and soft layers are magnetized in the same direction along the axial direction of the wire, the magnetization direction of the soft layer is reversed when the external magnetic field strength in the opposite direction increases and reaches a certain magnetic field strength. This reversal of the magnetization direction starts at a certain point in the magnetic wire and propagates throughout the wire, causing the magnetization direction of the soft layer to reverse simultaneously. At this time, the large Barkhausen effect occurs, inducing a pulse signal in the coil wound around the magnetic wire. When the external magnetic field strength is further increased and reaches a certain magnetic field strength, the magnetization direction of the hard layer is reversed.

[0004] In this specification, the magnetic field strength when the magnetization direction of the soft layer is reversed is called the "operating magnetic field," and the magnetic field strength when the magnetization direction of the hard layer is reversed is called the "stabilizing magnetic field."

[0005] The output voltage obtained from the coil is constant regardless of the speed at which the input magnetic field (external magnetic field) changes, and has hysteresis characteristics with respect to the input magnetic field, so there is no chattering. For this reason, the pulse signal generated from the coil is used in rotation detection devices, etc. Because the output from the coil contains power, it is possible to create a power-generating sensor (power-generating sensor) that does not require an external power supply. In other words, the output energy of the coil can also operate peripheral circuits without an external power supply.

[0006] For the large Barkhausen effect to occur, the magnetization direction of only the soft layer must be reversed from a state in which the magnetization directions of the hard and soft layers are aligned. Even if the magnetization direction of only the soft layer is reversed when the magnetization directions of the hard and soft layers are not aligned, no pulse signal will be generated, or even if it is generated, it will be very small.

[0007] Furthermore, to maximize the power output, it is important that the magnetization direction of the entire magnetic wire is aligned, and that the magnetization reversal of the soft layer extends across the entire magnetic wire. If the magnetization direction of the magnetic wire is not aligned in parts, only a very small pulse signal is obtained. Therefore, it is preferable that a uniform magnetic field is applied to the entire magnetic wire.

[0008] When an alternating magnetic field is applied to a power generating sensor, two pulse signals are generated per cycle: one positive pulse signal and one negative pulse signal. A magnet is used as the source of the magnetic field, and the rotational movement of the magnet applies an alternating magnetic field to the power generating sensor. The rotational position can be detected by counting the generated pulse signals.

[0009] Rotation detectors that detect magnetic field changes associated with the rotation of a magnet around a rotation axis using a magnetic wire that exhibits the large Barkhausen effect can be broadly divided into axial gap and radial gap types. The axial gap type has a configuration in which a power generating sensor is arranged at a distance from the magnet in a direction parallel to the rotation axis. On the other hand, the radial gap type has a configuration in which a power generating sensor is arranged at a distance from the magnet in the direction of the rotation radius, which is perpendicular to the rotation axis. The radial gap type is more advantageous when constructing a small-diameter rotation detector. The radial gap type also has three configurations depending on the direction in which the magnetic wire is arranged: a configuration in which the magnetic wire is arranged along the rotation radius (see FIG. 1 of Patent Document 1), a configuration in which the magnetic wire is arranged along the tangential direction on the circumference around the rotation axis (see FIG. 2 of Patent Document 1), and a configuration in which the magnetic wire is arranged parallel to the rotation axis (see FIGS. 3 to 10 of Patent Document 1). Of these, the configuration in which the magnetic wire is arranged parallel to the rotation axis has the advantage that it is easier to fabricate a small-diameter rotation detector because its projected area in the direction parallel to the rotation axis is small.

[0010] Figures 3 to 10 of Patent Document 1 show a radial gap rotation detector in which a magnetic wire is arranged parallel to the rotation axis. That is, the magnetic wire is arranged on the outer periphery of the tone wheel with its length parallel to the rotation axis of the tone wheel. In the configuration shown in Figures 3 to 7 of Patent Document 1, the tone wheel is composed of a multi-pole magnet in which N-pole and S-pole magnetized portions are arranged alternately in the circumferential direction. The magnetization direction of the magnetized portions is the radial direction of rotation. In the configuration shown in Figures 8 to 10 of Patent Document 1, the tone wheel is composed of a multi-pole magnet magnetized in a direction parallel to the rotation axis, and the magnetization directions of adjacent magnetized portions in the circumferential direction are opposite to each other.

[0011] As shown in FIG. 4 of Patent Document 1, in the configurations shown in FIGS. 3 and 5 of Patent Document 1, where the magnetization direction is in the direction of the radius of rotation, a semicircular magnetic flux is formed around the multi-pole magnet, and this magnetic flux enters not only both ends of the magnetic wire but also the middle portion. This results in uneven magnetic field strength at different positions along the axial length of the magnetic wire. If the length of the magnet parallel to the rotation axis is shortened (for example, shorter than the magnetic wire), most of the magnetic flux emitted from the magnet enters the middle portion of the magnetic wire, resulting in even more uneven magnetic field strength within the magnetic wire. In the configuration shown in FIG. 6 of Patent Document 1, the south and north poles are separated in the direction parallel to the rotation axis, with a non-magnetized portion between them. This reduces the magnetic flux entering the middle portion of the magnetic wire, as shown in FIG. 7 of Patent Document 1. However, the semicircular magnetic flux is still formed, and the magnetic flux cannot be efficiently concentrated at both ends of the magnetic wire, and the magnetic flux entering the middle portion of the magnetic wire cannot be sufficiently reduced. Therefore, the problem of non-uniform magnetic field strength at different positions along the axial length of the magnetic wire cannot be fully resolved. If the distance between the north and south poles in the direction parallel to the rotation axis is made shorter (for example, shorter than the magnetic wire), most of the magnetic flux emitted from the magnet will enter the middle part of the magnetic wire, making the magnetic field strength within the magnetic wire even more non-uniform.

[0012] On the other hand, as shown in FIG. 9 of Patent Document 1, in the configurations shown in FIGS. 8 and 10 in which the magnetization direction is parallel to the rotation axis, the main direction of the magnetic flux emitted from the magnet is parallel to the rotation axis. Therefore, only a portion of the magnetic flux leaves the magnet and makes a large detour to reach both ends of the magnetic wire. This makes it difficult to efficiently transmit a sufficient magnetic field to the magnetic wire. If the length of the magnet is shortened (for example, shorter than the magnetic wire), the magnetic flux emitted from the magnet will enter the middle part of the magnetic wire, resulting in uneven magnetic field strength within the magnetic wire. Therefore, the length of the magnet must be approximately the same as or longer than the magnetic wire.

[0013] Such a magnet, which is long in a direction parallel to the rotation axis and magnetized in a direction parallel to the rotation axis, cannot be produced by multi-pole magnetization of a cylindrical hard magnetic body. In reality, it can only be produced by attaching a bar-shaped magnet to a cylindrical yoke. The thickness of a hard magnetic body that can be magnetized by the magnetic flux from the magnetizing yoke used for multi-pole magnetization is at most about 3 mm. Even when multi-pole magnetization is performed by sandwiching the hard magnetic body between magnetizing yokes, the maximum thickness that can be magnetized is about 5 mm. Increasing the number of poles to improve rotation detection resolution further reduces the thickness that can be magnetized. Meanwhile, attaching a bar-shaped magnet to a cylindrical yoke requires labor. In particular, the task of adhering a magnet to a predetermined position on a cylindrical yoke against the magnetic force between the magnets is difficult. Furthermore, reducing the diameter or increasing the number of poles increases the labor required and the difficulty of the process.

[0014] On the other hand, cylindrical multi-pole magnets with multiple magnetic poles magnetized in the direction of the rotation radius can be fabricated by magnetizing a cylindrical hard magnetic material with multiple poles, thereby reducing the labor required. However, it is difficult to achieve the complex magnetic pole patterns shown in Figures 3 to 7 of Patent Document 1 with the multi-pole magnetization of a single cylindrical magnet. In practice, two cylindrical multi-pole magnetized magnets must be installed with their polarities shifted out of phase. This requires more materials and labor than a single cylindrical magnet. Furthermore, a large circumferential magnetization pitch (the circumferential width of the magnetic poles) is required to apply a stabilizing magnetic field of a certain strength to the magnetic wire. Therefore, the diameter of the cylindrical multi-pole magnet is inevitably large, and the rotation detection device is correspondingly large.

[0015] Patent Document 2 explains the problems with a configuration (corresponding to the configuration shown in FIGS. 8 to 10 of Patent Document 1) that uses magnets magnetized in a direction parallel to the rotation axis and magnetic wires extending in a direction parallel to the rotation axis (paragraphs 0004 to 0006 of the same document). Specifically, when attempting to reduce the diameter or increase the resolution, the circumferential spacing between the magnets becomes shorter, which makes it easier for magnetic flux to concentrate in the path that short-circuits the north and south poles of adjacent magnets. As a result, less magnetic flux passes through the magnetic wire, making it difficult to obtain output from the power generation sensor.

[0016] To solve this problem, Patent Document 2 discloses a rotation detection device having a detection unit and a magnetic field generating section. The detection unit includes a magnetic flux inductor between the magnetic field generating section and a detection element formed by winding a coil around a magnetic wire. The detection element is disposed on the inner periphery of the track of the magnetic field generating section so that the length of the magnetic wire is parallel to the rotation axis. The magnetic field generating section includes a cylindrical rotating body made of soft magnetic material and multiple permanent magnets arranged circumferentially around the rotating body. These multiple permanent magnets are magnetized (magnetized) in a direction perpendicular to the rotation axis and are installed on the inner periphery of the rotating body so that their opposite poles are aligned circumferentially. This configuration is described as enabling the device to be made compact.

[0017] In the structure shown in Figures 1 to 8 of Patent Document 2, each magnet is magnetized in a direction perpendicular to the rotation axis and extends in a direction parallel to the rotation axis. Therefore, magnetic poles of the same polarity face each other at both ends of a magnetic wire extending in a direction parallel to the rotation axis. Therefore, two magnetic flux conductors (yokes) are provided, and the two magnetic flux conductors use magnets of opposite polarities as their detection areas. Specifically, the two magnetic flux conductors have plate-shaped base portions facing each end of the magnetic wire, and protruding portions protruding from the base portions toward the magnets of opposite polarities. Therefore, the protruding portions of the two magnetic flux conductors protrude in different directions.

[0018] Such a complex configuration not only complicates the manufacturing process, but also affects detection performance due to factors such as the orientation of the protrusions, the spacing between adjacent magnets, and the distance (gap) between the magnetic flux conductor and the magnet. Therefore, the performance of the rotation detector depends on the assembly accuracy. Furthermore, because the two magnetic flux conductors must induce magnetic flux from magnets with poles at different positions in the circumferential direction, the structure depends on the circumferential magnetic pole pitch. Therefore, individual designs are required for each rotation detector configuration, which makes them less versatile.

[0019] In the structure shown in Figure 10 of Patent Document 2, almost no magnetic field is applied to one side of the magnetic flux conductor, so the distance (gap) from the magnetic flux conductor to the magnet is very narrow, and measures must be taken to prevent cogging that occurs during rotation due to the attractive force between the magnetic flux conductor and the magnet. The structure shown in Figure 12 of the same document arranges two permanent magnets adjacent to each other in a direction parallel to the rotation axis, so that a magnetic field is applied to both sides of the magnetic flux conductor. However, this structure requires twice the number of magnets, making the device difficult to assemble.

[0020] Furthermore, as shown in Figures 5, 6, 9, and 11 of Patent Document 2, a large portion of the magnetic flux from the magnet magnetized in a direction perpendicular to the rotation axis enters the middle part of the magnetic wire. As a result, the magnetic field strength is not uniform at different positions in the axial direction of the magnetic wire. Even in the configurations shown in Figures 5 and 6 of the same document, in which magnetic flux conductors extend near both ends of the magnetic wire, the magnetic resistance of the path from the magnet to both ends of the magnetic wire is not sufficiently low, and the magnetic flux cannot be efficiently concentrated at both ends of the magnetic wire.

[0021] In this way, when the magnetic field source is a multi-pole rotating body, if the magnetic wire is aligned parallel to the axis of rotation and an attempt is made to apply a magnetic field parallel to the axial direction with uniform strength to the entire magnetic wire, the structure becomes complex, it is difficult to miniaturize, and it lacks versatility.

[0022] JP-A-8-136558 Patent No. 6535270

[0023] Therefore, one embodiment of the present invention provides a rotation detection device that can solve at least one of the above-mentioned problems.

[0024] For example, one embodiment of the present invention provides a rotation detection device that has a simple structure and can detect rotation by combining a multi-pole magnetic pattern on the outer periphery and / or inner periphery of a rotating body with a power generation sensor.

[0025] Furthermore, for example, one embodiment of the present invention provides a rotation detection device that is simple and can obtain a high-output signal by combining a power generating sensor having a magnetic flux conducting piece with a magnetic field generating source having a magnetization pattern parallel to the rotation axis on the outer and / or inner circumference of a rotating body.

[0026] One embodiment of the present invention provides a rotation detection device having the following exemplary features.

[0027] 1. A rotation detection device comprising: a power generating sensor disposed on a first support; and a magnetic field generating source fixed to a second support that rotates relative to the first support about a rotation axis, wherein the power generating sensor comprises a magnetic wire that exhibits the large Barkhausen effect, a coil wound around the magnetic wire, and a pair of magnetic flux conducting pieces made of soft magnetic materials that are symmetrical with respect to a symmetry plane set at the center position of the magnetic wire in the axial direction, wherein the pair of magnetic flux conducting pieces comprises a pair of axis-orthogonal portions extending parallel to each other in a direction orthogonal to the axial direction from both ends of the magnetic wire, and a pair of axis-parallel portions extending in directions approaching each other along the axial direction from tips of the axis-orthogonal portions, with proximal ends facing each other with a gap in the axial direction, the axis-orthogonal portions having wire placement portions formed of holes or grooves that penetrate in the axial direction and to which both ends of the magnetic wire are fixed, and the power generating sensor is configured so that a detection region is on the opposite side of the axis-parallel portions from the magnetic wire, a rotation detection device in which the magnetic field generating source is arranged to pass through the detection area, is magnetized in a direction parallel to the rotation axis, and has a plurality of magnetic poles arranged (typically arranged at equal intervals) in a circumferential direction around the rotation axis, and the plurality of magnetic poles are arranged alternately so that they have alternating polarities in the circumferential direction; the power generation sensor faces the magnetic field generating source with a gap in a direction perpendicular to the rotation axis; the center of the magnetic wire is located in the space between a first imaginary plane and a second imaginary plane that pass through one end and the other end of the magnetic field generating source in a direction parallel to the rotation axis, and are perpendicular to the rotation axis, and the axis-orthogonal portion is located outside the space between the first imaginary plane and the second imaginary plane.

[0028] According to this configuration, the center of the magnetic wire is located in the space between the first and second imaginary planes that pass through both ends of the magnetic field generating source in the direction parallel to the rotation axis and are perpendicular to the rotation axis. Furthermore, the axis-orthogonal portion is located outside this space. This results in an arrangement of the power generating sensor in which the magnetic wire intersects with the plane perpendicular to the rotation axis. This arrangement of the power generating sensor reduces the projection area of ​​the rotation detection device in the direction parallel to the rotation axis.

[0029] On the other hand, by arranging the axis-orthogonal portion outside the space between the first and second imaginary planes, the length of the magnetic field generating source in the direction parallel to the rotation axis (i.e., the distance between the first and second imaginary planes) becomes shorter than the length of the power generating sensor in the same direction. Therefore, the magnetic field generating source can be configured with a magnet that has a small length (thickness) in the direction parallel to the rotation axis and whose magnetization direction (magnetization direction) is parallel to the rotation axis. Such a magnetic field generating source can be configured, for example, with a ring-shaped magnet made by magnetizing a hard magnetic material with multiple poles parallel to the rotation axis.

[0030] Because the axis-orthogonal portions are positioned outside the space between the first and second imaginary planes, the pair of axis-parallel portions are located closer to the magnetic field source than the pair of axis-orthogonal portions. In addition, the pair of axis-parallel portions are magnetically coupled to magnetic poles of opposite polarities (magnetic poles located opposite each other in a direction parallel to the rotation axis) of the magnetic field source. Because the axis-parallel portions parallel to the axial direction of the magnetic wire are located between the magnetic field source and the magnetic wire, the magnetic field applied from the magnetic field source is collected by the soft magnetic flux conduction pieces and guided to both ends of the magnetic wire. Therefore, the magnetic poles do not need to be located near both ends of the magnetic wire. In addition, the magnetic flux directed toward the axially intermediate portion of the magnetic wire is shielded by the axis-parallel portions. Therefore, the magnetic field can be efficiently collected at both ends of the magnetic wire using a magnetic field source that is small in length (thickness) in a direction parallel to the rotation axis and whose magnetization direction is parallel to the rotation axis. This allows for uniform magnetic field strength at different axial positions of the magnetic wire.

[0031] Furthermore, both ends of the magnetic wire are fixed to wire placement sections provided in the axially orthogonal section, and the wire placement sections are configured with holes or grooves penetrating the axially orthogonal section. This ensures reliable magnetic coupling between the magnetic wire and the axially orthogonal section, allowing the magnetic wire and the magnetic flux conduction pieces to form a magnetic circuit. This prevents magnetic flux from passing through the magnetic flux conduction pieces and entering the middle part of the magnetic wire, allowing the magnetic flux to be efficiently guided to both ends of the magnetic wire. This makes it possible to more uniform the magnetic field strength at different positions in the axial direction of the magnetic wire.

[0032] In this way, the axial magnetic field can be applied efficiently and uniformly to the magnetic wire, so that the large Barkhausen effect can be sufficiently generated even if the magnetic pole pitch in the rotation direction is small. In other words, a rotation detection device that is small and can obtain a high-output signal can be realized.

[0033] 2. The rotation detection device according to item 1, wherein the magnetic wire of the power generation sensor is arranged parallel to the rotation axis.

[0034] This configuration minimizes the projected area of ​​the power generation sensor in the direction parallel to the rotation axis, making it possible to configure a compact rotation detection device.

[0035] In this configuration, it is preferable that the extension direction of the magnetic wire is parallel to the rotation axis of the rotational motion, the axis-parallel portion faces the magnetic field source, and the symmetry plane passes through the center of the magnetic field source in a direction parallel to the rotation axis.

[0036] With this configuration, while the power generating sensor is arranged with the axial direction of the magnetic wire parallel to the rotation axis of the rotor, for example, a magnetic field generating source can be formed using a multi-pole magnet with a multi-pole magnetization pattern magnetized parallel to the rotation axis, and magnetic flux from magnetic poles of opposite polarities can be concentrated at both ends of the magnetic wire via a pair of magnetic flux conducting pieces. As a result, when the multi-pole magnet rotates together with the rotation axis, the magnetic wire exhibits the large Barkhausen effect, generating a pulse voltage.

[0037] "Parallel" means that the axial direction of the magnetic wire is parallel to the rotation axis within a range that allows for assembly errors and also allows for tilt within a range that allows the magnetic wire to exhibit the large Barkhausen effect. For example, it is acceptable for the axial direction of the magnetic wire to be tilted within 20 degrees (more preferably within 10 degrees) with respect to the direction parallel to the rotation axis.

[0038] 3. The rotation detection device according to item 1 or 2, wherein the length of the magnetic field generation source in the direction parallel to the rotation axis is equal to or less than half the length of the magnetic wire.

[0039] This configuration makes it possible to realize a rotation detection device equipped with a small magnetic field generating source.

[0040] 4. The rotation detection device according to any one of items 1 to 3, wherein the length of the magnetic field generation source in the direction parallel to the rotation axis is equal to or less than the distance between the inner surfaces of the pair of axis-orthogonal portions of the power generation sensor on the symmetry plane side.

[0041] This configuration makes it possible to realize a rotation detection device equipped with a small magnetic field generating source.

[0042] 5. The rotation detection device according to any one of items 1 to 4, wherein the length of the magnetic field generation source in a direction parallel to the rotation axis is equal to or greater than two-thirds of the axial spacing (distance) between the proximal ends of the pair of axis-parallel portions.

[0043] This configuration makes it possible to almost completely extract the output due to the large Barkhausen effect inherent in the magnetic wire, and furthermore, it is possible to realize a rotation detection device with a thin and lightweight magnetic field generating source.

[0044] 6. The rotation detection device according to any one of items 1 to 5, wherein the axial spacing (distance) between the proximal ends of the pair of axis-parallel portions is 5% to 50% of the axial distance between the pair of axis-orthogonal portions at the coupling position with the magnetic wire.

[0045] This configuration improves the efficiency of magnetic collection and magnetic shielding by the axially parallel portion, allowing the magnetic field from the magnetic field source to be efficiently concentrated at both ends of the magnetic wire, thereby making the magnetic field strength more uniform at different positions in the axial direction of the magnetic wire and making it possible to utilize the large Barkhausen effect inherent to the magnetic wire.

[0046] 7. A rotation detection device according to any one of items 1 to 6, wherein the plurality of magnetic field generating sources include one magnet that forms the plurality of magnetic poles, which are formed by magnetizing a ring-shaped hard magnetic body in multiple poles, or a plurality of magnets that are substantially the same shape and size and that respectively form the plurality of magnetic poles.

[0047] Multi-pole magnets, which are ring-shaped hard magnetic materials magnetized in multiple poles, can typically be applied to magnets used in electric motors. Magnets magnetized in a direction parallel to the rotation axis can be manufactured using a simple yoke, allowing for the use of inexpensive magnets. Combining such multi-pole magnets with power generating sensors having magnetic flux conducting pieces is easy to manufacture, and power generating sensors that can efficiently collect magnetism using magnetic flux conducting pieces can be used for general purposes regardless of the design of the magnet, etc. Therefore, a rotation detection device that can detect rotation with a versatile, simple, and compact structure can be realized.

[0048] 8. The rotation detection device according to any one of items 1 to 7, wherein the power generation sensor is located outside the outer circumferential circle of the magnetic field generation source. The outer circumferential circle is a circle that defines the edge farthest from the rotation axis when the rotation locus of the magnetic field generation source when rotated around the rotation axis is viewed parallel to the rotation axis.

[0049] This configuration allows for a small, high-output rotation detection device to be realized while ensuring a large hollow area in the magnetic field generation source.

[0050] 9. The rotation detection device according to any one of items 1 to 7, wherein the power generation sensor is located inside an inner circumferential circle of the magnetic field generation source. The inner circumferential circle is a circle that defines an edge close to the rotation axis when the rotation locus of the magnetic field generation source when rotated around the rotation axis is viewed parallel to the rotation axis.

[0051] This configuration reduces the influence of external stray magnetic fields other than those of the magnetic field generating source on the power generating sensor, thereby realizing a small, high-output rotation detection device. In particular, by constructing the second support body in a cylindrical shape using a soft magnetic material and arranging the magnetic field generating source inside it, the influence of external stray magnetic fields can be further reduced.

[0052] 10. The rotation detector according to any one of items 1 to 9, wherein the wire placement portion is provided on a surface of the magnetic flux conduction piece that does not face the magnetic field generation source.

[0053] This configuration reduces the influence on the power generation sensor of stray magnetic fields other than those of the magnetic field generating source (particularly on the opposite side of the magnetic field generating source), thereby realizing a small, high-output rotation detection device.

[0054] 11. The rotation detection device according to any one of items 1 to 10, comprising a plurality of the power generation sensors.

[0055] According to this configuration, the resolution and other factors are improved by using a plurality of power generation sensors, thereby improving the rotation detection accuracy. Also, a rotation detection device can be realized that improves the total amount of power generated during one rotation.

[0056] The plurality of power generating sensors may be arranged inside the inner circumferential circle of the magnetic field generating source or inside the outer circumferential circle of the magnetic field generating source. Alternatively, some of the power generating sensors may be arranged inside the inner circumferential circle of the magnetic field generating source, and other parts of the power generating sensors may be arranged outside the outer circumferential circle of the magnetic field generating source.

[0057] 12. The rotation detection device according to any one of items 1 to 11, further comprising a magnetic sensor that identifies the magnetic pole at a predetermined position in the circumferential direction around the rotation axis.

[0058] With this configuration, the state of the magnetic field applied to the power generation sensor can be determined by identifying the magnetic poles using the magnetic sensor at predetermined positions in the circumferential direction around the rotation axis. Therefore, by using the output signal of the magnetic sensor, a rotation detection device can be realized that can distinguish between forward and reverse rotation of the relative rotational motion, i.e., detect the direction of rotation.

[0059] FIG. 1A is a perspective view of a rotation detection device according to a first embodiment. FIG. 1B is a front view, as viewed in the direction of arrow 1B in FIG. 1A. FIG. 2A is an enlarged perspective view of a power generation sensor included in the rotation detection device. FIG. 2B is a front view, as viewed in the direction of arrow 101 in FIG. 2A. FIGS. 3A and 3B are perspective views showing modified examples of the power generation sensor. FIGS. 4A, 4B, and 4C are diagrams showing the results of a two-dimensional magnetic simulation for a configuration (comparative example) without a magnetic flux conduction piece. FIG. 5 is a graph showing the magnetic field strength at different positions in the axial direction of the magnetic wire in the two-dimensional magnetic simulation of FIGS. 4A, 4B, and 4C. FIGS. 6A, 6B, and 6C are diagrams showing the results of a two-dimensional magnetic simulation for a configuration (example) with a magnetic flux conduction piece. FIG. 7 is a graph showing the magnetic field strength at different positions in the axial direction of the magnetic wire in the two-dimensional magnetic simulation of FIGS. 6A, 6B, and 6C. FIG. 8 shows experimental results of investigating the relationship between the thickness of a ring-shaped multi-pole magnet and output pulse height when the distance between the axially orthogonal portions of a pair of magnetic flux conduction pieces is set to various values. FIG. 9 is a perspective view of a rotation detection device according to a second embodiment. FIG. 10 is a perspective view of a rotation detection device according to a third embodiment. FIG. 11A is a perspective view of a rotation detection device according to a fourth embodiment. FIG. 11B is a cross-sectional view of the rotation detection device according to the fourth embodiment. FIG. 12 is a perspective view of a rotation detection device according to a fifth embodiment. FIG. 13 is a perspective view of a rotation detection device according to a sixth embodiment. FIG. 14 is a diagram showing the definitions of first, second, and third imaginary planes for explaining the relative arrangement of the power generation sensor and the magnetic field generation source. FIGS. 15A, 15B, and 15C are diagrams for explaining examples of the relative arrangement of the power generation sensor and the magnetic field generation source.

[0060] The present invention will be described below based on the illustrated embodiments, but the present invention is not limited to the embodiments described below.

[0061] 1A and 1B show a rotation detection device 10 according to a first embodiment. Fig. 1A is a perspective view of the rotation detection device 10, and Fig. 1B is a front view seen in the direction of arrow 1B in Fig. 1A.

[0062] The rotation detection device 10 includes a power generation sensor 100 arranged on a first support 300 and a magnetic field generating source 200 fixed to a second support 400 that rotates relative to the first support around a rotation axis 201.

[0063] The power generating sensor 100 includes a magnetic wire 110 that exhibits a large Barkhausen effect when an alternating magnetic field is applied, a coil 120 wound around the magnetic wire 110, and a pair of magnetic flux conduction pieces 130, 131 each having wire placement sections 130a, 131a (see FIGS. 2A and 2B) that secure both ends of the magnetic wire 110. In this embodiment, the wire placement sections 130a, 131a (see FIGS. 2A and 2B) are formed as through holes. The pair of magnetic flux conduction pieces 130, 131 are symmetrical with respect to a symmetry plane 115 set at the axial center of the magnetic wire 110, and each include a pair of axis-orthogonal sections 133 that extend parallel to each other in a direction perpendicular to the axial direction, and a pair of axis-parallel sections 134 that extend from the tips of the axis-orthogonal sections 133 toward each other along the axial direction. In this embodiment, the magnetic wire 110 is linear.

[0064] The magnetic field generator 200 includes a plurality of magnetic poles arranged at equal intervals in the circumferential direction around the rotation axis 201 with respect to the second support 400. The magnetization direction of each of the plurality of magnetic poles is parallel to the rotation axis 201. The plurality of magnetic poles are arranged with magnetic poles of opposite polarities alternately in the circumferential direction so that adjacent magnetic poles in the circumferential direction have different polarities. In this embodiment, the magnetic field generator 200 (hereinafter sometimes referred to as "multi-pole magnet 200") is configured by a single multi-pole magnet made of a ring-shaped hard magnetic material magnetized into multiple poles.

[0065] To create a ring-shaped hard magnetic material magnetized with multiple poles, for example, a magnetizing yoke with an area equivalent to a predetermined magnetization pitch λ is used to simultaneously magnetize both the top and bottom surfaces of the ring-shaped hard magnetic material (here, the top and bottom surfaces are based on the case where the rotation axis 201 is aligned vertically). This results in magnetization along the rotation axis 201, with magnetic poles appearing on the top, bottom, outer, and inner surfaces of the hard magnetic material, creating a multi-pole magnet 200 with adjacent poles of different polarities along the circumferential direction. This allows a single magnet to serve as an inexpensive, compact magnetic field generator. Furthermore, if the magnet's thickness T is thin or if the material is ferrite, a multi-pole magnet 200 with adjacent poles of different polarities along the circumferential direction can be produced even by magnetizing only the top or bottom surface with a magnetizing yoke, offering the added benefit of being more cost-effective.

[0066] The power generating sensor 100 is disposed so that the axial direction of the magnetic wire 110 is parallel to the rotation axis 201 and the axially parallel portion 134 faces the outer peripheral surface of the ring-shaped multi-pole magnet 200. That is, the power generating sensor 100a is located outside the outer peripheral circle formed by the outer edge of the rotation locus of the magnetic field generating source around the rotation axis 201 when viewed in a direction parallel to the rotation axis 201. In this embodiment, the power generating sensor 100a is disposed so that a symmetry plane 115 (a plane perpendicular to the axial direction) set at the center position of the axial direction of the magnetic wire 110 of the power generating sensor 100 passes through approximately the center of the magnetic field generating source (the multi-pole magnet 200) in the direction parallel to the rotation axis 201. Therefore, with respect to the direction parallel to the rotation axis 201, the center position of the magnetic wire 110 coincides with the center 202 of the ring-shaped multi-pole magnet 200, i.e., a position half the thickness T of the magnet. Even if the center position of the magnetic wire 110 and the center of the magnet 200 in the direction parallel to the rotation axis 201 are not precisely aligned due to assembly errors or the like, there is no substantial effect on the rotation detection performance.

[0067] 2A is a perspective view of the power generating sensor 100, and FIG. 2B is a front view as viewed in the direction of arrow 101 in FIG. 2A . The power generating sensor 100 includes a magnetic wire 110 exhibiting the large Barkhausen effect, a coil 120 wound around the magnetic wire 110, and a pair of magnetic flux conducting pieces 130 and 131 made of soft magnetic material. The coil 120 is wound around the magnetic wire 110 so that the first end 111 and the second end 112 of the magnetic wire 110 are exposed at the same length. In this embodiment, the coil 120 is wound around the magnetic wire 110 between the pair of magnetic flux conducting pieces 130 and 131. The pair of magnetic flux conducting pieces 130 and 131 are fixed with resin to the first end 111 and the second end 112 of the magnetic wire 110 near and within the through-holes, respectively, so that the pair of magnetic flux conducting pieces 130 and 131 and the magnetic wire 110 are magnetically coupled.

[0068] The pair of magnetic flux conduction pieces 130, 131 have a configuration that is substantially the same shape and same size. More specifically, the pair of magnetic flux conduction pieces 130, 131 are configured symmetrically with respect to a symmetry plane 115 (a virtual plane for explaining the geometric arrangement) that is perpendicular to the axial direction x at a center position (hereinafter referred to as the "axial center position") 113 in the axial direction x (line length direction) of the magnetic wire 110. The pair of magnetic flux conduction pieces 130, 131 include axial-orthogonal portions 133 that extend parallel to each other in an axial-orthogonal direction z that is perpendicular to the axial direction x from both end portions 111, 112 of the magnetic wire 110, and axial-parallel portions 134 that extend from the tip ends of the axial-orthogonal portions 133 in directions that approach each other along the axial direction x. More specifically, the magnetic flux conduction pieces 130, 131 have an axis-orthogonal portion 133 having an approximately rectangular parallelepiped shape and an axis-parallel portion 134 having an approximately rectangular parallelepiped shape connected to the tip thereof, and have an L-shape bent at a right angle at the junction between the axis-orthogonal portion 133 and the axis-parallel portion 134.

[0069] In this example, the axis-orthogonal portion 133 has a thickness W in the axial direction x. If the width of the hole formed through the magnetic flux conduction pieces 130, 131, i.e., the thickness W of the axis-orthogonal portion 133 (see FIG. 2A ), is too large, the arrangement width of the coil 120 becomes narrow, reducing the efficiency of picking up the Large Barkhausen effect of the magnetic wire 110. If it is too small, the magnetic path between the magnetic wire 110 and the axis-orthogonal portion 133 becomes narrow. Therefore, based on experimental findings, the thickness W is preferably 10% to 20% of the total length of the magnetic wire 110. At the coupling position with the magnetic wire 110, the opposing inner surfaces of the pair of axis-orthogonal portions 133 face each other with a distance D in the axial direction x. The proximal ends 134a of the pair of axis-parallel portions 134 face each other with a distance L in the axial direction x.

[0070] Both ends 111, 112 of the magnetic wire 110 are fixed to the base ends of the axis-orthogonal portions 133 of the pair of magnetic flux conduction pieces 130, 131. More specifically, the base ends of the axis-orthogonal portions 133 are provided with wire placement portions 130a, 131a, each having a hole penetrating in the axial direction x and formed at the center of the width t of the magnetic flux conduction pieces 130, 131.

[0071] The axially parallel portions 134 of the pair of magnetic flux conduction pieces 130, 131 have their proximal ends 134a facing each other across a plane of symmetry 115 that passes through the axial center position 113 of the magnetic wire 110. That is, the proximal ends 134a face each other across a gap in the axial direction x. The midpoint of this gap in the axial direction x corresponds to the position of the axial center position 113 in the axial direction x, and therefore the distances in the axial direction x from the proximal ends 134a of the pair of axially parallel portions 134 to the plane of symmetry 115 are equal.

[0072] More specifically, the distance D is the distance in the axial direction x between the inner surfaces 130b, 131b (inner surfaces of the axially orthogonal portions 133) of a pair of magnetic flux conduction pieces 130, 131 that face each other in the axial direction x at the connection position with the magnetic wire 110.

[0073] The power generating sensor 100 is designed so that the area on the opposite side of the axially parallel portion 134 from the magnetic wire 110 is the detection area 140. A magnetic field source that generates the magnetic field to be detected is disposed in the detection area 140. In the rotation detection device 10 of FIGS. 1A and 1B , the magnetic field source is a ring-shaped multi-pole magnet 200. The magnetic poles of the multi-pole magnet 200 (at least the magnetic poles on the outer periphery) move relative to the power generating sensor 100 so as to pass through the detection area 140. In other words, the detection area 140 is disposed on the magnetic pole movement path of the ring-shaped multi-pole magnet 200. When viewed in the axial direction x, the magnetic pole movement path is on a circumference centered on the rotation axis 201, and the circumference has a tangent in the detection area 140 that is parallel to the width direction y, which is perpendicular to the axial direction x and the axis-orthogonal direction z.

[0074] The pair of magnetic flux conduction pieces 130, 131 are configured to correct the magnetic field formed in the space including the magnetic flux conduction pieces 130, 131 by a magnetic field generating source (ring-shaped multi-pole magnet 200) arranged in the detection area 140 into a magnetic field in the axial direction x and apply it to the magnetic wire 110. The axially parallel portion 134 can collect magnetic flux from the surface (detection area-facing surface) 134b facing the detection area 140 and guide it into the magnetic flux conduction pieces 130, 131. In this embodiment, the detection area-facing surface 134b is a surface parallel to the axial direction x. The detection area-facing surface 134b may be a flat surface parallel to the width direction y, or may be a cylindrically curved surface that matches the cylindrical outer peripheral surface of the ring-shaped multi-pole magnet 200.

[0075] The magnetic flux conducting pieces 130, 131 are made of a soft magnetic material with a coercive force equal to or less than that of the magnetic wire 110 and a magnetic permeability of 500 or more. Such materials have properties such as low magnetic resistance, low hysteresis, and low self-dielectric strength. As a result, even when a high-frequency alternating magnetic field generated by a magnetic field source moving at high speed is applied, the output characteristics of the power generating sensor 100 are not significantly affected. The thickness W (see FIG. 2A) of the axis-orthogonal portion 133 may be set to a value that does not impair the magnetic flux collecting and shielding (shielding) effects of the selected material.

[0076] 1A and 1B, an axially parallel portion 134 parallel to the axial direction x of the magnetic wire 110 is located between the magnetic pole faces of the magnetization pattern provided on the outer peripheral surface of the ring-shaped multi-pole magnet 200 and the magnetic wire 110. Therefore, the applied magnetic field is collected by a pair of magnetic flux conduction pieces 130, 131 made of soft magnetic material and guided to both ends of the magnetic wire 110. Furthermore, magnetic flux directed perpendicular to the axial direction x of the magnetic wire 110 is shielded by the axially parallel portion 134 and hardly enters the middle portion of the magnetic wire 110. Therefore, the applied magnetic field is corrected to the axial direction x of the magnetic wire 110 and applied from both ends of the magnetic wire 110, thereby sufficiently inducing the large Barkhausen effect and obtaining a high-output signal. The spacing (distance L) in the axial direction x between the proximal ends 134a of the pair of axially parallel portions 134 is preferably 5% to 50% of the distance D in the axial direction x between the pair of axially orthogonal portions 133 at the coupling position with the magnetic wire 110. This improves the magnetic collection efficiency and magnetic shielding efficiency of the axially parallel portions 134, and allows the magnetic field from the magnetic field generation source to be efficiently concentrated at both ends of the magnetic wire 110. This makes it possible to make the magnetic field strength at different positions in the axial direction of the magnetic wire 110 more uniform, thereby making it possible to bring out the large Barkhausen effect inherent to the magnetic wire 110.

[0077] The axial direction x (wire length direction) of the magnetic wire 110 of the power generation sensor 100 is arranged parallel to the rotation axis 201 .

[0078] In this case, "parallel" means approximately parallel, and means that the axial direction x of the magnetic wire 110 is aligned with the direction parallel to the rotation axis 201 within a range that allows for assembly errors and also allows for tilt within a range that allows the magnetic wire 110 to exhibit the large Barkhausen effect. For example, it is allowed for the axial direction x of the magnetic wire 110 to have a tilt of 20 degrees or less (more preferably 10 degrees or less) with respect to the direction parallel to the rotation axis 201.

[0079] The magnetic flux conduction pieces 130, 131, which are made of soft magnetic material, and the coil 120 are fixed to a case (not shown) that covers them by adhesive resin, fitting, or other suitable fixing means. As described above, the two ends 111, 112 of the magnetic wire 110 are fixed with resin (not shown) to wire placement sections 130a, 131a, which are made of two through-holes or grooves. Therefore, the power generation sensor 100 is configured by a structure in which the pair of magnetic flux conduction pieces 130, 131, the coil 120, and the magnetic wire 110 are fixed to each other and integrated.

[0080] In the first embodiment, the power generating sensor 100 is mounted on the first support 300 at one of its axis-parallel planes (planes parallel to the axial direction x of the magnetic wire 110), but this is not limiting. That is, the power generating sensor 100 may be mounted on the first support 300 at another axis-parallel plane, or may be supported by the first support at a plane other than the axis-parallel plane. In either case, it is necessary for the magnetic field source to pass through the detection region 140 (see FIG. 2B ) of the power generating sensor 100.

[0081] The magnetization pattern on the outer periphery of the ring-shaped multi-pole magnet 200 is a form in which multiple magnet regions polarized as north and south poles along the z direction are arranged circumferentially, and the magnetization directions of adjacent magnet regions are reversed so that the north and south poles are arranged alternately circumferentially. In this embodiment, six magnetic poles (magnetic pole bands) are configured around the rotation axis 201, but of course the number of magnetic poles may be other than this.

[0082] When the axially parallel portion 134 of one of the magnetic flux conduction pieces 130, 131 of the power generating sensor 100 faces a north pole, the axially parallel portion 134 of the other of the magnetic flux conduction pieces 130, 131 faces a south pole. This positional relationship allows magnetic flux from magnetic poles of opposite polarity to be efficiently conducted to the pair of magnetic flux conduction pieces 130, 131 of the power generating sensor 100, thereby achieving a compact, high-output power generating sensor 100. The circumferential magnetization pitch λ (magnetic pole pitch) can be shortened to the width t of the magnetic flux conduction pieces 130, 131 (see FIG. 2A ). Therefore, a larger magnetization pitch can be generally accommodated, resulting in a versatile, compact rotation detection device.

[0083] 3A shows a power generating sensor 100a, which is a modification of the power generating sensor 100. Fig. 3B is a perspective view of magnetic flux conduction pieces 130 and 131. In this modification, the wire placement portions 130a and 131a are formed as grooves rather than through holes.

[0084] The grooves constituting the wire placement portions 130a, 131a are preferably recessed in the axial-orthogonal direction z so as to open at the end face of the axial-orthogonal portion 133 on the opposite side of the axial-parallel portion 134 with respect to the magnetic wire 110 (the opposite side of the detection region 140 (see FIG. 2B )), and extend in the axial direction x at the center position of the width t of the magnetic flux conduction pieces 130, 131. The first end 111 and the second end 112 of the magnetic wire 110 are fixed to the axial-orthogonal portion 133 in the wire placement portions 130a, 131a, while passing through the axial-orthogonal portion 133. More specifically, resin (not shown) is placed in the grooves constituting the wire placement portions 130a, 131a, so that the ends 111, 112 of the magnetic wire 110 are fixed to the axial-orthogonal portion 133 and are coupled to each other. As a result, the magnetic wire 110 and the pair of magnetic flux conduction pieces 130, 131 are mechanically and magnetically coupled to each other.

[0085] The magnetic field from the magnetic field generating source 200 is not applied to the side of the magnetic wire 110 opposite the axially parallel portion 134. Therefore, in the axially orthogonal portions 133 of the magnetic flux conducting pieces 130, 131 shown in Figures 2A and 2B, the portion located on the side of the magnetic wire 110 opposite the axially parallel portion 134 contributes little to guiding or shielding the magnetic flux from the magnetic field generating source 200. Therefore, even in a configuration in which the magnetic wire 110 is exposed as shown in Figures 3A and 3B, it is possible to efficiently guide the magnetic flux from the magnetic field generating source 200 to both ends of the magnetic wire 110.

[0086] Moreover, this structure has the advantage of being able to reduce the influence on the power generation sensor 100a of magnetic fields other than those from the magnetic field generating source 200, particularly stray magnetic fields from the outside on the opposite side of the magnetic field generating source 200. This is a significant advantage, for example, when the power generation sensor 100a is installed on the inner periphery side of the magnetic field generating source 200 (see FIG. 9 described later).

[0087] Another advantage is that assembly is simplified because it eliminates the need to insert the magnetic wire 110 into the holes in the magnetic flux conduction pieces 130 and 131. In Figures 3A and 3B, the groove (groove with a semicircular cross section) is configured to accommodate a portion (e.g., about half) of the magnetic wire 110, but the groove may also be a U-shaped cross section that accommodates the entire magnetic wire 110, or the cross section may be another shape such as a triangle or a square.

[0088] [First Model] Figures 4A, 4B, 4C, and 5 show the results of a two-dimensional magnetic simulation of a longitudinal section passing through the axis of the magnetic wire 110 when no magnetic flux conduction pieces are provided (comparative example). Meanwhile, Figures 6A, 6B, 6C, and 7 show the results of a two-dimensional magnetic simulation of a longitudinal section passing through the axis of the magnetic wire 110 when magnetic flux conduction pieces 130, 131 are magnetically coupled to both ends (example). Figures 5 and 7 are graphs showing the magnetic field strength applied to the magnetic wire 110. The wire position on the horizontal axis represents the position in the axial direction x of the magnetic wire 110. The center position in the longitudinal direction of the magnetic wire 110 (11 mm long in this example) is represented as "0," and the two end positions are represented as -5.5 mm and +5.5 mm, respectively. The vertical axis represents the magnetic field strength, which is normalized to a stabilizing magnetic field of 1. The operating magnetic field is approximately 0.5. Curves 4A, 4B, and 4C in Figure 5 correspond to the configurations of Figures 4A, 4B, and 4C, respectively. Curves 6A, 6B, and 6C in Figure 7 correspond to the configurations of Figures 6A, 6B, and 6C, respectively.

[0089] The magnetic field generating sources are magnets 210, 211, and 212 magnetized in a direction parallel to the axial direction x of the magnetic wire 110. FIGS. 4A and 6A show simulation results for a magnet 210 whose length (thickness, e.g., 11 mm) in the direction parallel to the axial direction x is approximately the same as the length (e.g., 11 mm) of the magnetic wire 110. FIGS. 4B and 6B show simulation results for a magnet 211 whose length (thickness, e.g., 5 mm) in the direction parallel to the axial direction x is approximately half the length of the magnetic wire 110. FIGS. 4C and 6C show simulation results for a magnet whose length (thickness) in the direction parallel to the axial direction x is further shortened, e.g., by 1.5 mm. The configuration in FIG. 6A is an example in which the length (thickness) of the magnet 210 is approximately equal to the distance between the outer surfaces of a pair of axis-orthogonal portions 133 that do not face each other. The configuration of Fig. 6B is an example in which the length (thickness) of the magnet 211 is shorter than the distance between the opposing inner surfaces of the pair of axis-orthogonal portions 133 and longer than the distance (e.g., 2 mm) between the proximal ends of the pair of axis-parallel portions 134. The configuration of Fig. 6C is an example in which the length (thickness) of the magnet 212 is shorter than the distance between the proximal ends of the pair of axis-parallel portions 134.

[0090] In order for the magnetic flux distribution in the magnetic wire 110 to be uniform over the entire axial length range, it is desirable for the magnetic flux to enter from one end of the magnetic wire 110 and exit from the other end. In other words, it is desirable for the amount of magnetic flux entering and exiting the intermediate portion (midway in the axial direction) between both ends of the magnetic wire 110 to be as small as possible.

[0091] 4A, 4B, 4C, and 5 show that most of the magnetic flux generated by the magnets 210, 211, and 212 enters and exits the middle of the magnetic wire 110. This results in a higher magnetic field strength in the central region of the magnetic wire 110 than in the end regions. Furthermore, the shorter (thinner) the magnet, the more magnetic flux enters the middle of the magnetic wire 110, resulting in a worse uniformity of the magnetic field strength. To achieve a uniform magnetic field strength, the length (thickness) of the magnet must be approximately the same as or longer than the length of the magnetic wire 110 (see curve 4A in FIG. 5).

[0092] As shown by curve 4C in Figure 5, a magnet thickness of 1.5 mm fails to apply a stabilizing magnetic field to the magnetic wire 110. As shown by curve 4B in Figure 5, when a magnet thickness of 5 mm (slightly less than half the length of the magnetic wire 110) is used, a magnetic field strength exceeding the stabilizing magnetic field is obtained in the range of -3.5 mm to +3.5 mm, but the difference in magnetic field strength is significant depending on the position. When attempting to detect the relative rotation between the magnet and the power generation sensor, when the magnetic field strength at the center of the magnetic wire 110 reaches the operating magnetic field, the soft layer of the magnetic wire 110 begins to reverse its magnetization from the axial center. However, the magnetic field strength is insufficient in areas away from the axial center, preventing magnetization reversal from occurring along the entire length of the magnetic wire 110. Therefore, a magnet thickness of 5 mm fails to generate sufficient pulse voltage. As shown by curve 4A in Figure 5, when a magnet thickness of 11 mm, which is approximately equal to the length of the magnetic wire, a generally uniform magnetic field strength exceeding the stabilizing magnetic field is obtained in the range of -5 mm to +5 mm. Therefore, it is thought that, when detecting rotation, simultaneous reversal of the soft layer can be achieved along the entire length of the magnetic wire 110. However, since it is not possible to manufacture a ring-shaped magnet with such a magnet thickness (11 mm) by multi-pole magnetization, there are many design limitations, and problems arise such as miniaturization of the rotation detection device, assembly man-hours, and manufacturing costs.

[0093] 6A, 6B, 6C, and 7 show that most of the magnetic flux from the magnets 210, 211, and 212 is attracted and collected by the magnetic flux conduction pieces 130 and 131, which are L-shaped soft magnetic parts. When a strong magnetic field is applied, the magnetic wire 110 becomes magnetically saturated, and some of the magnetic flux leaks through the gap (distance L) between the pair of axially parallel portions 134, but most of the magnetic flux passes through a path from one end of the magnetic wire 110 to the other, so there is no effect on the output of the power generation sensor.

[0094] The magnetic flux from the magnets 210, 211, and 212 toward the intermediate portion of the magnetic wire 110 is blocked (shielded) by the magnetic flux conduction pieces 130 and 131 made of soft magnetic material, particularly by their axially parallel portions 134, and almost no magnetic flux enters the magnetic wire 110 from the intermediate portion. More specifically, the magnetic flux from the magnets 210, 211, and 212 enters from the detection-area-facing surface 134b of the axially parallel portion 134 of one of the magnetic flux conduction pieces 130, is conducted within the magnetic flux conduction piece 130, and reaches one of the first end 111 and the second end 112 of the magnetic wire 110. The magnetic flux from the other of the first end and the second end 112 of the magnetic wire 110 is conducted through the other magnetic flux conduction piece 131, reaches its axially parallel portion 134, and then reaches the magnets 210, 211, and 212 from its detection-area-facing surface 134b. Therefore, a uniform magnetic flux distribution is achieved over the entire length of the magnetic wire 110. In other words, a magnetic field of uniform strength that is parallel to the axial direction x of the magnetic wire 110 can be formed over the entire length of the magnetic wire 110.

[0095] As shown by curves 6A, 6B, and 6C in Figure 7, for magnet thicknesses of 1.5 mm, 5 mm, and 11 mm, a nearly uniform magnetic field strength exceeding the stabilizing magnetic field is achieved in the positional range of -4 mm to +4 mm, which corresponds to the distance between the opposing inner surfaces of the axis-orthogonal portion 133. Therefore, during rotation detection, simultaneous reversal of the soft layer occurs along the entire axial length of the magnetic wire 110, allowing for sufficient pulse output. Furthermore, for magnet thicknesses of 5 mm or less, a ring-shaped multipole magnet can be fabricated using existing multipole magnetization technology, resulting in fewer design limitations and various advantages, such as a smaller rotation detection device, reduced assembly time, and reduced manufacturing costs.

[0096] In order to maximize the power output, it is important that the magnetization direction of the entire magnetic wire is aligned, and that the magnetization reversal of the soft layer extends to the entire magnetic wire. For example, in the configuration without the magnetic flux conducting piece shown in Figure 4B, the magnetization direction of the magnetic wire is partially misaligned, and only a very small pulse signal is obtained.

[0097] 6A, 6B, 6C, and 7, in the power generating sensor 100 of the first embodiment, for all three types of magnets 210, 211, and 212 of different lengths, the magnetic flux conduction pieces 130 and 131 (particularly the axially parallel portion 134) function to correct the applied magnetic field in the axial direction x of the magnetic wire 110. As a result, a uniform magnetic field is applied to the entire magnetic wire 110, and a stable, high-power pulse signal can be output.

[0098] 6A of the first model, the length T (thickness) of the magnets 210, 211, and 212, which are magnetic field generating sources, is approximately the same as the distance D (see FIGS. 2A and 2B) between the inner surfaces of the pair of axis-orthogonal portions 133 of the power generation sensor 100 plus the width W (see FIGS. 2A and 2B) of the pair of axis-orthogonal portions 133. In this case, the first magnetic flux conduction piece 130 and the second magnetic flux conduction piece 131 correct the magnetic field in the axial direction x of the magnetic wire 110, and a uniform magnetic field is applied to the entire magnetic wire 110, as described above.

[0099] On the other hand, consider a second model that uses a ring-shaped multi-pole magnet as a magnetic field generating source. The ring-shaped multi-pole magnet is magnetized in a direction parallel to the central axis of the ring (a direction parallel to the rotation axis 201 when the rotation detection device is constructed). Due to this magnetization, the ring-shaped multi-pole magnet has N poles and S poles arranged alternately in the circumferential direction on the top and bottom surfaces perpendicular to the rotation axis 201 and on the inner and outer circumferential surfaces parallel to the rotation axis 201. Each magnetic pole has the same magnetization pitch in the circumferential direction. In the second model, the relationship between the magnetic wire 110 and the length (thickness) of the magnet in the axial direction x corresponds to the configuration of Figure 6B or 6C of the first model.

[0100] A sample of the second model was produced, and the ring-shaped multi-pole magnet was rotated around the central axis (rotation axis 201; see Figures 1A and 1B) to investigate experimentally whether the correction function of the magnetic flux conduction pieces 130, 131 was exerted in the same manner as in the first model.

[0101] In the sample of power generation sensor 100 used in the experiment, the magnetic wire length was 11 mm, the distance D between the axis-orthogonal portions 133 of magnetic flux conduction pieces 130, 131 was 7 mm, and the distance L between the proximal ends 134a of a pair of axis-parallel portions 134 was 2 mm. The sample of ring-shaped multi-pole magnet used in the experiment had an outer diameter of 14 mm, an inner diameter of 10 mm, a thickness T in the rotation axis direction of 5 mm, and six magnetic poles.

[0102] Using these samples, the ring-shaped multi-pole magnet was rotated forward and backward in the arrangement of the first embodiment, and the output characteristics were confirmed. As a result, the power generation sensor 100 output a stable, high-output pulse signal.

[0103] Even in a structure in which the thickness T of the ring-shaped multi-pole magnet, which is the magnetic field generating source, is less than the distance D at which the inner surfaces of a pair of axially orthogonal portions 133 of the power generating sensor 100 face each other (see Figures 6B and 6C), i.e., a structure in which the magnetic pole surfaces do not face both ends 111, 112 of the magnetic wire 110, when the magnetic pole boundary line (polarization) is aligned with the axial center position 113 of the magnetic wire 110 (see Figures 2A and 2B), it has been confirmed that the magnetic flux conducting pieces 130, 131 have the magnetic collecting and blocking (shielding) functions to effectively correct the magnetic field in the axial direction x of the magnetic wire 110.

[0104] [In-depth Experiment] In-depth experiments were conducted to determine whether the compensation function of the magnetic flux conduction pieces 130 and 131 was exhibited while changing the configuration of the sample of the second model power generation sensor 100.

[0105] In the in-depth experiment, the distance D between the axis-orthogonal portions 133 of the first and second magnetic flux conduction pieces 130 and 131 was set to 7 mm, and the distance L between the proximal ends 134a of the axis-parallel portions 134 was set to three values: 1.5 mm, 2 mm, and 3 mm. For each of these, the ring-shaped multi-pole magnet sample configuration was changed to six poles, an outer diameter of 14 mm, and an inner diameter of 10 mm, and the thickness T in the direction of rotation was varied between 1 mm and 5 mm to confirm the output. The results are shown in Figure 8. The horizontal axis represents the magnet thickness T, and the vertical axis represents the output pulse height, normalized to a maximum value of 1. The pulse height of the pulse signal is the average of the absolute values ​​of two positive and negative pulses when the ring-shaped multi-pole magnet is rotated in one direction (forward rotation) and two positive and negative pulses when the ring-shaped multi-pole magnet is rotated in the other direction (reverse rotation).

[0106] As can be seen from Figure 8, when the distance L is 1.5 mm, stable high output with a wave height of 0.8 or more is obtained when the magnet thickness T is approximately 1 mm or more. Also, when the distance L is 2 mm, stable high output with a wave height of 0.8 or more is obtained when the magnet thickness T is approximately 1.5 mm or more. And when the distance L is 3 mm, stable output with a wave height of 0.8 or more is obtained when the magnet thickness T is approximately 2 mm or more. From these results, it was confirmed that stable output can be obtained if the magnet thickness T is at least two-thirds of the distance L.

[0107] Even for a thin magnet with a thickness T equal to or less than the distance L, it is believed that as long as the ratio of thickness T to distance L is in the range of 2 / 3 to 1, the magnet and magnetic flux conduction pieces 130, 131 face each other with a small, constant gap between them, and magnetic flux lines flow radially from the magnet, so that the magnetic flux collection and shielding functions of the magnetic flux conduction pieces 130, 131 are not impaired. However, it is believed that the radial magnetic flux lines are affected by the magnetic path formed through the gap between the pair of magnetic flux conduction pieces 130, 131 when the magnet thickness T is less than 2 / 3 of the distance L.

[0108] As described above, the structure of this embodiment makes it possible to reduce the thickness T of the magnet to ⅔ of the distance L, and the rotation detector 10 can be configured using a thin ring-shaped multi-pole magnet that is magnetized in a direction parallel to the rotation axis 201. This makes it possible to realize a compact rotation detector 10 that is thin in the direction of the rotation axis 201.

[0109] [Second embodiment] A rotation detection device of a second embodiment is shown in Figure 9. The rotation detection device 11 includes the power generation sensor 100a of the modified example (see Figures 3A and 3B) arranged on a first support (not shown), and a magnetic field generation source 200 fixed to a second support 410 that rotates relative to the first support.

[0110] In the first embodiment, the power generation sensor 100a is disposed facing the outer circumferential surface of the ring-shaped multi-pole magnet, but in the second embodiment, the power generation sensor 100a is positioned on the inner circumferential surface side of the ring-shaped multi-pole magnet. In other words, the power generation sensor 100a is positioned inside the inner circumferential circle formed by the inner edge when the rotation locus around the rotation axis 201 of the magnetic field generating source is viewed in a direction parallel to the rotation axis 201.

[0111] A multi-pole magnet, which is a ring-shaped hard magnetic material magnetized in multiple poles, is magnetized simultaneously on both the top and bottom surfaces of the ring-shaped hard magnetic material (here, the top and bottom surfaces are based on the case where the rotating shaft 201 is aligned in the up-down direction) using a magnetizing yoke with an area equivalent to a predetermined magnetization pitch λ. This results in magnetization in the direction of the rotating shaft 201, and at this time, magnetic poles also appear on the inner peripheral surface of the hard magnetic material. Therefore, even if the power generation sensor 100a is placed on the inner peripheral surface, i.e., in the hollow region of the ring-shaped multi-pole magnet, a good output can be obtained, similar to that of the first embodiment.

[0112] In this structure, if a soft magnetic material is used for the second support 410, external stray magnetic fields other than those from the ring-shaped multi-pole magnet will not affect the power generating sensor 100a, thereby realizing a compact, high-output rotation detection device 11. Furthermore, by using the power generating sensor 100a of the modified example, the outer diameter of the rotation detection device 11 can be further reduced. Compared to the power generating sensor 100, the magnetic flux conduction pieces 130, 131 of the power generating sensor 100a do not protrude significantly on the side where the magnetic wire 110 is exposed. Therefore, the power generating sensor 100a is hardly affected by the magnetic field leaking from the inner circumferential portion (180 degrees out of phase with the rotation axis 201) on the opposite side of the inner circumferential portion of the ring-shaped multi-pole magnet that the axially parallel portion 134 of the power generating sensor 100a faces.

[0113] 10 shows a perspective view of a rotation detection device 12 according to a third embodiment. In addition to the rotation detection device 10 according to the first embodiment, the third embodiment further includes a magnetic sensor 500 that identifies the magnetic poles of a ring-shaped multi-pole magnet 200 at a predetermined position in the circumferential direction around the rotation axis 201. The magnetic sensor 500 may be formed of, for example, a Hall IC.

[0114] In this embodiment, the power generating sensor 100 is mounted on a first support 300 (e.g., a printed circuit board) disposed so as to face the magnetic pole faces of the multi-pole magnet 200. Specifically, the power generating sensor 100 is mounted on the main surface of the printed circuit board constituting the first support 300, opposite the ring-shaped multi-pole magnet 200. Therefore, the printed circuit board (first support 300) is interposed between the power generating sensor 100 and the ring-shaped multi-pole magnet 200, and the magnetic flux conduction pieces 130, 131 of the power generating sensor 100 face the magnetic pole faces of the ring-shaped multi-pole magnet 200 via the printed circuit board (first support 300). In this example, the magnetic sensor 500 is mounted on the printed circuit board constituting the first support 300.

[0115] For example, when the rotating shaft 201 rotates in the forward direction, the magnetic sensor 500 is in an ON state (first output state) when the power generation sensor 100 outputs a positive signal, and is in an OFF state (second output state different from the first output state) when the power generation sensor 100 outputs a negative signal. Also, when the rotating shaft 201 rotates in the reverse direction, the magnetic sensor 500 is in an OFF state (second output state) when the power generation sensor 100 outputs a positive signal, and is in an ON state (first output state) when the power generation sensor 100 outputs a negative signal. The relative arrangement of the power generation sensor 100, the ring-shaped multi-pole magnet 200, and the magnetic sensor 500 is designed so that the magnetic sensor 500 is in these output states.

[0116] This makes it possible to detect the direction of rotation of the rotary motion by combining the output signal of the power generation sensor 100 and the output signal of the magnetic sensor 500. The combination of the ON / OFF of the magnetic sensor 500 and the forward / reverse rotation of the rotating shaft 201 may be opposite to that described above.

[0117] 11A shows a perspective view of a rotation detector 13 according to a fourth embodiment. The magnetic field generator 200 of the first to third embodiments is configured with a single magnet made of a ring-shaped hard magnetic material magnetized with multiple poles. The magnetic field generator 200 of the fourth embodiment includes a plurality of individual magnets 240 of the same shape and size attached to the second support 420 at equal intervals along the circumferential direction. The individual magnets 240 are arranged so that the magnetization direction of each individual magnet is parallel to the rotation axis 201 and that adjacent magnetic poles in the circumferential direction have different polarities, thereby constituting a multi-pole magnetic field generator 200.

[0118] The power generation sensor 100 has the same configuration as that of the first embodiment. The position of this power generation sensor 100 is such that the axial direction x of the magnetic wire 110 is parallel to the rotation axis 201, and the axially parallel portion 134 (detection region 140; see FIG. 2B ) faces the inner circumferential surface of the cylindrical rotation locus of the multiple individual magnets 240. The symmetry plane 115, which is set at the axial center position of the magnetic wire 110 of the power generation sensor 100, coincides with the center 242 of the multiple individual magnets 240 in the direction parallel to the rotation axis 201, i.e., the position corresponding to half the thickness T of the magnets (see FIG. 11B ). The configuration shown in FIG. 11B is substantially the same as the configuration shown in FIG. 1B .

[0119] 11A shows a 14-pole configuration in which 14 individual magnets 240 are arranged at equal intervals in the circumferential direction around the rotation axis 201. Of course, the number of individual magnets 240 may be other than 14. Furthermore, the power generation sensor 100 may be installed so as to face the outer circumferential surface of the cylindrical rotation locus of the individual magnets 240 that make up the magnetic field generation source 200. Although FIGS. 11A and 11B show individual magnets 240 that are rectangular parallelepiped shaped, individual magnets of other shapes may also be used.

[0120] The configuration of the fourth embodiment is advantageous for detecting the rotation of a large rotating object, such as the hub of a bicycle wheel. Specifically, if a single ring-shaped multi-pole magnet were used to detect the rotation of a large rotating object, the mechanical strength would be insufficient, resulting in the risk of cracking. Therefore, by configuring the magnetic field generator 200 using multiple individual magnets 240, durability can be improved.

[0121] 12 and 13 are perspective views of rotation detection devices 14 and 15 of the fifth and sixth embodiments, respectively. While the rotation detection devices 10, 11, 12, and 13 of the first to fourth embodiments each include a single power generation sensor 100, 100a, the rotation detection devices 14 and 15 of the fifth and sixth embodiments each include a plurality of power generation sensors 100.

[0122] For example, in a rotation detection device 14 of a fifth embodiment shown in Fig. 12, three power generation sensors 100 are arranged at phase intervals of 120 degrees on a circle centered on a rotation axis 201 along the outer periphery of a magnetic field generation source 200 composed of a ring-shaped multi-pole magnet. In this example, the ring-shaped multi-pole magnet that constitutes the magnetic field generation source 200 has six poles. With this configuration, the number of output signals from the rotation detection device 14 of the fifth embodiment is three times that of the first embodiment.

[0123] 13 includes a magnetic field generation source 200 configured with a plurality of individual magnets 240 (14 in the illustrated example) as in the fourth embodiment, and a plurality of power generation sensors 100 (three in this example) arranged at phase intervals of 120 degrees on a circumference centered on the rotation axis 201, along the inner circumference of a ring-shaped rotation locus centered on the rotation axis 201 of the magnetic field generation source 200. With this configuration, the number of output signals from the rotation detection device 15 of the sixth embodiment is three times that of the fourth embodiment.

[0124] According to these configurations, providing multiple power generating sensors 100 improves resolution and rotation detection accuracy. The total amount of power generated by the rotation detection devices 14, 15 during one rotation of the magnetic field generating source 200 also improves. While the fifth and sixth embodiments show examples in which the number of power generating sensors 100 is three and they are arranged at phase intervals of 120 degrees, the number and phase interval of the power generating sensors 100 are not limited to these. Of course, the power generating sensor 101a of the modified example described above may also be used.

[0125] In the above-described embodiment, the power generating sensors 100 and 100a are mainly arranged so that the axial direction x of the magnetic wire 110 is parallel to the rotation axis 201. However, as mentioned above, "parallel" in this case does not mean strictly parallel. In addition, the power generating sensors 100 and 100a, which are configured to induce magnetic flux to both ends of the magnetic wire 110 using the magnetic flux conduction pieces 130 and 131, can generate a sufficient pulse voltage in response to the rotation of the magnetic field generating source 200, even if the magnetic wire 110 and the rotation axis 201 are not necessarily parallel. Furthermore, the power generating sensors 100 and 100a can generate a sufficient pulse voltage in response to the rotation of the magnetic field generating source 200, even if the axial center of the magnetic wire 110 does not exactly coincide with the center position of the magnet constituting the magnetic field generating source 200 in the direction parallel to the rotation axis 201.

[0126] 14 and 15A to 15C, consider a first imaginary plane P1 and a second imaginary plane P2 that pass through one end and the other end, respectively, of the magnetic field generation source 200 in a direction parallel to the rotation axis 201 and are perpendicular to the rotation axis 201. In this case, it is sufficient that the center of the magnetic wire 110 (axial center position 113) is located in a space V between the first imaginary plane P1 and the second imaginary plane P2, and the axis-orthogonal portions 133 are located outside the space V. In FIGS. 15A to 15C, the inner surfaces of the pair of axis-orthogonal portions 133 that face each other are located outside the space V, and the entire axis-orthogonal portions 133 are located outside the space V.

[0127] With this configuration, the power generation sensors 100 and 100a are arranged so that the magnetic wire 110 intersects with a plane perpendicular to the rotation axis 201. By arranging the power generation sensors 100 and 100a in this manner, the projection area of ​​the rotation detection device in a direction parallel to the rotation axis 201 can be reduced.

[0128] On the other hand, by arranging the axis-orthogonal portion 133 outside the space V between the first imaginary plane P1 and the second imaginary plane P2, the length of the magnetic field generation source 200 in the direction parallel to the rotation axis 201 (i.e., the distance between the first imaginary plane P1 and the second imaginary plane P2) becomes shorter than the length of the power generation sensors 100, 100a in the same direction. Therefore, since the length (thickness) of the magnetic field generation source 200 in the direction parallel to the rotation axis 201 is small, it can be formed by a magnet whose magnetization direction (magnetization direction) is parallel to the rotation axis 201. As described above, such a magnetic field generation source 200 can be formed by a ring-shaped magnet made by multi-pole magnetizing a hard magnetic material in a direction parallel to the rotation axis 201.

[0129] Because the axis-orthogonal portions 133 are arranged outside the space V between the first imaginary plane P1 and the second imaginary plane P2, the pair of axis-parallel portions 134 are located closer to the magnetic field generating source 200 than the pair of axis-orthogonal portions 133. In addition, the pair of axis-parallel portions 134 are magnetically coupled to magnetic poles of different polarities (magnetic poles located opposite each other in a direction parallel to the rotation axis 201) of the magnetic field generating source 200. Since the axis-parallel portions 134, which are parallel to the axial direction of the magnetic wire 110, are located between the magnetic field generating source 200 and the magnetic wire 110, the magnetic field applied from the magnetic field generating source 200 is collected by the magnetic flux conducting pieces 130, 131 made of soft magnetic material and guided to both ends of the magnetic wire 110. Therefore, the magnetic poles do not need to be located near both ends of the magnetic wire 110. Additionally, the magnetic flux directed toward the middle of the magnetic wire 110 is shielded by the axis-parallel portions 134. Therefore, by using the magnetic field generating source 200 having a small length (thickness) in the direction parallel to the rotation axis 201 and magnetic poles whose magnetization direction is parallel to the rotation axis 201, it is possible to efficiently concentrate the magnetic field at both ends of the magnetic wire 110. This makes it possible to make the magnetic field strength uniform at different positions in the axial direction of the magnetic wire 110.

[0130] Moreover, as described above, both ends of the magnetic wire 110 are fixed to the wire placement portions 130a, 131a provided in the axis-orthogonal portion 133, and the wire placement portions 130a, 131a are configured as holes or grooves penetrating the axis-orthogonal portion 133. Therefore, the magnetic wire 110 and the axis-orthogonal portion 133 can be reliably magnetically coupled, and a magnetic circuit can be formed by the magnetic wire 110 and the magnetic flux conduction pieces 130, 131. This makes it possible to suppress magnetic flux entering the middle portion of the magnetic wire 110 through the magnetic flux conduction pieces 130, 131, and to efficiently guide the magnetic flux to both ends of the magnetic wire 110. This makes it possible to make the magnetic field strength at different positions in the axial direction of the magnetic wire 110 more uniform.

[0131] In this way, the magnetic field in the axial direction can be applied efficiently and uniformly to the magnetic wire 110, so that the large Barkhausen effect can be sufficiently induced even if the magnetic pole pitch λ in the rotation direction is small. In other words, a rotation detection device that is small and can obtain a high-output signal can be realized.

[0132] Next, as shown in Figure 14 and Figures 15A to 15C, consider a third imaginary plane P3 that passes through the center of the magnetic wire 110 and is perpendicular to the rotation axis 201. In this case, as shown in Figures 15A and 15B, the pair of axis-parallel portions 134 are preferably arranged on opposite sides of the third imaginary plane P3 so as not to intersect with the third imaginary plane P3. With this configuration, the pair of axis-parallel portions 134 are efficiently magnetically coupled to magnetic poles of different polarities (magnetic poles located opposite each other in a direction parallel to the rotation axis 201) of the magnetic field generation source 200, so that magnetic flux can be more efficiently concentrated at both ends of the magnetic wire 110.

[0133] Although several embodiments of the present invention have been described, the present invention is not limited to the above-described embodiments, and various design modifications can be made within the scope of the claims.

[0134] 10, 11, 12, 13, 14, 15: Rotation detection device 100, 100a: Power generation sensor 110: Magnetic wire 111: First end 112: Second end 113: Axial center position 120: Coil 130: Flux conduction piece 130a: Wire arrangement portion 131: Flux conduction piece 131a: Wire arrangement portion 133: Axial-orthogonal portion 134: Axial-parallel portion 134a: Proximal end 140: Detection area 200: Magnetic field generation source (ring-shaped multi-pole magnet) 201: Rotation axis 202: Magnet center 240: Individual magnet 242: Magnet center 300: First support 400, 410, 420: Second support 500: Magnetic sensor D: Distance L: Distance T: Thickness x: Axial direction y: Width direction z: Orthogonal to the axis λ: Magnetic pole pitch

Claims

1. A rotation detection device comprising: a power generating sensor disposed on a first support; and a magnetic field generating source fixed to a second support which rotates around a rotation axis relative to the first support; wherein the power generating sensor comprises a magnetic wire which exhibits a large Barkhausen effect, a coil wound around the magnetic wire, and a pair of magnetic flux conducting pieces made of soft magnetic bodies which are symmetrical with respect to a symmetry plane set at the center position of the axial direction of the magnetic wire; wherein the pair of magnetic flux conducting pieces comprises a pair of axis-orthogonal portions extending parallel to each other in a direction perpendicular to the axial direction from both ends of the magnetic wire, and a pair of axis-parallel portions which extend from tips of the axis-orthogonal portions in directions approaching each other along the axial direction, with the proximal ends facing each other with a gap in the axial direction, and the axis-orthogonal portions have wire arrangement portions consisting of holes or grooves which penetrate in the axial direction and to which both ends of the magnetic wire are fixed; and the power generating sensor is configured so that the opposite side of the axial parallel portions to the magnetic wire is a detection area, A rotation detection device in which the magnetic field generating source is arranged to pass through the detection area, is magnetized in a direction parallel to the rotation axis, and has a plurality of magnetic poles arranged in a circumferential direction around the rotation axis, the plurality of magnetic poles being arranged alternately to have different polarities alternately in the circumferential direction, the power generation sensor faces the magnetic field generating source with a gap in a direction perpendicular to the rotation axis, the center of the magnetic wire is located in the space between a first imaginary plane and a second imaginary plane perpendicular to the rotation axis, passing through one end and the other end of the magnetic field generating source in a direction parallel to the rotation axis, and the axis-orthogonal portion is located outside the space between the first imaginary plane and the second imaginary plane.

2. A rotation detection device as claimed in claim 1, wherein the magnetic wire of the power generating sensor is arranged parallel to the rotation axis.

3. A rotation detection device according to claim 1 or 2, wherein the length of the magnetic field source in a direction parallel to the rotation axis is equal to or less than half the length of the magnetic wire.

4. A rotation detection device as described in any one of claims 1 to 3, wherein the length of the magnetic field generating source in a direction parallel to the rotation axis is less than the distance between the inner surfaces of the pair of axis-orthogonal portions of the power generating sensor on the symmetrical plane side.

5. A rotation detection device as claimed in any one of claims 1 to 4, wherein the length of the magnetic field generating source in a direction parallel to the rotation axis is at least 2 / 3 of the axial distance between the adjacent ends of the pair of axial parallel portions.

6. A rotation detection device as claimed in any one of claims 1 to 5, wherein the axial spacing between the adjacent ends of the pair of axially parallel portions is 5% to 50% of the axial distance between the pair of axially orthogonal portions at the position where they are joined to the magnetic wire.

7. A rotation detection device as claimed in any one of claims 1 to 6, wherein the magnetic field generating source includes a single magnet in which a ring-shaped hard magnetic body is magnetized in multiple poles to form the multiple magnetic poles, or a plurality of magnets of substantially the same shape and size which respectively constitute the multiple magnetic poles.

8. A rotation detection device according to any one of claims 1 to 7, wherein the power generation sensor is positioned outside the outer circumferential circle of the magnetic field generation source.

9. A rotation detection device according to any one of claims 1 to 7, wherein the power generation sensor is positioned inside an inner circumference of the magnetic field generation source.

10. A rotation detection device as claimed in any one of claims 1 to 9, wherein a groove constituting the wire placement section is provided on the surface of the magnetic flux conducting piece not facing the magnetic field source.

11. A rotation detection device according to any one of claims 1 to 10, comprising a plurality of said power generation sensors.

12. A rotation detection device according to any one of claims 1 to 11, further comprising a magnetic sensor for identifying the magnetic pole at a predetermined position in the circumferential direction about the rotation axis.

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