Rotation detection device

Abstract

To provide a rotation detection device which is compact and is capable of obtaining a high output signal by a power generation sensor having a magnetic flux conduction piece and a magnetic field generation source.SOLUTION: A rotation detection device 10 includes: a power generation sensor 100 disposed to a first support body 300; and a magnetic field generation source 200 that rotates around and relatively to a revolving shaft 201 and is secured to a second support body 400. The power generation sensor includes: a magnetic wire 110; a coil 120; and a pair of magnetic flux conduction pieces 130, 131 in which is formed a wire arrangement unit for securing both ends of the magnetic wire and composed of penetrations or grooves. The magnetic flux conduction pieces have an axis orthogonal part 133 and an axis parallel part 134. The magnetic field generation source is provided with a plurality of magnetic poles arranged in the circumferential direction around the revolving shaft, and the plurality of magnetic poles is arranged alternately in the circumferential direction so that their polarities are differentiated alternately. The direction of magnetization of each magnetic pole is parallel to the revolving shaft.SELECTED DRAWING: Figure 1A

Description

Technical Field

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

Background Art

[0002] A magnetic wire having the giant Barkhausen effect (giant Barkhausen jump) is known as a Weigand wire or a pulse wire. This magnetic wire includes a core portion and a skin portion provided so as to surround the core portion. One of the core portion and the skin portion is a soft (soft magnetic) layer in which the magnetization direction reverses even with a weak magnetic field, and the other of the core portion and the skin portion is a hard (hard magnetic) layer in which the magnetization direction does not reverse unless a strong magnetic field is applied. By winding a coil around such a magnetic wire, a power generation sensor can be configured.

[0003] When the hard layer and the soft layer are magnetized in the same direction along the axial direction of the wire, when the external magnetic field strength in the direction opposite to the magnetization direction increases and reaches a certain magnetic field strength, the magnetization direction of the soft layer reverses. This reversal of the magnetization direction propagates throughout the wire with a certain portion of the magnetic wire as the starting position, and the magnetization directions of the soft layers reverse all at once. At this time, the giant Barkhausen effect appears, and a pulse signal is induced in the coil wound around the magnetic wire. When the above-described external magnetic field strength further increases and reaches a certain magnetic field strength, the magnetization direction of the hard layer reverses.

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

[0005] The output voltage obtained from the coil is constant regardless of the change speed of the input magnetic field (external magnetic field), and has characteristics such as no chattering because it has hysteresis characteristics with respect to the input magnetic field. Therefore, the pulse signal generated from the coil is used in a rotation detection device or the like. Since the output from the coil has power, a power generation type sensor (power generation sensor) that does not require the supply of external power can be configured. That is, the peripheral circuit can also be operated by the output energy of the coil without the supply of external power.

[0006] In order for the large Barkhausen effect to occur, it is necessary for the magnetization direction of only the soft layer to reverse from the state where the magnetization directions of the hard layer and the soft layer are the same. Even if the magnetization direction of only the soft layer reverses in a state where the magnetization directions of the hard layer and the soft layer do not match, no pulse signal is generated, or if it is generated, it is very small.

[0007] Also, in order to maximize the obtained power, it is important that the magnetization reversal of the soft layer spreads throughout the entire magnetic wire from the state where the magnetization directions of the entire magnetic wire are aligned. If the magnetization directions of the magnetic wire are not partially aligned, only a very small pulse signal can be 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 the power generation sensor, a total of two pulse signals, one positive pulse signal and one negative pulse signal, are generated per cycle. By using a magnet as the source of the magnetic field and applying an alternating magnetic field to the power generation sensor by the rotational movement of the magnet, and counting the generated pulse signals, the rotational position can be detected.

[0009] A rotation detection device that detects a magnetic field change associated with the rotation of a magnet around a rotation axis using a magnetic wire that exhibits the large Barkhausen effect can be broadly classified into an axial gap type and a radial gap type. The axial gap type has a configuration in which a power generation 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 generation sensor is arranged at a distance from the magnet in the radial direction of the rotation radius orthogonal to the rotation axis. When it is desired to configure a rotation detection device with a small diameter, the radial gap type is more advantageous. In the case of the radial gap type, there are further three types of configurations depending on the arrangement direction of the magnetic wire. That is, a configuration in which the magnetic wire is arranged along the radial direction of rotation (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). Among these, the configuration in which the magnetic wire is arranged parallel to the rotation axis has the advantage that it is easy to fabricate a rotation detection device with a small diameter because the projected area in the direction parallel to the rotation axis is small.

[0010] FIGS. 3 to 10 of Patent Document 1 show a rotation detection device having a configuration in which a magnetic wire is arranged parallel to the rotation axis in the radial gap type. That is, the magnetic wire is arranged on the outer peripheral portion of the tone wheel with its line length direction parallel to the rotation axis of the tone wheel. In the forms of FIGS. 3 to 7 of Patent Document 1, the tone wheel is composed of a multi-pole magnet in which the magnetized portions of the N pole and the S pole are alternately arranged in the circumferential direction. The magnetization direction of the magnetized portion is the radial direction of rotation. In the forms of FIGS. 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 the magnetized portions adjacent to each other in the circumferential direction are opposite to each other.

[0011] As shown in FIG. 4 of Patent Document 1, in the configurations of FIGS. 3 and 5 of the same document in which the magnetization direction is the radial direction of the rotation radius, semicircular magnetic fluxes are formed around the multi-pole magnet, and the magnetic fluxes enter not only both ends of the magnetic wire but also the intermediate portion. Therefore, the magnetic field strength becomes non-uniform in each part in the axial length direction of the magnetic wire. When the length of the magnet in the direction 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 intermediate portion of the magnetic wire, so that the magnetic field strength in the magnetic wire becomes even more non-uniform. In the configuration of FIG. 6 of the same document, the S pole and the N pole are separated in the direction parallel to the rotation axis, and a demagnetized portion is provided therebetween. As a result, as shown in FIG. 7 of the same document, the magnetic flux entering the intermediate portion of the magnetic wire is reduced. However, the formation of the semicircular magnetic flux remains unchanged, and the magnetic flux cannot be efficiently concentrated at both ends of the magnetic wire, and the magnetic flux entering the intermediate portion of the magnetic wire cannot be sufficiently reduced. Therefore, the problem that the magnetic field strength becomes non-uniform in each part in the axial length direction of the magnetic wire cannot be sufficiently solved. When the distance between the N pole and the S pole in the direction 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 intermediate portion of the magnetic wire, so that the magnetic field strength in the magnetic wire becomes even more non-uniform.

[0012] On the other hand, as shown in FIG. 9 of Patent Document 1, in the configurations of 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 the direction parallel to the rotation axis. Therefore, only a part of the magnetic flux exits the magnet and greatly wraps around to reach both ends of the magnetic wire. Therefore, it is difficult to efficiently transmit a sufficient magnetic field to the magnetic wire. When the length of the magnet is shortened (for example, shorter than the magnetic wire), the magnetic flux emitted from the magnet enters the intermediate portion of the magnetic wire, so that the magnetic field strength in the magnetic wire becomes non-uniform. Therefore, the length of the magnet must be equal to or longer than that of the magnetic wire.

[0013] A magnet that is long in a direction parallel to the rotation axis and magnetized in a direction parallel to the rotation axis cannot be manufactured by multi-pole magnetization of a cylindrical hard magnetic material. In reality, the only option is to attach a bar magnet to a cylindrical yoke. The thickness of the hard magnetic material that can be magnetized by the magnetic flux from the magnetization yoke used for multi-pole magnetization is at most about 3 mm. Even when the hard magnetic material is sandwiched between magnetization yokes from both sides for multi-pole magnetization, the magnetizable thickness is at most about 5 mm. If the number of poles is increased to enhance the rotation detection resolution, the magnetizable thickness becomes even smaller. On the other hand, it takes a lot of man-hours to attach a bar magnet to a cylindrical yoke. In particular, the work of adhering the magnet to a predetermined position on the cylindrical yoke against the magnetic force between the magnets is difficult. Moreover, if the diameter is reduced or the number of poles is increased, the man-hours increase further and the work difficulty also increases.

[0014] On the other hand, a cylindrical multi-pole magnet having a plurality of magnetic poles magnetized in the radial direction of the rotation radius can be manufactured by performing multi-pole magnetization on a cylindrical hard magnetic material, thereby reducing the man-hours. However, it is difficult to realize a complex magnetic pole pattern such as those in FIGS. 3 to 7 of Patent Document 1 by multi-pole magnetization of a single cylindrical magnet. In reality, it is necessary to install two cylindrical multi-pole magnetization magnets with their phases shifted so that their polarities are opposite. Therefore, it requires more materials and man-hours compared to a single cylindrical magnet. Also, unless the width of the magnetization pitch in the circumferential direction (the circumferential width of the magnetic poles) is large, a stabilizing magnetic field with a certain intensity cannot be applied to the magnetic wire. Thus, the diameter of the cylindrical multi-pole magnet inevitably becomes large, and accordingly, the rotation detection device becomes large.

[0015] Patent Document 2 explains the problems of a configuration using a magnet magnetized in a direction parallel to the rotation axis and a magnetic wire extending in a direction parallel to the rotation axis (corresponding to the forms in FIGS. 8 to 10 of Patent Document 1) (paragraphs 0004 to 0006 of the same document). That is, when trying to reduce the diameter or increase the resolution, the interval between the magnets in the circumferential direction becomes short, and magnetic flux tends to concentrate in a path that shorts the N pole and S pole of adjacent magnets. As a result, the magnetic flux passing through the magnetic wire decreases, making it difficult to obtain the 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 forming unit. The detection unit includes a magnetic flux conductor between a detection element formed by winding a coil around a magnetic wire and the magnetic field forming unit. The detection element is disposed on the inner peripheral side of the orbit of the magnetic field forming unit such that the longitudinal direction of the magnetic wire is parallel to the rotation axis. The magnetic field forming unit includes a cylindrical rotating body made of a soft magnetic material and a plurality of permanent magnets arranged in the circumferential direction of the rotating body. These plurality of permanent magnets are magnetized (polarized) in a direction perpendicular to the rotation axis and are installed on the inner peripheral surface of the rotating body such that different poles are arranged adjacent to each other in the circumferential direction. With this configuration, it is described that a small-sized device can be achieved.

[0017] In the structure shown in FIGS. 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, like-polarity magnetic poles face each other at both ends of the magnetic wire extending in the direction parallel to the rotation axis. Thus, two magnetic flux conductors (yokes) are provided, and the two magnetic flux conductors use magnets of different poles as detection regions. Specifically, the two magnetic flux conductors each have a plate-shaped base portion facing both ends of the magnetic wire and a protruding portion protruding from the base portion toward magnets of two different poles. Therefore, the protruding portions of the two magnetic flux conductors protrude in different directions.

[0018] Such a complicated configuration not only makes the manufacturing process complicated, but also the direction of the protruding portion, the interval between adjacent magnets, the distance (gap) from the magnetic flux conductor to the magnet, etc. affect the detection performance. Therefore, the performance of the rotation detection device depends on the assembly accuracy. Moreover, since the two magnetic flux conductors need to induce magnetic flux from magnets of poles at different positions in the circumferential direction, the structure depends on the circumferential magnetic pole pitch. Therefore, an individual design according to the configuration of each rotation detection device is required, lacking in versatility.

[0019] In the structure of FIG. 10 of the same document, since almost no magnetic field is applied to the magnetic flux conductor on one side, the distance (gap) from the magnetic flux conductor to the magnet becomes very narrow, and measures must be taken against the cogging that occurs during rotational movement due to the attractive force between the magnetic flux conductor and the magnet. The structure of FIG. 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 the magnetic flux conductors on both sides. However, in this structure, twice the number of magnets is required, and the assembly of the device is complicated.

[0020] Furthermore, as shown in FIGS. 5, 6, 9, and 11 of the same document, many parts of the magnetic flux from the magnet magnetized in a direction perpendicular to the rotation axis enter the middle part of the magnetic wire. Therefore, the magnetic field strength in each part in the axial direction of the magnetic wire does not become uniform. Even in the configurations of FIGS. 5 and 6 of the same document where the magnetic flux conductor extends 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] Thus, when the magnetic field generation source is a multi-pole rotating body and an attempt is made to apply a magnetic field parallel to the axial direction with uniform intensity to the entire magnetic wire with the magnetic wire parallel to the rotation axis, the structure becomes complicated, miniaturization is difficult, and versatility is also lacking.

Prior Art Documents

Patent Documents

[0022]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0023] Therefore, one embodiment of the present invention provides a rotation detection device that can solve at least one of the above-described 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 peripheral portion and / or the inner peripheral portion of a rotating body and a power generation sensor.

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

Means for Solving the Problems

[0026] One embodiment of this invention provides a rotation detection device having the features exemplified below.

[0027] 1. A power generation sensor disposed on a first support, and A magnetic field generation source fixed to a second support that rotates relative to the first support about a rotation axis, the rotation detection device comprising: The power generation sensor includes a magnetic wire that exhibits the giant Barkhausen effect, a coil wound around the magnetic wire, and a magnetic flux conduction piece composed of a pair of soft magnetic bodies that are symmetric with respect to a symmetry plane set at the central position in the axial direction of the magnetic wire. The pair of magnetic flux conduction pieces includes a pair of axially orthogonal portions that extend parallel to each other in a direction orthogonal to the axial direction from both ends of the magnetic wire, and a pair of axially parallel portions that extend in a direction approaching each other along the axial direction from the tip ends of the axially orthogonal portions, and the proximal ends face each other with a space in the axial direction. The axially orthogonal portion has a wire arrangement portion formed by a hole or a groove that penetrates in the axial direction and to which both ends of the magnetic wire are fixed. The power generation sensor is configured such that a region opposite to the magnetic wire with respect to the axially parallel portion is a detection region. The magnetic field generation source is arranged to pass through the detection region, magnetized (magnetized) in a direction parallel to the rotation axis, and includes a plurality of magnetic poles arranged in a circumferential direction around the rotation axis (typically arranged at equal intervals), and the plurality of magnetic poles are alternately arranged so as to have different polarities alternately in the circumferential direction. The power generation sensor has a gap in a direction perpendicular to the rotation axis and faces the magnetic field generation source. A rotation detection device in which the center of the magnetic wire is located in a space between a first virtual plane and a second virtual plane perpendicular to the rotation axis through one end and the other end in a direction parallel to the rotation axis of the magnetic field generation source, and the axis orthogonal portion is located outside the space between the first virtual plane and the second virtual plane.

[0028] According to this configuration, the center of the magnetic wire is located in a space between a first virtual plane and a second virtual plane perpendicular to the rotation axis through both ends in a direction parallel to the rotation axis of the magnetic field generation source. Further, the axis orthogonal portion is located outside that space. Thereby, the power generation sensor is arranged such that the magnetic wire intersects a plane perpendicular to the rotation axis. With such an arrangement of the power generation sensor, the projected area in a direction parallel to the rotation axis of the rotation detection device can be reduced.

[0029] On the other hand, by arranging the axis orthogonal portion outside the space between the first virtual plane and the second virtual plane, the length of the magnetic field generation source in the direction parallel to the rotation axis (that is, the distance between the first virtual plane and the second virtual plane) becomes shorter than the length of the power generation sensor in the same direction. Therefore, the magnetic field generation source can be configured by a magnet having a small length (thickness) in a direction parallel to the rotation axis and a magnetization direction parallel to the rotation axis. Such a magnetic field generation source can be configured, for example, by a ring-shaped magnet produced by performing multi-pole magnetization on a hard magnetic material in a direction parallel to the rotation axis.

[0030] With a configuration in which the axial orthogonal portions are arranged outside the space between the first virtual plane and the second virtual plane, the pair of axial parallel portions will be located closer to the magnetic field generation source than the pair of axial orthogonal portions. In addition, the pair of axial parallel portions are each magnetically coupled to magnetic poles of different polarities of the magnetic field generation source (magnetic poles located on opposite sides of each other with respect to the direction parallel to the rotation axis). Since an axial parallel portion parallel to the axial direction of the magnetic wire is located between the magnetic field generation source and the magnetic wire, the magnetic field applied from the magnetic field generation source is collected by the magnetic flux conduction piece of the soft magnetic material and guided to both ends of the magnetic wire. Therefore, it is not necessary for the magnetic poles to be located near both ends of the magnetic wire. In addition, the magnetic flux heading toward the intermediate portion in the axial direction of the magnetic wire is shielded by the axial parallel portion. Therefore, while using a magnetic field generation source with a small length (thickness) in the direction parallel to the rotation axis and a magnetization direction parallel to the rotation axis, the magnetic field can be efficiently collected at both ends of the magnetic wire. Thereby, the magnetic field strength in each part in the axial direction of the magnetic wire can be made uniform.

[0031] Moreover, both ends of the magnetic wire are fixed to the wire arrangement portion provided in the axial orthogonal portion, and the wire arrangement portion is composed of a hole or a groove penetrating the axial orthogonal portion. Therefore, reliable magnetic coupling can be achieved between the magnetic wire and the axial orthogonal portion, and a magnetic circuit can be formed by the magnetic wire and the magnetic flux conduction piece. Thereby, the magnetic flux entering the intermediate portion of the magnetic wire through the magnetic flux conduction piece can be suppressed, and the magnetic flux can be efficiently guided to both ends of the magnetic wire. As a result, the magnetic field strength in each part in the axial direction of the magnetic wire can be made even more uniform.

[0032] In this way, since the magnetic field in the axial direction can be efficiently and uniformly applied to the magnetic wire, even if the magnetic pole pitch in the rotation direction is fine, the large Barkhausen effect can be sufficiently induced. In other words, a rotation detection device capable of obtaining a small-sized and 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] With this configuration, the projected area of the power generation sensor in the direction parallel to the rotation axis is minimized, so that a small rotation detection device can be configured.

[0035] In this configuration, it is preferable that the extending direction of the magnetic wire is parallel to the rotation axis of the rotational movement, the shaft parallel portion side faces the magnetic field generation source, and the symmetry plane passes through the center of the magnetic field generation source in the direction parallel to the rotation axis.

[0036] According to this configuration, while the power generation sensor is arranged such that the axial direction of the magnetic wire is parallel to the rotation axis of the rotating body, for example, a magnetic field generation source is configured by a multi-pole magnet having a multi-pole magnetization pattern magnetized parallel to the rotation axis, and magnetic fluxes from magnetic poles of different polarities can be concentrated at both ends of the magnetic wire via a pair of magnetic flux conduction pieces. Thereby, when the multi-pole magnet rotates together with the rotation axis, the magnetic wire exhibits the giant Barkhausen effect and a pulse voltage is generated.

[0037] "Parallel" means that within the range allowing assembly errors and within the range allowing an inclination within the range where the magnetic wire can exhibit the giant Barkhausen effect, the axial direction of the magnetic wire follows the direction parallel to the rotation axis. For example, it is allowed that the axial direction of the magnetic wire has an inclination of 20 degrees or less (more preferably 10 degrees or less) with respect to the direction parallel to the rotation axis.

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

[0039] With this configuration, a rotation detection device including a small magnetic field generation source can be realized.

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

[0041] With this configuration, a rotation detection device including a small magnetic field generation source can be realized.

[0042] 5. The length of the magnetic field generating source in the direction parallel to the rotation axis is 2 / 3 or more of the axial interval (distance) between the proximal ends of the pair of axially parallel portions. The rotation detection device according to any one of items 1 to 4.

[0043] With this configuration, the output due to the large Barkhausen effect of the properties of the magnetic wire can be almost completely extracted, and furthermore, a rotation detection device with a thin and lightweight structure can be realized by the magnetic field generating source.

[0044] 6. The axial interval (distance) between the proximal 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 coupling position with the magnetic wire. The rotation detection device according to any one of items 1 to 5.

[0045] With this configuration, the magnetic field collection efficiency and the magnetic shielding efficiency by the axially parallel portions are improved, and the magnetic field from the magnetic field generating source can be efficiently concentrated at both ends of the magnetic wire. Thereby, the magnetic field intensity in each part in the axial direction of the magnetic wire can be made more uniform, and the large Barkhausen effect of the properties of the magnetic wire can be extracted.

[0046] 7. The plurality of magnetic field generating sources include one magnet in which a plurality of magnetic poles are formed by multi-pole magnetization of a ring-shaped hard magnetic material, or a plurality of substantially identical-shaped and same-sized magnets each constituting the plurality of magnetic poles. The rotation detection device according to any one of items 1 to 6.

[0047] For a multi-pole magnet formed by multi-pole magnetization of a ring-shaped hard magnetic material, typically, a magnet used in an electric motor can be applied. Since a magnet magnetized (magnetized) in a direction parallel to the rotation axis can be manufactured using a simple yoke, an inexpensive magnet can be used. A combination of such a multi-pole magnet and a power generation sensor having a magnetic flux conduction piece can be easily manufactured, and a power generation sensor that can efficiently collect magnetic flux by the magnetic flux conduction piece can be generally used regardless of the design of the magnet or the like. Therefore, a rotation detection device that is versatile, simple and small in structure and can detect rotation can be realized.

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

[0049] With this configuration, a small and high-output rotation detection device can be realized while securing a large hollow area for the magnetic field generation source.

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

[0051] With this configuration, the influence of an external stray magnetic field other than the magnetic field of the magnetic field generation source on the power generation sensor is reduced, so a small and high-output rotation detection device can be realized. In particular, by configuring the second support body in a cylindrical shape with a soft magnetic material and arranging the magnetic field generation source inside it, the influence of the external stray magnetic field can be further reduced.

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

[0053] With this configuration, the influence of the stray magnetic field outside the magnetic field of the magnetic field generating source (especially on the opposite side of the magnetic field generating source) on the power generation sensor is reduced, so that a small-sized and high-output rotation detection device can be realized.

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

[0055] According to this configuration, since the resolution and the like are improved by the plurality of power generation sensors, the rotation detection accuracy is improved. In addition, a rotation detection device in which the total amount of electric power generated during one rotation is also improved can be realized.

[0056] The plurality of power generation sensors may be arranged inside the inner circumferential circle of the magnetic field generating source, or may be arranged inside the outer circumferential circle of the magnetic field generating source. Further, a part of the plurality of power generation sensors may be arranged inside the inner circumferential circle of the magnetic field generating source, and another part of the plurality of power generation 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 claims 1 to 11, further comprising a magnetic sensor that identifies the magnetic poles at a predetermined position in the circumferential direction around the rotation axis.

[0058] According to this configuration, by identifying the magnetic poles by the magnetic sensor at a predetermined position in the circumferential direction around the rotation axis, the state of application of the magnetic field to the power generation sensor can be known. Therefore, by using the output signal of the magnetic sensor, a rotation detection device capable of discriminating the forward rotation and the reverse rotation of the relative rotational motion, that is, detecting the rotation direction, can be realized.

Brief Description of the Drawings

[0059]

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DETAILED DESCRIPTION OF THE INVENTION

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

[0061] [First Embodiment] FIG. 1A and FIG. 1B show a rotation detection device 10 according to the 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 disposed on a first support 300 and a magnetic field generation source 200 fixed to a second support 400 that rotates relative to the first support about a rotation axis 201.

[0063] The power generation sensor 100 includes a magnetic wire 110 that exhibits the giant Barkhausen effect by an applied alternating magnetic field, a coil 120 wound around the magnetic wire 110, and a pair of magnetic flux conduction pieces 130, 131 in which wire arrangement portions 130a, 131a (see FIGS. 2A and 2B) for fixing both ends of the magnetic wire 110 are formed. In this embodiment, an example in which the wire arrangement portions 130a, 131a (see FIGS. 2A and 2B) are formed by through holes is shown. The pair of magnetic flux conduction pieces 130, 131 are symmetric with respect to a symmetry plane 115 set at the axial center position of the magnetic wire 110, and include a pair of axis-orthogonal portions 133 that extend parallel to each other in a direction orthogonal to the axial direction, and a pair of axis-parallel portions 134 that extend in a direction approaching each other along the axial direction from the tip ends of the axis-orthogonal portions 133. The magnetic wire 110 is linear in this embodiment.

[0064] The magnetic field generating source 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 such that the polarities of the magnetic poles adjacent in the circumferential direction are different, and the magnetic poles with different polarities are alternately arranged in the circumferential direction. In this embodiment, the magnetic field generating source 200 (hereinafter sometimes referred to as "multipole magnet 200") is constituted by one multipole magnet obtained by multi-pole magnetizing a ring-shaped hard magnetic material.

[0065] To produce a magnet obtained by multi-pole magnetizing one ring-shaped hard magnetic material, for example, using a magnetization yoke having an area corresponding to a predetermined magnetization pitch λ, simultaneous magnetization is performed on both the upper and lower surfaces (here, the upper and lower surfaces based on the case where the rotation axis 201 is along the vertical direction) of the ring-shaped hard magnetic material which is the material of the magnet. Then, magnetization is performed in the direction of the rotation axis 201, magnetic poles appear on the upper surface, lower surface, outer circumference and inner circumference surface of the hard magnetic material, and a multipole magnet 200 in which adjacent magnetic poles in the circumferential direction have different polarities is produced. Therefore, it becomes a magnetic field generating source that can be made inexpensive and miniaturized with one magnet. Further, when the thickness T of the magnet is thin or the material is ferrite or the like, a multipole magnet 200 in which the polarities of adjacent magnetic poles in the circumferential direction are different can be produced by single-sided magnetization with a magnetization yoke on only the upper surface or the lower surface, and there is an advantage that it can be made even more inexpensive.

[0066] The power generation sensor 100 is arranged such that the axial direction of the magnetic wire 110 is parallel to the rotation axis 201, and the axial parallel portion 134 side faces the outer peripheral surface of the ring-shaped multi-pole magnet 200. That is, when the rotation locus around the rotation axis 201 of the magnetic field generation source is viewed in a direction parallel to the rotation axis 201, the power generation sensor 100a is located outside the outer peripheral circle formed by the outer edge thereof. In this embodiment, the symmetry plane 115 (a plane orthogonal to the axial direction) set at the central position in the axial direction of the magnetic wire 110 of the power generation sensor 100 is arranged to pass through the approximate center of the magnetic field generation source (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 central position of the magnetic wire 110 coincides with the center 202 of the ring-shaped multi-pole magnet 200, that is, the position of 1 / 2 of the magnet thickness T. Even if the central position of the magnetic wire 110 and the center in the direction parallel to the rotation axis 201 of the magnet 200 are not exactly aligned due to assembly errors or the like, there is no substantial influence on the rotation detection performance.

[0067] FIG. 2A is a perspective view of the power generation sensor 100, and FIG. 2B is a front view seen in the direction of arrow 101 in FIG. 2A. The power generation sensor 100 includes a magnetic wire 110 that exhibits the large Barkhausen effect, a coil 120 wound around the magnetic wire 110, and a pair of magnetic flux conduction pieces 130, 131 made of soft magnetic components. The coil 120 is wound around the magnetic wire 110 so that the first end portion 111 and the second end portion 112 of the magnetic wire 110 are exposed with the same length. In this embodiment, the coil 120 is wound around the magnetic wire 110 between the pair of magnetic flux conduction pieces 130, 131. The pair of magnetic flux conduction pieces 130, 131 are fixed to the vicinity of and inside the through holes in the first end portion 111 and the second end portion 112 of the magnetic wire 110 with resin, respectively, whereby the pair of magnetic flux conduction pieces 130, 131 and the magnetic wire 110 are magnetically coupled.

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

[0069] In this example, the axially orthogonal portion 133 has a thickness W in the axial direction x. If the width of the hole formed through the magnetic flux conducting pieces 130 and 131, that is, the thickness W of the axially orthogonal portion 133 (see FIG. 2A), is too large, the arrangement width of the coil 120 becomes narrow, so the efficiency of picking up the large Barkhausen effect of the magnetic wire 110 decreases. If it is too small, the magnetic path between the magnetic wire 110 and the magnetic wire 110 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 axially orthogonal portions 133 face each other with a distance D in the axial direction x. The proximal ends 134a of the pair of axially parallel portions 134 face each other with a distance L in the axial direction x.

[0070] Both end portions 111 and 112 of the magnetic wire 110 are respectively fixed to the base end portions of the axially orthogonal portions 133 of the pair of magnetic flux conducting pieces 130 and 131. More specifically, at the base end portions of the axially orthogonal portions 133, wire arrangement portions 130a and 131a are provided with holes penetrating in the axial direction x formed at the central positions of the widths t of the magnetic flux conducting pieces 130 and 131.

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

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

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

[0074] A pair of magnetic flux conduction pieces 130 and 131 are configured to correct a magnetic field formed by a magnetic field generation source (ring-shaped multi-pole magnet 200) disposed in the detection region 140 in the space including the magnetic flux conduction pieces 130 and 131 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 region facing surface) 134b facing the detection region 140 and guide it into the magnetic flux conduction pieces 130 and 131. In this embodiment, the detection region facing surface 134b is a plane parallel to the axial direction x. The detection region facing surface 134b may be a flat surface parallel to the width direction y, or may be a cylindrical curved surface that matches the cylindrical outer peripheral surface of the ring-shaped multi-pole magnet 200.

[0075] The magnetic flux conduction pieces 130 and 131 are made of a soft magnetic material, have a coercive force equal to or less than the coercive force of the magnetic wire 110, and are made of a material having a magnetic permeability of 500 or more. Such a material has characteristics such as low magnetic resistance, low hysteresis, and low self-capacitance. Thereby, even when a high-frequency alternating magnetic field generated when the magnetic field generation source moves at high speed is applied, the influence on the output characteristics of the power generation sensor 100 is small. The thickness W (see FIG. 2A) of the axially orthogonal portion 133 may be set to a value that does not impair the magnetic flux collection and blocking (shielding) effect of the magnetic flux lines depending on the selected material.

[0076] As shown in FIGS. 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 surface 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 concentrated by a pair of magnetic flux conduction pieces 130 and 131 made of a soft magnetic component and guided to both ends of the magnetic wire 110. Moreover, the 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. Thus, the applied magnetic field is corrected in the axial direction x of the magnetic wire 110 and applied from both ends of the magnetic wire 110, so that the large Barkhausen effect can be sufficiently caused and a high-output signal can be obtained. The axial distance (distance L) between the proximal ends 134a of the pair of axially parallel portions 134 is preferably 5% to 50% of the axial distance D between the pair of axially orthogonal portions 133 at the coupling position with the magnetic wire 110. Thereby, the magnetic flux concentration efficiency and the magnetic shielding efficiency by the axially parallel portion 134 are improved, and the magnetic field from the magnetic field generation source can be efficiently concentrated on both ends of the magnetic wire 110. Thereby, the magnetic field strength in each axial portion of the magnetic wire 110 can be made more uniform, and the large Barkhausen effect of the property possessed by the magnetic wire 110 can be extracted.

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

[0078] In this case, "parallel" means substantially parallel, and in addition to allowing an assembly error, it means that the axial direction x of the magnetic wire 110 follows a direction parallel to the rotation axis 201 within a range allowing an inclination within the range in which the magnetic wire 110 can exhibit the large Barkhausen effect. For example, it is allowed that the axial direction x of the magnetic wire 110 has an inclination 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 and 131 made of soft magnetic components and the coil 120 are fixed to a case (not shown) covering them by an adhesive resin, fitting, or other appropriate fixing means. As described above, both ends 111 and 112 of the magnetic wire 110 are fixed by resin (not shown) to wire arrangement portions 130a and 131a each consisting 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 and 131, the coil 120, and the magnetic wire 110 are fixed to each other and integrated.

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

[0081] The magnetization pattern of the outer peripheral portion of the ring-shaped multi-pole magnet 200 is a form in which a plurality of magnet regions polarized into N poles and S poles along the z direction are arranged in the circumferential direction, and the magnetization directions of adjacent magnet regions are reversed so that the N poles and S poles are alternately arranged in the circumferential direction. In this embodiment, six magnetic poles (magnetic pole bands) are formed around the rotation axis 201. Of course, the number of magnetic poles may be other than this.

[0082] When one axial parallel portion 134 of the magnetic flux conduction pieces 130 and 131 of the power generation sensor 100 faces one N pole, the other axial parallel portion 134 of the magnetic flux conduction pieces 130 and 131 faces an S pole. Due to such a positional relationship, magnetic flux can be efficiently conducted from magnetic poles of different polarities to the pair of magnetic flux conduction pieces 130 and 131 of the power generation sensor 100, so that a small-sized and high-output power generation sensor 100 can be realized. The circumferential magnetization pitch λ (magnetic pole pitch) can be shortened to the width t of the magnetic flux conduction pieces 130 and 131 (see FIG. 2A). Therefore, since it can generally cope with a magnetization pitch longer than that, a general-purpose small-sized rotation detection device can be realized. [Modified Example] FIG. 3A shows a power generation sensor 100a which is a modified example of the power generation sensor 100. FIG. 3B is a perspective view of the magnetic flux conduction pieces 130, 131. In this modified example, the wire arrangement portions 130a, 131a are constituted by grooves instead of through holes.

[0083] The grooves constituting the wire arrangement portions 130a, 131a are preferably grooves that are recessed in the axial orthogonal direction z so as to open at the end face of the axial orthogonal portion 133 on the side opposite to the axial parallel portion 134 with respect to the magnetic wire 110 (the side opposite to 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 portion 111 and the second end portion 112 of the magnetic wire 110 are fixed to the axial orthogonal portion 133 in a state of passing through the axial orthogonal portion 133 in the wire arrangement portions 130a, 131a. More specifically, by disposing resin (not shown) in the grooves constituting the wire arrangement portions 130a, 131a, the end portions 111, 112 of the magnetic wire 110 are fixed to the axial orthogonal portion 133 and they are coupled to each other. Thereby, the magnetic wire 110 and the pair of magnetic flux conduction pieces 130, 131 are mechanically coupled to each other and magnetically coupled to each other.

[0084] No magnetic field from the magnetic field generation source 200 is applied to the side of the magnetic wire 110 opposite to the axial parallel portion 134. Therefore, in the axial orthogonal portion 133 of the magnetic flux conduction pieces 130, 131 shown in FIGS. 2A and 2B, etc., the portion located on the side opposite to the axial parallel portion 134 with respect to the magnetic wire 110 contributes little to the induction and shielding of the magnetic flux from the magnetic field generation source 200. Therefore, as shown in FIGS. 3A and 3B, even with a configuration in which the magnetic wire 110 is exposed, it is possible to efficiently induce the magnetic flux from the magnetic field generation source 200 to both ends of the magnetic wire 110.

[0085] Moreover, this structure has the advantage of being able to reduce the influence on the power generation sensor 100a from external stray magnetic fields other than the magnetic field from the magnetic field generation source 200, particularly from the opposite side of the magnetic field generation source 200. This is a great advantage, for example, when the power generation sensor 100a is installed on the inner peripheral side of the magnetic field generation source 200 (see FIG. 9 described later).

[0086] Furthermore, since there is no need to insert the magnetic wire 110 into the holes of the magnetic flux conduction pieces 130, 131, there is also the advantage that the assembly becomes simple. In FIGS. 3A and 3B, it is a groove (a groove with a semicircular cross-section) in which a part (for example, about half) of the magnetic wire 110 fits, but it may be a groove with a U-shaped cross-section in which the entire magnetic wire 110 fits, and the cross-sectional shape may be other shapes such as triangular or square.

[0087] [First Model] FIGS. 4A, 4B, 4C and FIG. 5 show the results of two-dimensional magnetic simulations in a longitudinal section passing through the axis of the magnetic wire 110 in the case without magnetic flux conduction pieces (comparative example). On the other hand, FIGS. 6A, 6B, 6C and FIG. 7 show the results of two-dimensional magnetic simulations in a longitudinal section passing through the axis of the magnetic wire 110 in the case where the magnetic flux conduction pieces 130, 131 are magnetically coupled to both ends (example). FIGS. 5 and 7 graphically represent the magnetic field strength applied to the magnetic wire 110. The wire position on the horizontal axis represents the position of each part in the axial direction x of the magnetic wire 110. The central position in the length direction of the magnetic wire 110 (11 mm in this example) is represented as "0", and the end positions are represented as -5.5 mm and +5.5 mm, respectively. The vertical axis represents the magnetic field strength, which is normalized with the stabilizing magnetic field as 1. The operating magnetic field is about 0.5. The curves 4A, 4B, 4C in FIG. 5 correspond to the configurations of FIGS. 4A, 4B, and 4C, respectively. The curves 6A, 6B, 6C in FIG. 7 correspond to the configurations of FIGS. 6A, 6B, and 6C, respectively.

[0088] The magnetic field generation sources are magnets 210, 211, and 212 magnetized (polarized) in a direction parallel to the axial direction x of the magnetic wire 110. FIGS. 4A and 6A show simulation results when using 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 of the magnetic wire 110 (e.g., 11 mm). FIGS. 4B and 6B show simulation results when using a magnet 211 whose length (thickness, e.g., 5 mm) in the direction parallel to the axial direction x is approximately half of the length of the magnetic wire 110. FIGS. 4C and 6C show simulation results when the length (thickness), e.g., 1.5 mm, in the direction parallel to the axial direction x is further shortened. The configuration of FIG. 6A is an example where the length (thickness) of the magnet 210 is approximately equal to the distance between the outer surfaces of the pair of axially orthogonal portions 133 that do not face each other. The configuration of FIG. 6B is an example where the length (thickness) of the magnet 211 is shorter than the distance between the inner surfaces of the pair of axially orthogonal portions 133 that face each other and longer than the distance between the proximal ends of the pair of axially parallel portions 134 (e.g., 2 mm). The configuration of FIG. 6C is an example where the length (thickness) of the magnet 212 is shorter than the distance between the proximal ends of the pair of axially parallel portions 134.

[0089] In order for the magnetic flux distribution in the magnetic wire 110 to be uniform over the entire axial length range, it is desirable that the magnetic flux enters from one end of the magnetic wire 110 and exits from the other end. That is, it is desirable that the entry and exit of magnetic flux at the intermediate portion (axial mid - position) between both ends of the magnetic wire 110 be as little as possible.

[0090] In the magnetic simulation results of the comparative examples shown in FIGS. 4A, 4B, 4C, and FIG. 5, most of the magnetic flux generated by the magnets 210, 211, and 212 enters from the intermediate portion of the magnetic wire 110 and exits at the intermediate portion. Therefore, the magnetic field strength in the central region of the magnetic wire 110 is higher than that in the both - end regions. Furthermore, the shorter (thinner) the magnet is, the more magnetic flux enters the intermediate portion of the magnetic wire 110, so the uniformity of the magnetic field strength becomes even worse. In order 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).

[0091] As shown by curve 4C in FIG. 5, when the magnet thickness is 1.5 mm, a stabilizing magnetic field cannot be applied to the magnetic wire 110. As shown by curve 4B in FIG. 5, when the magnet thickness is 5 mm (slightly less than half the wire length of the magnetic wire 110), a magnetic field strength exceeding the stabilizing magnetic field can be obtained in the position range of -3.5 mm to +3.5 mm, but the difference in magnetic field strength due to position is large. 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 starts magnetization reversal from the axial center. However, the magnetic field strength in the portion away from the axial center is insufficient, and magnetization reversal does not occur over the entire length of the magnetic wire 110. Therefore, when the magnet thickness is 5 mm, a sufficient pulse voltage cannot be obtained. As shown by curve 4A in FIG. 5, when the magnet thickness is 11 mm, which is approximately equal to the magnetic wire length, a substantially uniform magnetic field strength exceeding the stabilizing magnetic field can be obtained in the position range of -5 mm to +5 mm. Therefore, it is considered that simultaneous reversal of the soft layer can be achieved over the entire length of the magnetic wire 110 during rotation detection. However, since such a ring-shaped magnet with a magnet thickness of 11 mm cannot be manufactured by multi-pole magnetization, there are many design limitations, and problems such as miniaturization of the rotation detection device, assembly man-hours, and manufacturing costs are faced.

[0092] From the magnetic simulation results shown in FIGS. 6A, 6B, 6C, and 7, it can be seen that most of the magnetic fluxes of the magnets 210, 211, and 212 are attracted and collected by the magnetic flux conduction pieces 130 and 131 made of L-shaped soft magnetic components. When a strong magnetic field is applied, the magnetic wire 110 becomes magnetically saturated, and some magnetic fluxes leak through the gap (distance L) between the pair of axially parallel portions 134. However, since most of the magnetic fluxes pass through the path from one end to the other end of the magnetic wire 110, it has no effect on the output of the power generation sensor.

[0093] The magnetic fluxes from the magnets 210, 211, and 212 toward the middle part of the magnetic wire 110 are blocked (shielded) by the magnetic flux conduction pieces 130, 131 made of soft magnetic body parts, particularly by their axially parallel parts 134, and there is almost no magnetic flux entering the magnetic wire 110 from its middle part. More specifically, the magnetic fluxes from the magnets 210, 211, and 212 enter from the detection region facing surface 134b of the axially parallel part 134 of one of the magnetic flux conduction pieces 130, are conducted inside the magnetic flux conduction piece 130, and reach one of the first end 111 and the second end 112 of the magnetic wire 110. Also, the magnetic fluxes from the other of the first end and the second end 112 of the magnetic wire 110 are conducted through the other magnetic flux conduction piece 131 and reach its axially parallel part 134, and then reach the magnets 210, 211, and 212 from its detection region facing surface 134b. Therefore, a uniform magnetic flux distribution is obtained over the entire length of the magnetic wire 110. That is, a magnetic field parallel to the axial direction x of the magnetic wire 110 and having a uniform intensity can be formed over the entire length of the magnetic wire 110.

[0094] As shown in curves 6A, 6B, and 6C in FIG. 7, in any of the magnet thicknesses of 1.5 mm, 5 mm, and 11 mm, in the position range of -4 mm to +4 mm corresponding to the inner surfaces facing each other of the axially orthogonal part 133, a substantially uniform magnetic field strength exceeding the stabilizing magnetic field is achieved. Therefore, during rotation detection, simultaneous inversion of the soft layer can occur over the entire axial length of the magnetic wire 110, and a sufficient pulse output can be obtained. And when the magnet thickness is 5 mm or less, a ring-shaped multipolar magnet can be manufactured by the existing technology of multipolar magnetization, so there are various advantages such as fewer design restrictions, miniaturization of the rotation detection device, reduction of assembly man-hours, and reduction of manufacturing costs.

[0095] In order to maximize the obtained power, it is important that the magnetization inversion of the soft layer spreads over the entire magnetic wire from the state where the magnetization directions of the entire magnetic wire are aligned. For example, in the configuration without the magnetic flux conduction piece as shown in FIG. 4B, the magnetization directions of the magnetic wire are in a state where they are not partially aligned, and only a very small pulse signal can be obtained.

[0096] As shown in FIGS. 6A, 6B, 6C, and 7, in the power generation sensor 100 of the first embodiment, regardless of which of the three different lengths of magnets 210, 211, and 212 is used, due to the function of the magnetic flux conduction pieces 130, 131 (particularly the axially parallel portion 134), the applied magnetic field is corrected 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-output pulse signal can be output.

[0097] [Second Model] In the configuration of FIG. 6A of the first model, the length T (thickness) of the magnets 210, 211, 212, which are magnetic field generation sources, in the detection region 140 of the power generation sensor 100 is substantially the same as the length obtained by adding the length of the width W (see FIGS. 2A and 2B) of the pair of axially orthogonal portions to the distance D (see FIGS. 2A and 2B) between the inner surfaces of the pair of axially orthogonal portions of the power generation sensor 100, and they face each other. In this case, as described above, the magnetic field is corrected in the axial direction x of the magnetic wire 110 by the first magnetic flux conduction piece 130 and the second magnetic flux conduction piece 131, and a uniform magnetic field is applied to the entire magnetic wire 110.

[0098] On the other hand, consider a second model that uses a ring-shaped multi-pole magnet as the magnetic field generation source. The ring-shaped multi-pole magnet is magnetized in a direction parallel to the central axis of the ring shape (the direction parallel to the rotation axis 201 when a rotation detection device is configured). Due to this magnetization, the ring-shaped multi-pole magnet has N poles and S poles alternately arranged in the circumferential direction on the upper and lower surfaces perpendicular to the rotation axis 201 and 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 FIG. 6B or FIG. 6C of the first model.

[0099] A sample of the second model was fabricated, and the ring-shaped multi-pole magnet was rotated around the central axis (rotation axis 201. See FIGS. 1A and 1B)), and it was experimentally investigated whether the correction function of the magnetic flux conduction pieces 130, 131 was exhibited in the same manner as in the first model.

[0100] In the samples of the power generation sensor 100 used in the experiment, the magnetic wire length was 11 mm, the distance D between the orthogonal portions 133 of the magnetic flux conduction pieces 130 and 131 was 7 mm, and the distance L between the proximal ends 134a of the pair of parallel portions 134 was 2 mm. The configuration of the sample of the ring-shaped multipole magnet used in the experiment was an outer peripheral diameter of 14 mm, an inner peripheral diameter of 10 mm, a thickness T in the rotation axis direction of 5 mm, and 6 magnetic poles.

[0101] Using these samples, with the arrangement of the first embodiment, the ring-shaped multipole magnet was rotated in forward and reverse rotations, and as a result of checking the output characteristics, the power generation sensor 100 output a stable high-output pulse signal.

[0102] Even in a structure where the thickness T of the ring-shaped multipole magnet, which is the magnetic field generation source, is equal to or less than the distance D between the inner surfaces of the pair of orthogonal portions 133 of the power generation sensor 100 (see FIGS. 6B and 6C), that is, a structure in which the magnetic pole faces do not face both ends 111 and 112 of the magnetic wire 110, when the magnetic pole boundary line (polarization) coincides with the axial center position 113 of the magnetic wire 110 (see FIGS. 2A and 2B), it was confirmed that the function of magnetic field correction in the axial direction x of the magnetic wire 110 is effective due to the function of magnetic flux collection and blocking (shielding) of the magnetic flux conduction pieces 130 and 131.

[0103] [In-depth experiment] While changing the configuration of the sample of the power generation sensor 100 of the second model, an in-depth experiment was conducted to determine whether the correction function of the magnetic flux conduction pieces 130 and 131 is exhibited.

[0104] In the in-depth experiment, the distance D between the axis-orthogonal parts 133 of the first magnetic flux conducting piece 130 and the second magnetic flux conducting piece 131 was set to 7 mm, and the distance L between the adjacent ends 134a of the axis-parallel parts 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 was configured with 6 poles, an outer diameter of 14 mm, and an inner diameter of 10, and the thickness T in the direction of the rotation axis was changed between 1 mm and 5 mm to confirm the output. The results are shown in Figure 8. The horizontal axis is the thickness T of the magnet, and the vertical axis is the output pulse height normalized with the maximum value set to 1. The pulse height of the pulse signal is the average value of the absolute values ​​of the two positive and negative pulses when the ring-shaped multi-pole magnet is rotated in one direction (forward rotation) and the two positive and negative pulses when the ring-shaped multi-pole magnet is rotated in the other direction (reverse rotation).

[0105] 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. 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 2 / 3 or more of the distance L.

[0106] Even for a thin magnet with thickness T less than distance L, it is believed that when the ratio of thickness T to distance L is in the range of 2 / 3 to 1, the magnet and magnetic flux conducting 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 collecting and blocking (shielding) functions of magnetic flux conducting pieces 130, 131 are not impaired. However, it is presumed that the radial magnetic flux lines are affected by the magnetic path formed through the gap between the pair of magnetic flux conducting pieces 130, 131 when the magnet thickness T is less than 2 / 3 of distance L.

[0107] As described above, the structure of the present embodiment can reduce the thickness T of the magnet to 2 / 3 of the distance L, and the rotation detection device 10 can be configured using a thin ring-shaped multi-pole magnet magnetized in the direction parallel to the rotation axis 201. Thereby, a thin and small rotation detection device 10 in the direction of the rotation axis 201 can be realized.

[0108] [Second Embodiment] FIG. 9 shows the rotation detection device of the second embodiment. The rotation detection device 11 includes a power generation sensor 100a of the modification (see FIGS. 3A and 3B) disposed 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.

[0109] In the first embodiment, the power generation sensor 100a is arranged to face the outer peripheral surface of the ring-shaped multi-pole magnet. In the second embodiment, the power generation sensor 100a is located on the inner peripheral surface side of the ring-shaped multi-pole magnet. That is, the power generation sensor 100a is located inside the inner peripheral circle formed by the inner edge when the rotation locus around the rotation axis 201 of the magnetic field generation source is viewed in the direction parallel to the rotation axis 201.

[0110] A multi-pole magnet obtained by multi-pole magnetizing a single ring-shaped hard magnetic material is simultaneously magnetized on both the upper and lower surfaces (here, the upper and lower surfaces based on the case where the rotation axis 201 is along the vertical direction) of the ring-shaped hard magnetic material that is the material of the magnet by a magnetizing yoke having an area corresponding to a predetermined magnetization pitch λ. Then, it is magnetized in the direction of the rotation axis 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 arranged on the inner peripheral surface side, that is, in the hollow inner region of the ring-shaped multi-pole magnet, a good output can be obtained as in the first embodiment.

[0111] If a soft magnetic material is used for the second support 410, this structure can eliminate the influence of an external stray magnetic field other than the magnetic field from the ring-shaped multipole magnet on the power generation sensor 100a, enabling the realization of a small and high-output rotation detection device 11. Further, by using the power generation sensor 100a of the modification example, the outer diameter of the rotation detection device 11 can be further reduced. Compared with the power generation sensor 100, since the magnetic flux conduction pieces 130 and 131 do not protrude significantly on the side where the magnetic wire 110 of the power generation sensor 100a is exposed, the power generation sensor 100a is hardly affected by the magnetic field leaking from the inner circumferential portion on the opposite side of the inner circumferential portion where the axial parallel portion 134 of the power generation sensor 100a faces (the portion with a 180-degree phase around the rotation axis 201) of the ring-shaped multipole magnet.

[0112] [Third Embodiment] FIG. 10 shows a perspective view of a rotation detection device 12 according to the third embodiment. The third embodiment further includes a magnetic sensor 500 for identifying the magnetic poles of the ring-shaped multipole magnet 200 at a predetermined position in the circumferential direction around the rotation axis 201 in addition to the rotation detection device 10 of the first embodiment. The magnetic sensor 500 may be constituted by, for example, a Hall IC.

[0113] In this embodiment, the power generation sensor 100 is mounted on a first support 300 (for example, a printed circuit board) arranged to face the magnetic pole surface of the multipole magnet 200. Specifically, the power generation sensor 100 is mounted on the main surface of the printed circuit board constituting the first support 300 on the side opposite to the ring-shaped multipole magnet 200. Therefore, a printed circuit board (first support 300) is interposed between the power generation sensor 100 and the ring-shaped multipole magnet 200, and the magnetic flux conduction pieces 130 and 131 of the power generation sensor 100 face the magnetic pole surface of the ring-shaped multipole magnet 200 through the printed circuit board (first support 300). And in this example, the magnetic sensor 500 is mounted on the printed circuit board constituting the first support 300.

[0114] The magnetic sensor 500 is in the ON state (first output state) when the power generation sensor 100 outputs a positive signal and in the OFF state (second output state different from the first output state) when the power generation sensor 100 outputs a negative signal, for example, when the rotation axis 201 rotates in the forward rotation direction. Further, the magnetic sensor 500 is in the OFF state (second output state) when the power generation sensor 100 outputs a positive signal and in the ON state (first output state) when the power generation sensor 100 outputs a negative signal when the rotation axis 201 rotates in the reverse rotation direction. The relative arrangements of the power generation sensor 100, the ring-shaped multi-pole magnet 200, and the magnetic sensor 500 are designed so that the magnetic sensor 500 has such output states.

[0115] Thereby, the rotation direction of the rotational motion can be detected by the combination of 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 rotation axis 201 may be opposite to the above.

[0116] [Fourth Embodiment] FIG. 11A shows a perspective view of the rotation detection device 13 according to the fourth embodiment. The magnetic field generation source 200 from the first to the third embodiments is composed of one magnet in which a ring-shaped hard magnetic material is multi-pole magnetized. The magnetic field generation source 200 according to the fourth embodiment includes a plurality of identical and same-sized individual magnets 240 attached at equal intervals along the circumferential direction with respect to the second support 420. The plurality of individual magnets 240 are arranged such that the magnetization direction of each is parallel to the rotation axis 201 and the polarities of the magnetic poles adjacent in the circumferential direction are different. Thereby, the plurality of individual magnets 240 constitute a multi-pole magnetic field generation source 200.

[0117] 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 axial parallel portion 134 side (detection region 140; see FIG. 2B) faces the inner peripheral surface of the cylindrical rotation locus of the plurality of individual magnets 240. And the symmetry plane 115 set at the axial center position of the magnetic wire 110 of the power generation sensor 100 coincides with the center 242 in the direction parallel to the rotation axis 201 of the plurality of individual magnets 240, that is, the position of 1 / 2 of the magnet thickness T (see FIG. 11B). The configuration shown in FIG. 11B is substantially the same as the configuration shown in FIG. 1B.

[0118] FIG. 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. Further, the power generation sensor 100 may be installed so as to face the outer peripheral surface of the cylindrical rotation locus of the individual magnets 240 that make up the magnetic field generation source 200. FIGS. 11A and 11B show rectangular parallelepiped-shaped individual magnets 240, but individual magnets of other shapes may be used.

[0119] The configuration of this fourth embodiment is advantageous, for example, when detecting the rotation of a large rotating body such as a hub of a bicycle wheel. That is, when applying one ring-shaped multipole magnet to the rotation detection of a large rotating body, there is a risk of insufficient mechanical strength and breakage. Therefore, by using a plurality of individual magnets 240 to form the magnetic field generation source 200, the durability can be improved.

[0120] [Fifth and Sixth Embodiments] FIGS. 12 and 13 respectively show perspective views of the rotation detection devices 14 and 15 of the fifth and sixth embodiments. The rotation detection devices 10, 11, 12, and 13 from the first embodiment to the fourth embodiment include one power generation sensor 100 or 100a each, but these rotation detection devices 14 and 15 of the fifth and sixth embodiments include a plurality of power generation sensors 100.

[0121] For example, in the rotation detection device 14 of the fifth embodiment shown in FIG. 12, three power generation sensors 100 are arranged at 120-degree phase intervals on a circumference centered on the rotation axis 201 along the outer circumference of a magnetic field generation source 200 constituted by a ring-shaped multi-pole magnet. The ring-shaped multi-pole magnet constituting the magnetic field generation source 200 is constituted by six poles in this example. With this configuration, the number of output signals of the rotation detection device 14 of the fifth embodiment becomes three times that of the first embodiment.

[0122] Also, the rotation detection device 15 of the sixth embodiment shown in FIG. 13 includes a magnetic field generation source 200 constituted by a plurality (14 in the example of the figure) of individual magnets 240, similar to the fourth embodiment, and a plurality (three in this example) of power generation sensors 100 arranged at 120-degree phase intervals 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 of the rotation detection device 15 of the sixth embodiment becomes three times that of the fourth embodiment.

[0123] According to these configurations, by providing a plurality of power generation sensors 100, the resolution and the like are improved, and the rotation detection accuracy is improved. Also, the total amount of electric power generated by the rotation detection devices 14 and 15 during one rotation of the magnetic field generation source 200 is improved. In the fifth and sixth embodiments, an example in which the number of power generation sensors 100 is three and they are arranged at 120-degree phase intervals is shown, but the number and phase interval of the power generation sensors 100 are not limited to this. Of course, the power generation sensor 101a of the above-described modification example may be used.

[0124] In the foregoing embodiments, mainly, an example in which the power generation sensors 100 and 100a are arranged such that the axial direction x of the magnetic wire 110 is parallel to the rotation axis 201 has been shown. However, as described above, the "parallel" in this case does not mean strict parallelism. In addition, the power generation sensors 100 and 100a configured to induce magnetic flux at both ends of the magnetic wire 110 by the magnetic flux conduction pieces 130 and 131 can generate a sufficient pulse voltage as the magnetic field generation source 200 rotates even if the magnetic wire 110 and the rotation axis 201 are not necessarily parallel. Further, even if the axial center of the magnetic wire 110 and the center position of the magnet constituting the magnetic field generation source 200 do not exactly coincide in the direction parallel to the rotation axis 201, the power generation sensors 100 and 100a can generate a sufficient pulse voltage as the magnetic field generation source 200 rotates.

[0125] Specifically, as shown in FIGS. 14 and 15A to 15C, consider a first virtual plane P1 and a second virtual plane P2 that are perpendicular to the rotation axis 201 and pass through one end and the other end, respectively, in the direction parallel to the rotation axis 201 of the magnetic field generation source 200. In this case, it is only necessary that the center (axial center position 113) of the magnetic wire 110 is located in the space V between the first virtual plane P1 and the second virtual plane P2, and the axially orthogonal portion 133 is located outside the space V. FIGS. 15A to 15C show an arrangement in which the inner surfaces of the pair of axially orthogonal portions 133 facing each other are located outside the space V and the entire axially orthogonal portion 133 is located outside the space V.

[0126] With this configuration, the power generation sensors 100 and 100a are arranged such that the magnetic wire 110 intersects the plane perpendicular to the rotation axis 201. With such an arrangement of the power generation sensors 100 and 100a, the projected area in the direction parallel to the rotation axis 201 of the rotation detection device can be reduced.

[0127] On one hand, since the axial orthogonal part 133 is arranged outside the space V between the first virtual plane P1 and the second virtual 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 virtual plane P1 and the second virtual plane P2) becomes shorter than the lengths of the power generation sensors 100, 100a in the same direction. Therefore, since the magnetic field generation source 200 has a small length (thickness) in the direction parallel to the rotation axis 201, it can be constituted by a magnet whose magnetization direction (magnetic polarization direction) is parallel to the rotation axis 201. Such a magnetic field generation source 200 can be constituted by a ring-shaped magnet produced by performing multi-pole magnetization on a hard magnetic material in a direction parallel to the rotation axis 201 as described above.

[0128] Due to the configuration in which the axial orthogonal part 133 is arranged outside the space V between the first virtual plane P1 and the second virtual plane P2, the pair of axial parallel parts 134 will be located closer to the magnetic field generation source 200 than the pair of axial orthogonal parts 133. In addition, the pair of axial parallel parts 134 are magnetically coupled to the magnetic poles of different polarities of the magnetic field generation source 200 (the magnetic poles located on opposite sides of each other with respect to the direction parallel to the rotation axis 201). Since the axial parallel part 134 parallel to the axial direction of the magnetic wire 110 is located between the magnetic field generation source 200 and the magnetic wire 110, the magnetic field applied from the magnetic field generation source 200 is collected by the magnetic flux conduction pieces 130, 131 of the soft magnetic material and guided to both ends of the magnetic wire 110. Therefore, it is not necessary for the magnetic poles to be located near both ends of the magnetic wire 110. In addition, the magnetic flux heading towards the middle part of the magnetic wire 110 is shielded by the axial parallel part 134. Therefore, while using the magnetic field generation source 200 having a small length (thickness) in the direction parallel to the rotation axis 201 and having magnetic poles whose magnetization direction is parallel to the rotation axis 201, the magnetic field can be efficiently collected at both ends of the magnetic wire 110. Thereby, the magnetic field intensity at each part in the axial direction of the magnetic wire 110 can be made uniform.

[0129] Moreover, as described above, both ends of the magnetic wire 110 are fixed to the wire arrangement portions 130a and 131a provided in the axial orthogonal portion 133, and the wire arrangement portions 130a and 131a are constituted by holes or grooves penetrating the axial orthogonal portion 133. Therefore, magnetic coupling can be surely achieved between the magnetic wire 110 and the axial orthogonal portion 133, and a magnetic circuit can be constituted by the magnetic wire 110 and the magnetic flux conduction pieces 130 and 131. Thereby, the magnetic flux entering the intermediate portion of the magnetic wire 110 through the magnetic flux conduction pieces 130 and 131 can be suppressed, and the magnetic flux can be efficiently guided to both ends of the magnetic wire 110. As a result, the magnetic field strength in each part in the axial direction of the magnetic wire 110 can be made more uniform.

[0130] In this way, since the axial magnetic field can be efficiently and uniformly applied to the magnetic wire 110, even if the magnetic pole pitch λ in the rotational direction is fine, the large Barkhausen effect can be sufficiently caused. In other words, a rotation detection device capable of obtaining a small-sized and high-output signal can be realized.

[0131] Next, as shown in FIGS. 14 and 15A to 15C, consider a third virtual plane P3 perpendicular to the rotation axis 201 passing through the center of the magnetic wire 110. At this time, as shown in FIGS. 15A and 15B, it is preferable that the pair of axis parallel portions 134 are arranged on opposite sides with respect to the third virtual plane P3 so as not to intersect the third virtual plane P3. With this configuration, since the pair of axis parallel portions 134 are efficiently magnetically coupled to different-polarity magnetic poles of the magnetic field generation source 200 (magnetic poles located on opposite sides with respect to the direction parallel to the rotation axis 201), the magnetic flux can be more efficiently concentrated at both ends of the magnetic wire 110.

[0132] Although some embodiments of the present invention have been described, the present invention is not limited to the above-described embodiments, and various design changes can be made within the scope of the matters described in the claims.

Explanation of Reference Numerals

[0133] 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: Magnetic flux conduction piece 130a: Wire arrangement part 131: Magnetic flux conduction piece 131a: Wire arrangement part 133: Axial orthogonal part 134: Axial parallel part 134a: Proximal end 140: Detection region 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: Axial orthogonal direction λ: Magnetic pole pitch

Claims

1. A power generation sensor disposed on a first support, and a magnetic field generation source fixed to a second support that rotates relative to the first support about a rotation axis, the rotation detection device comprising: the power generation sensor includes a magnetic wire that exhibits the giant Barkhausen effect, a coil wound around the magnetic wire, and a magnetic flux conduction piece composed of a pair of soft magnetic bodies that are symmetric with respect to a symmetry plane set at a central position in the axial direction of the magnetic wire; the pair of magnetic flux conduction pieces includes a pair of axially orthogonal portions that extend parallel to each other in a direction orthogonal to the axial direction from both ends of the magnetic wire, and a pair of axially parallel portions that extend from the tip ends of the axially orthogonal portions in a direction approaching each other along the axial direction, and the proximal ends face each other with a space therebetween in the axial direction. The axially orthogonal portions have a wire arrangement portion that is a hole or groove penetrating in the axial direction where both ends of the magnetic wire are fixed; the power generation sensor is configured such that a side opposite to the magnetic wire with respect to the axially parallel portion is a detection region; the magnetic field generation source is disposed so as to pass through the detection region, is magnetized in a direction parallel to the rotation axis, and includes a plurality of magnetic poles arranged in a circumferential direction around the rotation axis. The plurality of magnetic poles are alternately arranged so as to have different polarities alternately in the circumferential direction; the power generation sensor has a gap in a direction perpendicular to the rotation axis and faces the magnetic field generation source; a center of the magnetic wire is located in a space between a first virtual plane and a second virtual plane perpendicular to the rotation axis, passing through one end and the other end of the magnetic field generation source in a direction parallel to the rotation axis, and the axially orthogonal portions are located outside the space between the first virtual plane and the second virtual plane. Rotation detection device.

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

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

4. The rotation detection device according to claim 1 or 2, wherein a length of the magnetic field generation source in a direction parallel to the rotation axis is equal to or less than a distance at which inner surfaces on the symmetry plane side of the pair of axially orthogonal portions of the power generation sensor face each other.

5. The rotation detection device according to claim 1 or 2, wherein the length of the magnetic field generation source in the direction parallel to the rotation axis is 2 / 3 or more of the axial distance between the proximal ends of the pair of axially parallel portions.

6. The rotation detection device according to claim 1 or 2, wherein the axial distance between the proximal 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 coupling position with the magnetic wire.

7. The rotation detection device according to claim 1 or 2, wherein the magnetic field generation source includes one magnet in which a ring-shaped hard magnetic body is multi-pole magnetized to form the plurality of magnetic poles, or a plurality of substantially identical-shaped and same-sized magnets each constituting the plurality of magnetic poles.

8. The rotation detection device according to claim 1 or 2, wherein the power generation sensor is located outside the outer peripheral circle of the magnetic field generation source.

9. The rotation detection device according to claim 1 or 2, wherein the power generation sensor is located inside the inner peripheral circle of the magnetic field generation source.

10. The rotation detection device according to claim 1 or 2, wherein a groove constituting the wire arrangement portion is provided on a surface of the magnetic flux conduction piece that does not face the magnetic field generation source.

11. The rotation detection device according to claim 1 or 2, comprising a plurality of the power generation sensors.

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