Rotation detection device

Abstract

To provide a rotation detector with which, of a simple and compact structure though, it is possible to detect rotations by a combination of a multipolar magnet and a power generation sensor.SOLUTION: A rotation detector 10 comprises: a ring-shaped multipolar magnet 200 which is provided to a revolving shaft 300; and a power generation sensor 100 for detecting a magnetic field that changes along with the rotation of the multipolar magnet. The power generation sensor includes a magnetic wire 110 that exhibits a large Barkhausen effect, a coil 120 which is wound around the magnetic wire, and a pair of magnetic flux conduction pieces 130, 131 that are composed of soft magnetic material components magnetically joined to both ends of the magnetic wire, respectively. The ring-shaped multipolar magnet has a magnetization pattern on the outer circumference which is aslant to the revolving shaft. The power generation sensor faces the magnetization pattern of the multipolar magnet in an attitude that the axial direction of the magnetic wire 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 a giant Barkhausen effect (giant Barkhausen jump) is known by the name of 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 is reversed even by 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 is not reversed 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 is reversed. 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 are reversed 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 is reversed.

[0004] In this specification, the magnetic field strength when the magnetization direction of the soft layer is reversed is referred to as an "operating magnetic field", and the magnetic field strength when the magnetization direction of the hard layer is reversed is referred to as a "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 due to its 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, without the supply of external power, the peripheral circuit can also be operated by the output energy of the coil.

[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 aligned. 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 are misaligned, 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 for the magnetization reversal of the soft layer to spread 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, the rotational position can be detected by counting the generated pulse signals.

[0009] Examples of devices for detecting magnetic field changes associated with the rotation of a magnet using a magnetic wire that exhibits a large Barkhausen jump are described in Patent Document 1 and Patent Document 2.

[0010] Patent Document 1 discloses a rotational speed detection device including a sensor composed of a tone wheel magnetized in multiple poles and a magnetic wire that exhibits a large Barkhausen jump. In the configuration of FIG. 1 in Patent Document 1, the magnetic wire is arranged on the outer peripheral portion of the tone wheel with its longitudinal direction as the radial direction of the rotation axis of the tone wheel. One end of the magnetic wire is arranged close to the outer peripheral surface of the tone wheel, and one end of a ferromagnetic pole piece is coupled to the other end of the magnetic wire. And the other end of the pole piece is arranged close to the outer peripheral surface of the tone wheel. With this configuration, it is explained that the magnetic field from the tone wheel is induced by the pole piece, and a predetermined magnetic field strength necessary for exhibiting a large Barkhausen jump can be adjusted.

[0011] In the configuration of FIG. 2 in Patent Document 1, the magnetic wire is arranged on the outer peripheral portion of the tone wheel with its longitudinal direction parallel to the tangential direction with respect to the circumference of the rotation axis of the tone wheel. Ferromagnetic pole pieces are provided at both ends of the magnetic wire, and the magnetic field from the tone wheel is induced by the pole pieces. Thereby, it is explained that a predetermined magnetic field strength necessary for exhibiting a large Barkhausen jump can be adjusted.

[0012] In the configurations of FIGS. 3 to 10 in Patent Document 1, the magnetic wire is arranged on the outer peripheral portion of the tone wheel with its longitudinal direction parallel to the rotation axis of the tone wheel. The magnetic wire is not provided with a pole piece. For this arrangement of the magnetic wire, in various forms of the tone wheel shown in FIGS. 3, 5, 8, and 10 of Patent Document 1, it is explained that a magnetic field of a predetermined strength necessary for exhibiting a large Barkhausen jump is applied.

[0013] In the pole pieces shown in FIGS. 1 and 2 of Patent Document 1, since a shape corresponding to the pitch is essential for magnetization, the assembly of the device is complicated, and the device performance depends on the assembly accuracy. Further, in the configuration of FIG. 1 of the same document, the magnetic field strength is not uniform between one end of the magnetic wire directly facing the tone wheel and the other end through which the magnetic field is induced through the pole piece. In the configuration of FIG. 2 of the same document, the area of the pole piece facing the tone wheel is small. Therefore, in any of these configurations, as a means of applying a uniform operating magnetic field and a stabilizing magnetic field to the entire magnetic wire, the effect is not sufficient.

[0014] In the state without the pole piece of Patent Document 1, as shown in FIGS. 4, 7, and 9 of the same document, the magnetic flux lines leaking from the magnet are not parallel to the longitudinal direction of the magnetic wire. Therefore, in order to make the magnetic flux lines parallel to the longitudinal direction of the magnetic wire, various forms as shown in FIGS. 3, 5, 8, and 10 of the same document are required. Compared with the configurations of FIGS. 11 and 12 of the same document, even if the number of poles arranged in the circumferential direction is the same (that is, the detection resolution is the same), the number of magnetic poles provided on the outer periphery of the tone wheel must be doubled or quadrupled. Therefore, there is a problem that the magnetic pole pattern has to be complicated.

[0015] Such a magnetic pole pattern can be realized by attaching a magnetized magnet to a cylindrical yoke, but attaching the magnet takes a lot of man-hours. Generally, by performing multipolar magnetization on a cylindrical ring-shaped magnet instead of attaching the magnet, it is possible to reduce the man-hours, but it is very difficult to realize such a complicated magnetic pole pattern by magnetization. It is difficult to magnetize, or even if magnetization is possible, the magnetization yoke used for magnetization becomes complicated and expensive.

[0016] Further, unless the width of the magnetization pitch (the circumferential width of the magnetic pole) is increased, a stabilizing magnetic field having a certain strength cannot be applied to the magnetic wire. Therefore, there is a problem that the device becomes large.

[0017] Patent Document 2 discloses a rotation detection device provided with a magnetic sensor in which a coil is wound around a magnetic wire that exhibits a large Barkhausen jump. The magnetic sensor is disposed on the outer peripheral side of the orbit of the magnetic field forming portion such that the longitudinal direction of the magnetic wire is parallel to the axial direction of the rotation axis. The magnetic field forming portion has two permanent magnets configured with four poles in the circumferential direction. These two permanent magnets are installed on the rotation axis such that different poles are arranged in the axial direction of the rotation axis. With this configuration, it is explained that miniaturization of the device is possible.

[0018] The structure of Patent Document 2 is similar to the structure of FIG. 6 of Patent Document 1, and an unmagnetized portion (a portion without magnetic poles) is provided by arranging two magnetic field forming portions (permanent magnets) apart from each other in the axial direction of the rotation axis. However, since it is necessary to mount two components (permanent magnets), the assembly of the device is complicated. In addition, since the phase alignment of the magnetic poles of the two magnets affects the performance, the device performance depends on the assembly accuracy. Furthermore, since there is no magnetic flux conduction piece (magnetic flux induction piece), similar to Patent Document 1, unless the width of the magnetization pitch (the circumferential width of the magnetic poles) is made large, a stabilized magnetic field having a certain strength cannot be applied to the magnetic wire. Therefore, there is a problem that the device becomes large.

Prior Art Documents

Patent Documents

[0019]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0020] Thus, when the magnetic field generating 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 by aligning the magnetic wire parallel to the rotation axis, the structure becomes complicated and miniaturization is difficult. Further, when the magnetic wire is installed with its axial direction (wire length direction) as the circumferential tangent direction or the radial direction of the rotation axis, magnetic members with shapes and arrangements designed according to the magnetization pitch are required, adding the drawback of lacking versatility.

[0021] Therefore, an embodiment of the present invention provides a rotation detection device that can detect rotation by a combination of a multi-pole magnet and a power generation sensor with a simple and small structure.

Means for Solving the Problems

[0022] An embodiment of the present invention provides a rotation detection device that can obtain a simple, small, and high-output signal by combining a power generation sensor having a magnetic flux conduction piece (magnetic flux induction piece) and a ring-shaped multi-pole magnet having an oblique magnetization pattern on its outer peripheral portion.

[0023] An embodiment of this invention provides a rotation detection device having the features exemplified below.

[0024] 1. It includes a ring-shaped multi-pole magnet provided on a rotation axis and a power generation sensor (for example, one power generation sensor) that detects a magnetic field that changes as the multi-pole magnet rotates. The power generation sensor comprises a magnetic wire that exhibits the giant Barkhausen effect, a coil wound around the magnetic wire, and consists of soft magnetic body parts magnetically coupled to both ends of the magnetic wire, and includes a pair of magnetic flux conduction pieces that are symmetric with respect to a symmetry plane set at the central position in the axial direction of the magnetic wire. The ring-shaped multi-pole magnet has an oblique magnetization pattern with respect to the rotation axis on its outer peripheral portion. The power generation sensor faces the magnetization pattern of the multi-pole magnet with the axial direction (wire length direction) of the magnetic wire parallel to the rotation axis. Rotation detection device.

[0025] According to this configuration, while the axial direction of the magnetic wire is arranged parallel to the rotation axis of the ring-shaped multi-pole magnet, different magnetic poles can be opposed to a pair of magnetic flux conduction pieces magnetically coupled to both ends of the magnetic wire due to the oblique magnetization pattern of the multi-pole magnet. Thereby, as the multi-pole magnet rotates together with the rotation axis, the magnetic wire exhibits the giant Barkhausen effect and a pulse voltage is generated.

[0026] Moreover, for the ring-shaped multi-pole magnet having an oblique magnetization pattern on the outer peripheral portion, typically, a simple and inexpensive magnet such as a skew magnet used in an electric motor can be used. The combination of such a multi-pole magnet and a power generation sensor having a magnetic flux conduction piece is easy, resulting in a versatile rotation detection device.

[0027] In this way, by combining a ring-shaped multi-pole magnet having an oblique magnetization pattern and a power generation sensor having a magnetic flux conduction piece, a rotation detection device capable of detecting rotation with a simple and compact structure can be realized.

[0028] 2. The pair of magnetic flux conduction pieces A pair of axially orthogonal portions in which both ends of the magnetic wire are respectively fixed and extend parallel to each other in an axially orthogonal direction orthogonal to the axial direction from both ends of the magnetic wire; A pair of axially parallel portions extending in a direction approaching each other along the axial direction from the tip portions of the pair of axially orthogonal portions, and the proximal ends thereof facing each other with a space therebetween in the axial direction, and The rotation detection device according to item 1, wherein the pair of axially parallel portions faces the magnetization pattern of the multi-pole magnet.

[0029] According to this configuration, an axially parallel portion parallel to the axial direction of the magnetic wire is located between the magnetic pole surface of the oblique magnetization pattern formed on the outer peripheral portion of the ring-shaped multi-pole magnet and the magnetic wire. Thereby, the applied magnetic field is collected by the magnetic flux conduction piece made of a soft magnetic body part and guided to both ends of the magnetic wire. Moreover, the magnetic flux directed in a direction intersecting the axial direction of the magnetic wire is shielded by the axially parallel portion. Thus, since the magnetic field in the axial direction can be applied to the magnetic wire, the large Barkhausen effect can be sufficiently induced even with a fine magnetization pitch. In other words, a rotation detection device capable of obtaining a small-sized and high-output signal can be realized.

[0030] 3. The rotation detection device according to item 2, wherein the axial distance of the interval is 5% to 50% of the axial distance between the pair of axially orthogonal portions at the coupling position with the magnetic wire.

[0031] With this configuration, since the large Barkhausen effect of the properties of the magnetic wire can be almost completely extracted, a small-sized and high-output power generation sensor can be realized.

[0032] 4. The rotation detection device according to any one of items 1 to 3, wherein the magnetization pattern includes a plurality of magnetic poles arranged in a circumferential direction around the rotation axis and formed in a belt shape inclined with respect to the rotation axis, and the plurality of magnetic poles include N poles and S poles alternately arranged in the circumferential direction.

[0033] With this configuration, since magnetic flux can be conducted from magnetic poles of different polarities to the pair of magnetic flux conduction pieces of the power generation sensor, a small-sized and high-output power generation sensor can be realized.

[0034] 5. When one of both ends of the magnetic wire of the power generation sensor faces one of the N poles (typically facing in the radial direction of the rotation radius of the rotation axis via a magnetic flux conduction piece), the other of both ends of the magnetic wire faces one of the S poles adjacent to the N pole (typically facing in the radial direction of the rotation radius of the rotation axis via a magnetic flux conduction piece). The inclination angle (skew angle) of the plurality of magnetic poles with respect to the rotation axis is determined. The rotation detection device according to item 4.

[0035] With this configuration, since magnetic fluxes can be efficiently conducted from magnetic poles with different polarities to both ends of the magnetic wire, a small-sized and high-output power generation sensor can be realized.

[0036] 6. When one of the pair of magnetic flux conducting pieces of the power generation sensor faces one of the N poles (typically facing in the radial direction of the rotation radius of the rotation axis), the other of the pair of magnetic flux conducting pieces faces one of the S poles adjacent to the N pole (typically facing in the radial direction of the rotation radius of the rotation axis), and the inclination angle (skew angle) of the plurality of magnetic poles with respect to the rotation axis is determined, The rotation detection device according to item 4.

[0037] With this configuration, since magnetic fluxes from magnetic poles with different polarities can be efficiently conducted to the pair of magnetic flux conducting pieces of the power generation sensor, a small-sized and high-output power generation sensor can be realized.

[0038] 7. The rotation detection device according to any one of items 1 to 6, further including a magnetic sensor that identifies the magnetic poles of the ring-shaped multi-pole magnet at a predetermined position in the circumferential direction around the rotation axis.

[0039] According to this configuration, by identifying the magnetic poles with a magnetic sensor at a predetermined position in the circumferential direction, 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, it is possible to identify the forward rotation and reverse rotation of the rotational movement of the rotation axis, that is, to detect the rotation direction.

[0040] 8. Further including a substrate disposed between the power generation sensor and the multi-pole magnet, The rotation detection device according to any one of items 1 to 7, wherein the power generation sensor is mounted on a main surface of the substrate opposite to the multi-pole magnet.

[0041] The magnetic sensor may be mounted on the substrate together with the power generation sensor. Thereby, the relative arrangement between the power generation sensor and the magnetic sensor can be accurately determined.

Advantages of the Invention

[0042] According to the present invention, a rotation detection device capable of obtaining a simple, small-sized, and high-output signal can be provided by combining a power generation sensor having a magnetic flux conduction piece and a ring-shaped multi-pole magnet having an oblique magnetization pattern on its outer peripheral portion.

Brief Description of the Drawings

[0043]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figures 3A - 3C

Figures 4A - 4C

Figure 5

Figure 6

Figures 7A - 7B

Figure 8

Embodiments for Carrying Out the Invention

[0044] Hereinafter, the present invention will be described based on the illustrated embodiments. However, the present invention is not limited to the embodiments described below.

[0045] [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 11 in FIG. 1A.

[0046] The rotation detection device 10 includes a ring-shaped multipolar magnet 200 provided on a rotation shaft 300 and one power generation sensor 100. The rotation shaft 300 rotates about a rotation axis 300a that coincides with its central axis, and together with the rotation shaft 300, the multipolar magnet 200 also rotates about the rotation axis 300a.

[0047] The power generation sensor 100 includes a magnetic wire 110 that exhibits the giant Barkhausen effect and a coil 120 wound around the magnetic wire 110. The power generation sensor 100 further includes a pair of magnetic flux conduction pieces 130 and 131 (magnetic flux induction pieces) each formed of a pair of soft magnetic body parts magnetically coupled to both ends of the magnetic wire 110.

[0048] The ring-shaped multipolar magnet 200 has a magnetization pattern that is oblique to the rotation shaft 300 on its outer peripheral portion. The ring shape is a rotating body with the rotation axis 300a as the central axis, and in this embodiment, it is cylindrical. The magnetization pattern on the outer peripheral portion is inclined with respect to the direction parallel to the rotation axis 300a.

[0049] The power generation sensor 100 is arranged with the axial direction (linear length direction) of the magnetic wire 110 parallel to the rotation axis 300a, and the pair of magnetic flux conduction pieces 130 and 131 face the magnetization pattern.

[0050] FIG. 2A is a perspective view of the power generation sensor 100, and FIG. 2B is a front view of FIG. 2A as viewed in the direction of arrow 101. The power generation sensor 100 includes a magnetic wire 110 that exhibits the giant Barkhausen effect, a coil 120 wound around the magnetic wire 110, and a pair of magnetic flux conduction pieces 130 and 131 made of soft magnetic components. The coil 120 is wound around the magnetic wire 110 so that the first end 111 and the second end 112 of the magnetic wire 110 are exposed at the same length. In this embodiment, the coil 120 is wound around the magnetic wire 110 between the pair of magnetic flux conduction pieces 130 and 131. The pair of magnetic flux conduction pieces 130 and 131 are magnetically coupled to the first end 111 and the second end 112 of the magnetic wire 110, respectively.

[0051] The pair of magnetic flux conduction pieces 130 and 131 have substantially the same shape and size. More specifically, the pair of magnetic flux conduction pieces 130 and 131 are configured symmetrically with respect to a symmetry plane 115 (a virtual plane for explaining the geometric arrangement) that is orthogonal to the axial direction x (the line length direction) at the central position (hereinafter referred to as the "axial center position") 113 of the magnetic wire 110. The pair of magnetic flux conduction pieces 130 and 131 include an axially orthogonal portion 133 that extends parallel to each other in the axially orthogonal direction z that is orthogonal to the axial direction x from both ends 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 of the axially orthogonal portion 133. More specifically, the magnetic flux conduction 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 thereof, and have an L-shaped bend at a right angle at the joint between the axially orthogonal portion 133 and the axially parallel portion 134.

[0052] The axially orthogonal portion 133 has a thickness W in the axial direction x in this example. At the connection 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 therebetween in the axial direction x.

[0053] Both ends 111 and 112 of the magnetic wire 110 are respectively fixed to the base end portions of the axial-orthogonal portions 133 of the pair of magnetic flux conducting pieces 130 and 131. More specifically, wire placement portions 130a and 131a, in which holes or grooves penetrating in the axial direction x are formed, are provided at the base end portions of the axial-orthogonal portions 133. FIGS. 2A etc. show an example in which the wire placement portions 130a and 131a are configured by holes. When the wire placement portions 130a and 131a are configured by grooves, it is preferable that the grooves deepen along the axial-orthogonal direction z so as to open to the end faces on the side opposite to the axial-parallel portions 134. 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 penetrating the axial-orthogonal portion 133 in the wire placement portions 130a and 131a. More specifically, by disposing resin (not shown) in the holes or grooves constituting the wire placement portions 130a and 131a, the end portions 111 and 112 of the magnetic wire 110 are fixed to the axial-orthogonal portion 133 and are coupled to each other. Thereby, the magnetic wire 110 and the pair of magnetic flux conducting pieces 130 and 131 are mechanically coupled to each other and magnetically coupled to each other.

[0054] The axial-parallel portions 134 of the pair of magnetic flux conducting pieces 130 and 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 space therebetween in the axial direction x. The intermediate position in the axial direction x of this space 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 axial-parallel portions 134 to the symmetry plane 115 are equal. The distance L in the axial direction x of the said space is set to be 5% - 50% of the distance D between the pair of axial-orthogonal portions 133 at the coupling position of the magnetic wire 110 and the axial-orthogonal portion 133.

[0055] The distance D is, more specifically, the distance in the axial direction x between the inner surfaces 130b and 131b (the inner surfaces of the axial-orthogonal portion 133) of the pair of magnetic flux conducting pieces 130 and 131 facing each other in the axial direction x at the coupling position with the magnetic wire 110.

[0056] The power generation sensor 100 is designed such that the detection region 140 is an area on the side opposite to the magnetic wire 110 with respect to the axially parallel portion 134. 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 a ring-shaped multi-pole magnet 200 in the rotation detection device 10 of FIGS. 1A and 1B. The magnetic poles 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 multi-pole magnet 200. The magnetic pole movement path is on a circumference centered on the rotation axis 300a when viewed in the axial direction x, and the circumference has a tangent parallel to the width direction y that is orthogonal to the axial direction x and the axis-orthogonal direction z in the detection region 140.

[0057] The pair of magnetic flux conduction pieces 130 and 131 are configured to correct the magnetic field formed by the magnetic field generation source (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 134b facing the multi-pole magnet 200 (the detection region facing surface facing the detection region 140; hereinafter referred to as the “detection region facing surface 134b”) and guide it into the magnetic flux conduction pieces 130 and 131. In this embodiment, the detection region facing surface 134b is a surface 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 multi-pole magnet 200.

[0058] As shown in FIGS. 1A and 1B, between the magnetic pole surface of the oblique magnetization pattern provided on the outer peripheral portion of the ring-shaped multi-pole magnet 200 and the magnetic wire 110, there is an axially parallel portion 134 parallel to the axial direction x of the magnetic wire 110. Therefore, the applied magnetic field is collected by a pair of magnetic flux conduction pieces 130, 131 made of soft magnetic components 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. Thus, since the applied magnetic field is corrected in the axial direction x of the magnetic wire 110, the large Barkhausen effect can be sufficiently induced, and a high-output signal can be obtained. The axial direction x (line length direction) of the magnetic wire 110 of this power generation sensor 100 is arranged parallel to the rotation axis 300.

[0059] The magnetic flux conduction pieces 130, 131 made of soft magnetic components and the coil 120 are fixed by an adhesive resin, fitting, or other appropriate fixing means to a case (not shown) covering them. As described above, both ends 111, 112 of the magnetic wire 110 are fixed by resin (not shown) to the wire arrangement portions 130a, 131a formed of two through holes or grooves. Therefore, the power generation sensor 100 is configured by a structure in which the pair of magnetic flux conduction pieces 130, 131, the coil 120, and the magnetic wire 110 are fixed to each other and integrated.

[0060] The magnetization pattern on the outer peripheral portion of the ring-shaped multi-pole magnet 200 is arranged in the circumferential direction around the rotation axis 300 and includes a plurality (12 in this embodiment) of magnetic poles (magnetic pole bands) n1, s1, n2, s2,... formed in a band shape inclined with respect to the rotation axis 300. The plurality of magnetic poles include N poles n1, n2,... and S poles s1, s2,... arranged alternately in the circumferential direction. In this embodiment, as an example, a configuration in which six N poles n1 to n6 and six S poles s1 to s6 are provided is shown. However, of course, the number of magnetic poles may be other than this.

[0061] When one of the both ends of the magnetic wire 110 of the power generation sensor 100 faces one N pole (more specifically, faces in the radial direction of the rotation axis 300 of the magnetic flux conduction pieces 130, 131), the other of the both ends of the magnetic wire 110 faces one S pole adjacent to the N pole (more specifically, faces in the radial direction of the rotation axis 300 of the magnetic flux conduction pieces 130, 131). The inclination angle θ (skew angle) of a plurality of magnetic poles with respect to the rotation axis 300 is determined so as to have such a positional relationship. In the example of FIG. 1B, one end 112 of the magnetic wire 110 faces the N pole n1, and the other end 111 thereof faces the S pole s1.

[0062] In this embodiment, further, when one of the pair of magnetic flux conduction pieces 130, 131 of the power generation sensor 100 faces one N pole (more specifically, faces in the radial direction of the rotation axis 300), the other of the pair of magnetic flux conduction pieces 130, 131 faces one S pole adjacent to the N pole (more specifically, faces in the radial direction of the rotation axis 300). The inclination angle θ (skew angle) of a plurality of magnetic poles with respect to the rotation axis 300 is determined. In the example of FIG. 1B, one magnetic flux conduction piece 131 faces the N pole n1, and the other magnetic flux conduction piece 130 faces the S pole s1.

[0063] With such a configuration, magnetic fluxes can be efficiently conducted from magnetic poles of different polarities to the pair of magnetic flux conduction pieces 130, 131 of the power generation sensor 100, so that a small-sized and high-output power generation sensor 100 can be realized.

[0064] When looking at the rotating shaft 300 from the magnetic wire 110 (see Fig. 1B), at the angular position of the multi-pole magnet 200 where the center line 201 of one N pole (n1) faces one of the magnetic flux conduction pieces (131), and the center line 202 of one S pole (s1) adjacent to the N pole (n1) faces the other magnetic flux conduction piece (130), this design is most preferable. If the circumferential distance around the rotating shaft 300 from the center line 201 of one N pole (n1) to the center line 202 of the adjacent S pole (s1) is defined as the pole pitch λ, the above design corresponds to an inclination angle θ (skew angle) that is displaced by a circumferential distance equal to the pole pitch λ in the circumferential direction with respect to the axial distance corresponding to the distance (D + 2W) between the outer ends of the pair of magnetic flux conduction pieces 130 and 131 (this distance is approximately equal to the total length of the magnetic wire 110). This circumferential distance is most preferably equal to the pole pitch λ, but if it is appropriately determined within the range of not less than half of the pole pitch λ and not more than three-halves of the pole pitch λ, a pulse voltage can be output from the power generation sensor 100. The plurality of magnetic poles n1, s1, n2, s2,... are typically formed with equal widths along the circumferential direction around the rotation axis line 300a. In this case, the pole pitch λ is approximately equal to the width of each magnetic pole.

[0065] In the example of Fig. 1B, the skew angle (inclination angle θ) of the skew magnet constituting the multi-pole magnet 200 is approximately the same as the angle of the diagonal of a rectangle with the width t of the pair of axially parallel portions 134 as the length of the two opposing sides and D + 2W as the length of the other two opposing sides. The circumferential magnetization pitch (pole pitch λ) is approximately equal to the width t of the magnetic flux conduction pieces 130 and 131. Thus, since it can correspond to a magnet with a narrow magnetization pitch, a small rotation detection device can be realized.

[0066] [First Model] Figs. 3A, 3B, and 3C show the results of two-dimensional magnetic simulations in a vertical cross-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. 4A, 4B, and 4C show the results of two-dimensional magnetic simulations in a vertical cross-section passing through the axis of the magnetic wire 110 in the case where the magnetic flux conduction pieces 130 and 131 are magnetically coupled at both ends (example).

[0067] In FIGS. 3A and 4A, the magnetic field generation source is a magnet 210 magnetized in the direction of the arrow (one direction of the axial direction x) parallel to the magnetic wire 110. In FIGS. 3B and 4B, the magnetic field generation sources are two individual magnets 220, 220 magnetized in the directions of the arrows perpendicular to the magnetic wire 110 (opposite directions of the axial orthogonal direction z) and arranged close to the axial direction x. In FIGS. 3C and 4C, the magnetic field generation sources are two individual magnets 230, 230 magnetized in the directions of the arrows perpendicular to the magnetic wire 110 (opposite directions of the axial orthogonal direction z) and arranged away from the axial direction x.

[0068] 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 the magnetic flux at an intermediate position (hereinafter referred to as the "intermediate part") in the axial direction between both ends of the magnetic wire 110 be as small as possible.

[0069] In the magnetic simulation results of the comparative examples shown in FIGS. 3A and 3B, most of the magnetic flux generated by the magnets 210, 220 enters from the intermediate part of the magnetic wire 110 and exits at the intermediate part. Therefore, the magnetic flux density in the central region of the magnetic wire 110 becomes higher than that in the both-end regions. Further, even when no magnet is located at the central part (near the axial center position) of the magnetic wire 110 as shown in FIG. 3C, a similar magnetic flux density distribution is obtained.

[0070] From the magnetic simulation results shown in FIGS. 4A to 4C, it can be seen that most of the magnetic flux of the magnets 210, 220, 230 is attracted and collected by the magnetic flux conduction pieces 130, 131 made of L-shaped soft magnetic body parts. A very small part of the magnetic flux leaks through the interval (distance L) between the pair of axially parallel parts 134, but most of the magnetic flux passes through the path from one end to the other end of the magnetic wire 110.

[0071] The magnetic fluxes from the magnets 210, 220, 230 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 no magnetic flux entering the magnetic wire 110 from its middle part. More specifically, the magnetic fluxes from the magnets 210, 220, 230 enter from the detection region facing surface 134b of the axially parallel part 134 of one of the magnetic flux conduction pieces 131, are conducted inside the magnetic flux conduction piece 131, and reach the second end 112 of the magnetic wire 110. Also, the magnetic flux from the first end 111 of the magnetic wire 110 is conducted through the other magnetic flux conduction piece 130 and reaches its axially parallel part 134, and then reaches the magnets 210, 220, 230 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.

[0072] In order to maximize the obtained power, it is important that the magnetization reversal of the soft layer spreads over the entire magnetic wire from the state where the magnetization directions of the entire magnetic wire are aligned. FIG. 3A corresponds to the configuration of FIG. 9 of Patent Document 1, and FIG. 3C corresponds to the configurations of FIG. 7 of Patent Document 1 and FIG. 1 of Patent Document 2. In these configurations without magnetic flux conduction pieces, the magnetization directions of the magnetic wire are not partially aligned, and only a very small pulse signal can be obtained.

[0073] As shown in FIGS. 4A, 4B, and 4C, in any of the three different magnetization patterns, in the power generation sensor 100 of the first embodiment, due to the action of the magnetic flux conduction pieces 130, 131 (particularly the axially parallel part 134), the applied magnetic field is corrected in the axial direction x of the magnetic wire 110. Thereby, a uniform magnetic field is applied to the entire magnetic wire 110, and a stable high-output pulse signal can be output.

[0074] [Second Model] In the first model, magnetic poles with different polarities face each other on the axially parallel portions 134 of the first magnetic flux conducting piece 130 and the axially parallel portions 134 of the second magnetic flux conducting piece 131 (see FIGS. 4A to 4C). 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 conducting piece 130 and the second magnetic flux conducting piece 131, and a uniform magnetic field is applied to the entire magnetic wire 110.

[0075] On the other hand, consider a second model that uses a skewed magnet, which is a skewed cylindrical multi-pole magnet, as a magnetic field generation source. The skewed magnet has a plurality of magnetic poles alternately arranged in the circumferential direction around the central axis of the cylindrical shape on its outer peripheral surface, and the plurality of magnetic poles have N poles and S poles alternately arranged in the circumferential direction. Each magnetic pole is inclined with respect to the central axis at a predetermined skew angle. In the second model, the skewed magnet has its central axis parallel to the axial direction x of the magnetic wire 110, and in the detection region 140, the outer peripheral surface faces the first magnetic flux conducting piece 130 and the second magnetic flux conducting piece 131.

[0076] When the axially parallel portion 134 of the first magnetic flux conducting piece 130 and the axially parallel portion 134 of the second magnetic flux conducting piece 131 face magnetic poles with different polarities, unlike the first model, the magnetic pole boundary line becomes oblique with respect to the line length direction of the magnetic wire 110 at the axial center position 113 of the magnetic wire 110 (see FIG. 1B).

[0077] A sample of the second model was fabricated, the skewed magnet was rotated around the central axis, and it was experimentally investigated whether the correction function of the magnetic flux conducting piece was exhibited in the same manner as in the first model.

[0078] In the sample of the power generation sensor 100 used in the experiment, the length of the magnetic wire was 11 mm, the distance D between the axially orthogonal portions 133 of the magnetic flux conducting pieces 130 and 131 was 7 mm, and the distance L between the proximal ends 134a of the pair of axially parallel portions 134 was 2 mm. The configuration of the skewed magnet sample used in the experiment was an outer peripheral diameter of 14 mm, an inner peripheral diameter of 10, a length in the central axis direction of 8 mm, and 12 magnetic poles.

[0079] FIG. 5 is an actual image of the magnetization pattern obtained by observing the skew magnet used for the sample with a magnet viewer. The magnetization pitch is about 3.7 mm. This is almost the same as the lateral width (width t shown in FIG. 2A) of 3.5 mm of the opposing magnetic flux conduction pieces 130 and 131.

[0080] Using these samples, with the arrangement of the first embodiment, the skew 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.

[0081] Thus, even when the magnetic pole boundary line is oblique with respect to the longitudinal direction of the magnetic wire 110 at the axial center position 113 of the magnetic wire 110, 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 action of the magnetic flux conduction pieces 130 and 131. The structure in which the magnetic pole boundary line is oblique with respect to the longitudinal direction of the magnetic wire 110 at the axial center position 113 of the magnetic wire 110 is not described in either Patent Document 1 or Patent Document 2.

[0082] Note that the technique of skew magnetization is mainly established for magnetizing the magnets of electric motors. For example, skew magnetization can be performed by magnetizing a cylindrical magnetic body part while rotating it and moving it parallel to its central axis.

[0083] In the sample of the power generation sensor 100 of the second model used in the experiment, the distance D between the shaft orthogonal portions 133 of the first magnetic flux conduction piece 130 and the second magnetic flux conduction piece 131 was set to 7 mm, and the distance L between the proximal ends 134a of their shaft parallel portions 134 was set to 2 mm. In this case, the ratio of the distance L between the proximal ends 134a to the distance D between the pair of shaft orthogonal portions 133 is 29%. The relationship between this distance ratio L / D and the output characteristics was investigated.

[0084] The results are shown in Fig. 6. The horizontal axis represents the ratio L / D (%), and the vertical axis represents the output wave height normalized with the maximum value being 1. The wave height of the pulse signal is the average value of the absolute values of the positive and negative two pulses when the skew magnet rotates in one direction (forward rotation) and the positive and negative two pulses when the skew magnet rotates in the other direction (reverse rotation).

[0085] From Fig. 6, it can be seen that stable high output is achieved when the ratio L / D is from 5% to 50%. When it is less than 5%, it is presumed that due to the narrow interval between the proximal ends 134a (small distance L), it is affected by the magnetic path formed through this narrow interval. Also, when the ratio L / D exceeds 50%, it is presumed that this is because the magnetic flux concentration effect decreases due to the decrease in the area of the soft magnetic component (magnetic flux conduction pieces 130, 131. More specifically, the surface 134b facing the detection region) facing the magnet surface. In addition, it is also presumed that it is affected by the fact that the axial parallel part 134 of the magnetic flux conduction pieces 130, 131 covers a small area of the magnetic wire 110 from the magnet, thereby reducing the shielding effect.

[0086] If the ratio L / D is in the range of 5% or more and 50% or less, it becomes possible to sufficiently cause the large Barkhausen effect possessed by the properties of the magnetic wire 110. It is more preferable that the ratio L / D is 15% or more and 45% or less, and even more preferable that it is 20% or more and 40% or less.

[0087] [Comparative Example] Fig. 7A is a perspective view of a rotation detection device according to a comparative example, and Fig. 7B is a top view of the configuration of Fig. 7A. This rotation detection device is an example of a structure in which the magnetic pole boundary line of the magnetization pattern of the magnet is oblique with respect to the line length direction of the magnetic wire 110 at the axial center position of the magnetic wire 110. Compared with the structure of the first embodiment (see Figs. 1A and 1B), the configuration of the ring-shaped multi-pole magnet 240 is different, and the arrangement of the power generation sensor 100 with respect to the ring-shaped multi-pole magnet 240 is different.

[0088] The ring-shaped multi-pole magnet 240 has a plurality of magnetic poles in the circumferential direction around the central axis (rotation axis 300a), and the plurality of magnetic poles include N poles and S poles alternately arranged in the circumferential direction. Each magnetic pole is parallel to the central axis, and accordingly, the magnetic pole boundary line is parallel to the rotation axis 300.

[0089] Facing the outer periphery of this ring-shaped multi-pole magnet 240, the power generation sensor 100 is arranged in a posture where the central axis 110a (i.e., the wire length direction) of the magnetic wire 110 is inclined with respect to the rotation axis 300. As a result, the magnetic pole boundary line of the magnetization pattern is inclined with respect to the wire length direction of the magnetic wire 110 at the axial center position of the magnetic wire 110.

[0090] However, as shown in Fig. 7B, if the ring shape diameter of the multi-pole magnet 240 is small, the distance g between the axially parallel portions 134 of the two magnetic flux conduction pieces 130, 131 and the magnetic pole surface of the magnet 240 will increase. Therefore, it becomes difficult to obtain the magnetic field strength required for reversing the magnetization direction of the magnetic wire 110. This problem can be solved by increasing the magnetization pitch or increasing the outer ring diameter. However, both solutions go against the requirement of downsizing the device.

[0091] In the first embodiment using a skewed magnet, such a problem does not occur. In the first embodiment, the axial direction x of the magnetic wire 110 of the power generation sensor 100 is parallel to the rotation axis 300a, and the detection region facing surface 134b of the axially parallel portion 134 faces the magnetic pole surface of the multi-pole magnet 200 composed of a skewed magnet. With such an arrangement of the power generation sensor 100, magnetic poles of different polarities can be opposed to the pair of axially parallel portions 134. As a result, a rotation detection device 10 with a small ring diameter and small size is realized.

[0092] [Second Embodiment] FIG. 8 shows a rotation detection device according to the second embodiment. In addition to the rotation detection device 10 of the first embodiment, the second embodiment further includes a magnetic sensor 400 that identifies the magnetic poles of a multi-pole magnet 200 composed of skew magnets at a predetermined position in the circumferential direction around the rotation axis 300. This magnetic sensor 400 may be composed of, for example, a Hall IC. In this embodiment, a power generation sensor 100 is mounted on a printed circuit board 500 (an example of a substrate) arranged to face the magnetic pole surface of the multi-pole magnet 200. Specifically, the power generation sensor 100 is mounted on the main surface of the printed circuit board 500 opposite to the multi-pole magnet 200. Therefore, the printed circuit board 500 is interposed between the power generation sensor 100 and the multi-pole magnet 200, and the magnetic flux conduction pieces 130 and 131 of the power generation sensor 100 face the magnetic pole surface of the multi-pole magnet 200 through the printed circuit board 500. And the magnetic sensor 400 is mounted on the printed circuit board 500 in this example.

[0093] For example, when the rotation axis 300 rotates in the forward rotation direction, the magnetic sensor 400 is in the ON state when the power generation sensor 100 outputs a positive signal, and in the OFF state when the power generation sensor 100 outputs a negative signal. Also, when the rotation axis 300 rotates in the reverse rotation direction, the magnetic sensor 400 is in the OFF state when the power generation sensor 100 outputs a positive signal, and in the ON state when the power generation sensor 100 outputs a negative signal. The relative arrangement of the power generation sensor 100, the multi-pole magnet 200, and the magnetic sensor 400 is designed so that the magnetic sensor 400 has such an output state. 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 400. The combination of the ON / OFF of the magnetic sensor 400 and the forward / reverse rotation of the rotation axis 300 may be opposite to the above.

[0094] The soft magnetic components constituting the magnetic flux conduction pieces 130 and 131 preferably have a coercive force equal to or less than that of the magnetic wire 110 and are made of a magnetic material with high magnetic permeability (for example, a relative magnetic permeability of 500 or more). Specifically, a material containing Ni-based ferrite or Mn-based ferrite is preferred. These materials have excellent properties such as low hysteresis, low self-capacitance, and low iron loss. Therefore, when a high-frequency alternating magnetic field generated when the magnetic field source moves at high speed is applied to the power generation sensor 100, there is an advantage that the output characteristics are not affected.

[0095] Furthermore, if the width of the hole formed through the magnetic flux conduction pieces 130 and 131, that is, the thickness W of the shaft orthogonal part 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 becomes narrow. Therefore, based on experimental findings, the thickness W is preferably 10% to 20% of the total length of the magnetic wire 110.

[0096] In addition, various design changes can be made within the scope of the matters described in the claims.

Explanation of symbols

[0097] 10: Rotation detection device 100: 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: Shaft orthogonal part 134: Axial parallel part 134a: Proximity end 134b: Detection area facing surface 140: Detection area 200: Multi-pole magnet 210: Magnet 220: Magnet 230: Magnet 240: Multi-pole Magnet 300: Rotation Axis 400: Magnetic Sensor 500: Printed Circuit Board D: Distance L: Distance t: Width W: Thickness g: Distance x: Axial Direction y: Width Direction z: Direction Orthogonal to the Axis θ: Inclination Angle λ: Magnetic Pole Pitch

Claims

1. A ring-shaped multi-pole magnet provided on a rotating shaft, and a power generation sensor for detecting a magnetic field that changes as the multi-pole magnet rotates, wherein the power generation sensor comprises a magnetic wire that exhibits the giant Barkhausen effect, a coil wound around the magnetic wire, and soft magnetic components magnetically coupled to both ends of the magnetic wire, respectively, and includes a pair of magnetic flux conduction pieces that are symmetric with respect to a symmetry plane set at the axial center position of the magnetic wire, the ring-shaped multi-pole magnet has a magnetization pattern obliquely with respect to the rotating shaft on the outer peripheral portion, the power generation sensor is in a posture where the axial direction of the magnetic wire is parallel to the rotating shaft and faces the magnetization pattern of the multi-pole magnet, a rotation detection device.

2. The pair of magnetic flux conduction pieces comprises a pair of axially orthogonal portions where both ends of the magnetic wire are respectively fixed and extend parallel to each other in an axially orthogonal 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 pair of 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 pair of axially parallel portions facing the magnetization pattern of the multi-pole magnet, the rotation detection device according to claim 1.

3. The axial distance of the space 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 claim 2.

4. The magnetization pattern includes a plurality of magnetic poles arranged in a circumferential direction around the rotating shaft and formed in a belt shape inclined with respect to the rotating shaft, and the plurality of magnetic poles include N poles and S poles alternately arranged in the circumferential direction, the rotation detection device according to any one of claims 1 to 3.

5. When one of both ends of the magnetic wire of the power generation sensor faces one of the N poles, the inclination angle of the plurality of magnetic poles with respect to the rotating shaft is determined such that the other of both ends of the magnetic wire faces one of the S poles adjacent to the N pole, the rotation detection device according to claim 4.

6. When one of the pair of magnetic flux conduction pieces of the power generation sensor faces one of the N poles, the inclination angle of the plurality of magnetic poles with respect to the rotating shaft is determined such that the other of the pair of magnetic flux conduction pieces faces one of the S poles adjacent to the N pole, the rotation detection device according to claim 4.

7. The rotation detection device according to any one of claims 1 to 3, further comprising a magnetic sensor that identifies magnetic poles of the ring-shaped multi-pole magnet at a predetermined position in the circumferential direction around the rotation axis.

8. further comprising a substrate disposed between the power generation sensor and the multi-pole magnet, The rotation detection device according to any one of claims 1 to 3, wherein the power generation sensor is mounted on a main surface of the substrate opposite to the multi-pole magnet.

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