Motion detection device

Abstract

Provided is a motion detection device with little difference in pulse generation position according to the motion direction. 【Solution means】The rotation detection device 5 includes a first support 51, a second support 52 that moves relative to the first support, a power generation sensor 100 disposed on the first support, and a magnetic field generation source 400 supported by the second support. The power generation sensor includes a magnetic wire 110, a coil 120, and magnetic flux conduction pieces 130 and 131. The magnetic flux conduction pieces have an axis orthogonal portion and an axis parallel portion, and the axis orthogonal portion has a wire arrangement portion to which both ends of the magnetic wire are fixed. The power generation sensor is configured such that a detection region 140 is on the side opposite to the magnetic wire with respect to the axis parallel portion. The magnetic field generation source has a plurality of magnetic poles. Magnetic poles with different polarities enter the detection region in order along an orbit 30 parallel to the axial direction of the magnetic wire and face the power generation sensor. The direction of the magnetic flux of each magnetic pole is perpendicular to its moving direction and intersects the magnetic wire.

Description

Technical Field

[0001] This invention relates to a motion detection device including a power generation sensor using a magnetic wire that exhibits the giant Barkhausen effect.

Background Art

[0002] A magnetic wire having the 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 part and a skin part provided so as to surround the core part. One of the core part and the skin part 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 part and the skin part 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 through the entire wire with a certain part 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 is exhibited, 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 the "operating magnetic field", and the magnetic field strength when the magnetization direction of the hard layer is reversed 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 due to the hysteresis characteristic with respect to the input magnetic field. Therefore, the pulse signal generated from the coil is used in a position 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.

[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 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] A motion detection device using a power generation sensor is disclosed in Patent Documents 1, 2, and 3, for example.

[0009] Patent Document 1 discloses a configuration for detecting rotation around a rotation axis. This configuration includes a two-pole magnet magnetized in the rotation axis direction and a power generation sensor arranged offset radially from the rotation axis. The power generation sensor is arranged with the axial direction of the magnetic wire parallel to the tangential direction of the circumference around the rotation axis. Due to the rotation of the magnetic poles, the magnetic field in the axial direction of the magnetic wire changes. After a unidirectional stabilizing magnetic field is applied to prepare for pulse generation and then an operating magnetic field in the opposite direction is applied, the giant Barkhausen effect appears and a pulse voltage is generated. In Patent Document 1, it is proposed to change the magnetization strength of the magnet to increase the change in magnetic flux density with respect to the rotation angle and suppress the variation in the pulse voltage generation position. The change in the magnetic flux density near the magnetic wire with respect to the magnetization state in FIG. 2 of Patent Document 1 is shown by line M1 in FIG. 3 of the same document. In this case, although the variation in the pulse voltage generation position is suppressed due to the steep magnetic flux change, a flat portion with no change occurs near where the magnetic flux density is 0. Therefore, the phase difference in the pulse voltage generation position due to the rotation direction becomes large. FIG. 4 of Patent Document 1 shows a configuration in which the region for changing the magnetization strength is devised. In this case, the change in the magnetic flux density is as shown by line M3 in FIG. 5 of the same document, and no flat portion occurs near where the magnetic flux density is 0.

[0010] However, in the arrangement where the power generation sensor is offset with respect to the two-pole magnet, there is an angular interval in which both ends of the power generation sensor face magnetic poles of the same polarity, and this angular interval becomes wider as the arrangement of the power generation sensor moves farther from the rotation center. Therefore, the characteristic of not causing a flat portion in the magnetic flux density change as shown by line M3 in FIG. 5 of Patent Document 1 is limited to the case where the power generation sensor is arranged near the rotation center. Therefore, for example, it cannot be applied to the rotation detection of a large-diameter hollow shaft. Also, the change in the magnetic flux density with respect to the rotation angle is not necessarily steep enough, and the pulse voltage generation position varies.

[0011] In the configuration of FIG. 2 of Patent Document 2, the ring-shaped magnet magnetized by dividing the circumferential region into two halves in the circumferential direction into the inner peripheral side and the outer peripheral side, respectively, and further dividing into a total of four regions, the power generation sensor is arranged in the radial direction. In this case, when the angle at which the direction of the boundary of the magnetized region in the circumferential direction coincides with the axial direction of the magnetic wire of the power generation sensor, the magnetic flux density near the magnetic wire becomes 0, and the magnetic flux density changes greatly in the vicinity thereof. Therefore, the variation in the pulse voltage generation position is small, and the phase difference in the pulse voltage generation position due to forward / reverse rotation is also small.

[0012] However, since a special magnetized ring magnet having a width close to the length of the power generation sensor is required, the cost of the magnet becomes high. In addition, there is a problem that the magnet weight and inertia increase. Further, when manufacturing detection devices of different sizes, dedicated magnets are required for each size of the detection device.

[0013] FIG. 30(A) of Patent Document 2 shows a configuration devised so that similar characteristics can be obtained by using a bar magnet instead of a ring magnet. However, since the long axis direction of the power generation sensor is arranged in the radial direction, a large width in the radial direction is required, and accordingly, the detection device becomes large. In addition, when attempting to configure a hollow shaft rotation detection device, there is a problem that the ratio of the hollow diameter to the outer diameter cannot be made large.

[0014] FIG. 6 of Patent Document 3 discloses a configuration in which a plurality of individual magnets magnetized in the radial direction are arranged in the circumferential direction without using a ring magnet, and the long axis direction of the power generation sensor is arranged in the radial direction. The plurality of individual magnets are arranged along the circumference so that the directions of the magnetic poles are alternately different. When using individual magnets, unlike ring magnets, dedicated magnets are not required even when manufacturing detection devices of different sizes, and general-purpose two-pole magnets can be used, so the magnet cost is low.

[0015] However, in the angular range between adjacent magnets, since the power generation sensor does not face the magnetic pole, there is an angular section where the magnetic flux density becomes flat near 0. Therefore, the phase difference due to the rotation direction becomes large. Also, since the change in the magnetic flux density with respect to the angle is gentle, the variation in the generation position of the pulse voltage also becomes large.

Prior Art Documents

Patent Documents

[0016]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0017] One embodiment of this invention provides a motion detection device that solves at least one of the problems arising in the aforementioned prior art.

Means for Solving the Problems

[0018] One embodiment of the present invention provides a motion detection device including a first support, a second support that moves relative to the first support, a power generation sensor disposed on the first support, and a magnetic field generation source supported by the second support. 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 symmetric plane set at the axial center position 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 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 gap in the axial direction. The axially orthogonal portion has a wire arrangement portion formed by a hole or 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 has a plurality of magnetic poles arranged on the second support such that when the second support moves relative to the first support, the magnetic field generation source sequentially enters the detection region along an orbit parallel to the axial direction of the magnetic wire, and magnetic poles of different polarities face each other through a gap in the power generation sensor. The direction of the magnetic flux of each magnetic pole is perpendicular to the moving direction of the magnetic pole (the moving direction of the magnetic pole when the second support moves relative to the first support), and is a direction (gap direction) that intersects the magnetic wire when facing the power generation sensor. The arrangement interval of the plurality of magnetic poles on the orbit is longer than the total length of the magnetic wire. The length of the magnetic poles on the orbit is shorter than the total length of the magnetic wire and is 50% or less of the arrangement interval.

[0019] With this configuration, when the magnetic poles pass through the detection region of the power generation sensor, the magnetic flux density passing through the magnetic wire changes steeply from a stabilizing magnetic field in one direction to a stabilizing magnetic field in the other direction, and in the process of this change, a flat portion where the change in magnetic flux density stagnates does not occur. Therefore, it is possible to provide a motion detection device with less variation in the pulse generation position and less difference in the pulse generation position depending on the motion direction.

[0020] In addition, a magnetic field generation source having a plurality of magnetic poles that generate magnetic flux in a direction (gap direction) that is perpendicular to the moving direction of the magnetic poles and intersects the magnetic wire when facing the power generation sensor can be configured using a plurality of individual magnets magnetized in the gap direction. Such individual magnets may be, for example, general-purpose two-pole magnets that can be magnetized by an air-core coil, so that the magnet cost can be reduced. In addition, since the magnetization direction is the gap direction, the work of fixing the individual magnets to the second support is easy, so the assembly cost can be reduced.

[0021] It is preferable that the length of the magnetic poles on the orbit is equal to or less than half of the total length of the magnetic wire. Thereby, the change in magnetic flux density when the magnetic poles pass through the detection region can be made steeper.

[0022] In addition, it is preferable that the arrangement interval of the magnetic poles on the orbit is 1.5 times or more the total length of the magnetic wire. Thereby, when a certain magnetic pole passes through the detection region, the influence of the magnetic field from other magnetic poles can be suppressed, so that the change in magnetic flux density can be made even steeper.

[0023] The motion detection device preferably further includes a sensor that discriminates the polarity of the magnetic poles located at the central portion in the axial direction of the power generation sensor. With this configuration, in addition to detecting the position, the motion direction can be detected.

Brief Description of the Drawings

[0024]

Figure 1A-1B

Figure 1C

Figure 2A-2B

Figure 2C

Figure 3A-3B

Figure 3C

Figure 4A-4B

Figure 4C

Figure 5A-5B

Figure 5C

Figure 6A

Figure 6B

Figure 7A

Figure 7B

Figure 7C

Figure 8

[0025] Hereinafter, in order to understand the principle of the embodiment of the present invention, several comparative examples will be shown, and then the embodiments of the present invention will be described.

[0026] FIGS. 1A and 1B show the rotation detection device 1 of the first comparative example, and FIG. 1C shows the change in magnetic flux density with respect to the rotation angle.

[0027] This rotation detection device 1 includes a two-pole magnet 12 that rotates around a rotation axis 11 and a power generation sensor 13 in which a magnetic wire 14 is arranged so as to be orthogonal to the rotation axis 11. The power generation sensor 13 includes a magnetic wire 14, a coil 15 wound around the magnetic wire 14, and a pair of cylindrical ferrite cores 16 respectively coupled to both ends of the magnetic wire 14. The axial direction 17 of the magnetic wire 14 is orthogonal to the rotation axis 11, and the axial center position 18 (the center position in the axial direction 17) of the magnetic wire 14 is on the rotation axis 11. The two-pole magnet 12 is disc-shaped, magnetized in the radial direction, with half of the region being the N pole and the remaining half being the S pole.

[0028] Taking the angle at the time of FIG. 1A when the axial direction 17 of the magnetic wire 14 and the magnetic pole boundary line 12a are aligned as 0 degrees and assuming that the value of the angle increases in the counterclockwise direction CCW, the change in the magnetic flux density accompanying the rotation of the two-pole magnet 12 around the rotation axis 11 becomes sinusoidal as shown in FIG. 1C. The magnetic flux density here refers to the magnetic flux density passing through the magnetic wire 14, that is, the density of the magnetic flux component in the direction parallel to the axial direction 17 of the magnetic wire 14 in the vicinity of the magnetic wire 14. The same applies to the description of other comparative examples and embodiments to be described later. The operating magnetic field and the stabilizing magnetic field of the magnetic wire 14 are shown together in FIG. 1C.

[0029] When the two-pole magnet 12 rotates in the counterclockwise direction CCW, when the magnetic flux density falls below the negative stabilizing magnetic field, it enters the positive pulse preparation state (positive set state), and then when the magnetic flux density exceeds the positive operating magnetic field, a positive pulse PP is generated. Also, when the two-pole magnet 12 rotates in the counterclockwise direction CCW, when the magnetic flux density exceeds the positive stabilizing magnetic field, it enters the negative pulse preparation state (negative set state), and then when the magnetic flux density falls below the negative operating magnetic field, a negative pulse NP is generated. Therefore, as shown in FIG. 1C, a positive pulse PP is generated near 0 degrees, and a negative pulse NP is generated near 180 degrees.

[0030] Similarly, when the two-pole magnet 12 rotates in the clockwise direction CW, when the magnetic flux density falls below the negative stabilizing magnetic field, it enters the positive pulse preparation state (positive set state), and then when the magnetic flux density exceeds the positive operating magnetic field, a positive pulse PP is generated. Also, when the two-pole magnet rotates in the clockwise direction CW, when the magnetic flux density exceeds the positive stabilizing magnetic field, it enters the negative pulse preparation state (negative set state), and then when the magnetic flux density falls below the negative operating magnetic field, a negative pulse NP is generated. Therefore, as shown in Figure 1C, a negative pulse NP is generated near 0 degrees, and a positive pulse PP is generated near 180 degrees.

[0031] Since the change in magnetic flux density with respect to the angle has a finite slope, the pulse generation position (the angle at which the pulse is generated) will not match between counterclockwise rotation CCW and clockwise rotation CW, resulting in a shift in the pulse generation position, that is, a phase difference PS. More specifically, a phase difference PS occurs near 0 degrees and near 180 degrees.

[0032] In this comparative example, as shown in Figure 1C, since the change in magnetic flux density with respect to the rotation angle is gentle, the variation in the pulse generation position is large, and the phase difference PS due to the rotation direction is also large.

[0033] In the configuration of this comparative example, since the power generation sensor 13 is arranged on the rotation axis 11, it cannot be applied to a configuration in which mechanical components are coupled to both ends of the rotation axis, nor can a hollow shaft-shaped detection device be configured.

[0034] Figures 2A and 2B show the rotation detection device 2 of the second comparative example, and Figure 2C shows the change in magnetic flux density with respect to the rotation angle.

[0035] This rotation detection device 2 includes a two-pole magnetized ring magnet 22 that rotates around the rotation axis 11 and a power generation sensor 13. The configuration of the power generation sensor 13 is the same as that of the first comparative example. The axial center position 18 of the magnetic wire 14 is offset radially from the rotation axis 11, the axial direction 17 of the magnetic wire 14 is perpendicular to the rotation axis 11, and it is along the tangential direction at a point on the circumference around the rotation axis 11. The two-pole magnetized ring magnet 22 is annular with the rotation axis 11 as the center, magnetized in a direction parallel to the rotation axis 11, and on the surface facing the power generation sensor 13 with a gap, half of the angular region is the N pole and the remaining half of the angular region is the S pole.

[0036] Taking the angle at the time of FIG. 2A when the axial direction 17 of the magnetic wire 14 is parallel to the magnetic pole boundary line 22a as 0 degrees and assuming that the value of the angle increases in the counterclockwise direction CCW, the change in the magnetic flux density accompanying the rotation of the two-pole magnetized ring magnet 22 around the rotation axis 11 becomes trapezoidal as shown in FIG. 2C.

[0037] The operation of the power generation sensor 13 due to the change in the magnetic flux density is the same as that of the first comparative example.

[0038] Since the magnetic flux density becomes 0 in the angular region where both ends of the power generation sensor 13 face magnetic poles of the same polarity, flat portions with a magnetic flux density of 0 centered on 0 degrees and 180 degrees respectively appear. Accordingly, a large phase difference PS due to the rotation direction occurs near 0 degrees and near 180 degrees. This phase difference PS increases as the offset from the rotation axis 11 to the power generation sensor 13 increases.

[0039] The configuration of this comparative example requires a ring magnet 22 magnetized over the entire circumference, so it is necessary to prepare a dedicated magnetization yoke for its production. Also, a ring magnet 22 that matches the size (diameter) of the detection device is required. Therefore, since a general-purpose magnet cannot be used, there is also a problem that the magnet cost increases.

[0040] The configuration of Patent Document 1 can be classified into the category of the second comparative example.

[0041] Figs. 3A and 3B show the rotation detection device 3 of the third comparative example, and Fig. 3C shows the change in magnetic flux density with respect to the rotation angle.

[0042] This rotation detection device 3 includes a ring magnet 23 that rotates around the rotation axis 11 and a power generation sensor 13. The configuration of the power generation sensor 13 is the same as that of the first comparative example. The axial center position 18 of the magnetic wire 14 is offset in the radial direction from the rotation axis 11, and the axial direction 17 of the magnetic wire 14 is along the radial direction. The ring magnet 23 is annular with the rotation axis 11 as the center, is magnetized with multiple poles in a direction parallel to the rotation axis 11, and has four magnetization regions 24 on the surface facing the power generation sensor 13 with a gap therebetween.

[0043] Specifically, the surface of the ring magnet 23 facing the power generation sensor 13 is divided into an inner diameter part and an outer diameter part in the radial direction and is also divided into two parts in the circumferential direction around the rotation axis 11, and is thus divided into four magnetization regions 24. More specifically, the angular region of half of the inner diameter part is an arc-shaped N-pole region, and the remaining half of the angular region is an arc-shaped S-pole region. Also, the angular region of half of the outer diameter part is an arc-shaped S-pole region, and the remaining half of the angular region is an arc-shaped N-pole region. The N-pole region of the outer diameter part is adjacent to the outside of the S-pole region of the inner diameter part, and the S-pole region of the outer diameter part is adjacent to the outside of the N-pole region of the inner diameter part. The inner diameter part and the outer diameter part are aligned at the boundary of the circumferential magnetization region 24, and the magnetic pole boundary line 25 is along the radial direction.

[0044] Taking the angle at the time of Fig. 3A when the axial direction 17 of the magnetic wire 14 and the magnetic pole boundary line 25 are parallel as 0 degrees and assuming that the value of the angle increases in the counterclockwise direction CCW, the change in magnetic flux density accompanying the rotation of the ring magnet 23 around the rotation axis 11 becomes trapezoidal as shown in Fig. 3C.

[0045] The operation of the power generation sensor 13 due to the change in magnetic flux density is the same as that of the first comparative example.

[0046] The changes in magnetic flux density near 0 degrees and 180 degrees where the magnetic flux density becomes 0 are steep. Therefore, the variation in the pulse generation position is small, and the phase difference PS due to the rotation direction is also small.

[0047] On the other hand, since the major axis direction of the power generation sensor 13 is the radial direction, there is a problem that the outer diameter of the detection device becomes large.

[0048] Also, in the configuration of this comparative example, since a ring magnet 23 magnetized over the entire circumference is required, it is necessary to prepare a dedicated magnetization yoke for its production. Also, a ring magnet 23 that matches the size (diameter) of the detection device is required. Therefore, since a general-purpose magnet cannot be used, there is also a problem that the magnet cost becomes high.

[0049] The configuration of Patent Document 2 can be classified into the category of the third comparative example.

[0050] Figures 4A and 4B show the rotation detection device 4 of the fourth comparative example, and Figure 4C shows the change in magnetic flux density with respect to the rotation angle.

[0051] This rotation detection device 4 includes a ring-shaped support substrate 26 that rotates around the rotation axis 11, two individual magnets 27 arranged at intervals in the circumferential direction on the support substrate 26, and a power generation sensor 13. The configuration of the power generation sensor 13 is the same as that of the first comparative example.

[0052] The axial center position 18 of the magnetic wire 14 is offset radially from the rotation axis 11, and the axial direction 17 of the magnetic wire 14 is along the radial direction. Two individual magnets 27 are magnetized in the radial direction and are arranged at an angular interval of 180 degrees around the rotation axis 11. One of the two individual magnets 27 has an N pole arranged inwardly close to the rotation axis 11 and is fixed to the support substrate 26, and the other has an S pole arranged inwardly close to the rotation axis 11 and is fixed to the support substrate 26. The magnetic pole boundary line 27a of each individual magnet 27 is along the tangential direction of the circumference around the rotation axis 11 (more precisely, the tangential direction at the position of each individual magnet 27). Each individual magnet 27 is arranged on the support substrate 26 such that when facing the power generation sensor 13, one magnetic pole faces one end portion of the magnetic wire 14 and the other magnetic pole faces the other end portion of the magnetic wire 14.

[0053] Taking the angle at the time of FIG. 4A when the power generation sensor 13 is located in the middle of the two individual magnets 27 as 0 degrees and assuming that the value of the angle increases in the counterclockwise direction CCW, the change in the magnetic flux density accompanying the rotation of the individual magnet 27 around the rotation axis 11 shows a waveform as shown in FIG. 4C.

[0054] The operation of the power generation sensor 13 due to the change in the magnetic flux density is the same as that of the first comparative example.

[0055] In this comparative example, since the change in the magnetic flux density with respect to the angle is small, variations in the generation position of the pulse voltage are likely to occur. Also, the vicinity of 0 degrees and 180 degrees where the magnetic flux density becomes 0 belongs to the angular interval between adjacent individual magnets 27 and is a flat portion where the magnetic flux density does not change. Therefore, the phase difference PS due to the rotation direction is large.

[0056] Also, similar to the third comparative example, since the major axis direction of the power generation sensor 13 is the radial direction, there is a problem that the outer shape of the detection device becomes large.

[0057] On the one hand, in this comparative example, a general-purpose two-pole magnet that can be magnetized by an air-core coil can be used as the individual magnet 27, so the magnet cost is low. In addition, there is an advantage that magnets 27 with the same configuration can be used for detection devices of different sizes.

[0058] However, for the individual magnet 27, in practice, it is necessary to align and fix it to the support substrate 26 so that the magnetic pole boundary line 27a that cannot be visually recognized is along the circumferential tangent direction. Therefore, the assembly work is complicated, and accordingly, there is a problem that the assembly cost increases.

[0059] The configuration of Patent Document 3 can be classified into the category of the fourth comparative example.

[0060] Figures 5A and 5B show a rotation detection device 5 which is an example of a motion detection device according to an embodiment of the present invention, and Figure 5C shows the change in magnetic flux density with respect to the rotation angle.

[0061] This rotation detection device 5 includes a first support 51, a second support 52 that moves relative to the first support 51, a power generation sensor 100 supported by the first support 51, and a magnetic field generation source 400 supported by the second support 52.

[0062] In this embodiment, the first support 51 is a support substrate, and the power generation sensor 100 is supported on one main surface thereof. In this embodiment, the second support 52 is a ring-shaped support substrate that rotates around the rotation axis 40. The magnetic field generation source 400 includes a plurality (two in this embodiment) of individual magnets M1 and M2 arranged at intervals in the circumferential direction on the second support 52.

[0063] The power generation sensor 100 includes a magnetic wire 110, a coil 120 wound around the magnetic wire 110, and a pair of L-shaped magnetic flux conduction pieces 130 and 131 respectively coupled to both ends of the magnetic wire 110, and is configured such that the second support 52 side (the lower side in Figure 5B) is the detection region 140. A specific configuration example of the power generation sensor 100 will be described later with reference to Figures 6A and 6B.

[0064] The axial center position 113, which is the axial center position of the magnetic wire 110, is offset radially from the rotation axis 40, and the axial direction x of the magnetic wire 110 is along the circumferential direction around the rotation axis 40 (more specifically, on the circumference around the rotation axis 40 passing through the axial center position 113 of the magnetic wire 110, the direction of the tangent at the axial center position 113).

[0065] The two individual magnets M1 and M2 are magnetized in a direction parallel to the rotation axis 40 and are arranged at equal intervals, that is, at an angular interval of 180 degrees, on the circumference around the rotation axis 40. One of the two individual magnets M1 and M2 is fixed to the second support 52 so that the N pole n1 faces the power generation sensor 100 when approaching the power generation sensor 100, and the other is fixed to the second support 52 so that the S pole s1 faces the power generation sensor 100 when approaching the power generation sensor 100. When the second support 52 rotates around the rotation axis 40, each magnetic pole n1, s1 moves along the circumferential orbit 30.

[0066] Thus, the magnetic field generation source 400 has a plurality of magnetic poles n1, s1 arranged on the second support 52. When the second support 52 rotates relative to the first support 51 (an example of relative movement), these magnetic poles n1, s1 enter the detection region 140 in order along the orbit 30 substantially parallel to the axial direction x of the magnetic wire 110. At this time, the magnetic poles n1, s1 of different polarities face the power generation sensor 100 alternately through the gap 31. Since the individual magnets M1, M2 are magnetized in a direction parallel to the rotation axis 40, the direction of the magnetic flux of each magnetic pole n1, s1 is perpendicular to the moving direction of the magnetic pole n1, s1 and intersects the magnetic wire 110 when facing the power generation sensor 100, that is, the direction in which the gap 31 between the magnetic pole n1, s1 and the power generation sensor 100 opens (gap direction).

[0067] The arrangement interval λ of a plurality of magnetic poles n1, s1 on the track 30, that is, the interval between adjacent magnetic poles n1, s1 in the circumferential direction, is longer than the total length Lw of the magnetic wire 110 (see FIG. 6B). More specifically, in this example, the arrangement interval λ is 1.5 times or more the total length Lw of the magnetic wire 110. Also, the length α (the length along the track 30) of the magnetic poles n1, s1 on the track 30 is shorter than the total length Lw of the magnetic wire 110 and is 50% or less of the magnetic pole arrangement interval λ. In this example, the length α of the magnetic poles n1, s1 on the track 30 is less than half of the total length Lw of the magnetic wire 110.

[0068] When the two individual magnets M1, M2 rotate in the counterclockwise direction CCW together with the second support 52, when the magnetic flux density falls below the negative stabilization magnetic field, it enters the positive pulse preparation state (positive set state), and then when the magnetic flux density exceeds the positive operating magnetic field, a positive pulse PP is generated. Also, when the two individual magnets M1, M2 rotate in the counterclockwise direction CCW together with the second support 52, when the magnetic flux density exceeds the positive stabilization magnetic field, it enters the negative pulse preparation state (negative set state), and then when the magnetic flux density falls below the negative operating magnetic field, a negative pulse NP is generated. Therefore, as shown in FIG. 5C, a negative pulse NP is generated near 90 degrees, and a positive pulse PP is generated near 270 degrees.

[0069] Similarly, when the two individual magnets M1, M2 rotate in the clockwise direction CW together with the second support 52, when the magnetic flux density falls below the negative stabilization magnetic field, it enters the positive pulse preparation state (positive set state), and then when the magnetic flux density exceeds the positive operating magnetic field, a positive pulse PP is generated. Also, when the two individual magnets M1, M2 rotate in the clockwise direction CW together with the second support 52, when the magnetic flux density exceeds the positive stabilization magnetic field, it enters the negative pulse preparation state (negative set state), and then when the magnetic flux density falls below the negative operating magnetic field, a negative pulse NP is generated. Therefore, as shown in FIG. 5C, a positive pulse PP is generated near 90 degrees, and a negative pulse NP is generated near 270 degrees.

[0070] Near 90 degrees and 270 degrees, the change in magnetic flux density with respect to the rotation angle is very steep. Therefore, the variation in the pulse generation position is small, and moreover, the shift in the pulse generation position according to the rotation direction, that is, the phase difference PS, is extremely small. In addition, since the angular difference from the operating magnetization to the stabilizing magnetic field is very small, the range (inversion range) in which so-called pulse dropout occurs when the moving direction (rotation direction) is reversed is narrow.

[0071] Also, since the major axis direction of the power generation sensor 100 is the circumferential tangent direction, the outer shape of the rotation detection device 5 can be made small. Viewed from another perspective, the diameter of the hollow portion of the second support 52 can be increased. In addition, since general-purpose individual magnets M1 and M2 that can be manufactured by magnetizing in the thickness direction with an air-core coil can be used, the magnet cost can be reduced. Of course, since the individual magnets M1 and M2 of the same design can be generally used for rotation detection devices of different sizes, a special magnet with a dedicated design is not required. Moreover, the N poles or S poles of the individual magnets M1 and M2 magnetized in the thickness direction can be alternately oriented in one direction and fixed to the second support 52. Compared with the fourth comparative example in which the magnetic pole boundary needs to be aligned with the radial direction, the assembly work is simple, and accordingly, the assembly cost can be reduced.

[0072] As described above, since the arrangement interval λ of the plurality of magnetic poles n1 and s1 on the orbit 30 is longer than the total length of the magnetic wire 110 (preferably 1.5 times or more), as shown in FIG. 5C, in the intermediate region between 90 degrees and 270 degrees where pulses are generated, a flat portion where the magnetic flux density becomes 0 appears. Thereby, the influence of the magnetic fields from the adjacent magnetic poles n1 and s1 on the orbit 30 can be separated, and the change in the magnetic flux density near 90 degrees and 270 degrees can be made steep. This tendency is further enhanced by setting the length α of the magnetic poles n1 and s1 on the orbit 30 to 50% or less of the arrangement interval λ of the magnetic poles.

[0073] Also, as described above, the length α of the magnetic poles n1 and s1 on the orbit 30 is shorter than the total length of the magnetic wire 110. Thereby, in the vicinity of 90 degrees and 270 degrees, a steep change in magnetic flux density can be ensured without causing a flat portion in the change of magnetic flux density. It is preferable to set the length α of the magnetic poles n1 and s1 to be less than or equal to half of the total length of the magnetic wire 110, as this can make the change in magnetic flux density steeper.

[0074] FIG. 6A is a perspective view for explaining a configuration example of the power generation sensor 100, and FIG. 6B is a front view seen in the direction of arrow 101 in FIG. 6A. When the power generation sensor 100 and the magnetic pole 401 of the magnetic field generation source 400 (for example, an individual magnet) move relative to each other, the power generation sensor 100 generates a pulse signal. The relative movement between the power generation sensor 100 and the magnetic field generation source 400 is achieved by the movement of at least one of the power generation sensor 100 and the magnetic field generation source 400. Hereinafter, an example in which the relative movement is mainly achieved by the movement of the magnetic field generation source 400 will be described.

[0075] 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 having soft magnetic components. The coil 120 is wound around the magnetic wire 110 such that the first end 111 and the second end 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 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.

[0076] 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 length direction, the wire length direction) at the central position 113 of the magnetic wire 110 in the axial direction x (hereinafter referred to as the "axial center position"). 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 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 ends of the axially orthogonal portion 133.

[0077] Both ends 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, wire arrangement portions 130a and 131a having holes or grooves penetrating in the axial direction x are provided at the base end portions of the axially orthogonal portions 133. FIGS. 6A and the like show an example in which the wire arrangement portions 130a and 131a are configured by holes. When the wire arrangement portions 130a and 131a are configured by grooves, the grooves are preferably grooves that extend along the axially orthogonal direction z so as to open to the end surface on the side opposite to the detection region 140 described later. The first end 111 and the second end 112 of the magnetic wire 110 are fixed to the axially orthogonal portion 133 in a state of penetrating the axially orthogonal portion 133 in the wire arrangement portions 130a and 131a. More specifically, by disposing a resin (not shown) in the holes or grooves constituting the wire arrangement portions 130a and 131a, the ends 111 and 112 of the magnetic wire 110 are fixed to the axially 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.

[0078] The axially 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 axially parallel portions 134 to the symmetry plane 115 are equal. The distance L in the axial direction x of this space is set to be 5% to 50% of the distance D between the pair of axially orthogonal portions 133 at the coupling position between the magnetic wire 110 and the axially orthogonal portion 133, and more preferably 20% to 40%. More specifically, the distance D is the distance in the axial direction x between the inner surfaces 130b and 131b (the inner surfaces of the axially 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.

[0079] The soft magnetic component constituting the magnetic flux conducting pieces 130 and 131 is preferably made of a material having a coercive force equal to or less than that of the magnetic wire 110 and a relative 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 source 400 moves at high speed is applied, the influence on the output characteristics of the power generation sensor 100 is small. Specifically, the soft magnetic component is preferably made of a Ni-based ferrite or Mn-based ferrite material.

[0080] This power generation sensor 100 is configured such that a region on the side opposite to the magnetic wire 110 with respect to the axially parallel portion 134 is defined as a detection region 140. A magnetic field generation source 400 that generates a magnetic field to be detected is disposed in this detection region 140. The power generation sensor 100 and the magnetic field generation source 400 are arranged so as to have a gap 31 in the direction z orthogonal to the axis. This gap 31 may be a complete air gap, or for example, a printed circuit board 45 constituting the first support 51 may be interposed. That is, the power generation sensor 100 may be disposed on one main surface side of the printed circuit board 45, and the magnetic field generation source 400 may be disposed on the other main surface side. Electrical components and / or electronic components may be mounted on one or both main surfaces of the printed circuit board 45. In one specific example, the power generation sensor 100 is mounted on one main surface of the printed circuit board 45.

[0081] Typically, the magnetic field generation source 400 moves 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 movement path of the magnetic field generation source 400. In this embodiment, the magnetic field generation source 400 is composed of a plurality of individual magnets magnetized in the direction z orthogonal to the axis. Thereby, the magnetic field generation source 400 has a plurality of magnetic poles 401 that face the power generation sensor 100 (more specifically, the axially parallel portion 134) when moving along an orbit 30 passing through the detection region 140.

[0082] In this embodiment, the plurality of magnetic poles 401 are arranged such that when the second support 52 moves relative to the first support 51 (printed circuit board 45), magnetic poles 401 of different polarities face the power generation sensor 100 alternately. Due to the change in the magnetic field that occurs when the magnetic poles 401 move through the detection region 140, the power generation sensor 100 outputs a pulse voltage. By signal-processing and counting this pulse voltage, a position detection device that generates position information, that is, an encoder (an example of a motion detection device), can be configured.

[0083] The moving direction of the magnetic pole 401 in the detection region 140, that is, the motion direction, is along the axial direction x. That is, it is substantially parallel to the magnetic wire 110. In other words, the track 30 has a portion that is substantially parallel to the axial direction x in the detection region 140. In one specific example, the track 30 has a straight portion parallel to the axial direction x in the detection region 140. The track 30 may be entirely linear or may have a curved portion. In another specific example, the track 30 has an arc portion with a tangent parallel to the axial direction x in the detection region 140. This arc portion may have a center on the rotation axis 40 parallel to the axial orthogonal direction z. The track 30 may be entirely an arc portion, that is, circular. Also, the track 30 may have a portion with a shape other than an arc shape, such as a straight portion or an elliptical portion. In the examples shown in FIGS. 5A and 5B, the track 30 is circular.

[0084] The pair of magnetic flux conduction pieces 130, 131 are configured to correct the magnetic field formed by the magnetic field generation source 400 disposed in the detection region 140 in the space including the magnetic flux conduction pieces 130, 131 into a magnetic field in the axial direction x and apply it to the magnetic wire 110.

[0085] More specifically, the magnetic flux conduction pieces 130 and 131 made of soft magnetic components have a substantially rectangular parallelepiped-shaped axis orthogonal portion 133 and a substantially rectangular parallelepiped-shaped axis parallel portion 134 continuously provided at the tip portion on the side facing the magnetic field generation source 400 of the axis orthogonal portion 133, that is, on the detection region 140 side. The magnetic flux conduction pieces 130 and 131 have an L-shaped bend at a right angle at the joint portion between the axis orthogonal portion 133 and the axis parallel portion 134. The axis parallel portion 134 extends along the axial direction x so as to cover the magnetic wire 110, that is, to shield between the magnetic wire 110 and the detection region 140. The axis parallel portions 134 of the pair of magnetic flux conduction pieces 130 and 131 having symmetrical shapes extend toward the axial center side of the magnetic wire 110, and their proximal ends 134a face each other with a space therebetween near the axial center position 113 of the magnetic wire 110. The proximal ends 134a form a plane orthogonal to the axial direction x, and the two planes forming the two proximal ends 134a are parallel to each other and face each other in the axial direction x. The distance L in the direction x of the interval between the two proximal ends 134a is the distance between the two planes forming the two proximal ends 134a.

[0086] The magnetic flux conduction pieces 130 and 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 and 112 of the magnetic wire 110 are fixed by resin (not shown) to wire arrangement portions 130a and 131a each composed 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.

[0087] Both ends of the coil 120 may be connected to external electrodes provided on the axis parallel portion 134. By joining this external electrode to a wiring conductor provided on one main surface of the printed circuit board 45, the power generation sensor 100 may be surface-mounted on the printed circuit board 45.

[0088] In the power generation sensor 100 configured as described above, the magnetic field in the detection region 140 is guided to both ends 111 and 112 of the magnetic wire 110 by the magnetic flux conduction pieces 130 and 131 having soft magnetic parts. Moreover, since the axial parallel part 134 parallel to the axial direction x of the magnetic wire 110 is located between the detection region 140 and the magnetic wire 110, the magnetic flux directed from the detection region 140 to the axial intermediate part (axial mid-position) of the magnetic wire 110 is shielded by the axial parallel part 134. In particular, when the distance L in the axial direction x between the proximal ends 134a of the axial parallel parts 134 of the pair of magnetic flux conduction pieces 130 and 131 is 5% to 50% of the distance D between the axial orthogonal parts 133 at the coupling position with the magnetic wire 110, an excellent magnetic shielding effect can be obtained. Therefore, since the magnetic field in the axial direction x can be applied over a wide range 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.

[0089] Moreover, since the power generation sensor 100 is provided with the magnetic flux conduction pieces 130 and 131, and the magnetic flux conduction pieces 130 and 131 and the magnetic wire 110 are fixed and coupled to each other, a magnetic field source 400 (typically a magnet) as a detection medium may be arranged in the detection region 140. Therefore, combinations with magnetic field sources 400 having different shapes and / or polarities are easy.

[0090] When the power generation sensor 100 and the magnetic field source 400 are in relative motion, the magnetic pole 401 of the magnetic field source 400 moves along the orbit 30 passing through the detection region 140. The orbit 30 includes a straight line part parallel to the axial direction x in the detection region 140 or an arc part having a tangent parallel to the axial direction x in the detection region 140. Therefore, when the magnetic pole 401 passes through the detection region 140, the magnetic pole 401 faces the axial parallel part 134, so that the magnetic flux generated by the magnetic pole 401 is applied to the magnetic wire 110 through the magnetic flux conduction pieces 130 and 131.

[0091] Since the axially parallel portions 134 of the magnetic flux conduction pieces 130 and 131 extend in the axial direction x of the magnetic wire 110, due to their magnetic shielding effect, it is difficult for magnetic flux to enter the axially intermediate portion of the magnetic wire 110 from the magnetic pole 401. The axially parallel portions 134 extending in the axial direction x of the magnetic wire 110 can collect a large amount of magnetic flux. Therefore, even if the magnetic flux generated from the magnetic pole 401 is weak, a magnetic field necessary for the manifestation of the large Barkhausen effect can be applied to the magnetic wire 110. Further, the axially parallel portions 134 can face the magnetic pole 401 over a wide range within the detection region 140 and suppress the entry of magnetic flux into the axially intermediate portion of the magnetic wire 110.

[0092] Therefore, when the magnetic pole 401 moves slightly in any direction along the orbit 30 from a state where the magnetic flux guided from the pair of magnetic flux conduction pieces 130 and 131 to both ends 111 and 112 of the magnetic wire 110 is balanced with the magnetic pole 401 facing the axial center position 113 of the magnetic wire 110, the magnetic flux density in the magnetic wire 110 changes abruptly. Thereby, the change in the magnetic flux density with respect to the fluctuation of the position of the magnetic pole 401 becomes steep.

[0093] FIG. 7A is a perspective view for explaining a specific structural example of the rotation detection device 5A, and FIG. 7B is a plan view thereof. Further, FIG. 7C is a front view showing the configuration in the vicinity of the power generation sensor 100 as viewed from the right side of FIG. 7B.

[0094] The rotation detection device 5A is an example of an encoder and detects the rotational position around the rotation axis 40 that coincides with the central axis of the rotation axis 50. The rotation detection device 5A includes a power generation sensor 100 and a magnetic field generation source 400. In this example, the rotation detection device 5A further includes a sensor 55 (for example, a magnetic sensor). Although illustration is omitted, the rotation detection device 5A may further include a count processing circuit that processes and counts the pulse output generated by the power generation sensor 100, a non-volatile memory that stores the count result by the count processing circuit, and the like. The count processing circuit may be configured to perform a counting operation in consideration of the output of the sensor 55.

[0095] The power generation sensor 100 is disposed on the first support 51 and is supported by the first support 51. In this embodiment, the sensor 55 is also mounted on the first support 51.

[0096] The magnetic field generation source 400 is fixed to the second support 52. The second support 52 moves relative to the first support 51. Specifically, the second support 52 is coupled (fixed) to the rotation axis 50 and rotates about the rotation axis 40 together with the rotation axis 50. Therefore, the second support 52 can be a part of the rotating body. In contrast, the first support 51 is fixedly arranged and held in a non-rotating state. Thereby, the magnetic field generation source 400 rotates about the rotation axis 40 together with the second support 52 and moves relative to the first support 51.

[0097] The rotation axis 50 is typically rotated by a driving force from the driving shaft of an electric motor (not shown). When the electric motor is driven in both directions, accordingly, the rotation axis 50 rotates in both directions, counterclockwise direction CCW and clockwise direction CW. The first support 51 may be a printed circuit board 45 arranged along a plane orthogonal to the rotation axis 40.

[0098] In this example, the magnetic field generation source 400 includes a plurality of, that is, 2k (k = 2 in the illustrated example) individual magnets M1, M2,... These are fixed to the second support 52. The individual magnets M1, M2,... are magnetized in a direction parallel to the rotation axis 40, that is, in the axis-orthogonal direction z, and are arranged at equal angular intervals about the rotation axis 40. In this example, the individual magnets M1, M2,... are plate-shaped (more specifically, disk-shaped) magnetized in the thickness direction, but the shape of the individual magnets M1, M2,... is not limited to this. It may be a rectangular parallelepiped shape or a rectangular plate shape as shown in FIG. 6A, or a magnet having an arc shape (specifically, a sector shape with the radially inner part cut off) in plan view may be used.

[0099] In a plan view (see FIG. 7B) seen from a direction parallel to the rotation axis 40, the N poles n1, n2,... and the S poles s1, s2,... are arranged alternately in the circumferential direction. That is, as the second support 52 rotates in one direction around the rotation axis 40, the N pole and the S pole, which are magnetic poles of different polarities, alternately enter the detection region 140 (see FIG. 7C) of the power generation sensor 100, and an alternating magnetic field is generated in the vicinity of the power generation sensor 100.

[0100] The power generation sensor 100 is mounted on one main surface of the first support 51 (printed circuit board 45). The magnetic wire 110 of the power generation sensor 100 is on a tangent to a circle centered on the rotation axis 40, and the axial center position 113 of the magnetic wire 110 is on the contact point of the tangent. The power generation sensor 100 is arranged such that when the center of one of the individual magnets M1, M2,... (i.e., the center of any of the plurality of magnetic poles n1, n2,..., nk; s1, s2,..., sk) coincides with the axial center position 113 of the magnetic wire 110, the magnetism conducted from the two magnetic flux conduction pieces 130, 131 is balanced.

[0101] The axially parallel portions 134 of the magnetic flux conduction pieces 130, 131 form a detection region facing surface 134b facing the detection region 140 on the detection region 140 side. The detection region facing surface 134b is a flat surface parallel to the axial direction x. This detection region facing surface 134b forms a magnetic flux conduction end that guides the magnetic flux from the magnetic pole into the magnetic flux conduction pieces 130, 131 when a magnetic pole is arranged in the detection region 140.

[0102] The axially parallel portions 134 of the magnetic flux conduction pieces 130 and 131 are joined to a wiring pattern (not shown) formed on one main surface of the first support 51 (printed circuit board 45), whereby the power generation sensor 100 is surface-mounted on the first support 51 (printed circuit board 45). The power generation sensor 100 is arranged such that the axial direction x of the magnetic wire 110 is along the tangent at one point (contact point) on the circumference having the center on the rotation axis 40, and the axial center position 113 of the magnetic wire 110 coincides with the contact point. The detection region 140 of the power generation sensor 100 is on the side opposite to the magnetic wire 110 with respect to the axially parallel portion 134. In this example, it is the region on the other main surface side of the first support 51 (printed circuit board 45).

[0103] In this example, the second support 52 is configured in an annular shape surrounding the rotation axis 40. More specifically, the second support 52 is composed of an annular plate-like body, is arranged along a plane orthogonal to the rotation axis 40, and is parallel to the first support 51 (printed circuit board 45). On the surface of the second support 52 facing the other main surface of the first support 51 (printed circuit board 45), a plurality of individual magnets M1, M2,... are fixed. In this embodiment, the plurality of individual magnets M1, M2,... are arranged at equal intervals in the circumferential direction around the rotation axis 40. In the illustrated specific example, four individual magnets M1, M2, M3, M4 are arranged at an angular interval of 90 degrees around the rotation axis 40 and are fixed to the second support 52 so as to face the first support 51 (printed circuit board 45). The distance from the rotation axis 40 to the centers of the individual magnets M1, M2,... may be equal to the distance from the rotation axis 40 to the axial center position 113 of the magnetic wire 110. That is, in a plan view along the rotation axis 40, the magnetic wire 110 and the individual magnets M1, M2,... may be located on a circumference with an equal radius having the rotation axis 40 as the central axis, whereby they may have a positional relationship that allows them to face each other in a direction parallel to the rotation axis 40. The second support 52 is preferably a yoke made of a soft magnetic material.

[0104] As the second support 52 rotates about the axis of rotation 40 together with the axis of rotation 50, the individual magnets M1, M2, … move on a circumferential orbit 30 centered on the axis of rotation 40 and passing through the detection region 140. The axial direction x of the magnetic wire 110 is parallel to the tangent passing through a certain point (contact point) on the circumferential orbit 30, and the axial center position 113 is on the perpendicular line (in this example, a perpendicular line parallel to the axis of rotation 40) erected on the tangent at the contact point. In other words, the axial center position 113 of the magnetic wire 110 has its center on the axis of rotation 40 and is located at a certain point (contact point) on a circumference having the same radius as the circumferential orbit 30, and the magnetic wire 110 is along the tangent at the contact point.

[0105] The distance in the direction along the axis of rotation 40 between the first support 51 and the second support 52 is determined to be an appropriate value that allows the individual magnets M1, M2, … to enter the detection region 140 of the power generation sensor 100 by the rotation of the second support 52.

[0106] On the main surface of the printed circuit board 45 constituting the first support 51, on which the power generation sensor 100 is mounted, a sensor 55 made of, for example, a magnetic sensor is further mounted. Other electrical components or electronic components such as the above-described count processing circuit and non-volatile memory may be further mounted on the main surface of the printed circuit board 45.

[0107] The sensor 55 is arranged so as to be able to detect the polarity of the magnetic pole facing the central part of the power generation sensor 100. The sensor 55 is composed of, for example, a magnetic sensor such as a Hall IC. When it detects the N pole (when the N pole faces the central part of the power generation sensor 100), it outputs an H signal, and when it detects the S pole (when the S pole faces the central part of the power generation sensor 100), it outputs an L signal. Thereby, the sensor 55 discriminates the polarity of the magnetic pole passing near it, and as a result, outputs an identification signal for identifying the polarity of the magnetic pole facing the central part of the power generation sensor 100. In this embodiment, the sensor 55 is arranged to detect the magnetic pole at a position with a phase difference of 180 degrees around the rotation axis 40 with respect to the power generation sensor 100, that is, at a position symmetric with respect to the rotation axis 40. If k is an even number (for example, 2), the sensor 55 detects a magnetic pole with the same polarity as the magnetic pole facing the central part of the power generation sensor 100. When k is an odd number (for example, 3), the sensor 55 detects a magnetic pole with the opposite polarity to the magnetic pole facing the central part of the power generation sensor 100. In any case, the sensor 55 can detect the polarity of the magnetic pole facing the central part of the power generation sensor 100.

[0108] With such a configuration, every time a pair of magnetic poles n1, s1; n2, s2;...; nk, sk passes through the detection region 140 along the circumferential orbit 30 due to the counterclockwise rotation CCW around the rotation axis 40, one negative pulse NP and one positive pulse PP are generated in sequence (see Fig. 5C). Also, every time a pair of magnetic poles n1, s1; n2, s2;...; nk, sk passes through the detection region 140 along the circumferential orbit 30 due to the clockwise rotation CW around the rotation axis 40, one positive pulse PP and one negative pulse NP are generated in sequence (see Fig. 5C). Then, based on these pulses and the sensor 55 that outputs an identification signal representing the polarity of the magnetic poles on the circumferential orbit 30 between the magnetic flux conduction pieces 130, 131, the rotation position and the rotation direction can be identified.

[0109] Specifically, when the sensor 55 detects the N pole when the negative pulse NP occurs, and when the sensor 55 detects the S pole when the positive pulse PP occurs, the rotation direction may be identified as the counterclockwise direction CCW. On the other hand, when the sensor 55 detects the N pole when the positive pulse PP occurs, and when the sensor 55 detects the S pole when the negative pulse NP occurs, the rotation direction may be identified as the clockwise direction CW.

[0110] Similar to the case of the configuration shown in FIGS. 6A and 6B, the arrangement interval λ of the plurality of magnetic poles on the track 30 is longer than the total length of the magnetic wire 110. In this example, the arrangement interval λ is 1.5 times or more the total length Lw of the magnetic wire 110. Also, the length α of the magnetic poles on the track 30 (the length along the track 30) is shorter than the total length Lw of the magnetic wire 110 and is 50% or less of the magnetic pole arrangement interval λ. In this example, the length α of the magnetic poles on the track 30 is half or less of the total length Lw of the magnetic wire 110.

[0111] With such a configuration, an effect similar to that of the configuration shown in FIGS. 6A and 6B can be achieved.

[0112] FIG. 8 is a plan view for explaining the configuration of a rotation detection device 6, which is an example of a motion detection device according to another embodiment of the present invention.

[0113] This rotation detection device 6 includes a first support 51A, a second support 52A that moves relative to the first support 51A, a power generation sensor 100 supported by the first support 51A, and a magnetic field generation source 400 supported by the second support 52A. The first support 51A is a support substrate in this embodiment, and the power generation sensor 100 is supported on one main surface thereof. The second support 52A is cylindrical and rotates around the rotation axis 40 in this embodiment. The magnetic field generation source 400 includes a plurality (two in this embodiment) of individual magnets M1, M2 arranged at intervals in the circumferential direction on the outer peripheral surface of the second support 52A.

[0114] The power generation sensor 100 has the same configuration as in the case of FIG. 6A and the like, and includes a magnetic wire 110, a coil 120 wound around the magnetic wire 110, and a pair of L-shaped magnetic flux conduction pieces 130 and 131 respectively coupled to both ends of the magnetic wire 110, and is configured such that the second support 52A side (rotation axis 40 side) is the detection region 140. That is, this rotation detection device 6 is a radial gap type with the direction in which the gap between the magnetic field generation source 400 (individual magnet) and the power generation sensor 100 opens (gap direction) as the radial direction.

[0115] The axial center position 113 of the magnetic wire 110 is offset radially from the rotation axis 40, and the axial direction x of the magnetic wire 110 is along the circumferential direction around the rotation axis 40 (more specifically, on the circumference around the rotation axis 40 passing through the axial center position 113 of the magnetic wire 110, the direction of the tangent at the axial center position 113). The two individual magnets M1 and M2 are magnetized in the radial direction (gap direction) orthogonal to the rotation axis 40 and are arranged at equal intervals, that is, at an angular interval of 180 degrees, on the circumference around the rotation axis 40. One of the two individual magnets M1 and M2 is fixed to the second support 52A so that the N pole n1 faces the power generation sensor 100 when approaching the power generation sensor 100, and the other of them is fixed to the outer peripheral surface of the second support 52A so that the S pole s1 faces the power generation sensor 100 when approaching the power generation sensor 100.

[0116] When the second support 52A rotates around the rotation axis 40, each of the magnetic poles n1, s1 moves along the circumferential orbit 30. Thus, the magnetic field generation source 400 has a plurality of magnetic poles n1, s1 arranged on the second support 52A. When the second support 52A rotates relative to the first support substrate (an example of relative movement), these plurality of magnetic poles n1, s1 sequentially enter the detection region 140 along an orbit substantially parallel to the axial direction x of the magnetic wire 110. At this time, magnetic poles n1, s1 of different polarities face the power generation sensor 100 alternately through the gap. Since the individual magnets M1, M2 are magnetized in the radial direction orthogonal to the rotation axis 40, the direction of the magnetic flux of each magnetic pole n1, s1 is perpendicular to the moving direction of the magnetic pole n1, s1 and intersects the magnetic wire 110 when facing the power generation sensor 100, that is, the direction in which the gap between the magnetic pole n1, s1 and the power generation sensor 100 opens (gap direction).

[0117] The arrangement interval λ between the plurality of magnetic poles n1, s1 on the orbit 30 is longer than the total length of the magnetic wire 110. More specifically, in this example, the arrangement interval λ is 1.5 times or more the total length Lw of the magnetic wire 110. Also, the length α (length along the orbit 30) of the magnetic poles n1, s1 on the orbit 30 is shorter than the total length Lw of the magnetic wire 110 and is 50% or less of the magnetic pole arrangement interval λ. In this example, the length α of the magnetic poles n1, s1 on the orbit 30 is half or less of the total length Lw of the magnetic wire 110.

[0118] With this configuration as well, the same effects as the configurations shown in FIGS. 6A and 6B can be obtained.

[0119] As described above, the embodiments of the present invention have been explained. However, as exemplified below, the present invention can be implemented in still other forms.

[0120] In the foregoing embodiments, a device mainly for detecting rotation, that is, a device for detecting relative movement along an endless track has been described. However, a detection device for detecting movement (such as linear movement) along a finite track, such as an arc or a straight line, can be configured in the same manner. In this case, at least one of the first support on which the power generation sensor 100 is supported and the second support on which the magnetic field generation source is supported moves along the track. The magnetic field generation source is supported by the second support such that, by moving in one direction, magnetic poles of different polarities alternately enter the detection region of the power generation sensor 100. On the second support, the N poles and the S poles may be alternately arranged along the track, and the total number of magnetic poles may be even or odd.

[0121] Also, in the foregoing embodiments, an example of a magnetic field generation source in which a plurality of magnetic poles are formed by a plurality of individual magnets has been shown. However, the magnetic field generation source may be configured by a multi-pole magnetized magnet designed according to the shape of a desired track. Specifically, in the case of a rotation detection device, the magnetic field generation source may be configured by a ring-shaped multi-pole magnetized magnet surrounding the rotation axis 40. For example, in the case of the configuration shown in FIG. 7A and the like, local magnetization regions (four magnetization regions) spaced circumferentially at the same positions as the individual magnets M1 to M4 are provided for the ring-shaped hard magnetic material to form a plurality of magnetic poles, whereby it can be used as a magnetic field generation source. The magnetization direction is parallel to the rotation axis 40, that is, in the axial orthogonal direction z. The thus formed four-pole magnetized ring magnet has a configuration in which N poles and S poles are alternately arranged on a circumference centered on the rotation axis 40 when viewed from one direction of the rotation axis 40. There are k (k is a natural number. Preferably k ≧ 2. In the illustrated example, k = 2) magnetic pole pairs (pairs of N poles and S poles) arranged, and has k N poles n1, n2,..., nk and k S poles s1, s2,..., sk. The arrangement interval λ of the plurality of magnetic poles (magnetization regions) on the track 30 is longer than the total length Lw of the magnetic wire 110, and preferably 1.5 times or more the total length Lw of the magnetic wire 110. Also, the length α (length along the track 30) of the magnetic pole (magnetization region) on the track 30 is shorter than the total length Lw of the magnetic wire 110 and is 50% or less of the magnetic pole arrangement interval λ. The length α of the magnetic pole on the track 30 is preferably half or less of the total length Lw of the magnetic wire 110.

[0122] Also, the magnetic pole does not have to be a magnet (a magnetized hard magnetic material). For example, a soft magnetic material (yoke) that induces magnetic flux from a magnet can be provided, and the surface (typically the end face) of the soft magnetic material can be used as the magnetic pole.

[0123] Also, in the above-described embodiment, the portion of the magnetic flux conduction piece orthogonal to the axis has a first portion extending from the magnetic wire 110 toward the detection region 140 and a second portion extending from the magnetic wire 110 toward the side opposite to the detection region 140. However, even if the second portion is omitted, there is no substantial influence on the magnetic flux conduction function (magnetic flux collecting function).

[0124] In addition, various design changes can be made within the scope of the matters described in the claims.

Explanation of Reference Numerals

[0125] 5, 5A, 6: Rotation detection device 30: Orbit 31: Gap 40: Axis of rotation 45: Printed circuit board 50: Rotation shaft 51, 51A: First support 52, 52A: Second support 55: Sensor 100: Power generation sensor 110: Magnetic wire 113: Axial center position 115: Symmetry plane 120: Coil 130, 131: Magnetic flux conduction piece 130a, 131a: Wire arrangement portion 133: Portion orthogonal to the axis 134: Portion parallel to the axis 134a: Proximal end 140: Detection region 400: Magnetic field generation source 401: Magnetic pole Lw: Total length of the magnetic wire M1, M2, M3, M4: Individual magnets PP: Positive pulse NP: Negative pulse PS: Phase difference n1, n2: North pole (magnetic pole) s1, s2: South pole (magnetic pole) x: Axial direction z: Direction perpendicular to the axis λ: Arrangement interval of magnetic poles α: Length of magnetic poles

Claims

1. A first support; A second support that moves relative to the first support; A power generation sensor disposed on the first support; a magnetic field source supported by the second support; The power generation sensor includes a magnetic wire that exhibits a large Barkhausen effect, a coil wound around the magnetic wire, and a pair of magnetic flux conducting pieces made of soft magnetic bodies that are symmetrical 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 each include a pair of axially orthogonal portions extending parallel to each other from both ends of the magnetic wire in an axially orthogonal direction perpendicular to the axial direction, and a pair of axially parallel portions extending in a direction approaching each other from tips of the pair of axially orthogonal portions along the axial direction, with adjacent ends facing each other with a gap in the axial direction, and each of the pair of axially orthogonal portions has a wire placement portion consisting of a hole or groove penetrating in the axial direction to which the axially orthogonal portions and both ends of the magnetic wire are fixed, the power generation sensor is configured to have a detection area on an opposite side of the axially parallel portion from the magnetic wire, the magnetic field generation source has a plurality of magnetic poles arranged on the second support such that, when the second support moves relative to the first support, the magnetic field generation source sequentially enters the detection region along a path parallel to the axial direction of the magnetic wire, and magnetic poles of different polarities alternately face the power generation sensor via an air gap; The direction of the magnetic flux of each magnetic pole is perpendicular to the moving direction of the magnetic pole and crosses the magnetic wire when facing the power generation sensor, an arrangement interval between the plurality of magnetic poles on the track is longer than an entire length of the magnetic wire; A motion detection device, wherein the length of the magnetic poles on the track is shorter than the overall length of the magnetic wire and is 50% or less of the arrangement interval.

2. 2. The motion detection device of claim 1, wherein the length of the magnetic pole on the track is less than or equal to half the total length of the magnetic wire.

3. The motion detection device according to claim 2 , wherein the arrangement interval of the magnetic poles on the track is 1.5 times or more the total length of the magnetic wire.

4. 4. The motion detection device according to claim 1, further comprising a sensor for determining the polarity of the magnetic pole located at a central portion of the power generation sensor in the axial direction.

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