Motion detection device

Abstract

A motion detection device (5) comprises: a first support body (51); a second support body (52) that moves relative to the first support body (51); a power generation sensor (100) that is disposed on the first support body; and a magnetic field generation source (400) that is supported by the second support body. The power generation sensor comprises a magnetic wire (110), a coil (120), and magnetic flux conduction pieces (130, 131). The magnetic flux conduction pieces each have an axially orthogonal part and an axially parallel part and have a wire arrangement part to which both end parts of the axially orthogonal part and the magnetic wire are fixed. The power generation sensor is configured such that a detection region (140) is on the opposite side from the magnetic wire with respect to the axially parallel part. The magnetic field generation source has a plurality of magnetic poles. Magnetic poles having different polarities sequentially enter the detection region along a track (30) that is 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 the movement direction of that magnetic pole and intersects the magnetic wire.

Description

Motion detection device

[0001] The present invention relates to a motion detection device equipped with a power generation sensor that utilizes a magnetic wire that exhibits the large Barkhausen effect.

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

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

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

[0005] The output voltage obtained from the coil is constant regardless of the speed at which the input magnetic field (external magnetic field) changes, and has hysteresis characteristics with respect to the input magnetic field, so there is no chattering. For this reason, the pulse signal generated from the coil is used in position detection devices, etc. Because the output from the coil contains power, it can be used to create a power-generating sensor (power-generating sensor) that does not require an external power supply.

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

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

[0008] Motion detection devices using a power generation sensor are disclosed in, for example, Patent Documents 1, 2 and 3.

[0009] Patent Document 1 discloses a configuration for detecting rotation around a rotation axis. This configuration includes a two-pole magnet magnetized in the direction of the rotation axis and a power generating sensor positioned radially offset from the rotation axis. The power generating sensor is positioned with the axial direction of the magnetic wire parallel to the tangential direction of the circumference around the rotation axis. Rotation of the magnetic poles changes the magnetic field in the axial direction of the magnetic wire. After a stabilizing magnetic field is applied in one direction to prepare for pulse generation, a large Barkhausen effect occurs, generating a pulse voltage when an operating magnetic field in the opposite direction is applied. Patent Document 1 proposes changing the magnetization strength of the magnet to increase the change in magnetic flux density with respect to the rotation angle and reduce variation in the pulse voltage generation position. The change in magnetic flux density near the magnetic wire relative to the magnetization state shown in Figure 2 of Patent Document 1 is shown by line M1 in Figure 3 of the same document. In this case, although the abrupt magnetic flux change reduces variation in the pulse voltage generation position, a flat portion with no change occurs near the magnetic flux density of zero. This results in a large phase difference in the pulse voltage generation position depending on the direction of rotation. Figure 4 of Patent Document 1 shows a configuration in which the area where the magnetization strength is changed is devised. In this case, the change in magnetic flux density is as shown by line M3 in Figure 5 of the same document, and no flat area occurs near where the magnetic flux density is 0.

[0010] However, when the power generating sensor is offset from the two-pole magnet, there is an angular interval where both ends of the power generating sensor face magnetic poles of the same polarity, and this angular interval becomes wider the farther the power generating sensor is positioned from the center of rotation. Therefore, the characteristic of not producing a flat portion in the magnetic flux density change, as shown by line M3 in Figure 5 of Patent Document 1, is limited to cases where the power generating sensor is positioned near the center of rotation. Therefore, it cannot be applied to detecting the rotation of, for example, a large-diameter hollow shaft. Furthermore, the change in magnetic flux density with respect to the rotation angle is not necessarily sufficiently steep, resulting in variations in the position where the pulse voltage is generated.

[0011] In the configuration shown in Figure 2 of Patent Document 2, a ring-shaped magnet is magnetized in four regions, with each half of the circumferential region divided into an inner and an outer circumferential region, and a power generation sensor is placed facing radially relative to the magnet. In this case, when the orientation 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 is zero, and the magnetic flux density varies greatly in that vicinity. As a result, there is little variation in the pulse voltage generation position, and there is also little phase difference in the pulse voltage generation position due to forward and reverse rotation.

[0012] However, this requires a specially magnetized ring magnet with a width close to the length of the power generation sensor, which increases the cost of the magnet. It also poses issues of increased magnet weight and inertia. Additionally, when creating detection devices of different sizes, dedicated magnets are required for each size of detection device.

[0013] Figure 30(A) of Patent Document 2 shows a configuration that uses a bar magnet instead of a ring magnet to achieve similar characteristics. However, since the long axis direction of the power generation sensor is arranged in the radial direction, a large radial width is required, which makes the detection device correspondingly large. Furthermore, when attempting to configure a rotation detection device for a hollow shaft, there is an issue that the ratio of the hollow diameter to the outer diameter cannot be made large.

[0014] Figure 6 of Patent Document 3 discloses a configuration in which, instead of using a ring magnet, multiple individual magnets magnetized in the radial direction are arranged circumferentially, with the long axis direction of the power generation sensor being arranged in the radial direction. The multiple individual magnets are arranged circumferentially so that the orientation of their magnetic poles alternates. Unlike a ring magnet, when using individual magnets, dedicated magnets are not required even when creating detection devices of different sizes, and general-purpose two-pole magnets can be used, so magnet costs are low.

[0015] However, in the angular region between adjacent magnets, the power generation sensor does not face the magnetic pole, so there is an angular region where the magnetic flux density is flat near 0. This results in a large phase difference depending on the direction of rotation. The change in magnetic flux density with respect to angle is also gradual, so the variation in the position where the pulse voltage is generated also increases.

[0016] Patent No. 6647478 International Publication No. 2016 / 010141 U.S. Patent No. 8,283,914

[0017] SUMMARY OF THE INVENTION One embodiment of the present invention provides a motion detection device that solves at least one of the problems encountered in the prior art described above.

[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 source supported by the second support. The power generation sensor includes a magnetic wire that exhibits the large Barkhausen effect, a coil wound around the magnetic wire, and a pair of magnetic flux conduction pieces made of soft magnetic materials that are symmetrical with respect to a symmetry plane set at the axial center of the magnetic wire. The pair of magnetic flux conduction pieces includes a pair of axis-orthogonal portions extending parallel to each other in an axis-orthogonal direction perpendicular to the axial direction from both ends of the magnetic wire, and a pair of axis-parallel portions extending toward each other from tips of the pair of axis-orthogonal portions along the axial direction, with their proximal ends facing each other with a gap in the axial direction. The axis-orthogonal portions and a wire placement portion formed of a hole or groove penetrating in the axial direction, to which both ends of the magnetic wire are fixed, are also included. The power generation sensor is configured so that a detection region is located on the opposite side of the axis-parallel portions from the magnetic wire. The magnetic field generating source has a plurality of magnetic poles arranged on the second support such that, when the second support moves relative to the first support, they sequentially enter the detection region along a trajectory parallel to the axial direction of the magnetic wire, and magnetic poles of different polarities alternately face the power generating sensor across a gap. The direction of magnetic flux of each magnetic pole is perpendicular to the movement direction of the magnetic pole (the movement direction of the magnetic pole when the second support moves relative to the first support) and is a direction that intersects with the magnetic wire when facing the power generating sensor (the gap direction). The arrangement interval of the plurality of magnetic poles on the trajectory is longer than the total length of the magnetic wire. The length of the magnetic poles on the trajectory is shorter than the total length of the magnetic wire and is 50% or less of the arrangement interval.

[0019] With this configuration, when a magnetic pole passes through the detection area of ​​the power generating sensor, the magnetic flux density passing through the magnetic wire changes abruptly from a stabilized magnetic field in one direction to a stabilized magnetic field in the other direction, and during this change, no plateau where the change in magnetic flux density stagnates occurs. As a result, a motion detection device can be provided with little variation in pulse generation position and little difference in pulse generation position depending on the direction of movement.

[0020] Furthermore, a magnetic field generator having multiple magnetic poles that generate magnetic flux perpendicular to the direction of movement of the magnetic poles and in a direction that intersects the magnetic wire when facing the power generation sensor (the air-gap direction) can be constructed using multiple individual magnets magnetized in the air-gap direction. Such individual magnets may be, for example, general-purpose two-pole magnets that can be magnetized using an air-core coil, thereby reducing magnet costs. In addition, because the magnetization direction is in the air-gap direction, the individual magnets can be easily fixed to the second support, thereby reducing assembly costs.

[0021] The length of the magnetic pole on the track is preferably equal to or less than half the total length of the magnetic wire, thereby making it possible to make the change in magnetic flux density when the magnetic pole passes through the detection area more abrupt.

[0022] Furthermore, it is preferable that the spacing between the magnetic poles on the track is 1.5 times or more the total length of the magnetic wire, thereby suppressing the influence of the magnetic field from other magnetic poles when a magnetic pole passes through the detection area, thereby making the change in magnetic flux density even more abrupt.

[0023] Preferably, the motion detection device further includes a sensor located at the center of the power generation sensor in the axial direction for determining the polarity of the magnetic poles. With this configuration, it is possible to detect the direction of motion in addition to detecting the position.

[0024] FIG. 1A is a plan view of a rotation detection device of a first comparative example, and FIG. 1B is a front view thereof. FIG. 1C is a waveform diagram showing changes in magnetic flux density with respect to the rotation angle in the rotation detection device of the first comparative example. FIG. 2A is a plan view of a rotation detection device of a second comparative example, and FIG. 2B is a front view thereof. FIG. 2C is a waveform diagram showing changes in magnetic flux density with respect to the rotation angle in the rotation detection device of the second comparative example. FIG. 3A is a plan view of a rotation detection device of a third comparative example, and FIG. 3B is a front view thereof. FIG. 3C is a waveform diagram showing changes in magnetic flux density with respect to the rotation angle in the rotation detection device of the third comparative example. FIG. 4A is a plan view of a rotation detection device of a fourth comparative example, and FIG. 4B is a front view thereof. FIG. 4C is a waveform diagram showing changes in magnetic flux density with respect to the rotation angle in the rotation detection device of the fourth comparative example. FIG. 5A is a plan view of a rotation detection device according to one embodiment of the present invention, and FIG. 5B is a front view thereof. FIG. 5C is a waveform diagram showing changes in magnetic flux density with respect to the rotation angle in the rotation detection device of the above embodiment. Fig. 6A is a perspective view illustrating an example of the configuration of a power generation sensor used in one embodiment of the present invention. Fig. 6B is a front view of the power generation sensor. Fig. 7A is a perspective view illustrating an example of the configuration of a rotation detection device according to another embodiment of the present invention. Fig. 7B is a plan view of the rotation detection device of Fig. 7A. Fig. 7C is a front view of the rotation detection device of Fig. 7A. Fig. 8 is a plan view illustrating the configuration of a rotation detection device according to another embodiment of the present invention.

[0025] In the following, in order to understand the principles of the embodiments of the present invention, some comparative examples will be presented, and then the embodiments of the present invention will be described.

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

[0027] The 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 perpendicular to the rotation axis 11. The power generation sensor 13 includes the 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. An axial direction 17 of the magnetic wire 14 is perpendicular to the rotation axis 11, and an axial center position 18 of the magnetic wire 14 (center position of the axial direction 17) is on the rotation axis 11. The two-pole magnet 12 is disk-shaped and magnetized radially, with half of the area being a north pole and the other half being a south pole.

[0028] 1A, where the axial direction 17 of the magnetic wire 14 and the magnetic pole boundary line 12a are aligned, is set to 0 degrees, and if the angle value increases in the counterclockwise direction CCW, the change in magnetic flux density with rotation of the two-pole magnet 12 about the rotation axis 11 will be sinusoidal as shown in FIG. 1C. The magnetic flux density here refers to the magnetic flux density passing through the magnetic wire 14, i.e., the density of the magnetic flux component in a direction parallel to the axial direction 17 of the magnetic wire 14 near the magnetic wire 14. The same applies to the explanations of other comparative examples and embodiments described later. The operating magnetic field and stabilizing magnetic field of the magnetic wire 14 are also shown in FIG. 1C.

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

[0031] Since there is a finite gradient in the change in magnetic flux density with respect to angle, the pulse generation position (angle at which the pulse is generated) does not match when rotating counterclockwise (CCW) and when rotating clockwise (CW), resulting in a shift in the pulse generation position, i.e., a phase difference PS. More specifically, the phase difference PS occurs near 0 degrees and near 180 degrees.

[0032] In this comparative example, as shown in FIG. 1C, the change in magnetic flux density with respect to the rotation angle is gradual, so there is a large variation in the pulse generation position and the phase difference PS depending on the rotation direction is also large.

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

[0034] 2A and 2B show a rotation detection device 2 of a second comparative example, and FIG. 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 similar to that of the first comparative example. 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 perpendicular to the rotation axis 11 and follows the tangential direction at one point on the circumference around the rotation axis 11. The two-pole magnetized ring magnet 22 has an annular shape centered on the rotation axis 11 and is magnetized in a direction parallel to the rotation axis 11. On the surface facing the power generation sensor 13 across a gap, half of the angular region is a north pole and the other half is a south pole.

[0036] If the angle is set to 0 degrees when the axial direction 17 of the magnetic wire 14 and the magnetic pole boundary line 22a are parallel as shown in Figure 2A, and the angle value increases in the counterclockwise direction CCW, the change in magnetic flux density as the two-pole magnetized ring magnet 22 rotates around the rotation axis 11 will have a trapezoidal wave shape as shown in Figure 2C.

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

[0038] In the angular region where both ends of the power generation sensor 13 face magnetic poles of the same polarity, the magnetic flux density is zero, resulting in flat areas of zero magnetic flux density centered at 0 degrees and 180 degrees. Accordingly, a large phase difference PS occurs depending on the direction of rotation near 0 degrees and 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 that is magnetized all around, so a dedicated magnetizing yoke must be prepared for its manufacture. Furthermore, the ring magnet 22 must be tailored to the size (diameter) of the detection device. Therefore, since a general-purpose magnet cannot be used, there is also the issue of high magnet costs.

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

[0041] 3A and 3B show a rotation detector 3 of a 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. An axial center position 18 of the magnetic wire 14 is offset radially from the rotation axis 11, and an axial direction 17 of the magnetic wire 14 is along the radial direction. The ring magnet 23 is annular in shape centered on the rotation axis 11, is multi-pole magnetized in a direction parallel to the rotation axis 11, and has four magnetized regions 24 on its 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 two halves in the radial direction, an inner diameter portion and an outer diameter portion, and also in the circumferential direction around the rotation axis 11, resulting in four magnetized regions 24. More specifically, half of the angular region of the inner diameter portion is an arc-shaped north pole region, and the other half is an arc-shaped south pole region. Half of the angular region of the outer diameter portion is an arc-shaped south pole region, and the other half is an arc-shaped north pole region. The north pole region of the outer diameter portion is adjacent to the outside of the south pole region of the inner diameter portion, and the south pole region of the outer diameter portion is adjacent to the outside of the north pole region of the inner diameter portion. The boundaries of the magnetized regions 24 in the circumferential direction of the inner diameter portion and the outer diameter portion are aligned, and the magnetic pole boundary line 25 runs along the radial direction.

[0044] If the angle is set to 0 degrees when the axial direction 17 of the magnetic wire 14 and the magnetic pole boundary line 25 are parallel as shown in Figure 3A, and the angle value increases in the counterclockwise direction CCW, the change in magnetic flux density as the ring magnet 23 rotates around the rotation axis 11 will have a trapezoidal wave shape as shown in Figure 3C.

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

[0046] The change in magnetic flux density is steep near 0 degrees and 180 degrees where the magnetic flux density becomes 0, and therefore the variation in pulse generation position is small, and the phase difference PS depending on the direction of rotation 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 in that the outer diameter of the detection device becomes large.

[0048] Furthermore, the configuration of this comparative example also requires a ring magnet 23 that is magnetized all around, so a dedicated magnetizing yoke must be prepared for its manufacture. Furthermore, the ring magnet 23 must be matched to the size (diameter) of the detection device. Therefore, since a general-purpose magnet cannot be used, there is also the issue of high magnet costs.

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

[0050] 4A and 4B show a rotation detector 4 of a fourth comparative example, and FIG. 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 circumferentially spaced apart 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 aligned along the radial direction. The two individual magnets 27 are magnetized radially and arranged at an angular interval of 180 degrees around the rotation axis 11. One of the two individual magnets 27 is fixed to the support substrate 26 with its north pole positioned inward and closer to the rotation axis 11, and the other is fixed to the support substrate 26 with its south pole positioned inward and closer to the rotation axis 11. The magnetic pole boundary line 27a of each individual magnet 27 is aligned along the tangent direction of the circumference around the rotation axis 11 (more precisely, the tangent direction at the position of each individual magnet 27). Each individual magnet 27 is arranged on the support substrate 26 so that, when facing the power generation sensor 13, one magnetic pole faces one end of the magnetic wire 14 and the other magnetic pole faces the other end of the magnetic wire 14.

[0053] If the angle when the power generation sensor 13 is positioned midway between the two individual magnets 27 in Figure 4A is taken as 0 degrees, and the angle value increases in the counterclockwise direction CCW, the change in magnetic flux density accompanying the rotation of the individual magnet 27 around the rotation axis 11 will exhibit a waveform such as that shown in Figure 4C.

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

[0055] In this comparative example, the change in magnetic flux density with respect to angle is small, so the position at which the pulse voltage is generated is likely to vary. Also, the areas near 0 degrees and 180 degrees where the magnetic flux density is 0 belong to the angle section between adjacent individual magnets 27, and are flat areas where the magnetic flux density does not change. Therefore, the phase difference PS depending on the direction of rotation is large.

[0056] Furthermore, as in the third comparative example, the major axis direction of the power generation sensor 13 is the radial direction, which poses a problem of increasing the external dimensions of the detection device.

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

[0058] However, the individual magnets 27 must be fixed to the support substrate 26 in such a way that the magnetic pole boundary line 27a, which is not actually visible, is aligned along the circumferential tangent direction, which makes the assembly work complicated and increases the assembly costs accordingly.

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

[0060] 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 FIG. 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, one of whose main surfaces supports the power generation sensor 100. In this embodiment, the second support 52 is a ring-shaped support substrate that rotates around the rotation axis 40. The magnetic field generator 400 includes a plurality of individual magnets M1 and M2 (two in this embodiment) that are spaced apart in the circumferential direction on the second support 52.

[0063] The power generating sensor 100 includes a magnetic wire 110, a coil 120 wound around the magnetic wire 110, and a pair of L-shaped magnetic flux conducting pieces 130, 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 FIG. 5B ) is used as a detection area 140. A specific configuration example of the power generating sensor 100 will be described later with reference to FIGS. 6A and 6B .

[0064] The axial center position 113, which is the axial center position of the magnetic wire 110, is radially offset 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, the direction of the tangent at the axial center position 113 on the circumference around the rotation axis 40 that passes through the axial center position 113 of the magnetic wire 110).

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

[0066] As described above, the magnetic field generator 400 has a plurality of magnetic poles n1, s1 arranged on the second support 52. When the second support 52 rotates (an example of relative movement) relative to the first support 51, the plurality of magnetic poles n1, s1 sequentially enter the detection region 140 along a trajectory 30 substantially parallel to the axial direction x of the magnetic wire 110. At this time, the magnetic poles n1, s1 of opposite polarities alternately face the power generation sensor 100 via the gap 31. Because 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 direction of movement of the magnetic pole n1, s1 and also intersects with the magnetic wire 110 when facing the power generation sensor 100, i.e., the direction in which the gap 31 opens between the magnetic pole n1, s1 and the power generation sensor 100 (gap direction).

[0067] The arrangement interval λ of the multiple magnetic poles n1, s1 on the orbit 30, i.e., 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. Furthermore, the length α of the magnetic poles n1, s1 on the orbit 30 (the length along 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.

[0068] When the two individual magnets M1 and M2 rotate counterclockwise (CCW) together with the second support 52, a positive pulse ready state (positive set state) is entered when the magnetic flux density falls below the negative stabilizing magnetic field, and a positive pulse PP is generated when the magnetic flux density subsequently exceeds the positive operating magnetic field. Also, when the two individual magnets M1 and M2 rotate counterclockwise (CCW) together with the second support 52, a negative pulse ready state (negative set state) is entered when the magnetic flux density exceeds the positive stabilizing magnetic field, and a negative pulse NP is generated when the magnetic flux density subsequently falls below the negative operating magnetic field. 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 and M2 rotate in the clockwise direction CW together with the second support 52, a positive pulse ready state (positive set state) is entered when the magnetic flux density falls below the negative stabilizing magnetic field, and a positive pulse PP is generated when the magnetic flux density subsequently exceeds the positive operating magnetic field. Also, when the two individual magnets M1 and M2 rotate in the clockwise direction CW together with the second support 52, a negative pulse ready state (negative set state) is entered when the magnetic flux density subsequently exceeds the positive stabilizing magnetic field, and a negative pulse NP is generated when the magnetic flux density subsequently falls below the negative operating magnetic field. 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] The change in magnetic flux density with respect to the rotation angle is very steep near 90 degrees and 270 degrees. Therefore, there is little variation in the pulse generation position, and the deviation of the pulse generation position depending on the direction of rotation, i.e., the phase difference PS, is extremely small. In addition, because the angle difference from the operating magnetization to the stabilizing magnetic field is very small, the range (reversal range) in which so-called pulse missing occurs when the direction of movement (direction of rotation) is reversed is narrow.

[0071] Furthermore, because the longitudinal axis of the power generation sensor 100 is tangent to the circumference, the external dimensions of the rotation detection device 5 can be reduced. From another perspective, the diameter of the hollow portion of the second support 52 can be increased. Furthermore, because general-purpose individual magnets M1 and M2 can be used, which can be manufactured by magnetizing the thickness direction using an air-core coil, magnet costs can be reduced. Of course, individual magnets M1 and M2 of the same design can be used universally for rotation detection devices of different sizes, eliminating the need for specially designed magnets. Moreover, the individual magnets M1 and M2, which are magnetized in the thickness direction, can be fixed to the second support 52 by orienting their north and south poles alternately in one direction. This simplifies assembly compared to the fourth comparative example, which requires aligning the magnetic pole boundaries in the radial direction, thereby reducing assembly costs.

[0072] As described above, by making the spacing λ of the magnetic poles n1 and s1 on the orbit 30 longer than the total length of the magnetic wire 110 (preferably 1.5 times or more), a flat portion where the magnetic flux density is 0 appears in the intermediate region between 90 degrees and 270 degrees where the pulse is generated, as shown in Fig. 5C. This makes it possible to separate the influence of the magnetic field from the adjacent magnetic poles n1 and s1 on the orbit 30, and to make the change in the magnetic flux density in the vicinity of 90 degrees and 270 degrees steeper. This tendency is further strengthened by making the length α of the magnetic poles n1 and s1 on the orbit 30 50% or less of the spacing λ of the magnetic poles.

[0073] 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. This ensures a steep change in magnetic flux density near 90 degrees and 270 degrees without creating a flat portion in the change in magnetic flux density. Setting the length α of the magnetic poles n1 and s1 to half or less of the total length of the magnetic wire 110 is preferable because it allows for a steeper change in magnetic flux density.

[0074] Fig. 6A is a perspective view illustrating an example of the configuration of the power generating sensor 100, and Fig. 6B is a front view seen in the direction of arrow 101 in Fig. 6A. The power generating sensor 100 generates a pulse signal when the power generating sensor 100 and the magnetic pole 401 of the magnetic field generating source 400 (e.g., an individual magnet) move relative to each other. The relative movement between the power generating sensor 100 and the magnetic field generating source 400 is achieved by movement of at least one of the power generating sensor 100 and the magnetic field generating source 400. The following mainly describes an example in which relative movement is achieved by movement of the magnetic field generating source 400.

[0075] The power generating sensor 100 includes a magnetic wire 110 that exhibits the large Barkhausen effect, a coil 120 wound around the magnetic wire 110, and a pair of magnetic flux conducting pieces 130 and 131 having 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 conducting pieces 130 and 131. The pair of magnetic flux conducting 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 conduction pieces 130, 131 have a configuration that is substantially the same shape and same size. More specifically, the pair of magnetic flux conduction pieces 130, 131 are configured symmetrically with respect to a symmetry plane 115 (a virtual plane for explaining the geometric arrangement) that is perpendicular to the axial direction x at a center position (hereinafter referred to as the "axial center position") 113 in the axial direction x (length direction, wire length direction) of the magnetic wire 110. The pair of magnetic flux conduction pieces 130, 131 include axial-orthogonal portions 133 that extend parallel to each other in an axial-orthogonal direction z that is perpendicular to the axial direction x from both end portions 111, 112 of the magnetic wire 110, and axial-parallel portions 134 that extend from the tip ends of the axial-orthogonal portions 133 in directions that approach each other along the axial direction x.

[0077] Both ends 111, 112 of the magnetic wire 110 are fixed to the base ends of the axis-orthogonal portions 133 of the pair of magnetic flux conduction pieces 130, 131, respectively. More specifically, wire placement sections 130a, 131a having holes or grooves penetrating in the axial direction x are provided at the base ends of the axis-orthogonal portions 133. FIG. 6A and other figures show an example in which the wire placement sections 130a, 131a are formed as holes. When the wire placement sections 130a, 131a are formed as grooves, the grooves preferably extend along the axis-orthogonal direction z so as to open to the end faces opposite the detection area 140, which will be described later. The first end 111 and the second end 112 of the magnetic wire 110 are fixed to the axis-orthogonal portions 133 in the wire placement sections 130a, 131a while passing through the axis-orthogonal portions 133. More specifically, resin (not shown) is placed in the holes or grooves that form the wire placement portions 130a, 131a, whereby the ends 111, 112 of the magnetic wire 110 are fixed to the axis-orthogonal portions 133 and coupled to each other. As a result, the magnetic wire 110 and the pair of magnetic flux conduction pieces 130, 131 are mechanically coupled to each other and magnetically coupled to each other.

[0078] The near ends 134a of the axially parallel portions 134 of the pair of magnetic flux conduction pieces 130, 131 face each other across a plane of symmetry 115 that passes through the axial center position 113 of the magnetic wire 110. That is, the near ends 134a face each other with a gap in the axial direction x. The midpoint of this gap in the axial direction x corresponds to the position of the axial center position 113 in the axial direction x, and therefore the distances in the axial direction x from the near ends 134a of the pair of axially parallel portions 134 to the plane of symmetry 115 are equal. The distance L of this gap in the axial direction x is set to 5% to 50%, and more preferably 20% to 40%, 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 portions 133. More specifically, the distance D is the distance in the axial direction x between the inner surfaces 130b, 131b (inner surfaces of the axially orthogonal portions 133) of a pair of magnetic flux conduction pieces 130, 131 that face each other in the axial direction x at the connection position with the magnetic wire 110.

[0079] The soft magnetic parts constituting the magnetic flux conduction pieces 130, 131 are preferably made of a material whose coercive force is equal to or less than that of the magnetic wire 110 and whose relative permeability is 500 or more. Such materials have properties such as low magnetic resistance, low hysteresis, and low self-dielectric strength. As a result, even when a high-frequency alternating magnetic field generated when the magnetic field generating source 400 moves at high speed is applied, the output characteristics of the power generation sensor 100 are less affected. Specifically, the soft magnetic parts are preferably made of Ni-based ferrite or Mn-based ferrite.

[0080] The power generating sensor 100 is configured such that the detection region 140 is the region on the opposite side of the axially parallel portion 134 from the magnetic wire 110. A magnetic field generating source 400 that generates a magnetic field to be detected is disposed in this detection region 140. The power generating sensor 100 and the magnetic field generating source 400 are disposed to have a gap 31 (gap) in the direction perpendicular to the axis z. 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 therebetween. That is, the power generating sensor 100 may be disposed on one main surface of the printed circuit board 45, and the magnetic field generating source 400 may be disposed on the other main surface. Electrical 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 generating 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 arranged 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 axis-orthogonal direction z. As a result, the magnetic field generation source 400 has a plurality of magnetic poles 401 that face the power generation sensor 100 (more specifically, the axis-parallel portion 134) when it moves along the trajectory 30 that passes through the detection region 140.

[0082] In this embodiment, the multiple magnetic poles 401 are arranged so that when the second support 52 moves relative to the first support 51 (printed circuit board 45), the magnetic poles 401 of different polarities alternately face the power generating sensor 100. The power generating sensor 100 outputs a pulse voltage due to changes in the magnetic field that occur when the magnetic poles 401 move through the detection area 140. By signal processing and counting this pulse voltage, a position detection device that generates position information, i.e., an encoder (an example of a motion detection device), can be configured.

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

[0084] The pair of magnetic flux conducting pieces 130, 131 are configured to correct the magnetic field formed in the space including the magnetic flux conducting pieces 130, 131 by the magnetic field generating source 400 arranged in the detection area 140 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, 131 made of soft magnetic material have an axis-orthogonal portion 133 having a substantially rectangular parallelepiped shape and an axis-parallel portion 134 also having a substantially rectangular parallelepiped shape connected to the end of the axis-orthogonal portion 133 facing the magnetic field source 400, i.e., the end on the detection area 140 side, and have an L-shape bent at a right angle at the junction between the axis-orthogonal portion 133 and the axis-parallel portion 134. The axis-parallel portion 134 extends along the axial direction x so as to cover the magnetic wire 110, i.e., to shield the magnetic wire 110 from the detection area 140. The axis-parallel portions 134 of the pair of magnetic flux conduction pieces 130, 131, which have mutually symmetrical shapes, extend toward the axial center of the magnetic wire 110, and their proximal ends 134a face each other with a gap therebetween near the axial center position 113 of the magnetic wire 110. The proximal ends 134a form planes perpendicular to the axial direction x, and the two planes forming each of 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 spacing 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, 131, which are made of soft magnetic material, and the coil 120 are fixed to a case (not shown) that covers them by adhesive resin, fitting, or other suitable fixing means. As described above, the two ends 111, 112 of the magnetic wire 110 are fixed with resin (not shown) to wire placement sections 130a, 131a, which are made of two through-holes or grooves. Therefore, the power generation sensor 100 is configured by a structure in which the pair of magnetic flux conduction pieces 130, 131, the coil 120, and the magnetic wire 110 are fixed to each other and integrated.

[0087] Both ends of the coil 120 may be connected to external electrodes provided on the axially parallel portion 134. The power generation sensor 100 may be surface-mounted on the printed circuit board 45 by joining these external electrodes to wiring conductors provided on one main surface of the printed circuit board 45.

[0088] In the power generating sensor 100 configured as described above, the magnetic field in the detection region 140 is guided to both ends 111, 112 of the magnetic wire 110 by the magnetic flux conduction pieces 130, 131 having soft magnetic components. Furthermore, because an axially parallel portion 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 traveling from the detection region 140 to the axially intermediate portion (mid-way position) of the magnetic wire 110 is shielded by the axially parallel portion 134. In particular, an excellent magnetic shielding effect can be achieved when the distance L in the axial direction x between the adjacent ends 134a of the axially parallel portions 134 of the pair of magnetic flux conduction pieces 130, 131 is 5% to 50% of the distance D between the axially orthogonal portions 133 at the coupling position with the magnetic wire 110. Therefore, since the magnetic field in the axial direction x can be applied over a wide range of the magnetic wire 110, the large Barkhausen effect can be sufficiently induced, resulting in a high-output signal.

[0089] Moreover, since the power generation sensor 100 includes the magnetic flux conducting pieces 130, 131, which are fixedly connected to the magnetic wire 110, it is sufficient to arrange the magnetic field generating source 400 (typically a magnet) as a detection medium in the detection region 140. Therefore, it is easy to combine magnetic field generating sources 400 with different shapes and / or polarities.

[0090] When the power-generating sensor 100 and the magnetic field generating source 400 move relative to each other, the magnetic pole 401 of the magnetic field generating source 400 moves along a trajectory 30 that passes through the detection region 140. The trajectory 30 includes a straight line portion parallel to the axial direction x in the detection region 140, or includes an arc portion 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 axially parallel portion 134, and the magnetic flux generated by the magnetic pole 401 is applied to the magnetic wire 110 through the magnetic flux conducting pieces 130 and 131.

[0091] Because the axially parallel portions 134 of the magnetic flux conduction pieces 130, 131 extend in the axial direction x of the magnetic wire 110, their magnetic shielding effect makes it difficult for magnetic flux to enter from the magnetic pole 401 into the axially intermediate portion of the magnetic wire 110. 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, the magnetic field required to exhibit the large Barkhausen effect can be applied to the magnetic wire 110. Furthermore, 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 faces the axial center position 113 of the magnetic wire 110 and the magnetic fluxes guided from the pair of magnetic flux conduction pieces 130, 131 to both ends 111, 112 of the magnetic wire 110 are balanced, the magnetic flux density in the magnetic wire 110 changes suddenly when the magnetic pole 401 moves slightly in either direction along the track 30. As a result, the change in the magnetic flux density in response to the change in the position of the magnetic pole 401 becomes steep.

[0093] Fig. 7A is a perspective view illustrating a specific example of the structure of the rotation detection device 5A, Fig. 7B is a plan view thereof, and Fig. 7C is a front view showing the configuration around 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 rotation position around the rotation axis 40, which coincides with the central axis of the rotating shaft 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 (e.g., a magnetic sensor). Although not shown, the rotation detection device 5A may further include a counting circuit that processes and counts the pulse output generated by the power generation sensor 100, a non-volatile memory that stores the counting results by the counting circuit, and the like. The counting circuit may be configured to perform a counting operation taking into account 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, a 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 shaft 50 and rotates together with the rotation shaft 50 about the rotation axis 40. Therefore, the second support 52 can be part of a rotating body. In contrast, the first support 51 is fixedly disposed and held in a non-rotating state. As a result, the magnetic field generation source 400 rotates together with the second support 52 about the rotation axis 40 and moves relative to the first support 51.

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

[0098] In this example, the magnetic field generator 400 includes a plurality of individual magnets, i.e., 2k (k=2 in the illustrated example) individual magnets M1, M2, ..., which are fixed to the second support 52. The individual magnets M1, M2, ... are magnetized in a direction parallel to the rotation axis 40, i.e., in the axis-orthogonal direction z, and are arranged at equal angular intervals around 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 thereto. They may be rectangular or rectangular plate-shaped as shown in FIG. 6A , or magnets having an arc-shaped planar shape (specifically, a sector shape with the radially inner portion cut off) may be used.

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

[0100] The power generating sensor 100 is mounted on one main surface of the first support 51 (printed circuit board 45). The magnetic wire 110 of the power generating sensor 100 is located on a tangent to a circumference having a center on the rotation axis 40, and the axial center position 113 of the magnetic wire 110 is located on the tangent point of the tangent. The power generating sensor 100 is positioned so that the magnetic fields conducted from the two magnetic flux conducting pieces 130, 131 are balanced when the axial center position 113 of the magnetic wire 110 is aligned with the center of one of the individual magnets M1, M2, ..., i.e., the center of one of the multiple magnetic poles n1, n2, ..., nk; s1, s2, ..., sk.

[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. When a magnetic pole is arranged in the detection region 140, this detection region-facing surface 134b forms a magnetic flux conduction end that guides magnetic flux from the magnetic pole into the magnetic flux conduction pieces 130, 131.

[0102] The axially parallel portions 134 of the magnetic flux conduction pieces 130, 131 are joined to a wiring pattern (not shown) formed on one main surface of the first support 51 (printed circuit board 45), thereby surface-mounting the power generating sensor 100 on the first support 51 (printed circuit board 45). The power generating sensor 100 is arranged so that the axial direction x of the magnetic wire 110 is aligned with a tangent to a point (contact point) on a circumference centered 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 generating sensor 100 is on the opposite side of the axially parallel portions 134 from the magnetic wire 110, and in this example, is an area on the other main surface 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 configured as an annular plate-like body, is disposed along a plane perpendicular to the rotation axis 40, and is parallel to the first support 51 (printed circuit board 45). A plurality of individual magnets M1, M2, ... are fixed to the surface of the second support 52 facing the other main surface of the first support 51 (printed circuit board 45). 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 example, four individual magnets M1, M2, M3, and M4 are arranged at 90-degree angular intervals 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 center 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. In other words, in a plan view along the rotation axis 40, the magnetic wire 110 and the individual magnets M1, M2, ... may be located on circumferences of equal radius with the rotation axis 40 as the central axis, thereby being positioned so as to be able 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 around the rotation axis 40 together with the rotation shaft 50, the individual magnets M1, M2, ... move on a circumferential orbit 30 centered on the rotation axis 40 and passing through the detection area 140. The axial direction x of the magnetic wire 110 is parallel to a tangent passing through a certain point (contact point) on the circumferential orbit 30, and the axial center position 113 is on a perpendicular line (in this example, a perpendicular line parallel to the rotation axis 40) erected to the tangent line at the contact point. In other words, the axial center position 113 of the magnetic wire 110 has its center on the rotation axis 40 and is located at a certain point (contact point) on a circumference of a circle with the same radius as the circumferential orbit 30, and the magnetic wire 110 is along the tangent line at the contact point.

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

[0106] In the printed circuit board 45 constituting the first support 51, a sensor 55, such as a magnetic sensor, is mounted on the main surface on which the power generation sensor 100 is mounted. Other electric or electronic components, such as the counting circuit and nonvolatile memory, may also be mounted on the main surface of the printed circuit board 45.

[0107] The sensor 55 is positioned so as to detect the polarity of the magnetic pole facing the center of the power generation sensor 100. The sensor 55 is, for example, a magnetic sensor such as a Hall IC, and outputs an H signal when it detects a north pole (when the north pole faces the center of the power generation sensor 100) and an L signal when it detects a south pole (when the south pole faces the center of the power generation sensor 100). The sensor 55 thereby determines the polarity of the magnetic pole passing nearby and, as a result, outputs an identification signal identifying the polarity of the magnetic pole facing the center of the power generation sensor 100. In this embodiment, the sensor 55 is positioned so as 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, i.e., a position symmetrical with respect to the rotation axis 40. If k is an even number (e.g., 2), the sensor 55 detects a magnetic pole of the same polarity as the magnetic pole facing the center of the power generation sensor 100. When k is an odd number (for example, 3), the sensor 55 detects a magnetic pole of the opposite polarity to the magnetic pole facing the center of the power generation sensor 100. In either case, the sensor 55 can detect the polarity of the magnetic pole facing the center of the power generation sensor 100.

[0108] With this configuration, when one of the magnetic pole pairs n1, s1; n2, s2; ...; nk, sk passes through the detection area 140 along the circumferential orbit 30 during counterclockwise CCW rotation about the rotation axis 40, one negative pulse NP and one positive pulse PP are generated in sequence (see FIG. 5C ). When one of the magnetic pole pairs n1, s1; n2, s2; ...; nk, sk passes through the detection area 140 along the circumferential orbit 30 during clockwise CW rotation about the rotation axis 40, one positive pulse PP and one negative pulse NP are generated in sequence (see FIG. 5C ). These pulses, along with the sensor 55 outputting an identification signal indicating the polarity of the magnetic poles on the circumferential orbit 30 between the magnetic flux conducting pieces 130, 131, allow the rotational position and direction to be identified.

[0109] Specifically, if the sensor 55 detects a north pole when a negative pulse NP is generated and if the sensor 55 detects a south pole when a positive pulse PP is generated, the rotation direction may be identified as counterclockwise CCW. On the other hand, if the sensor 55 detects a north pole when a positive pulse PP is generated and if the sensor 55 detects a south pole when a negative pulse NP is generated, the rotation direction may be identified as clockwise CW.

[0110] 6A and 6B , the spacing λ between the multiple magnetic poles on the track 30 is longer than the total length of the magnetic wire 110. In this example, the spacing λ is 1.5 times or more the total length Lw of the magnetic wire 110. In addition, 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 spacing 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 this configuration, it is possible to achieve the same effect as the configuration shown in FIGS. 6A and 6B.

[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] The 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. In this embodiment, the first support 51A is a support substrate, and the power generation sensor 100 is supported on one of its main surfaces. In this embodiment, the second support 52A is cylindrical and rotates about a rotation axis 40. The magnetic field generation source 400 includes a plurality of individual magnets M1 and M2 (two in this embodiment) that are spaced apart circumferentially on the outer circumferential surface of the second support 52A.

[0114] 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, 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. In other words, this rotation detection device 6 is a radial gap type in which the direction in which the gap between the magnetic field generating source 400 (individual magnet) and the power generation sensor 100 opens (gap direction) is the radial direction.

[0115] An 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 aligned along the circumferential direction about the rotation axis 40 (more specifically, along the direction of a tangent at the axial center position 113 on the circumference around the rotation axis 40 that passes through the axial center position 113 of the magnetic wire 110). The two individual magnets M1 and M2 are magnetized in a radial direction (gap direction) perpendicular to the rotation axis 40 and are arranged at equal intervals on the circumference around the rotation axis 40, i.e., at angular intervals of 180 degrees. One of the two individual magnets M1 and M2 is fixed to the second support 52A and positioned so that its north pole n1 faces the power generation sensor 100 when it approaches the power generation sensor 100, and the other is fixed to the outer peripheral surface of the second support 52A and positioned so that its south pole s1 faces the power generation sensor 100 when it approaches 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 a circumferential orbit 30. In this way, the magnetic field generating source 400 has a plurality of magnetic poles n1, s1 arranged on the second support 52A, and when the second support 52A rotates relative to the first support substrate (an example of relative movement), these magnetic poles n1, s1 sequentially enter the detection region 140 along orbits that are substantially parallel to the axial direction x of the magnetic wire 110. At this time, the magnetic poles n1, s1 of different polarities alternately face the power generation sensor 100 via an air gap. Since the individual magnets M1 and M2 are magnetized in a radial direction perpendicular to the rotation axis 40, the direction of the magnetic flux of each magnetic pole n1 and s1 is perpendicular to the direction of movement of the magnetic pole n1 and s1, and is also a direction that intersects with the magnetic wire 110 when facing the power generation sensor 100, i.e., the direction in which the gap between the magnetic pole n1 and s1 and the power generation sensor 100 opens (gap direction).

[0117] The spacing λ between the multiple magnetic poles n1, s1 on the track 30 is longer than the total length of the magnetic wire 110. More specifically, in this example, the spacing λ is 1.5 times or more the total length Lw of the magnetic wire 110. Furthermore, the length α (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 spacing λ. In this example, the length α of the magnetic poles n1, s1 on the track 30 is half or less of the total length Lw of the magnetic wire 110.

[0118] This configuration also provides the same effects as the configurations shown in FIGS. 6A and 6B.

[0119] Although the embodiment of the present invention has been described above, the present invention can be embodied in other forms as exemplified below.

[0120] In the above-described embodiment, a device for detecting rotation, i.e., a device for detecting relative movement along an endless track, has been described. However, a detection device for detecting movement (e.g., linear movement) along an endless track, such as an arc or a straight line, can also be configured in a similar manner. In this case, at least one of the first support supporting the power generation sensor 100 and the second support supporting the magnetic field generating source moves along the track. The magnetic field generating source is supported by the second support such that, as the source moves in one direction, magnetic poles of opposite polarity alternately enter the detection region of the power generation sensor 100. The second support only needs to have north and south poles alternately arranged along the track, and the total number of magnetic poles may be either an even number or an odd number.

[0121] Furthermore, while the above-described embodiment illustrates an example of a magnetic field generator comprising multiple individual magnets forming multiple magnetic poles, the magnetic field generator may also be formed using a multi-pole magnetized magnet designed to match the shape of the desired orbit. Specifically, in the case of a rotation detection device, the magnetic field generator may also be formed using a ring-shaped multi-pole magnetized magnet surrounding the rotation axis 40. For example, in the configuration shown in FIG. 7A etc., a ring-shaped hard magnetic material can be used as a magnetic field generator by providing localized magnetized regions (four magnetized regions) spaced apart circumferentially at positions similar to those of the individual magnets M1 to M4 to form multiple magnetic poles. The magnetization direction is parallel to the rotation axis 40, i.e., the direction orthogonal to the axis z. The four-pole magnetized ring magnet thus produced has, when viewed from one direction of the rotation axis 40, k (k is a natural number, preferably k≧2; in the illustrated example, k=2) magnetic pole pairs (pairs of north and south poles) arranged alternately on a circumference centered on the rotation axis 40, with k north poles n1, n2, ..., nk and k south poles s1, s2, ..., sk. The spacing λ between the multiple magnetic poles (magnetized regions) on the track 30 is longer than the total length Lw of the magnetic wire 110, preferably 1.5 times or more the total length Lw of the magnetic wire 110. Furthermore, the length α (length along the track 30) of the magnetic poles (magnetized regions) 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 spacing λ. The length α of the magnetic poles on the track 30 is preferably half or less of the total length Lw of the magnetic wire 110.

[0122] Furthermore, the magnetic poles do not have to be magnets (magnetized hard magnetic materials); for example, a soft magnetic material (yoke) that guides magnetic flux from the magnet can be provided, and the surface (typically the end face) of that soft magnetic material can be used as the magnetic pole.

[0123] In addition, in the above-described embodiment, the axially orthogonal portion of the magnetic flux conduction piece has a first portion extending from the magnetic wire 110 toward the detection area 140 and a second portion extending from the magnetic wire 110 toward the opposite side of the detection area 140, but omitting the second portion does not have a substantial effect on the magnetic flux conduction function (magnetic collection function).

[0124] In addition, various design modifications can be made within the scope of the claims.

[0125] 5, 5A, 6: Rotation detection device 30: Track 31: Gap 40: Rotation axis 45: Printed circuit board 50: Rotation axis 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 placement section 133: Axial orthogonal section 134: Axial parallel section 134a: Proximal end 140: Detection area 400: Magnetic field generation source 401: Magnetic pole Lw: Total length of magnetic wire M1, M2, M3, M4: Individual magnets PP: Positive pulse NP: Negative pulse PS: Phase difference n1, n2: North poles (magnetic poles) s1, s2: South poles (magnetic poles) x: Axial direction z: Orthogonal direction to the axis λ: Distance between magnetic poles α: Length of magnetic pole

Claims

1. A magnetic field generating device comprising: a first support; a second support that moves relative to the first support; a power generating sensor disposed on the first support; and a magnetic field generating source supported by the second support, wherein the power generating sensor comprises a magnetic wire that exhibits the large Barkhausen effect, a coil wound around the magnetic wire, and a pair of magnetic flux conducting pieces made of soft magnetic materials that are symmetrical with respect to a symmetry plane set at the center position of the axial direction of the magnetic wire, wherein the pair of magnetic flux conducting pieces comprises a pair of axis-orthogonal portions extending parallel to each other in an axis-orthogonal direction perpendicular to the axial direction from both ends of the magnetic wire, and a pair of axis-parallel portions extending from tips of the pair of axis-orthogonal portions in directions approaching each other along the axial direction, with proximal ends facing each other with a gap in the axial direction, and wherein the axis-orthogonal portions and wire arranging portions consisting of holes or grooves that penetrate in the axial direction and to which both ends of the magnetic wire are fixed, and the power generating sensor is configured so that a detection area is on the opposite side of the axis-parallel portions from the magnetic wire, A motion detection device in which the magnetic field generating source has a plurality of magnetic poles arranged on the second support so that when the second support moves relative to the first support, they sequentially enter the detection area along a trajectory parallel to the axial direction of the magnetic wire, and magnetic poles of different polarities alternately face the power generating sensor across a gap, the direction of magnetic flux of each magnetic pole is perpendicular to the direction of movement of the magnetic pole and intersects with the magnetic wire when facing the power generating sensor, the spacing between the plurality of magnetic poles on the trajectory is longer than the total length of the magnetic wire, and the length of the magnetic poles on the trajectory is shorter than the total length of the magnetic wire and is 50% or less of the spacing.

2. A motion detection device according to claim 1, wherein the length of said magnetic pole on said track is less than half the total length of said magnetic wire.

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

4. A motion detection device according to any one of claims 1 to 3, further comprising a sensor for determining the polarity of the magnetic pole located at the center of the power generation sensor in the axial direction.

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