JP5202343B2 - Rotation angle detector - Google Patents

Description

  The present invention relates to a magnetic rotation angle detector used in various fields such as industrial FA equipment and in-vehicle use.

  In a general configuration example of a conventional magnetic rotation angle detector, as shown in FIG. 15, one S pole and N pole are provided in each region corresponding to a semicircle with respect to a disc rotating with the rotary shaft 3. A magnet unit 1 magnetized pole by pole and a detection unit 2 that is disposed above the magnet unit 1 and has a magnetic detection element whose output changes in response to a change in the direction of a magnetic field such as an AMR element or a GMR element. ing. Here, the above is the direction opposite to the rotating shaft 3 in the magnet portion 1. The magnet 1 may be magnetized in the same polarity in the thickness direction of the disk or in different layers in the thickness direction. In addition, as shown in FIG. 1 in Patent Document 1, there is a configuration in which a magnetic detection element is arranged in the inner hole of the ring-shaped magnet portion.

  In any of these configurations, the direction of the magnetic field applied to the magnetic detection element changes due to the rotation of the magnet unit 1 accompanying the rotation of the rotary shaft 3, and the output of the magnetic detection element changes accordingly. The rotation angle of the magnet unit 1 is calculated from this output change.

  Further, as shown in FIG. 16, a ring-shaped ring is formed due to the limitation of the fastening method between the rotating shaft 3 and the magnet unit 1, the structural limitation of the magnet unit 1, or the installation position of the detection unit 2. A configuration in which the detection unit 2 is disposed above the magnet unit 4 made of a disk is also generally known. Even in this configuration, the magnet part 4 may be magnetized in the same polarity in the thickness direction of the disk and in the case where the different polarities are magnetized in layers in the thickness direction. . The installation position of the detection unit 2 is on the extension of the rotating shaft 3 that rotates the magnet unit 4, that is, above the inner hole 4 a in the magnet unit 4 or above the peripheral edge 4 b in the magnet unit 4. And which of the ring-shaped magnet parts 4 is optimal is determined by the difference in outer diameter.

Japanese Patent Laid-Open No. 2002-22406 JP 2007-256250 A

  In the above-described magnetic rotation angle detector, in the form in which the detection unit 2 includes a magnetic detection element whose output changes in response to a change in the direction of the magnetic field, the magnetic field from the magnet unit 1 or the magnet unit 4 acting on the magnetic detection element. The direction needs to rotate in conjunction with the rotation of the magnet unit 1 or the magnet unit 4. Further, since the magnetic detection element has a certain area, an area of a certain area or more is required so that the intensity and direction of the magnetic field acting on the magnetic detection element from the magnet unit 1 or the magnet unit 4 is uniform. . Furthermore, even when there is an assembly position error of the detection unit 2 with respect to the magnet units 1 and 4 or an eccentricity in which the magnet units 1 and 4 are assembled with a deviation from the rotary shaft 3, stable rotation angle detection with a specified accuracy is possible. As possible, the area of the region needs to be increased as much as possible.

  However, when the ring-shaped magnet portion 4 is used, the direction of the magnetic field generated above the ring-shaped magnet portion 4 is distorted by the ring inner hole 4a. Therefore, there is a problem that a region where a uniform magnetic field is obtained in the magnetic detection element becomes small. The concept is shown in FIG. In FIG. 17, the direction of the magnetic field at a position away from the magnet unit 4 by a distance G is shown in a plan view. Above the peripheral edge portion 4b of the ring-shaped magnet portion 4, a uniform magnetic field is generated straight from left to right in the figure, but in the vicinity of the inner hole 4a of the magnet portion 4 (dotted line portion in the figure). ), The direction of the magnetic field is oriented along the diameter direction of the inner hole 4a, so the direction of the magnetic field is distorted and a uniform magnetic field region cannot be maintained. Thus, since the region where a uniform magnetic field acts on the magnetic detection element becomes small, there arises a problem that the measurement accuracy in the rotation angle detector is lowered.

  Further, as shown in FIG. 15, when magnetized along the diameter direction of the magnet parts 1 and 4, a uniform magnetic field can be obtained up to the vicinity of the outer periphery of the magnet parts 1 and 4, whereas the magnet When magnetized in layers along the thickness direction of the disks forming the parts 1 and 4, the position of the center of gravity of each pole becomes the position of the pole of the magnetic field lines, compared with the case of magnetization along the diameter direction. Thus, there is a problem that the pole interval is narrowed and the uniform magnetic field region is narrowed. Therefore, also in this case, there arises a problem that the measurement accuracy in the rotation angle detector is lowered.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a rotation angle detector capable of detecting a rotation angle with higher accuracy than in the past.

In order to achieve the above object, the present invention is configured as follows.
That is, the rotation angle detector according to one embodiment of the present invention, there is provided a rotation angle detector for measuring the rotational angle of the measuring object, is rotated by the measured object, the including middle empty section a central axis of rotation A magnet unit that is magnetized to change the direction of the magnetic field by the rotation, and a magnet that is installed above or below the magnet unit in the axial direction of the rotation center axis and whose output changes due to a change in the direction of the magnetic field. An inner peripheral portion and an outer periphery of the magnet portion in the axial direction that defines a distance between the facing surface of the magnet portion facing the magnetic detection element and the magnetic detection element. portion of the thickness, characterized by stepwise increasing size to the thickness of the central portion located between the inner peripheral portion and the outer peripheral portion in the diameter direction of the rotary.

  According to the rotation angle detector of one aspect of the present invention, the magnet part having the hollow part in the central part is obtained by changing the thickness of the magnet part having the hollow part in the central part locally or stepwise in the diameter direction. The magnetic sensing element arranged above or below the magnetic field can be shaped to provide a uniform magnetic field, that is, a region where the magnetic field is uniform, in a wider range than in the past. As a result, the measurement accuracy of the magnetic detection element is improved as compared with the conventional case, and the rotation angle can be detected with higher accuracy than the conventional case. In addition, since a uniform magnetic field region is widened, it is possible to assemble a detection unit that is coarser than in the past. Therefore, the cost of the rotation angle detector can be reduced.

It is a perspective view which shows schematic structure of the rotation angle detector by Embodiment 1 of this invention. FIG. 2 is a schematic cross-sectional view of the rotation angle detector shown in FIG. 1. It is a figure which shows the outline in the magnet cross section of the magnetic field direction distribution generated from the magnet in the magnet part shown in FIG. It is a figure which shows the outline in the magnet cross section of the magnetic field direction distribution generate | occur | produced from a magnet in the rotation angle detector using the magnet magnetized by the radial direction by the conventional general ring shape. It is a figure which shows the outline in the magnet cross section of the magnetic field direction distribution generated from the magnet in this modification while showing the modification of the magnet part shown in FIG. It is a perspective view which shows schematic structure of the rotation angle detector by Embodiment 2 of this invention. FIG. 7 is a schematic cross-sectional view of the rotation angle detector shown in FIG. 6. It is a perspective view which shows schematic structure of the rotation angle detector by Embodiment 3 of this invention. FIG. 9 is a schematic cross-sectional view of the rotation angle detector shown in FIG. 8. It is a figure which shows the outline in the magnet cross section of the magnetic field direction distribution generated from the magnet in the magnet part shown in FIG. It is a figure which shows the outline in the magnet cross section of the magnetic field direction distribution generate | occur | produced from a magnet in the rotation angle detector using the magnet magnetized by the thickness direction by the conventional general ring shape. It is sectional drawing in the modification of the rotation angle detector shown in FIG. It is sectional drawing in the modification of the rotation angle detector shown in FIG. It is sectional drawing in the modification of the rotation angle detector shown in FIG. It is a perspective view which shows the structural example of the conventional general rotation angle detector using a disk-shaped magnet and a magnetic detection element. It is a perspective view which shows the structural example of the conventional general rotation angle detector using a ring-shaped magnet and a magnetic detection element. It is a conceptual diagram which shows the spatial distribution of the direction of the magnetic field above the ring-shaped magnet shown in FIG.

  A rotation angle detector that measures the rotation angle of an object to be measured, which is an embodiment of the present invention, will be described below with reference to the drawings. In each figure, the same or similar components are denoted by the same reference numerals.

Embodiment 1 FIG.
The configuration of the rotation angle detector according to Embodiment 1 of the present invention will be described below with reference to FIGS.
FIG. 1 shows a schematic configuration of the rotation angle detector 101 according to the first embodiment, and FIG. 2 shows a cross-sectional view thereof. The rotation angle detector 101 includes a magnet unit 110 and a detection unit 120 as basic components.

  The detection unit 120 detects the rotation angle of the measurement object from the magnetic detection element 121 whose output changes due to a change in the direction of the magnetic field, such as an AMR element or a GMR element, and the output information of the magnetic detection element 121 connected to the magnetic detection element 121. And a measuring unit 122 to be obtained.

  The magnet unit 110 is a member that is rotated by the measurement object in order to obtain the rotation angle of the measurement object. In the present embodiment, as shown in FIG. 1, the measurement object is a rotating shaft 3 such as a motor shaft, and is rotated around the rotation center axis 3 a of the rotating shaft 3 in the rotation direction 3 b by the drive source 31. In this embodiment, the magnet part 110 has a disk shape, and has a hollow part 111 penetrating the magnet part 110 in the thickness direction at the central part 110a of the magnet part 110 including the rotation center shaft 3a. Here, the thickness direction of the magnet portion 110 is a direction along the axial direction 3c of the rotation center shaft 3a in the present embodiment. The hollow portion 111 is fixed to one end of the rotating shaft 3 by a method such as adhesion or fitting, and the magnet portion 110 rotates as the rotating shaft 3 rotates.

  Such a magnet part 110 is magnetized such that the direction of the magnetic field acting on the magnetic detection element 121 is changed by the rotation of the magnet part 110 accompanying the rotation of the rotary shaft 3. That is, as shown in FIGS. 1 and 2, each of the regions 112 a and 112 b that bisect the facing surface 110 b of the magnet unit 110 facing the magnetic detection element 121 in 180 ° increments in the rotation direction 3 b is provided in the N pole and the S pole. Are magnetized one pole at a time. In the present embodiment, the magnetized regions 112a and 112b are opposed to each other and above the opposing surface 110b along the axial direction 3c of the rotation center shaft 3a, more specifically, above the central portion 110f of the magnet portion 110 described below. The magnetic detection element 121 is disposed on the surface. The upper direction means a direction opposite to the rotating shaft 3 in the magnet portion 110.

  Further, as shown in FIG. 2, the thickness of the magnet part 110 in the axial direction 3 c that defines the distance G between the facing surface 110 b of the magnet part 110 and the magnetic detection element 121 is the diameter direction 110 c in the rotation of the magnet part 110. Varies locally or stepwise. Specifically, in the present embodiment, as shown in FIGS. 1 and 2, the thickness of the magnet portion 110 in the inner peripheral portion 110d and the outer peripheral portion 110e of the magnet portion 110 is the central portion of the magnet portion 110 in the diameter direction 110c. Thick with respect to the thickness of 110f. Here, the central portion 110f is a region sandwiched between the inner peripheral portion 110d and the outer peripheral portion 110e. The thickness of the magnet portion 110 is the thinnest and there is no change in the thickness in the diameter direction 110c. Equivalent to. In FIG. 2, for the sake of convenience, the distance between the central portion 110f and the magnetic detection element 121 is shown as “G”. However, as described above, the distance G includes not only the central portion 110f but also the inner peripheral portion 110d. And the distance between the opposing surface 110b of the magnet part 110 including the outer peripheral part 110e and the magnetic detection element 121. The distance G is determined in consideration of the magnetic characteristics of the magnet unit 110, the sensitivity of the magnetic detection element 121 to the magnetic field, the restrictions on the assembly of the rotation angle detector 101, and the like.

  In the present embodiment, the inner peripheral end 113d in the inner peripheral portion 110d and the outer peripheral end 114 in the outer peripheral portion 110e are set to be the thickest, and from the inner peripheral end 113 and the outer peripheral end 114 toward the central portion 110f. The inner peripheral portion 110d and the outer peripheral portion 110e are formed so that the thickness of the magnet portion 110 is reduced at a uniform rate, in other words, linearly.

  Further, in the present embodiment, as described above, the magnet unit 110 is configured by being magnetized, but the magnet unit 110 may be configured by attaching a permanent magnet to a disk-shaped base material or using only a permanent magnet. Good. Such a configuration may include a member for fastening the magnet.

A magnetic field acting on the magnetic detection element 121 from the magnet unit 110 configured as described above will be described below.
What produces the magnetization direction in the magnet part 110 mentioned above is generally called radial magnetization, and in the magnet part 110, the same pole exists in the axial direction 3c. In such a magnet part 110, the schematic of magnetic field direction distribution generated from a magnet is shown in FIG. On the other hand, FIG. 4 shows a schematic diagram of a magnetic field direction distribution generated from a magnet when a conventional general ring-shaped magnet is used. In addition, the arrow 5 shown in FIG.3 and FIG.4 has shown the magnetization direction of the magnet.

  As is clear from comparison between FIG. 3 and FIG. 4, in the magnet portion 110, the slope 110 d − formed on the inner peripheral portion 110 d and the outer peripheral portion 110 e, which connects the inner peripheral portion 110 d and the outer peripheral portion 110 e and the central portion 110 f. 1 and the presence of the inclined surface 110e-1, and by appropriately setting the distance G, the region where the direction of the magnetic field with respect to the magnetic detection element 121 is uniform, that is, uniform, can be widened compared to the conventional case. . Therefore, the inner peripheral portion 110d and the outer peripheral portion 110e having the slope 110d-1 and the slope 110e-1 can be referred to as a magnetic field improving portion. Here, in the case of the magnet portion 110, the distance G preferably has a size that slightly exceeds the maximum thickness of the inner peripheral end 113 and the outer peripheral end 114 in the inner peripheral portion 110d and the outer peripheral portion 110e as shown in FIG. . Note that the magnitude of the distance G varies depending on the ratio of the thickness change in the diameter direction 110c in the inner peripheral portion 110d and the outer peripheral portion 110e, the magnetic characteristics of the magnet portion 110, and the like.

  In general, the magnetic detection element has a certain area, and there is an assembly position error of the magnetic detection element with respect to the magnet part, and there is an eccentricity that occurs when the magnet part is assembled off the rotating shaft. In this case, if the magnetic detection element is out of the uniform magnetic field region, the angle detection accuracy deteriorates.

  On the other hand, in the rotation angle detector 101 according to the present embodiment, the region where the direction of the magnetic field is uniform with respect to the magnetic detection element 121 can be made wider as compared with the conventional case. Even when there is an error or the eccentricity described above, the rate at which the magnetic detection element 121 deviates from the uniform magnetic field region is lower than in the prior art. Therefore, the rotation angle detector 101 of the present embodiment can improve the angle detection accuracy as compared with the conventional one. In addition, since the rotation angle detector 101 according to the present embodiment can secure a wide range of uniform magnetic field, it is possible to increase the margin for assembling the magnet unit 110 and the magnetic detection element 121. A simple assembly method is possible. Therefore, it is possible to reduce the cost of the rotation angle detector 101.

  In the present embodiment, as described above, the thickness is increased in both the inner peripheral portion 110d and the outer peripheral portion 110e of the magnet portion 110, but only one of them may be increased. In the present embodiment, as described above, the thickness change in the inner peripheral portion 110d and the outer peripheral portion 110e is uniform in the diameter direction 110c, that is, linearly increases or decreases. However, the present invention is not limited to this, and other change rates, for example, a quadratic curve as shown in FIG. 5 may be used. In short, the thickness change in the inner peripheral portion 110d and the outer peripheral portion 110e may be changed stepwise in the diameter direction 110c. On the other hand, the thickness of at least one of the inner peripheral portion 110d and the outer peripheral portion 110e may be simply increased as compared with the central portion 110f, that is, the thickness of the magnet portion 110 may be locally increased in the diameter direction 110c.

  In the present embodiment, the magnet part 110 has a ring shape having the hollow part 111, but is not limited to this. For example, the outer shape and the hollow part shape may be a polygonal shape such as a quadrangle. good.

  Further, in the present embodiment, the magnetic detection element 121 is disposed so as to face the central portion 110f of the magnet unit 110. However, the present invention is not limited to this, for example, above the rotation center axis 3a of the rotation shaft 3 or other assembly. It can be arranged at an arbitrary position in consideration of the restrictions of the above.

  In addition, as shown in FIG. 12, the magnet unit 110 may be turned upside down and the magnetic detection element 121 may be disposed below the magnet, that is, on the side where the rotating shaft 3 exists, as shown in FIG. Is possible. In the case of this form, the material of the rotating shaft 3 needs to be a non-magnetic material. In the form shown in FIG. 12, the size of the entire rotation angle detector 101 can be made compact as compared with the form shown in FIGS.

Embodiment 2. FIG.
Next, the configuration of the rotation angle detector 102 according to the second embodiment of the present invention will be described below with reference to FIGS.
Similarly to the rotation angle detector 101 described above, the rotation angle detector 102 according to the second embodiment also includes a magnet unit 130 and a detection unit 120 as basic components. The difference in configuration from the above-described rotation angle detector 101 is the magnet unit 130, and the other configuration is the same as the configuration of the rotation angle detector 101 described above. Therefore, only the magnet unit 130 will be described below.

  In this embodiment, the magnet part 130 has a disk shape, and has a hollow part 131 that penetrates the magnet part 130 in the thickness direction in the central part 130a of the magnet part 130 including the rotation center shaft 3a. The hollow portion 131 is fixed to one end of the rotating shaft 3 by a method such as bonding or fitting, and the magnet portion 130 rotates as the rotating shaft 3 rotates. Like the magnet unit 110, the magnet unit 130 has N poles in each of the regions 132 a and 132 b that bisect the facing surface 130 b of the magnet unit 130 facing the magnetic detection element 121 by 180 degrees in the rotation direction 3 b. And S poles are magnetized one by one.

  Moreover, the magnet part 110 in Embodiment 1 has the center part 110f in which the thickness of the magnet part 110 does not change as described above and as shown in FIG. On the other hand, in magnet part 130 in the second embodiment, as shown in FIG. 7, the cross section of magnet part 130 excluding hollow part 131 is V-shaped and corresponds to a central part 110 f having a constant thickness. Does not exist.

  More specifically, in the present embodiment, as shown in FIGS. 6 and 7, at the intermediate point 135 between the inner peripheral end 133 and the outer peripheral end 134 of the magnet portion 130 in the diameter direction 130 c of the rotation of the magnet portion 130. With the thickness of the magnet portion 130 being the minimum, the thickness of the magnet portion 130 in the inner peripheral portion 130d and the outer peripheral portion 130e of the magnet portion 130 is increased or decreased uniformly, that is, linearly in the diameter direction 130c. That is, the thickness in the axial direction 3c of the magnet portion 130 at the inner peripheral end 133 and the outer peripheral end 134 in the inner peripheral portion 130d and the outer peripheral portion 130e is the largest, and the thickness at the intermediate point 135 is the smallest.

  In FIG. 7, for the sake of convenience, the distance between the intermediate point 135 and the magnetic detection element 121 is shown as “G”, but the distance G is not only the intermediate point 135 but also the inner peripheral portion 130d and the outer peripheral portion 130e. This corresponds to the distance of the magnet part 130 including the opposite face 130b to the magnetic detection element 121. The distance G is determined in consideration of the magnetic characteristics of the magnet unit 130, the sensitivity of the magnetic detection element 121 to the magnetic field, the restrictions on the assembly of the rotation angle detector 102, and the like.

  Also in the rotation angle detector 102 having the magnet unit 130 configured as described above, the same effect as the rotation angle detector 101 of the first embodiment can be obtained. That is, also in the magnet part 130, the magnetic field with respect to the magnetic detection element 121 is set by appropriately setting the distance G due to the existence of the slopes 130d-1 and 130e-1 formed in the inner peripheral part 130d and the outer peripheral part 130e. The area where the direction of the angle is uniform can be made wider than in the conventional case. Here, in the case of the magnet portion 130, the distance G is, for example, a distance that slightly exceeds the maximum thickness of the inner peripheral end 133 and the outer peripheral end 134 in the inner peripheral portion 130d and the outer peripheral portion 130e as shown in FIG. It is done. Note that the magnitude of the distance G varies depending on the ratio of the thickness change in the diameter direction 130c in the inner peripheral portion 130d and the outer peripheral portion 130e, the magnetic characteristics of the magnet portion 130, and the like.

  Further, in comparison with the configuration of the first embodiment, the central portion 110f is not provided in the second embodiment. Therefore, even when the distance G is set to be relatively smaller than that of the configuration of the first embodiment, a uniform magnetic field region can be ensured wider than that of the first embodiment.

  As described above, in the magnet unit 130, the region in which the direction of the magnetic field is uniform with respect to the magnetic detection element 121 can be made wider than in the conventional case. Therefore, in the rotation angle detector 102 of the present embodiment as well, Compared to the angle detection accuracy can be improved. In addition, the rotation angle detector 102 can also provide a large margin for assembling the magnet unit 130 and the magnetic detection element 121, and a simpler assembly method is possible. Therefore, the cost of the rotation angle detector 102 can be reduced.

  Further, in the present embodiment, as described above, the thickness is changed in both the inner peripheral portion 130d and the outer peripheral portion 130e of the magnet portion 130, but the thickness may be changed only in one of them. In the present embodiment, as described above, the thickness changes in the inner peripheral portion 130d and the outer peripheral portion 130e are uniform in the diameter direction 130c, that is, linearly increase / decrease. However, the present invention is not limited to this, and other change rates such as a quadratic curve may be used. In short, the thickness change in the inner peripheral portion 130d and the outer peripheral portion 130e may be changed stepwise in the diameter direction 130c.

Further, although the magnet part 130 is provided with a cylindrical ring magnet having the hollow part 131, the present embodiment is not limited to this, and for example, the outer shape and the shape of the hollow part 131 may be a square or the like. A square shape may be used.
In addition, the modified configuration example described in the first embodiment can also be applied to this embodiment.

  Further, as shown in FIG. 13, the magnet unit 130 may be turned upside down and the magnetic detection element 121 may be arranged below the magnet, that is, on the side where the rotating shaft 3 exists, as shown in FIG. 13. Is possible. In the case of this embodiment, the material of the rotating shaft 3 needs to be a non-magnetic material. In the form shown in FIG. 13, compared with the form of FIG.6 and FIG.7, the size of the rotation angle detector 102 whole can be made compact.

Embodiment 3 FIG.
Next, the configuration of the rotation angle detector 103 according to the third embodiment of the present invention will be described below with reference to FIGS.
The rotation angle detector 103 according to the third embodiment also includes a magnet unit 140 and a detection unit 120 as basic components, similar to the rotation angle detector 101 described above. The difference in configuration from the above-described rotation angle detector 101 is the magnet unit 140, and the other configuration is the same as the configuration of the rotation angle detector 101 described above. Therefore, only the magnet unit 140 will be described below.

  In this embodiment, the magnet part 140 has a disk shape, and has a hollow part 141 penetrating the magnet part 140 in the thickness direction at the center part 140a of the magnet part 140 including the rotation center shaft 3a. The hollow portion 141 is fixed to one end of the rotating shaft 3 by a method such as bonding or fitting, and the magnet portion 140 rotates as the rotating shaft 3 rotates.

  In such a magnet unit 140, similarly to the above-described magnet unit 110, the opposing surface 140b of the magnet unit 140 that opposes the magnetic detection element 121 is divided into N regions 142a and 142b that bisect the rotation direction 3b by 180 degrees. A pair of poles and S poles are magnetized, and further, different poles are magnetized along the thickness direction of the magnet portion 140, that is, the axial direction 3c of the rotation center axis 3a, as shown in FIGS. What produces such a magnetization direction in the magnet part 140 is generally called thickness direction magnetization or double-sided quadrupole magnetization.

  In the present embodiment, the magnetic detection element 121 is disposed on an extension line in the axial direction 3 c of the rotation center shaft 3 a of the magnet unit 140.

  Furthermore, in the magnet part 140, as shown in FIG.8 and FIG.9, the thickness of the magnet part 140 in the axial direction 3c which prescribes | regulates the distance G between the opposing surface 140b of the magnet part 140 and the magnetic detection element 121 is the magnet part. It varies locally or stepwise in the diametrical direction 140c at 140 revolutions. More specifically, in the present embodiment, as shown in FIGS. 8 and 9, the thickness of the magnet portion 140 in the outer peripheral portion 140 e of the magnet portion 140 in the diameter direction 140 c is equal to the thickness of the inner peripheral portion 140 d of the magnet portion 140. It is thick. Here, the thickness of the inner peripheral portion 140d is constant in the diameter direction 140c. The thickness of the magnet part 140 in the outer peripheral part 140e is the thickest at the outer peripheral end 144 of the magnet part 140, and decreases linearly toward the inner peripheral side to reach the thickness of the inner peripheral part 140d. In the present embodiment, the outer peripheral portion 140e corresponds to a region from the outer peripheral end 144 to a substantially intermediate point 145 between the outer peripheral end 144 and the inner peripheral end 143 of the magnet part 140 in the diameter direction 140c.

  In FIG. 9, for the sake of convenience, the distance between the inner peripheral portion 140d and the magnetic detection element 121 is shown as “G”. However, as described above, the distance G includes not only the inner peripheral portion 140d but also the outer peripheral portion. This corresponds to the distance from the facing surface 140b of the magnet part 140 including 140e. The distance G is determined in consideration of the magnetic characteristics of the magnet part 140, the sensitivity of the magnetic detection element 121 to the magnetic field, the restrictions on the assembly of the rotation angle detector 103, and the like.

A magnetic field acting on the magnetic detection element 121 from the magnet unit 140 configured as described above will be described below.
In the magnet part 140, the schematic of magnetic field direction distribution generated from a magnet is shown in FIG. On the other hand, FIG. 11 shows a schematic diagram of a magnetic field direction distribution generated from a conventional general ring-shaped magnet generally called thickness direction magnetization or double-sided quadrupole magnetization.

In the conventional magnet part 1 with thickness direction magnetization as shown in FIG. 11, the direction of the magnetic field is formed in the outer peripheral part of the magnet part 1 from the surface of the magnet part 1 to the back surface or from the back surface to the surface. Is done. As a result, the position of the center of gravity of each pole of the magnet in the magnet unit 1 becomes the position of the pole of the magnetic field line from the left side to the right side in the figure, and the pole interval is narrowed. Therefore, in the conventional magnet part 1 magnetized in the thickness direction, there is a problem that a region where a uniform magnetic field can be obtained becomes narrow.
Further, in the case of the above-mentioned radial magnetization, a magnetic field from the front surface to the back surface, for example, is not formed in the outer peripheral portion of the magnet portion. There is a problem that a region where a uniform magnetic field can be obtained is narrower than in the case of magnetism.

  On the other hand, in the magnet part 140 according to the present embodiment, as apparent from a comparison between FIG. 10 and FIG. 11, the distance G is appropriately set by the presence of the inclined surface 140e-1 formed in the outer peripheral part 140e. In spite of the thickness direction magnetization type, the region where the direction of the magnetic field with respect to the magnetic detection element 121 is uniform, that is, uniform, is compared with the conventional thickness direction magnetization type, and the conventional radial direction magnetization. Can be wider than type. From this, the outer peripheral part 110e which has the slope 140e-1 can also be called a magnetic field improvement part. Here, in the case of the magnet portion 140, the distance G preferably has a size that slightly exceeds the maximum thickness at the outer peripheral end 144 of the outer peripheral portion 140e as shown in FIG. The size of the distance G varies depending on the thickness change rate in the diameter direction 140c of the outer peripheral portion 140e, the magnetic characteristics of the magnet portion 140, and the like.

  Also in the rotation angle detector 103 having the magnet unit 140 configured as described above, the same effect as that of the rotation angle detector 101 of the first embodiment can be obtained. That is, also in the magnet part 140 in this embodiment, since the area | region where the direction of the magnetic field with respect to the magnetic detection element 121 is uniform, that is, uniform as mentioned above can be made wider than before, Embodiment 1, 2 is possible. Similarly to the above, the angle detection accuracy can be improved, a simpler assembling method can be realized, and the cost of the rotation angle detector 103 can be reduced.

  Further, in the case of a configuration in which radial magnetization is performed as in the magnet portions 110 and 130 in the first and second embodiments described above, the magnetic field strength above the rotation center shaft 3a is weak. Therefore, in the rotation angle detectors 101 and 102 in the first and second embodiments, it is not a good idea to dispose the magnetic detection element 121 above the rotation center axis 3a. On the other hand, in the magnet part 140 of the third embodiment, so-called double-sided quadrupole magnetization is performed, so that the magnetic field intensity above the rotation center shaft 3a is relatively strong, compared to the first and second embodiments. A uniform magnetic field region can be taken widely. Therefore, in the third embodiment, the magnetic detection element 121 can be arranged above the rotation center shaft 3a, and there is an effect that the selection range of the installation position of the magnetic detection element 121 is widened.

  In the present embodiment, the magnetic detection element 121 is preferably provided above the rotation center shaft 3a with respect to the magnet portion 140 in order to achieve the above-described effects. However, the present invention is not limited to this, and restrictions on assembly are provided. It can be arranged at an arbitrary position in consideration of the above.

  In the present embodiment, the thickness change in the outer peripheral portion 140e is a uniform ratio in the diameter direction 110c, that is, a linear increase / decrease as described above, but is not limited to this, and other change rates, for example, quadratic curves May be changed. In short, the thickness change in the outer peripheral portion 140e may be changed stepwise in the diameter direction 140c.

  In the present embodiment, a locally thick portion is provided in the outer peripheral portion 140e. However, the present invention is not limited to this, and for example, a stepwise thick portion from the inner peripheral portion to the outer peripheral portion of the ring-shaped magnet. May be provided.

  In this embodiment, a cylindrical ring magnet having a hollow portion 141 is provided as the magnet portion 140. However, the present invention is not limited to this, and the magnet portion 140 has, for example, a rectangular shape or the like. It may be a polygonal shape.

  Further, as shown in FIG. 14, the magnet unit 140 may be turned upside down and the magnetic detection element 121 may be disposed below the magnet, that is, on the side where the rotating shaft 3 exists, as shown in FIG. 14. Is possible. In the case of this form, the material of the rotating shaft 3 needs to be a non-magnetic material. In the form shown in FIG. 14, the magnetic detection element 121 cannot be arranged on the rotation center axis 3a of the rotary shaft 3 as compared with the forms shown in FIGS. Although smaller, the size of the entire rotation angle detector 103 can be made compact as compared with the embodiments of FIGS.

  The modification described in the first embodiment can also be applied to the rotation angle detector 103 of the third embodiment.

3 rotation shaft, 3a rotation center axis, 3b axial direction,
101-103 rotation angle detector,
110 magnet part, 110d inner peripheral part, 110e outer peripheral part, 110f central part,
111 hollow part, 120 detection part, 121 magnetic detection element.

Claims (4)

A rotation angle detector for measuring the rotation angle of a measurement object,
Is rotated by the measured object, a magnet portion magnetized is made to change the direction of the magnetic field by the rotation has a including middle empty section a rotation center axis,
A detection unit having a magnetic detection element that is installed above or below the magnet unit in the axial direction of the rotation center axis and whose output changes due to a change in the direction of the magnetic field,
The thickness of the inner peripheral portion and the outer peripheral portion of the magnet portion in the axial direction that defines the distance between the opposing surface of the magnet portion facing the magnetic detection element and the magnetic detection element is the diameter direction in the rotation. rotation angle detector, characterized by stepwise increasing size to the thickness of the central portion located between the inner peripheral portion and the outer peripheral portion.   The rotation angle detector according to claim 1, wherein the magnet part is a double-sided quadrupole magnetized type magnetized on the facing surface of the magnet part in the axial direction and the back surface with respect to the facing surface. The rotation angle detector according to claim 2, wherein the magnetic detection element is installed above or below the central portion of the magnet portion along the axial direction.   The rotation angle detector according to claim 1 or 3, wherein the magnet part is magnetized by magnetizing an S pole and an N pole one by one in each region that bisects the facing surface of the magnet part. .

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