JP2017053776A - Rotation angle detection magnet, rotation angle detector and method for manufacturing rotation angle detection magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation angle detection magnet being a diameter 2 pole type magnet having excellent magnetization workability even in a small shape and capable of increasing a distance to a sensor element; a rotation angle detector capable of achieving a small size; and a method for manufacturing the rotation angle detection magnet, capable of manufacturing the small rotation angle detection magnet.SOLUTION: A entire magnet 1 has approximately a disc shape and is magnetized in the radial direction, and a central portion thereof has a convex shaped portion 11 comprising a pair of inclined parts 12 and 12 facing each other in the magnetization direction and inclined on the central portion side and a flat part 13 continuous to the pair of inclined parts 12 and 12. The longitudinal size of the flat part 13 is approximately equal to the diameter of the magnet 1. A sensor element for detecting a leakage magnetic flux component from the magnet 1 is provided above the flat part 13.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rotation angle detection magnet that is used when magnetically detecting the rotation angle of a rotating object to be detected, and a rotation angle detection that includes the rotation angle detection magnet and detects the rotation angle of the object to be detected. The present invention relates to a rotation angle detection magnet manufacturing method for manufacturing the rotation angle detection magnet.

  In general, the shape of a magnet used in a detection device that magnetically detects the rotation angle of a rotating object to be detected is a substantially disk shape. And this substantially disk-shaped magnet is classified into two types by the difference in the magnetization direction.

  One type is one in which N poles and S poles are magnetized one by one in each semicircle region, and the magnetization direction is a radial direction perpendicular to the rotation axis. Called a magnet. The other type is one in which different poles are magnetized along the rotation axis direction so that the magnetization direction is parallel to the rotation axis direction, and is called a plane two-pole magnetized magnet. Patent Document 1 discloses a rotation angle detector using such a diameter dipole magnetized magnet or a surface dipole magnetized magnet.

JP 2010-160036 A

  Regardless of the magnetizing direction of the magnet, the sensor element for magnetic detection detects the leakage magnetic flux component in the direction orthogonal to the rotation axis, and which magnet type to use depends on the magnet Is determined in consideration of the distance between the sensor element and the sensor element, the sensitivity of the sensor element, the strength of the magnetic force of the magnet, and the like.

  In the case of a surface dipole magnetized magnet, the leakage magnetic flux easily reaches far from the magnet surface, so that the distance between the magnet and the sensor element can be increased. On the other hand, in the case of a two-diameter magnet, the leakage magnetic flux is difficult to reach farther than the magnet surface, so that the sensor element must be arranged near the magnet. If the distance between the magnet and the sensor element can be increased, for example, it is possible to increase the thickness of the mold resin for fixing the sensor element to the control board, etc., or to cover it with a cover such as nonmagnetic stainless steel. This improves the reliability and increases the degree of freedom in structural design. Therefore, there are many advantages as the distance between the magnet and the sensor element increases.

  On the other hand, the workability of magnetization is remarkably different between the surface dipole magnetized magnet and the diameter dipole magnetized magnet. When magnetizing two poles on a surface, it is common to magnetize magnets one by one using a dedicated magnetizing yoke (combining magnetized coil and iron yoke) that matches the size of the magnet. It is. This is because the magnetic field strength necessary for magnetization is as high as 2 Tesla or more, and it is difficult to construct a magnetic circuit for magnetizing a plurality of magnets at once. On the other hand, when magnetizing to two poles in diameter, a magnetic field strength of 2 Tesla or more can be easily generated in a relatively large space by using an air-core coil. it can. That is, it can be said that the diameter dipole magnetization is a low cost and suitable for mass production.

  As described above, the diameter dipole magnetized magnet has an advantage of good workability of magnetization, but has a drawback that it is difficult to increase the distance from the sensor element.

  As a measure for increasing the distance between the magnet and the sensor element, the two-diameter magnetized magnet in Patent Document 1 has a shape in which the surface facing the sensor element in the substantially disk-shaped magnet is recessed from the periphery. However, in Patent Document 1, only the surface of the magnet facing the sensor element (the central part of the magnet) is recessed, and the edge of the magnet that does not face the sensor element remains as it is. For this reason, the distance from the control board for fixing the sensor element remains short, and the structural reliability is not improved. Also, if the size of the magnet is to be maintained in order to obtain the required detection sensitivity, the magnet diameter must be increased, and the size of the magnet and the size of the detector using this magnet increase. There is.

  The present invention has been made in view of such circumstances, and is a two-diameter magnetized magnet having a good magnetization workability and a large distance to the sensor element even in a small shape. An object of the present invention is to provide a rotation angle detection magnet, a rotation angle detection device capable of reducing the size, and a method of manufacturing a rotation angle detection magnet capable of manufacturing a small rotation angle detection magnet.

  The rotation angle detection magnet according to the present invention is a rotation angle detection magnet that is used when magnetically detecting the rotation angle, and has a substantially disk shape that is magnetized in the radial direction. The convex portion has a pair of inclined portions that are inclined to the central portion side in opposition to the magnetization direction, and a flat portion that is continuous with the pair of inclined portions, and the flat portion The longitudinal dimension of is substantially equal to the diameter.

  The rotation angle detection magnet of the present invention has a substantially disc shape as a whole, is magnetized in the radial direction, and is opposed to the magnetizing direction, and has a pair of inclined portions inclined toward the central portion side, The central portion has a convex portion composed of a flat portion connected to the pair of inclined portions. Further, the longitudinal dimension of the flat portion is substantially equal to the diameter. Even if it is small in size, such a convex portion is provided in the central portion facing the sensor element, so that the distance from the sensor element can be increased, and since the diameter is dipole magnetization, magnetization can be easily performed.

  In the rotation angle detection magnet according to the present invention, the short dimension of the flat part is ¼ or more and ½ or less of the diameter, and the angle formed between the rotation surface of the flat part and the inclined part is 30 degrees or more and 60 degrees. It is characterized by being less than or equal to degrees.

  In the rotation angle detecting magnet of the present invention, the long dimension of the flat portion having a substantially rectangular shape is substantially equal to the diameter, and the short dimension is not less than ¼ and not more than ½ of the diameter. The angle formed between the rotating surface and the inclined portion, that is, the angle formed between the rotating surface orthogonal to the rotation axis and the inclined portion when incorporated in the rotation angle detecting device is 30 degrees or more and 60 degrees or less. Therefore, even if it is a comparatively small shape, a leakage magnetic flux can be made to reach | attain far, and arrangement | positioning of the sensor element in the position far away is enabled.

  A rotation angle detection device according to the present invention is a rotation angle detection device that detects a rotation angle of a rotating object to be detected. The rotation angle detection magnet described above and a sensor element that detects a leakage magnetic flux component in a direction orthogonal to the rotation axis due to the rotation of the rotation angle detection magnet are provided.

  In the rotation angle detection device of the present invention, the sensor element detects a leakage magnetic flux component in a direction orthogonal to the rotation axis due to the rotation of the rotation angle detection magnet, and based on the detection result, the rotation angle of the object to be detected is detected. Ask.

  The rotation angle detection device according to the present invention is characterized in that the sensor element is arranged to face the flat portion of the rotation angle detection magnet.

  In the rotation angle detection device of the present invention, the sensor element is disposed opposite to the flat portion of the rotation angle detection magnet. Therefore, the detection accuracy is not impaired even if the axial deviation between the rotation angle detection magnet and the sensor element occurs.

  The rotation angle detection device according to the present invention further includes a metal fixing jig having a claw portion for fixing the rotation angle detection magnet.

  In the rotation angle detection device of the present invention, the rotation angle detection magnet is fixed by the claw portion of the metal fixing jig. Therefore, since the rotation angle detection magnet rotates reliably with the rotation shaft, the detection accuracy of the rotation angle is increased.

  A method for manufacturing a rotation angle detection magnet according to the present invention is a method for manufacturing a rotation angle detection magnet used when magnetically detecting a rotation angle. In this method, a mixture of magnetic powder and a thermosetting resin is compressed. It is characterized by manufacturing the above-described rotation angle detecting magnet.

  In the method for manufacturing a rotation angle detection magnet of the present invention, the rotation angle detection magnet is manufactured by compression molding. Therefore, the proportion of the magnetic powder in the material can be increased as compared with the injection molding, and a rotation angle detecting magnet having a necessary and sufficient magnetic force while being small can be manufactured.

  According to the present invention, it is possible to provide a magnet for rotational angle detection of a diameter two-pole magnetized type that has good workability in magnetization even in a small shape and can increase the distance to the sensor element. A rotation angle detection device with high detection accuracy using this rotation angle detection magnet can be provided. Further, this small-sized rotation angle detecting magnet having a necessary and sufficient magnetic force can be manufactured.

It is a perspective view which shows the magnet for rotation angle detection which concerns on this invention. It is a perspective view which shows the whole structure of the rotation angle detection apparatus which concerns on this invention. It is sectional drawing, the side view, and top view which show the rotation angle detection apparatus based on this invention. It is the top view and side view showing each dimension in the magnet for rotation angle detection which concerns on this invention. It is a graph showing each dimension of the magnet for rotation angle detection in each Example, and the distance between sensor elements. It is a chart showing the diameter of the magnet in a prior art example, a comparative example, and an Example, a magnetization system, and the distance between sensor elements. It is the schematic which shows the shape of a magnet and magnetic field direction distribution in a comparative example and an Example.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a perspective view showing a rotation angle detection magnet according to the present invention.

  A rotation angle detection magnet 1 (hereinafter simply referred to as a magnet 1) according to the present invention is, for example, an Nd—Fe—B bond magnet, and has a substantially disk shape as a whole. The magnet 1 is a two-diameter type magnetized magnet with one N pole and one S pole magnetized in each region that bisects 180 degrees in the rotational direction.

  The central portion of the magnet 1 is a convex portion 11 that protrudes upward (to the side facing a sensor element 4 described later). The convex portion 11 includes a pair of inclined portions 12 and 12 that are inclined toward the central portion side in opposition to the magnetization direction (the arrow direction in FIG. 1), and a flat portion 13 that is continuous with the pair of inclined portions 12 and 12. have. In other words, in the convex portion 11, the contour viewed from the magnetizing direction has a rectangular shape with no inclination, and the contour viewed from the direction rotated 90 degrees from the magnetizing direction has a pair of symmetrical left and right. The both ends have a flat slope, and a flat portion connected to the pair of slopes is provided at the central portion.

  The flat surface which is the upper surface of the flat portion 13 has a strip shape in which the magnetization direction is a short dimension and the direction perpendicular to the magnetization direction is a long dimension. The long dimension of the strip is approximately equal to the diameter of the magnet 1, and the short dimension is ¼ or more and ½ or less of the diameter of the magnet 1. Moreover, the upper surfaces of the inclined portions 12 and 12 are inclined surfaces, and the inclined angles of the inclined portions 12 and 12 are 30 degrees or more and 60 degrees or less. This inclination angle is an angle formed between the rotating surface of the magnet 1 and the inclined portions 12 and 12.

  FIG. 2 is a perspective view showing the overall configuration of the rotation angle detection device according to the present invention. FIG. 3 is a cross-sectional view, a side view, and a top view showing the rotation angle detection device according to the present invention. The rotation angle detection device 10 includes the above-described magnet 1 having the configuration shown in FIG. 1, the rotation shaft 2 that is attached to a rotating detection target (not shown) by, for example, fastening and rotates around an axis, and the magnet 1. A fixing jig 3 for supporting and fixing, a sensor element 4 for detecting a leakage magnetic flux from the magnet 1, and a calculation unit 5 connected to the sensor element 4 are provided.

  The fixing jig 3 is made of, for example, iron and has a thin plate shape. The fixing jig 3 covers the lower surface and the side surface portion of the magnet 1, and fixes the magnet 1 by claw portions 3a and 3a provided on both sides in the magnetization direction. The upper surface of the magnet 1 is not covered with the fixing jig 3, and the inclined surfaces of the inclined portions 12 and 12 and the strip-like flat surface of the flat portion 13 are open.

  The rotating shaft 2 has a long cylindrical shape, and is made of, for example, low carbon steel such as stainless steel so as to withstand press-fitting. One end of the rotating shaft 2 is caulked and fixed to the center of the fixing jig 3. At the time of detecting the rotation angle, the other end of the rotating shaft 2 is attached to the detected object, and the rotating shaft 2, the fixing jig 3 and the magnet 1 rotate integrally according to the rotation of the detected object. ing.

  The sensor element 4 is provided above the flat portion 13 of the magnet 1 by an appropriate distance (d) (see FIG. 3). The sensor element 4 is a magnetic detection element such as an AMR element or a GMR element whose output changes with a change in the direction of the magnetic field. The distance d from the magnet 1 to the sensor element 4 may be appropriately set in consideration of the sensitivity of the sensor element 4 and the strength of the magnetic force of the magnet 1.

  The sensor element 4 detects the leakage magnetic flux from the magnet 1 in the direction orthogonal to the rotation axis 2 and outputs it to the calculation unit 5. The calculation unit 5 calculates the rotation angle of the detected object based on the output result from the sensor element 4.

  Since the flat part 13 is provided in the center part of the magnet 1 and the sensor element 4 is provided above the flat part 13, even if an axial misalignment occurs between the magnet 1 and the sensor element 4, the detection function is provided. It becomes hard to be damaged. Therefore, it is preferable that the short width of the flat portion 13 is substantially equal to the design value of the axial deviation.

  Next, a method for manufacturing the magnet 1 according to the present invention as described above will be described. The magnet 1 of the present invention is specifically manufactured by the following procedure using a compression molding method.

  First, a material is obtained by adding and mixing a thermosetting resin (eg, epoxy resin) to anisotropic Nd—Fe—B magnetic powder. If a large amount of thermosetting resin is contained, the magnetic properties of the magnet will deteriorate, so addition of 1% by mass or more and 8% by mass or less is preferable.

  Next, the obtained material is filled in a press mold at a predetermined temperature in the molding machine, and a molding pressure is applied by the molding machine to form a predetermined shape, and a magnetic field perpendicular to the rolling direction is applied by an air-core coil to be applied. By magnetizing, the magnet 1 as shown in FIG. When isotropic magnetic powder is used, it is not necessary to apply a magnetic field for molding.

  The magnetic powder used includes hard ferrite powder, Sm-Fe-N magnetic powder, and Sm-Co magnetic powder in addition to anisotropic Nd-Fe-B magnetic powder. In addition to the thermosetting resin, a lubricant may be added to the anisotropic Nd—Fe—B based magnetic powder. An example of the lubricant is calcium stearate. The addition amount is preferably 0.1% by mass or more and 2% by mass or less.

  Compared to the injection molding method, the compression molding method does not require a large fluidity of the material, so that the filling rate (ratio) of the magnetic powder in the material can be increased. Therefore, in the present invention, since the magnet 1 is manufactured by the compression molding method, it is possible to manufacture a small magnet 1 having a shape as described above and having good magnetic properties as compared with the injection molding.

  Next, specific examples of the magnet 1 according to the present invention as described above will be described. FIG. 4 is a top view and a side view showing the dimensions of the rotation angle detection magnet according to the present invention, and FIG. 5 shows the dimensions of the rotation angle detection magnet in each example (Example 1-3). And it is a chart showing the distance between sensor elements.

  4 and 5, Φ (mm) represents the diameter of the magnet 1, h (mm) represents the height of the magnet 1 (distance from the lower surface to the upper surface of the flat portion 13), and w (mm). Represents a short width in the flat portion 13, and θ (degree) represents an inclination angle of the inclined portion 12, and is formed by the rotating surface of the magnet 1 orthogonal to the rotating shaft 2 and the inclined portion 12 of the magnet 1. This represents the 12 inclination angles of the inclined portion, which is an angle. Further, d (mm) shown in FIG. 5 represents the distance between the magnet 1 and the sensor element 4 as described above, and in each example, when Φ, h, w, θ is changed, The distance when the sensitivity of the sensor element 4 is 50 mT is shown.

  In addition, since it is common to make a rotation angle detection apparatus very small compared with a to-be-detected object, the diameter ((PHI)) of the magnet used is about 5-30 mm, More preferably, about 10-20 mm is desired. Therefore, as examples, as shown in FIG. 5, three types of examples 1-3 having diameters (Φ) of 10 mm, 15 mm, and 20 mm are presented.

  In the magnet 1 of the present invention, the flat portion 13 has a strip shape, the longitudinal dimension of the flat portion 13 is substantially equal to the diameter (Φ), and the short dimension (w) of the flat portion 13 is 1 of the diameter (Φ). It is preferable that the inclination angle (θ) of the inclined portion 12 is 30 degrees or more and 60 degrees or less. The preferable reason is as follows.

  When the short dimension (w) of the flat portion 13 of the magnet 1 is less than 1/4 of the diameter (Φ) and is too small, the uniform region of the magnetic field is narrowed. It becomes necessary to increase the assembly accuracy, and the usability becomes worse. On the other hand, when the short dimension (w) exceeds 1/2 of the diameter (Φ) and is too large, the magnetic flux hardly flows to the upper surface side, and the distance (d) between the sensor element 4 can be increased. Disappear. When the tilt angle (θ) is less than 30 degrees and is too small, the magnetic flux hardly flows to the upper surface side, and the distance (d) between the sensor element 4 cannot be increased. On the other hand, when the inclination angle (θ) exceeds 60 degrees and is too large, the height (h) of the magnet 1 is increased, which hinders downsizing.

Next, the relationship between the embodiment of the present invention, a comparative example for comparison with the present invention, and the conventional example disclosed in Patent Document 1 will be described. In all of the examples, comparative examples, and conventional examples, 2% by mass of an epoxy resin, which is a thermosetting resin, was added to and mixed with anisotropic Nd—Fe—B based magnetic powder and molded at 1 × 10 ³ MPa. After that, it was heated to 200 ° C.

  FIG. 6 is a chart showing the diameter of the magnet, the magnetization method, and the distance between the sensor elements in the conventional example, the comparative example, and the example. The distance between the sensor elements is a distance when the sensitivity of the sensor elements is 50 mT. FIG. 7 is a schematic diagram showing the shape of the magnet and the magnetic field direction distribution in the comparative example and the example.

  Conventional example 1 in FIG. 6 is a magnet in which the surface facing the sensor element in the example disclosed in Patent Document 1 is recessed, and a surface two-pole magnetized magnet having a diameter of 10 mm is used. Further, Conventional Example 2 in FIG. 6 is a magnet in which a surface facing the sensor element in the example disclosed in Patent Document 1 is recessed, and a dipole magnetized magnet having a diameter of 20 mm is used. Yes. The comparative example 1 in FIG.6 and FIG.7 uses the surface 2 pole magnetization type | mold magnet whose diameter is 10 mm. The comparative example 2 in FIG.6 and FIG.7 has made the disk shape completely as a whole, and uses the diameter 2 pole magnetization type magnet whose diameter is 10 mm. 6 and 7 is different from the configuration of the present invention in which the inclined surface is provided only in a partial region in the circumferential direction, and has a configuration in which the inclined surface is formed over the entire region in the circumferential direction. A dipole magnet with a diameter of 10 mm is used. 6 and 7 uses the magnet according to the present invention having the shape shown in FIG.

  In the case of a surface dipole magnetized magnet, a yoke is usually attached to the main surface of the magnet which is the back surface of the surface facing the sensor element and in contact with the rotating shaft in order to suppress magnetic flux leakage. In Example 1, Comparative Example 1-3, and Conventional Examples 1 and 2, the heights are all 5 mm, but in Conventional Example 1 and Comparative Example 1, the height of the magnet and the height of the yoke are matched. 5 mm.

  In the case of using the surface two-pole magnetized magnets as in Conventional Example 1 and Comparative Example 1, the magnets with the diameter dipole magnetized as in Conventional Example 2, Comparative Example 2 and Comparative Example 3 are used. It can be seen that the distance to the sensor element can be increased as compared with the case where the sensor element is provided. On the other hand, in Example 1, the distance to the sensor element, which is approximately the same as the case of using the surface dipole magnetized magnet, is used although the dipole magnet is used. It has been realized.

  When the comparative example 2 and the comparative example 3 are compared, in the comparative example 3 in which the inclined surface is formed over the entire circumferential direction, the distance to the sensor element is larger than that of the comparative example 2 due to the presence of the inclined surface. Have been able to. However, in Comparative Example 3, a large separation distance cannot be achieved as in the example (Conventional Example 1 and Comparative Example 1) in which two-surface magnets having the same diameter are used.

  When comparing Comparative Example 3 and Example 1, in Comparative Example 3 in which an inclined surface is formed over the entire circumferential direction, a drop in magnetic flux is seen near the center, and the distance to the sensor element is reduced. In Example 1 in which the inclined surface is formed only in the direction opposite to the magnetization direction, the distance to the sensor element can be increased without such a drop in the magnetic flux. Moreover, in Example 1, a distance as large as that of the example using the surface dipole magnetized magnet having the same diameter (conventional example 1 and comparative example 1) can be achieved.

  From the above, in the present invention, by using the dipole magnet 1 having the above-mentioned shape, the good workability of magnetization inherent in the dipole magnet has been maintained. However, it is possible to realize a distance to the sensor element that is equivalent to the case of the surface dipole magnetized magnet. That is, in the present invention, it is possible to achieve both good workability of magnetization (in other words, mass productivity at low cost) and a large distance to the sensor element (in other words, improvement in structural reliability and design flexibility). Is possible.

  In the above-described embodiment, the magnet 1, the fixing jig 3, and the rotating shaft 2 are integrated. However, the magnet 1 and the rotating shaft 2 are integrated without using the fixing jig 3. It may be configured. In addition, the fixing jig 3 and the rotating shaft 2 are not used, and the magnet 1 can be directly attached to the detected object to detect the rotation angle of the detected object.

  The disclosed embodiments should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 Magnet (Rotation angle detection magnet)
2 Rotating shaft 3 Fixing jig 3a Claw part 4 Sensor element 5 Calculation part 11 Convex part 12 Inclination part 13 Flat part

Claims (6)

In the rotation angle detection magnet used when magnetically detecting the rotation angle,
It has a substantially disk shape magnetized in the radial direction, the central part is a convex part, and the convex part is a pair of inclined parts that incline toward the central part facing the magnetization direction And a flat portion connected to the pair of inclined portions, and the longitudinal dimension of the flat portion is substantially equal to the diameter.   The short dimension of the flat part is ¼ or more and ½ or less of the diameter, and an angle formed between the rotation surface of the flat part and the inclined part is 30 degrees or more and 60 degrees or less. 1. A magnet for detecting a rotation angle according to 1. In the rotation angle detection device for detecting the rotation angle of the rotating object to be detected,
A rotating shaft attached to the detected object and rotating;
The rotation angle detection magnet according to claim 1 or 2, wherein the rotation angle detection magnet rotates integrally with the rotation shaft;
A rotation angle detection device comprising: a sensor element that detects a leakage magnetic flux component in a direction orthogonal to the rotation axis due to rotation of the rotation angle detection magnet.   The rotation angle detection device according to claim 3, wherein the sensor element is disposed to face the flat portion of the rotation angle detection magnet.   The rotation angle detection device according to claim 3, further comprising a metal fixing jig having a claw portion for fixing the rotation angle detection magnet. In a method of manufacturing a rotation angle detection magnet used when magnetically detecting a rotation angle,
A method for producing a rotation angle detection magnet according to claim 1 or 2, wherein a mixture of magnetic powder and thermosetting resin is compression molded to produce the rotation angle detection magnet according to claim 1 or 2.

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