JP2012037243A - Rotation detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide technology of simply and surely fixing a magnet to a rotary shaft in a rotation detection device for detecting rotation based on a rotational magnetic field generated by rotating the magnet.SOLUTION: A rotational member 1 of the rotation detection device for detecting the rotational state of the rotational member 1 based on the change of a magnetic field formed around the rotational member 1 includes a magnet 2 where an N-pole area and an S-pole area are alternatively formed around a rotational center, and a resin housing 3 for holding the magnet 2. In a magnet outer shape forming step, the outer shape of the magnet 2 is formed by using a magnetic material. In a housing forming step, the magnet 2 having the outer shape formed is located in housing molds 50 and 70, and the housing 3 including the magnet 2 is molded by a resin. In a magnetization step, the magnet 2 integrated with the housing 3 is magnetized.

Description

  The present invention relates to a rotation detection device that detects rotation based on a rotating magnetic field generated by rotation of a magnet.

  2. Description of the Related Art A rotation detection device that detects rotation, particularly a rotation angle based on a rotating magnetic field generated by rotation of a magnet magnetized in a radial direction using a sensor having sensitivity to two magnetic flux densities orthogonal to each other is known. Japanese Patent Application Publication No. JP-A-2001-259707, which is cited below, discloses a technique of a magnetic position sensor and a speed sensor having a Hall element as an example of such a rotation detection device. In the magnetic position sensor and speed sensor disclosed in Patent Document 1, the annular magnet is attached to the shaft by an adhesive. Or the magnet which consists of two semicircular washers cross-magnetized in the opposite direction is adhere | attached on one surface of the disk-shaped member which comprises a stator, and a magnetic position sensor and a speed sensor are comprised.

  Japanese Patent Application Laid-Open No. H10-228707, which is cited below, discloses a technique of a rotation angle detection device. The magnet of this rotation angle detection device is formed in a rectangular shape with poles on both sides in the length direction, or in an oval shape (track shape for athletics). A through hole extending in the axial direction of the rotation shaft is provided in the central portion of the magnet. The protruding end of the rotating shaft member is fitted into the through hole, and the protruding end that has come out of the through hole is caulked and fixed, whereby the magnet is fixed to the rotating shaft member.

Japanese Patent No. 2842482 (column 8, column 10, etc.) Japanese Patent Laid-Open No. 11-264711 (paragraph 33, FIGS. 1 and 2 etc.)

  In a rotation detection device such as a magnetic position sensor, a speed sensor, and a rotation angle detection device, the accuracy of fixing the magnet with respect to the rotation shaft (rotation shaft) has a great influence on the detection accuracy. Therefore, the method of fixing the magnet to the rotating shaft (rotating shaft) is a very important technical problem. For this reason, in the apparatus described in Patent Document 1 and Patent Document 2, the magnet is securely fixed to the shaft or the rotating shaft member serving as the rotating shaft by being bonded or caulked with an adhesive. . However, bonding with an adhesive or caulking is not an optimal method for mass production because it requires man-hours necessary for production in a mass production process.

  The present invention was devised in view of the above problems, and provides a technique for simply and reliably fixing a magnet to a rotation shaft in a rotation detection device that detects rotation based on a rotating magnetic field generated by rotation of a magnet. For the purpose.

In order to achieve the above object, based on the change in the magnetic field formed around the rotating member according to the technical means (hereinafter referred to as the first technical means) taken in claim 1 of the present invention, The characteristic configuration of the rotation detection device that detects the rotation state including the rotation angle of the rotation member is as follows:
N pole regions showing N polarity toward the radially outer side of the rotating member and S pole regions showing S polarity toward the radially outer side of the rotating member are alternately formed around the rotation center of the rotating member. With magnets,
The rotating member has a housing that holds the magnet and is resin-molded integrally with the magnet.

  According to a second aspect of the present invention, there is provided a rotation detecting device according to the technical means (hereinafter referred to as second technical means), wherein the magnet is formed by mixing a resin material with a magnetic material. It is good to be a plastic magnet.

  Further, in the rotation detection device according to the technical means (hereinafter referred to as third technical means) taken in claim 3 of the present invention, the N pole region and the S pole region are rotated by the rotating member. It is good to be provided in the fan-shaped range centering on the center.

  The present invention has the following effects.

  That is, according to the first technical means, the magnet is firmly fixed to the housing in the rotating member after the magnet and the housing in which the magnet is installed are integrally molded with resin. Therefore, the possibility of occurrence of a magnet position shift due to secular change is reduced, and a highly reliable rotation detection device can be obtained. Moreover, by integrally resin-molding the magnet and the housing, the process of fixing the magnet to the housing can be simplified, and a structure suitable for mass production can be obtained.

  If the material composition of the magnet and the housing is different, when the operating temperature environment of the rotating member fluctuates, the magnet may be stressed due to the difference in linear expansion coefficient of the constituent material, and the magnet may crack. is there. However, according to the second technical means, if the magnet is a plastic magnet formed by mixing a resin material with a magnetic material made of powder or particles, the method of manufacturing the plastic magnet is a resin molding. The manufacturing method is similar to the manufacturing method. For this reason, the magnet and the housing are integrated with the same composition as the resin housing. Since the magnetic material is dispersed as powder or particles in the molded plastic magnet, the thermal expansion or contraction of the magnetic material of the powder or particles due to temperature change is reduced. As a result, the influence of the difference in linear expansion coefficient based on the difference between the material of the housing and the material of the magnet is reduced, and a rotation detection device having a strong resistance to fluctuations in the operating temperature environment can be obtained.

  According to the third technical means, the range of the rotating magnetic field provided in the rotation detecting device may be set in accordance with the use of the rotation detecting device, and is not necessarily N around the rotation center of the rotating member. It is not necessary to provide the polar region and the S-polar region. As such a case, for example, it corresponds to a case where it is used for a purpose of detecting a mechanical rotation angle of about 120 degrees to 180 degrees and less than 360 degrees. In such a case, when the N-pole region and the S-pole region are provided in a fan-shaped range with the rotation center of the rotation member as the center, the volume occupied by the magnet in the rotation member compared to the case where it is provided over the entire circumference. Can be reduced. Therefore, the amount of the magnetic material constituting the magnet is reduced, and the cost required to form the magnet can be reduced, thereby reducing the cost of the rotation detection device. Even when the magnet is composed of a plastic magnet, the amount of the magnetic material can naturally be reduced, and the cost can be reduced. In particular, when the magnet is a rare earth magnet, since the material cost of the rare earth magnet is higher than that of other magnet materials, the cost reduction effect as a rotating device is great.

The perspective view which shows an example of the rotation member of the rotation detection apparatus (angle detection apparatus) of this invention Side view of rotating member III-III sectional view of Fig. 2 Explanatory drawing which shows the structure of an angle detection apparatus typically Explanatory drawing which shows the structure of an angle detection apparatus typically The perspective view which shows an example of a structure of the magnetic field detection part of an angle detection apparatus. Explanatory diagram showing the principle of detection of magnetic field components by the magnetic field detector Explanatory diagram showing the principle of detection of magnetic field components by the magnetic field detector Explanatory drawing which shows typically the procedure which shape | molds a rotating member by insert molding

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, an example of an angle detection device that detects a rotation angle will be described as an example of the rotation detection device. Such an angle detection device is used, for example, as a steering angle sensor for an automobile or a shift position sensor for a transmission.

  FIG. 1 is a perspective view showing an example of a rotating member 1 of an angle detection device (rotation detection device) according to the present invention. 2 is a side view of the rotating member 1, and FIG. 3 is a cross-sectional view taken along the line III-III of FIG. 4 and 5 are explanatory diagrams schematically showing the configuration of the angle detection device, and FIG. 6 is a perspective view showing an example of the configuration of the magnetic field detection unit 5 of the angle detection device.

  As shown in FIGS. 4 and 5, the rotating member 1 shown in FIG. 1 is fitted to a shaft 7 which is a rotating body (rotating shaft) of a rotating body or rotating body such as a steering or a shift lever to be detected. Is done. The rotating member 1 rotates (rotates) together with the shaft 7. Hereinafter, unless otherwise specified, “rotation” and “rotation” will be referred to as “rotation” without distinction. The angle detection device detects a rotating magnetic field generated around the rotating member 1 and calculates the rotation angle of the rotating member 1 with respect to the magnetic field detecting unit 5 based on detection information of the magnetic field detecting unit 5 (not shown). And an arithmetic unit.

  The magnetic field detection unit 5 is realized, for example, in the form of an integrated circuit (Hall IC) as shown in FIG. The magnetic field detector 5 detects the magnitude of the magnetic field component in two directions. That is, the magnetic field detection unit 5 includes two pairs of detection elements 9 (a pair of 9a and 9b and a pair of 9c and 9d) arranged so as to be orthogonal to each other on the same plane. In the example shown in FIG. 6, the pair of detection elements 9 c and 9 d are provided separately along the X direction of the three-dimensional orthogonal coordinate system, and the pair of detection elements 9 a and 9 b along the Y direction are separated from each other. Are provided. The magnetic field detector 5 has a circular magnetic plate 8 made of a soft magnetic material. The two pairs of detection elements 9 are arranged at the peripheral portion immediately below the magnetic plate 8, that is, at a position where the peripheral surface of the magnetic plate 8 exists on the plane of the detection element 9. In this example, the two pairs of detection elements 9 are Hall elements. The magnetic field detection unit 5 is configured as a Hall IC incorporating a signal processing circuit that performs signal processing on the output of the detection element 9. The magnetic field detection apparatus having such a configuration is described in, for example, Japanese Patent Application Laid-Open Nos. 2002-71381, 2003-294818, and WO 03/081182.

  As described above, the angle detection device includes a calculation unit (not shown), and calculates the rotation angle of the rotary member 1 based on the output of the magnetic field detection unit 5. The calculation unit is preferably configured by a processor such as a microcomputer or a DSP (digital signal processor) and mounted on the same substrate as the magnetic field detection unit 5. Note that the arithmetic unit may be incorporated in the Hall IC together with the signal processing circuit.

  FIG. 4 shows one configuration example of the angle detection device. The rotation member 1 included in the angle detection device includes a magnet 2 having an arch shape in cross section. The magnet 2 has an N-pole region and an S-pole region that are alternately arranged along the circumferential direction, and is externally fitted to the shaft 7. The magnetic field detection unit 5 is disposed to face the magnet 2 so that the plane on which the two pairs of detection elements 9 are disposed is parallel to the radial direction of the rotating member 1. The two pairs of detection elements 9 are provided apart from each other along the X direction and the Y direction of the three-dimensional orthogonal coordinate system. In this example, the magnetic field detector 5 faces the rotating member 1 with the radial direction of the rotating member 1 as the Y direction.

  FIG. 5 shows another configuration example of the angle detection device. The magnetic field detection unit 5 is arranged so as to face the magnet 2 so that the plane on which the two pairs of detection elements 9 are arranged is orthogonal to the radial direction of the rotating member 1. As described above, the two pairs of detection elements 9 are provided apart from each other along the X direction and the Y direction of the three-dimensional orthogonal coordinate system. In this example, the magnetic field detector 5 faces the rotating member 1 with the radial direction of the rotating member 1 as the Z direction of three-dimensional orthogonal coordinates.

  Hereinafter, the principle of the angle detection device will be described. FIG. 7 is a cross-sectional view of the magnetic field detection unit 5 viewed from the X-axis direction in FIG. 4 and shows a state of leakage magnetic flux distribution by the magnet 2 applied to the magnetic field detection unit 5. As shown in FIG. 7, when an external magnetic field leaking from the magnet 2 in the Y direction is applied to the magnetic field detector 5, the magnetic flux is directed in the direction of the magnetic plate 8 due to the magnetic flux collecting effect of the magnetic plate 8 made of a soft magnetic material. Bend. The magnitude of the magnetic field component perpendicular to the magnetic plate 8 applied to the pair of detection elements 9a and 9b is proportional to the magnitude of the external magnetic field. The direction of the magnetic field component in the Z direction is opposite between the detection elements 9a and 9b. Therefore, a vector quantity proportional to the magnitude of the external magnetic field in the Y direction is obtained by obtaining a difference in the vector quantity output of the pair of detection elements 9a and 9b in the signal processing section of the magnetic field detection section 5 or a calculation section (not shown). Is detected.

  On the other hand, the same applies when an external magnetic field is applied in the X direction, and a magnetic field component in the Z direction perpendicular to the magnetic plate 8 is generated. In the same manner as described above, the vector amount proportional to the magnitude of the external magnetic field in the X direction is detected by obtaining the difference between the outputs of the pair of detection elements 9c and 9d. From the detection results (magnitude and direction of the magnetic field) in the X direction and the Y direction, the rotation angle of the rotating member 1 is obtained using an inverse trigonometric function (tan-1).

  Here, the principle of the angle detection device will be described in more detail. As described above with reference to FIG. 7, when an external magnetic field leaking from the magnet 2 in the Y direction is applied to the detection unit 5, the magnetic flux of the magnetic plate 8 is caused by the magnetic flux collecting effect of the magnetic plate 8 made of a soft magnetic material. Bent in the direction. Thereby, the magnitude | size of the magnetic flux density applied to a pair of detection elements 9a and 9b spaced apart along the Y direction of the peripheral part of the magnetic plate 8 changes with the following relationships. That is, the magnitude of the magnetic flux density varies depending on the distance between the magnet 2 and the magnetic plate 8, the relative positional relationship between the magnet 2 and the magnetic plate 8, and the positional relationship between the detection elements 9a and 9b with respect to the magnetic plate 8. For this reason, when the magnet 2 rotates in the vicinity of the detection unit 5, the relative positional relationship between the magnet 2 and the magnetic plate 8 changes, and accordingly, the magnetic flux leaking from the magnet 2 is moved to the vicinity of the magnetic plate 8. The state of magnetic flux distribution to be formed changes greatly.

  Here, the magnetic flux density in the X direction detected by the detection element 9 will be considered. Since the X direction and the Y direction are orthogonal coordinates on the same plane, it can be easily understood that the difference in magnetic flux density in the X direction detected by the two detection elements 9c and 9d changes in the same manner as in the Y direction. That is, the difference in the magnetic flux density in the X direction continuously changes the value between zero and the value of the X direction component of the magnetic flux density applied to the detection element 9c or 9d in a sine wave form.

  The magnetic flux density applied to the pair of detection elements including the detection elements 9a and 9b and the subtraction value or addition value of each direction component have been described above. For the other pair of detection elements consisting of the detection elements 9c and 9d, the center line of the detection elements 9c and 9d forms 90 degrees with the center line of the detection elements 9a and 9b. For this reason, the phase of the sine wave which shows the change of the magnitude | size of the magnetic flux density of each direction component differs. However, the difference in the magnetic flux density component generated in the X direction due to the rotation of the magnet 2 continuously changes in a sinusoidal manner from zero to the maximum value of the X direction component of the magnetic flux density applied to the detection element 9c or 9d. Similarly, the difference in the magnetic flux density component generated in the Y direction continuously changes in a sinusoidal manner from zero to the maximum value of the Y direction component of the magnetic flux density applied to the detection element 9a or 9b.

  Further, based on the same idea, the sum of the components of the magnetic flux density in the Z direction is between zero and twice the Z direction component applied to the detection element 9c or 9d (or from Z to the Z direction applied to the detection element 9a or 9b). Continuously change in a sinusoidal shape (between twice the component values).

  Next, the operation of the calculation unit that calculates the rotation angle based on the magnetic flux vector amount applied to the detection element 9 described above will be described. As described above, the calculation unit includes a processor such as a microcomputer, and the contents of the calculation process can be selected by a program or the like. First, a voltage signal proportional to the magnitude of the magnetic flux detected by each of the detection elements 9a to 9d is input to the calculation unit. The calculation unit performs subtraction processing on the magnetic field component signals in the X direction and Y direction, and performs addition processing on the Z direction component signals. Note that the addition process and the subtraction process can be changed by a program constructed according to the configuration of the angle detection apparatus as described above. That is, the addition process can be changed to the subtraction process, or the subtraction process can be changed to the addition process according to the configuration of the angle detection device.

  Thereafter, the calculation unit uses the value after the subtraction process or the addition process, and uses tan -1 (Z direction component addition process value / X direction component subtraction process value), tan -1 (Z direction component addition process). Value / Y-direction component subtraction processing value), tan −1 (Y-direction component subtraction processing value / X-direction component subtraction processing value) and the like are performed. As described above, the phase of the sine wave indicating the change in the magnitude of the magnetic flux density of each direction component differs depending on the rotation angle. By using this phase difference, the rotation angle is obtained from the calculation of the inverse trigonometric function.

  Note that the selection of these three types of arithmetic processing is preferably performed by a processor such as a microcomputer using a program constructed according to the configuration of the angle detection device as described above. In other words, the above three types of arithmetic processing are selected according to the above-described distance and relative positional relationship between the magnet 2 and the magnetic plate 8 and the positional relationship of the detection element 9 with respect to the magnetic plate 8 to obtain the rotation angle.

  Hereinafter, the principle regarding the angle detection apparatus of FIG. 5 having a configuration different from that of FIG. 4 will be briefly described. As described above, in the angle detection device illustrated in FIG. 5, the magnetic field detection unit 5 faces the rotation member 1 with the radial direction of the rotation member 1 as the Z direction of three-dimensional orthogonal coordinates.

  FIG. 8 is a cross-sectional view of the magnetic field detection unit 5 viewed from the X-axis direction in FIG. 5 and shows the state of magnetic flux applied to the detection unit 5. As shown in FIG. 8, when an external magnetic field is applied in the Z direction, a vertical Z direction magnetic field is applied to the pair of detection elements 9a and 9b arranged along the Y direction. At this time, unlike the previous example shown in FIG. 7, the direction of the magnetic field component in the Z direction is the same in the detection elements 9a and 9b. Therefore, in the signal processing unit of the magnetic field detection unit 5 or the calculation unit (not shown), the vector amount proportional to the magnitude of the external magnetic field in the Z direction is obtained by adding the vector amount outputs of the pair of detection elements 9a and 9b. Detected.

  On the other hand, when an external magnetic field is applied in the X direction, the magnetic field component in the Z direction basically differs in one or both of the magnitude and direction between the pair of detection elements 9c and 9d. Here, “basically” is because there is a point having the same size and direction. Therefore, with respect to the X direction, as in the angle detection apparatus shown in FIG. 4, the vector amount proportional to the magnitude of the external magnetic field is detected by obtaining the difference between the outputs of the pair of detection elements 9c and 9d.

  From the detection results (magnitude and direction of the magnetic field) in the X direction and the Z direction, as described above, the rotation angle of the rotating member 1 is obtained using the inverse trigonometric function (tan-1). The calculation of the rotation angle is performed by a calculation unit (not shown) configured with a processor such as a microcomputer, as described above. However, the rotation angle cannot be obtained by the same calculation process as the configuration shown in FIG. This is because the signal processing methods for the pair of detection elements 9a and 9b arranged in the Y direction are different. However, as described above, the processor constituting the calculation unit is configured to be able to select the contents of the calculation process by a program or the like. Therefore, it is possible to use the detection unit 5 similar to the angle detection apparatus having the configuration shown in FIG.

  Note that the program change does not only indicate a change in software that functions on hardware, but also includes a change in hardware structure. The hardware structure may be changed using reconfigurable hardware, FPGA (field programmable gate array), PLD (programmable logic device), or the like. Also included is a method of selecting a plurality of electronic circuits built in the processor in advance by switching an input signal to a terminal of one processor to a high level or a low level. As a result, a different processor is constructed, but the change of the hardware description language that defines the structure of the processor is also included in the change of the program.

  Although the angle detection device having a different configuration has been described with reference to FIGS. 4 and 5, it can be easily understood that the rotation member 1 having the same configuration can be applied to any configuration. This indicates that the rotation member 1 can be shared in various angle detection devices (rotation detection devices). And it is highly expected in the industrial field that the rotating member 1 having excellent mass productivity and high durability and reliability is provided.

  Here, the details of the rotating member 1 of the present embodiment will be described with reference to FIGS. 1 to 3 again. The rotating member 1 includes a magnet 2 and a resin housing 3 formed integrally with the magnet 2. The magnet 2 has an N-pole region showing N polarity toward the radially outer side of the rotating member and an S-pole region showing S polarity toward the radially outer side of the rotating member 1 around the rotation center of the rotating member 1. Are alternately formed. In this embodiment, for the purpose of detecting a mechanical angle of 120 degrees with a resolution of an electrical angle (magnetic angle) of 360 degrees, the magnet 2 has two Ss with a pitch of a mechanical angle of 40 degrees with the N pole 23 interposed therebetween. The poles 22 and 24 are formed.

  Further, N poles 21 and 25 are formed on the magnet 2 adjacent to the S poles 22 and 24 as auxiliary magnetic poles for forming an auxiliary magnetic field. Since the auxiliary magnetic poles 21 and 25 are formed for the purpose of forming an auxiliary magnetic field, the auxiliary magnetic poles 21 and 25 are formed to be approximately half the size of the other magnetic poles 22 to 24. When the auxiliary magnetic poles 21 and 25 are provided, the linearity between the magnetic field angle and the rotation angle of the rotating member is improved in a range of ± 180 degrees (electrical angle) with respect to the center of the N pole 23 that is the central magnetic pole of the detection range. .

  When the auxiliary magnetic poles 21 and 25 are not formed on the magnet 2, good linearity is exhibited near the center (approximately ± 120 degrees (electrical angle)) with respect to the center of the N pole 23, but at the end. In the vicinity of a certain ± 180 degrees (electrical angle), the linearity may be impaired. When high accuracy is not particularly required, or when linear correction is performed in the arithmetic unit or the like, the magnet 2 may be configured without the auxiliary magnetic poles 21 and 25 being provided.

  In the present embodiment, a configuration is shown in which a rotation angle of 120 degrees of the rotating member 1, that is, a mechanical angle of 120 degrees is detected in correspondence with an electrical angle of 360 degrees. For this reason, the magnet 2 is formed in a part of the periphery of the rotating member 1. In other words, the N-pole region and the S-pole region are provided in a fan-shaped range (including a case where a semicircle and a semicircle are exceeded) centered on the rotation center of the rotating member 1. Of course, when the detection of the electrical angle exceeding 360 degrees is performed, the range in which the magnet 2 is formed is not limited to the sector shape, and may extend over the entire circumference of the rotating member 1.

  The magnet 2 can be formed by sintering a magnetic material to make a sintered magnet and magnetizing the sintered magnet. The magnet 2 can also be formed by making a plastic magnet by resin molding using a mixed resin material obtained by mixing magnetic powder, which is a magnetic material, with a resin material, and magnetizing the plastic magnet.

  The housing 3 of the rotating member 1 according to the present invention holds the magnet 2 and is integrally formed with the magnet 2 by a resin material. As disclosed in Patent Documents 1 and 2, conventionally, a magnet is fixed to a shaft serving as a rotating shaft or a housing of a rotating member by being bonded or caulked with an adhesive. As described above, bonding with an adhesive or caulking is not an optimal method for mass production because it requires man-hours in a mass production process. On the other hand, the rotating member 1 in this embodiment is suitable for mass production because the magnet 2 and the housing 3 are integrally formed.

  Since the housing 3 is formed by resin molding, when the magnet 2 is a plastic magnet, the entire rotating member 1 is resin-molded. The resin materials of the magnet 2 and the housing 3 have different compositions as is apparent from the fact that the plastic magnet that constitutes the magnet 2 includes a magnetic material. However, since both are mainly composed of a resin material, the linear expansion coefficients of the magnet 2 and the housing 3 are close to each other as compared with the case where the magnet 2 is a sintered magnet. Thereby, when the use environment temperature of an angle detection apparatus changes, the stress applied to the magnet 2 resulting from the difference in the linear expansion coefficient of the magnet 2 and the housing 3 is reduced. Of course, when the magnet 2 is a plastic magnet, it is preferable that a magnetic material is mixed with the same resin material as the housing 3.

  Further, when a rare earth magnet is used for the magnetic powder, the magnetic force of the rare earth magnet is larger than that of the other magnets, so that the amount of magnetic powder filled in the resin material can be reduced. As a result, the composition of the magnet 2 and the housing 3 can be made closer. However, since rare earth magnets have a limited production area and are expensive, it is preferable that the magnet 2 be appropriately sized according to the range where angle detection is required. As described above, when the magnet 2 is formed in a sector shape without being formed over the entire circumference, the amount of magnetic powder used is suppressed, and the material cost (production cost) is reduced.

  The housing 3 and the magnet 2 are integrally formed. Of course, when the magnet 2 is a sintered magnet, even if it is a plastic magnet, there is an interface between them. Therefore, ingenuity in the shape is applied in order to prevent the displacement and omission of both. As shown in FIG. 2, a flange 3 a is formed in the housing 3 along the circumferential direction of the rotating member 1, and the magnet 2 is prevented from coming off in the extending direction of the rotating shaft of the rotating member 1. As shown in FIG. 3, the magnet 2 has notches 2b formed at both ends in the circumferential direction, and the housing 3 has protrusions 3b that engage with the notches 2b. By engaging the notch 2b of the magnet 2 and the protrusion 3b of the housing 3, the displacement of the magnet 2 in the circumferential direction and the radial direction of the rotating member 1 is suppressed.

  In particular, in the case of the magnet 2 having the auxiliary magnetic poles 21 and 25 as in the present embodiment, the notch portion 2b can be provided at the position of the auxiliary magnetic poles 21 and 25, which is preferable. Since the cutout portion 2b is provided, the volume of the magnet 2 is reduced. However, since the portion corresponds to the auxiliary magnetic poles 21 and 25, the function of the magnet 2 is not impaired.

  In this embodiment, since the magnet 2 is formed in a semi-annular shape instead of an annular shape over the entire circumference, the notches 2b are provided at both ends in the circumferential direction. When the magnet 2 is formed in an annular shape, since there is no end portion in the circumferential direction, a notch is appropriately provided. Moreover, when the magnet 2 is annular, it is not necessary to consider the deviation in the radial direction, and it is only necessary to suppress the deviation in the circumferential direction. Therefore, the notch 2b may be formed only at one place.

  In this embodiment, the magnet 2 is provided with the notch 2b and the housing 3 is provided with the protrusion 3b. Conversely, the magnet 2 is provided with the protrusion, and the housing 3 is provided with the notch. It may be a structure. However, when the circumferential length of the magnet 2 is the same, the structure of the present embodiment in which the notch 2b is provided in the magnet 2 is preferable because the volume of the magnet 2 is suppressed. That is, since the magnetic material composing the magnet 2 is very expensive particularly in the case of rare earth, it is preferable that the volume of the magnet 2 is suppressed and the usage amount of the magnetic material is suppressed.

  As shown in FIG. 1, the housing 3 is formed with a shaft through-hole 35 for allowing the shaft 7 to pass therethrough and sandwiching and fixing the shaft 7. As shown in FIG. 3, a buffer space 37 is formed along the axial direction outside the shaft through hole 35 in the radial direction. Since the shaft through-hole 35 is sandwiched and fixed, the shaft through-hole 35 is formed with a tolerance that is smaller than the outer dimension of the shaft 7. In addition, as shown in FIG. 1, a linear protrusion 33 having a taper that reduces the amount of protrusion toward the opening is formed on a part of the inner wall of the shaft through hole 35, so Improve contact strength. Therefore, when the shaft 7 is penetrated through the housing 3, mechanical stress is applied from the center of the housing 3 toward the outside in the radial direction. This stress is further applied to the magnet 2 integrated with the housing 3, thereby causing distortion, cracking, cracking, and the like in the magnet 2, which may greatly affect the accuracy of the angle detection device. When the buffer space 37 is provided, the mechanical stress applied to the housing 3 from the shaft 7 is absorbed by the buffer space 37, and the mechanical stress applied to the magnet 2 is greatly reduced.

〔Insert molding〕
When the required specification for the positional accuracy of the magnet 2 with respect to the housing 3 is relatively low, the magnet 2 and the housing 3 may be integrally formed by insert molding. Hereinafter, insert molding will be described with reference to FIGS.

[Magnet outline forming process]
For convenience, the step shown in FIG. 9A is referred to as a first step, which is a subsequent step, and the step shown in FIG. 9B is referred to as a second step. The first step and the second step are steps for resin-molding the outer shape of the magnet 2 and correspond to the magnet outer shape forming step of the present invention. As described above, the formation of the magnet 2 is not limited to “molding”, but can be performed by “sintering”. Therefore, the name of the process is referred to as “magnet outer shape“ formation ”process”. In this embodiment, since the magnet is formed by resin molding, the magnet outer shape forming process can also be referred to as a “magnet“ molding ”process”.

  As shown in FIGS. 9A and 9B, the first step and the second step are performed using the lower magnet mold 40A and the upper magnet mold 60A. As shown in FIG. 9A, in the first step, the lower magnet mold 40A and the upper magnet mold 60A are combined. Next, a pellet, which is a mixed resin material obtained by mixing magnetic powder and a resin material, is injected into the hollow portion 44 generated when the lower magnet mold 40A and the upper magnet mold 60A are combined. Note that it is preferable to use the resin material having the same composition as that of the resin material for molding the housing 3. When the above-mentioned pellets are sufficiently filled in the cavity 44, pressure is applied in the second step to cool the filled pellets, thereby completing the shaping of the outer shape of the magnet 2 (FIG. 9B). The magnet 2 that has been molded is taken out from the lower magnet mold 40A.

  In insert molding, the mold for molding the housing 3 and the mold for molding the magnet 2 can be completely independent. That is, the magnet 2 is molded without using any housing molds (reference numerals 50A and 70A described later) for molding the housing 3. Therefore, the mold for molding the magnet 2 can have a very simple structure.

  In the present embodiment, an example in which a plastic magnet is used as the magnet 2 has been shown, but a sintered magnet can also be used in insert molding. When a sintered magnet is used as the magnet 2 instead of a plastic magnet, the adhesive force at the interface is lower than that of the plastic magnet. However, as described above, the housing 3 is provided with a retaining function for each of the axial direction, the radial direction, and the circumferential direction. Therefore, you may produce the rotating member 1 as shown in FIGS. 1-3 by insert molding according to use environment, a required specification, etc. FIG.

[Housing molding process]
For convenience, the step shown in FIG. 9C is the third step, followed by the step shown in FIG. 9D as the fourth step, followed by the step shown in FIG. 9E as the fifth step. Called. The fourth and fifth steps are steps for integrally molding the housing 3 with the magnet 2 and correspond to the housing molding step of the present invention. Since the third step is a step that is a preparation for the fourth step and the fifth step, it corresponds to a housing molding step. Hereinafter, the third to fifth steps will be described as a housing molding step. As shown in FIGS. 9C to 9E, the housing molding process is performed using a housing lower mold 50A and a housing upper mold 70A.

  The magnet 2 taken out from the lower magnet mold 40A is attached to the lower housing mold 50A in the third step. At this time, a slight clearance is provided between the housing lower mold 50 </ b> A and the magnet 2. In insert molding, the magnet molding mold (upper mold 60A and lower mold 40A) and the housing molding mold (upper mold 70A and lower mold 50A) are not used in common. Positioning of the magnet 2 and the lower mold 50A for housing is necessary. For example, the magnet 2 is provided with an engaging notch 29 for positioning, and the housing lower die 50A is provided with an engaging protrusion 29A that engages with the engaging notch 29.

  As shown in FIG. 9 (d) for explaining the fourth step, when the upper housing mold 70A is set on the lower housing mold 50A, the protruding pin 52A corresponding to the shaft 7 is moved from the lower housing mold 50A to the housing. It is extended until it comes into close contact with the upper mold 70A. A shaft through hole 35 is formed in the housing 3 by the protruding pin 52A. The protruding pin 52A may not be movable.

  Subsequently, pellets made of a resin material are injected into a cavity 56A formed when the lower housing mold 50A and the upper housing mold 70A are combined. When the pellet is sufficiently filled in the hollow portion 56A, pressure is applied to cool the pellet to complete the molding of the housing 3 integrated with the magnet 2 (FIG. 9 (e)). Thereby, the rotating member 1 in which the magnet 2 and the housing 3 are integrated is formed.

[Magnetization process]
As shown in FIG. 1, a magnetization marker 31 serving as a reference for magnetization is formed on the rotating member 1 (housing 3). Further, a position marker 32 serving as a reference when the shaft 7 is attached or after being attached to the shaft 7 is also formed. The rotating member 1 formed through the first to fifth steps is set on a known magnetization jig (not shown) with the magnetization marker 31 as a reference, and the magnet 2 is magnetized. As described above, the rotating member 1 in which the magnet 2 is fixed to the shaft 7 simply and reliably can be obtained through the magnet outer shape forming process, the housing molding process, and the magnetization process.

  As described above, according to the present invention, it is possible to provide a technique for simply and reliably fixing a magnet to a rotation shaft in a rotation detection device that detects rotation based on a rotating magnetic field generated by rotation of a magnet. Become.

1: Rotating member 2: Magnet 3: Housing 50: Lower mold (housing mold)
60: First upper mold 70: Second upper mold (housing mold)
50A: Lower mold for housing 70A: Upper mold for housing

Claims (3)

A rotation detection device that detects a rotation state including a rotation angle of the rotation member based on a change in a magnetic field formed around the rotation member,
The rotating member is
N pole regions showing N polarity toward the radially outer side of the rotating member and S pole regions showing S polarity toward the radially outer side of the rotating member are alternately formed around the rotation center of the rotating member. With magnets,
A rotation detection device comprising: a housing that holds the magnet and is resin-molded integrally with the magnet.   The rotation detection device according to claim 1, wherein the magnet is a plastic magnet formed by mixing a resin material with a magnetic material.   The rotation detection device according to claim 1, wherein the N pole region and the S pole region are provided in a fan-shaped range centering on a rotation center of the rotating member.

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