JP4373157B2 - Angle detector - Google Patents

Description

  The present invention relates to an angle detection device that detects a rotation angle of an object to be detected using a magnet and a Hall element.

Various structures have been proposed for angle detection devices that detect the angle using a Hall element and a magnet. For example, Patent Documents 1 to 3 below describe.
JP-A-10-132506 JP 2000-121309 A JP 63-145903 A

  Patent Document 1 discloses a rotation angle sensor. As shown in FIG. 1, a rotor portion 3 is formed on a rotating shaft 2 of the throttle opening sensor 1, and a cylindrical permanent magnet 6 is fixed to the rotor portion 3. A hall element 11 is accommodated in the support 10 fixed to the housing 7, and the hall element 11 detects a magnetic field orthogonal to the rotating shaft 2 in the magnetic path of the permanent magnet 6. In addition, an annular recess 13 is formed on the inner peripheral surface of the permanent magnet 6 at substantially the center thereof. Since the Hall element 11 is disposed at the axial center position of the permanent magnet 6, the position of the recess 13 coincides with the center position of the magnetic field sensing by the Hall element 11. In this case, the magnetic flux is made uniform with respect to the Hall element 11, and even if the relative position between the permanent magnet 6 and the Hall element 11 is changed, the error in the sensor output due to the change is reduced. However, this structure has the following drawbacks. First, since the output waveform is a sine wave, the straight line portion of the waveform can be obtained in terms of an angle of only about 90 degrees. Secondly, since two Hall elements cannot be arranged at intervals of 90 degrees, it is impossible to set the detection angle to 360 degrees. Thirdly, the structure cannot be made to penetrate the shaft. Fourth, since the magnetic lines of force pass in parallel to the substrate plane, it is not possible to use a general-purpose hall element of a small and inexpensive substrate mounting type.

  Patent Document 2 discloses a small rotation angle sensor. As shown in FIG. 1, the Hall element and the attached circuit are fitted in a small size integrated hybrid Hall IC 103 and a side groove 3 formed in the upper part of the rotating shaft 2 provided rotatably in the case body 100. The hybrid hall IC 103 is held vertically close to and facing the exposed portion of the side surface of the magnet 1, and the center O of the rotating shaft 2 and the center P of the magnet 1 are eccentric. This small rotation angle sensor has a structure that can penetrate the shaft and enlarges the approximate straight line portion of the sine wave. However, this structure has the following drawbacks. First, if the relative position in the axial direction or radial direction changes between the magnet and the magnetic transducer, the output is affected. Secondly, since magnetic lines of force pass in parallel to the substrate plane, a small and inexpensive substrate mounting type general-purpose Hall element cannot be used.

  Patent Document 3 discloses a rotary positioner. As shown in FIG. 1, this rotary positioner detects a closed magnetic circuit structure 3 including a permanent magnet 2 in a part of an annular magnetic member 1 and a leakage magnetic flux from the closed magnetic circuit structure 3. The closed magnetic circuit structure 3 and the magnetic sensor 6 are rotatable relative to each other about the central axis C of the closed magnetic circuit structure, and the rotation angle is detected based on the detection output of the magnetic sensor. Another magnetic member 7 having an annular shape having the same central axis as that of the closed magnetic path structure 3 is arranged so that the magnetic sensor 6 is sandwiched between the other magnetic member 7 and the closed magnetic path structure 3. However, in the shape of this rotary positioner, the magnetic flux almost flows in the magnetic member, the leakage magnetic flux flowing through the magnetic sensor is very small, and the leakage magnetic flux cannot be changed as shown in the illustrated characteristic graph.

  In order to cope with the recent low cost, it is necessary to change the bearing member from a bearing to a metal. However, when a metal bearing is used, thrust backlash (axial backlash) and radial backlash (radial backlash) of the shaft (rotating shaft) increase. If the output shaft of the geared motor and the shaft of the angle detector are used in common for the purpose of cost reduction and space efficiency improvement, thrust play and radial play corresponding to the play of the gear are required. However, in conventional magnetic angle detectors as disclosed in Patent Documents 2 to 3, thrust backlash and radial backlash affect the output, and fluctuations and errors appear.

  In view of the above-described problems of the conventional technology, an object of the present invention is to provide a magnetic angle detector that is less influenced by thrust backlash and radial backlash. In addition, since the detection angle may be 90 degrees or more, it is an object to provide a magnetic angle detector that has a small diameter (for example, about φ8 mm to φ30 mm) and has a measurable detection angle of 90 degrees or more. . In order to achieve this purpose, the following measures were taken. That is, a case, a shaft rotatably attached to the case, a pair of disk-shaped magnets fixed to the shaft so as to be spaced apart in the rotation axis direction, and a position between the pair of magnets In addition, in the angle detection device that includes a Hall element mounted thereon and a substrate held in the case, and the shaft rotates, the output voltage of the Hall element changes according to the angle. Are magnetized in the thickness direction, and the semicircular portions divided by the magnetic pole boundary along the disk-shaped diameter are magnetized in the opposite directions, and the two magnets are on the opposite side facing each other. The magnetic poles are opposite to each other, and a yoke plate is attached to the opposite surfaces of the two magnets that do not face each other.

  Preferably, each magnet is magnetized using an axial rectangular wave magnetizing yoke and a cylindrical back yoke, and the magnet is set in the axial rectangular wave magnetizing yoke, and the magnet By placing the cylindrical axis of the cylindrical back yoke in a direction perpendicular to the magnetic pole boundary line and magnetizing it, the magnetic flux density change near the magnetic pole boundary line is smoothed, and the magnet is rotated in the circumferential direction. The magnetic flux density on the magnet plane is changed to a shape close to a sine wave or a triangular wave with respect to the angle when moved. The substrate is mounted with two Hall elements spaced 90 degrees apart in the circumferential direction of the disk-shaped magnet, and detects the angle at which the shaft rotates within a range exceeding 120 degrees. . Or the said board | substrate mounts one Hall element, and detects the angle which this shaft rotates within the range which does not exceed 120 degree | times.

  According to the present invention, the Hall element is disposed between a pair of disk-shaped magnets. Each magnet is magnetized in the thickness direction of the disk shape, and the semicircular parts divided by the magnetic pole boundary along the diameter of the disk shape are magnetized in opposite directions. As a result, the magnetic flux passing through the Hall element is perpendicular to the substrate plane, unlike the conventional case. At that time, the magnetic flux density change in the vicinity of the magnetic pole boundary of the magnet is made smooth, and the magnetic flux density on the magnet plane is changed to a shape close to a sine wave or triangular wave with respect to the angle when the magnet is rotated in the circumferential direction. Yes. With this configuration, it is possible to realize a magnetic angle detector that is less affected by thrust backlash and radial backlash. In addition, the size can be reduced as compared with the prior art, and an angle range of about 120 degrees can be detected with only one Hall element.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1A is a schematic cross-sectional view showing a magnetic and non-contact angle detecting device according to the present invention. As shown in the figure, this angle detection device basically includes a case 12, a shaft 9, a pair of magnets 3 and 7, and a substrate 6. The case 12 has a substantially cylindrical shape, and both upper and lower end surfaces are open. The shaft 9 is rotatably attached to the case 12 via a pair of metal bearings 11 and 13. In the present embodiment, the shaft 9 has a flange 9S at the intermediate portion. The shaft lower portion 9R is held in the case 12 by the metal bearings 11 and 13 with the flange 9S as a boundary. Magnets 3 and 7, a substrate 6 and other components are attached to the shaft upper portion 9T above the flange 9S. The shaft lower portion 9 </ b> R is attached to the metal bearings 11 and 13 by washers 10 and 14 and a C ring 15. Each of the pair of magnets 3 and 7 has a disk shape and is fixed to the shaft upper portion 9T so as to be spaced apart in the rotation axis direction. The distance between the magnets 3 and 7 is regulated by the collar 4. The substrate 6 is positioned between the pair of magnets 3 and 7 and is held by the case 12. The substrate 6 has the Hall element 5 mounted thereon. The Hall element 5 may be mounted on the substrate 6 in the form of a Hall IC. The magnets 3 and 7 incorporated in the shaft upper portion 9T are accommodated in the case 12 and covered with the lid 1. In the magnetic non-contact type angle detection device having such a configuration, when the shaft 9 rotates, the output voltage of the Hall element 5 changes according to the angle.

  As a feature, the magnets 3 and 7 are magnetized in the thickness direction of the disk shape, and the semicircular portions divided by the magnetic pole boundary along the diameter of the disk shape are magnetized in opposite directions. ing. The magnets 3 and 7 have opposite magnetic poles facing each other, and yoke plates 2 and 8 are attached to the opposite surfaces of the magnets that do not face each other.

(B) represents the magnetizing method of the magnets 3 and 7. In the present embodiment, the magnets 3 and 7 are magnetized by using an axial rectangular wave magnetizing yoke 16 and a cylindrical back yoke 17. Magnets 3 and 7 are set on the axial rectangular wave magnetizing yoke 16, and the cylindrical shaft of the cylindrical back yoke 17 is arranged on the magnets 3 and 7 in a direction perpendicular to the magnetic pole boundary MD and magnetized. As a result, the magnetic flux density change in the vicinity of the magnetic pole boundary MD of the magnets 3 and 7 is smoothed, and the magnetic flux density on the magnet plane is close to a sine wave or triangular wave with respect to the angle when the magnet is rotated in the circumferential direction. It has come to change. For example, in this embodiment, magnets 3 and 7 having an outer diameter of φ9.8 mm, an inner diameter of φ3 mm, and a thickness of 0.8 mm are magnetized by the method shown in FIG. That is, an axial rectangular wave magnetizing yoke 16 is used, one magnet 3 and 7 is set, and a back yoke 17 of φ12 mm is arranged and magnetized. When the magnets 3 and 7 magnetized in this way are incorporated into the angle detection device shown in FIG. 5A, the outer diameter φ9.8 mm, the inner diameter φ3 mm, Yoke plates 2 and 8 having a thickness of 0.3 mm are brought into close contact with each other and fixed to the shaft 9.
Here, the axial rectangular wave magnetizing yoke is, for example, a yoke for magnetizing a disk-shaped magnet in the axial direction (thickness direction). The surface magnetic flux density is measured with a probe while rotating the magnet magnetized by this yoke as shown in FIG. The measurement results are shown in the waveform diagram of FIG. The magnet is magnetized so that the surface magnetic flux density is distributed in a rectangular wave shape along the circumferential direction. As shown in FIG. 9, the magnets 3 and 7 used in the present invention are magnetized by an axial rectangular wave magnetizing yoke 16 as shown in FIG.

  As shown in FIG. 1A, the surfaces of the pair of magnets 3, 7 that are not provided with the yoke plates 2, 8 face each other, and are fixed to the shaft 9 with the collar 4 interposed therebetween. At this time, the magnetic poles of the magnet 3 and the magnet 7 are opposite to each other. Thus, a magnetic circuit is formed by the upper and lower magnets 3 and 7 and the yoke plates 2 and 8, and a magnetic field is generated between the magnet 3 and the magnet 7. A Hall element 5 and a substrate 6 are disposed between the magnet 3 and the magnet 7. If the magnets 3 and 7 are rotated by the shaft 9, a desired Hall output voltage waveform can be obtained.

  Since the direction of the lines of magnetic force between the magnet 3 and the magnet 7 is the axial direction of the shaft 9, the Hall element 5 can be small and can use a mounting component such as a general-purpose Hall IC, and can be reduced in size at low cost. Further, since the space between the outer diameter of the collar 4 and the inner diameter of the case 12 can be assigned to the area of the substrate 6, the signal amplifying circuit, the constant current circuit, or the constant voltage circuit of the Hall element 5 are all composed of the two magnets 3, 7 Therefore, downsizing is possible. Furthermore, since the direction of the magnetic lines of force between the magnet 3 and the magnet 7 is almost parallel to the axial direction of the shaft 9 and is nearly uniform, even if the relative position of the Hall element fluctuates with respect to the magnet due to the backlash of the shaft 9, There is little change in magnetic flux density perceived by the Hall element.

  FIG. 2 is a graph showing a Hall output voltage waveform obtained from the angle detection device shown in FIG. As is apparent from the graph, a Hall element output voltage close to a triangular wave from a sine wave can be formed depending on the magnetization conditions and the thickness of the yoke plate. The Hall element output voltage changes linearly with respect to the shaft rotation angle at about 120 degrees rising and about 120 degrees falling during 360 degrees. Therefore, the magnetic angle detector of this structure has a measurable detection angle range of about 120 degrees. According to this structure, one Hall element has a detection angle of about 120 degrees. When a detection angle exceeding 120 degrees is required, a method of detecting two angles from two sine waves having a 90-degree phase difference by arranging two Hall elements at 90-degree intervals can be employed. Further optimization of the magnetizing conditions and the shape of the yoke plate may further improve the linearity of the Hall element output voltage with respect to the shaft rotation angle and the range of the electrical angle.

  FIG. 3 is a schematic diagram showing the relationship between the play of the shaft 9 and the position of the Hall element 5. The X direction represents the radial play direction, and the Z direction represents the thrust play direction. The Y direction is the tangential direction of the circumference. As described above, the direction of the magnetic lines of force between the magnet 3 and the magnet 7 is almost parallel to the axial direction of the shaft 9 and is almost uniform. Even if it moves slightly in the X direction or the Z direction, the change in magnetic flux density sensed by the Hall element 5 is small. Since the influence of the relative position change in the Y direction on the output is almost the same as that of a contact angle detector composed of a brush and a resistor, there is no particular problem. A structure in which the magnet is only on one side is also conceivable, but in this case, when the relative position of the Hall element moves slightly in the X direction or Z direction with respect to the magnet, the change in magnetic flux density sensed by the Hall element 5 is large. turn into.

  Even if the magnet 7 is slightly moved in the X direction or the Z direction, there is almost no change in the magnetic flux density perceived by the Hall element 5, but strictly all magnetic lines of force are formed in parallel with the shaft 9. However, the magnetic flux density is unstable on the magnet surface. When there is a sensing part of the Hall element 5 near the middle of the upper and lower magnets 3, 7, the effect of the position of the Hall element moving in the vertical direction (thrust direction) or radial direction (radial direction) relative to the magnet Is the least.

  FIG. 4 is a graph showing measured values of the rate of change when the relative position of the Hall element with respect to the magnet is slightly changed in the Z direction. The zero point in the Z direction indicates the point where the Hall element sensing part is located between the upper and lower magnets. The parameters are the relative distances from the shaft center of the Hall element sensing part when the relative position of the Hall element with respect to the magnet is slightly changed in the X direction. As is clear from the graph of FIG. 4, the change rate of the Hall output is 0.5% or less with respect to a thrust backlash of about 0.2 mm.

  The graph of FIG. 5 is the reverse of the graph of FIG. 4 and shows the measured value of the rate of change when the relative position of the Hall element with respect to the magnet is slightly changed in the X direction. The parameter has six relative distances in the Z direction. As is apparent from the graph, the angle detection apparatus has little output fluctuation even for radial backlash.

  FIG. 6 is an exploded perspective view of the angle detection apparatus shown in FIG. As shown in the figure, the shaft 9 is divided into an upper shaft portion 9T and a lower shaft portion 9R with a flange 9S as a boundary. The components shown in the drawing are incorporated into the shaft upper portion 9T, while the shaft lower portion 9R is incorporated into the case shown in FIG. The magnet 7 is magnetized in the axial direction, and a yoke plate 8 is joined to the surface that was on the magnetized yoke side when magnetized. The magnet 3 is similarly magnetized in the axial direction, and the yoke plate 2 is joined to the surface that was on the magnetized yoke side when magnetized. The magnet 3 and the magnet 7 are attached to the shaft upper portion 9T with the surfaces without the yoke plate 2 and the yoke plate 8 facing each other. The relative positional relationship in the rotational direction of the magnet 3 and the magnet 7 is arranged so that the magnetic poles of the magnet 3 and the magnet 7 are different from each other in the vertical direction. A collar 4 is mounted between the magnet 3 and the magnet 7. The substrate 6 on which the Hall element 5 is mounted around the collar 4 is arranged so as not to contact the outer periphery of the collar 4. The substrate 6 is attached to the case 12 and does not come into contact with the collar 4 or the magnets 3 and 7 even when the shaft 9 rotates, and has a so-called non-contact structure. The vertical position of the sensing part of the Hall element 5 is arranged in the middle between the magnet 3 and the magnet 7. The lid 1 is attached so as to cover the upper end surface of the case 12. A part of the substrate 6 protrudes outward from the outer periphery of the case. A terminal that performs electrical input / output of the Hall element 5 is formed in a portion that protrudes outside the substrate 6. When the detection angle needs to exceed 120 degrees, two hall elements 5 are mounted on the circuit board 6 with an interval of 90 degrees as shown in the figure. When the detection angle does not exceed 120 degrees, one Hall element 5 is sufficient.

  FIG. 7 is an exploded perspective view around the case where the shaft lower portion 9R shown in FIG. 6 is inserted. Since the pair of metal bearings 11 and 12 are attached to the case 12, the shaft 9 is structured to be rotatable with respect to the case 12. The shaft 9 has a structure that does not fall off in the thrust direction by the C ring 15. The thrust backlash is adjusted by the washer 10 and the washer 14. In some cases, one metal bearing may be used. The washer 10 and the washer 14 may be omitted.

It is the longitudinal cross-sectional view of the angle detection apparatus which concerns on this invention, and the schematic diagram which shows the magnetizing method of the magnet integrated in an angle detection apparatus. It is a graph which shows the output characteristic of the angle detection apparatus which concerns on this invention. It is a schematic diagram showing the positional relationship of a Hall element and a magnet. It is a graph which shows the output fluctuation | variation with respect to thrust backlash. It is a graph showing the output fluctuation | variation with respect to radial backlash. It is a disassembled perspective view of the angle detection apparatus which concerns on this invention. It is a disassembled perspective view of the angle detection apparatus which concerns on this invention. It is a typical perspective view which shows axial direction rectangular wave magnetization. It is a typical wave form diagram which shows an axial rectangular wave magnetization.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Lid, 2 ... York plate, 3 ... Magnet, 4 ... Collar, 5 ... Hall element, 6 ... Substrate, 7 ... Magnet, 8 ... Yoke plate , 9 ... Shaft, 10 ... Washer, 11 ... Metal bearing, 12 ... Case, 13 ... Metal bearing, 14 ... Washer, 15 ... C-ring

Claims (4)

A case, a shaft rotatably attached to the case, a pair of disk-shaped magnets fixed to the shaft so as to be spaced apart from each other in the rotation axis direction, and positioned between the pair of magnets; A Hall element mounted thereon and a substrate held in the case,
In the angle detection device in which the output voltage of the Hall element changes according to the angle when the shaft rotates,
Each magnet is magnetized in the thickness direction of the disk shape, and each semicircular part divided by the magnetic pole boundary along the diameter of the disk shape is magnetized in the opposite direction,
Both magnets have opposite magnetic poles facing each other,
An angle detection device, wherein a yoke plate is attached to opposite sides of the magnets that do not face each other. Each magnet is magnetized using an axial rectangular wave magnetizing yoke and a cylindrical back yoke. A magnet is set on the axial rectangular wave magnetizing yoke, and the magnet is placed on the magnet. By arranging and magnetizing the cylindrical axis of the cylindrical back yoke in a direction perpendicular to the magnetic pole boundary, the magnetic flux density change in the vicinity of the magnetic pole boundary of the magnet is smoothed, and the magnet is rotated in the circumferential direction. 2. The angle detection device according to claim 1, wherein the magnetic flux density on the magnet plane changes to a shape close to a sine wave or a triangular wave with respect to the angle of time. The substrate is equipped with two Hall elements arranged 90 degrees apart in the circumferential direction of the disk-shaped magnet, and detects the angle at which the shaft rotates within a range exceeding 120 degrees. The angle detection device according to claim 1, wherein 2. The angle detection device according to claim 1, wherein the substrate has one Hall element mounted thereon, and detects an angle at which the shaft rotates within a range not exceeding 120 degrees.

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