JP5013535B2 - Rotation angle detector - Google Patents

Description

  The present invention relates to an improvement in a rotation angle detection device that detects a rotation angle of a rotation shaft by detecting rotation in a magnetic flux direction due to rotation of the rotation shaft. The present invention can be employed in, for example, a vehicle steering angle detection device.

  A steering angle detection device using a rotation angle detection device that detects a change in rotation angle of a magnet (including a magnetized body) by a magnetic detection element is known. In this rotation angle detection device, a device that detects a rotation angle exceeding 360 degrees of a rotation axis to be detected (hereinafter also referred to as a 360-degree super rotation angle detection device) is known in Patent Document 1. The 360-degree super-rotation angle detection device of Patent Document 1 detects the rotation angles of two magnet shafts that mesh independently with one detected rotation shaft whose rotation angle is to be detected, by means of a magnetic detection unit. It has been proposed that two magnetic detectors generate outputs having different phase angles, and a signal processor calculates a rotation angle of more than 360 degrees from the difference in phase angle between these two outputs.

Further, in the following Patent Document 2 which is the invention of the present inventor, a male screw portion is provided at a blade edge of a second gear that rotates around a magnetic detection element while meshing with a first gear provided on a detected rotation shaft. A rotation angle detector provided is proposed. The male screw portion is screwed into a female screw portion provided on a partially cylindrical screw receiver that is in contact with the outer periphery of the second gear, and the second gear is urged by the screw receiver as it rotates and advances and retreats in the axial direction. The magnetized body provided inside the second gear forms a magnetic flux density that continuously changes in the axial direction of the second gear. The magnetic flux density detected by the magnetic detection element provided on the axis of the second gear continuously changes according to the rotation angle of the second gear. As a result, it is possible to calculate a rotation angle of more than 360 degrees from the difference between the phase angle of the two outputs output from the magnetic detection element and the intensity. For further explanation, see Patent Document 2 below.
JP 2005-3625 A JP 2007-256250 A

  Although the rotation angle detection device of Patent Document 1 described above can detect a rotation angle exceeding 360 degrees, two sets of a gear mechanism, a magnet, and a magnetic detection unit must be arranged around the detected rotation shaft. However, there are problems that the number of parts and the size of the apparatus increase and the manufacturing cost also increases.

  In the rotation angle detection device of Patent Document 2, the first gear and the screw receiver are screwed together to form a screw mechanism. In addition to the alignment of the first gear (drive gear) and the magnetic detection element, Skilled work is required for attaching the screw receiver to the first gear and the magnetic detection element with high accuracy. Further, although the screw receiver is fixed to the housing, there is a problem that the detection accuracy is lowered due to the variation in the dimensions of the mass-produced housing.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a rotation angle detection device capable of detecting more than 360 degrees with excellent detection accuracy while avoiding complicated manufacturing processes.

  A rotation angle detection device of the present invention that solves the above-described problems includes a detected rotation shaft that is rotatably supported by a housing, a driven gear that meshes with a drive gear fixed to the detected rotation shaft, and a permanent magnet. And a magnetic field forming portion that is fixed inside the driven gear and forms a magnetic field at the axial center position of the driven gear, a screw receiver that is supported by the housing and is screwed into the driven gear, and an axial center of the driven gear. A magnetic detection unit fixed to the housing, and a signal processing unit for processing an output signal of the magnetic detection unit to detect a rotation angle of the detected rotation shaft, and the driven gear is rotated by the drive gear. The signal processing unit is moved and moved forward and backward in the axial direction by being biased by the screw receiver, and the signal processing unit is arranged to change in the direction perpendicular to the magnetic field due to the rotation of the magnetic field forming unit. It applied to the rotation angle detector for detecting more than 360 degrees of rotation angle of the object to be detected rotation axis based on changes in magnetic field strength due to the axial advance and retreat of the driven gear.

  That is, in this rotation angle detection device, the driven gear, to which the magnetic field forming part with a built-in magnet is fixed, meshes with the drive gear of the detected rotation shaft and is screwed with the female thread surface of the screw receiver. Thus, when the detected rotation shaft rotates, the driven gear rotates and advances and retracts in the axial direction. The magnetic field forming unit forms a magnetic flux in a direction perpendicular to the predetermined axis on the axis of the driven gear, and the direction of the magnetic flux acting on the magnetic detection unit changes as the driven gear and the magnetic field forming unit rotate. The signal processing unit detects the rotation angle based on the change in the magnetic field direction. Further, as the driven gear advances and retreats in the axial direction, the magnetic field strength that the magnetic field forming unit applies to the magnetic detection unit continuously changes. Thereby, it is possible to determine the rotation of the detected rotation shaft exceeding 360 degrees.

  The above-described configuration is essentially the same as the device disclosed in Patent Document 2 described above.

  The rotation angle detection device of the present invention further includes a circuit board that is fixed to the housing and on which the signal processing unit is mounted, the magnetic detection unit is fixed to a support member supported by the circuit board, and a screw receiver is attached to the circuit board. It is characterized by being fixed. If it does in this way, the following problem in the rotation angle detector of patent documents 2 which this inventor recognized can be solved satisfactorily.

  That is, in the present invention, since the magnetic detection unit and the screw receiver can be aligned in advance through the circuit board without going through the housing, the circuit board is aligned with the first gear (drive gear). Accordingly, both the magnetic detection unit and the screw receiver can be aligned at a stroke with respect to the first gear. In addition, the position of the magnetic detection unit and the screw receiver does not shift due to the alignment of the magnetic detection unit and the first gear. In addition, it is easy to perform the work of fixing the magnetic detection unit and the screw receiver to the circuit board in advance, the assembly work can be facilitated, and the automation thereof is also easy. Further, since the screw receiver is positioned with respect to the magnetic detection unit without passing through the housing, it is not affected by the dimensional variation of the housing. As a result, the rotation angle detection device of the present invention can detect rotation angles with a high accuracy exceeding 360 degrees in spite of being able to reduce skilled work.

  In a preferred embodiment, the circuit board extends in a direction perpendicular to the axis of the driven gear. As a result, the assembly work is facilitated, and the detection accuracy can be improved.

  In a preferred embodiment, the screw receiver is formed of a partial cylindrical body having a female screw surface having an arc-shaped cross section perpendicular to the axis, and the male screw surface formed on the radially outer end surface of the tooth of the driven gear is a radially inner surface of the screw receiver. The circumferential center point of the screw receiver, the axis of the driven gear, and the axis of the drive gear are arranged in a straight line. Thereby, detection accuracy can be improved.

  In a preferred embodiment, the screw receiver has a fixing protrusion that is fitted into the support hole of the circuit board. Accordingly, the screw receiver can be fixed to the circuit board with high accuracy by an easy mounting operation.

  In a preferred aspect, the circuit board has a support protrusion standing on the circuit board, and the support protrusion is fitted into a support hole recessed in the screw receiver. Accordingly, the screw receiver can be fixed to the circuit board with high accuracy by an easy mounting operation.

  In a preferred embodiment, the detected rotation shaft is a vehicle steering shaft. As a result, it is possible to realize a vehicle steering angle detection device that is highly accurate and easy to manufacture.

  A preferred embodiment of a steering angle detection device using the rotation angle detection device of the present invention will be described below. However, the present invention is not limited to the following embodiments, and the technical idea of the present invention may be realized by combining other techniques.

(Embodiment 1)
(Basic structure)
The steering angle detection apparatus of Embodiment 1 is demonstrated with reference to FIG. FIG. 1 is a schematic cross-sectional view in the axial direction of the apparatus, and FIG. 2 is a plan view of the main part of the apparatus.

  This steering angle detection device is a device for detecting a rotation angle of a steering shaft (a detected rotation shaft), and a detected rotation shaft 2 that is rotatably supported by the housing 1 and a detected rotation shaft 2. Drive gear 3 fixed to drive gear 3, driven gear 4 meshing with drive gear 3, permanent magnet (magnetic field forming portion) 5 and yoke (magnetic field forming portion) 6 fixed to the inner peripheral surface of driven gear 4, and driven gear 4 A screw receiver 7 to be screwed, a magnetic detection element (magnetic detection unit) 8 disposed on the axis of the driven gear 4, and an output signal of the magnetic detection element 8 are processed to detect the rotation angle of the detected rotating shaft 2. The signal processing unit 9 is mounted on a substrate (a circuit board in the present invention) 10.

  The housing 1 includes a pedestal portion 11 and an upper lid portion 12 that is put on the pedestal portion 11 and fastened to the pedestal portion 11, and is manufactured by resin molding, aluminum die casting, or mild steel plate press molding. The upper lid portion 12 has a side frame over its entire circumference, and the front end surface of the side frame is in close contact with the upper surface of the pedestal portion 11 to form a sealed space inside. However, the base portion 11 and the upper lid portion 12 have holes 13 and 14 through which the detected rotation shaft 2 passes.

  The substrate 10 is a printed circuit board on which circuit elements such as a microcomputer constituting the signal processing unit 9 are mounted. The substrate 10 is fastened to a support protrusion 15 provided on the upper surface of the base portion 11. Of course, the support protrusion 15 is formed at a position where there is no problem in mounting the signal processing unit 9 and the like. M is the axis of the driven gear 4 and is arranged in parallel with the axis of the detected rotating shaft 2.

  The magnetic detection element 8 is fixed to the tip of a support projection 80 that is erected from the substrate 10 along the axis M of the driven gear 4. That is, the position of the magnetic detection element 8 with respect to the pedestal portion 11 is set by mounting the support protrusion (supporting member in the present invention) 80 to which the magnetic detection element 8 is fixed on the substrate 10. The pedestal 11 of the housing 1 is fixed to a vehicle body structure not shown. The position of the detected rotating shaft 2 with respect to the vehicle body structure that supports the detected rotating shaft 2 is set by a bearing structure (not shown) that rotatably supports the detected rotating shaft 2. Eventually, the substrate 10 is positioned with respect to the detected rotation shaft 2 through the pedestal portion 11 and the vehicle body structure that supports the base portion 11.

  Similarly, the lower end portion of the screw receiver 7 is also fixed to the substrate 10, and the screw receiver 7 is erected upward from the base portion 11. As a result, the screw receiver 7 is aligned with the magnetic detection element 8 through the substrate 10. The screw receiver 7 has a partial cylindrical shape in which a part of the cylinder is cut and removed in the axial direction, and an internal thread surface is formed on the inner peripheral surface thereof. As will be described later, this female thread surface is screwed into a male thread surface formed on the radially outer end surface of each tooth of the driven gear 4.

  The permanent magnet 5 is a ferrite magnet formed in a cylindrical shape, and is rotationally symmetrical around the axis M of the driven gear 4 and is fixed to the inner peripheral surface of the cylindrical yoke 6. The soft magnetic yoke 6 is fitted and fixed to the inner peripheral surface of the driven gear 4. As shown in FIG. 1, the inner peripheral surface of the permanent magnet 5 is a conical surface that continuously decreases in diameter as it is displaced in the axial direction. The permanent magnet 5 is magnetized in the left-right direction (that is, the X direction) in FIG. The yoke 6 forms a return magnetic path for the magnetic flux flowing between the pair of permanent magnets 5 and has a magnetic shielding function.

  Thereby, a DC magnetic flux that flows in a predetermined direction orthogonal to the axis M is formed in the space in the permanent magnet 5. The direction of the DC magnetic flux rotates with the rotation of the driven gear 4. The magnetic detection element 8 disposed on the axis M has two Hall elements that detect the magnetic flux density components that are orthogonal to each other and orthogonal to the axis M, respectively. Hereinafter, the detected magnetic flux density direction of the first Hall element is X, and the detected magnetic flux density direction of the second Hall element is Y. Therefore, the first Hall element detects the X direction component Bx of the magnetic flux density B formed on the axis M, and the second Hall element detects the Y direction component By of the magnetic flux density B formed on the axis M. Is detected. Further, the magnetic flux density B on the axis M is continuously decreased as the gap in the permanent magnet 5 continuously increases downward, and moves downward. The signal processing unit 9 fixed on the substrate 10 processes the signal voltages Vx and Vy that are proportional to the X-direction magnetic flux density component Bx and the Y-direction magnetic flux density component By input from the magnetic detection element 8 to detect rotation. The rotation angle of the shaft 2 is calculated. In FIG. 2, 41 is a tooth of the driven gear 4, and 31 is a tooth of the drive gear 3.

(Operation)
Next, the operation of this apparatus will be described below.

When the drive gear 3 rotates together with the rotation shaft 2 to be detected, the driven gear 4 that meshes with the drive gear 3 rotates, and the driven gear 4 is urged by the screw receiver 7 that engages with the driven gear 4 by the rotation of the driven gear 4. 5 and the yoke 6 move forward and backward in the axial direction (up and down). As a result, for example, when the permanent magnet 5 is displaced downward in FIG. 1, the magnetic flux density detected by the magnetic detection element 8 decreases, and the amplitudes of the signal voltages Vx and Vy input to the signal processing unit 9 decrease. Conversely, when the permanent magnet 5 is displaced upward in FIG. 1, the magnetic flux density detected by the magnetic detection element 8 increases, and the amplitudes of the signal voltages Vx and Vy input to the signal processing unit 9 increase. Therefore, when the rotation angle is θ with respect to the X direction of the permanent magnet 5 fixed on the axis M, the X direction magnetic flux density component Bx and the Y direction magnetic flux density component By are
Bx = f (θ) · cos θ
By = f (θ) · sinθ
It becomes. Note that f (θ) is a function value indicating a change in the vector length of the magnetic flux density B at the position of the magnetic detection element 8 due to the axial displacement of the permanent magnet 5. f (θ) is a value determined by the shape and material of the magnet and yoke. However, in this embodiment, the displacement increases monotonously when the shaft center M is displaced in one axial direction (in this embodiment, upward in FIG. 1), and decreases monotonically when the shaft center M is displaced toward one axial direction. Although set, it is not limited to this. The signal processing unit 9 stores the relationship between the function value f (θ) indicating the vector length of the magnetic flux density B and the number of rotations of the driven gear 4.

The signal processing unit 9 has a function of calculating an arctangent of the X direction magnetic flux density component Bx and the Y direction magnetic flux density component By input from the magnetic detection element 8. By this arc tangent calculation,
θ = arctan (By / Bx)
And the angle information within 360 degrees of the permanent magnet 5 can be obtained from the rotation angle θ of the magnetic detection element 8. Further, the signal processing unit 9 has a function of calculating the square root of the square sum of the X-direction magnetic flux density component Bx and the Y-direction magnetic flux density component By. By this calculation, the square root of the square value of Bx + By, that is, the vector length of the magnetic flux density B, is calculated as f (θ), and the function value f (θ) indicating the vector length of the magnetic flux density B is stored. From the above relationship, the number of rotations of the magnet rotation shaft is calculated.

  After all, in this embodiment, the rotation number θ of rotation from a predetermined axial reference position is calculated from the magnitude of f (θ), and the current rotation angle θ of the permanent magnet 5 is calculated from arctan (By / Bx). By calculating, a rotation angle θ ′ of 360 degrees or more is calculated from these. For example, if the current rotation is the second rotation and θ is 55 degrees, the final rotation angle θ ′ is calculated and output as 415 degrees. FIG. 3 shows the relationship between the rotation angle φ of the detected rotation shaft 2 and the rotation angle θ of the driven gear 4 and the X-direction magnetic flux density component Bx and the Y-direction magnetic flux density component By.

  The 360-degree super-rotation angle detection method of this embodiment described above is the same as that of Patent Document 2 described above.

(Fixing method of screw receiver 7)
Next, various forms for fixing the screw receiver 7 to the substrate 10 will be described with reference to the drawings. In each of the following drawings, cross-sectional hatching is omitted.

  FIG. 4 shows an embodiment in which the screw receiver 7 is fixed to the upper surface of the substrate 10 by adhesion. An unillustrated stopper member for restricting displacement of the substrate 10 in the plane parallel direction (hereinafter simply referred to as plane parallel direction) is fixed in advance on the substrate 10. Displacement to is prevented. Since the upper surface of the substrate 10 is disposed at a right angle to the axis M, the screw receiver 7 can be fixed to the substrate 10 with high accuracy.

  In FIG. 5, a through hole is provided in the substrate 10, and a screw hole is provided in the lower end surface of the screw receiver 7. The screw receiver 7 can be fixed to the substrate 10 with high accuracy by fastening the screw 20 to the screw hole of the screw receiver 7 from the lower surface side of the substrate 10. A rivet or a pin may be used instead of the screw. In the case of a pin, it is preferable to press-fit the pin into the substrate 10. In addition, when the pins are made of resin, it is also preferable to perform heat caulking. Note that it is preferable to provide the pins at a plurality of locations from the viewpoint of securing positioning accuracy.

  FIG. 6 shows a support protrusion 30 projecting downward from the lower end surface of a resin or aluminum screw receiver 7. The support protrusion 30 protrudes downward through the through hole of the substrate 10. The support protrusion 30 can be satisfactorily fixed to the substrate 10 by crushing, soldering, or bonding the tip of the support protrusion 30.

  In FIG. 7, the lower part 70 of the screw receiver 7 is formed in a cylindrical shape. Thereby, the rigidity of the screw receiver 7 can be improved. A screw surface may be provided on the peripheral surface of the lower portion 70 of the complete cylindrical screw receiver 7 and screwed with a screw member fixed to the circuit board side.

  In FIG. 8, the upper part 72 of the screw receiver 7 of FIG. 7 is also formed in a cylindrical shape. Thereby, the rigidity of the screw receiver 7 can be further improved.

  FIG. 9 is an example in which the inner peripheral surface of the lower portion 70 of the screw receiver 7 in FIG. 7 is modified so as not to interfere with the drive gear 3 and the driven gear 4.

  FIG. 10 shows a screw receiver 7 manufactured by a resin molded product in which a partially cylindrical metal plate member 75 is insert-molded. Thereby, the rigidity of the screw receiver 7 can be improved.

  FIG. 11 shows a cylindrical shape of the lower part of the metal plate member 75 to be insert-molded in the screw receiver 7 shown in FIG. Thereby, the rigidity of the screw receiver 7 can be improved. If the metal plate member 75 is made of a soft magnetic metal material, a magnetic shielding effect can be expected.

  FIG. 12 shows a screw receiver 7 manufactured by a resin molded product in which a partially cylindrical metal plate member 75 is insert-molded as in FIG. However, in this embodiment, a female screw surface is formed on the inner peripheral surface of the metal plate member exposed from the screw receiver 7.

  As a result, it can be seen that various known manufacturing techniques can be selected and used as the material used for the screw receiver 7, the manufacturing method, and the fixing method to the substrate 10. When the screw receiver 7 is fixed to the substrate 10, the alignment of the screw receiver 7 and the substrate 10 is inspected, and then a sub-assembly that has passed the inspection can be assembled to the housing. There is also an advantage that can be reduced.

(Example effect)
As described above, in this embodiment, since the driven gear 4 and the magnetic detection element 8 are fixed to the substrate 10, it is possible to achieve high detection accuracy even though the manufacturing work can be simplified. it can.

  Of course, the tooth shapes of the drive gear 3 and the driven gear 4 can be variously selected and employed other than those shown in the drawings.

FIG. 3 is a schematic axial sectional view showing the rotation angle detection device of the first embodiment. FIG. 2 is a schematic radial sectional view showing a driven gear, a drive gear, and a screw receiver of FIG. 1. It is a figure which shows the relationship between rotation angle (phi) and (theta), X direction magnetic flux density component Bx, and Y direction magnetic flux density component By. It is a typical axial direction sectional view showing the mode which adheres a screw receiver to a substrate. It is a typical axial direction sectional view showing a mode which fixes a screw receiver to a substrate with a pin etc. It is a schematic axial direction sectional view which shows the aspect which fixes a screw receiver to a board | substrate by press injection. It is a typical axial direction sectional view showing the mode where the lower end portion adopted the cylindrical screw support. (A) is a schematic cross-sectional view thereof, and (B) is a schematic vertical cross-sectional view thereof. It is a typical axial direction sectional view showing the mode which adopted a screw holder with a lower end part and an upper end part being cylindrical. (A) is a schematic cross-sectional view thereof, and (B) is a schematic vertical cross-sectional view thereof. It is a typical axial direction sectional view showing the mode where the inner peripheral surface of a lower end part adopted the unusual shape screw holder. (A) is a schematic cross-sectional view thereof, and (B) is a schematic vertical cross-sectional view thereof. It is a typical axial direction sectional view showing the mode which carried out insert molding of the metal plate member. (A) is a schematic cross-sectional view thereof, and (B) is a schematic vertical cross-sectional view thereof. It is a typical axial direction sectional view showing the mode which carried out insert molding of the ring-shaped metal plate member. (A) is a schematic cross-sectional view thereof, and (B) is a schematic vertical cross-sectional view thereof. It is a schematic axial direction sectional view which shows the aspect which insert-molded the ring-shaped metal plate member in which the internal thread surface was formed in the internal peripheral surface. (A) is a schematic cross-sectional view thereof, and (B) is a schematic vertical cross-sectional view thereof.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Detected rotating shaft 3 Drive gear 4 Driven gear 5 Permanent magnet 6 Yoke 7 Screw receiver 8 Magnetic detection element 9 Signal processing unit 10 Substrate (circuit board)
11 Base (housing)
12 Upper lid (housing)
13 hole 15 support protrusion 30 support protrusion 75 metal plate member 80 support protrusion

Claims (6)

A detected rotation shaft that is rotatably supported by a housing, a driven gear that meshes with a drive gear fixed to the detected rotation shaft, a permanent magnet, and a fixed gear shaft that is fixed inside the driven gear. A magnetic field forming unit that forms a magnetic field at a position; a screw receiver that is supported by the housing and screwed into the driven gear; a magnetic detection unit that is positioned on an axis of the driven gear and is fixed to the housing; and A signal processing unit that processes an output signal of the detection unit and detects a rotation angle of the detected rotation shaft;
The driven gear is rotated by the drive gear and is urged by the screw receiver to advance and retreat in the axial direction.
The signal processing unit sets a rotation angle of more than 360 degrees of the detected rotation shaft based on a change in the direction perpendicular to the magnetic field due to the rotation of the magnetic field forming unit and a change in the magnetic field strength due to the advance / retreat of the driven gear in the axial direction. In the rotation angle detection device to detect,
A circuit board that is fixed to the housing and on which the signal processing unit is mounted;
The magnetic detection unit is fixed to a support member supported by the circuit board,
The rotation angle detecting device, wherein the screw receiver is fixed to the circuit board. The rotation angle detection device according to claim 1,
The circuit board is a rotation angle detection device extending in a direction perpendicular to the axis of the driven gear. The rotation angle detection device according to claim 2,
The screw receiver is composed of a partial cylindrical body having a female thread surface with an arc-shaped cross section perpendicular to the axis,
The male thread surface formed on the radially outer end surface of the tooth of the driven gear is screwed to the female thread surface formed on the radially inner surface of the screw receiver,
A rotation angle detection device in which a circumferential center point of the screw bearing, an axis of the driven gear, and an axis of the drive gear are arranged in a straight line. In the rotation angle detection device according to claim 3,
The rotation angle detecting device, wherein the screw receiver has a fixing protrusion to be inserted into a support hole of the circuit board. In the rotation angle detection device according to claim 3,
Having a support protrusion standing on the circuit board;
The rotation angle detection device, wherein the support protrusion is inserted into a support hole recessed in the screw receiver. In the rotation angle detection device according to claim 1 or 2,
The detected rotation shaft is a rotation angle detection device including a steering shaft of a vehicle.

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