JP2007240177A - Rotation angle detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation angle detecting apparatus with improved detection accuracy. <P>SOLUTION: First and second detecting means are provided with first and second magnetic detecting elements 18, 20, arranged facing magnetic poles arranged on first and second targets 14, 16 and detect a change in the magnetic field of the magnetic poles by the first and second magnetic detecting elements 18, 20. At least two magnetic poles, arranged on the first target 14, are formed so that their magnetic pole widths are different from each other. One first magnetic detecting element 18 is made to face one magnetic pole from either of the magnetic poles having different magnetic pole widths, and the other first magnetic detecting element 18 is made to face the other magnetic pole out of the magnetic poles having different magnetic pole widths. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rotation angle detection device used for vehicle power steering and the like.

Conventionally, as a method for detecting a rotation angle, for example, a method as disclosed in Patent Document 1 is known. In FIG. 4, reference numeral 51 denotes a gear portion, which is fixedly attached to a rotation shaft (not shown) whose rotation angle is to be detected via an engagement spring 52. The gear portion 51 is meshed with a gear portion 55 having a code plate 54 having a plurality of magnetic poles 53 magnetized on its outer peripheral end face, and the magnetic poles provided on the code plate 54 according to the rotation of the rotating shaft to be detected. 53 moves. The rotation angle is detected by counting the number of the magnetic poles 53 by a magnetic detection element 56 provided to face the outer peripheral end face. In addition, by attaching the above mechanisms to two shafts connected via a torsion bar, when a torque acts between the two shafts and a twist between the shafts occurs, the rotation angle of each shaft , The amount of applied torque can also be detected.
JP-A-11-194007

  In the rotation angle detection device having the above configuration, the magnetic pole widths of the magnetic poles 53 magnetized on the code plate 54 are the same. Reducing the magnetic pole width improves the resolution (detection accuracy of the rotation angle) and increases the magnetic pole width. If so, the resolution will deteriorate.

  In general, when the relative rotation angle is detected, the same electrical angle is generated with respect to the mechanical angle only by reducing the magnetic pole width in order to improve the resolution. FIG. 5 is a characteristic waveform diagram of the triangular wave signal 57 showing the change in the electrical angle with respect to the mechanical angle. As shown in FIG. 5A, the triangular wave signal 57 in the high-resolution rotation angle detection device is every 15 degrees of mechanical angle. As shown in FIG. 5 (b), the triangular wave signal 57 in the low-resolution rotation angle detector generates the same electrical angle every 30 degrees. For example, when a magnetic field change is detected by a magnetic sensing element at a period of 10 msec, the shaft part is rotated at a high speed exceeding this period (the rotational speed of the shaft part is faster than the detection period of the magnetic sensing element). Then, the rotation angle (mechanical angle) may be skipped and detected, resulting in a detection error. In FIG. 5, FIG. 5A is easier to detect by skipping the rotation angle (mechanical angle) than FIG. 5B.

  In particular, in order to suppress vehicle battery consumption, for example, the rotation angle detection device is provided with a normal drive mode for reducing power consumption and a sleep drive mode (mode for reducing power consumption when the vehicle engine is stopped). In this case, if detection is performed at a cycle of 10 msec in the normal drive mode and detection is performed at a cycle of 50 msec in the sleep drive mode, the angle may be more easily detected in the sleep drive mode, which may cause a detection error.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and to provide a rotation angle detection device that suppresses detection by skipping an angle (mechanical angle) and improves detection accuracy.

  In order to achieve the above object, the present invention particularly provides a detecting means provided with a magnetic sensing element facing a magnetic pole disposed on a target, and detecting and detecting a magnetic field change of the magnetic pole by the magnetic sensing element. Two magnetic sensing elements are provided, and at least two magnetic poles arranged on the target have different magnetic pole widths. One of the magnetic sensing elements is opposed to one magnetic pole having a different magnetic pole width, and the other The magnetic sensing element is configured to face the other magnetic pole having a different magnetic pole width.

  With the above configuration, if one magnetic sensing element is opposed to one magnetic pole having a small magnetic pole width and the other magnetic sensing element is opposed to the other magnetic pole having a large magnetic pole width, the magnetic pole width is large when the detection cycle is slow. If a magnetic field change is detected by the other magnetic sensing element opposed to the other magnetic pole, it is possible to suppress detection by skipping the angle. In particular, if detection is performed without skipping the angle with the other magnetic pole having a larger magnetic pole width, and a detailed angle is detected with one magnetic pole with a smaller magnetic pole width, the rotation angle with improved accuracy can be detected without skipping the angle.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  1 is a cross-sectional view of a rotation angle detection device according to an embodiment of the present invention, FIG. 2 is an enlarged plan view of a portion A in FIG. 1, and FIG. 3 is a characteristic waveform of an electrical angle with respect to a mechanical angle when the rotating body rotates left and right. FIG.

  In FIG. 1, a rotation angle detection device according to an embodiment of the present invention includes a shaft portion 8 that is the same rigid body in which an input shaft 4 and an output shaft 6 are connected to both ends of a torsion bar 2, and an input of the shaft portion 8. The first rotating body 10 connected to the shaft 4, the second rotating body 12 connected to the output shaft 6 of the shaft portion 8, and the first and second rotating bodies 10, 12 detecting the rotation angle of the first rotating body 10. 1 and second detection means.

  The first rotating body 10 holds the first target 14 in which magnetic poles having different polarities are alternately arranged in the circumferential direction, and the second rotating body 12 is a second in which magnetic poles having different polarities are alternately arranged in the circumferential direction. The target 16 is held, and the first and second targets 14 and 16 are formed of multipolar ring magnets in which different magnetic poles are alternately arranged in the circumferential direction. Two first magnetic sensing elements 18 and a second magnetic sensing element 20 for detecting a change in the magnetic field are arranged at positions facing the magnetic poles arranged on the first target 14 and the second target 16. is doing. When the 1st rotary body 10 and the 2nd rotary body 12 rotate, the 1st target 14 and the 2nd target 16 will rotate in conjunction with this.

  As shown in FIG. 2, at least two magnetic poles arranged on the first target 14 have different magnetic pole widths (W1, W2), and one of the first magnets is stationary when the first rotating body 10 is stationary. The sensing element 18 is opposed to one magnetic pole having a different magnetic pole width (the magnetic pole having the magnetic pole width (W1)), and the other first magnetic sensing element 18 is disposed to the other magnetic pole having a different magnetic pole width (the magnetic pole width (W2)). It faces the magnetic pole). Further, a first magnetic pole group 30 in which a plurality of one magnetic poles are arranged adjacent to each other and a second magnetic pole group 32 in which a plurality of other magnetic poles are arranged adjacent to each other are provided, and the first target 14 is a first magnetic pole group. The region is divided into two regions, 30 regions and the second magnetic pole group 32 region.

  In the above configuration, the first and second detection means are means for detecting the magnetic field change of the magnetic poles disposed on the first and second targets 14 and 16 by the first and second magnetic sensing elements 18 and 20, respectively. . For example, when the first magnetic sensing element 18 detects a magnetic field change of the first target 14, the signal shown in FIG. 3 is detected. FIG. 3 is a characteristic waveform diagram showing a rotation angle (electrical angle) detected by the first magnetic sensing element due to a magnetic field change with respect to the rotation angle (mechanical angle) of the first rotating body. FIG. 3A is a characteristic waveform diagram showing the rotation angle (electrical angle) detected by one of the first magnetic sensing elements 18 when the first target 14 in FIG. 2 is rotated to the right, and FIG. These are characteristic waveform charts showing the rotation angle (electrical angle) detected by the other first magnetic sensing element 18. Points (a) to (i) in FIG. 3A are rotation angles (electrical angles) detected by the first magnetic sensing element 18 at points (a) to (i) in FIG. A single sine wave signal and cosine wave signal are detected for one magnetic pole arranged on the first target 14 (per one rotation (mechanical angle 360 degrees) of the first rotating body 10). As many sine wave signals and cosine wave signals as the number of magnetic poles are detected), as shown in FIG. 3A or FIG. ) Is detected. When the first target 14 is rotated counterclockwise, the characteristic waveform diagrams of FIGS. 3A and 3B are reversed. When this rotation angle detection device is used in a mechanism for detecting the rotation angle of a steering wheel for a vehicle, the rotation angle (mechanical angle) of the first target 14 is substantially the same as the rotation angle of the steering wheel (about two rotations left and right). FIG. 3 shows only the mechanical angle up to 180 °, but this is repeated up to 720 °.

  With the above configuration, one first magnetic sensing element 18 is opposed to one magnetic pole having a small magnetic pole width (a magnetic pole having a magnetic pole width (W1)), and the other first magnetic sensing element 18 is disposed to the other magnetic pole having the large magnetic pole width. Since it is opposed to the magnetic pole (the magnetic pole having the magnetic pole width (W2)), when the detection period of the first magnetic sensing element 18 is slow (when the shaft portion 8 rotates at a high speed), the other magnetic pole having the larger magnetic pole width is used. If a change in the magnetic field is detected by the other first magnetic sensing element 18 opposed to, it is possible to suppress detection by skipping the angle. In particular, if the rotation angle (mechanical angle) is first detected roughly without skipping the angle with the other magnetic pole having a large magnetic pole width, and the detailed rotation angle (mechanical angle) is detected with one magnetic pole having a small magnetic pole width, Even if the shaft portion 8 is rotated at a high speed, the rotation angle can be detected with improved resolution without skipping the angle. At this time, one first magnetic sensing element 18 and the other first magnetic sensing element 18 always compare the detected waveforms of the magnetic field changes with each other to determine a rough rotation angle (mechanical angle) and a detailed rotation angle. (Mechanical angle) is selected and detected. At any time, one of the first magnetic sensing elements 18 is opposed to a magnetic pole having a large magnetic pole width (magnetic pole width (W2)), and the other is opposed to a magnetic pole having a small magnetic pole width (magnetic pole width (W1)). Detection is possible because the characteristic waveform of the magnetic field change is different due to the difference in width.

  A first magnetic pole group 30 having a plurality of adjacent one magnetic poles and a second magnetic pole group 32 having a plurality of other magnetic poles arranged adjacent to each other are provided. Since the region and the second magnetic pole group 32 are separated into two regions, the triangular wave signal 34 having a short cycle and the triangular wave signal 34 having a long cycle can be continuously generated. When the rotation angle is up to about 180 degrees, it is possible to detect a rough rotation angle without skipping the angle by the triangular wave signal 34 having a long period, and to detect a detailed rotation angle with a high resolution by the triangular wave signal 34 having a short period.

  Furthermore, the torque can be calculated by detecting the difference in rotation angle between the first and second rotating bodies 10 and 12 and multiplying this by the torsion bar constant.

  In addition, if a comparison unit that constantly compares the amount of change in the rotation angle of each triangular wave signal 34 is provided for the two first magnetic sensing elements 18, when a foreign object such as a metal adheres to the first target 14, Since the amount of change changes, an abnormal state can be detected.

  In the embodiment of the present invention, the first and second rotating bodies 10 and 12 and the first and second targets 14 and 16 are separate bodies, and the first and second rotating bodies 10 and 12 are separated from each other. 12, the first and second targets 14 and 16 are held respectively. However, the first and second rotating bodies 10 and 12 and the first and second targets 14 and 16 are formed of the same material. May be. In this case, a magnetic disk may be arranged on the peripheral surface of a metal disk-shaped rotating body. Furthermore, instead of holding the first target 14 in the first rotating body 10, a third rotating body that rotates synchronously with the first rotating body 10 is provided via a gear, and the third rotating body is provided with a third rotating body. One target 14 may be held.

  The rotation angle detection device according to the present invention improves detection accuracy and can be used for power steering of various vehicles.

Sectional drawing of the rotation angle detection apparatus in one embodiment of this invention Enlarged plan view of part A in FIG. Characteristic waveform diagram of electrical angle with respect to mechanical angle when rotating body is rotated left and right Sectional view of a conventional rotation angle detector Characteristic waveform diagram of electrical angle with respect to mechanical angle during rotation of rotating body

Explanation of symbols

2 torsion bar 4 input shaft 6 output shaft 8 shaft portion 10 first rotating body 12 second rotating body 14 first target 16 second target 18 first magnetic sensing element 20 second magnetic sensing element 30 second 1 magnetic pole group 32 second magnetic pole group 34 triangular wave signal 51 gear part 52 engaging spring 53 magnetic pole 54 code plate 55 gear part 56 magnetic detection element 57 triangular wave signal

Claims (5)

A shaft portion, a target that rotates in conjunction with the rotation of the shaft portion, and alternately arranges magnetic poles having different polarities in the rotation direction, and a detection means that detects a rotation angle of the target, and the detection means includes: A magnetic sensing element is provided opposite to the magnetic pole disposed on the target, and means for detecting and detecting a magnetic field change of the magnetic pole by the magnetic sensing element, and two magnetic sensing elements are provided and at least disposed on the target The two magnetic poles have different magnetic pole widths, one of the magnetic sensing elements is opposed to one magnetic pole having a different magnetic pole width, and the other magnetic sensing element is opposed to the other magnetic pole having a different magnetic pole width. Rotation angle detector. The rotation angle detecting device according to claim 1, wherein a first magnetic pole group in which a plurality of one magnetic poles are arranged adjacent to each other and a second magnetic pole group in which a plurality of other magnetic poles are arranged adjacent to each other are provided. The rotation angle detection device according to claim 3, wherein the target is separated into two regions, a region of the first magnetic pole group and a region of the second magnetic pole group. The rotation angle detection device according to claim 1, wherein the target is a multipolar ring magnet in which magnetic poles having different polarities are alternately arranged on an outer peripheral surface. 2. The shaft portion is provided with a torsion bar, and the shaft portion is provided with two rotating bodies so as to sandwich the torsion bar, and has a detection mechanism for detecting torque from a difference in rotation angle between the two rotating bodies. The rotation angle detection device described.

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