JP2004125679A - Rotation angle sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation angle sensor with enhanced detection accuracy even if a single hall element or the like is used, and to provide its manufacturing method. <P>SOLUTION: This method is for manufacturing the rotation angle sensor 1 equipped with a ring magnet 3 for forming a magnetic field and the hall element (magnetic flux density detection part) 7 relatively rotating in this magnetic field. Magnetizing energy given to the ring magnet 3 is circumferentially varied so that a waveform outputted from the hall element 7 due to the relative rotation of the ring magnet 3 makes substantially a triangular wave. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in a rotation angle sensor and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, as this kind of rotation angle sensor, a ring-shaped magnet is fixed to one end of a shaft, and a plurality of Hall elements are provided inside or outside the magnet, and as the Hall elements rotate relative to each other, Some devices output a voltage corresponding to a changing magnetic flux density as a signal (see Patent Documents 1 and 2).
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 11-356024 [Patent Document 2]
Japanese Patent Application No. 2001-352683 [0004]
[Problems to be solved by the invention]
In such a conventional rotation angle sensor, since a ring-shaped magnet magnetized in parallel in the radial direction is used, the ring-shaped magnet attached to a rotating body such as a shaft rotates with rotation. The output waveform becomes a sine waveform, and the rotation angle can be detected by measuring this waveform.
[0005]
However, when detecting the rotation angle, since the output waveform has a sine wave shape, the change in output with respect to the rotation angle is small at the peak portion, and this may cause an error in angle detection. Therefore, in order to eliminate this error factor, when two Hall elements are arranged on the rotation center line, there is a method of selecting the output of each Hall element having the larger output gradient. In this case, as shown in FIG. 3, the outputs A and B of the first and second Hall elements are sine waves whose phases are different by 90 degrees. As a signal for detecting the rotation angle, one of the outputs A and B of the first and second Hall elements, which has a larger voltage change with respect to the rotation angle, is used.
[0006]
However, when a plurality of Hall elements are used as described above, there is a problem that a detection error increases due to a variation in a positional relationship between the Hall elements.
[0007]
The present invention has been made in view of the above problems, and has as its object to provide a rotation angle sensor capable of improving detection accuracy even by using a single Hall element or the like, and a method of manufacturing the same.
[0008]
[Means for Solving the Problems]
The first invention is applied to a method of manufacturing a rotation angle sensor including an annular ring magnet that generates a magnetic field and a magnetic flux density detection unit that relatively rotates in the magnetic field.
[0009]
Then, the magnetizing energy applied to the ring magnet is changed in the circumferential direction so that the waveform output from the magnetic flux density detection unit becomes substantially a triangular wave with the relative rotation of the ring magnet. did.
[0010]
The second invention is applied to a rotation angle sensor including an annular ring magnet that generates a magnetic field and a magnetic flux density detection unit that relatively rotates in the magnetic field.
[0011]
Then, the magnetization density of the ring magnet is formed differently in the circumferential direction so that the waveform output from the magnetic flux density detection unit becomes substantially triangular with the relative rotation of the ring magnet. did.
[0012]
Function and Effect of the Invention
According to the first and second aspects of the present invention, the output waveform of the magnetic flux density detecting section is substantially a triangular wave, thereby preventing the output of the magnetic flux density detecting section from having a small output change at the peak portion unlike the conventional apparatus. A substantially constant output change can be obtained in any region. For this reason, even if a single magnetic flux density detection unit is provided, the detection error can be reduced by increasing the sensor output resolution. Also, in the case where a plurality of magnetic flux density detection units are provided, the detection error does not need to be large even if the positional relationship among them varies.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0014]
As shown in FIG. 1A, the rotation angle sensor 1 is mainly composed of a ring magnet 3 made of a permanent magnet fixed to a shaft 2 and a single Hall element 7 provided as a magnetic flux density detecting unit. You.
[0015]
The Hall element 7 outputs a voltage corresponding to the magnetic flux density that changes as the ring magnet 3 relatively rotates, as a signal.
[0016]
The Hall element 7 is arranged outside the rotation path of the ring magnet 3 and is fixed to the case 4.
[0017]
As a gist of the present invention, the ring magnet 3 is rotated such that the waveform output from the Hall element 7 as the ring magnet 3 relatively rotates becomes a substantially triangular wave as shown in FIG. The configuration is such that the magnetizing energy given to No. 3 is changed in the circumferential direction.
[0018]
The ring magnet 3 is radially magnetized by a magnetizing yoke (not shown) and changes its magnetizing energy in the circumferential direction. That is, the magnetizing density is not uniform, but changes in the circumferential direction to change the magnetic field into a ring. The magnets 3 are distributed symmetrically about a rotation center line orthogonal to the rotation center axis.
[0019]
In this way, by magnetizing the output waveform of the Hall element 7 so as to be a substantially triangular wave, the output of the Hall element 7 can be prevented from having a small output change at the peak portion unlike the conventional device. However, a substantially constant output change can be obtained, and the detection error can be reduced by increasing the sensor output resolution.
[0020]
Further, by arranging the Hall element 7 outside the rotation path of the ring magnet 3, the degree of freedom of arrangement of the rotation angle sensor 1 can be increased. That is, when the Hall element is arranged inside the rotation path of the sensor magnet, the rotation angle sensor 1 can be arranged only at the end of the rotor shaft 2, but the Hall element is arranged outside the rotation path of the sensor magnet. Thereby, the rotation angle sensor 1 can be arranged in the middle of the shaft 2.
[0021]
By the way, if it is intended to detect the rotation direction, it is necessary to further add a Hall element. This can solve the problem that the detection error increases due to the variation in the positional relationship between the Hall elements and the like. Therefore, as another embodiment, as shown in FIG. 2A, first and second Hall elements 7 and 8 may be provided. The first and second Hall elements 7, 8 are arranged on a rotation center line that intersects at a predetermined angle.
[0022]
The first and second Hall elements 7 and 8 are arranged outside the rotation path of the ring magnet 3 and fixed to the case 4.
[0023]
The magnetizing energy applied to the ring magnet 3 is changed in the circumferential direction so that the output waveforms from the first and second Hall elements 7 and 8 become substantially triangular waves as the ring magnet 3 relatively rotates. Configuration. FIG. 2B shows how the voltages output from the first and second Hall elements 7 and 8 change according to the rotation angle. The outputs A and B of the first and second Hall elements 7 and 8 are substantially triangular waves whose phases differ by a predetermined angle.
[0024]
As described above, since the output waveforms of the first and second Hall elements 7 and 8 become substantially triangular waves, the outputs A and B of the first and second Hall elements 7 and 8 are different from those of the conventional apparatus in the peak portion. A small output change is eliminated, a substantially constant output change is obtained in any region, and a detection error can be reduced.
[0025]
One of the outputs A and B of the first and second Hall elements 7 and 8 is used as a signal for detecting a rotation angle, and the other is used as a signal for determining a rotation angle area. For example, while the second Hall element 8 makes one rotation, the same output can be obtained at, for example, two points by the output B. However, the rotation angle is specified by monitoring the output A.
[0026]
Since the output waveforms of the first and second Hall elements 7 and 8 are substantially triangular waves, even if the positional relationship between the first and second Hall elements 7 and 8 varies, a detection error does not increase.
[0027]
It is apparent that the present invention is not limited to the above-described embodiment, and that various changes can be made within the scope of the technical idea.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the present invention, in which (a) is a configuration diagram of a rotation angle sensor, and (b) is a diagram showing output characteristics of the rotation angle sensor.
FIG. 2 shows another embodiment, in which (a) is a configuration diagram of a rotation angle sensor, and (b) is a diagram showing output characteristics of the rotation angle sensor.
FIG. 3 is a diagram showing output characteristics of a rotation angle sensor showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotation angle sensor 2 Shaft 3 Ring magnet 4 Cases 7 and 8 First and second Hall elements (magnetic flux density detector)

Claims (2)

In a method of manufacturing a rotation angle sensor including an annular ring magnet that creates a magnetic field and a magnetic flux density detecting unit that relatively rotates in the magnetic field, the magnetic flux density is output from the magnetic flux density detecting unit as the ring magnet relatively rotates. A method of manufacturing a rotation angle sensor, comprising changing magnetization energy applied to a ring magnet in a circumferential direction so that a waveform becomes a substantially triangular wave. In a rotation angle sensor including an annular ring magnet that creates a magnetic field and a magnetic flux density detection unit that relatively rotates in the magnetic field, the waveform output from the magnetic flux density detection unit as the ring magnet relatively rotates is approximately 2. The rotation angle sensor according to claim 1, wherein the ring magnets are formed so that the magnetization densities of the ring magnets are different in the circumferential direction so as to form a triangular wave.

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