JPH10318784A - Revolution sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect rotation accurately where the middle point output of a magnetic sensor cannot deviate by using a bias magnet where an angle is set so that a magnetization direction axis is directed toward the rotary center of a rotary magnetic body. SOLUTION: A rotation detection device used, for example, for an ignition timing control system is constituted of a rotary magnetic body 3, a bias magnet 1, and magnetic sensors 2a and 2b. A tooth mark 4 is formed at a constant interval at the rotation magnetic body 3 that is a ferromagnetic body and rotates around a rotary center O. The bias magnet 1 is arranged so that a position that is shifted by a desired distance L while orthogonally crossing an extension line K in a diameter direction from the rotary center O becomes a longer side center line M and its magnetization direction axis H is set to an angle that orthogonally crosses the rotary axis of the rotary magnetic body 3. The magnetic sensors 2a and 2b such as Hall elements are arranged at symmetrical positions for the longer side central axis M of the bias magnet 1. Since the magnetization direction axis H is directed toward the center of the rotary magnetic body 3, the deviation of the center output of the magnetic sensors 2a and 2b can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation detecting device which can be used for detecting a rotational speed of an ignition timing control system or the like.

[0002]

2. Description of the Related Art FIG. 3 is a view showing a conventional rotation detecting device. In the drawing, 1 is a bias magnet, 2a and 2b are magnetic sensors, 3 is a rotating magnetic body, and 4 is a fixed space around the outer periphery of the rotating magnetic body 3. And the bias magnet 1
Is perpendicular to the rotation axis of the rotating magnetic body 3.
The magnetic sensors 2a and 2b have a bias magnet 1 in a magnetic path formed by the rotating magnetic body 3 and the bias magnet 1.
Are arranged symmetrically with respect to the center axis of the long side, and the rotating magnetic body 3 is configured to rotate around the magnetic body center point O as an axis.

In the above-described configuration, the rotation of the rotating magnetic body 3 in the magnetic path including the magnetic sensors 2a and 2b causes a change in the magnetic path formed by the bias magnet 1, and changes in the magnetic field applied to the magnetic sensors 2a and 2b. And an output is obtained at the midpoint of the magnetic sensors 2a and 2b.

[0004]

However, in the above-mentioned conventional configuration, since the magnetization direction axis of the bias magnet 1 is not directed to the center of the rotating magnetic body 3, the magnetic sensors 2a and 2b are not provided.
The magnetic field applied to the magnetic field becomes unstable, and the midpoint output of the magnetic sensors 2a and 2b is largely shifted.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and can suppress the deviation of the output of the midpoint of the magnetic sensor. The bias magnet and the magnetic sensor extend from the center of the rotating magnetic body in the radial direction. It is an object of the present invention to provide a highly accurate rotation detection device even if it is not located on a line.

[0006]

In order to achieve this object, a rotation detecting device according to the present invention comprises a rotating magnetic body having teeth formed at regular intervals on an outer periphery, and extending radially from a rotation center of the rotating magnetic body. It comprises a bias magnet provided at a position shifted by a desired distance in a direction perpendicular to the extension line, and a pair of magnetic sensors provided between the rotating magnetic body and the bias magnet.

In this configuration, when the magnetization direction axis of the bias magnet is set to a certain angle θ at which the rotation magnetic body is directed to the center of rotation, it is possible to suppress the deviation of the output of the magnetic sensor at the midpoint.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a rotating magnetic body 3 is made of a ferromagnetic material and has a predetermined number n of tooth profiles 4 formed at regular intervals on the outer periphery, and rotates about O in the direction of the arrow shown in the figure. At a position shifted by a desired distance L on a line perpendicular to an extension line K extending in the radial direction from the rotation center O of the rotating magnetic body 3, a rectangular bias magnet 1 is formed so as to have a long side center line M.
Is disposed, and the magnetization direction axis H of the rotating magnetic body 3
Is perpendicular to the rotation axis at a certain angle θ. On the bias magnet 1, magnetic sensors 2a and 2b including a Hall element or a magnetoresistive element are provided at symmetric positions. The two magnetic sensors 2a and 2b have the same sensitivity characteristic to the magnetic flux, and are located symmetrically with respect to the long side center axis M of the bias magnet 1.

In the rotation detecting device having the above structure, when the tooth profile 4 passes near the bias magnet 1 with the rotation of the rotating magnetic body 3, the magnetic field distribution between the bias magnet 1 and the rotating magnetic body 3 changes, and the magnetic sensor 2a , 2b changes, and a midpoint output of the magnetic sensors 2a, 2b is obtained.

The midpoint output is shown in FIGS. 2 and 4, wherein FIG. 2 shows the present invention and FIG. As can be seen, when the magnetization direction axis of the bias magnet 1 is not directed to the center of the rotating magnetic body 3, the midpoint output of the magnetic sensors 2a and 2b is:
It is significantly different from a certain standard. On the other hand, according to the present invention, by setting a certain angle θ so that the magnetization direction axis of the bias magnet 1 is directed to the center of the rotating magnetic body 3, the midpoint output of the magnetic sensors 2a and 2b as shown in FIG. Is suppressed to about 1/2.

[0011]

As described above, according to the present invention, the deviation of the output of the magnetic sensor at the midpoint can be suppressed, and the bias magnet and the magnetic sensor can be extended from the center of the rotating magnetic body in the radial direction. Even if provided at a desired distance on the right and left sides on an orthogonal line, highly accurate rotation detection is possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a rotation detection device according to an embodiment of the present invention.

FIG. 2 is a graph showing the effect of the present invention.

FIG. 3 is a configuration diagram of a conventional rotation detection device.

FIG. 4 is a graph showing a conventional effect.

[Explanation of symbols]

 Reference Signs List 1 bias magnet 2a, 2b magnetic sensor 3 rotating magnetic body

Claims (1)

[Claims] 1. A rotating magnetic body having teeth formed at regular intervals on an outer periphery thereof, and a desired distance shifted in a direction perpendicular to an extended line extending in a radial direction from a rotation center of the rotating magnetic body, and further, the magnetization direction axis is set to the above-mentioned direction. A rotation detecting device comprising: a bias magnet having an angle so as to be a rotation center of the rotating magnetic body; and a pair of magnetic sensors provided between the rotating magnetic body and the bias magnet.