JPS63205515A - Rotation detector - Google Patents

Abstract

PURPOSE:To obtain a stable rotation detection signal by slanting the surface of the magneto-resistance element of a detecting element to the axial direction of the teeth of a rotary body. CONSTITUTION:When teeth 121, 122,... of the rotary body 11 come close to a magneto-resistance element 132 through the rotation of the rotary body 11, a magnetic field operates on the teeth, which are magnetized. Then, when the teeth come to face the element 132, the teeth are magnetized in a constant direction corresponding to the direction of the magnetic field because the teeth 121, 122,... and the surface of the element 132 are at an angle theta. Namely, each tooth is magnetized in a rotating state every time it come close to and passes the element 132, and the resistance value of the element 132 varies continuously, so that the stable rotation detection signal is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention uses a magnetoresistive element (MR element) made of a ferromagnetic material as a detection element, and a period is set corresponding to the rotational speed of a rotating body. The present invention relates to a rotation detection device that generates a pulse-like signal.

[Prior Art] It is known that a rotation detection device that detects the rotational speed, rotational angular position, etc. of a rotating body can be effectively configured using an MR element. A rotation detection device using such an MR element is configured in combination with, for example, a multipolar magnet. That is, a large number of magnetic poles are formed at predetermined intervals on the outer periphery of the rotating body, and such a multipolar magnet is rotated synchronously with the rotating body to be measured. Then, the MR element is fixedly set so as to be close to the outer periphery of the rotating body on which the magnetic poles are formed.

In other words, in such a device, each time the rotating body rotates and one of the magnetic poles formed on the rotating body passes close to the MR detecting element, the resistance value of the detecting element increases. The magnetic field changes so that one electrical detection signal is obtained for each passage of one magnetic pole.

However, in a detection device configured in this way, it is necessary to perform magnetization to form a large number of magnetic poles on the outer periphery of the rotating body with high precision, which inevitably increases the cost. It is something.

Taking these points into consideration, a rotation detection device as shown in FIG. 6, for example, has been devised. That is, in this device, the rotating body 21, which is rotated synchronously with the object to be measured, is provided with a plurality of teeth 221, 222,
It has... It is composed of magnetic gears, and a small interval is set on the outer periphery of this rotating body 21, and the MR
The detection element 23 is fixedly set. Here M
The R detection element 23 is configured by setting a magnetoresistive element 232 made of a thin film-like ferromagnetic material so that the magnetic field from a permanent magnet 231 acts perpendicularly to the magnetoresistive element 232. The surface of each tooth 2 of the rotating body 21 is
211222, . . . in a parallel state.

In such a rotation detection device, as the rotating body 21 rotates, each time one of its teeth 221, 222, ... passes close to the detection element 23, the magnetic resistance element 23
The resistance value of 2 changes, and the state of the change rate of the resistance value changes as shown in FIG. 7 in response to the rotation of the rotating body 21. However, with such a configuration, as shown in FIG. 7, the resistance value does not change continuously and a discontinuous portion occurs.

In other words, distortion occurs in the detection output, and the rotation detection characteristics become unstable.

[Problems to be solved by the invention] This invention has been made in view of the above points, so that it is possible to obtain a continuous change in resistance value corresponding to each tooth formed on the rotating body, and to achieve a stable result. The present invention aims to provide a rotation detection device using an MR element capable of obtaining a rotation detection output.

[Means for Solving the Problems] That is, the rotation detecting device according to the present invention comprises a gear-shaped rotating body made of a magnetic material, and when the rotating body is close to the outer periphery of the rotating body, The MR detection element includes a magnetoresistive element made of a ferromagnetic material that is perpendicular to the direction of the rotation direction, and a magnetic field is applied thereto. It is set to be inclined with respect to the plane extending in the axial direction of the teeth of the body, and this inclination angle is, for example, 1°.
~33@.

[Function] In the rotation detection device configured as described above, when the teeth of the rotating body approach the MR detection element as the rotating body rotates, the teeth are moved in the direction corresponding to the rotation direction. A magnetic field comes into play. Therefore, the teeth become magnetized in accordance with the direction of the magnetic field. Furthermore, when the teeth reach a position facing the MR detection element, since the surfaces of the teeth and the magnetoresistive element of the detection element are inclined, the teeth move in a second direction perpendicular to the first direction. A magnetic field comes to act on the teeth, and the teeth become magnetized in a certain direction corresponding to the direction of the magnetic field. In other words, each tooth becomes magnetized in a rotating state each time it passes close to the detection element, and the resistance value of the magnetoresistive element changes continuously, producing a highly stable rotation detection signal. This will allow you to obtain

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows its configuration, in which a rotating body 11 is rotated synchronously with a rotating body to be measured, which is not shown in the figure.
This rotating body is made of magnetic material and has a plurality of teeth 121 on its outer periphery.

It is composed of gears having 122, . . . The MR detection element 13 is fixedly set so as to face the outer circumference of the rotating body 11 at a small interval.

Here, the detection element 18 is configured such that a thin film magnetoresistive element 132 made of a ferromagnetic material is set on a surface of an insulating substrate 131 facing the rotating body. The above magnetoresistive element 132 of
A permanent magnet 133 is installed on the opposite side of the
A bias magnetic field perpendicular to the surface of the magnetoresistive element 132 is applied.

The MR detection element 13, which is thus fixed in relation to the rotating body 11, is set to face each tooth 121, 122, . . . formed on the rotating body 11 in parallel. When this detection element 13 faces one of the teeth 121 instead of
The surface of the magnetoresistive element 132 is set to be inclined at an angle θ to a surface extending in a first direction parallel to the axis of the first rotating body.

In this way, if the teeth of the rotating body 11 and the detection surface of the detection element 13 are made to face each other in an inclined state instead of facing each other in parallel, a state in which the teeth pass close to the detection element 13 can be obtained. Then, the resistance value of the magnetoresistive element 132 changes continuously, and the resistance value changes continuously in response to the rotation of the rotating body 11, as shown in FIG. Therefore, the detection element 13 outputs a stable rotation detection signal.

Here, when one of the teeth of the rotating body 11, for example 121, passes close to the detection element 13 as the rotating body 11 rotates, the following situation will be considered.

First, before the tooth 121 reaches the position of the detection element 13, as shown in FIG. It comes to work. Therefore, in this condition, tooth 1
Each of the magnetic domains set in 21 is magnetized in the first direction as shown by the arrow in the figure. and,
When the rotating body 11 rotates and comes to face the detection element 13, in the case of the configuration shown in FIG. The component in the second direction parallel to the axis becomes zero. Therefore, although the magnetization state of each magnetic domain is random as shown in FIG. 3(B), there still remains a portion magnetized in the first direction. but,
Since there is no actual magnetic field, the state of magnetization is unstable, for example (C in Figure 3).
As shown in , the direction of magnetization suddenly turns to the opposite direction, and this sudden change in the direction of magnetization causes the detection signal to contain noise. That is, as shown in FIG. 7, a discontinuous portion occurs in the resistance value change.

However, if the angle θ is set between the tooth and the detection element 13 as shown in the embodiment, the distance from the magnetoresistive element 132 will be different at both ends of the tooth 121 in the second direction. A difference occurs in the strength of the magnetic field acting on 121. For example, in the diagram, the magnetic field strength is weaker at the top and stronger at the bottom. As a result, a bias magnetic field in the second direction is generated as shown in FIG. 3(D), and the tooth 121 is magnetized as shown by the arrow in this figure. In this case, the magnetic field rotates in the plane of the magnetoresistive element 132, and there are no discontinuities in magnetization, making it possible to obtain noise-free resistance changes as shown in Figure 2. It is something.

Here, the relationship between the magnetic field strength of the magnetoresistive element 132 and the rate of change in resistance is shown in FIG. 4. That is, the second
If you change the magnetic field strength in the direction of 0-5 in this figure,
It will return to its original state through the path 4D-4S→0. On the other hand, when the magnetic field strength is changed in the first direction, 0→
It passes through the path RE→R→A and returns only to point A when the magnetic field strength becomes zero, causing a loss in the O-A portion.

However, when a magnetic field is applied in the second direction, the resistance changes suddenly on S-D, and the resistance value changes between C-8, resulting in a large output. It becomes like this.

FIG. 5 shows the relationship between the tilt angle θ set for the detection element 13 and the rate of change in resistance value. When the tilt angle θ is smaller than 1 m, the rate of change in resistance value decreases rapidly.
Distortion due to noise is also likely to occur. Also, the above θ is 3
When the angle exceeds 3°, the rate of change in resistance value decreases rapidly in this case as well, making it susceptible to noise. Therefore, the above inclination angle θ is 1″ to 33
” is preferable.

In the above embodiment, the MR detection element 13 is set by tilting, but this is because the teeth 121.1 formed on the rotating body 11
Even if the surfaces of 22, .

[Effects of the Invention] As described above, according to the rotation detection device according to the present invention, the rotation detection device can be easily configured using a magnetoresistive element, for example, by using a commonly used gear as is. In addition, a detection signal with stable characteristics and no noise can be obtained. That is, a highly reliable rotation detection device with stable detection characteristics is provided.

[Brief explanation of the drawing]

FIG. 1 shows a rotation detection device according to an embodiment of the present invention, in which (A) is a block diagram seen from the front, (B) is a block diagram seen from a plane, and the first diagram shows the magnetic field in the detection device. Figures 3(A) to 3(A) are diagrams showing the state of the resistance value change rate of the resistive element.
D) is a diagram explaining the state of change in magnetization in relation to the conventional example, Figure 4 is a diagram explaining the relationship between magnetic field strength and resistance change rate, and Figure 5 is a diagram showing the tilt angle and resistance change rate in the above device. FIG. 6 is a diagram illustrating a conventional proximity sensor, and FIG. 7 is a diagram showing its resistance value change rate. 11...Rotating body, 121.122,...Teeth, 13
...MR detection element, 131... Insulating substrate, 132.
... Magnetoresistive element, 133... Permanent magnet. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 (B) Figure 6

Claims (2)

[Claims] (1) A gear-shaped rotating body that rotates synchronously with the object to be measured whose rotation is to be detected, has a plurality of teeth on its outer periphery, and is made of a magnetic material; The device includes a ferromagnetic magnetoresistive element fixedly set on the outer circumference of the body and opposed to the teeth at a small interval, and means for applying a bias magnetic field perpendicular to the surface of the magnetoresistive element. and an MR detection element, characterized in that a surface of the magnetoresistive element of the detection element and a surface extending in a direction parallel to the axis of the square tooth of the rotating body are set to be inclined. Rotation detection device. (2) The rotation detection device according to claim 1, wherein the angle of inclination of the surface of the magnetoresistive element with respect to the surface of the tooth is set to 1° to 33° with respect to the tangent.