JP2503481B2 - Rotation detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention uses a magnetoresistive element (MR element) composed of a ferromagnetic material as a detection element, and sets a cycle corresponding to the rotation speed of a rotating body. The present invention relates to a rotation detecting device for generating a pulsed signal.

[Prior Art] It is known that a rotation detection device that detects the rotation speed of a rotating body, the rotation angle position, and the like is effectively configured using MR elements. A rotation detection device using such an MR element is configured in combination with, for example, a multi-pole magnet. That is, a large number of magnetic poles are formed on the outer peripheral portion of the rotating body at predetermined intervals, and such a multi-pole magnet is rotated in synchronization with the measured rotating body. Then, the MR element is fixedly set so as to be close to the outer peripheral portion of the rotating body on which the magnetic pole is formed.

That is, in such a device, the resistance value of the detection element changes each time the rotation element rotates and one of the magnetic poles formed on the rotation element passes near the MR detection element. It changes and one electric detection signal is obtained every time one magnetic pole passes.

However, in the detection device configured in this way,
Magnetization must be performed so that a large number of magnetic poles are formed on the outer peripheral portion of the rotating body with high accuracy, which inevitably increases the cost.

In consideration of such a point, a rotation detecting device as shown in FIG. 6, for example, has been considered. That is, in this device, the rotating body 21 is configured to rotate synchronously with the object to be measured, and the magnetic gear having the plurality of teeth 221, 222, ... This rotating body 21
The MR detecting element 23 is fixedly set by setting a small interval on the outer peripheral portion of the. Here, the MR detection element 23 is a permanent magnet.
A magnetic resistance element 232 made of a thin-film ferromagnetic material is set so that a magnetic field from 231 is vertically applied, and the surface of the magnetic resistance element 232 is the rotating body 21. The teeth 221, 222, ... Are faced in parallel with each other.

In such a rotation detecting device, the resistance value of the magnetoresistive element 232 is changed every time one of the teeth 221, 222, ... The state of the rate of change of the resistance value is
Corresponding to the rotation of 21, it changes as shown in FIG. However, in such a structure, as shown in FIG. 7, the resistance value does not continuously change, and a discontinuity occurs. That is, the detected output is distorted, and the rotation detection characteristic becomes unstable.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and it becomes possible to continuously obtain a resistance value change corresponding to each tooth formed on a rotating body, and to stabilize the stability. An object of the present invention is to provide a rotation detecting device using an MR element that can obtain the above rotation detection output.

[Means for Solving the Problems] That is, the rotation detecting device according to the present invention constitutes a rotating body in the form of a gear made of a magnetic body, and the surface is The MR detecting element including a magnetoresistive element made of a ferromagnetic material that is perpendicular to the magnetic field is fixedly set. The plane extending parallel to the axis of each tooth of the body is set to be inclined in the direction in which the rotation axis extends, and this inclination angle is set to, for example, 1 ° to 33 °.

[Operation] In the rotation detecting device configured as described above, when the teeth of the rotating body come close to the MR detection element as the rotating body rotates, the direction corresponding to the rotation direction of the tooth The magnetic field comes into play. Therefore, the teeth are magnetized corresponding to the magnetic field direction. Further, when the tooth reaches the position facing the MR detecting element, the tooth and the surface of the magnetoresistive element of the detecting element are inclined, so that the second direction perpendicular to the first direction is obtained. A magnetic field acts on the teeth, and the teeth are magnetized in a constant direction corresponding to the direction of the magnetic field. In other words, each tooth is magnetized in a rotating state every time it passes near the detection element, the resistance value of the magnetoresistive element is changed continuously, and the rotation detection signal with high stability is obtained. Will be obtained.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration, and is a rotating body which is rotated in synchronization with a rotating body to be measured, which is not shown in the figure.
11, the rotating body is made of a magnetic material and is composed of a gear having a plurality of teeth 121, 122, ... Then, the MR detection element 13 is fixedly set so as to face the outer peripheral portion of the rotating body 11 at a small interval.

Here, the detection element 13 is configured by setting a thin film magnetoresistive element 132 made of a ferromagnetic material on the surface of the insulating substrate 131 facing the rotating body. A permanent magnet 133 is attached and set on the surface opposite to the magnetic resistance element 132 so that a bias magnetic field perpendicular to the surface of the magnetic resistance element 132 is applied.

As described above, the MR detection element 13 that is fixedly set in relation to the rotating body 11 includes the teeth 121, 1 formed on the rotating body 11.
When the detecting element 13 is in a state of facing one of the teeth 121, it is not set so as to face the teeth 22 in parallel with the rotor 121. The surface of the magnetoresistive element 132 is set to be inclined with respect to the surface extending in the first direction by an angle θ.

As described above, when the teeth of the rotating body 11 and the detection surface of the detection element 13 do not face each other in parallel but are made to face each other in an inclined state, a state in which the teeth pass near the detection element 13 Then, the resistance value of the magnetoresistive element 132 is continuously changed, and the resistance value is continuously changed corresponding to the rotation of the rotating body 11 as shown in FIG. Therefore, a stable rotation detection signal is output from the detection element 13.

Here, as the rotor 11 rotates, one of its teeth, for example,
Considering the state when the 121 passes close to the detection element 13, the following is obtained.

First, in the state before the tooth 121 reaches the position of the detecting element 13, as shown in FIG. 3A, a magnetic field is applied to the tooth 121 in the lateral direction (first direction perpendicular to the axis). To work. Therefore, in such a state, each magnetic domain set in the tooth 121 is magnetized corresponding to the first direction as indicated by an arrow in the figure. And the rotating body
When 11 rotates to face the detecting element 13, the sixth
When configured as shown in the figure, the magnetic field acts perpendicularly, so that the magnetic field has a zero component in the first direction and in the second direction parallel to the axis. Therefore, the magnetization state of each magnetic domain is random as shown in FIG. 3B, but there is still a portion magnetized in the first direction. However, since the magnetic field is not actually present, the magnetization state is unstable. For example, as shown in FIG. 3C, the magnetization direction suddenly turns to the opposite direction. However, due to this sudden change in the magnetization direction, the detection signal contains noise. That is, as shown in FIG. 7, a discontinuity 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 between the tooth 121 and the magnetoresistive element 132 becomes different at both ends in the second direction.
A difference occurs in the magnetic field strength acting on the tooth 121. For example, in the figure, the magnetic field strength in the upper part is weak and the magnetic field strength in the lower part is strong. Therefore, as a result, a bias magnetic field in the second direction is generated as shown in FIG.
121 becomes magnetized as shown by the arrow in this figure. In this case, the magnetic field rotates on the surface of the magnetoresistive element 132, and the discontinuity of magnetization disappears.
The resistance change without noise as shown in FIG. 2 can be obtained.

Here, the relationship between the magnetic field strength of the magnetoresistive element 132 and the rate of resistance change is as shown in FIG. That is, the second
When the magnetic field strength in the direction of is changed, O → S
->D->S-> O route will be resumed. On the other hand, when the magnetic field strength is changed in the first direction, O → R
It goes through the route of → E → R → A and returns only to the point A when the magnetic field strength becomes zero, resulting in a loss in the O−A portion. However, in the state where the magnetic field is applied in the second direction, it changes on S-D all at once and the resistance change changes between C-B, so that a large output is obtained. become.

FIG. 5 shows the relationship between the set inclination angle θ of the detection element 13 and the resistance value change rate. When the inclination angle θ is smaller than 1 °, the resistance value change rate sharply decreases,
Distortion due to noise is also likely to occur. The above θ is 33
If it becomes larger than 0 °, the rate of change of the resistance value sharply decreases in this case as well, and it is also susceptible to the influence of the nozzle. Therefore, the inclination angle θ is preferably 1 ° to 33 °.

In the above-described embodiment, the MR detection element 13 is set to be tilted, but this is formed by tilting the surfaces of the teeth 121, 122, ... Formed on the rotating body 11 with respect to the axis of the rotating body 11. Also, the same effect as described above can be obtained.

As described above, according to the rotation detecting device of the present invention,
By using a magnetoresistive element, it becomes possible to easily configure a rotation detection device in a state where, for example, a gear that is normally used is used as it is, and detection of stable characteristics without noise is possible. The signal can be obtained. That is, the rotation detection device having stable detection characteristics and high reliability is provided.

[Brief description of drawings]

FIG. 1 shows a rotation detecting device according to an embodiment of the present invention. (A) is a front view of the configuration, (B) is a top view of the configuration, and FIG. 2 is a view of the detection device. The figure which shows the state of the resistance value change rate of a magnetoresistive element, FIG. 3 (A)-
(D) is a diagram for explaining the state of magnetization change in relation to the conventional example, FIG. 4 is a diagram for explaining the relationship between magnetic field strength and resistance change rate, and FIG. 5 is a tilt angle and resistance change in the above device. FIG. 6 is a diagram showing the relationship with the rate, FIG. 6 is a diagram for explaining a conventional proximity sensor, and FIG. 7 is a diagram showing the rate of change in resistance value. 11 ... Rotator, 121,122, ... Tooth, 13 ... MR detector,
131 ... Insulating substrate, 132 ... Magnetoresistive element, 133 ... Permanent magnet.

Claims (2)

(57) [Claims] 1. A magnetic body having a plurality of teeth, which are adapted to be rotated synchronously with a measured body whose rotation is to be detected and whose axis extends in a direction coinciding with a rotation axis. And a ferromagnet magnetoresistive element fixedly set on the outer peripheral portion of the rotor and set to face the teeth at small intervals, and the magnetoresistive element. An MR detection element configured to include a means for applying a bias magnetic field perpendicular to the surface of the element, a surface of the magnetoresistive element of the detection element, and a surface extending parallel to the axis of each tooth of the rotating body. However, the rotation detection device is set so as to be tilted in the extending direction of the rotation axis. 2. The inclination angle between the surface of the magnetoresistive element and the surface of the tooth is 1 ° to the direction in which the rotating shaft extends.
The rotation detecting device according to claim 1, wherein the rotation detecting device is set at 33 °.