JPH0834141B2 - Non-contact position sensor - Google Patents

Description

The present invention relates to a non-contact position sensor using a ferromagnetic magnetoresistive element (hereinafter referred to as "MR element").

[Conventional technology]

The magnetic circuit of a non-contact potentiometer is conventionally configured as a closed magnetic circuit with a cylindrical core with a bottom, a rotating magnetic body and a permanent magnet, and InSb, which is a magnetoresistive element, is placed in the gap formed at the tip of the rotating magnetic body. Then, an output is generated according to the rotation of the rotating magnetic body, and by changing the size of the gap formed at the tip portion of the rotating magnetic body, in other words, the tip of the rotating magnetic body is set to a predetermined function. By processing, a predetermined function output is obtained from the InSb magnetoresistive element as described above.

[Problems to be solved by the invention]

However, in the non-contact potentiometer shown in the above-mentioned prior art, it is very difficult to process the tip of the rotating magnetic body so as to have a predetermined function shape, and if the gap has a narrow portion and a wide portion, the magnetic flux becomes narrow. The magnetic flux density is concentrated on the part, and the uniformity of the magnetic flux density cannot be obtained. Therefore, the linearity of the output of InSb, which is a magnetoresistive element, varies,
The manufacturing yield of the non-contact potentiometer was very low.

In view of such a point, the present inventors have proposed Japanese Patent Application No. 61-72201.
As a magnetic field generating means for applying a magnetic field to the MR element as disclosed in No. 1, a non-contact position sensor using, for example, a fan-shaped permanent magnet magnetized so that its magnetic poles are oriented in the radial direction is disclosed. Proposed. In this case, although the output linearity is good and the manufacturing yield can be relatively high, there is a problem that it is not easy to magnetize the fan-shaped permanent magnet and it is difficult to magnetize it.

Therefore, the present invention was devised to improve the non-contact position sensor disclosed in the above-mentioned Japanese Patent Application No. 61-72201, in which the magnetic field generating means can be easily magnetized and the output linearity can be improved. An object is to provide a non-contact position sensor that can be improved.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention provides a movable portion rotatably provided, and an annular shape which is concentric with the movable portion and is arranged at a predetermined distance from the movable portion. And a magnetic field generating means having its magnetic pole oriented in the direction of the rotation axis of the movable part. The magnetic field from the magnetic field generating means is directed to a part of the ferromagnetic magnetoresistive element in the radial direction. The magnetic field generating means so that its central axis in the direction of the rotation axis passes over the ferromagnetic magnetoresistive element. A non-contact position sensor is used, which is characterized by being rotatable and movable.

[Action]

Therefore, according to the present invention, the magnetizing direction of the magnetic field generating means is only required to be in the direction parallel to the rotation axis of the movable part, which facilitates the magnetizing. Further, since the central axis of the magnetic field generating means in the direction of the rotation axis is rotatably movable so as to pass over the MR element, the MR element near the central axis has a plane formed by the MR element from the magnetic field generating means. It is possible to apply the magnetic field of only the vertical component without applying the magnetic field of the parallel component. Therefore, the resistance value of the MR element does not decrease in the vicinity of the central axis, and the difference in the resistance value from a part of the decrease in the resistance value of the MR element becomes large, and the linearity of the output is improved accordingly.

〔Example〕

The present invention will be described below with reference to the embodiments shown in the drawings.
FIG. 1 shows a first embodiment of the present invention, in which FIG. 1 (a) is a sectional view thereof, FIG. 1 (b) is a partial top view of FIG. 1 (a), and FIG. The sectional view on the AA line of b) is shown.
In the figure, a circular or polygonal (the former is the figure) MR film 2a, 2b made of a thin film of Ni-Fe, Ni-Co or the like having an opening is formed on an insulating substrate 1, and both terminals are formed. The electrode terminals 3, 4 and 5 are formed at the central portion and the central portion, respectively.

The power source terminal V _{cc is set} to the electrode terminal 3 of the MR elements 2a and 2b, the electrode terminal 4 is set to the ground GND, and the output V is output from the electrode terminal 5 at the midpoint.
_{Derive out} . A bearing 8 formed of a ball bearing of the housing 9 is provided at the center of the annular pattern formed by the MR elements 2a and 2b. The bearing 8 has a movable part 6
Is rotatably supported around a rotary shaft 6a. A prismatic permanent magnet 7 magnetized along the direction of the rotation axis 6a is used as a magnetic field generating means in the movable portion 6, and its central axis c in the direction of the rotation axis is on the pattern of the annular MR elements 2a, 2b. It is attached to the movable portion 6 so as to rotate and move therethrough. In addition, 10 is a substrate on which the insulating substrate 1 is mounted, 11 is a wire harness, and 12 is a lid of the housing 9.

Then, for example, when the permanent magnet 7 is arranged with respect to the MR elements 2a and 2b as shown in the figure, the magnetic field from the permanent magnet 7 is
With respect to the MR element 2a mainly arranged on the opposite side to the rotating shaft 6a, a direction parallel to the plane formed by the annular patterns of the MR elements 2a and 2b and orthogonal to the direction of current flow, that is, the present invention. A magnetic field H ₂ directed in the radial direction is applied, and with respect to the MR element 2b mainly arranged on the same side with respect to the rotation axis 6a, a direction perpendicular to the plane formed by the annular patterns of the MR elements 2a and 2b. A magnetic field H ₁ oriented in the direction parallel to the central axis c is applied. By rotating the permanent magnet 7, the magnetic fields H ₁ , H
_The portion to which ₂ is applied continuously changes between the MR elements 2a and 2b.
The absolute value of the magnetic field strength of the magnetic fields H ₂ and H ₁ applied by the permanent magnet 7 to the MR elements 2a and 2b is equal to or higher than the saturation magnetic field strength of the MR elements 2a and 2b.

By the way, the following facts are known in the MR elements 2a and 2b. That is, the MR element has the characteristic that the resistance value of the MR element decreases when it receives a magnetic field from a direction orthogonal to the direction of current flow. Has a characteristic that a stable output can be obtained unlike a semiconductor type magnetoresistive element or a Hall element.

Therefore, in this embodiment, the MR element 2a receives the magnetic field H ₂ from the radial direction as described above, and the resistance value thereof decreases. or,
The MR element 2b receives the magnetic field H ₁ from the vertical direction, and its resistance value does not change. And with the rotational movement of the permanent magnet 7,
The resistance values of the MR elements 2a and 2b continuously change, and the output V _out of the non-contact position sensor is as shown by the solid line in the graph showing the relationship between the rotation angle of the movable part 6 and the output V _{out in} FIG. It becomes a substantially straight line state.

Here, in the present embodiment, the central axis c of the permanent magnet 7 is the MR element.
If the MR element 2b near the central axis c has a resistance of the permanent magnet 7 and a resistance of the MR element 2b, the MR element 2b near the central axis c has a resistance of the MR element 2b. It is possible to apply the magnetic field H ₁ of only the vertical component whose resistance value does not change, without applying the magnetic field containing the radial component that decreases the value. Therefore, the difference between the resistance values of the MR element 2a and the MR element 2b can be maximized, so that the magnitude of the output V _out can be increased and the linearity with respect to the rotation angle can be optimized. When the central axis c and the MR element 2b are relatively deviated, the resistance value near the central axis c of the MR element 2b is partially reduced, so that the output is as shown by the dotted line in FIG. The linearity deteriorates a little.

Further, the prismatic permanent magnet 7 is used as the magnetic field generating means, and by constructing as in this embodiment, the magnetization can be done only in the direction parallel to the rotation axis 6a, and the magnetization can be facilitated.

Further, since the permanent magnet 7 applies a magnetic field that is equal to or higher than the saturation magnetic field strength of the MR elements 2a and 2b, the decrease in resistance becomes constant, and the magnetic field due to variations in the distance between the MR elements 2a and 2b and the permanent magnet 7 is caused. This has the effect of obtaining a stable output V _out without depending on the slight variation in intensity.

Next, a second embodiment of the present invention will be described with reference to FIG. Part (A) of the same figure is a partial top view, and Part (b) of the same is a sectional view taken along the line BB of Part (a). This second embodiment is the first
The difference from the embodiment is that the second embodiment uses a cylindrical permanent magnet 7a as the magnetic field generating means, and this embodiment can also be expected to have the same effect as the first embodiment. As shown in the present embodiment, the shape of the magnetic field generating means in the present invention is not limited, and its central axis may be rotatable along the MR element. Also, the central axis c is MR
The elements 2a and 2b do not have to pass through the center of the pattern, but need only pass through the line width of the pattern.

〔The invention's effect〕

As described above, according to the non-contact position sensor of the present invention, the magnetic field generating means can be magnetized only in the direction parallel to the rotation axis of the movable part, and the magnetization can be facilitated.
In addition, since the central axis of the magnetic field generating means in the rotation axis direction can be rotationally moved so as to pass over the MR element, there is an excellent effect that the linearity with respect to the rotation angle of the output can be improved.

[Brief description of drawings]

1 (a) is a sectional view of the first embodiment of the present invention, FIG. 1 (b) is a partial top view of FIG. 1 (a), and FIG. 1 (c) is A in FIG. 1 (b). -A line sectional view, FIG. 2 is a graph showing the output characteristics of the first embodiment, FIG. 3 (a) is a partial top view of the second embodiment of the present invention, and FIG. 3 (b) is the same. It is the BB sectional view taken on the line in FIG. 1 ... Insulating substrate, 2a, 2b ... MR element, 3, 4, 5 ... Electrode terminal, 6
...... Movable part, 6a …… Rotary shaft, 7,7a …… Permanent magnet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ichiro Izawa, 1-1, Showa-cho, Kariya city, Aichi Prefecture, Nihon Denso Co., Ltd. (72) Inventor, Toshikazu Matsushita, 1-1, Showa-cho, Kariya city, Aichi prefecture Co., Ltd. (72) Inventor Katsuhiko Ariga 1-1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd.

Claims (3)

[Claims] 1. A movable portion rotatably provided, and a ferromagnetic magnetoresistive element which is concentric with the movable portion and which is arranged so as to be separated from the movable portion by a predetermined distance. ,
Magnetic field generating means having its magnetic poles directed in the direction of the rotation axis of the movable part, and the magnetic field from the magnetic field generating means is directed in a radial direction to a part of the ferromagnetic magnetoresistive element. It is characterized in that it is oriented vertically to the other part of the resistance element, and that the magnetic field generating means can be rotationally moved so that its central axis in the rotation axis direction passes over the ferromagnetic magnetoresistive element. Non-contact position sensor. 2. The non-contact position according to claim 1, wherein the absolute value of the magnetic field strength applied to the ferromagnetic magnetoresistive element by the magnetic field generating means is equal to or higher than the saturation magnetic field strength of the ferromagnetic magnetoresistive element. Sensor. 3. The non-contact position sensor according to claim 1 or 2, wherein the magnetic field generating means comprises a permanent magnet.