JP2012255683A - Displacement amount detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement amount detector that can be size-reduced.SOLUTION: A displacement amount detector comprises a detection coil 2 held in a displaceable manner in a predetermined displacement direction A1 relative to a detection object 1 made of metal, and a detection circuit for detecting a displacement amount of the detection object 1 relative to the detection coil 2 on the basis of a change in electrical characteristics of the detection coil 2. The detection object 1 has two portions 11, 12 to be detected, with the two portions disposed across a movable range of the detection coil 2 in a direction orthogonal to the displacement direction A1. The portions 11, 12 to be detected respectively have different dimensions in the displacement direction A1. The width of a detectable displacement amount is larger compared to a case where only one of the parts 11, 12 to be detected is provided or where the dimensions of the parts 11, 12 to detected are the same. Namely, The dimensions of the detection coil 2 is reduced relative to the width of the detectable displacement amount so that a size reduction can be realized.

Description

  The present invention relates to a displacement detection device.

  Conventionally, a metal detection object and a detection coil that is displaced relative to the detection object are provided, and the magnitude of the displacement is determined based on a change in inductance of the detection coil accompanying the displacement. A displacement amount detection device for detecting (hereinafter referred to as “displacement amount”) is provided.

  The displacement amount detection device as described above is used for detecting the displacement amount of the handle relative to the main body, for example, in an apparatus having a handle that can be displaced relative to the main body by receiving an operating force. In this case, the detection coil is fixed to one of the main body and the handle, and the detection target is fixed to the other.

  Further, as shown in FIG. 5, the detected object 1 is orthogonal to the displacement direction of the detection coil 2 viewed from the detected object 1 (hereinafter referred to as “displacement direction”) A1. There is provided a displacement amount detection device arranged to be shifted to one side of a direction (a direction perpendicular to the paper surface of FIG. 5; hereinafter referred to as “opposing direction”) (see, for example, Patent Document 1). The axial direction of the detection coil 2 is directed in the opposite direction. In such a displacement amount detection device, the magnetic flux generated by the detection coil 2 is mainly generated in the opposite direction, and accordingly, as the magnitude of the overlap between the detected object 1 and the detection coil 2 as viewed from the opposite direction changes. The inductance of the detection coil 2 changes.

Japanese Patent Laid-Open No. 2002-22402

  In the displacement amount detection device described above, since the change in the displacement amount cannot be detected unless the size of the overlap between the detection object 1 and the detection coil 2 as viewed from the opposite direction changes, For both the coil 2 and the coil 2, the dimension in the displacement direction A1 needs to be larger than the width of the displacement to be detected. For this reason, it was easy to enlarge the displacement detection device.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide a displacement amount detection device that can be miniaturized.

  The displacement amount detection apparatus according to the present invention includes a detection coil, a holding unit that holds the detection coil so as to be relatively displaceable in a predetermined displacement direction with respect to a detection object, and changes in electrical characteristics of the detection coil. And a detection circuit for detecting a displacement amount of the detected object relative to the detection coil, and the detected object has a plurality of detected parts each made of a material having at least one of conductivity and magnetism. Each of the detected parts overlaps with the detection coil in at least a part of the movable range as seen from a predetermined facing direction orthogonal to the displacement direction. The dimensions in the displacement direction are different from each other.

  In the above displacement amount detection device, each of the detection coils is a planar coil whose axial direction is directed in a direction intersecting the displacement direction, and the orthogonal portions through which current flows in a direction orthogonal to the displacement direction are separated from each other. 3 or more, and the interval between the orthogonal portions may be non-uniform.

  Further, in the above displacement amount detection device, each of the detection coils is a planar coil having an axial direction in a direction intersecting the displacement direction, and the dimensions in the direction orthogonal to the displacement direction are non-uniform. It may be.

  Furthermore, the displacement amount detection apparatus may include the detected body.

  According to the present invention, the width of the detectable displacement amount is larger than when only one detected portion is provided or when the size of the detected portion is common. That is, since the size of the detection coil can be reduced with respect to the width of the detectable displacement amount, the size can be reduced.

It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows the shape of the detection coil in the same as the above. It is explanatory drawing which shows the relationship between the inductance and displacement amount of a detection coil in the same as the above. (A) (b) is explanatory drawing which shows the example of a change of the shape of the detection coil in each same. It is explanatory drawing which shows a prior art example.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  In the present embodiment, as shown in FIG. 1, a metal detection object 1 and a detection coil held by a holding means (not shown) so as to be relatively displaceable in a predetermined displacement direction A1 with respect to the detection object 1. 2 is provided. For example, aluminum or copper can be used as the material of the body 1 to be detected. Further, since the above holding means can be realized by a well-known technique, detailed illustration and description are omitted.

  The detection coil 2 is formed of a spiral conductive pattern as shown in FIG. 2 formed on the printed wiring board 20. The thickness direction of the printed wiring board 20 is directed to a predetermined facing direction A2 orthogonal to the displacement direction A1, and thus the axial direction of the detection coil 2 is also directed to the facing direction A2. The detection coil 2 has a rectangular outer shape, and a set of sides (upper and lower sides in FIG. 1) are parallel to the displacement direction A1.

  In addition, the present embodiment includes a detection circuit (not shown) that detects the amount of displacement based on the change in the electrical characteristics of the detection coil 2 due to the relative displacement as described above. In general, an inductance is used as the electrical characteristic, but the present invention is not limited to this. For example, a conductance may be used. According to the experiment of the present inventor, when the detected object 1 is made of iron, it has been confirmed that the conductance of the detection coil 2 increases linearly with respect to the displacement amount. In any case, since the detection circuit can be realized by a well-known technique, detailed illustration and description are omitted.

  The detected body 1 has a total of two detected portions 11 and 12, one on each side of the facing direction A 2 with respect to the movable range of the detection coil 2 (that is, both sides in the axial direction of the detection coil 2).

  Each of the detected parts 11 and 12 overlaps the detection coil 2 when viewed from the facing direction A2 in at least a part of the movable range. Each of the detected portions 11 and 12 has a flat plate shape with the thickness direction facing the facing direction A2, and one detected portion (hereinafter referred to as a “first detected portion”) 11 in the displacement direction A1. The dimension is set to be larger than the dimension d of the detection coil 2 than the dimension of the other detected part (hereinafter referred to as “second detected part”) 12. Also in the second detected part 12, the dimension in the displacement direction A1 is larger than the dimension d of the detection coil 2, and the movable range of the detection coil 2 is within the second detected part when viewed from the facing direction A2. A position that completely overlaps the portion 12 is included.

  Here, the displacement amount at the position where the detection coil 2 begins to overlap the first detected portion 11 when viewed from the displacement direction A1 is set to 0, and the overlap between the detection coil 2 and the first detection portion 11 increases from there. Is defined as positive. In the present embodiment, when the displacement amount is from 0 to d, the electrical characteristics of the detection coil 2 change due to the change in the size of the overlap between the detection coil 2 and the first detection unit 11 when viewed from the facing direction A2. When the amount of displacement is from d to 2d, the electrical characteristics of the detection coil 2 change as the size of the overlap between the detection coil 2 and the second detection unit 12 changes as viewed from the facing direction A2. That is, in this embodiment, the width of the displacement amount that can be detected as a whole is twice the dimension d of the detection coil 2 in the displacement direction A1.

  In addition, for each of the detected parts 11 and 12, the width by which the inductance of the detection coil 2 is reduced is directly proportional to the area of overlap with the detection coil 2 viewed from the facing direction A2, and the proportionality coefficient is the detected part. If it is assumed that 11 and 12 are common, as shown in FIG. 3, the inductance of the detection coil 2 changes linearly with respect to the displacement amount over the entire width of the displacement amount.

  According to the above configuration, the size can be reduced by reducing the dimension d of the detection coil 2 for the width of the detectable displacement amount.

  Even when the dimensional difference between the detected parts 11 and 12 in the displacement direction A1 is smaller than the dimension d of the detection coil 2, the width of the displacement amount that can be detected as a whole is the dimension of the detection coil 2. It becomes larger than d. Moreover, you may vary a dimension shape and material for every to-be-detected parts 11 and 12. FIG.

  Further, in order to enable detection of the displacement amount as described above, each of the detected portions 11 and 12 only needs to have at least one of conductivity and magnetism.

  By the way, when the detection coil 2 is a spiral planar coil as in the present embodiment, the magnetic flux density generated by the detection coil 2 is closer to the inner peripheral side of the detection coil 2 (that is, surrounded by more conductive patterns). The higher the position). Due to such distribution of magnetic flux density, the change in inductance is not actually linear as shown in FIG. In order to make the change in inductance linear, it is conceivable to make the shape of the detection coil 2 as shown in FIGS.

  In the example of FIG. 4A, the interval between the orthogonal portions 21 that are portions where the extending direction (that is, the direction in which the current flows) is the width direction A3 other than the outermost periphery of the detection coil 2 is the innermost periphery. On the other hand, it is different on one side and the other side in the displacement direction A1. Specifically, the above interval is shorter on one side (left side in FIG. 4A) that overlaps the detected parts 11 and 12 than on the other side (right side in FIG. 4A). . According to the experiment of the present inventor, when the shape of the detection coil 2 is as shown in FIG. 4A, the displacement amount and the inductance are compared with the case where the shape of the detection coil 2 is as shown in FIG. It has been confirmed that the relationship is close to a straight line.

  In the example of FIG. 4B, in the detection coil 2, one end side in the displacement direction A1 and the other end side from the one end side (left side in FIG. 4B) that overlaps the detected parts 11 and 12 first ( The dimension in the width direction A3 is gradually reduced toward the right side in FIG. Even with such a detection coil 2, it is considered that the relationship between the amount of displacement and the inductance is closer to a straight line compared to the case where the shape of the detection coil 2 is as shown in FIG.

DESCRIPTION OF SYMBOLS 1 Detected object 2 Detection coil 11, 12 Detected part 21 Orthogonal part

Claims (4)

A detection coil;
Holding means for holding the detection coil so as to be relatively displaceable in a predetermined displacement direction with respect to the detection object;
A detection circuit that detects a displacement amount of the detected object with respect to the detection coil based on a change in electrical characteristics of the detection coil;
The detected object has a plurality of detected parts each made of a material having at least one of conductivity and magnetism,
Each of the detected parts overlaps the detection coil as seen from a predetermined facing direction orthogonal to the displacement direction in at least a part of the movable range,
The displacement amount detection apparatus according to claim 1, wherein each of the detected parts has a different dimension in the displacement direction.   Each of the detection coils is a planar coil whose axial direction is in a direction crossing the displacement direction, and has three or more orthogonal portions that are separated from each other and through which current flows in a direction orthogonal to the displacement direction, The displacement amount detection device according to claim 1, wherein the intervals between the orthogonal portions are non-uniform.   2. The detection coil according to claim 1, wherein each of the detection coils is a planar coil having an axial direction in a direction intersecting the displacement direction, and the dimensions in the direction orthogonal to the displacement direction are non-uniform. The displacement amount detection device described.   The displacement detection device according to claim 1, further comprising the detected body.

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