JP2007101299A - Magnetic displacement sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the displacement of a movable body, of which the linear displacement is to be detected, with high precision free of influence from the wobble of the movable body. <P>SOLUTION: The magnetic displacement sensor comprises: a pair of magnets 31, 32 arranged on the fixed side in the displacement direction of the movable body; a magnetic sensor 33 arranged between the magnets 31, 32; a nonmagnetic spacer 34 arranged on the magnets 31, 32; a nonmagnetic slider 36 attached to the movable body; and a yoke 35 which is made of a soft magnetic substance, is held by the slider 36, and slides over the spacer 34 in accordance with the displacement of the movable body. The pair of magnets 31, 32 are magnetized in a direction opposite to the Z direction. The magnetic sensor 33 detects a change in magnetic flux in the Z direction. The yoke 35 is held by the slider 36 movably in the Z direction. Even when the movable body wobbles, the yoke 35 is constantly kept in contact with the spacer 34, and thereby the distance between the yoke 35 and the magnets 31, 32 in the Z direction is not changed through the wobble of the movable body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic displacement sensor for detecting linear displacement and rotational displacement using magnetism.

FIG. 12 shows a configuration of a displacement sensor described in Patent Document 1 as a conventional configuration example of this type of magnetic displacement sensor. In this example, the displacement sensor detects a linear displacement. .
The yoke 11 made of a soft magnetic material has a rectangular parallelepiped shape, and is attached to a movable body that is not shown in the drawing but should detect a linear displacement. In FIG. 12, the arrow indicates the displacement direction of the yoke 11 that linearly displaces together with the movable body.
A back yoke 12 made of a soft magnetic material is disposed on the fixed side with respect to the movable body, and a pair of magnets 13 and 14 and a magnetic sensor 15 are mounted and fixed on the back yoke 12.

The pair of magnets 13 and 14 has a rectangular plate shape and is arranged in the displacement direction of the yoke 11, and a magnetic sensor 15 is arranged between the magnets 13 and 14.
The pair of magnets 13 and 14 are magnetized in the plate thickness direction, that is, opposite to each other in the direction facing the yoke 11, and the yoke 11 is displaced in close proximity to the magnets 13 and 14 through a predetermined gap. Are arranged to be.
The magnetic sensor 15 uses a Hall IC in which circuits such as a Hall element and an amplifier circuit are integrated, and changes the magnetic flux in the direction perpendicular to the plate surface of the back yoke 12, that is, in the plate thickness direction of the magnets 13 and 14. Arranged to detect.

FIG. 13 shows how the magnetic flux lines (shown by dotted lines) formed by the magnets 13 and 14 change according to the displacement of the yoke 11 in the magnetic displacement sensor having the above-described configuration. As shown in C, the magnetic flux density between the magnets 13 and 14 and the direction of the magnetic flux change according to the displacement of the yoke 11, and the magnetic sensor 15 outputs a voltage according to the change of the magnetic flux. Therefore, the linear displacement of the movable body to which the yoke 11 is attached can be detected by the change in the output voltage of the magnetic sensor 15.
On the other hand, FIG. 14 shows the configuration of a magnetic displacement sensor that detects the rotational displacement described in Patent Document 1, and in this example, the rotational displacement (rotation angle) of the rotary shaft 20 is detected. ing.

The yoke 21 made of a soft magnetic material has a semicircular flat plate shape, and is attached to the end of the rotating shaft 20 with its plate surface being perpendicular to the rotating shaft center of the rotating shaft 20.
A back yoke 22 made of a soft magnetic material is disposed on the fixed side with respect to the rotating shaft 20, and a pair of magnets 23 and 24 and a magnetic sensor 15 are mounted and fixed on the back yoke 22.
The pair of magnets 23 and 24 are formed in a substantially semicircular flat plate shape and are arranged on a disc-like back yoke 22 as shown in FIG. 14, and the magnetic sensor 15 is disposed on the periphery of the back yoke 22. It is disposed between the pair of magnets 23 and 24.

The pair of magnets 23 and 24 positioned on a plane perpendicular to the rotation axis of the rotary shaft 20 are magnetized in opposite directions in the plate thickness direction, and the yoke 21 is formed on the magnets 23 and 24 in a predetermined manner. It is located via a gap and is arranged so as to be rotationally displaced in close proximity to the magnets 23 and 24.
Also in the magnetic displacement sensor shown in FIG. 14, when the yoke 21 is rotationally displaced together with the rotary shaft 20, the magnetic flux between the magnets 23 and 24 arranged in the rotational displacement direction is changed, and the change of the magnetic flux is determined. By detecting with the magnetic sensor 15, the rotational displacement (rotation angle) of the rotating shaft 20 can be detected.
JP 2004-354237 A

As described above, in a conventional magnetic displacement sensor, a yoke made of a soft magnetic material is attached to a movable body that should detect linear displacement and a rotary shaft that should detect rotational displacement, and the magnetization directions are opposite to each other on the fixed side. A magnetic sensor in which a pair of magnets are arranged so that the yoke moves close to and opposed to the magnets in the arrangement direction of the magnets, and a change in magnetic flux accompanying the displacement of the yokes is arranged between the pair of magnets. Is to be detected.
However, since the yoke is conventionally fixed to the movable body and the rotating shaft, for example, when the movable body and the rotating shaft are shaken during the displacement operation, the yoke is also moved accordingly. If the distance (gap) between the yoke and the pair of magnets fluctuates due to shaking, the flow of magnetic flux (magnetic field distribution) is greatly affected, causing errors in the output of the magnetic sensor and greatly reducing the detection accuracy. It was.

  In view of the above-described problems, the object of the present invention is to detect the displacement in the original displacement direction with high accuracy without being affected by the shake even if the movable body or the rotation shaft to be detected is shaken. Another object of the present invention is to provide a magnetic displacement sensor.

  According to the first aspect of the present invention, a magnetic displacement sensor for detecting a displacement of a movable body that is linearly displaced is a pair of magnets arranged in the displacement direction on the fixed side with respect to the movable body, and between the magnets. A magnetic sensor arranged, a spacer made of a non-magnetic material arranged on a pair of magnets, a slider made of a non-magnetic material attached to the movable body, and a spacer held by the slider, along with the displacement of the movable body, And a yoke made of soft magnetic material that slides on top of each other. The pair of magnets are magnetized in directions opposite to each other in the direction orthogonal to the spacer arrangement surface, and the magnetic sensor detects the change in magnetic flux in the orthogonal direction. The yoke is held by the slider so as to be movable in the orthogonal direction.

  According to the second aspect of the present invention, the magnetic displacement sensor for detecting the rotational displacement of the rotating shaft is arranged in a circumferential direction centered on the rotating shaft center of the rotating shaft and is disposed on the fixed side with respect to the rotating shaft. A magnet, a magnetic sensor arranged between the magnets, a spacer made of a nonmagnetic material arranged on a pair of magnets in the direction of the rotation axis, a rotor made of a nonmagnetic material attached to the rotation shaft, and A yoke made of a soft magnetic material that is held by the rotor and slides on the spacer in accordance with the rotational displacement of the rotating shaft, and the pair of magnets are magnetized in directions opposite to each other in the direction of the rotating shaft. The sensor detects a change in magnetic flux in the direction of the rotation axis, and the yoke is held by the rotor so as to be movable in the direction of the rotation axis.

According to a third aspect of the present invention, in the first aspect of the present invention, the yoke is housed in a recess formed on the surface of the slider facing the spacer.
According to a fourth aspect of the present invention, in the second aspect of the present invention, the yoke is housed in a recess formed on the surface of the rotor facing the spacer.
According to a fifth aspect of the present invention, in the first aspect of the present invention, the yoke is held by the slider via the suspension, and is pressed against the spacer by the suspension.
According to a sixth aspect of the present invention, in the second aspect of the present invention, the yoke is held by the rotor via the suspension and is pressed against the spacer by the suspension.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects, a back yoke made of a soft magnetic material is disposed on a surface opposite to the spacer disposed surface of the pair of magnets.

  According to the present invention, the distance (interval) between the yoke and the pair of magnets is defined by the spacer interposed therebetween, and the yoke is always slid and displaced on the spacer. Even if the movable body to detect the linear displacement or the rotation shaft to detect the rotational displacement is not affected, the distance between the yoke and the pair of magnets is always kept constant. Therefore, even if the movable body or the rotating shaft is shaken, the displacement only in the displacement direction that should be detected can be detected with high accuracy.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of a magnetic displacement sensor for detecting linear displacement according to the present invention. In this example, the magnetic displacement sensor includes a pair of magnets 31, 32, a magnetic sensor 33, a spacer 34, and a yoke 35. And a slider 36, a case 37, and a back yoke 38.
The case 37 has a U-shaped cross section, and a back yoke 38 having a rectangular plate shape is disposed on the open surface of the U shape, and the open surface (bottom surface) is covered with the back yoke 38. . A window 37 a is formed on the upper surface of the case 37.

The slider 36 includes a base portion 36 a housed in the case 37 and a connecting portion 36 b protruding from the center of the upper surface of the base portion 36 a, and the connecting portion 36 b protrudes from the window 37 a of the case 37 to the outside. The slider 36 is connected and fixed to a movable body (not shown) whose linear displacement is to be detected, and is displaced along with the displacement of the movable body. Here, the displacement direction of the slider 36 that linearly displaces together with the movable body is defined as the X direction here.
A pair of magnets 31 and 32 and a magnetic sensor 33 are mounted and fixed on the inner surface of the back yoke 38 on the fixed side with respect to the slider 36 attached to the movable body, and a spacer 34 is mounted and fixed thereon. The The pair of magnets 31 and 32 is formed in a rectangular plate shape and arranged in the displacement direction (X direction) of the slider 36, and the magnetic sensor 33 is arranged between the magnets 31 and 32. The pair of magnets 31 and 32 are magnetized in opposite directions in the plate thickness direction, that is, in the Z direction perpendicular to the arrangement surface of the spacer 34, and the magnetic sensor 33 is arranged to detect a change in magnetic flux in the Z direction. Has been.

  As shown in FIG. 1, the spacer 34 is sized to cover the magnets 31 and 32 and is disposed on the magnets 31 and 32 and the magnetic sensor 33, and the yoke 35 is positioned on the spacer 34. The yoke 35 has a rectangular plate shape and is accommodated in a recess 36c formed on the surface of the slider 36 facing the spacer 34, that is, on the lower surface of the base portion 36a. Note that the size of the recess 36c is slightly larger than the size of the yoke 35, and the yoke 35 is not fixed to the slider 36, but is simply housed and held in the recess 36c.

In the above-described structure, both the yoke 35 and the back yoke 38 are made of a soft magnetic material, and the yoke 35 and the back yoke 38 are manufactured by laminating, for example, pressed electromagnetic steel sheets. For example, bond magnets are used for the magnets 31 and 32, and the magnetic sensor 33 is, for example, a Hall IC. On the other hand, the spacer 34, the slider 36, and the case 37 are all made of a nonmagnetic material, for example, made of resin.
In the magnetic displacement sensor having such a configuration, the slider 36 holding the yoke 35 is displaced in accordance with the displacement of the movable body, whereby the yoke 35 is displaced on the spacer 34 in the X direction. Accordingly, like the conventional magnetic displacement sensor shown in FIGS. 12 and 13, the magnetic flux between the magnets 31 and 32 changes according to the displacement of the yoke 35, and the magnetic sensor 33 outputs a voltage according to the change of the magnetic flux. To do. Therefore, the linear displacement of the movable body can be detected by the change in the output voltage of the magnetic sensor 33.

In this example, the yoke 35 is not fixed to the slider 36 but is held by the slider 36 so as to be movable in the Z direction, and the yoke 35 is subjected to a magnetic attractive force from the magnets 31 and 32 so that the yoke 35 is Since the movable body is always attracted to the magnets 31 and 32 and the movable body is shaken in the displacement operation and includes movements other than the X direction, the yoke 35 is always slid and displaced on the spacer 34. .
2 and 3 show this state, and the force as shown by an arrow A in each figure acts on the slider 36 due to the shaking of the movable body, so that the slider 36 tilts, and one end side in the X direction is Even if the yoke 35 moves away from the magnets 31 and 32 in the Z direction, the yoke 35 is not interlocked with the movement and always maintains the state in contact with the spacer 34, that is, between the yoke 35 and the pair of magnets 31 and 32. The distance in the Z direction is always kept constant in this example.

FIG. 4 shows a case where the yoke 35 is fixedly attached to the slider 36 as a comparative example. In this example, when a force as shown by an arrow A acts on the slider 36, the yoke 35 is moved from the spacer 34. The gap 39 is lifted and an error is generated in the output of the magnetic sensor 33. Note that the generation of such a gap 39 in the Z direction when detecting the displacement of the movable body greatly impairs the detection accuracy of the displacement of the movable body.
As described above, in this example, there is no gap between the yoke 35 that is displaced together with the movable body and the pair of magnets 31 and 32 that are fixedly arranged, as in the prior art, but there is a spacer 34, The distance between the yoke 35 and the magnets 31 and 32 is defined by the thickness of the spacer 34, and the yoke 35 is always in contact with the spacer 34 to be displaced. Displacement only in the displacement direction can be detected stably and with high accuracy.

Next, the configuration of a magnetic displacement sensor that detects rotational displacement will be described.
FIG. 5 shows the appearance of an embodiment of the magnetic displacement sensor according to the present invention for detecting the rotational displacement of the rotating shaft, and FIGS. 6A and 6B show the cross-sectional structures thereof, respectively. FIG. 7 shows a state in which a rotating shaft 40 for detecting rotational displacement is attached. In this example, the magnetic displacement sensor includes a pair of magnets 41, 42, a magnetic sensor 43, a case 44, a yoke 45, a rotor 46, a cover 47, and a back yoke 48.
The back yoke 48 has a ring shape, and a pair of magnets 41 and 42 and a magnetic sensor 43 are disposed on the back yoke 48. As shown in FIG. 5, the pair of magnets 41 and 42 has an arc shape centered on the rotation axis of the rotation shaft 40 (indicated by a point C in the figure), and extends in the circumferential direction about the rotation axis C. Arranged and arranged. The magnetic sensor 43 is disposed between the magnets 41 and 42 in the circumferential direction in which the magnets 41 and 42 are arranged. The pair of magnets 41 and 42 are magnetized in directions opposite to each other in the direction of the rotation axis of the rotation shaft 40, and the magnetic sensor 43 is arranged to detect a change in magnetic flux in the direction of the rotation axis. In FIG. 5, reference numeral 43a denotes a terminal of the magnetic sensor.

The back yoke 48, the pair of magnets 41 and 42, and the magnetic sensor 43 are housed and fixed in the lower half of a substantially cylindrical case 44, and on the pair of magnets 41 and 42, that is, the magnets 41 and 42. On the surface opposite to the surface on which the back yoke 48 of 42 is located, a thin portion 44 a is formed that protrudes toward the center so as to form a ring shape from the inner wall of the intermediate portion of the case 44. The thin portion 44 a corresponds to the spacer 34 in the magnetic displacement sensor shown in FIG. 1 described above, that is, functions to define the distance between the pair of magnets 41 and 42 and the yoke 45.
On the other hand, a rotor 46 and a yoke 45 are accommodated in the upper half of the case 44. The rotor 46 includes a shaft portion 46a and a flange portion 46b provided on the outer periphery thereof, and a through hole 46c into which the rotating shaft 40 is inserted and fitted is formed in the shaft portion 46a. The through hole 46c has a D-shape in this example, and is a so-called D-cut hole.

As shown in FIG. 5, the yoke 45 has a semicircular arc shape centered on the rotational axis C, and is formed on the lower surface of the flange portion 46b of the rotor 46, that is, on the surface facing the thin portion 44a of the case 44. The recessed portion 46d is accommodated and positioned on the thin portion 44a. The yoke 45 is not fixed to the rotor 46 but is simply housed and held in the recess 46 d and is movable in the direction of the rotation axis of the rotation shaft 40.
The shaft 46a of the rotor 46 is rotatably supported by being pivotally supported by a hole 44b formed at the center of the thin portion 44a of the case 44. .

Both the yoke 45 and the back yoke 48 are made of a soft magnetic material, and are produced, for example, by laminating pressed steel sheets. For example, bond magnets are used for the magnets 41 and 42, and the magnetic sensor 43 is, for example, a Hall IC. The rotor 46, the case 44, and the cover 47 are made of a nonmagnetic material. The rotor 46 and the case 44 are made of, for example, resin, and the cover 47 is formed of a metal plate.
In the magnetic displacement sensor having the above configuration, the rotor 46 attached to the rotary shaft 40 is rotationally displaced along with the rotational displacement of the rotary shaft 40, and the yoke 45 held by the rotor 46 rotates on the thin portion 44a. Displace. Accordingly, the magnetic flux between the magnets 41 and 42 changes according to the rotational displacement of the yoke 45, and the magnetic sensor 43 outputs a voltage corresponding to the change of the magnetic flux, that is, the rotational displacement of the rotary shaft 40, thereby The rotational displacement (rotation angle) of the rotating shaft 40 can be detected.

At this time, even if the rotating shaft 40 is shaken and includes movements other than the rotational displacement direction, the yoke 45 is held by the rotor 46 so as to be movable in the rotational axis direction and is attracted by the magnets 41 and 42. Without being affected by the shake of the shaft 40, it always slides on the thin portion 44 a, so that the distance between the yoke 45 and the pair of magnets 41, 42 in the rotational axis direction is always kept constant. ing. Therefore, the rotational displacement of the rotating shaft 40 can be detected with high accuracy.
FIG. 8 shows a state in which the rotating shaft 40 is shaken and the rotor 46 is tilted. Even in such a state, the yoke 45 remains in contact with the thin portion 44a.

FIG. 9 shows the structure of the main part of another embodiment of the magnetic displacement sensor according to the present invention for detecting the rotational displacement of the rotating shaft in a state where it is disassembled into each part, and the embodiment shown in FIGS. Corresponding parts are denoted by the same reference numerals. In FIG. 9, reference numeral 49 denotes a spacer which is interposed between the magnets 41 and 42 and the yoke 45 and defines the distance therebetween.
In the example shown in FIG. 9, the rotor 46 is not formed with the concave portion 46d as described above, but is formed with a hole 46e having a semicircular arc shape corresponding to the shape of the yoke 45. 45 is accommodated and held. Since the yoke 45 is held so as to be movable in the direction of the rotation axis and is always attracted by the magnets 41 and 42, such a shape of the hole 46e can be adopted instead of the recess 46d.

FIG. 10 shows a holding structure of the yoke 45 as shown in FIG. 9 in which the yoke 45 is not separated from the spacer 49 when an impact or the like is applied. The yoke 45 is pressed by the spacer 49.
On the other hand, FIG. 11 shows another structure in which the yoke 45 is pressed against the spacer 49. In this example, three leaf spring-like suspensions 52 are insert-molded in the rotor 46, and the suspensions 52 are yoked. 45 is attached. In this structure, the yoke 45 is pressed against the spacer 49 by the suspension 52, so that the yoke 45 is not separated from the spacer 49 even when an impact or the like is applied. In this example, the yoke 45 is attached and fixed to the suspension 52 by a rivet 53, but the yoke 45 may be fixed to the sun pension 52 by welding instead of riveting.

  In each of the above-described embodiments, the movable body that linearly displaces and the yoke made of a soft magnetic material that linearly displaces or rotationally displaces together with the rotation shaft directly with the spacer (in the configuration shown in FIG. 6, the thin portion 44a of the case 44 that functions as a spacer). Although it has a sliding structure, a low friction, non-magnetic thin resin plate such as a fluorine resin may be attached to the sliding surface of the yoke. The durability can be improved and the durability can be improved. In addition, although the spacer (case 44 in the structure shown in FIG. 6) is made of resin, it is not limited to resin but may be made of metal.

Sectional drawing which shows one Example of the magnetic displacement sensor which detects the linear displacement by this invention. FIG. 2 is a partial enlarged cross-sectional view illustrating an example of a state in which the slider is tilted by a shake of a movable body that detects displacement in the magnetic displacement sensor illustrated in FIG. 1. In the magnetic displacement sensor shown in FIG. 1, a partial enlarged cross-sectional view showing another example of the state in which the slider is inclined due to the shake of the movable body that detects the displacement. FIG. 4 is a partial enlarged cross-sectional view showing a state in which a gap is generated between the yoke and the spacer when the yoke is fixed to the slider as a comparative example with respect to FIG. 3. The top view which shows one Example of the magnetic displacement sensor which detects the rotational displacement of the rotating shaft by this invention. A is a sectional view taken along line AA in FIG. 5, and B is a sectional view taken along line BB in FIG. Sectional drawing which shows the state by which the rotating shaft was fitted by the magnetic displacement sensor shown in FIG. FIG. 8 is a partial enlarged cross-sectional view showing a state in which the rotor is inclined due to the shake of the rotation shaft in the magnetic displacement sensor shown in FIG. 7. The disassembled perspective view for demonstrating the other Example of the magnetic displacement sensor which detects the rotational displacement of the rotating shaft by this invention. The perspective view for demonstrating an example of the structure which presses a yoke to a spacer. The perspective view for demonstrating the other example of the structure which presses a yoke to a spacer. The perspective view which shows the example of a conventional structure of the magnetic displacement sensor which detects a linear displacement. FIG. 13 is a diagram illustrating a state in which magnetic flux lines change due to the displacement of the yoke in the magnetic displacement sensor illustrated in FIG. 12. The perspective view which shows the example of a conventional structure of the magnetic displacement sensor which detects the rotational displacement of a rotating shaft.

Claims (7)

A sensor that detects the displacement of a movable body that undergoes linear displacement,
A pair of magnets arranged in the displacement direction on the fixed side with respect to the movable body; and
A magnetic sensor disposed between the magnets;
A spacer made of a non-magnetic material disposed on the pair of magnets;
A slider made of a non-magnetic material attached to the movable body;
A yoke made of a soft magnetic material that is held by the slider and slides on the spacer as the movable body is displaced;
The pair of magnets are magnetized in directions opposite to each other in a direction orthogonal to the arrangement surface of the spacer,
The magnetic sensor detects a change in the magnetic flux in the orthogonal direction,
The magnetic displacement sensor, wherein the yoke is held by the slider so as to be movable in the orthogonal direction. A sensor for detecting the rotational displacement of the rotary shaft,
A pair of magnets arranged in a circumferential direction around the rotation axis of the rotation shaft and disposed on a fixed side with respect to the rotation shaft;
A magnetic sensor disposed between the magnets;
A spacer made of a non-magnetic material disposed on the pair of magnets in the rotational axis direction;
A rotor made of a non-magnetic material attached to the rotating shaft;
A yoke made of a soft magnetic material that is held by the rotor and slides on the spacer as the rotary shaft rotates.
The pair of magnets are magnetized in directions opposite to each other in the rotational axis direction,
The magnetic sensor detects a change in magnetic flux in the direction of the rotation axis,
The magnetic displacement sensor, wherein the yoke is held by the rotor so as to be movable in the direction of the rotation axis. The magnetic displacement sensor according to claim 1, wherein
The magnetic displacement sensor, wherein the yoke is accommodated in a recess formed on a surface of the slider facing the spacer. The magnetic displacement sensor according to claim 2, wherein
The magnetic displacement sensor, wherein the yoke is housed in a recess formed on a surface of the rotor facing the spacer. The magnetic displacement sensor according to claim 1, wherein
The magnetic displacement sensor, wherein the yoke is held by the slider via a suspension and is pressed against the spacer by the suspension. The magnetic displacement sensor according to claim 2, wherein
The magnetic displacement sensor, wherein the yoke is held by the rotor via a suspension and is pressed against the spacer by the suspension. The magnetic displacement sensor according to any one of claims 1 to 6,
A magnetic displacement sensor, characterized in that a back yoke made of a soft magnetic material is disposed on a surface opposite to the spacer disposition surface of the pair of magnets.

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