JP2014167440A - Displacement sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement sensor which is compact and can be simply attached.SOLUTION: A displacement sensor 100 includes an exciting coil 11 to which an AC voltage is applied; a movable body 12 which is composed of a non-magnetic metal material, and moves relative to the exciting coil 11 while facing the exciting coil 11; a detection unit 13 including at least three detection coils 31, 32, and 33 which are stacked and arranged between the exciting coil 11 and the movable body 12 along a facing direction of the exciting coil 11 and the movable body 12, and are magnetically coupled with the exciting coil 11; a characteristic memory unit 14 for preliminarily storing a displacement quantity characteristic in which a relation between outputs of the detection coils 31, 32, and 33 and the displacement quantity of the movable body is defined; and a displacement quantity identifying unit 15 for identifying the displacement quantity of the movable body relative to the detection unit 13 on the basis of the outputs of the three detection coils 31, 32, and 33 obtained according to the displacement of the movable body 12, and the displacement quantity characteristic.

Description

  The present invention relates to a displacement sensor that detects a displacement amount of a movable body that is a detection target.

  Conventionally, as a technique for detecting a displacement amount of a moving body, for example, there is a technique described in Patent Documents 1-3. Patent Literature 1 describes a cylinder position detection device that detects the position of a cylinder. This cylinder position detecting device has a magnetic response portion formed in a pattern in which the area gradually increases or decreases along the stroke direction on the surface of the piston rod, and is fixed to the cylinder body side and faces the magnetic response portion. And a coil to be arranged. The cylinder position is detected based on the voltage between the terminals of the coil corresponding to the stroke position of the piston rod.

  In Patent Document 2, a linearly elongated movable element, a corrugated part formed on one surface of the movable element, a stator having an excitation winding and an output winding, and arranged opposite to the corrugated part, Are described. As the mover moves linearly, the gap between the mover and the stator changes, and a signal is output from the output winding. The linear position detection device detects the position of the mover based on the signal from the output winding.

  Patent Document 3 describes a position sensor including an exciting coil and a receiving coil arranged in the vicinity of the exciting coil. The receiving coils are formed on the same plane so as to form two sections, and are arranged so that the winding directions are opposite to each other. Thereby, magnetic fluxes in different directions are generated from the two sections of the receiving coil. This position sensor detects the position of a magnetic body based on the magnetic flux which arises from such two divisions.

JP 2010-145423 A JP 2000-314606 A Special table 2008-544293 gazette

  The technique described in Patent Documents 1-3 described above is based on the premise that the distance between the coil and the detection target is constant, and if this distance fluctuates, the detection result is affected. For this reason, it is impossible to accurately detect the amount of displacement of the detection object. Therefore, it is necessary to perform the assembly of the coil and the detection target with high accuracy, and there are restrictions on the assembly intersection, inclination, and the like. In addition, since the structure of the coil or the detection object is changed in the stroke direction, there is a problem that the size of the sensor or the size of the detection object increases.

  In view of the above problems, an object of the present invention is to provide a displacement sensor that is compact and can be easily assembled.

  In order to achieve the above object, the displacement sensor according to the present invention is characterized by an excitation coil to which an alternating voltage is applied and a nonmagnetic metal material, and is moved relative to the excitation coil while facing the excitation coil. A movable body, and a stack having at least three detection coils magnetically coupled to the excitation coil, wherein the excitation coil and the movable body are stacked between the excitation coil and the movable body in a direction opposite to each other. A characteristic storage unit preliminarily storing a displacement amount characteristic in which a relationship between the output of the detection coil and the displacement amount of the movable body is defined, and the at least 3 acquired according to the displacement of the movable body There is a displacement amount specifying unit that specifies a displacement amount of the movable body with respect to the detection unit based on outputs of two detection coils and the displacement amount characteristic.

With such a characteristic configuration, the displacement amount of the movable body can be easily specified by fitting the output from the detection coil to the displacement amount characteristic stored in advance in the characteristic storage unit. In addition, since at least three detection coils are stacked along the direction in which the exciting coil and the movable body face each other, even if the position of the movable body changes three-dimensionally, the displacement in the height direction (that is, The displacement along the stacking direction of the detection coil) and the in-plane displacement (that is, the displacement in the direction orthogonal to the stacking direction of the detection coil) can be detected appropriately. Moreover, even if it is the displacement of the direction which combined them, it becomes possible to detect appropriately. Thus, with this configuration, it is only necessary to stack at least three detection coils and excitation coils, so that a displacement sensor that is compact and can be easily assembled can be realized.
Further, since the output from each detection coil is due to mutual induction when the exciting coil is converted to an electromagnet, no permanent magnet is required. For this reason, it is hard to receive the influence of foreign materials, such as iron powder, and it does not raise the cost by soaring of rare earths.

  In addition, it is preferable that the excitation coil and the at least three detection coils are formed in the same shape when viewed in the stacking direction of the at least three detection coils.

  With such a configuration, the magnetic coupling between the excitation coil and the detection coil is facilitated. Therefore, it is possible to accurately detect the displacement amount of the movable body by appropriately obtaining the outputs from the respective detection coils.

  Further, it is preferable that the excitation coil and the at least three detection coils are constituted by a single multilayer printed board.

  With such a configuration, the excitation coil and the detection coil can be easily formed. Therefore, since the positional accuracy with respect to each stacking direction can be increased, the detection accuracy can be increased. In addition, since the same size can be easily produced, the manufacturing cost can be reduced.

It is a figure which shows the structure of a displacement sensor typically. It is the figure which expanded the exciting coil and the detection coil. It is a figure which shows the stroke characteristic of a detection coil. It is a figure which shows the gap characteristic of a detection coil. It is a figure which shows the relationship between the gap of a detection coil, and an output. It is a figure which shows an example of a displacement amount characteristic.

  The displacement sensor according to the present invention has a function of detecting the displacement amount of the movable body. Hereinafter, the displacement sensor 100 of the present embodiment will be described in detail. The displacement sensor 100 includes an exciting coil 11, a movable body 12, a detection unit 13, a characteristic storage unit 14, a displacement amount specifying unit 15, and an energization control unit 21. In particular, the characteristic storage unit 14, the displacement amount specifying unit 15, and the energization control unit 21 have a CPU as a core member, and functional units for performing various processes for detecting the displacement amount of the movable body 12 are hardware and / or software. Has been built. Here, in the present embodiment, an example in which such a functional unit is configured by one ECU (Electronic Control Unit) will be described.

  An alternating voltage is applied to the exciting coil 11. The exciting coil 11 according to the present embodiment is formed by patterning on a printed board 1 such as a glass epoxy board. Such an exciting coil 11 is shown in FIG. In the present embodiment, the spiral coil pattern 3 is formed by etching copper on the insulating layer 1A of the printed circuit board 1. Therefore, the exciting coil 11 is formed in a planar shape. In addition, through holes 4 penetrating the printed circuit board 1 are formed at both ends (start point and end point) of the coil pattern 3. An AC voltage is applied to the coil pattern 3 from the back surface of the printed circuit board 1 through the through hole 4. As a result, a magnetic flux in a direction perpendicular to the printed circuit board 1 is generated. In the present embodiment, as shown in FIG. 1, the application of the AC voltage is controlled by the energization control unit 21.

  Returning to FIG. 1, the movable body 12 is configured to move relative to the excitation coil 11 while facing the excitation coil 11. As described above, in the present embodiment, the exciting coil 11 is formed in a planar shape on the printed board 1. Here, the movable body 12 is formed of a nonmagnetic metal material. In this embodiment, it is comprised, for example with the flat plate of copper or aluminum. Such a flat movable body 12 is disposed so as to face the planar exciting coil 11.

  The movable body 12 corresponds to an object for detecting the amount of displacement by the displacement sensor 100. The movable body 12 can move in a gap direction that is a direction orthogonal to the printed circuit board 1 on which the exciting coil 11 is formed and a stroke direction that is a direction parallel to the surface of the printed circuit board 1. The present displacement sensor 100 can detect such displacement in the gap direction and stroke direction.

  The detection unit 13 includes at least three detection coils that are magnetically coupled to the excitation coil 11. In the present embodiment, description will be made assuming that the three detection coils are the detection coils 31, 32, and 33. Magnetic coupling refers to a state in which current is also generated in the detection coils 31, 32, and 33 by electromagnetic induction due to a magnetic field based on the magnetic flux generated from the exciting coil 11 to which an AC voltage is applied as described above. That is, it means a state in which mutual induction occurs in the excitation coil 11 and the detection coils 31, 32, 33.

  The detection coils 31, 32, and 33 according to the present embodiment are also formed by patterning on a printed board 7 such as a glass epoxy board, for example, as with the above-described exciting coil 11. FIG. 2 shows such detection coils 31, 32, and 33. The copper on the insulating layer 7A of the printed circuit board 7 is etched to form a spiral coil pattern 8. Therefore, the detection coils 31, 32, and 33 are also formed in a planar shape like the excitation coil 11. Further, through holes 9 penetrating the printed circuit board 7 are formed at both ends of each coil pattern 8. The voltage generated in each of the detection coils 31, 32 and 33 through the through hole 9 is measured. In FIG. 2, the voltage of the detection coil 31 is “V1”, the voltage of the detection coil 32 is “V2”, and the voltage of the detection coil 33 is “V3”.

  As shown in FIG. 1, the detection coils 31, 32, and 33 are stacked between the excitation coil 11 and the movable body 12 along the direction in which the excitation coil 11 and the movable body 12 face each other. As described above, the exciting coil 11 and the movable body 12 are disposed so as to face each other. The facing direction corresponds to the gap direction in FIG. The detection coils 31, 32, and 33 are stacked in a state of being insulated from each other, and the stacked direction is disposed along the gap direction. Therefore, the detection coils 31, 32, and 33 are stacked and arranged so that the surfaces of the respective printed circuit boards 1 and 7 are orthogonal to the gap direction.

  In the present embodiment, the exciting coil 11 and the detection coils 31, 32, 33 are formed in the same shape as viewed in the stacking direction of the detection coils 31, 32, 33. “Looking in the stacking direction of the detection coils 31, 32, 33” means looking at the displacement sensor 100 in the vertical direction. That is, this means that the displacement sensor 100 is viewed in the gap direction. The same shape means that the coil patterns 3 and 8 formed on the printed boards 1 and 7 are formed so as to overlap each other. However, since the through holes 4 and 9 are formed at both ends of each of the coil patterns 3 and 8 as described above, these portions are excluded. With this configuration, in the present embodiment, when the displacement sensor 100 is viewed in the gap direction, the coil patterns 3 and 8 of the excitation coil 11 and the detection coils 31, 32, and 33 are identical in shape so as to overlap each other. Formed with.

  Such an excitation coil 11 and detection coils 31, 32, 33 can be constituted by a single multilayer printed circuit board. That is, it is preferable that the excitation coil 11 and the detection coils 31, 32, and 33 are configured by a four-layer substrate. Accordingly, an insulating layer can be disposed between at least the excitation coil 11 and the detection coils 31, 32, and 33 while being close to each other. Therefore, mutual induction can be caused to act on each of the detection coils 31, 32, and 33 by the magnetic field generated from the excitation coil 11. In addition, the coil patterns 3 and 8 of the exciting coil 11 and the detection coils 31, 32, and 33 can be formed in the same shape by a known patterning technique.

  The characteristic storage unit 14 stores in advance a displacement amount characteristic in which a relationship between the output of the detection coils 31, 32, and 33 and the displacement amount of the movable body 12 is defined. Here, the characteristics when the movable body 12 moves in the stroke direction with respect to the detection coils 31, 32, 33 are shown in FIG. In FIG. 3, the horizontal axis represents the movement amount (stroke amount) of the movable body 12 in the stroke direction, and the vertical axis represents the impedance of the detection coils 31, 32, and 33. As shown in FIG. 3, when the movable body 12 moves in the stroke direction, the impedance of the detection coils 31, 32, and 33 changes linearly. In addition, although the vertical axis | shaft of FIG. 3 has shown with the impedance of the detection coils 31, 32, and 33, it is the same even if it shows with the output voltage of the detection coils 31, 32, and 33. FIG.

  On the other hand, the characteristics when the movable body 12 moves in the gap direction with respect to the detection coils 31, 32, and 33 are shown in FIG. In FIG. 4, the horizontal axis represents the amount of movement (gap amount) of the movable body 12 in the gap direction, and the vertical axis represents the impedance of the detection coils 31, 32, 33. As shown in FIG. 4, when the movable body 12 moves in the gap direction, the impedances of the detection coils 31, 32, and 33 change nonlinearly. The characteristics shown in FIGS. 3 and 4 are examples, and the impedance value changes by changing the cross-sectional area of the coil patterns 3 and 8. The vertical axis in FIG. 4 indicates the impedance of the detection coils 31, 32, and 33, but the same applies to the output voltages of the detection coils 31, 32, and 33.

  As described above, the characteristics are different between the case where the movable body 12 moves in the stroke direction and the case where the movable body 12 moves in the gap direction. On the other hand, the detection coils 31, 32, and 33 are stacked and arranged as described above. Therefore, the gap between the three detection coils 31, 32, and 33 is constant as shown in FIG. 5 (for example, 0.5 mm), but the output of the three detection coils 31, 32, and 33 is the amount of movement in the stroke direction and It differs depending on the amount of movement in the gap direction. Therefore, the displacement amount of the movable body 12 is uniquely determined by the outputs of the three detection coils 31, 32, and 33 and the gaps of the three detection coils 31, 32, and 33. Such a displacement amount characteristic is stored in advance in the characteristic storage unit 14 (see FIG. 6).

  The displacement amount specifying unit 15 specifies the displacement amount of the movable body 12 with respect to the detection unit 13 based on the outputs of the three detection coils 31, 32, 33 acquired according to the displacement of the movable body 12 and the displacement amount characteristics. To do. The outputs of the three detection coils 31, 32, and 33 are transmitted to the displacement amount specifying unit 15 through the through holes 4 and 9 formed at both ends of the respective coil patterns 3 and 8, as shown in FIG. Measured. Further, the displacement amount specifying unit 15 also stores gaps between these three detection coils 31, 32, and 33 in advance. The displacement amount specifying unit 15 fits the previously stored gaps of the detection coils 31, 32, and 33 and the transmitted output to the displacement amount characteristics as shown in FIG. Specify the amount of displacement.

  Specifically, three virtual lines indicating impedances corresponding to the measured output voltages of the detection coils 31, 32, and 33 are set on the displacement characteristic. Next, the three virtual lines are sequentially cut on a plane that defines the same stroke amount. It is determined whether or not the cut surface thus cut has a known gap (for example, “0.5 mm”) relationship between the detection coils 31, 32, and 33. The corresponding stroke amount becomes the actual displacement amount of the movable body 12. That is, the “stroke amount” and the “gap amount” in the coordinates thus detected correspond to the displacement amount of the movable body 12. Thus, according to the present displacement sensor 100, the displacement amount of the movable body 12 in the stroke direction and the displacement amount in the gap direction can be easily detected. Note that the displacement amount of the movable body 12 in the gap direction can be specified by reading the gap amount from the detection coil based on the displacement amount characteristic with reference to any one of the detection coils 31, 32, and 33. it can.

[Other Embodiments]
In the embodiment described above, the detection unit 13 has three detection coils. However, the scope of application of the present invention is not limited to this. Of course, the detection unit 13 may include four or more detection coils. Even in such a case, it is possible to appropriately detect the displacement amount of the movable body 12 by specifying the corresponding displacement amount from the displacement amount characteristic. In addition, the detection accuracy can be increased by increasing the number of detection coils as compared with the case of three.

  In the above embodiment, the excitation coil 11 and the detection coils 31, 32, 33 have been described as being formed in the same shape when viewed in the stacking direction of the detection coils 31, 32, 33. However, the scope of application of the present invention is not limited to this. That is, it is naturally possible to configure the exciting coil 11 and the detection coils 31, 32, and 33 in different shapes when viewed in the stacking direction.

  In the embodiment described above, the excitation coil 11 and the detection coils 31, 32, and 33 are described as being configured by a single multilayer printed board. However, the scope of application of the present invention is not limited to this. That is, it is possible to configure each of them with different printed boards and then stack them, or to use them without using the printed board 1. That is, for example, the exciting coil 11 and the detection coils 31, 32, and 33 can be configured by so-called “chip laminated inductors”.

  The present invention can be used in a displacement sensor that detects the amount of displacement of a movable body that is a detection target.

1: Printed circuit board (multilayer printed circuit board)
11: Excitation coil 12: Movable body 13: Detection unit 14: Characteristic storage unit 15: Displacement amount specifying unit 31: Detection coil 32: Detection coil 33: Detection coil 100: Displacement sensor

Claims (3)

An exciting coil to which an alternating voltage is applied;
A movable body made of a non-magnetic metal material and moving relative to the excitation coil while facing the excitation coil;
A detection unit having at least three detection coils that are stacked between the excitation coil and the movable body along a direction in which the excitation coil and the movable body face each other and are magnetically coupled to the excitation coil;
A characteristic storage unit in which a displacement characteristic in which a relationship between the output of the detection coil and the displacement of the movable body is defined is stored in advance;
A displacement amount specifying unit that specifies the displacement amount of the movable body relative to the detection unit based on the outputs of the at least three detection coils acquired according to the displacement of the movable body and the displacement amount characteristics;
A displacement sensor comprising:   The displacement sensor according to claim 1, wherein the excitation coil and the at least three detection coils are formed in the same shape when viewed in the stacking direction of the at least three detection coils.   The displacement sensor according to claim 1 or 2, wherein the excitation coil and the at least three detection coils are configured by a single multilayer printed circuit board.

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