JPH05264203A - Displacement detector - Google Patents

Abstract

PURPOSE:To provide a displacement detector capable of detecting the displacement of a displacing body as electric signals. CONSTITUTION:A short-circuit ring 8 serving as a displacing body is displaced along the arm portion of a core 2, changing the range over which magnetic flux can be distributed. A change in the range changes the inductance of a detecting coil 7 attached to the core 2. The inductance of the detecting coil 7 is detected as a voltage signal between the terminals of the coil by means of application of an AC signal to the coil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement detector used for detecting the position of a displaced member, and more particularly to a displacement detector adapted to obtain an electric signal corresponding to the position of the displaced member. ..

[0002]

2. Description of the Related Art As a displacement detector of this type, there is a differential transformer. This is a structure in which an exciting coil and a detecting coil are arranged in a column in the axial direction, and a core is provided inside them so as to be movable in the axial direction. By connecting the core to the displacement member, an electric signal corresponding to the displacement of the displacement member can be obtained from the detection coil.

[0003]

Such a displacement detector has a problem that the detectable stroke is shorter than the length of the displacement detector as a whole.

The present invention has been made in order to solve the above-mentioned problems (technical problems) of the prior art, so that a relatively long detectable stroke can be obtained with respect to the entire length of the detector. An object of the present invention is to provide a displacement detector having the above structure.

[0005]

In order to achieve the above object, a displacement detector according to the present invention applies magnetic fluxes having opposite polarities to both arm portions to a core having a pair of arm portions. A detection coil for one arm is provided along the surface facing the other arm, and at least one of the arms is made of a good conductive material for blocking the passage of magnetic flux in the arm. The short-circuiting ring is provided around and is displaceable in the longitudinal direction along the arm portion.

[0006]

When the short-circuit ring is displaced along the arm portion of the core, the range in which the magnetic flux can be distributed between the pair of arm portions changes. As a result, the inductance of the detection coil changes correspondingly.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In the displacement detector 1 shown in FIG. 1, reference numeral 2 denotes a core, which is composed of a material having a small high frequency loss, such as a ferrite core. Reference numerals 3 and 4 denote two arm portions of the core 2, which are arranged in parallel with each other with a gap 5 therebetween. The arm portion 3 is formed in a round bar shape, and the arm portion 4 is formed in a cylindrical shape surrounding the arm portion 3. Reference numeral 6 denotes a connecting portion that mechanically and magnetically connects the respective ends of the arm portions 3 and 4 to each other. The core 2 having such a shape is known as a pot core. An example of the dimensions of each part of the core 2 is that the length A is 8 m.
m, the diameter B is 9 mm, the arm 3 has a diameter of 3 mm, the arm 4 has a thickness of 1 mm, the gap 5 has a width of 2 mm, and the connecting portion 6 has a thickness of 1 mm. As the core 2, any other core such as a U-shaped or E-shaped core may be used as long as it has at least two arm portions. Reference numeral 7 denotes a cylindrical detection coil, which is provided along the inner peripheral surface of the arm portion 4 in the gap 5 so that magnetic flux having opposite polarities can be applied to the both arm portions 3 and 4.

Next, 8 is a short-circuit ring provided around the arm 3,
The arm 5 is provided in the gap 5 so as to be movable in the longitudinal direction thereof, that is, in the left-right direction in FIG. The short-circuit ring 8 is made of a material having good conductivity such as copper. The thickness T of the short circuit ring 8 is 0.75 mm, for example. 9 is a detection piece, and the tip 9a
Is slightly sharpened as a detection portion for contacting the displacement member to be detected. Reference numeral 10 denotes a connecting member for connecting the short-circuit ring 8 and the detection piece 9, which is constituted by a tubular body which is integral with the short-circuit ring 8 and which moves back and forth in the axial direction with the arm portion 3 as a guide. The connecting member 10 is also integrated with the detection piece 9. These three members may be integrated and then integrated. The detection piece 9 and the connecting member 10 may be made of an insulating material. Reference numeral 11 is a return spring for returning the detection piece 9 and the short-circuit ring 8 to the preparatory position shown in FIG. 1, and a conical coil spring is used. One end of the spring 11 is fitted in a recess 12 formed around the inner peripheral surface of the arm portion 4, and the other end is fitted in a recess 13 formed around the outer peripheral surface of the connecting member 10. Reference numeral 15 is a detection resistor for detecting the inductance of the detection coil 7 as a voltage signal, 16
Is an AC signal source, and an oscillating circuit that generates a sine wave of a constant voltage with a constant frequency of, for example, several kilohertz or more is used as an AC signal for exciting the detection coil. 18 is an output terminal. Reference numeral 17 shown in FIG. 2 denotes an attraction magnet attached to the core 2 for attaching the displacement detector 1 to a member serving as a reference of a measurement target. Four magnets 17 are arranged around the magnet 17 at equal intervals. Two or three may be used.

Next, the operation of the above displacement detector will be described. When the voltage from the signal source 16 is applied to the detection coil 7, the detection coil 7 generates a magnetic flux φ as shown in FIG.
In this case, since the short-circuit ring 8 is made of the above-mentioned material, the magnetic flux φ is prevented from passing through the arm 3 where the short-circuit ring 8 is located. That is, when a magnetic flux tries to pass therethrough, an eddy current corresponding to the magnetic flux is generated in the short-circuit ring 8, and the eddy current generates the same number of magnetic fluxes as the magnetic flux to be passed in the opposite direction. Therefore, the magnetic flux cannot substantially pass through the arm portion 3 where the short-circuit ring 8 is located. Therefore, the magnetic flux generated by the detection coil 7 can pass only on the side of the connecting portion 6 with respect to the short-circuit ring 8, and the distribution thereof is as shown in FIG.
When the short-circuit ring 8 is displaced as shown in FIG. 3 or 4, the magnetic flux φ is in the state as shown in the figure. The relationship between the magnitude of the stroke x of the short-circuit ring 8 and the number of the magnetic fluxes φ is shown in a graph as shown in FIG.

As is well known, the inductance of the detection coil 7 corresponds to the ease of passage of the magnetic flux in the core. Therefore, FIG.
As shown in, the inductance L of the detection coil 7 is
It changes corresponding to the change in the stroke x of the short-circuit ring 8. In the detection circuit, the detection coil 7 and the detection resistor 15 form a voltage dividing circuit. Therefore, the inductance of the detection coil 7 is detected as a voltage signal generated across the detection coil 7. That is, by measuring the terminal voltage of the detection coil 7, the change of the stroke x, that is, the displacement of the short-circuit ring 8 can be known.

Next, the positional relationship between the detection coil 7 and the short-circuit ring 8 may be reversed inside and outside. That is, the detection coil 7 may be arranged along the outer peripheral surface of the arm portion 3, and the short-circuit ring 8 may move between the coil 7 and the arm portion 4.

Next, an example of use of the displacement detector 1 will be described with reference to FIG. This usage example is an example in which the size of the packing gap between the body and the door is measured when the vehicle is assembled. FIG. 6A is a sectional view schematically showing the completed state of the automobile, in which 21 is a body, 22 is a roof, and 23 is a door.
Reference numeral 24 is a rubber stopper for determining the closed position of the door 23, which is provided near the door lock device.
A packing gap 25 has a width W of, for example, about 10 mm, and the packing 26 is disposed here in a known manner. The packing 26 may be disposed at the position indicated by the chain double-dashed line.

When the door 23 is attached to the body 21 (the state before the packing 26 is attached) at the time of assembling such an automobile, the displacement detector 1 is provided at each position of the packing gap 25 as shown in FIG. Attach to body 21.
Then, the door 23 is closed to a predetermined position as is well known. In this state, packing gaps detected by displacement detectors 1 at various places
Measure the size W'of 25. Measured packing gap 25
If the size of the
You can see that there are twists and discrepancies in 23.
In that case, the attachment of the door 23 is corrected.

Next, FIG. 7 shows another usage example of the displacement detector 1. This example is an example of measuring the crushing margin of packing in a distribution box (which may be a control box or the like). In the distribution box, as shown in (A), the packing 34 is attached to the inner surface of the lid 33 that can be opened and closed with respect to the main body 31,
When the lid 33 is closed to the main body 31, the contact piece 32
It abuts 34 and crushes a part of it. Therefore, by measuring the size of the gap between the lid 33 and the abutting piece 32 by using the displacement detector 1 as shown in (B) before attaching the packing 34, it is possible to determine the size of the gap after attaching the packing 34. Can be crushed to a degree.

Next, FIGS. 8 to 10 show a different embodiment of the present application, showing an example in which the shape of the arm portion 3e of the core 2e is different. The magnetic flux φ when the short-circuit ring 8e is displaced by changing the thickness of the arm portion 3e along its longitudinal direction and sequentially changing the distance between the facing surfaces of the arm portion 3e and the arm portion 4e.
10 can be changed substantially linearly as shown in FIG. 10, and as a result, the inductance of the detection coil 7e is changed substantially linearly with respect to the stroke x, and the change of the output voltage is made linear with respect to the stroke. be able to. Figure 8
Corresponds to FIG. 1, and FIGS. 9A and 9B correspond to FIGS. 3 and 4, respectively. Further, the parts which are considered to be the same or equivalent in structure to those in the previous figure in terms of function are denoted by the same reference numerals as those in the previous figure and the letter e is added to omit duplicate description.

[0016]

As described above, according to the present invention, when the short-circuit ring 8 is displaced along the arm portion 3, the inductance of the detection coil 7 changes due to the displacement, so that the mechanical structure of the short-circuit ring 8 is increased. There is an effect that the displacement can be detected in the form of an electric signal.

Moreover, since the detection coil 7 is arranged along with the arm portion 4, the stroke x of displacement of the short-circuit ring 8 can be made large without taking the presence of the coil 7 into consideration, and therefore the displacement There is an effect that a relatively large detectable stroke can be obtained with respect to the entire length of the detector 1.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a displacement detector.

FIG. 2 is a perspective view of a displacement detector.

FIG. 3 is a vertical sectional view showing an operating state of the displacement detector.

FIG. 4 is a vertical cross-sectional view showing different operation states of the displacement detector.

FIG. 5 is a graph showing the relationship between stroke, magnetic flux and inductance.

6 (A) and 6 (B) are views showing a usage example of the displacement detector.

7A and 7B are views showing different usage examples of the displacement detector.

FIG. 8 is a vertical sectional view showing another example of the displacement detector.

9A and 9B are vertical cross-sectional views showing an operating state of the displacement detector of FIG.

10 is a graph showing the relationship between the stroke and the magnetic flux and inductance of the displacement detector of FIG.

[Explanation of symbols]

 2 cores 3 and 4 arms 7 detection coil 8 short-circuit ring

Claims (1)

[Claims] 1. A core having a pair of arm portions is provided with a detection coil for giving magnetic fluxes having opposite polarities to the both arm portions on one surface facing the other arm portion. A short circuit ring made of a good conductive material is provided around at least one of the arm portions so as to block the passage of magnetic flux in the arm portion, and the short circuit ring extends along the arm portion. A displacement detector characterized by being configured to be displaceable in any direction.