JPH01265112A - Noncontact displacement sensor - Google Patents

Abstract

PURPOSE:To detect displacement with low power and high accuracy by setting the end surface shape of at least one of leg parts of an iron core so that the rate of variation in its opposition area to a movable body accompanying the displacement of the movable body is different. CONSTITUTION:When a magnetic circuit is viewed from the center leg part 13 of the iron core 11, said circuit 11 passes the movable body 20 across a slight gap and returns to the center leg part 13 through leg parts 12 and 14 on both sides. When the movable body 20 is displaced to either side of an arrow A, both leg parts 12 and 14 face the movable body 20 and its area varies according to the quantity of the displacement. Consequently, the quantities of magnetic flux passing through a closed magnetic path C passing through the leg part 14 increases at the time of the displacement and that of a close magnetic path B passing through the leg part 12 decreases; and variation in the quantity of magnetic flux is outputted between detection terminals (a) and (b) as the sum of the outputs of detection coils wound around the leg parts 12 and 14 and the polarity and value of the output are proportional to the direction and value of the displacement of the movable body 20.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a non-contact displacement sensor that detects displacement of a movable body.

(Prior Art) A differential transformer is a displacement sensor that magnetically detects the amount and direction of displacement of an object. To explain its configuration and detection principle with reference to FIGS. 4 and 5, an excitation coil 2 and a detection coil 3 are respectively wound around a common bobbin 1 to form two air-core transformers 4 and 5. A short cylindrical iron piece 6 is housed therein so as to be movable in the axial direction, and the object to be measured 7 is connected to one end of the iron piece 6 via a rod-shaped connecting member 8. Then, as shown in FIG. 5, two exciting coils 2a,
2b are connected in series, and the two detection coils 3a and 3b are connected in anti-series, and when the object to be measured 7 is not displaced,
The position of the iron piece 6 is adjusted so that the induced electromotive force generated in the two detection coils 3a and 3b cancel each other out and no voltage is generated between the output terminals a and b of the detection coil 3. When the object to be measured 7 is displaced, for example, in the direction shown by the arrow in FIG. A difference occurs between the voltages generated at the terminals 3b, and a voltage corresponding to the difference value appears between the output terminals a and b. Therefore, the amount and direction of displacement of the object to be measured 7 can be detected based on the amount of change and polarity of the voltage between the terminals.

In addition, as another displacement sensor, the amount of change in the inductance of an iron piece as the iron piece moves in and out of the air core of one air-core coil is measured, and the displacement of the iron piece as the object to be measured or the object to be measured connected to this iron piece is measured. There are some that seek.

(Problem to be Solved by the Invention) However, in all of the above displacement sensors, the magnetic path that causes a change in induced electromotive force or a change in inductance in the detection coil is an open magnetic path, and the magnetic resistance is small. Since the large air gap occupies a large area, there is a drawback that a large amount of power is required to improve detection accuracy.

In addition, when the object to be measured is a magnetic material, if you try to directly use it like the iron piece 6 to detect its displacement, it is necessary to use a magnetic material specifically designed for each object to be measured, corresponding to the size of the object to be measured. It was necessary to create a differential transformer or a detection coil with a size of

The present invention has been made in view of the above circumstances, and therefore, a first object of the present invention is to provide a non-contact displacement sensor that can perform highly accurate detection with lower power than conventional sensors. be.

A second object of the present invention is to provide a non-contact displacement sensor that can directly detect an object to be measured, which is a magnetic material, without having to be modified to suit its size.

[Structure of the Invention] (Means for Solving the Problems) A non-contact displacement sensor according to the present invention has an iron core that forms a closed magnetic path in cooperation with a movable body made of a magnetic material whose displacement is detected. This iron core has a plurality of legs whose tips face the movable body with a predetermined gap, and the end face shape of at least one of the legs is formed so that the end face of the leg and the movable body meet. The feature is that the facing area is set to change at a rate different from the amount of displacement of the movable body, and the iron core is wound with a coil that produces an electrical characteristic value that changes depending on the change in the magnetic flux passing through the closed magnetic path. have

(Function) The non-contact displacement sensor according to the present invention has an end face shape of at least one of the plurality of legs of the iron core such that the rate of change in the area facing the movable body as the movable body is displaced is different. Therefore, when the movable body is displaced, the magnetic flux passing through the closed magnetic path changes. By detecting changes in this magnetic flux as changes in electrical characteristic values such as voltage, current, and inductance using a coil wound around the iron core, the amount or direction of displacement of the movable body can be detected.

Unlike conventional displacement sensors, which have an open magnetic path, this non-contact displacement sensor forms a closed magnetic path through the cooperation of the iron core and the movable body, eliminating leakage of magnetic flux. The power supply required for operation is small. Furthermore, if the object to be measured is a magnetic material, the amount of displacement can be detected by directly using it as a movable object even if its size varies.

(Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

11 is an iron core, which is E-shaped as a whole and 3
It has two legs 12, 13 and 14. The lower end surface 12a of the leg portion 12 on one end side (the right end side in FIG. 1) forms a right triangle, and a triangular slope 12c whose base is the hypotenuse side 12b of this triangle is formed on the side surface of the leg portion 12. ing. The leg 14 at the other end (the left end in FIG. 1) has a right triangle shape that is inversely symmetrical to the leg 12, and the oblique side 14b of the lower end surface 14a is parallel to the oblique side 12b of the leg 12. It has become. The lower end surface of the central leg portion 13 is rectangular. An excitation coil 15 is wound around this central leg portion 13, and this excitation coil 15 is connected to a DC power source 16 to excite the iron core 11. 17
18 is a first detection coil wound around the leg 12 at one end;
is a second detection coil wound around the leg portion 14 on the other end side, and the rain detection filters 17 and 18 are connected in anti-series as shown in FIG. A and b are detection terminals for the induced voltage generated in this detection circuit 19. Reference numeral 20 denotes a movable body made of a magnetic material as an object to be measured, which is made of, for example, a square iron plate. The upper surface of this movable body 20 is connected to each end surface 12 of each leg portion 12, 13 and 14 of the iron core 11.
a, 13a, and 14a, respectively, facing each other with a predetermined gap, and in the normal position (hereinafter referred to as the original position), one end edge 20a of the movable body 20 is connected to each of the legs 12, 13, and 14a.
4 (Fig. 1, Fig. 2).
(shown as a solid line in the figure).

In this case, the movable body 20 placed at such an original position is
It is displaced in the front-rear direction indicated by arrow A in the figure, that is, in the direction perpendicular to the end edge 20a.

Next, the operation of the second configuration will be explained. If the current flowing through the excitation coil 15 is alternating current, it is better to take measures such as changing the ratio of the number of windings in the detection coils 17 and 18 so that the value that cancels out each other's output becomes zero. It's easy. Here, excitation by direct current will be explained. When viewed from the central leg 13 of the iron core 11, the magnetic circuit passes through the movable body 20 through a large gap, passes through the legs 12.14 on both sides, and returns to the central leg 13. are shown as closed magnetic circuits B and C by two-dot chain lines in FIG.

These magnetic circuits B and C have a small gap and are almost closed, so their magnetic resistance is small.

Now, when the movable body 20 is displaced in either direction of the arrow A, the area of each leg portion 12.14 facing the movable body 2° increases or decreases in accordance with the amount of displacement of the movable body 2o. Since the rate of increase when the movable body 20 is displaced forward with respect to the cross-sectional area when the displacement is zero is larger for the leg portions 14 than for the leg portions 12,
The magnetic resistance relatively decreases in the closed magnetic path C passing through the legs 14, and increases in the closed magnetic path B passing through the legs 12.

As a result, the amount of magnetic flux that passes through each of the closed magnetic paths B and C before and after the displacement increases in the closed magnetic path C that passes through the legs 14, and conversely decreases in the closed magnetic path B that passes through the legs 12. The change is output between the detection terminals a and b as a superimposed output (in this example, a difference) of the respective outputs of the detection coils 17 and 18 wound around the legs R12 and 14, and the polarity and value of this output are determined by the movable body. It is proportional to the displacement direction and displacement value of 2o.

In this way, the magnetic path that generates the voltage between terminals a and b based on the electromagnetic induction phenomenon is different from the conventional one, which is an open magnetic path. Since it is composed of two closed magnetic circuits B and C formed by the cooperation of the two, magnetic leakage in the magnetic circuit is reduced to an incomparably low level compared to conventional magnetic circuits. Therefore, the amount of electric power (power of the power supply) passed through the excitation coil 15 to generate a required level of potential between the terminals a and b can be considerably smaller than in the past, and the device can be made more compact. Furthermore, if the object to be measured is a magnetic material, the object to be measured itself can be used as a movable object, and detection can be performed using the same displacement sensor regardless of the size of the object. I can do it.

Next, a second embodiment of the present invention will be described with reference to FIG.

Reference numeral 21 denotes a substantially U-shaped iron core, and one of the two legs in this case, one leg 22, has a lower end surface 22a in the form of a right triangle, and the side surface of the leg 22 has a shape of this triangle. A triangular slope 22c whose base is the hypotenuse 22b is formed. The other leg portion 23 has a prismatic shape with a rectangular lower end surface. 24 is a detection coil wound around a yoke 25 bridging the two opposing legs 22 and 23, and C and d are its terminals. 26 is a movable body made of magnetic material, which is made of a square iron plate. The upper surface of the movable body 26 faces the end surfaces 22a and 23a of the legs 22 and 23 with a predetermined gap therebetween. In the normal position (original position) where the movable body 26 is not displaced, one end edge 26a of the movable body 26 is connected to the base 22a of the end surface 22a of one leg 22.
d and the apex, and the end face 23a of the other leg 23 is disposed so that its entire surface faces the movable body 26. In this case, the end edge 26a of the movable body 26 is displaced in the direction orthogonal to the bottom side 22d, that is, in the front-rear direction indicated by arrow A in the figure. Under such an arrangement, the iron core 21 and the movable body 26 cooperate to form a closed magnetic path as shown by the two-dot chain line in the figure.

Next, the operation of the above configuration will be explained.

When the movable body 26 is set at the above-mentioned original position and power is applied between the terminals c and d of the detection coil 24 via a bridge (not shown), this displacement sensor enters into use. When the movable body 26 is displaced in either the forward or backward direction indicated by the arrow A, the movable body 26 shown with diagonal lines in the figure, which is involved in increasing or decreasing the magnetic resistance of the closed magnetic path, The facing area E of the leg portion 22 with the end surface 22a changes at a rate different from the change of the movable body 26 (iLQ. Therefore,
The magnetic resistance of the closed magnetic path changes, and the inductance of the detection coil 24 increases or decreases at a rate that amplifies the amount of displacement of the movable body 26, and the displacement of the movable body 26 is determined based on the value of the current change occurring in the galvanometer of the bridge. amount can be detected with high accuracy. In this case, the magnetic path for changing the inductance of the detection coil 24 is a closed magnetic path and there are few air gaps with large magnetic resistance, so less power is required to be applied to the detection coil 24, and the inductance of the movable body 26 is reduced. Since the change is made at a rate different from the displacement rate, detection accuracy can be significantly improved.

In the configuration shown in FIG. 3, an excitation coil may be wound around the other leg 23, and the amount of displacement of the movable body 26 may be detected from the degree of increase/decrease in the induced voltage generated in the detection coil 24. good.

Further, an excitation coil may be provided in place of the detection coil 24, and a constant voltage power source may be connected to the excitation coil, so that the amount of displacement of the movable body 26 may be detected from the degree of increase or decrease in the current value of the excitation circuit.

In each of the above embodiments, the end face shape of the leg whose area facing the movable body changes at a rate different from the amount of displacement of the movable body is, for example, a chevron shape such as an isosceles triangle or a hyperbolic shape. You can. By arbitrarily changing the angle of the slope of this chevron, the rate of change in the output level of the electrical characteristic value generated in the coil can be increased or decreased with respect to the amount of displacement of the movable body, thereby adjusting the detection accuracy of the displacement sensor. It can be carried out.

[Effects of the Invention] The non-contact displacement sensor according to the present invention has a plurality of legs, and forms a closed magnetic path by cooperating with a movable body placed opposite to each other with a predetermined gap between the end faces of each leg. and an iron core in which the shape of the end face of at least one leg is set such that the area facing the movable body changes at a rate different from the amount of displacement of the movable body; Since the configuration includes a coil that causes changes in electrical characteristic values such as voltage, current, and inductance due to changes in magnetic flux in the closed magnetic path, magnetic leakage in the magnetic path that detects the displacement of the movable body is significantly lower than in conventional methods. Unlike in the past, there are almost no more, and high-precision detection can be performed with less power supply.Moreover, if the object to be measured is a magnetic material, the object to be measured can be moved regardless of its size. It can be used as a body.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention, FIG. 1 is a perspective view, FIG. 2 is a bottom view, and FIG. 3 is a second embodiment of the invention. FIG. FIGS. 4 and 5 are a perspective view and a schematic explanatory view of a conventional example. In the figure, 11.21 is an iron core, 12, 13, 14°2'2 and 23 are legs, 15 is an excitation coil, 17.18 and 24 are detection coils, 20.26 is a movable body, 12
a, 13a, 14a, and 22a are end faces, respectively, and B, C, and D are closed magnetic circuits, respectively. Agent Patent Attorney Nobuaki Chika Ken Maru Figure 1

Claims (1)

[Claims] 1. A movable body made of a magnetic material that is subjected to displacement has a plurality of legs whose tips face each other with a predetermined gap, and cooperates with the movable body to form a closed magnetic path. An iron core whose end face shape of at least one of the legs is set such that the area facing the end face of the leg and the movable body changes at a rate different from the amount of displacement of the movable body, and a winding around the iron core. A non-contact displacement sensor comprising: a coil that is mounted on a coil and produces an electrical characteristic value that changes depending on a change in magnetic flux passing through the closed magnetic path.