JPH04301703A - Capacitance type displacement measuring device - Google Patents

Abstract

PURPOSE:To make such an arrangemennt that a capacitance type displacement measuring device may not be easily affected by changes of the external environment, such as looseness due to vibrations, moisture or the like. CONSTITUTION:There are provided in a capasitance type displacement measuring device a cylinder 11, a piston 12 which moves in the cylinder, a liquid storing means 14 which fills a high dielectric substance of liquid type within a space formed by the cylinder and the piston, and electrodes 24, 25 which are formed in the cylinder and positioned opposite to each other.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement measuring device for measuring the displacement of an object using capacitance.

0002

2. Description of the Related Art Conventionally, there have been a number of measuring devices that utilize capacitance to measure the displacement of an object. among them,
This is a device that uses a piston rod and a cylinder to measure the displacement of the piston rod. Electrodes are provided on each of the piston rod and cylinder, and the capacitance between the piston rod and cylinder is measured. A measuring device designed to measure the relative displacement of is disclosed in Japanese Unexamined Patent Publication No. 14001/1983. In addition, by applying this technology, the part that forms the capacitor between the piston rod and the cylinder is always filled with a dielectric material made of liquid, so that relative displacement can always be detected with high precision. It is disclosed in Kaisho 62-14002.

0003

[Problems to be Solved by the Invention] When a piston rod and a cylinder are used as electrodes, if there is play between the piston rod and the cylinder, it will be detected as a capacitance change even though the displacement itself does not change. Also, there is a part where the piston rod protrudes from the cylinder where the piston rod and cylinder do not overlap, but this protruding piston rod part causes a change in capacity due to moisture or proximity to other metals. , which reduces the detection accuracy of the measuring device.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to make a displacement measuring device using capacitance less susceptible to changes in the external environment such as backlash due to vibration and moisture.

[0005]

[Means for Solving the Problems] In order to solve the above problems, the present invention includes a cylinder, a piston moving within the cylinder, and a fluid having a high dielectric constant in a space formed by the cylinder and the piston. The cylinder includes a reservoir means for filling the cylinder with a dielectric material, and a pair of electrodes formed on the cylinder.

[0006]

According to the present invention, when the piston or cylinder moves to the side that increases the volume of the space formed by the piston and cylinder, the dielectric material flows into the space by the liquid reservoir means. Further, when the piston or cylinder moves to the side that reduces the volume of the space formed by the piston and cylinder, the dielectric material flows out from the space by the liquid reservoir means. Therefore, displacement can be measured because movement of the piston or cylinder changes the amount of dielectric between the electrodes, which changes the capacitance of the capacitor formed by the electrodes.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, and a displacement detecting device 10 includes a cylinder 11, a piston 13, and a reservoir 14 serving as a liquid reservoir. The piston 13 is connected to the piston rod 12 and moves within the cylinder 11 in accordance with the movement of the piston rod 12. A space 17 in the storage tank 14 is connected to a chamber 3 formed by one surface of the cylinder 11 and the piston 13 in the cylinder 11 via a connecting portion 26.
It is connected to 3.

The storage tank 14 and the chamber 33 are filled with a dielectric material 18 having a high relative dielectric constant. The dielectric material having a high relative dielectric constant includes synthetic oil, mineral oil, etc., and in this embodiment, silicone oil is used. The storage tank 14 is provided with an air hole 16. Therefore, when the piston moves upward in the drawing, the dielectric 18 in the chamber 33 is sent to the reservoir 14 via the connecting portion 26. Further, when the piston moves downward in the figure, the dielectric 18 in the reservoir 1 is sent to the chamber 33 via the connecting portion 26.

As shown in FIG.
It has two electrodes 24, 25, insulators 36, 37, and a holding part 39 for holding these, and the internal space is coated with a coating material 38. The piston 13 moves while contacting the surface of the coating material 38. Since the amount of dielectric between the electrodes 24, 25 corresponds to the displacement of the piston, the capacitance of the capacitor formed by the electrodes 24, 25 changes in response to the displacement of the piston.

Two electrodes 24 and 25 inside the cylinder are electrically connected to a circuit section 27 via lead wires 31 and 32.

The circuit section 27 is a section for detecting the capacitance of a capacitor consisting of electrodes 24 and 25. There are many conventional methods for detecting capacitance, but in this example, the method shown in FIG.
A method is used in which a transmission circuit 28 using a capacitor made up of electrodes 24 and 25 is created using the electric circuit shown in FIG. 2, and the transmission frequency is measured. Here, the transmission frequency is F
/V(Frequency-Voltage; Frequency-
A voltage conversion circuit 29 converts the voltage into a voltage, and an amplifier circuit 30 amplifies the voltage. When the circuit diagram shown in FIG. 3 is used, the relationship between the displacement and the output voltage can be adjusted to the relationship shown in FIG. 4, so that the displacement can be measured as a voltage.

A chamber 34 is formed by the other surface of the cylinder 11 and the piston 13, and this space is filled with the bushing packing 2.
1, the possibility of moisture entering the chamber 34 is low.

FIG. 5 shows an example in which the first embodiment shown in FIG. 1 is applied to a vehicle suspension. The cylinder 11 is connected to the vehicle body side, and the piston rod 12 is connected to the wheel side via a ball joint 20. This allows the relative distance between the vehicle body and the wheels to be measured.

FIG. 6 shows a second embodiment in which the chamber 34 is also filled with a dielectric material. The chamber 33 is connected to the first reservoir 14 via the connecting tube 22. The chamber 34 is the connecting tube 23
It is connected to the second storage tank 15 via. Storage tank 1
The dielectric constant of the dielectric material 18 filled in the storage tank 15 is set lower than that of the dielectric material 19 filled in the storage tank 15. Therefore, as shown in the figure, when the piston 13 rises, the amount of the dielectric material 18 with a high relative permittivity increases in the cylinder 11, so the capacitance increases, and when the piston 13 descends, the relative permittivity inside the cylinder 11 increases. Dielectric with low index 1
Since the amount of 9 increases, the capacitance decreases. in this way,
The capacitance of the capacitor formed by the electrodes 24, 25 changes in response to the displacement of the piston. In this example, since the inside of the cylinder is always filled with dielectric material, the capacitance generated other than between the electrodes is at a negligible level. Further, even if some moisture enters the chambers 33 and 34, the change in capacitance does not affect detection accuracy to the extent that it deteriorates.

FIG. 7 shows a third embodiment in which the embodiment of FIG. 6 is directly applied to a vehicle suspension. A piston rod 12 is fixed to the vehicle body side, and a cylinder 11 is fixed to the wheel side, thereby forming a shock absorber 35. This configuration only adds electrodes 24, 25 and a circuit section 27 to the conventional shock absorber 35, and changes the fluid used to a dielectric, so there is no need to increase the size of the shock absorber 35 itself. Can be applied.

[0017]

Effects of the Invention In the present invention, the electrodes are fixed and there is no play in the electrodes, and play between the piston rod and the cylinder does not affect the measured value, so the detection accuracy is improved.

Furthermore, even if some moisture gets on the electrode, the capacitance being detected is much larger, so it is less affected. Furthermore, since the capacitance between the external metal and the electrode is smaller than the detected capacitance, the influence of the capacitance between the external metal and the electrode is reduced, improving detection accuracy.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a first embodiment.

FIG. 2 is a sectional view taken along line AA in FIG. 1;

3 is a circuit diagram of the circuit section 20 of FIG. 1. FIG.

FIG. 4 is a graph for explaining the first example.

FIG. 5 is an explanatory diagram of an example in which the first embodiment is used in a vehicle suspension.

FIG. 6 is an explanatory diagram of a second embodiment.

FIG. 7 is an explanatory diagram of a third embodiment.

[Explanation of symbols]

10 Displacement detection device 11 Cylinder 12 Piston rod 13 Piston 14,15 Storage tank 16 Air hole 17 Space 18, 19 Dielectric 20 Ball joint 21 Bush packing 22, 23 Connection tube 24, 25 Electrode 26 Connecting part 27 Circuit section 28 Transmission circuit 29 F/V conversion circuit 30 Amplifier circuit 31, 32 Lead wire Room 33, 34 35 Shock absorber 36, 37 Insulator 38 Coating material 39 Holding part

Claims (1)

[Claims] 1. A cylinder, a piston that moves within the cylinder, a liquid reservoir means for filling a space formed by the cylinder and the piston with a fluid-like dielectric material having a high relative dielectric constant, and a liquid reservoir formed in the cylinder. A displacement measurement device that uses capacitance and has a pair of electrodes.