JPS6214002A - Electrostatic capacity type cylinder displacement gage - Google Patents

Abstract

PURPOSE:To enable the relative positions of an inner cylinder and a rod to be always detected with a high accuracy by always filling a portion wherein an inner cylinder and a rod constitute a capacitor with a dielectric. CONSTITUTION:A conductive inner cylinder 32 is provided in an outer cylinder 31 and a conductive rod 33 that is inserted into the inner cylinder 32 for displacement is provided. A storage tank 41 is provided on the top end of the outer cylinder 31 above an insulating member 35. The cylinders 31 and 32 and the storage tank 41 contain an oil 48 and the cylinders are adapted to be always filled with the oil 48 regardless of the relative displacement of the rod 33. A coiled spring 47 is provided between a ring-shaped member and the insulating member 35. The spring 47 absorbs both an error in machining dimensions and the expansion and contraction due to a temperature change of the inner cylinder 32 in the direction of the relative displacement of the rod 33, always positioning the rod 33 to a predetermined position in the inner cylinder 32. Thus, the electrostatic capacities of the inner cylinder 32 and the rod 33 constituting a capacitor can be always stably measured and therefore the relative positions thereof can be detected with a high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a capacitive cylinder displacement meter suitable for use, for example, in detecting changes in vehicle height due to changes in the load of an automobile.

(Prior Art) Conventionally, as a device for detecting a change in vehicle height due to a load displacement of an automobile, a device that detects changes in expansion and contraction of a shock absorber is disclosed in, for example, Utility Model Application No. 57-88609 and No. 57-177113. (disclosed in the official gazette).

In these conventional shock absorbers that detect changes in vehicle height, a coil is embedded over the entire stroke detection area inside a cover made of non-conductive and non-magnetic material, separate from the shock absorber body. The displacement of the piston rod relative to the cylinder tube is detected by connecting it to an LC oscillator and detecting changes in the inductance of the coil. However, burying the coil in this way increases the number of parts and assembly man-hours, resulting in high costs. This has the disadvantage that changes in inductance cannot be detected accurately and stably due to the influence of noise from the sensor, resulting in low displacement detection accuracy.

In order to eliminate such drawbacks, the applicant of the present application filed a patent application filed in 1973.
In No. 9-107685, a shock absorber as shown in FIG. 6 was proposed. This shock absorber is of a so-called twin-tube type in which oil 3 is housed in tubes of different diameters, an inner cylinder 1 and an outer cylinder 2. is electrically insulated to form a capacitor, and by detecting the capacitance of this capacitor, the inner cylinder l and piston rod 4 are
It is designed to detect the relative position with respect to the

In FIG. 6, the inner cylinder 1 and the piston rod 4 are insulated by an insulating member 7 interposed between the piston 5 and the sliding ring 6 and an insulating member 9 interposed between the rod guide 8 and the piston rod 4. ing. In addition, the inner cylinder 1 and the outer cylinder 2 have a chamber 11 formed in the upper part by a rod guide 8 and an oil seal 10 provided between the outer cylinder 2 and the bitten rod 4 above it, and a chamber 11 formed in the rod guide 8. It communicates via a bypass 12, and a lower odor communicates via an orifice 13 and a plate 14. The detection circuit unit 15 is attached to the upper end of the shock absorber, and includes a CR oscillation circuit that uses the capacitance between the inner cylinder 1 and the piston rod 4 as a parameter, and a detection circuit unit 15 that divides the oscillation frequency of the OCR oscillation circuit. The oscillation frequency of the CR oscillation circuit is determined based on the capacitance that changes as the piston 5 moves up and down in the inner cylinder 1 as the load changes. is detected, and the relative position between the inner cylinder 1 and the piston rod 4 is detected, and furthermore, a change in vehicle height is detected based on the relative position.

In such a shock absorber, a capacitor is formed by electrically insulating between the inner cylinder 1 and the piston rod 4, which are originally provided in the shock absorber, and by detecting the capacitance of this capacitor, the inner cylinder l Since the structure is configured to detect the relative position between the piston rod 4 and the piston rod 4, the number of parts and the number of assembly steps are reduced, and costs can be significantly reduced. Furthermore, since it detects capacitance, it is less affected by external noise than conventional methods that detect coil inductance, and the amount of displacement can be detected more accurately. Furthermore, unlike the conventional method where the coil is provided separately, there are no restrictions on mounting the sensing part, and it can be applied to shock absorbers of any structure as long as it is well-shaped, increasing the range of application. It also has the advantage of significantly expanding.

(Problems to be solved by the invention) However, according to various experiments conducted by the present inventors, the sixth
It has been found that the shock absorber shown in the figure has points to be improved as described below.

That is, the inner cylinder 1 and the outer cylinder 2 have a chamber 1 in the upper part.
1 and a bypass 12, and the lower part communicates via an orifice 13 and a plate 14, so when the piston rod 4 moves upward, the air and oil 3 in the inner cylinder 1 are It passes through the gap between the piston rod 4 and the rod guide 8, and enters the chamber 11 and the bypass 12.
When the piston rod 4 moves downward, a bypass 12 and a chamber 11 are formed in the upper part of the inner cylinder 1.
Only the air that was extracted during the upward movement process enters,
The oil 3 extracted from the inner cylinder 1 passes through the plate 14 and the orifice 13 while the piston rod 4 is stationary, and then flows into the inner cylinder 1.
The liquid level of the oil 3 in the inner cylinder 1 and the outer cylinder 2 becomes the same level.

In this way, the amount of oil 3 and the amount of air in the inner cylinder l are
The inner cylinder 1 changes due to the movement of the piston rod 4.
There is a problem in that the dielectric constant of the portion forming the capacitor, where the piston rod 4 and the piston rod 4 face each other, changes due to the intrusion of air, resulting in poor accuracy.

The present invention has been made in view of this problem, and is designed to ensure that at least the part between the cylinder and the rod that constitutes the capacitor is always filled with a dielectric material made of liquid, regardless of the relative movement of the cylinder and rod. It is an object of the present invention to provide a capacitive cylinder displacement meter that is appropriately configured and arranged so that relative positions can always be detected with high accuracy.

(Means for Solving the Problems) The capacitive cylinder displacement meter of the present invention includes a cylinder, a rod that moves relatively within the cylinder, and at least a portion where the cylinder and the rod face each other are made of liquid. a dielectric storage tank connected to the cylinder and provided above the part so as to be constantly filled with the dielectric, the cylinder and the rod being respectively used as electrodes;
The present invention is characterized in that the relative position between the cylinder and the rod is detected by measuring the capacitance formed between these electrodes.

FIG. 1 shows a principle diagram of a capacitive cylinder displacement meter according to the present invention. In the present invention, a rod 22 is provided within the cylinder 21 so as to be relatively movable. cylinder 21
An insulating oil seal 23 is provided at the lower end of the rod 22 for sealing so that the rod 22 can slide in a liquid-tight manner, and a storage tank 24 is provided at the upper end so as to communicate with the inside of the cylinder 21. Also,
An insulating guide member 25 is provided at the upper end of the rod 22 that enters into the cylinder 21 so as to be able to slide on the inner peripheral surface of the cylinder 21.
5, two bypasses are provided to connect the upper and lower parts of the cylinder 21. In the present invention, the cylinder 2
1 and a storage tank 24 containing a dielectric substance made of liquid, such as oil 27, and measuring the capacitance formed between the cylinder 21 and the rod 22 using the cylinder 21 and the rod 22 as electrodes. Detects the relative position with. Here, the amount of oil 27 is such that at least the portion where these face each other is always filled with oil 27, regardless of the relative movement of cylinder 21 and rod 22.

Note that the storage tank 24 may be provided above the portion where the cylinder 21 and the rod 22 face each other to form a capacitor. Therefore, when the cylinder 21 and the rod 22 move relatively in the horizontal direction, the capacitor For example, it may be attached to the circumferential surface of the cylinder 21 above the portion forming the cylinder 21.

(Function) In FIG. 1, the cylinder 21 and the rod 22 move in the direction in which the amount of penetration of the rod 22 into the cylinder 21 increases.
When the guide member 2 moves relatively, the guide member 2
The oil 27 in the upper part of the guide member 25 flows into the lower part through the bypass 26, and the lower part of the guide member 25, that is, the space between the rod 22 and the cylinder 21 that constitutes the condenser, is always filled with oil 27, and eventually becomes a storage tank. The liquid level of the oil 27 in the rod 24 rises by an amount corresponding to the increased volume of the rod 22 due to the intrusion. Moreover, when these move relatively in a direction in which the amount of penetration of the rod 22 into the cylinder 21 decreases, the oil 27 at the lower part of the guide member 25 is pushed out to the upper part via the bypass 26, and the lower part always oil 27
Eventually, the liquid level of the oil 27 in the storage tank 24 will drop by an amount corresponding to the volume of the rod 22 whose amount has decreased due to movement. Therefore, the portion where the cylinder 21 and rod 22 that constitute the capacitor face each other is always filled with oil 27 regardless of their relative movement.

(Embodiment) FIG. 2 shows an embodiment of the present invention, in which a shock absorber for a suspension of an automobile is constructed separately and exclusively used as a displacement meter for detecting displacement in an approximately vertical direction. The outer cylinder 31 is made of a conductive material with excellent corrosion resistance, mechanical strength, and heat resistance, such as a plastic with a conductivity of 10° to 10' Ω-am, which is made of a base of 6-nylon mixed with brass pieces. This outer cylinder 31 is formed with a V of 2 mm or more.
A conductive (mainly made of metal) inner cylinder 32 is provided therein, and a conductive rod 33 that enters the inner cylinder 32 and moves relative thereto is provided.

The inner cylinder 32 is fixed at the lower end within the outer cylinder 31 by an insulating guide 34, and the upper end is coaxially insulated from each other within the outer cylinder 31 by interposing an insulating member 35 between the inner cylinder 32 and the outer cylinder 31. Extend. Further, the rod 33 is slidably held by a guide 34 so as to be able to move coaxially within the inner cylinder 32, and its tip end that enters the inner cylinder 32 slides on the inner circumferential surface of the inner cylinder 32. An insulating piston 36 is provided so as to be movable,
The guide 34 and the piston 36 are configured to allow movement relative to the inner cylinder 32 while being insulated from each other.

At the lower end of the outer cylinder 31, the outer cylinder 3 is located below the guide 34.
A seal 37 is provided between the seal 1 and the rod 33, a cover 38 is provided below the seal 37, and a storage tank 41 is provided above the insulating member 35 at the upper end.

The storage tank 41 includes a bottom portion 41a formed integrally with the outer cylinder 31, and a container portion 4 made of the same material as the outer cylinder 31, which is integrally welded to the bottom portion 41a and is attached to the chassis of the vehicle.
1b. As shown in a partial plan view in FIG. 3 and a sectional view taken along line I-1 in FIG. 3A in FIG. Projections 44 are formed radially on the bottom surface 43 toward the bottom surface 43, and openings 42 are formed at the tips of these projections 44 above the bottom surface 43.
A ring-shaped member 45 is formed concentrically with the arc-shaped outlet 46a and a circular outlet 46b.

Further, in this embodiment, a coil spring 47 is provided between the ring-shaped member 45 and the insulating member 35, and this presses and biases the inner cylinder 32 toward the guide 34 side, thereby pushing the inner cylinder 32 in the direction of relative movement of the rod 33. The structure is such that the inner tube 33 is always positioned at a predetermined position within the outer tube 31 by absorbing expansion and contraction due to machining dimensional errors and temperature changes.

In this embodiment, oil 48 is contained in the outer cylinder 31 and the inner cylinder 32, respectively, and the relative positions thereof are detected by measuring the capacitance formed between the inner cylinder 32 and the rod 33 as electrodes. However, in order to ensure that the space between the inner cylinder 32 and the rod 33 is always filled with oil 48 regardless of their relative movement, the oil 48 is also stored in the storage tank 41 and the storage tank 41 and the inner cylinder 32 are connected to each other. communicate.

Therefore, as shown in FIG. 3B, the insulating member 35 has
Opening 35a for communicating between inner cylinder 32 and storage tank 41
form. In addition, the outer cylinder 3L, the inner cylinder 32 and the storage tank 41
The amount of oil 48 accommodated in the storage tank 41 is such that even when the rod 33 protrudes most vertically from the inner cylinder 32, the amount of oil 48 stored in the storage tank 41 is determined.
is the amount that remains. In addition, in order to prevent reaction forces caused by the relative movement of the inner cylinder 32 and the rod 33, damping force of the oil 48, etc. from occurring, air is mixed into the inner cylinder 32 due to the generation of these forces. In order to prevent
Bypass 35 for communicating the upper and lower chambers in 1
A bypass 3 is formed in the guide 34 as well.
4a, and the piston 36 is also formed with a through hole 36a for communicating the upper and lower chambers in the inner cylinder 32, so that the oil 48
be configured so that it flows smoothly.

On the other hand, at the end of the rod 33 protruding from the inner cylinder 32, a mounting screw 49 is movably provided for mounting it on the axle of a vehicle, etc., and the rod end and the lower end of the outer cylinder 31 In order to ensure that the outer cylinder 31 and the rod 33 are at the same potential to prevent the formation of undesired stray capacitance, and at the same time, to prevent the rod 33 from being damaged by stones etc. in consideration of the usage environment where it is installed under the floor of the vehicle. A conductive dust boot 50 is provided to prevent damage. This dust boot 50 is
For example, it is formed into a bellows structure using a material with an electrical conductivity of about 10° to 101 Ω-am, which is made by dispersing carbon black in a base resin made by polymerizing styrene-butadiene rubber and ethylene. Constructed so that it can expand and contract.

Further, the outer cylinder 31 is provided with a detection circuit 51 that detects the capacitance of the capacitor constituted by the inner cylinder 32 and the rod 33 and outputs a required signal corresponding to their relative positions. In order to prevent the formation of undesired stray capacitance, this detection circuit 51 is connected to the inner cylinder 32 which forms a desired capacitance.
The printed circuit board 51a is mounted at a position close to the portion where the rod 33 and the rod 33 face each other, and the CR oscillation is performed using the electrostatic capacitance between the inner cylinder 32 and the rod 33 as a parameter, as described in the sixth rIA. A signal processing circuit for dividing the oscillation frequency of the CR oscillation circuit and outputting a low frequency pulse signal is provided.

In this embodiment, the rod 33 as one electrode forming the required capacitance is connected to the dust boot 50 and the outer cylinder 31.
However, in order to electrically connect this outer cylinder 31 and the detection circuit 51, one electrode wiring of the niblint board 51a is brought into contact with the conductive pin 52. 52 is attached to the receiver 31a integrally molded on the outer cylinder 31, thereby electrically connecting the outer cylinder and therefore the rod 33 to one electrode wiring of the detection circuit 51, and at the same time connecting the printed circuit board 51a and the detection circuit 51. is fixed to the outer cylinder 31. In addition, the inner tube 32 as the other electrode that forms the required capacitance is connected to the other electrode wiring of the printed circuit board 51a via an electrode rod 53 extending through the outer tube 31 and the printed circuit board 51a. Connecting. For this reason; the outer cylinder 31 has a hole 31 into which the electrode rod 53 loosely fits.
b, and a case 31C that projects so as to surround this hole 31b is formed integrally with the outer cylinder 31. Further, an insulating seal rubber 54 is hot-glued to the electrode rod 53 to form an integral structure, and this seal rubber 54 is attached to an insulating collar 55.
is pressed and held within the case 31C. Thereby, the tip of the electrode rod 53 is pressed into contact with the outer peripheral surface of the inner cylinder 32 without contacting the outer cylinder 31, and oil leakage from the hole 31b is prevented. Further, a cord 56 is connected to the other electrode wiring and the signal output terminal connected to the electrode rod 53 of the printed circuit board 51a, and after the detection circuit 51 is mounted on the outer cylinder 31 in this way, the detection circuit 51
The mounting portion, including between each component, is molded with an insulating material.

In this embodiment, the container portion 41b of the storage tank 41 and the rod 33 are attached to, for example, the chassis and axle of an automobile, respectively, so that the rod 33 extends substantially vertically, and the detection circuit 51 is connected to the chassis and the electrode rod 53. The required power is supplied from the battery mounted on the vehicle through the connected cord 56, and the inner cylinder 32 is thereby obtained from the cord 56 connected to the signal output terminal of the detection circuit 51.
The vehicle height and its changes are detected based on the relative position information between the rod 33 and the vehicle height.

In the above-mentioned configuration, the 0 and 7 doors 33 relative to the inner cylinder 32
When these move relatively in a direction in which the amount of intrusion increases, the outer cylinder 31, inner cylinder 32, and storage tank 4
The oil 48 in the piston 36 flows into the inner cylinder 32 at the bottom of the piston 36.
Oil 48 flows into the interior through the through hole 36a formed in the piston 36, the bypass 34a formed in the guide 34, and the gap between the guide 34 and the rod 33, and flows into the inner cylinder 32 forming the lower part of the piston 36, that is, the condenser. rod 3
The space between the rod 33 and the rod 33 is always filled with oil 48, and eventually the liquid level of the oil 48 in the storage tank 41 rises by an amount corresponding to the increased volume of the rod 33 due to the intrusion. In addition, the inner cylinder 32
When these move relative to each other in a direction in which the intrusion l of the rod 33 decreases, the oil 48 at the bottom of the piston 36 flows through the through hole 36a, the gap between the guide 34 and the rod 33, and the bypass 34a. piston 36
The oil 48 is pushed out to the upper part of the oil 48 and the outer cylinder 31, and the lower part of the piston in the inner cylinder 33 is always filled with oil 48.
Rod 3 with oil 48 in 1 whose amount of penetration has decreased due to movement
The liquid level is replenished into the inner cylinder 32 by an amount corresponding to the volume of 3, and the liquid level is lowered. Therefore, the portion where the inner cylinder 32 and the rod 33 that constitute the capacitor face each other is always filled with oil 48 regardless of their relative movement.

Here, the inner diameter of the inner cylinder 32 is a, the outer diameter of the rod 33 is b,
When the penetration length of the rod 33 into the inner cylinder 32 is β, and the dielectric constant of the oil 48 is ε, the electrostatic field 1c of the capacitor composed of the inner cylinder 32 and the rod 33 is expressed by the following equation.

C= 2yr t: l/Aog (a/b) As is clear from the above equation, the capacitance C is the inner cylinder 32 of the rod 33.
Since it changes depending on the penetration length l, the electrostatic field 1c
By detecting the penetration length β of the rod 33, the relative position between the inner cylinder 32 and the rod 33 can be detected. Note that the dielectric constant of oil generally has a dependence on temperature with a negative coefficient, but this temperature dependence is due to the temperature characteristic of a part of the oscillation resistance of the CR oscillation circuit, which is opposite to the temperature dependence of the dielectric constant. It can be offset by having
This allows highly accurate detection to be performed at all times without being affected by temperature changes.

5A-D show other embodiments of the present invention, FIG. 5A is a sectional view, FIG. 5B is a plan view, and FIG. 5C is a left side view (for clarity, the storage tank is 74 external shape is not shown),
The fifth diagram represents a right side view.

In this embodiment, it is constructed exclusively for a displacement meter that detects displacement in a substantially horizontal direction, and similarly to the above-mentioned embodiment, it includes a conductive outer cylinder 61 and a conductive inner cylinder 62 mounted inside this outer cylinder 61.
and a conductive rod 63 that is provided so as to be able to enter into the inner cylinder 62.

The inner tube 62 is held at one end of the outer tube 61 via an insulating member 64, and at the other end is held at the other end of the outer tube 61 via an insulating guide 65, so that the inner tube 62 is held inside the outer tube 61. Extend coaxially. Further, the rod 63 is slidably held by a guide 65 so as to be able to move coaxially within the inner cylinder 62, and the tip portion that enters the inner cylinder 62 has an inner cylinder 63.
An insulating piston 66 is provided so as to be able to slide on the inner peripheral surface of the inner cylinder 62, and the guide 65 and the piston 66 are configured to be able to move relative to the inner cylinder 62 while being insulated from each other.

One end surface of the outer cylinder 61 is closed with a cover 67.
7 is provided with a metal fitting 68 for attachment. A seal 69 is provided between the other end of the outer cylinder 61 and the rod 63, and a cover 70 is provided on the other surface of the outer cylinder 61 through which the rod 63 passes.

A metal fitting 71 is provided at the end of the rod 63 protruding from the inner cylinder 62, and a conductive extensible metal fitting 71 is provided between the end and the other end of the outer cylinder 61, as in the embodiment described above. A dust boot 72 is provided.

In this embodiment, oil 73 is stored in the outer cylinder 61 and the inner cylinder 62, respectively, and the relative position in the horizontal direction is measured by measuring the capacitance formed between the inner cylinder 62 and the rod 63 as electrodes. is detected, but the inner cylinder 62 and rod 6
In order to ensure that the space between the outer cylinder 61 and the inner cylinder 3 is always filled with oil 73 regardless of their relative movement, the outer cylinder 61 and the inner cylinder 62 are communicated with each other, and the outer cylinder 61 above the inner cylinder 62 is provided with the oil 73. A storage tank 74 communicating with 61 and containing oil 73 is provided. Therefore, the outer cylinder 6 is attached to the insulating member 64 and the guide 65.
1 and the inner cylinder 62 through communication holes 64a and 6.
5a respectively.

In addition, a bypass 65b is formed in the guide 65 so that the oil 73 can smoothly flow according to the relative movement of the inner cylinder 62 and the rod 63, and a through hole 66 is formed in the piston 66.
form a. Here, the amount of oil 73 accommodated in the outer cylinder 61, inner cylinder 62, and storage tank 74 is such that the rod 63 is
The amount of oil 73 remains in the storage tank 74 even when the oil 73 protrudes the most in the horizontal direction.

Further, the outer cylinder 61 includes an inner cylinder 6, as in the above-mentioned embodiment.
A detection circuit 75 is molded to detect the capacitance of the capacitor constituted by the rod 63 and the rod 63, and output a necessary signal corresponding to their relative positions. In this embodiment, the detection circuit 75 and the inner cylinder 62 are connected via an electrode rod 76 and a conductive spring 77. For this purpose, as shown in detail in FIG. 5E, a cylindrical case 78 made of an insulating material is provided in communication with the outer cylinder 61. In addition, the electrode rod 76
A resin 79 is glued to the unit to form an integral structure, and the electrode n76
A spring 77 is attached to the tip of the electrode rod 76 and the resin 79 is pressed and held in the case 78 by the collar 80.
The spring 77 is brought into pressure contact with the outer circumferential surface of the inner cylinder 62 via. Note that an O-ring 81 is provided between the stepped portion 78a of the case 78 and the resin 79 to prevent oil leakage.

In this embodiment, as in the embodiments described above, the opposing portion of the inner cylinder 62 and rod 63 constituting the capacitor is always filled with oil 73 regardless of their relative movement.
Its relative position can always be detected with high precision. Therefore, it can be installed approximately horizontally between the chassis of a forklift and a drag rod or tie rod, for example, and used to detect and display the direction and angle of a steered wheel from its displacement.

Note that the present invention is not limited only to the embodiments described above, and numerous modifications and changes are possible. for example,
The capacitance of the capacitor consisting of the inner cylinder and rod is C
Detection is not limited to the R oscillation circuit, but can also be performed using other circuits such as an LC oscillation circuit.

Further, in the above-mentioned embodiments, a twin-tube type structure having an outer cylinder is used, but it is also possible to use a monochineve type structure without an outer cylinder. Further, in the embodiments described above, the detection circuit is unitized and mounted directly on the outer cylinder, but this is not always necessary and the detection circuit can be mounted separately from the displacement meter body. Further, although the above-described embodiment is configured exclusively for a displacement meter, it can also be effectively applied to a shock absorber for an automobile. Further, in the embodiment described above, the outer cylinder and the dust boot are made conductive, and the rod is maintained at, for example, ground potential via the outer cylinder and the dust boot. The rod and the outer cylinder can be electrically connected to each other by a suitable conductive member, such as a conductive brush or a coil wire, at a portion protruding from the inner cylinder so as not to interfere with the relative movement of the rod. The reservoir can also be filled with oil separated from the outside air and can be configured with, for example, a bellows whose volume can be varied in accordance with the relative movement of the rods.

In this case, displacement in any direction can be detected by attaching it to any part of a vehicle or the like.

(Effects of the Invention) As described above, according to the present invention, above the opposing portion of the cylinder and rod constituting the capacitor, the opposing portion is always filled with a dielectric made of liquid.
Since a dielectric storage tank is provided in communication with the cylinder, its capacitance can always be measured stably regardless of the relative movement between the cylinder and the rod, thereby detecting their relative positions with high precision. can do.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the present invention in detail, FIG. 2 is a diagram showing an embodiment of the present invention, FIGS. 3A, B, and 4 are partial detailed diagrams thereof, and FIG. 5A
-E is a diagram showing another embodiment of the present invention, and FIG. 6 is a diagram showing a shock absorber previously proposed by the applicant. 21...Cylinder 23...Rod 23...Oil seal 24...Storage tank 25...
- Guide member 26... Bypass 27... Oil 31... Outer cylinder 32... Inner cylinder
33...Rod 34...Guide 35
... Insulating member 36 ... Piston 37.・
... Seal 38 ... Cover 41 ... Storage tank 47 ... Coil spring 48 ... Oil 49 ... Mounting screw 50 ... Dust boot 51 ... Detection circuit 53 ... Electrode rod 61...outer cylinder
62...Inner cylinder 63...Rod 64
...Insulating member 65...Guide 66...
・Piston 67...Cover 68...Metal fitting 69...Seal 70...Cover 71...Metal fitting 72...Dust boot 73...Oil 74...Storage tank 75・・・
・Detection circuit 76... Electrode rod 77... Spring

Claims (1)

[Claims] 1. A cylinder, a rod that moves relatively within the cylinder, and at least a portion where the cylinder and the rod face each other are always filled with a dielectric material made of liquid,
a dielectric reservoir connected to the cylinder and provided above the portion; the cylinder and the rod are respectively used as electrodes, and the capacitance formed between these electrodes is measured; A capacitive cylinder displacement meter, characterized in that it is configured to detect the relative position between the rod and the rod.