JPH0522804Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a capacitive cylinder displacement meter for 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 change in the load of an automobile, a device that detects changes in the expansion and contraction of a shock absorber has been developed, for example, in 1983-
It is disclosed in No. 88609 and No. 57-177113.

In these conventional shock absorbers that detect changes in vehicle height, a coil is buried inside a cover made of non-conductive and non-magnetic material over the entire stroke detection area, separately 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, which increases costs. This has the disadvantage that changes in inductance cannot be detected accurately and stably due to the influence of noise, resulting in low displacement detection accuracy.

In order to eliminate such drawbacks, the applicant of the present application proposed a shock absorber as shown in FIG. 7 in Japanese Patent Application No. 107685/1983. This shock absorber is of a so-called twin-inch tube type in which oil 3 is housed in tubes of different diameters in an inner cylinder 1 and an outer cylinder 2. An electrically insulated capacitor is constructed, and the relative position between the inner cylinder 1 and the piston rod 4 is detected by detecting the capacitance of this capacitor.

In FIG. 7, 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. There is. The inner cylinder 1 and the outer cylinder 2 also have a chamber 11 formed in the upper part by a rod guide 8 and an oil seal 10 provided above it between the outer cylinder 2 and the piston rod 4, and a chamber 11 formed in the rod guide 8. It communicates via a bypass 12, and communicates via an orifice 13 and a plate 14 at the bottom. The detection circuit unit 15 is attached to the upper end of the shock absorber.
This includes a CR oscillation circuit that uses the capacitance between the inner cylinder 1 and the piston rod 4 as a parameter, a signal processing circuit that divides the oscillation frequency of this CR oscillation circuit, and outputs a low-frequency pulse signal, etc. , detects the oscillation frequency of the CR oscillation circuit based on the capacitance that changes as the piston 5 moves up and down within the inner cylinder 1 as the load changes, and connects the inner cylinder 1 and the piston rod 4.
The vehicle height change is detected based on the relative position of the vehicle and the relative position of the vehicle.

In such a shock absorber, a capacitor is formed by electrically insulating the inner cylinder 1 and the piston rod 4, which are originally provided in the shock absorber, and the inner cylinder is connected by detecting the capacitance of this capacitor. Since the structure is configured to detect the relative position between the piston rod 1 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 in which the coil is provided separately, there are no restrictions on mounting the sensing section, and it can be applied to shock absorbers of any structure as long as they are co-cylindrical. It also has the advantage of greatly expanding the range of applications.

(Problems to be Solved by the Invention) However, according to various experiments conducted by the inventors of the present invention, it has been found that the shock absorber shown in FIG. 7 has some points to be improved as described below.

That is, in the shock absorber shown in FIG. 7, by installing the shock absorber in an automobile or the like, the inner cylinder 1 is connected to the negative terminal of a DC power source mounted on the automobile or the like through the outer cylinder 2 and the chassis. are connected to the positive terminal of the DC power source through terminals and lead wires provided in the detection circuit 15, but when the piston rod 4 is brought to a positive potential in this way, it protrudes from the inner cylinder 1. At this point, an undesired stray capacitance is formed between the piston rod 4 and other members at ground potential in the vicinity, which causes a decrease in detection accuracy.

One idea to solve this problem is to electrically insulate the inner cylinder 1 from the outer cylinder 2 and piston rod 4, so that the outer cylinder 2 and piston rod 4 are at ground potential, and the inner cylinder 1 is at a positive potential. It will be done. In this way, even if there are other members at ground potential near the outer cylinder 2 or the portion of the piston rod 4 that protrudes from the inner cylinder 1, undesired stray capacitance will not be formed since they are at the same potential. It never happens.

In this case, in order to connect the inner tube 1 to the positive terminal of the DC power source, it is necessary to provide a connecting electrode on the inner tube 1, and the configuration shown in FIG. 8 can be considered as the electrode structure. That is, a cord 21 is soldered to the outer surface of the inner cylinder 1, and the cord 21 is extended to the outside through a hole formed in the outer cylinder 2. Further, a cylindrical case 22 is provided in the hole formed in the outer cylinder 2 so as to surround the hole, and this case 22
A sealing rubber 23 and a nut 24 are provided through the cord 21, and the cord 21 is sealed by screwing the nut 24 into the case 22 and compressing the sealing rubber 23.

However, in the electrode structure shown in FIG. 8, the cord 21 is made into metal contact with the inner tube 1 by soldering, and the cord 21 is inserted into the seal rubber 23 and sealed against the outer tube 2 by the tightening force of the nut 24. Because of this configuration, manufacturing is troublesome, and there are problems in that the solder comes off due to vibration, causing poor contact, and oil leakage occurs if the nut 24 is insufficiently tightened.

This idea was created by focusing on these problems, and it is easy to manufacture, and it can reliably maintain the inner cylinder at the required potential without causing poor contact or oil leakage, and it can handle changes in vehicle height. It is an object of the present invention to provide a capacitance type cylinder displacement meter suitably configured to stably and accurately detect capacitance for detecting.

(Means for Solving the Problems) The capacitive cylinder displacement meter of the present invention includes an outer cylinder made of conductive resin that is electrically connected to the vehicle body, and an external cylinder inside the outer cylinder. A conductive inner cylinder provided insulated from the cylinder, an insulating piston slidably provided inside the inner cylinder, an upper end supported by the piston, and a lower end connected to the vehicle via a rubber bushing. an electrically conductive rod connected to a swinging portion of the piston so as to be movable relative to the piston while electrically insulating the inside of the inner cylinder from the inner cylinder; and the rod and the outer cylinder. a means for electrically connecting the rod and the rod, the means being provided on the outer surface of the outer cylinder, using the outer cylinder and the rod as the same electrode, and using the inner cylinder as a common electrode to detect the capacitance formed between these electrodes; a detection circuit that detects the displacement of the swinging portion with respect to the vehicle body; and a liquid that is provided at the upper part of the outer cylinder so as to communicate with the inside of the outer cylinder and that is made of a dielectric material that compensates for the volume of the liquid in the outer cylinder. a liquid chamber formed between an outer circumferential wall of the inner cylinder and an inner circumferential wall of the outer cylinder, and one liquid chamber and the other liquid chamber in the inner cylinder separated by the piston. A communication hole that communicates between the outer cylinder and the storage tank; A liquid chamber that is formed in the piston and that is separated from the other liquid chamber in the inner cylinder and that is separated by the piston. a communication hole that communicates with the chamber; and an electrode connected to the detection circuit and extending through a hole formed in the outer cylinder and having a potential opposite to that of the vehicle body, is elastically attached to the outer surface of the inner cylinder. The present invention is characterized by comprising an electrode structure attached to the outer cylinder so as to press into contact with each other and seal the hole and between the electrodes so that the dielectric does not leak.

(Function) In the above structure, the outer cylinder and the rod are electrically connected, so that by attaching the outer cylinder to the chassis of an automobile, the outer cylinder and the rod are reliably grounded to the body. Therefore, even if there are other grounded members in the vicinity of the rod protruding from the inner cylinder, undesirable stray capacitance will not be formed, and since the entire exposed part is conductive, it will not cause external damage. Acts as a shield against noise. In addition, the electrodes constituting the electrode structure are
It elastically presses into contact with the outer surface of the inner cylinder while being sealed against the outer cylinder. Therefore, even if there is vibration, the vibration is absorbed by the elastic action, so that poor contact between the electrode and the inner cylinder and leakage of the dielectric from the outer cylinder do not occur.

(Embodiment) FIG. 1 shows an embodiment of the present invention, which is separate from a shock absorber for an automobile suspension and is constructed exclusively for a displacement meter. Outer cylinder 3
1 is made of a conductive material with excellent corrosion resistance, mechanical strength, and heat resistance, such as plastic with a conductivity of 10 ⁰ to ^{10 1} Ω-cm, which is made of 6-nylon and mixed with brass pieces. A conductive inner cylinder 32 is provided inside this outer cylinder 31, and a conductive rod 33 that penetrates into this inner cylinder 32 and moves relatively is provided.

The inner cylinder 32 has an insulating guide 34 at its lower end.
An insulating member 35 is interposed between the upper end portion and the outer tube 31 so that the upper end portion is insulated from the outer tube 31 and extends coaxially. 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 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.

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

The storage tank 41 has a bottom portion 41a formed integrally with the outer cylinder 31, and is integrally welded to the bottom portion 41a.
It is comprised of an outer cylinder 31 that is attached to the chassis of a vehicle and a container portion 41b made of the same material. As shown in FIG. 2A, which is a partial plan view, and FIG. 2B, which is a sectional view taken along the line II in FIG. Protrusions 44 are formed radially on the bottom surface 43 toward the bottom surface 43, and a ring-shaped member 45 is formed concentrically with the opening 42 above the bottom surface 43 at the tips of these projections 44.
A plurality of arc-shaped outlets 46a and a circular outlet 46b
and form.

Further, in this embodiment, a coil spring 47 is provided between the ring-shaped member 45 and the insulating member 35, which presses and biases the inner cylinder 32 toward the guide 34, thereby pushing the inner cylinder 32 in the direction of relative movement of the rod 33. The structure is such that the inner cylinder 32 is always positioned at a predetermined position within the outer cylinder 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 oil 48 is contained in the outer cylinder 31 and the inner cylinder 32,
3 are used as electrodes, and the capacitance formed between them is measured to detect their relative positions. However, the space between the inner cylinder 32 and the rod 33 is always filled with oil 48 regardless of their relative movement. In order to
Oil 48 is also stored in the storage tank 41.
and the inner cylinder 32 are communicated with each other. Therefore, as shown in FIG. 2B, the insulating member 35 has an opening (communication hole) for communicating the inner cylinder 32 and the storage tank 41.
35a is formed. The amount of oil 48 accommodated in the outer cylinder 31, inner cylinder 32, and storage tank 41 is such that even when the rod 33 protrudes the most from the inner cylinder 32 in the vertical direction, the oil 48 remains in the storage tank 41. . 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 may be mixed into the inner cylinder 32 due to the generation of these forces. In order to prevent this, the insulating member 35 is provided with a bypass (communication hole) 35b for communicating the upper and lower chambers in the outer cylinder 31, as shown in a partial plan view in FIG. Similarly, a bypass (communication hole) 34a is formed in the piston 34, and a through hole (communication hole) 36a is formed in the piston 36 for communicating the upper and lower chambers in the inner cylinder 32. The oil 48 is configured to flow smoothly in accordance with the relative movement of the rod 33.

On the other hand, the end of the rod 33 protruding from the inner cylinder 32 is movably provided with a mounting screw 49 for attaching it to the axle of a vehicle via a rubber bushing. In order to ensure that the outer cylinder 31 and the rod 33 are at the same potential to prevent the formation of undesirable stray capacitance, and at the same time, to prevent the rod from being hit by stones etc., considering the usage environment where it is installed under the floor of the vehicle. To prevent damage to 33, a conductive dust boot 50 is provided. This dust boot 50 is made by dispersing carbon black in a base resin made by polymerizing styrene-butadiene rubber and ethylene, and has an electrical conductivity of ^100.
Formed into a bellows structure with a material of ~10 ¹ Ω-cm,
It is configured to be able to expand and contract in accordance with the relative movement of the rod 33.

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. This detection circuit 51 prevents the formation of undesired stray capacitance.
Inner cylinder 32 and rod 33 forming desired capacitance
The CR oscillation circuit, which uses the capacitance between the inner cylinder 32 and the rod 33 as a parameter, is mounted on the printed circuit board 51a in the same way as explained in FIG. A signal processing circuit, etc. that divides the oscillation frequency of the CR oscillation circuit and outputs 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 detection circuit 51 via the outer cylinder 31. In order to electrically connect the outer cylinder 31 and the detection circuit 51, one electrode wiring of the printed circuit board 51a is brought into contact with the conductive pin 52. The conductive pin 52 is integrally formed with the outer cylinder 31 to form the receiver 3.
1a, thereby electrically connecting the outer cylinder and therefore the rod 33 and one electrode wiring of the detection circuit 51, and at the same time fixing the printed circuit board 51a and therefore the detection circuit 51 to the outer cylinder 31. Also,
The inner cylinder 32 as the other electrode that forms the required capacitance is connected to the electrode rod 54 that constitutes the electrode structure 53.
It is connected to the other electrode wiring of the printed circuit board 51a through. For this reason, a hole 31b into which the electrode rod 54 is loosely fitted is formed in the outer cylinder 31, and the hole 31b is formed in the outer cylinder 31.
The case 31c that protrudes so as to surround the outer cylinder 31
molded integrally with In addition, an insulating seal rubber 55 is vulcanized and bonded to the electrode rod 54 to form an integral structure.
This seal rubber 55 is pressed and held in close contact with the inside of the case 31c by an insulating collar 56. Thereby, the tip of the electrode rod 54 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 57 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 41 of the storage tank 41
b and the rod 33 are respectively attached to the chassis and axle of the automobile so that the rod 33 extends substantially vertically, and the rod 33 is connected to ground potential via the outer sleeve 31 and the dust boot 50.
The inner tubes 32 are each held at a positive potential via the electrode rods 54, and the relative position information of the inner tubes 32 and the rods 33 is obtained based on the capacitance formed by the inner tubes 32 and the rods 33 in the detection circuit 51. to detect vehicle height and its changes.

In the above-described configuration, a sealing rubber 55 is vulcanized and bonded to the electrode rod 54, and this sealing rubber 55 is pressed and held in close contact with the inside of the case 31c by a collar 56. Therefore, the oil 4 inside the outer cylinder 31
No. 8 does not leak from the hole 31b. In addition, since the electrode rod 54 comes into elastic pressure contact with the outer surface of the inner cylinder 32 due to the sealing rubber 55 being held under pressure, even if there is vibration, the vibration is absorbed by the elasticity of the sealing rubber 55. Therefore, the electrode rod 5
4 will surely come into contact with the outer surface of the inner cylinder 32.

Here, if the inner diameter of the inner cylinder 32 is a, the outer diameter of the rod 33 is b, the penetration length of the rod 33 into the inner cylinder 32 is l, and the dielectric constant of the oil 48 is ε, then the inner cylinder 32 and the rod 33 are The capacitance C of the configured capacitor is expressed by the following equation.

C=2πεl/log(a/b) As is clear from the above equation, the capacitance C changes depending on the penetration length l of the rod 33 into the inner cylinder 32, so the capacitance C is detected. As a result, the penetration length l of the rod 33 and, therefore, 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 negative coefficient dependence on temperature, but this temperature dependence is CR
The temperature dependence of the dielectric constant can be offset by providing a part of the oscillation circuit with a temperature characteristic that is opposite to the temperature dependence of the dielectric constant. This allows for always high-accuracy detection without being affected by temperature changes. It can be performed.

FIG. 4 shows the configuration of another example of the electrode structure. In the electrode structure 61 of this embodiment,
The electrode connected to the inner cylinder 32 is constructed with an electrode rod 62 and a conductive spring 63, and the electrode rod 62 is connected to the inner cylinder 32 via the spring 63. For this purpose, a hole 31b is formed in the outer cylinder 31, and a cylindrical case 64 made of an insulating material is provided in communication with the hole 31b. Further, a sealing rubber 65 is vulcanized and bonded to the electrode rod 62 to form an integral structure, a spring 63 is attached to the tip of the electrode rod 62, and the sealing rubber 65 is attached to the case by a collar 66.
4 and press and hold. This allows hole 3
While preventing oil leakage from 1b, the spring 63 is pressed into contact with the outer surface of the inner cylinder 32 via the electrode rod 62. In this embodiment, in order to more reliably prevent oil leakage from the case 64 through the hole 31b, the step 64a of the case 64 and the seal rubber 65 are
An O-ring 67 is provided between the two.

In this embodiment, as in the above-mentioned embodiment, the electrode rod 62 can be reliably sealed against the outer cylinder 31, and the electrode rods 62 and 63 can form an electrode with the inner cylinder 32 without being affected by vibration. It is possible to make sure that they come into contact with each other.

FIG. 5 shows the configuration of still another example of the electrode structure. In the electrode structure 71 of this embodiment, a large diameter part 72a is formed at the end of the electrode rod 72 that contacts the outer surface of the inner cylinder 32, and this large diameter part 72a is connected to the inner cylinder 32 by a sealing rubber 73. It is designed to be brought into pressure contact with the outer surface. For this reason, in this embodiment, the electrode rod 72 and the seal rubber 73 are separated, and the seal rubber 73 is pressed and held in close contact with a collar 75 inside a case 74 that is provided in communication with a hole 31b formed in the outer cylinder 31. This brings the large diameter portion 72a of the electrode rod 72 into pressure contact with the outer surface of the inner cylinder 32, and seals the electrode rod 72 against the outer cylinder 31.

In this embodiment, as in the above-described embodiment, the electrode rod 72 can be reliably sealed against the outer cylinder 31, and the electrode rod 72 can be brought into stable and reliable contact with the inner cylinder 32 without being affected by vibration.

FIG. 6 shows the configuration of still another example of the electrode structure. In the electrode structure 81 of this embodiment, both the electrode rod 82 and the conductive spring 83 are pressed into contact with the outer surface of the inner cylinder 32. For this reason, in this embodiment, a flange 82a is integrally formed on the electrode rod 82, a spring 83 is wound around the flange 82a, and these are connected to a hole 31b formed in the outer cylinder 31 in an insulating case 84 provided with an O. ring 85
After insertion, the flange 82a and therefore the electrode rod 82 are pressed and held in the case 84 by the collar 87 via the O-ring 86.

In this way, the electrode rod 82 can be attached to the O-ring 85.
and 86, the spring 83 is elastically pressed into contact with the inner cylinder 32, and one end of the spring 83 is connected to the flange 8.
It comes into elastic pressure contact with the inner cylinder 32 in a state where it is latched to 2a. In addition, the electrode rod 82 and the outer cylinder 3
1 is sealed by O-rings 85 and 86 via case 84, so no oil leakage occurs. Therefore, in this embodiment as well, the electrode rod 82 can be reliably sealed against the outer cylinder 31, and the spring 83 can elastically contact the electrode rod 82 and the inner cylinder 32. Together with this, the electrode rod 82 and the inner cylinder 32 can be electrically contacted more stably and reliably.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified or changed in many ways. For example, the storage tank 41 can be filled with oil separated from the outside air, and the volume can be changed according to the relative movement of the inner cylinder 32 and the rod 33. In this case, the storage tank 41 can be configured with a bellows. It can be attached to any part of 31. Furthermore, the inner cylinder 3
The capacitance of the capacitor constituted by the rod 2 and the rod 33 can be detected using not only the CR oscillation circuit but also other circuits such as the LC oscillation circuit. Furthermore, the electrical connection between the outer cylinder 31 and the rod 33 can be made through the rod 33 without going through the dust boot 50.
The rod 33 and the outer cylinder 31 are electrically connected to each other at a portion protruding from the inner cylinder 32 using a suitable conductive member, such as a conductive brush or a coil wire, so as not to interfere with the relative movement of the rod 33. You can also do that. Furthermore, the present invention is not limited to displacement meters, but can also be applied to shock absorbers.

(Effects of the invention) As described above, according to the invention, the outer cylinder is attached to the automobile chassis and the outer cylinder and the rod are electrically connected, so that the outer cylinder and the rod are securely connected. It can be made to the same potential as the chassis,
This effectively prevents the formation of undesired stray capacitance, and also effectively shields external noise. In addition, a detection circuit is provided on the outer surface of the outer cylinder, and the electrodes constituting the electrode structure are connected to this detection circuit, and the electrodes are elastically pressed into contact with the outer surface of the inner cylinder while being sealed to the outer cylinder. Since the inner cylinder is made to have an opposite potential to the chassis, the inner cylinder can be reliably maintained at an opposite potential to the chassis without causing poor contact or oil leakage due to vibration, and the detection circuit and internal Since the electrode structure connecting the cylinder is not exposed to the outside, formation of undesired stray capacitance can be effectively prevented. Therefore, capacitance can be measured stably, and thus changes in vehicle height can always be detected with high accuracy. Also,
In the present invention, a storage tank is provided at the top of the outer cylinder, which stores a liquid made of a dielectric material that communicates with the inside of the outer cylinder and compensates for the volume of the liquid inside the outer cylinder, and a liquid chamber between the inner cylinder and the outer cylinder is provided. A communication hole that communicates with both liquid chambers in the inner cylinder separated by the piston, a communication hole that communicates the outer cylinder and the storage tank, and a communication hole that communicates both liquid chambers in the inner cylinder through the piston. , it is possible to effectively prevent the generation of reaction force and damping force of the liquid due to relative movement between the inner cylinder and the rod.Therefore, it is possible to effectively prevent the generation of reaction force and damping force of the liquid due to the relative movement between the inner cylinder and the rod.Therefore, it is possible to effectively prevent the generation of air from the seal part due to the generation of negative pressure inside the liquid, and the occurrence of cavitation. It is possible to effectively prevent the generation of air, and also to effectively compensate for changes in the volume within the inner cylinder due to relative movement, and to constantly fill the portions of the capacitor with dielectric material.

Therefore, it is possible to effectively prevent the variable capacitance formed between the inner cylinder and the rod and the fixed capacitance formed between the outer cylinder and the inner cylinder from changing due to the inclusion of air. Since this can be prevented, the relative position between the inner cylinder and the rod, that is, the displacement of the swinging portion with respect to the vehicle body, can always be detected with high precision.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the present invention, Figs. 2A, B, and 3 are partial detailed views thereof, Fig. 4,
5 and 6 are views showing modified examples of the electrode structure, FIG. 7 is a view showing a shock absorber previously proposed by the applicant, and FIG. 8 is an electrode structure developed prior to the present invention. FIG. 31... Outer cylinder, 31b... Hole, 31c... Case, 32... Inner cylinder, 33... Rod, 34... Guide, 35... Insulating member, 36... Piston, 3
7...Seal, 38...Cover, 41...Storage tank, 47...Coil spring, 48...Oil, 49...
Mounting screw, 50...Dust boot, 51...
...Detection circuit, 53, 61, 71, 81... Electrode structure, 54, 62, 72, 82... Electrode rod, 5
5, 65, 73... Seal rubber, 56, 66, 7
5, 87...Color, 63...Conductive spring, 6
4, 74, 84... Case, 67, 85, 86...
...O-ring.

Claims (1)

[Scope of claim for utility model registration] An outer cylinder made of conductive resin that is electrically connected to the vehicle body, and a conductive inner cylinder provided within the outer cylinder insulated from the outer cylinder. and an insulating piston that is slidably provided inside the inner cylinder, the upper end of which is supported by the piston, and the lower end of which is connected to a swinging part of the vehicle via a rubber bushing. an electrically conductive rod that is movable relative to the piston while being electrically insulated from the inner cylinder; means for electrically connecting the rod and the outer cylinder; a detection circuit that is provided on an outer surface and uses the outer cylinder and the rod as the same electrode, uses the inner cylinder as a common electrode, and detects the capacitance formed between these electrodes to detect the displacement of the swinging portion with respect to the vehicle body; and a storage tank for storing a liquid made of a dielectric substance, which is provided in an upper part of the outer cylinder so as to communicate with the inside of the outer cylinder, and which compensates for the volume of the liquid in the outer cylinder; an outer peripheral wall of the inner cylinder; a communication hole that communicates a liquid chamber formed between the inner circumferential walls of the outer cylinder with one liquid chamber and the other liquid chamber in the inner cylinder separated by the piston; and the outer cylinder and the reservoir. a communication hole that communicates with the tank; a communication hole that is formed in the piston and communicates between one liquid chamber and the other liquid chamber in the inner cylinder that are separated by the piston; and a communication hole that is connected to the detection circuit. An electrode having a potential opposite to that of the vehicle body, which extends through a hole formed in the outer cylinder, is elastically pressed into contact with the outer surface of the inner cylinder, and the dielectric is connected between the hole and the electrode. and an electrode structure attached to the outer cylinder in a sealed manner to prevent leakage.