JPH0518507Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vehicle suspension system used for the suspension of automobiles, companion vehicles, and the like.

[Prior Art] A conventional shock absorber includes a cylinder having a liquid chamber inside, a rod inserted movably in the axial direction of the cylinder, and a damping force generating section provided inside the cylinder. It is configured. In this type of device, when the cylinder and rod move relative to each other in the axial direction, a desired damping force is obtained by causing the hydraulic fluid to flow through the orifice of the damping force generating section. Also, since the volume inside the cylinder changes depending on the amount of push of the rod into the cylinder,
It is also practiced to provide a variable volume air chamber within the cylinder. Furthermore, a suspension system equipped with a hydraulic unit capable of adjusting the amount of oil in the cylinder has also been proposed. This suspension system is capable of adjusting the axial relative position of the rod with respect to the cylinder, that is, the vehicle height, by feeding oil into the cylinder or discharging oil from the cylinder using a hydraulic pump or the like.

In any of the above cases, a sealing means is required at the sliding portion between the cylinder and the rod, and various measures have been taken to improve sealing performance. For example, as seen in Japanese Utility Model Application Publication No. 62-176536, a sealing means combining a high-pressure seal, a bush, and a low-pressure seal has been proposed.

Normal shock absorbers are used in combination with suspension springs such as coil springs, and because the suspension springs share the load support of the vehicle body, the internal pressure in the cylinder is small. However, the pneumatic-hydraulic suspension system that combines gas springs (so-called hydro-pneumatic suspension), as proposed by the present inventors, uses a gas spring enclosed in a gas spring to perform the function instead of the conventional suspension spring. The gas pressure must be extremely high, reaching around 100 kgf/cm ² .

[Problems to be solved by the invention] When the pressure of the sealed gas increases, oil leaks are more likely to occur in the sliding parts of the rod. Further, as illustrated in FIG. 6, the sliding resistance tends to increase as the pressure acting on the sealing material (O-ring) increases. If the tightening force of the sealing material is increased in order to reduce oil leakage, the sliding resistance of the rod will become even greater. Regarding such problems, the above-mentioned prior art (Utility Model Application No. 176536/1983)
This cannot be a sufficient countermeasure. In other words, in this case, the hydraulic pressure inside the cylinder acts directly on the high-pressure seal, creating extremely high frictional resistance between it and the piston rod.Moreover, the oil is blocked by the high-pressure seal, so the bushing located on the low-pressure side and the low-pressure Seals cannot be lubricated with oil,
Frictional resistance increases. Therefore, the movement of the rod is no longer smooth, leading to a deterioration in the ride comfort of the suspension system. Furthermore, a large amount of frictional heat is generated, which causes deterioration in the durability of the sealing material and the like. Furthermore, in a suspension system with a vehicle height adjustment function that allows oil to be taken in and taken out of the cylinder, if the sliding resistance of the rod is large, the controllability when adjusting the vehicle height will deteriorate. Furthermore, if oil leaks to the outside from the seal, it is impossible to recover the oil.

Therefore, the object of the present invention is to provide a suspension system for a vehicle that has low frictional resistance at the sealing part even when the internal pressure of the cylinder is high, allowing the rod to slide smoothly, and which prevents hydraulic fluid from leaking to the outside. Our goal is to provide the following.

[Means for Solving the Problems] The suspension device devised by the present inventor in order to achieve the above-mentioned purpose includes a cylinder equipped with a liquid chamber filled with hydraulic fluid, and a suspension device that is movable in the axial direction of the cylinder. a rod with one end located inside the cylinder and the other end outside the cylinder; a hydraulic unit connected to the fluid chamber; The sealing means has a labyrinth groove in the circumferential direction on the side opposite to the circumferential surface of the rod, and the hydraulic fluid can flow between the circumferential surface of the rod and the circumferential surface of the rod. 3~
a bearing member with a 20 μm bearing gap; an elastic sealing material that is provided on the lower pressure side of the bearing gap and whose inner circumferential surface is in close contact with the circumferential surface of the rod over the entire circumference;
The elastic sealing material has a drain recovery flow section that communicates with the bearing member, and the elastic sealing material has an inner circumferential portion that slides on the rod and an outer circumferential portion located outside the inner circumferential portion. a synthetic resin seal body having a side portion and a spring accommodating groove located between these two portions and opening toward the bearing gap side; The bearing gap has a spring biased in a direction of pushing it apart, and the end of the bearing gap is opened at a position facing the inner circumferential side, and the end of the drain recovery flow section is opened near the outer circumferential side. It is characterized by being open.

[Function] In the device of the present invention having the above configuration, since high pressure is always applied to the liquid chamber inside the cylinder, a part of the working liquid in the liquid chamber passes through the bearing gap between the bearing member and the rod and gradually passes through the bearing gap between the bearing member and the rod. Flows to the low pressure side (elastic sealing material side). Then, it is collected through the drain collection distribution section. Since a uniform lubricating liquid film is formed in the circumferential direction on the inner peripheral side of the bearing member having the labyrinth groove by the working fluid flowing through the bearing gap, the frictional resistance of the rod is extremely small. Moreover, the hydraulic fluid flowing through the bearing gap causes pressure loss due to expansion/contraction of the flow path due to the labyrinth groove and changes in the flow direction, and the hydraulic fluid whose pressure has dropped is completely sealed by the elastic sealing material. . When the rod moves to the extended side, the film of hydraulic fluid adhering to the outer circumferential surface of the rod is scraped outward from the bearing gap, but in this case, the film of hydraulic fluid adhering to the outer circumferential surface of the rod is scraped outward from the bearing gap. The flowing liquid flows in the direction of the spring housing groove of the elastic sealing material and is smoothly taken into the drain recovery flow section. Therefore, excessive hydraulic pressure is prevented from acting on the elastic sealing material, and a portion of the hydraulic pressure acts in a direction that brings the inner peripheral side portion of the elastic sealing material into close contact with the rod. For these reasons, the elastic sealing material completely seals the hydraulic fluid and prevents leakage of the fluid to the outside.

[Example] An example of the present invention will be described below with reference to the drawings.

The pneumatic suspension system 1 shown in FIG. 2 includes a cylinder 2 and a rod 3 inserted into the cylinder 2 so as to be movable in the axial direction. One end of the rod 3 is located inside the cylinder 2, and the other end of the rod 3 is located outside the cylinder 2.

The cylinder 2 includes an outer cylinder 5, an inner cylinder 6 disposed concentrically inside the outer cylinder 5, an annular bearing housing 7, a lid 8, and the like. The space between the outer cylinder 5 and the inner cylinder 6 is sealed by a sealing material 9 such as an O-ring. The connecting component 10 attached to the lower part of the outer cylinder 5 is fixed to a wheel side member (not shown).

Inside the cylinder 2, a partition member 17 consisting of a metal bellows 15 and a bellows cap 16 separates an air chamber 20 on the lower side in the figure and a liquid chamber 20 on the upper side in the figure.
It is divided into a and 21b. Liquid chamber 21a, 2
1b is filled with oil as a working fluid. The pressure of the inert gas such as nitrogen gas sealed in the air chamber 20 is, for example, around 100 Kgf/cm ² when the partition member 17 is bent to the neutral position. The pressure of the gas in the air chamber 20 is transferred to the liquid chamber 21 via the partition member 17.
a, 21b, the internal pressure of the air chamber 20 acts in a direction to push the rod 3 out of the cylinder 2.
The bellows cap 16 can be moved into and out of contact with the open end of the inner cylinder 6. The fixed end side of the bellows 15 is fixed to the cylinder 2 by a bellows fixing member 23 provided with a sealing material 22. The area where the cylinder 2 and the rod 3 slide is sealed by a sealing means 25, which will be described later. On the upper end side of the rod 3 in the drawing, there is a connecting part 26 connected to a member on the vehicle body side (not shown),
A rubber bumper 27, a dust cover 28, and the like are provided.

A damping force generating section 30 is provided at the end of the rod 3 inside the cylinder 2. The damping force generating section 30 is located at a first section where the hydraulic fluid flows when the cylinder 2 and the rod 3 move relative to each other in the axial direction.
It is provided between the liquid chamber 21a and the second liquid chamber 21b. The damping force generating section 30 includes a variable orifice mechanism 3 that includes a piston-shaped portion 31 that partitions a first liquid chamber 21a and a second liquid chamber 21b, and an actuator 32.
3 and a constant orifice 34.
Orifice case 35 of variable orifice mechanism 33
is fixed to the lower part of the rod 3, and a rotating spool 36 is provided in the orifice case 35. This spool 36 is rotated around an axis by an actuator 32. The orifice of the variable orifice mechanism 33 is configured to open the first liquid chamber 21a and the second liquid chamber 2 when the spool 36 is at a predetermined rotational position.
1b. In other words, by changing the rotational position of the spool 36 by a predetermined angle, the flow path area can be changed and the damping force can be switched. The actuator 32 is preferably a stepping motor, but a DC
In some cases, a motor or rotary solenoid can be used. A lead wire 37 of the actuator 32 passes through the rod 3 and exits to the outside.

A liquid feed port 41 is provided in a liquid path 40 provided inside the rod 3, and a hydraulic unit 42 is connected to this liquid feed port 41. The hydraulic unit 42 is
It is configured with a hydraulic pump, a tank containing a hydraulic fluid, an electromagnetic on-off valve (none of which are shown), etc.
A desired amount of hydraulic fluid can be put in and taken out of the a.

The sealing means 25 is constructed as follows. As shown in an enlarged view in FIG. 1, a bearing member 45 is provided on the inner peripheral surface of the bearing housing 7, that is, on the side facing the rod 3. The space between the bearing housing 7 and the outer cylinder 5 is sealed by a sealing material 47. The material of the bearing member 45 is as follows:
Aluminum bronze is desirable as a material that does not damage the sliding surface of the rod 3 and has excellent wear resistance.

A plurality of labyrinth grooves 50 are provided on the inner peripheral surface of the bearing member 45 along the circumferential direction. FIG. 3 shows an example of the shape and dimensions of the labyrinth groove 50. The inner diameter of the bearing member 45 is larger than the outer diameter of the rod 3;
Therefore, a predetermined bearing gap 51 is secured between the circumferential surface of the rod 3 and the bearing member 45. The dimension b of the gap 51 is, for example, about 3 to 20 μm, and in short, it is sufficient that there is a diameter difference that causes a pressure loss in the hydraulic fluid passing through the gap 51. The length L of the bearing member 45 is determined by the outer diameter D of the rod 3 in order to obtain sufficient pressure loss in the bearing gap 51 and to reduce the surface pressure even if the bearing member 45 contacts the rod 3. It is desirable that it be about 1 to 2 times as large.

An elastic sealing material 53 is provided on the low pressure side of the bearing gap 51. This elastic sealing material 53
As shown in the enlarged figure, the synthetic resin seal body 5 has a substantially U-shaped cross section (inverted U-shaped in the drawing).
4, and a metal spring 55 having a substantially v-shaped cross section (inverted v-shaped in the drawing). The seal body 54 has an inner circumferential portion 5 that comes into sliding contact with the circumferential surface of the rod 3.
6, an outer peripheral part 57 located outside the inner peripheral part 56, a part 58 connecting these parts 56 and 57, and a spring housing located between the inner peripheral part 56 and the outer peripheral part 57. It is configured to include a groove 59 and the like. The spring 55 is made of stainless steel, for example, and has a large number of v-shaped segments connected in the circumferential direction. Each segment of the spring 55 biases the inner circumferential side portion 56 and the outer circumferential side portion 57 of the seal body 54 in a direction to spread them apart.
The inner circumferential portion 56 is in close contact with the rod 3 uniformly in the circumferential direction. This elastic seal material 53 is attached to the seal body 5.
The spring 55 is inserted into the groove 59 of the rod 3, and the load of the spring 55 can provide sufficient elasticity, so the elasticity of the body 54 can be lower than that of a general O-ring or U-shaped packing, and the body 54 can be in contact with the rod 3. The frictional resistance of the part can also be reduced.

Further, one end side of a drain recovery flow section 62 communicates with a gap 61 between the bearing member 45 and the elastic sealing material 53. The other end of the flow section 62 is connected to a tank (not shown) of the hydraulic unit 42.
The inner peripheral surface of the dust seal 63 provided on the lid 8 is in sliding contact with the rod 3. The lid 8 is fixed to the cylinder 2 by bolts 64.

Next, the operation of the embodiment of the apparatus configured as described above will be explained.

When the rod 3 moves relatively from the neutral position in the direction in which it is pushed into the cylinder 2, a part of the hydraulic fluid in the first fluid chamber 21a flows into the second fluid chamber 21b through the damping force generating section 30. The movement of the rod 3 is damped by the fluid friction that occurs. When the rod 3 moves in the pushing direction, the air chamber 20 is compressed as the amount of pushing of the rod 3 into the cylinder 2 increases, and the repulsive force of the gas increases.

Conversely, when the rod 3 moves relative to the direction in which it exits the cylinder 2, a portion of the hydraulic fluid in the second fluid chamber 21b passes through the damping force generating section 30 and flows into the first fluid chamber 21a.
By flowing to the side, the movement of the rod 3 is attenuated, and as the volume of the rod 3 in the cylinder 2 decreases, the air chamber 20 expands. Since the pressure of the gas sealed in the air chamber 20 is extremely high compared to a normal shock absorber, the load applied to the vehicle body can be supported solely by the repulsive force of the gas in the air chamber 20 without using a separate suspension spring. I can do it.

The gas pressure in the air chamber 20 acts on the liquid chambers 21a and 21b. Moreover, when the rod 3 moves in the direction of exiting from the cylinder 2, the pressure in the liquid chamber 21b increases. Since high pressure acts on the liquid chamber 21b in this way,
A portion of the working fluid in the fluid chamber 21b flows little by little toward the elastic sealing material 53 through the bearing gap 51. The hydraulic fluid passing through this gap 51 flows toward the low pressure side, that is, the elastic sealing material 53 side, while causing a pressure loss due to repeated expansion and contraction of the flow path by the labyrinth groove 50 and changes in the flow direction, and finally flows to the low pressure side, that is, the elastic sealing material 53 side. Distribution department 6
It is collected after 2 steps. The recovered hydraulic fluid is appropriately returned to the fluid chamber 21a by the hydraulic unit 42.

Due to the existence of the labyrinth groove 50, the working fluid flowing through the bearing gap 51 circulates around the rod 3 in the circumferential direction, and as shown schematically in FIG. In order to apply pressure, the bearing member 45 and the rod 3 are made coaxial, thereby forming a uniform lubricating liquid film around the rod 3, avoiding metal-to-metal contact, and at the same time coaxially forming the bearing member 45 and the rod 3. Drain flow rate (amount of laminar flow of viscous fluid flowing through the gap) compared to the case without
is theoretically reduced by 1/2.5, so the frequency of adjusting the vehicle height using the hydraulic unit 42 can be reduced. Since the pressure of the hydraulic fluid that has reached the elastic sealing material 53 through the bearing gap 51 has been sufficiently reduced, the pressure acting on the elastic sealing material 53 is small. As shown in FIG. 7, when the rod 3 moves to the extension side, the film of hydraulic fluid adhering to the outer peripheral surface of the rod 3 is scraped outward from the bearing gap 51. In this case, the liquid coming out from the bearing gap 51 to the elastic sealing material 53 side flows in the direction of the spring housing groove 59 of the elastic sealing material 53 and is smoothly taken into the drain recovery flow section 62. Therefore, excessive hydraulic pressure is prevented from acting on the elastic sealing material 53, and a portion of the hydraulic pressure acts in a direction that brings the inner circumferential portion 56 into close contact with the rod 3. For these reasons, the elastic sealing material 53 completely seals the hydraulic fluid and prevents leakage of the fluid to the outside, and the frictional resistance generated when the rod 3 moves is extremely small. In addition, the labyrinth groove 5
If 0 is not provided, the rod 3 and the bearing member 45 come into partial contact as shown by the two-dot chain line in FIG. 5, which increases sliding resistance and wear.

The pressure loss ΔP ₁ due to the bearing gap 51 is expressed as ΔP ₁ =12 μLQ/b ³ πD.

(μ: Absolute viscosity L: Bearing length Q: Flow rate
b: bearing clearance D: rod diameter) In addition, the pressure losses ΔP ₂ and ΔP ₃ based on the expansion and contraction of the flow path due to the bearing clearance 51 and the labyrinth groove 50 are as follows: ΔP ₂ =ζ ₂ (v ₁ ² /2g) ΔP ₃ =ζ ₃ (v ₁ ² /2g).

(ζ: loss coefficient v ₁ : average speed of expansion v ₂ : average speed of contraction) Since the pressure acting on the elastic seal material 53 can be reduced in this way, the elastic seal material 5
This not only greatly reduces the sliding resistance between the rod 3 and the rod 3, but also simplifies the elastic sealing material 53 by lowering the pressure, reduces frictional resistance and frictional heat, and improves the durability of the sliding part. Extremely effective.

In addition, by providing the dust seal 63,
It can prevent solid foreign matter from entering from outside. Even if minute solid foreign matter mixed into the hydraulic fluid enters between the bearing member 45 and the rod 3 for some reason, this foreign matter will enter the labyrinth groove 50, so malfunctions due to the foreign matter being wedged can be prevented.

[Effects of the invention] According to the invention, even in a suspension system with high internal pressure, the shaft seal portion of the rod is well lubricated and the frictional resistance of the seal portion of the rod is reduced, resulting in favorable characteristics for the suspension system. In addition, the hydraulic fluid will not leak to the outside.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a seal portion of a suspension system showing an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of a suspension system incorporating the seal portion shown in FIG. 1, and FIG. FIG. 4 is an enlarged sectional view of the labyrinth groove in the bearing member in FIG. 1, FIG. 4 is a sectional view of the elastic seal material in FIG. 1, and FIG. 5 conceptually shows the relationship between the bearing member and the rod in FIG. 1. FIG. 6 is a diagram showing the relationship between O-ring pressure and frictional resistance, and FIG. 7 is an enlarged view of the vicinity of the elastic sealing material in the suspension system shown in FIG. 1. 1...Air-hydraulic suspension system, 2...Cylinder, 3
... Rod, 20... Air chamber, 21a, 21b...
Liquid chamber, 25... Sealing means, 30... Damping force generating section, 42... Hydraulic pressure unit, 45... Bearing member,
50... Labyrinth groove, 51... Bearing gap, 53
...Elastic sealing material, 54...Seal body, 56
...Inner circumference side part, 57...Outer circumference side part, 59...
Spring accommodation groove, 62...Drain recovery circulation section.

Claims (1)

[Claims for Utility Model Registration] (1) A cylinder with a liquid chamber filled with hydraulic fluid, and a cylinder that is inserted movably in the axial direction of the cylinder, with one end located inside the cylinder and the other end outside the cylinder. a rod located at the cylinder, a hydraulic unit connected to the liquid chamber and capable of supplying hydraulic fluid to the liquid chamber, and a seal provided at a portion where the cylinder and rod move to seal the inside and outside of the cylinder. In the vehicle suspension system, the sealing means has a labyrinth groove in the circumferential direction on the side opposite to the circumferential surface of the rod, and a hydraulic fluid can flow between the sealing means and the circumferential surface of the rod. ~
A bearing member that forms a bearing gap of 20 μm, an elastic sealing material that is provided on the lower pressure side of the bearing gap and whose inner circumferential surface is in close contact with the circumferential surface of the rod over the entire circumference, and this elastic sealing material and the above-mentioned rod. and a drain recovery flow section that communicates with the bearing member, and the elastic sealing material includes an inner circumferential side portion that slides on the rod, an outer circumferential side portion located outside the inner circumferential side portion, and both of these. a synthetic resin seal body having a spring accommodating groove located between the parts and opening toward the bearing gap side; an end of the bearing gap is opened at a position facing the inner circumferential side, and an end of the drain recovery flow section is opened near the outer circumferential side. A vehicle suspension system featuring: (2) The vehicle suspension system according to claim 1, wherein the bearing member having the labyrinth groove is made of aluminum bronze.