JPH01172006A - Damper - Google Patents

Abstract

PURPOSE:To make a constitution compact by arranging for the constitution in which a bellows unit is provided at one end of a cylinder partitioned into two liquid chambers by means of a piston portion provided with a damping force generating portion and likewise, a liquid chamber and air chamber is partitioned by means of a partitioning member provided with a damping force generating portion. CONSTITUTION:This damper 10 has a cylinder 11 of a cylindrical shape and a piston 22 inserted into it and a rod 12 whose lower end portion is connected with the piston portion 22 and which protrudes to the outside through a rod guide 18. The inside of the cylinder 11 is divided into the 1st and 2nd liquid chambers 23, 24 by means of the piston portion 22, and both liquid chambers 23, 24 are made to be communicatable by means of a damping force generating portion 26 provided at the piston portion 22. In addition, a bellows unit 33 is provided at the lower part of the cylinder 11, and partitioning is made between the 3rd liquid chamber 41 and an air chamber 42 by means of the bellows shaped partitioning member 36 of the unit 33, and communicating is made possible between the 2nd and 3rd liquid chambers 24, 41 by means of the 2nd damping force generating portion 44 provided at the partitioning member 36.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shock absorber used, for example, in a suspension mechanism of a vehicle.

[Prior Art] A conventional single cylinder shock absorber used in the suspension mechanism of a vehicle, as illustrated in FIG. It consists of a rod 3 provided so as to be able to move relatively reciprocally in the direction, a damping force generating section 5 provided on a piston portion 4, and the like. In this, when the rod 3 moves axially relative to the cylinder 2,
Damping force is generated by oil flowing into the damping force generating section 5. When the rod 3 moves in the axial direction in this manner, the volume of the rod 3 entering the cylinder 2 changes, so an air chamber 6 is provided to absorb this change. Further, in order to prevent the gas in the air chamber 6 from dissolving into the oil in the liquid chamber 1, a free piston 7 is normally used. High-pressure gas is sealed in the air chamber 6 to prevent cavitation from occurring in the liquid chamber 1, and prepressurizes the oil in the liquid chamber 1.

In this type of device, when the rod 3 moves toward the contraction side (in the direction of six arrows), the pressure in the lower liquid chamber 1a in the figure increases and the pressure in the upper liquid chamber 1b in the figure decreases, thereby generating a damping force. Oil in the lower liquid chamber 1a flows into the upper liquid chamber 1b through the portion 5. At this time, since the volume of the rod 3 pushed into the cylinder 2 increases, the free piston 7 descends and the volume of the air chamber 6 decreases. Conversely, when the rod 3 moves to the extension side (in the direction of arrow B), the pressure in the liquid chamber 1b on the upper side in the figure increases and the pressure in the liquid chamber 1b on the lower side in the figure increases.
The pressure in the upper liquid chamber 1b becomes lower, and the oil in the upper liquid chamber 1b flows into the lower liquid chamber 1a through the damping force generating section 5. At this time, the free piston 7 rises by the volume of the rod 3 removed from the cylinder 2, and the volume of the air v6 increases.

[Problems to be Solved by the Invention] In the conventional device described above, when the piston portion 4 moves relative to the cylinder 2, the liquid chamber 1a.

The greater the differential pressure between 1b, the greater the damping force. In other words, when trying to increase the damping force, the liquid chambers 1a, 1
The differential pressure generated between b and b also increases. However, if the differential pressure becomes too large, when the rod 3 moves toward the contraction side, the pressure of the oil in the liquid chamber 1b on the upper side in the figure becomes negative, and cavitation is likely to occur. In order to prevent cavitation, it is necessary to fill the air chamber 6 with gas at a considerably high pressure.
It was filled with gas at a pressure of ci.

However, if the gas filling pressure is increased, the gas in the air chamber 6 may easily leak into the liquid chamber 1 side through the sliding part of the free piston 7, or the repulsive force of the air chamber 6 may become too large, causing the spring constant to decrease. Problems such as exceeding the desired value may arise. In order to prevent gas leakage from the sliding part of the free piston 7, an O-ring with high sealing performance must be used.
The sliding resistance of the free piston 7 increases. In addition, since the free piston 7 itself has a considerable inertial mass, there are problems with followability and damping force characteristics for minute amplitude inputs, which causes a deterioration of ride comfort in the case of vehicle suspension systems. Therefore, an object of the present invention is to provide a shock absorbing device that does not cause cavitation even if the pressure of the gas sealed in is lowered, and also does not generate sliding resistance like a free piston.

[Means for Solving the Problems] In order to achieve the above object, the shock absorbing device of the present invention includes a cylinder, a rod inserted in the axial direction of the cylinder so as to be relatively reciprocating, and a cylinder provided on the rod. a piston part that partitions the inside of the cylinder into a first liquid chamber and a second liquid chamber; a bellows-like partition member that defines the first liquid chamber and the second liquid chamber;
A first damping force generating section provided between the liquid chamber and the M3 liquid seedling, and a second damping force generating section located between the second liquid chamber and the M3 liquid seedling and housed inside the bellows-shaped partition member. It was established.

[Operation] In the device of the present invention having the above configuration, when the rod moves in the contraction direction, the pressure in the M2 liquid chamber increases and the pressure in the first liquid chamber decreases as the piston portion moves. Therefore, the hydraulic fluid in the second fluid chamber flows into the first fluid chamber through the first damping force generating section, and an amount of hydraulic fluid corresponding to the volume of the rod pushed into the cylinder flows into the second damping force generator. The liquid flows from the second liquid chamber to the third liquid chamber through the force generating section. Therefore, the bellows-like partition member expands and the volume of the air chamber decreases.

When the rod moves in the extension direction, the pressure in the first liquid chamber increases and the pressure in the second liquid chamber decreases as the piston moves. Therefore, the working fluid in the first fluid chamber flows into the second fluid chamber through the first damping force generating section, and the working fluid equivalent to the volume of the rod that has been removed from the cylinder is transferred to the second damping force. The liquid flows from the third liquid chamber to the second liquid chamber through the force generating section. Therefore, the bellows-like partition member contracts and the volume of the air chamber increases.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

The illustrated example shows a shock absorber 10 used in a suspension mechanism of a vehicle. This shock absorber 10 has a cylindrical cylinder 1
1 and a rod 12 inserted into this cylinder 11. At the lower end of the cylinder 11 in the drawing, an eye ring 13 is provided as an example of a part for connecting to a member on the wheel side.
A gas sealing port 14 is also provided.

A spring seat 16 is fixed to an axially intermediate portion of the cylinder 11 for receiving the lower end of a suspension spring (not shown). A seal housing 17 and a rod guide 18 are provided on the upper end side (opening end side) of the cylinder 11 in the drawing, and a seal material 19 such as an oil seal is housed in the inner circumference of the seal housing 17.Seal housing 17 has a hydraulic oil supply port 20.

The rod 12 has a rod guide 18 and a seal housing 1.
7. This rod 12 is capable of reciprocating in the axial direction with respect to the cylinder 11.

The upper end of the rod 12 is attached to, for example, a frame of a vehicle body. A piston portion 22 is provided at the tip of the rod 12 inside the cylinder 11 . This piston portion 22 partitions the inside of the cylinder 11 into a first liquid chamber 23 and a second liquid chamber 24 . These liquid chambers 23°24
is filled with oil as a working fluid. A first damping force generating section 26 is provided between the seventh liquid chamber 23 and the second liquid chamber 24, that is, in the piston portion 22. The damping force generating section 26 includes a constant orifice 27 that is always in communication with the first liquid chamber 23 and the second liquid chamber 24, and a normally closed plate valve 30 using well-known valve plates 28 and 29.

Further, inside the cylinder 11, a bellows unit 33 is provided below the piston portion 22. The bellows unit 33 includes a cylindrical body 34 concentric with the cylinder 11 and open at both ends, and a metal bellows-shaped partition member 36 having a bellows lid 35. One end 37 of this partition member 36 is fixed to a base 38 of the cylindrical body 34.

Most of the cylindrical body 34 is housed inside the partition member 36. This partition member 36 is provided concentrically with the cylinder 11 and is expandable and retractable in the axial direction of the cylinder 11. When the partition member 36 is fully contracted, the bellows lid 35 is attached to the open end 39 of the cylindrical body 34. They are becoming closer.

A third liquid chamber 4 is provided on the inner peripheral surface side of the bellows-shaped partition member 36.
There is 1. An air chamber 42 is defined on the outer peripheral surface side of the bellows-shaped partition member 36. The air chamber 42 is filled with an inert gas such as nitrogen gas or air at a rate of 5 to 15 to 9 f/c!
sealed under pressure. Since the gas in the air chamber 42 and the oil in the third liquid chamber 41 are completely isolated from each other by the bellows-like partition member 36, problems such as gas dissolving into the oil do not occur.

A second damping force generating section 44 is provided inside the cylindrical body 34. This damping force generating section 44 includes a valve body 45 fixed to the cylindrical body 34, and a valve body 45 that is fixed to the cylindrical body 34.
The orifice bolt 46 and nut 47 provided in the valve plate 49.50 constituting the plate valve 48
It is equipped with such things as The orifice bolt 46 is provided with a constant orifice 51 that penetrates in the axial direction, and this constant orifice 51 is always in communication with the second liquid chamber 24 and the third liquid chamber 41. The plate valve 48 is configured such that the damping force is smaller when the rod 12 moves toward the contraction side than when it moves toward the expansion side.

Next, the effect of the above implementation individual packaging @10 will be explained.

As shown in FIG. 2, when the rod 12 moves toward the contraction side (in the direction of the arrow shown) with respect to the cylinder 11, as long as the moving speed of the piston portion 22 is small, the first damping force generating portion 26 The oil in the second liquid chamber 24 flows into the first liquid chamber 23 only through the constant orifice 27 without opening the plate valve 30. When the rod 12 begins to move at high speed, one of the valve plates 28 opens, causing oil in the second liquid chamber 24 to flow from the second liquid chamber 24 through both the plate valve 30 and the constant orifice 27. The liquid flows into the liquid chamber 23. The flow rate Q1 of oil flowing into the first damping force generating section 26 is such that the area of the piston portion 22 is 81
．． Let the area of the rod 12 be s2. If the moving stroke is ρ, it is expressed as Ql = (St -52)X°C, regardless of the piston speed. When the rod 12 moves in the contraction direction in this way, the amount of push-in of the rod 12 that occupies the inside of the cylinder 11 increases, so the amount of oil corresponding to the increased amount is transferred to the constant orifice 5 of the second damping force generating section 44.
1, when the piston speed is high, the valve plate 50 also opens, so that oil flows from the second liquid chamber 24 to the third liquid chamber 41. Therefore, the bellows-shaped partition member 36 expands at the same time as the air chamber 42 is compressed. At this time the second
The condition Q2 of the oil flowing into the damping force generating portion 44 is expressed as Q2=rod area s2×stroke distance. The damping force on the compression side is determined by the flow path resistance in the first damping force generation section 26 and the flow path resistance in the second damping force generation section 44.

Contrary to the above, when the rod 12 moves to the extension side (in the direction of arrow B), as long as the moving speed of the piston portion 22 is slow,
Constant orifice 27 of first damping force generating section 26
The oil in the first liquid chamber 23 flows to the second liquid chamber 24 through the first liquid chamber 23 . When the rod 12 moves toward the extension side at high speed, the valve plate 29 opens, and the oil in the first liquid chamber 23 flows into the second liquid chamber 24 through the plate valve 30 and the constant orifice 27. In this case, the flow rate Q1 of oil flowing into the first damping force generating section 26 is expressed as Q1=(st -52) xffi, similarly to when the rod 12 moves to the contraction side. In this way, when the rod 12 moves to the extension side, the amount of pushing of the rod 12 into the cylinder 11 decreases, so that the amount of oil corresponding to the decrease is transferred to the constant orifice 51 of the second damping force generating section 44. When the piston speed is high, the four valve plates open, and oil flows from the third liquid chamber 41 to the second liquid chamber 24.

Therefore, the volume of the air chamber 42 increases and at the same time the bellows-shaped partition member 36 contracts. At this time, the second damping force generating section 4
Similarly to when the rod 12 moves to the contraction side, the amount Q2 of oil flowing into the rod 4 is expressed as: Q2=rod area s2 x stroke g. Most of the damping force on the extension side is determined by the flow path resistance of the first damping force generating section 26.

As can be seen from the above description, in the shock absorbing device 1o, when the rod 12 moves relative to the cylinder 11, the rod 12 moves at two locations, the first damping force generating section 26 and the second damping force generating section 44. A damping force will be generated. That is, when the rod 12 moves toward the contraction side, the pressure in the second liquid chamber 24 becomes high, and the pressures in the first liquid chamber 23 and the third liquid chamber 41 become relatively low. However, in this case, the second
Since the pressure in the liquid chamber 24 is transmitted to the third liquid chamber 41 via the second damping force generator 44, the high pressure generated in the second liquid chamber 24 is not directly applied to the air chamber 42, that is, the bellows-shaped partition member 36. Moreover, an excessive pressure difference does not occur between the first liquid chamber 23 and the second liquid chamber 24. Therefore, even if the gas filling pressure is lower than in conventional high-pressure gas-filled shock absorbers, negative pressure in the first liquid chamber 23 is suppressed, and cavitation does not occur. You can gain strength.

When the rod 12 moves to the extension side, the pressure in the first liquid chamber 23 increases, and the pressure in the second liquid chamber 24 and the third liquid chamber 41 increases.
However, since a pressure difference occurs in two stages between the first damping force generating section 26 and the second damping force generating section 44, there is an excessive difference between the respective liquid chambers 23, 24, 41. No pressure is generated.

Moreover, since the pressure of the air chamber 42 is always applied to the second liquid chamber 24 and the third liquid chamber 41, negative pressure will not occur. Therefore, the desired damping force can be obtained without causing cavitation even on the extension side.

In this way, the above-mentioned shock absorber 10 uses a conventional high-pressure gas-containing shock absorber. Since the gas filling pressure in the air chamber 42 can be lowered compared to the li device (which does not have the second damping force generating section 44), the reaction force of the air chamber 42, that is, the gas spring constant, is small. The change in spring constant will also be small. The tube wall thickness of the cylinder 11 can be made thinner to the extent that the gas sealing pressure is lower, and the reliability of the gas sealing portion is also improved. In addition, since the bellows-like partition member 36 is used, there are problems such as large frictional resistance occurring in the sliding part and gas in the air chamber dissolving into the liquid chamber through the sliding part, unlike the conventional free piston. will not occur. Furthermore, since the inertial mass when the bellows-like partition member 36 expands and contracts can be made sufficiently smaller than that of a free piston,
Coupled with the fact that the sliding resistance is substantially zero, it has good followability to minute inputs and good vibration absorption characteristics, resulting in a comfortable ride. And the installation of the cylinder 11 (there are no restrictions in the direction).

The second damping force generating section 44 is housed inside the bellows-shaped partition member 36, and the dead space of the partitioning member 36 is effectively utilized. However, the axial dimension of the cylinder 11 can be made compact. This, together with the ability to reduce the wall thickness of the cylinder 11 as described above, is extremely advantageous in terms of weight reduction.

Note that the bellows-like partition member 36 is not limited to metal. For example, a bellows-like partition member made of resin and having a gas barrier film superimposed on an oil-resistant elastomer body may be used. In addition, the damping force generating section 26.44 may be of any type as long as it provides flow path resistance to the working fluid.
It may also be a constant sub-recess with a constriction part such as a simple small hole.

[Effects of the Invention] According to the present invention, the gas sealing pressure can be lowered, and the followability to minute inputs is better than that using a free piston. Moreover, since the second damping force generating section is accommodated by utilizing the internal space of the bellows-like partition member, it is advantageous in terms of making the cylinder more compact.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a shock absorber showing an embodiment of the present invention;
FIG. 2 is a longitudinal cross-sectional view of the shock absorber shown in FIG. 1 in a state in which the rod has moved, and FIG. 3 is a longitudinal cross-sectional view of the conventional shock absorber. 10...Buffer device, 11...Cylinder, 12...
Rod, 22... Piston portion, 23... First liquid chamber, 24... Second liquid chamber, 26... First damping force generating section, 36... Bellows-shaped partition member, 41... . . . third liquid chamber, 42 . . . air chamber, 44 . . . second damping force generating section. 17-1

Claims (1)

[Claims] a cylinder, a rod inserted in the cylinder so as to be relatively reciprocating in the axial direction; a piston portion provided on the rod to partition the inside of the cylinder into a first liquid chamber and a second liquid chamber; and an inside of the cylinder. a bellows-like partition member that is extendable and retractable in the axial direction of the cylinder and has a third liquid chamber on the inner surface side and defines an air chamber on the outer circumferential side; a first damping force generating section provided between the second liquid chamber and the third liquid chamber, and a second damping force generating section housed inside the bellows-shaped partition member between the second liquid chamber and the third liquid chamber. A buffer device characterized by comprising: