JPH03134303A - Accumulator - Google Patents

Abstract

PURPOSE:To enable operation of an accumulator under a high gas sealing pressure and improve the durability thereof by providing a stopper member whose axial length is more than the closed length of a bellows inside the bellows, and thereby supporting the bending more than a specified length. CONSTITUTION:A bellows 30 and a stopper member 31 thereinside are arranged in a housing 15. The axial length of the stopper member 31 is longer than the closed length of the bellows, while an rubber elastic seal member 45 is arranged on an inner surface side of a bellow cap 38 composing the bellows 30, opposing to the seat 34 of the stopper member 31. It is thus possible to enable operation under a high gas sealing pressure and improve durability of the bellows 30.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an accumulator used as a gas spring for a vehicle suspension system or for absorbing pulsation in a hydraulic system.

[Prior Art] In the conventional accumulator 1 shown in FIG.
By the bellows 3 provided inside the housing 2,
An air chamber 4 and a liquid chamber 5 are partitioned. The bellows 3 consists of a bellows body 6 and a bellows cap 7. A large number of pleats 8 are formed in the bellows body 6 so that it can expand and contract in the axial direction of the housing 2.

Compressed gas is supplied to the air chamber 4 through a gas supply port 9. When gas is supplied to the air chamber 4, the bellows body 6 is brought into close contact with the gas and lengthened by the pressure of the gas, as shown in FIG. Shrink to. In this specification, the adhesion length L0 means the dimension when the adjacent pleats 8 provided on the bellows body 6 come into contact with each other at least in part.

The metal bellows 3 itself has some degree of elasticity in the axial direction. Therefore, when compressing the bellows 3 in the axial direction, if a load larger than the load when the bellows 3 is in close contact is applied, the bellows 3 will further bend in the axial direction as shown in FIG. FIG. 7 shows the relationship between the deflection of the bellows 3 and the load when a compressive load is applied to the bellows 3.

As shown in FIG. 7, the bellows 3 exhibits a relatively small spring constant until reaching the length of close contact, but exhibits a spring characteristic in which the spring constant rapidly increases after the close contact.

[Problem to be solved by the invention] The bellows 3 is in close contact with each other. If compressed to a length below, a portion of the pleats 8 will be plastically deformed, and in extreme cases, the pleats 8 will be destroyed. Moreover, since large stress is generated locally in the pleats 8, even if the folds do not break statically, fatigue failure occurs due to repeated bending, leading to early breakage.

To prevent the above problem from occurring, make sure that the bellows 3 are tightly attached. It should be used within the range of deflection that does not reach . However, bellows 3 remains in close contact for a long time.

The sealing pressure of gas that does not reach is several kg f at most.
/ am 2 is the limit. For this reason, the gas sealing pressure is too low to be suitable for practical use.

Therefore, an object of the present invention is to provide an accumulator that can enhance the durability of the bellows built into the housing and can be used at high gas filling pressures.

[Means for Solving the Problems] The accumulator of the present invention developed to achieve the above object includes a housing, a bellows body built into the housing and having a plurality of folds that are expandable and retractable in the axial direction of the housing, and A bellows consisting of a bellows cap provided on the free end side of the bellows body;
An air chamber defined between the inner surface of the housing and the outer surface of the bellows and filled with compressed gas, and a liquid chamber defined on the inner surface of the bellows, the inner surface of the bellows having: A stopper member is provided that prevents the bellows from further contracting by supporting the bellows cap when the bellows is contracted by a predetermined length or more in the axial direction. It is characterized in that the adhesion length is greater than or equal to .

[Operation] The bellows expands and contracts in the axial direction in response to pressure acting inside the housing. When the bellows bends toward the contraction side, the bellows cap is supported by the stopper member before reaching the close contact length of the bellows, and the bellows no longer bends toward the contraction side.
bending is prevented. This prevents excessive deformation of the folds of the bellows and generation of large local stress in the folds.

[Example] An example of the present invention will be described below with reference to FIGS. 1 and 2. The illustrated pulsation absorbing accumulator 10 is connected to a conduit 13 that connects a hydraulic pump 11 and a hydraulic device 12 operated by the pump 11.

The housing 15 constituting the outer wall of the accumulator 10 consists of a cylindrical shell 16 and a pair of end plates 17 and 18 that close both ends of the shell 16. One end plate 17
A gas supply port 20 is provided at. The gas supply port 20 can be closed by a plug 21. The other end plate 18 is provided with ports 22, 23 for liquid flow. - side port 22 is connected to the discharge port of the pump 11,
The other port 23 is connected to the inlet of the hydraulic equipment 12 .

A bellows 30 is provided inside the housing 15, and an inner cylinder 31 is provided inside the bellows 30. The housing 15, the bellows 30, and the inner cylinder 31 are arranged concentrically with each other. One end 31a of the inner cylinder 31 is fixed to the housing 15. A seat 34 having an opening 33 is provided at the other end 31b of the inner cylinder 31.

The bellows 30 consists of a metal bellows body 37 and a bellows cap 38. One end 37a of the bellows body 37 is fixed to the housing 15. The free end 37b of the bellows body 37 is closed by a bellows cap 38.

A bellows guide 39 is provided on the outer periphery of the bellows 30.

A large number of folds 41 are formed in the axial direction of the bellows body 37, and the bellows 30 can expand and contract in the axial direction of the housing 15 by bending the folds 41. The folds 41 in the illustrated example correspond to the bellows body 37.
When the deflection is in a neutral state, it is formed into a roughly U-shaped cross section. However, pleats with a V-shaped or Ω-shaped cross section may also be adopted. Further, the bellows body 37 may be a so-called molded bellows formed by forming a cylindrical thin metal plate into the above shape by appropriate plastic processing such as hydroforming, or a plurality of molded bellows elements connected together in the axial direction by welding. It may be made by other processing methods, such as a welded bellows or a brazed bellows.

A self-sealing member 45 is provided on the inner surface of the bellows cap 38. This sealing member 45 is made of a rubber-like elastic body and faces the seat 34 of the inner cylinder 31. This seal member 45 is used to create a sealed backup liquid chamber 46 between the inner surface of the bellows 30 and the outer surface of the inner cylinder 31 when the seal member 45 is brought into close contact with the seat 34.

The inner cylinder 31 and the seal member 45 function as a stopper member that prevents the bellows 30 from being bent toward the contraction side by a predetermined amount or more. The length of this stopper member in the axial direction, that is, the sum of the length of the inner cylinder 31 and the thickness of the seal member 45 is the length of the close contact of the bellows 30. It's bigger than that. The contact length of bellows 30 here. -Z in the axial direction when the folds 41 of the bellows body 37 come into contact with each other at least in part (see Fig. 5).
This is the J method. By making the length of the stopper member longer than the contact length of the bellows 30, the bellows 30
Even if 0 is bent all at once toward the contraction side, it will not reach the adhesion length.

An air chamber 50 defined by the inner surface of the housing 15 and the outer surface of the bellows 30 is filled with a chemically inert high pressure gas such as nitrogen. A liquid chamber 51 defined by the inner surface of the bellows 30 is filled with oil as a working fluid.

When filling the air chamber 50 with gas, remove the plug 21 of the gas supply port 20 and connect the gas supply pipe 5 as shown in FIG.
A gas supply source 56 is connected via 5. Gas supply source 56
The compressed gas to be sealed in the air chamber 50 is accommodated. The liquid chamber 51 is filled with oil. When the gas in the gas supply source 56 is sent into the air chamber 50 by opening the valve 57, the bellows 30 bends toward the contraction side as the pressure in the air chamber 50 increases.

Before the bellows 30 reaches the contact length, the self-sealing member 4
5 comes into close contact with the seat 34, the bellows 30 no longer bends toward the contraction side, and the opening 3 of the seat 34
3 is occluded. In addition, the inner surface of the bellows 30 and the inner cylinder 31
A sealed backup liquid chamber 46 is created between the outer surface of the cylinder and the outer surface of the cylinder, and oil is trapped in this backup liquid chamber 46.

Since oil is substantially incompressible, the entire surface of the inner surface of the bellows 30 is evenly supported by the bulges confined in the backup liquid chamber 46. Therefore, even if gas pressure acts on the bellows body 37, the bellows body 37 can be prevented from being bent excessively.

After gas is supplied until the pressure in the air chamber 50 reaches a predetermined value, the gas supply port 20 is closed with the plug 21. Since the metal bellows 30 exhibits excellent gas barrier performance, the gas in the air chamber 50 and the oil in the liquid chamber 51 are completely separated from each other.

In the accumulator 10 equipped with the self-sealing member 45, the pressures acting on the bellows 30 are gas pressure pc and hydraulic pressure P. and the pressure PB generated by the spring constant of the bellows 30 itself. The balance between these pressures is expressed by the following formula: P a = P o + P B . Further, the pressure PB generated based on the spring constant k of the bellows 30 itself is expressed by the following equation.

P, -(k・6g)/A...0 From the formula, Pg-Pa Pa, so in the state where oil is trapped in the backup liquid chamber 46 by gas pressure (self-sealing state), the bellows 30 A differential pressure PR (difference between gas pressure and oil pressure) is generated, and stress corresponding to this differential pressure P is applied to the bellows 30. Therefore, in order to increase the durability of the bellows 30, it is necessary to make PR as small as possible. However, as can be seen from the above formula 0, PB is
It also depends on the spring constant k of 0. The spring constant of the bellows 30 has the characteristics shown in FIG. becomes large.

However, in this embodiment, since the bellows 30 does not reach the tight contact length as described above, the bellows 30 can be bent in a small region corresponding to the spring constant, and the differential pressure pH only needs to be small. This is advantageous in increasing the durability of the bellows 30.

The accumulator 10 is used for absorbing pulsation. The pressure of the oil discharged from the hydraulic pump 11 is
The liquid acts on the liquid chamber 51 via the port 22, and is also sent out from the boat 23 to the hydraulic equipment 12 to operate the hydraulic equipment 12. The pulsating component of the hydraulic pressure caused by the rotation of the pump 11 is absorbed by the compression and expansion of the gas in the air chamber 50. When the air chamber 50 is compressed, the bellows 30 bends toward the expansion side, and when the air chamber 50 expands, the bellows 30 bends toward the contraction side.

When the bellows 30 is fully bent toward the contraction side, the bellows 30 is supported by the inner tube 31 before reaching the close contact length, and is prevented from contracting any further. Therefore, excessive bending of the folds 41 of the bellows body 37 and occurrence of large stress in the folds 41 are suppressed.

Note that the present invention is also effective when applied to an accumulator 60 that does not have a self-sealing member as shown in FIG. The length of the inner cylinder 31 used as a stopper member is
As in the previous embodiment, the bellows 30 is in close contact with the body. Therefore, the amount of deflection of the bellows 30 on the contraction side is
Therefore, the bellows 30 does not become shorter than the contact length. In this case, the bellows 30 is not crushed to the tight length by the gas pressure, so the bellows 30
Can be used up to its own pressure resistance.

Generally, the pressure required for the bellows 30 to reach its full length is several kgf/am2 at most, whereas the pressure resistance of the bellows 30 itself is several tens of kgf/cm2. In comparison, it can be used at a gas filling pressure several ten times higher.

Note that the present invention can be similarly applied to accumulators other than those for absorbing pulsation. For example, it may be applied to a gas spring for a vehicle suspension system. Further, the material of the bellows 30 is not limited to metal. For example, a synthetic resin with excellent gas barrier properties may be used.

[Effects of the Invention] According to the present invention, an accumulator having a bellows for partitioning an air chamber and a liquid chamber inside the housing can be used at a high gas filling pressure, and the durability of the bellows is improved. be able to.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an accumulator showing one embodiment of the present invention, FIG. 2 is a sectional view showing how the accumulator shown in FIG. 1 is filled with gas, and FIG. 3 is another embodiment of the present invention. FIG. 4 is a cross-sectional view of a conventional accumulator, FIG. 5 is a cross-sectional view showing the bellows bent to the tight length, and FIG. 6 is a cross-sectional view showing the bellows bent to the tight length. FIG. 7 is a cross-sectional view showing the state in which the metal bellows is bent, and FIG. 7 is a diagram showing the relationship between the deflection of the metal bellows and the load. 10...Accumulator, 20...Gas supply port, 3
0... Bellows, 31... Inner cylinder (stopper member),
37...Bellows body, 38...Bellows cap.
Knob, 41... Fold, 45... Self-sealing member, 4
6...ノ(・Tuck-up liquid chamber, 50... Air chamber, 51
...liquid chamber, 60...accumulator.

Claims (2)

[Claims] (1) A bellows consisting of a housing, a bellows body built into the housing and having a plurality of folds that are expandable and retractable in the axial direction of the housing, and a bellows cap provided on the free end side of the bellows body, and an inner surface of the housing. an air chamber defined between the bellows and the outer surface of the bellows, in which compressed gas is sealed; and a liquid chamber defined on the inner surface of the bellows; A stopper member is provided that prevents the bellows from further contracting by supporting the bellows cap when the bellows cap is contracted by a predetermined length or more in the axial direction. An accumulator characterized by the following. (2) An inner cylinder as a stopper member is provided on the inner surface of the bellows cap, and when the bellows is contracted by a predetermined length or more, it comes into close contact with the open end of the inner cylinder, thereby causing a connection between the inner surface of the bellows and the inner cylinder. 2. The accumulator according to claim 1, further comprising a seal member for creating a sealed backup liquid chamber between the accumulator and the outer surface.