JPH02236001A - Accumulator - Google Patents

Abstract

PURPOSE:To obtain good responsiveness and prevent liquid spill due to variation in temperature by setting the thickness of the bellows body of an accumulator, which is provided with a metallic bellows, which separates a gas chamber from a liquid chamber, and a self-sealing means, in a specified range. CONSTITUTION:A ratio D/d of an outside diameter D to a root diameter d, of a bellows body 31 is limited to a value smaller than 2.0, while the thickness t of the bellows is limited to a value between 0.05mm to 0.3mm. This is because, if D/d is 2.0 or greater, plastic forming work of a bellows material into a bellows shape is very difficult, while, if D/d is smaller than 1.5, the work can be done easily. On the other hand, if the thickness is smaller than 0.05mm, the plastic work of a belows body 31 into a billows shape becomes difficult, and, if either the thickness becomes 0.3mm or greater or if D/d becomes 1.1 or smaller, the responsiveness grows worse because the bellows 31 becomes hard to deform in the axial direction. Thus, a volume change of the oil discharged from a pump 11 is effectively replaced with a volume change of the gas in a gas chamber 45, thereby it becomes possible to lessen the fluctuation amplitude of pressure P2 in a liquid chamber 41, in comparison with the pulsation of pressure P1 in a pipe 24 on the inflow side.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an accumulator used for absorbing pulsations in various hydraulic systems, or in pneumatic-hydraulic suspension systems for vehicles.

[Prior Art] Various types of accumulators have been put into practical use according to various uses. For example, it is known that a hollow housing is provided with a liquid chamber and an air chamber, the air chamber is filled with compressed gas, and the liquid chamber is filled with oil. An accumulator of this type has been developed that uses a metal bellows to separate an air chamber and a liquid chamber. The bellows is expandable and retractable in the axial direction of the housing, and the liquid chamber is defined on either the inner or outer surface of the bellows,
An air chamber is defined on the other side. The bellows expands and contracts in response to pressure changes in the liquid chamber or air chamber. In this specification, the ability of the bellows body to quickly expand and contract following pressure changes in the liquid or air chamber is referred to as "
I would like to express it as ``good responsiveness''.

In the accumulator using the metal bellows, the present inventors developed an accumulator equipped with a so-called self-sealing means in order to prevent the bellows from being deformed beyond the allowable limit when gas is sealed in the air chamber. Gansho 6
The application was filed as No. 2-219254. This prior art accumulator has a flow port at a portion through which liquid flows as the bellows expands and contracts, and the self-sealing means is provided at a portion where the flow port and the bellows cap portion face each other. When the bellows expands or contracts beyond a predetermined stroke while gas is being filled, the self-sealing means closes the flow port and traps the liquid in the liquid chamber. Since the liquid is substantially incompressible, the liquid trapped in the liquid chamber evenly backs up the entire surface of the bellows body. This prevents the bellows from deforming excessively.

[Problems to be Solved by the Invention] According to research conducted by the present inventor regarding the responsiveness of the accumulator, it was found that the responsiveness of this type of accumulator is greatly influenced by the plate thickness of the bellows. That is, the thicker the bellows is, the more pronounced the decrease in response becomes. Furthermore, if a temperature change occurs while the liquid is confined by the self-sealing means, the liquid may leak from the self-sealing means. When we investigated the cause, we surprisingly found that the thickness of the bellows was involved. That is, in the above-mentioned accumulator, the increase or decrease in the volume of the liquid due to the temperature change that occurs when the self-sealing means is in the closed state is absorbed by the bending of easily bendable parts such as between the peaks and valleys of the bellows. Therefore, if the bellows has a large thickness, the bellows will not be able to bend elastically and will not be able to fully follow pressure changes.As a result, a gap will be created in the self-sealing means, resulting in liquid leakage. On the other hand, if the thickness of the bellows is made too thin, the shape of the bellows becomes unstable, and not only does the expansion and contraction operation become unstable, but it also becomes difficult to plastically process the bellows into a predetermined shape.

Therefore, an object of the present invention is to provide an accumulator with a built-in self-sealing means that has good responsiveness to pressure fluctuations and can prevent liquid leakage from the self-sealing means due to temperature changes. be.

[Means for Solving the Problems] The present invention, developed to achieve the above object, provides an accumulator equipped with a metal bellows and self-sealing means for partitioning the air chamber and the liquid chamber as described above. Therefore, the thickness of the bellows body was set to 0. 0.5 mm to 0.3 mm.

[Function] When the self-sealing means is in the closed state, if the volume of the liquid in the accumulator changes due to a change in liquid temperature, the volume change will be handled by elastic bending between the peaks and valleys of the bellows body. It is absorbed by The metal bellows body with the above thickness can easily follow changes in the volume of the liquid. Therefore, troubles such as liquid leakage from the self-sealing means are prevented from occurring.

Furthermore, when this accumulator is used, the bellows body responds sensitively to even the slightest pressure change in the liquid chamber or air chamber and flexes, providing excellent responsiveness. As long as the plate thickness is within the above range, plastic working into a predetermined bellows shape can be carried out without any problem.

[Example] The first example of the present invention will be described below with reference to Figures 1 to 4.
This will be explained with reference to the figures.

The accumulator 10 shown in FIG.
1, and a hydraulic device 12 operated by this pump 11.
is established between. This accumulator 10 is
It has a hollow housing 15, and an inner cylinder part 16 is provided inside the housing 15 concentrically with the housing 15. A flow port 18 is opened at the center of an end member 17 located at the lower end of the inner cylinder portion 16 in the drawing.

An inflow port 21 and an outflow port 22 are provided at the upper end of the housing 15 in the drawing. One end of an inflow side pipe 24 is connected to a female thread 23 provided in the inflow port 21 via a pipe joint (not shown).

The other end of the pipe 24 is connected to the discharge port of the pump 11. One end side of an outflow side pipe 26 is connected to the female thread 25 provided in the outflow port 22 via a pipe joint (not shown).

The other end of the pipe 26 is connected to an inlet of the hydraulic equipment 12.

A metal bellows 30 is housed inside the housing 15. The bellows 30 includes a bellows body 31 that is expandable and retractable in the axial direction of the housing 15, and a bellows cap portion 32 that closes one end of the bellows body 31. The bellows body 31 is formed by forming a thin stainless steel plate having a thickness described later into a predetermined bellows shape by plastic working such as hydraulic forming or roll forming.

However, metals other than stainless steel may be used.

The other end 33 of the bellows body 31 is hermetically fixed to an end wall 34 of the housing 15.

A valve body 35 is provided on the inner surface side of the bellows cap portion 32. This valve body 35 is made of a material with rubber-like elasticity such as urethane elastomer or silicone resin, and faces the annular valve seat 36 located around the above-mentioned flow port 18. The valve body 35 and the valve seat 36 constitute a self-sealing means 37 for trapping oil between the inner cylinder part] 6 and the bellows body 31 when the bellows 30 is contracted by a predetermined stroke or more.

A resin guide member 38 is attached to the outer periphery of the bellows body 31. This guide member 38 is used to ensure a predetermined clearance between the bellows body 31 and the inner surface of the housing 15 and to reduce sliding resistance between the bellows body 31 and the housing 15.

In the internal space of the housing 15 partitioned by the bellows 30, a liquid chamber 41 is defined on the inner surface side of the bellows 30, and this liquid chamber 41 is filled with oil. Further, an air chamber 45 is provided on the side defined by the outer surface of the bellows 30 and the inner wall of the housing 15. This air chamber 45 is filled with an inert gas such as nitrogen. This gas is supplied to the gas supply port 4 which can be closed by a plug 46.
7 to the air chamber 45. The pressure at which the gas is charged is determined depending on the pulsation absorption characteristics of the accumulator 10, and is, for example, at a pressure of several kg/eI#2 or more. The gas pressure acts in a direction to contract the bellows 30.

When gas is supplied to the air chamber 45, the liquid chamber 41 is filled with oil in advance. Thereafter, by connecting the high pressure gas supply source 48 to the gas supply port 47 as shown in FIG.
Gas is supplied to the air chamber 45.

As the amount of gas in the air chamber 45 increases, the bellows body 31 contracts in the axial direction. Therefore, excess oil in the liquid chamber 41 is discharged to the outside of the housing 15. Bellows 30
When the valve body 35 is bent to a predetermined stroke, the valve body 35 comes into close contact with the valve seat 36, thereby closing the flow port 18. When this state is reached, the bellows body 31 no longer bends in the axial direction, and the inner surface of the bellows body 31 and the inner cylindrical portion 1
Oil is trapped in the gap 50 (part of the liquid chamber 41) between the outer surface of the liquid chamber 6 and the outer surface of the liquid chamber 41. Since gas continues to be supplied to the air chamber 45 even after the valve body 35 comes into close contact with the valve seat 36, the pressure in the air chamber 45 gradually increases. The oil trapped in the gap 50 is substantially incompressible. Therefore, the entire inner surface of the bellows body 31 is evenly backed up by the oil trapped in the gap 50. Therefore, even if gas is continuously supplied at high pressure, the bellows body 31
is prevented from deforming beyond its capacity limit.

When the pressure in the air chamber 45 reaches a predetermined value, the gas supply is stopped and the supply port 47 is closed by the stopper 46.

Stress σ (kg'f) generated when the bellows body 31 bends
/mm2) can be calculated using the following formula.

t: Plate thickness (+nm) N: Number of peaks P: Pitch (mm) h: Height difference between peaks and valleys (+nm) E: Young's modulus (kgf/mm2) Δg: Deflection size (mm) Above calculation formula As can be seen, the thinner the plate thickness t of the bellows body 31 is, the smaller the stress σ generated in the bellows body 31 for the same amount of deformation Δg is, which is preferable in terms of durability.

The volume of gas and liquid changes with temperature. For example, when the oil temperature changes from -30℃ to +120℃, the volume of oil is approximately 1
l% also changes. When the liquid is confined in the liquid chamber 41 by the self-sealing means 37, if the volume of the oil changes due to an increase in oil temperature, etc., the thinner the bellows body 31 is, the more likely the body 31 will be elastically deformed. Since the differential pressure between the liquid chamber 41 and the air chamber 45 can be easily followed, the absolute value of the differential pressure between the two becomes small. Therefore, it is possible to suppress the generation of excessive differential pressure in the direction in which the self-sealing means 37 opens the valve.

When the plate thickness is made thinner than 0.05++++n, it becomes difficult to plastically process the bellows body 31 into a bellows shape. Considering the formability of the bellows body 31, the ratio D/d between the peak diameter D and the valley diameter d (see FIG. 1) of the bellows body 31 is preferably less than 2.0.

In particular, if D/d is less than 1.5, plastic working can be easily performed. When D/d is 2.0 or more, it becomes extremely difficult to mold the material into a bellows shape. Also, the board thickness is 0. ．． 3mm
If D/d exceeds 1.1, or if D/d becomes 1.1 or less, the bellows body 31 becomes difficult to bend in the axial direction, and responsiveness deteriorates.

For these reasons, in the present invention, the value of D/d is set to 2.0.
The plate thickness of the bellows body 31 is limited to less than t.
0. It is limited to between 0.5 mm and 0.3 mm.

More preferably, it is recommended that 1.1 < (D/d) < 1.5.

Next, the operation of the accumulator 10 having the above structure when it is used will be explained.

Oil discharged from the hydraulic pump 11 flows into the liquid chamber 41 via the inflow side pipe 24 and the inflow port 21. The oil that has flowed into the liquid chamber 41 is sent to the hydraulic equipment 12 through the outflow port 22. The pulsating component of the hydraulic pressure generated by the rotation of the pump 11 acts on the liquid chamber 41 and
It acts on the air chamber 45 through the oil in 1. Therefore, the pulsating component is absorbed by the compression and expansion of the gas within the air chamber 45.

When the air chamber 45 is compressed, the bellows 30 is bent in the direction of extension, and when the air chamber 45 is expanded, the bellows 30 is bent in the direction of contraction. In this way, the volume change of the oil discharged from the pump 11 is effectively replaced by the volume change of the gas in the air chamber 45, so that the inflow side piping 2
Compared to the pulsation of the pressure P1 of No. 4, the fluctuation range of the pressure P2 within the liquid chamber 41 can be reduced. Furthermore, in this embodiment, since the inner diameter of the outflow port 22 is smaller than that of the inflow port 21, the pressure P3 in the outflow side piping 26 is equal to the pressure P2 in the liquid chamber 41.
The pulsation is further flattened, although it is slightly lower.

If the pressure in the liquid chamber 41 decreases for some reason,
The bellows 30 is bent in the direction of contraction due to the pressure of the gas in the air chamber 45. When the bellows 30 bends to a predetermined stroke,
The flow port 18 is closed by the valve body 35 of the self-sealing means 37 coming into close contact with the valve seat 36. Therefore, the bellows body 31 no longer bends in the axial direction, and
Oil is trapped in the gap 50 between the outer peripheral surface of the inner cylinder portion 16 and the inner surface of the bellows body 31. Oil is substantially incompressible. Therefore, the entire surface of the inner surface of the bellows body 31 is evenly supported from the inside by the oil trapped in the gap 50. Therefore, excessive bending of the bellows body 31 can be prevented. Therefore, the pressure resistance required of the bellows body 31 is relaxed, and the plate thickness of the bellows body 31 can be reduced to the above numerical range. Since the bellows 30 is made of metal, it exhibits extremely good gas barrier properties even if the bellows 30 is thin.
There is no possibility that the gas in the air chamber 45 will dissolve into the oil in the liquid chamber 41.

Next, a second embodiment of the present invention shown in FIG. 5 will be described.

This second embodiment is an example in which a metal bellows 30 is built into a pneumatic-hydraulic vehicle suspension system 60. The housing 61 consists of an outer cylinder 62 and an inner cylinder 63, and a hollow rod 65 is inserted into the housing 61 so as to be movable in the axial direction.

The housing 61 is provided with an oil seal 66, a seal fixing part 67, bearings 68, 69, and the like. The illustrated upper end of the rod 65 is connected to a member (not shown) on the vehicle body side using a connecting part 71. The lower end side of the housing 61 is connected to a member on the axle side by a connecting part 72. A liquid chamber 7 is provided inside the housing 61 and inside the rod 65.
5, and this liquid chamber 75 is filled with oil. Liquid chamber 7
A hydraulic circuit (not shown) is connected to a liquid feeding port 76 used for supplying oil to the liquid pump 5 .

The sliding portion of the rod 65 and the housing 61 is surrounded by a bellows-shaped dust force bar 80. rod 65
At the bottom of the damping force generating mechanism 81 using a plate valve etc.
is provided.

This suspension device 60 includes a second housing 85. The inside of the housing 85 is partitioned into a liquid chamber 86 and an air chamber 87 by a metal bellows 30. This air chamber 87 is filled with an inert gas such as nitrogen. The gas is
Gas is supplied to the air chamber 87 through a gas supply port 91 that can be closed by a stopper 90 . For example, the gas pressure is several tens of kg.
/cIil1 or more, and the gas pressure acts in the direction of contracting the bellows 30. Liquid chamber 8 of second housing 85
6 communicates with a liquid chamber 75 in the first housing 61 via a flow port 93 and a flow path 94.

The bellows 30 includes a bellows body 31 that is expandable and retractable in the axial direction of the housing 85 as in the first embodiment described above;
A bellows cap portion 32 that closes one end of this bellows body 31 is provided.

The bellows body 31 has a thickness of 0 or 0 for the reason mentioned above.
．． A metal plate (for example, a thin stainless steel plate) with a thickness of 0.05 mm to 0.3 mm is formed by plastic working. However, metals other than stainless steel may be used. The other end 33 of the bellows body 31 is hermetically fixed to an end wall 95 of the housing 85.

When the mountain diameter of the bellows body 31 is D and the valley diameter is d, (D/d) <2. o, more preferably D such that 1.1 < (D/d) < 1.5.
The relationship between and d is determined.

A valve body 35 is provided on the inner surface of the bellows cap portion 32, and an annular valve seat 36 is provided at the open end of the flow port 93. The procedure for supplying gas to the air chamber 87 of this suspension device 60 is as follows:
This is similar to the case where gas is filled in the air chamber 45 in the first embodiment described above. The self-sealing means 37 can prevent the bellows body 31 from being excessively deformed.

When the suspension device 60 is mounted on a vehicle and moves relative to the first housing 61 in the direction in which the hollow rod 65 is pushed in, the gas in the air chamber 87 is further compressed. As the repulsive force increases, the bellows 30 expands in the axial direction in response to this pressure change. Conversely, when the rod 65 moves in the direction of protruding from the housing 61, the volume of gas in the air chamber 87 increases and the bellows 30 bends in the direction of contraction.

Furthermore, as oil flows into the damping force generation mechanism 81,
Movement of the rod 65 is suppressed. Therefore, this suspension device 60 can function as a gas spring and a shock absorber.

Note that the present invention can be similarly applied to an accumulator having a structure in which a liquid chamber is provided on the outer surface of the bellows and an air chamber is provided on the inner surface of the bellows.

[Effects of the Invention] According to the present invention, in an accumulator that has a built-in metal bellows and self-sealing means, it is possible to prevent liquid leakage problems at the self-sealing part due to temperature changes, etc., and to reduce the pressure in the liquid chamber or air chamber. Good responsiveness to fluctuations etc. can be obtained.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view schematically showing a part of an accumulator according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing how gas is supplied to the accumulator shown in FIG. 1.
FIG. 3 is a sectional view of a hydraulic system using the accumulator shown in FIG. 1, FIG. 4 is a diagram showing the pulsation absorption performance of the hydraulic system shown in FIG. 3, and FIG. FIG. 1 is a cross-sectional view of an exemplary vehicle suspension system. 10...Accumulator, 15...Housing, 1
8... Distribution port, 30... Metal bellows, 31...
Bellows body, 32... Bellows cap part, 37
...Self-sealing means, 41...Liquid chamber, 45...Air chamber, 50...Gap (part of liquid chamber), 60...Vehicle suspension system (accumulator), 85... housing,
86...liquid chamber, 87...air chamber, 93...distribution port. Applicant's agent Patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) A metal bellows having a hollow housing, a bellows body housed inside the housing and made of a metal plate formed into a bellows shape, and a bellows cap portion at the end of the bellows body; A liquid chamber is defined on either the inner or outer surface and is filled with liquid, an air chamber is defined on the other side and is filled with compressed gas, and the bellows is located within the liquid chamber and expands and contracts. a circulation port through which the liquid in the liquid chamber flows during operation;
The communication port is provided at a mutually opposing portion of the communication port and the bellows cap portion, and when the bellows body is bent beyond a predetermined stroke, the communication port is liquid-tightly closed to trap liquid in the liquid chamber. 1. An accumulator comprising a self-sealing means, characterized in that the bellows body has a thickness of 0.05 mm to 0.3 mm. (2) The accumulator according to claim 1, wherein D/d is less than 2.0, where D is the peak diameter and d is the valley diameter of the bellows body.