JP3409431B2 - Fluid pressure device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to, for example, an accumulator, a pulsation absorbing device, an actuator for a hydraulic piping system of an automobile suspension or a braking system, or an accumulator, a pulsation absorbing device, an actuator, an air spring for a water pipe system. , Regarding fluid pressure device that uses gas on at least one side and operates by fluid, especially because of small gas permeation / leakage, it is possible to downsize the device, extend its service life, facilitate policy, and widen the operating pressure range. Fluid pressure device that is capable of

[0002]

2. Description of the Related Art Conventionally, as a fluid pressure device of this type, there has been known a device using a rubber diaphragm or a metal bellows. A fluid pressure device using a rubber diaphragm is excellent in responsiveness due to the flexibility and deformability of rubber, and can also be made lightweight. However, when gas is used in one of the chambers of a pressure vessel partitioned by a rubber diaphragm, the rubber material is inferior in gas-shielding property, so the diaphragm thickness increases and the addition of filler is added. Although it can be improved to some extent by the above, there was a problem that the pressure of the enclosed gas drops with the time of use.

On the other hand, in a fluid pressure device using a metal bellows having an excellent gas shielding property, the Young's modulus of a metal is usually 2
Since the pressure is 50,000 kgf / mm ² or more, it is necessary to increase the number of peaks of the bellows in order to expand the operating range of the fluid pressure device. For this reason, the fluid pressure device has a drawback that it is heavy in terms of weight as well as being contrary to the demand for miniaturization due to the increase in the overall length of the fluid pressure device. By the way, in order to solve such a weight problem, a fluid pressure device using a resin bellows has been proposed. Since resin has low rigidity with respect to metal, the number of bellows can be reduced compared to metal bellows within the same operating pressure range, resulting in a shorter overall length of the fluid pressure device and a reduction in weight. It has the advantage of being able to.

[0004]

However, in the fluid pressure device using the conventional resin bellows, unlike the metal, the permeation / leakage of gas from the bellows itself cannot be ignored, so that the performance of the fluid pressure device is high. In order to maintain the gas for a long period of time, it is necessary to effectively prevent permeation / leakage of gas on the gas chamber side. For this reason, it is necessary to select a resin having a high gas shielding property as a material forming the bellows. Generally, a resin material excellent in a gas shielding layer has a high elastic modulus and a low elastic limit against deformation. When the gas is filled in the gas chamber or when the amount of working deformation is large, the bellows may undergo buckling deformation, and in addition, due to the high rigidity, it is difficult to secure the sealing property with the pressure vessel. There was also the problem of being there.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a fluid pressure device capable of preventing permeation / leakage of enclosed gas and preventing buckling deformation. To do.

[0006]

In order to achieve the above object, in a fluid pressure device according to the present invention, the inside of a pressure vessel (1, 2) is a gas chamber (5) and a liquid by a bellows (3) made of a resin material. In a fluid pressure device having a multi-layer structure, which is partitioned into a chamber (4) and the bellows (3) has at least a gas shielding layer (7) and an elastic flexible layer (8), the elastic modulus is 300 kgf.
/ Mm ² or less elastic soft layer (8) is provided at least in the gas chamber (5) side, the mounting portion of the bellows
(3a) is held in the fitting portion of the pressure vessel (1,2), before
The gas permeability coefficient of the gas shielding layer (7) is P _B , and the elastic flexibility is
The gas permeability coefficient of the soft layer (8) is P _E , and the attachment portion (3a) is
The average thickness of the elastic flexible layer (8) is d _E , and the attachment portion (3
a), the number of laminated elastic flexible layers (8) is N,
The average thickness of the gas shielding layer (7) of the bellows excluding a) is d
_B , the minimum inner diameter of the mounting portion (3a) is R, the mounting portion
Effective surface area of the bellows excluding (3a) on the gas chamber (5) side
Where A is the axial length of the mounting portion (3a)
L, characterized in that it is _{L ≧ (P E · R ·} d B · d E) / (P B · A · N).

A fluid permeation preventive layer (11) is preferably provided between the elastic soft layer (8) on the liquid chamber (4) side of the bellows (3) and the gas shielding layer (7).

[0008]

Further, if a structure is adopted in which the mounting portion of the bellows is sandwiched by the fitting portion of the pressure container due to the difference in the materials forming the pressure vessel and the bellows, gas tends to permeate and leak from the mounting portion of the bellows. . In particular, there is a high risk of permeation and leakage through the elastic and flexible layer, which is inferior to the gas shielding layer. Therefore, in the present invention, the gas permeability coefficient of the gas shielding layer, the gas permeability coefficient of the elastic flexible layer, the average thickness of the elastic flexible layer of the mounting portion, the number of laminated elastic flexible layers of the mounting portion, the gas of the bellows excluding the mounting portion Average thickness of the shielding layer, minimum inner diameter of the mounting part,
Since the axial length L of the mounting portion is specified while taking into consideration the conditions of the effective surface area of the bellows other than the mounting portion, the gas flow path in the mounting portion of the bellows becomes longer, resulting in As a result, the amount of gas leakage is reduced and the life of the accumulator is extended. Furthermore, if a fluid permeation preventive layer is provided between the elastic flexible layer on the liquid chamber side of the bellows and the gas shielding layer, even if the liquid flowing into the liquid chamber tries to deteriorate the performance of the gas shielding layer, the permeation preventing effect on the liquid is improved. It will be controlled by the fluid permeation preventive layer composed of an excellent resin.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Accumulator FIG. 1 is a half sectional view showing an accumulator embodying the fluid pressure device of the present invention, and FIGS. 2 (A) to 2 (D) are main part sectional views showing other aspects of the bellows of the accumulator, FIG. 3 (A). )
FIG. 3B is a sectional view of an essential part showing another structure of the attachment part of the bellows.

The accumulator of this embodiment is a resin material bellows type accumulator, which can be used, for example, for a hydraulic piping system of a suspension or a braking system of an automobile, or for a water piping system. Not limited. As shown in FIG. 1, in the accumulator of this embodiment, the shell 1 and the end plate 2 are
(These correspond to the pressure vessel of the present invention) An accumulator chamber 6 surrounded by a bellows 3 made of a resin material is elastically mounted. By mounting the resin material bellows 3 in the accumulator chamber 6 as described above, the accumulator chamber 6 is formed in the liquid chamber 4 formed inside the bellows 3.
And a gas chamber 5 surrounded by the bellows 3 and the shell 1.

The resin bellows 3 is formed in a so-called bellows shape in which a disk-shaped top portion is alternately and continuously formed with a divergent conical surface and a divergent conical surface. The bellows-like portion of the resin bellows expands and contracts in the axial direction by the pressure difference between the inside and the outside acting on the bellows 3 made of a material, so that it functions as an accumulator. The mounting portion 3a, which is the open end of the resin bellows 3, is sandwiched between the joints between the shell 1 and the end plate 2. As a result, the gas chamber 5 and the liquid chamber 4 are sealed. The mounting structure of this bellows will be described later. Incidentally, in order to join the end plate 2 to the shell 1, the open end 1a of the shell 1 may be caulked.

The end plate 2 is provided with a stopper 2a which projects into the liquid chamber 4 so as to regulate the minimum compression device for the resin bellows 3. Also,
The end plate 2 is provided with a liquid inflow port 2b communicating with a liquid chamber 4 formed inside the resin bellows 3. An inclined surface corresponding to the inclined surface of the bellows 3 is formed at the foot of the stopper 2a, while a gas chamber formed between the resin bellows 3 and the inner surface of the shell 1 is formed at the top of the shell 1. 5 is formed with a gas charging port 23, and a plug 24 for sealing the inside of the gas chamber 5 is fitted into the gas charging port 23 via an O-ring 25.

A gas having a predetermined pressure (for example, an inert gas such as nitrogen gas) is sealed in the gas chamber 5 from the gas charging port 11, and the liquid inflow port 2b formed in the end plate 2 is connected to a liquid pipe or the like (not shown). For example, the resin material bellows 3 is axially expanded and contracted in a direction in which a pressure difference between the liquid chamber 4 inside and the gas chamber 5 outside acts on the resin bellows 3 to reduce the pressure fluctuation of the liquid pipe. Will move. As a result, it is possible to effectively prevent pressure fluctuations in the liquid piping and the like, such as water hammer.

The bellows 3 of this embodiment has a multi-layer structure made of a plurality of resins as shown in an enlarged view in FIG.
That is, the gas shielding layer 7 made of a material having an excellent gas shielding property is sandwiched between elastic flexible layers 8 made of a material having a low elastic modulus and a high elastic deformation limit. In this case, the gas shielding layer 7 has a function of preventing the gas enclosed in the gas chamber 5 from permeating the bellows 3 and permeating to the liquid chamber 4 side, and has, for example, excellent gas shielding property and workability. It is preferable to use a thermoplastic resin in consideration of goodness.

Examples of such resins include ethylene vinyl alcohol copolymers, polyvinylidene chloride resins, polyacrylonitrile resins, and cellulose resins. Also, gas shielding and processability,
In order to improve durability, various additives such as fillers and stabilizers, or other polymers may be blended appropriately. The material composition, shape, wall thickness, etc. of the gas shielding layer are determined by the environment of use such as gas permeability, temperature and operability.

Further, the elastic flexible layer 8 is provided on the front and back sides of the above-mentioned gas shielding layer 7 to relieve the shear stress applied to the gas shielding layer 7 having poor flexibility and prevent the bellows 3 from buckling deformation. It has a function of protecting the gas shielding layer 7 from the liquid flowing into the liquid chamber 4. A thermoplastic elastomer, a soft resin, rubber, or the like can be used as the resin forming the elastic and flexible layer 8, and it is preferable to use the thermoplastic resin from the viewpoint of workability. However, after being laminated with the gas shielding layer 7, it may be crosslinked by heating, irradiation with radiation, or a chemical reaction.

This elastic flexible layer 8 is used for the environmental temperature used.
The elastic modulus below is smaller than that of the resin forming the gas shielding layer 7.
It is necessary that the elastic modulus is 300 kgf /
mm ²Or less, more preferably the elastic modulus is 150 kgf /
mm²It is the following.

When the fluid flowing into the liquid chamber 4 deteriorates the performance of the gas shielding layer 7, it is necessary to prevent the permeation of the fluid.

For example, when the fluid is a mineral oil type, a resin having a high oil resistance such as polyurethane type, polyester type, polyamide type resin, etc. is effective. In the case of a liquid, a non-polar resin such as a polyolefin resin or a styrene-butadiene resin is effective. In particular, polymer blend type thermoplastic elastomers (e.g., dynamically vulcanized elastomers such as Santoprene Diorast manufactured by ASE Japan) and soft resins (for example, Flexroy manufactured by Sumitomo Chemical Co., Ltd. and Zitel manufactured by DuPont). FN, Sumiflex manufactured by Sumitomo Bakelite Co., Ltd.) are preferable because the elastic modulus and workability can be changed to some extent by changing the blend composition or the grade of the resin to be blended. The material composition, the wall thickness, etc. of the elastic flexible layer 8 are appropriately determined depending on the use environment such as resistance to a fluid to be contacted and temperature and operability.

When laminating the gas shielding layer 7 and the elastic flexible layer 8, a method such as co-extrusion formation, multi-layer injection, or coating is effective from the viewpoint of workability, but at the laminated interface. When the adhesive strength is weak, it is desirable to use an adhesive (adhesive layer 9). This is because it is desirable that the interfaces are securely bonded to alleviate the stress concentration when the gas shielding layer 7 having high rigidity is deformed, and it is also necessary in terms of operating life. The adhesive according to the present embodiment is preferably a hot-melt type, block copolymer or graft modified resin from the viewpoint of workability, but a method of adding an adhesive component to the elastic flexible layer 8 to impart adhesiveness, coating, etc. It is also possible to apply directly to the surface of the gas shielding layer 7.

However, for example, when the gas shielding layer 7 is made of ethylene vinyl alcohol and the elastic flexible layer 8 is made of polyamide, a sufficient adhesive strength can be secured, so that FIG.
The adhesive can be omitted as shown in FIG. As the method of manufacturing the resin material bellows 3, various molding methods utilizing the characteristics of the thermoplastic resin can be adopted, but it can be said that multi-layer blow molding that can simplify the processing step is preferable.

On the other hand, as the material forming the end plate 2, synthetic resin can be adopted in addition to metal. The synthetic resin is not particularly limited, but it is possible to use a resin having excellent durability such as rigidity and heat resistance, and particularly when the accumulator is applied to a drinking water pipe or the like, there is no effect on the human body. It is preferable to use polypropylene that does not exist at all. In this case, if the bellows 3 and the end plate 2 are made of the same synthetic resin, it becomes possible to attach the bellows to the end plate and then to integrate the two by means such as welding, thereby sealing the liquid chamber and the gas chamber. The performance will increase.

However, the end plate 2 does not necessarily have to be made of synthetic resin, and in addition to the above-mentioned resins, a material which is excellent in rust prevention and hygienic, such as stainless steel or brass, may be selected. Such joining of the metal pressure vessel and the bellows cannot be performed by welding. Therefore, the mounting portion 3 is attached to the opening of the bellows 3.
It is desirable to form a and to laminate the elastic flexible layer 8 on at least the gas chamber 5 side of the mounting portion 3a so as to ensure the sealing property.

In this case, since the elastomer generally used for the elastic flexible layer 8 is inferior in gas shielding property, in particular, in this embodiment, gas permeation in the bellows mounting portion 3a is prevented.
In order to prevent leakage, the length of the bellows mounting portion 3a is taken into consideration. That is, according to what the inventors of the present invention have sought, the elastic flexible layer 8 of the mounting portion 3a is permeated (sideways leaked) more than the amount of gas that permeates and leaks from the bellows portion other than the mounting portion 3a of the bellows. More gas leaks.
Therefore, in this embodiment, the gas passage length in the mounting portion 3a is increased to prevent lateral leakage of the mounting portion 3a.

Specifically, it can be considered as follows. That is, the leakage of gas from the gas chamber is determined by the surface area A of the bellows which is in contact with the gas, the average thickness d of the site and the gas permeability coefficient P of the bellows. That is, the amount of leakage per unit time is expressed by P × A × gas pressure / d (1) At this time, since the bellows forming a multi-layer structure as in the present embodiment described above, the gas permeability coefficient P _E of the gas permeability coefficient P _B and the elastic flexible layer of gas blocking layer is a P _B << P _E, It can be said that it is governed by the gas permeability coefficient and average wall thickness of the gas shielding layer. Therefore, the amount of leakage per unit time is P _B × A × gas pressure / d _B (2) However, when the elastic flexible layer is made of a flexible material such as rubber, its gas permeation coefficient becomes large, and the leak amount of gas passing through the bellows mounting portion per unit time adopts the caulking structure shown in FIG. Even if this is done, P _E × gas pressure × surface area of the elastic portion on the gas side of the mounting portion / length of the mounting portion, and this portion will leak to the outside of the accumulator. Assuming that the minimum inner diameter of the bellows mounting portion is R, the average thickness of the elastic soft layer of the bellows mounting portion is d _E , and the axial length L of the bellows mounting portion is P _E × gas pressure × πRd _E / It is represented by L (3). In this case, even if the caulking portion is welded to prevent it from leaking to the outside of the accumulator, it will eventually leak to the liquid chamber side, and when the elastic flexible layer is provided on the gas chamber side and the liquid chamber side. Since the gas passage length only doubles, the leakage amount per unit time is P _E × gas pressure × πRd _E / 2L (4) If there is no elastic flexible layer on the liquid chamber side,
It becomes the same as the above formula (3). Therefore, from Equations (3) and (4), the leakage amount per unit time is P _E × gas pressure × πRd _E / NL (5) when the number of elastic flexible layers in the mounting portion is N. ) Is represented by. Here, if the amount of gas leakage from the bellows mounting portion (Equation (5) above) is made smaller than the amount of gas leakage through the bellows (Equation (2) above), the amount of gas leakage throughout the accumulator will be reduced. From the above equations (2) and (5), P _B × A × gas pressure / d _B ≧ P _E × gas pressure × πRd _E / N
L becomes, and when this is arranged about L, L ≧ P _E · π · R · d _E · d _B / P _B · A · N. The average thickness d _E of the elastic flexible layer of the bellows attachment portion in this equation, since the bellows is reduced is compressed when assembled into the shell, is regarded as [pi] d _E ≒ d _E, above equation, L ≧ P _E · R · d _E · d _B / P _B · A · N By forming the mounting portion 3a having such a length, it is possible to secure a sealing property that suppresses lateral leakage, and when the internal pressure applied to the pressure vessel is not relatively high, the pressure vessels 1 and 2 and the bellows The joining with the mounting portion 3a can be performed only by caulking or fitting and tightening, and the working process can be simplified.

In the embodiment shown in FIG. 1, the shell 1 is crimped with the bellows mounting portion 3a held between the shell 1 and the end plate 2. However, in the fluid pressure device of the present invention, In addition to this, for example, as shown in FIG. 3 (A), the convex portion 10 is formed on the end plate 2, or as shown in FIG. 3 (B), the tip 1a of the shell and the tip (mounting portion) 3a of the bellows are formed. You may caulk so that it may go around the end plate 2. In short, it suffices that the length of the gas flow path in the mounting portion 3a be long enough to satisfy the above formula.

The multi-layer structure of the bellows 3 according to the present invention is composed of two elastic flexible layers shown in FIG. 1, one gas shielding layer, and five adhesive layers for adhering these layers. Besides, various modes are conceivable. Figure 2
FIGS. 2A to 2D are enlarged cross-sectional views of a main part showing another multilayer structure of the present invention, and FIG. 2A is an elastic flexible layer 8 on the gas chamber 5 side and a gas shielding layer on the liquid chamber 4 side. 7 is arranged, and both layers 7 and 8 are adhered to each other by the adhesive layer 9. Also, FIG.
The bellows 3 shown in (B) is an embodiment in which the elastic flexible layer 8 and the gas shielding layer 7 can obtain sufficient adhesive strength without using an adhesive.

Further, the bellows shown in FIG. 2C has a multilayer structure in which a fluid permeation preventive layer 11 is provided in addition to the elastic soft layer 8, the gas shielding layer 7 and the adhesive layer 9. This is because when the fluid flowing into the liquid chamber 4 may deteriorate the performance of the gas shielding layer 7, the elastic flexible layer 8 is preferably formed of a resin having excellent fluid resistance as described above. However, in the present embodiment, the fluid permeation preventive layer 11 is formed of a resin having an excellent effect of preventing permeation of a fluid in order to further suppress the performance deterioration of the gas shielding layer 7.

Since the fluid permeation preventive layer 11 is not required to have a low elastic modulus like the elastic flexible layer 8, its material may be selected according to the kind of fluid flowing into the liquid chamber 4. For example, when the fluid is a mineral oil-based resin, a resin having a high oil resistance such as a polyurethane-based resin, a polyester-based resin, or a polyamide-based resin is effective. Further, in the case of a polar liquid such as water-based or brake liquid, a non-polar resin such as a polyolefin-based resin or a styrene-butadiene-based resin is effective. FIG. 2D is a bellows in which a fluid permeation preventive layer 11 and an elastic flexible layer 8 are combined in multiple layers with an adhesive layer 9 around the gas shielding layer 7 in order to further enhance the fluid permeation preventive effect. is there.

In the embodiment shown in FIG. 1, the interior of the bellows is the liquid chamber 4, and the space between the bellows 3 and the shell 1 is the gas chamber 5.
However, as shown in FIG. 4, the inside of the bellows may be a gas chamber 5 and the space between the bellows 3 and the shell 1 may be a liquid chamber 4.

Shock Absorber Although the present invention has been described by taking the accumulator as an example of the fluid pressure device in the above embodiment, the present invention is not limited to the above-mentioned embodiment, and may be applied to other fluid pressure devices. Can be applied. 5A and 5B are half sectional views showing an embodiment in which the present invention is applied to a shock absorber (shock absorber).

The shock absorber shown in FIG. 5 (A) has a rod 13 slidable with respect to the cylinder case 12. The rod 13 has an upper end that holds the mounting portion 3a of the bellows 3 therebetween. The plate 14 is screwed. Gas filling port 2 for filling gas in end plate 14
3 is opened, and gas is enclosed in the gas chamber 5 formed by the bellows 3 through the gas introduction valve 15 attached to the gas inlet 23. On the other hand, a chamber defined by the lower end of the rod 13 and the inner surface of the cylinder case 12, and a chamber defined by the bellows 3 and the inner surface of the rod 13 communicated via a through hole 16 formed in the lower end of the rod 13. Serves as a liquid chamber 4 for liquid, for example. Various types of multilayer structures shown in FIGS. 1 and 2 can be applied to the bellows 3 of this type of shock absorber, and the structure of the mounting portion 3a of the bellows and the length L of the mounting portion 3a can be changed as shown in FIG. 1 and various configurations shown in FIG. 3 can be adopted. In the shock absorber thus configured, when the external force in the relative compression direction acts on the cylinder case 12 and the rod 13, the fluid sealed in the liquid chamber 4 is compressed while the bellows 3 in which the gas is sealed is compressed. . Thereby, the cylinder case 12 and the rod 1
The external force in the compression direction acting on 3 can be relaxed.

The basic operation of the shock absorber shown in FIG. 5 (B) is similar to that of the shock absorber shown in FIG. 5 (A), but in this embodiment, the rod 13 having the piston 13a in the cylinder case 12 is used. Is slidably provided, and an end plate 14 is welded to the lower end of the cylinder case 12 with the mounting portion 3a of the bellows 3 being sandwiched therebetween. The end plate 14 has a gas filling port 23 for filling gas.
Is opened, and the chamber partitioned by the inside of the bellows 3 and the end plate 14 becomes the gas chamber 5. On the other hand, a chamber defined by the lower surface of the piston 3a and the inner surface of the cylinder case 12 becomes a liquid chamber 4 such as a liquid. As the bellows 3 of this type of shock absorber, various multi-layered structures shown in FIGS. 1 and 2 can be applied, and the structure of the mounting portion 3a of the bellows and the length L of the mounting portion 3a are different from those shown in FIG. 1 and various configurations shown in FIG. 3 can be adopted.

Fluid Actuator and Fluid Pump The fluid pressure device of the present invention can be applied to, for example, actuators and fluid pumps in addition to the accumulators and shock absorbers described above. 6 and 7 are cross-sectional views showing an embodiment in which the fluid pressure device of the present invention is applied to an actuator or a fluid pump (which can be applied to either of the driving side and the driven side by exchanging them). In FIG. 6, the inside of the pressure vessel formed by the cylinder case 17, the piston 18 and the end plate 19 is partitioned into two chambers by the bellows 3, the inside of the bellows is the liquid chamber 4 and the outside of the bellows is the gas chamber 5. On the contrary, the one shown in FIG. 7 has a gas chamber 5 inside the bellows 3 and a liquid chamber 4 outside the bellows. In addition, "21" shown in FIG. 7 is a check valve.

In the embodiment shown in FIG. 6, when the fluid side introduced into the bellows 3 is used as the drive source and the piston 18 side is used as the driven side, the gas chamber 5 is filled with gas at a constant pressure in advance. In this state, a high-pressure fluid is circulated in the liquid chamber 4 from the fluid inlet / outlet port 20 formed in the end plate 19. As a result, the bellows 3 expands to compress the gas in the gas chamber 5, and the piston 18 moves up (the piston moves down if the operation is reversed). On the contrary, in the embodiment shown in FIG. 6, when the piston 18 side is used as the driving side and the fluid side introduced into the bellows 3 is used as the driven source,
The piston 18 is moved down in a state where the gas chamber 5 is filled with a gas having a constant pressure in advance. As a result, the gas in the gas chamber 5 is compressed and the bellows 3 is pushed down, so that the liquid chamber 4
The fluid inside is discharged from a fluid inlet / outlet port 20 formed in the end plate 19. When used as such a fluid pump, it is desirable to provide a check valve at the fluid inlet / outlet port 20. Further, as shown in FIG. 6, a guide ring 22 that slides along the inner surface of the cylinder case 17 may be provided on the bellows head in order to smoothly expand and contract the bellows head.

On the other hand, also in the embodiment shown in FIG. 7, the gas side introduced into the bellows 3 is used as the drive source and the piston 1
When the 8 side is used as a driven side, a high-pressure fluid is circulated in the gas chamber 5 from the gas inlets / outlets 20a, 20b opened in the end plate 19 in a state where a fixed amount of fluid is sealed in the liquid chamber 4 in advance. . As a result, the bellows 3 expands and compresses the fluid in the liquid chamber 4, and the piston 18 moves to the left side in the figure (if the operation is reversed, the piston moves to the right side in the figure). On the contrary, in the embodiment shown in FIG. 7, when the piston 18 side is used as the driving side and the gas side introduced into the bellows 3 is used as the driven source, the liquid chamber 4
The piston 18 is moved to the right side in the drawing in a state where a fixed amount of fluid is sealed in. As a result, the fluid in the liquid chamber 4 is compressed and the bellows 3 is compressed, so that the gas in the gas chamber 5 is opened in the end plate 19 and the gas outlet 20b is opened.
(If the reverse operation is performed, the gas is sucked into the gas chamber 5 from the gas inlet 20a formed in the end plate 19.)

It should be noted that the above-described embodiments have been described for facilitating the understanding of the present invention, and not for limiting the present invention. Therefore, each element disclosed in each of the above-described embodiments is intended to include all design changes and equivalents within the technical scope of the present invention.

[0039]

The bellows of the fluid pressure device of the present invention comprises 30
Since an elastic flexible layer made of a resin having a low elastic modulus of 0 kgf / mm ² or less and a high elastic deformation limit is provided, the gas shielding layer should be made of a resin having poor flexibility to prevent gas permeation. However, the elastic modulus of the bellows as a whole is small, and the elastic deformation limit can be increased. As a result, the shear stress applied to the gas shielding layer can be relieved and buckling deformation of the bellows can be prevented. Further, as a result, the gas shielding layer can be formed from a resin having excellent gas impermeability, so that the gas enclosed in the gas chamber permeates the liquid chamber side.
Even if it tries to leak, it is blocked by the gas shielding layer, and problems such as a decrease in gas pressure are solved even after long-term use. Also,
If a structure is adopted in which the mounting part of the bellows is sandwiched between the fitting parts of the pressure container due to the difference in the materials that make up the pressure vessel and the bellows, gas will try to permeate and leak from the mounting part of the bellows. Although there is a high possibility of permeation / leakage through an inferior elastic flexible layer, in the present invention, the gas permeability coefficient of the gas shielding layer, the gas permeability coefficient of the elastic flexible layer, the average thickness of the elastic flexible layer of the mounting portion, the mounting portion Number of laminated elastic and flexible layers, average thickness of gas shield layer of bellows excluding mounting part,
The axial length L of the mounting portion is increased while taking into consideration various conditions such as the minimum inner diameter of the mounting portion and the effective surface area of the bellows excluding the mounting portion on the gas chamber side. As a result, gas permeation is suppressed in the middle of the gas passage in the bellows mounting portion, and gas permeation / leakage in the bellows mounting portion is significantly reduced.

[Brief description of drawings]

FIG. 1 is a half sectional view showing an embodiment in which a fluid pressure device of the present invention is applied to an accumulator.

2 (A) to (D) are cross-sectional views of a main part showing an aspect of a multilayer structure of the bellows shown in FIG.

3 (A) and 3 (B) are cross-sectional views of essential parts showing another embodiment of the structure of the mounting portion of the bellows shown in FIG. 1, respectively.

FIG. 4 is a half cross-sectional view showing another embodiment in which the fluid pressure device of the present invention is applied to an accumulator.

5 (A) and 5 (B) are half sectional views showing an embodiment in which the fluid pressure device of the present invention is applied to a shock absorber.

FIG. 6 is a sectional view showing an embodiment in which the fluid pressure device of the present invention is applied to a fluid actuator or a fluid pump.

FIG. 7 is a cross-sectional view showing another embodiment in which the fluid pressure device of the present invention is applied to a fluid actuator or a fluid pump.

[Explanation of symbols]

1 ... Shell (pressure vessel) 1a ... Open end 2 ... End plate (pressure vessel) 2a ... Stopper 2b ... Liquid inflow port 3 ... Bellows 3a ... Mounting part 4 ... Liquid chamber 5 ... Gas chamber 6 ... Accumulator room (room) 7 ... Gas shielding layer 8 ... Elastic flexible layer 9 ... Adhesive layer 10 ... Convex part 11 ... Fluid permeation preventive layer 12 ... Cylinder case (pressure vessel) 13 ... Rod (pressure vessel) 14 ... End plate (pressure vessel) 15 ... Gas introduction valve 16 ... Through hole 17 ... Cylinder case (pressure vessel) 18 ... Piston (pressure vessel) 19 ... End plate (pressure vessel) 20 ... Fluid inlet / outlet 20a ... fluid inlet 20b ... Fluid outlet 21 ... Check valve 22 ... Guide ring 23 ... Gas sealing hole 24 ... Plug 25 ... O-ring

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F15B 1/00-1/26

Claims (2)

(57) [Claims] 1. A pressure chamber (1, 2) is partitioned into a gas chamber (5) and a liquid chamber (4) by a resin bellows (3), and the bellows (3) is at least a gas shielding layer (3). In a fluid pressure device having a multilayer structure having 7) and an elastic flexible layer (8), an elastic flexible layer (8) having an elastic modulus of 300 kgf / mm ² or less is provided at least on the gas chamber (5) side. And the mounting portion (3a) of the bellows of the pressure vessel (1, 2)
The gas permeation coefficient of the gas shielding layer (7), which is sandwiched between the fitting portions, is P _B , and the elasticity is
The gas permeability coefficient of the flexible layer (8) is P _E , and the attachment portion (3
a), the average thickness of the elastic flexible layer (8) is d _E , and the attachment portion is
(3a) the number of laminated elastic flexible layers (8) is N, and the attachment portion is
Average thickness of gas shield layer (7) of bellows excluding (3a)
The d _B, the attachment portion minimum inner diameter of the (3a) R, the attachment
Effective surface on the gas chamber (5) side of the bellows excluding the part (3a)
When the product is A, the axial length of the mounting portion (3a)
A fluid pressure device characterized in that L is L ≧ (P _E · R · d _B · d _E ) / (P _B · A · N) . 2. A fluid permeation preventive layer (11) between the elastic flexible layer (8) on the liquid chamber (4) side of the bellows (3) and the gas shielding layer (7). Item 2. A fluid pressure device according to item 1.