JPH09242703A - Metal bellows type accumulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the damage to a bellows by providing a stopper for preventing the shrinking of the bellows to a size smaller than a minimum stroke in the metal bellows. SOLUTION: A stopper 16 is formed to be cylindrical, both ends thereof being opened, and one end thereof is attached to the inner surface of the gas injection side end plate 6a of a shell 6. For its material, any may be used as long as it has a strength for supporting a bellows 8 when the high pressure of hydraulic oil 15 is applied after injected gas 7 is leaked from the bellows 8, a length L is set longer than a minimum stroke for compressing the bellows 8 and leading to damage and an outer diameter R is set a little smaller than the inner diameter of the bellows 8. If the leakage of the injected gas 7 occurs because of the damage of a gas injection spigot 12 or a sealing 13, the bellows 8 is compressed by the pressure of the hydraulic oil 15, but since the bellows 8 is supported from the inside by the stopper 16 and the bellows 8 is never compressed to a size smaller than a minimum stroke, leakage in a radial direction is prevented and the damaging of the bellows 8 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to compression of a sealed gas,
The present invention relates to a metal bellows accumulator that absorbs pressure fluctuations of a fluid by expansion.

[0002]

2. Description of the Related Art In a cylinder type hydraulic pump mounted on a main body of a construction machine such as a hydraulic excavator, the discharge of the hydraulic pump is changed every time the cylinder facing the discharge port of the hydraulic oil is switched as the hydraulic pump rotates. When the hydraulic pressure in the pipeline is higher than the hydraulic pressure on the cylinder side, a backflow of hydraulic oil occurs in the valve plate each time, and the backflow propagates to the discharge pipeline of the hydraulic pump as pulsation of hydraulic pressure in the pipeline. . The frequency of the pulsation of the hydraulic pressure is obtained by multiplying the number of cylinders by the number of rotations of the hydraulic pump. For example, when the number of cylinders is 7 and the rotation speed is 3000 rpm, the pulsation frequency is 350 Hz. Such pulsation causes vibration or resonance in a pipe or the like, thereby generating noise.

Conventionally, in order to prevent such a pulsation that generates noise, a discharge pipe near the discharge port of a hydraulic pump has a distal end made of a steel pipe or a rubber pipe having a length of 1/4 of the pulsation wavelength. Is provided in a branched manner, and in the branched pipe, the pulsation wave directed toward the tip and the pulsation wave reflected and returned cancel each other, thereby suppressing pulsation.

However, the suppression of pulsation by such a branch pipe has a high frequency dependence, cannot suppress higher-order pulsation, and is not necessarily satisfactory in terms of the pulsation attenuation rate. As shown in FIG. 3, instead of this branch pipe, a metal bellows type accumulator 3 is attached to a discharge pipe 2 of a hydraulic pump 1 as a pulsation suppressing means (4 is an actuator including a hydraulic cylinder and a hydraulic motor). Are already developing).

The accumulator is disclosed in, for example,
As disclosed in Japanese Laid-Open Patent Publication No. 40401, as shown in FIG. 4, the port 5 is attached to the mouthpiece 5 for attachment to the discharge conduit 2.
a shell 6 having a, and a metal bellows 8 housed in the shell 6 and having one end fixed to the side opposite to the port 5a and having a high-pressure filled interior gas 7 such as nitrogen gas. And a cap 9 fixed to the bellows 8.
And a sealing material 11 made of rubber or the like provided on the cap 9 and brought into close contact with the receiving surface 10 at the inner end of the port 5a. 12 is a gas sealing plug, 13 is its seal ring,
Reference numeral 14 is a seal ring made of rubber or the like that is fitted to the male screw-shaped mounting portion of the shell 6.

In this accumulator, when the hydraulic pressure of the hydraulic oil 15 flowing through the discharge pipe line 2 becomes equal to or higher than the cracking pressure of the accumulator, the sealing material 11 made of rubber or resin fixed to the cap 9 at the tip of the bellows 8 and the receiving surface 10 are provided. After the seal portion between and opens the cap 9 of the bellows 8 away from the port 5a, the bellows 8 expands and contracts to absorb the pulsation of hydraulic pressure in the discharge conduit 2 to which the actuator group 4 is attached. .

If such accumulators are used, these accumulators have a relatively small frequency dependency and a high pulsation damping rate, so that pulsation can be sufficiently suppressed.

[0008]

However, when the metal bellows type accumulator as shown in FIG. 4 is used in the hydraulic circuit of the construction machine as shown in FIG. 3, the bellows 8 is filled with the filled gas 7 and then the gas is discharged. When gas leakage occurs due to damage to the plug 12 or the seal ring 13 thereof, the bellows 8 is compressed by the pressure of the hydraulic oil 15 in the discharge pipe line 2 and is damaged by more than the stroke of the bellows 8. When the bellows 8 is broken in this way, debris enters the discharge conduit 2 from the port 5a, and the hydraulic motor or hydraulic pump 1 in the actuator group 4 is broken.
There is a problem in that the product may be damaged or stick may occur.

In view of the above problems, the present invention provides a metal bellows type accumulator which can prevent the metal bellows from being damaged by fluid pressure such as hydraulic pressure when the enclosed gas in the metal bellows leaks. The purpose is to provide.

[0010]

In order to achieve the above-mentioned object, the present invention comprises a shell having a port in the mouthpiece, and a metal bellows housed in the shell and filled with an enclosed gas. The fluid pressure from the port causes the seal portion between the cap at the tip of the bellows and the port to open and the bellows cap to separate from the port. In the metal bellows type accumulator that absorbs, the bellows is provided with a stopper that prevents the bellows from contracting to a minimum stroke or less.

[0011]

In the present invention, even if the gas enclosed in the bellows leaks and the fluid pressure from the port acts on the bellows, the bellows is supported by the stopper and the bellows is prevented from contracting below the minimum stroke. It is possible to prevent damage.

[0012]

1 (A) is a longitudinal sectional view showing an embodiment of an accumulator according to the present invention in a state in which a bellows is supported by being stopped from contracting by a stopper.
2B is a sectional view taken along the line EE of FIG. 2A, and FIG. 2 is a vertical sectional view showing a state in which the actuator of the embodiment is performing a pulsation absorbing operation of hydraulic pressure by the hydraulic pressure of the hydraulic oil 15. In the figure, FIG.
4 that are the same as those in FIG. 4 are members that perform the same function.

Reference numeral 16 denotes a stopper provided in the bellows 8 according to the present invention. The stopper 16 has a cylindrical shape with both ends open, and one end of the stopper 16 is an end of the shell 6 on the gas charging side. Welding, bonding, to the inner surface of the plate 6a,
It is fixedly attached by fitting. The stopper 16 may be made of any material as long as it has strength enough to support the bellows 8 when the high pressure of the hydraulic oil 15 acts after the enclosed gas 7 leaks from the bellows 8.
Is set to a length longer than the minimum stroke that compresses the bellows 8 to cause damage, and the outer diameter R is set to be slightly smaller than the inner diameter of the bellows 8.

In this accumulator, hydraulic oil 15
When the hydraulic pressure is below the cracking pressure,
As indicated by the chain double-dashed line, the sealing material 11 is in contact with the receiving surface 10 of the shell 6. When the pressure of the hydraulic oil 15 becomes equal to or higher than the cracking pressure, as shown in FIG. 2, the seal portion between the seal material 11 and the receiving surface 10 is opened and the cap 9 of the bellows 8 is separated from the port 5a. By expanding and contracting, the pulsation of hydraulic pressure in the discharge pipe line 2 is absorbed.

When the sealed gas 7 leaks due to damage to the gas sealing plug 12 or its seal ring 13, the balance between the pressure of the hydraulic oil 15 in the discharge conduit 2 and the gas pressure in the bellows 8 is lost. Although the bellows 8 is compressed by the pressure of the hydraulic oil 15, the bellows 8 is supported from the inside by the stopper 16, the bellows 8 is not compressed below the minimum stroke, and it is prevented from being crushed in the radial direction. It is possible to prevent damage. Therefore bellows 8
It is possible to prevent damage to hydraulic equipment such as hydraulic motors and hydraulic pumps due to the debris circulated in the pipeline.

The present invention can be applied to a pneumatic circuit and can be used not only for excavators such as hydraulic excavators and loader excavators, but also for other various construction machines using hydraulic pumps such as cranes and pile drivers. In addition to construction machines, it can be applied to other machines using fluid pressure.

[0017]

According to the present invention, since the stopper for preventing the bellows from shrinking to the minimum stroke or less is provided in the bellows of the metal bellows type accumulator, when the enclosed gas in the bellows leaks, it is connected to the accumulator. It is possible to prevent the bellows from being damaged by the fluid pressure of the pipe line. As a result, the fragments of the bellows circulate in the fluid pressure circuit, and the fluid pressure circuit can be prevented from being damaged.

[Brief description of drawings]

FIG. 1A is a vertical sectional view showing an embodiment of an accumulator of the present invention in a state where a bellows is prevented from contracting by a stopper, and FIG. 1B is a sectional view taken along line EE of FIG.

FIG. 2 is a vertical cross-sectional view showing the accumulator of the embodiment of FIG. 1 in a hydraulic pulsation absorbing operation state.

FIG. 3 is a hydraulic circuit diagram showing an application example of a metal bellows type accumulator.

FIG. 4 is a vertical sectional view showing a conventional accumulator.

[Explanation of symbols]

2: Discharge pipe line, 5: Cap portion, 5a: Port, 6: Shell, 7: Filled gas, 8: Bellows, 9: Cap, 1
0: receiving surface, 11: sealing material, 12: gas sealing plug, 13,
14: seal ring, 15: hydraulic oil, 16: stopper

Claims (1)

[Claims] 1. A bellows tip having a shell having a port in a mouthpiece and a metal bellows housed in the shell and filled with a high-pressure enclosed gas therein. In the metal bellows type accumulator that absorbs the pulsation of the fluid pressure in the pipeline by the expansion and contraction of the bellows after the seal between the cap and the port of the bellows is opened and the bellows cap is separated from the port. A metal bellows type accumulator, characterized in that a stopper is provided to prevent the bellows from contracting below a minimum stroke.