JPH09242705A - Metal bellows type accumulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the damage to fluid pressure equipment by providing a filter for preventing the flowing-out of broken pieces from a shell when a bellows is damaged in a base part. SOLUTION: A filter 16 is made of a metallic net or a porous plate and firmly fixed to the tip of a base part 5 so as to cover a port 5a. The attaching of the filter 16 is performed by welding or pressure-connecting the same to the base part 5, but it may be performed by holding the filter 16 between a welding ring and the tip of the base part 5 and fixing the ring by a screw or the like. If the leakage of injected gas 7 occurs because of the damaging of a gas injecting spigot 12 or a seal ring 13 or the like, a balance between the pressure of the hydraulic oil 15 of an outlet pipe path 2 and a gas pressure in the bellows 8 is lost and even if the bellows 8 is compressed by the pressure of the hydraulic oil 15 and broken into pieces, the broken pieces are prevented from flowing out from the shell 6 to the outlet pipe path 2. Thus, the damaging of hydraulic equipment caused by the circulation of the broken pieces in the pipe path 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. 3A, a metal bellows type accumulator 3 is attached to a discharge pipe 2 of a hydraulic pump 1 as pulsation suppressing means instead of the branch pipe (4 is a hydraulic cylinder or a hydraulic motor). Has already been developed.

The accumulator is disclosed in, for example,
As disclosed in Japanese Patent No. 40401 and the like, FIG.
(B) As shown in FIG.
6 having a port 5a in the mouthpiece 5
And one end of the base 5
A metal bellows 8 fixed on the opposite side to the inside and filled with a sealed gas 7 such as nitrogen gas at a high pressure, a cap 9 fixed to the bellows 8, and a port provided on the cap 9. The seal member 11 is made of rubber or the like and closes the port 5a by closely contacting 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, and 17 is a resin guide mounted on the cap 9 of the bellows 8, and between the guide 17 and the inner wall of the shell 6. A gap is formed, and the hydraulic oil 15 flows through the gap.

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, a seal between the seal material 11 fixed to the cap 9 at the tip of the bellows 8 and the receiving surface 10 is obtained. After the part opens and the cap 9 of the bellows 8 separates from the port 5a,
When the bellows 8 expands and contracts, the actuator group 4
Is for absorbing the pulsation of hydraulic pressure in the discharge pipe line 2 to which 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. 3 (B) is used in the hydraulic circuit of the construction machine as shown in FIG. 3 (A), the bellows 8 is used.
When a gas leak occurs due to damage to the gas sealing plug 12 or its seal ring 13 after filling the sealed gas 7 into the inside,
Due to the pressure of the hydraulic oil 15 in the discharge pipe line 2, the bellows 8
It is compressed beyond the stroke of the bellows 8 and is damaged. When the bellows 8 is broken in this way, there is a problem that debris enters the discharge conduit 2 from the port 5 and damages the hydraulic motor or hydraulic pump in the actuator group 4 or causes sticking.

In view of the above-mentioned problems, it is an object of the present invention to provide a metal bellows type accumulator having a structure capable of preventing damage to a fluid pressure device due to outflow of debris into a pipe due to breakage of a metal bellows.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a shell having a port at a mouth portion, and a metal bellows housed in the shell and filled with a high-pressure sealed gas. After the seal portion between the cap at the tip of the bellows and the port is opened by the fluid pressure from the port and the cap of the bellows is separated from the port,
In the metal bellows type accumulator that absorbs the pulsation of fluid pressure in the pipeline by expanding and contracting the bellows, the mouthpiece part is provided with a filter for preventing outflow of fragments from the shell when the bellows is broken. To do.

[0011]

In the present invention, when the bellows is damaged, the filter provided on the mouthpiece prevents the outflow of the bellows fragments from the inside of the shell to the fluid pressure pipeline, so that the equipment installed on the pipeline is protected. You can avoid damage from debris.

[0012]

1A is a longitudinal sectional view showing an embodiment of an accumulator according to the present invention in a pulsation absorbing operation state, and FIG. 1B is a view taken in the direction of arrow E in FIG. In the figure, FIG.
The same reference numerals as are members that perform the same function.

Reference numeral 16 is a filter added according to the present invention, and the filter 16 is a wire mesh or a perforated plate,
It is fixed to the tip of the base portion 5 so as to cover the port 5a.
The filter 16 is attached by welding or pressure welding to the mouthpiece portion 5, but the filter 16 is sandwiched between the welding ring and the tip of the mouthpiece portion 5 and the ring is fixed with a screw or the like so that the filter 16 is attached. You may go.

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, 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 5 as shown by the solid line in FIG. Thereafter, the bellows 8 expands and contracts to absorb the pulsation of hydraulic pressure in the discharge pipe line 2.

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. Even if the bellows 8 is compressed due to the pressure of the hydraulic oil 15 and breaks to generate debris, since the filter 16 is provided in the mouthpiece portion 5, the debris may flow out from the shell 6 to the discharge pipe line 2 because of the filter 16. Be blocked.
Therefore, the fragments of the bellows 8 are circulated in the pipeline, and the hydraulic equipment such as the hydraulic motor and the hydraulic pump can be prevented from being damaged.

FIG. 2 is a vertical sectional view showing another embodiment of the present invention. In this embodiment, a filter 16 is made of rubber or resin on the inner wall of the shell 6 which constitutes the inner end of the port 5a. It is incorporated in the sealing material 11 and attached. In this example, the cap 9 is formed into a smooth surface, and the cap 9 comes into contact with the sealing material 11 fixed to the inner wall of the shell 6 to perform sealing. At the center of the sealing material 11, an opening 11a for allowing the hydraulic oil 15 to flow is provided. Also in this embodiment, similarly, the filter 16 prevents debris from flowing out into the pipe line when the bellows is broken.

The present invention can be applied not only to excavators such as hydraulic excavators and loader excavators, but also to various other construction machines using hydraulic pumps such as cranes and pile drivers.
Further, the present invention is applicable not only to construction machines but also to other machines utilizing hydraulic pressure, and further to machines utilizing pneumatic pressure.

[0018]

According to the present invention, a filter is provided so as to cover the port of the mouthpiece of the metal bellows type accumulator and prevent the debris generated when the bellows is broken from flowing out into the pipe line. It is possible to prevent the fluid pressure device from being damaged by debris because the filter prevents the fluid from flowing into the passage.

[Brief description of drawings]

FIG. 1A is a vertical cross-sectional view showing an embodiment of an accumulator of the present invention in a hydraulic pulsation absorption operation state, and FIG. 1B is a view taken in the direction of arrow E of FIG.

FIG. 2 is a longitudinal sectional view showing another embodiment of the present invention.

FIG. 3A is a hydraulic circuit diagram showing an application example of a metal bellows type accumulator, and FIG. 3B is a vertical sectional view showing a conventional accumulator.

[Explanation of symbols]

2: Discharge pipe, 5: Cap portion, 5a: Port, 6: Shell,
7: Filled gas, 8: Bellows, 9: Cap, 10: Receiving surface, 11: Sealing material, 12: Gas filling plug, 13, 14:
Seal ring, 15: hydraulic oil, 16: stopper, 17:
guide

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 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 opens and the cap of the bellows separates from the port, A metal bellows type accumulator characterized by being provided with a filter for preventing debris from flowing out of the shell when the bellows is broken.