JPH0542241Y2 - - Google Patents

Description

[Detailed Description of the Invention] <<Industrial Application Field>> This invention relates to a free piston type accumulator used in a hydraulic circuit.

《Prior art》 A free piston type accumulator separates a gas chamber containing gas from a liquid chamber into which liquid is taken in and taken out by a free piston that is airtightly fitted inside a cylinder. The chamber is defined by the piston and a cap secured to the open end of the cylinder. When the pressure of the liquid introduced into the liquid chamber from the liquid inlet/outlet formed in the cap becomes higher than the pressure in the gas chamber, this pressure presses the piston and compresses the gas in the gas chamber. When the liquid pressure in the liquid chamber decreases from this state,
The gas in the gas chamber expands and pushes the piston in the opposite direction. By repeating this operation, fluid pressure fluctuations in the hydraulic circuit are absorbed. Such an accumulator is shown in, for example, Japanese Patent Laid-Open No. 188601/1983.

<<Problems to be solved by the invention>> However, in conventional free piston type accumulators, when the liquid pressure in the liquid chamber drops below the initial sealing pressure in the gas chamber, the piston closes the cap on the liquid pressure chamber side. Because of this impactful contact, impact noise is generated and the vibrations are transmitted to the sealing member for sealing gas and liquid, resulting in a problem of deterioration of sealing performance.

Therefore, an object of this invention is to provide a free piston type accumulator that can prevent the generation of collision noise and the deterioration of sealing performance.

<Means for Solving the Problems> The accumulator according to this invention is a free piston type accumulator that isolates a gas chamber and a liquid chamber by a free piston that is airtightly fitted inside a cylinder whose both ends are closed. A bellows whose free length is set to protrude beyond the end surface of the piston on the liquid chamber side is fixed to the pressure receiving surface on the liquid chamber side of the piston, and the bellows has an internal space and a liquid chamber. It is characterized by providing a communication hole for communicating with the.

<<Operation>> When the liquid pressure in the liquid chamber falls below the initial pressure in the gas chamber, the piston attempts to collide with the cap on the liquid chamber side, but the bellows provided on the pressure receiving surface of the piston on the liquid chamber side prevents the collision. This reduces the impact and prevents the occurrence of collision noise and the deterioration of sealing performance due to its vibration.

<<Embodiment>> FIG. 1 shows an embodiment of this invention. This free piston type accumulator includes a cylinder 1, a free piston 4 provided airtightly and slidably inside the cylinder 1 via an O-ring 2 and a bearing 3, and one open end of the cylinder 1. A bottom plate 6 is press-fitted on the inside and welded on the outside with solder 5, a cap 8 is press-fitted inside the other open end of the cylinder 1 via an O-ring 7, and the cap 8 is covered with a cylinder. A cover packing gland 9 is screwed onto the outer periphery of the other open end of the cover. As a result, both ends of the cylinder 1 are closed. In this cylinder 1, a gas chamber 10 is formed between the piston 4 and the bottom plate 6, and a liquid chamber 11 is formed between the piston 4 and the cap 8.

A screw hole 12 for attaching the accumulator to another member is formed in the bottom plate 6, and a plug 14 for closing an inlet 13 for sealing gas into the gas chamber 10 is attached.

Further, the cap 8 is formed with a liquid inlet/outlet 15 to which a hose for introducing and removing liquid into the liquid chamber 11 is attached.

A bellows 17 is fixed to the recessed liquid side pressure receiving surface 16 of the piston 4. This bellows 17 is made of a material such as resin, rubber, or metal, and its free length is approximately 180 mm from the end surface of the piston 4 on the liquid chamber 11 side when attached to the liquid pressure receiving surface 16.
It is determined to protrude by a length L from the center. This protrusion length L is determined by the spring constant of the bellows 17, the initial filling pressure of the gas chamber 10, and the liquid chamber 1.
It is determined by the viscosity of the liquid in 1. Further, in the free end surface 19 of the bellows 17, there is a communication hole 2 that communicates the internal space 20 of the bellows 17 with the liquid chamber 11.
1 is formed. Therefore, bellows 17
The internal space 20 of will be filled with the liquid introduced into the liquid chamber 11.

Next, the operation of this accumulator will be explained. Gas is sealed in the gas chamber 10 at a predetermined pressure from an injection port 13 and sealed by a plug 14 . A liquid in the hydraulic circuit is introduced into the liquid chamber 11 from a liquid inlet/outlet 15 . When the pressure of the introduced liquid becomes higher than the pressure of the gas in the gas chamber 10, the piston 4 is pressed by the pressure of the liquid, and the gas in the gas chamber 10 is compressed. When the liquid pressure in the liquid chamber 11 decreases from this state, the gas chamber 1
The gas inside the piston 4 expands and presses the piston 4 toward the liquid chamber 11. By repeating such operations, pulsations in the hydraulic circuit are absorbed or pressure is accumulated.

Now, when the hydraulic pressure in the hydraulic circuit suddenly decreases and the hydraulic pressure in the liquid chamber 11 falls below the initial sealing pressure in the gas chamber 10, the piston 4 is suddenly pressed toward the cap 8. . At this time, in the past, the end surface 18 of the piston 4 collided with the cap 8, causing abnormal noise, but in this invention, before the end surface 18 of the piston 4 hits the cap 8, the end surface 19 of the bellows 17 collides with the cap 8. It is compressed in the process. The impact is absorbed by the elastic force of the bellows 17 itself, and the liquid filling the internal space 20 passes through the communication hole 21 to the liquid chamber 10.
The impact is also absorbed by the flow resistance at that time. In this way, the occurrence of collision noise when the end surface 18 of the piston 4 bottoms out against the cap is suppressed, and the occurrence of vibration is also suppressed, and the O-ring 2 around the piston 4 and the O-ring around the cap 8 are suppressed. 7, etc., is prevented from deteriorating in sealing performance.

<<Effect of the invention>> As described above, the free piston type accumulator according to this invention has a free length set on the pressure receiving surface of the piston on the liquid chamber side so as to protrude beyond the end surface of the piston on the liquid chamber side. In addition to fixing the bellows, the bellows is provided with a communication hole that communicates the internal space with the liquid chamber, so that the generation of collision noise and vibration when the piston bottoms out on the cap is suppressed. This has the effect of stabilizing the gas and liquid sealing properties in the accumulator and improving durability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a free piston type accumulator showing an embodiment of this invention. 1... Cylinder, 2... O-ring, 3... Bearing, 4... Piston, 6... Bottom plate, 7... O-ring, 8... Cap, 9... Cover packing gland, 10... Gas chamber , 11...
...Liquid chamber, 16...Liquid chamber side pressure receiving surface, 17...Bellows, 20...Internal space, 21...Communication hole.

Claims (1)

[Scope of utility model registration request] A free piston type accumulator that isolates a gas chamber and a liquid chamber by a free piston that is airtightly fitted inside a cylinder whose both ends are closed, the piston having a pressure-receiving surface on the liquid chamber side, A bellows whose free length is set to protrude beyond the end surface of the piston on the liquid chamber side is fixed, and a communication hole is provided in the bellows to communicate the internal space with the liquid chamber. Accumulator.