JP2000002393A - Liquid pressure pulsation-reducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid pressure pulsation-reducing device having excellent durability and reliability for reducing a pressure pulsation and/or surge pressure in a liquid pressure circuit such as a hydraulic circuit. SOLUTION: A liquid pressure pulsation-reducing device 1 is equipped with a tubular resilient member 11 containing independent bubbles and a means 5e to prevent the resilient member 11 from breakage and outflow. The means 5e is a filter pipe 5e which is provided with a plurality of holes 5g and inserted into a hole 11a formed in the resilient member 11. Since the filter pipe 5e exerts a filter action for the whole surface of the hole 11a, it transmits the liquid pressure to the resilient member 11 uniformly to every corner, and prevents eventual splinters from outflow in good performance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic pulsation reducing device used for reducing pressure pulsation and surge pressure in a hydraulic circuit such as a hydraulic circuit. In particular, the present invention relates to a hydraulic pulsation reducing device including an elastic body including a closed cell having a hydraulic pulsation reducing function. In addition, "pulsation" in this specification
Means in a broad sense also includes surge pressure.

[0002]

2. Description of the Related Art The prior art will be described by taking a hydraulic circuit as an example. In a hydraulic circuit, pressure pulsation occurs due to the mechanical structure of a hydraulic pump, resonance of a control system, and the like. Further, when an impact load is applied to the actuator or when the valve is switched, a surge pressure (impact pressure) is applied. These pressure pulsations and surge pressures are undesirable phenomena that cause vibration, noise, and breakage of the pipeline and the actuator. In conventional hydraulic circuits, accumulators of a bladder type, a piston type, and the like, and a muffler type pulsation absorber have been used to reduce pulsation. However, the former accumulator is rather expensive. In addition, maintenance such as management of the enclosed N ₂ gas is required. On the other hand, the latter silencer type pulsation absorber generally has a large size and is difficult to mount in a narrow space. Further, the frequency of the pulsation that can be absorbed is limited.

Therefore, there is a need for an inexpensive hydraulic pulsation reduction device having a simple structure. One such device is proposed in JP-A-8-240201. FIG. 7 is a cross-sectional view schematically showing the structure of a hydraulic pulsation reducing device (pulsation filter) proposed in JP-A-8-240201.
In this device, a space 192 connected to a pressure pipe 191 is provided, and an elastic body 193 having closed cells is accommodated therein. The closed cells in the elastic body are referred to as “fine”, but the publication does not specifically describe the dimensions of the cells.

[0004]

SUMMARY OF THE INVENTION The above-mentioned JP-A-8-24
The pulsation filter proposed in No. 0201 has a simple structure and takes up little space. If the function of reducing hydraulic pressure pulsation lasts for a long time, the possibility of cost reduction can be greatly expected. However, it has been found that there is a problem in durability of the elastic body when used in a hydraulic circuit under severe conditions as described below. In recent hydraulic circuits, there is a remarkable tendency to increase the pressure. In particular, the use conditions are severe for construction machinery. The frequency of the pulsation is as high as several hundred to several thousand Hz.

Further, when the elastic body deteriorates and is damaged in the pulsating filter, there is a high possibility that the broken piece flows out into the hydraulic circuit and causes a malfunction of the valve or the cylinder.

The present invention has been made to address such a problem, and is an apparatus for reducing pressure pulsation and surge pressure in a hydraulic circuit such as a hydraulic circuit.
It is an object of the present invention to provide a highly reliable hydraulic pulsation reducing device.

[0007]

Means for Solving the Problems and Action / Effect To solve the above problems, a hydraulic pulsation reducing device according to a first aspect of the present invention comprises: an elastic body (11) containing closed cells; Means (5e) for preventing breakage and outflow.

[0008] The above means has an effect of suppressing remarkable deformation of the surface of the elastic body and can prevent breakage of the elastic body. Further, even if the elastic body is damaged, it acts as a filter, preventing the broken pieces from flowing out to the hydraulic circuit, and preventing malfunction of various devices in the hydraulic circuit.

According to a second aspect of the present invention, there is provided a hydraulic pulsation reducing device, comprising: an elastic body (11) including a closed cell disposed in a hydraulic circuit; and preventing breakage and outflow of the elastic body (11). Means (5e), the elastic body (11)
Is a tubular filter, and the means (5e) is a tubular filter tube (5e) having a plurality of holes (5g) formed therein and inserted into the inner hole (11a) of the tubular elastic body (11). There is a feature.

[0010] The filter tube (5e) acts as a filter over the entire surface of the inner hole (11a) of the tubular elastic body (11). In addition, the contact area is increased to transmit the hydraulic pressure evenly to the elastic body (11), and the outflow of broken pieces can be prevented well.

According to a third aspect of the present invention, there is provided a hydraulic pulsation reducing device comprising: a pressure receiving chamber (9c) having a connection portion (3, 15) with a hydraulic circuit; and an independent pressure receiving chamber (9c) installed in the chamber (9c). An elastic body (11) containing air bubbles; a tubular filter tube (5e) formed with a plurality of holes (5g) inserted into an inner hole (11a) of the tubular elastic body (11); A tubular casing (9) covering the outer periphery of the tubular elastic body (11);
Hydraulic passages (5) mounted on both ends of the casing (9)
f, 15f) and a bushing (5, 15) having a joint for holding down an end of the elastic body (11).

The hydraulic pulsation reducing device of this embodiment can be arbitrarily inserted into a pipe or a hose as a standard part. Therefore, versatility is high. Further, vibration, noise, failure and the like of the hydraulic circuit can be effectively prevented.

According to a fourth aspect of the present invention, there is provided a hydraulic pressure pulsation reducing apparatus comprising: a pressure receiving chamber (30) provided in a hydraulic circuit (23, 37);
An elastic body (33) containing closed cells installed in the chamber (30); and a plurality of holes (31a) installed between the hydraulic circuits (23, 37) and the elastic body (33). And (3) a filter plate (31) formed with:

Since the hydraulic pulsation reducing device of this aspect has a connection portion to the hydraulic circuit, it can be arbitrarily installed in a pipe, a valve body, or the like.

According to a fifth aspect of the present invention, there is provided a cartridge type hydraulic pulsation reducing device, comprising: a cartridge casing (87);
And an elastic body (89) containing closed cells installed in the casing (87), and means (88) for preventing the elastic body (89) from being damaged and flowing out. .

This cartridge type hydraulic pulsation reducing device is prepared as a standard part and can be arbitrarily installed in a pipe or a valve body. Also, it can be easily replaced.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a specific structure of the hydraulic pulsation reducing device according to the first embodiment of the present invention. The hydraulic pulsation reducing device 1 includes a tubular casing 9 on an outer periphery, a tubular elastic body 11 on an inner surface thereof, and a bushing 5 having a filter tube section 5 inserted into an inner hole 11a of the elastic body 11. The casing 9 is a pipe made of steel or the like. Internal threads 9a and 9b are cut on the inner surfaces of both ends. The bushing 5 is screwed into the female screw 9a on the left side. A bushing 15 is screwed into the right female thread 9b. The inner hole 9c at the center of the casing 9 is a straight round hole. A tubular elastic body 11 is fitted into the inner hole 9c.

The bushing 5 on the left side is basically a thick hollow cylinder and has an external thread 5a and a flange 5b for assembling with the casing 9 on the outer periphery. The flange 5b is in contact with the side end surface of the casing 9, and an O-ring 7 for sealing is sandwiched in that portion. On the inner surface of the bushing 5, a female screw 5d
The joint 3 is screwed to the female screw 5d. The right bushing 15 also has the same brim 15b and rim 15a as the left bushing 5. The flange 15b is in contact with the side end surface of the casing 9 and has a sealing O
The ring 13 is sandwiched. A hydraulic path 15 f is opened at the center of the bushing 15. A male screw 15d is cut at an end of the right bushing 15, and a joint (not shown) is connected thereto. The coupling may be of a coupler type. The elastic body 11 is made of rubber having a number of closed cells inside, and is formed in a pipe shape. The details of the material example of the elastic body will be described later.

On the right side of the left bushing 5, an integrally formed filter tube 5e is provided so as to extend rightward in the drawing. The filter tube 5e has a relatively thin pipe shape, and has many holes 5g on the side wall. Many of these holes 5g are formed at equal pitches in the longitudinal direction of the filter tube 5e, and in the cross section, four are formed at 90 ° distribution. The filter tube 5e is
It is inserted into the inner hole 11a of the tubular elastic body 11 over substantially the entire length. In the assembled state, the elastic body 11 is slightly longer than the filter tube 5e.
There is a gap between the right end 5i and the left end of the bushing 15. The inside diameter of the filter tube 5e is
Are substantially equal to the inner holes (the hydraulic passages 3a and 15f).

The operation of the hydraulic pulsation reducing device of FIG. 1 will be described. The casing 9 is a strength member that can withstand the internal liquid pressure, and is connected via the bushings 5 and 15 to the front and rear pipes (not shown) so that the liquid (fluid) does not leak under pressure. The material and thickness of the casing 9 are appropriately selected according to the working pressure. A pressure fluid (hydraulic oil) flows through the inner hole of the filter pipe 5e of the hydraulic pulsation reduction device 1. This oil fills the periphery of the elastic body 11 through many holes 5g of the filter tube 5e. The pulsation in the oil is absorbed by a change in the volume of the closed cells in the elastic body 11 or the deformation of the elastic body, and the pulsation of the hydraulic pressure is reduced in the outlet side pipeline of the hydraulic pulsation reduction device 1. Note that pulsation absorption can be realized over a fairly wide range of frequencies.

The filter tube 5e extends over substantially the entire inner surface of the elastic body 11, and is made of a material and a wall having considerable strength. Therefore, when the elastic body 11 attempts to deform inward, the outer circumference of the filter tube 5e
Support the inner hole of the. Therefore, remarkable deformation of the elastic body 11 is suppressed, and breakage of the elastic body can be prevented. Further, even if the elastic body is broken, a broken piece larger than the hole 5g of the filter tube 5e does not flow out of the filter tube 5e into the circuit.

When the left and right bushings 5 and 15 are tightened in the casing 9, the elastic body 11 is preloaded from the left and right. The hydraulic pressure pulsation reducing device 1 has an outer diameter only as large as the hydraulic hose, and can be easily inserted between the hydraulic cylinder and the hose. Alternatively, it can be incorporated in a hydraulic hose. Therefore, pressure pulsation and surge pressure can be reduced in each part of the hydraulic circuit.

FIG. 2 is a sectional view showing the structure of a hydraulic pulsation reducing device according to a second embodiment of the present invention. The hydraulic pulsation reducing device 21 includes a casing 29 having a cylindrical shape having a top as a whole, and an elastic body 33 housed in a pressure receiving chamber 30 therein. At the lower end of the casing 29, a flange 27 is formed as a connection with a hydraulic line. This flange 27 is fitted with the flange 25 on the pipeline side,
It is fastened by bolts 28. Double flange 2
A packing (not shown) is inserted between 5, 27. The connection with the hydraulic line may be of a screw type, a coupler type, or the like. The pipe side flange 25 is connected to the pipe 2
It is provided in a T-shape on the side surfaces of 3, 37.

At the lower part of the pressure receiving chamber 30, there is provided a filter plate 31 which extends over substantially the entire lower surface of the elastic body 33. The filter plate 31 has a large number of holes 31a. The operation of the filter plate 31 and the holes 31a is the same as the operation of the filter tube of the hydraulic pulsation reduction device of FIG. The hydraulic pulsation reducing device according to the second embodiment also has a connection portion to a hydraulic line, so that the versatility is improved, and the hydraulic pulsation reducing device can be applied as a standard component to various hydraulic circuits. The filter plate 31 has holes 31.
It has been found that even if the filter plate 31 is made to adhere to the elastic body 33 without providing a, there is a slight pulsation reduction effect. However, it is a matter of course that providing the holes 31a in the filter plate 31 is more effective.

FIG. 3 is a sectional view showing a configuration of a hydraulic pulsation reducing device according to a third embodiment of the present invention. The hydraulic pulsation reducing device 51 includes a hollow cylindrical casing 55 and a hollow cylindrical hydraulic pulsation reducing material 61 disposed therein.
Consists of The casing 55 is a strength member that can withstand the internal hydraulic pressure, and is connected to the front and rear pipelines 53 and 57 so that pressure does not leak. The hydraulic pressure pulsation reducing material 61 has a protective layer 63 formed around a closed-cell elastic body 65. The protective layer 63 is made of a flexible material (detailed example below), and follows the deformation of the elastic body 65. The protective layer 63 is a means for preventing the elastic body from being damaged and flowing out according to the present invention. Such a protective layer without holes also has a pulsation reducing effect. The inner diameter of the hydraulic pressure pulsation reducing material 61 is substantially
Equal to the inner diameter of

The operation of the hydraulic pulsation reducing device according to this embodiment will be described. The hydraulic pulsation reducing action of the elastic body 65 is the same as that of the first embodiment. The protective layer 63 has a function of preventing hydraulic oil from entering the closed cells of the elastic body 65 and a function of preventing gas in the closed cells from escaping to the outside of the elastic body 65 or a function of preventing the gas in the closed cells from flowing out of the elastic body 65. It acts to prevent fatigue destruction. Thereby, it is possible to prevent oil from entering into the closed cells in the elastic body 65 and escape of gas from the closed cells, and to prolong the hydraulic pulsation reducing function.
Further, it is possible to prevent the elastic body from being damaged, and to prevent the damaged member piece from flowing into the hydraulic circuit.

Next, a detailed example of the elastic body and the protective layer will be described. A suitable material for the elastic body 65 of the hydraulic pulsation reducing material 61 is, for example, NBR (acrylonitrile-
It is a thermosetting resin having oil resistance and a certain strength such as butadiene rubber) and fluoro rubber. By mixing particles of a foaming material such as diazoaminobenzene in an uncured resin, and then driving the mixture into a mold and heating, an elastic body in which closed cells having an appropriate diameter are dispersed can be obtained. The diameter and porosity of the closed cells can be controlled by the diameter and amount of the foam.

Examples of the material for forming the protective layer 63 include NBR, which is the same as the closed-cell elastic body, a fluorine-based resin, acrylic, other plastic material different from the closed-cell elastic body,
Metal foil such as aluminum or stainless steel can be used. Table 1 below shows a relative comparison of the properties of these materials.

[0029]

[Table 1]

The thickness of the protective layer can be determined from the type of material, strength, hydraulic pressure, dimensions of the hydraulic pulsation reducing material, and the like. Typically, it is several tens μm to several mm. The protective layer is basically a dense body having a porosity of almost 0%. Depending on the material and the conditions of use, it may contain some pores. Various methods can be used for forming the protective layer on the surface of the elastic body, such as a method of immersing the elastic body in a molten resin and a method of filling an elastic material in a metal foil.

Although the protective layer can be composed of one layer,
A liquid-tight layer provided with a protective layer on the outside of the elastic body to prevent the pressure liquid from entering the closed cells, and a gas in the closed cells provided between the liquid-tight layer and the elastic body to escape to the outside of the elastic body. It is also possible to have a double-layer structure of an airtight layer to be prevented.

FIG. 4 is a cross-sectional view schematically showing a surface portion of a hydraulic pulsation reducing material having a protective layer having a double structure. A lower air-tight layer 133 and an upper liquid-tight layer 131 are stacked on the surface of an elastic body 135 having a number of closed cells 137. The material examples of both layers 133 and 131 are as described above. With such a protective layer having a double structure, it is possible to provide a hydraulic pressure pulsation reducing material having more excellent durability.

In the embodiment shown in FIG. 3, the hydraulic pressure pulsation reducing device 51 is constituted by providing the casing 55 having a slightly larger diameter in a part of the pipeline, so that special equipment space is almost unnecessary, and the hydraulic piping is not required. Hydraulic pulsation reduction devices can be provided at various locations along the road.

FIG. 5 shows a fourth (cartridge type) of the present invention.
It is a sectional view showing the composition of the hydraulic pulsation reduction device concerning an embodiment. The hydraulic pressure pulsation reducing device 81 includes a pipe-shaped casing 87 and a pipe-shaped elastic body 8 inserted therein.
9 mag. The outer surface of the elastic body 89 is covered with the above-described protective layer 88. The casing 87 has a brim 87 at the right end.
It is a pipe having d. At the left end of the casing 87, a screw hole 87a with a spot facing is formed on the outer surface. A screw 85 for fixing the bushing 83 is fitted in the hole 87a. An O-ring groove 87c is cut into the outer surface of the right end of the casing 87. Same groove 87c
Is equipped with an O-ring 91.

The inner hole 87b of the casing 87 has a straight cylindrical shape. Collar 87 at the right end of casing 87
d protrudes in the inner circumferential direction. A hole 87e is formed in the center of the brim portion 87d. The hole 87e is provided in the
9 and the inner diameter of the bushing 93. The brim portion 87d serves to hold down the bushing 93. The bushing 93 has a small-diameter protruding portion 93 a that enters the inner hole at the right end of the elastic body 89. The portion 93a has a function of expanding the inner hole at the right end of the elastic body 89.

The left bushing 83 has a small diameter projection 83c at the right end. The same portion 83c is fitted stepwise on the inner surface of the left end of the elastic body 89. Bushing 83
Has a screw hole 83a on one side, and is fixed to the casing 87 by the screw 85 described above. The bushing 83 acts to hold down the left end surface of the elastic body 89 and expand the left end inner hole of the elastic body 89.

FIG. 6 is a view showing a state in which the cartridge type hydraulic pulsation reducing device of FIG. 5 is incorporated in a valve body. (A) shows a perspective view of the entire valve body,
(B) is a sectional view of a state in which the hydraulic pulsation reducing device is incorporated. The valve body 111 is a block made of steel or the like, has many oil passages inside, and has a pipe connection port 1 on the outer surface.
13 appears. In addition, only one pipe connection port is displayed, and the others are omitted.

As shown in FIG. 6B, a cartridge type hydraulic pulsation reducing device 81 is inserted into the pipe connection port 113. The rear end (the left end in the figure) of the hydraulic pressure pulsation reducing device 81 abuts on a step 113 a of the valve body 111. The front end of the hydraulic pulsation reduction device 81 (the right end in the figure)
Is held down by the piping flange 115. The flange 115 is fixed to the valve body 111 by a bolt (not shown). Piping 1 on the flange 115
17 are connected. As described above, the cartridge type hydraulic pulsation reducing device can be easily installed in various devices in the hydraulic circuit. Also, replacement is easy.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a specific structure of a hydraulic pulsation reducing device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a structure of a hydraulic pulsation reduction device according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a configuration of a hydraulic pulsation reducing device according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view schematically illustrating a surface portion of a hydraulic pressure pulsation reducing material having a double-layered protective layer.

FIG. 5 is a sectional view showing a configuration of a hydraulic pulsation reducing device according to a fourth (cartridge type) embodiment of the present invention.

6 is a diagram showing a state in which the cartridge type hydraulic pulsation reduction device of FIG. 4 is incorporated in a valve body. (A)
1 is a perspective view of the entire valve body, and FIG. 1 (B) is a cross-sectional view showing a state where a hydraulic pulsation reducing device is incorporated.

FIG. 7 is a cross-sectional view schematically showing the structure of a hydraulic pulsation reducing device (pulsation filter) proposed in Japanese Patent Application Laid-Open No. 8-240201.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Hydraulic pulsation reduction device 3 Joint 5 Bushing 5e Filter pipe 5g Hole 7 O-ring 9 Casing 11 Elastic body 13 O-ring 15 Bushing 21 Hydraulic pulsation reduction device 23 Inlet side pipe 25 Flange 27 Flange (Pipe connection part) 28 Bolt 29 Casing 30 Pressure receiving chamber 31 Filter plate 33 Elastic body 35 Closed cell elastic body 37 Outgoing line 51 Hydraulic pulsation reducing device 53 Inlet side line 55 Casing 57 Outgoing line 61 Hydraulic pulsation reducing device 63 Protective layer 65 Closed bubble Elastic body 81 Hydraulic pulsation reduction device 83 Bushing 85 Screw 87 Casing 89 Elastic body 91 O-ring 93 Bushing 111 Valve body 113 Piping connection port 115 Flange 117 Piping 131 Liquid tight layer 133 Airtight layer 135 Closed cell elastic body 137 Closed bubble 191 Pressure tube Road 1 92 Empty part 193 Elastic body

Claims (5)

[Claims] An elastic body (11) containing closed cells, and means (5) for preventing breakage and outflow of the elastic body (11).
e) and a hydraulic pulsation reducing device comprising: 2. An elastic body (11) including closed cells installed in a hydraulic circuit, and means (5) for preventing breakage and outflow of the elastic body (11).
e) the elastic body (11) is tubular, and the means (5e) is a plurality of holes (5) inserted into the inner hole (11a) of the tubular elastic body (11). 5g) is a tubular filter tube (5e) formed with a hydraulic pulsation reducing device. 3. A pressure receiving chamber (9c) having a connection part (3, 15) to a hydraulic circuit, and an elastic body (1) including closed cells installed in the chamber (9c).
1), a tubular filter tube (5e) having a plurality of holes (5g) formed therein, inserted into an inner hole (11a) of the tubular elastic body (11), and the tubular elastic body (11) A tubular casing (9) covering the outer periphery of the casing, and a hydraulic passage (5) attached to both ends of the casing (9).
f, 15f) and a bushing (5, 15) having a joint for holding down an end of the elastic body (11). 4. A pressure receiving chamber (30) provided in a hydraulic circuit (23, 37), and an elastic body (3) containing closed cells installed in the chamber (30).
3), and a filter plate (31) having a plurality of holes (31a) formed between the hydraulic circuits (23, 37) and the elastic body (33). Hydraulic pulsation reducing device. 5. A cartridge casing (87), an elastic body (89) containing closed cells installed in the casing (87), and means (8) for preventing breakage and outflow of the elastic body (89).
8) A hydraulic pulsation reducing device, comprising: