JP2005054850A - Hydraulic pulse reducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic pulse reducing device capable of showing a pulse reducing effect in a relatively wide frequency zone and having excellent durability and simple structure light and easy to handle. <P>SOLUTION: This hydraulic pulse reducing device 1 is provided with a joint tube 2 as a hose-like member formed from a high-pressure rubber, an upstream side connecting member 3 and a downstream side connecting member 4 fitted to both ends of the joint tube. This hydraulic pulse reducing device 1 is arranged between an upstream side tube 5 and a downstream side tube 6, and fitted to each of ends thereof, and arranged inside a hydraulic circuit. The inner diameter D2 of the joint tube 2 is larger than the inner diameter D3 of the upstream side connecting member 3, and a connection part between the joint tube 2 and the upstream side connecting member 3 is formed with a stage difference 10a for generating a reflected wave. Pulse of the pressure transmitted from the upstream side is attenuated by the reflected wave generated in the step 10a, and level of the pulse transmitted from the step 10a to the downstream side is reduced than that of the upstream side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hydraulic pulsation reducing device, and more particularly to an apparatus for reducing pressure pulsation and surge pressure in a hydraulic circuit such as a hydraulic circuit.

  For example, in a hydraulic circuit of construction machinery such as a hydraulic excavator, pressure pulsation occurs due to the mechanical structure of the hydraulic pump or resonance of the control system, or when an impact load is applied to the actuator or when the valve is switched. Surge pressure may be generated. These pressure pulsations and surge pressures can vibrate pipes and actuators and damage them, and vibrations are radiated as sound from the vehicle structure, resulting in noise problems.

  Therefore, in order to reduce such pulsation, conventionally, an accumulator, a side branch, or the like is generally used. However, the accumulator is quite expensive and has a problem that maintenance such as management of gas to be enclosed takes time. On the other hand, since the frequency range of the pulsation that can be reduced is limited in the side branch, the pulsation of the pressure generated by the hydraulic pump is usually in a high frequency band consisting of a fundamental order frequency of about 300 Hz and harmonics of the multiple sound components. Considering that there are many cases over a wide range, a sufficient pulsation reducing effect cannot be expected.

  In order to solve the problems of the accumulator and side branch as described above, a configuration for absorbing pulsation using an elastic body containing closed cells has been devised. For example, a configuration in which a device in which an elastic body including closed cells is inserted into the inner surface of a casing and a filter tube having a large number of holes formed in the inner hole of the elastic body is inserted is installed in a part of the hydraulic circuit (patent Reference 1), and a structure in which an elastic body including closed cells is provided in a part of the layers of the hydraulic circuit piping (see Patent Document 2) are disclosed.

In addition, as a pulsation reduction effect that can be obtained in a relatively wide frequency band, an expansion chamber larger than the diameter of the main pipe is provided, and so-called “expansion chamber type” pulsation is achieved in which pulsation is reduced by pulsation interference in the expansion chamber. There is a reduction device. In the prior art, the expansion chamber is generally constituted by a steel pipe.
JP 2000-2393 A (page 2, FIG. 1) JP 2000-55250 A (page 3, FIG. 1)

  However, in the conventional “expansion chamber type” pulsation reducing device, the expansion chamber is composed of a steel pipe, and therefore, it is heavy and difficult to handle. Further, since a support member is further required to support the weight of the pulsation reducing device including the steel pipe, the number of parts is increased, which is disadvantageous in terms of cost.

  Further, when an elastic body containing closed cells is used, durability becomes a problem due to the recent trend toward higher pressure in hydraulic circuits. In particular, in order to increase the pulsation reduction effect in the high frequency band, it is necessary to use a very soft elastic body. In such a case, if compression and expansion due to pulsation are repeated, the influence of the heat of the oil also overlaps, resulting in elasticity. The body tends to deteriorate. In Patent Document 1, additional members such as a casing and a perforated tube for fixing the elastic body are required. Therefore, the structure becomes complicated as the number of parts increases, and the manufacturing cost increases.

  Accordingly, an object of the present invention is to provide a hydraulic pulsation reducing device that can exhibit a pulsation reducing effect over a relatively wide frequency band, has excellent durability, is lightweight and easy to handle, and has a simple configuration. It is to be.

Means and effects for solving the problem

  In order to achieve the above object, the first feature of the hydraulic pulsation reducing device according to the present invention is to connect a joint pipe disposed along a pipe line through which the pulsation propagates, and a joint pipe and an upstream pipe in the pipe line. And a second connecting part for connecting the joint pipe and the downstream pipe in the pipe line, the joint pipe is made of high-pressure rubber, and the inner diameter of the joint pipe is that of the first connecting part. A step that is larger than the inner diameter and that generates a reflected wave is formed at the connection portion between the joint pipe and the first connecting portion on the side where the pulsation propagates.

  The above-described configuration is a so-called “expanded chamber type” pulsation reduction device that can obtain a pulsation reduction effect in a relatively wide frequency band, and the pulsation is reduced at the step formed at the connection portion between the first connecting portion and the joint pipe. By generating a reflected wave, the level of pulsation is reduced. Here, since the joint pipe constituting the expansion chamber is made of high-pressure rubber instead of a steel pipe as in the prior art, it is lightweight and easy to handle. And the supporting member which supports weight like the case of a steel pipe is also unnecessary, and a number of members does not increase or it does not become disadvantageous in terms of cost.

  Moreover, the problem of durability when using an elastic body containing closed cells can be reduced. In other words, when an elastic body containing closed cells is used, it is easy to deteriorate because of its soft material, but the above configuration uses a relatively hard high-pressure rubber, so it does not easily deteriorate even under high-pressure conditions and has excellent durability. ing. Furthermore, since an additional member for fixing the elastic body is not necessary, the number of parts and the manufacturing cost can be suppressed. And it is a simple structure which only forms a level | step difference in the connection part of a joint pipe and a 1st connection part, Comprising: It can manufacture easily.

  In this specification, “pulsation” includes surge pressure.

  Moreover, it is preferable that the internal diameter of a joint pipe is 2 times or more of the internal diameter of a 1st connection part. This is a configuration in which the level of pulsation is reduced by generating a reflected wave at the level difference formed at the connection portion between the first connecting portion and the joint pipe. It will be big. Therefore, when the inner diameter of the joint pipe is set to be twice or more the inner diameter of the first connecting portion, the step becomes large and pulsation can be reduced favorably.

  Moreover, it is preferable that the length along the pipe line of the expansion chamber constituted by the joint pipe is substantially equal to the fundamental quarter wavelength of the pulsation frequency. According to this configuration, reflected waves and interference are strengthened by a resonance phenomenon in the expansion chamber, and a high pulsation reduction effect is obtained.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a hydraulic pulsation reducing device according to an embodiment of the present invention. The hydraulic pulsation reducing device 1 according to the present embodiment is disposed between a pipe through which pressure pulsation propagates, that is, an upstream pipe 5 and a downstream pipe 6 in a hydraulic circuit of a construction machine such as a hydraulic excavator. The coupling pipe 2, the upstream coupling member 3, and the downstream coupling member 4 are connected. The arrows in the figure indicate the propagation direction of the pressure pulsation. In FIG. 1, the arrows propagate from the left side to the right side, with the left side being the upstream side and the right side being the downstream side.

  The joint pipe 2 is a hose-like member made of high-pressure rubber, and both ends thereof are inserted into the insertion ports 3a and 4a of the upstream side connection member 3 and the downstream side connection member 4, respectively. When assembling the hydraulic pulsation reducing device 1 according to the present embodiment, both ends of the joint pipe 2 are inserted into the insertion ports 3a and 4a of the upstream connection member 3 and the downstream connection member 4, respectively. Tighten from the outside of the mouths 3a, 4a and fix. The hydraulic pulsation reducing device 1 assembled in this way is arranged along the pipeline between the upstream pipe 5 and the downstream pipe 6 through which the pulsation propagates, and the upstream linking member 3 and the downstream linking member 4. Is fitted into one end of each of the upstream side pipe 5 and the downstream side pipe 6 to be installed in the hydraulic circuit.

  The high-pressure rubber constituting the joint pipe 2 is used as a flexible piping material for various high-pressure devices. For example, one or more braided reinforcing layers are provided on the upper layer of the inner rubber tube, and the upper layer of the braided reinforcing layer is provided. The outer layer rubber is coated. The material of the inner layer rubber tube is preferably a rubber that can withstand the fluid moving through the inner layer rubber tube. In this embodiment, the fluid is oil, and therefore oil resistant rubber is preferable. Examples of the oil resistant rubber include nitrile rubber, styrene butadiene rubber, chloroprene rubber, and ethylene propylene diene rubber. The material of the braided reinforcing layer is preferably a high-strength fiber that can prevent deformation of the rubber hose due to high pressure. For example, strong rayon, polyester fiber, polyamide fiber, polyvinyl alcohol fiber, and glass fiber are preferable. When there are two or more braided reinforcing layers, an intermediate rubber layer is generally provided in the middle to prevent mutual rubbing between the braided layers and to improve the strength of the reinforcing layers. The material of the outer layer rubber is preferably a material that can withstand mechanical stress and environmental stress from the outside. For example, chloroprene rubber and ethylene propylene diene rubber are preferable.

  The upstream pipe 5 and the downstream pipe 6 constituting the hydraulic circuit are also hose-like members made of high-pressure rubber, and both have the same size such as an inner diameter and an outer diameter.

  Both the upstream side connecting member 3 and the downstream side connecting member 4 have the same configuration, and one end side has inner diameters D3 and D4 (D3 = D4), and the end portion of the joint pipe 2 is inserted into the end surface of the one end side. Possible circular insertion ports 3a and 4a are formed along the pipe direction. On the other hand, the other end side of the upstream side connection member 3 and the downstream side connection member 4 is thinner than the one end side, has an inner diameter larger than the inner diameters D3 and D4 on one end side, and the upstream side pipe 5 and the downstream side pipe 6. Have the same outer diameter. That is, the other end side of the upstream side connection member 3 and the downstream side connection member 4 forms a protrusion that can be fitted inside the upstream side tube 5 and the downstream side tube 6.

  The inner diameter D2 of the joint pipe 2 is larger than the inner diameters D3 and D4 of the upstream side connecting member 3 and the downstream side connecting member 5, and when these are assembled, there is a step 10a on each connecting portion on the side where pulsation propagates, that is, inside the pipe. , 10b are formed. That is, the steps 10a and 10b in the present embodiment are formed by the difference between the inner diameter D2 of the joint pipe 2 and the inner diameters D3 and D4 of the upstream and downstream connecting members 3 and 4, and the step amount t is the inner diameter. Difference (D2-D3, D2-D4).

  A space between the steps 10 a and 10 b inside the joint pipe 2 is referred to as an expansion chamber 10.

  The step 10a at the connection portion between the upstream connecting member 3 and the joint pipe 2 generates a reflected wave when the pressure pulsation propagates through this portion. More specifically, the step 10a of the 3/4 inch pipe In this case, the step amount t needs to be approximately 10 mm or more. As described later in detail, the hydraulic pulsation reducing device 1 according to the present embodiment is configured to reduce the level of pulsation by generating a reflected wave at the step 10a, so that the amount t of the step 10a increases. The effect of reducing pulsation is great. In the simple calculation, 4 times the inner diameter ratio (D2 / D3) is the reduced volume (dB) of pressure pulsation. The inner diameter D2 of the joint pipe 2 is preferably at least twice as large as the inner diameter D3 of the upstream connecting member 3, whereby the pulsation can be reduced satisfactorily.

  FIG. 2 shows, as a comparative example, a hydraulic pulsation reducing device in which no step is formed in a pipeline through which pulsation propagates. In this hydraulic pressure pulsation reducing device 101, the wall thickness on the connection side of each of the upstream side connecting member 103 and the downstream side connecting member 104 with the joint pipe 102 is thinner than that in FIG. 1, and the inner diameters D3 and D4 have joint pipes. 2 is substantially the same as the inner diameter D2. That is, in the hydraulic pulsation reducing device 101 of FIG. 2, the steps 10a and 10b are not substantially formed as in the hydraulic pulsation reducing device 1 of FIG. 1, and the upstream connecting member 103, The inner diameter of the pipe line leading to the joint pipe 102, the downstream side connecting member 104, and the downstream side pipe 106 is substantially constant.

  Conventionally, as shown in FIG. 2, a configuration in which steps are eliminated in each connecting portion is generally taken, and even if a minute step is unavoidably produced in manufacturing, as in the present embodiment shown in FIG. It does not cause a reflected wave. More specifically, in the case of a 3/4 inch tube, the level difference t is conventionally less than about 1 mm.

  Here, propagation of pressure pulsations in the hydraulic pulsation reducing devices 1 and 101 of FIGS. 1 and 2 will be described with reference to FIGS. 3 (a) and 3 (b). In the case of the hydraulic pulsation reducing device 1 of the present embodiment shown in FIG. 1, as shown in FIG. 3 (a), when the pulsation propagates from the left side, that is, from the upstream side, a reflected wave is generated at the step 10a. The level of pulsation that occurs and propagates downstream from the step 10a is reduced. On the other hand, in the case of the hydraulic pulsation reducing device 101 shown as a comparative example in FIG. 2, there is almost no step as shown in FIG. The incoming pulsation propagates downstream without being attenuated.

  In addition, the length L1 along the conduit of the expansion chamber 10 constituted by the joint pipe 2, that is, the distance between the upstream step 10a and the downstream step 10b (see FIG. 1) is expected to be reduced. It is preferably substantially equal to the fundamental quarter wavelength of the pulsation frequency. By doing so, reflected waves and interference are strengthened by the resonance phenomenon in the expansion chamber 10, and a high pulsation reducing effect is obtained. FIG. 4 is a graph showing the relationship between the volume reduction and the frequency when the hydraulic pulsation reducing device 1 of FIG. 1 is used. Here, a case where the quarter wavelength of the frequency f1 on the horizontal axis is equal to the length L1 of the expansion chamber 10 is shown, and the frequencies f2 and f3 are higher-order components that are twice and three times f1, respectively. . From this graph, it can be seen that the volume reduction is large at the frequency f1 at which the length L1 of the expansion chamber 10 is ¼ wavelength and the higher-order components f2 and f3. This is more clearly shown in the examples described later.

  As described above, the hydraulic pulsation reducing device 1 according to the present embodiment is a so-called “expansion chamber type” that can obtain a pulsation reducing effect in a relatively wide frequency band, and includes an upstream connecting member 3 and a joint pipe. The level of the pulsation is reduced by generating a pulsating reflected wave at the step 10a formed at the connection portion with the No. 2. Here, since the joint pipe 2 constituting the expansion chamber 10 is made of high-pressure rubber instead of a steel pipe as in the prior art, it is lightweight and easy to handle. And the supporting member which supports weight like the case of a steel pipe is also unnecessary, and a number of members does not increase or it does not become disadvantageous in terms of cost.

  Moreover, the problem of durability when using an elastic body containing closed cells can be reduced. In other words, when an elastic body containing closed cells is used, it is easy to deteriorate because of its soft material, but in this embodiment, since it uses a relatively hard high-pressure rubber, it is difficult to deteriorate even under high-pressure conditions, making it durable. Are better. Furthermore, since an additional member for fixing the elastic body is not necessary, the number of parts and the manufacturing cost can be suppressed. And it is a simple structure which only forms the level | step difference 10a in the connection part of the coupling pipe 2 and the upstream connection member 3, Comprising: It can manufacture easily.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various design changes can be made as long as they are described in the claims.

  For example, the upstream side connecting member 3 and the downstream side connecting member 4 are not formed with the insertion ports 3a, 4a as in the above-described embodiment, but are simpler than fitting inside or outside the joint pipe 2. Various shapes such as various shapes may be used.

  Further, the upstream step 10a only needs to generate a reflected wave, and is not limited to being formed at a right angle as in the above-described embodiment. For example, the taper which narrows toward the downstream may be formed in the inner surface of the upstream connection member 3 in the cross section of FIG. However, in any case, the inner diameter of the opening to the expansion chamber 10 of the upstream connection member 3 is smaller than the inner diameter of the expansion chamber 10, that is, the inner diameter of the joint pipe 2, and a step that generates a reflected wave needs to be formed. .

  Moreover, although the level | step difference 10b similar to the upstream is formed in the connection part of the coupling pipe 2 and the downstream connection member 4, this level | step difference 10b does not contribute directly to a pulsation reduction effect. Therefore, if only pulsation reduction is taken into consideration, there is no need for the downstream step 10b. However, in terms of design, it is preferable that the same step is formed on both the upstream and downstream sides as in the above-described embodiment.

  Further, the inner diameter D2 of the joint pipe 2 is not limited to being twice or more than the inner diameter D3 of the upstream connecting member 3. Furthermore, the length L1 along the pipe line of the expansion chamber 10 constituted by the joint pipe 2 may not be substantially equal to the fundamental quarter wavelength of the pulsation frequency at which a reduction effect is expected. All of the above conditions are advantageous in the pulsation reduction effect, but the hydraulic pulsation reduction device according to the present invention does not require that such conditions be satisfied.

  In the above-described embodiment, the upstream pipe 5 and the downstream pipe 6 are made of high-pressure rubber similar to that of the joint pipe 2, but may be made of other materials.

  In the hydraulic pulsation reducing device according to the present invention, the inner diameter D2 of the joint pipe 2 is 38.6 mm, the inner diameter D3 of the upstream connecting member 3 is 19.0 mm, and the length L1 along the pipe line of the expansion chamber 10 is 380 mm. A pressure sensor was attached to each of the upstream pipe 5 and the downstream pipe 6 to measure the pressure. FIG. 5 shows the result of examining the pressure transfer function of pulsation propagating from the upstream side to the downstream side. In this graph, the dotted line indicates the hydraulic pulsation reducing device (with a step) according to the present invention under the above conditions, A solid line is a result about the conventional hydraulic pressure pulsation reducing device (no step) as a comparative example. The horizontal axis of the graph is the pulsation frequency (Hz), the vertical axis is the pressure transfer function, and the difference between the values on the vertical axis is the volume reduction.

  From FIG. 5, the hydraulic pulsation reducing device according to the present invention under the above conditions can obtain a reduction effect higher than that of the conventional one, more specifically, a reduction effect of 10 dB or more, particularly at around 750 Hz, 1500 Hz, and 2250 Hz. Understand. Considering that the speed of sound in oil is approximately 1200 m / s, the value fx of the frequency where L1 (380 mm) and 1/4 wavelength are equal is fx = 1200 / (0.38 × 4) = 780 Hz. This is almost the same as 750 Hz where a high reduction effect was confirmed. If this 750 Hz is the basic order, the higher order components of 2 times and 3 times correspond to 1500 Hz and 2250 Hz. From this, it can be said that a high pulsation reduction effect can be obtained by making the length L1 of the expansion chamber 10 substantially equal to the fundamental quarter wavelength of the pulsation frequency at which the reduction effect is expected.

It is a cross-sectional view showing a hydraulic pulsation reducing device according to an embodiment of the present invention. It is a cross-sectional view which shows the hydraulic pressure pulsation reduction apparatus in which the level | step difference is not formed in the pipe line which a pulsation propagates as a comparative example. (A) is explanatory drawing which shows propagation of the pressure pulsation in the hydraulic pressure pulsation reduction apparatus of FIG. (B) is explanatory drawing which shows propagation of the pressure pulsation in the hydraulic pressure pulsation reduction apparatus of FIG. It is a graph which shows the relationship between the frequency of a pulsation at the time of using the hydraulic pulsation reduction apparatus of FIG. 1, and a volume reduction. It is a graph which shows the result of having investigated the pressure transfer function of the pulsation which propagates from the upstream to the downstream in each case of the hydraulic pulsation reducing device according to the present invention and the conventional hydraulic pulsation reducing device without a step.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydraulic pressure pulsation reduction apparatus 2 Joint pipe 3 Upstream side connection member (1st connection part)
4 Downstream side connection member (second connection part)
5 upstream pipe 6 downstream pipe 10 expansion chamber 10a level difference D2 inner diameter of joint pipe D3 inner diameter of upstream connecting member (inner diameter of first connecting portion)
L1 Extended room length

Claims (3)

A joint pipe arranged along a pipeline through which pulsation propagates;
A first connecting part for connecting the joint pipe and the upstream pipe in the pipe;
A second connecting part for connecting the joint pipe and the downstream pipe in the pipe line;
The joint pipe is made of high-pressure rubber;
The inner diameter of the joint pipe is larger than the inner diameter of the first connecting portion, and a step is formed in the connecting portion between the joint pipe and the first connecting portion on the side where the pulsation is propagated to generate a reflected wave. A hydraulic pulsation reducing device characterized by that.   2. The hydraulic pulsation reducing device according to claim 1, wherein an inner diameter of the joint pipe is at least twice an inner diameter of the first connecting portion. 3. The liquid according to claim 1, wherein a length of the expansion chamber formed by the joint pipe along the pipe line is substantially equal to a fundamental quarter wavelength of the pulsation frequency. Pressure pulsation reduction device.

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