JP3413738B2 - Pulsation reduction device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulsation reducing device for reducing the pulsation of fluid generated in piping or hydraulic equipment through which the fluid is pumped, in a device for pumping the fluid and performing various works by this fluid.

[0002]

2. Description of the Related Art An apparatus for pumping a fluid, for example, a liquid such as oil or water, or a gas such as air, and performing various works by using the pressure is used in many fields. A typical device thereof is a hydraulic device such as a hydraulic excavator that works by hydraulic pressure.
Hereinafter, oil will be described as an example of the fluid. In hydraulic equipment, a hydraulic pump is driven to discharge pressure oil, and this discharged pressure oil is pressure-fed to a hydraulic actuator such as a hydraulic cylinder or hydraulic motor via piping, and this is driven to perform the desired work. To do.

In such hydraulic equipment, pulsation occurs in the pressure oil discharged from the hydraulic pump, and this pulsation causes not only noise but also resonance in some cases, causing piping and various components of the hydraulic equipment. May damage the
It is necessary to reduce the pulsation as much as possible. Conventionally, a side branch has been used as one means for reducing pulsation. This side branch will be described with reference to FIG.

FIG. 8 is a sectional view of the side branch. In this figure, reference numeral 1 denotes a pipe for sending pressure oil from a hydraulic pump.
Reference numeral 2 denotes a side branch branched from the pipe 1 and connected to the side branch, which communicates with the pipe 2. The side branch 2 is composed of a pipe body 21 and is closed at an end portion of the pipe 1 opposite to the connecting end. Reference numeral 22 denotes this closed end portion (closed end), and 21T denotes the closed portion inner surface (reflection surface) of the closed end 22. The length of such side branch 2 is indicated by L ₀ .

The pulsation of the pressure oil discharged from the hydraulic pump is
It is composed of the fundamental frequency and its harmonics, propagates in the pipe 1 and also in the pipe body 21 of the side branch 2, and the pulsation propagated in the pipe body 21 is reflected by the reflection surface 21T and again in the pipe body 21. Return to pipe 1 through. The pulsation that reciprocates through the side branch 2 and returns to the pipe 1 becomes a pulsation whose phase is inverted by 180 degrees from the pulsation of the pipe 1, and interferes with the pulsation of the pipe 1 at the inlet portion of the side branch 2 to reduce the pulsation. In this way, the length L ₀ of the side branch 2 required to obtain the pulsation in which the phase is inverted is represented by the following equation, where λ is the wavelength of the specific frequency component to be reduced. L ₀ = λ / 4 (1) The conventional side branch 2 as shown in FIG. 7 has a damping effect on the pulsation of a certain specific frequency, but has a damping effect on the pulsation of a frequency other than the frequency. On the other hand, the damping effect is small. This is shown in FIG. FIG. 9 is a characteristic diagram showing the pulsation damping effect of the side branch. In this figure, the horizontal axis represents the frequency of pulsation and the vertical axis represents the pulsation damping rate. As is clear from the figure, although a large attenuation is exhibited at a specific frequency f ₀ , the attenuation effect rapidly decreases as the frequency f ₀ is deviated. The relationship between the specific frequency f ₀ and the length L ₀ of the side branch 2 is represented by the following equation, where C is the speed of sound in the fluid. f ₀ = C / 4L ₀ (2) Therefore, the length L ₀ of the side branch 2 is determined according to the pulsating frequency of the pressure oil to be attenuated.

However, for example, the pulsation of a hydraulic excavator is generated by a hydraulic pump driven by an engine. The most commonly used hydraulic pump is a piston pump having seven or nine pistons, and the pulsation frequency f is n when the number of pistons is N and the rotational speed of the hydraulic pump is N. , F (Hz) = n × N × i / 60 (i = 1, 2, 3 ... ......) (3) In this equation (3), (i = 1) is a fundamental frequency, and (i = 2, 3, ...) Is a high-order frequency component.

From the above expressions (2) and (3), in order to effectively reduce the pulsation in the hydraulic excavator, it is impossible for one side branch 2 to correspond, and a plurality of side branches having different lengths cannot be used. It turns out that you must have a side branch.

By the way, in compressors and vacuum pumps,
For silencing, a side-branch silencer that can deal with multiple wavelengths of the sound to be silenced has been disclosed.
It is disclosed in Japanese Patent No. 9368. Its schematic configuration is shown in FIG.
Shown in. FIG. 10 is a sectional view of a conventional side branch. In this figure, 1 is a main pipe corresponding to the pipe 1 shown in FIG.
3 is a side branch, 31 is a tube 32, and the closed end.
Reference numeral 320 denotes a step formed on the closed end 32, and the step forms a reflecting surface 321 and a reflecting surface 322. 33
Is a partition plate for partitioning the inside of the tubular body 31, and the partition plate 3
One of the chambers partitioned by 3 communicates with the reflection surface 321 and the other chamber communicates with the reflection surface 322. L ₁ represents the length from the entrance of the side branch 3 to the reflecting surface 321, and L ₂ represents the length from the entrance of the side branch 3 to the reflecting surface 322. From the above formula (1), it is clear that the side branch 3 can effectively muffle sound waves of two wavelengths.

[0009]

In the side-branch silencer disclosed in the above publication, if a large number of reflecting surfaces having different lengths from the entrance of the side-branch 3 are formed, it is possible to reduce the number of wavelengths. Can respond to sound waves.
However, the number of reflecting surfaces is limited in order to effectively muffle sound. If the wavelength of the sound wave to be silenced is limited to some wavelengths, one side branch can handle this. However, for example, in a hydraulic excavator, the engine speed, that is, the speed N of the hydraulic pump changes depending on the temperature and the quality of the fuel. Therefore, even if a side branch for some of the pulsation frequencies in the above formula (2) is used. However, it is not always possible to obtain the expected pulsation reduction effect for the pulsation frequency. Therefore, in various other machines is not limited to a hydraulic excavator, if an attempt is made effective pulsation reduction, FIG. 10
Even with a side branch having a plurality of reflecting surfaces shown in
It is necessary to prepare a plurality of these, and a large space is required to store the side branch having a considerable length, and it takes a lot of time and labor to attach them to the pipe 1.

An object of the present invention is to solve the above problems in the prior art and to provide a pulsation reducing device which can easily deal with pulsations of a large number of wavelengths.

[0011]

To achieve the above object, the present invention provides a pulsation reducing device for suppressing pulsation of a pressure-feeding fluid by guiding the pressure-feeding fluid to the side-branch. A pipe body connected to a pipe or hydraulic equipment through which a fluid to be pumped flows, and a plug that constitutes a closed end including a reflection surface and is detachably attached to the other end of the pipe body, and the reflection surface. Is formed by a plurality of reflecting surfaces having different lengths from the pipe.

[0012]

The pulsation in the pipe enters the side branch, is reflected by the reflecting surface, and then returns to the inside of the pipe through the side branch again. In this case, since the step is formed on the reflecting surface, a plurality of reflecting surfaces having different lengths are formed, and the pulsation having the frequency corresponding to each length can be reduced. Further, since the plurality of reflecting surfaces are formed in one plug, it is possible to cope with pulsations of many wavelengths by preparing plugs having reflecting surfaces of various lengths, and Replacing is much easier than replacing the side branch itself.

[0013]

The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a sectional view of a pulsation reducing device according to a first embodiment of the present invention. In this figure, 1 is the same pipe as that shown in FIG. Reference numeral 4 is a side branch connected to the pipe 1, and is composed of a pipe body 41 and a closed end 42 thereof. In this embodiment, the closed end 42 of the side branch is composed of the plug 43. That is, 43 is a plug attached to the open end of the pipe 41 on the side opposite to the pipe 1, and 44 is the pipe 4
1 is a seal for sealing the plug 43 and 45 is a plug 43
Is a tightening metal fitting for attaching to the pipe body 41 with a screw. A step 433 is formed on the surface of the plug 43 on the tube body 41 side, and the step 433 forms reflection surfaces 431 and 432. The lengths of the reflecting surface 431 and the reflecting surface 432 from the pipe 1 (from the inlet of the side branch 4) are indicated by L ₁₀ and L ₂₀ .

Next, the operation of this embodiment will be described. Piping 1
Pulsations enter the side branch 4 from the entrance of the side branch 4, part of which is reflected by the reflecting surface 431, and the other of which is reflected by the reflecting surface 432, and returns to the entrance again. In this case, the pulsating wave reflected by the reflecting surface 431 travels along a path having a length of 2L ₁₀ and the pulsating wave reflected by the reflecting surface 432 has a length of 2L.
It will take ₂₀ routes. Therefore, according to the equation (1), the pulsation frequency f ₁ effectively reduced on the reflecting surface 431 is f ₁ = C / 4L ₁ (3), and is effectively reduced on the reflecting surface 432. The pulsation frequency f ₂ is: f ₂ = C / 4L ₂ (4) That is, the side branch 3 of this embodiment can exert its reducing effect on the pulsations of _two different frequencies f ₁ and f ₂ .

For example, if the fundamental frequency component of the hydraulic pulsation of the hydraulic excavator is 200 Hz and the secondary frequency component is 400 Hz, the sonic velocity C in oil is 1300 m / s. Is the reflective surface 432.
For the pulsation of the secondary frequency component of L ₂₀ = 1.625 m, the plug having the reflecting surface 431 of L ₁₀ = 0.8125 m may be selected. Further, when considering only the pulsation of the fundamental frequency as a reduction target, when there is a possibility that the engine speed varies by about 10% for the reason described above, the length of the side branch corresponding to the fundamental frequency is set to L. _{If S} , the length L ₁₀ of the reflecting surface 431 is L ₁₀ = L _S − (L _S /
10), the length L ₂₀ of the reflecting surface 432 is set to L ₂₀ = L _S + (L
_S / 10) makes it possible to cope with changes in the engine speed.

As described above, in this embodiment, since the two reflecting surfaces having different lengths are formed on the plug, the pulsation of two different frequencies corresponding to these reflecting surfaces can be reduced by one side branch. You can Then, by preparing plugs having steps of various lengths and selectively exchanging them, it is easy to reduce pulsation,
In addition, it is possible to respond reliably. Moreover, replacing the plug is much easier than replacing the side branch itself.

The plug may be attached by screws as shown in the drawing, by fitting and crimping, or by welding in some cases. The same applies to the specific examples shown in FIGS. 2 to 6 below.

2 to 6 are sectional views of other specific examples of the plug shown in FIG. In each figure, 41 is a tubular body, 44 is a seal, and 45 is a clamp, and these are the same as those shown in FIG. The plug 43a shown in FIG. 2 has a step formed by projecting a cylinder from the bottom surface, and the step forms two reflecting surfaces 431a and 432a having different lengths.
The plug 43b shown in FIG. 3 has a step formed by projecting a column in two steps from the bottom surface, and the step forms three reflecting surfaces 431b, 432b, 433b having different lengths. The plug 43c shown in FIG. 4 has a step formed by projecting two cylinders or prisms having different lengths from the bottom surface, the bottom surface is a reflecting surface 431c, and the top surfaces of the pillars are independent reflecting surfaces 432c and 433c. Has become. The plug 43d shown in FIG. 5 has two recesses 430d having different depths on the bottom surface.
₁ , 430d ₂ are formed, the bottom surface of the concave portion 430d ₁ is a reflecting surface 431d, and the bottom surface of the concave portion 430d ₂ is a reflecting surface 432d.
In addition, the recesses 430d ₁ and 430d _{2 are}
The peripheral surface of is a reflecting surface 433d. The plug 43e shown in FIG. 6 (only the plug is shown in this figure) is substantially the same as the plug 43 shown in FIG. However, in this plug 33e, two semi-circular blocks 46 and 47 having different heights are provided with screws 48 and 49, respectively.
The surface of the block 46 is a reflecting surface 431e, and the surface of the block 47 is a reflecting surface 432e.

Each of these specific examples has the same effect as that of the embodiment shown in FIG. 1, but in particular, in the specific example shown in FIG. 6, the plug bodies are commonly used, and only blocks of various lengths are prepared. Therefore, the configuration is simplified as compared with the case where various plugs are prepared.

Although the above embodiment shows the case where the side branch 4 is connected to the pipe 1, the pulsation can be reduced by attaching the side branch 4 to not only the pipe but also other equipment. Such an example is shown in FIG. FIG. 7 is a sectional view of the oblique-axis hydraulic piston pump. In this figure, 51 is a casing of a hydraulic piston pump, 52 is a rotary shaft connected to a prime mover (not shown), and 53 is a rotary shaft 52.
The bearing 54 is a rotating disk fixed to the rotating shaft 52. 55 is a center shaft rotatably connected to the center of rotation of the rotary disk 54, 55S is a spring of the center shaft 55, and 56 is a casing 51 connected to the casing 51.
The valve plate slidably contacts A. Reference numeral 57 denotes a rotor, which is rotatably supported by the center shaft 55 and the valve plate 56, and can be tilted at an arbitrary angle with respect to the rotation shaft 52 in a direction perpendicular to the paper surface. Reference numeral 58 is a cylinder formed on the rotor 57, and one or a plurality of cylinders 58 are arranged on the circumference of the rotor 57. Reference numeral 59 denotes a piston inserted in the cylinder 58, one end of which is rotatably connected to the rotary disc 54. Reference numeral 61 is a discharge port formed in the casing 51A, and reference numeral 62 is a suction port also formed in the casing 51A. 61H indicates a passage formed in the middle of the discharge port 61.

In this embodiment, as shown in the figure, the side branch 4 equivalent to that shown in FIG. 2 is connected to the passage 61H. 41 is a tubular body, 43a is a plug, 432a
Is a reflecting surface and 45 is a base, which are equivalent to those shown in FIG. Reference numeral 47 is a connecting portion that connects the side branch 4 to the passage 61H.

When the rotary shaft 52 rotates, the piston 59 operates in a known manner to suck oil from the suction port 62,
Pressure oil is discharged from the discharge port 61. At this time, as in the case of the embodiment shown in FIG. 1, the pulsating pressure oil enters the side branch 4, and the pulsation entering the side branch 4 is the tube body 4.
The reflected wave returns to the entrance of the side branch 4 while repeating the reflection on the inner surface of the tubular body 41, and reduces the pulsation.

This embodiment has the same effects as those of the previous embodiment, and also has the following effects. That is, in the present embodiment, since the side branch is connected to the discharge port of the pump, it is possible to reduce the pulsation at the pump outlet that is the source of the pulsation, thereby increasing the pulsation reduction rate. In addition, the transmission of pulsation to downstream pipes and equipment can be largely prevented.

In the embodiment shown in FIG. 7, an example in which the side branch is installed in the pump has been shown, but it is not limited to the pump, and it is obvious that it can be applied to other devices such as a directional control valve. Is.

In the description of each of the above embodiments, the side branch is applied to the hydraulic pipe and the hydraulic equipment. However, not only the hydraulic pipe and the hydraulic equipment but also the fluid pressure of other fluid such as water or air can be applied. As a matter of course, it can be applied to the used device. Also, the tubular body that constitutes the side branch is
It may be a metal tube or an elastic hose such as rubber.

[0026]

As described above, in the present invention, the plug having the plurality of reflecting surfaces is attached to the closed end of the side branch, so that the pulsation of different frequencies can be reduced by one side branch. You can Then, by preparing plugs having steps of various lengths and selectively exchanging them, it is possible to easily and surely deal with the pulsation that requires reduction. Moreover, replacing the plug is much easier than replacing the side branch itself.

[Brief description of drawings]

FIG. 1 is a sectional view of a pulsation reducing device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing another specific example of the embodiment shown in FIG.

FIG. 3 is a cross-sectional view showing another specific example of the embodiment shown in FIG.

FIG. 4 is a sectional view showing another specific example of the embodiment shown in FIG.

5 is a cross-sectional view showing another specific example of the embodiment shown in FIG.

FIG. 6 is a sectional view showing another specific example of the embodiment shown in FIG.

FIG. 7 is a sectional view of a pulsation reducing device according to another embodiment of the present invention.

FIG. 8 is a sectional view of a conventional pulsation reducing device.

9 is a characteristic diagram of pulsation damping of the device shown in FIG.

FIG. 10 is a sectional view of a conventional pulsation reducing device.

[Explanation of symbols] 1 piping 4 side branch 41 tube 42 closed end 43 plugs 44 seal 45 Tightening bracket 431, 432 Reflective surface 433 steps

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-6-11091 (JP, A) JP-A-54-114801 (JP, A) Actually open Sho-56-138108 (JP, U) Actual-open Sho-59- 147987 (JP, U) Actual development 4-84891 (JP, U) Actual development 57-127991 (JP, U) Actual development 61-132160 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F16L 51/00-55/24 F04B 11/00

Claims (7)

(57) [Claims] 1. A pulsation reducing device that suppresses pulsation of a pressure-feeding fluid by guiding the pressure-feeding fluid to the side branch, wherein the side branch has a pipe connected to a pipe or hydraulic equipment through which the pressure-feeding fluid passes. A plug that is detachably attached to the other end of the tubular body and that forms a closed end including a reflective surface, and the reflective surface is formed of a plurality of reflective surfaces having different lengths from the pipe. A pulsation reducing device characterized in that 2. The pulsation reducing device according to claim 1, wherein the pipe body is made of a metal pipe. 3. The pulsation reducing device according to claim 1, wherein the tubular body is formed of a hose. 4. The pulsation reducing device according to claim 1, wherein the reflecting surface is formed integrally with the plug. 5. The pulsation reducing device according to claim 1, wherein the reflection surface is formed separately from the plug. 6. The pulsation reducing device according to claim 1, wherein the reflecting surfaces are coaxially arranged. 7. The pulsation reducing device according to claim 1, wherein each of the reflecting surfaces is arranged on a different axis.