JPH0942575A - Pressure oil pulsation reduction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a side branch type pressure oil pulsation reduction device which can increase a frequency range capable of reducing the pulsation of pressure oil developed by a hydraulic pump. SOLUTION: In a pressure oil pulsation reduction device reducing pulsation of pressure oil which is developed by a hydraulic pump 1, and is propagated in the inside of a main pipe line 2, a first side branch 3 is branched so as to be provided for the main pipe line 2, and concurrently, a second side branch 4 is branched so as to be provided for the circumferential surface identical to the circumferential surface for which the first side ranch 3 for the main pipe line 2 is provided, in such a way as to be faced to the first side branch 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure oil pulsation reducing device for reducing pulsation of pressure oil generated by a hydraulic pump and propagating in a flow path of pressure oil at a side branch, and more particularly to a hydraulic excavator and a hydraulic crane. It is useful as a hydraulic working machine for construction work.

[0002]

2. Description of the Related Art In a hydraulic drive circuit composed of a hydraulic pump, a hydraulic actuator, etc., the hydraulic pump causes pressure fluctuations in the pressure oil to be discharged in the course of repeated discharge and suction of the oil. Pulsation of pressure oil occurs in the flow path. Such pulsation of pressure oil is transmitted to various hydraulic equipment connected to it via piping that serves as a flow path for pressure oil, causing noise, and in some cases, causing resonance and damaging the piping and hydraulic equipment. Therefore, it is necessary to reduce it as much as possible. Conventionally, as one of the means for reducing the pulsation of the pressure oil, for example, a side-branch silencer such as the side-branch silencer described in the section of (Prior Art) of Japanese Utility Model Laid-Open No. 62-97391. A pressure oil pulsation reducer was used.

The side-branch silencer described in this publication has a bottom-branched side branch branched in a duct, such as a hydraulic line, through which a pulsating fluid passes, so that a fluid of a specific frequency component is provided. The pulsation of the fluid that passes through the duct is propagated into the side branch, and then reflected by the reflecting surface that forms the bottom of the side branch and returned to the inside of the duct. . Since the conventional pressure oil pulsation reducer adopts such a configuration, the pulsation wave of the pressure oil of the specific frequency component to be reduced is predetermined, and the length of the side branch passage is appropriately adjusted according to the frequency. If adjusted, the pulsating wave of pressure oil that travels back and forth through the side branch and returns to the hydraulic conduit can interfere with the pulsating wave that passes through the hydraulic conduit so that the peaks and troughs of the waves collide. Therefore, the pulsation of the specific frequency component of the pulsation of the pressure oil passing through the hydraulic pipe can be reduced intensively. The pulsation of the pressure oil generated by the hydraulic pump is composed of a fundamental frequency and a harmonic having a frequency that is an integral multiple of the fundamental frequency. The fundamental frequency f at the pulsation-reducing center frequency reduced by the side branch is
Is the speed of sound of the pressure oil, and the length of the side branch passage is L.
Then, it can be obtained by the following equation (1).

F = V / 4L (1) The pulsation reducing center frequency is the largest among the hydraulic pressure pulsations of various frequency components, because it interferes with the hydraulic pulsation reflected and returned by the side branch. It is the frequency of the pulsation that is reduced.
The pulsation of the pressure oil reflected and returned by the side branch not only interferes with the pulsation of the pressure oil of such a pulsation reduction center frequency, but also interferes with the pulsation of the pressure oil of the frequency around it.
By using such a side branch, it is possible to reduce the pulsation of the pressure oil in the frequency range around the pulsation reduction center frequency to some extent.

[0005]

As is clear from the above description, in the conventional side-branch type pressure oil pulsation reducing device, the pulsation of the pressure oil propagating in the flow path of the pressure oil is expressed by the formula (1). It is possible to reduce only the pulsation of the pressure oil having the fundamental frequency f as a component and the pulsation of the pressure oil of the frequency in the peripheral region, and it is possible to reduce only the pulsation of the pressure oil in the limited frequency region. It was The pulsation of the pressure oil generated by the hydraulic pump is a pulsation in which various frequency components are mixed, and the frequency also changes if the rotational speed of the hydraulic pump changes, so in the side-branch type pressure oil pulsation reducer, It is required to increase the frequency domain of pressure oil pulsation that can be reduced as much as possible.

The present invention meets the demand for such a conventional pressure oil pulsation reducing device, and an object thereof is to provide a side branch type device capable of increasing the frequency range in which the pressure oil pulsation generated by a hydraulic pump can be reduced. It is to provide a pressure oil pulsation reducing device.

[0007]

The object of the present invention is to provide a "pressure oil pulsation reducing device for reducing pulsation of pressure oil generated by a hydraulic pump and propagating in the pressure oil flow path. The first side branch is branched and provided on the same side, and the second side branch is branched and provided on the same circumferential surface as the circumferential surface on which the first side branch is provided in the pressure oil flow path. " It is achieved by a pressure oil pulsation reducing device as set forth in claim 1 of the invention.

[0008]

Since the present invention has such a structure,
The pulsation of the pressure oil generated by the hydraulic pump and propagating in the flow path of the pressure oil propagates in the flow path of the pressure oil, and then in the first side branch and the second side branch, respectively. The pulsation of the pressure oil propagating in the first side branch is
It is reflected by the reflecting surface of the first side branch and returns to the flow path of the pressure oil, and then a part of it passes through the flow path of the pressure oil and in turn propagates into the second side branch. It is reflected by the reflective surface of the side branch of and returns to the flow path of pressure oil.
On the other hand, the pulsation of the pressure oil that has propagated from the pressure oil flow path into the second side branch is reflected by the reflecting surface of the second side branch and returns to the pressure oil flow path, and then part of it is Propagating into the first side branch through the pressure oil flow path,
It is reflected by the reflective surface of the side branch of and returns to the flow path of pressure oil. Then, in such a process, the pulsation of each pressure oil reflected and returned to the flow path of the pressure oil interferes with the pulsation of the pressure oil propagating in the flow path of the pressure oil, respectively, and a plurality of frequency regions Exhibits a pulsation reduction effect.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view of a pressure oil pulsation reducing device according to a first embodiment of the present invention, and FIG. 2 describes a pulsation reducing effect relating to a first side branch in the pressure oil pulsation reducing device according to the first embodiment of the present invention. FIG. 3 is a characteristic diagram for explaining the pulsation reducing effect on the second side branch in the pressure oil pulsation reducing device of the first embodiment of the present invention, and FIG. 4 is a characteristic diagram for explaining the present invention. A characteristic diagram for explaining the pulsation reducing effect of the entire pressure oil pulsation reducing device of the first embodiment,
FIG. 5 is a sectional view of a pressure oil pulsation reducing device according to a second embodiment of the present invention.

First, the technical contents of the pressure oil pulsation reducing device according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 4. In FIG. 1, reference numeral 1 denotes an oblique shaft type plunger which is a source of hydraulic pressure. Hydraulic pumps such as pumps and swash plate type plunger pumps, 2
Is a main pipe which is connected to the discharge side of the hydraulic pump 1 and constitutes a main flow path for guiding the pressure oil to various parts of the hydraulic drive circuit.
First side branch with a bottomed branch functioning to reduce the pulsation of the pressure oil inside, 4 is also a second side branch, 5
Is a throttle valve provided in a hydraulic line downstream of the main pipe 2, and 6 is a tank from which the pressure oil supplied to each place via the main pipe 2 is discharged. The pressure oil of the hydraulic pump 1 supplied to the main pipe 2 is guided to various hydraulic devices as loads such as a control valve, an actuator, and a relief valve through a branch flow path. The throttle valve is shown collectively. The first side branch 3 is provided with a passage 3b, and the branch point of the main pipe 2 so that the pulsation of the pressure oil in the main pipe 2 entering the passage 3b is reflected and returned. The reflection surface 3a is formed by closing the end portion on the opposite side. The second side branch 4 is provided with a passage 4b and forms a reflection surface 4a in the same manner as the first side branch 3. The second side branch 4 is provided on the same peripheral surface of the main pipe 2 as the peripheral surface on which the first side branch 3 is provided so as to be branched so as to face the first side branch 3. Passage 3b of the first side branch 3
Has a length of L ₁ and the passage 4 of the second side branch 4
The length of b distance is L _2. In the present embodiment, each of the side branches 3 and 4 is formed by using a flexible hose which is bendable and formed by sandwiching a metal net between synthetic rubbers. The side branches 3 and 4 are not limited to such flexible hoses, and may be steel pipes.

Since the pressure oil pulsation reducing apparatus of the first embodiment has such a structure, the pulsation of the pressure oil discharged from the hydraulic pump 1 propagates into the main pipe 2 and then the first
To the passage 3b of the side branch 3 and the passage 4b of the second side branch 4. The pulsation of the pressure oil propagating to the passage 3b of the first side branch 3 passes through the passage 3b having the length L ₁ and is reflected by the reflecting surface 3 of the first side branch 3.
It is reflected by a and returns to the main pipe 2 again through the passage 3b. Then, a part thereof passes through the main pipe 2 and, in turn, propagates to the passage 4b of the second side branch 4, and then passes through the passage 4b of the second side branch 4 having the length L ₂ . It is reflected by the reflecting surface 4a, and then returns to the main pipe 2 through the passage 4b again. On the other hand, the pulsation of the pressure oil propagating from the main pipe 2 to the passage 4b of the second side branch 4 passes through the passage 4b of the length L ₂ and is reflected by the reflecting surface 4a of the second side branch 4 to be again , Returns to the main pipe 2 through the passage 4b. Then, a part thereof passes through the main pipe 2 and propagates to the passage 3b of the first side branch 3, passes through the passage 3b having the length L ₁ and is reflected by the reflecting surface 3a thereof, and then the passage again. It returns to the main pipe 2 through 3b. In such a process, the pulsation of the pressure oil propagating to and reflected in the passage 3b of the first side branch 3 and the passage 4b of the second side branch 4 interferes with the pulsation of the pressure oil propagating in the main pipe 2. Although the pulsation reducing effect is exerted, the pulsation reducing effect is exerted as follows in the following four processes.

Pulsation of the pressure oil propagated from the main pipe 2 to the passage 3b of the first side branch 3 is reflected by the reflecting surface 3a of the first side branch 3 and passes through the passage 3b again to the main pipe 2 It is the process of returning to. The basic frequency f ₁ of the pulsation-reducing center frequency related to the pulsation of the pressure oil which is reduced in this process is as follows when calculated according to the equation (1).

F ₁ = V / 4L ₁ Second stroke After the first stroke, the pulsation of the pressure oil passing through the main pipe 2 is the second.
Propagated to the passage 4b of the side branch 4 of the
It is a process in which the light is reflected by the reflecting surface 4a of the second side branch 4 after passing through, and returns to the main pipe 2 through the passage 4b again. The fundamental frequency f ₂ of the pulsation reduction center frequency relating to the pulsation of the pressure oil reduced in this process is as follows.

F ₂ = V / 4 (L ₁ + L ₂ ) Third stroke The pulsation of the pressure oil propagating from the main pipe 2 to the passage 4b of the second side branch 4 is reflected on the reflecting surface 4a of the second side branch 4. This is the process of being reflected and returning to the main pipe 2 through the passage 4b again. The fundamental frequency f ₃ of the pulsation reducing center frequency related to the pulsation of the pressure oil reduced in this process is as follows.

F ₃ = V / 4L ₂ 4th stroke After the 3rd stroke, the pulsation of the pressure oil passing through the main pipe 2 is the first.
Propagates to the passage 3b of the side branch 3 of the
It is a process in which the light is reflected by the reflection surface 3a of the first side branch 3 through the passage, and returns to the main pipe 2 through the passage 3b again. The fundamental frequency f ₄ of the pulsation reduction center frequency relating to the pulsation of the pressure oil reduced in this process is as follows.

[0016] f ₄ = V / ₄ Note (L ₁ + L _2), when calculating these basic frequency f ₁ to f _4, theoretically, L ₁ in consideration of the tube diameter of the main pipe 2, L
_It is necessary to add the radius of the main pipe 2 to 2, but since the radius is so small that it can be ignored with respect to the length of the passages 3b and 4b of the side branches 3 and 4, the main pipe 2 It does not consider the pipe diameter. The pulsation reducing effect exhibited in the first stroke and the second stroke is shown in a diagram in FIG. The points of frequencies f ₁ and f ₂ that form the vertices in the diagram of FIG. 2 have the largest pulsation reduction effect. In other words, among the pulsations of the pressure oil having various frequencies propagating in the main pipe 2, the pulsations that interfere with the pulsations of the pressure oil from the side branches 3 and 4 and are most greatly reduced have the fundamental frequencies f ₁ and f ₂ . It is a thing. Side branch 3,4
The pulsation of the pressure oil reflected by and returning to the main pipe 2 not only interferes with the pulsation of the pressure oil having the fundamental frequencies f ₁ and f ₂ but also with the pulsation of the pressure oil having the frequency in the peripheral region. , The peripheral area is also reduced to some extent. As a result, in the diagram of FIG. 2, both of the diagrams relating to the frequencies f ₁ and f ₂ draw a bilaterally symmetrical mountain-like curve.
Therefore, the pressure oil pulsation reducing device of the first embodiment exhibits the pulsation reducing effect in the two types of frequency regions centering on the frequencies f ₁ and f ₂ by the first stroke and the second stroke.

Next, the pulsation reducing effect exhibited in the third and fourth strokes is shown in a diagram in FIG. As is apparent from FIG. 3, the pressure oil pulsation reducing device according to the first embodiment performs the frequency f by the third stroke and the fourth stroke.
_The pulsation reducing effect is exhibited in two types of frequency regions centered on ₃ and f ₄ . As is clear from the above description regarding the second and fourth strokes, the frequency f ₄ and the frequency f ₂ are the passages 3 b of the two side branches 3 and 4,
No matter how the lengths L ₁ and L ₂ of 4b are set, they are exactly the same. Therefore, in the entire pressure oil pulsation reducing apparatus of this embodiment, the frequencies f ₁ , f ₂ (= f ₄ ) and f ₃ are maximized. Centered on 3
The pulsation reducing effect can be obtained in various frequency regions. Further, when the lengths L ₁ and L ₂ of the passages 3b and 4b are equalized, the pulsation reducing effect exhibited by the entire pressure oil pulsation reducing device of the present embodiment is as shown in FIG.
According to the present embodiment, the pulsation reducing effect can be obtained in at least two kinds of frequency regions.

Therefore, by adjusting the lengths L ₁ and L ₂ of the passages 3b and 4b of the side branches 3 and 4 to appropriate values, among the pulsations of pressure oil in various frequency regions propagating in the main pipe 2, , For example, pulsations in the frequency domain with large amplitude,
It is possible to reduce the pulsation of pressure oil in a plurality of types of frequency regions that are desired to be reduced. As described above, according to the first embodiment, the side-branch type pressure oil pulsation reducing device capable of increasing the frequency range in which the pressure oil pulsation generated by the hydraulic pump can be reduced can be obtained, and
It is possible to effectively reduce the pulsation of pressure oil. In the present embodiment, when the second side branch 4 is provided in the main pipe 2 in a branched manner, the second side branch 4 is provided on the same peripheral surface as the peripheral surface on which the first side branch 3 is provided. , 4 are provided, the number of connection points of the side branches 3 and 4 to the main pipe 2 is only one. Therefore, the two side branches 3,
The connection work of No. 4 can be done in one step using one pipe joint, inexpensively and efficiently, and the connection point of the side branch can be minimized, and the flow of pressure oil flowing in the main pipe 2 Do not disturb. As described above, each of the first side branch 3 and the second side branch 4 is made of a flexible hose that can be bent, and can be bent in a desired direction and fixed in place. Therefore, it is convenient to install and can be installed so as not to interfere with peripheral devices and work.

The technical contents of the side branch type pressure oil pulsation reducing device of the second embodiment of the present invention will be described with reference to FIG.
In FIG. 5, the parts denoted by the same reference numerals as those in FIG. 1 represent the same parts as those in FIG. 1, and therefore will not be described in detail to avoid duplication of description. As is clear from FIG. 5, the pressure oil pulsation reducing device of the present embodiment reduces the pressure pulsation of the pressure oil propagating in the main pipe 2 which is the flow path of the pressure oil, like the device of the first embodiment. In the oil pulsation reduction device, the first side branch 3 is provided in the main pipe 2 in a branched manner, and the second side branch is provided on the same peripheral surface as the main pipe 2 on which the first side branch 3 is provided. 4 is provided so as to be branched so as to face the first side branch 3, and the essential configuration is the same as that of the side branch type pressure oil pulsation reducing device of the first embodiment.

The characteristic technical contents of the pressure oil pulsation reducing device of the second embodiment will be described. The pressure oil pulsation reducing device of this embodiment is the same as the pressure oil pulsation reducing device of the first embodiment. For side branch 3 and second side branch 4,
Each of the reflectors 7 and 8 is provided with an elastic force. That is, the reflectors 7 and 8 are connected to the branch tips 3 of the passages 3b and 4b of the side branches 3 and 4, respectively.
c, 4c side, that is, the end portion side opposite to the main pipe 2, the respective reflecting surfaces 7a, 8a are respectively directed to the main pipe 2 side, and elastic force is applied by the springs 9 and 10. ing. Further, in the present embodiment, these reflectors 7,
8, fine holes 7b and 8 for passing pressure oil, respectively.
b is drilled.

Since the pressure oil pulsation reducing device of the second embodiment is provided with such a configuration, the pulsation reducing effect as already described in the first embodiment can be exhibited, and the following action and effect can be obtained. Can be demonstrated together. That is, when the hydraulic pump is driven by an engine or the like, generally, when the load applied to the hydraulic pump 1 increases, the rotational speed thereof decreases and the pulsation of the pressure oil generated by the hydraulic pump 1 shifts to the low frequency side. However, the pressure oil pulsation reducing device of this embodiment can lower the pulsation reducing center frequency in response to such changes. Regarding this point, when the load applied to the hydraulic pump 1 increases, the hydraulic pressure in the flow path of the pressure oil including the main pipe 2 increases, but in such a case, of course, the first side branch 3 Passage 3b and second
The hydraulic pressure in the passage 4b of the side branch 4 also increases. Then, the reflectors 7 provided in these passages 3b and 4b,
In response to such an increase in hydraulic pressure, 8 respectively moves a predetermined distance to the branch tip 3c, 4c side against the elastic force of the springs 9, 10 and lengths L ₁ , L of the passages 3b, 4b. ₂
Will be substantially increased. As a result, as is apparent from the equation (1), the frequencies f _{1 to} f ₄ described above can be reduced and the pulsation reduction center frequency can be lowered.
On the contrary, when the load applied to the hydraulic pump 1 is decreased and the rotational speed thereof is increased, the pulsation reduction center frequency can be similarly increased this time. Therefore, according to this embodiment, even if the rotational speed of the hydraulic pump 1 increases or decreases and the pulsation of the pressure oil propagating in the main pipe 2 shifts to the high frequency side or the low frequency side, the pulsation responds to such changes. The pulsation of the pressure oil can always be effectively reduced by increasing or decreasing the reduction center frequency. In this embodiment, in particular, since the fine holes 7b and 8b for circulating the pressure oil are formed in the reflecting plates 7 and 8, the reflecting plates 7 and 8 are adapted to the increase and decrease of the hydraulic pressure of the passages 3b and 4b. It is possible to move smoothly when moving.

[0022]

As is apparent from the above description, according to the present invention, in the pressure oil pulsation reducing device for reducing the pulsation of the pressure oil generated by the hydraulic pump and propagating in the flow path of the pressure oil, the pressure oil is reduced. The first side branch is branched and provided in the flow passage of, and the second side branch is branched and provided on the same peripheral surface on which the first side branch is provided in the pressure oil flow passage. Therefore, unlike the conventional side-branch type pressure oil pulsation reducer, a side-branch type pressure oil pulsation reducer capable of increasing the frequency range in which the pressure oil pulsation generated by the hydraulic pump can be reduced can be obtained. As a result, the pulsation of pressure oil can be effectively reduced. In the case of embodying the present invention, in particular, if the configuration described in claim 2 of the claim is adopted, in addition to such an effect, the rotational speed of the hydraulic pump is increased or decreased to cause a change in the flow path of the pressure oil. Even if the pulsation of the propagating pressure oil shifts to the high frequency side or the low frequency side, the pulsation reduction center frequency is increased or decreased in response to such a change, and the effect that the pulsation of the pressure oil can always be effectively reduced is obtained. It can be demonstrated together.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram for explaining the pulsation reducing effect on the first side branch in the pressure oil pulsation reducing device of the first embodiment of the present invention.

FIG. 3 is a characteristic diagram for explaining a pulsation reducing effect regarding a second side branch in the pressure oil pulsation reducing device of the first embodiment of the present invention.

FIG. 4 is a characteristic diagram for explaining the pulsation reducing effect of the entire pressure oil pulsation reducing device of the first embodiment of the present invention.

FIG. 5 is a sectional view of a pressure oil pulsation reducing device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic pump 2 Main piping 3 1st side branch 3a 1st side branch reflective surface 3b 1st side branch passage 3c Branch tip 4 2nd side branch 4a 2nd side branch reflective surface 4b 2nd Side branch passage 4c Branch tip 6 Oil tank 6 Side branch 6a Side branch reflecting surface 6b Side branch passage 7,8 Reflecting plate 7a, 8a Reflecting surface 7b, 8b Pore 9,10 Spring

Claims (2)

[Claims] 1. A pressure oil pulsation reducing device for reducing the pulsation of pressure oil generated by a hydraulic pump and propagating in the pressure oil flow passage, wherein a first side branch is provided branching in the pressure oil flow passage. A pressure oil pulsation reducing device, characterized in that the second side branch is branched and provided on the same peripheral surface as the peripheral surface on which the first side branch is provided in the flow path of the pressure oil. 2. A reflection plate is provided on each of the first side branch and the second side branch so as to provide elastic force to the end side of the passage opposite to the pressure oil passage. The pressure oil pulsation reducing device according to claim 1, wherein