JP3212384B2 - accumulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accumulator. More specifically, the present invention relates to an accumulator for absorbing pulsation of hydraulic oil generated in a hydraulic circuit.

[0002]

2. Description of the Related Art In a hydraulic device such as a hydraulic suspension, pulsation of hydraulic oil in a high-pressure pipe connected to the discharge side of a hydraulic source such as a hydraulic pump causes harmful vibration noise. Conventionally, a vane pump was used as a hydraulic pump, but the pressure generated by this pump is relatively low (about 80 kg / cm ² ), so pulsation can be absorbed by the expansion and contraction of a rubber hose in the hydraulic circuit. Was. However, recently, hydraulic suspension circuits have been higher than before (about 180
kg / cm ² ), a hydraulic pump such as a gear pump for high pressure or a reciprocating pump has been adopted. When these pumps are used, the inside of the hydraulic circuit becomes high pressure, and with the conventional high expansion and contraction rubber hoses, fatigue is caused by excessive repeated stress, and the life is significantly shortened,
Could not be used. As a result, a hose and an accumulator whose strength is improved at the expense of elasticity have come to be used in combination. In addition, the pulsation absorbing function is almost dependent on the accumulator.

[0003] Two types of accumulators are known: a spring-free piston type and a bellows type. As a spring / free piston type accumulator, for example,
The one disclosed in 58-146786 is known. As shown in FIG. 6, a flow path 22 is formed inside a valve housing 21, a first pressure chamber 23 is formed in the middle of the flow path 22, and the volume of the first pressure chamber 23 is changed inside the first pressure chamber 23. Piston 24 to make
Are slidably provided. A small-diameter portion 25 protrudes from a rear portion of the piston 24. A second pressure chamber 26 having an inner diameter smaller than that of the first pressure chamber 23 is provided at the back of the first pressure chamber 23 so that the small-diameter portion 25 is inserted. Are formed. A spring 27 is provided inside the second pressure chamber 26 so as to repel the piston 24 toward the flow path 22. The second pressure chamber 26 is connected to the flow path 22 via a throttle 28 formed of a thin oil passage. Further, a second pressure chamber 26 and the flow path 22 are provided inside the valve housing 21.
An oil passage 29 is formed so as to communicate with the oil passage. Oilway 29
A check valve 30 that allows only the flow of hydraulic oil from the second pressure chamber 26 to the flow path 22 is provided in the middle of the check valve 30. In addition,
31 is an oil drain hole, and 32 is a pump.

The above accumulator works as follows. That is, the pulsation of the hydraulic oil pumped into the flow path 22 by the pump 32 is hardly transmitted to the second pressure chamber 26 due to the throttle 28 formed of a thin oil passage, and the hydraulic pressure of the second pressure chamber 26 is It becomes almost the average pressure of the pulsation pressure. When the hydraulic pressure of the first pressure chamber 23 is at the peak of the pulsating pressure (greater than the average pressure),
Due to the difference in oil pressure between the first pressure chamber 23 and the second pressure chamber 26, the piston 24 and the small-diameter portion 25 both move toward the back of the first pressure chamber 23 and the second pressure chamber 26 while receiving a reaction force from the spring 27. Thus, the volume of the space 23a of the first pressure chamber 23 communicating with the flow path 22 is increased. As a result, the pressure in the flow channel 22 decreases to substantially the average pressure, and the pulsation is absorbed. At this time, part of the oil inside the second pressure chamber 26 is supplied to the oil passage 29 having the check valve 30.
And the diaphragm 28 to return to the flow path 22. On the other hand, the hydraulic pressure of the first pressure chamber 23 is the bottom of the pulsating pressure (lower than the average pressure).
In this case, the piston 24 and the small-diameter portion 25 move toward the flow channel 22 while receiving the reaction force of the spring 27, and the volume of the space 23a is reduced. Rise to the average pressure. In this way, the pulsation is absorbed.

[0005]

However, the above-mentioned spring
Since the free piston type accumulator absorbs pulsation only by changing the volume of the space 23a,
Although it is effective mainly for pulsation in the low frequency band, the effect in the high frequency band is not sufficient due to its structure.

On the other hand, the accumulator of the bellows type has a narrow hydraulic pressure range in which the effect of pulsation absorption can be obtained in consideration of the function of the bellows, and the bellows is liable to be damaged and broken by repeated expansion and contraction, so that its durability is poor. There's a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide an accumulator which can obtain a pulsation absorbing effect in a wide pressure range and a wide frequency band and can be downsized. I do.

[0008]

According to the present invention, there is provided an accumulator comprising a container having an inlet and an outlet for hydraulic oil, an oil chamber formed in the container, and a spring chamber communicating with and adjacent to the oil chamber. A piston having a cross-sectional area smaller than a cross-sectional area of the oil chamber housed slidably in the spring chamber, and a spring interposed between the piston and a bottom of the spring chamber; A first orifice is formed in the piston, a second orifice is formed in a hole communicating the oil chamber and the spring chamber in the piston, and a riser pipe projects from an oil chamber side opening of the discharge hole. I do.

Further, it is preferable that the introduction hole and the discharge hole are formed in parallel.

[0010]

According to the accumulator of the present invention, when the pulsation of the hydraulic oil is transmitted to the oil chamber through the first orifice of the introduction hole, the pulsation is rectified by the throttle action, and the high frequency component is partially attenuated. . Further, since the oil chamber having a cross-sectional area larger than the cross-sectional area of the piston becomes a volume chamber, a pressure drop (pulsation damping) occurs. The pulsation thus reduced is further transmitted to the spring chamber through the second orifice of the piston, but the pulsation is smoothed by the second orifice, so that the pressure in the spring chamber is maintained at substantially the average pressure of the pulsation. It is. Therefore, when the oil pressure in the oil chamber is higher than the oil pressure in the spring chamber (peak pulsation pressure), the piston moves to the back of the spring chamber while receiving the reaction force of the spring, so that the volume of the oil chamber expands and the oil pressure in the oil chamber increases. Can be lowered. At this time, most of the pulsation pressure is in opposition to the oil pressure inside the spring chamber, so that pulsation in a pressure range considerably different from the resilience of the spring can be effectively absorbed.

Similarly, when the oil pressure in the oil chamber is lower than the oil pressure in the spring chamber (the bottom of the pulsation pressure), the piston moves toward the inlet side of the spring chamber while receiving the reaction force of the spring.
The volume of the oil chamber is reduced, and the oil pressure of the oil chamber is increased. Thus, the pulsation in the low frequency band is absorbed by the expansion and contraction of the oil chamber due to the movement of the piston.

Next, the pulsation in the high frequency band remaining in the oil chamber is narrowed in a longer section than the orifice when passing through the riser pipe protruding from the oil chamber side opening of the discharge hole.
Rectified (absorbed) in the pipe.

The protruding riser pipe has a pulsating component to be absorbed by a change in the volume of the oil chamber caused by the piston.
It also serves as a "rectifier plate" that prevents it from flowing out of the discharge holes.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway perspective view of an accumulator according to an embodiment of the present invention before assembly, FIG. 2 is a cross-sectional view of the accumulator of FIG. 1 after assembly, and FIG. 3 is a system showing an example of a pulsation absorption test apparatus of the accumulator. FIG.

As shown in FIGS. 1 and 2, the accumulator is configured as follows.

An oil chamber 2 is formed at the opening side inside a cylindrical main body 1 having one end closed, and an oil chamber 2
A cylindrical spring chamber 3 having a smaller cross-sectional area is formed. The opening end of the oil chamber 2 can be sealed by a substantially cylindrical lid 4. The cover 4 is connected to the main body 1 by screwing a male screw 5 formed on a side surface thereof into a female screw 6 formed at an open end of the oil chamber 2. further,
A compression coil spring 7 (hereinafter simply referred to as a spring 7) is inserted into the spring chamber 3, one end of which is fixed to the back of the spring chamber 3, and the other end is attached to a piston 8. The piston 8 is slidably accommodated in the spring chamber 3 and has a cylindrical shape with a bottom. The upper and lower limits of the stroke of the spring 7 are set by a stopper (not shown) provided on the main body 1 (which may be provided on the piston 8).

The cover 4 has an inlet 9 and an outlet 10 formed in parallel with each other. A first orifice 11 is formed inside the introduction hole 9. Meanwhile, the discharge hole
A straight pipe (hereinafter, referred to as a riser pipe) 12 protrudes from an opening end of the oil chamber 2 on the side of the oil chamber 2.

A second orifice 13 is formed in the center of the bottom of the piston 8. Also, on the side of the piston 8,
A plurality of labyrinth grooves 14 and a plurality of holes 15 for an oil seal are formed.

The accumulator is connected in series with a hydraulic circuit in a section between the pump 16 and the actuator 17 as shown in FIG. That is, the pump 16
Is sent from the inlet hole 9 into the oil chamber 2 and then discharged from the outlet hole 10 to the actuator 17.

The accumulator configured as described above absorbs the pulsation of the hydraulic circuit as follows.

When the pulsation which is rectified by passing through the first orifice 11 of the introduction hole 9 and the pulsation of which the high-frequency component is partially reduced is transmitted to the oil chamber 2, the oil chamber having a larger cross-sectional area than the piston cross-section A pressure drop (pulsation damping) occurs because the chamber becomes a chamber. The pulsation thus reduced is further transmitted to the spring chamber 3 through the second orifice 13 of the piston, but the pulsation is smoothed by the second orifice 13, and the pressure in the spring chamber 3 is reduced to approximately the average pressure of the pulsation. Will be kept. Therefore, when the oil pressure of the oil chamber 2 is higher than the oil pressure of the spring chamber 3, the piston 8 moves to the back of the spring chamber 3 while receiving the reaction force of the spring 7, so that the volume of the oil chamber 2 is increased and the oil chamber 2 The oil pressure is reduced. At this time, most of the pulsation pressure is in opposition to the oil pressure in the spring chamber 3, so that pulsation in a pressure range considerably different from the elastic force of the spring 7 can be effectively absorbed.
That is, a small spring (a spring having a small spring constant and using a necessary deflection margin) is sufficient for a high-pressure hydraulic circuit. Similarly, when the oil pressure of the oil chamber 2 is lower than the oil pressure of the spring chamber 3, the piston 8 moves toward the inlet side of the spring chamber 3 while receiving the reaction force of the spring 7, thereby reducing the volume of the oil chamber 2, The oil pressure in the oil chamber 2 is increased. Thus, the pulsation in the low frequency band is absorbed by the expansion and contraction of the oil chamber 2 due to the movement of the first orifice 11 and the piston 8.

A part of the hydraulic oil in the spring chamber 3 is moved by the movement of the piston 8 in the spring compression direction.
Is returned to the oil chamber 2 through the gap between the oil chamber 2 and the piston 8. In addition, the gap communicates with the oil chamber 3 through the hole 15 and the labyrinth groove 14 is formed on the outer periphery of the piston 8, so that the oil pressure in the gap is averaged over the entire circumference of the piston 8. You. Therefore, the piston 8 is always in the spring chamber 3
Centered internally.

Finally, the hydraulic oil inside the oil chamber 2 is a riser pipe.
The riser pipe 12 is sent from the discharge hole 10 to the downstream actuator 17 through the outlet 12. The riser pipe 12 narrows the pulsation in a longer section than the orifices 11 and 13, so that rectification is further performed, and the high-frequency Pulsation is also absorbed.

The riser pipe 12 is provided with a pulsating component to be absorbed by a change in the volume of the oil chamber 2 caused by the piston 8 and a discharge hole 10.
It also serves as a "rectifier plate" that prevents it from flowing out through.
In this way, the pulsation of the hydraulic oil is absorbed in a wide pressure range and a wide frequency band.

Next, the accumulator of the present invention will be described in more detail based on specific examples thereof and Comparative Examples 1 and 2, which are examples of a conventional accumulator.

Embodiment An accumulator according to the present invention is shown in FIG. The dimensions of each part are as follows.

[0027] Comparative Example 1 A spring / free piston type accumulator, the basic structure of which is shown in FIG. The external dimensions are the same as in the example,
The dimensions of other parts are as follows.

External dimensions 63 mm Length 155 mm Diameter of the orifice 28 3.0 mm Outer diameter of the piston 24 40 mm Maximum stroke of the piston 24 40 mm Spring constant of the spring 27 7.6 kgf / cm Comparative Example 2 An accumulator with a built-in metal bellows. The basic structure is shown in FIG. The external dimensions are the same as in the example,
The dimensions and numerical values of the other parts in FIG. 4 are as follows.

Appearance Dimensions Outer diameter 63 mm Length 155 mm Gas filling pressure of gas chamber 41 400 kgf / cm ² Outer diameter of bellows 42 55 mm Inner diameter of bellows 42 35 mm Maximum stroke of bellows 42 37 mm Example and comparative example configured as described above The pulsation absorption test of the accumulators related to 1 and 2 was performed. The measuring method is as follows.

As shown in FIG. 3, the measuring device comprises a servo valve S
Sample accumulator A
CC is connected, and it has a closed-loop pipeline configuration for returning to the tank T by a return circuit. The sine wave generator SW includes a pump P, a tank T, a servo valve S, and a controller C. The servo valve S regulates the oil pressure as a function of the sinusoidal signal sent from the controller C.
An input pulse pressure measurement sensor ΔP1 is provided on the introduction hole side of the accumulator ACC, and an output pulse pressure measurement sensor Δ
P2 are respectively arranged, and the pulse pressure measurement sensors ΔP1, ΔP
2 converts the detected pressure fluctuation into a voltage signal by the amplifier AMP, then measures the attenuation rate by the FFT analyzer, and
-Recorded on a Y plotter. The average pressure downstream of the accumulator was measured by the average pressure measurement sensor PO. In FIG. 3, F indicates a flow meter.

FIG. 5 shows the test results. In FIG. 5, the horizontal axis represents the frequency of the sine wave modeled as a pulsation (unit: H).
z), and the vertical axis indicates the pulsation attenuation rate (unit: dB) by the accumulator. Here, the attenuation rate is obtained by the following equation: attenuation rate = 20 Log (y / x).

Here, x indicates the amplitude of the input pulse pressure, and y indicates the amplitude of the output pulse pressure. 5 (a), (b) and (c) show average pressures of 30 kgf / cm ² , 100 kgf / cm ² and 180 kgf / cm, respectively.
^In case of ² . The measured value of the example is indicated by a solid line A, the measured value of the comparative example 1 is indicated by a broken line B, and the measured value of the comparative example 2 is indicated by a chain line C.

According to the results shown in FIG. 5, the comparative example 1 (indicated by the broken line B) has a value of 150 to 50 at any average pressure.
In a high frequency band of 0 Hz, the pulsation absorption effect is reduced.

[0034] Comparative Example 2 (indicated by a one-dot chain line C) is if the average pressure of ^{100kgf / cm 2, 180kgf / cm} 2, although good pulsation is absorbed, the average pressure of 30 kgf / cm ² Ba In the meantime, the effect of pulsation absorption is hardly seen.

In the embodiment (shown by the solid line A), a pulsation absorbing effect is observed in a wide frequency range of 50 to 500 Hz at any average pressure.

As described above, the spring-free piston type accumulator of Comparative Example 1 absorbs pulsation by the movement of the piston, and therefore has a low pulsation absorbing effect in a high frequency band, and the bellows type accumulator of Comparative Example 2 has a gas chamber. Since the effective pressure range is determined by the pressure of the gas sealed in the chamber, the pulsation absorption effect is lost in other pressure ranges (when the average pressure is 30 kgf / cm ² in this measurement). In contrast, the accumulator according to the embodiment of the present invention can stably absorb the pulsation in a wide pressure range and a wide frequency band.

Therefore, the accumulator according to the present embodiment can be applied to a hydraulic system (such as an oil suspension of an automobile) in which the pressure generally fluctuates in a wide range without any problem.
It exerts effects that cannot be achieved in 2).

[0038]

According to the present invention, by providing the riser pipe at the opening end of the oil chamber discharge hole on the oil chamber side, the accumulator can also absorb the pulsation in the high frequency band. The pulsation over a wide range from the low frequency band to the high frequency band can be absorbed. In addition, by providing the second orifice in the piston for keeping the oil pressure in the spring chamber constant, the structure of the accumulator can be simplified, so that the size can be reduced.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an accumulator according to an embodiment of the present invention before assembly.

FIG. 2 is a sectional view of the accumulator of FIG. 1 after assembly.

FIG. 3 is a system diagram showing an example of a pulsation absorption test device of an accumulator.

FIG. 4 is a sectional view showing a comparative example 2 of the conventional bellows type accumulator.

FIG. 5 is a graph showing the results of a pulsation absorption test.

FIG. 6 is a sectional view showing an example of a conventional accumulator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body 2 Oil chamber 3 Spring chamber 7 Spring 8 Piston 9 Inlet hole 10 Discharge hole 11 First orifice 12 Riser tube 13 Second orifice

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichi Kobayashi 1118 Sado, Bessho-cho, Himeji-shi, Hyogo Nichirin Himeji Plant Co., Ltd. (72) Inventor Masami Matsubara 1-7-19 Minamishinagawa, Shinagawa-ku, Tokyo Stock Company Otsuka Corporation (56) References Japanese Utility Model Sho 55-158390 (JP, U) Japanese Utility Model Sho 51-34015 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16L 55/04 -55/055 F15B 1/04-1/24

Claims (1)

(57) [Claims] A container having an inlet and an outlet for hydraulic oil, an oil chamber formed inside the container, a spring chamber communicating with and adjacent to the oil chamber, and reciprocally slidably housed in the spring chamber. A piston having a cross-sectional area smaller than the cross-sectional area of the oil chamber, and a spring interposed between the piston and the bottom of the spring chamber. A first orifice is formed in the introduction hole, and the piston An accumulator, wherein a second orifice is formed in a hole communicating between the oil chamber and the spring chamber, and a riser pipe projects from an opening of the discharge hole on the oil chamber side.