JPH0255641B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic accumulator, in particular:
It comprises two chambers separated by a deformable membrane such as rubber, one of the chambers being filled with a pressurized gas and the remaining chambers being filled with a pressurized working liquid. The present invention relates to a hydraulic accumulator, characterized in that each member is connected and held by a prestressing device.

(Prior art) French patent application filed on February 27, 1980
No. 80.04313 and additional patent application No. 80.09781 to the above application filed April 30, 1980, disclose a method comprising two generally hemispherical chambers separated from each other by a flexible membrane and a cylindrical member. A hydraulic accumulator is disclosed. The inventions corresponding to these two French patent applications are disclosed in Japanese Patent Application Laid-Open No. 153101/1983. This hydraulic accumulator is
Prior to assembly, the two chambers and the cylindrical member are pressed together by a circumferential belt and prestressed to provide a bond greater than the forces that would cause them to disintegrate under maximum pressure during use. It is characterized by being given.

Further, French Patent Application No. 81.00740, filed by the same applicant on January 16, 1981, discloses a method for manufacturing a hydraulic accumulator including a cylinder whose both ends are sealed with plugs.

(Problems to be Solved by the Invention) Although the prestress type accumulator disclosed in French Patent Application No. 80.04319 and Additional Patent Application No. 80.09781 has excellent effects, it also has many drawbacks. ing.

First, in order to surround a member under prestress with a cylindrical belt, the structure becomes complicated and the work requires a lot of time, which is not suitable for mass production of accumulators. Further, when the force applying the prestress is removed, a portion of the prestress disappears due to relative contraction of the cylindrical member and slight deformation of the thread groove. Therefore, after the members are assembled, the value of the remaining prestress changes.

The accumulator disclosed in French Patent Application No. 81.00740 has the great advantage that it is very cheap to manufacture. but,
It is unsuitable because it cannot withstand large operating pressures and cannot be used in high-pressure hydraulic circuits.

The object of the present invention is to provide a hydraulic accumulator that has the advantages of the two manufacturing methods described above, is prestressed, can withstand extremely high pressures, and is cheaper to manufacture than conventional ones. It is about providing.

(Means for Solving the Problems) According to the present invention, the first
a cylinder having a first open end and a second open end; a second chamber for pressurized fluid; and a flexible membrane disposed therebetween; , a first plug provided at the first open end, a second plug provided at the second open end, and having a tension corresponding to a predetermined fluid pressure, the first end and the second end are connected to each other. at least one pre-tensioned screw, one end of which connects with one of said plugs and the other end of which is provided with a threaded hole for a nut for connection with the rest of said plugs.
and a tie rod, so that when the pressure exceeds the predetermined pressure, the cylindrical body is separated from the second plug to reduce the fluid pressure and return it to below the predetermined pressure. A hydraulic accumulator is provided.

(Operation and Effects of the Invention) According to the present invention, a first chamber holds a pressurized gas, a second chamber holds a pressurized fluid, and these two chambers are partitioned by a membrane. Despite this simple structure, an accumulator is provided in which the upper end of the membrane is locked near the upper open end of the cylinder end and is supported by a prestressed tie rod. , the membrane separating the two chambers is tightly locked at the upper end, which increases the stability of the structure, and the pre-stressing of the tie rods for connecting the two plugs increases the strength. , can withstand extremely high pressure.

Particularly, in the conventional technology, for example, the hydraulic accumulator disclosed in JP-A-56-153101, a pretension is applied to a cylindrical belt, and this belt is pressed against a hemispherical shell, but the structure is complicated. Not suitable for mass production.

In contrast, the accumulator of the present invention has a simple structure in which prestress is applied to the straight tie rods that connect the plugs.
It enables mass production.

Also, based on FIG. 8, as explained later,
According to an example in which the accumulator according to the present invention was subjected to an experiment under high pressure, there was no evidence of deterioration, and it was found to be strong and have excellent leakage properties compared to conventional ones.

(Example) This will be explained below based on the drawings.

The accumulator includes a cylindrical body 1 whose both ends are closed by plugs 2 and 3. A peripheral edge of a flexible membrane 5 is clamped between the upper end surface of the cylinder 1 and the lower surface of the plug 2. In FIGS. 1 and 2, the diameters of the two plugs 2, 3 are larger than the diameter of the cylinder 1.

The two plugs 2 and 3 are connected by a plurality of tie rods 6. Compressive force is applied to the cylindrical body 1 by the tie rod 6.

As shown in FIGS. 1 and 2, both ends of the tie rod 6 are threaded. The upper end 6a of this tie rod 6 is screwed into the screw hole of the plug 2,
Similarly, a nutshell 7 is screwed onto the lower end 6b. The nut 7 is fitted into a recessed hole 8 provided in the plug 3, as shown.

The lower end surface of the cylindrical body 1 is a conical surface 1a, and is in close contact with the recessed surface 3a on the upper surface of the plug 3.

The upper plug 2 is equipped with a gas filling valve 9, and the lower plug 3 is equipped with a duct 10 communicating with the hydraulic circuit.

According to the invention, prestressing is provided by a hydraulic jack. Hydraulic jack body 11
is connected to the tie rod 6 by a tie rod 12. The jack piston 13 supports the outer surface of the plug 3. Body 11 pulls plug 2 through tie rods 12 and 16.

Preferably, the internal bore of the body 11 is exactly equal to the internal bore of the cylinder 1.

Hydraulic pressure is introduced into the chamber 14 of the jack, and when the desired prestress pressure P is reached, the nut 7 is screwed into contact with the outer surface of the plug 3, and then the hydraulic pressure is removed.

The pressure of the working fluid reaches the prestress pressure P,
Slightly beyond this point, the conical surface 1a and the recessed surface 3a separate slightly, and the working fluid leaks out of the accumulator through the relief valve. The value of the maximum pressure at which leakage from the accumulator begins is determined by the pressure P used to create the prestress;
Almost exact match. In this way, the characteristics of the accumulator can be precisely determined.

On the other hand, before said pressure is removed, the various components are subjected to a prestressing action, so that the prestressing pressure P is removed in the same way as disclosed in French Patent Application No. 80.04313. The deformation that occurs before this occurs causes the member to contract and deform elastically, without reducing the prestress value.

Since the convex conical surface 1a of the cylinder 1 is in close contact with the concave surface 3a of the plug 3, excellent tightness, centripetal force of each member, and centrifugal prestress effect can be obtained. The prestress acts toward the center, as shown by arrow f in FIG.

3 to 9 show further embodiments of the device according to the invention.

In this embodiment, instead of the tie rod 6 on the outer periphery of the cylinder body 1 in the previous embodiment, one tie rod 17 is provided at the center, thereby connecting the two plugs 2, 3, the cylinder body 1 and the membrane 4. I support it.

A method for manufacturing a hydraulic accumulator with a deformable membrane and a tie rod in the center is known per se, as disclosed in French Patents Nos. 1,150,762 and 1,378,955.

However, what is disclosed in these patents is that when applying a prestress pressure of a precise value corresponding to the maximum working pressure of the accumulator, the working fluid automatically begins to leak out as soon as said maximum working pressure is reached. There is no such thing.

As shown in FIGS. 3 to 9, this accumulator is composed of a hollow cylindrical body 1 and two plugs 2 and 3 provided at both ends of the cylindrical body 1.

The upper plug 2 flatly supports the upper end of the cylinder 1. The lower plug 3 includes a side wall 3b continuous to the lower end of the cylindrical body 1. An aperture 15 is provided in the center of the upper plug 2, and an aperture 16 is provided in the center of the lower plug 3.

The cylinder 1 and the plugs 2 and 3 constituting the accumulator are connected by a tie rod 17 provided at the center. The tie rod 17 includes a head 18 that comes into contact with the outer surface of the plug 3 and a nut 20 that comes into contact with the outer surface of the plug 2.

As shown in the third figure, the membrane 4 is fixed by sandwiching a bead 5 provided at the upper end between the plug 2 and the upper end of the cylindrical body 1. The membrane 4 also has a hollow cylindrical sleeve 2 into which the tie rod 17 can be inserted.
1. A flange 22 is provided at the upper end of the sleeve 21.
is adapted to engage with a groove 23 provided in the aperture 15 of the plug 2.

The lower end surface 4a of the membrane 4 has an annular shape and is adapted to approximately match the shape of the annular cavity 24 formed between the inner wall of the side wall 3b of the plug 3 and the tie rod 17.

Further, a recessed hole 25 is provided outside the plug 3,
This recessed hole 25 communicates with the annular cavity 24 via a plurality of small holes 26 . Female thread 27 in recessed hole 25
is cut. Thereby, the recessed hole 25 is connected to an appropriate hydraulic circuit (not shown) via a socket or the like. Lower end surface 4a of membrane 4
, the seat piece 28 is placed so as to face the small hole 26.
It is good to have .

The plug 2 is provided with a side hole 29. This side hole 29 communicates with an inner chamber filled with pressurized gas via a duct 30 provided with a check valve 31.

Two further embodiments are shown in FIGS. 4 and 5.

In this embodiment, the length of the sleeve 21 in the middle of the membrane is less than the total height of the accumulator interior and is very short.

4 and 5, the length of the central sleeve 21 of the membrane 4 is 1/4 of the total height of the interior chamber. This sleeve 21 is fixed simply by fitting a snap ring 32 into an annular groove 33 provided in the tie rod 17.

To prevent the membrane 4 from being sucked into the hole 26 when the working liquid is completely drained from the accumulator.
As shown in the fourth figure, a washer-like movable plate 34 supported by a spring 35 may be brought into contact with the lower end surface 4a, or as shown in the fifth figure, a seat piece 36 may be provided.

While the seat piece 28 in FIG. 3 is embedded in rubber, this seat piece 36 is made of two members riveted together.

The central tie rod 17 supports the barrel 1 and the plugs 2, 3 with prestressing. When the hydraulic pressure exceeds a predetermined value, the tie rod 17 expands and a gap is created between the cylinder body 1 and the plug 2 or 3.
Leakage is starting to occur. Therefore, under no circumstances will the hydraulic pressure exceed a predetermined maximum critical value. This maximum critical value is a function of the elasticity of tie rod 17 and the prestress applied to each member.

FIG. 6 shows a different embodiment of the accumulator from that shown in FIGS. 3 to 5, which improves the operation of the accumulator under overpressure.

As shown in FIGS. 3 to 5, if the cross-sectional area of the inner chamber of the cylindrical body 1 is constant, when overpressure occurs, the lower part
That is, it was found that leakage occurred not only between the plug 3 and the lower surface of the cylinder 1 but also at the upper part, that is, between the plug 2 and the upper surface of the cylinder 1. If leakage occurs between the plug 2 and the top surface of the cylinder 1, there is a risk that the membrane sandwiched between the plug 2 and the top surface of the cylinder 1 will come off or be torn off, causing the accumulator to malfunction. .

In order to overcome this drawback, the cylinder body 1 and the plug 3
An enlarged diameter portion 1b is provided on the inner surface of the connecting portion with the side wall 3b. Further, the upper surface of the side wall 3b and the lower end of the cylindrical body 1 are aligned with each other.

The inner diameter D ₂ at the bottom of the cylinder 1 is larger than the inner diameter D ₁ at the top of the cylinder 1 . The inner diameter D ₁ is a portion that receives the hydraulic pressure within the annular cavity 24 .

With such a structure, even if an overpressure condition occurs, leakage will occur not between the cylinder 1 and the plug 2 but between the cylinder 1 and the side wall 3b.

FIG. 7 shows yet another embodiment.

As shown in FIGS. 3 to 6, when the membrane 4 is attached with the bead 5, the above-mentioned inner diameter D ₁
The disadvantage is that the value of cannot be determined accurately. That is, when the clamp is tightened or loosened, the working fluid leaks from between the membrane and the top end of the cylinder 1.

Therefore, the inner diameter D ₁ to which the hydraulic pressure is applied is the cylinder body 1
It is always slightly larger than the diameter of the inner hole. However, it is not possible to strictly determine the dimensions of the multi-section. Therefore, as shown in Figure 6, the inner diameter D ₁
is made larger than the inner diameter of the cylindrical body 1. However, the figure merely shows the outline.

In the event of overpressure, leakage occurs only between the side wall 3a and the lower end 1a' of the cylinder 1, so that the risk of the membrane becoming dislodged is eliminated.

The membrane 4 can therefore be fixed with a simple elastic washer 40. This elastic washer 40
A hole is drilled in the center. The tie rod 17 and the upper end of the sleeve 21 pass through this hole.

An annular groove 33 is formed in the tie rod 17 at a height corresponding to the hole in the elastic washer 40. The sleeve 21 is pressed against the annular groove 33 by the rounded inner end 40a of the washer 40. The upper end 4b of the membrane 4 is clamped between the upper end of the cylinder 1 and the plug 2 by the rounded outer edge 40b of the washer 40.

The greater the tension applied to the tie rod 17, the more the elastic washer 40 presses the sleeve 21 against the annular groove 33.

Devices such as those described above are particularly advantageous in that they are reliable and inexpensive.

The accumulators shown in FIGS. 3 to 7 are prestressed.

In order to achieve this state, the rod 3 of the piston 37 of the hydraulic jack 38 in the one shown in FIG.
The end of 7a is connected to the plug 2 via the cylindrical member 39.
Supported by The rod 37a is also screwed into the engagement end 19 of the tie rod 17.

When a compressive force is applied to the cylinder body 1 and one end of the plugs 2 and 3 by the hydraulic jack 38, this compressive force is absorbed by the elasticity of the metal constituting each member. Further, the force applied to the tie rod 17 itself is also absorbed by the elasticity of the metal forming the tie rod 17.

Once the predetermined maximum pressure is reached, the nut 20 will fit tightly into the plug 2 and the pressure in the jack 38 will be released. Due to the elasticity applied to the cylinder body 1, plugs 2, 3, and tie rod 17, the cylinder body 1, plugs 2, 3,
3, prestress is applied.

The following is an example in which the performance of the accumulator according to the present invention was confirmed through experiments.
This will be explained based on FIG.

A hydraulic accumulator as shown in Figure 8, having a total volume of 1, was used.

A working fluid at a pressure of 100 bar was introduced into the chamber 38a of the jack 38. Next, a powered wrench was used to tighten the nut 20 into the threaded groove 19 to create a connection. Next, remove the jack, place the accumulator on the test stand, and then
From between the lower end 1a' of the plug and the side wall 30a of the plug,
Working liquid was supplied to holes 25, 26, 24 until the working liquid leaked out.

The pressure at which the leakage occurred was P ₁ . A pressure of 120 bar is again applied to the chamber 38a, the nut 20 is tightened with the same tightening member, the jack 38 is removed and the pressure is increased to 25, 26, 25, 26, until leakage occurs.
24 was supplied with pressurized liquid. The pressure at which leakage occurred was _P2 .

The test was repeated with increasing pressure in chamber 38a in 20 bar increments. The pressures at which leakage occurred were P ₃ , P ₄ .

In this way, we were able to track the characteristics of the accumulator's curve point by point. These operations are
It was stopped when the value of P _o reached 400 bar.

The accumulator was then adjusted to operate at a maximum value of 400 bar.

The safety of conventional acumulators when used to operate in hydraulic circuits at a maximum pressure of N bar was maintained only when tested below 1.5 N bar.

The accumulator according to the invention has a pressure of 400 bar.
Applying a pressure of 1.5 times, or 600 bar, leakage started when the pressure reached 410 bar, and it was impossible to exceed this value. Therefore, the safety of operation of such an accumulator is absolute, which is not found in conventional accumulators.

Conventionally, after manufacturing, accumulators undergo durability tests that apply maximum pressure many times, and then
It was dismantled to inspect the deteriorated parts.

When the accumulator according to the present invention was tested 5,000,000 times and then disassembled, even the slightest sign of deterioration was not observed. In contrast, conventional accumulators showed signs of deterioration even after 150,000 cycles.

As mentioned above, the accumulator according to the invention exhibits high reliability and can therefore be used not only as an accumulator but also as an overpressure control valve.

Conventional overpressure control valves are very simple, consisting of a ball supported by a spring. When the oil pressure exceeds a predetermined value, the sphere is lifted and the working fluid flows into the tank.

However, a well-known drawback of such overpressure control valves is that they often momentarily reach 1.3 or even 1.5 times the maximum pressure. The reason is that when the pressure suddenly increases, the valve suddenly opens,
This is because the spring is compressed excessively, its scale increases, and an oil layer effect proportional to the square of the flow rate appears. Furthermore, due to this oil layer effect, metal is removed as the oil flows.

Although these drawbacks are well known to hydraulic engineers, to date there have been no spring-loaded overpressure control valves that do not suffer from these drawbacks.

An accumulator according to the invention having leakage properties as described above is provided in a bypass of a hydraulic circuit;
By enclosing it with a cover to prevent leakage and directing leakage water to a tank, a completely satisfactory overpressure control valve is obtained.

The capacity of the accumulator is determined experimentally as a function of the maximum flow rate through the tube. The overpressure control valves described above are less expensive than larger sized spring valves, are less susceptible to contaminants present in the liquid, and maintain a low flow rate to avoid corroding metals. , and can operate without overpressure.

As shown in FIG. 9, it is preferable to cut both ends of the cylindrical body 1 diagonally. In FIG. 1, the lower end of the cylindrical body 1 forms a conical surface 1a.

As in the case shown in Figure 1, in this improved embodiment as well, not only is a centripetal force acting on each member and good tightness is maintained, but the prestress is also applied radially.

As shown in the figure, by providing the cylindrical membrane 4 inside the cylindrical body 1, the inner diameter D ₃ of the part that pressurizes the upper plug 2 can pressurize the lower plug 3 due to the thickness of the membrane. The inner diameter of the part D will be slightly smaller than ₄ .

Furthermore, when a force exceeding the prestress is applied to the center tie rod 17 due to the pressure applied to the accumulator, the cylinder body 1 and the lower plug 3 are slightly separated from each other, and liquid leaks from there, causing the upper plug 2 and the cylinder body 1 to separate. At the connection point, they will never separate.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a first embodiment of the hydraulic accumulator according to the present invention, FIG. 2 is a vertical cross-sectional view of the operating process of the hydraulic accumulator of FIG. 1, and FIG. FIGS. 4 and 5 are views showing different embodiments each having separate membranes; FIG. 6 is a longitudinal sectional view of the accumulator shown in FIG. 3 and another embodiment;
FIG. 7 is a vertical cross-sectional view of yet another embodiment of the device having a separation membrane, FIG. 8 is a vertical cross-sectional view showing a method of applying prestress, and FIG. 9 is a longitudinal cross-sectional view of the accumulator of FIGS. 3 and 6. FIG. 3 is a longitudinal cross-sectional view of a further different embodiment. 1... Cylindrical body, 1a... Conical surface, 1a'... Lower end, 1
b... Expanded diameter part, 2, 3... Plug, 3a... Concave surface, 3
b...Side wall, 4...Membrane, 4a...Lower end, 4b...Upper end, 5...Bead, 6...Tie rod, 6a...Upper end,
6b...lower end, 7...nut, 8...recessed hole, 9...gas filling valve, 10...duct, 11...body, 12...tie rod, 14...chamber, 15, 16...opening, 1
7... Tie rod, 18... Head, 19... Engagement end, 2
0... Nut, 21... Sleeve, 22... Flange,
23...groove, 24...ring cavity, 25...recessed hole, 26...small hole, 27...female thread, 28...seat piece, 29...side hole, 3
0...Duct, 31...Check valve, 32...Snat spring, 33...Ring groove, 34...Movable plate, 35...Spring, 3
6... Seat piece, 37... Piston, 37a... Rod, 3
8...Hydraulic jack, 38a...Chamber, 39...Cylindrical member, 40...Elastic washer, 40a...Inner edge part,
40b...Outer edge.

Claims (1)

[Claims] 1. A first chamber for pressurized gas;
A hydraulic accumulator comprising a second chamber for pressurized fluid and a flexible membrane disposed therebetween, comprising: a cylinder having a first open end and a second open end; a first plug provided at the open end of the second plug, and a second plug provided at the second open end; at least one pre-tensioned tie rod having one end connected to one of said plugs and the other end provided with a threaded hole for a nut for connection with the remainder of said plugs; the cylindrical body is separated from the second plug when the pressure exceeds the predetermined pressure;
A hydraulic accumulator, characterized in that the fluid pressure is reduced and returned to below the predetermined pressure. 2. A tie rod is disposed centrally, the plug, the cylinder body and the membrane are supported under pressure against each other between the head of the tie rod, and a nut is provided which fits into the second end of the tie rod. A hydraulic accumulator according to claim 1. 3. The hydraulic accumulator according to claim 1 or 2, wherein at least one end of the cylinder has a beveled surface that matches the beveled surface of the plug. 4. The hydraulic accumulator according to claim 1, wherein both ends of the cylinder form beveled surfaces to match the beveled surfaces of the plug. 5. A hydraulic accumulator according to claim 1, wherein the tie rod is made of an elastic material. 6. The hydraulic accumulator according to any one of claims 1 to 5, wherein the inner hole of the cylinder has a larger cross section at the top than at the bottom. 7. The hydraulic accumulator according to claim 6, wherein the cylinder has a beveled surface at its lower end, and the side wall of the plug has a thickness equal to the beveled surface. 8. The membrane is fixed by an elastic washer having a hole in the center, the outer edge of this washer supports the upper end of the membrane at the corner formed by the junction of the upper plug and the top of the cylinder, and the inner edge of said washer Claim 1, wherein the top of the membrane sleeve is fixed in the annular groove provided in the tie rod by the
Hydraulic accumulator according to item 1 or 2. 9. According to claim 1 or 2, the membrane has a sleeve engaged with the central tie rod, which sleeve extends over the entire length of the accumulator and is latched at the upper end to the upper plug. Hydraulic accumulator. 10 The lower end of the cylinder has a beveled surface, and this beveled surface abuts the beveled surface of the lower plug, thereby
The cylindrical body is arranged in the center, and the cylindrical body is maintained in the center even when the beveled surfaces are slightly shifted from each other as a result of hydraulic pressure exceeding a predetermined maximum value. Hydraulic accumulator according to item 1 or 2 of the range. 11. The hydraulic accumulator according to claim 1, wherein the second plug is in sealing contact with the second open end of the cylinder.