JPS5847561B2 - fluid cylinder device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluid cylinder device, and particularly to a fluid cylinder device suitable for a thrust bearing device, a pressurizing device, etc. of a large-capacity water turbine generator.

Hydraulic cylinders are used for purposes such as applying large loads, supporting heavy objects, or performing linear motion. Hydraulic cylinders apply hydraulic force to a piston and slide the piston against the cylinder tube. Since this is necessary, sealing between the cylinder tube and the piston is a problem, and conventionally O-rings, ■, L packings, etc. have been used.

However, O-rings do not provide a sufficient sealing effect because their mechanical properties deteriorate over time, and even when other packings are used, due to the surface roughness of the cylinder tube and packing and the permeability of the packing itself, In other words, ■Leather is often used for packing, etc., but since leather has the property of being permeable to high-pressure oil,
Small oil leaks are inevitable.

Generally, when a hydraulic cylinder is used as part of a hydraulic machine, oil is supplied by an auxiliary machine such as a hydraulic pump, so even a small amount of oil leakage is unlikely to cause any problems to the system being used. .

Further, it is also possible to take measures such as reducing oil leakage by using high viscosity hydraulic oil.

However, depending on where it is used, even a small amount of oil leakage may not be allowed for a long period of time, or the use of auxiliary equipment such as pumps may be restricted.Hydraulic cylinders have a relatively simple structure and cannot be used to apply or support large loads. On the other hand, there are advantages such as being able to
In the above-mentioned cases, there was a problem in that the use had to be suspended.

The present invention has been made in view of this point, and its object is to provide a fluid cylinder device that does not leak working fluid.

In order to achieve this object, the present invention uses a plastic fluid fluid as a working fluid, and calculates the difference between the pressure of the plastic fluid fluid in a chamber configured by a bottomed cylinder tube and a piston and the pressure outside the room. The sliding stress in the gap between the bottomed cylinder tube and the piston is maintained within a range below the yield stress of the plastic flow fluid.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

Conventional fluid cylinder devices are often hydraulic cylinders that use petroleum-based hydraulic oil, water-soluble hydraulic oil, synthetic hydraulic oil, etc. as their working fluid, and additives have been added to the hydraulic oil depending on the application. The working fluid in is a fluid that exhibits fluid fluidity, and when a certain stress τ acts on the fluid, it always produces a strain rate ε, and these relationships are expressed by the curve a as shown in Figure 1.
, b or C.

In other words, if a fluid exhibiting fluidity is used, there is an advantage that the working fluid can be easily supplied by an oil pump, etc., but the gap between the cylinder tube and the piston is If there is a pressure difference between both ends, a strain rate will always occur (flow will occur), which means that the working fluid will leak.

This gap can be made very small by 01J ringing or packing, but as mentioned above, the surface of the cylinder tube has surface roughness, so when high pressure is applied, fluid leakage can occur over a long period of time. It is impossible to eliminate it.

Therefore, in the present invention, fluid fluidity is shown as an operation body.

Instead of a fluid, the yield stress τ, as shown in FIG.

exists, and this yield stress τ. In the following, it exhibits properties like an elastic body without producing a strain rate ε, but the yield stress τ.

In the above, the characteristics of curves d, e, f that flow like fluid,
A fluid with so-called plastic fluidity is used.

Examples of this plastic fluid fluid include oil sludge, grease paste, cream, wax, etc.0 Now, the gap between the cylinder tube and the piston is modeled, and the inner diameter R1 and outer diameter are set as shown in Figure 3. Diameter R2
, a cylindrical gap having a radial gap interval C and a length l, a pressure difference JP acts on both ends of the gap, and a state in which the cylindrical gap is filled with a plastic flow fluid is considered.

The shear stress on the wall due to the viscoelastic resistance of the plastic flow fluid is τ
d, then in an equilibrium state, the external force due to the pressure difference JP and the resistance force due to the shear stress τd are balanced, and if the shear stress τd is less than the yield stress τ0 of a plastic flowing fluid, the fluid has properties like an elastic body. , and does not flow.

In other words, if it is an umbrella, there will be no leakage.

For example, C=0.05mm, l=501+Tomi, τ0=0
．． If it is 0 0 5 kg/xi2, then the following is true, and if the pressure difference is 1 0 00 kg/cIrL2 or less, the flowing fluid will not leak.

Therefore, if the radial clearance C between the cylinder tube and the piston is made sufficiently small using an O-ring or packing, a condition can be created in which the working fluid does not leak even at a short distance l.

FIG. 4 shows a fluid cylinder device according to an embodiment of the present invention.

The piston 1 is fitted into the bottomed cylinder tube 2 with a small radial gap C so that they can slide against each other,
In the chamber composed of the piston 1 and the bottomed cylinder tube 2, there is a supply hole 3? A plastic flow fluid 5 having a yield stress, such as grease, oil sludge, paste, etc., is supplied and filled through the pipes 4 and 4.

Further, the radial gap interval C and the gap length l are set so as to satisfy the condition of equation (3) above for the maximum operating pressure.

Note that in reality, when the piston is shifted to one side, the maximum value of the gap is lτ, which is 2C.

Therefore, the condition JP< is satisfied.

C If the gap length l cannot be made large enough due to the structure, or if very high pressure is applied, the radial gap C must be made smaller. Since there are assembly limitations, it is preferable to attach packing or the like between the cylinder tube and the piston in close contact with each other, and to minimize the gap between the two.

Note that a lubricant is applied to the gap between the piston and the cylinder tube, or a plastic fluid such as grease, which is also a lubricant, is selected as the working fluid.

Since the fluid cylinder device of the present invention uses plastic flow fluid as the working fluid, it has a large flow resistance and is not very suitable for the purpose of converting the working fluid into motion by pumping it with a pump etc., but for example, it supports heavy objects. It is suitable for cases where the load is applied or when the load is applied.

As one such application example, FIGS. 5 and 6 show an example in which the present invention is applied to a support device for a tailing pad type thrust bearing of a water turbine generator.

The thrust bearing supports a thrust load applied to a runner rotating together with the rotating shaft 6 via an oil film 8 by a plurality of pads 9 arranged in the circumferential direction and tiltably supported by a pivot 10.

At this time, the thickness t of each pad 9, the runner and the pace plate 1
There are variations in the spacing H between pads 1 and 1 due to processing errors and installation errors, and it is not possible to maintain the same oil film thickness on each pad 9, that is, to share the load equally. There will be pads that are more severe than the load conditions.

Therefore, it is necessary to equalize the load shared by each pad, and for this purpose, a hydraulic cylinder may be used as a support device for each pad, and the inside of each cylinder may be communicated with a communication pipe.

However, despite these advantages, as previously mentioned, it has been impossible to stably eliminate oil leaks over a long period of time, so a high degree of safety and reliability is required. For thrust bearings used in rotating machines, support using hydraulic cylinders is not widespread, and in reality adjustment bolts or mechanical elastic support structures are used.

However, by using the fluid cylinder device without fluid leakage according to the present invention, bearing support by the fluid cylinder device can be easily realized.

That is, as shown in FIG. 6, the insides of each cylinder tube 2 of a plurality of fluid cylinder devices using plastic flow fluid 5 as a working fluid are communicated with each other through a communication pipe 12, and the insides of piston 1 and cylinder tube 2 are The load applied to the pad 9 is supported by the fluid pressure of the plastic fluid 5 acting on the pad 9.

Therefore, the same fluid pressure acts on each piston 1, and the load applied to the butt 9 can be equalized.

Moreover, there is no fluid leakage from the cylinder tube 2.

It goes without saying that the flow cross-sectional area of the communication pipe 12 needs to be sufficiently larger than the area of the gap between the cylinder tube 2 and the piston 1.

Further, FIG. 7 shows an example in which the fluid cylinder device of the present invention is applied to a press machine.

Conventionally, press machines have been vibration-proofed by mitigating large impact loads using the elastic force and damping force of mechanical springs such as countersunk springs. stand 14
If a fluid cylinder device using the plastic fluid fluid 5 according to the present invention is interposed between the cylinder tube 2 and the machine to support the machine, the spring stiffness and damping due to the viscoelastic properties of the plastic fluid fluid 5 in the cylinder tube 2 can be improved. It can absorb shock loads by force.

Of course, in this case as well, it is required that the fluid does not leak even if the pressure of the working fluid increases due to an impact load, so the fluid cylinder device using the plastic flow fluid according to the present invention is extremely suitable.

Although two application examples of the present invention have been described, it goes without saying that the present invention is not limited to these applications, and can be widely applied to other vibration-proof support structures for vibrating bodies such as reciprocating compressors. do not have.

As explained above, according to the present invention, a plastic fluid fluid is used as the working fluid of a fluid cylinder device, and the difference between the pressure of the plastic fluid fluid in a chamber configured by a bottomed cylinder tube and a piston and the pressure outside the room is was maintained so that the friction stress in the gap between the bottomed cylinder tube of the plastic flow fluid and the piston was within the range below the yield stress of the plastic flow fluid, so the gap between the cylinder tube and the piston As a result, there is no need for measures against leakage of working fluid or auxiliary equipment.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between stress and strain rate in a fluid with fluidity, Figure 2 is a characteristic diagram showing the relationship between stress and strain rate in a plastic fluid, and Figure 3 is a model of a cylindrical gap. 4 is a cross-sectional view of a fluid cylinder device showing an embodiment of the present invention, FIG. 5 is a longitudinal cross-sectional view of a pad type two-stroke bearing, and FIG. FIG. 7 is a developed vertical cross-sectional view of a pad type thrust bearing, and is a sectional side view of a main part of a vibration-proof support portion of a press machine to which the fluid cylinder device of the present invention is applied. 1... Piston, 2... Cylinder tube, 5... Plastic flow fluid, 12...
Communication pipe.

Claims (1)

[Scope of Claims] 1. A fluid cylinder device including a bottomed cylinder tube and a piston, in which a chamber formed by the bottomed cylinder tube and the piston is filled with a working fluid, using a plastic flow fluid as the working fluid, The difference between the pressure of the plastic fluid fluid in the chamber and the pressure outside the room is within a range where the friction stress in the gap between the bottomed cylinder tube and the piston of the plastic fluid fluid is equal to or less than the yield stress of the plastic fluid fluid. A fluid cylinder device characterized in that the fluid cylinder device is held in such a manner that 2. A fluid cylinder device comprising a bottomed cylinder tube and a piston, and in which a chamber formed by the bottomed cylinder tube and the piston is filled with a working fluid, in which a plurality of said chambers are provided, and each of these chambers is filled with said chamber. The bottomed cylinder tube and the piston communicate with each other through a passageway having a flow cross-sectional area larger than the gap area between the cylinder tube and the piston. The difference between the pressure of the plastic fluid and the piston is maintained such that the friction stress in the gap between the bottomed cylinder tube and the piston of the plastic fluid is within a range equal to or less than the yield stress of the plastic fluid. Fluid cylinder device. 3. The fluid cylinder device according to claim 2, wherein a thrust load is supported by the plurality of pistons.