JPS597602Y2 - hydraulic cylinder - Google Patents

Description

[Detailed description of the invention] Fig. 1 shows an example of the cushion part of a conventional hydraulic cylinder, where 1 is a cylinder tube, 2 is a cylinder head, and 3 is a cushion part of a conventional hydraulic cylinder.
is a rod, 4 is a piston, 5 is a nut for fixing the piston 4 to the rod 3, 6 is an oil hole connected to the oil supply and drain pipe, 7
8 is the cushion part of the rod, 8 is the cushion part of the head,
9 and 10 are pressure chambers, 11 is a wandering oil pipe flange, and 12 is a piston packing.

In FIG. 1, the hydraulic cylinder alternately supplies high pressure oil to pressure chambers 9 and 10 that sandwich a piston 4, and causes a rod 3 to expand and contract with respect to a cylinder tube 1 to perform work.

Generally, at the end of the stroke on the contraction side, the tip of the rod 3 touches the cylinder head 2, but when the speed of the rod 3 is high, a large impact force acts, and the cylinder tube 1
There was a risk that the welded portion of the cylinder head 2 would crack or the structure to which the hydraulic cylinder was attached would be damaged.

In FIG. 1, in order to prevent the above-mentioned drawbacks, a cushion portion 7 is provided at the tip of the rod, and the rod is inserted into the cushion portion 8 of the cylinder head 2, so that both of them constrict the drain oil flow path.

Therefore, the oil in the pressure chamber 9 flows through the oil hole 6 through the narrow annular gap formed by the rod cushion part 7 and the head cushion part 8.
is discharged through the

At this time, the pressure in the pressure chamber 9 increases due to the annular gap, and a brake force acts on the rod 3 to soften the collision between the rod 3 and the head 2.

However, since the above-mentioned throttle uses the viscosity of the oil in the annular gap, as the temperature of the oil increases, the viscosity decreases and the squeezing effect deteriorates.

It is also known that the squeezing effect is also reduced when the cushion portion 7 of the rod and the cushion portion 8 of the head are eccentric.

On the other hand, if the annular gap is made smaller, there is a risk that the outer periphery of the rod cushion portion 7 and the inner periphery of the head cushion portion 8 will come into contact and seize due to machining or assembly errors.

Furthermore, when the oil temperature is low in the winter, the cushioning becomes too strong and the pressure in the pressure chamber 9 becomes excessive, posing the risk that the cylinder tube may burst.

On the other hand, when starting in the opposite direction with this cushion at the stroke end, the high pressure oil sent from the oil hole 6 acts on the narrow area at the tip of the cushion part 7 of the rod. In case of rod cushion part 7
The problem is that the head moves at a high speed until it leaves the cushion part 8 of the head.

As mentioned above, the cushion of conventional hydraulic cylinders utilizes the viscosity of oil as described above, and the cylinder does not have a pressure relief function, so the cushion has no effect on oil temperature changes. It changed drastically, and it was not possible to always operate in a constant manner.

The present invention was proposed in order to solve the above-mentioned conventional drawbacks, and by providing a plurality of small oil holes opening on the outer periphery of the cushion part of the rod and a thin floating ring fitted into the cushion part. The purpose is to provide a hydraulic cylinder that is not affected by machining or assembly errors by providing pressure relief for high hydraulic pressure and preventing the cushion pressure from becoming excessive. .

In order to achieve the above object, the present invention has been devised so that when the cushion part of a sliding rod inserted into a cylinder enters a chamber communicating with an oil supply and drainage pipe, the cushion part of the rod is inserted through an oil hole drilled in the rod. A pressure chamber communicating with the rod, a plurality of small oil holes branching from the oil hole of the same rod and opening on the outer periphery of the cushion part of the same rod, and a hole formed so as to cover the opening of the small oil hole and through a radial gap. The rod has a structure consisting of a thin-walled floating ring fitted into the cushion part of the rod, and when the cushion part of the rod enters a chamber communicating with the oil supply and drain pipe, the oil in the pressure chamber flows into the oil hole of the rod. The oil flows from the small hole into the head cushion through the gap between the floating ring and the rod cushion, but this gap has a large throttling effect, making it difficult for the oil to flow, increasing the pressure in the pressure chamber. , it acts as a brake force on the rod and can alleviate the impact with the head.

Further, when excessive pressure is generated in the pressure chamber, the floating ring is deformed and the condensation becomes large, which can prevent the pressure in the pressure chamber from becoming excessive.

The embodiment of the present invention will be explained below with reference to the drawings. Fig. 2 is a side sectional view showing a cushion device of a hydraulic cylinder showing an embodiment of the present invention, Fig. 3 A, and the mouth are details of the floating ring shown in Fig. 2. FIG. 2 is a diagram and an explanatory diagram.

In addition, in FIG. 2, the same parts as in FIG. 1 are indicated using the same reference numerals.

In Figures 2 and 3, 1 is the cylinder tube, 2 is the cylinder head, 3 is the rod, 4 is the piston, 5 is the piston fixing nut, 6 is the oil hole connected to the oil supply and drain pipe, and 7 is the rod. Cushion part, 8 is the cushion part of the head, 9
1 is a pressure chamber, 11 is an oil supply/discharge pipe flange, and 12 is a piston packing, and these functions are the same as in the case of FIG.

Reference numeral 13 denotes a floating ring that is fitted to the outer circumferential portion of the cushion portion 7 of the rod with a small radial clearance therebetween. , a plurality of small oil holes 14 are provided in the circumferential direction, and the oil holes 14 are connected to a large diameter oil hole 15.
, 16 communicate with the pressure chamber 9.

17 is an oil relief groove provided in the radial direction on both sides of the floating ring 13; 18 is an oil relief groove provided in the floating ring 13;
This is a snap ring provided to prevent the cushion from slipping out from the cushion portion 7.

The floating ring 13 is shaped like a thin ring, and has a narrow gap 1 between the oil hole 14 and the cushion part 7.
When oil flows through 9, if the oil pressure is large, it will be elastically deformed.

Further, an oil hole 20 communicating with the oil hole 15 and communicating with the cushion portion 8 is formed at the tip of the cushion portion 7 by a valve seat 21 screwed onto the tip of the same cushion portion 7. 20 is provided with a check valve 22 and a spring 23,
The oil in the pressure chamber 9 is prevented from flowing directly to the cushion part 8 of the head, and on the contrary, the oil is allowed to flow from the cushion part 8 to the pressure chamber 9 with little resistance.

24 is a groove 2a provided in the inner peripheral part of the cushion part 8 of the head.
This is a cushion ring inserted inside the rod, and is provided to prevent oil leakage from the gap 25 provided between the outer diameter of the rod cushion portion 7 and the inner diameter of the head cushion portion 8. A gap is provided between the outer diameter and both sides of the cushion ring 24 and the groove portion 2a provided in the head 2, and a gap is provided between the outer diameter and both sides of the cushion ring 24 and the cushion portion 7 of the rod.
Even if there is some eccentricity between the two, they fit together easily.

Further, Po is the pressure in the pressure chamber 9, and Pd is the pressure in the cushion portion 8 of the head.

Next, the effect will be explained.

First, in Fig. 2, the rod 3 moves from the left to the right, the cushion part 7 of the rod is inserted into the cushion part 8 of the head, and when the cushion ring 24 comes into contact with the cushion part 7 of the rod, pressure is generated. The oil flow path in chamber 9 is closed,
The oil passes through the oil holes 16, 15, and 14, passes through the gap 19 formed by the floating ring 13 and the rod cushion part 7, is divided into left and right parts, flows into the head cushion part 8, and flows to the outside from the oil hole 6. .

The oil holes 16 and 15 have a larger diameter than the oil hole 14, so the resistance is small. Here, the number of oil holes 14 is n, the diameter of the oil hole 14 is d, and the floating ring 13 and the cushion part 7 of the rod are If the size of the gap 19 made by h is h, the flow path area of the gap is A=n. It becomes πdh.

However, since the sizes of h and d are small, the throttling effect here becomes large, and therefore the oil becomes difficult to flow, so the pressure chamber 9
The pressure Po increases.

This increased pressure of Po acts on the piston 4, which acts on the rod 3 as a braking force.

Therefore, the speed of the rod 3 is reduced, and the impact with the head 2 can be alleviated.

Also, when the speed of the rod 3 is very high, the amount of oil to be discharged from the pressure chamber 9 is large, and if the flow path area A is constant, the pressure chamber 9
Excessive pressure is generated.

This pressure oil flows out into the gap 19 through the oil holes 16, 15, and 14, but since viscous resistance is generated in the oil in this gap 19, the pressure at the oil hole 14 is Po as shown in the opening in Figure 3. However, when it enters the gap 19, a pressure loss occurs, and the pressure beyond that point is reduced at a gentle gradient due to viscous resistance.

Internal pressure acts on the floating ring 13 due to this pressure distribution.

However, since the floating ring 13 is thin,
This pressure oil deforms and the size h of the gap 19 increases.

Therefore, the flow path area A becomes large, the viscous resistance becomes small, the oil flows easily, and the pressure Po in the pressure chamber 9 does not become excessive.

Next, in Fig. 2, after the rod 3 reaches the right stroke end, the oil hole 6 is inserted into the cushion part 8 of the head.
When the rod 3 is moved to the right after being filled with more oil, the cushion ring 24 prevents oil from leaking, so no oil flows into the pressure chamber 9 from here.

Instead, the check valve 22 provided in the center of the rod's cushion part 7 opens, and oil flows into the pressure chamber 9 through this valve part, so that the supplied hydraulic pressure acts on a wide area of the entire piston 4. Rod 3 starts smoothly.

As explained in detail above, the present invention includes a floating ring fitted into the cushion portion of the rod through a radial gap so as to cover a plurality of small oil holes opening on the outer periphery of the cushion portion of the rod. As a result, once the oil comes out of the small oil hole, it flows radially within the radial gap and is depressurized.The flow velocity is very high in the immediate vicinity of the small oil hole, but as the flow spreads radially, the oil flows radially within the radial gap. At the outlet, the flow path area becomes larger and the flow velocity becomes smaller.

Therefore, the flow velocity does not cause damage to members near the oil hole.

Also, if the rod moves at high speed toward the chamber that communicates with the oil supply and drain pipe, the amount of oil that must be discharged from the pressure chamber will increase, so the pressure oil flowing out from the multiple small oil holes in the rod will The floating ring is elastically deformed and the radial gap between it and the cushion section becomes larger.

Therefore, the throttling effect is reduced and the pressure in the pressure chamber can be prevented from becoming excessive.

As mentioned above, the aperture in the cushion of the present invention utilizes the inertia effect and the viscosity effect, so unlike conventional cushions that use only the viscosity of oil, the cushion changes depending on the temperature (viscosity) of the oil. There are no drawbacks such as changes in performance.

Incidentally, by increasing the number of the small oil holes, increasing their diameter, and reducing the radial gap, it is possible to create a cushion that is strong against clogging due to dust, etc. A check valve is located on the side of the chamber that communicates with the oil supply and drain pipe from the branch part, and controls the opening and closing of the oil hole of the rod so that oil flows from the same chamber side to the pressure chamber side, but not in the opposite direction. If provided, when oil is supplied to the same chamber side and the rod moves toward the pressure chamber, the check valve will open and oil will flow into the pressure chamber from the same chamber side, allowing the rod to operate smoothly at startup.

[Brief explanation of drawings]

Fig. 1 is a side sectional view showing an example of the cushion part of a conventional hydraulic cylinder, Fig. 2 is a side sectional view of the cushion part of a hydraulic cylinder showing an embodiment of the present invention, and Fig. 3 A is the same as Fig. 2. 3 is an explanatory diagram showing the same pressure distribution state. Explanation of the main parts of the diagram: 1... Cylinder tube, 3... Rod, 6... Oil hole connected to the oil supply and drain pipe, 7... Rod Cushion part, 8.
...Head cushion part (chamber communicating with oil supply and drainage pipe), 9 ...Pressure chamber, 13 ...Floating ring, 14 ...Small oil hole ,15,
16...Oil hole, 19...Radial clearance.

Claims (1)

[Scope of utility model registration request] When the cushion part of the rod that is inserted into the cylinder and slides enters the chamber that communicates with the oil supply and drain pipe, the pressure chamber that communicates with the chamber through the oil hole drilled in the rod, and the oil hole of the rod. A plurality of small oil holes branch out and open on the outer periphery of the cushion portion of the same rod, and a thin-walled oil hole is fitted into the cushion portion of the rod through a radial gap so as to cover the openings of the small oil holes. A hydraulic cylinder characterized by a floating ring.