JPS5934887B2 - hydraulic cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION As shown in FIG.
By alternately supplying high pressure oil to pistons 9 and 010, the piston rod 03 is made to expand and contract with respect to the cylinder 01 to perform work.

In such a hydraulic cylinder, the tip of the piston rod 03 hits the cylinder head 02 at the end of the stroke on the contraction side, but at that time, if the contact speed of the piston condo 030 is slow, the piston rod 03 and the cylinder head 02 Since a large impact force is applied to the cylinder head 02, cracks may appear in the welded portion of the cylinder head 02, and the structure to which the hydraulic cylinder is attached may be damaged.

Therefore, in order to prevent such damage accidents from occurring,
When the cushion rod 07 is protruded from the tip of the piston rod 03, a cushion oil chamber 08 is formed into which the cushion rod 07 is inserted into the cylinder head 02, and at the stroke end on the contraction side, the cushion rod 07 is inserted into the cushion oil chamber 08. It rushes into the piston rod 03 and narrows the drain oil flow path in the gap between them, thereby increasing the pressure in the pressure chamber 09 and exerting a braking force on the piston rod 03 to alleviate the collision between the piston rod 03 and the cylinder head 02. There is.

However, if the cushion rod 07 and the cushion oil chamber 08 are eccentric, the throttling effect will be reduced, and the annular gap between them must be made small; The cushion rod 07 and the cushion oil chamber 08 may come into contact with each other, causing seizure.

Therefore, in order to solve this problem, conventionally, as shown in FIG.
20 is inserted in the axial direction, and a multistage orifice 021 is inserted in series into this axial oil hole 020, and the orifice screw 021
The plurality of orifices are fixed within the shaft oil hole 020 with '.

Each orifice 021 is provided with an eccentric small hole 022, so that when the orifice 021 is inserted in series, the pressure oil with the flow velocity does not blow straight through the small hole of the succeeding orifice 021. A plurality of orifices 021 are set so that the holes 022 are alternated.

Further, a cushion ring 013 is interposed between the two to seal them so that when the cushion rod 07 enters the cushion oil chamber 08, pressure oil does not flow through the annular gap between the two.

The outer diameter of the cushion ring 013 is made smaller than the outer diameter of the annular groove formed in the cushion oil chamber 08, so that the cushion ring 013 can freely move in the radial direction.

By using such means, even if the cushion rod 07 is slightly eccentric with respect to the cushion oil chamber 08, the cushion ring 013 has a degree of freedom in positioning in the radial direction, so that the two can be moved without coming into contact with each other. Sealing is achieved and a stable aperture effect is achieved.

However, the pressure in the pressure chamber 09 during the cushioning action reaches several 100 kg/cr; t in some cases, and the flow velocity in the orifice hole 022 caused by this pressure reaches several 110 m/s. Durability problems arise in that the orifice 021 of the succeeding stage is punctured by the jet of pressure oil, and the orifice hole 022 is severely eroded by erosion.

In view of the above circumstances, it is an object of the present invention to provide a hydraulic cylinder that exhibits a cushioning effect with stable performance and durability. A tapered cushion rod core having an outer diameter portion whose cross section changes stepwise or continuously in a hydraulic cylinder which is equipped with a cushion oil chamber and which performs a cushioning action by fitting the two at the stroke end. and a cylindrical cushion sleeve that is fitted onto the tapered cushion rod core and has a tapered inner diameter portion whose cross section changes stepwise or continuously, and an oil groove penetrated through the large diameter abutting end of the tile. The present invention is characterized by comprising a cushion rod made of an elastic member that attaches the cushion sleeve to the cushion rod so as to be displaceable in the axial direction.

An embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a longitudinal sectional view thereof, FIG. 4 is an enlarged view of the threaded portion between the cushion rod core and the cushion sleeve in FIG. 3, and FIG. FIG. 4 is an enlarged view of a screwed portion showing another embodiment different from FIG. 4;

First, in Fig. 3, 1 is a cylinder, 2 is a cylinder head forming the end of the cylinder 1, 3 is a piston rod to which a piston 4 that slides inside the cylinder 1 is fixed, and 5 is a piston 4 fastened to the piston rod 3. 6 is a nut screwed onto the end of the piston rod 3 in order to
7 is an oil supply and discharge hole for supplying and discharging oil in the cylinder 1; 7 is a cushion rod core that protrudes from the tip of the piston rod 3 and has a multi-step outer diameter portion that tapers in the axial direction; 8
is the cushion sleeve 14 which will be described later when the piston moves to the right.
a cushion oil chamber bored in the cylinder head 2 to perform a cushioning action in cooperation with the piston 4; 9 is a pressure chamber formed on the right side of the piston 4 between the cylinder head 2;
10 is a pressure chamber formed on the left side of the piston 4 between the cylinder head (not shown), 11 is a piping mounting flange protruding from the oil supply and drain hole 6, and 12 is an annular shape carved on the outer periphery of the piston 4. A piston seal 13 is fitted into a groove to seal the gap between the piston 4 and the cylinder 1, and a piston seal 13 is fitted into an annular groove carved on the outer periphery of a cushion sleeve 14, which will be described later, to connect the cushion sleeve 14 and the cushion oil chamber 8. A cushion ring 14 is fitted over the cushion rod core 7 and has a tapered multi-stage inner diameter part so as to have a radial gap 17 between the cushion ring 14 and the multi-stage outer diameter part of the cushion rod core 7 on the inner surface. A perforated cushion sleeve, 15 a pair of lock nuts screwed onto the tip of the cushion rod core 7 to fasten the cushion sleeve 14 to the cushion rod core 7 via a spring washer 16, and 18 an adjacent gap 17. and the gap 17; 19 is an oil groove extending radially through the large-diameter end of the cushion sleeve 14 that abuts the shoulder of the piston rod 3; and δ1. δ2. ...δ is the size of the gap 11 at each stage, 1 is the axial length of the gap 17, p
o is the oil pressure in the pressure chamber 9, and pd is the oil pressure in the cushion oil chamber 8.

In such a device, the piston rod 3 moves from the left to the right, and when it comes near the end of its stroke, the cushion ring 13 is inserted into the cushion oil chamber 8.

As a result, the outer periphery of the cushion sleeve 14 and the inner periphery of the cushion oil chamber 8 are sealed, so that pressure oil cannot flow directly into the cushion oil chamber 8 either through the pressure chamber 9 or through the cushion sleeve 140 oil groove 19. 14 and the cushion iron core 7, and flows into the cushion oil chamber 8.

At this time, as shown in FIGS. 4a and 4b, the pressure oil is subjected to a multistage throttling effect by flowing through the gaps 17 in multiple stages.

This throttling effect is caused by a pressure drop Δpv that occurs in the gap 17 due to the viscosity of the pressure oil, and a pressure drop that occurs due to the inertia of the pressure oil due to the sudden expansion of the oil passage from the gap 17 to the annular space 18. Δp1 (see Figure 4).

The multi-stage throttling effect on the diagonal is too large, causing the pressure in the pressure chamber 9 to drop to p.

When the pressure becomes high, the pressure oil flows into the gap 17 as shown in Figure 4a
While the pressure is sequentially throttled and reduced, a thrust force T acts in the axial direction on the left end surface of the cushion sleeve 14 that comes into contact with the shoulder of the piston rod 3, as shown by the arrow.

Therefore, the pressure p is such that this thrust force T overcomes the force of the spring washer 16.

When the oil pressure increases, the cushion sleeve 14 responds to this thrust T.
It will slide slightly to the right.

If the cushion sleeve 14 moves to the right, the length l of the gap 17 decreases, thus reducing the throttling effect and reducing the pressure p in the pressure chamber 9.

soaring prices will stop.

That is, the elasticity of the spring washer 16 and the cooperative action of the tapered multi-stage gap 17 of the cushion rond core 7 and the cushion sleeve 14 produce a pressure relief effect, so that the oil pressure p of the pressure chamber 9 decreases.

There is no risk of damage to related equipment or parts due to excessive pressure.

To give another example different from the above-mentioned example, as shown in FIG. 5, 7' is a tapered conical cushion rond core, 14' is a cushion sleeve whose inner surface is also formed with a tapered conical surface, 17' is a conical gap with a clearance δ formed between the outer surface of the cushion rond core 7' and the inner surface of the cushion sleeve 14', and 13' is an annular groove carved in the cushion oil chamber 8 of the cylinder head 2. 16' is a coil spring inserted between the cushion sleeve 14' and the lock nut 15', and 18' is the cushion ring which seals between the cushion sleeve 14' and the cushion oil chamber 8. ' is a plurality of annular grooves carved at appropriate pitches on the surface of the cylinder.

In this embodiment as well, the piston rod 3 moves to the right to move the cushion sleeve 1 as in the previous embodiment.
4' enters the cushion oil chamber 8, direct communication between the pressure chamber 9 and the cushion oil chamber 8 is blocked by the cushion ring 13'. The pressure oil flows through the space 18' and flows into the cushion oil chamber 8, and at this time, the pressure of the pressure oil is reduced by the multistage throttling effect through the gap 17' and the annular space 18'.

Pressure p in pressure chamber 9.

If this becomes too large, the thrust acting on the left end surface of the cushion sleeve 14' overcomes the force of the coil spring 16' and moves the cushion sleeve 14' to the right.

If the cushion sleeve 14' changes to the right, the gap 17
The clearance δ' between the gaps 17' and 17' becomes a dog, the flow resistance of the gap 17' is reduced, a pressure relief effect is performed, and the pressure in the pressure chamber 9 is reduced to p.

Relieve pressure before it becomes excessive.

That is, in the above embodiment, the length 1 of the gap 17 was changed, but in this embodiment, the pressure relief is achieved by changing the clearance δ' of the gap 17.

As described through the above two embodiments, according to the present invention, the lever and cushion rod are composed of a cushion ront core and a cushion sleeve elastically fitted over the cushion ront core in the axial direction, and the lever and cushion rod of the present invention are composed of a cushion ront core and a cushion sleeve elastically fitted in the axial direction. By allowing the pressure oil in the pressure chamber to flow through the annular tapered space formed by the cushion sleeve, the pressure in the pressure chamber increases by utilizing the pressure drop caused by viscosity and inertia. This will displace the cushion sleeve, increase the gap between the cushion sleeve and the cushion rond core, and automatically reduce the throttling effect, thereby preventing the generation of excessive pressure, resulting in a stable and durable cushioning effect. Because we obtain a hydraulic cylinder that performs
The present invention is extremely useful industrially.

[Brief explanation of drawings]

1 and 2 are longitudinal sectional views showing a cushion portion of a known hydraulic cylinder, respectively, FIG. 3 is a longitudinal sectional view showing an embodiment of the present invention, and FIGS. FIG. 5 is a pressure distribution diagram showing the pressure distribution in the gap between the cushion sleeve and the cushion rod shown in the figure, and FIG. 5 is a longitudinal sectional view showing another embodiment different from FIG. 3. 1... Cylinder, 2... Cylinder head, 3... Piston rod, 4... Piston, 5... Nut 8... ...Cushion oil chamber, 9,10...Pressure chamber, 11...
Piping installation 7 lange, 12...Piston seal, 13...Cushion ring, 14...-
・Cushion sleeve, 15...Lock nut, 16...Spring washer, 17...
... Gap, 18... Annular space, 19...
・Oil groove.

Claims (1)

[Claims] 1. A hydraulic cylinder that includes a cushion rod protruding from the end of the piston rod and a cushion oil chamber recessed in the cylinder head, and which performs a cushioning action by fitting the two at the end of the stroke,
A tapered cushion rod core having an outer diameter portion whose cross section changes stepwise or continuously, and a tapered inner diameter portion whose cross section changes stepwise or continuously, which is inserted into the tapered cushion rod core, are bored. It is characterized by comprising a cushion rod consisting of a cylindrical cushion sleeve with an oil groove extending through the large-diameter abutting end, and an elastic member that attaches the cushion sleeve so as to be displaceable in the axial direction with respect to the cushion rod. hydraulic cylinder.