JPH0835505A - Cushion device of fluid pressure cylinder - Google Patents

Abstract

PURPOSE:To prevent the increase of excessive cushion pressure at the final stage of cushion stroke by producing an oil path in the peripheral surface of the cushion by a pressure releasing flow path at the final stage of the cushion stroke to release the cushion pressure inside an oil chamber therethrough. CONSTITUTION:The diameter of a cushion ring 21 is decreased by force according to the pressure distribution of cushion pressure acting on the inner and outer circumferential surfaces of the cushion ring 21 at the first half of cushion stroke and the opening area of the aperture of an annular gap 6 is increased to reduce the generation of a shock. At the second half of the cushion stroke, the force according to the pressure distribution of the cushion pressure is reversed to start increasing the diameter of the cushion ring 21, and the opening area of the aperture of the annular gap 6 is decreased, so that most of hydraulic operating fluid returned from an oil chamber (A) is shut off by the annular gap between the cushion ring 21 and a seal member 15. When the cushion stroke reaches the final stage, the tip end side of a pressure opening flow path 24 provided in the cushion ring 21 is projected into the annular groove 19 of a cylinder head 5 to open to a supply and exhaust port 9 side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cushion device for a hydraulic cylinder using hydraulic pressure or the like, and more particularly to improvement of cushion characteristics in a floating type cushion device of this type.

[0002]

2. Description of the Related Art Conventionally, as a floating type cushion device used in a fluid pressure cylinder, for example,
The one as seen in Japanese Utility Model Laid-Open No. 63-24409 is known.

That is, as shown in FIG. 5, in this device, a piston rod 4 having a piston 3 fixed by a piston nut 2 is slidably inserted into the cylinder 1 from the outside, and the piston 3 is inserted into the cylinder. By making sliding contact with the inner wall of the cylinder 1, the inside of the cylinder 1 is divided into two oil chambers A and B.
It is divided into

These oil chambers A and B are connected to an annular clearance 6 between the piston rod 4 and the cylinder head 5 and an oil passage 8 formed in the cylinder bottom 7 to supply / exhaust ports 9 and 9, respectively.
It communicates with the outside through 10.

On the outer peripheral surface of the piston rod 4 with the piston nut 2 and the piston 3 sandwiched therebetween, a flow path 1 formed of an annular gap is formed.
Cushion ring 1 consisting of thick-walled cylinders 1 and 12
3, 14 are provided respectively.

Both ends of these flow paths 11 and 12 are provided with radiating grooves 13a provided at both ends of the cushion rings 13 and 14,
Like 13b, it is opened to the outside through the radial grooves 14a and 14b.

Sealing members 15 and 16 exhibiting a check valve function only at the return stroke from the cushion stroke are arranged at the substantially central portions of the flow passages 11 and 12.

Thus, in the above-mentioned cushion device, the hydraulic cylinder that expands and contracts reaches near the working end on the extension end side so that the cushion ring 13 reaches the inside of the cylinder head 5 or near the compression end side and the cushion ring 14 passes. When starting to fit into the oil hole 8, these cushion rings 13, 1
At 4, the annular gap 6 or the oil passage hole 8 is narrowed.

As a result, the flow resistance of the hydraulic oil discharged from the oil chamber A or the oil chamber B to the supply / discharge ports 9, 10 through the annular gap 6 or the oil passage 8 increases, and these oil chambers A
Alternatively, the hydraulic oil pressure (cushion pressure) in the oil chamber B rises to exert a braking action on the piston 3, and the hydraulic cylinder enters the cushion stroke.

On the other hand, during the return stroke in the opposite direction, while the cushion rings 13 and 14 come out of the annular gap 6 or the oil passage hole 8, the seal members 15 and 16 exert the check valve function and the flow passages 11 and 14. The working oil supplied from 12 is made to flow into the oil chambers A and B to ensure the prompt operation of the piston 3.

[0011]

However, in the above-mentioned conventional cushion device, the cushion ring 13,
At the beginning of the cushion stroke in which 14 starts to be fitted into the cylinder head 5 or the oil passage hole 8, the cushion ring 1
The opening area of the annular gap 6 or the oil passage hole 8 is sharply narrowed by 3, 14 and the cushion pressure generated in the oil chamber A or the oil chamber B is rapidly increased depending on the expansion / contraction speed of the hydraulic cylinder to cause a shock. It will be.

Therefore, in order to reduce the occurrence of this shock as much as possible and thereafter to smoothly decelerate the piston 3 and bring it to a stop, the outer peripheral surfaces of the cushion rings 13 and 14 are provided on the distal end side in actual implementation. Axial split grooves (or tapered surfaces or notches) 17 and 18 are formed deeper toward and toward the divergent side.

As a result, the aperture opening areas of the annular gap 6 and the oil passage 8 in the initial stage of the cushion stroke are divided into these split grooves 1.
Keeping 7 and 18 big to reduce shock and
After that, it is usual that the throttle opening area is gradually reduced by the split grooves 17 and 18 so that the piston 3 can be smoothly stopped.

However, even if this is done, the relationship between the cushion pressures acting on the inner and outer peripheral surfaces of the cushion rings 13 and 14 in the cushion stroke is shown, for example, in FIG. 6 and FIG. 7 causes the following inconvenience.

That is, when the tip of the cushion ring 13 is fitted into the cylinder head 5 and the hydraulic cylinder starts the cushion stroke, the seal member 15 is moved toward the cylinder head 5 by the cushion pressure generated in the oil chamber A. Move
By blocking the flow passage 11, the cushion pressure does not act on the inner peripheral surface of the cushion ring 13 on the tip side of the seal member 15.

Therefore, in the initial stage of the cushion stroke shown in FIG. 6, the cushion ring 13 receives a force on the diameter reducing side due to the pressure distribution difference of the cushion pressure acting on the inner and outer peripheral surfaces of the cushion ring 13.

However, as the cushion stroke progresses, the pressure gradient portion of the pressure distribution acting on the outer peripheral surface of the cushion ring 13 increases, and due to the pressure distribution of the cushion pressure acting on the outer peripheral surface side of the cushion ring 13. Power gradually decreases.

Then, this force balances with the force due to the pressure distribution on the inner peripheral surface side during the cushion stroke,
After that, on the contrary, the force due to the pressure distribution on the inner peripheral surface side becomes larger, and the cushion ring 13 receives the force on the radially expanded side.

As a result, at the end of the cushion stroke, the aperture area of the annular gap 6 formed by the cushion ring 13 is reduced, and the cushion pressure is increased.
As shown in FIG. 7, since the pressure distribution difference of the cushion pressure acting on the inner and outer peripheral surfaces of the cushion ring 13 is also the maximum, the cushion ring 13 is expanded to the maximum in the radial direction.

As a result, the area of the throttle opening of the annular gap 6 is reduced beyond the set value, the cushion pressure generated in the oil chamber A rises abnormally, and the desired cushion characteristic cannot be obtained. There is also a risk that the oil itself may expand and cause hydraulic oil leakage.

Therefore, in order to solve the above-mentioned problems, the cushion ring 1 is made of a material having a higher strength.
3 may be made, but this has the disadvantage that the material cost increases and the cost increases.

Of course, there is also a means for making the cushion ring 13 thick so as to have pressure resistance, but if the inner diameter side is made thicker, the diameter of the mounting portion of the piston 3 on the piston rod 4 is inevitably small. Then, the surface pressure on the contact surface with the piston 3 becomes too large.

Therefore, the diameter of the mounting portion of the piston 3 on the piston rod 4 must be reduced, and
This results in insufficient strength of the mounting portion of the piston 3 on the piston rod 4.

On the other hand, on the contrary, if the outer diameter side is made thicker, the cushion ring 13 becomes the cylinder head 5.
In order to keep the aperture area of the diaphragm when it is fitted inside, the clearance between the cylinder head 5 and the cushion ring 13 must be reduced by the amount that the outer diameter of the cushion ring 13 increases due to the increase in the wall thickness. I don't get it.

As a result, the cylinder head 5 and the cushion ring 13 must be machined with high precision in consideration of the galling and the like of the cushion ring 13 during the cushion stroke, which not only complicates the manufacturing but also significantly increases the cost. It causes the inconvenience.

Therefore, an object of the present invention is to provide a cushion device for a fluid pressure cylinder capable of preventing an excessive increase in cushion pressure at the end of the cushion stroke of a fluid pressure cylinder having a floating cushion device. Is.

[0027]

SUMMARY OF THE INVENTION In the present invention, the above object is to provide a cushion ring which has an inner diameter larger than the diameter of the small diameter portion formed in the piston rod and has substantially the same axial length. Is formed to form a flow path composed of an annular gap between the cushion ring and the small diameter portion, and both ends of this flow path are opened to both outer side portions of the cushion ring, and are located at substantially the center of the flow path. Then, in a fluid pressure cylinder equipped with a floating type cushion device in which a seal member that exhibits a check valve function is arranged only during the return stroke from the cushion stroke,
An axial pressure release channel is formed on the outer peripheral surface of the cushion ring to gradually increase the cross-sectional area toward the base end side, and the axial length of the cushion ring is fitted with the cushion ring during the cushion stroke. This is achieved by making the length longer than the length of the annular gap on the cylinder head side.

[0028]

In other words, with the above-described structure, in the first half of the cushion stroke, the cushion ring is reduced in diameter by the force due to the pressure distribution of the cushion pressure acting on the inner and outer peripheral surfaces of the cushion ring, and the aperture opening area is reduced. Increases to reduce the occurrence of shock at the beginning of the cushion stroke.

In the latter half of the cushion stroke, the force due to the pressure distribution of the cushion pressure reverses, the diameter of the cushion ring begins to expand, and the throttle opening area of the annular gap becomes smaller, so that the return hydraulic oil from the oil chamber is The annular gap between the cushion ring and the seal member, which is formed as the diameter of the cushion ring expands, is mostly reduced.

When the cushion stroke further progresses and reaches the end, the tip end side of the pressure release groove provided in the cushion ring penetrates the annular gap of the cylinder head and opens toward the supply / discharge port side.

At this point, an oil passage is formed on the outer peripheral surface of the cushion ring by the pressure release groove, and the oil passage increases the area of the oil passage as the cushion stroke progresses due to the shape of the pressure release groove. Thus, the cushion pressure is prevented from being increased at the end of the cushion stroke to prevent a shock from occurring due to the rapid deceleration of the hydraulic cylinder.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. In the description, the structure of the cushion ring is different from that of the conventional example shown in FIG. 5, and the cushion ring is extended. Since the same configuration can be adopted for the side and the pressure side, only the portion of the cushion device on the extension side will be illustrated and described here as in FIGS. 6 and 7 above.

In FIG. 1, from a piston 3 slidably inserted into a cylinder 1, a piston rod 4 carrying the piston 3 penetrates a cylinder head 5 fitted to an end of the cylinder 1 to the outside. The piston 3 extends to define an oil chamber A in the cylinder 1.

The oil chamber A communicates with the outside through an annular gap 6 formed between the piston rod 4 and the cylinder head 5 through an annular groove 19 and a supply / discharge port 9 on the inner peripheral surface of the cylinder head 5.

Adjacent to the piston 3, the piston rod 4
A small diameter portion 20 is formed on the outer peripheral surface of the
A thick-walled cylindrical cushion ring 21 is fitted into the inside of the cylinder 0.

The inner diameter of the cushion ring 21 is the small diameter portion 20.
And has an axial length substantially equal to the entire length of the small-diameter portion 20, whereby the flow passage 11 formed of an annular gap is formed between the small-diameter portion 20 and the cushion ring 21.

Cushion rings 21 are provided at both ends of the flow path 11.
Through the radial groove 21a provided in the front end side portion and the radial groove 21b bored in the base end side portion, and open to the outside.

An annular groove 22 is formed on the outer peripheral surface of the small-diameter portion 20 of the pithron rod 4 so as to form a concave portion at a substantially central portion of the flow path 11. The annular groove 22 has an axial length of the annular shape. A seal member 15 shorter than the axial length of the groove 22.
Are arranged so as to be movable in the axial direction.

The seal member 15 has a piston 3 from the inner peripheral surface.
Has a groove 23 extending over the side surface, and the inner and outer peripheral surfaces are in sliding contact with the bottom surface of the annular groove 22 and the inner peripheral surface of the cushion ring 21.
The flow path 11 is secured by restricting the radial movement of the.

Although not particularly shown, the annular groove 2
2 is provided on the inner peripheral surface side of the cushion ring 21 instead of being provided on the small diameter portion 20 side of the piston rod 4, and the groove 2 is formed from the outer peripheral surface of the seal member 15 to the side surface on the piston 3 side.
3 may be formed.

In the cushion device according to this embodiment, an axial pressure release passage 24 is formed on the outer peripheral surface of the cushion ring 21 to gradually increase the cross-sectional area toward the base end side, and The axial length of the cushion ring 21 is made longer than the length of the annular gap 6 on the cylinder head 5 side into which the cushion ring 21 is fitted during the cushion stroke.

Next, the operation of the above embodiment will be described.

When the piston 3 is pushed toward the cylinder head 5, the hydraulic cylinder extends while pushing the working oil in the oil chamber A from the annular gap 6 to the outside through the annular groove 19 and the supply / discharge port 9 by the piston 3. Operate.

When the hydraulic cylinder extends and reaches near the working end and the tip portion of the cushion ring 21 starts to be fitted into the cylinder head 5 as shown in FIG.
The annular gap 6 is narrowed by the cushion ring 21.

Therefore, the flow resistance of the working oil discharged from the oil chamber A through the annular gap 6 to the supply / discharge port 9 increases, and the working oil pressure (cushion pressure) in the oil chamber A rises to increase the piston 3 The brake action is applied to the hydraulic cylinder and the hydraulic cylinder enters the cushion stroke.

As described above, when the hydraulic cylinder starts the cushion stroke, the flow passage 11 on the tip side of the seal member 15 which has been communicated with the oil chamber A through the radial groove 21a until then.
The portion of is communicated with the annular gap 6 side.

As a result, the cushion pressure generated in the oil chamber A does not act on the portion of the flow passage 11 on the tip side of the seal member 15.

Therefore, the hydraulic oil pressure in the portion of the flow passage 11 is reduced, and the reduction of the hydraulic oil pressure causes the seal member 15 to be pressed against the side surface of the small diameter portion 22 on the cylinder head 5 side to shut off the flow passage 11. To do.

At the same time, since the cushion pressure does not act on the inner peripheral surface of the cushion ring 21 in the portion closer to the tip than the seal member 15, the cushion ring 21
Is reduced due to the force distribution of the pressure distribution of the cushion pressure acting on the inner and outer peripheral surfaces thereof, and the area of the throttle opening of the annular gap 6 is increased to reduce the occurrence of shock in the initial stage of the cushion stroke.

Subsequently, when the cushion stroke progresses from this state and the cushion ring 21 is fitted into the cylinder head 5, the cushion ring 21 is accompanied by it.
Since the length of the pressure gradient portion of the cushion pressure acting on the outer peripheral surface of the cushion ring 21 increases (see FIG. 3), the degree of diameter reduction of the cushion ring 21 gradually decreases.

Then, for example, as shown in FIG. 3, when the cushion stroke reaches the middle, the force due to the pressure distribution of the cushion pressure acting on the inner and outer peripheral surfaces is balanced, and the cushion ring 21 moves in the normal state before the cushion stroke. Return to the state.

Next, when the cushion stroke further progresses and enters the latter half, the force due to the pressure distribution of the cushion pressure is reversed and the cushion ring 21 begins to expand.

As a result, the throttle opening area of the annular gap 6 becomes smaller, and the return working oil from the oil chamber A is caused by the annular gap between the seal ring 15 and the seal member 15 formed as the cushion ring 21 is expanded. Most of them are throttled, the cushion pressure in the oil chamber A rises, and the deceleration effect of the piston 3 is enhanced.

When the cushion stroke further progresses and reaches the end, as shown in FIG. 4, the tip end side of the pressure release flow path 24 provided in the cushion ring 21 projects into the annular groove 19 of the cylinder head 5 and the supply / discharge port. Open to the 9 side.

At this point, the cushion ring 21
An oil passage is formed on the outer peripheral surface of the pressure release passage 24, and the cushion pressure in the oil chamber A is released to the supply / discharge port 9 side through this oil passage.

Moreover, the oil passage increases the area of the oil passage as the cushion stroke progresses due to the shape of the pressure release passage 24.

As a result, the increase of the cushion pressure at the end of the cushion stroke is prevented, and the shock caused by the rapid deceleration of the hydraulic cylinder is prevented.

As described above, the annular clearance 6 formed by the cushion ring 21 during the cushion stroke.
The size of the diaphragm opening area is maximum at the beginning of the cushion stroke, and then smoothly decreases as the cushion stroke progresses.

In this case, the cushion ring 21
Since the degree of contraction and expansion of the cushion ring 21 changes depending on the cushion pressure determined by the magnitude of the load in the cushion stroke at that time.
The size of the opening area of the throttle that is created by changes only in response to the magnitude of the load, regardless of the expansion / contraction speed of the hydraulic cylinder and the stroke position.

Thus, while reducing the shock generated at the initial stage of the cushion stroke due to the diameter reduction of the tip side portion of the cushion ring 21, the shock absorbing ability corresponding to the expansion and contraction speed of the hydraulic cylinder is secured, and at the same time, the cushion stroke It will prevent an excessive rise in cushion pressure at the end of the period.

On the other hand, in the return stroke in which the hydraulic cylinder performs the compression operation from the above state, the seal member 15 is moved to the piston 3 of the annular groove 22 by the pressure hydraulic oil fed from the supply / discharge port 9.
It is pressed against the side surface of the side and keeps the flow path 11 open through the groove 23.

As a result, the pressure hydraulic oil fed from the supply / discharge port 9 is supplied from the radial groove 21a on the tip side of the cushion ring 21 to the flow channel 11 and the radial groove 21b on the base end side.
Through the oil chamber A to smooth the propulsion force of the piston 3 in the return stroke.

[0063]

As described above, according to the present invention,
At the end of the cushion stroke, an oil passage is generated in the outer peripheral surface of the cushion by the pressure release flow passage formed in the outer peripheral surface of the cushion ring in the axial direction, and the cushion pressure in the oil chamber is released through this oil passage. Because I did
It is possible to prevent an excessive increase in cushion pressure at the end of the cushion stroke regardless of the diameter of the cushion ring.

Further, this eliminates the need for the cushion ring and the cylinder to have pressure resistance.
It is also possible to reduce the weight and cost of the hydraulic cylinder.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of an essential part showing an embodiment of a cushion device for a fluid pressure cylinder according to the present invention.

FIG. 2 is a vertical sectional front view of an essential part showing the state in the initial stage of the cushion stroke.

FIG. 3 is likewise a vertical cross-sectional front view of essential parts showing a state in the middle of the cushion stroke.

FIG. 4 is a vertical cross-sectional front view of essential parts showing a state near the end of the cushion stroke.

FIG. 5 is a partial vertical sectional front view of a fluid pressure cylinder equipped with a conventional cushion device.

FIG. 6 is a vertical sectional front view of relevant parts showing an initial state of a cushion stroke in the conventional apparatus.

FIG. 7 is a longitudinal sectional front view of essential parts showing a state near the end of the cushion stroke in the conventional device.

[Explanation of symbols]

 1 Cylinder 3 Piston 4 Piston Rod 6 Annular Gap 9 Supply / Discharge Port 11 Flow Path 15 Seal Member 20 Small Diameter Part 21 Cushion Ring 21a, 21b Radial Groove 22 Annular Groove 23 Groove 24 Pressure Release Flow Path

Claims (1)

[Claims] 1. A cushion ring having an inner diameter larger than the diameter of the small diameter portion and having substantially the same axial length is provided in the small diameter portion formed on the piston rod, and the cushion ring and the small diameter portion are connected to each other. A flow path consisting of an annular gap is formed between both ends of the flow path, and both ends of this flow path are opened to the outside of both ends of the cushion ring, and the check valve is located approximately in the center of the flow path and only during the return stroke from the cushion stroke. In a fluid pressure cylinder provided with a floating type cushion device in which a seal member exhibiting a function is arranged, an axial pressure release flow passage is formed on the outer peripheral surface of the cushion ring, the cross sectional area of which gradually increases toward the base end side. The length of the annular gap on the cylinder head side that is formed and the axial length of the cushion ring is fitted with the cushion ring during the cushion stroke. A cushion device for a fluid pressure cylinder, which is configured to be longer than the above.