JP2002070810A - Cushion structure for cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the cushion structure for a cylinder that can control cavitation generation and large impact noise. SOLUTION: This cylinder has the cushion ring 6 at a piston rod side, and multiple metal cushion seals 21, 22 that can axially move at a cylinder head side. When the cushion functions, the cushion ring 6 sequentially approaches to multiple cushion seals 21, 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder cushion structure for reducing impact at the stroke end of a piston.

[0002]

2. Description of the Related Art As a cylinder cushion device shown in FIGS. 3 and 4 is conventionally known, its structure is as follows. As shown in FIG. 3, a piston 2 is slidably incorporated in a cylinder tube 1, and a piston rod 3 is provided on the piston 2. The piston 2 partitions the inside of the cylinder tube 1 into cylinder chambers 4 and 5. Moreover, the piston rod 3 is located at a position adjacent to the piston 2,
The cushion ring 6 is fixed. The cushion ring 6 has a slit 7 that gradually becomes shallower from the end opposite to the piston 2 toward the piston.

[0003] A cylinder head 8 is fitted to the end of the cylinder tube 1, and a bearing 9 is provided on the inner periphery of the cylinder head 8. And
The piston rod 3 is slidably supported by the bearing 9 and protrudes outward from the cylinder head 8. Reference numeral 10 in the drawing denotes a seal provided inside the bearing 9.

A holder 11 is fixed to the inner end of the cylinder head 8 as described above, and a collar 1 is provided on the inner periphery of the holder 11 in order from the cylinder head 8 side.
2 and a metal cushion seal 13 are fitted.
The collar 12 is pressed into the holder 11 and
One end is in close contact with the inner end of the cylinder head 8. A notch 14 is formed at the other end of the collar 12, that is, at a surface facing the cushion seal 13, and the collar 12 is formed.
When the cushion seal 13 abuts on the other end, an orifice is formed. When the cushion seal 13 is separated from the collar 12, the notch 14 is released, and the function as an orifice is lost.

On the other hand, the cushion seal 13 is provided with a stopper 15 formed at the inner end of the collar 12 and the holder 11.
It is possible to move between. As shown in FIG. 4, the cushion seal 13 maintains a small gap 16 between the holder 11 and the holder 11, and maintains an inner diameter in which the cushion ring 6 can enter when the piston 2 reaches the stroke end portion. ing. The holder 11 has a free-flow passage 17 formed therein.
When it is in contact with the collar 12 and the cushion seal 1
3, the cylinder chamber 4 and the cylinder port 18 are communicated in a free flow state.

[0006] Each member is assembled as described above. However, in practice, a gap is formed in the following portion. First, the cushion ring 6 is
There is a mating gap required for assembly. In addition, a fitting gap also occurs between the bearing 9 and the piston rod 3. Furthermore, the cylinder tube 1
A gap is also formed between the piston and the piston 2. The engagement gap as described above causes a shift in the axis of each member. The piston rod 3 is eccentric due to the integration of the respective engagement gaps described above. In order to absorb the eccentricity, the cushion seal 13 is allowed to move to some extent in the radial direction.

If the cushion seal 13 cannot move at all in the radial direction, when the piston rod 3 is eccentric due to the integration of the above-mentioned engagement gap, the cushion ring 6 is attached to the cushion seal 13 at the stroke end portion of the piston. You will not be able to enter. However, if the cushion seal 13 moves in the radial direction as described above, the eccentricity of the piston rod 3 can be absorbed.

Now, when the piston 2 is moved from the state shown in FIG.
When the fluid moves in the nine directions, the working fluid in the cylinder chamber 4 is discharged from the cylinder port 18 through the inside of the cushion seal 13 and the collar 12. When the cushion ring 6 attempts to enter the cushion seal 13, the cushion seal 13 is pressed against the collar 12 by the fluid pressure at that time. In this state, the free flow passage 17 communicates with the notch 14 through a gap 16 formed on the outer periphery of the cushion seal 13.

When the cushion ring 6 enters the cushion seal 13 from the above state, as shown in FIG.
The cylinder chamber 4 and the cylinder port 18 communicate with each other via the following two flow paths. One is a throttle passage that passes between the cushion seal 13 and the slit 7 formed in the cushion ring 6, and the other is a passage that passes through an orifice including the gap 16 and the notch 14. is there. In any case, since the two flow paths have large flow path resistance, the resistance increases the pressure in the cylinder chamber 4, and the increased pressure reduces the movement speed of the piston 2, thereby exhibiting a cushion effect. Let it.

Further, as described above, the piston rod 3 is eccentric when the integration gap is integrated, as described above, but in order to absorb the eccentricity, the cushion seal 13 can be moved to some extent in the radial direction. I have to. Therefore, when the cushion ring 6 enters the cushion seal 13, the axes of the cushion rings 6 often do not completely coincide.

However, even if the axes of the cushion ring 6 and the cushion seal 13 are slightly displaced from each other, the cushion ring 13 gradually moves while the cushion seal 13 is rattling.
And eventually the two axes will be exactly aligned. This principle is analogous to pushing a stick into a hole with a slight knock when the rod is inserted into a neat hole.

On the other hand, when the piston 2 is moved in the direction opposite to the arrow 19, a pressurized fluid is supplied from the cylinder port 18. When the pressure fluid is supplied from the cylinder port 18 in this way, the cushion action moves to the stopper 15 side by the pressure action. When the cushion seal 13 moves in this manner, the orifice formed by the notch 14 is released, and the cylinder chamber 4 and the cylinder port 18 are directly connected between the collar 12 and the cushion seal 13 and via the free flow passage 17. Will be in communication. Therefore, the pressure fluid supplied from the cylinder port 18 is supplied to the cylinder chamber 4 through the notch 14 → the space between the collar 12 and the cushion seal 13 and through the free flow passage 17, and the piston 2
9 is moved in the opposite direction.

[0013]

In the conventional cushion structure as described above, there is a problem that cavitation is generated and a large noise is generated when the cushion effect is exerted. That is, when the cushion ring 6 penetrates through the cushion seal 13, the high pressure in the cylinder chamber 4 flows into the cylinder port 18 via the throttle passage formed by the gap between the cushion seal 13 and the cushion ring 6. , The pressure of the fluid gradually decreases by passing through the throttle channel. FIG. 5 is a graph showing the relationship between the pressure of the fluid passing through the throttle channel and the position of the throttle channel.

As is apparent from this graph, the pressure of the fluid gradually decreases in proportion to the length of the throttle passage, with the pressure P1 in the cylinder chamber 4 being maximized. Then, the pressure at the outlet immediately before exiting from the cushion seal 13 is P
It becomes 2. On the other hand, since the pressure of the cylinder port 18 is substantially equal to the tank pressure and is set to 0, the pressure difference at the outlet becomes P2. If the differential pressure P2 is small, cavitation hardly occurs.

However, when the size of the cylinder is increased, the flow rate discharged from the cylinder chamber 4 via the throttle passage also increases. As described above, when the flow rate passing through the throttle passage increases, the pressure P2 near the outlet cannot be sufficiently reduced only by the throttle passage formed by the cushion seal 13. Therefore, the differential pressure P near the outlet
2 becomes large, and cavitation occurs there. As a result, there is a problem that loud noise is generated due to cavitation.

Here, by increasing the length of the cushion seal 13 in the axial direction, cavitation can be prevented. Because, if the throttle flow path is made longer, the pressure decreases in proportion to the length of the throttle flow path, so that the differential pressure near the outlet can be made sufficiently small, and if the differential pressure is made sufficiently small, cavitation will also occur. This is because it does not occur.
However, when the length of the cushion seal in the axial direction is increased, the mass of the cushion seal 13 increases, the rigidity of the cushion seal 13 also increases, and the cushion seal 13 is hardly deformed. If the mass of the cushion seal 13 is increased and it is difficult to deform as described above, when the cushion ring 6 enters, the cushion ring 6 collides with the cushion seal 13 and a loud collision sound is generated. That is, if the length of the cushion seal 13 in the axial direction is slightly increased, loud noise is generated in another portion. It is an object of the present invention to provide a cylinder cushion structure that can suppress the occurrence of cavitation and that does not increase collision noise.

[0017]

According to the present invention, a piston is slidably provided on a cylinder tube, a cylinder head is provided at an end of the cylinder tube, and a piston rod provided on the piston is outwardly provided from the cylinder head. The piston is reciprocated by projecting and supplying or discharging the pressure fluid from a cylinder port formed in the cylinder tube, while providing a cushion ring on the piston rod side and a cylinder head side. In addition, a plurality of metal cushion seals movable in the axial direction are provided, and the cushion ring sequentially enters the plurality of cushion seals when the cushion function is exhibited.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment shown in FIG.
1 is characterized in that two cushion seals 20 and 21 are incorporated in the inner periphery and that the shape of the collar 22 is changed. Also, the cylinder chamber 4 of the holder 11
A notch 25 is formed on the side, but the configuration of the cylinder itself is the same as that of the conventional example. Therefore, the following description will focus on the cushion seals 20, 21 and the collar 22, and the same reference numerals will be given to the same components as in the related art, and detailed description thereof will be omitted.

As shown in the drawing, a cushion seal 20 and a cushion seal 21 are incorporated in the inner periphery of the holder 11. These two cushion seals 20,
Reference numeral 21 is exactly the same as the conventional cushion seal 13 and has the same length in the axial direction. On the other hand, the collar 22 has its axial length shorter than before,
A space is formed in the inner periphery of the holder 11 for only two cushion seals 20 and 21 to be incorporated. Further, the two cushion seals 20, 21 can be moved in the axial direction. The collar 22 has a notch 23 as in the prior art.

Next, the operation of this embodiment will be described. However, the cushion ring 6 is the cushion seal 2
The operation when exiting from 0, 21 is almost the same as that of the conventional example, and therefore, only the operation when the cushion effect is exhibited, that is, the operation when the cushion ring 6 enters the cushion seals 20, 21 will be described below. explain.

When the tip of the cushion ring 6 enters the cushion seal 20, the pressure in the cylinder chamber 4 increases, and a cushion effect is exerted. As shown in the figure, the cushion ring 6 includes two cushion seals 2.
The pressure in the cylinder chamber 4 at the time of passing through
Then, the fluid of the pressure P1 in the cylinder chamber 4 decreases in the process of passing through the throttle channel formed by the gap between the cushion ring 6 and the cushion seals 20, 21. FIG. 2 shows the relationship between the pressure of the fluid passing through the throttle channel and the position of the throttle channel.

As shown in the drawing, the pressure of the fluid discharged from the cylinder chamber 4 is first reduced to P2 by the throttle passage a formed by the cushion seal 20. Then, the fluid pressure of P2 is further reduced by the throttle channel b formed by the cushion seal 21, and becomes P3 near the outlet. This pressure P3 is almost half of the pressure P2. If the fluid pressure near the outlet of the throttle passage is reduced by half in this way, the differential pressure near this outlet can be sufficiently reduced. Therefore, when the cushion effect is exerted, the occurrence of cavitation can be prevented, and thereby no noise is generated.

Further, according to this embodiment, since the mass and the rigidity of each cushion seal are not different from the conventional one, the collision sound does not increase when the cushion ring enters the cushion seal. In other words, this embodiment
The use of the two cushion seals 20 and 21 can prevent cavitation and also prevent an increase in collision noise when the cushion ring 6 enters the cushion seals 20 and 21.

In the above embodiment, two cushion seals 20 and 21 are used.
The numbers 0 and 21 may be determined according to the size of the cylinder. For example, in the case of a larger cylinder, if three cushion seals are used, the differential pressure near the outlet of the throttle passage can be reduced accordingly. Therefore, noise due to cavitation can be prevented.

[0025]

According to the present invention, since a plurality of cushion seals are incorporated, the fluid pressure near the outlet of the throttle passage formed by the cushion seals can be sufficiently reduced. Therefore, cavitation generated near the exit can be prevented, and no noise is generated. In addition, since the individual cushion seals are not easily deformed, the collision sound does not increase when the cushion rings enter these cushion seals.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an embodiment.

FIG. 2 is a graph showing a relationship between a pressure of a fluid passing through a throttle channel formed between cushion seals 20, 21 and a cushion ring 6, and a position of the throttle channel.

FIG. 3 is a sectional view of a conventional example.

FIG. 4 is an enlarged sectional view showing a conventional example, and is a view showing a state in which a cushion ring 6 has entered a cushion seal 13. FIG.

FIG. 5 is a graph showing a relationship between a pressure of a fluid passing through a throttle channel formed between a cushion seal 13 and a cushion ring 6, and a position of the throttle channel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder tube 2 Piston 3 Piston rod 6 Cushion ring 8 Cylinder head 18 Cylinder port 20 Cushion seal 21 Cushion seal

Claims (1)

[Claims] A piston is slidably provided on a cylinder tube, a cylinder head is provided on an end of the cylinder tube, and a piston rod provided on the piston is projected outward from the cylinder head to form a cylinder tube. Supply pressure fluid from cylinder port,
Alternatively, by discharging the pressure fluid therefrom, the piston is reciprocated, while a cushion ring is provided on the piston rod side, and a plurality of metal cushion seals that are movable in the axial direction are provided on the cylinder head side, A cushion structure for a cylinder, wherein a cushion ring sequentially enters the plurality of cushion seals when the cushion function is exhibited.