JP3946424B2 - Cylinder cushion structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylinder cushion structure for mitigating an impact at a stroke end of a piston.
[0002]
[Prior art]
As a cylinder cushioning device, those shown in FIGS. 3 and 4 are conventionally known, and the structure thereof is as follows.
As shown in FIG. 3, a piston 2 is slidably incorporated in the cylinder tube 1, and a piston rod 3 is provided on the piston 2. The piston 2 divides the inside of the cylinder tube 1 into cylinder chambers 4 and 5.
Moreover, a cushion ring 6 is fixed at a position adjacent to the piston 2 in the piston rod 3. The cushion ring 6 is formed with a slit 7 that gradually becomes shallower from the end opposite to the piston 2 toward the piston side.
[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. The piston rod 3 is slidably supported by the bearing 9 and protrudes outward from the cylinder head 8.
In the figure, reference numeral 10 denotes a seal provided inside the bearing 9.
[0004]
A holder 11 is fixed to the inner end of the cylinder head 8 as described above, and a collar 12 and a metal cushion seal 13 are fitted to the inner periphery of the holder 11 in this order from the cylinder head 8 side.
The collar 12 is press-fitted into the holder 11 and one end thereof is in close contact with the inner end of the cylinder head 8. Further, a notch 14 is formed on the other end of the collar 12, that is, the surface facing the cushion seal 13, and an orifice is formed when the cushion seal 13 contacts the other end of the collar 12. When the cushion seal 13 is separated from the collar 12, the notch 14 is released and the function as an orifice is lost.
[0005]
On the other hand, the cushion seal 13 is movable between the collar 12 and a stopper 15 formed at the inner end of the holder 11. The cushion seal 13 thus configured maintains a slight gap 16 between the holder 11 and the holder 11 as well as an inner diameter that allows the cushion ring 6 to enter when the piston 2 reaches the stroke end portion. ing.
In addition, a free flow passage 17 is formed in the holder 11, and this free flow passage 17 is interposed between the collar 12 and the cushion seal 13 when the cushion seal 13 is in contact with the stopper 15. Thus, the cylinder chamber 4 and the cylinder port 18 are communicated in a free flow state.
[0006]
Although each member is assembled as described above, a gap is actually formed in the following portion. First, the cushion ring 6 has a mating clearance required between the cushion ring 6 and the piston rod 3 for assembly. Further, a mating gap is also generated between the bearing 9 and the piston rod 3. Further, a mating gap is generated between the cylinder tube 1 and the piston 2.
Such a mating gap causes a shift in the axis of each member. The above-mentioned mating gaps are integrated and the piston rod 3 is eccentric. In order to absorb the eccentricity, the cushion seal 13 is allowed to move to some extent in the radial direction.
[0007]
If the cushion seal 13 cannot move at all in the radial direction, the cushion ring 6 cannot enter the cushion seal 13 at the stroke end portion of the piston when the above-mentioned mating gap is integrated and the piston rod 3 is eccentric. .
However, if the cushion seal 13 moves in the radial direction as described above, the eccentricity of the piston rod 3 can be absorbed.
[0008]
Now, when the piston 2 moves from the state of FIG. 3 in the direction of the arrow 19, the working fluid in the cylinder chamber 4 is discharged from the cylinder port 18 through the cushion seal 13 and the inside of the collar 12. When the cushion ring 6 tries 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 via a gap 16 formed on the outer periphery of the cushion seal 13.
[0009]
As shown in FIG. 4, when the cushion ring 6 enters the cushion seal 13 from the above state, the cylinder chamber 4 and the cylinder port 18 communicate with each other through 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 the orifice formed by the gap 16 and the notch 14. is there.
In any case, since the flow resistance of the two flow paths is large, the pressure of the cylinder chamber 4 is increased by the resistance, and the moving speed of the piston 2 is reduced by the increased pressure, thereby exhibiting a cushioning effect. Let
[0010]
Further, as described above, the mating gap on the assembly causes the piston rod 3 to be eccentric when it is integrated, but the cushion seal 13 is allowed to move to some extent in the radial direction in order to absorb the eccentricity. . For this reason, when the cushion ring 6 enters the cushion seal 13, their axial centers often do not completely coincide.
[0011]
However, even if the axial center of the cushion ring 6 and the cushion seal 13 is slightly shifted, the cushion seal 13 is gradually loosened and gradually adjusts to the cushion ring 6, and finally the axial center of both is perfect. To match. This principle, when placed in tightly and the hole of the rod, is similar to that of pushing into the hole with little to rattle the bar.
[0012]
On the other hand, when the piston 2 is moved in the direction opposite to the arrow 19, pressure fluid is supplied from the cylinder port 18. When pressure fluid is supplied from the cylinder port 18 in this way, the cushion seal 13 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 through the free flow passage 17. You will communicate.
Accordingly, the pressure fluid supplied from the cylinder port 18 is supplied to the cylinder chamber 4 between the notch 14 → the collar 12 and the cushion seal 13 and via the free flow passage 17, and the piston 2 is connected to the arrow 19 and the above. Move in the opposite direction.
[0013]
[Problems to be solved by the invention]
In the conventional cushion structure as described above, there is a problem that cavitation occurs and a large noise occurs when the cushion effect is exhibited. That is, when the cushion ring 6 penetrates the cushion seal 13, the high pressure in the cylinder chamber 4 flows into the cylinder port 18 side through the throttle channel formed by the gap between the cushion seal 13 and the cushion ring 6. The fluid pressure 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.
[0014]
As is apparent from this graph, the pressure of the fluid gradually decreases in proportion to the length of the throttle channel with the pressure P1 in the cylinder chamber 4 being maximized. And the pressure of the exit part just before pulling out from the cushion seal 13 becomes P2.
On the other hand, since the pressure of the cylinder port 18 is substantially tank pressure, if it is set to 0, the differential pressure at the outlet portion becomes P2. If this differential pressure P2 is small, cavitation hardly occurs.
[0015]
However, when the size of the cylinder is increased, the flow rate discharged from the cylinder chamber 4 through the throttle channel increases. When the flow rate passing through the throttle passage increases as described above, the pressure P2 near the outlet cannot be sufficiently reduced only by the throttle flow path formed by the cushion seal 13. Therefore, the differential pressure P2 near the outlet increases, and cavitation occurs there. As a result, there is a problem that a large noise is generated due to cavitation.
[0016]
Here, if the length of the cushion seal 13 in the axial direction is increased, the occurrence of cavitation can be prevented. This is because if the throttle channel is lengthened, the pressure decreases in proportion to the length of the throttle channel, so that the differential pressure near the outlet can be made sufficiently small. This is because it does not occur.
However, if the length of the cushion seal in the axial direction is increased, the mass of the cushion seal 13 is increased, and the rigidity of the cushion seal 13 is increased, which makes it difficult to deform. When the mass of the cushion seal 13 increases and it becomes difficult to deform, the cushion ring 6 hits the cushion seal 13 when the cushion ring 6 enters, and a large collision sound is generated. That is, if the length of the cushion seal 13 in the axial direction is simply increased, a large noise is generated in another portion.
An object of the present invention is to provide a cylinder cushion structure that can suppress the occurrence of cavitation and does not increase the impact noise.
[0017]
[Means for Solving the Problems]
In this 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 protruded outward from the cylinder head to form a cylinder tube. The piston is reciprocated by supplying or discharging the pressure fluid from the port, while providing a cushion ring adjacent to the piston on the piston rod side and a shaft on the cylinder head side. A plurality of metal cushion seals that are movable in the 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 INVENTION
The embodiment shown in FIG. 1 is characterized in that two cushion seals 20 and 21 are incorporated in the inner periphery of the holder 11 and the shape of the collar 22 is changed.
Further, a notch 25 is formed on the cylinder chamber 4 side of the holder 11, but the configuration of the cylinder itself is the same as that of the conventional example.
Therefore, in the following, the cushion seals 20 and 21 and the collar 22 will be mainly described, and the same constituent elements as those in the related art will be denoted by the same reference numerals and detailed description thereof will be omitted.
[0019]
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 and 21 are exactly the same as the conventional cushion seal 13 and have the same length in the axial direction.
On the other hand, the length of the collar 22 in the axial direction is shorter than that of the conventional one, and a space for incorporating two cushion seals 20 and 21 is formed on the inner periphery of the holder 11. Further, the two cushion seals 20 and 21 are movable in the axial direction.
The collar 22 has a notch 23 as in the conventional case.
[0020]
Next, the operation of this embodiment will be described. However, since the action when the cushion ring 6 comes out of the cushion seals 20 and 21 is almost the same as the conventional example, the action when the cushion effect is exhibited, that is, the cushion ring 6 is the cushion seals 20 and 21 below. Only the action when entering is described.
[0021]
When the tip of the cushion ring 6 enters the cushion seal 20, the pressure in the cylinder chamber 4 increases, and the cushion effect is exhibited. As shown in the figure, when the pressure in the cylinder chamber 4 when the cushion ring 6 passes through the two cushion seals 20 and 21 is P1, the fluid of the pressure P1 in the cylinder chamber 4 is It decreases in the process of passing through the throttle channel formed by the gap between the cushion seals 20 and 21. FIG. 2 shows the relationship between the pressure of the fluid passing through the throttle channel and the position of the throttle channel.
[0022]
As shown in the drawing, the pressure of the fluid discharged from the cylinder chamber 4 is first reduced to P2 by the throttle channel 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.
Thus, if the fluid pressure near the outlet of the throttle channel is reduced to half, the differential pressure near the outlet can be made sufficiently small.
Therefore, when the cushion effect is exerted, the occurrence of cavitation can be prevented, and no noise is generated.
[0023]
Further, according to this embodiment, since the mass and rigidity of each cushion seal are the same as in the conventional case, the collision noise does not increase when the cushion ring enters the cushion seal. That is, in this embodiment, the use of the two cushion seals 20 and 21 can prevent the occurrence of cavitation, and can also prevent an increase in collision noise when the cushion ring 6 enters the cushion seals 20 and 21.
[0024]
In the above embodiment, two cushion seals 20 and 21 are used, but the number of cushion seals 20 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 channel can be reduced accordingly. Therefore, noise due to cavitation can be prevented.
[0025]
【The invention's effect】
According to the present invention, since a plurality of cushion seals are incorporated, the fluid pressure in the vicinity of the outlet of the throttle passage constituted by the cushion seals can be sufficiently reduced.
Therefore, cavitation occurring in the vicinity of the exit can be prevented, and no noise is generated.
In addition, since the individual cushion seals are not easily deformed, the collision noise does not increase when the cushion rings enter these cushion seals.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part of an embodiment.
FIG. 2 is a graph showing the relationship between the pressure of the fluid passing through the throttle channel formed between the cushion seals 20 and 21 and the cushion ring 6 and the position of the throttle channel.
FIG. 3 is a cross-sectional view of a conventional example.
FIG. 4 is an enlarged cross-sectional view showing a conventional example, and shows a state in which a cushion ring 6 has entered a cushion seal 13;
FIG. 5 is a graph showing the relationship between the pressure of the fluid passing through the throttle channel formed between the cushion seal 13 and the cushion ring 6 and the position of the throttle channel.
[Explanation 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)

A piston is slidably provided on the cylinder tube, and a cylinder head is provided at the end of the cylinder tube. A piston rod provided on the piston is projected outward from the cylinder head, and pressure fluid is supplied from a cylinder port formed on the cylinder tube. The piston is reciprocated by supplying or discharging the pressure fluid from it, while providing a cushion ring adjacent to the piston on the piston rod side and moving in the axial direction on the cylinder head side A cylinder cushion structure, wherein a plurality of metal cushion seals are provided, and the cushion ring sequentially enters the plurality of cushion seals when the cushion function is exhibited.

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