JP3659683B2 - Cushioning device for fluid pressure cylinder - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a cushion device that applies braking at a stroke end of a fluid pressure cylinder.
[0002]
[Prior art]
Conventionally, as a floating type cushioning device for a fluid pressure cylinder, for example, there is one disclosed in Japanese Utility Model Publication No. 63-24409.
[0003]
As shown in FIG. 6, a piston 2 is slidably inserted into the cylinder 1, and cylinder chambers 3a and 3b are defined on the left and right sides thereof. The piston rod 4 connected to the piston 2 freely slidably penetrates the cylinder head 5 at the end of the cylinder 1, and a bearing 6 and a seal 7 are provided in parallel in the penetrating portion.
[0004]
A port 8 is formed in the cylinder head 5 in communication with the cylinder chamber 3 a of the cylinder 1, and hydraulic oil flows into or out of the cylinder chamber 3 a from this port 8.
[0005]
In this cylinder 1, when the piston rod 4 is operated to the extension side, in order to prevent mechanical collision of the piston 2 with the cylinder head 5 in the vicinity of reaching the stroke end, The hydraulic cushion is effective.
[0006]
For this reason, the piston rod 4 is provided with a cushion ring 10 adjacent to the piston 2, and this cushion ring 10 is fitted in the fitting hole 11 of the cylinder head 5 in the vicinity of the stroke end and operates in the contracting cylinder chamber 3a. The oil is contained, the movement of the piston 2 is braked by the generated pressure (cushion pressure), and a hydraulic cushion action is generated.
[0007]
Specifically, as shown in FIG. 7, the cushion ring 10 slidably contacting the inner periphery of the insertion hole 11 is sandwiched between the stepped portion 12 of the piston rod 4 and the piston 2, and longitudinal grooves are formed on both end surfaces thereof. 10 a and 10 b are formed, and a predetermined gap 14 is formed between the outer periphery of the piston rod 4.
[0008]
An annular groove 15 is formed in the piston rod 4, and a seal ring 13 is disposed in the annular groove 15. The width of the seal ring 13 is narrower than the width of the annular groove 15, and a vertical groove 13 a is formed on the side surface on the cylinder chamber 3 a side, and the outer periphery of the seal ring 13 is in close contact with the inner periphery of the cushion ring 10, The inner circumference holds a predetermined gap from the groove bottom of the annular groove 15.
[0009]
Therefore, when the piston 2 reaches near the stroke end when the piston rod 4 is extended, the cushion ring 10 enters the fitting hole 11, and the hydraulic oil from the cylinder chamber 3 a that is contracted by the cushion ring 10 is absorbed by the cushion ring 10. The cylinder chamber 3a is subjected to a high cushion pressure and a large braking force is applied to the movement of the piston 2, and the piston 2 is mechanically moved. Colliding with the inner wall of the cylinder head 5 is prevented.
[0010]
At this time, the hydraulic oil flowing from the cylinder chamber 3a into the longitudinal groove 10b of the cushion ring 10 and the gap 14 between the cushion ring 10 and the piston rod 4 is pressed against the left side in the figure by the pressure of the cylinder chamber 3a. Since the gap 14 is cut off halfway, it is not possible to escape from the inner peripheral side of the cushion ring 10.
[0011]
On the other hand, when the piston rod 4 moves in the reverse direction from the stroke end, that is, when hydraulic fluid is supplied from the port 8, the cushion ring 10 is fitted in the insertion hole 11, so that the seal ring is caused by the pressure of the hydraulic fluid. 13 is pressed to the right side in the figure, and a gap is formed between the side surfaces of the annular groove 15. For this reason, the port 8 and the cylinder chamber are connected via the vertical groove 10a on the left side of the cushion ring 10, the gap 14 on the inner circumference, the gap on the seal ring 13, the vertical groove 13a, the gap 14 on the inner circumference, and the vertical groove 10b on the right side. 3a communicates and permits the inflow of hydraulic oil, so that this functions as a suction check valve, and the cylinder chamber 3a smoothly expands until the cushion ring 10 comes out of the insertion hole 11.
[0012]
[Problems to be solved by the invention]
By the way, in the above cushion device, when the cushion ring 10 enters the fitting hole 11 as shown in FIG. 7 near the piston rod 4, a high cushion pressure is generated inside the cylinder chamber 3. However, the pressure acting on the fitting gap between the cushion ring 10 and the fitting hole 11 has the lowest pressure gradient on the low pressure port 8 side and the highest pressure gradient on the cylinder chamber 3a side.
[0013]
On the other hand, on the inner peripheral side of the cushion ring 10, the gap 14 is substantially constant until it is blocked by the seal ring 13 and is larger than the fitting gap. The same pressure as the inner pressure is evenly distributed.
[0014]
Therefore, the pressure on the inner peripheral surface and the outer peripheral surface applied to the cushion ring 10 is different, and the pressure receiving area itself is cut off in the middle by the seal ring 13, so the inner peripheral surface is smaller, but the average pressure is much higher. Therefore, the cushion ring 10 is deformed (expanded) in the diameter increasing direction due to the pressure difference.
[0015]
For this reason, especially from the middle of the cushion stroke to the later stage, as the diameter of the cushion ring 10 is increased, the fitting hole 11 is strongly entrapped, the degree of sealing of the contracting cylinder chamber 3a is increased, and the cushion pressure in the cylinder chamber 3a is rapidly increased.
[0016]
As a result, there is a problem that the cushion action becomes too strong in the vicinity of the full extension of the piston rod 4 and an impact is generated. Further, galling and wear between the cushion ring 10 and the insertion hole 11 are large, and the stability of the cushion characteristics is impaired.
[0017]
An object of the present invention is to eliminate the pressure difference applied to the inner and outer peripheral surfaces of the cushion ring, thereby preventing the deformation and exhibiting stable cushion characteristics.
[0018]
[Means for Solving the Problems]
In the first invention, a cylinder chamber is defined by a slidable piston in the cylinder, a cushion ring is attached to the piston rod connected to the piston, and the cushion ring is fitted in the vicinity of the stroke end of the piston rod. In the fluid pressure cylinder cushion device in which a hole is provided on the cylinder side and the cylinder chamber communicates with the cylinder port via the fitting hole, a cylinder is provided between the inner peripheral surface of the cushion ring and the outer peripheral surface of the piston rod. A predetermined gap communicating with the chamber is provided, a pressure guiding gap communicating with the cylinder chamber is formed in the fitting gap between the cushion ring and the fitting hole, and a seal ring is disposed on the inner periphery of the cushion ring. The seal ring interrupts the gap with the piston rod outer peripheral surface when the pressure in the cylinder chamber rises. Open in communication with the cylinder port when the pressure in the dust chamber is decreased, the seal ring is disposed on the inner peripheral surface of the cushion ring at almost the same position as the front end of the guide圧間gap.
[0021]
In a second aspect based on the first aspect, the pressure guide gap is formed by providing a small diameter portion on the outer peripheral surface of the cushion ring.
[0022]
In a third aspect based on the first aspect, the pressure guide gap is formed by providing a tapered portion on the outer peripheral surface of the cushion ring.
[0023]
In a fourth aspect based on the first aspect, the pressure guide gap is formed by providing an enlarged diameter portion on the inner peripheral surface of the insertion hole.
[0024]
In a fifth aspect based on the first aspect, the pressure guiding gap does not communicate with the port even when reaching the stroke end.
[0025]
[Action]
In the first invention, when the cushion ring enters the insertion hole in the vicinity of the stroke end of the piston rod, the hydraulic oil from the contracting cylinder chamber is throttled through the fitting gap between the cushion ring and the insertion hole, and the cylinder A high cushion pressure is generated in the chamber, which causes a great brake on the movement of the piston.
[0026]
In this case, pressure acts on the fitting gap with the fitting hole of the cushion ring at a pressure gradient that is highest on the cylinder chamber side. The same pressure is distributed.
[0027]
On the other hand, the high pressure in the cylinder chamber is guided to the inner peripheral surface of the cushion ring by the gap between the piston rod and the pressure distribution on the inner peripheral surface and outer peripheral surface of the cushion ring is balanced, and the cushion ring is deformed. Is prevented.
[0028]
This prevents the cushion ring from expanding in the vicinity of the stroke end and biting into the fitting hole, preventing a sudden rise in cushion pressure, providing a stable cushioning action, and biting or wearing the cushion ring into the fitting hole. Can also be reduced.
[0029]
In addition, the seal ring placed on the inner circumference of the cushion ring guarantees cushioning at the stroke end, while the seal ring opens and expands the gap on the inner circumference of the cushion ring at the start of movement in the opposite direction. The hydraulic oil can be sucked in, allowing smooth movement.
[0030]
Moreover, the pressure receiving area of the cushion pressure applied to the outer peripheral surface of the cushion ring is substantially equal depending on the position of the seal ring, and the deformation of the cushion ring can be reliably prevented.
[0031]
In the second invention, the pressure guide gap is formed by the small diameter portion of the outer peripheral surface of the cushion ring, the size of the pressure guide gap is easy to set, and the workability is also good.
[0032]
In the third invention, since the pressure guide gap is formed by the tapered portion, the bending strength of the cushion ring continuously changes, and local load concentration can be prevented.
[0033]
In the fourth invention, the pressure guide gap is formed by the enlarged diameter portion of the insertion hole, so that the strength of the cushion ring is not lowered and the workability is good.
[0034]
In the fifth aspect of the invention, the pressure guiding gap is prevented from communicating with the port at the stroke end, so that the hydraulic oil does not leak to the port side via the pressure guiding gap at the stroke end, so that the cushioning action is ensured. It can be performed.
[0035]
【Example】
FIG. 1 is a cross-sectional view showing a main part of an embodiment of the present invention. A stepped portion 22 is provided on the outer periphery of the cushion ring 10 in order to form a pressure guide gap 20 on a fitting surface with the fitting hole 11. The small-diameter portion 21 extends to the joint end with the piston 2, and even when the cushion ring 10 enters the fitting hole 11, the pressure guide gap 20 is always in communication with the cylinder chamber 3a. .
[0036]
However, the pressure guide gap 20 is set so as not to communicate with the port 8 at the stroke end of the piston rod 4.
[0037]
The seal ring 13 that comes into contact with the inner periphery of the cushion ring 10 is disposed at substantially the same position in the axial direction as the step portion 22 where the small diameter portion 21 starts. The cushion pressure of the surface and the guiding pressure acts to prevent the cushion ring 10 from being bent.
[0038]
Since other configurations are the same as those in FIG. 7, the same portions are denoted by the same reference numerals, and the operation will be described next.
[0039]
As shown in FIG. 2, when the piston rod 4 reaches the vicinity of the stroke end on the expansion side and the cushion ring 10 enters the insertion hole 11, the pressure in the cylinder chamber 3 a increases, and this high pressure is applied to the piston 2. Acting, a cushion that hydraulically prevents the piston rod 4 from fully extending.
[0040]
At this time, substantially the same high pressure as that of the cylinder chamber 3a acts equally on the outer peripheral surface of the cushion ring 10 in the portion of the small diameter portion 21, and the fitting gap between the stepped portion 22 and the fitting hole 11 ahead is A pressure gradient is formed in which the pressure gradually decreases toward the intrusion destination approaching the port 8.
[0041]
On the other hand, on the inner peripheral surface of the cushion ring 10, the section until the seal ring 13 is in close contact with one side surface of the annular groove 15 and the gap 14 is blocked is almost the same pressure as the high pressure of the cylinder chamber 3 a. Works equally. Note that, in the gap 14, the low pressure port pressure acts on the intrusion destination side than the seal ring 13.
[0042]
For this reason, the pressure distribution applied to the inner and outer peripheral surfaces of the cushion ring 10 is almost balanced as shown in FIG. 2, and the cushion ring 10 has a large force in either the diameter increasing direction or the diameter reducing direction. Does not work, and deformation of the seal ring 13 is prevented.
[0043]
Therefore, the cushion ring 10 is deformed in the diameter-expanding direction as in the conventional case, so that the problem that the cushion pressure in the cylinder chamber 3a suddenly increases and an impact is generated in the second half of the cushion stroke is ensured. In addition to being able to avoid this, it is possible to solve the problem that the sliding wear between the cushion ring 10 and the insertion hole 11 becomes excessive, or that the cushion characteristics become unstable due to biting.
[0044]
Next, the embodiment of FIG. 3 will be described. This is formed by providing a pressure guide gap 20 formed in the fitting gap between the cushion ring 10 and the fitting hole 11 by providing a tapered portion 23 on the outer peripheral surface of the cushion ring 10. To do. In addition, the outer diameter of the taper part 23 becomes small as it goes to the joining end with the piston 2.
[0045]
Thus, by forming the taper part 23 in the outer peripheral surface of the cushion ring 10, the intensity | strength of the cushion ring 10 changes continuously to an axial direction, and local concentration of a bending stress is avoided.
[0046]
Further, the embodiment of FIG. 4 is an embodiment in which the seal ring 13 is not disposed on the inner peripheral surface of the cushion ring 10 and is a floating cushion.
[0047]
Also in this case, by providing the small diameter portion 21 on the outer periphery of the cushion ring 10 and roughly balancing the pressure distribution applied to the inner and outer peripheral surfaces, the cushion ring 10 is prevented from being greatly bent in the diameter increasing direction. The cushion pressure can be rapidly increased and the cushion ring 10 can be prevented from biting.
[0048]
In the above embodiment, the small diameter portion 21 and the taper portion 23 are provided on the outer periphery of the cushion ring 10 in forming the pressure guide gap 20 in the intrusion fitting gap of the cushion ring 10, but as in the embodiment of FIG. A part of the inner peripheral surface of the insertion hole 11 of the cylinder head 5 may be enlarged to provide the enlarged diameter portion 24.
[0049]
The position of the stepped portion 25 of the enlarged diameter portion 24 is a position facing the seal ring 13 when the piston rod 4 enters the stroke end.
[0050]
In this way, the outer peripheral surface of the cushion ring 10 remains the same diameter, and the bending strength in the axial direction of the cushion ring 10 can be kept the same.
[0051]
【The invention's effect】
According to the first invention, when the cushion ring enters the fitting hole in the vicinity of the stroke end of the piston rod, pressure is applied to the fitting gap with a pressure gradient that is highest on the cylinder chamber side. In the portion having the pressure guide gap, the same pressure as the cylinder chamber is distributed. On the other hand, the same pressure as that of the cylinder chamber is guided to the inner peripheral surface of the cushion ring by the gap between the piston rod. Therefore, the pressure distribution on the inner and outer peripheral surfaces of the cushion ring is balanced, the deformation of the cushion ring is prevented, the sudden increase in cushion pressure is prevented, a stable cushion action is exhibited, and the cushion ring is inserted into the insertion hole. Biting and wear can be reduced.
[0052]
In addition, the seal ring arranged on the inner circumference of the cushion ring guarantees cushioning action at the stroke end, while the seal ring opens the gap on the inner circumference of the cushion ring at the start of movement in the opposite direction and expands the cylinder chamber The hydraulic oil can be sucked in, allowing smooth movement.
[0053]
Moreover, the pressure receiving area of the cushion pressure applied to the outer peripheral surface of the cushion ring is substantially equal depending on the position of the seal ring, and the deformation of the cushion ring can be reliably prevented.
[0054]
According to the second invention, the pressure guiding gap is formed by the small diameter portion of the outer peripheral surface of the cushion ring, the size of the pressure guiding gap can be easily set, and the workability is also improved.
[0055]
According to the third invention, since the pressure guide gap is formed by the tapered portion, the bending strength of the cushion ring continuously changes, and local load concentration can be prevented.
[0056]
According to the fourth invention, since the pressure guide gap is formed by the enlarged diameter portion of the insertion hole, the strength of the cushion ring is not lowered and the workability is good.
[0057]
According to the fifth aspect of the present invention, the pressure guiding gap is prevented from communicating with the port at the stroke end, so that the hydraulic oil does not leak to the port side via the pressure guiding gap at the stroke end, so that Cushioning can be performed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part of a first embodiment of the present invention.
FIG. 2 is an explanatory view showing the operating state of the same.
FIG. 3 is a cross-sectional view showing the main part of the second embodiment.
FIG. 4 is a cross-sectional view showing the main part of the third embodiment.
FIG. 5 is a cross-sectional view showing the main part of the fourth embodiment.
FIG. 6 is an overall sectional view of a conventional example.
FIG. 7 is an explanatory diagram of an operating state showing the main part of the same.
[Explanation of symbols]
2 Piston 3a, 3b Cylinder chamber 4 Piston rod 8 Port 10 Cushion ring 13 Seal ring 14 Gap 20 Pressure guide gap 21 Small diameter part 23 Tapered part 24 Large diameter part

Claims (5)

A cylinder chamber is defined by a freely slidable piston in the cylinder, a cushion ring is attached to the piston rod connected to the piston, and a fitting hole is provided on the cylinder side to fit the cushion ring near the stroke end of the piston rod. In the fluid pressure cylinder cushion device, the cylinder chamber communicates with the cylinder port via the fitting hole. The cylinder chamber communicates with the cylinder chamber between the inner peripheral surface of the cushion ring and the outer peripheral surface of the piston rod. A gap is provided, a pressure guide gap communicating with the cylinder chamber is formed in the fitting gap between the cushion ring and the fitting hole, and a seal ring is disposed on the inner periphery of the cushion ring. When the pressure rises, the gap with the outer surface of the piston rod is interrupted, and the pressure in the cylinder chamber It is communicated open communication with the cylinder port when the beat, the seal ring cushion apparatus of a fluid pressure cylinder, characterized in that disposed on the inner circumferential surface of the cushion ring at almost the same position as the front end of the guide圧間gap.   The fluid pressure cylinder cushion device according to claim 1, wherein the pressure guide gap is formed by providing a small diameter portion on an outer peripheral surface of the cushion ring.   The fluid pressure cylinder cushion device according to claim 1, wherein the pressure guide gap is formed by providing a tapered portion on an outer peripheral surface of the cushion ring.   The fluid pressure cylinder cushion device according to claim 1, wherein the pressure guide gap is formed by providing an enlarged diameter portion on an inner peripheral surface of the insertion hole.   2. The fluid pressure cylinder cushion device according to claim 1, wherein the pressure guiding gap is not communicated with a port even when the stroke end is reached.

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