JP2003049807A - Cushion device for hydraulic cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cushion device operated at an extension side of a piston rod capable of improving the reliability by improving the strength of a piston fastening part, and stabilizing the cushioning performance to exercise high performance. SOLUTION: An annular mounting groove 3b is formed on a tip part of the piston rod 3, a ring-shaped stopper ring member 29 is fitted to the mounting groove 3b, and a ring-shaped stopping member 100 is mounted in adjacent to the stopper ring member 29 to surround the stopper ring member 29 by an inner diameter stepped part 100a. A cushion ring 30 is freely fitted to a ring inserting part 3a between the stopping member 100 and a piston end face, and an end face 100b of the stopping member 100 is used an axial stopping face of a tip-side end face of the cushion ring 30. When the piston rod 3 is extended and the cushion ring 30 enters into the cushion hole 31, a returning oil channel 32 at the rod chamber 7a side is throttled to exercise the cushioning action.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided in a hydraulic cylinder used for a hydraulic actuator of a construction machine,
The present invention relates to a cushion device that relieves an impact near a stroke end in a cylinder extending direction, and particularly relates to a cushion device for a hydraulic cylinder including a floating type cushion ring having an aligning function and a one-way flow path function.

[0002]

2. Description of the Related Art A construction machine, for example, a hydraulic cylinder used as a hydraulic actuator of a hydraulic excavator is constructed so that a piston connected to a piston rod slides in the cylinder body. It is divided into two chambers by a piston, a rod side cylinder chamber (hereinafter appropriately referred to as a rod chamber) and a bottom side cylinder chamber (hereinafter appropriately referred to as a bottom chamber). This hydraulic cylinder is mounted by pivotally attaching the tip end of the piston rod and the bottom end of the cylinder body between predetermined members, supplies pressure oil to the bottom chamber side, and connects the rod chamber side to the tank. Then, the piston rod expands. Conversely, when pressure oil is supplied to the rod chamber side and the bottom chamber side is connected to the tank, the piston rod contracts. If the hydraulic cylinder is operated in the extension or contraction direction while a large load is applied between the piston rod and the cylinder, a large impact is applied at the stroke end. For this reason, the hydraulic cylinder to which a large load acts is provided with a cushion device for cushioning the impact of the piston rod near the stroke end.

In the cushion device, generally, a back pressure is raised in these chambers to obtain a cushioning action by throttling the discharge passage of the hydraulic oil from the rod chamber or the bottom chamber in the cylinder. For example, a cushion device that operates on the extension side of a piston rod is provided with a cushion ring having a predetermined outer diameter on the piston rod, and an insertion hole (hereinafter referred to as a cushion hole) for the cushion ring is formed near the end of the rod chamber. By fitting the cushion ring into the cushion hole near the stroke end and narrowing the flow path of the return oil, back pressure is generated in the rod chamber and a cushioning action is obtained. Further, the cushion device includes a fixed type in which the cushion ring is fixed to the piston rod and a floating type in which the cushion ring is loosely fitted in the ring insertion portion of the piston rod to obtain the centering action and the one-way flow path function.

FIG. 1 of Japanese Patent Laid-Open No. 2000-337315
1 shows a conventional general floating type cushion device which operates on the extension side of a piston rod. In this general cushioning device, a ring insertion portion having a diameter smaller than that of the rod body and larger than that of the piston fastening portion is provided between the rod body of the piston rod and the piston fastening portion,
A cushion ring is loosely fitted in this ring insertion portion.
When the piston rod extends, the tip of the cushion ring (the end on the rod body side) comes into close contact with the radial step surface (axial stop surface) of the rod, which is the boundary between the rod body and the ring insertion part.
The gap between the cushion ring and the ring insertion part is closed to the cushion hole side. As a result, when the cushion ring enters the cushion hole, the cylinder chamber on the rod side communicates with the cushion hole side only through the outer peripheral side of the cushion ring, and the cushion hole is throttled.
Back pressure (cushion pressure) rises in the cylinder chamber on the rod side, and a cushioning action is obtained. When the piston rod moves in the opposite direction and the cushion ring comes out of the cushion hole, the cushion ring is pushed by the pressure oil supplied from the cushion hole side, and the rear end of the cushion ring (piston side end) contacts the piston end surface. To do. A recess groove in the thickness direction is formed at the rear end of the cushion ring, and when the rear end contacts the piston end surface, the gap between the cushion ring and the ring insertion portion communicates with the rod chamber through the recess groove. . As a result, the pressure oil supplied from the cushion hole side flows into the rod chamber through both the outer and inner flow paths of the cushion ring, and the piston rod is quickly drawn into the cylinder. In addition, there is no noise when the cushion ring comes out of the cushion hole.

FIG. 1 of Japanese Patent Laid-Open No. 2000-337315
Discloses a floating type cushion device in which the ring insertion portion has the same diameter as the rod body and a retaining ring member is mounted as an axial stop surface of the cushion ring. That is, in this cushion device, the ring insertion portion is formed as an extension of the rod body, an annular mounting groove is formed between the ring insertion portion and the rod body, and a retaining ring member having a fitting gap in the mounting groove is formed. When the piston rod is extended, the end surface of the cushion ring on the tip side abuts on the end surface of the retaining ring member.

Further, FIG. 4 of Japanese Patent Laid-Open No. 2000-337315 discloses a hydraulic cylinder having a piston bolt fastening structure provided with the cushion device. In this bolt fastening structure, the end face of the piston rod is brought into face-to-face contact with the end face of the piston rod at least partially, and the bolt is inserted from the bolt through hole opened in the piston into the screw hole provided in the piston rod to tighten the piston rod. Is fastened to the piston rod.
When using a plurality of bolts, bolt holes are formed at equal intervals on a pitch circle having a predetermined diameter with respect to the tip end surface of the piston rod, and the bolts are inserted into the bolt holes through the piston.

[0007]

However, the above-mentioned prior art has the following problems.

FIG. 1 of Japanese Patent Laid-Open No. 2000-337315
In the general floating type cushion device as shown in FIG. 1, since the axial stop surface of the cushion ring is formed between the rod body and the ring insertion portion, the diameter of the ring insertion portion must be smaller than that of the rod body. Therefore, it is necessary to perform a grinding process for reducing the diameter of the rod body over a predetermined length.

Further, since the piston fastening portion provided at the tip of the piston has a diameter smaller than that of the ring insertion portion, there is a problem that the strength of the piston fastening portion is insufficient. In other words, in a normal piston fastening structure, a male screw is cut on the outer periphery of the piston fastening part, and after inserting the piston into the piston fastening part and pressing it against the step surface between the ring insertion part and the piston fastening part, The piston is fixed by tightening the nut on the male thread. In such a piston fastening structure, when a cushioning action is obtained on the extension side of the piston rod, an excessive tensile stress acts on the piston fastening portion, and the tensile stress may be repeatedly acted to break the portion. is there.

Further, when the bolt fastening structure is adopted as the piston fastening structure, when the piston fastening portion has a small diameter, the cross-sectional area of the tip end face of the piston rod correspondingly becomes small, and therefore the diameter of the bolt arrangement pitch circle becomes small. It becomes difficult to use a large-diameter bolt, which causes a problem of insufficient strength.

FIG. 1 of Japanese Patent Laid-Open No. 2000-337315
In the floating type cushion device shown in
Since the ring insertion portion has the same diameter as the rod body and the retaining ring member is mounted as the axial stop surface of the cushion ring, there is no need to make the diameter of the ring insertion portion small, and the manufacture is easy. In addition, with a normal piston fastening structure, the diameter of the piston fastening part can be made larger than before, and with the bolt fastening structure adopted as the piston fastening structure, the diameter of the bolt arrangement pitch circle can be expanded, which is larger than before. Bolts can be used and the strength of the piston fastening part can be improved.

However, since the retaining ring member which is mounted as the axial stop surface of the cushion ring can be mounted in the annular mounting groove, for example, a cut is made at one position in the circumferential direction to form an abutment gap, It is attached to an annular mounting groove like a snap ring. For this reason, when the cushion ring rushes into the cushion hole near the stroke end when the piston is extended to obtain a cushioning action, even if the tip of the cushion ring comes into close contact with the end face (axial stop face) of the retaining ring member, the abutment gap The gap between the cushion ring and the ring insertion portion communicates with the cushion hole side via the.
Therefore, the throttle area between the cylinder chamber on the rod side and the cushion hole side is the sum of the annular gap on the outer peripheral side of the cushion ring and the abutment gap. The effect (cushion performance) decreases. Also, if there is an abutment gap in the snap ring member, cushion pressure acts on the inner diameter of the snap ring member when the cushion ring rushes into the cushion hole, so that the snap ring member expands in the external direction and the opening area of the abutment gap is increased. Increase and further reduce the cushioning performance.

An object of the present invention is to provide a cushion device which operates on the extension side of a piston rod, and which has a highly reliable hydraulic cylinder capable of improving the strength of the piston fastening portion and exhibiting stable and high cushion performance. A cushion device is provided.

[0014]

(1) In order to achieve the above object, the present invention has a structure in which a piston is fastened to a piston rod, and the piston is slidably inserted into the cylinder body so that the inside of the cylinder body is closed. In a cushion device of a hydraulic cylinder divided into two chambers, a rod side cylinder chamber and a bottom side cylinder chamber, a cushion ring is loosely fitted to a ring insertion portion provided between the rod body of the piston rod and the piston fastening portion, An annular mounting groove is formed between the ring insertion portion and the rod body of the piston rod, and a retaining ring member having a fitting gap is mounted in the mounting groove, and the retaining ring is adjacent to the retaining ring member. A ring-shaped stop member having an inner diameter step portion formed on the member side and a circular end surface formed on the opposite side is mounted, and the retaining ring member is included in the inner diameter step portion of the stop member, The end face at the circumferential end faces the tip side of the cushion ring and that forms an axial stop surface abuts.

By thus forming the mounting groove in the piston rod, mounting the retaining ring member in the mounting groove, and mounting the ring-shaped stop member adjacent thereto, the shaft of the end face of the cushion ring is By forming the direction stop surface, the ring insertion part of the cushion device can have the same diameter as the rod body of the piston rod, and no special grinding process is required to make the ring insertion part smaller than the rod body. Easy to manufacture. Further, since the ring insertion portion has the same diameter as the rod body, the piston fastening portion can also have a large diameter accordingly, and the strength can be improved.

Further, since the axial stop surface of the tip end side end surface of the cushion ring is formed by the end surface of the ring-shaped stop member without a break, the axial stop surface does not have an opening portion as in the prior art, When the tip end surface of the cushion ring comes into close contact with the axial stop surface (end surface of the stop member), that portion can be sealed 100%, so that an unintended decrease in cushion pressure does not occur and an appropriate cushioning effect is obtained. .

Further, since the abutment gap of the retaining ring member is not directly related to the sealing mechanism with the tip of the cushion ring,
The diameter of the snap ring member does not increase and the cushion pressure does not decrease due to the cushion pressure.The cushion ring can freely move in the axial direction relative to the end surface of the stop member even when the cushion device is pulled out and started, and the slip-out characteristics are smooth. Therefore, the cushioning performance can be stably exhibited with high performance.

(2) Further, in order to achieve the above object,
According to the present invention, a piston is fastened to a piston rod, and the piston is slidably inserted into the cylinder body to divide the cylinder body into two chambers, a rod side cylinder chamber and a bottom side cylinder chamber. At least partially face-to-face contact the end face of the piston rod with the rod-side end face, insert a bolt from the bolt through hole formed in the piston into a screw hole provided in the piston rod, and tighten the piston to the piston. In a cushion device of a hydraulic cylinder fastened to a rod, a cushion ring is loosely fitted in a ring insertion part provided between the rod body of the piston rod and the piston fastening part, and the ring insertion part and the rod body of the piston rod are A ring-shaped mounting groove is formed between the mounting ring member and the retaining ring member with the gap A ring-shaped stop member having an inner diameter step portion formed on the side of the stop ring member and having a circumferential end surface on the opposite side is mounted adjacent to the stop ring member, and the stop ring is attached to the inner diameter step portion of the stop member. It is assumed that the member is included, and that the circumferential end surface forms an axial stop surface with which the end surface on the tip side of the cushion ring abuts.

Also in the present invention constructed as described above, the hydraulic cylinder adopting the bolt fastening structure as the piston fastening structure does not require the special grinding of the ring insertion portion as described in the above (1), and the cushion is used. Stable performance and high performance.

Further, since the piston fastening portion can be made thicker than the conventional one, the pitch pitch circle diameter of the bolts can be enlarged, and the bolts of large diameter can be used, so that the strength of the bolt fastening structure can be improved.

(3) In the above (1) or (2), preferably, a throttle groove is formed on the end surface of the cushion ring on the front end side.

Thus, since the cushion throttle passage is constituted by the combination of the annular gap on the outer peripheral side of the cushion ring and the throttle groove formed on the end surface on the tip side of the cushion ring, it is easy to adjust the width and depth of the throttle groove. The cushion pressure can be finely adjusted and an appropriate cushioning effect can be obtained.

(4) In the above (1) or (2), a throttle groove may be formed on the circumferential end surface of the stop member.

This also makes it possible to easily finely adjust the cushion pressure as described in (3) above, and obtain an appropriate cushioning effect.

(5) Further, in the above (1) or (2), preferably, the abutment gap of the retaining ring member is provided at at least one location of a ring shape.

As a result, the retaining ring member can be prevented from detaching from the mounting groove by itself, and the retaining ring member can be securely mounted.

(7) In the above (1) or (2), the retaining ring member may be composed of a plurality of arcuate segments, and there may be a plurality of gaps.

Even when the retaining ring member is composed of a plurality of arc-shaped segments as described above, the retaining ring member can be prevented from being detached from the mounting groove by including the retaining ring member in the inner diameter step portion of the stop member. Further, since the arcuate segments are plural, it is easy to mount them in the mounting groove.

(8) Further, in the above (1) or (2), preferably, the stop member is fitted to the outer periphery of the ring insertion portion by an interference fit at the inner peripheral portion thereof.

Thus, it is possible to prevent the cushion pressure from entering the fitting portion between the inner diameter side of the stop member and the ring insertion portion to form a gap and reduce the cushion pressure.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, 1 is a hydraulic cylinder,
The hydraulic cylinder 1 has a cylinder body 2, a piston rod 3 and a piston 4, and the cylinder body 2 has one end 5a.
Cylindrical tube 5 with one side closed and the other end 5b side open
And a head cover 6 fixedly provided on the open end portion 5b of the tube 5. The piston rod 3 penetrates the head cover 6 and extends inside and outside the tube 5, and is located inside the cylinder body 2.
A piston 4 is fastened to the tip of the. The piston 4 is slidable in the tube 5 and the inside of the cylinder body 2 is a rod side cylinder chamber (hereinafter referred to as a rod chamber) 7
a and the cylinder chamber on the bottom side (hereinafter referred to as the bottom chamber) 7
It is divided into two rooms, b. A seal ring 13, wear rings 14a and 14b, and contamination seals 15a and 15b are provided on the outer circumference of the piston 4. Head cover 6
Is provided with a hydraulic oil supply / discharge port 8 for the rod chamber 7a, and a closed end portion 5a of the tube 5 is provided with a hydraulic oil supply / discharge port 9 for the bottom chamber 7b.

When pressure oil is supplied from the supply / discharge port 9 to the bottom chamber 7b and the supply / discharge port 8 leading to the rod chamber 7a is connected to the tank, the piston 4 is slidably displaced to the head cover 6 side on the left side in the drawing. The rod 3 is moved so as to project from the cylinder body 3, and the hydraulic cylinder 1 extends. Also,
When the pressure oil is supplied to the rod chamber 7a through the supply / discharge port 8 and the supply / discharge port 9 leading to the bottom chamber 7b is connected to the tank, the piston 4 causes the closed end 5a of the tube 5 on the right side of the drawing.
The piston rod 3 is slidably displaced to the side to move the piston rod 3 into the cylinder body 2, and the hydraulic cylinder 1 contracts. Therefore, one of the mounting portion 10 provided at the tube closed end 5a of the cylinder body 2 and the mounting portion 11 provided at the outer tip of the piston rod 3 is pivotally attached to the fixed side member, and the other is pivotally attached to the movable side member. By doing so, the moving member can be driven.

Next, the cushion device according to the present embodiment will be described together with the piston fastening structure.

A ring insertion portion 3a having the same diameter as the rod body of the piston rod 3 is provided at the tip end portion of the piston rod 3, and a radial step surface 3e is further provided at the tip end side of the ring insertion portion 3a of the piston rod 3. Is provided with a piston insertion portion 3f having a diameter smaller than that of the ring insertion portion 3a.
f has a piston mounting portion 3f1 at the base end portion and a nut fastening portion 3f2 having a male screw portion 3g at the distal end portion, and the piston 4 is inserted into the piston mounting portion 3f1 of the piston insertion portion 3f, and the piston 4 is stepped. The piston 4 is fastened to the piston rod 3 by tightening the nut 12 into the male screw portion 3g of the nut fastening portion 3f2 so as to come into contact with the surface 3e.

As a rod side cushioning device for cushioning the impact at the stroke end of the extension direction of the piston rod, the rod body of the piston rod 3 and the ring insertion portion 3a.
An annular mounting groove 3b is formed between the mounting groove 3b and
A ring-shaped stop ring member 29 is attached to the ring insertion portion 3a, and a ring-shaped stop member 100 is attached to a portion of the ring insertion portion 3a adjacent to the stop ring member 29 so as to include the stop ring member 29. A rod-side cushion ring 30 is loosely fitted in the rod so as to be movable in the radial direction and the axial direction.

A cushion hole 31 into which the cushion ring 30 is inserted is formed in the inner end portion 6a of the head cover 6 at one end of the cylinder body 2, and a flow passage 32 communicating with the supply / discharge port 8 is formed on the inner peripheral surface side of the cushion hole 31. Is formed, the piston rod 3 extends and the cushion ring 3
When 0 enters the cushion hole 31, the cushion ring 30 throttles the return oil passage 32 on the rod chamber 7a side, and as a result, back pressure (cushion pressure) is generated in the rod chamber 7a.
The back pressure exerts a cushioning action in the extending direction of the piston rod 3.

FIG. 2 shows an enlarged view of the cushion device portion, FIG. 3 shows an enlarged perspective view of the retaining ring member 29, and FIG. 4 shows an enlarged perspective view of the stop member 100.

As shown in FIGS. 2 and 3, the retaining ring member 29 has a notch 29 at one position in the circumferential direction of a ring having a rectangular cross section.
The retaining ring member 2 is formed by using a jig.
When 9 is expanded, the piston 9 is inserted into the ring insertion portion 3a from the piston insertion portion 3f side and fitted into the mounting groove 3b. In this fitted state, the notch 29a becomes a gap.

As shown in FIGS. 2 and 4, the stop member 100 is a ring-shaped ring having a cross section in which an inner diameter stepped portion 100a is formed on the retaining ring member 29 side and a circumferential end surface 100b is formed on the opposite side. Yes, the inner end surface 10 in the inner diameter step 100a
0c is closely attached to the end surface of the retaining ring member 29, and the inner diameter step portion 10
Ring insertion part 3 so that retaining ring member 29 is included in 0a.
It is fitted in a. Circumferential end face 100b of stop member
Forms an axial stop surface against which the end surface of the cushion ring 30 on the tip side abuts.

Here, the inner diameter portion 100d of the stop member 100
The fitting between the ring insertion portion 3a and the ring insertion portion 3a is preferably a fitting with an allowance (tight fit), whereby cushion pressure enters the fitting portion to create a gap and reduce cushion performance. Can be prevented. In addition, the stop member 100
When the cushion ring 30 is pulled out, the tip of the cushion ring 30 can be reliably separated from the end surface 100b of the stop member 100, so that the opening can be stably secured.

The retaining ring member 29 is fitted by an outer fitting method. That is, the inner diameter of the retaining ring member 29 is larger than the outer diameter of the mounting groove 3b, and the outer diameter is the inner diameter step portion 100 of the stop member 100.
The outer diameter side of the retaining ring member 29 is in contact with the surface of the inner diameter stepped portion 100a of the stop member 100 in the state shown in FIG. ing. As a result, the retaining ring member 2 can be
It becomes easy to spread 9 and insert it into the ring insertion portion 3a and fit it into the mounting groove 3b. Moreover, the retaining ring member 29 and the stop member 100 are integrated, and the effect of preventing the stop member 100 from freely moving in the axial direction is further enhanced.

The retaining ring member may be fitted by an inner fitting method as shown in FIG. In this case, the retaining ring member 29A has an inner diameter smaller than the outer diameter of the mounting groove 3b, and an outer diameter of the retaining ring member 29A.
00 is made smaller than the surface of the inner diameter stepped portion 100a, and the inner diameter side of the retaining ring member 29A is in close contact with the bottom surface of the mounting groove 3b in the state of being fitted in the mounting groove 3b, and a gap is formed on the outer diameter side. Becomes In this case, there is an effect that the stop member 100 can be easily fitted.

As shown in FIG. 2, the cushion ring 30 is loosely fitted into the ring insertion portion 3a so that the end surfaces on both sides face the stop member 100 and the end surface (hereinafter referred to as piston end surface) 4a of the piston 4 and are cushioned. Ring 30
An annular gap 30c is formed between the ring insertion portion 3a and the ring insertion portion 3a. The length of the cushion ring 30 in the axial direction is determined by the piston end surface 4a and the end surface 100b of the stop member 100.
The distance between the cushion ring 30 and the piston end surface 4a is slightly shorter than the distance between the cushion ring 30 and a plurality of communication concave grooves 30a that open from the outer peripheral surface side to the inner peripheral surface side of the cushion ring 30. The cushion ring 30 has a cushion hole 3 at the tip end of the cushion ring 30.
The entrance taper portion 30b is formed so as to smoothly and surely enter the cushion hole 31 when entering into the inside 1.

Here, the annular gap 30 between the inner peripheral surface of the cushion hole 31 and the outer peripheral surface of the cushion ring 30 when the cushion ring 30 is positioned concentrically with the ring insertion portion 3a.
The dimension of e is A, and the annular gap 30 between the inner peripheral surface of the cushion ring 30 and the outer peripheral surface of the ring insertion portion 3a of the piston rod 3
When the dimension of c is B, the dimension relationship is A <B. Here, the flow passage cross-sectional area of the throttle flow passage when performing the cushioning action is determined by the dimension A of the annular gap 30e. Therefore, in order to exert the cushioning effect more effectively, it is preferable to make the dimension A of the annular gap 30e as small as possible.

By constructing the cushion device as described above, the cushioning action can be exerted near the stroke end when the piston rod 3 extends.

First, when the piston rod 3 is in the contracted state, the supply / discharge port 9 on the bottom chamber 7b side is connected to a hydraulic source such as a hydraulic pump, and the supply / discharge port 8 on the rod chamber 7a side is connected to the tank. The bottom chamber 7b has a high pressure and the rod chamber 7
Since the pressure a becomes low, the piston rod 3 extends. At this time, if a large load is applied to the piston rod 3 in opposition to the extension direction, the piston rod tries to overcome the load to extend the piston rod 3, so that the pressure in the bottom chamber 7b becomes even higher and the bottom chamber 7b The differential pressure between the rod chamber 7a and the rod chamber 7a becomes extremely large.

When the piston rod 3 reaches the vicinity of the stroke end, the cushion ring 30 enters the cushion hole 31 and enters the cushion stroke as shown in FIG.
The return oil flow path 32 is narrowed. As a result, the rod chamber 7a
Since a back pressure is generated on the side, the difference between the pressure in the bottom chamber 7b acting on both end surfaces of the piston 4 and the pressure on the rod chamber 7a side is reduced, and the movement is decelerated. At this time, since the pressure in the rod chamber 7a is higher than that in the supply / discharge port 8, the cushion ring 30 is stopped by the pressure (back pressure) in the rod chamber 7a.
It is pressed against the end surface 100b of 0 to close the flow path by the annular gap 30c between the cushion ring 30 and the ring insertion portion 3a (one-way flow path function). As a result, the return oil flows only from the annular gap 30e on the outer diameter side of the cushion ring 30, so that the pressure on the rod chamber 7a side is further increased, and the annular gap depends on the degree of penetration of the cushion ring 30 into the cushion hole 31. Since the length of 30e becomes long,
As the stroke end is approached, the back pressure in the rod chamber 7a further increases and the rod chamber 7a smoothly stops at the stroke end, and the impact at the time of stop is remarkably alleviated.

Further, since the cushion ring 30 is loosely fitted in the ring inserting portion 3a of the piston rod 3,
When the cushion ring 30 enters the cushion hole 31, even if the entire piston rod 3 or the ring insertion portion 3a of the cushion ring 31 is slightly deviated from the cushion hole 31, the cushion ring 30 moves from the tapered portion 30b to the cushion hole 30. It moves so as to follow 31 (centering function). Therefore, the dimensional difference between the outer diameter of the cushion ring 30 and the hole diameter of the cushion hole 31 is minimized, and the annular gap 3
Even if the channel cross-sectional area of 0e is made extremely small and a larger cushioning effect is exhibited, the cushion ring 30
Has no possibility of metal contact with the cushion hole 31 causing galling, fretting, etc.
Further, there is no possibility that abrasion powder will be generated.

On the other hand, when pressure oil is supplied to the supply / discharge port 8 on the side of the rod chamber 7a in order to contract the piston rod 3 from its stroke end, the pressure of the pressure oil supplied from this supply / discharge port 8 serves to cushion the cushion. The ring 30 is pushed and separated from the end surface 100b of the stop member 100, and comes into contact with the piston end surface 4a. As a result, the cushion ring 3
In addition to the flow path of the annular gap 30e on the outer diameter side of 0, the annular gap 30 between the cushion ring 30 and the ring insertion portion 3a.
c and the one-way flow path including the concave groove 30a between the cushion ring 30 and the piston end surface 4a is formed, the flow path cross-sectional area increases, the piston rod 3 extends smoothly and quickly, and the cushion ring 30 There is also no noise when the is getting out of the cushion flow path.

Here, the role of the cushion device is to generate a cushion pressure in the rod chamber 7a when the cushion ring 30 enters the cushion hole 31 in the vicinity of the stroke end when the piston rod extends, and to mitigate the impact at the stroke end. That is. In order to exert the optimum cushioning effect, it is necessary to generate an appropriate cushion pressure. Since the cushion pressure is determined by the throttle area of the annular gap 30e on the outer peripheral surface side of the cushion ring 30 as described above, proper setting of this value is important. From this point of view, JP-A-2000-33731
In the prior art shown in FIG. 1 and the like of Japanese Patent Laid-Open No. 5 publication, the end surface of the retaining ring member 29 serves as an axial stop surface with which the end surface on the tip end side of the cushion ring 30 directly abuts, and the tip end surface of the cushion ring and the retaining ring member 29 directly contact. Then cushion ring 30
Is configured to form a sealing surface of the annular gap 30c on the inner peripheral side. Therefore, the retaining ring member 29 has an abutment gap 29a.
Therefore, there is a partial opening on the sealing surface, and the throttle area between the rod chamber 7a and the supply / discharge port 8 is
Ring gap 30e on the outer peripheral side of the cushion ring and abutment gap 2
This is the sum of the opening areas of 9a, and the throttle area is equal to or larger than the set value, resulting in a decrease in cushion pressure and a decrease in cushioning effect (cushion performance).

On the other hand, in the present embodiment, the stop member 100 forming the axial stop surface for the cushion ring 30 is formed in a continuous ring shape,
There is no opening in the axial stop surface as in the prior art, and 100% sealing is possible. Therefore, the cushion pressure does not decrease, and an appropriate cushioning effect can be obtained.

Further, in the prior art shown in FIG. 1 of Japanese Patent Laid-Open No. 2000-337315, since there is a gap in the retaining ring member, when the cushion ring rushes into the cushion hole, the cushion is formed on the inner diameter portion of the retaining ring member. When pressure is applied, the retaining ring member expands in the outer shape direction, the opening area of the abutment gap increases, and the cushioning performance further deteriorates.

On the other hand, in the present embodiment, as described above, since the abutment gap 29a of the retaining ring member 29 is not directly related to the sealing mechanism with the tip of the cushion ring, the retaining ring member 29 is not fitted. Such a problem does not occur in the outer fitting method (FIG. 2) or the inner fitting method (FIG. 5), and stable cushioning performance can be obtained.

FIG. 9 of Japanese Patent Laid-Open No. 2000-337315
, The inner diameter step is formed at the tip of the cushion ring,
A configuration in which the retaining ring member is included in the inner diameter step portion is shown. With this configuration, if the gap between the outer diameter of the retaining ring member and the step portion of the inner diameter of the cushion ring is made small, it is possible to prevent the retaining ring member from expanding in the outer direction due to the cushion pressure when the cushion ring rushes into the cushion hole. It is possible to prevent deterioration of cushioning performance.

However, the characteristics of the cushion device at the time of extraction start are also important, and when starting in the contraction direction from the stroke end on the extension side, if pressure oil cannot be sufficiently supplied to the rod chamber 7a, negative pressure is generated and the rod stroke An arrhythmia defect phenomenon occurs. In the configuration shown in FIG. 9 of Japanese Patent Application Laid-Open No. 2000-337315, the cushion ring can freely move in the axial direction if the outer diameter of the retaining ring member and the inner diameter step portion of the cushion ring are made small as described above. It becomes impossible to prevent such trouble phenomenon.

On the other hand, in the present embodiment, the stop ring member 29 is enclosed by the stop member 100, and the cushion ring 30 can freely move in the axial direction with respect to the end surface of the stop member 10. Therefore, as described above, the cushion ring tip and the stop member 1 are activated at the time of extraction start as described above.
It is possible to quickly open the sealing surface with respect to 00 using the pressure difference before and after the cushion ring, and replenish the pressure oil to the rod chamber 7a through the annular gap 30c on the inner peripheral side of the cushion ring 30. It is possible to prevent such a trouble phenomenon.

According to the present embodiment configured as described above, since the ring insertion portion 3a of the cushion device has the same diameter as the rod body of the piston rod 3, the ring insertion portion 3a has a smaller diameter than the rod body. No grinding process required,
The cushion device can be easily manufactured.

The ring insertion portion 3a of the cushion device
Since the rod has the same diameter as the rod body of the piston rod 3, the piston insertion portion 3f can also have a large diameter accordingly, and the strength of the piston fastening portion can be improved.

Further, a continuous ring-shaped stop member 100 is mounted as an axial stop surface on the tip end side end surface of the cushion ring 30.
Since the retaining ring member 29 is enclosed by 00a, there is no opening portion in the axial stop surface unlike the prior art,
When the tip end surface of the cushion ring 30 comes into close contact with the axial stop surface (the end surface 100b of the stop member 100), that portion can be 100% sealed, so that an unintended decrease in cushion pressure does not occur and a proper cushioning is achieved. The effect is obtained.

Further, since the abutment gap 29a of the retaining ring member 29 is not directly related to the sealing mechanism with the tip of the cushion ring, the diameter of the retaining ring member 29 is increased by the cushion pressure and the cushion pressure is not reduced. No
Even when the cushion device is pulled out and started, the cushion ring 30 can freely move in the axial direction with respect to the end surface 100b of the stop member 100, the withdrawal characteristic becomes smooth, and the cushioning performance can be stably exhibited with high performance.

Further, the retaining ring member 2 by the cushion pressure
Since the diameter of 9 does not increase, the pressure-resistant life of the retaining ring member is improved compared to the case where the retaining ring member repeatedly expands due to the cushion pressure each time a cushioning action is obtained, and the cushioning device has high reliability and high durability. Can be

A second embodiment of the present invention will be described with reference to FIGS. 6 and 7.
Will be described. In the figure, the same members as those shown in FIGS. 1 and 2 are designated by the same reference numerals. In this embodiment, an additional throttle passage is provided so that the cushion pressure can be finely adjusted.

In FIG. 6, a cutout groove 30f is formed in the end surface of the cushion ring 30A on the front end side. The notch groove 30f has a predetermined width as shown in FIG.
The tip of the cushion ring 30A is provided at a position near the stroke end on the piston rod extension side and the stop member 1 is provided.
When it comes into close contact with the end surface 100b of No. 00, the cushion throttle passage is formed by the combination of the annular gap 30e on the outer peripheral side of the cushion ring and the cutout groove 30f.

As described above, in order to exert an appropriate cushioning effect, it is necessary to generate an appropriate cushion pressure. In the first embodiment, the cushion pressure is the annular gap on the outer peripheral surface side of the cushion ring 30. It is determined by the aperture area of 30e. However, due to processing error etc., the annular gap 3
It is difficult to accurately set the throttle area of 0e, and if the throttle area is smaller than the design value, the cushion pressure becomes excessive and the operation of the hydraulic cylinder near the stroke end becomes slow. In addition, the cushion ring expands and deforms due to the cushion pressure that has entered the annular gap 30c on the inner peripheral side of the cushion ring, and the throttle area of the annular gap 30e on the outer peripheral side is further reduced. The operation near the stroke end of the cylinder becomes even slower.

According to the present embodiment, since the cushion throttle passage is constituted by the combination of the annular gap 30e on the outer peripheral side of the cushion ring and the cutout groove 30f formed on the end surface on the tip side of the cushion ring, the depth of the cutout groove 30f and The cushion pressure can be easily fine-tuned by adjusting the width, and an appropriate cushioning effect can be obtained.

Further, since it is possible to prevent the cushion pressure from becoming excessive, it is possible to prevent a reduction in the withstand pressure life of a strength member such as a cushion ring that supports the cushion pressure, and to obtain a highly reliable and durable cushion device. .

8 and 9 show a modification of the additional throttle passage as the third embodiment of the present invention. In the embodiment shown in FIGS. 6 and 7, the notch groove is formed in the cushion ring, but as shown in FIGS.
A notched groove 100f may be formed in the end surface 100b of A,
This also provides the same effect as that of the second embodiment.

FIG. 10 shows a modification of the retaining ring member as the fourth embodiment of the present invention. In FIG. 10, the retaining ring member 29B has a split ring structure composed of two half ring segments 29b1 and 29b2 obtained by dividing one ring into two.
By being included in the inner diameter stepped portion 100a (see FIG. 1 etc.), the detachment from the mounting groove 3b is prevented.

According to the present embodiment, the same effect as the above embodiment can be obtained.

Further, according to the present embodiment, since the retaining ring member 29B has the split ring structure, the retaining ring member 29B can be efficiently mounted in the mounting groove 3b.

The fifth embodiment of the present invention will be described with reference to FIGS. In the figure, the same members as those shown in FIGS. 1 and 2 are designated by the same reference numerals. In this embodiment,
The present invention is applied to a hydraulic cylinder having a piston fastening structure in which a piston is bolted to a piston rod.

In FIG. 1, a ring insertion portion 3Aa having the same diameter as the rod body is provided at the tip portion of the piston rod 3A, and a piston 4A is inserted at the tip portion of the piston rod 3A which is an extension portion of the ring insertion portion 3Aa. It A recess 21 is formed on the end surface 20 of the piston 4A on the piston rod 3A side as a fitting portion for the spigot in the axial direction, and the tip end portion of the piston rod 3A is fitted into the recess 21 by the spigot.

Further, an axial screw hole 24 is formed in the end surface 23 of the tip end portion of the piston rod 3A, so that the piston 4A
An axial bolt through hole 25 is formed in the end face of the piston rod, and the end face 23 of the piston rod tip portion is inserted into the recess 21 of the piston 4A.
The piston 4A is fastened to the piston rod 3A by inserting the bolt 22 into the screw hole 24 from the bolt through hole 25 and tightening the bolt 22 in a state of being in close contact with the bottom surface 26 of the piston 4A. The number of bolts 22 may be an appropriate number, but is six in the present embodiment.

In the piston fastening structure of this embodiment, since the piston 4A is fastened directly to the piston rod 3A by the bolt 22, the force due to the pressure of the rod chamber 7a acting on the piston 4A is received by the plurality of bolts 22. At this time, a tensile stress acts on the bolt 22.
2 is a ready-made material with sufficient strength, and the piston rod 3
Since the screw portion of the screw hole 24 of A is a female screw, the strength of the ordinary rod material does not pose a problem.

A mounting groove 3b is formed between the rod body of the piston rod 3A and the ring insertion portion 3Aa, and a retaining ring member 29 is mounted in the mounting groove 3b. Retaining ring member 2 adjacent to 29
Stop member 10 having an inner diameter stepped portion 100a containing 9
0 is fitted, and the cushion ring 30 is loosely fitted to the ring insertion portion 3Aa so as to be movable in the radial direction and the axial direction.

In the present embodiment, unlike the first embodiment, the structure is such that the bolt 22 receives the cushion pressure acting on the piston end face, but by using the snap ring member 29 and the stop member 100, the radial direction is reduced. Since it is not necessary to reduce the diameter of the piston rod itself in order to provide the step surface, the diameter of the ring insertion portion 3Aa can be increased. as a result,
Since the cross-sectional area of the rod tip into which the bolt 22 is screwed is also enlarged, the pitch circle diameter for arranging the plurality of bolts 22 is also enlarged, and a large-diameter bolt can be used for reinforcement.

FIG. 12 shows actual dimensions according to an actual design example. FIG. 12A shows a design example of the one having the stop surface structure of the present embodiment, and FIG.
This is a case where a bolt fastening structure as shown in FIG. 11 is adopted as a piston fastening structure in a hydraulic cylinder having a general floating type cushion device shown in FIG. 11 of Japanese Patent No. 37315.

In a general floating type cushion device, since the ring insertion portion has a smaller diameter than the rod body, the arrangement area of the bolts is limited to the cross-sectional area of this small diameter ring insertion portion, and the usable bolt size also. Limited accordingly. Therefore, in the design example of FIG. 12B, when 6 bolts are arranged in an annular shape, the bolt pitch diameter is 62 mm, and the usable bolt size is M20 having a shaft diameter of 20 mm.

On the other hand, in the present embodiment, the diameter of the ring insertion portion 3Aa can be increased and the arrangement area of the bolt 22 is increased as described above. Therefore, in the design example of FIG.
When 6 bolts are arranged in an annular shape, the bolt pitch diameter can be increased from 62 mm to 67 mm, and the bolt size can be increased by one size from M20 to M22 having a shaft diameter of 22 mm. Therefore, it is possible to secure further strength of the piston fastening portion.

Also in the present embodiment configured as described above, the hydraulic cylinder adopting the bolt fastening structure as the piston fastening structure is used to reduce the diameter of the ring insertion portion 3Aa as in the first embodiment. No need for special grinding, and stable cushion performance can be achieved with high performance.

Further, since the piston fastening portion can be made larger in diameter than in the conventional case, the arrangement pitch circle diameter of the bolts can be expanded and the bolts of large diameter can be used, so that the strength of the bolt fastening structure can be improved.

[0084]

According to the present invention, in the cushion device which operates on the extension side of the piston rod, the strength of the piston fastening portion can be improved and the cushion performance can be stably exerted at high performance. In addition, the pressure-resistant life of the retaining ring member is improved, and a highly reliable and durable cushion device can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a hydraulic cylinder provided with a cushion device on an extension side of a piston rod according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a cushion device portion of the hydraulic cylinder shown in FIG.

FIG. 3 is a perspective view of the retaining ring member shown in FIG.

FIG. 4 is a perspective view of the stop member shown in FIG.

FIG. 5 is an enlarged cross-sectional view of the same portion and a stop member portion when the snap ring member is of an internal fitting type.

FIG. 6 is an enlarged view of a cushion device portion of a hydraulic cylinder provided with a cushion device on a piston rod extension side according to a second embodiment of the present invention.

FIG. 7 is an end view of the cushion ring according to the second embodiment on the front end side.

FIG. 8 is an enlarged view of a cushion device portion of a hydraulic cylinder provided with a cushion device on a piston rod extension side according to a third embodiment of the present invention.

FIG. 9 is an end view of a stop member according to a third embodiment.

FIG. 10 is an enlarged perspective view of a retaining ring member used in the fourth embodiment of the present invention.

FIG. 11 is a sectional view of relevant parts of a hydraulic cylinder provided with a cushion device on the extension side of a piston rod according to a fifth embodiment of the present invention.

FIG. 12 shows the actual dimensions of the embodiment shown in FIG. 11 in comparison with those of the prior art, and FIG. 11 (a) shows the actual dimensions of the one adopting the stop surface structure of the present embodiment. 11B shows the actual dimensions of the conventional technique.

[Explanation of symbols]

1 hydraulic cylinder 2 cylinder body 3,3A piston rod 3a, 3Aa ring insertion part 3b mounting groove 3e Radial step surface 3f Piston insertion part 3f1 Piston mounting part 3f2 nut fastening part 3g screw part 4,4A piston 4a Piston end surface (radial step surface) 5 tubes 6 head cover 6a inner end part 7a Rod chamber 7b Bottom chamber 8, 9 supply / discharge port 20 Piston end face 21 recess 22 volts 23 Piston end face 24 bolt screw hole 25 bolt through hole 26 Bottom 29, 29A, 29B retaining ring member 29a Notch 29b1, 29b2 ring segment 30,30A cushion ring 30a groove 30b taper part 30c annular gap 30e annular gap 30f notch groove 31 cushion hole 32 channels 100 stop member 100a Inner diameter step 100b Circumferential end face 100c inner end face 100d inner diameter

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mitsuhiro Yoshimoto             Hitachi Construction Machinery Co., Ltd.             Ceremony Company Tsuchiura Factory F term (reference) 3H081 AA01 AA03 BB02 CC15 CC24                       FF19 FF34 HH01

Claims (7)

[Claims] 1. A hydraulic cylinder in which a piston is fastened to a piston rod, and the piston is slidably inserted into the cylinder body to divide the inside of the cylinder body into two chambers, a rod side cylinder chamber and a bottom side cylinder chamber. In the cushion device, the cushion ring is loosely fitted in a ring insertion portion provided between the rod body of the piston rod and the piston fastening portion, and an annular mounting groove is provided between the ring insertion portion and the rod body of the piston rod. A retaining ring member having an abutment gap is mounted in the mounting groove, and an inner diameter step portion is formed on the retaining ring member side adjacent to the retaining ring member and a circular end face is formed on the opposite side. The formed ring-shaped stop member is mounted, and the snap ring member is included in the step of the inner diameter of the stop member,
A cushion device for a hydraulic cylinder, wherein an axial stop surface with which the end surface on the tip side of the cushion ring contacts is formed by the circumferential end surface. 2. A piston is fastened to a piston rod, and the piston is slidably inserted into the cylinder body to divide the inside of the cylinder body into a rod side cylinder chamber and a bottom side cylinder chamber. The rod-side end surface of the piston is at least partially face-to-face contacted with the end surface of the tip of the piston rod, and a bolt is inserted from a bolt through hole formed in the piston into a screw hole provided in the piston rod to tighten the piston. In a cushion device of a hydraulic cylinder fastened to a piston rod, a cushion ring is loosely fitted in a ring insertion portion provided between the rod body of the piston rod and the piston fastening portion, and the ring insertion portion and the rod body of the piston rod are A ring-shaped mounting groove is formed between the two, and a snap ring member with a gap is installed in this mounting groove. A ring-shaped stop member having an inner diameter step portion formed adjacent to the snap ring member on the side of the snap ring member and a circular end surface formed on the opposite side is mounted, and the stopper is attached to the inner diameter step portion of the stop member. Including the ring member,
A cushion device for a hydraulic cylinder, wherein an axial stop surface with which the end surface on the tip side of the cushion ring contacts is formed by the circumferential end surface. 3. The cushion device for a hydraulic cylinder according to claim 1 or 2, wherein a throttle groove is formed on an end surface of the cushion ring on the front end side. 4. The cushion device for a hydraulic cylinder according to claim 1, wherein a throttle groove is formed on a circumferential end surface of the stop member. 5. A cushion device for a hydraulic cylinder according to claim 1 or 2, characterized in that an abutment gap of the snap ring member is provided at at least one location of a ring shape. 6. The cushion device for a hydraulic cylinder according to claim 1, wherein the retaining ring member is composed of a plurality of arc-shaped segments, and the plurality of gaps are provided. 7. The hydraulic cylinder cushion device according to claim 1 or 2, wherein the stop member is fitted to the outer periphery of the ring insertion portion by an interference fit at an inner peripheral portion thereof. Cylinder cushion device.