JP3435082B2 - Hydraulic cylinder with cushion device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic cylinder provided with a cushion device for absorbing impact at the stroke end of a piston rod, and more particularly to a piston of a hydraulic cylinder used in a hydraulic working machine such as a hydraulic construction machine. The present invention relates to a hydraulic cylinder having an improved fastening structure and a simplified mounting structure for a bottom cushion device.

[0002]

2. Description of the Related Art In a hydraulic working machine such as a hydraulic excavator which is a typical example of hydraulic construction machines, a hydraulic cylinder is used as an actuator for driving a working member. As shown in FIG. 15, this hydraulic cylinder is provided with a cylinder body 102, a piston rod 103 that moves in the cylinder body 102, and a tip of the piston rod 103.
07a and a piston 104 that divides into a chamber 107b on the bottom side.

The piston fastening structure of such a hydraulic cylinder is generally as described in, for example, Japanese Utility Model Publication No. 7-16888 and Japanese Utility Model Publication No. 6-62207. That is, the step portion 1 is formed at the tip of the piston rod 103.
The piston insertion portion 103f is provided via 03e, the male threaded portion 103g is formed at the tip end portion of the piston insertion portion 103f, the piston 104 is inserted into the piston insertion portion 103f, and the nut 112 is attached so that the piston 104 contacts the stepped portion 103e. The piston 104 is fixed by tightening with the male screw portion 103g, and is fastened to the piston rod 103.

Also, a piston fastening structure as shown in FIG. 16 has been proposed. This example is the actual exploitation 57-20310
No. 3, the piston insertion portion 103j having a small diameter is further provided with an annular groove 103k.
Is fitted to the stepped portion 103m, a half ring-shaped flange 160 obtained by dividing a circular ring into two in the radial direction is fitted into the annular groove 103k.
Is fixed to the piston 104 with a bolt 170 so that the piston 104 is fixed and fastened to the piston rod 103. In this case, in order to seal the space between the chambers 107a and 107b in the cylinder body 102 that is partitioned by the piston 104, the piston insertion portion 103j and the piston 104
An O-ring 180 is provided between them.

On the other hand, as a cushioning device for alleviating the impact at the stroke end of the piston rod, the fairness 7-
There is one using a floating type (floating type) cushion ring as disclosed in Japanese Patent No. 16888 and Japanese Utility Model Laid-Open No. 6-62207. That is, actual fairness 7-168
Japanese Unexamined Patent Publication No. 88 discloses a floating type cushion ring for the rod side and bottom side cushion devices, and Japanese Utility Model Laid-Open No. 6-62207 discloses a floating type cushion ring for the bottom side cushion device. Disclosure.

FIG. 15 shows an example of Japanese Utility Model Publication No. 7-16888. In FIG. 15, a rod-side cushion ring insertion portion 103a is provided between the piston rod 103 and the piston insertion portion 103f, and a bottom-side cushion ring insertion portion 103h is provided at the tip of the male screw portion 103g of the piston rod 103. 103, rod side cushion ring insertion portion 103a, piston insertion portion 1
03f and the bottom side cushion ring insertion portion 103h in order, and the rod side cushion ring 130 is loosely fitted in the rod side cushion ring insertion portion 103a so as to be movable in the axial direction and the radial direction. Bottom side cushion ring 140 on part 103h
Is movably fitted in the axial direction and the radial direction, and screw holes 103i are formed in the end surface of the cushion ring insertion portion 103h.
Then, the cushion ring 140 is locked by the cushion stopper 150 such as a plug.

When pressure oil is supplied to the chamber 107a on the rod side, the piston rod 103 moves to the right in the drawing and the hydraulic cylinder extends. At this time, the bottom side cushion ring 140 projects into the cushion hole 105c provided at the inlet of the supply / discharge port 109 of the bottom side cylinder head in the vicinity of the stroke end, and the cushion ring 140 closes a substantial portion of the cushion hole 105c. The oil passage is squeezed, the cushion pressure rises in the chamber 107b,
The stroke speed is reduced and the impact at the stroke end is reduced. At this time, the cushion ring 140 is in the axial direction,
Cushion hole 1 because it is movable in the radial direction
At the time of rushing into 05c, it will rush along the inner circumference of the cushion hole 105c (alignment function), and there is no concern about galling between the cushion ring 140 and the wall of the cushion hole. In addition, the cushion pressure at the time of entry is in the bottom chamber 1
07b, a pressure difference is generated between the cushion hole side of the cushion ring 140 and the chamber 107b side, and the cushion ring 140 is pressed against the cushion stopper member 150 and closely adheres thereto. Therefore, the outer peripheral surface of the cushion ring insertion portion 103h and the cushion ring 140b. The pressure oil does not flow out from the chamber 107b on the bottom side to the supply / discharge port 109 through the inner peripheral surface (one-way flow path function).

After reaching the stroke end, the port 109
When more pressure oil is supplied, the piston rod 103 starts moving in the extending direction to the left in the drawing, and the cushion ring 140 is pulled out from the cushion hole 105c. At this time, the pressure oil supplied from the supply / discharge port 109 flows into the chamber 107b through the gap between the outer peripheral surface of the cushion ring 140 and the inner peripheral surface of the cushion hole 105c. The cushion ring 140 is pressed against the end surface of the piston insertion portion 103f by the hydraulic pressure from the port 109. At this time, the piston insertion portion 104f of the cushion ring 140
A groove 140a is provided at the end on the side, and the pressure oil flows between the outer peripheral surface of the cushion ring insertion portion 103h and the inner peripheral surface of the cushion ring 140, and flows into the chamber 107b through the groove 140a. (One-way flow path function),
It pulls out and works well.

Although the bottom cushion ring 140 has been described above, the rod cushion ring 130 functions similarly. That is, the rod-side cushion ring 130 is also movable in the axial direction and the radial direction, the groove 130a is provided at the piston-side end, and the piston rod 103 and the cushion ring insertion portion 103a are provided at the opposite end. When the hydraulic cylinder extends and rushes into the cushion hole in front of the supply / discharge port near the stroke end, it can perform the centering function and the one-way flow path function with respect to the cushion hole. , Decrease the stroke speed to reduce the impact at the stroke end. Also,
When the hydraulic cylinder contracts from its stroke end position, it works well by being pulled out from the cushion hole by the one-way flow path function.

As the bottom cushion device,
There are some which use a cushion plunger instead of the cushion ring, and an example thereof is shown in Japanese Utility Model Laid-Open No. 1-166105. In this plunger type cushion device, the base portion of the cone-shaped cushion plunger (buffer rod) is engaged with the engagement hole that is opened in the end surface of the piston rod, and is engaged with the groove provided on the outer periphery of the base portion. Insert the ball into the groove provided on the inner surface of the hole from the lateral screw hole in the radial direction opened from the outer peripheral part of the piston rod end, insert the screw into the horizontal screw hole and hold the ball, and the cushion plunger will engage. It is loosely fitted and fixed in the dowel hole, and fulfills the centering function when decelerating at the stroke end.

[0011]

In the hydraulic cylinder shown in FIG. 15, the chamber 1 on the bottom side as described above is used.
When pressure oil is supplied to 07b, the piston rod 103 moves to the left in the drawing, the hydraulic cylinder extends, and when pressure oil is supplied to the rod-side chamber 107a, the piston rod 1
03 moves to the right in the drawing, and the hydraulic cylinder contracts. In a hydraulic work machine such as a hydraulic excavator, such a hydraulic cylinder is frequently expanded and contracted, and the pressure of the chamber 107a or 107b acts on the piston 104 each time.

By the way, in the conventional piston fastening structure shown in FIG. 15, when the pressure of the chamber 107a or 107b acts on the piston 104, the piston 104 closes the nut 112 on the male screw portion 103g provided on the piston insertion portion 103f. Since it is fastened by inserting it, the pressure in the chamber 107a or 107b is
The cross section of the male threaded portion 103g of 3f was applied, and the piston rod 103 was more easily damaged than the male threaded portion 103g.

FIG. 17 shows the relationship between the maximum principal stress acting on the male screw portion 103g of the piston insertion portion 103f and the number of threads. Here, the number of threads is counted from the tip end side of the piston insertion portion 103j. As can be seen from this figure, the maximum tensile stress is applied to the first screw thread portion of the male screw portion 103g, and the male screw portion 103g is damaged at the first screw thread portion. Therefore, it is necessary to increase the strength of the first screw thread portion of the male screw portion 103g by making the material of the piston rod 103 a high-strength material or by subjecting the male screw portion 103g to heat treatment.

Further, in the conventional piston fastening structure shown in FIG. 16, the pressure applied to the piston 104 is received by the cross section of the annular groove 103k portion of the piston insertion portion 103j, which is easily damaged from this portion. Similarly to the above, it is necessary to increase the strength of the piston rod 103. Also,
This structure requires two half-ring shaped flanges 160, which are further separated by the piston 104.
An O-ring 18 is provided between the piston insertion portion 103j and the piston 104 to seal between the two chambers 107a and 107b.
There is also a problem that 0 is required and the number of parts is increased.

Further, in the hydraulic cylinder equipped with the cushion device, it is necessary to specially process the tip of the piston rod as described above in order to mount the cushion device on the bottom side.

That is, in the floating type cushion device on the bottom side, as shown in FIG. 15, the cushion ring insertion member 103h, the screw hole 103i and the like are processed on the end portion of the long piston rod to form the cushion stopper member 1.
It is necessary to lock the cushion ring 140 with a locking element such as 50. Further, in the bottom side cushion device using the cushion plunger as described in Japanese Utility Model Laid-Open No. 1-166105, similarly, fine processing such as an engagement hole and a lateral screw hole is required at the end of the long piston rod. Becomes

Therefore, in any case, the tip of the piston rod needs to be complicatedly processed, resulting in poor productivity. Further, when a problem occurs in the cushion ring insertion portion 103h, the screw hole 103i for the cushion stop member 150, or the cushion plunger engagement hole or the lateral screw hole, it is necessary to replace an expensive piston rod. is there.

Further, in the bottom cushion device using the cushion plunger as described in Japanese Utility Model Laid-Open No. 1-166105, there is no one-way flow path function in terms of function, and the removal performance is poor.

A first object of the present invention is to provide a hydraulic cylinder equipped with a cushion device which can improve the strength of the piston fastening portion with a simple structure without using a special high strength material for the piston rod or performing heat treatment. It is to be.

A second object of the present invention is to improve the strength of the piston fastening portion with a simple structure without using a special high-strength material for the piston rod or heat-treating, and further to provide a cushion device on the bottom side. Another object of the present invention is to provide a hydraulic cylinder that can easily process a piston rod.

A third object of the present invention is to improve the strength of the piston fastening portion with a simple structure without using a special high-strength material for the piston rod or performing heat treatment. An object of the present invention is to provide a hydraulic cylinder that uses a plunger and has both a centering function and a one-way flow path function.

[0022]

Means for Solving the Problems (1) First and Second Above
In order to achieve the object of the present invention, the present invention fastens a piston to the tip of a piston rod, and the piston divides the inside of the cylinder body into a rod-side chamber and a bottom-side chamber.
The pressure of the rod side chamber and the bottom side chamber.
Work by expanding and contracting the piston rod by supplying and discharging oil
In hydraulic cylinders of hydraulic construction machines that drive members ,
In a state that at least partially to face contact with end faces of the rod side of the piston to the end surface of the distal end of the piston rod, before
In the cross section of the piston rod, the bottom side of the piston
At multiple positions surrounding the center of the end face, open the end face of the piston rod from the multiple bolt through holes drilled in the piston.
Insert a plurality of bolts into the plurality of screw holes that are cut out, tighten the bolts, fix the piston directly to the piston rod with these bolts, and project the piston from the center of the bottom end face of the piston to the bottom side. A cushion device is provided, and when this bottom side cushion device contracts the piston rod,
The cylinder body is made to project into a cushion hole connected to the hydraulic oil port on the bottom side.

By directly fixing the piston to the piston rod with bolts, the force applied to the piston is received by the bolts when the hydraulic cylinder operates.
Tensile stress acts on the bolt, but since the material of the bolt is strong, sufficient strength can be obtained. Further, since the threaded portion of the threaded hole of the piston rod is a female thread, there is no problem in strength even if the rod material is not so strong. For this reason, it is not necessary to use a high-strength material for the piston rod and it is not necessary to increase the strength by heat treatment, so that the piston rod can be manufactured at low cost with a low-cost material. Further, since the bolts are directly fixed, the fatigue strength against external force is improved, the strength of the piston fastening portion is improved with a simple structure, and the life of the piston rod can be improved.

Further, since the bolts are directly fixed, the number of parts can be minimized.

Furthermore, since the conventional small-diameter piston insertion portion with a step portion is unnecessary, it is not necessary to provide an extra step on the piston rod, and the problem of damage at the step portion is reduced.

Further, by providing the bottom side cushion device so as to protrude from the bottom side end surface of the piston,
The shock at the stroke end when the piston rod contracts can be alleviated, and the piston rod need not be complicatedly machined to attach the bottom cushion device, which facilitates machining of the piston rod.

(2) In the above item (1), preferably,
The bottom side cushion device has a centering function of aligning the axes of the bottom side cushion device when the bottom side cushion device is thrust into the cushion hole.

As a result, the bottom side cushion device smoothly enters the cushion hole following the cushion hole, and there is no fear of galling with the cushion hole.

(3) Further, in the above (1), preferably, the bottom side cushion device has an aligning function of aligning the axes of the bottom side cushion device at the time of thrusting into the cushion hole, and the above-mentioned function when thrusting into the cushion hole. It has a one-way flow path function of blocking the flow of pressure oil from the bottom side chamber to the hydraulic oil port and allowing the flow of pressure oil from the hydraulic oil port to the bottom side chamber when exiting from the cushion hole. I shall.

As a result, the cushion device on the bottom side has a one-way flow path function in addition to the centering function, and the performance of exiting from the cushion hole is also improved.

(4) Further, in the above (1), preferably, the bottom side cushion device has a cushion plunger projecting from an end surface on the bottom side of the piston and projecting into the cushion hole when the piston rod contracts. I shall.

By using the cushion plunger in this manner, the problem of bulging due to the difference in pressure distribution between the inner and outer diameter surfaces, such as the cushion ring, does not occur, and stable cushioning performance can always be secured.

(5) In the above item (4), preferably
The cushion plunger has an enlarged base end portion located between the end surface of the piston rod and the rod-side end surface of the piston, and a shaft portion that penetrates the piston and projects from the bottom-side end surface of the piston. Then, the piston is fixed to the piston rod with the bolt, and at the same time, the cushion plunger is held by the enlarged proximal end portion of the cushion plunger and the cushion plunger is attached so as to be movable or tiltable in the radial direction. A hydraulic cylinder characterized by having an aligning function of aligning the axes of the cylinders when they enter the cushion hole by moving or tilting in the radial direction.

By thus fixing the piston to the piston rod with the bolt and holding the cushion plunger at the enlarged proximal end portion of the cushion plunger, the cushion plunger is attached and locked, and the engagement of the cushion plunger with the piston rod is performed. The work related to the stop is unnecessary or minimized, and the work of the piston rod is facilitated. Further, since the piston also serves as a locking element for the cushion plunger, the number of parts can be reduced.

By mounting the cushion plunger so as to be movable or tiltable in the radial direction, the centering function can be achieved when the cushion hole is inserted.

(6) In the above item (5), preferably
The enlarged base end portion of the cushion plunger is a flange portion provided at the base end of the cushion plunger, and a through hole through which the shaft portion of the cushion plunger passes and a counterbore hole for receiving the flange portion are provided in the center of the piston, The flange portion is located in the counterbore between the end surface of the piston rod and the wall of the counterbore, and the through hole and the counterbore are sized to have a gap between the shaft portion and the flange portion of the cushion plunger. The cushion plunger can be moved in the radial direction.

As a result, as described in (5) above, the cushion plunger can be mounted at the same time when the piston is fixed to the piston rod with the bolt, and can be moved in the radial direction.

(7) In the above item (6), preferably,
Elastic means is inserted between the flange portion at the base end of the cushion plunger and the end surface of the piston rod or the end surface of the piston on the rod side to elastically restrain the axial movement of the cushion plunger.

As a result, even when the center of the cushion plunger and the cushion hole into which the cushion plunger deviates during assembly, the position is maintained at that position once the center is adjusted.
After that, you can rush into the hole without aligning.

(8) Further, in the above (5), the enlarged base end portion of the cushion plunger is a spherical surface portion provided at the base end of the cushion plunger, and this spherical surface portion serves as the end surface of the piston rod and the piston. The piston is provided with a through hole through which the shaft portion of the cushion plunger passes, which is held so as to make spherical contact with the end surface on the rod side, and the through hole has a gap with respect to the shaft portion of the cushion plunger. Alternatively, the cushion plunger may be tiltable.

As a result, as described in the above (5), the cushion plunger can be attached at the same time when the piston is fixed to the piston rod with the bolt and can be tilted. Further, since the cushion plunger can be tilted, it fulfills a centering function even with respect to an angular deviation between the cushion plunger and the axial center of the cushion hole, and the spherical contact prevents uneven wear.

(9) Further, in the above (4), the cushion plunger may be a fixed type integrated with the piston.

Even when the cushion plunger is of the fixed type as described above, it is not necessary to provide the cushion plunger on the piston rod, and the piston rod can be easily processed. Moreover, the number of parts can be reduced by integrating the piston and the cushion plunger.

(10) Further, in order to achieve the above first to third objects, the present invention provides the above-mentioned (5), wherein the cushion plunger is open at the tip of the shaft portion and is inside the shaft portion. An axially formed first passage, a second passage that allows the first passage to communicate with the bottom chamber, and a check valve means provided between the first passage and the second passage. The first and second passages and the check valve means prevent the flow of pressure oil from the bottom chamber to the hydraulic oil port when the cushion plunger rushes into the cushion hole. When the plunger comes out of the cushion hole, it has a one-way flow passage function that allows the flow of pressure oil from the hydraulic oil port to the bottom chamber.

As a result, the bottom side cushion device uses the cushion plunger and has both the centering function and the one-way flow path function, so that the bottom side cushion device can smoothly follow the cushion hole when entering the cushion hole, and The ability to get out of is good.

(11) In the above (10), preferably, the second passage is formed in an end surface of the cushion plunger on the side of the enlarged base end portion, and an inner diameter hole through which the first passage is opened, and an inner diameter thereof. A small hole in a radial direction that communicates the hole with the bottom chamber, the check valve means is arranged in the inner diameter hole, and a ball capable of opening and closing the opening of the first passage, and arranged in the inner diameter hole. And a spring that presses the ball in a direction to close the opening of the first passage.

By thus constructing the second passage and the check valve means, a one-way flow path function is obtained, and the spring presses the cushion plunger against the wall of the counterbore through the ball, so that the cushion is formed. After the plunger is once centered in the cushion hole, the centering property is maintained.

(12) Further, in the above (10), preferably, the enlarged proximal end portion of the cushion plunger is
A flange portion provided at a base end of the cushion plunger, and the piston has a shaft portion of the cushion plunger inserted through a central portion of an end surface of the piston on the piston rod side with a radial gap. A through hole,
A counterbore hole for receiving the flange portion with an end face of the piston rod with a radial and axial gap, and the second passage has an outer peripheral end face portion on the piston side end face of the cushion plunger. An inner diameter recess formed to leave the first passage open, and a communication passage that communicates a radial gap between the flange portion and the wall of the counterbore with the bottom chamber, The check valve means
The radial step surface of the flange portion on the shaft side and the outer peripheral end surface portion of the piston side end surface of the cushion plunger, and the piston side end surface portion of the piston rod with which the outer peripheral end surface portion contacts, the inner diameter concave portion The size is such that when the cushion plunger projects into the cushion hole, the axial hydraulic pressure acting on the outer peripheral end face portion is smaller than the axial hydraulic pressure acting on the radial step surface. Is set to.

By constructing the second passage and the check valve means in this way, a one-way flow path function is obtained, and since the check valve means is constructed by utilizing the hydraulic balance, the number of parts is small. , High productivity and high reliability.

(13) Further, in any one of the above (4) to (14), preferably, an inclined groove widened toward the tip of the plunger is formed on the outer peripheral portion of the cushion plunger.

By providing the cushion plunger with the inclined groove in this manner, the cushion characteristic can be adjusted, and in particular, the change of the aperture opening area at the initial entry into the cushion hole can be moderated and the cushion performance at the initial entry is improved.

(14) Further, in the above (1), preferably, the bottom side cushion device is provided with a shaft portion projecting from a bottom side end surface of the piston, and the shaft portion is loosely fitted in the shaft portion, so that the radial direction and the axial direction. A cushion ring of a floating type that is movable to, and a locking plug provided at the tip of the shaft portion, and by the cushion ring, an aligning function that aligns the shaft centers when the cushion hole is thrust into the cushion hole, When rushing into the cushion hole, blocking the flow of pressure oil from the bottom chamber to the hydraulic oil port,
When it comes out of the cushion hole, it has a one-way flow path function that allows the flow of pressure oil from the hydraulic oil port to the bottom chamber.

As a result, the bottom side cushion device has both the centering function and the one-way flow path function by the cushion ring, so that the bottom side cushion device can smoothly follow the cushion hole when it is inserted into the cushion hole, Good escape performance.

(15) Further, in any one of the above (1) to (14), preferably, a floating type which is loosely fitted to a portion of the piston rod adjacent to the piston and is movable in a radial direction and an axial direction. A rod-side cushion device that has a cushion ring, and cushions the cushion ring into a cushion hole that communicates with a hydraulic oil port on the rod side of the cylinder body to reduce the impact at the stroke end when the piston rod extends. Further provide.

By further providing the rod side cushion device as described above, the impact at the stroke end is alleviated even when the piston rod is extended, and the centering function and the one-way flow path function are obtained.

(16) Further, in any one of the above (1) to (14), there is provided a fixed type cushion ring integrated with the piston, and this cushion ring has a hydraulic fluid on the rod side of the cylinder body. A rod-side cushion device is further provided to absorb the impact at the stroke end when the piston rod extends by protruding into the cushion hole communicating with the port.

By further providing the rod side cushion device in this way, the impact at the stroke end is alleviated even when the piston rod extends.

Also, with regard to the rod side cushion device, the number of parts can be reduced. Especially, in the combination with the above (9), since both the rod side and the bottom side cushion members are integrated with the piston, the number of parts can be minimized. .

[0059]

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

FIG. 1 shows a hydraulic cylinder 1 according to an embodiment of the present invention. The hydraulic cylinder 1 has a cylinder body 2, a piston rod 3 and a piston 4, and the cylinder body 2 is closed at one end 5a side. It is composed of a cylindrical tube 5 having an open end on the other end 5b side, and a rod-side cylinder head 6 fixedly provided on the open end 5b of the tube 5. The piston rod 3 penetrates the rod-side cylinder head 6 and extends in and out of the tube 5, and the tip of the piston rod 3 located in the cylinder body 2 is slidable in the tube 5 and inside the cylinder body 2. The piston 4 that divides the rod-side chamber 7a and the bottom-side chamber 7b is fastened. 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. The rod-side cylinder head 6 is provided with a hydraulic oil supply / discharge port 8 for the chamber 7a, and the closed end 5a of the tube 5 is provided with a hydraulic oil supply / discharge port 9 for the chamber 7b.

Chamber 7b on the bottom side from the supply / discharge port 9
When pressure oil is supplied to the tank and the supply / discharge port 8 communicating with the rod side chamber 7a is connected to the tank, the piston 4 is slidably displaced to the rod side cylinder head 6 side on the left side in the drawing, and the piston rod 3 is moved to the cylinder body 3 The hydraulic cylinder 1 extends so that the hydraulic cylinder 1 extends. Further, when the pressure oil is supplied to the rod side 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 of the tube 5 on the right side in the drawing. Part 5a
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. Mounting part 1 provided on the tube closed end 5a of the cylinder body 2
0 and a mounting portion 11 provided at the outer tip of the piston rod 3.
The movable side member can be driven by pivotally attaching one side to the fixed side member and the other side to the movable side member.

Next, the piston fastening structure and the cushion device which are the features of the present invention will be described.

A small-diameter cushion ring insertion portion 3a is provided at the tip of the piston rod 3, and a rod-side cushion ring 30 is loosely fitted in the cushion ring insertion portion 3a so as to be movable in the axial direction and the radial direction. A recess 21 is formed as an axial fitting portion on the end surface 20 of the piston 4 on the piston rod 3 side, and the tip of the cushion ring insertion portion 3a of the piston rod 3 (hereinafter referred to as the piston rod 3) is formed in the recess 21. The piston 4 is attached and the coaxiality with the piston rod 3 is secured by inserting the end of the piston 4). Further, an axial screw hole 24 is formed in the end face 23 of the tip of the piston rod 3, an axial bolt through hole 25 is formed in the piston 4, and the end face 20 of the piston 4 is attached to the end face 23 of the tip of the piston rod 3. The bolts 22 are inserted from the bolt through holes 25 into the screw holes 24 in a state where they are in face-to-face contact, and the bolts 22 are tightened to fix the piston 4, and the piston 4 is fastened to the piston rod 3. Bolt 22
However, in this embodiment, six bolts 22 are used as shown in FIG. Also, the bolt 22
Although an example of a round head bolt is shown, a hexagon head bolt may be used.

In the piston fastening structure according to the present embodiment, the bolt 4 directly fastens the piston 4 to the piston rod 3 so that the force applied to the piston 4 is applied to the plurality of bolts 22.
Will be received at. At this time, tensile stress acts on the bolt 22, but if the material of the bolt 22 is strong, the strength of the bolt 22 is sufficient. Further, since the threaded portion of the screw hole 24 of the piston rod 3 is a female thread, there is no problem in strength even if the rod material is not so strong.

Further, in FIG. 1, reference numeral 40 denotes a bottom side cushion plunger having a flange portion 40a at its base end.
Is provided. A through hole 41 through which the shaft portion 40b of the cushion plunger 40 passes is formed in the center of the piston 4, and a counterbore hole 42 for receiving the flange portion 40a of the cushion plunger 40 is formed around the through hole 41 on the recess 21 side. , These through holes 41 and counterbore holes 42
Has a diameter such that a gap is formed between the shaft portion 40b of the cushion plunger 40 and the flange portion 40a, and the depth of the counterbore 42 is made deeper than the length of the flange portion 40a.

At the time of assembly, the cushion ring 30 is inserted into the cushion ring insertion portion 3a of the piston rod 3, and the cushion plunger 40 is attached to the flange portion 40a.
Is inserted into the through hole 41 of the piston 4 until it hits the bottom portion 42a of the counterbore hole 42 of the piston 4, and the piston 4 is inserted into the tip of the cushion ring insertion portion 3a in this state,
The bottom surface of the recess 21 of the piston 4 is brought into contact with the end surface 23 of the piston rod 3. In this state, bolt 22 as described above.
Is inserted into the bolt through hole 25 and the screw hole 24 to fix the piston 4 directly to the piston rod 3. At this time, the flange portion 40 a of the bottom side cushion plunger 40 is held between the piston end surface 20 and the counterbore hole 42.
By thus fastening the piston 4 with the bolt 22, the rod side cushion ring 30 and the bottom side cushion plunger 40 can be locked.

As described above, the rod side cushion ring 3
No. 0 is loosely fitted in the cushion ring insertion portion 3a so as to be movable in the axial direction and the radial direction, and has a floating structure. Also, in the bottom side cushion plunger 40, the shaft portion 40b and the flange portion 40a have through holes 41 and It is sized to have a gap with the counterbore 42, and
Since the length of a is also smaller than the depth of the counterbore 42, it can be moved in the radial direction and the axial direction and has a floating structure.

Reference numeral 3b denotes a step portion formed at the boundary between the main body of the piston rod 4 and the rod side cushion ring insertion portion 3a, and the rod side cushion is provided at a portion adjacent to the step portion 3b of the rod side cushion ring insertion portion 3a. An R portion 3c is formed which serves as an escape portion when the ring insertion portion 3a is polished. A groove 30a is provided on the piston-side end surface of the cushion ring 30.

When the hydraulic cylinder 1 is extended, the rod-side cushion ring 30 projects near the stroke end into the cushion-ring fitting portion 6a provided on the rod-side cylinder head 6 as shown by the imaginary line A, and the fitting portion. The oil passage of 6a is throttled, cushion pressure is set up in the chamber 7a, the stroke speed is reduced, and the impact at the stroke end is alleviated. At this time, the cushion ring 30 is movable both in the radial direction and the axial direction, and when the cushion ring 30 is pushed in, the cushion ring 30 is pushed in while aligning with the hole shape of the cushion ring fitting portion 6a so as to be aligned. Ring 30 and fitting part 6a
There is no worry of galling (alignment function).

At the time of entry, the cushion pressure is set in the chamber 7
a, a pressure difference is generated between the side of the cushion ring 30 that has entered the fitting portion 6a of the cushion ring 30 and the piston 4 side (chamber 7a side), and the cushion ring 30 is pressed against the end surface of the stepped portion 3b and adheres closely to it. The pressure oil does not flow out to the supply / discharge port 8 through the space between the ring insertion portion 3a and the inner peripheral surface of the cushion ring 30. After reaching the stroke end, the piston rod 3 starts to move in the contracting direction (to the right in the drawing), and when the cushion ring 30 comes out of the fitting portion 6a, the pressure oil from the supply / discharge port 8 is the outer peripheral surface of the cushion ring 30. Flows into the chamber 7a through a gap between the inner peripheral surface of the fitting portion 6a and the inner peripheral surface of the fitting portion 6a. At this time, the cushion ring 30 is pressed against the piston 4 by the hydraulic pressure from the supply / discharge port 8. However, since the groove 30a is provided in the end face of the cushion ring 30 on the piston side, the pressure oil is absorbed by the cushion ring insertion portion 3a and the cushion ring 30. It flows between the inner peripheral surface of the ring 30 and the groove 30a, flows into the chamber 7a, and works well for extraction (one-way flow path function).

When the hydraulic cylinder 1 is contracted, the bottom cushion plunger 40 near the stroke end moves the tube closing end 5a of the cylinder body 2 as shown by the imaginary line B.
To squeeze the oil passage in the cushion hole 5c to make a cushion pressure in the chamber 7b, reduce the stroke speed, and reduce the impact at the stroke end. At this time, the cushion plunger 40 is movable in the radial direction.
At the time of rushing in, since it rushes in while aligning according to the hole shape of the cushion hole 5c, there is no worry of galling between the cushion plunger 40 and the cushion hole 5c (alignment function).
After reaching the stroke end, the piston rod 3 starts to move in the extension direction (left side in the drawing), and when the cushion plunger 40 comes out of the cushion hole 5c, the pressure oil from the supply / discharge port 9 passes through the outer peripheral surface of the cushion plunger 40. It flows into the chamber 7b.

According to this embodiment, the following effects can be obtained.

First, the following effects can be obtained regarding the piston fastening structure.

1) In the conventional general piston fastening structure shown in FIG. 9, it is necessary to provide a male rod portion 103g (see FIG. 9) on the piston rod, and tensile stress acts on this male screw portion 103g. High strength material had to be used for the piston rod. On the other hand, in the piston fastening structure of the present invention, since it is not necessary to provide the piston rod 3 with a male screw portion, it is not necessary to use a high-strength material for the piston rod 3, and it is not necessary to increase the strength by heat treatment, so that the cost is low. The piston rod 3 can be inexpensively made of various materials.

2) Conventionally, the tensile stress acts on the male screw portion of the piston rod, but in the present invention, it is applied to the bolt 22.
It is easy to make the material of the bolt 22 strong,
With a simple structure, the strength of the piston fastening part can be improved, and the life of the piston rod can be significantly improved.

3) By fixing with the bolt 22,
Fatigue strength against external force is also improved.

4) In the conventional piston fastening structure shown in FIG. 10, two flanges 160 and O-rings 180 were required, and the number of parts was large. However, in the present invention, such parts are unnecessary and the minimum number is required. It can be configured with the number of parts.

5) The conventional small-diameter piston insertion portion with a stepped portion is not required, and only the insertion portion 3a of the rod side cushion ring 30 needs to be provided on the piston rod 3. Therefore, an extra step is added to the piston rod. No need to
The problem of breakage at the step is also reduced.

6) The entire length of the rod is determined by the length of the head of the bolt 22, and the effective stroke of the hydraulic cylinder 1 can be made longer than in the case where a large nut 112 is used as in the conventional case.

7) Since a plurality of bolts 22 are used, the tightening torque of each bolt can be reduced and the assembly and disassembly are easy.

8) Conventionally, the piston rod
The piston assembly is often disassembled for maintenance. For example, when replacing the rod-side cylinder head or replacing the rod seal attached to this cylinder head, remove the nut 112 (see FIG. 9). I had to put it on a special machine to loosen the nut each time, and use this special machine to loosen the nut. The tightening torque of the nut 112 is about 1000k.
gf · m. In the present invention, the tightening torque of one bolt 22 is as small as about 70 kgf · m. For this reason, the bolt 22 can be loosened manually, and the bolt can be loosened without the need for a large-scale dedicated machine, and the serviceability is high.

The following effects can be obtained regarding the structure of the cushion device.

1) The cushion plunger 40 locked by the piston 4 has a through hole 41 and a counterbore hole 42 of the piston 4.
On the other hand, there is a gap, and since it can move by that gap, it performs the centering action when the cushion hole is inserted, like the conventional ring-shaped floating type bottom side cushion device.

2) In the structure of the conventional floating type bottom cushion device, as shown in FIG. 9, the cushion ring insertion portion 103h is attached to the long piston rod.
It was necessary to process the screw holes 103i and the like and lock the cushion ring 140 with a locking element such as the cushion stopper member 150. Further, even in the bottom side cushion device using the cushion plunger as described in Japanese Utility Model Laid-Open No. 1-166105, it is necessary to perform fine processing such as an engagement hole and a lateral screw hole at the end of the long piston rod. . In the bottom cushion device according to the present embodiment, the piston 4
Since the cushion plunger 40 is inserted into and the cushion plunger 40 is locked at the same time when the piston 4 is fixed, the piston rod 3 does not require a process for locking the cushion plunger 40. Particularly, in the conventional bottom side cushion device, since the diameter of the cushion ring insertion portion 103h is small, the insertion portion 103h has to be machined considerably from the piston rod diameter, which requires a long machining time and the screw hole 103i and the like. It was also necessary to process the locking elements of the. In the present embodiment, such processing is not necessary for the piston rod 3, the mounting structure of the cushion device on the bottom side is simplified, and the workability and productivity of the piston rod 3 are improved. Moreover, when the cushion device is worn or damaged, the piston rod 3
By separating the cushion plunger 40 from
Since the small parts can be replaced individually, the maintainability is excellent.

3) The piston 4 is the cushion plunger 4
Since it also serves as a locking element of 0, the cushion stopper 150
The number of parts can be reduced because the locking elements such as are unnecessary.

4) The conventional floating type cushion device on the bottom side has a ring shape (cushion ring), but in the present embodiment, it has a rod shape (cushion plunger 40) instead of a ring. The cushion device reduces the shock by raising the cushion pressure by squeezing the oil passage of the cushion hole, and if the gap to the cushion hole is the same, the smaller the diameter of the cushion ring or the plunger,
The cross-sectional area of the gap becomes small, the throttling effect of the oil passage is large, and it is advantageous in the performance as a cushion device. The rod-shaped cushion device of this embodiment can have a smaller diameter, which was not possible with the conventional cushion ring structure, and a high-performance bottom cushion device can be obtained.

5) In the conventional floating type bottom cushion device using the cushion ring, the distribution characteristic of the pressure acting on the cushion ring when the hydraulic cylinder is in the vicinity of the stroke end when the hydraulic cylinder is contracted has a distribution characteristic of the cushion ring outer diameter side. Becomes a distribution pressure of the cushion pressure and the tank pressure because it becomes the cushion pressure and the tank pressure, and becomes an even distribution pressure of the cushion pressure because the tank side is almost sealed on the inner diameter side of the cushion ring. When pressure is applied to the inner and outer diameter sides of the cushion ring in this way, the cushion ring is deformed to the outer diameter side due to the pressure difference between the inner diameter side and the outer diameter side, and the annular gap set in the cushion hole is greatly reduced. Therefore, the cushion pressure rises, and a higher pressure than necessary is generated. As a result, the sudden increase in pressure increases the impact due to hydraulic pressure and deteriorates the cushion performance. Moreover,
Since the cushion pressure becomes high, the withstand pressure life of the member in the portion where the cushion pressure acts is shortened, and the worst destruction occurs. However, in the present embodiment, since the cushion plunger 40 is rod-shaped, the occurrence of pressure distribution on the inner diameter side can be avoided, there is no change in the annular gap as in the prior art, and stable cushioning performance can always be secured. Also,
In the case of the cushion ring, since the ring thickness is thin, there is a problem in processing accuracy, but since the cushion plunger 40 is rod-shaped, it can be processed with high accuracy.

Another embodiment of the present invention will be described with reference to FIGS. In the figure, the same members as those shown in FIG. 1 are designated by the same reference numerals.

FIG. 3 shows a second embodiment of the present invention, in which the cushion ring 30A on the rod side is a fixed type cushion device integrated with the piston 4A. A recess 50 is provided on the end surface of the piston 4A on the chamber 7b side so that the head of the bolt 22 does not protrude from the end surface of the piston.

FIG. 4 shows a third embodiment of the present invention, in which the bottom side cushion plunger 40B is a fixed type cushion device integrated with the piston 4B. Further, a counterbore hole 50B is provided on the end surface of the piston 4B on the chamber 7b side so that the head of the bolt 22 does not protrude from the piston end surface.

FIG. 5 shows a fourth embodiment of the present invention, in which both the rod side cushion ring 30A and the bottom side cushion plunger 40B are a fixed type cushion device integrated with the piston 4C.

FIG. 6 shows a fifth embodiment of the present invention, which is a flange portion 40 of the cushion plunger 40D.
A step 40c is provided on Da, and this step and piston 4D
A disc spring 51 is inserted between the counterbore hole 42 and the bottom portion 42a, and the disc plunger 51 is used to insert the cushion plunger 40.
The flange portion 40Da of D is attached to the end surface 23 of the piston rod 3.
It is urged in the axial direction between the counterbore bottom 42a. Flange portion 40 of cushion plunger 40D
Da is locked by being pressed against the piston end surface 23 by the action of the disc spring 51. By doing so, the axial movement of the cushion plunger 40D is restricted, and the flange portion 40Da or the bottom portion 4 of the counterbore hole 42 is restricted.
The wear of 2a is eliminated.

Further, the cylinder body 2 and the piston rod 3
And when the hydraulic cylinder is assembled with the piston 4D,
Cushion plunger 40D and cushion hole 5c (Fig. 1
(See) and the cushion plunger 40
Even if D interferes at the entrance of the cushion hole 5c,
Since the cushion plunger 40D is movable in the radial direction, the cushion plunger 40D is aligned and projects into the cushion hole 5c. Since the cushion plunger 40D is pressed by the disc spring 51, it is held at the moved position after the center alignment. Therefore, the cushion plunger 40D does not interfere with the cushion hole 3c during the subsequent rush into the cushion hole 5c.

FIG. 7 shows a sixth embodiment of the present invention. A recess 53 is provided in the end surface 23 of the piston rod 3, a coil spring 54 is arranged in the recess 53, and the coil spring 54 is used. The flange portion 40a of the cushion plunger 40 is pressed against the bottom portion 42a of the counterbore hole and locked. With this coil spring 54, the same effect as that of the fifth embodiment can be obtained.

FIG. 8 shows a seventh embodiment of the present invention, in which the spherical surface portion 4 is provided at the base end of the cushion plunger 40E.
0d, and the end face 23 of the piston rod 3 and the piston 4
It is also possible to provide spherical concave portions 55 and 56 for receiving the spherical portion 40d on the end face of D (bottom surface of the concave portion 21), and bring the spherical portion 40d into spherical contact with the spherical concave portions 55 and 56. In this way, the cushion plunger 40E can be tilted by the difference in diameter between the through hole 41 of the piston 4D and the shaft portion 40b of the cushion plunger 40E, and when the cushion plunger 40E is thrust into the cushion hole 5c (see FIG. 1). The centering function is achieved not only for the parallel displacement of the axial center of the cushion hole 5c but also for the angular displacement. Further, in the case of the flange portion 40a shown in FIG. 1, the cushion plunger 40E
When the direction of the axial force acting on the flange changes, the flange 4
0a oscillates in the axial direction and uneven wear is likely to occur. However, in the present embodiment, the cushion plunger 40E makes spherical contact with the spherical surface portion 40d even if a force that oscillates the cushion plunger 40E in the axial direction acts. Therefore, uneven wear does not occur.

The above-mentioned effects 1) to 8) can be obtained with respect to the piston fastening structure according to the respective embodiments shown in FIGS. 3 to 8, and according to the respective embodiments shown in FIGS. 3 and 6 to 9. With respect to the cushion device, the effects of 1) to 5) above can be obtained.

Further, in each of the embodiments shown in FIGS. 3 to 5, the number of parts can be reduced by integrating the piston and the cushion member (cushion ring or cushion plunger). Particularly, in the embodiment shown in FIG. Since both the ring and the cushion plunger are integrated with the piston, the number of parts is minimized.

Further, in each of the embodiments shown in FIGS. 6 and 7, even if the cushion plunger and the cushion hole are displaced from each other at the time of assembly, the position is maintained at that position once the center is adjusted. After that, you can rush into the hole without aligning.

Further, according to the embodiment shown in FIG. 8, the cushion plunger can be tilted by the amount of the gap between the shaft portion 40b of the cushion plunger and the through hole of the piston.
Even if the axial center of the cushion plunger 40E and the cushion hole 5c is misaligned, the centering function is achieved and uneven wear at the spherical contact portion does not occur.

The eighth embodiment of the present invention will be described with reference to FIG. In this embodiment, the cushion plunger is provided with a centering function and a one-way flow path function. In the figure, the same members as those shown in FIG. 1 are designated by the same reference numerals.

In FIG. 9, the bottom cushion device of this embodiment has a cushion plunger 40F. This cushion plunger 40F has a proximal flange portion 40Fa and a shaft portion 40Fb having a spherical tip. Then
Similar to the above-described embodiment, the shaft portion 40Fb is inserted in the through hole 41 of the piston 4 in a loosely fitted state with a radial gap, and the flange portion 40Fa is the end surface of the piston rod 3 (the end surface of the cushion ring insertion portion 3a). It is arranged in a loosely fitted state with a gap in the radial direction and the axial direction between the counterbore hole 42.

Further, an inner diameter hole 40f having a tapered bottom portion is formed on the end surface of the cushion plunger 40F on the side of the flange portion 40Fa, and the shaft portion 40Fb has an opening at a spherical tip, and the inside of the shaft portion 40Fb is opened. Axial extension 4
A small hole 40g penetrating to 0f and a small hole 40i in the radial direction that communicates the inner diameter hole 40f with the bottom chamber 7b are formed. Inside the inner diameter hole 40f, the tapered surface at the bottom of the inner diameter hole 40f comes into contact with the small hole. Ball 6 to open and close the 40g opening
0, and a spring 6 that is supported by the end surface 23 of the piston rod 3 and presses the ball 60 in the direction of contacting the tapered surface of the bottom of the inner diameter hole 40f (the direction of closing the opening of the small hole 40g).
1 and are arranged.

Here, as shown in FIG. 9, the annular gap between the cushion hole 5c and the shaft portion 40Fb of the cushion plunger 40F is A, and the annular gap between the through hole 41 of the piston 4 and the shaft portion 40Fb of the cushion plunger 40F. B, the annular gap between the counterbore 42 of the piston 4 and the flange portion 40Fa of the cushion plunger 40F is C, A <B
The dimensional relationship is <C or A <C <B. As a result, the shaft portion 40Fb of the cushion plunger can freely move in the radial direction by the annular clearance A, and the annular clearance A sets the flow passage cross-sectional area of the throttle flow passage when performing the cushioning action. Therefore, in order to exert the cushioning effect more effectively, the annular gap A should be made as small as possible.

The ball 60 and the spring 61 constitute a check valve means, and the ball 60 and the spring 61 and the small holes 40g, 40.
i and the inner diameter hole 40f are provided in the bottom chamber 7 when the cushion plunger 40F projects into the cushion hole 5c.
A one-way flow path function that blocks the flow of pressure oil from b to the supply / discharge port 9 and allows the flow of pressure oil from the supply / discharge port 9 to the bottom chamber 7b when the cushion plunger 40F comes out of the cushion hole 5c. Is playing.

With the above structure, a cushioning action can be exerted near the stroke end when the piston rod 22 is contracted. That is, since the cushion plunger 40F is loosely fitted to the piston 4 at the beginning of the operation, even if the contraction movement of the piston rod 3 is started, the cushion plunger 40F is not restrained unless the cushion plunger 40F is particularly restrained. Plunger 40F
The shaft center of is in a position displaced from the shaft center of the piston 4.
However, when the cushion plunger 40F is displaced to a position facing the cushion hole 5c near the end of the stroke, the spherical surface of the tip end of the cushion plunger 40F abuts, and the cushion plunger 40F is displaced so as to follow the cushion hole 5c. When the cushion plunger 40F further enters into the cushion hole 5c, the axial center of the cushion plunger 40F is aligned with the axial center of the cushion hole 5c (alignment function). At the same time, the ball 60 mounted in the inner diameter hole 40f of the cushion plunger 40F closes the opening of the small hole 40g by the spring 61 (one-way flow path function). As a result, the bottom chamber 7b and the supply / discharge port 9 are connected. The communication is limited to the annular gap A between the wall portion of the cushion hole 5c and the cushion plunger 40F, and the flow passage is narrowed. Therefore, back pressure is generated in the bottom side chamber 7b, and the cushion action is exerted. Moreover, the further the cushion plunger 40F enters into the cushion hole 5c, the longer the annular throttle flow passage and the larger the flow passage resistance. Therefore, a greater cushioning effect is exerted, and the smooth and smooth stop at the stroke end is achieved. As a result, the impact at the time of stopping is remarkably reduced.

On the other hand, when the piston rod 3 extends from the most contracted state, the pressure oil is supplied to the supply / discharge port 9 and the bottom side chamber 7b tries to expand, so the cushion pressure is generated by this pressure difference. The ball 60 in the inner diameter hole 40f of the plunger 40F overcomes the pressing force of the spring 61 and moves in the axial direction, and is separated from the bottom tapered surface of the inner diameter hole 40f. As a result, in addition to the annular flow passage between the shaft portion 40Fb of the cushion plunger 40F and the wall portion of the cushion hole 5c, a flow passage that flows from the small hole 40g of the cushion plunger 40F through the inner diameter hole 40f to the small hole 40i is formed. Therefore, the cross-sectional area of the flow channel is considerably larger than that in the contraction direction. Therefore, the extension operation of the piston rod 3 is smoothly performed, and there is no possibility that noise is generated when the cushion plunger 40F comes out of the cushion hole 5c.

As described above, the cushion plunger 40
The flow path from the small hole 40g of F through the inner diameter hole 40f to the small hole 40i is such that when the piston rod 3 contracts, the ball 6
It becomes a one-way flow path that is closed by 0 and opened when the piston rod 3 expands, whereby the flow path can be greatly narrowed when the piston rod 3 contracts, and the flow path can be expanded when the piston rod 3 extends (one-way flow path function). ).

Further, the centering property of the cushion plunger 40F with respect to the cushion hole 5c is such that, once fitted, the flange of the cushion plunger 40F is caused by the action of the spring force of the spring 61 at the moment when the cushion plunger 40F is pulled out from the cushion hole 5c. Since it is held by the contact surface pressure between the portion 40Fa and the wall of the counterbore 42 of the piston 4,
After that, the centering property is maintained (centering maintaining function).

Therefore, although the cushion plunger 40F may initially come into sliding contact with the wall portion of the cushion hole 5c, the cushion plunger 40F has a learning function for the centering property as described above, and therefore has long-term wear resistance. There are no worries.

Therefore, according to this embodiment as well, the effects of 1) to 8) above can be obtained with respect to the piston fastening structure, the effects of 1) to 5) above can be obtained with respect to the cushion device, and the bottom cushion device can be 6 and FIG. 7, the function of maintaining the centering property is obtained, and further, the small holes 40g and 40i, the inner diameter hole 40f, and the one-way flow path function of the ball 60 and the spring 61 allow the cushion plunger 40F to be guided through the cushion hole 5c. The performance at the time of extraction can be improved.

FIG. 10 and FIG. 1 show the ninth embodiment of the present invention.
This will be described with reference to 1. In the present embodiment, a check valve means is configured by using a hydraulic balance instead of a ball and a spring, and has a one-way flow path function. In the figure, the same members as those shown in FIGS. 1 and 9 are designated by the same reference numerals.

In FIG. 10, the bottom cushion device of this embodiment has a cushion plunger 60G,
The cushion plunger 60G has a flange portion 40Ga on the base end side and a shaft portion 40Gb having a spherical distal end, and the shaft portion 40Gb has a radial gap in the through hole 41 of the piston 4 as in the above-described embodiment. And the flange portion 40Ga is inserted into the end face of the piston rod 3 (the end face of the cushion ring insertion portion 3a) and the counterbore hole 42.
Are arranged in a loosely fitted state with a radial and axial gap therebetween.

Further, an inner diameter recess 40k is formed on the end surface of the cushion plunger 40G on the side of the flange portion 40Ga except the outer peripheral end surface portion 40j, and the shaft portion 40Gb has
A small hole 40m that opens at the spherical tip and extends axially in the shaft portion 40Gb and penetrates to the inner diameter recess 40k is formed. Also, on the outer peripheral portion of the cushion plunger 40G,
A long groove 40n is formed from the inner portion of the bottom chamber 7b to the flange portion 40Ga, and a radial gap between the flange portion 40Ga and the wall portion of the counterbore 42 is communicated with the bottom chamber 7b.

Further, when the cushion plunger 40G is inserted into the cushion hole 5c, the inner diameter recess 40k has an outer peripheral end surface portion 40j more than the axial hydraulic pressure F2 acting on the radial step surface of the flange portion 40Ga on the shaft portion 40Gb side. Is set to a value such that the axial hydraulic pressure F1 that acts on the cushion plunger 40G is small, and the outer peripheral end face portion 40i of the cushion plunger 40G includes a radial step surface and an outer peripheral end face portion of the flange portion 40Ga on the shaft portion 40Gb side. The end face portion of the piston rod 3 with which 40j contacts constitutes a check valve means.

That is, FIG. 10 shows the cushion plunger 4
Assuming that 0G rushes into the cushion hole 5c, in this state, as shown in an enlarged view in FIG. 11, cushion pressure acts on the entire surface of the radial step surface of the flange portion 40Ga on the shaft portion 40Gb side. On the other hand, the distributed pressure of the cushion pressure and the tank pressure acts on the outer peripheral end surface portion 40j which is a contact surface between the end surface of the cushion plunger 40G and the end surface of the piston rod 3 except for the inner diameter recess 40k. now,
The products of the pressure distribution and the pressure receiving area of both are F1 and F2, respectively.
Then, since the inner diameter dimension of the inner diameter recess 40k is set so that F1> F2 as described above, the contact end face can be hermetically sealed. Therefore, the flow path from the bottom chamber 7b as the cushion chamber to the supply / discharge port 9 is only the annular gap between the cushion plunger 40g and the wall portion of the cushion hole 5c, and the cushion performance can be exhibited.

On the other hand, when the piston rod 3 is extended, pressure oil enters from the supply / discharge port 9 through the small hole 40m into the inner diameter recess 40k, and the bottom chamber 7b becomes low in pressure. As a result, the cushion plunger 40G moves to the right in the figure, and as a result, the pressure oil in the inner diameter recess 40k further enters the bottom side chamber 7b via the long groove 40n, and accelerates the extension speed of the piston rod 3.

Therefore, according to the present embodiment, as compared with the eighth embodiment shown in FIG. 9, although the cushion plunger does not have the function of maintaining the centering of the cushion plunger, it has all the other performances, and the hydraulic balance is further improved. Since a check valve function is provided by using, the number of parts is small, and the productivity is excellent and the reliability is high.

FIG. 12 shows a modification of the ninth embodiment shown in FIG. In the ninth embodiment, the flange portion 40G
Although a long groove 40n was formed in the outer peripheral portion of the cushion plunger 40G as a passage communicating with the bottom side chamber 7b through the radial gap between the a and the wall portion of the counterbore 42, as shown in FIG. A gap in the radial direction between the flange portion 40Ga and the wall portion of the counterbore 42 is formed in the bottom chamber 7
The communication small hole 40p may be formed in b, and this also cooperates with the small hole 40m and the outer peripheral end surface portion 40j of the cushion plunger 40G to fulfill the one-way flow path function.

The tenth embodiment of the present invention will be described with reference to FIG. In this embodiment, the cushion plunger 40H is used.
The outer peripheral portion of the shaft portion 40Hb is formed with an inclined groove 40q that widens toward the tip end side of the plunger, and the other configurations are the same as those of the previous embodiments shown in FIGS. Is.

In the embodiments shown in FIGS. 1 and 9, etc., the aperture area of the diaphragm is reduced by the fixed annular gap formed between the cushion plunger and the cushion hole 5c and the fitting length which changes depending on the stroke at the time of contraction. Although it is determined, by forming the inclined groove 40q in addition to this, a wider aperture opening area can be set and the cushion characteristic can be adjusted. In particular, the change in the aperture area of the diaphragm at the initial stage of entry into the cushion hole 5c can be moderated, which is effective in improving the cushioning performance at the initial stage of entry.

The eleventh embodiment of the present invention will be described with reference to FIG. In this embodiment, a cushion ring is used for the bottom side cushion device. In the figure, the same members as those shown in FIGS. 1 and 9 are designated by the same reference numerals.

In FIG. 14, the bottom side cushion device of this embodiment projects from the bottom side end surface of the piston 4I and has a shaft portion 70 having a step surface 71 on the piston body side.
And a floating type cushion ring 72 that is loosely fitted to the shaft portion 70 and is movable in the radial and axial directions,
And a locking plug 73 provided at the tip of the shaft portion 70,
The locking plug 73 is composed of a male screw portion 73a and a flange portion 73b, and is screwed and fixed to the screw hole 70a formed in the tip surface of the shaft portion 70 by the male screw portion 73a. The tip of the cushion ring 72 has a tapered guide surface 72a.
The groove 72b is formed at the rear end portion of the cushion ring 72, that is, at the end portion on the side of the step surface 71.

The cushion action of the cushion ring 72 is the same as that of the cushion device using the conventional floating type cushion ring shown in FIG.
That is, when the hydraulic cylinder contracts and the cushion ring 72 projects into the cushion hole 5c near the stroke end,
The cushion ring 72 enters along the cushion hole 5c (aligning function), and the tip surface of the cushion ring 72 is brought into close contact with the flange portion 73b of the locking plug 73 by the pressure of the bottom side chamber 7b, so that the shaft portion 70 and the cushion portion are cushioned. The flow path due to the annular gap between the rings 72 is closed (one-way flow path function), and the throttle flow path between the cushion ring 72 and the cushion hole 5c reduces the stroke speed to reduce the impact at the stroke end. Further, when the hydraulic cylinder extends from its stroke end position, the rear end surface of the cushion ring 72 comes into close contact with the step surface 71 due to the inflow pressure from the supply / discharge port 9, but the groove 72b causes a gap between the shaft portion 70 and the cushion ring 72. A flow path is formed by the annular gap (one-way flow path function) so that it can be pulled out from the cushion hole 5c and operate well.

Therefore, according to this embodiment, the same performance as that of the above embodiment using the cushion plunger can be obtained for the cushion device on the bottom side.

Also according to the present embodiment, when wear or damage is caused between the inner diameter portion of the cushion ring 72 and the shaft portion 70, the small component can be replaced by itself, which is excellent in maintainability. It becomes a thing.

The embodiment shown in FIGS. 9 to 14 is
Although the bottom side cushion device using the cushion plunger of the embodiment shown in FIG. 1 is provided with an aligning function and a one-way flow path function, the embodiment shown in FIGS. The bottom cushion device may be provided with the centering function and the one-way flow path function by appropriately combining with the embodiment shown in FIG. For example, the piston fastening structure of the embodiment shown in FIG. 3 may be combined with the plunger type bottom side cushion device having the aligning function and the one-way flow path function shown in FIGS. 9 to 13, and FIG. The flange portion of the cushion plunger having the hydraulic balance structure shown in FIG. 11 may be provided with an elastic means as shown in FIG. 6 or 7 to have a centering maintaining function. Further, in any of the embodiments shown in FIGS. 2 to 8, the inclined groove shown in FIG. 13 can be provided in the cushion plunger to obtain the same effect.
Further, the cushion ring type bottom side cushion device shown in FIG. 14 can be adopted in any of the embodiments shown in FIGS.

[0127]

According to the present invention, the following effects can be obtained regarding the piston fastening structure.

1) Since it is not necessary to provide a male screw portion on the piston rod, it is not necessary to use a high-strength material for the piston rod, and it is not necessary to increase the strength by heat treatment.
The piston rod can be made inexpensively with low cost materials.

2) It is easy to make the bolt material strong, and the strength of the piston fastening portion can be improved with a simple structure, and the life of the piston rod can be extended.

3) Fixing with bolts also improves fatigue strength against external force.

4) No components other than bolts are required, and the number of components can be minimized.

5) Since the conventional piston insertion portion with a step portion is unnecessary, it is not necessary to provide an extra step on the piston rod, and the problem of damage at the step portion is reduced.

6) The length of the entire rod is the length up to the head of the bolt, and the effective stroke of the hydraulic cylinder can be lengthened.

[0134] 7) Runode using a plurality of bolts, it is possible to reduce the tightening torque of one single bolt assembly, disassembly is easy.

[0135] 8) using a plurality of bolts Runode, 1 tightening torque of bolts is small no longer, it can also loosen the bolts by human power without using a large-scale exclusive machine which has heretofore been required , Serviceability is improved.

Further, according to the present invention, the following effects can be obtained regarding the structure of the cushion device.

1) Since the bottom cushion device is provided so as to project from the bottom end face of the piston, it is not necessary to perform complicated machining on the tip of the piston rod, and machining of the piston rod is facilitated.

2) Since the bottom side cushion device is provided with the centering function, when entering the cushion hole, it smoothly enters following the cushion hole and there is no fear of galling with the cushion hole.

3) Since the cushion device on the bottom side is provided with the one-way flow path function in addition to the centering function, the performance of exiting from the cushion hole is also improved.

4) Since the cushion plunger on the bottom side is used, the problem of bulging due to the difference in pressure distribution on the inner and outer diameter surfaces unlike the cushion ring does not occur, and stable cushioning performance can always be secured.

5) The piston is fixed to the piston rod with bolts, and at the same time, the cushion plunger is held by the enlarged proximal end portion of the cushion plunger, and the cushion plunger is attached and locked. Therefore, the piston rod is related to the locking of the cushion plunger. Machining of the piston rod becomes easy, with no or minimal machining required. Further, since the piston also serves as a locking element for the cushion plunger, the number of parts can be reduced. Furthermore, by mounting the cushion plunger so that it can move or tilt in the radial direction,
Similar to the conventional ring-shaped floating type bottom cushion device, it can perform the centering function when the cushion hole is inserted.

6) Since the through hole and the counterbore provided in the piston have a size having a gap with respect to the shaft portion and the flange portion of the cushion plunger, and the cushion plunger can be moved in the radial direction, the cushion plunger moves the piston It is fixed to the piston rod with bolts and is attached at the same time and can be moved in the radial direction.

7) Since the axial movement of the radially movable cushion plunger is elastically restrained, even if the centers of the cushion plunger and the cushion hole are deviated,
Once the center is aligned, the position is maintained, so that it is possible to rush into the cushion hole without centering thereafter.

8) Since the rod-side cushion plunger can be tilted, the cushion plunger and the cushion hole fulfill a centering function even with respect to an angular deviation between the axial centers of the cushion hole and spherical contact, so that uneven wear does not occur. .

9) Since the cushion plunger is a fixed type, the number of parts can be reduced by integrating the piston and the cushion plunger.

10) A cushion plunger is used for the bottom side cushion device so as to have both the aligning function and the one-way flow path function. Therefore, when the cushion hole is inserted, it smoothly follows the cushion hole, and at the same time, the cushion The performance of exiting from the hole is improved, and the problem of bulging due to the difference in pressure distribution on the inner and outer diameter surfaces, such as the cushion ring, does not occur, and stable cushioning performance can always be secured.

11) Since the check valve means is composed of the spring and the ball and has a one-way flow path function, the spring pushes the cushion plunger through the ball, so that the cushion plunger once aligns with the cushion hole. After that, the alignment property is maintained.

12) Since the check valve means is constructed by utilizing the hydraulic balance to have the one-way flow path function, the number of parts is small, the productivity is excellent, and the reliability is high.

13) Since the cushion plunger is provided with the inclined groove, the cushion characteristic can be adjusted, and in particular, the change of the aperture opening area at the initial entry into the cushion hole can be moderated and the cushion performance at the initial entry is improved.

14) Since a cushion ring is used for the bottom side cushion device so as to have both the aligning function and the one-way flow path function, when the cushion hole is inserted, it smoothly follows the cushion hole and at the same time, the cushion Good escape performance from the hole.

15) Since the rod side cushion device having the floating type cushion ring is further provided, the impact at the stroke end is alleviated even when the piston rod is extended, and the aligning function and the one-way flow path function are obtained. .

16) Since the rod side cushion device having the fixed type cushion ring is further provided, the impact at the stroke end is alleviated even when the piston rod is extended, and the number of parts of the rod side cushion device can be reduced. In particular, in the combination with the above (9), since both the rod side cushion member and the bottom side cushion member are integrated with the piston, the number of parts can be minimized.

[Brief description of drawings]

FIG. 1 is a sectional view of a hydraulic cylinder according to a first embodiment of the present invention.

FIG. 2 is a front view of the piston fastening portion shown in FIG.

FIG. 3 is a sectional view of a main part of a hydraulic cylinder according to a second embodiment of the present invention.

FIG. 4 is a sectional view of an essential part of a hydraulic cylinder according to a third embodiment of the present invention.

FIG. 5 is a sectional view of an essential part of a hydraulic cylinder according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view of an essential part of a hydraulic cylinder according to a fifth embodiment of the present invention.

FIG. 7 is a sectional view of an essential part of a hydraulic cylinder according to a sixth embodiment of the present invention.

FIG. 8 is a sectional view of an essential part of a hydraulic cylinder according to a seventh embodiment of the present invention.

FIG. 9 is a sectional view of an essential part of a hydraulic cylinder according to an eighth embodiment of the present invention.

FIG. 10 is a sectional view of an essential part of a hydraulic cylinder according to a ninth embodiment of the present invention.

11 is an enlarged view of a portion XI of the main part of the hydraulic cylinder shown in FIG.

12 is a cross-sectional view of a main part of a similar hydraulic cylinder showing a modification of the embodiment shown in FIG.

FIG. 13 is an external view of a cushion plunger used for the hydraulic cylinder according to the tenth embodiment of the present invention,
(A) is the figure which looked at the inclined groove from the upper part, (b) is the figure which looked at the inclined groove from the side.

FIG. 14 is a sectional view of an essential part of a hydraulic cylinder according to an eleventh embodiment of the present invention.

FIG. 15 is a sectional view of a main part of a hydraulic cylinder provided with a conventional cushion device.

FIG. 16 is a sectional view showing a piston fastening structure of a conventional hydraulic cylinder.

FIG. 17 is a diagram showing a stress state acting on a male screw portion of a piston rod.

[Explanation of symbols]

1 hydraulic cylinder 2 cylinder body 3 piston rod 4 pistons 5 tubes 6 Rod side cylinder head 7a, 7b chamber 8, 9 supply / discharge port 20 End face of piston on rod side 21 recess 22 volts 23 End face of piston rod 24 screw holes 25 bolt through hole 30 Rod side cushion ring 40 Bottom cushion plunger 40a flange part 40b shaft 40d spherical surface 40f inner diameter hole 40g small hole 40i small hole 40j Outer peripheral end face portion (check valve means) 40k inner diameter recess 40m small hole 40n long groove 40p small hole 40q inclined groove 41 through hole 42 counterbore 42a Counterbore bottom 51 Disc spring (elastic means) 53 Coil spring (elastic means) 55,56 spherical recess 60 balls (check valve means) 61 Spring (check valve means) 70 Shaft 71 Step surface 72 cushion ring 72b groove 73 Flange

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-49507 (JP, A) JP-A-59-93538 (JP, A) JP-A-9-68206 (JP, A) Actual development Sho-60- 34576 (JP, U) Actually opened 57-121403 (JP, U) Actually opened 55-22595 (JP, U) Actually opened 56-17297 (JP, U) Actually Kohei Hei 7-16888 (JP, Y2) (58) Fields surveyed (Int.Cl. ⁷ , DB name) F15B 15/00-15/28 F16F 9/00-9/58 F16J 1/00-1/24

Claims (16)

(57) [Claims] 1. A signed a piston at the distal end of the piston rod, divides the inside the piston in the cylinder body to the chamber on the rod side chamber and bottom side, tea of the rod-side
By supplying and discharging pressure oil from the chamber and the bottom chamber,
Hydraulic construction that expands and contracts the piston rod to drive the work member
The machine of the hydraulic cylinder, the end surface of the rod side of the piston to the end surface of the distal end of the piston rod in a state of being at least partially face contact, before
In the cross section of the piston rod, the bottom side of the piston
At multiple positions surrounding the center of the end face, open the end face of the piston rod from the multiple bolt through holes drilled in the piston.
Insert a plurality of bolts into the plurality of screw holes that are cut out, tighten the bolts, fix the piston directly to the piston rod with these bolts, and project the piston from the center of the bottom end face of the piston to the bottom side. A cushion device is provided, and when this bottom side cushion device contracts the piston rod,
A hydraulic cylinder characterized by being inserted into a cushion hole connected to a hydraulic oil port on the bottom side of the cylinder body. 2. The hydraulic cylinder according to claim 1, wherein the bottom side cushion device has a centering function of aligning axial centers when the bottom side cushion device is thrust into the cushion hole. 3. The hydraulic cylinder according to claim 1, wherein the bottom side cushion device has an aligning function of aligning the axes of the bottom side chamber and the bottom side chamber when the bottom side cushion device is inserted into the cushion hole. From the hydraulic oil port to the hydraulic oil port, and allows the hydraulic oil to flow from the hydraulic oil port to the bottom chamber when the hydraulic oil port exits from the cushion hole. And hydraulic cylinder. 4. The hydraulic cylinder according to claim 1, wherein the bottom side cushion device has a cushion plunger that projects from an end surface of the piston on the bottom side and that projects into the cushion hole when the piston rod contracts. And hydraulic cylinder. 5. The hydraulic cylinder according to claim 4, wherein the cushion plunger penetrates the piston and an enlarged base end portion located between the end surface of the piston rod and the end surface of the piston on the rod side. A shaft portion projecting from an end surface on the bottom side of the piston, the piston is fixed to the piston rod by the bolt, and at the same time, the cushion plunger is held by an enlarged base end portion of the cushion plunger and the diameter of the cushion plunger is increased. A hydraulic cylinder characterized in that the hydraulic cylinder is mounted so as to be movable or tiltable in any direction, and has a centering function of aligning the axial centers when the cushion plunger is thrust into the cushion hole by moving or tilting in the radial direction. 6. The hydraulic cylinder according to claim 5, wherein an enlarged base end portion of the cushion plunger is a flange portion provided at a base end of the cushion plunger, and a shaft portion of the cushion plunger is provided at a center of the piston. A through hole passing therethrough and a counterbore hole for receiving the flange portion are provided, and the flange portion is located in the counterbore hole between the end surface of the piston rod and the wall portion of the counterbore hole, and the through hole and the counterbore hole are provided in the cushion. A hydraulic cylinder characterized in that it has a size having a gap with respect to a shaft portion and a flange portion of the plunger so that the cushion plunger can be moved in a radial direction. 7. The hydraulic cylinder according to claim 6, wherein an elastic means is inserted between a flange portion at a base end of the cushion plunger and an end surface of the piston rod or an end surface of the piston on a rod side, and the cushion plunger is inserted. A hydraulic cylinder characterized by elastically restraining the axial movement of the. 8. The hydraulic cylinder according to claim 5, wherein an enlarged base end portion of the cushion plunger is a spherical surface portion provided at a base end of the cushion plunger, and the spherical surface portion is provided on the end surface of the piston rod and the piston. Is provided so as to make spherical contact with the rod-side end face of the cushion plunger, and a through hole through which the shaft portion of the cushion plunger passes is provided in the center of the piston, and the through hole has a gap with respect to the shaft portion of the cushion plunger. A hydraulic cylinder having a size such that the cushion plunger can be tilted. 9. The hydraulic cylinder according to claim 4, wherein the cushion plunger is a fixed type integrated with the piston. 10. A hydraulic cylinder according to claim 5, wherein
The cushion plunger has a first passage opened at a tip end of the shaft portion and formed in the shaft portion in an axial direction; a second passage capable of communicating the first passage with the bottom chamber; A check valve means provided between the passage and the second passage, and the bottom side when the cushion plunger rushes into the cushion hole by the first and second passages and the check valve means. A one-way flow path function that blocks the flow of pressure oil from the chamber to the hydraulic oil port and allows the flow of pressure oil from the hydraulic oil port to the bottom chamber when the cushion plunger comes out of the cushion hole. A hydraulic cylinder characterized by having it. 11. The hydraulic cylinder according to claim 10, wherein the second passage is formed in an end surface of the cushion plunger on the side of the enlarged base end portion, and an inner diameter hole through which the first passage is opened, and the inner diameter hole. And a small hole in the radial direction communicating with the bottom chamber, the check valve means is arranged in the inner diameter hole, and a ball capable of opening and closing the opening of the first passage, and arranged in the inner diameter hole. And a spring for pressing the ball in a direction of closing the opening of the first passage. 12. The hydraulic cylinder according to claim 10, wherein an enlarged base end portion of the cushion plunger is a flange portion provided at a base end of the cushion plunger, and the piston is on the piston rod side of the piston. Has a radial hole and an axial gap between the through hole through which the shaft portion of the cushion plunger is inserted with a radial gap and the flange portion with the end face of the piston rod. The second passage is formed by leaving an outer peripheral end face portion on the piston-side end face of the cushion plunger, the inner diameter recess for opening the first passage, the flange portion, and the counterbore. And a communication passage that communicates a radial gap between the wall portion of the hole and the bottom chamber with the check valve means, the check valve means is provided on the shaft portion side of the flange portion. The cushion plunger includes a radial step surface and an outer peripheral end surface portion of the piston side end surface of the cushion plunger, and a piston side end surface portion of the piston rod with which the outer peripheral end surface portion contacts, and the inner diameter recess is formed by the cushion plunger. When rushing into the hole, the axial hydraulic pressure acting on the outer peripheral end face portion is smaller than the axial hydraulic pressure acting on the radial step surface. Hydraulic cylinder to. 13. A hydraulic cylinder according to any one of claims 4 to 12, characterized in that an inclined groove that widens toward the tip of the plunger is formed on the outer peripheral portion of the cushion plunger. 14. The hydraulic cylinder according to claim 1, wherein
The bottom side cushion device includes a shaft portion projecting from a bottom side end surface of the piston, a floating type cushion ring that is loosely fitted to the shaft portion and movable in a radial direction and an axial direction, and a tip end of the shaft portion. An engaging plug provided, and by the cushion ring, an aligning function of aligning an axis center when the cushion hole is rushed into; and a hydraulic oil port from the bottom chamber when rushing into the cushion hole A hydraulic cylinder characterized by having a one-way flow path function of blocking the flow of pressure oil to the bottom side chamber and preventing the flow of pressure oil to the bottom chamber when the pressure oil flows out from the cushion hole. . 15. The hydraulic cylinder according to claim 1, further comprising a floating type cushion ring which is loosely fitted in a portion of the piston rod adjacent to the piston and is movable in a radial direction and an axial direction. A rod-side cushion device is further provided, which has a cushion ring that penetrates into a cushion hole that communicates with a hydraulic oil port on the rod side of the cylinder body, and absorbs impact at the stroke end when the piston rod extends. A hydraulic cylinder characterized in that 16. The hydraulic cylinder according to any one of claims 1 to 14, further comprising a fixed type cushion ring integrated with the piston, the cushion ring being a hydraulic fluid on a rod side of the cylinder body. A hydraulic cylinder characterized in that a rod side cushion device is further provided to absorb a shock at a stroke end when the piston rod extends when the piston rod extends into a cushion hole communicating with the port.