JP2000356203A - Cushion structure for hydraulic cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide cushion structure for hydraulic cylinders allowing a plurality of hydraulic cylinders to absorb the inertia force of one working tool almost equally. SOLUTION: This cushion structure has boom cylinders 1, 1a for driving a boom provided in a hydraulic shovel, and forms cushion chambers comprising rod side chambers 4b, 24b for relaxing impact caused by pistons 5, 25 moving following the elongating action of the boom cylinders 1, 1a, near the respective stroke ends of the boom cylinders 1, 1a when elongated. A communicating means is provided for communicating the respective cushion chambers of the boom cylinders 1, 1a. The communicating means comprises oil ducts 50, 51 respectively provided at the boom cylinders 1, 1a and communicated at one ends with the respective cushion chambers of the boom cylinders 1, 1a while being opened at the other ends to the outside of the boom cylinders 1, 1a, and a communicating line 52 for communicating these oil ducts 50, 51.

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 in a construction machine such as a hydraulic shovel having a plurality of hydraulic cylinders for driving one work implement, and for reducing an impact generated by the operation of the hydraulic cylinder. It relates to a cushion structure.

[0002]

2. Description of the Related Art FIG. 6 is a perspective view showing a hydraulic excavator as an example of a construction machine provided with a cushion structure of a hydraulic cylinder to which the present invention is applied. As shown in FIG. 6, the excavator includes a revolving body 40 and the revolving body 40.
A boom 41 connected to the end of the boom 41 so as to be vertically rotatable, and an arm 42 connected to the tip of the boom 41 so as to be rotatable in the vertical direction. Bucket 43. The boom 41, the arm 42, and the bucket 43 described above each form a working tool for performing an excavation operation or the like. In addition, a front work machine is constituted by these work tools as a whole.

The boom 41 is driven by a pair of hydraulic cylinders, that is, a first boom cylinder 1 and a second boom cylinder 1a, the arm 42 is driven by an arm cylinder 44 which is a hydraulic cylinder, and the bucket 43 is a bucket cylinder 45 which is a hydraulic cylinder. Drive with

[0004] In this excavator, a large load acts on the front working machine during excavation work or the like, so that
At the stroke end of each hydraulic cylinder described above, the piston built in the hydraulic cylinder is likely to collide with the inner wall of the cylinder. In the case of such a collision, an extremely large impact is generated, which adversely affects the hydraulic cylinder, the working tool, or the connecting portion of the working tool, and the hydraulic cylinder, the working tool, or the connecting portion of the working tool. Will accelerate the wear of the device. For this reason,
Various cushion structures that utilize oil pressure to absorb the impact at the stroke end of the hydraulic cylinder have been considered. Among these hydraulic cylinder cushion structures, the present invention is particularly applicable to a plurality of hydraulic cylinders that drive one work implement, such as the first boom cylinder 1 and the second boom cylinder 1a that drive the boom 41 described above. It is intended for cushion structures.

FIG. 7 shows an example of a conventional cushion structure of a hydraulic cylinder provided in the hydraulic excavator shown in FIG. 6, that is, an entire configuration diagram including a cross-sectional portion showing a cushion structure of a first boom cylinder 1 and a second boom cylinder 1a. 8 is a side view showing the appearance of one of the two boom cylinders forming the cushion structure shown in FIG. 7, FIG. 9 is an operation explanatory view showing a cross section of a main part of the boom cylinder shown in FIG. FIG. 10 is an operation explanatory view showing a state of main parts at the start of a cushion stroke in the boom cylinder shown in FIG.
FIG. 9 is an operation explanatory view showing a state of a main part at the end of a cushion stroke in the boom cylinder shown in FIG. 8.

The first boom cylinder 1 and the second boom cylinder 1a have substantially the same structure as shown in FIG. Also, P shown in FIG. 7 is a pump for supplying pressure oil to each of the boom cylinders 1 and 1a, T is a tank, and 35 is a pump for controlling the flow of pressure oil supplied from the pump P to each of the boom cylinders 1 and 1a. Directional control valve, 3
Reference numerals 6 and 37 denote a first main line and a second main line which connect the direction control valve 35 to each of the boom cylinders 1 and 1a.

For example, the first boom cylinder 1 of the boom cylinders 1 and 1a has a cylinder tube 2 as shown in FIGS. One end of the cylinder tube 2 is closed and the other end is open, and a head cover 3 is attached to the open end. The cylinder tube 2 and the head cover 3 constitute a cylinder 4 forming a main body. In the cylinder 4, a piston 5 which is divided into a bottom chamber 4a and a rod chamber 4b is slidably mounted.
A rod 5a is connected to the piston 5, and the rod 5a is provided so as to project from the head cover 3 to the outside. The above-described bottom side chamber 4a and rod side chamber 4b are provided with oil passages 6, 7 for supplying and discharging pressure oil, respectively. Among these oil paths 6, 7, the oil path 6 is connected to the above-mentioned first main line 36, and the oil path 7 is connected to the above-mentioned second main line 37. At the end of the rod 5a, there is provided a connecting portion 8 rotatably connected to the boom 41 shown in FIG. 6, and at the closed end of the cylinder 4, the revolving body shown in FIG. A connecting portion 9 is provided to be rotatably connected to 40.

A cushion structure provided on the first boom cylinder 1 having such a basic structure will be described below.

Reference numeral 12 denotes a cushion ring fitted to a connecting portion between the piston 5 and the rod 5a, which constitutes a cushion member. The end of the head cover 3 is fitted into the cylinder tube 2, and the rod-side chamber 4b in this portion is fitted.
Has a step shape. Cushion ring 1 described above
2 has an outer diameter of the insertion hole 3 formed in the head cover 3.
a is slightly smaller than the inner diameter of the insertion hole 3 when the rod 5a is extended.
a. The above-described oil path 7 is formed in the head cover 3. As shown in FIG. 11, when the cushion ring 12 enters the insertion hole 3 a until the piston 5 comes into contact with the end of the head cover 3, as shown in FIG. It is provided in advance so as to be located at a position ahead of the position of the cushion ring 12, that is, at the side of the connecting portion 8.

A cushion structure for performing a cushioning operation, which will be described later, is formed by the above-described cushion ring 12, the head cover 3 including the insertion hole 3a, the surface of the piston 5 facing the head cover 3, and the inner wall of the cylinder tube 2. It is configured.

The cylinder 2 including the cylinder tube 22 and the head cover 3 in the second boom cylinder 1a
4, a piston 25 disposed in the cylinder 24, a bottom chamber 24a, a rod-side chamber 24b defined in the cylinder 24 by the piston 25,
Connecting portions 28 connected to the oil passages 26 and 27, the boom 41,
The basic structure including the connecting part 29 connected to the revolving superstructure 40 is as follows.
It is almost the same as in the first boom cylinder 1 described above.

Also, the cushion ring 32 and the insertion hole 2
Head cover 23 including head 3a,
And the inner wall of the cylinder tube 22 constitute a cushion structure similar to that of the first boom cylinder 1 described above.

The cushioning operation in the cushion structure of the boom cylinders 1 and 1a configured as described above will be described below.

For example, from the state shown in FIG.
Is switched to the right position, the pressure oil of the pump P
5 to the first main line 36, and from the oil passages 6, 26 of the boom cylinders 1, 1a to the bottom side chambers 4a, 2a.
4a. This causes the pistons 5, 25 to move to the left in FIG. 7, that is, to approach the head covers 3, 23, and to move integrally with the rods 5a, 25a. The return oil from the rod-side chambers 4b, 24b is guided to the oil passages 7, 27, the second main conduit 37, and is returned to the tank T via the direction control valve 35.

In the state where the rods 5a and 25a gradually extend, as shown in FIG. 10, when the rod 5a reaches the vicinity of the stroke end at the time of extension, for example, in the first boom cylinder 1, the cushion ring 12 begin to enter the insertion hole 3a of the head cover 3, and a cushion stroke is started. Thus, cushion ring 1
2 enters the insertion hole 3a, the flow path from the rod side chamber 4b to the oil path 7 is
Changes to the cross-sectional area of the diameter difference between the outer diameter of the hole and the inner diameter of the insertion hole 3a, and the state is reduced. Therefore, the flow rate of the return oil to the tank T is reduced as compared with before, and a cushion pressure is generated in the rod side chamber 4b. That is, FIG.
The rod-side chamber 4b from the state shown in FIG. 11 to the state shown in FIG. 11 forms a cushion chamber for generating a cushion pressure for preventing the piston 5 from hitting the cylinder 4 by impact. The movement distance of the cushion ring 12 from the state shown in FIG. 10 to the state shown in FIG. 11 is a cushion stroke section. While the cushion ring 12 moves in the cushion stroke section, the piston 5 approaches the end of the head cover 3, so that the cushion pressure in the cushion chamber gradually increases, and the increased cushion pressure acts on the first boom cylinder 1. The load, that is, the inertia force is absorbed, the operating speed is reduced, and the piston 5
Gently contacts the end of the head cover 3. In this way, the shock is alleviated.

Although the cushion operation in the first boom cylinder 1 has been described above, the cushion operation in the second boom cylinder 1a is similarly performed.

By the extension operation of the boom cylinders 1 and 1a as described above, the boom 41 shown in FIG. 6 performs an upward turning operation, that is, a boom raising operation.

When the directional control valve 35 shown in FIG. 7 is switched to the left position, the pressure oil of the pump P is supplied to the second main line 37 and the oil passages 7 and 27 of the boom cylinders 1 and 1a. The return oil 1a is returned to the tank T via the oil paths 6 and 26 and the first main line 36, and the rods 5a and 25a are contracted, and the boom 41 is turned downward, that is, the boom is lowered. Is performed. In this prior art, the cushion structure during contraction is not shown. For such a contracting operation, a cushion structure may not be provided, or a cushion structure having a different form from the above-described cushion structure may be provided. By raising and lowering the boom, for example, excavation work of earth and sand is performed.

A known technique having a pair of boom cylinders as described above is described, for example, in Japanese Patent Application Laid-Open No. 8-303409.

[0020]

By the way, the above-mentioned 2
It is generally difficult to manufacture the boom cylinders 1 and 1a so that they have exactly the same cylinder stroke. Also, a boom 4 to which the boom cylinders 1 and 1a are attached.
1 is a welded structure, it is difficult to make the distance between the pins for attaching the boom cylinders 1 and 1a the same, and by these, the boom cylinders 1 and 1a are hardened.
Normally, the cylinder stroke of 1a is slightly different.

For this reason, for example, when one of the boom cylinders 1 extends to reach the vicinity of the stroke end and the cushion ring 12 enters the insertion hole 3a and the cushion stroke starts, the other boom cylinder 1 starts to move. The cushion ring 32 of 1a may be located in front of the insertion hole 23a. In such a case, the cushion pressure rises and starts to decelerate in the boom cylinder 1 in which the cushion stroke has started earlier, and the cushion pressure rises to a high pressure. In this state, the stroke ends, but the other boom cylinder 1 a The cushion stroke starts with a delay, and the cushion pressure does not rise so much.
In this state, the stroke ends. That is, only the cushion pressure of the boom cylinder 1a which has started the cushion stroke first becomes extremely high, and the inertia force of the boom 41 is absorbed by the single boom cylinder 1a.

The cushion rings 12, 32 are formed when the cushion rings 12, 32 are inserted into the insertion holes 3a, 23a of the head covers 3, 23 of the boom cylinders 1, 1a.
It is generally difficult to manufacture the gaps between the cushion rings 12, 32 and the insertion holes 3a, 23a so that they have exactly the same dimensions, and a manufacturing error is usually caused. For this reason, the cushion performance of the boom cylinders 1 and 1a tends to differ from each other. That is, the magnitude of the cushion pressure generated during the same cushion stroke tends to be different. In this case, the cushion pressure is generated first in the boom cylinder having the better cushion performance, and the cushion pressure is increased, so that the boom cylinder having the poor cushion performance does not have much cushion pressure. From another viewpoint, only one of the boom cylinders 1 and 1a absorbs the inertial force of the boom 41.

In any case, the prior art shown in FIGS. 7 to 11 tends to absorb the inertial force of the boom 41 with only one of the two boom cylinders 1 and 1a. The cushion pressure of one of the boom cylinders becomes too high, and the corresponding one of the cylinder tubes 2, 22 expands and breaks, or the flange mating surfaces of the head covers 3, 23 with the expansion. There is a problem that the high pressure acts on the O-rings 3b and 23b located at the position (1) to damage the corresponding O-ring or cause oil leakage due to the damage.

Also, one of the boom cylinders 1 and 1a
If the boom 41 alone receives the inertia force of the boom 41, the single boom cylinder may not be able to absorb the inertia force of the boom 41. In such a case, the piston 5 or the piston 25 may be used at the cylinder stroke end. However, there is a problem in that the front work machine including the boom cylinder 1, 1a or the boom 41 is liable to be damaged by the collision with the head cover 3 or the head cover 23 to generate an impact.

Further, since only one of the boom cylinders 1 and 1a absorbs the inertial force of the boom 41, a large difference occurs in the support force on both sides of the boom 41. Easy to occur, the boom 41
May cause damage.

Although the cushion structure of the boom cylinders 1 and 1a for rotating the boom 41 provided in the excavator has been described above as an example, the invention is not limited to the boom 41 provided in the excavator as described above. A cushion structure for the hydraulic cylinder in a mode in which one work implement is driven by a plurality of hydraulic cylinders has the same problem as described above.

The present invention has been made in view of the above-mentioned situation in the prior art, and an object thereof is to allow the inertial force of one work implement to be almost equally absorbed by each of a plurality of hydraulic cylinders. An object of the present invention is to provide a cushion structure for a hydraulic cylinder.

[0028]

To achieve the above object, the invention according to claim 1 of the present application has a plurality of hydraulic cylinders for driving one work implement, and the same operation of the plurality of hydraulic cylinders Communication means for communicating the cushion chambers of the plurality of hydraulic cylinders in a cushion structure of a hydraulic cylinder which forms a cushion chamber for mitigating an impact of a piston moving in accordance with the above-mentioned operation form near each stroke end in the form Is provided.

According to the first aspect of the present invention, the plurality of hydraulic cylinders operate near the stroke end in accordance with the inertial force of the work implement, and one of the plurality of hydraulic cylinders operates as one of the plurality of hydraulic cylinders. Even when the pressure first rises in the cushion chamber, the pressure is also supplied to the cushion chamber of another hydraulic cylinder through the communication means,
Each of the plurality of hydraulic cylinders can substantially equally absorb the inertial force of the work implement.

In order to achieve the above object, the invention according to claim 2 of the present application is the invention according to claim 1, wherein the communication means is provided in each of the plurality of hydraulic cylinders, and one end is provided. It is characterized by including an oil passage communicating with the cushion chamber of each of the plurality of hydraulic cylinders and having the other end opened to the outside of the hydraulic cylinder, and a communication conduit connecting these oil passages.

In order to achieve the above object, the invention according to claim 3 of the present application is directed to the invention according to claim 1 or 2, further comprising a main conduit for introducing pressure oil to the hydraulic cylinder, and A branch pipe that branches from the path and communicates with the communication pipe; and a branch pipe that is provided in the branch pipe and allows a flow of pressure oil from the main pipe in the direction of the communication pipe. A check valve for preventing the flow of pressure oil in the road direction.

According to the third aspect of the present invention, in particular, when the plurality of hydraulic cylinders reach the stroke end while performing the cushioning operation, and the subsequent operation changes, for example, from the extending operation mode to the contracting operation mode. Thus, when changing to the next operation mode, the pressure oil supplied directly from the main line into the hydraulic cylinder, the branch line,
With the pressure oil supplied to the hydraulic cylinder via the check valve, the pistons of the plurality of hydraulic cylinders can be operated at a high speed, and can be quickly changed to a corresponding operation mode.

In order to achieve the above object, the invention according to claim 4 of the present application is the invention according to any one of claims 1 to 3, wherein the operation mode is an operation mode for extending the hydraulic cylinder. It is characterized by having.

According to a fifth aspect of the present invention, there is provided a hydraulic shovel according to any one of the first to fourth aspects, wherein the work implement is a boom. Along with the plurality of hydraulic cylinders,
A first boom cylinder and a second boom cylinder for driving the boom are characterized.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a cushion structure for a hydraulic cylinder according to the present invention will be described below with reference to the drawings. FIG.
1 to 3 are explanatory diagrams showing a first embodiment of the present invention, FIG. 1 is an overall configuration diagram including a cross-sectional portion, FIG. 2 is an operation explanatory diagram showing a state of main parts at the start of a cushion stroke of the first embodiment,
FIG. 3 is an operation explanatory view showing a state of a main part at the end of the cushion stroke according to the first embodiment.

In FIGS. 1 to 3, FIG.
The components equivalent to those shown in FIGS. That is, the first embodiment is also provided, for example, on the boom 41 of the hydraulic excavator shown in FIG. 6, and includes a first boom cylinder 1 and a second boom cylinder 1a having substantially the same structure.

The first boom cylinder 1 has a cylinder tube 2, and a head cover 3 is provided at an open end of the cylinder tube 2. The cylinder tube 2 and the head cover 3 constitute a cylinder 4 forming a main body. A piston 5 is slidably disposed in the cylinder 4, and the piston 5 partitions the inside of the cylinder 4 into a bottom chamber 4a and a rod chamber 4b. Also, it has a rod 5a connected to the piston 5,
The rod 5a protrudes from the head cover 3 to the outside. Bottom side chamber 4a and rod side chamber 4b
Are provided with oil passages 6 and 7 for supplying and discharging pressure oil, respectively. Among these oil paths 6, 7, the oil path 6 is connected to a first main line 36, and the oil path 7 is connected to a second main line 37. At the end of the rod 5a, there is provided a connecting portion 8 rotatably connected to the boom 41 shown in FIG. 6, and at the closed end of the cylinder 4, the revolving body shown in FIG. The connecting portion 9 is provided to be rotatably connected to the connecting member 40.

The second boom cylinder 1a is also provided with the first boom cylinder 1a.
Similarly to the boom cylinder 1, a cylinder 24 including a cylinder tube 22, a head cover 3, a piston 25 disposed in the cylinder 24, and a bottom chamber 24 defined in the cylinder 24 by the piston 25.
a, a rod-side chamber 24b, oil passages 26 and 27, a connecting portion 28 connected to a boom 41 shown in FIG. 6, and a connecting portion 29 connected to a revolving unit 40 shown in FIG.

Note that P shown in FIG.
A pump for supplying pressure oil to each of the pumps 1a, T is a tank to which return oil from the boom cylinders 1 and 1a is led, and 35 controls a flow of the pressure oil supplied from the pump P to each of the boom cylinders 1 and 1a. The direction control valves 36 and 37 are a first main line and a second main line that connect the direction control valve 35 to each of the boom cylinders 1 and 1a.

Further, as a cushion structure provided in the boom cylinders 1 and 1a having the above-described basic structure, for example, as a cushion structure of the first boom cylinder 1, the cushion structure is fitted to a connecting portion between the piston 5 and the rod 5a. A cushion ring 12 constituting a member and an insertion hole formed on the head cover 3 and having an inner diameter slightly larger than the outer diameter of the cushion ring 12 so that the cushion ring 12 can be inserted when the rod 5a extends. And a hole 3a. During a cushion stroke performed by the rod 5a extending, the cushion chamber is formed by the surface of the piston 5 located on the head cover 3 side, the end of the head cover 3 facing this surface, and the inner wall of the cylinder tube 2. Is formed.

Similarly, the cushion structure of the second boom cylinder 1a is fitted to the connecting portion between the piston 25 and the rod 25a, and is formed on the cushion ring 32 constituting the cushion member and the head cover 23. It has an inner diameter slightly larger than the diameter, and when the rod 25a extends, the cushion ring 3
And an insertion hole 23a that allows the insertion of the rod 5
A cushion chamber is formed by the surface portion of the piston 25 located on the head cover 23 side, the end portion of the head cover 23 facing this surface portion, and the inner wall of the cylinder tube 32 during the cushion stroke performed by the extension operation of “a”. It has become. For each of the above configurations,
It is equivalent to that shown in FIGS.

In the first embodiment, in particular, there is provided a communicating means for communicating the respective cushion chambers of the boom cylinders 1 and 1a. This communication means is provided in each of the first boom cylinder 1 and the second boom cylinder 1a,
One end communicates with each cushion chamber of the boom cylinders 1 and 1a, for example, the rod-side chambers 4b and 24b, and the other end opens to the outside of the boom cylinders 1 and 1a. A communication pipe 52 is provided for connecting the pipes 50 and 51 to each other.

The cushioning operation in the first embodiment having the above-described configuration will be described below. The operation until the cushion stroke is started is described in FIGS.
1 is the same as that shown in FIG. First, this operation will be described repeatedly.

For example, from the state shown in FIG.
Is switched to the right position, the pressure oil of the pump P
5 to the first main line 36, and from the oil passages 6, 26 of the boom cylinders 1, 1a to the bottom side chambers 4a, 2a.
4a. Thereby, the pistons 5, 25 move leftward in FIG. 1, that is, move in the direction approaching the head covers 3a, 23a, and move integrally in the direction in which the rods 5a, 25a extend. The return oil from the rod-side chambers 4b, 24b is guided to the oil passages 7, 27, the second main conduit 37, and is returned to the tank T via the direction control valve 35.

In the state where the rods 5a and 25a are gradually extended, for example, the rod 5a of the first boom cylinder 1 is moved closer to the stroke end at the time of extension than the rod 25a of the second boom cylinder 1a. Shall be reached. In this state, as shown in FIG.
The cushion ring 12 starts to enter the insertion hole 3a of the head cover 3, and a cushion stroke is started. When the cushion ring 12 enters the insertion hole 3a in this manner, the cross-sectional area of the flow path from the rod-side chamber 4b to the oil path 7 becomes smaller than the diameter difference between the outer diameter of the cushion ring 12 and the inner diameter of the insertion hole 3a. It changes to the cross-sectional area, and the flow path is in a state of being narrowed. Therefore, the amount of the return oil to the tank T decreases, and a cushion pressure is generated in the rod side chamber 4b. That is, the inside of the rod-side chamber 4b forms a cushion chamber.

At this time, the pressure of the rod-side chamber 4b forming the cushion chamber is guided to the oil passage 51 via the oil passage 50 and the connecting pipe line 52, and further the second boom cylinder 1
a is guided into the rod side chamber 24b. That is,
The pressure in the rod-side chamber 4b forming the cushion chamber of the first boom cylinder 1 and the pressure in the rod-side chamber 24b forming the cushion chamber of the second boom cylinder 1a become the same pressure. 1a substantially equally absorbs the inertial force of the boom 41 shown in FIG. Therefore, it is possible to avoid a situation in which a high cushion pressure is generated only in the rod-side chamber 4b of the first boom cylinder 1.

The movement distance of the cushion rings 12, 32 from the state shown in FIGS. 2 to 3 corresponds to a cushion stroke section. As the pistons 5, 25 approach the ends of the head covers 3, 23 while the cushion rings 12, 32 move in these cushion stroke sections, the cushion pressure in the cushion chamber gradually increases, and the cushion pressure thus increased. As a result, the inertial force acting on the boom cylinders 1 and 1a is absorbed as described above, the operating speed is reduced, and the pistons 5 and 25 come into gentle contact with the ends of the head covers 3 and 23. In this way,
The impact of the cushion structure of both the boom cylinders 1 and 1a can be reduced.

When the boom cylinders 1 and 1a extend as described above, the boom 41 shown in FIG.
Performs an upward turning operation, that is, a boom raising operation.

When the directional control valve 35 shown in FIG. 1 is switched to the left position, the pressure oil of the pump P is supplied to the second main line 3
7, oil is supplied to the oil passages 7, 27 of the boom cylinders 1, 1a, and return oil of the boom cylinder 1, 1a is supplied to the oil passages 6, 26
Returned to the tank T via the first main line 36, the rod 5a,
The operation of contracting 25a is performed, and the downward rotation operation of the boom 41, that is, the boom lowering is performed. In the first embodiment, the cushion structure at the time of contraction is not provided. However, a cushion structure equivalent to the cushion structure at the time of extension may be provided if necessary, or a cushion structure different from the first embodiment. May be provided.

In the first embodiment configured as described above, even if the cushion pressure rises first in one of the boom cylinders 1 and 1a, the oil passages 50 and 51 and the connecting pipe 5
2, the pressures in the rod-side chambers 4b and 24b are made the same, and the inertia force of the boom 41 shown in FIG. 6 can be almost equally absorbed by both the boom cylinders 1 and 1a. , 1a can be prevented from becoming too high. As a result, the cylinder tubes 2 and 2
2 can be suppressed, and breakage of these cylinder tubes 2 and 22 can be prevented. Along with this, it is possible to suppress the high pressure from acting on the O-rings 3b, 23b, and it is possible to prevent the O-rings 3b, 23b from being damaged. Further, it is possible to prevent the occurrence of oil leakage due to the damage of these O-rings 3b, 23b.

Since both the boom cylinders 1 and 1a can absorb the inertial force of the boom 41 shown in FIG. 6, the inertial force can be reliably absorbed. 3,23
Can be suppressed, and the boom cylinders 1, 1 due to such an impact can be suppressed.
a, or damage to the front work machine including the boom 41 shown in FIG. 6 can be reliably prevented.

Further, both the boom cylinders 1 and 1a absorb the inertial force of the boom 41 shown in FIG. Of the boom 41 can be suppressed, and the boom 41 can be prevented from being damaged by such a twist.

FIGS. 4 and 5 are explanatory views showing a second embodiment of the present invention. FIG. 4 is an overall configuration diagram including a cross-sectional portion, and FIG.
It is operation | movement explanatory drawing which shows the state of the principal part at the time of the end of a cushion stroke in embodiment.

The second embodiment is particularly applicable to the second main conduit 37.
And a branch pipe 53 communicating with a communication pipe 52 connecting the oil paths 50 and 51, and a pressure oil from the second main pipe 37 toward the communication pipe 52 provided in the branch pipe 53. A check valve 54 is provided to allow the flow and prevent the flow of the pressurized oil from the communication pipe 52 to the second main pipe 37. Other configurations are the same as those of the above-described first embodiment.

In the second embodiment thus constructed, the same operation and effect as those of the above-described first embodiment are obtained, and the directional control valve 35 is switched to the right position in FIG. 4 to extend the boom cylinders 1 and 1a. To the stroke end while performing the cushioning operation.
When it is attempted to change from the extension operation mode to the contraction operation mode by the switching operation to the left position in FIG. 4, the pressure oil is guided from the pump P to the second main line 37 via the directional control valve 35, and further. While being supplied from the second main line 37 directly into the boom cylinders 1 and 1a via the oil passages 7 and 27, the pressure oil guided to the second main line 37 is supplied to the branch line 53 and the connecting line 52. Boom cylinder 1, 1a via oil passages 50, 51
The pistons 5 and 25 of the boom cylinders 1 and 1a can be operated at a high speed by the combined pressure oil and can be quickly changed to a desired contraction operation mode. Therefore, work efficiency of excavation work and the like performed via the boom cylinders 1 and 1a can be improved.

Although the cushion structure of the boom cylinders 1 and 1a for driving the boom 41 shown in FIG. 6 has been described above as an example, the present invention is limited to the cushion structure of the boom cylinders 1 and 1a. Instead, the present invention is applicable to a cushion structure of a plurality of hydraulic cylinders that drive one work implement.

[0057]

As described above, according to the invention of each claim of the present application, even if a cushion pressure is first raised on one of a plurality of hydraulic cylinders for driving one work implement, the work implement is not affected. The inertial force can be almost equally absorbed by each of the plurality of hydraulic cylinders, and the occurrence of a situation in which the cushion pressure of only a specific one of the hydraulic cylinders becomes too high as in the past. Can be prevented. Thereby, the expansion of the cylinder tube due to the cushion pressure, which has conventionally occurred, can be suppressed, and the cylinder tube can be prevented from being damaged. Along with this, it is possible to suppress the high pressure from acting on the O-ring as in the related art, and it is possible to prevent the occurrence of oil leakage due to damage to these O-rings.

Further, since the inertial force of the work implement can be absorbed by the plurality of hydraulic cylinders, the inertial force can be reliably absorbed, and the piston collides with the head cover at the cylinder stroke end which has conventionally occurred. A situation in which an impact is generated can be suppressed, and therefore, damage to the hydraulic cylinder, the working tool, and a construction machine including the working tool due to such a shock can be reliably prevented.

Further, since the plurality of hydraulic cylinders absorb the inertial force of the work implement, it is possible to secure a supporting force around the work implement that does not cause the work implement to be twisted. In addition, it is possible to prevent the working tool from being damaged due to the above-described twist.

In particular, according to the third aspect of the present invention, when the plurality of hydraulic cylinders change from the extending operation mode to the contracting operation mode to the next operation mode, the main pipe is changed. The hydraulic oil supplied directly into the hydraulic cylinder from the path and the hydraulic oil supplied into the hydraulic cylinder via the branch line and the check valve cause the pistons of these hydraulic cylinders to move at high speed. It can be activated and can be quickly changed to the corresponding operation mode.

[Brief description of the drawings]

FIG. 1 is a first view of a cushion structure of a hydraulic cylinder according to the present invention.
FIG. 1 is an overall configuration diagram including a cross section showing an embodiment.

FIG. 2 is an operation explanatory diagram showing a state of a main part at the start of a cushion stroke in the first embodiment shown in FIG. 1;

FIG. 3 is an operation explanatory diagram showing a state of main parts at the end of a cushion stroke in the first embodiment shown in FIG. 1;

FIG. 4 is an overall configuration diagram including a cross section showing a second embodiment of the present invention.

FIG. 5 is an operation explanatory view showing a state of a main part at the end of a cushion stroke in the second embodiment shown in FIG. 4;

FIG. 6 is a perspective view showing a hydraulic excavator as an example of a construction machine provided with a cushion structure of a hydraulic cylinder to which the present invention is applied.

7 is an overall configuration diagram including a cross-sectional portion showing an example of a cushion structure of a conventional hydraulic cylinder provided in the hydraulic excavator shown in FIG.

FIG. 8 is a side view showing the appearance of one of two boom cylinders forming the cushion structure shown in FIG. 7;

FIG. 9 is an operation explanatory view showing a cross section of a main part of the boom cylinder shown in FIG. 8;

FIG. 10 is an operation explanatory diagram showing a state of a main part at the start of a cushion stroke in the boom cylinder shown in FIG. 8;

11 is an operation explanatory view showing a state of a main part at the end of a cushion stroke in the boom cylinder shown in FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st boom cylinder (hydraulic cylinder) 1a 2nd boom cylinder (hydraulic cylinder) 2 Cylinder tube 3 Head cover 3a Insertion hole 3b O-ring 4 Cylinder 4a Bottom side chamber 4b Rod side chamber 5 Piston 5a Rod 6 Oil path 7 Oil path 8 Connecting part 9 Connecting part 12 Cushion ring 22 Cylinder tube 23 Head cover 23a Insertion hole 23b O-ring 24 Cylinder 24a Bottom side chamber 24b Rod side chamber 25 Piston 25a Rod 26 Oil path 27 Oil path 28 Connection part 29 Connection part 32 Cushion ring 35 Direction control valve 36 First main line 37 Second main line 40 Revolving body 41 Boom 42 Arm 43 Bucket 44 Arm cylinder 45 Bucket cylinder 50 Oil path (communication means) 51 Oil path (communication means) 5 2 Communication line (communication means) 53 Branch line 54 Check valve P Pump T Tank

Continuing on the front page (72) Inventor Roh Akitoku Futami, Tsuchiura Plant, Tsuchiura-shi, Ibaraki Pref. JJ02 3J069 AA50 CC05

Claims (5)

[Claims] 1. A plurality of hydraulic cylinders for driving one work implement are provided, and a shock caused by a piston moving in accordance with the operation mode is reduced near each stroke end in the same operation mode of the plurality of hydraulic cylinders. A cushion structure for a hydraulic cylinder forming a cushion chamber to be provided, wherein a communication means for communicating the cushion chambers of the plurality of hydraulic cylinders is provided. 2. The hydraulic device according to claim 1, wherein the communication means is provided in each of the plurality of hydraulic cylinders, one end of which communicates with each of the cushion chambers of the plurality of hydraulic cylinders, and the other end of which opens to the outside of the hydraulic cylinder. 2. The cushion structure for a hydraulic cylinder according to claim 1, further comprising a road and a communication pipe connecting the oil paths. 3. A branch line for introducing pressure oil to the hydraulic cylinder, a branch line branching from the main line and communicating with the communication line, and a branch line provided in the branch line, and The check valve according to claim 1, further comprising a check valve that allows a flow of the pressure oil in a direction of the communication line and blocks a flow of the pressure oil from the communication line in the direction of the main line. Hydraulic cylinder cushion structure. 4. The cushion structure for a hydraulic cylinder according to claim 1, wherein the operation mode is an operation mode for extending the hydraulic cylinder. 5. The hydraulic excavator, wherein the work implement is a boom, and the plurality of hydraulic cylinders are a first boom cylinder and a second boom cylinder for driving the boom. A cushion structure for a hydraulic cylinder according to any one of claims 1 to 4.