JPH09317717A - Oil pressure cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a weld zone and improve productivity by extending a cylindrical part from a valve case, which is arranged in a space in a rod shaft center core part, to the top end side and providing a check valve in the bottom base part of the case. SOLUTION: A cylindrical body which is arranged in a hollow part formed in the shaft center part of a rod body 2 is set by a top end side extension cylinder part 12a of a valve case 12 which penetrates the central part of a piston body 3 from the bottom end side. The valve case 12 incorporates a check valve 10 in the bottom base part 12b, the bottom base part 12b is inserted in a through hole 3b opened in the central part of the piston body 3 with a seal member 13 arranged thereto, the top end side extension cylinder part 12a is so arranged as to project upward of the piston body 3, and the bottom end of the valve case 12 is locked to a stopper 14. The valve case 12 can be thus separated from the piston body 3 by removal of the stopper 14 and the welding of the cylinder body to the piston body is eliminated so that welding spatter, scale generation, etc., can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a hydraulic cylinder for a forklift.

[0002]

2. Description of the Related Art A hydraulic cylinder for a forklift is set so as to expand when supplied with hydraulic pressure and contract when it receives its own weight or load. When it is fully expanded, a so-called cushion function is exerted and a seal member is used. It is said that consideration will be given to ensuring durability.

That is, for example, a hydraulic cylinder as a conventional example shown in FIG. 3 has a cylinder body 1 as a lower end side member and a rod as an upper end side member, the lower end side of which is retractably inserted into the cylinder body 1. A hydraulic chamber R1 having a body 2 and slidably accommodated in the cylinder body 1 and communicating with an external hydraulic supply / discharge source (not shown in the figure only by P) in the cylinder body 1. A piston body 3 that divides the rod body is connected to the lower end of the rod body 2 to form a ram type.

By the way, the upper end which is the open end of the cylinder body 1 is sealed by the shaft sealing member 4, and a through hole (shown in FIG. 1) which is opened in the shaft core portion of the shaft sealing member 4 and allows the rod body 2 to be inserted therethrough. No)
The bush 5, the oil seal 6 and the dust seal 7 are arranged in series on the inner circumference of the bush 5, and the respective inner circumferences of the bush 5, the oil seal 6 and the dust seal 7 are in sliding contact with the outer circumference of the rod body 2. .

A piston ring 8 and upper and lower oil seals 9 are arranged on the outer circumference of the piston body 3, and the outer circumferences of the piston ring 8 and the oil seal 9 are in sliding contact with the inner circumference of the cylinder body 1, respectively. I am trying.

On the other hand, the rod body 2 is formed so as to have a cylindrical hollow portion (not shown) at the shaft core portion, the upper end of which is previously closed and the lower end of which is closed by the piston body 3. The empty portion is formed between the outer circumference of the rod body 2 and the inner circumference of the cylinder body 1 via the communication hole 2a opened at the lower end side of the rod body 2 and the orifice 2b opened below the communication hole 2a. The piston body 3 is communicated with the rear chamber R2.
It is said that the hydraulic chamber R1 is communicated with the check valve 10 located at.

The lower part of the empty space and the rear side chamber R2 is an oil chamber (not shown) and the upper part thereof is an air chamber (not shown) with the oil surface O as a boundary. The communication hole 2a opened at 2 allows communication between the empty oil chamber and the oil chamber of the rear side chamber R2 when the hydraulic cylinder expands and contracts, and is provided on the inner peripheral side of the bush 5 when the hydraulic cylinder is fully extended. It is positioned so that it will be present (FIG. 4).
reference).

Further, the lower orifice 2b is set so as to communicate with the rear side chamber R2 at all times via the annular gap 3a formed in the inner periphery of the upper end of the piston body 3, that is, even when the hydraulic cylinder is fully extended. Has been done.

Further, the check valve 10 is of a ball type having a steel ball 10a and a spring 10b for urging the steel ball 10a from the rear side, and is a relief valve which is opened by hydraulic action from the empty side. Is set to work as well.

By the way, a cylindrical body 11 of a proper length, that is, a length of which the upper end is positioned above the communication hole 2a for opening the rod body 2 is erected in the hollow portion,
By arranging the cylindrical body 11 upright, the empty portion is defined inside and outside the cylindrical body 11, and the amount of oil is secured at the same level between the outer peripheral side of the cylindrical body 11 and the rear side chamber R2.

Therefore, according to this conventional hydraulic cylinder, when the hydraulic pressure from the external hydraulic pressure supply / discharge source P is supplied to the hydraulic chamber R1 in the most contracted state shown in FIG. It is pushed up in the body 1 and thus the rod body 2 performs an extension operation protruding from the inside of the cylinder body 1.

At this time, the oil in the rear side chamber R2 flows into the empty portion, that is, the outer peripheral side of the cylinder body 11 defined by the cylinder body 11 through the communication hole 2a opened in the rod body 2. ,
In addition, the air in the rear side chamber R2 flows into the void through the communication hole 2a.

Then, as the extension operation proceeds, the communication hole 2
When a comes to exist on the inner peripheral side of the bush 5, the oil in the rear side chamber R2, that is, the oil that becomes trapped between the upper end of the piston body 3 and the lower end of the shaft sealing member 4, is located at the lower orifice. The oil flows into the empty space via 2b, and the rising speed of the piston body 3 in the cylinder body 1 is slowed by the resistance when the oil passes through the orifice 2b.

Further, at this time, the orifice 2
Oil that cannot pass through b will flow into the void through the annular gap formed between the inner periphery of the bush 5 and the outer periphery of the rod body 2 and the communication hole 2a. Even when the resistance is passed, the rising speed of the piston body 3 in the cylinder body 1 is delayed.

As a result, when the hydraulic cylinder is fully extended,
A so-called cushion function is exerted, and the upper end of the piston body 3 is in the most extended state while being prevented from colliding with the lower end of the shaft sealing member 4 in advance (see FIG. 4).

When the supply of the hydraulic pressure to the hydraulic chamber R1 is stopped and the hydraulic pressure in the hydraulic chamber R1 is released, the rod body 2 is loaded by the weight of the rod body 2 or the load acting on the rod body 2. The piston body 3 descends inside the cylinder body 1 to discharge the oil in the hydraulic chamber R1 to the hydraulic pressure supply / discharge source P side, and the hydraulic cylinder is contracted. Will be.

At the time of reversing the contraction operation, the oil from the empty space flows into the rear side chamber R2 through the communication hole 2a and the orifice 2b, and the occurrence of a so-called vacuum phenomenon in the rear side chamber R2 is prevented. It

When the communication hole 2a comes out of the inner peripheral side of the bush 5, the oil from the empty space will flow into the rear side chamber R2 through the communication hole 2a, so that the hydraulic cylinder can be quickly operated. Different contraction operation will be realized.

On the other hand, when the expansion and contraction of the hydraulic cylinder, that is, the supply of the hydraulic pressure to the hydraulic chamber R1 is repeated, the outer circumference of the oil seal 9 disposed on the outer circumference of the piston body 3 and the cylinder body 1 are repeated.
The oil gradually flows through the inner circumference of the
2

As a result, when the hydraulic cylinder is repeatedly used, the hydraulic pressure in the rear side chamber R2 gradually increases, but the hydraulic pressure in the rear side chamber R2 becomes higher than the hydraulic pressure in the hydraulic chamber R1, and the pressure difference is checked. When the set pressure of the valve 10 is reached, the check valve 10 is opened and released to the hydraulic chamber R1 though the void.

As a result, the abnormal high pressure in the rear chamber R2 is released before the oil seal 6 disposed on the open end side of the cylinder body 1 is damaged, so that the durability of the so-called seal member can be guaranteed. become.

By the way, by disposing the cylindrical body 11 whose upper end extends upward beyond the communication hole 2a in the empty space, the check valve 10 is opened and the oil on the empty space side is kept in the hydraulic chamber. When flowing out to R1, it prevents the oil on the empty side from flowing out into the hydraulic chamber R1 without limitation, that is, the cylinder 11
It is possible to leave the oil in the outer peripheral side and the back side chamber R2 communicating with the outer peripheral side through the communication hole 2a.

[0023]

However, in the above-described conventional hydraulic cylinder, there is a fear that the following inconvenience cannot be avoided.

That is, in the above-described conventional hydraulic cylinder, the lower end of the tubular body 11 is connected to the piston body 3 by welding (indicated by symbol M in FIG. 3) so as to be in a desired standing state. Although it is supposed to be placed, welding spatter and oxide scale are generated during this welding.

Therefore, in order to completely remove the weld spatter and oxide scale, so-called labor-intensive work is indispensable, which makes it difficult to improve productivity and reduce cost.

If the welding spatter and the oxide scale are not completely removed, the welding spatter and the oxide scale are mixed in the oil. For example, when the hydraulic cylinder is fully extended, the inner circumference of the bush 5 and the rod body 2 are prevented. It penetrates into the annular gap formed between the outer periphery and the outer periphery and adheres to the inner periphery of the bush 5, which causes a galling phenomenon with the rod body 2.

Further, when the galling phenomenon occurs, the outer periphery of the rod body 2 is damaged, and the damage phenomenon occurs on the inner periphery of the oil seal 6 and the dust seal 7. As a result, the sealing property is deteriorated.

Further, when welding spatter or oxide scale penetrates into the check valve 10 part and particularly adheres to a so-called seat part where the steel ball 10a is seated on and off, oil leakage in the check valve 10 part is caused. As a result, the malfunction of the hydraulic cylinder may be caused.

Further, by connecting the lower end of the cylindrical body 11 to the piston body 3 by welding, when the distortion due to welding heat is introduced into the piston body 3, especially, the steel ball 10a in the check valve 10 is separated. When the seat portion to be seated is distorted, the check valve 1
You can't expect zero operation at all.

The present invention was devised in view of the above-mentioned circumstances, and an object thereof is to prevent the generation of welding spatter and oxide scale, and to improve the productivity and reduce the cost. To provide a ram-type hydraulic cylinder that is optimal for a forklift truck, which can guarantee the function of a check valve having the function of a relief valve while ensuring the sealing function. Is.

[0031]

In order to achieve the above-mentioned object, the structure of the present invention is configured such that a lower end side member is a cylinder body, and an upper end side member is a lower end side that can be inserted into and retracted from the cylinder body. A ram having a rod body and a piston body that is slidably accommodated in the cylinder body and defines a hydraulic chamber that communicates with an external hydraulic pressure supply / discharge source in the cylinder body and that is connected to the lower end of the rod body. As it is set to type,
The rod body has a cylindrical hollow portion whose upper end is closed and the lower end is closed by a piston body in the shaft core portion, and the hollow portion is provided on the lower end side of the rod body with the outer periphery of the rod body through a communication hole opened. It is connected to the rear side chamber formed between the inner circumference of the cylinder body and the hydraulic chamber via a check valve arranged in the piston body, and the void is located above the communication hole at the upper end. In a hydraulic cylinder in which a cylinder to be determined is erected on the shaft core, the cylinder defines an empty space inside and outside the cylinder, and the lower end of the cylinder is opposed to the check valve, the cylinder is It is set by the upper extension cylinder part of the valve case that penetrates the center part of the piston body from the lower end side, and the poppet type check valve facing the upper extension cylinder part is arranged in the lower end base part of the valve case. Suppose

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the drawings. The hydraulic cylinder according to the present invention is basically the same as the hydraulic cylinder as the conventional example (see FIG. 3). It is configured.

Therefore, the same portions of the configuration are denoted by the same reference numerals in the drawings unless necessary, and detailed description thereof will be omitted. Hereinafter, the features of the present invention will be mainly described. Explained.

First, in a hydraulic cylinder according to an embodiment of the present invention, as shown in FIG. 1, a cylinder body disposed in an empty space formed in the axial center portion of the rod body 2, that is, the above-mentioned conventional body. A cylinder body corresponding to the cylinder body 11 (see FIG. 3) in the example is set as an upper end side extension cylinder portion 12a of the valve case 12 which penetrates the center portion of the piston body 3 from the lower end side.

The valve case 12 has a lower end base 12b.
It has a check valve 10 inside, and is set in a manner of a valve assembly, so to speak. In the illustrated embodiment, the lower end base portion 12b seals in a through hole 3b opened in the central portion of the piston body 3. It is inserted under the distribution of the member 13, and is arranged so that the upper end side extension cylindrical portion 12a is projected upward from the upper end of the central portion of the piston body 3.

By the way, the lower end of the valve case 12, that is, the lower end of the lower end base 12b is locked by the stopper 14 fitted on the inner circumference of the through hole 3b. It will be fixedly fixed in.

The check valve 10 includes a valve case 12
Inside, it is arranged so as to face the upper end side extension cylinder portion 12a, and in the illustrated embodiment, it is set to a poppet type having a poppet 10c biased by a spring 10b from the rear side. .

Incidentally, in the poppet 10c, the lower end base portion 12b is formed by expanding the inner circumference of the upper end side extension cylinder portion 12a.
It is slidably mounted on a sliding portion (not shown) formed inside, that is, it is vertically movable, and its tip is set to face the inside of the upper extension cylinder portion 12a. It is set so that the oil in the upper extension cylinder portion 12a flows out into the hydraulic chamber R1 when the barrel retreats.

The spring 10b has its upper end brought into contact with the back side of the poppet 10c, while its lower end, the base end, is locked to a spring receiver 10d arranged in a fixed state.
The lower end of the spring receiver 10d is locked by the stopper 10e.

Therefore, in the valve case 12, the stopper 10e can be removed so that the spring 10b and the poppet 10c can be taken out, that is, the check valve 10 can be disassembled, and the parts can be replaced as well as the poppet. 10c is a steel ball 10a (Fig. 3
It is also possible to change the check valve 10 to a ball type, which is economically advantageous by replacing the check valve 10 with the ball type.

When the check valve 10 is set to the poppet type as in this embodiment, the centering of the poppet 10c is facilitated, and the seating property with respect to the seat portion, that is, the seating property is improved. Therefore, it is advantageous in that stable functions can be expected.

Further, in this valve case 12,
The stopper 14 can be removed from the piston body 3 so that the valve assembly can be replaced, and the cylinder body corresponding to the cylinder body 11 can be installed in the empty space. It ’s enough
Since the welding to the piston body 3 becomes unnecessary, there is no need to worry about the generation of welding spatter and oxide scale accompanying the welding and the distortion of the piston body 3 due to the welding heat.

By the way, the upper extension cylinder portion 12a of the valve case 12 is set so as to have an outer diameter of approximately 1/3 of the inner diameter of the empty portion, as can be understood from the drawings. However, as compared with the case of the above-mentioned conventional example, this increases the volume defined on the outer peripheral side of the cylindrical body having the same wall thickness, that is, the upper end side extended cylindrical portion 12a by about 50%. It becomes possible to

Therefore, in the illustrated embodiment, welding spatter and oxide scale are not mixed in the oil, but even when contaminants or the like instead of this are present in the oil, these contaminants and the like extend above the upper end side. The cylindrical portion 12a is likely to accumulate in a so-called chamber portion where the volume on the outer peripheral side is increased, so that contaminants or the like enter the check valve 10 portion or between the inner periphery of the bush 5 and the outer periphery of the rod body 2. It is possible to significantly reduce the chances of breaking into.

Further, according to the valve case 12, since it is, so to speak, one part, it is possible to reduce the number of parts as compared with the case where the cylindrical body 11 is a separate body as in the above-mentioned conventional example. In addition to the need for welding work and welding spatter removal work, the cost can be significantly reduced.

The following consideration has been given to the hydraulic cylinder according to this embodiment formed as described above.

That is, first, the empty portion formed in the axial center portion of the rod body 2 is the orifice 2b in the above-mentioned conventional example.
It is assumed that the rear side chamber R2 formed between the outer circumference of the rod body 2 and the inner circumference of the cylinder body 1 is communicated with the orifice 15a corresponding to (see FIG. 3). In the embodiment, it is formed on the shaft core of the set screw 15 screwed to the cylinder body 1.

As described above, since the orifice 15a is formed in the set screw 15 and the set screw 15 is screwed to the cylinder body 1, the set screw 15 having an appropriately set orifice diameter is selected. It becomes possible to dispose it on the cylinder body 1, and so to speak, it becomes easy to set the orifice.

Next, in the illustrated embodiment, the piston body 3 is assumed to be connected to the rod body 2 by utilizing the snap ring 16. The lower end of the rod body 2 is the central portion of the piston body 3. In other words, as long as it is kept in contact with the upper end, when the hydraulic pressure from the outside is supplied to the hydraulic chamber R1 and the piston body 3 rises in the cylinder body 1, the rod body 2 always rises at the same time. To be done
The extension operation in this hydraulic cylinder can be realized.

Further, when the contraction operation is performed by reversing the extension operation, the rod body 2 is subjected to its own weight or load.
Since the piston body 3 is soaked in the cylinder body 1, the piston body 3 may be connected to the lower end of the rod body 2, so to speak, and at this time, it is sufficient if the snap ring 16 has a predetermined strength. become.

Therefore, when the snap ring 16 is used to connect the piston body 3 to the rod body 2 as in this embodiment, the lower end of the rod body 2 is screwed onto the piston body 3. Compared with the case of the above-mentioned conventional example, a part which is the snap ring 16 is required, and a concave groove (not shown) for accommodating the snap ring 16 is required. Since it is not necessary to form a long thread on the piston body 3, the productivity of so-called parts such as the rod body 2 and the piston body 3 can be significantly improved.

The hydraulic cylinder formed as described above basically operates in the same manner as the hydraulic cylinder as the conventional example described above.

That is, when the hydraulic pressure from the external hydraulic pressure supply / exhaust source P is supplied to the hydraulic chamber R1 in the maximum contraction state shown in FIG. 1, the hydraulic chamber R1 is extended, and the hydraulic pressure in the hydraulic chamber R1 is released. It contracts.

Then, when it approaches the maximum extension, the rod body 2
The open communication hole 2a is inserted into the inner peripheral side of the bush 5,
At this time, the oil in the rear side chamber R2 is exposed to the orifice 15a below
Alternatively, it flows into an empty portion, that is, the outer peripheral side of the upper end side extension cylindrical portion 12a of the valve case 12 through an annular gap formed between the inner periphery of the bush 5 and the outer periphery of the rod body 2, and at this time, The cushion function of will be demonstrated.

When reversing the contraction operation, the hydraulic chamber R
1, the release of the hydraulic pressure and the self-weight of the rod body 2 or the load acting on the rod body 2 start the contraction operation. This prevents the so-called vacuum phenomenon from occurring in the rear side chamber R2.

Then, when the communication hole 2a comes out of the inner peripheral side of the bush 5, oil from the empty portion flows into the rear side chamber R2 through the communication hole 2a, and the hydraulic cylinder is swiftly contracted.

On the other hand, while the hydraulic cylinder is repeatedly expanded and contracted, the oil supplied to the hydraulic chamber R1 is slightly subdivided, and the rear chamber R
2, the hydraulic pressure in the rear chamber R2 gradually increases, but this hydraulic pressure becomes higher than the hydraulic pressure supplied to the hydraulic chamber R1, and when the pressure difference reaches the set pressure of the check valve 10, The check valve 10 is opened and released to the hydraulic chamber R1.

As a result, the abnormally high pressure in the rear chamber R2 is released before the oil seal 6 disposed on the open end side of the cylinder body 1 is damaged, so that the durability of the so-called seal member is ensured.

[0059]

As described above, according to the present invention, in the valve case in which the cylindrical body disposed in the empty portion formed in the axial center portion of the rod body penetrates the central portion of the piston body from the lower end side. It is assumed that the check valve is set in the upper extension cylinder, and the check valve facing the upper extension cylinder is provided in the lower base of the valve case. That is, with this assembly, there is no need to prepare a so-called cylinder as a separate component when providing the above-mentioned cylinder, and welding work or welding spatter or oxide scale removal work that occurs during welding is no longer necessary. It is possible to improve productivity and reduce the number of parts, and also reduce costs.

Since welding is not required, there is no fear of distortion of the piston body due to welding heat.
Therefore, the disposition of the assembled check valve is not hindered.

Further, since there is no fear of generation of welding spatter or oxide scale, there is no fear of welding spatter being mixed in oil, and an annular gap formed between the inner circumference of the bush and the outer circumference of the rod body. It is possible to guarantee the durability of the sealing member without worrying about the deterioration of the sealing property caused by the intrusion of welding spatter into the.

Further, in the present invention, the check valve is set to the poppet type having the poppet urged by the spring, so that the predetermined check valve function and the relief valve are provided because of the excellent centering property of the poppet. The function will be demonstrated stably.

Further, according to the present invention, the outer diameter of the upper extension cylinder portion of the valve case is set to about 1/3 of the inner diameter of the empty portion, so that the outer circumference of the upper extension cylinder portion is set. It is possible to increase the volume defined by the above by about 50% compared to the conventional example, and even if contaminants etc. are mixed in the oil, these contaminants etc. will be It is easy for the above-mentioned contaminants to enter the check valve portion, or the annular shape formed between the inner circumference of the bush and the outer circumference of the rod body. It is possible to significantly reduce the chance of entering the gap.

Further, according to the present invention, the set screw is formed with the orifice for communicating between the empty portion in the rod body and the back side chamber formed on the outer peripheral side of the rod body. By being screwed to the cylinder body, it becomes possible to select a set screw having an appropriately set orifice diameter and dispose the set screw on the cylinder body, which makes the orifice setting easy.

Further, according to the present invention, since the piston body is connected to the rod body by using the snap ring, compared with the case where the lower end of the rod body is screwed to the piston body. , A snap ring component is required, and a groove for accommodating the snap ring is required, but it is not necessary to form a thread over a long stroke on the rod body or the piston body.
The productivity of so-called parts such as rod bodies and piston bodies can be greatly improved.

As a result, according to the present invention, welding spatter and oxide scale are not generated, which makes it possible not only to improve productivity and reduce cost, but also to ensure the sealing function. There is an advantage that the function of the check valve having the function of the relief valve can be guaranteed, and it is most suitable for a ram type forklift.

[Brief description of drawings]

FIG. 1 is a partial vertical sectional view showing a hydraulic cylinder according to an embodiment of the present invention in a most contracted state.

FIG. 2 is a partial vertical cross-sectional view showing the hydraulic cylinder of FIG. 1 in a most extended state.

FIG. 3 is a partial vertical cross-sectional view showing a hydraulic cylinder as a conventional example similar to FIG.

FIG. 4 is a partial vertical cross-sectional view showing the hydraulic cylinder of FIG. 3 similarly to FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 cylinder body 2 rod body 2a communication hole 3 piston body 4 pipe body 10 check valve 10c poppet constituting a check valve 12 valve case 12a upper end side extension cylinder portion constituting a cylinder body 12b lower end base portion P hydraulic pressure supply / discharge source R1 hydraulic chamber R2 back room

Claims (1)

[Claims] 1. A cylinder body serving as a lower end side member, a rod body serving as an upper end side member, the lower end side of which is inserted into and retractable from the cylinder body, and a slidably housed in the cylinder body and external to the cylinder body. A piston body connected to the lower end of the rod body and defining a hydraulic chamber communicating with the hydraulic pressure supply / discharge source of, and the rod body closes the upper end and the lower end of the piston body. The shaft core has a cylindrical hollow portion that is closed by the body, and the hollow portion is formed between the outer circumference of the rod body and the inner circumference of the cylinder body through a communication hole opened at the lower end side of the rod body. Of the rear side chamber of the piston and the hydraulic chamber through a check valve located in the piston body, and
A hollow cylinder is positioned upright above the communication hole so that the hollow portion stands upright on the shaft core. The hollow body defines the hollow portion inside and outside of the hollow cylinder, and the lower end of the hollow cylinder checks the above. In the hydraulic cylinder that faces the valve, the cylinder is set in the upper extension cylinder of the valve case that penetrates the center of the piston from the lower end, and the upper extension cylinder is in the lower base of the valve case. Cylinder with poppet type check valve located opposite to