JP3635787B2 - Hydraulic cylinder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a hydraulic cylinder used for a forklift.
[0002]
[Prior art]
The hydraulic cylinder used for forklifts is set to extend when it is supplied with hydraulic pressure and to operate under contraction with its own weight or load, but at its maximum extension, the so-called cushion function is exhibited and the durability of the seal member is guaranteed. To be considered.
[0003]
That is, for example, a hydraulic cylinder as a conventional example shown in FIG. 3 includes a cylinder body 1 which is a lower end side member, and a rod body 2 which is an upper end side member and is inserted into the cylinder body 1 so that the lower end side can be projected and retracted. A hydraulic chamber R1 that is slidably accommodated in the cylinder body 1 and that communicates with an external hydraulic supply / exhaust source (not shown) is defined in the cylinder body 1. The piston body 3 is connected to the lower end of the rod body 2 and is set in a ram shape.
[0004]
Incidentally, the upper end which is the opening end of the cylinder body 1 is sealed by the shaft sealing member 4, and a through hole (not shown) which is opened in the shaft core portion of the shaft sealing member 4 and through which the rod body 2 is inserted. The bush 5, the oil seal 6 and the dust seal 7 are arranged in series on the inner circumference, and the 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, respectively.
[0005]
In addition, a piston ring 8 and upper and lower oil seals 9 are disposed on the outer periphery of the piston body 3, and each outer periphery of the piston ring 8 and the oil seal 9 is in sliding contact with the inner periphery of the cylinder body 1.
[0006]
On the other hand, the rod body 2 is formed so as to have a cylindrical hollow portion (not shown) whose upper end is closed in advance and whose lower end is closed by the piston body 3 in the shaft core portion. The rear side chamber R2 formed between the outer periphery of the rod body 2 and the inner periphery of the cylinder body 1 through 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. And a fluid pressure chamber R1 through a check valve 10 disposed on the piston body 3.
[0007]
The empty portion and the rear side chamber R2 are respectively an oil chamber (not shown) at the lower side and an air chamber (not shown) at the upper side with the oil surface O as a boundary. The bored communication hole 2a 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 resides on the inner peripheral side of the bush 5 when the hydraulic cylinder is fully extended. It is positioned so as to be (see FIG. 4).
[0008]
Further, the lower orifice 2b is set so as to always communicate with the rear side chamber R2 through the annular gap 3a formed on the inner periphery of the upper end of the piston body 3, that is, when the hydraulic cylinder is extended most. .
[0009]
Further, the check valve 10 is set in a ball shape having a steel ball 10a and a spring 10b for energizing the steel ball 10a from the back side, and functions as a relief valve that is opened by a hydraulic action from the air side. It is set to be.
[0010]
By the way, a cylinder 11 having an appropriate length, i.e., a length of which the upper end is positioned above the communicating hole 2a opened in the rod body 2 is erected. By erecting, the empty part 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 back side chamber R2.
[0011]
Therefore, according to this conventional hydraulic cylinder, when the hydraulic pressure from the external hydraulic supply / discharge source P is supplied to the hydraulic chamber R1 in the most contracted state shown in FIG. Therefore, the rod body 2 is extended to project from the cylinder body 1.
[0012]
At this time, the oil in the rear side chamber R2 flows into the hollow portion, that is, the outer peripheral side of the cylinder 11 defined by the cylinder 11 through the communication hole 2a opened in the rod body 2, and The air in the back side chamber R2 flows into the empty portion through the communication hole 2a.
[0013]
When the extension operation proceeds and the communication hole 2a is present on the inner peripheral side of the bush 5, the oil in the rear side chamber R2, that is, between the upper end of the piston body 3 and the lower end of the shaft seal member 4 is used. The oil to be trapped in the cylinder flows into the empty portion through the lower orifice 2b, and the rising speed of the piston body 3 in the cylinder body 1 is slow due to the resistance when the oil passes through the orifice 2b. Will be converted.
[0014]
At this time, oil that cannot pass through the orifice 2b flows into the empty space 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 oil passes through the annular gap, the rising speed of the piston body 3 in the cylinder body 1 is slowed down.
[0015]
As a result, when the hydraulic cylinder is fully extended, a so-called cushion function is exhibited, and the piston 3 is fully extended while being prevented from colliding with the lower end of the shaft seal member 4 in advance (see FIG. 4).
[0016]
When the supply of 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 moved to the cylinder body by the weight of the rod body 2 or a load acting on the rod body 2. 1, the piston body 3 descends in the cylinder body 1 and the oil in the hydraulic chamber R1 is discharged to the hydraulic supply / discharge source P side, and the hydraulic cylinder is contracted. Become.
[0017]
At the time of reversal to the contraction operation, oil from the empty portion flows into the back side chamber R2 through the communication hole 2a and the orifice 2b, and the so-called vacuum phenomenon is prevented from occurring in the back side chamber R2.
[0018]
When the communication hole 2a comes out from the inner peripheral side of the bush 5, the oil from the empty portion flows into the rear side chamber R2 through the communication hole 2a, and the hydraulic cylinder quickly contracts. Will be realized.
[0019]
On the other hand, when expansion and contraction of the hydraulic cylinder, that is, supply of hydraulic pressure to the hydraulic chamber R <b> 1 is repeated, a slight amount is passed between the outer periphery of the oil seal 9 disposed on the outer periphery of the piston body 3 and the inner periphery of the cylinder body 1. Then, oil flows into the back side chamber R2.
[0020]
As a result, if the use of the hydraulic cylinder is repeated, 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 between the check valve 10 When the set pressure is reached, through the empty portion, the check valve 10 is opened and released to the hydraulic chamber R1.
[0021]
As a result, the abnormally high pressure in the rear side chamber R2 is released before the oil seal 6 disposed on the opening end side of the cylinder body 1 is damaged, and the durability of the so-called seal member can be ensured.
[0022]
Incidentally, since the cylinder 11 whose upper end extends upward beyond the communication hole 2a is disposed in the empty portion, the check valve 10 is opened, and the oil on the empty portion side flows into the hydraulic chamber R1. When doing so, the oil on the empty side is prevented from flowing into the hydraulic chamber R1 indefinitely, that is, the oil is left in the outer peripheral side of the cylinder 11 and the back side chamber R2 communicating with this via the communication hole 2a. It becomes possible to.
[0023]
[Problems to be solved by the invention]
However, in the hydraulic cylinder as the conventional example described above, there is a concern that the following inconveniences cannot be avoided.
[0024]
In other words, in the above-described conventional hydraulic cylinder, the lower end of the cylindrical body 11 is connected to the piston body 3 by welding (indicated by symbol M in FIG. 3) and placed in a desired standing state. However, welding spatter and oxide scale are generated during this welding.
[0025]
Therefore, in order to completely remove the welding spatter and oxide scale, a so-called troublesome work is essential, and it is difficult to improve productivity and reduce costs.
[0026]
When the weld spatter and oxide scale are not completely removed, the weld spatter and oxide scale are mixed in the oil. For example, when the hydraulic cylinder is fully extended, the inner periphery of the bush 5 and the outer periphery of the rod body 2 are mixed. It penetrates into the annular gap formed between them and adheres to the inner periphery of the bush 5, thereby causing a caulking phenomenon with the rod body 2.
[0027]
In addition, when this galling phenomenon is caused, the outer periphery of the rod body 2 is damaged, and this damage phenomenon causes a damage phenomenon to be expressed on each inner periphery of the oil seal 6 and the dust seal 7. The sealing performance will be reduced.
[0028]
Further, when welding spatter or oxide scale penetrates into the check valve 10 portion, and particularly adheres to a so-called seat portion where the steel ball 10a is seated, the oil leakage in the check valve 10 portion is caused. As a result, the malfunction of the hydraulic cylinder is caused.
[0029]
Further, when the lower end of the cylinder 11 is connected to the piston body 3 by welding, when the distortion due to welding heat is caused to the piston body 3, in particular, the seat on which the steel ball 10a in the check valve 10 is seated. When distortion is induced in the portion, the operation of the check valve 10 cannot be expected at all.
[0030]
The present invention was devised in view of the above-described circumstances, and the object thereof is that there is no generation of welding spatter and oxide scale, and it is possible to improve productivity and reduce costs. Of course, it is to provide a ram type hydraulic cylinder that can guarantee the function of a check valve having a relief valve function while ensuring the sealing function and is optimal for use in a forklift.
[0031]
[Means for Solving the Problems]
In order to achieve the above-described object, the configuration of the present invention is divided into a cylinder body that is a lower end side member, a rod body that is an upper end side member and is inserted into the cylinder body so that the lower end side can be projected and retracted, and slides into the cylinder body. And a piston body that is disposed in a cylinder body and that defines a hydraulic chamber that communicates with an external hydraulic supply / exhaust source and that is provided at the lower end of the rod body. A cylindrical hollow part whose body closes its upper end and whose lower end is closed by a piston body is provided in the shaft core part, and the outer part of the rod body and the cylinder are connected to the lower end side of the rod body through a communicating hole. It communicates with the back side chamber formed between the inner periphery of the body and communicates with the hydraulic chamber via a check valve disposed on the piston body, and the empty portion positions the upper end above the communication hole. The cylinder is erected on the shaft core, and the cylinder is empty In a hydraulic cylinder that is defined inside and outside the cylinder body and whose lower end is opposed to the check valve, the cylinder body is an extended cylinder part on the upper end side of the valve case that penetrates the center part of the piston body from the lower end side. It is assumed that a poppet type check valve is set in the lower end base portion of the valve case and is opposed to the upper end side extension cylinder portion.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings. The hydraulic cylinder according to the present invention is basically configured in the same manner as the conventional hydraulic cylinder (see FIG. 3).
[0033]
Therefore, the same parts of the configuration are denoted by the same reference numerals in the drawings unless otherwise necessary, and detailed description thereof will be omitted. The following description will focus on the features of the present invention. .
[0034]
First, in the hydraulic cylinder according to the embodiment of the present invention, as shown in FIG. 1, a cylinder disposed in a hollow portion formed in the axial core portion of the rod body 2, that is, the cylinder in the conventional example described above. The cylinder corresponding to the body 11 (see FIG. 3) is set by the upper end side extended cylinder portion 12a of the valve case 12 that penetrates the central portion of the piston body 3 from the lower end side.
[0035]
This valve case 12 has a check valve 10 in a lower end base 12b, which is set in a valve assembly mode. In the illustrated embodiment, the lower end base 12b is opened at the center of the piston body 3. The upper end side extended cylindrical portion 12 a is inserted into the perforated through hole 3 b under the arrangement of the seal member 13 so as to protrude upward from the upper end of the central portion of the piston body 3.
[0036]
Incidentally, the lower end of the valve case 12, that is, the lower end of the lower end base portion 12b is engaged with a stopper 14 fitted to the inner periphery of the through hole 3b. In this state, the valve case 12 is fixed to the piston body 3. It is going to be established.
[0037]
The check valve 10 is disposed in the valve case 12 so as to be opposed to the upper end side extended cylinder portion 12a. In the illustrated embodiment, the check valve 10 has a poppet 10c biased by a spring 10b from the back side. It is set to have a poppet type.
[0038]
Incidentally, the poppet 10c is slidable on a sliding portion (not shown) formed in the lower end base portion 12b so as to expand the inner circumference of the upper end side extended cylindrical portion 12a, that is, is retractable. It is set so that the tip is opposed to the upper end side extended cylinder part 12a, and is set so that the oil in the upper end side extended cylinder part 12a flows out into the hydraulic chamber R1 when retreating when it is lowered. Yes.
[0039]
The spring 10b has an upper end abutting on the back side of the poppet 10c, and a base end as a lower end is locked to a spring receiver 10d arranged in a fixed state. The spring receiver 10d has a lower end at a stopper 10e. It is supposed to be locked to.
[0040]
Therefore, in the valve case 12, the spring 10b and the poppet 10c can be taken out by removing the stopper 10e, that is, the check valve 10 can be disassembled, and parts can be replaced. By replacing with the ball 10a (see FIG. 3), the check valve 10 can be changed to a ball type that is economically advantageous.
[0041]
When the check valve 10 is set to a poppet type as in this embodiment, the centering of the poppet 10c is facilitated, so that seating on the so-called seat portion, that is, the seating property is improved and stable. This is advantageous in that it can be expected to demonstrate its functions.
[0042]
The valve case 12 can be separated from the piston body 3 by removing the stopper 14 and can be replaced for each so-called valve assembly. Since the cylinder body is provided in the empty space, only the assembling work is sufficient, and welding to the piston body 3 is not required. You don't have to worry about distortion.
[0043]
By the way, the upper end side extended cylinder portion 12a in the valve case 12 is set so as to have an outer diameter of approximately 1/3 with respect to the inner diameter of the empty portion, as can be understood from the drawing. However, this increases the volume defined on the outer peripheral side of the upper end side extended cylinder portion 12a by almost 50%, as compared with the case of the conventional example described above. Is possible.
[0044]
Therefore, in the illustrated embodiment, welding spatter and oxide scale are not mixed into the oil. However, even when contamination or the like instead of this is contained in the oil, this contamination or the like is the above-described upper end side extension cylinder portion 12a. Therefore, contamination or the like enters the check valve 10 portion or enters between the inner periphery of the bush 5 and the outer periphery of the rod body 2. It is possible to greatly reduce the chances of
[0045]
Further, according to the valve case 12, since it is a single part, the number of parts can be reduced as compared with the case where the cylindrical body 11 is separated as in the conventional example described above. In addition to the fact that welding work, welding spatter removal work, and the like are unnecessary, it is possible to significantly reduce the cost.
[0046]
In the hydraulic cylinder according to this embodiment formed as described above, the following considerations are made.
[0047]
That is, first, the hollow portion formed in the shaft core portion of the rod body 2 is connected to the outer circumference of the rod body 2 and the inner circumference of the cylinder body 1 via the orifice 15a corresponding to the orifice 2b (see FIG. 3) in the conventional example. The orifice 15a is formed in the shaft core portion of the set screw 15 screwed to the cylinder body 1 in the illustrated embodiment. It is said.
[0048]
In this way, the orifice 15a is formed in the set screw 15, and the set screw 15 is screwed to the cylinder body 1, so that the set screw 15 having an appropriately set orifice diameter is selected and the cylinder body is selected. 1 can be arranged, which makes it easier to set the orifice.
[0049]
Next, the piston body 3 is in the embodiment shown in the figure, and is assumed to be connected to the rod body 2 by using the snap ring 16, but the lower end of the rod body 2 is the upper end of the central portion of the piston body 3. As long as 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 is always raised at the same time as long as it is maintained in contact with the cylinder body 1. Thus, the extension operation in the hydraulic cylinder can be realized.
[0050]
Further, when the retraction operation is reversed from the extension operation, the rod body 2 is immersed in the cylinder body 1 by the weight or load of the rod body 2, so that the piston body 3 is connected to the lower end of the rod body 2. In this case, it is sufficient if the snap ring 16 has a predetermined strength.
[0051]
Therefore, when the piston body 3 is connected to the rod body 2 by using the snap ring 16 as in this embodiment, the above-described conventional technique in which the lower end of the rod body 2 is screwed to the piston body 3 is described above. Compared to the case of the example, a part that is a snap ring 16 is required, and a concave groove (not shown) that accommodates the snap ring 16 is required. Therefore, it is not necessary to form a thread over a long stroke, and the productivity of so-called parts as the rod body 2 and the piston body 3 can be greatly improved.
[0052]
The hydraulic cylinder formed as described above basically operates in the same manner as the conventional hydraulic cylinder described above.
[0053]
That is, when the hydraulic pressure from the external hydraulic supply / discharge source P is supplied to the hydraulic chamber R1 in the most contracted state shown in FIG. 1, the expansion operation is performed, and the hydraulic pressure in the hydraulic chamber R1 is released to perform the contraction operation. .
[0054]
Then, when it is close to the maximum extension, the open communicating hole 2a enters the rod body 2 into the inner peripheral side of the bush 5, and at this time, the oil in the rear side chamber R2 is in the lower orifice 15a or the inner periphery of the bush 5 and the rod It flows into an empty portion, that is, an outer peripheral side of the upper end side extended cylindrical portion 12a in the valve case 12 through an annular gap formed between the outer periphery of the body 2 and a predetermined cushion function is exhibited at this time. become.
[0055]
Further, when reversing to the contraction operation, the contraction operation is started by releasing the hydraulic pressure in the hydraulic chamber R1 and by the weight of the rod body 2 or the load acting on the rod body 2. At this time, the oil in the empty portion is caused to flow into the communication hole 2a. And, it flows into the back side chamber R2 through the orifice 15a and the so-called vacuum phenomenon is prevented from appearing in the back side chamber R2.
[0056]
When the communication hole 2a comes out from 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 quickly contracted.
[0057]
On the other hand, when the hydraulic cylinder is repeatedly expanded and contracted and oil supplied to the hydraulic chamber R1 gradually flows into the rear side chamber R2, the hydraulic pressure in the rear side chamber R2 gradually increases. When the hydraulic pressure is higher than the supplied hydraulic pressure and 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.
[0058]
As a result, the abnormally high pressure in the rear side chamber R2 is released before the oil seal 6 disposed on the opening end side of the cylinder body 1 is damaged, so that the durability of the so-called seal member is ensured.
[0059]
【The invention's effect】
As described above, according to the present invention, the upper end side extension cylinder portion of the valve case in which the cylinder body disposed in the hollow portion formed in the shaft core portion of the rod body passes through the central portion of the piston body from the lower end side. In addition, since the check valve facing the inside of the upper end side extension cylinder portion is arranged in the lower end base portion of the valve case, so-called assembly of the check valve becomes possible. As a result, the need to prepare a so-called cylindrical body as a separate part when providing the above-described cylindrical body is eliminated, and the need for welding work and the removal of weld spatter and oxide scales generated during welding are eliminated. It is possible to reduce the number of parts and reduce the cost.
[0060]
And since welding is not required, generation | occurrence | production of the distortion by the welding heat with respect to a piston body is not concerned, Therefore, arrangement | positioning of the said assembled check valve will not be prevented.
[0061]
In addition, since there is no concern about the occurrence of weld spatter or oxide scale, there is no risk of welding spatter being mixed into the oil, and welding spatter is formed in the annular gap formed between the inner periphery of the bush and the outer periphery of the rod body. It is not necessary to be concerned about the deterioration of the sealing performance caused by the intrusion of the material, and the durability of the sealing member can be ensured.
[0062]
In the present invention, since the check valve is set to a poppet type having a poppet biased by a spring, the predetermined check valve function and the relief valve function are stable due to the excellent centering property of the poppet. Will be demonstrated.
[0063]
Furthermore, according to the present invention, the outer diameter of the upper end side extension cylinder part in the valve case is set to about 1/3 of the inner diameter of the empty part, so that the upper end side extension cylinder part is defined on the outer peripheral side. It is possible to increase the volume to be increased by almost 50% compared to the conventional example, and even if contamination or the like is mixed in the oil, the contamination or the like is on the outer peripheral side of the above-mentioned upper end side extension cylinder portion. Therefore, the above-mentioned contamination or the like enters the check valve portion or enters the annular gap formed between the inner periphery of the bush and the outer periphery of the rod body. It is possible to greatly reduce the chance of doing so.
[0064]
In the present invention, an orifice is formed in the set screw to communicate between an empty portion in the rod body and a back side chamber formed on the outer peripheral side of the rod body, and the set screw is formed in the cylinder body. By being screwed, it becomes possible to select a set screw having an appropriately set orifice diameter and dispose it on the cylinder body, so that the orifice setting is facilitated.
[0065]
Further, in the present invention, since the piston body is connected to the rod body by using the snap ring, the snap ring is compared with the case where the lower end of the rod body is screwed to the piston body. It is necessary to form a concave groove to accommodate the snap ring, but it is not necessary to form a long-strand thread on the rod body or piston body. The productivity of so-called parts as the piston body can be greatly improved.
[0066]
As a result, according to the present invention, there is no generation of weld spatter and oxide scale, and it is possible to improve the productivity and reduce the cost, while ensuring the sealing function, The function of the check valve having the function can be ensured, and there is an advantage that it is optimum to be used for a ram type forklift.
[Brief description of the drawings]
FIG. 1 is a partial longitudinal sectional view showing a hydraulic cylinder according to an embodiment of the present invention in a most contracted state.
FIG. 2 is a partial longitudinal sectional view showing the hydraulic cylinder of FIG. 1 in a fully extended state.
FIG. 3 is a partial longitudinal sectional view showing a hydraulic cylinder as a conventional example, similar to FIG.
4 is a partial longitudinal sectional view showing the hydraulic cylinder of FIG. 3 in the same manner as 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 12 which comprises a check valve Valve case 12a Upper end side extended cylinder part 12b which comprises a cylinder Lower end base P Hydraulic supply / discharge source R1 Hydraulic chamber R2 back side room

Claims (1)

A cylinder body which is a lower end side member, a rod body which is an upper end side member and is inserted into the cylinder body so that the lower end side can be projected and retracted, and an external hydraulic pressure supply / exhaust source which is slidably accommodated in the cylinder body And a piston body that is connected to the lower end of the rod body and is set in a ram shape. The rod body closes the upper end and the lower end is closed by the piston body. It has a cylindrical hollow part in the shaft core part, and the hollow part communicates with the back side chamber formed between the outer periphery of the rod body and the inner periphery of the cylinder body through a communication hole opened on the lower end side of the rod body. And a cylinder that communicates with the hydraulic chamber through a check valve disposed on the piston body and that has a hollow portion that positions the upper end above the communication hole. The body defines the empty part inside and outside the cylinder, and the lower end of the cylinder is In the hydraulic cylinder facing the check valve, the cylinder body is set by the upper end side extension cylinder part of the valve case that penetrates the center part of the piston body from the lower end side, and in the upper end side extension cylinder part in the lower end base part of the valve case. Cylinder with poppet-type check valve facing

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