JPH0481041B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to hydraulic application equipment, and more particularly to a hydraulic cylinder whose operating force can be varied, and in which the operating speed and acting stress of a piston rod can be varied.

[Conventional technology]

2. Description of the Related Art Hydraulic cylinders have been known as mechanisms that move in a linear direction using hydraulic pressure generated by a hydraulic pump or the like. This hydraulic cylinder is widely used in construction machinery, vehicles, jacks, machine tools, etc. Conventional hydraulic cylinders consist of an internally hollow cylinder body and a piston rod that is slidably inserted into the cylinder body, and the operating speed and applied stress are set by the internal cross-sectional area of the cylinder body. It was hot.

[Problem that the invention seeks to solve]

As mentioned above, the internal cross-sectional area of the cylinder body is determined when the hydraulic cylinder is manufactured. This cross-sectional area cannot be changed once it is incorporated into equipment or assembled into a machine. Therefore, if you want to change the capacity of a hydraulic cylinder, you must either increase the amount of hydraulic pressure supplied or increase the hydraulic pressure. The applied stress was determined by the capacity of the hydraulic pump. For this reason, the capacity of a hydraulic cylinder is automatically determined at the design stage, and if you try to change the capacity when operating a device incorporating a hydraulic cylinder, you will have to change the hydraulic pump, and in reality was almost impossible.

[Means for Solving the Problems] The present invention comprises a cylinder tube which is closed at one end by a cylinder bottom and has a cylinder head fixed to the other end with a sliding opening formed therein, and which slides within the cylinder tube and moves from side to side. A piston with a sliding opening penetrating through the side, a cylindrical piston rod with its tip fixed to one side of the piston so as to communicate the inside of the piston with the sliding opening, and a cylinder bottom in a cylinder tube and the piston. A control piston that slides between the pistons, a guide rod that is inserted into the piston's sliding opening and whose tip is fixed to one side of the control piston, a control hole that is formed in a concave shape in the cylinder bottom, and the control piston. a control rod fixed to the other side and retractable from the control hole;
A communication port penetrates through both sides of the control piston, a return port that communicates with the internal space of the cylinder tube divided by the piston and the piston rod, and a return port that communicates with the piston and the control piston when the control piston is in contact with the cylinder bottom. The present invention provides a hydraulic cylinder whose operating force can be changed, characterized in that it is constituted by an operating port that communicates with the interior space of a cylinder tube divided by the above-mentioned structure, and a control port that communicates with a control hole.

[Effect]

In the present invention, pressure oil from a hydraulic pump is supplied into a space formed by a cylinder tube and a piston rod, and the piston is caused to slide within the cylinder tube. In this case, if the moving speed of the piston rod is to be increased, the control piston is brought into contact with the cylinder bottom. Therefore, the pressure oil acts on an area obtained by subtracting the cross-sectional area of the piston rod from the cross-sectional area of the cylinder tube, thereby reducing the cross-sectional area on which the pressure oil acts and increasing the moving speed of the piston rod. Also, when increasing the stress exerted by the piston rod,
Move the control piston to the piston side and bring the control piston and piston into close contact. Therefore, the cross-sectional area of the control piston is the area on which the pressure oil acts,
The cross-sectional area on which the pressure oil acts becomes larger, which makes it possible to increase the output of the piston rod.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, an example in which the hydraulic cylinder of the present invention is applied to an aerial work vehicle will be described.

There are front wheels 2 and rear wheels 3 on the front, rear, left and right sides of the vehicle body 1, respectively.
is pivotally supported so that the vehicle body 1 can move freely, and a power source box 4 containing an engine, a hydraulic pump, etc. is attached to the lower part of the vehicle body 1. A pair of shaft support pieces 5 are fixed to one end of the upper surface of the vehicle body 1 at a distance, and a lower outer boom 6 having a hollow interior and a square cross section is inserted between the shaft support pieces 5. The support piece 5 and the lower outer boom 6 are connected by a pin 7 so as to be able to swing up and down. A pair of pins 8 are fixed to the left and right sides of the upper surface of the vehicle body 1 at positions opposite to the shaft support piece 5, and a downward restraint is provided between the pins 8 and the outside of the lower outer boom 6. A hydraulic cylinder 9 for use is interposed.

The tip of the lower outer boom 6 has a square opening, and an internal hollow boom 10 having a square cross section is slidably inserted into this opening. A rectangular hollow end boom 11 is slidably inserted therethrough. A hollow upper and outer boom 12 with a rectangular cross section is inserted through the tip of the tip boom 11, and the tip of the tip boom 11 and the upper end of the upper and outer boom 12 are connected and fixed, and the outer circumference of the tip boom 11 and the upper and outer booms are connected and fixed. Equally spaced gaps are formed between the booms 12.

The lower outer boom 6 and the upper outer boom 12 are each set to have a length of about half the length of the vehicle body 1.
The middle boom 10 and the front boom 11 are each set to have approximately the same length as the vehicle body 1, and include a lower outer boom 6, a middle boom 10, a front boom 11, and an upper outer boom 1.
2 forms a telescopic boom body 13. A hydraulic cylinder (not shown) is provided inside the telescopic boom body 13, and this hydraulic cylinder operates the middle boom 10, the front boom 11, and the upper and outer booms 1.
2 extends from the lower outer boom 6 and extends from the telescopic boom body 13
The total length of can be varied.

Reference numeral 16 in FIG. 1 is a flat lifting platform having almost the same floor area as the vehicle body 1, and a pair of shaft support pieces 1 are provided at one end of the lower surface of the lifting platform 16 at intervals.
4 is fixed. The upper and outer booms 12 are inserted between the two shaft support pieces 14, and the shaft support pieces 14 and the upper and outer booms 12 are rotatably connected by pins 15. Also, on the lower surface of the lifting platform 16, the shaft support piece 1
A pair of pins 17 are fixed on both sides of the position opposite to 4, and hydraulic cylinders 18 for adjusting the horizontal position are interposed between each pin 17 and both sides of the upper and outer booms 12. . In addition,
A handrail 19 is installed around the upper surface of the lifting platform 16.

Next, FIG. 5 shows the inside of the aforementioned hydraulic cylinder 9, and the outer shell of this hydraulic cylinder 9 is formed by a cylindrical hollow cylinder tube 21. As shown in FIG. This cylinder tube 2
One end (lower in the figure) of the cylinder head 23 is closed by a cylinder bottom 22, and the other end (upper in the figure) has a diameter smaller than the inner diameter of the cylinder tube 21 and has a sliding opening communicating with the outside. is fixed. Further, in the center of the cylinder bottom 22 and on the surface facing the inside of the cylinder tube 21, a control hole 26 having a small inner diameter is formed in a concave shape.

Inside the cylinder tube 21 is a piston 28 which has an annular shape with a sliding opening opening in the center.
is slidably inserted into the inner circumferential wall 35 of the cylinder tube 21 so as to be airtight. The top surface of the piston 28 is connected to the tip of a piston rod 29 which is hollow inside and has a pipe shape, and the internal space of the piston rod 29 and the sliding opening formed in the piston 28 are communicated with each other. Therefore, the inner upper half of the cylinder tube 21 is connected to the piston 2.
8 and the piston rod 29 form a closed pressure chamber C. And piston rod 2
The outer periphery of the piston rod 9 is in airtight contact with the sliding opening of the cylinder head 23, and the upper half of the piston rod 29 is projected to the outside of the cylinder head 23.

An elongated cylindrical guide rod 30 is inserted into the sliding opening opened at the center of the piston 28 in an airtight manner and slidable therein. A guide body 38 having a large diameter is formed at the upper end of the guide rod 30, and the outer periphery of the guide body 38 is brought into airtight and slidable contact with the inner peripheral wall 36 of the piston rod 29. Therefore, the guide rod 30 can move into and out of the internal space of the piston rod 29,
The guide body 38 forms a pressure chamber D in the inner space of the upper half of the piston rod 29.

A control piston 31 is inserted between the piston 28 and the cylinder bottom 22 inside the cylinder tube 21 and slides in airtight contact with the inner circumferential wall 35 of the cylinder tube 21. The lower end of a guide rod 30 is fixed to one side of the piston 31 (the upper surface in the figure). For this reason, the piston 28, the guide rod 30,
Cylinder tube 21 by control piston 31
This means that a pressure chamber A is formed in the internal space. A control rod 37 is fixed to the center of the lower surface of the control piston 31 so as to protrude, and the control rod 37 is inserted into the control hole 26 so as to be freely retractable. Therefore, when the control rod 37 is inserted into the control hole 26, the control rod 37 is inserted into the control hole 26.
A pressure chamber B will be formed at the back of 6. This control piston 31 is provided with a through opening 32 extending upwardly and downwardly in FIG.
An O-ring 33 that is in close contact with 7 is provided.

Furthermore, an operating port 24 communicating with the pressure chamber A and a return port 25 communicating with the pressure chamber C are provided on the side surface of the cylinder tube 21 above and below. The position of the operating port 24 is such that the operating port 24 is located on the upper surface of the control piston 31 when the control piston 31 is in close contact with the cylinder bottom 22. Furthermore, a control port 27 is provided at the back of the control hole 26 to communicate with an external pipe. Furthermore, a discharge port 34 is provided at the upper part of the piston rod 29 and communicates with the pressure chamber D located inside.

Further, FIG. 6 shows a hydraulic circuit for operating the hydraulic cylinder 9 of this embodiment.

A hydraulic pump 4 is installed in an oil tank 41 that stores pressure oil.
The suction sides of the hydraulic pump 42 are connected to each other, and the discharge side of the hydraulic pump 42 has a switching valve 43 and a solenoid valve 44 that switch between three directions.
are connected in parallel. One of the outputs of this switching valve 43 is connected to the operating port 24 via a pressure control circuit 45, and the return port 25 is connected to the push side of the hydraulic cylinder 18 via a pressure control circuit 46. A switching valve 43 is connected to the discharge side of the hydraulic cylinder 18. Further, a control port 27 is connected to the solenoid valve 44 via a check valve, and a control switch 47 for operation is connected to the solenoid valve 44. A drain 48 connected to the oil tank 41 is connected to the discharge port 34.

Next, the operation of this embodiment will be explained.

FIGS. 2 and 3 show the state in which the lifting boom body 13 is reduced and the lifting platform 616 is lowered to the lowest position. In this state, a worker gets on the lifting platform 16 and materials are loaded. and then raise the lifting platform 16.

First, in order to raise the lifting platform 16, the engine in the power supply box 4 is activated to generate oil pressure, and the oil pressure is supplied to each hydraulic cylinder 9, 18 and a hydraulic cylinder (not shown) in the telescopic boom 13. To do this. When hydraulic pressure is supplied to the hydraulic cylinder in the telescoping beam 13, the middle boom 10 is slid and pulled out from the lower outer boom 6, and the front boom 11 is slid and pulled out from the middle boom 10. Increase the spacing. In addition, as the hydraulic cylinder 9 extends, the lower outer boom 6 is lifted up and down about the pin 7, and the telescopic boom body 13 is lifted so as to be tilted with respect to the vehicle body 1. At this time, if the extension speed of the telescopic boom body 13 and the tilting speed of the telescopic boom 13 by the hydraulic cylinder 9 are synchronized, the pin 1 of the upper and outer boom 12
5 will rise in a direction perpendicular to the vehicle body 1.

Further, the elevating table 16 rotates around the pin 15 due to the extension force of the hydraulic cylinder 18, which acts to enlarge the angle between the upper and outer booms 12 and the elevating table 16. At this time, by synchronizing the extension amounts of the hydraulic cylinders 9 and 18, the lifting platform 16 is always parallel to the vehicle body 1, and the vehicle body 1 and the telescopic boom 1
3. The lifting platform 16 is formed in a Z-shape when viewed from the side. Once this lifting platform 16 has been raised to a predetermined height position, the operator stops the operation of each hydraulic cylinder 9, 18, and the lifting platform 16 is held at that height position, allowing assembly and repair at a high location. , can perform work such as painting.

Next, the operation of the hydraulic cylinder 9 will be explained in more detail.

The state in FIG. 5 is the normal operating state,
The lower end of the indoor rod 30 is inserted into the control hole 26, and the lower surface of the control piston 31 is in close contact with the upper surface of the cylinder bottom 22. In this state,
The extension speed of the piston rod 29 is set to be fast and the operating stress is set to be small.

In the state shown in FIG. 5, the switching valve 43 is turned on in the forward direction, and hydraulic pressure is supplied from the hydraulic control circuit 45 and the operating port 24 to the pressure chamber A in the cylinder tube 21. Then, the pressure oil acts in the pressure chamber A and pushes the piston 28 upward in the figure. Therefore, the piston 28 slides along the inner circumferential wall 35, and the piston rod 29 moves toward the cylinder head 23.
It is drawn out more. Piston 28 and inner peripheral wall 35, piston 28 and guide rod 30, cylinder head 2
3 and the piston rod 29 are in airtight contact, so pressure oil will not leak.

As the piston 28 moves, the volume of the pressure chamber C decreases, but the pressure oil in the pressure chamber C is pushed out from the return port 25 and supplied to the hydraulic cylinder 18 via the pressure control circuit 46. Extend 18. Pressure oil discharged from the discharge side of the hydraulic cylinder 18 returns to the oil tank 41 via the switching valve 43.

The function of the hydraulic cylinder 9 in this operation is as follows:
This is a case where it is desired to increase the speed of expansion and contraction of the piston rod 29. As previously mentioned, the guide rod 30 does not move within the cylinder tube 21, but rather
8. Only the piston rod 29 moves. Therefore, the pressure oil injected from the operating port 24 is transferred from the inner cross-sectional area of the cylinder tube 21 to the guide rod 3.
It is added to the annular cross-sectional area after subtracting the cross-sectional area of 0. From this, the piston rod 29
Unlike a conventional hydraulic cylinder whose internal space is filled with pressure oil, the moving speed of the piston tube 21 is faster than that of a conventional hydraulic cylinder having the same inner diameter.

Next, when the load mounted on the lifting platform 16 is heavy, the acting stress of the hydraulic cylinder 9 must be increased to forcefully lift the telescopic boom body 13. This action stress switching operation is performed by pushing the control switch 47 to operate the solenoid valve 44 and transmitting a portion of the pressure oil from the hydraulic pump 42 to the control port 27.

In the state shown in FIG. 5, when the solenoid valve 44 is opened and pressure oil is injected into the pressure chamber B through the control port 27, this pressure oil expands in the pressure chamber B and acts to push up the control rod 37. This control rod 3
7 slides through the control hole 26 and is pushed up, the guide rod 30 and control piston 31 also move upward in the figure, and while the guide rod 30 is in contact with the sliding opening of the piston 28, the control piston 31 is pushed up. It slides airtightly while contacting the inner circumferential wall 35 of the tube 21. FIG. 7 shows a state in which the control piston 31 is sliding, its outer periphery is located above the opening of the operating port 24, and it is in the middle of movement.
During the movement of the control piston 31, the pressure oil in the cylinder tube 21 can flow through the communication port 32, so that even if the pressure oil is present on the guide rod 30 during movement, there is no burden.

As mentioned above, when the pressure chamber B is filled with pressure oil, the control rod 37 is pushed out from the control hole 26, and the lower end of the control rod 37 finally reaches the control hole 26.
(The next state shown in FIG. 7) will be drawn out. After this, the guide rod 30, the control piston 31, and the control rod 37 are still pushed in the direction of the piston 28 because pressure oil is applied from the operating port 24 to the pressure chamber E on the lower surface of the control piston 31. Ru. Finally, as shown in FIG. 8, the lower surface of the piston 28 and the upper surface of the control piston 31 come into close contact, and the piston 28 and piston rod 2
9. The guide rod 30, control piston 31, and control rod 37 are integrated into the cylinder tube 21.
It begins to slide inside. When the state shown in FIG. 8 is reached, the pressure oil injected from the operating port 24 acts on the entire cross-sectional area of the control piston 31 and the control rod 37, and the pressure oil is applied to the entire cross-sectional area of the inner diameter of the cylinder tube 21. become. Therefore, the piston 28 and the piston rod 29 are pushed out from the cylinder head 23 by the pushing force exerted by the control piston 31 and the control rod 37, and the stress acting thereon is increased.

Next, the piston rod 29 of the hydraulic cylinder 9
When attempting to shorten the overall length by forcing the cylinder tube 21 into the cylinder tube 21, the switching valve 43 is reversed and pressure oil from the hydraulic pump 43 is transmitted to the hydraulic cylinder 18. Pressure oil discharged from the hydraulic cylinder 18 flows into the upper space of the cylinder tube 21 from the return port 25 via the pressure control circuit 46. Then, this pressure oil acts to push down the piston 28, and the piston 28, piston rod 29, guide rod 30, control piston 31, and control rod 37 are integrally slid downward within the cylinder tube 21, and the hydraulic cylinder The total length of 9 is shortened. The pressure oil remaining in the pressure chamber E below the control piston 31 in the cylinder tube 21 is removed from the operating port 24.
The oil returns to the oil tank 41 via the pressure control circuit 45 and the switching valve 43. When the piston 28 slides to its lowest position, the control rod 37 is pushed into the control hole 26 and returns to the state shown in FIG.

〔Effect of the invention〕

Since the present invention is configured as described above, it is possible to vary the expansion/contraction speed and acting stress of the piston rod according to the purpose of the hydraulic cylinder's operation, and it has greater applicability than conventional hydraulic cylinders that can only be expected to operate in a simple manner. becomes wider.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an aerial work vehicle showing an embodiment of the present invention, Fig. 2 is a side view of the platform with the height lowered, Fig. 3 is a front view of the above, and Fig. 4 The figure is a side view of the lifting platform raised to a higher height, Figure 5 is a sectional view of the hydraulic cylinder, Figure 6 is a hydraulic circuit diagram, and Figures 7 and 8 show the operating state of the hydraulic cylinder. FIG. 9... Hydraulic cylinder, 21... Cylinder tube, 22... Cylinder bottom, 23... Cylinder head, 26... Control hole, 28... Piston, 29... Piston rod, 30... Guide rod, 31... Control Piston, 37...control rod.

Claims (1)

[Claims] 1 A cylinder tube with one end closed by the cylinder bottom and a cylinder head fixed to the other end with a sliding opening formed therein, and a piston that slides within this cylinder tube and forms a sliding opening passing through the left and right sides. , a cylindrical piston rod whose tip is fixed to one side of the piston so as to communicate with the inside of the piston, a control piston that slides between the cylinder bottom in the cylinder tube and the piston, and a control piston that slides between the cylinder bottom and the piston in the cylinder tube. A guide rod is inserted into the sliding opening and its tip is fixed to one side of the control piston, a control hole is formed by drilling a concave shape in the cylinder bottom, and a guide rod is fixed to the other side of the control piston and has a control hole that protrudes and retracts. a control rod that can be opened, a communication port penetrated through both sides of the control piston, a return port that communicates with the internal space of the cylinder tube divided by the piston and the piston rod, and when the control piston is in contact with the cylinder bottom, 1. A hydraulic cylinder capable of changing operating force, comprising an operating port that communicates with an internal space of a cylinder tube defined by a piston and a control piston, and a control port that communicates with a control hole.