JP3720646B2 - Hydraulic cylinder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic cylinder, and more particularly to a hydraulic cylinder that serves as both a front chamber in the hydraulic cylinder and a hydraulic oil storage tank.
[0002]
[Prior art]
In general, a hydraulic cylinder is provided with a piston integrated with a cylinder rod in a cylinder tube, and the piston separates the inside of the cylinder tube into a base chamber and a tip chamber on the cylinder rod side, and the piston is moved hydraulically. Thus, the hydraulic cylinder is expanded and contracted.
[0003]
By the way, some hydraulic cylinders have a tank that stores hydraulic oil and the front chamber side is also used as the tank (see FIG. 8). In this type of hydraulic cylinder, a compressible air space 95 is formed in the front chamber 91 in order to absorb the volume difference of the cylinder rod 94 between the base chamber 93 and the front chamber 91. In addition, a restricting member 96 made of a small piece is locally protruded at a predetermined position of the front chamber 91, and a passage 97 for communicating the base chamber 93 and the front chamber 91 is formed in the piston 92. A poppet valve 98 is provided in the passage 97 (see FIG. 9).
[0004]
When pressure oil is supplied from the base port 93 a to the base chamber 93 by the hydraulic pump, the hydraulic cylinder expands by pressing the poppet valve 98 and closing the passage 97. Is discharged from the front port 91a to the suction side of the pump. When the piston 92 reaches the full stroke, the poppet valve 98 hits the restricting member 96 to open the passage 97, and the hydraulic oil in the base chamber 93 flows toward the front chamber 91, thereby stopping the extension of the hydraulic cylinder. Further, when the hydraulic oil in the base chamber 93 can be discharged from this state, the hydraulic oil in the base chamber 93 returns to the front chamber 91 through the base port 93a and the front port 91a by the external force acting on the cylinder rod 94, and the hydraulic cylinder Shrinks. At this time, the volume difference between the base chamber 93 and the front chamber 91 due to the piston rod 94 is absorbed by the air space 95. When the hydraulic cylinder is extended, the air in the air space 95 expands and the front chamber is expanded. The oil level of 91 is lowered, and when the hydraulic cylinder is reduced, the air is compressed and the oil level of the front chamber 91 is raised.
[0005]
[Problems to be solved by the invention]
In the hydraulic cylinder, when the piston 92 reaches the full stroke, the poppet valve 98 hits the regulating member 96 and the passage 97 is opened. At this time, the pressure of the base chamber 93 with respect to the pressure in the front chamber 91 is increased. Therefore, the hydraulic oil in the base chamber 93 flows into the front chamber 91 vigorously.
However, when the piston 92 has moved a full stroke, the oil level in the front chamber 91 is lowered and approaches the piston 92, so that the hydraulic oil that has flowed into the front chamber 91 passes over the oil surface and the air space 95. The air in the air space 95 is entrained. In particular, since the restriction member 96 is provided locally, the hydraulic oil flowing into the front chamber 91 from the passage 97 is diverted by the restriction member 96 without receiving much flow resistance and blown up in all directions. become. For this reason, the hydraulic oil discharged | emitted from the front part port 91a will be in the state containing many air bubbles.
[0006]
Thus, when the hydraulic cylinder is expanded and contracted by the hydraulic pump in a state where a large amount of bubbles are mixed in the hydraulic oil, the pressing force of the piston 92 becomes unstable due to the compressibility of the bubbles, and the poppet valve 98 is closed. There are problems such as instability, so-called chattering and cavitation.
Accordingly, an object of the present invention is to provide a hydraulic cylinder capable of preventing air bubbles from being mixed in hydraulic oil, stabilizing the piston pressing force, and preventing chattering and cavitation of the poppet valve. And
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a hydraulic cylinder according to the present invention is provided with a piston integrated with a piston rod in a cylinder tube, and the cylinder tube has the base chamber and an air space on the piston rod side in the piston. The front chamber is divided into a front chamber, a passage through which the hydraulic fluid in the base chamber is released to the front chamber, and a poppet valve that opens and closes the passage is provided. When the piston is fully stroked, the poppet valve is provided in the front chamber. In the hydraulic cylinder that opens against the restriction member and opens the passage, the tip chamber is supported by a cylindrical body that surrounds the piston rod with a gap and an annular flange provided at the end of the cylindrical body on the piston side. A chamber is defined, and a relief hole is formed on the peripheral surface of the cylindrical body to allow a part of the hydraulic oil flowing from the base chamber to the front chamber to escape to the auxiliary chamber. Characterized in that it is arranged on the piston rod nearer the passage inner periphery of the flange portion (claim 1).
[0008]
According to the hydraulic cylinder having the above-described configuration, since the flange portion is annular, and the inner periphery thereof is disposed closer to the piston rod than the passage, when the piston reaches the full stroke, it passes from the base chamber through the passage. The flow resistance can be effectively imparted to the hydraulic oil flowing into the chamber by the flange portion, and the flow velocity can be reduced. In addition, most of the hydraulic oil can be introduced into the gap between the cylindrical body and the piston rod, and a part of the hydraulic oil can be released to the auxiliary chamber through the escape hole of the cylindrical body. The pressure can be reduced, and when the hydraulic oil is allowed to escape to the auxiliary chamber, the traveling direction of the hydraulic oil changes almost at right angles, so that the flow velocity can be further reduced. For this reason, it can suppress that the hydraulic fluid which flowed into the front part chamber from the base room greatly entrains the air of the air space of a front part room over an oil level.
[0009]
It is preferable that the flange portion also serves as the restriction member (Claim 2). In this case, the number of parts can be reduced and the restriction member can be positioned at a predetermined position by the cylindrical body. .
[0010]
Preferably, the auxiliary chamber is configured by a section surrounded by a lid that seals the front end opening of the front chamber, the cylindrical body and the flange, and a cylinder tube (Claim 3). The auxiliary chamber can be configured easily.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIGS. 1 and 2 are general views when the hydraulic cylinder of the present invention is used in a dump truck. FIG. 1 shows a state in which a dump box of a dump truck is stored, and FIG. 2 shows a state in which the dump box is fully dumped.
The dump truck 1 pivotally supports a cargo box 3 on a vehicle body 2 so as to tilt backward, and a dump link 6 including a tension link 4 and a lift arm 5 is provided between the vehicle body 2 and the cargo box 3. The cargo box 3 can be tilted backward by extending the hydraulic cylinder 7 provided on the dump link 6. In the dump truck 1, the hydraulic cylinder 7 is in a substantially horizontal state in the state in which the cargo box 3 is stored, that is, in the state shown in FIG. 7 is inclined about 60 degrees, and may be close to 90 degrees depending on the mounting position of the hydraulic cylinder 7.
[0012]
As shown in FIG. 3, the hydraulic circuit of the hydraulic cylinder 7 is provided with a switching valve 9 between a hydraulic pump 8 using a vehicle engine (not shown) as a drive source and the hydraulic cylinder 7, and this switching valve. 9 can be switched by the operation lever 10. The switching valve 10 is formed by three blocks: a block 9A for extending the hydraulic cylinder 7, a block 9B for stopping the hydraulic cylinder 7, and a block 9C for making the hydraulic cylinder 7 free.
[0013]
As shown in FIGS. 4 and 5, the hydraulic cylinder 7 is provided with a piston 14 in a cylinder tube 11, and the piston 14 divides the inside of the cylinder tube 11 into a base chamber 12 and a front chamber 13. The opening of the cylinder tube 11 is sealed with a lid 15, and a piston rod 16 integral with the piston 14 is slidably inserted in the center of the lid 15 while maintaining hermeticity. is there.
A base port 17 communicates with the base chamber 12, and the base port 17 communicates with a discharge port of the hydraulic pump 8. A front port 18 communicates with the front chamber 13, and the front port 18 communicates with a suction port of the hydraulic pump 8. The front port 18 faces downward so that the hydraulic cylinder 7 is attached to the dump link 6 and is always immersed in the hydraulic oil in the front chamber 13.
[0014]
As shown in FIG. 7, a passage 19 that connects the base chamber 12 and the front chamber 13 is formed in a part of the piston 14. A poppet valve 20 that opens and closes the passage 19 is inserted into the passage 19, and when the hydraulic cylinder 7 is expanded and contracted, the poppet valve 20 is pressed by the hydraulic pressure on the base chamber 12 side to close the passage 19, and the piston 14 When the full stroke is moved, the poppet valve 20 is pressed by the regulating member 21 provided in the front chamber 13, thereby opening the passage 19 so that the hydraulic oil in the base chamber 12 flows into the front chamber 13. The poppet valve 20 is provided in the vicinity of the front port 18 so that the hydraulic oil passing through the passage 19 can be easily discharged from the front port 18.
[0015]
An annular auxiliary chamber 25 is formed in the front chamber 13 so as to surround the piston rod 16. The auxiliary chamber 25 is defined by a cylindrical body 23 provided concentrically with the piston rod 16 and a flange 22 provided at an end portion of the cylindrical body 23 on the piston 14 side. The lid body 15 that seals the opening, the cylindrical body 23, the flange portion 22, and the section surrounded by the cylinder tube 11 are configured. The flange portion 22 is also used as the restriction member 21. Therefore, the auxiliary chamber 25 can be configured easily and at a low cost.
[0016]
The cylindrical body 23 is set to have an inner diameter that can form a sufficient gap with the piston rod 16, and is set to a length that allows the collar portion 22 to be positioned slightly above the front port 18. The inner periphery coincides with the inner periphery of the collar portion 22. The other end of the cylindrical body 23 is fitted to the lid body 15 of the cylinder tube 11.
The flange portion 22 has an outer periphery that matches the inner periphery of the cylinder tube 11, and the inner periphery is located closer to the piston rod 16 than the passage 19 of the piston 14. When the piston 14 moves full stroke, a poppet is formed on one side surface. The valve 20 comes to abut.
[0017]
A plurality of escape holes 24 are formed through the circumferential surface of the cylindrical body 23 (see FIG. 6). The escape hole 24 is for letting a part of the hydraulic oil flowing into the gap between the cylindrical body 23 and the piston rod 16 from the base chamber 12 through the passage 19 to the auxiliary chamber 25. A plurality of the relief holes 24 are formed at positions close to the flange portion 22 and at positions slightly apart from each other, so that the hydraulic oil can move smoothly between the front chamber 13 and the auxiliary chamber 25. Yes.
[0018]
In the dump truck having the above configuration, when dumping from the state in which the cargo box 3 is stored, the operation lever 10 shown in FIG. 3 is tilted to the left to switch the switching valve 9 to the right block 9A. Then, the hydraulic oil from the hydraulic pump 8 passes through the base port 17 and enters the base chamber 12, and the hydraulic oil in the front chamber 13 is discharged from the front port 18 and supplied to the hydraulic pump 8, as shown in FIGS. The piston 14 rises from the state shown in FIG. The dump link 6 is rotated by the extension of the hydraulic cylinder 7 and the cargo box 3 is tilted. At this time, since pressure acts on the poppet valve 20 from the base chamber 12 side, the passage 19 is always kept closed.
[0019]
When the piston 14 reaches the full stroke position, the cargo box 3 is fully dumped as shown in FIG. 2, but the poppet valve 20 hits the restricting member 21 (the flange 22) as shown in FIGS. Since the passage 19 is opened and the hydraulic oil in the base chamber 12 passes through the passage 19 and enters the front chamber 13, the extension of the hydraulic cylinder 7 stops.
[0020]
Further, the hydraulic oil entering the front chamber 13 from the base chamber 12 through the passage 19 suddenly enters the front chamber 13 due to a large pressure difference between the base chamber 12 and the front chamber 13, and a part of the hydraulic oil Although it goes out from the port 18, most of the fluid is introduced into the gap between the cylindrical body 23 and the piston rod 16 in a state where the flow velocity is lowered due to the flow resistance by the flange 22. Since most of the hydraulic oil introduced into the gap escapes to the auxiliary chamber 25 through the relief hole 24 of the cylindrical body 23, the pressure of the hydraulic oil can be reduced. In addition, when the hydraulic oil escapes to the auxiliary chamber 25, the traveling direction changes substantially at right angles, so that the flow velocity can be further reduced. For this reason, it can suppress that the hydraulic oil which flowed into the auxiliary | assistant chamber 25 greatly exceeds the oil level 27, and entrains the air of the air space 26. FIG. On the other hand, the hydraulic oil remaining in the gap between the piston rod 16 and the cylindrical body 23 is also hardly ejected from the oil surface 27 due to a decrease in pressure and flow velocity. For this reason, it is possible to effectively prevent bubbles from being mixed in the hydraulic oil.
[0021]
【The invention's effect】
As described above, according to the hydraulic cylinder of the first aspect, when the piston reaches the full stroke position, the hydraulic oil that enters the front chamber through the passage of the piston from the base chamber flows from the oil level of the front chamber. Since it is possible to suppress a large jump, it is possible to prevent air bubbles from being mixed in the hydraulic oil. For this reason, the pressing force of the piston when the hydraulic cylinder is extended can be stabilized, and chattering and cavitation of the poppet valve can be prevented.
[0022]
According to the hydraulic cylinder of claim 2, since the flange also serves as the restriction member, the number of parts can be reduced correspondingly, and the restriction member can be positioned at a predetermined position by the cylindrical body. Since it can do, arrangement | positioning of a control member becomes easy.
[0023]
According to the hydraulic cylinder of claim 3, the auxiliary chamber is configured by a section surrounded by a lid body that seals the front end opening of the front chamber, the cylindrical body and the flange portion, and the cylinder tube. Auxiliary room can be configured easily [Brief description of the drawings]
FIG. 1 is an overall view of a dump truck equipped with a hydraulic cylinder of the present invention.
FIG. 2 is a state diagram in which a dump truck's packing box is fully dumped.
FIG. 3 is a hydraulic circuit diagram.
4 is an enlarged cross-sectional view of a hydraulic cylinder in the state of FIG.
FIG. 5 is an enlarged cross-sectional view of the hydraulic cylinder in the state of FIG.
FIG. 6 is a perspective view of a cylindrical body and a regulating member.
7 is an enlarged view of a main part of FIG.
FIG. 8 is an overall cross-sectional view of a conventional hydraulic cylinder.
9 is an enlarged view of a main part of FIG.
[Explanation of symbols]
7 Hydraulic cylinder 11 Cylinder tube 12 Base chamber 13 Front chamber 14 Piston 15 Lid 16 Piston rod 19 Passage 20 Poppet valve 21 Restricting member 22 Ridge portion 23 Cylindrical body 24 Relief hole 25 Auxiliary chamber 26 Air space 27 Oil surface

Claims (3)

A piston with an integrated piston rod is provided in the cylinder tube, and the inside of the cylinder tube is divided into a base chamber and a front chamber having an air space on the piston rod side by the piston, and the operation of the base chamber is performed on the piston. In the hydraulic cylinder that provides a passage for oil to escape to the front chamber and a poppet valve that opens and closes the passage, and when the piston makes a full stroke, the poppet valve hits a regulating member provided in the front chamber and opens the passage.
An auxiliary chamber is defined by a cylindrical body surrounding the piston rod with a gap in the front chamber, and an annular flange provided at an end of the cylindrical body on the piston side,
On the peripheral surface of the cylindrical body, a relief hole is formed to allow a part of the hydraulic oil flowing from the base chamber to the front chamber to escape to the auxiliary chamber,
The hydraulic cylinder, wherein an inner periphery of the flange portion is arranged closer to the piston rod than the passage. The hydraulic cylinder according to claim 1, wherein the flange portion also serves as the restriction member. 2. The hydraulic cylinder according to claim 1, wherein the auxiliary chamber is configured by a section surrounded by a lid that seals a front end opening of the front chamber, the cylindrical body and the flange, and a cylinder tube.

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