KR20150047610A - Hydraulic cylinder - Google Patents

Abstract

A single acting hydraulic cylinder (1) which is operated to contract by a pressure of a working fluid guided from a fluid pressure source to a rod chamber (6) among a rod chamber (6) and a bottom chamber (5) A cylindrical cylinder tube 10 in which a piston 40 is slidably received and has a rod chamber 6 and a bottom chamber 5 in the interior thereof and a cylindrical cylinder tube 10 connected to the piston 40, A tank chamber 7 communicating with the bottom chamber 5 and a charging port 26 for charging the bottom chamber 5 or the tank chamber 7 from the outside with a lubricant, And a sealing portion 14 that seals the charging port 26. As shown in Fig.

Description

Hydraulic cylinder {HYDRAULIC CYLINDER}

The present invention relates to a single acting hydraulic cylinder which is contracted and operated by a pressurized working fluid derived from an external hydraulic pressure source.

As a single acting hydraulic cylinder of this kind, a hydraulic cylinder disclosed in JP08-135609A has a cylinder partitioned into a second oil chamber and an air chamber by a main piston.

The second oil chamber communicates with an external hydraulic pressure source through a pipe. The hydraulic cylinder is contracted by increasing the pressure of the hydraulic fluid guided to the second oil chamber, and when the pressure of the hydraulic fluid is lowered, the hydraulic cylinder is actuated by an external force such as a spring.

The air chamber communicates with the outside through an air hole. During the expansion and contraction operation of the hydraulic cylinder, the outside air passes through the air chamber through the air chamber.

In the hydraulic cylinder disclosed in JP08-135609A, since the air chamber communicates with the outside through the air hole, when the operation stoppage state continues for a long period of time, the case where the air chamber is dried and the working fluid of the air chamber is depleted have. When the working fluid in the air chamber becomes depleted, the internal rubbing occurs, and the piston seal interposed in the main piston sticks to the inner wall surface of the cylinder and sticks to it. If the piston seal adheres to the inner wall surface of the cylinder, there is a problem that the piston seal is deformed at the same time as the ash, thereby impairing the sealability of the piston seal.

An object of the present invention is to prevent the internal seizure of a single acting type hydraulic pressure cylinder and prevent the piston seal from sticking to the inner wall surface of the cylinder tube and sticking.

According to an aspect of the present invention, there is provided a single-acting hydraulic cylinder which is operated to contract by a pressure of an operating fluid that is guided from a hydraulic pressure source to a rod chamber of a rod chamber and a bottom chamber divided by a piston, A piston seal which is interposed in the piston and slidably contacts the inner wall surface of the cylinder tube; and a piston connected to the piston and projecting outward from the cylinder tube, A tank chamber communicating with the bottom chamber, a charging port for charging the lubricant to the bottom chamber or the tank chamber from the outside, and a sealing portion sealing the charging port.

1 is a sectional view of a hydraulic cylinder according to a first embodiment of the present invention.
2 is a sectional view of a hydraulic cylinder according to a second embodiment of the present invention.
3 is a sectional view of a hydraulic cylinder according to a third embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(First Embodiment)

A hydraulic cylinder (hydraulic cylinder) 1 shown in Fig. 1 is mounted on a work vehicle (not shown) that performs, for example, grass cutting, and is used as an actuator for moving a grass cutter (grass cutter). Further, the present invention is not limited to an actuator mounted on a work vehicle, but can be used for an actuator installed in another machine or equipment.

A mechanism (not shown) for raising and lowering the lawn mower includes a car body side arm connected to the car body, a lawn mower side arm rotatably connected to the car body side arm and supporting the lawn mower, , And a hydraulic cylinder (1) for driving the lawn mower side arm in the rotating direction in which the lawn mower rises.

The hydraulic cylinder 1 is connected between the car body side arm of the working vehicle and the lawn mower side arm. As the hydraulic cylinder 1 is stretched and contracted, the lawn mower side arm rotates and the grass mower is raised and lowered.

Hereinafter, the configuration of the hydraulic cylinder 1 will be described. The hydraulic cylinder 1 is contracted by the pressure of the hydraulic fluid derived from the external fluid pressure source while the hydraulic pressure cylinder 1 is contracted by the pressure of the hydraulic fluid from the single- will be.

The hydraulic cylinder 1 has a cylindrical cylinder tube 10 in which a piston 40 is slidably received and a piston rod 20 protruding outward from the cylinder tube 10.

To one end of the cylinder tube 10, a bottom block 50 is coupled. The bottom block 50 has an eye bracket portion 51 and is connected to the vehicle body side arm through a pin (not shown) inserted into the eye bracket portion 51.

An annular cylinder head 60 is fitted and engaged with the other end of the cylinder tube 10, and the piston rod 20 is slidably supported by the cylinder head 60.

At the front end portion of the piston rod 20, an eye bracket portion 21 is formed. The piston rod 20 is connected to the lawn mower side arm through a pin (not shown) inserted into the eye bracket portion 21. [

The piston 40 is fastened to the base end portion of the piston rod 20 inserted into the cylinder tube 10 through the nut 49. An O-ring (8) is interposed between the outer periphery of the proximal end of the piston rod (20) and the inner periphery of the piston (40). The O-ring (8) seals between the piston rod (20) and the piston (40).

The space inside the cylinder tube 10 is partitioned into a rod chamber 6 and a bottom chamber 5 by a piston 40. The rod chamber 6 is a space between the cylinder tube 10 and the piston rod 20 and is defined between the piston 40 and the cylinder head 60. The bottom chamber 5 is a space inside the cylinder tube 10 and is defined between the piston 40 and the bottom block 50.

The cylinder tube 10 is formed of a metal such as a steel material.

A piston seal 41 is mounted on the outer periphery of the piston 40. The piston seal 41 is brought into contact with the inner wall surface 11 of the cylinder tube 10 to seal the space between the bottom chamber 5 and the rod chamber 6. [

The piston seal 41 is formed of a low-friction resin material, but the present invention is not limited to this, and an O-ring made of rubber or the like may be used.

A cylindrical bush (bearing) 61 is interposed on the inner periphery of the cylinder head 60. The piston rod 20 is slidably supported by the cylinder head 60 by the bush 61.

A main seal 62 and a dust seal 63, which are in sliding contact with the outer peripheral surface of the piston rod 20, are interposed in the inner periphery of the cylinder head 60. The seal between the cylinder head 60 and the piston rod 20 is sealed by the main seal 62 and the rod seal chamber 6 is sealed to the outside. In addition, dust and the like are prevented from entering by the dust seal 63.

An annular port block 30 is joined to the outer periphery of the cylinder tube 10 in the axial direction by a welded portion 31. The port block (30) is provided with a supply port (32) for supplying working fluid to the rod chamber (6). A piping extending from a fluid pressure source (not shown) mounted on the work vehicle is connected to the delivery port 32. [ The working liquid fed by the hydraulic pressure source flows through the supply port 32 as indicated by the arrows in the figure.

Between the port block 30 and the cylinder head 60, a cylindrical outer tube 35 is spanned. Between the outer tube 35 and the cylinder tube 10, the delivery passage 33 is partitioned as a cylindrical space.

The operating fluid passes from the supply port 32 to the supply passage 33 and flows from the through hole 12 formed in the cylinder tube 10 to the load And is supplied to the chamber 6. The piston rod 20 moves in the rightward direction in the drawing along the central axis O with respect to the cylinder tube 10 by the operating fluid pressure so that the hydraulic cylinder 1 is contracted and operated. Fig. 1 shows a state in which the hydraulic cylinder 1 is in the most contracted state.

On the other hand, when the operating fluid pressure derived from the hydraulic pressure source drops, the piston rod 20 moves in the left direction with respect to the cylinder tube 10 on the basis of the pressing force of the spring 2, It works. The working fluid in the rod chamber 6 is discharged to the hydraulic pressure source through the through hole 12, the supply passage 33, and the supply port 32 as indicated by arrows in the drawing.

In the hydraulic cylinder 1, oil is used as an operating fluid fed from a hydraulic pressure source. Instead of the oil, for example, a working fluid such as a water-soluble substitute fluid may be used.

One end of the outer tube 35 is fitted to the port block 30 and joined by the welded portion 34. The other end of the outer tube 35 is threadably engaged with the outer threaded portion of the cylinder head 60.

An O-ring 64 is interposed between the outer tube 35 and the cylinder head 60. The O-ring 64 seals between the outer tube 35 and the cylinder head 60, and the delivery passage 33 is sealed to the outside.

On the outer circumference of the outer tube 35, a helical spring engagement groove 36 is formed. The spring 2 is formed in a coil shape and one end of the spring 2 is connected to the outer tube 35 by being wound in a helical spring engagement groove 36. The other end of the spring 2 is connected to the distal end side of the piston rod 20. The spring (2) presses the piston rod (20) in a direction in which the piston rod (20) protrudes from the cylinder tube (10) by the spring force.

The hydraulic cylinder 1 has a tank tube 25 disposed between the port block 30 and the bottom block 50 and disposed around the cylinder tube 10. A tank chamber (7) is provided between the cylinder tube (10) and the tank tube (25).

The cylinder tube 10 is formed with a through hole 13 that communicates the bottom chamber 5 and the tank chamber 7. [ 1, the through hole 13 is formed at a position where the piston rod 20 is at the stroke end and is not closed by the piston 40 even when the hydraulic cylinder 1 is in the most contracted state Is opened.

The tank chamber (7) is partitioned as a cylindrical space between the tank tube (25) and the cylinder tube (10). The bottom block 50 and the port block 30 are formed into an annular wall portion that defines both end portions in the axial direction of the tank chamber 7.

The volume ratio between the tank chamber 7 and the bottom chamber 5 is arbitrarily set in accordance with the allowable value of the pressure generated in the bottom chamber 5 during the expansion and contraction operation of the hydraulic cylinder 1. [ The volume of the tank chamber (7) is determined by the inner diameter of the tank tube (25).

The bottom block 50 has an eye bracket portion 51 connected to the vehicle body side arm and an annular flange portion 52 projecting from the periphery of the eye bracket portion 51.

At the end face of the flange portion 52 of the bottom block 50, a fitting concave portion 53 is formed at a central position in the radial direction. In the fitting concave portion 53, the cylinder tube 10 is fitted and fixed.

In the end surface of the flange portion 52 of the bottom block 50, a fitting concave portion 54 is formed at an outer side in the radial direction. One end of the tank tube 25 is fitted to the fitting concave portion 54 and joined by the welded portion 43. The other end of the tank tube 25 is fitted to the fitting concave portion 39 formed in the port block 30 and joined by the welded portion 42.

The hydraulic cylinder 1 has a charging port 26 that penetrates the tank tube 25 and opens to the tank chamber 7 and a sealing portion 14 that seals the charging port 26.

The sealing portion 14 includes a charging tube 15 that is coupled to the outer periphery of the tank tube 25 through a weld portion 16, a set screw 17 screwed to the charging tube 15, a set screw 17 And the ball 18 is pressed against the inner peripheral surface of the tapered shape of the filling tube 15 by means of the ball screw 18. An air vent hole 19 is formed in the filling tube 15 so as to be open between the set screw 17 and the ball 18. The sealing portion 14 is not limited to the above-described configuration, and may be a drain plug (stopper) screwed to the charging port 26 of the tank tube 25, for example.

At the time of manufacturing the hydraulic cylinder 1, a predetermined amount of lubricant is filled into the tank chamber 7 from the charging port 26. The same lubricant as the hydraulic fluid fed from the hydraulic pressure source to the hydraulic cylinder 1 is used as the lubricant. Further, the lubricant is not limited to this, and a different lubricant may be used.

The produced hydraulic cylinder 1 is assembled and mounted together with the spring 2 between the car body side arm of the working vehicle and the lawn mower side arm.

When the hydraulic cylinder 1 is in the most contracted state shown in Fig. 1 at the time of operation of the working vehicle, the lawn mower arm rotates upward and is held at a position where the grass mower is raised.

When the lawnmower is brought close to the ground by extending the hydraulic cylinder 1, the hydraulic pressure from the hydraulic pressure source to the rod chamber 6 of the hydraulic cylinder 1 is lowered by operation of the driver. Thereby, the hydraulic cylinder 1 is actuated to extend by the spring force of the spring 2, and the working fluid of the rod chamber 6 flows through the through hole 12, the supply passage 33 and the supply port 32 And flows out as a fluid pressure source.

Further, the hydraulic cylinder 1 is not limited to the spring force of the spring 2, and may be configured to be actuated by an external force such as gravity applied to the arm of the lawnmower, for example. When the gravity applied to the lawn-mowing arm is large, the spring force of the spring 2 may be pressurized so as to rotate in the direction in which the lawnmower raises with respect to the grass-mower side arm.

When the hydraulic pressure cylinder 1 is contracted to separate the mower from the ground, the hydraulic pressure applied to the hydraulic cylinder 1 from the hydraulic pressure source is increased by the operation of the driver. Thereby, the working fluid flows into the rod chamber 6 through the supply port 32, the supply passage 33 and the through hole 12, and the hydraulic cylinder 1 is driven by the spring force of the spring 2 Contraction works.

The lubricating liquid interposed in the bottom chamber 5 lubricates the sliding contact portion of the piston 40 and the inner wall surface 11 of the cylinder tube 10 when the hydraulic cylinder 1 is expanded and contracted in this way. Thereby, the piston 40 smoothly slides.

The bottom sealing space 5 is sealed by the sealing portion 14 so that the piston 40 slides and the volume of the bottom sealing space 5 expands and contracts and the pressure of the bottom sealing space 5 Respectively. Since the bottom chamber 5 communicates with the tank chamber 7 through the through hole 13 and the volume of the bottom chamber 5 expands and contracts and the gas in the bottom chamber 5 flows into the tank chamber 7 ). As a result, pressure fluctuations occurring in the bottom chamber 5 are alleviated. As a result, the hydraulic cylinder 1 is prevented from increasing in the negative pressure generated in the bottom chamber 5 during the extension operation, and can be smoothly extended by the spring force of the spring 2. Further, the hydraulic cylinder 1 is prevented from increasing in the positive pressure generated in the bottom chamber 5 during the shrinking operation, and smoothly contracts by the pressure of the hydraulic fluid received by the piston 40. [

The charging port 26 is sealed by the sealing portion 14 so that the bottom chamber 5 and the tank chamber 7 are sealed to the outside. As a result, the bottom chamber 5 can be prevented from drying out, the inner lubrication fluid can be prevented from being exhausted, and moisture, dust, and the like can be prevented from entering the bottom chamber 5 from the outside. This prevents the inner wall surface (11) of the cylinder tube (10) from being rusted. This makes it possible to prevent the piston seal 41 from sticking to and sticking to the inner wall surface 11 of the cylinder tube 10. It is also possible to abolish the anti-rust treatment on the inner wall surface 11 of the cylinder tube 10. Further, the durability required for the piston seal 41 is suppressed to be low, and the selection range of the piston seal 41 can be widened.

The hydraulic cylinder 1 is set in the most elongated state and the center axis O is inclined with respect to the horizontal direction so that the bottom chambers 5 are lower than the rod chambers 6 do. The filling amount of the lubricant is set so that at least a part of the piston seal 41 is immersed in the lubricant contained in the bottom chamber 5 in the state in which the hydraulic cylinder 1 is in the storage posture.

Even when the working vehicle is stored for a long period of time, since the piston seal 41 is partially immersed in the lubricant, the piston seal 41 is prevented from sticking to and sticking to the inner wall surface 11 of the cylinder tube 10 can do. This makes it possible to restrain the piston seal 41 from sticking to the inner wall surface 11 of the cylinder tube 10 and being deformed when the working vehicle is operated after being stored for a long period of time. It is also possible to prevent the working liquid supplied to the rod chamber 6 from leaking to the bottom chamber 5 through the piston seal 41. [

The hydraulic cylinder 1 is stretched and shrunk during operation of the working vehicle so that the piston 40 slides with respect to the cylinder tube 10 so that a slight amount of the working fluid flows from the rod chamber 6 to the bottom chamber 5 The sliding leakage may occur. Such sliding leakage leakage may increase the amount of the lubricating liquid interposed in the bottom chamber 5 or the tank chamber 7 beyond the predetermined amount. In this case, the charging port 26 may be opened through the sealing portion 14 during maintenance to discharge the excess lubricant through the charging port 26 to the outside. By slightly loosening the set screw 17, the ball 18 is separated from the tapered inner peripheral surface of the filling tube 15 so that the air or lubricating liquid in the bottom chamber 5 is discharged through the charging port 26 And can be discharged from the hole 19 to the outside.

Depending on the operating conditions of the hydraulic cylinder 1, there is a possibility that the amount of the lubricating liquid interposed in the bottom chamber 5 may be smaller than the set amount. In this case, the filling port 26 is opened through the sealing portion 14 at the time of maintenance, and the lubricating liquid is replenished from the outside to the tank chamber 7 through the filling port 26.

The hydraulic cylinder 1 has its central axis O extending in the vertical direction so that the piston rod 20 is displaced from the cylinder head 60 of the cylinder tube 10 (Posture) extending upward. In this state, when the set amount of lubricant is filled in the bottom chamber 5, the filling port 26 is opened at the position where the liquid level of the lubricant reaches in the tank tube 25. That is, the charging port 26 is provided at a position where the liquid level of the lubricant reaches when the set amount of lubricant is filled in the bottom chamber 5. The position at which the filling port 26 of the tank tube 25 is opened is determined by the attitude (predetermined attitude) taken by the hydraulic cylinder 1 and the filling amount of the lubricating liquid when the lubricating liquid is replenished at the time of maintenance And a preset amount).

When the lubricant is replenished from the charging port 26 at the time of maintenance, the operator replenishes the lubricant from the charging port 26 in a state in which the hydraulic cylinder 1 takes a posture in which the central axis O extends in the vertical direction And stops replenishing the lubricant at the time when the lubricant is overflowed from the tank chamber 7 and flows out from the charging port 26 or immediately before overflowing from the tank chamber 7. [ In this way, by adjusting the amount of replenishment so that the level of the lubricant reaches the vicinity of the charging port 26, it is easy to fill the bottom chamber 5 with the preset amount of lubricant.

Further, for example, in a large hydraulic cylinder provided in a forklift or the like, a check valve for returning surplus operating fluid (lubricant) in the bottom chamber to the rod chamber can be provided. However, in comparison with this, in a compact hydraulic cylinder 1, space for installing the check valve can not be ensured. The hydraulic cylinder 1 is provided with the charging port 26 and the sealing portion 14 in correspondence with the absence of valve means such as a check valve in which the working liquid is fed between the rod side chamber 6 and the bottom chamber 5 Is installed. Thereby, it is possible to seal the bottom chamber 5 with an appropriate amount of lubricant.

According to the first embodiment described above, the following effects are exhibited.

In the hydraulic cylinder 1, the slidably moving portion of the piston 40 is lubricated by the lubricant filled in the bottom chamber 5 from the charging port 26. The charging port 26 is sealed by the sealing portion 14 so that the bottom chamber 5 is sealed to the outside. As a result, the lubricating liquid is depleted and internal firing is prevented, so that the piston seal 41 can be prevented from sticking to the inner wall surface 11 of the cylinder tube 10 and sticking thereto. It is also possible to abolish the anti-rust treatment on the inner wall surface 11 of the cylinder tube 10. Further, the durability required for the piston seal 41 is suppressed to be low, and the selection range of the piston seal 41 can be widened.

Since the hydraulic cylinder 1 is provided with the tank tube 25 disposed around the cylinder tube 10 and the tank chamber 7 is provided between the cylinder tube 10 and the tank tube 25, The volume ratio between the tank chamber 7 and the bottom chamber 5 can be arbitrarily set by changing the inner diameter of the bottom chamber 25.

In the hydraulic cylinder 1, an annular port block 30 for guiding a working fluid fed to the rod chamber 6 is coupled to the outer periphery of the cylinder tube 10, and the end of the tank tube 25 is connected to the port block (30). This makes it possible to install the tank chamber 7 in the space around the cylinder tube 10 adjacent to the port block 30 and to prevent the hydraulic cylinder 1 from being enlarged by the tank chamber 7 have.

In the hydraulic cylinder 1, an outer tube 35 partitioning the supply and return passage 33 and a tank tube 25 partitioning the tank chamber 7 are provided around the cylinder tube 10, And a spring 2 for pressing the hydraulic cylinder 1 in the shrinking direction is connected to the outer tube 35. [ As a result, the spring 2 can be disposed along the outer tube 35, and the size of the device can be prevented from being increased by the spring 2.

The hydraulic cylinder 1 is provided with a bottom block 50 for closing the opening end of the cylinder tube 10 and a flange portion 52 to which the end portion of the tank tube 25 is fitted is formed in the bottom block 50 do. As a result, the bottom chamber 5 and the tank chamber 7 can be partitioned by the common bottom block 50, and the number of parts constituting the hydraulic cylinder 1 can be suppressed. In addition, the bottom tube 50 can be made more rigid by coupling the tank tube 25, which is thicker than the cylinder tube 10, to the bottom block 50.

(Second Embodiment)

Next, a second embodiment of the present invention will be described with reference to Fig. Hereinafter, the differences from the first embodiment will be mainly described, and the same reference numerals are assigned to the same components as those of the hydraulic cylinder according to the first embodiment, and the description is omitted.

The hydraulic cylinder 1 according to the first embodiment has a structure in which the bottom block 50 has the flange portion 52 to which the end portion of the tank tube 25 is coupled. In the hydraulic cylinder 101 according to the second embodiment, an annular outer block 110 is coupled to the outer periphery of the cylinder tube 10 separately from the bottom block 150, Is different from the hydraulic cylinder 1 according to the first embodiment in that the end of the tank tube 125 is coupled to the hydraulic cylinder 1 according to the first embodiment.

The end of the cylinder tube 10 is joined to the outer periphery of the bottom block 150 by the welded portion 151. The bottom block 150 is connected to the body-side arm through a pin (not shown).

The outer block 110 is joined to the outer periphery of the cylinder tube 10 by the welded portion 109. The outer block 110 is formed in an annular L-shaped cross section so as not to block the through hole 13 opened at the end of the cylinder tube 10.

The outer tube 35 is interposed between the port block 130 and the cylinder head 60 and defines a supply passage 33 in the inside thereof.

A cylindrical tank tube 125 extends over the port block 130 and the outer block 110, and defines a tank chamber 7 inside the tank tube 125.

One end of the tank tube 125 is fitted through the O-ring 132 to the fitting recess 131 formed in the port block 130. The other end of the tank tube 125 is fitted to the outer periphery of the outer block 110 through the O-ring 112.

An annular groove 113 is formed on the outer periphery of the outer block 110 and the tank tube 125 is prevented from slipping out in the axial direction through a retaining ring 108 fitted to the annular groove 113 .

The hydraulic cylinder 101 includes a charging port 126 that penetrates the tank tube 125 and opens to the tank chamber 7 and a sealing portion 114 that seals the charging port 126. [

The sealing portion 114 has a filling tube 115 which is coupled to the outer periphery of the tank tube 125 through a weld portion 116 and a drain plug 117 which is screwed to the filling tube 115.

The hydraulic cylinder 101 is elongated by a predetermined stroke so that the center axis O is inclined at a predetermined angle with respect to the horizontal direction so that the bottom chamber 5 is in contact with the rod chamber 6 Take a low attitude. The filling port 126 is provided at a position where the level of the lubricant reaches the liquid level in the tank tube 125 when the set amount of lubricant is filled in the bottom chamber 5 in the state in which the hydraulic cylinder 101 takes this posture. Is opened. The set value of the charged amount of the lubricant can be changed by changing the rotational position of the tank tube 125 with respect to the cylinder tube 10 and changing the height position of the charging port 126. [

According to the second embodiment described above, the following effects are exhibited.

In the hydraulic cylinder 101, the sliding portion of the piston 40 is lubricated by the lubricant filled in the bottom chamber 5 from the charging port 126. The charging port 126 is sealed by the sealing portion 114 so that the bottom chamber 5 is sealed to the outside. As a result, the lubricating liquid is depleted and internal firing is prevented, so that the piston seal 41 can be prevented from sticking to the inner wall surface 11 of the cylinder tube 10 and sticking thereto.

The hydraulic cylinder 101 includes an outer block 110 coupled to the outer periphery of the cylinder tube 10 and an end of the tank tube 125 is coupled to the outer block 110. Therefore, a tank chamber 7 of a predetermined capacity can be provided around the cylinder tube 10. [ In addition, depending on the specification, the retaining ring 108 may be released to remove the tank tube 125, thereby abolishing the tank chamber 7.

(Third Embodiment)

Next, a third embodiment of the present invention will be described with reference to Fig. Hereinafter, the differences from the first embodiment will be mainly described, and the same reference numerals are assigned to the same components as those of the hydraulic cylinder according to the first embodiment, and the description is omitted.

In the hydraulic cylinder 1 according to the first embodiment, the tank chamber 7 is provided by the tank tube 25 arranged around the cylinder tube 10. On the contrary, in the hydraulic cylinder 201 according to the third embodiment, the piston rod 220 is formed in a hollow cylindrical shape and the tank chamber 207 is provided inside the piston rod 220 And is different from the hydraulic cylinder 1 according to the first embodiment.

The hydraulic cylinder 201 includes a cylindrical cylinder tube 210 in which the piston 240 is slidably received and a piston rod 220 protruding outward from the cylinder tube 210. An eye bracket portion 221 is formed at the distal end of the piston rod 220, and the eye bracket portion 221 is connected to the arm of the lawn mower. An eye bracket portion 251 is formed at the base end portion of the cylinder tube 210, and the eye bracket portion 251 is connected to the vehicle body side arm. A spring (not shown) is provided around the cylinder tube 210 to press the piston rod 220 in a direction in which the piston rod 220 protrudes from the cylinder tube 210.

A piston 240 is provided at the base end of the piston rod 220 inserted into the cylinder tube 210. The space inside the cylinder tube 210 is partitioned into a rod chamber 206 and a bottom chamber 205 by a piston 240. A piston seal 241 is interposed on the outer periphery of the piston 240. The piston seal 241 contacts the inner wall surface 211 of the cylinder tube 210 to seal between the bottom chamber 205 and the rod chamber 206. [

A tank chamber 207 is formed in the inside of the cylindrical piston rod 220. The base end of the piston rod 220 is opened in the bottom chamber 205. The tank chamber 207 and the bottom chamber 205 communicate with each other through the base end (opening) of the piston rod 220.

The cylinder tube 210 is formed with a supply port 232 which is open to the rod chamber 206. A piping extending from the hydraulic pressure source is connected to the delivery port 232. The working fluid dispensed by the fluid pressure source enters the dispensing port 232 as indicated by the arrow in the figure.

The cylinder tube 210 is provided with a filling port 226 which is open to the bottom chamber 205 and a sealing portion 214 for sealing the filling port 226 is provided.

The sealing portion 214 includes a charging tube 215 coupled to the outer periphery of the cylinder tube 210 and a drain plug 217 for removably closing the charging tube 215.

The hydraulic cylinder 201 is elongated by a predetermined stroke so that its central axis O is inclined at a predetermined angle with respect to the horizontal direction so that the bottom chambers 205 are engaged with the rod chambers 206, Lowering attitude. When the predetermined amount of lubricant is filled in the bottom chamber 205 in a state in which the hydraulic cylinder 201 is in this posture, the filling port 226 is provided at a position where the level of the lubricant reaches the liquid level in the cylinder tube 210, Is opened.

According to the third embodiment described above, the following effects are exhibited.

In the hydraulic cylinder 201, the sliding portion of the piston 240 is lubricated by the lubricant filled in the bottom chamber 205 from the charging port 226. The charging port 226 is sealed by the sealing portion 214 so that the bottom chamber 205 is sealed to the outside. As a result, the lubricant is depleted to prevent internal firing, and the piston seal 241 can be prevented from sticking to the inner wall surface 211 of the cylinder tube 210 and sticking to it.

In the hydraulic cylinder 201, the piston rod 220 is formed in a hollow cylindrical shape, and the tank chamber 207 is provided inside the piston rod 220. As a result, the tank chamber is provided around the cylinder tube, and the size and weight can be reduced.

Although the embodiments of the present invention have been described above, the above embodiments are only illustrative of some of the application examples of the present invention, and the technical scope of the present invention is not limited to the specific configurations of the above embodiments.

The tank container for partitioning the tank chamber may be provided outside the cylinder tube and the tank chamber inside the tank container and the bottom chamber inside the cylinder tube may communicate with each other through the pipe.

Claims (7)

A single acting hydraulic cylinder (1, 101, 201) which is operated to contract by a pressure of an operating fluid guided to a rod chamber from a fluid pressure source among a rod chamber and a bottom chamber separated by a piston,
A piston (40, 240) is slidably accommodated and has cylindrical cylinder tubes (10, 210) having rod side chambers (6, 206) and bottom side chambers (5, 205)
Piston seals 41 and 241 interposed between the pistons 40 and 240 and slidably contacting the inner wall surfaces 11 and 211 of the cylinder tubes 10 and 210,
Piston rods (20, 220) connected to the pistons (40, 240) and projecting outwardly from the cylinder tubes (10, 210)
A tank chamber (7, 207) communicating with the bottom chamber (5, 205)
A charging port (26, 126, 226) for charging the bottom chamber (5, 205) or the tank chamber (7, 207)
And sealing portions (14, 114, 214) for sealing said charging ports (26, 126, 226). The method according to claim 1,
Further comprising tank tubes (25, 125) arranged around the cylinder tube (10)
Wherein the tank chamber (7) is provided between the cylinder tube (10) and the tank tube (25, 125). 3. The method of claim 2,
An annular port block 30 for guiding a working fluid supplied to the rod chamber 5 is coupled to the outer periphery of the cylinder tube 10,
And an end of the tank tube (25) is coupled to the port block (30). The method of claim 3,
Further comprising a bottom block (50) for closing an opening end of the cylinder tube (10)
And a flange portion (52) to which the end of the tank tube (25) is fitted is formed in the bottom block (50). The method of claim 3,
Further comprising an annular outer block (110) coupled to the outer periphery of the cylinder tube (10)
Wherein the tank tube (125) extends over the port block (130) and the outer block (110). The method according to claim 1,
The piston rod 220 is formed in a hollow cylindrical shape,
And the tank chamber (207) is provided inside the piston rod (220). 7. The method according to any one of claims 1 to 6,
The charging ports 26, 126 and 226 are set in such a manner that the positions of the hydraulic cylinders 1, 101 and 201 are set so that the piston rods 20 and 220 extend upward from the cylinder tubes 10 and 210 (101, 201) which is provided at a position where the liquid level of the lubricant reaches when the bottom chamber (5, 205) or the tank chamber (7, 207) ).

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