JP2013164143A - Vertically-arranged cylinder, and forklift including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect leak of hydraulic oil from a lower chamber having the hydraulic oil stored therein to an upper chamber without storing the hydraulic oil.SOLUTION: A vertically-arranged cylinder 2 where an upper chamber 24 is separated from a lower chamber 25 by a piston 23, hydraulic oil is stored in the lower chamber 25, and no hydraulic oil is stored in the upper chamber 24 includes: a float plate 3 movably arranged along a piston rod 27 in the upper chamber 24, and structured to float on the hydraulic oil when the hydraulic oil has leaked to the upper chamber 24; a distance sensor 4 arranged on an upper cover 21 for detecting a separation distance to the float plate 3; an end detection sensor 5 for detecting a shortened-side stroke end of the piston rod 27; and a leak determination means 6 to determine leak of the hydraulic oil to the upper chamber 24. When the end detection sensor 5 detects the shortened-side stroke end, the leak detection means 6 determines the hydraulic oil to leak to the upper chamber 24 when the separation distance detected by the distance sensor 4 is smaller than a specified value (L1).

Description

  The present invention relates to a vertical cylinder that can detect an internal leak of hydraulic oil, and a forklift that includes the vertical cylinder.

  A lift cylinder provided in a cargo handling device such as a forklift is provided with, for example, a cylinder tube and slidable in the cylinder tube, and divides the cylinder tube into a lower chamber (bottom side chamber) and an upper chamber (top side chamber). A vertically installed internal drain cylinder is employed that includes a piston, hydraulic oil is stored in the lower chamber, and hydraulic oil is not stored in the upper chamber (for example, Patent Document 1).

  Such a vertical cylinder is provided with a seal member such as a packing on the outer surface of a piston that slides in the cylinder tube, for example, and seals between the cylinder tube and the piston. It is configured not to leak into the upper chamber that does not contain.

  However, if the piston repeats sliding, the seal member is worn out, so that the sealing performance of the seal member gradually decreases. Therefore, if the cylinder is continuously used, the hydraulic oil in the lower chamber will eventually leak into the upper chamber. An internal leak occurs in the upper chamber due to various causes such as wear of the sealing member.

  When an internal leak occurs in the upper chamber, there is a problem that the stroke amount of the piston rod is reduced. Further, an internal leak may cause an abnormal output of a device including the cylinder, or an internal leak may increase the pressure in the upper chamber and cause a failure of a device such as a sensor provided in the cylinder. Therefore, it is preferable that such an internal leak can be detected easily and reliably.

  Conventionally, the cylinder is provided with a stroke amount detection sensor for detecting the stroke amount of the piston rod (for example, Patent Document 2), an end detection sensor for detecting that the piston rod has reached the stroke end, and the like. . However, such a sensor does not detect an internal leak of hydraulic oil.

Japanese Patent Laid-Open No. 10-009209 Japanese Utility Model Publication No. 04-025005

  Accordingly, the problem to be solved by the present invention includes a vertical cylinder that can detect leakage of hydraulic oil from a lower chamber in which hydraulic oil is stored to an upper chamber in which hydraulic oil is not stored, and the vertical cylinder Is to provide a forklift.

In order to solve the above-described problems, a vertical cylinder according to the present invention includes a cylinder tube having an upper end covered with an upper cover and a lower end covered with a lower cover, and a cylinder tube slidably provided in the cylinder tube. A piston that divides the tube into an upper chamber and a lower chamber, and a piston rod that extends from the piston so as to penetrate the upper cover. The vertical fluid is stored in the lower chamber and the hydraulic fluid is not stored in the upper chamber. A stationary cylinder,
A float plate arranged in the upper chamber so as to be movable along the piston rod and configured to float against the hydraulic oil when the hydraulic oil leaks from the lower chamber to the upper chamber, and provided on the upper cover, the float plate Non-contact type distance detection means for detecting the separation distance to the stroke, stroke end detection means for detecting that the piston rod has reached the shortened stroke end, and leakage from the lower chamber to the upper chamber of the hydraulic oil is determined. A leak determination means,
When the stroke end detection means detects the shortened side stroke end and the separation distance detected by the distance detection means is smaller than the specified value, the leak determination means indicates that the hydraulic oil leaks from the lower chamber to the upper chamber. It is characterized by determining.

In order to solve the above problems, the vertical cylinder according to the present invention is provided with a cylinder tube whose upper end is covered with an upper cover and whose lower end is covered with a lower cover, and slidable within the cylinder tube. The piston tube that divides the cylinder tube into an upper chamber and a lower chamber, and a piston rod that extends from the piston so as to penetrate the upper cover, the hydraulic fluid is stored in the lower chamber, and the hydraulic fluid is stored in the upper chamber A vertical cylinder that is not
A float plate arranged in the upper chamber so as to be movable along the piston rod and configured to float against the hydraulic oil when the hydraulic oil leaks from the lower chamber to the upper chamber, and provided on the upper cover, the float plate Non-contact type distance detection means for detecting the separation distance to the stroke, stroke end detection means for detecting that the piston rod has reached the extension side stroke end, and leakage from the lower chamber to the upper chamber of the hydraulic oil is determined. A leak determination means,
The leak determination means is that when the separation distance detected by the distance detection means is zero and the stroke end detection means does not detect the extension side stroke end, the hydraulic oil leaks from the lower chamber to the upper chamber. It is characterized by determining.

  Preferably, the distance detection means is a stroke amount detection sensor that detects the stroke amount of the piston rod from the separation distance.

  Preferably, the float plate is formed in a ring shape and is externally fitted to the piston rod.

  In order to solve the above-mentioned problems, a forklift according to the present invention includes the above-described vertically placed cylinder and a fork for cargo handling, and is characterized in that the fork is moved up and down by the vertically placed cylinder.

  In the vertical cylinder according to the present invention, as described above, when hydraulic oil leaks into the upper chamber, the float plate floats on the hydraulic oil and moves along the piston rod. The vertical cylinder uses this configuration, and further uses a distance detection means for detecting the separation distance to the float plate and a stroke end detection means for detecting the stroke end. Detect leaks reliably.

  By detecting the internal leak, it becomes possible to prevent an abnormal output of the apparatus including the cylinder due to the internal leak, and the sensor inside the cylinder due to the increase of the pressure in the upper chamber due to the internal leak. Failure can be prevented.

It is a perspective view of the forklift provided with the vertical cylinder according to the present invention. It is sectional drawing which shows the structure of the vertical cylinder which concerns on this invention. It is a figure explaining the method to detect the leak from the lower chamber of hydraulic fluid to an upper chamber. It is a figure explaining the other method of detecting the leak from the lower chamber of hydraulic fluid to an upper chamber.

  Hereinafter, with reference to the drawings, an embodiment of a vertical cylinder according to the present invention and a forklift provided with the vertical cylinder will be described.

  As shown in FIG. 1, the forklift 1 includes a mast 11 erected in front of a vehicle body 10, a lift bracket 12 supported so as to be movable up and down along the mast 11, and a pair of left and right cargo handling supported by the lift bracket 12. Fork 13 is provided. Further, the forklift 1 includes a control unit 14 that controls the entire forklift 1 such as travel control and hydraulic control inside the vehicle body 10.

  Further, the forklift 1 includes a lift cylinder 2 installed upright along the mast 11. The forklift 1 raises and lowers the lift bracket 12 and the fork 13 by extending and shortening the lift cylinder 2. This lift cylinder 2 is a vertical cylinder according to the present invention.

  As shown in FIG. 2, the lift cylinder 2 includes a hollow cylindrical cylinder tube 20. An upper cover 21 covering the upper end is attached to the upper end of the cylinder tube 20, and a lower cover 22 covering the lower end is attached to the lower end of the cylinder tube 20, and both ends of the cylinder tube 20 are closed.

  The lift cylinder 2 includes a piston 23 in the cylinder tube 20. The piston 23 is slidable along the axial direction of the cylinder tube 20. The cylinder tube 20 is partitioned into an upper chamber 24 (head side chamber) and a lower chamber 25 (bottom side chamber) by a piston 23. The lift cylinder 2 is an internal drain cylinder in which hydraulic oil is accommodated in the lower chamber 25 and air is not accommodated in the upper chamber 24.

  A ring-shaped seal member 26 is provided on the outer peripheral surface of the piston 23 to seal between the cylinder tube 20 and the piston 23, thereby preventing the hydraulic oil in the lower chamber 25 from leaking into the upper chamber 24 (internal leak). ing. Further, the piston 23 is provided with a check valve (not shown) for discharging the air in the upper chamber 24 compressed by the ascent of the piston 23 to the lower chamber 25.

  The lift cylinder 2 includes a piston rod 27 extending from the piston 23 toward the upper chamber 24 along the axial direction of the cylinder tube 20. The piston rod 27 penetrates the upper cover 21 slidably and protrudes to the outside.

  The lower cover 22 is provided with a supply / discharge port 28 communicating with the lower chamber 25. The supply and discharge of the hydraulic oil to and from the lower chamber 25 are performed from the supply and discharge port 28 by a hydraulic oil tank and a hydraulic oil pump (not shown) provided in the forklift 1. When hydraulic oil is supplied from the supply / discharge port 28 to the lower chamber 24, the piston 23 rises and the piston rod 27 extends, and when the hydraulic oil in the lower chamber 25 is discharged from the supply / discharge port 28, the piston 23 descends. As a result, the piston rod 27 is shortened.

  The lift cylinder 2 is configured as follows so that an internal leak to the upper chamber 24 caused by wear of the seal member 26 or the like can be detected.

  The lift cylinder 2 includes a float plate 3 in an upper chamber 24 that does not contain hydraulic oil. The float plate 3 is formed in a flat ring shape, is fitted on the piston rod 27, and is disposed on the upper surface of the piston 23 so as to be movable along the piston rod 27. The float plate 3 is made of a material (for example, resin) having a specific gravity smaller than that of the hydraulic oil and floats with respect to the hydraulic oil.

  Further, the lift cylinder 2 includes a distance sensor 4 (distance detection means) that detects a separation distance L to the float plate 3 on the upper chamber 24 side. The distance sensor 4 is a non-contact type sensor. For example, the distance sensor 4 applies an ultrasonic wave to the float plate 3 and receives a reflected wave thereof to detect the separation distance L, or irradiates the float plate 3 with laser light and reflects the reflected light. It is an optical distance sensor that detects a separation distance L by receiving light.

  The distance sensor 4 is provided on the upper cover 21 so that the lower surface of the upper cover 21 and the front surface of the distance sensor 4 are flush with each other. The distance sensor 4 detects the separation distance L to the float plate 3 using the lower surface of the upper cover 21 as a reference position.

  This distance sensor 4 is for detecting an internal leak as will be described later, but simultaneously functions as a stroke amount detection sensor, and detects the stroke amount of the piston rod 27 from the detected separation distance L.

  In the case of the configuration in which the separation distance L is detected by using the reflection of ultrasonic waves or laser light to the float plate 3 as described above and the stroke amount is detected, the upper surface of the float plate 3 that is the reflection surface is reflected. If processed so as to be easy, the detection accuracy of the stroke amount becomes better than the conventional configuration in which the stroke amount is detected using the piston 23 as a reflection surface. Further, the lift cylinder 2 is configured to detect the stroke amount on the side of the upper chamber 24 that does not contain hydraulic oil, and detects the stroke amount from the configuration that detects the stroke on the side of the lower chamber 25 that contains hydraulic oil. The accuracy is good.

  Furthermore, the lift cylinder 2 includes an end detection sensor 5 (stroke end detection means) that detects that the piston rod 27 has reached the stroke end. As the end detection sensor 5, for example, a known sensor such as a limit switch, a magnetic sensor, or an encoder is applied. The end detection sensor 5 is installed above the upper cover 21. The end detection sensor 5 can detect both the shortening side stroke end and the extension side stroke end.

  Further, the lift cylinder 2 includes a leak determination unit 6 that determines that the hydraulic oil has leaked from the lower chamber 25 to the upper chamber 24. The leak determination means 6 detects an internal leak based on detection signals from the distance sensor 4 and the end detection sensor 5.

  With reference to FIG. 3, the leak determination method of the leak determination means 6 is demonstrated. 3A and 3B show a state in which the piston rod 27 is positioned at the shortened stroke end. FIG. 3A shows a state where there is no internal leak, and FIG. 3B shows a state where there is an internal leak.

  In both cases of FIG. 3A and FIG. 3B, the piston rod 27 is positioned at the shortened stroke end, so the end detection sensor 5 detects the shortened stroke end.

  When there is no internal leak as shown in FIG. 3A, the distance sensor 4 detects the distance L1 as the separation distance L to the float plate 3.

  On the other hand, consider a case where an internal leak has occurred. As described above, the float plate 3 has a specific gravity smaller than that of the hydraulic oil. Therefore, if the hydraulic oil leaks to the upper chamber 24, the float plate 3 floats on the leaked hydraulic oil. As a result, the float plate 3 is elevated from the piston 23 by the amount of leakage as shown in FIG. 3B. Therefore, the distance sensor 4 detects a distance L2 that is smaller than the distance L1 when there is no internal leak as the separation distance L to the float plate 3.

  That is, in the case where there is no internal leak and in the case where there is an internal leak, even if the piston 23 is in the same position, the float plate 3 is not in the same position but is higher in the case where there is an internal leak. The detected separation distance L is smaller when there is an internal leak (L2 <L1).

Therefore, when the end detection sensor 5 detects the shortened stroke end, the leak determination means 6 determines that the separation distance L to the float plate 3 detected by the distance sensor 4 is smaller than the distance L1 (specified value). Then, it is determined that the hydraulic oil is leaking from the lower chamber 25 to the upper chamber 24.

  Furthermore, another determination method of the leak determination means 6 will be described with reference to FIG. 4A and 4B show a state where the piston rod 27 is extended and the float plate 3 reaches the upper cover 21. FIG. 4A shows a state where there is no internal leak, and FIG. 4B shows a state where there is an internal leak. .

  4A and 4B, since the float plate 3 is in contact with the lower surface of the upper cover 21, the separation distance L to the float plate 3 detected by the distance sensor 4 is zero.

  When there is no internal leak as shown in FIG. 4A, the piston 23 has moved to the uppermost position, and the piston rod 27 has reached the extension stroke end. Therefore, the end detection sensor 5 detects the extension side stroke end. That is, when there is no internal leak and the separation distance L detected by the distance sensor 4 is zero, the end detection sensor 5 detects the extension side stroke end.

  On the other hand, as shown in FIG. 4B, when there is an internal leak, there is hydraulic oil leaked between the float plate 3 and the piston 23, so the piston 23 has not moved to the top. Therefore, unlike FIG. 4A, the piston rod 27 does not reach the extension stroke end, and the end detection sensor 5 does not detect the extension stroke end. That is, when there is an internal leak, the end detection sensor 5 does not detect the extension side stroke end even if the separation distance L detected by the distance sensor 4 is zero.

  Accordingly, when the detected separation distance L is zero and the end detection sensor 5 has not detected the extension side stroke end, the leak determination means 6 determines that there is an internal leak.

  As described above, when the hydraulic oil leaks to the upper chamber 24, the lift cylinder 2 detects an internal leak by utilizing the fact that the float plate 3 floats on the leaked hydraulic oil and moves up from the piston 23. For example, if the leak determination means 6 is connected to the control unit 14 of the forklift 1 so that a warning is issued when the forklift 1 detects an internal leak, the operator can easily know the occurrence of the internal leak. it can.

  It is preferable that the float plate 3 does not slide with respect to the piston rod 27 and the cylinder tube 20 so that the float plate 3 can move smoothly along the piston rod 27 when an internal leak occurs. . That is, it is preferable that the ring-shaped float plate 3 is fitted to the piston rod 27 with some play and has such a diameter that a slight gap is provided between the ring plate 3 and the cylinder tube 20.

  The lift cylinder 2 detects an internal leak using sensors generally provided in the cylinder, such as a stroke amount detection sensor (distance sensor 4) and an end detection sensor 5. Therefore, it is not necessary to provide a dedicated sensor for detecting an internal leak separately from the sensors 4 and 5.

As mentioned above, although preferable embodiment of this invention was described, the structure of this invention is not limited to this embodiment.
In the embodiment, the example in which the vertical cylinder is the lift cylinder 2 for raising and lowering the fork 13 of the forklift 1 has been described, but the application is not limited to the lift cylinder 2.

  In the embodiment, the cylinder tube 20, the upper cover 21, and the lower cover 22 are separate members, but the cylinder tube 20 and the upper cover 21 are integrally formed, or the cylinder tube 20 and the lower cover 22. May be formed integrally with each other.

  In the embodiment, the end detection sensor 5 is attached to the lift cylinder 2 and is configured to detect the shortening side and the extension side stroke end from the operation of the piston rod 27. Instead of this configuration, for example, the end detection sensor 5 may be attached to the mast 11 of the forklift 1 to detect the shortening side and the extension side stroke end from the operation of the lift bracket 12 or the fork 13.

1 Forklift 13 Fork2 Lift cylinder (vertical cylinder)
20 cylinder tube 21 upper cover 22 lower cover 23 piston 24 upper chamber 25 lower chamber 27 piston rod 3 float plate 4 distance sensor (distance detection means)
5 End detection sensor (stroke end detection means)
6 Leak determination means

Claims (5)

A cylinder tube having an upper end covered with an upper cover and a lower end covered with a lower cover; a piston slidably provided in the cylinder tube; and partitioning the cylinder tube into an upper chamber and a lower chamber; and A vertical cylinder that includes a piston rod extending through the upper cover, the hydraulic oil is stored in the lower chamber, and the hydraulic oil is not stored in the upper chamber;
A float plate arranged movably along the piston rod in the upper chamber and configured to float against the hydraulic fluid when the hydraulic fluid leaks from the lower chamber to the upper chamber; A non-contact type distance detecting means provided on the cover for detecting a separation distance to the float plate; a stroke end detecting means for detecting that the piston rod has reached the shortened stroke end; A leak determination means for determining a leak from a lower chamber to the upper chamber,
When the stroke end detection unit detects the shortening side stroke end and the separation distance detected by the distance detection unit is smaller than a predetermined value, the leak determination unit detects the hydraulic oil from the lower chamber. A vertical cylinder characterized in that it is determined that there is a leak into the upper chamber. A cylinder tube having an upper end covered with an upper cover and a lower end covered with a lower cover; a piston slidably provided in the cylinder tube; and partitioning the cylinder tube into an upper chamber and a lower chamber; and A vertical cylinder that includes a piston rod extending through the upper cover, the hydraulic oil is stored in the lower chamber, and the hydraulic oil is not stored in the upper chamber;
A float plate arranged movably along the piston rod in the upper chamber and configured to float against the hydraulic fluid when the hydraulic fluid leaks from the lower chamber to the upper chamber; A non-contact type distance detecting means provided on the cover for detecting a separation distance to the float plate; a stroke end detecting means for detecting that the piston rod has reached the extension side stroke end; A leak determination means for determining a leak from a lower chamber to the upper chamber,
The leak determination means is configured such that when the separation distance detected by the distance detection means is zero and the stroke end detection means does not detect the extension side stroke end, the hydraulic oil is discharged from the lower chamber. A vertical cylinder characterized in that it is determined that there is a leak into the upper chamber.   The vertical cylinder according to claim 1 or 2, wherein the distance detection means is a stroke amount detection sensor that detects a stroke amount of the piston rod from the separation distance.   The vertical cylinder according to any one of claims 1 to 3, wherein the float plate is formed in a ring shape and is externally fitted to the piston rod.   5. A forklift comprising the vertical cylinder according to claim 1 and a fork for cargo handling, wherein the fork is moved up and down by the vertical cylinder.

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