JP2000120610A - Hydraulic cylinder circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of liquid leakage even in the case where a rod seal is damaged or worn by returning the liquid leaked between double seals provided in a rod sliding part of a cylinder into the cylinder through a low-pressure selecting valve. SOLUTION: In the case where the liquid of a rod side liquid chamber R is leaked between a rod seal 8 and a dust seal 10 through the rod seal 8, the leaked liquid does not flow out and flows in a liquid passage 12. This leaked liquid flows to an inlet port 14b of a low-pressure selecting valve 14 through a check valve 16. In the low-pressure selecting valve 14, when the pressure of an outlet port 14d is higher than that of an outlet port 14c, a spool 14a connects the inlet port 14b to the outlet port 14c having a lower pressure with the hydraulic pressure of a signal line 14e. On the other hand, when the pressure of the outlet port 14c is higher than that of the outlet port 14d, the spool 14a connects the inlet port 14b to the outlet port 14d having a lower pressure with the hydraulic pressure of a signal line 14f. With this structure, the leaked liquid flows to a rod side liquid chamber R or a head side liquid chamber H having a lower pressure than the others.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic cylinder circuit, and more particularly, to a hydraulic cylinder circuit for preventing liquid from leaking out of a cylinder from a rod sliding portion of the cylinder.

[0002]

2. Description of the Related Art Hydraulic cylinders such as hydraulic cylinders
The rod sliding portion of the cylinder is provided with a rod seal for stopping liquid leakage through the sliding portion to the outside of the cylinder and a dust seal for stopping entry of foreign matter from outside. If the rod seal is damaged by a foreign substance such as a metal piece mixed in the liquid or earth and sand from the outside, or if the seal is worn, liquid leakage occurs.

[0003] Leakage outside the hydraulic cylinder not only contaminates the hydraulic cylinder and the area around the hydraulic cylinder, but also replenishes the hydraulic circuit when the hydraulic cylinder malfunctions or the amount of leakage increases. And other problems. In order to prevent liquid leakage, measures are taken to filter the liquid so that foreign matter does not enter the liquid, to provide a plurality of rod seals, and to cover the cylinder rod with a dustproof cover.

[0004]

However, in the conventional hydraulic cylinder of the type described above, when the rod seal is damaged or worn, the leakage cannot be stopped by the dust seal outside the rod seal. There is a problem that liquid leakage occurs outside.

[0005] The present invention has been made in view of the above-mentioned facts, and a technical problem thereof is to prevent the leakage of liquid from the hydraulic cylinder to the outside even if the rod seal for stopping the leakage of the hydraulic cylinder is damaged or worn. It is to provide a hydraulic cylinder circuit that can be prevented.

[0006]

According to the present invention, there is provided a hydraulic cylinder circuit for solving the above technical problems, comprising a first sealing means and a second sealing means provided on a rod sliding portion of a hydraulic cylinder. One end of which communicates between the first sealing means and the second sealing means, and the other end of the liquid passage is connected to one of a rod-side liquid chamber and a head-side liquid chamber of the hydraulic cylinder. A low-pressure selection valve connected to the low-pressure side, and a check valve provided in the liquid passage, which allows a flow in the direction of the low-pressure selection valve from the rod sliding portion and prevents a flow in the opposite direction, A hydraulic cylinder circuit is provided.

In the hydraulic cylinder circuit according to the present invention, a liquid passage communicating between the first sealing means and the second sealing means of the rod sliding portion of the hydraulic cylinder is provided, and the first sealing means is provided. If there is a leak through the fluid, the leaked fluid is returned to the hydraulic cylinder through the fluid path via the low pressure selection valve. Therefore, liquid leakage to the outside of the hydraulic cylinder is prevented.

[0008] In a preferred embodiment, the first sealing means is a rod seal for stopping liquid leakage from inside to outside of the hydraulic cylinder, and the second sealing means is outside the hydraulic cylinder. It is a dust seal that stops foreign matter from entering from inside. The low-pressure selection valve is switched based on the liquid pressure in the rod-side liquid chamber and the head-side liquid chamber.

Therefore, the leakage liquid passing through the rod seal is prevented from leaking outside through the dust seal. The low pressure selection valve automatically operates based on the magnitude of the hydraulic pressure in the hydraulic cylinder.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a hydraulic cylinder circuit constructed in accordance with the present invention will be described in more detail with reference to the accompanying drawings.

Referring to FIG. 2 together with FIG. 1,
The hydraulic cylinder circuit, which is designated by the numeral 2 in its entirety, includes a hydraulic cylinder 4 and a first end of a sliding portion of a rod 6 of the hydraulic cylinder 4 having one end.
A liquid passage 12 communicating between a rod seal 8 as a sealing means and a dust seal 10 as a second sealing means;
A low-pressure selector valve 14 for connecting the other end of the liquid passage 12 to a low-pressure liquid chamber of the rod-side liquid chamber R or the head-side liquid chamber H of the hydraulic cylinder 4;
And a check valve 16 that permits flow in the direction of the low pressure selection valve 14 from the dust seal 10 side and prevents flow in the reverse direction.

The hydraulic cylinder 4 has a cylinder body 4a having one end closed and the other end open, and a cap 5 having a sliding hole 5a attached to the open end and in which a rod 6 slides. The piston 7 attached to one end of the rod 6 is slidably inserted into the cylinder body 4a. Inside the hydraulic cylinder 4, a piston 7
Thus, the rod-side liquid chamber R is formed on the cap 5 side, and the head-side liquid chamber H is formed on the opposite side.
A rod port 4b communicating with the rod-side liquid chamber R from outside and a head port 4c communicating with the head-side liquid chamber H are formed in the cylinder body 4a. By supplying the hydraulic fluid from the fluid passage A to the rod-side fluid chamber R through the rod port 4b, the rod 6 of the hydraulic cylinder 4
Operates in a contracting direction (leftward in FIGS. 1 and 2). At this time, the hydraulic fluid in the head side liquid chamber H is discharged to the liquid passage B through the head port 4c. Conversely, by supplying the working fluid from the fluid passage B to the head-side liquid chamber H through the head port 4c, the rod 6 operates in the extending direction (rightward in FIGS. 1 and 2). At this time, the working fluid in the rod-side liquid chamber R is discharged to the liquid passage A through the rod port 4b. The liquid paths A and B are connected to a well-known directional control valve (not shown).

A plurality of annular grooves are formed in the inner peripheral surface of the rod sliding hole 5a of the cap 5 at intervals in the sliding direction of the rod 6, and each of the annular grooves is formed inside the cylinder body 4a. , A bearing 4e, a buffer seal 4f, a rod seal 8 and a dust seal 10 are provided. The bearing 4e is a sliding bearing for the rod 6, the buffer seal 4f is a seal for buffering an impact pressure applied to the rod seal 8, and the rod seal 8 has a U-shaped cross section that opens toward the inside of the hydraulic cylinder 4. The dust seal 7 has a seal lip facing the outside of the hydraulic cylinder 4 to prevent foreign matter from entering.

The cap 5 has a communication hole 5b communicating with the rod sliding hole 5a between the rod seal 8 and the dust seal 10 from the outer periphery of the cap 5. One end of the liquid passage 12 is connected to the communication hole 5b. A check valve 16 is provided in the middle of the liquid passage 12 to allow a flow from the communication hole 5b and prevent a flow in the opposite direction.

The low pressure selection valve 14 is provided with a built-in spool 1.
4a is a two-position three-port valve that is switched by a signal hydraulic pressure,
An inlet port 14b to which the liquid path 12 is connected, an outlet port 14c connected to the rod port 4b of the rod-side liquid chamber R, and an outlet port 14d connected to the head port 4c of the head-side liquid chamber H are provided. At one end of the spool 14a, the pressure at the outlet port 14d is provided by a signal path 14e, and at the other end of the spool 14a, the outlet port 14c is provided by a signal path 14f.
Are introduced respectively. And exit port 1
When the pressure at the outlet port 14d is higher than the pressure at 4c, the spool 14a connects the inlet port 14b to the low-pressure outlet port 14c by the hydraulic pressure of the signal path 14e (FIG. 1).
State). Conversely, when the pressure at the outlet port 14c is higher than the pressure at the outlet port 14d, the spool 14a connects the inlet port 14b to the low-pressure outlet port 14d by the hydraulic pressure of the signal path 14f (the state shown in FIG. 3). .

The operation of the hydraulic cylinder circuit 2 as described above will be described with reference to FIGS.

(1) When the liquid in the rod-side liquid chamber R leaks between the rod seal 8 and the dust seal 10 through the rod seal 8, the leaked liquid does not flow out through the dust seal 10 to the outside, and the communication hole is formed. 5b flows into the liquid passage 12.
The leaked liquid flowing into the liquid passage 12 flows through the check valve 16 to the inlet port 14a of the low-pressure selection valve 14. Then, the leaked liquid flows to the lower side of the pressure in the rod side liquid chamber R or the head side liquid chamber H selected by the low pressure selection valve 14. For example,
When the directional control valve (not shown) is operated to supply the hydraulic fluid from the fluid passage B to the head fluid chamber H to extend the rod 6, the rod fluid chamber R is connected via the fluid passage A at this time. And the pressure in the rod-side liquid chamber R becomes lower than that in the head-side liquid chamber H. Therefore, the low-pressure selection valve 14 connects the inlet port 14b to the rod-side liquid chamber R. (State shown in FIG. 1) The leaked liquid flows to the rod-side liquid chamber R.
On the other hand, when the hydraulic fluid is supplied from the fluid passage A to the rod-side fluid chamber R to contract the rod 6, the head-side fluid chamber H
Is released to a hydraulic tank (not shown) via the liquid passage B, and the pressure in the head-side liquid chamber H becomes lower than that in the rod-side liquid chamber R. Therefore, the low-pressure selection valve 14 connects the inlet port 14b to the head-side liquid chamber R. The leaked liquid connected to the liquid chamber H (the state shown in FIG. 3) flows into the liquid chamber H on the head side.

(2) Therefore, when a problem such as damage or wear occurs in the rod seal 8, leakage of liquid to the outside of the cylinder 4 is reliably prevented. In addition, the cylinder 4 and the periphery of the cylinder 4 are not stained, and the liquid does not need to be supplied to the hydraulic cylinder circuit 2.

(3) The check valve 16 controls the pressure in the rod-side liquid chamber R or the head-side liquid chamber H, which is selected at a low pressure, in the liquid path 1.
2 is higher than the pressure of the leaking liquid in
Through the rod seal 8 and the dust seal 10.

(4) The low pressure selection valve 14 is
Automatically operates based on the pressure in the rod-side liquid chamber R or the head-side liquid chamber H. Therefore, there is no need to provide a special signal source for operating the low-pressure selection valve 14, and the cost of the hydraulic cylinder circuit 2 can be reduced.

(5) When the present invention is applied to the hydraulic cylinder 4, the hydraulic cylinder 4 needs to be modified because the communication hole 5a may be provided between the rod seal 8 of the cap 5 and the dust seal 10. I can do it. Further, since the low-pressure selection valve 14 and the check valve 16 can be directly attached to the hydraulic cylinder 4, the structure for preventing leakage of the hydraulic cylinder 4 can be made compact.

As described above, the present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above-described embodiments, and can be variously modified or modified within the scope of the present invention. It is. For example, in the embodiment of the present invention, the liquid path for guiding the leaked liquid is connected between the rod seal as the first sealing means and the dust seal as the second sealing means. Both of the second sealing means may be leak-tight rod seals, and a fluid path may be connected therebetween.

[0023]

According to the hydraulic cylinder circuit constructed in accordance with the present invention, even if the rod seal for stopping the leakage of the hydraulic cylinder is damaged or worn, the leakage of the liquid from the hydraulic cylinder to the outside is reliably prevented. A hydraulic cylinder circuit is provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a hydraulic cylinder circuit configured according to the present invention, in a state where a rod-side liquid chamber is selected by a low-pressure selection valve.

FIG. 2 is a detailed sectional view of a rod sliding portion of the hydraulic cylinder.

FIG. 3 is a diagram showing a state in which the low-pressure selection valve shown in FIG. 1 has selected a head-side liquid chamber.

[Explanation of symbols]

 2: Hydraulic cylinder circuit 4: Hydraulic cylinder 6: Rod 8: Rod seal (first sealing means) 10: Dust seal (second sealing means) 12: Hydraulic path 14: Low pressure selection valve 16: Check valve H: Head side liquid chamber R: Rod side liquid chamber

Claims (3)

[Claims] 1. A first seal means and a second seal means provided on a rod sliding portion of a hydraulic cylinder, and one end thereof communicates between the first seal means and the second seal means. A fluid path, a low-pressure selection valve for connecting the other end of the fluid path to a low-pressure side of the rod-side fluid chamber or the head-side fluid chamber of the hydraulic cylinder, and the rod slide provided in the fluid path. A check valve that permits flow in the direction of the low-pressure selection valve from the section and prevents flow in the reverse direction. 2. The first sealing means is a rod seal for stopping liquid leakage from inside to outside of the hydraulic cylinder,
2. The hydraulic cylinder circuit according to claim 1, wherein said second sealing means is a dust seal for stopping entry of foreign matter from outside to inside of said hydraulic cylinder. 3. The hydraulic cylinder circuit according to claim 1, wherein the low-pressure selection valve is switched based on the hydraulic pressure of the rod-side liquid chamber and the head-side liquid chamber.