JPH1161888A - Hydraulic circuit for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve a work difficulty by providing a check valve blocking the backflow from an oil tank to a return line from a remote control valve on a line merged with the return line. SOLUTION: A check valve 30 is inserted directly after the manifold 27 of an oil pipe 28. During the normal operation, the flow of the return oil of an oil tank 11 is not blocked, and the check valve 30 is not provided. When all pipes are removed for repair or replacement, a hydraulic pump 15 is stopped, and a switch valve 19 is closed. Connecting portions between pipes 20, 21 and a remote control valve 16 are removed. The oil remaining in the pipes 20, 21 is a small quantity and can be received with a small container. Connecting portions between pipes 23a, 23b, 24a, 24b and the remote control valve 16 are likewise removed. Connection portions between return oil pipes 25, 28 and the remote control valve 16 are then removed. The back flow from the oil tank 11 is prevented by the check valve 30, and the connection portions of the pipes 25, 26 can be removed. The maintenance and inspection of the piping system of pilot pressure oil is facilitated, and the pollution of a work site can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of hydraulic circuits for construction machines.

[0002]

2. Description of the Related Art A hydraulic circuit of a construction machine stores hydraulic oil or pilot oil in an oil tank and supplies the oil in the oil tank to devices such as an actuator via a control valve by a main hydraulic pump, or a pilot hydraulic system. The pump supplies the oil to the pilot port of the control valve via the remote control valve, and at the same time, the return oil from the control valve or the remote control valve is returned to the oil tank and circulated for use.

In the above-mentioned hydraulic circuit, it is necessary to take out or replace devices such as hoses, pipes, seals at connection portions, actuators and the like, or parts thereof at the time of maintenance and inspection. In such a case, if the connection is disconnected because oil remains in the pipe, the oil flows out from that portion, making inspection work difficult and polluting the environment of the work site. For this reason, in the conventional apparatus, an on-off valve is provided before and after the equipment requiring maintenance and inspection, and when the equipment is removed, the on-off valve is closed so that the oil does not flow.

[0004] For example, Japanese Patent Laid-Open Publication No. 7-710
58 discloses the following hydraulic circuit. That is,
An open / close valve driven by an electric motor is provided before and after all actuators, an outlet and a return port of an oil tank, and before and after an oil cooler, and an operation switch for remotely controlling the open / close valve is provided in a driver's seat. Normally, all the operation switches are held in the open position, and when a circuit is opened for inspection of equipment, replacement of parts, etc., the switch at that location is switched to the closed side to prevent oil from flowing out. .

However, in the conventional apparatus, much consideration was not given to the pipeline for supplying the pilot oil.
FIG. 2 is a diagram illustrating an example of a pilot line of a conventional device. In FIG. 2, hydraulic oil is supplied from an oil tank 11 via a pipe 12 to a main hydraulic pump (not shown), and a return pipe 1
From 3, return oil that has passed through a control valve (not shown) is returned to the oil tank 11. On the other hand, the hydraulic fluid for pilot is supplied to the pilot hydraulic pump 15 through the pipe 14 and the hydraulic pump 1
Pressure oil from 5 is connected to the input port of remote control valve 16 by piping 1
7, supplied by branch pipes 20, 21. On the inlet side and the outlet side of the hydraulic pump 15, on-off valves 18 and 19 for checking and maintaining the hydraulic pump 15 are provided.

[0006] Pressure oil output from the remote control valve 16 is supplied to a pilot port of a control valve (not shown) via piping 23a, 24a or 23b, 24b, and return oil is supplied from a pilot port on the opposite side to piping 23a, 24a, or 23b. ,
24b, remote control valve 16, and return oil pipes 25, 26
, And are combined by the manifold 27, and the combined return oil is returned to the oil tank 11 via the return oil pipe 28.

[0007]

As described above, in the conventional apparatus, in order to facilitate maintenance and inspection of the equipment of the hydraulic circuit, on-off valves are inserted before and after the equipment, and this on-off valve is manually operated or operated. Remote control was used. However, this countermeasure has not been taken for a pilot line that controls a control valve or the like. Therefore, especially when the oil tank is installed above the pilot line, the pipe connection portion is removed for maintenance and inspection, and the pilot line (for example, the return pipes 25 and 26 in FIG. 2) is opened. Then, the oil in the oil tank spilled out of the location, making the work difficult and causing environmental pollution.

In order to solve this problem, it is conceivable to provide an electromagnetic on-off valve or the like also in the pilot line for remote control. However, if a large part such as an electromagnetic on-off valve is provided in a thin line, the design becomes unbalanced. Therefore, there is a problem that the cost increases. Further, if a large number of on-off valves are provided unnecessarily, there is a problem that the operation becomes complicated. On the other hand, if the oil tank is arranged below the pilot return pipe, the oil in the oil tank will not flow out, but there is a problem that the layout of the piping is limited.

The present invention has been made in view of the above background, and has as its object to provide an apparatus which solves the above-mentioned problem without providing any special operation and merely providing simple components.

[0010]

According to a first aspect of the present invention, there is provided an apparatus for supplying pilot pressure oil to a pilot port of a control valve via a remote control valve or other oil machines by a hydraulic pump. In the hydraulic circuit, a check valve for preventing a backflow from an oil tank is provided on a return line from the remote control valve or the like on a line that joins the return line.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment embodying the present invention. 1, the same components as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. A check valve 30 is inserted in the return oil pipe 28 immediately after the manifold 27.

With the above configuration, this embodiment functions as follows. During normal operation, the check valve 30 does not impede the flow of return oil from the manifold 27 to the oil tank 11, and thus functions in the same manner as the conventional device without the check valve 30. On the other hand, for example, when all the pipes connected to the remote control valve 16 (or other oil machines) are to be removed for repair and replacement, the following can be performed. The operation of the hydraulic pump 15 is stopped, and the on-off valve 19 is closed. Disconnect the connection between the pipes 20, 21 and the remote control valve 16. In this case, since the amount of oil remaining in the pipes 20 and 21 is small, the oil can be received in a small container. Pipe 23 in the same manner
a, 23b, 24a, 24b and the connection portion of the remote control valve are disconnected.

Next, the connection between the return oil pipes 25 and 26 and the remote control valve 16 is disconnected. In this case, in the conventional device, the oil in the oil tank 11 passed through the pipe 28 and the manifold 27, and a large amount of oil flowed off from the disconnected portion. However, in this embodiment, since the check valve 30 prevents the backflow from the oil tank 11, the oil that can flow out is limited to the oil remaining in the pipes 25 and 26 at most. Therefore, the connection portions of the pipes 25 and 26 can be removed in substantially the same manner as the pipes 20 and 21. In the above, the inspection and repair of the remote control valve 16 has been described as a representative case. Can be.

As described above, the present embodiment has an effect that operations such as removal of the remote control valve 16 for repair and inspection can be performed more easily than in the conventional apparatus. Also, there is no spill of a large amount of oil and no pollution of the work site. Furthermore, when an open / close valve is used instead of the check valve 30, not only the open / close operation is required, but also a trouble that causes an accident may occur if the open / close operation is forgotten. However, in the present embodiment, the opening / closing operation or an alternative operation is unnecessary, and no trouble occurs. Therefore, in this respect, there is an effect that the inspection operation can be easily performed.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific structure is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. Even this is included in the present invention. For example, the number of remote control valves is not limited to two, but may be one or three or more. Further, the piping system for pilot pressure oil is not limited to the one described in this embodiment, and a different piping system may be used.

[0016]

As described above, according to the structure of the present invention, since the oil in the oil tank does not flow backward and flows out, the maintenance and inspection of the piping system for pilot pressure oil is facilitated. There is. In addition, there is also an effect that the work site is not contaminated.

[Brief description of the drawings]

FIG. 1 shows a pilot piping system of a conventional apparatus.

FIG. 2 shows a pilot piping system according to an embodiment of the present invention.

[Explanation of symbols]

11 Oil Tank 15 Pilot Hydraulic Pump 20, 21 Pilot Oil Supply Side Hydraulic Tube 23a, 23b 24a, 24b Hydraulic Tube 25, 26 Pilot Oil Return Side Hydraulic Tube (Return Line) 27 Manifold 28 Pilot Oil Return Hydraulic Tube (Merging Line) 30 Check valve

Claims (1)

[Claims] 1. A hydraulic circuit for supplying pilot pressure oil to a pilot port of a control valve via a remote control valve or other oil machinery by a hydraulic pump, wherein oil is supplied to a return line from the remote control valve or other oil machinery. A hydraulic circuit for a construction machine, wherein a check valve for preventing backflow from a tank is provided in a line joining a return line.