JP2003097509A - Hydraulic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic driving device capable of releasing the excessive pressure generated between a piping breakdown control valve and a hydraulic actuator without providing a relief valve between them. SOLUTION: The piping breakdown control valve 10 provided in a boom cylinder 3 is provided with an actuator port 11, a piping port 12, a pilot port 14, a drain port 16, a seat valve 17, and a spool 18 possible to come close to and separate from the seat valve 17. The piping breakdown control valve 10 is also provided with a pressure detecting means for detecting a rise of the pressure of the pressure oil given to the actuator port 11 to the set pressure or more, and a spool driving means for moving the spool 18 to form an opening between the seat valve 17 and the spool 18 when the pressure more than the set pressure is detected. The pressure detecting means contains a poppet 30, a pressure setting spring for energizing the poppet 30 in a valve closing direction, and the pressure setting spring for energizing the poppet 30 in a valve closing direction, and the spool driving means contains a passage 31, a spring chamber 32 and a passage 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe breakage provided in a working machine such as a hydraulic excavator and capable of preventing pressure oil from flowing out from a hydraulic actuator to the main pipeline when the main pipeline breaks. The present invention relates to a hydraulic drive device having a control valve.

[0002]

2. Description of the Related Art FIG. 6 shows the structure of a conventional hydraulic drive system of this type, and is a hydraulic circuit diagram showing a neutral state.

The prior art shown in FIG. 6 is provided in a construction machine such as a hydraulic excavator, and includes a hydraulic pump 1 and
A tank 2, a hydraulic actuator that is driven by the pressure oil discharged from the hydraulic pump 1, for example, a boom cylinder 3 that drives a boom 3a and that drives the boom 3a, the hydraulic pump 1 and the tank 2 described above, and a boom cylinder 3. , The directional control valve 6 interposed in the main pipelines 4, 5 for controlling the flow of pressure oil supplied from the hydraulic pump 1 to the boom cylinder 3, and the directional control An operating device 7 for generating pilot pressure for switching and controlling the valve 6 and main relief valves 8 and 9 for defining the maximum pressure of the main pipe lines 4 and 5 are provided. The directional control valve 6 and the main relief valves 8 and 9 described above constitute one structure.

Further, the boom cylinder 3 is attached to the above-mentioned boom cylinder 3, is arranged between the boom cylinder 3 and the main pipe line 4, and the boom cylinder 3 is connected to the main pipe line in accordance with the pilot pressure generated by the operation of the operating device 7. 4 is provided with a pipe breakage control valve 10 capable of controlling the flow rate of pressure oil flowing out to the main pipe 4 and preventing the flow of pressure oil from the boom cylinder 3 to the main pipe 4 when the main pipe 4 is broken.

The pipe break control valve 10 has an actuator port 11 connected to the boom cylinder 3, a pipe port 12 connected to the main pipe 4, and a pilot pressure generated by the operating device 7 in the pilot pipe 13. Through the pilot port 14 and the drain line 1 to the tank 2.
And a drain port 16 which is communicated via Also, from the piping port 12 to the actuator port 1
1, a seat valve 17 that allows the flow of pressure oil into the valve 1, a spring 17a that urges the seat valve 17 to return to the neutral position, and a seat valve 17 that is provided so as to come in contact with and separate from the seat valve 17. And a spool 18 that moves in accordance with the pilot pressure and changes the area of the opening formed between the seat valve 17 and the seat valve 17 according to the magnitude of the pilot pressure. further,
A throttle 19 formed in the spool 18 and communicating with the actuator port 11, a spring chamber 20 communicating with the throttle 19 and formed inside the spool 18, and accommodated in the spring chamber 20. A first return spring 21 that biases the spring 21, a receiving member 22 that forms a spring receiver of the spring 21, and a surrounding of the receiving member 22.
A spring chamber 23 communicating with the drain port 16 and a second return spring 24 housed in the spring chamber 23 and biasing the spool 18 toward the seat valve 17 are provided.

Further, the pressure of the pressure oil that is attached to the boom cylinder 3 described above and that is arranged in the oil passage 25 that connects the boom cylinder 3 and the actuator port 11 of the pipe break control valve 10 is introduced into the oil passage 25. When the pressure becomes excessively high, that is, the set pressure, the relief valve 2 that allows the pressure oil guided to the oil passage 25 to escape to the tank 2 via the drain conduit 26.
Equipped with 7. The relief valve 27 and the pipe breakage control valve 10 described above are included in one structure.

The main pipelines 4 and 5, the drain pipeline 15 connected to the pipe break control valve 10, and the relief valve 27.
The drain pipe line 26 connected to is formed of, for example, a rubber pipe. Further, the main pipelines 4, 5 and the drain pipeline 26 are
It is much longer than the oil passage 25 that connects the boom cylinder 3 and the pipe break control valve 10, and the pipe diameter is also set to be large.

In the prior art thus constructed, for example, when the operation device 7 is operated to switch the directional control valve 6 to the right position in FIG. 6, the pressure oil of the hydraulic pump 1 is transferred to the directional control valve 6 and the main pipeline. 5 is supplied to the rod side chamber of the boom cylinder 3 and the pilot pressure of the operating device 7 is supplied to the pilot port 14 of the pipe break control valve 10 via the pilot pipe line 13, whereby the spool 18 is supplied. 6 to the right and away from the seat valve 17 to form an opening. Therefore, the pressure oil in the bottom side chamber of the boom cylinder 3 passes through the oil passage 25, the actuator port 11 of the pipe breakage control valve 10, and the seat valve 17 and the spool 18 described above.
It is guided to the opening formed between them, and further returned to the tank 2 via the main pipe line 4 and the direction control valve 6. As a result, the boom cylinder 3 contracts, and the boom is lowered. That is, when the boom is lowered, the return flow rate from the rod side chamber of the boom cylinder 3 to the tank 2 is controlled by the pipe breakage control valve 10 that operates according to the operation amount of the operation device 7.

Further, when the pipe break control valve 10 is closed, a large load is applied to the boom 3a, and the pressure in the bottom side chamber of the boom cylinder 3, that is, the bottom side chamber of the boom cylinder 3 and the pipe break control valve 10 is reduced. When the pressure in the communicating oil passage 25 becomes an excessive pressure equal to or higher than the set pressure of the relief valve 27, the excessive pressure is released to the tank 2 via the relief valve 27 and the drain conduit 26. This prevents the boom cylinder 3 from being damaged.

When a break occurs in the main pipe line 4,
By keeping the operating device 7 in the neutral position and keeping the directional control valve 7 in the neutral position, the spool 18 of the pipe break control valve 10 abuts the seat valve 17 and the opening is closed. As a result, it is possible to prevent the pressure oil applied to the actuator port 11 of the pipe breakage control valve 10 via the bottom chamber of the boom cylinder 3 and the oil passage 25 from flowing into the broken main pipe line 4.

[0011]

The above-mentioned conventional technique is
The structure attached to the boom cylinder 3 is the relief valve 27.
And the pipe break control valve 10 are included, the number of parts is increased, which increases the manufacturing cost, increases the weight, and requires the boom cylinder 3 to be large in size so as to have high rigidity. is there. In FIG. 6, the combination of the relief valve 27 and the pipe breakage control valve 10 is provided only on the bottom side of the boom cylinder 3, but when such a combination is also provided on the rod side of the boom cylinder 3, The number of parts increases, and the above problem becomes more prominent.

Further, the above-mentioned relief valve 27 is large in size because it can pass the whole amount of the pressure oil flowing from the bottom side chamber of the boom cylinder 3, and therefore, the relief valve 27 and the pipe break control are large. There is a problem that one structure including the valve 10 is upsized, the weight is increased from a viewpoint different from the above, and the boom cylinder 3 must be upsized so as to have high rigidity.

Further, as described above, as the structure including the relief valve 27 and the pipe breakage control valve 10 becomes larger, while the front working machine including the boom 3a is being driven,
This structure tends to collide with an obstacle such as rock, and when such a collision occurs, the pipe break control valve 10 included in the structure may be damaged.

Further, since the drain pipe 26 connecting the relief valve 27 and the tank 2 guides the entire amount of the pressure oil returned from the boom cylinder 3 via the relief valve 27, like the main pipe lines 4 and 5. Since the pipe diameter must be set large, this causes a problem of high manufacturing cost. Also,
Since the pipe diameter is large, it is difficult to draw the drain pipe 26 compactly, and there is a problem that the pipe design including the drain pipe 26 is restricted.

As a hydraulic drive system equipped with this type of pipe break control valve, the one disclosed in Japanese Patent Laid-Open No. 11-303810 is known.

The present invention has been made in view of the above-mentioned conventional state of the art, and an object thereof is to provide an excessive pressure generated between a pipe break control valve and a hydraulic actuator without providing a relief valve between the pipe break control valve and the hydraulic actuator. An object is to provide a hydraulic drive system that can release pressure.

[0017]

In order to achieve the above object, the invention according to claim 1 of the present invention comprises a hydraulic pump, a tank, and a hydraulic actuator driven by pressure oil discharged from the hydraulic pump. A main line connecting the hydraulic pump and the hydraulic actuator, a direction control valve interposed in the main line for controlling the flow of pressure oil supplied from the hydraulic pump to the hydraulic actuator, and a direction control valve An operating device for switching the control valve is provided, the operating device is attached to the hydraulic actuator, is disposed between the hydraulic actuator and the main pipe line, and operates according to pilot pressure generated by operating the operating device. If the flow rate of the pressure oil flowing out from the hydraulic actuator to the main pipeline is controlled and the main pipeline is broken, A pipe break control valve for preventing outflow of pressure oil to the main pipe is provided, and the pipe break control valve has an actuator port connected to the hydraulic actuator, a pipe port connected to the main pipe, and the pilot. A seat valve that has a pilot port to which pressure is supplied and a drain port that communicates with the tank and allows the flow of pressure oil from the piping port to the actuator port, and can be connected to and separated from the seat valve. A hydraulic drive device that includes a spool that is provided, moves according to the pilot pressure, and changes an area of an opening formed between the seat valve and the seat valve according to a magnitude of the pilot pressure,
The pipe break control valve detects pressure of the pressure oil applied to the actuator port of the pipe break control valve to a pressure equal to or higher than a set pressure, and the pressure detection unit detects the pressure equal to or higher than the set pressure. And a spool drive means for moving the spool so as to form an opening between the seat valve and the spool when the pressure is detected.

In the invention according to claim 1 having such a structure, when an excessive pressure is generated between the pipe break control valve and the hydraulic actuator, this excessive pressure is applied to the actuator port of the pipe break control valve. When the pressure exceeds the set pressure, this is detected by the pressure detection means, and the spool drive means operates. As a result, the spool of the pipe break control valve moves, and an opening is formed between the seat valve of the pipe break control valve and the spool. The main pipe to which the pipe break control valve is connected to the above excessive pressure through the opening. Can escape to the road. Here, both the pressure detecting means and the spool driving means are provided in the pipe break control valve, and therefore it is not necessary to provide a relief valve between the pipe break control valve and the hydraulic actuator, and the number of parts can be reduced. .

According to a second aspect of the present invention, in the first aspect of the invention, the spool of the pipe breakage control valve communicates with the throttle that communicates with the actuator port and the inside of the spool. A poppet which is opened when the pressure of the pressure oil introduced through the chamber of the spool reaches a pressure equal to or higher than the set pressure, and the poppet. And a pressure setting spring for urging the spool drive means in the valve closing direction, and the spool driving means is constituted by a path for communicating the chamber of the spool with the drain port when the poppet is opened.

According to the second aspect of the present invention having the above-described structure, an excessive pressure is generated between the pipe breakage control valve and the hydraulic actuator when the seat valve of the pipe breakage control valve and the opening of the spool are closed. When generated, this excessive pressure is applied to the chamber of this spool through the actuator port of the pipe break control valve and the throttle of the spool. When the pressure in this chamber becomes equal to or higher than the set pressure, the poppet opens against the force of the pressure setting spring, and the chamber of the spool and the drain port of the pipe break control valve communicate with each other via the path. As a result, the pressure in the chamber of the spool decreases, and the spool moves accordingly, forming an opening between the spool and the seat valve. Overpressure can be released to the main line via this opening.

The invention according to claim 3 is characterized in that, in the invention according to claim 2, the seat valve, the spool, and the poppet are arranged coaxially.

The invention according to claim 4 is characterized in that, in the invention according to claim 1, means for changing the set pressure is provided.

The invention according to claim 5 is characterized in that, in the invention according to claim 1, there is provided means for changing a movement amount of the spool of the pipe break control valve with respect to the pilot pressure.

The invention according to claim 6 is characterized in that, in the invention according to any one of claims 1 to 5, the hydraulic excavator is provided.

The invention according to claim 7 is the invention according to any one of claims 1 to 6, characterized in that the hydraulic actuator is a hydraulic cylinder.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a hydraulic drive system of the present invention will be described below with reference to the drawings.

FIG. 1 is a hydraulic circuit diagram showing a neutral state in one embodiment of the present invention.

In FIG. 1 and FIGS. 2 to 5 described later,
The same components as those shown in FIG. 6 described above are designated by the same reference numerals.

First, a description will be given of the same components as those shown in FIG.

The present embodiment shown in FIG. 1 is also provided in a construction machine such as a hydraulic excavator, and has a hydraulic pump 1, a tank 2, and a hydraulic actuator driven by pressure oil discharged from the hydraulic pump 1, such as a hydraulic cylinder. And the main cylinders 4 and 5 that connect the boom cylinder 3 that drives the boom 3a, the hydraulic pump 1 and the tank 2 described above, and the boom cylinder 3, and these main pipelines 4 and 5 are interposed. , A directional control valve 6 for controlling the flow of pressure oil supplied from the hydraulic pump 1 to the boom cylinder 3, an operating device 7 for generating a pilot pressure for switching and controlling the directional control valve 6, and the main pipelines 4, 5. It is provided with main relief valves 8 and 9 that regulate the maximum pressure. The directional control valve 6 and the main relief valves 8 and 9 described above constitute one structure.

Further, the boom cylinder 3 is attached to the above-mentioned boom cylinder 3 and is arranged between the boom cylinder 3 and the main pipe line 4. The boom cylinder 3 is connected to the main pipe line in accordance with the pilot pressure generated by the operation of the operating device 7. 4 is provided with a pipe breakage control valve 10 capable of controlling the flow rate of pressure oil flowing out to the main pipe 4 and preventing the flow of pressure oil from the boom cylinder 3 to the main pipe 4 when the main pipe 4 is broken.

The pipe break control valve 10 includes an actuator port 11 connected to the boom cylinder 3 via an oil passage 25, a pipe port 12 connected to the main pipe 4, and a pilot pressure generated by the operating device 7. Is pilot line 1
3 is connected to the pilot port 14 and the tank 2 is connected to the drain port 1 via the drain pipe 15.
6 and 6. Further, a seat valve 17 that allows the pressure oil to flow from the piping port 12 into the actuator port 11, a spring 17a that urges the seat valve 17 to return to the neutral position, and a seat valve 17 that can be contacted and separated from each other. The spool 18 is provided and moves according to the above-mentioned pilot pressure, and changes the area of the opening formed between the seat valve 17 and the spool 18 according to the magnitude of the pilot pressure. Further, a throttle 19 formed in the spool 18 and communicating with the actuator port 11, a spring chamber 20 formed in the spool 18 and communicating with the throttle 19, and a spring chamber 20 accommodated in the spring chamber 20 to store the spool 18 in the seat valve. 17
The first return spring 21 that urges in the direction, a receiving member 22 that forms a spring receiver for the spring 21, and a spring chamber 23 that is provided around the receiving member 22 and communicates with the drain port 16.
And a second return spring 24 housed in the spring chamber 23 and biasing the spool 18 toward the seat valve 17.

The above construction is the same as that shown in FIG.

In the present embodiment, particularly, the pipe break control valve 10
However, the actuator port 1 of this pipe break control valve 10
Between the seat valve 17 and the spool 18 when the pressure detected by the pressure detecting means detects that the pressure of the pressure oil applied to the first pressure exceeds the set pressure. And spool driving means for moving the spool 18 so as to form an opening in the.

The pressure detecting means described above includes a poppet 30 and
A passage 31 that is provided in the receiving member 22 and connects the spring chamber 20 of the spool 18 to the poppet 30, and a spring chamber 3 that is provided in the receiving member 22 and movably accommodates the poppet 30.
2 and a pressure setting spring 33 housed in the spring chamber 32 and biasing the poppet 32 in the valve closing direction. The seat valve 17, the spool 18, and the poppet 30 described above are arranged coaxially.

The above-mentioned spool drive means is the spool 18
The passage 31 communicating with the spring chamber 20 of
1 and the passage 3 provided in the receiving member 22 for communicating the spring chamber 32 and the spring chamber 23 with each other.
It consists of a path including 4 and.

The above-mentioned pressure setting spring 33 for urging the poppet 30 is supported by another receiving member 35 which is screwed into the receiving member 22. This receiving member 35 is
It constitutes a means for changing the above-mentioned set pressure. That is, the spring force of the pressure setting spring 33 can be changed by appropriately rotating the receiving member 35, and the set pressure described above can be changed accordingly.

The receiving member 22 that supports the first return spring 21 and the second return spring 24 described above constitutes means for changing the amount of movement of the spool 18 of the pipe breakage control valve 10 with respect to the pilot pressure output from the operating device 7. is doing. That is, by appropriately rotating the receiving member 22, the first
The spring force of the return spring 21 and the second return spring 24 can be changed,
Along with this, the movement amount of the spool 18 with respect to the pilot pressure can be changed.

The spool 18 of the pipe break control valve 10
The pressure receiving area of the seat valve 17 side and the pressure receiving area of the spring chamber 20 in the spool 18 are set to be equal, and the actuator port 11 and the spring chamber 20 are communicated with each other via the throttle 19 provided in the spool 18. Therefore, the spool 18 is held without being affected by the fluctuation of the load pressure.

The operation of this embodiment configured as described above will be sequentially described.

[Boom Raising Operation] FIG. 2 is a hydraulic circuit diagram showing a state during boom raising in the present embodiment.

The directional control valve 6 is operated by operating the operating device 7 as shown in FIG.
To the left position, the pressure oil discharged from the hydraulic pump 1 passes through the directional control valve 6 and the main pipe 4, and the pipe break control valve 10
Is provided to the piping port 12. The pressure oil moves the seat valve 17 to the left in FIG. 2 against the force of the spring 17a, and an opening is formed between the seat valve 17 and the spool 18. The pressure oil passes through this opening and is supplied to the bottom side chamber of the boom cylinder 3 via the actuator port 11 and the oil passage 25. On the other hand, the pressure oil in the rod side chamber of the boom cylinder 3 is returned to the tank 2 via the main pipe line 5 and the direction control valve 6. As a result, the boom cylinder 3 extends and the boom is raised.

[Boom Lowering Operation] FIG. 3 is a hydraulic circuit diagram showing a state when the boom is lowered in the present embodiment.

When the directional control valve 6 is switched to the right position in FIG. 3 by operating the operating device 7, the pressure oil discharged from the hydraulic pump 1 is passed through the directional control valve 6 and the main pipe 5 to the boom cylinder 3 Is supplied to the rod side chamber. The pressure oil in the bottom chamber is
The oil passage 25 is provided to the actuator port 11 of the pipe breakage control valve 10. During this period, the pilot pressure output from the operating device 7 is guided to the pilot port 14 of the pipe break control valve 10 via the pilot pipe line 13, and this pilot pressure moves the spool 18 to the right in FIG. An opening is formed between the valve 17 and the spool 18.
The area of this opening corresponds to the magnitude of the pilot pressure according to the operation amount of the operating device 7. As a result, as described above, the pressure oil in the bottom side chamber of the boom cylinder 3 applied to the actuator port 11 is controlled through the main pipe line 4 and the direction control valve 6 while its flow rate is controlled according to the movement amount of the spool 18. Returned to tank 2. With these,
The boom cylinder 3 contracts and the boom is lowered.

[When Main Pipe Line 4 is Broken] FIG. 4 is an explanatory view for explaining the function of the pipe break control valve when the main pipe line is broken in this embodiment.

For example, when the main pipe line 4 is broken when the boom is raised or when the boom is lowered as described above, the pipe break control is performed by returning the operating device 7 to the neutral position and returning the directional control valve 6 to the neutral position. The valve 10 is held neutral, and the spool 18 comes into contact with the seat valve 17. As a result, the oil passage 25 that connects the bottom side chamber of the boom cylinder 3 and the actuator port 11 of the pipe breakage control valve 10 and the main pipe line 4 are shut off, and the pressure oil from the bottom side chamber of the boom cylinder 3 is disconnected from the main pipe line 4. Is prevented from flowing out to. This can prevent the boom 3a from being lowered.

[Boom Lowering when Main Pipe Line 4 is Broken] FIG. 5 is a hydraulic circuit diagram for explaining the operation of the pipe breakage control valve when the boom is lowered when the main pipe line is broken in the present embodiment.

As shown in FIG. 4 described above, when the main pipeline 4 is broken and the pipe breakage control valve 10 prevents the pressure oil from flowing out from the bottom chamber side of the boom cylinder 3 to the main pipeline 4, For example, the boom 3a is in a state of being stopped and held in the air, but in such a case, it may be desired to lower the boom 3a for safety and the like.

In such a case, as shown in FIG. 5, the operating device 7 may be operated to switch the directional control valve 6 to the right position. As a result, the pressure oil of the hydraulic pump 1 is supplied to the rod side chamber of the boom cylinder 3 via the main pipe line 5, and the pilot pressure output from the operating device 7 is guided to the pilot pipe line 13 to cause the pipe breakage control valve. 10 spools 1
8 moves to the right, an opening is formed between the seat valve 17 and the spool 18, and through the opening, as described above, the pressure oil in the bottom side chamber of the boom cylinder 3 is broken into the main pipeline 4. It flows out, the boom cylinder 3 contracts, and the boom 3a
Can be lowered.

[Excessive Pressure Relief Operation] Further, when an excessive pressure is generated between the pipe break control valve 10 and the boom cylinder 3 in the neutral state shown in FIG. 1, this excessive pressure causes the actuator port of the pipe break control valve 10 to operate. 11, through the throttle 19 of the spool 18, the spring chamber 20 of the spool 18 is provided. When the pressure in the spring chamber 20 exceeds the set pressure, the poppet 30 opens against the force of the pressure setting spring 33, and the spring chamber 2 passes through the passage 31, the spring chamber 32, and the passage 34.
0 and the drain port 16 communicate with each other. As a result, the pressure in the spring chamber 32 of the spool 18 decreases, and accordingly, the spool 18 moves to the right in FIG. 1 and an opening is formed between the spool 18 and the seat valve 17. Excessive pressure can be released to the main conduit 4 via this opening, and to the tank 2 via the main relief valve 8. This prevents the boom cylinder 3 from being damaged.

As described above, according to the present embodiment, when an overpressure is generated between the pipe break control valve 10 and the boom cylinder 3, the pipe break control valve 10 moves the poppet through the movement of the poppet to the main pipe. Therefore, the desired function can be secured without providing a relief valve between the pipe break control valve 10 and the boom cylinder 3, and the number of parts can be reduced. As a result, the manufacturing cost can be reduced, the weight of the structure including the pipe breakage control valve 10 attached to the boom cylinder 3 can be reduced, and the size of the structure can be reduced, so that the rigidity of the boom cylinder 3 can be set low. It is possible to reduce the size.

Since the structure including the pipe break control valve 10 can be downsized as described above, the structure collides with an obstacle such as rock while the front working machine including the boom 3a is being driven. Can be reduced, which contributes to prevention of breakage of the pipe breakage control valve 10 due to such a collision.

Further, as described above, since it is not necessary to provide a relief valve arranged between the pipe break control valve 10 and the boom cylinder 3, a pipe diameter for connecting such a relief valve and the tank 2 is provided. The drain pipe line 15 that connects the drain port 16 of the pipe break control valve 10 and the tank 2 does not require a large drain pipe line, and guides a small flow amount that passes through the poppet 30. Therefore, it is possible to realize a compact layout of the drain pipe 15, and it is possible to relax restrictions on the piping design including the drain pipe 15.

[0054]

According to the invention according to each claim of the present invention,
Without providing a relief valve between the pipe break control valve and the hydraulic actuator, an excessive pressure generated between the pipe break control valve and the hydraulic actuator can be released, and the number of parts can be reduced as compared with the conventional case. As a result, the manufacturing cost can be reduced, the weight of the structure including the pipe break control valve attached to the hydraulic actuator can be reduced, and the size can be reduced. Is possible.

Since the structure including the pipe breakage control valve can be miniaturized as described above, the structure is protected against obstacles such as rocks during the driving of the working machine equipped with the hydraulic drive system. It is possible to reduce the occurrence of collision and contribute to the prevention of damage to the pipe break control valve due to such a collision.

Further, since it is not necessary to provide a relief valve arranged between the pipe break control valve and the hydraulic actuator, a drain pipe line for connecting such a relief valve and the tank with a large pipe diameter is also required. Therefore, the restrictions on the piping design can be relaxed more than before.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing a neutral state in an embodiment of a hydraulic drive system of the present invention.

FIG. 2 is a hydraulic circuit diagram showing a state when the boom is raised in the embodiment of the present invention.

FIG. 3 is a hydraulic circuit diagram showing a state when the boom is lowered in the embodiment of the present invention.

FIG. 4 is a hydraulic circuit diagram explaining the operation of the pipe breakage control valve when the main pipe line is broken in one embodiment of the present invention.

FIG. 5 is a view showing a main pipe line breakage in one embodiment of the present invention,
It is a hydraulic circuit diagram explaining operation | movement of the pipe rupture control valve at the time of implementing a boom lowering.

FIG. 6 is a hydraulic circuit diagram showing a state of the conventional hydraulic drive device in a neutral state.

[Explanation of symbols]

1 hydraulic pump 2 tanks 3 Boom cylinder (hydraulic actuator) 3a boom 4 main pipelines 5 main pipelines 6 directional control valve 7 Operating device 8 main relief valves 9 Main relief valve 10 Pipe break control valve 11 Actuator port 12 piping ports 13 Pilot line 14 Pilot port 15 Drain line 16 drain port 17 seat valve 17a spring 18 spool 19 aperture 20 spring chamber 21 1st return spring 22 Receiving member 23 Spring chamber 24 Second return spring 25 oil passage 30 poppets (pressure detection means) 31 passage (pressure detection means) (spool drive means) 32 Spring chamber (pressure detection means) (spool drive means) 33 Pressure setting spring (pressure detection means) 34 passage (spool drive means) 35 Receiving member

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kinya Takahashi             Hitachi Construction Machinery Co., Ltd.             Ceremony Company Tsuchiura Factory F-term (reference) 2D015 GA02 GB02                 3H059 AA04 AA17 BB06 BB22 BB28                       BB35 CA04 CA12 CA15 CB04                       CB12 CD05 CE01 CF01 CF11                       EE01 FF03 FF14                 3H089 AA20 BB27 BB28 CC01 DA02                       DB03 DB46 DB49 FF07 FF16                       GG02 JJ02

Claims (7)

[Claims] 1. A hydraulic pump, a tank, a hydraulic actuator driven by pressure oil discharged from the hydraulic pump, a main conduit connecting the hydraulic pump and the hydraulic actuator, and an intermediate member provided in the main conduit. And a directional control valve for controlling the flow of pressure oil supplied from the hydraulic pump to the hydraulic actuator, and an operating device for switching the directional control valve. The hydraulic actuator is attached to the hydraulic actuator. Is disposed between the main pipeline and the main pipeline, the flow rate of the pressure oil flowing out from the hydraulic actuator to the main pipeline is controlled according to the pilot pressure generated by the operation of the operating device, and the main pipeline is broken. When this occurs, a pipe break control valve is provided to prevent the flow of pressure oil from the hydraulic actuator to the main pipeline. The control valve has an actuator port connected to the hydraulic actuator, a piping port connected to the main pipeline, a pilot port supplied with the pilot pressure, and a drain port connected to the tank, A seat valve that allows the flow of pressure oil from the piping port to the actuator port and a seat valve that is provided so as to be able to come into contact with and separate from the seat valve, move according to the pilot pressure, and move according to the magnitude of the pilot pressure. In a hydraulic drive device including a spool that changes an area of an opening formed between the seat valve and the seat valve, the pipe break control valve is configured such that a pressure of pressure oil applied to the actuator port of the pipe break control valve is a set pressure. When a pressure detecting means for detecting that the pressure has reached the above pressure and a pressure higher than the set pressure is detected by the pressure detecting means, Hydraulic drive system is characterized in that a spool drive unit for moving the spool so as to form an opening between the seat valve and the spool. 2. The spool of the pipe break control valve,
The pressure detecting means has a throttle communicating with the actuator port and a chamber communicating with the throttle and formed inside the spool, and the pressure detecting means controls the pressure of the pressure oil introduced through the chamber of the spool. The spool drive means includes a poppet that opens when the pressure becomes equal to or higher than the set pressure, and a pressure setting spring that biases the poppet in the valve closing direction, and the spool drive means controls the spool of the spool when the poppet is opened. The hydraulic drive system according to claim 1, wherein the hydraulic drive system comprises a path for communicating the chamber with the drain port. 3. The hydraulic drive system according to claim 2, wherein the seat valve, the spool, and the poppet are coaxially arranged. 4. The hydraulic drive system according to claim 1, further comprising means for changing the set pressure. 5. The hydraulic drive system according to claim 1, further comprising means for changing a movement amount of the spool of the pipe breakage control valve with respect to the pilot pressure. 6. The hydraulic drive system according to claim 1, which is provided in a hydraulic excavator. 7. The hydraulic drive system according to claim 1, wherein the hydraulic actuator is a hydraulic cylinder.