JP4448634B2 - Hydraulic drive - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a hydraulic drive device having a pipe breakage control valve provided in a work machine such as a hydraulic excavator and capable of preventing the flow of pressure oil from a hydraulic actuator to the main pipe line when the main pipe line is broken. About.
[0002]
[Prior art]
FIG. 6 shows a configuration of this type of conventional hydraulic drive device, and is a hydraulic circuit diagram showing a neutral state.
[0003]
The prior art shown in FIG. 6 is provided in a construction machine such as a hydraulic excavator, and forms 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. The boom cylinder 3 that drives the boom 3a, the hydraulic pump 1 and the tank 2 described above, and the main pipelines 4 and 5 that communicate with the boom cylinder 3 are interposed in the main pipelines 4 and 5, and the hydraulic pump A directional control valve 6 for controlling the flow of pressure oil supplied from 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 maximum pressure in the main lines 4, 5. Main relief valves 8 and 9 are provided. The directional control valve 6 and the main relief valves 8 and 9 described above constitute one structure.
[0004]
Further, it is attached to the boom cylinder 3 described above, and is disposed between the boom cylinder 3 and the main pipeline 4, and flows out from the boom cylinder 3 to the main pipeline 4 according to the pilot pressure generated by the operation of the operating device 7. A pipe breakage control valve 10 is provided that can control the flow rate of the pressure oil to be flown and prevent the flow of pressure oil from the boom cylinder 3 to the main line 4 when the main line 4 is broken.
[0005]
The pipe break control valve 10 is supplied with an actuator port 11 connected to the boom cylinder 3, a pipe port 12 connected to the main pipeline 4, and a pilot pressure generated by the operating device 7 via the pilot pipeline 13. And a drain port 16 connected to the tank 2 via a drain line 15. Further, a seat valve 17 that allows inflow of pressure oil from the piping port 12 to the actuator port 11, a spring 17 a that urges the seat valve 17 to return to the neutral position, and the seat valve 17 can be contacted and separated. The spool 18 is provided and moves in accordance with the pilot pressure described above, and changes the area of the opening formed between the seat valve 17 and the pilot pressure. Furthermore, 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 housed in the spring chamber 20, the spool 18 is seated in the seat valve A first return spring 21 that is biased in the 17 direction; a receiving member 22 that forms a spring receiver for the spring 21; a spring chamber 23 that is provided around the receiving member 22 and communicates with the drain port 16; A second return spring 24 that is housed in the chamber 23 and biases the spool 18 toward the seat valve 17 is provided.
[0006]
Moreover, it is attached to the boom cylinder 3 described above, and is disposed in an oil passage 25 that connects the boom cylinder 3 and the actuator port 11 of the pipe breakage control valve 10, and the pressure of the pressure oil guided to the oil passage 25 is excessive pressure. That is, a relief valve 27 is provided for releasing the pressure oil guided to the oil passage 25 to the tank 2 through the drain pipe 26 when the set pressure is reached. The relief valve 27 and the pipe breakage control valve 10 described above are included in one structure.
[0007]
Note that the main pipelines 4 and 5, the drain pipeline 15 connected to the pipe breakage control valve 10, and the drain pipeline 26 connected to the relief valve 27 are formed of rubber pipes, for example. The main pipelines 4 and 5 and the drain pipeline 26 are much longer than the oil passage 25 that connects the boom cylinder 3 and the pipe breakage control valve 10, and the pipe diameter is set to be large.
[0008]
In the prior art configured as described above, for example, when the operation device 7 is operated to switch the direction control valve 6 to the right position in FIG. 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 breakage control valve 10 through the pilot pipe line 13. Moving in the direction away from the seat valve 17, an opening is formed. Therefore, the pressure oil in the bottom side chamber of the boom cylinder 3 is guided to the opening formed between the seat valve 17 and the spool 18 through the oil passage 25 and the actuator port 11 of the pipe breakage control valve 10, and further to the main pipeline. 4. Return to tank 2 via directional 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.
[0009]
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 oil that communicates the bottom side chamber of the boom cylinder 3 with the pipe break control valve 10 is applied. When the pressure in the passage 25 becomes an excessive pressure that is equal to or higher than the set pressure of the relief valve 27, the excessive pressure is released to the tank 2 through the relief valve 27 and the drain line 26. This prevents the boom cylinder 3 from being damaged.
[0010]
Further, when the main pipeline 4 is broken, the operating device 7 is neutral and the direction control valve 7 is held neutral, so that the spool 18 of the pipe fracture control valve 10 contacts the seat valve 17 and the opening thereof is opened. Closed. As a result, the pressure oil supplied to the actuator port 11 of the pipe breakage control valve 10 via the bottom side chamber and the oil passage 25 of the boom cylinder 3 can be prevented from flowing out to the broken main pipeline 4.
[0011]
[Problems to be solved by the invention]
Since the structure attached to the boom cylinder 3 includes the relief valve 27 and the pipe breakage control valve 10, the related art described above increases the number of parts, which increases the manufacturing cost and increases the weight. However, there is a problem that the boom cylinder 3 must be made large in order to increase the rigidity. 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. However, when such a combination is provided also on the rod side of the boom cylinder 3, The number of parts increases, and the above problem becomes more prominent.
[0012]
In addition, the relief valve 27 described above can pass the entire amount of pressure oil flowing from the bottom side chamber of the boom cylinder 3, and thus becomes large. For this reason, the relief valve 27 and the pipe breakage control valve 10 There is a problem that one structure including the size of the structure increases in size, the weight increases from a viewpoint different from the above, and the size of the boom cylinder 3 must be increased to increase the rigidity.
[0013]
Further, as described above, as the structure including the relief valve 27 and the pipe breakage control valve 10 is increased in size, the structure is damaged by rocks or the like while the front working machine including the boom 3a is being driven. It becomes easy to collide with an object, and when such a collision occurs, there is a concern that the pipe breakage control valve 10 included in the structure is damaged.
[0014]
Further, the drain pipe 26 connecting the relief valve 27 and the tank 2 guides the entire amount of pressure oil returned from the boom cylinder 3 via the relief valve 27, so that the pipe diameter is the same as that of the main pipelines 4 and 5. Therefore, there is a problem that the manufacturing cost becomes high. Further, since the pipe diameter is large, it is difficult to route the drain pipe 26 in a compact manner, and there is a problem that the piping design including the drain pipe 26 is restricted.
[0015]
In addition, as a hydraulic drive device provided with this kind of pipe breakage control valve, what is disclosed in Japanese Patent Laid-Open No. 11-303810 is known.
[0016]
The present invention has been made from the actual situation in the prior art described above, and its purpose is to relieve the excessive pressure generated between the pipe break control valve and the hydraulic actuator without providing a relief valve between the pipe break control valve and the hydraulic actuator. An object of the present invention is to provide a hydraulic drive device that can perform the above-described operation.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 of the present invention includes a hydraulic pump, a tank, a hydraulic actuator driven by pressure oil discharged from the hydraulic pump, the hydraulic pump, and the hydraulic actuator. 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. And is attached to the hydraulic actuator, disposed between the hydraulic actuator and the main pipeline, and flows out from the hydraulic actuator to the main pipeline in response to a pilot pressure generated in accordance with operation of the operating device. When the flow rate of pressure oil is controlled and the main pipeline breaks, the hydraulic oil flows out from the hydraulic actuator to the main pipeline. A pipe break control valve for stopping, the pipe break control valve comprising: an actuator port connected to the hydraulic actuator; a pipe port connected to the main line; a pilot port to which the pilot pressure is supplied; A seat port having a drain port connected to the tank, allowing a flow of pressure oil from the piping port to the actuator port, and being provided in contact with and separating from the seat valve and moving in accordance with the pilot pressure In the hydraulic drive device including a spool that changes an area of an opening formed between the seat valve and the pilot pressure according to the magnitude of the pilot pressure, the pipe breakage control valve includes the pipe breakage control valve. Pressure detecting means for detecting that the pressure of the pressure oil applied to the actuator port has exceeded the set pressure, and the pressure detecting means When the pressure on the set pressure is detected, are a configuration that includes a spool drive unit for moving the spool so as to form an opening between the seat valve and the spool.
[0018]
In the invention according to claim 1 configured as described above, when an excessive pressure is generated between the pipe breakage control valve and the hydraulic actuator, this overpressure is applied to the actuator port of the pipe breakage control valve. When the above pressure is reached, this is detected by the pressure detecting means, and the spool driving means is activated. As a result, the spool of the pipe breakage control valve moves and an opening is formed between the seat valve of the pipe breakage control valve and the spool, and the above-described excessive pressure is connected to the pipe breakage control valve through this opening. You can escape to the road. Here, both the pressure detecting means and the spool driving means are provided in the pipe breakage control valve. Therefore, it is not necessary to provide a relief valve between the pipe breakage control valve and the hydraulic actuator, and the number of parts can be reduced. .
[0019]
The invention according to claim 2 is the invention according to claim 1, wherein the spool of the pipe breakage control valve is formed inside the spool in communication with the throttle connected to the actuator port and the throttle. A poppet that opens when the pressure of the pressure oil introduced through the chamber of the spool becomes equal to or higher than the set pressure, and the poppet is closed. And a pressure setting spring urging in the direction, and the spool driving means comprises a path for communicating the chamber of the spool with the drain port when the poppet is opened.
[0020]
The invention according to claim 2 configured as described above is in a state where the opening of the seat valve and the spool of the pipe breakage control valve is closed, and when an excessive pressure is generated between the pipe breakage control valve and the hydraulic actuator, This excessive pressure is applied to the interior of the spool through the actuator port of the pipe break control valve and the throttle of the spool. When the pressure in the chamber becomes equal to or higher than the set pressure, the poppet opens against the force of the pressure setting spring, and the spool chamber and the drain port of the pipe breakage control valve communicate with each other through the path. As a result, the pressure in the spool chamber decreases, and the spool moves accordingly, and an opening is formed between the spool and the seat valve. Excessive pressure can be released to the main line through this opening.
[0021]
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.
[0022]
The invention according to claim 4 is characterized in that, in the invention according to claim 1, there is provided means for changing the set pressure.
[0023]
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 breakage control valve with respect to the pilot pressure.
[0024]
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.
[0025]
The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the hydraulic actuator is a hydraulic cylinder.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a hydraulic drive device of the present invention will be described with reference to the drawings.
[0027]
FIG. 1 is a hydraulic circuit diagram showing a neutral state in an embodiment of the present invention.
[0028]
In FIG. 1 and FIGS. 2 to 5 to be described later, the same components as those shown in FIG. 6 are denoted by the same reference numerals.
[0029]
First, an explanation will be given of what is the same as that shown in FIG.
[0030]
This embodiment shown in FIG. 1 is also provided in a construction machine such as a hydraulic excavator, and forms a hydraulic pump 1, a tank 2, and a hydraulic actuator that is driven by pressure oil discharged from the hydraulic pump 1, such as a hydraulic cylinder. The boom cylinder 3 that drives the boom 3a, the hydraulic pump 1 and the tank 2 described above, and the main pipelines 4 and 5 that communicate with the boom cylinder 3 are interposed in the main pipelines 4 and 5, and the hydraulic pump A directional control valve 6 for controlling the flow of pressure oil supplied from 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 maximum pressure in the main lines 4, 5. Main relief valves 8 and 9 are provided. The directional control valve 6 and the main relief valves 8 and 9 described above constitute one structure.
[0031]
Further, it is attached to the boom cylinder 3 described above, and is disposed between the boom cylinder 3 and the main pipeline 4, and flows out from the boom cylinder 3 to the main pipeline 4 according to the pilot pressure generated by the operation of the operating device 7. A pipe breakage control valve 10 is provided that can control the flow rate of the pressure oil to be flown and prevent the flow of pressure oil from the boom cylinder 3 to the main line 4 when the main line 4 is broken.
[0032]
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 as a pilot pipe. It has a pilot port 14 supplied via a passage 13 and a drain port 16 connected to the tank 2 via a drain conduit 15. Further, a seat valve 17 that allows inflow of pressure oil from the piping port 12 to the actuator port 11, a spring 17 a that urges the seat valve 17 to return to the neutral position, and the seat valve 17 can be contacted and separated. The spool 18 is provided and moves in accordance with the pilot pressure described above, and changes the area of the opening formed between the seat valve 17 and the pilot pressure. Furthermore, 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 housed in the spring chamber 20, the spool 18 is seated in the seat valve A first return spring 21 that is biased in the 17 direction; a receiving member 22 that forms a spring receiver for the spring 21; a spring chamber 23 that is provided around the receiving member 22 and communicates with the drain port 16; A second return spring 24 that is housed in the chamber 23 and biases the spool 18 toward the seat valve 17 is provided.
[0033]
The above configuration is the same as that shown in FIG.
[0034]
In the present embodiment, in particular, the pipe break control valve 10 has a pressure detecting means for detecting that the pressure of the pressure oil applied to the actuator port 11 of the pipe break control valve 10 is equal to or higher than a set pressure, and the pressure detecting means. And a spool driving means for moving the spool 18 so as to form an opening between the seat valve 17 and the spool 18 when a pressure equal to or higher than the set pressure is detected.
[0035]
The pressure detection means described above is provided in the poppet 30 and the receiving member 22, provided in the receiving member 22, and a passage 31 that connects the spring chamber 20 of the spool 18 and the poppet 30, and movably accommodates the poppet 30. The spring chamber 32 and a pressure setting spring 33 housed in the spring chamber 32 and biasing the poppet 32 in the valve closing direction are included. The seat valve 17, the spool 18 and the poppet 30 described above are arranged coaxially.
[0036]
The above-described spool driving means is provided in the aforementioned passage 31 that communicates with the spring chamber 20 of the spool 18, the aforementioned spring chamber 32 that can communicate with this passage 31, and the receiving member 22, and the spring chamber 32 and the spring chamber 23. And a passage 34 that communicates with each other.
[0037]
The pressure setting spring 33 that biases the poppet 30 is supported by another receiving member 35 that is screwed into the receiving member 22. The receiving member 35 constitutes means for changing the above-described set pressure. That is, by appropriately rotating the receiving member 35, the spring force of the pressure setting spring 33 can be changed, and the set pressure can be changed accordingly.
[0038]
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. . That is, by appropriately rotating the receiving member 22, the spring force of the first return spring 21 and the second return spring 24 can be changed, and accordingly, the amount of movement of the spool 18 with respect to the pilot pressure can be changed.
[0039]
The pressure receiving area on the seat valve 17 side of the spool 18 of the pipe breakage control valve 10 and the pressure receiving area of the spring chamber 20 in the spool 18 are set to be equal, and an actuator is provided via a throttle 19 provided in the spool 18. Since the port 11 and the spring chamber 20 are communicated with each other, the spool 18 is held without being affected by fluctuations in load pressure.
[0040]
The operation of the present embodiment configured as described above will be sequentially described.
[0041]
[Boom raising operation]
FIG. 2 is a hydraulic circuit diagram showing a state when the boom is raised in the present embodiment.
[0042]
When the directional control valve 6 is switched to the left position in FIG. 2 by operating the operating device 7, the pressure oil discharged from the hydraulic pump 1 passes through the directional control valve 6 and the main pipeline 4, and the piping port 12 of the piping rupture control valve 10. Given to. The pressure oil causes the seat valve 17 to move to the left in FIG. 2 against the force of the spring 17 a, and an opening is formed between the seat valve 17 and the spool 18. Pressure oil passes through this opening and is supplied to the bottom 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 pipeline 5 and the direction control valve 6. Thereby, the boom cylinder 3 is extended and the boom is raised.
[0043]
[Boom lowering operation]
FIG. 3 is a hydraulic circuit diagram showing a state when the boom is lowered in the present embodiment.
[0044]
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 connected to the rod side chamber of the boom cylinder 3 via the directional control valve 6 and the main pipeline 5. To be supplied. The pressure oil in the bottom side chamber is given to the oil passage 25 and the actuator port 11 of the pipe breakage control valve 10. During this time, the pilot pressure output from the operating device 7 is guided to the pilot port 14 of the pipe breakage control valve 10 via the pilot line 13, and the spool 18 moves to the right in FIG. An opening is formed between the valve 17 and the spool 18. The area of the opening corresponds to the magnitude of the pilot pressure corresponding to the operation amount of the operating device 7. As a result, the pressure oil in the bottom chamber of the boom cylinder 3 applied to the actuator port 11 as described above is controlled via the main line 4 and the direction control valve 6 while the flow rate is controlled according to the amount of movement of the spool 18. Returned to tank 2. As a result, the boom cylinder 3 contracts and the boom is lowered.
[0045]
[When main pipe 4 breaks]
FIG. 4 is an explanatory view for explaining the function of the pipe breakage control valve when the main pipe line breaks in this embodiment.
[0046]
For example, when the main pipeline 4 is broken when the boom is raised or lowered as described above, the piping breakage control valve 10 is returned to the neutral position by returning the operating device 7 to the neutral position. The spool 18 is brought into contact with the seat valve 17 while being held neutral. 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 flows into the main pipe line 4. Is prevented from leaking. Thereby, the lowering of the boom 3a can be prevented.
[0047]
[Boom lowering when main pipeline 4 breaks]
FIG. 5 is a hydraulic circuit diagram for explaining the operation of the pipe break control valve when the boom is lowered when the main pipe line is broken in this embodiment.
[0048]
As shown in FIG. 4 described above, when the main pipe 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 pipe 4, for example, the boom 3a. In such a case, there is a case where it is desired to lower the boom 3a for safety and the like.
[0049]
In such a case, as shown in FIG. 5, the operation device 7 may be operated to switch the direction 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 line 5, and the pilot pressure output from the operating device 7 is guided to the pilot line 13, and the pipe breakage control valve 10 spool 18 moves to the right, and an opening is formed between the seat valve 17 and the spool 18. As described above, the pressure oil in the bottom side chamber of the boom cylinder 3 is broken through this opening. It flows out to the path 4 and the boom cylinder 3 can be contracted to lower the boom 3a.
[0050]
[Relief action of excessive pressure]
Further, when an excessive pressure is generated between the pipe breaking control valve 10 and the boom cylinder 3 at the neutral time shown in FIG. 1, the excessive pressure is passed through the actuator port 11 of the pipe breaking control valve 10 and the throttle 19 of the spool 18. The spring chamber 20 of the spool 18 is given. 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 20 and the drain port 16 are connected via the passage 31, the spring chamber 32, and the passage 34. Communicate. As a result, the pressure in the spring chamber 32 of the spool 18 decreases, and the spool 18 moves to the right in FIG. 1 to form an opening with the seat valve 17. Excessive pressure can be released to the main pipeline 4 through this opening, and further to the tank 2 through the main relief valve 8. Thereby, the breakage of the boom cylinder 3 can be prevented.
[0051]
As described above, according to the present embodiment, when an excessive pressure is generated between the pipe break control valve 10 and the boom cylinder 3, the excessive pressure is transferred to the main pipeline 4 through the movement of the poppet of the pipe break control valve 10. Therefore, it is possible to ensure a desired function and reduce the number of parts without requiring a relief valve between the pipe breakage control valve 10 and the boom cylinder 3. Accordingly, the manufacturing cost can be reduced, the weight of the structure including the pipe break control valve 10 attached to the boom cylinder 3 can be reduced and the size can be reduced, and the rigidity of the boom cylinder 3 can be set low. It is possible to reduce the size.
[0052]
Further, since the structure including the pipe breakage control valve 10 can be reduced in size as described above, it is possible to cause the structure to collide with an obstacle such as a rock while driving the front work machine including the boom 3a. This contributes to preventing damage to the pipe breakage control valve 10 due to such a collision.
[0053]
Further, as described above, since there is no need to provide a relief valve arranged between the pipe breakage control valve 10 and the boom cylinder 3, a drain having a large pipe diameter connecting such a relief valve and the tank 2 is used. There is no need for a pipe line, and the drain pipe line 15 that connects the drain port 16 of the pipe breakage control valve 10 and the tank 2 leads a small flow rate that passes through the poppet 30 and has a small pipe diameter. Therefore, the compact piping of the drain pipe 15 can be realized, and the restriction on the piping design including the drain pipe 15 can be relaxed.
[0054]
【The invention's effect】
According to the inventions according to the respective claims of the present invention, an excessive pressure generated between the pipe breakage control valve and the hydraulic actuator can be released without providing a relief valve between the pipe breakage control valve and the hydraulic actuator. The number of parts can be reduced compared to. 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, the rigidity of the hydraulic actuator can be set low, and the size can be reduced. Is possible.
[0055]
In addition, since the structure including the pipe break control valve can be downsized as described above, occurrence of a collision of the structure with an obstacle such as a rock during driving of the work machine provided with the hydraulic drive device. This contributes to the prevention of breakage of the pipe breakage control valve accompanying such a collision.
[0056]
Furthermore, since there is no need to provide a relief valve that is arranged between the pipe break control valve and the hydraulic actuator, there is no need for a drain pipe having a large pipe diameter that connects the relief valve and the tank. The restriction on the piping design can be relaxed as compared with the conventional case.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram showing a neutral state in an embodiment of a hydraulic drive device of the present invention.
FIG. 2 is a hydraulic circuit diagram showing a state when the boom is raised in one embodiment of the present invention.
FIG. 3 is a hydraulic circuit diagram showing a state when the boom is lowered in an embodiment of the present invention.
FIG. 4 is a hydraulic circuit diagram illustrating the operation of a pipe breakage control valve when a main pipe line breaks in one embodiment of the present invention.
FIG. 5 is a hydraulic circuit diagram for explaining the operation of the pipe break control valve when the boom is lowered when the main pipeline breaks in one embodiment of the present invention.
FIG. 6 is a hydraulic circuit diagram showing a neutral state in a conventional hydraulic drive device.
[Explanation of symbols]
1 Hydraulic pump
2 tanks
3 Boom cylinder (hydraulic actuator)
3a boom
4 main pipelines
5 Main pipeline
6-way control valve
7 Operating device
8 Main relief valve
9 Main relief valve
10 Pipe break control valve
11 Actuator port
12 Piping port
13 Pilot pipeline
14 Pilot port
15 Drain line
16 Drain port
17 Seat valve
17a spring
18 spools
19 Aperture
20 Spring chamber
21 First return spring
22 Receiving member
23 Spring chamber
24 Second return spring
25 Oilway
30 Poppet (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

Claims (7)

A hydraulic pump; a tank; a hydraulic actuator driven by pressure oil discharged from the hydraulic pump; a main line connecting the hydraulic pump and the hydraulic actuator; and the hydraulic pump interposed in the main line A directional control valve for controlling the flow of pressure oil supplied to the hydraulic actuator from above, and an operating device for switching the directional control valve,
A flow rate of pressure oil attached to the hydraulic actuator and disposed between the hydraulic actuator and the main pipeline and flowing out from the hydraulic actuator to the main pipeline in response to a pilot pressure generated in accordance with operation of the operating device A pipe breakage control valve that prevents outflow of pressure oil from the hydraulic actuator to the main pipe line when the main pipe line breaks,
The pipe break control valve includes an actuator port connected to the hydraulic actuator, a pipe port connected to the main pipe line, 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 can be brought into contact with and separated from the seat valve, and moves according to the pilot pressure. In accordance with 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
Pressure detecting means for detecting that the pressure of the pressure oil applied to the actuator port of the pipe breakage control valve is equal to or higher than a set pressure;
And a spool driving means for moving the spool so as to form an opening between the seat valve and the spool when a pressure equal to or higher than the set pressure is detected by the pressure detecting means. Hydraulic drive device to do. The spool of the pipe breakage control valve has a throttle communicating with the actuator port, a chamber communicating with the throttle and formed in the spool,
A poppet that opens when the pressure of the pressure oil guided through the chamber of the spool becomes equal to or higher than the set pressure, and a pressure setting that biases the poppet in the valve closing direction. For springs,
2. The hydraulic drive apparatus according to claim 1, wherein the spool drive means comprises a path for communicating the chamber of the spool with the drain port when the poppet is opened. 3. The hydraulic drive apparatus according to claim 2, wherein the seat valve, the spool, and the poppet are arranged coaxially. 2. The hydraulic drive apparatus according to claim 1, further comprising means for changing the set pressure. 2. The hydraulic drive apparatus 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. The hydraulic drive device according to claim 1, wherein the hydraulic drive device is provided in a hydraulic excavator. The hydraulic drive device according to claim 1, wherein the hydraulic actuator is a hydraulic cylinder.

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