阅读说明：本技术 防漂移阀装置，刀片装置和工作机械 (Drift prevention valve device, blade device, and work machine ) 是由 居本周平 喜安浩一 前田宏 于 2019-10-15 设计创作，主要内容包括：提供一种能够以简单的结构操作致动单元并防止机体漂移的防漂移阀装置、刀片装置和工作机械。防漂移阀装置设置有单向阀41,该单向阀41允许液压油从控制阀28流动到刀片缸34的头室34h并且阻止液压油沿相反方向的流动；以及与单向阀41的容纳部70分开地设置的活塞容纳部42,被配置成可移动地容纳动力活塞43。动力活塞43限定第一活塞室42pl和第二活塞室42pl,第一活塞室42pl与刀片缸34的杆室34r连通,第二活塞室42pl用于排放并定位在单向阀41的提升阀71侧并与油箱52连通。动力活塞43连接到单向阀41的提升阀71,使得动力活塞43可以通过单向阀41的弹簧72的提升阀71的推动力和刀片缸34的杆室压力之间的差来操作。(Provided are an anti-drift valve device, a blade device, and a work machine, which are capable of operating an actuator unit with a simple structure and preventing a machine body from drifting. The anti-drift valve device is provided with a check valve 41, the check valve 41 allowing the hydraulic oil to flow from the control valve 28 to the head chamber 34h of the blade cylinder 34 and preventing the hydraulic oil from flowing in the opposite direction; and a piston housing portion 42 provided separately from the housing portion 70 of the check valve 41, configured to movably house the power piston 43. The power piston 43 defines a first piston chamber 42pl and a second piston chamber 42pl, the first piston chamber 42pl communicating with the rod chamber 34r of the blade cylinder 34, the second piston chamber 42pl for discharging and being positioned on the poppet valve 71 side of the check valve 41 and communicating with the oil tank 52. The power piston 43 is connected to the poppet 71 of the check valve 41, so that the power piston 43 can be operated by the difference between the urging force of the poppet 71 of the spring 72 of the check valve 41 and the rod chamber pressure of the blade cylinder 34.)

1. An anti-drift valve apparatus mounted on a fluid pressure cylinder configured to actuate an actuating unit by supplying/discharging a working fluid from a control valve to/from a first fluid chamber and a second fluid chamber opposite to the first fluid chamber, the first fluid chamber being for supporting an operation of a body, the anti-drift valve apparatus comprising:

a check valve including a receiving portion configured to communicate between the control valve and the first fluid chamber of the fluid pressure cylinder; a pushing member movably accommodated in the accommodating portion; and a pushing member for pushing the valve element in a valve closing direction, configured to allow the working fluid to flow from the control valve to the first fluid chamber of the fluid pressure cylinder and to suspend the flow of the working fluid in an opposite direction;

a piston housing part provided separately from a housing part of the check valve; and

a power piston movably accommodated in the piston accommodating portion, the power piston being configured to define a first piston chamber and a second piston chamber in the piston accommodating portion, the first piston chamber being in communication with the second fluid chamber of the fluid pressure cylinder, the second piston chamber being for discharge and being located on the valve element side of the check valve and being in communication with a tank, and being further connected to the valve element of the check valve and being operable by a difference between an urging force of the valve element generated by an urging member of the check valve and the second fluid chamber pressure of the fluid pressure cylinder.

2. The anti-drift valve arrangement according to claim 1, further comprising a valve body incorporating the one-way valve, the piston receptacle and the power piston, and further comprising a passage therein configured to communicate directly between the receptacle of the one-way valve and the first fluid chamber of the fluid pressure cylinder, and mounted directly on the fluid pressure cylinder.

3. An anti-drift valve arrangement according to claim 1 or 2, wherein the valve element and the power piston of the one-way valve are arranged in a separate configuration from each other.

4. The anti-drift valve device according to any one of claims 1 to 3, wherein the check valve is a pilot type check valve that accommodates the urging member, and further has a back pressure chamber in the accommodation portion to which the first fluid chamber pressure of the fluid pressure cylinder can be supplied.

5. The anti-drift valve apparatus of claim 4, further comprising:

a relief valve configured to open when the first fluid chamber pressure of the fluid pressure cylinder reaches a preset relief pressure; and

a selector valve configured to be switchable between a position for communicating between the back pressure chamber and the first fluid chamber of the fluid pressure cylinder and a position for communicating between the back pressure chamber and the oil tank by a pilot operation of hydraulic oil flowing out from the relief valve from the first fluid chamber pressure of the fluid pressure cylinder.

6. The anti-drift valve arrangement according to claim 4 or 5, wherein said anti-drift valve arrangement is mounted on a pair of fluid pressure cylinders, respectively, said anti-drift valve arrangement comprising:

a balance line communicating between the first fluid chambers of the paired fluid pressure cylinders, and,

a fuse valve disposed in the equalization line, the fuse valve configured to close when a pre-post differential pressure reaches a predetermined pressure that has been predetermined.

7. The anti-drift valve arrangement according to any of claims 4 to 6, wherein the area of the power piston receiving the second fluid chamber pressure of the fluid pressure cylinder is greater than the area of the valve element of the one-way valve receiving the first fluid chamber pressure of the fluid pressure cylinder.

8. A blade arrangement comprising:

a blade as an actuating unit;

a connecting arm for connecting the blade to the body to be movable up and down;

a fluid pressure cylinder including a head chamber serving as a first fluid chamber and a rod chamber serving as a second fluid chamber, the fluid pressure cylinder being configured to move the blade up and down by extension and contraction thereof;

an anti-drift valve arrangement according to any one of claims 1 to 7, mounted on said fluid pressure cylinder; and

a control valve configured to control a direction and a flow rate of the working fluid supplied to and discharged from the head chamber and the rod chamber of the fluid pressure cylinder.

9. The work machine includes:

a body; and

the blade arrangement of claim 8, disposed on the body.

10. The work machine of claim 9, wherein the machine body comprises:

a lower traveling body including a blade connected thereto by a connecting arm of the blade device and a fluid pressure cylinder provided therein;

an upper swing body having a control valve of the blade device provided therein and swingably provided on the lower traveling body; and

a rotary joint provided at a swing center of the upper swing body, configured to connect the control valve to the anti-drift valve device and the fluid pressure cylinder, respectively.

Technical Field

The present invention relates to an anti-drift valve device mounted on a fluid pressure cylinder configured to move an actuating unit up and down, a blade device having the anti-drift valve device, and a work machine having the anti-drift valve device.

Background

Conventionally, in a working machine such as a hydraulic excavator, there are some provided with a blade device for earth removal work. The blade arrangement may be used as a leg, for example to ground the blade when performing a digging operation with the bucket and to cause a reaction force from the ground associated with the digging operation to act on the body to make it difficult to tilt the body. In the case where the blade apparatus is used as a leg in this manner, it is necessary to prevent the blade cylinder from contracting and the body from being clamped even if the pipe connected to the blade cylinder is damaged.

A structure is known in which a pilot-type switching valve is switched by a pilot pressure supplied from a pilot line in response to, for example, switching of a spool of a control valve to prevent drift of a boom cylinder. (see, for example, patent document 1). In addition, a configuration for providing a pilot check valve that can be switched open and closed, for example, with respect to a blade cylinder by a pilot pressure supplied from a pilot line in a passage communicating between a rod chamber and a control valve, thereby preventing the blade from drifting is known. (see, for example, patent document 2).

However, in the case of the blade cylinder, since the blade cylinder is provided in the lower traveling body of the machine body, the blade cylinder is close to the ground, and the pipe in the blade cylinder is more likely to be damaged by sediment, rocks, or the like than the pipe in the blade cylinder, and it is difficult to additionally provide a hydraulic pipe, and further configured such that pressurized oil is supplied from the control valve via a rotary joint connecting the hydraulic pipe between the upper and lower traveling bodies of the machine body. As a result, in view of cost and layout, when providing a valve for preventing the drift of the engine body, it is desirable to be able to prevent the drift of the engine body without adding a new port for a hydraulic line or a pilot line to the rotary joint.

In this regard, a configuration is known for throttling the supply of hydraulic oil to the rod chamber of the blade cylinder when lowering the blade, for example, using a pilot type check valve to which a rod side pressure is supplied as a pilot pressure. (see, for example, patent document 3). In this configuration, since the control valve and the head chamber of the fluid pressure cylinder are directly connected by the pipe, if the pipe is damaged, the hydraulic oil flows out from the head chamber, so that it is difficult to prevent the machine body from drifting.

Further, a configuration is known, for example, for connecting a control valve to a head chamber and a rod chamber of a fluid pressure cylinder, respectively, for example, using a pilot type check valve supplied with a head side pressure as a pilot pressure (see, for example, patent document 4). In this configuration, when the piston of the pilot type check valve pushes the poppet valve in the valve opening direction, head-side pressure and rod-side pressure will be applied to the piston, and it is difficult to obtain proper operation of the piston.

Documents of the prior art

Patent document

[ patent document 1] Japanese Utility model publication No. 6-6247

[ patent document 2] Japanese patent application laid-open No. 11-336116

[ patent document 3] Japanese Utility model application laid-open No. 1976-

[ patent document 4] Japanese patent application laid-open No. 1973-

Disclosure of Invention

Problems to be solved by the invention

As mentioned above, it is necessary to operate the actuating unit, such as the blade, and to prevent the machine body from drifting, without creating complex hydraulic and pilot lines and similar lines associated with their addition.

The present invention has been made in view of the above problems, and an object thereof is to provide an anti-drift valve device capable of operating an actuator unit with a simple configuration, a blade device having the anti-drift valve device, and a work machine having the anti-drift valve device.

Means for solving the problems

According to a first aspect, the present invention is an anti-drift valve arrangement mounted on a fluid pressure cylinder configured to be extended/contracted to actuate an actuation unit by supplying/discharging a working fluid from a control valve to a first fluid chamber for supporting operation of a machine body by the actuation unit and a second fluid chamber opposite thereto, the anti-drift valve arrangement comprising a check valve including a receiving portion configured to communicate between the control valve and the first fluid chamber of the fluid pressure cylinder; a valve element movably accommodated in the accommodation portion; and a pushing member for actuating the valve element in a valve closing direction, the pushing member being configured to allow a working fluid to flow from the control valve to the first fluid chamber of the fluid pressure cylinder and to suspend a flow of the working fluid in an opposite direction; a piston housing part provided separately from the housing part of the check valve; and a power piston movably accommodated in the piston accommodating portion, the power piston being configured to define a first piston chamber and a second piston chamber for discharge in the piston accommodating portion, the first piston chamber being in communication with the second fluid chamber of the fluid pressure cylinder, the second piston chamber being located on a valve element side of the check valve and being in communication with the oil tank, and being further connected to the valve element of the check valve, and being operable by a difference between an urging force of the valve element generated by an urging member of the check valve and a pressure of the second fluid chamber of the fluid pressure cylinder.

An anti-drift valve arrangement according to a second aspect of the invention is the anti-drift valve arrangement according to the first aspect, further comprising a valve body incorporating the one-way valve, the piston housing and the power piston, and wherein further comprising a passage configured to communicate directly between the housing of the one-way valve and the first fluid chamber of the fluid pressure cylinder, and mounted directly on the fluid pressure cylinder.

An anti-drift valve device according to a third aspect of the present invention is the anti-drift valve device according to the first or second aspect, wherein the valve element of the check valve and the power piston are provided in a separate structure from each other.

An anti-drift valve device according to a fourth aspect of the invention is the anti-drift valve device according to any one of the first to third aspects, wherein the check valve is a pilot type check valve that accommodates the urging member and further has a back pressure chamber in the accommodation portion, the back pressure chamber being capable of being supplied with the first fluid chamber pressure of the fluid pressure cylinder.

An anti-drift valve device according to a fifth aspect of the present invention is the anti-drift valve device according to the fourth aspect, further comprising a safety valve configured to open when the first fluid chamber pressure of the fluid pressure cylinder reaches a preset relief pressure; and a selector valve configured to be pilot-operated by hydraulic oil of a first fluid chamber pressure of the fluid pressure cylinder flowing out from the pressure reducing valve to be switchable between a position for communicating the back pressure chamber with the first fluid chamber of the fluid pressure cylinder and a position for communicating the back pressure chamber with the tank.

An anti-drift valve device according to a sixth aspect of the present invention is the anti-drift valve device according to the fourth or fifth aspect, each of the anti-drift valve devices being mounted on a pair of the fluid pressure cylinders, including a balance line communicating between the first fluid chambers of the pair of the fluid pressure cylinders, and a fuse valve provided in the balance line, the fuse valve being configured to close when the front-rear pressure difference reaches a predetermined pressure determined in advance.

An anti-drift valve apparatus according to a seventh aspect of the present invention is the anti-drift valve apparatus according to any of the fourth to sixth aspects, wherein an area of the power piston receiving the second fluid chamber pressure of the fluid pressure cylinder is larger than an area of the valve element of the check valve receiving the first fluid chamber pressure of the fluid pressure cylinder.

A blade device according to an eighth aspect of the present invention is a blade device including a blade serving as an actuating unit; a connecting arm for connecting the blade to the body to be movable up and down; a fluid pressure cylinder including a head chamber serving as the first fluid chamber and a rod chamber serving as the second fluid chamber, the fluid pressure cylinder being configured to move the blade up and down by extension and contraction of the blade and move the anti-drift valve device mounted on the fluid pressure cylinder according to any one of the first to seventh aspects; and a control valve configured to control a direction and a flow rate of the working fluid supplied to and discharged from the head chamber and the rod chamber of the fluid pressure cylinder.

A work machine according to a ninth aspect of the present invention is a work machine including a machine body; and a blade device according to the eighth aspect provided on the machine body.

A work machine according to a tenth aspect of the present invention is the work machine according to the ninth aspect, wherein the body includes a lower traveling body including a blade connected thereto through a connecting arm of the blade device and a fluid pressure cylinder provided therein; an upper swing body having a control valve of a blade device provided therein and swingably provided on the lower traveling body; and a rotary joint provided at a swing center of the upper swing body, the rotary joint being configured to connect the control valve to the anti-drift valve device and the fluid pressure cylinder, respectively.

The invention has the advantages of

According to the first aspect of the invention, the power piston, on which the fluid pressure does not act from the second piston chamber on the valve element side of the check valve, is connected to the valve element of the check valve. Therefore, when the working fluid is supplied from the control valve to the second fluid chamber side of the fluid pressure cylinder, the second fluid chamber pressure of the fluid pressure cylinder exceeds the urging force of the valve element by the urging member of the check valve, the valve element of the check valve is moved in the opening direction of the valve by the power piston, and the working fluid can be discharged from the first fluid chamber of the fluid pressure cylinder to the control valve. Further, if the working fluid is supplied from the control valve to the first fluid chamber side of the fluid pressure cylinder, the valving element is moved in the valve opening direction against the urging force of the valving element by the urging member of the check valve. The working fluid may be supplied to the first fluid chamber of the fluid pressure cylinder. Further, for example, if a passage connecting between the housing portion of the check valve and the control valve is broken, the valve element of the check valve is held in the valve closing direction by the urging force of the urging member and the discharge of the working fluid from the first fluid chamber of the fluid pressure cylinder to the control valve is prevented, so that the actuating unit does not release the support of the machine body. Therefore, it is possible to operate the actuating unit with a simple configuration and prevent drift of the body supported by the actuating unit without newly adding a pilot line or the like from the control valve side.

According to the second aspect of the present invention, by directly connecting the valve main body, the piston housing portion, and the power piston incorporating the check valve to the fluid pressure cylinder and forming therein the passage that directly communicates between the housing portion of the check valve and the first fluid chamber of the fluid pressure cylinder, the piping for connecting the housing portion of the fluid pressure cylinder and the first fluid chamber can be omitted, and damage to the communication passage between the housing portion of the fluid pressure cylinder and the first fluid chamber can be prevented, and drifting of the machine body due to the damage can be prevented.

According to the third aspect of the present invention, by forming the valve element of the check valve and the power piston in a structure separate from each other, the sealability and manufacturability of the anti-drift valve device can be improved.

According to the fourth aspect of the invention, by making the check valve function as a pilot type check valve in which a back pressure chamber that accommodates the urging member and that can also be supplied with the first fluid chamber pressure of the fluid pressure cylinder is defined in the accommodating portion, the operation of the valve element of the check valve can be more finely controlled using the first fluid chamber pressure of the fluid pressure cylinder.

According to the fifth aspect of the invention, when an overload is applied to the first fluid chamber of the fluid pressure cylinder, the relief valve is opened, and the selector valve is pilot-operated by the working fluid from the first fluid chamber of the fluid pressure cylinder that flows out from the relief valve, and is switched to a position that allows communication between the back pressure chamber and the tank, whereby the valving element can be moved in the valve-opening direction by releasing the back pressure in the check valve, and the overload can be released by returning the working fluid from the first fluid chamber to the tank via the control valve.

According to the sixth aspect of the present invention, by providing the fuse valve in the balance line between the first fluid chambers communicating the paired fluid pressure cylinders, for example, when the balance line is broken, the differential pressure across the fuse valve reaches a predetermined pressure predetermined to close the fuse valve determined in advance, whereby the working fluid can be prevented from flowing out from the first fluid chambers of the fluid pressure cylinders via the balance line, and the drift of the body due to the flowing out can be prevented.

According to the seventh aspect of the invention, it is made possible to communicate both the first fluid chamber and the second fluid chamber with the oil tank, because by setting the area of the power piston that receives the second fluid chamber pressure of the fluid pressure cylinder larger than the area of the valve element of the check valve that receives the first fluid chamber pressure of the fluid pressure cylinder when attempting to communicate the first fluid chamber and the second fluid chamber of the fluid pressure cylinder with the oil tank, respectively, via the control valve, the force that the power piston receives based on the second fluid chamber pressure exceeds the force that the valve element of the check valve receives based on the first fluid chamber pressure, and the valve element of the check valve can be moved in the valve opening direction by the power piston. Therefore, the floating function can be easily imparted to the fluid pressure cylinder.

According to the eighth aspect of the present invention, it is possible to move the blade up and down and prevent the drift from occurring in the body supported by the reaction force of the blade contacting the ground with a simple configuration, by mounting the anti-drift valve device according to any one of the first to seventh aspects on the fluid pressure cylinder that moves the blade up and down using as the actuating unit, without newly adding a pilot line or the like from the control valve side.

According to a ninth aspect of the present invention, by providing the blade device according to the eighth aspect, it is possible to provide a working machine capable of moving the blade up and down with a simple configuration and preventing the body supported by the reaction force of the blade from coming into contact with the ground to cause drifting.

According to the tenth aspect of the present invention, it is possible to move the blade up and down with a simple configuration and prevent the body supported by the reaction force of the blade in contact with the ground from drifting without newly adding a port such as a pilot line to the rotary joint.

Drawings

Fig. 1 is a fluid pressure circuit diagram with a blade in a neutral position, showing one embodiment of a work machine equipped with a blade arrangement having an anti-drift valve arrangement according to the present disclosure.

FIG. 2 is a fluid pressure circuit diagram during a raising operation of the blade, showing the same work machine as described above.

Fig. 3 is a fluid pressure circuit diagram during a lowering operation of the blade, showing the same work machine as described above.

FIG. 4 is a fluid pressure circuit diagram during a floating operation of the blade, showing the same work machine as described above.

FIG. 5 is a fluid pressure circuit diagram during a pipe break showing the same work machine as described above.

Fig. 6 is a fluid pressure circuit diagram during release of an overload showing the same work machine as described above.

Fig. 7 is a sectional view showing the same anti-drift valve device as described above.

Detailed Description

The present invention will be described in detail based on one embodiment shown in fig. 1 to 7.

In fig. 1 to 6, reference numeral 10 denotes a work machine. The work machine 10 according to the present embodiment will be described by taking a hydraulic excavator type work machine as an example.

The work machine 10 includes a machine body 11. In the present embodiment, the upper swing body 13 is provided to be swingable on the lower traveling body 12. The lower traveling body 12 may be a wheel type or a crawler type, and is driven by a traveling engine. The upper swing body 13 is driven by a swing motor. The body 11 includes a cab 14. The cab 14 is mounted on the upper swing body 13.

In addition, the working device 15 is supported by the body 11. The working device 15 includes: a boom whose base is articulated with the upper swing body 13 so as to be freely rotatable in the vertical direction; an arm serving as a rod articulated with the distal end of the boom; and a bucket articulating with the distal end of the arm. The boom is rotated by a boom cylinder as a fluid pressure cylinder, the arm is rotated by an arm cylinder as a fluid pressure cylinder, and the bucket is rotated by a bucket cylinder as a fluid pressure cylinder. Hydraulic oil as a working fluid is supplied to and discharged from the boom cylinder, the arm cylinder, and the bucket cylinder via pipes via a control valve 28 as a control valve. The control valve 28 is mounted on the upper swing body 13.

Then, the cutter device 31 is provided on the body 11. The blade device 31 is a lower support device provided in the lower traveling body 12. The blade device 31 is provided with a blade 32, the blade 32 being an actuating unit that functions as a soil removing body extending in the vehicle width direction; a connecting arm 33 which rotatably supports the blade 32 with respect to the lower traveling body 12 of the body 11; and a blade cylinder 34 as a fluid pressure cylinder. In the present embodiment, the connecting arm 33 and the blade cylinder 34 are provided in a pair, for example, left and right. Hydraulic oil is supplied from the control valve 28 to the blade cylinder 34 and discharged from the blade cylinder 34 via the rotary joint 35. The rotary joint 35 is provided at the swing center of the upper swing body 13. Furthermore, an anti-drift valve device 36 is mounted on the blade cylinder 34. As shown in fig. 7, the anti-drift valve arrangement 36 includes a single block valve body 40 mounted directly on the blade cylinder 34. The check valve 41, the piston housing 42, and the power piston 43 are incorporated in the valve body 40.

A fluid pressure system serving as a hydraulic system is mounted on the work machine 10 as shown in fig. 1 to 6.

A main pump 50, which serves as a fluid pressure pump, mounted on the machine body 11 is driven by an engine mounted on the machine body 11. The main pump 50 is connected to a tank 52 through a center bypass passage 51 provided in the control valve 28, and is designed such that the flow rate of hydraulic oil returning from the main pump 50 to the tank 52 through the center bypass passage 51 is reduced depending on the displacement amount of the control spool 50 of the control valve 28. In the control valve 28, a check valve 54 is provided in a supply passage 53 branched from the center bypass passage 51. The control valve 28 is provided with a return passage 55 connected to the center bypass passage 51 and connected to the tank 52. In the control valve 28, connection passages 57 and 58 are provided, and the connection passages 57 and 58 are connected to respective actuators such as a left-right travel motor, a swing motor, a boom cylinder, an arm cylinder, a bucket cylinder, and the bucket cylinder 34. In the present embodiment, a line relief valve 62 including a check valve 61 for compensating for a check (preventing negative pressure) is provided in a passage 60 between the connection passage 57 and the center bypass passage 51.

In the control valve 28 of the present embodiment, a control spool, a travel engine, a swing engine, a boom cylinder, an arm cylinder, and a bucket cylinder may use known products, and thus their illustration will be omitted, and only the control spool 28BL for the blade cylinder 34 is shown. Here, the control spool valve 28BL allows the displacement direction and the displacement amount to be controlled in accordance with the operation direction and the operation amount of the pilot valve associated with the operation of the operation unit such as the lever or the pedal provided in the cab 14, and performs the direction control and the flow rate control of the hydraulic oil supplied and discharged to and from the head chamber 34h as the first fluid chamber and the rod chamber 34r as the second fluid chamber from the blade cylinder 34 of the main pump 50, and increases the flow rate of the hydraulic oil as the displacement increases with the operation amount. In the present embodiment, the control spool valve 28BL has a neutral position N, operation positions P1 and P2, and a floating position P3. The control spool 28BL is located at a neutral position N that does not allow pressurized oil to be supplied to the blade cylinder 34 without supplying pilot pressure. The control spool 28BL is configured to switch to the operating positions P1 and P2, which allow oil discharged from the main pump 50 to be supplied to and discharged from the head and rod chambers 34h and 34r of the blade cylinder 34, or to the floating position P3, which allows the head and rod chambers 34h and 34r of the blade cylinder 34 to be connected to the oil tank 52 by the supplied pilot pressure. In this case, the displacement amount (stroke) of the control spool 28BL is increased or decreased in correspondence with an increase or decrease in the input pilot pressure, and is controlled such that the larger the displacement amount, the larger the passing oil amount, that is, the larger the valve opening degree becomes.

The connecting passages 57 and 58 are typically connected to the actuator via a rotary joint 35; however, in this embodiment they are connected to an anti-drift valve arrangement 36 mounted on the blade cylinder 34.

In the present embodiment, the connection passage 57 is connected to the passage 65 of the anti-drift valve device 36, and the connection passage 58 is connected to the passage 66 of the anti-drift valve device 36, and further directly connected to the rod chamber 34r of the blade cylinder 34 via the branch passage 67.

The passage 65 of the anti-drift valve device 36 is connected to the check valve 41. The check valve 41 is configured such that a poppet 71 serving as a valve element is movably accommodated in an accommodation portion 70 formed in the valve main body 40, and the poppet 71 is urged toward a valve closing direction, i.e., toward a valve seat, by a spring 72 serving as an urging member. Inside the housing portion 70, a valve seat chamber 70r1 and a back pressure chamber 70r2 that communicate with the passage 65 including the valve seat are defined by the poppet 71. The passages 65 and 74 are connected to the seat chamber 70r1 through a valve seat. A passage 74 is formed in the valve body 40 and is directly connected to the head chamber 34h of the blade cylinder 34. In addition, a communication passage 75 formed in the valve main body 40 branches from the passage 74, and the communication passage 75 is connected to the oil tank 52 via a relief valve 77 and a throttle valve 78 provided in the valve main body 40. The relief valve 77 is set to open when the head chamber pressure of the blade cylinder 34 reaches a preset relief pressure.

A branch passage 80 formed in the valve main body 40 branches from the communication passage 75, and a selector valve 81 is provided in the branch passage 80. In other words, the head chamber 34h of the vane cylinder 34 communicates with the back pressure chamber 70r2 of the check valve 41 via the selector valve 81. The selector valve 81 is pilot-operated by hydraulic oil flowing from the relief valve 7 from the head chamber 34h of the blade cylinder 34. The selector valve 81 is switchable between a first position P4, which allows the backpressure chamber 70r2 of the check valve 41 to communicate with the head chamber 34h of the blade cylinder 34, and a second position P5, which allows the backpressure chamber 70r2 to communicate with the oil tank 52.

In addition, a balance line 83 connected to the anti-drift valve device 36 mounted on the blade cylinder 34 on the opposite side branches off from the communication passage 75, and a fuse valve 84 is provided on the balance line 83. In other words, the balance line 83 communicates between the head chambers 34h of the pair of blade cylinders 34. The balance line 83 is formed partially in the valve body 40, and the portion between the valve bodies 40 of the anti-drift valve device 36 on the opposite side is formed of, for example, a pipe. The fuse valve 84 serves to prevent oil from leaking from the head chamber 34h of the blade cylinder 34 when the balance line 83 is broken. The fuse valve 84 is built in the valve body 40, and is configured to close when the front-rear pressure difference reaches a predetermined pressure that has been determined in advance.

The passage 66 of the anti-drift valve device 36 is connected to the piston housing 42. The piston housing 42 is formed in the valve main body 40 independently of the housing 70 of the check valve 41. The piston accommodating portion 42 movably accommodates the power piston 43, and a first piston chamber 42pl and a second piston chamber 42p2 are further defined in the piston accommodating portion 42 by the power piston 43. The first piston chamber 42pl is connected to the passage 66. Therefore, the first piston chamber 42pl is connected to the rod chamber 34r of the blade cylinder 34 via the passage 66, the connection passage 58, and the branch passage 67. The pressure receiving area of the power piston 43, which is the surface area of the power piston 43 facing the first piston chamber 42pl, is much larger than the pressure receiving area of the poppet valve 71, which is the surface area of the poppet valve 71 facing the back pressure chamber 70r 2. The second piston chamber 42p2 is located on the poppet valve 71 side (left side in the drawing) of the check valve 41 with respect to the power piston 43, and is used for a drain purpose communicating with the oil tank 52 on the downstream side of the throttle valve 78. Therefore, although the hydraulic pressure acts on the power piston 43 in the piston housing portion 42 in the direction toward the check valve 41 side (poppet valve 71 side), the power piston 43 is configured not to receive the reaction force from the opposite direction, i.e., substantially no pressure is generated. As shown in fig. 7, the second piston chamber 42p2 communicates with the valve seat chamber 70r1 of the accommodating portion 70 of the check valve 41 via a communication portion 86 formed in the valve main body 40. In the communication portion 86, a link 87 serving as a connecting member is provided for transmitting the movement of the power piston 43 to the poppet 71 to interlock the movement of the poppet 71 with the movement of the power piston 43. The connecting rod 87 is formed as a separate structure from the power piston 43 and the poppet valve 71. Further, the connecting rod 87 is formed long, and the area of the end surface of the connecting rod 87 opposed to the power piston 43 and the poppet valve 71 is set small relative to the area of the power piston 43 and the poppet valve 71.

Next, the operation of the illustrated embodiment will be described.

[ neutral blade ]

In the case where the operator places the operation unit in the neutral position, as shown in fig. 1, when the control spool valve 28BL of the control valve 28 is located in the neutral position N, the main pump 50 is connected to the center bypass passage 51, and the check valve 41 moves the poppet valve 71 in the valve closing direction against the valve seat by the urging force of the spring 72 and cuts off the connection between the ports communicating with the passage 65 and the passage 74, respectively. Therefore, the hydraulic oil discharged from the main pump 50 is returned to the oil tank 52 via the center bypass path 51, so the hydraulic oil is no longer supplied to the blade cylinder 34, and the blade cylinder 34 maintains the current state without performing the expansion/contraction operation.

[ lifting blade ]

In the case where the operator operates the operation unit in the blade lifting direction, as shown in fig. 2, the control spool 28BL of the control valve 28 is switched to the operation position P1, and the main pump 50 is connected to the connection passage 58 via the check valve 54 of the supply passage 53, and the connection passage 57 is connected to the oil tank 52 via the return passage 55. Therefore, according to the operation amount of the control spool 28BL, the hydraulic oil discharged from the main pump 50 is supplied from the connection passage 58 to the rod chamber 34r of the blade cylinder 34 through the branch passage 67, and further supplied from the passage 66 of the anti-drift valve device 36 to the first piston chamber 42pl of the piston housing portion 42. As a result, the power piston 43 is pushed and moved by the rod-side pressure (pump pressure) toward the more proximal side (left side in the drawing) of the check valve 41, the poppet valve 71 of the check valve 41 is pushed via the connecting rod 87 against the urging force of the spring 72 and is forcibly moved, so the valve seat is opened to allow the passage 65 and the passage 74 to communicate with each other, and the connecting passage 57 is connected to the head chamber 34h of the blade cylinder 34 through the passage 65, the passage 74, and the hydraulic oil is returned from the head chamber 34h to the oil tank 52. Thus, the blade cylinder 34 is contracted and the blade 32 is subjected to the lifting operation. In this state, when the operator returns the operation unit to the neutral position, the hydraulic oil in the head chamber 34h and the rod chamber 34r of the blade cylinder 34 is not increased or decreased, and the blade 32 maintains the lift position.

(descending blade and elevator body 11)

In the case where the operator operates the operation unit in the blade-down direction, as shown in fig. 3, the control spool 28BL of the control valve 28 is switched to the operation position P2, the main pump 50 is connected to the connection passage 57 via the check valve 54 of the supply passage 53, and the connection passage 58 is connected to the oil tank 52 via the return passage 55. Therefore, according to the operation amount of the control spool 28BL, hydraulic oil discharged from the main pump 50 is supplied from the connection passage 57 to the valve seat chamber 70r1 of the check valve 41 via the passage 65 of the drift prevention valve device 36, and the poppet 71 is pushed in and moved against the urging force of the spring 72, the valve seat is opened to allow the passage 65 and the passage 74 to communicate with each other, the connection passage 57 is connected to the head chamber 34h of the blade cylinder 34 via the passage 65 and the passage 74, and hydraulic oil is supplied from the main pump 50 to the head chamber 34h of the blade cylinder 34. The link 87 is separated from the poppet 71. Further, from the rod chamber 34r of the blade cylinder 34, a connection is established with the oil tank 52 through the branch passage 67, the connection passage 58, and the return passage 55, and the hydraulic oil is returned from the rod chamber 34r to the oil tank 52. Thus, the blade cylinder 34 extends and causes the blade 32 to perform a lowering operation. Therefore, by causing the blade 32 to perform the lowering operation as described above, the body 11 can be raised with the blade 32 being brought into contact with the ground. In this state, when the operator returns the operation unit to the neutral position, the hydraulic oil in the head chamber 34h and the rod chamber 34r of the blade cylinder 34 is not increased or decreased, and the blade 32 is kept at the lowered position.

(blade floating)

If the operator switches the operating unit to the floating position, as shown in fig. 4, the control spool valve 28BL of the control valve 28 is switched to the floating position P3, the main pump 50 is connected to the center bypass passage 51, and further the passages 57 and 58 are connected to the oil tank 52, respectively. In other words, the rod chamber 34r of the blade cylinder 34 communicates with the oil tank 52 through the connecting passage 58 and the return passage 55. At this time, the rod chamber pressure (tank pressure) of the vane cylinder 34 is supplied to the first piston chamber 42pl of the power piston 43, and the head chamber pressure of the vane cylinder 34 acts on the back pressure chamber 70r2 of the check valve 41. However, since the pressure receiving area of the power piston 43 is much larger than the pressure receiving area of the poppet 71, the pressure applied to the power piston 43 exceeds the sum of the urging force of the spring 72 and the back pressure of the poppet 71 even with a slight tank pressure. Therefore, the power piston 43 is pushed in and moved to a side closer to the check valve 41 (left side in the drawing), and the poppet 71 of the check valve 41 is pushed in and moved against the urging force of the spring 72 via the connecting rod 87. Therefore, the valve seat of the check valve 41 is opened, allowing the passage 65 and the passage 74 to communicate with each other, and the head chamber 34h of the blade cylinder 34 is also connected to the oil tank 52 through the connecting passage 57 and the return passage 55. As a result, the head chamber 34h and the rod chamber 34r of the blade cylinder 34 are connected together to the oil tank 52 without pressure acting on them, so that the hydraulic oil can move freely between the head chamber 34h and the rod chamber 34 r. Accordingly, the blade 32 enters a floating state in which the blade 32 can freely move upward and downward by the weight of the work machine 10 without being fixed. By using this floating function, the ground can be leveled, for example, by the weight of the work machine 10.

(when the pipe is damaged and when the balance line is damaged)

For example, assuming that the connection passage 57 is damaged, as shown in fig. 5, the poppet 71 of the check valve 41 is held against the valve seat by the urging force of the spring 72, and a state is maintained in which the communication between the passage 65 and the passage 74 is cut off. Therefore, the head chamber 34h of the blade cylinder 34 is prevented from being connected to the connection passage 57, and the hydraulic oil in the head chamber 34h is prevented from leaking from the damaged portion in the connection passage 57 to the outside of the hydraulic system, thereby preventing the blade cylinder 34 from contracting. Therefore, even if the connection passage 57 is damaged when the blade 32 is in contact with the ground and the machine body 11 is lifted and supported, the machine body 11 can be prevented from drifting due to the contraction of the blade cylinder 34. Assuming that the connection passage 58 is damaged, hydraulic oil in the rod chamber 34r of the blade cylinder 34 may leak from the damaged portion in the connection passage 58 to the outside of the hydraulic system. However, such leakage acts in the extending direction of the blade cylinder 34, and does not cause contraction of the blade cylinder 34, and therefore does not cause drifting of the machine body 11.

In addition, for example, assuming that the balance line 83 is broken, the differential pressure across the fuse valve 84 provided in the balance line 83 will increase, so that the fuse valve 84 will close, and the head chamber 34h of the blade cylinder 34 is cut off with respect to the balance line 83. As a result, this will prevent the hydraulic oil in the head chamber 34h of the blade cylinder 34 from leaking from the balance line 83 to the outside of the hydraulic system. Therefore, even if the balance line 83 is damaged when the blade 32 is in contact with the ground and the body 11 is raised and supported, it is possible to suppress drifting of the body 11 due to contraction of the blade cylinder 34.

(during overload period)

For example, when an overload is applied to the blade 32, as shown in fig. 6, even if it is assumed that the control spool 28BL of the control valve 28 is in the neutral position N, the relief valve 77 is opened when the head chamber 34h of the blade cylinder 34 reaches a predetermined pressure, and the selector valve 81 is pilot-operated by hydraulic oil from the head chamber 34h of the blade cylinder 34 flowing out from the relief valve 77 and switched from the first position P4 to the second position P5. Thereby, the back pressure chamber 70r2 of the check valve 41 communicates with the tank 52. Therefore, the back pressure of the check valve 41 is released, the poppet 71 is forcibly moved in the valve opening direction against the bias of the spring 72 by the head chamber pressure of the blade cylinder 34, the valve seat is opened, the passage 65 and the passage 74 are allowed to communicate with each other, and the head chamber 34h of the blade cylinder 34 is connected to the connecting passage 57 via the passage 74 and the passage 65. Thus, by opening the line relief valve 62 of the passage 60, the pressurized oil from the head chamber 34h is returned from the connecting passage 57 to the oil tank 52 via the center bypass passage 51, thereby relieving the overload and preventing damage to the blade cylinder 34 or the piping.

Next, the advantageous effects of the illustrated embodiment will be listed.

The power piston 43 is connected to the poppet 71 of the check valve 41, and no hydraulic pressure from the second piston chamber 42p2 acts on the poppet 71 side of the check valve 41 on the power piston 43. Therefore, when hydraulic oil is supplied from the control valve 28 to the rod chamber 34r side of the blade cylinder 34, the rod chamber pressure of the blade cylinder 34 exceeds the urging force acting on the poppet 71 by the spring 72 of the check valve 41, whereby the poppet 71 of the check valve 41 is moved in the valve opening direction by the power piston 43, and hydraulic oil can be discharged from the head chamber 34h of the blade cylinder 34 to the control valve 28. Further, for example, in the case where damage is caused to a passage (e.g., a connecting passage) between the accommodating portion 70 of the communication check valve 41 and the control valve 28, the poppet 71 of the check valve 41 is held in the valve closing direction by the urging force of the spring 72, thereby preventing the hydraulic oil from being discharged from the head chamber 34h of the blade cylinder 34 to the control valve 28, so that the blade 32 is not released from the state of supporting the body 11. Therefore, it is possible to actuate the blade 32 and prevent drifting of the body 11 supported by the blade 32 with a simple structure without newly adding a pilot line or the like from the control valve 28 side.

By mounting the valve main body 40 incorporating the check valve 41, the piston housing 42 and the power piston 43 directly on the blade cylinder 34, and by forming therein the passage 74 that directly communicates between the housing 70 of the check valve 41 and the head chamber 34h of the blade cylinder 34, it is possible to eliminate the piping for connection between the housing 70 and the head chamber 34h of the blade cylinder 34, and it is possible to prevent damage to the passage 74 that communicates between the housing 70 and the head chamber 34h of the blade cylinder 34, and therefore it is possible to prevent drifting of the machine body 11 due to such damage.

By forming the poppet 71 and the power piston 43 of the check valve 41 as separate bodies from each other, the sealability and manufacturability of the anti-drift valve device 36 can be improved.

By designing the check valve 41 as a pilot check valve defining a backpressure chamber 70r2, the backpressure chamber 70r2 houses the spring 72 and may further be supplied with the head chamber pressure of the blade cylinder 34, which may be used to more finely control the actuation of the poppet valve 71 of the check valve 41 in the housing 70. Further, since the pilot pressure for actuating the check valve 41 can use the head chamber pressure of the blade cylinder 34, and a passage for this purpose can be formed inside the valve body 40, even when the check valve 41 is a pilot type check valve, an additional pipe does not need to be wired from the upper swing body 13 side.

When an overload is applied to the head chamber 34h of the blade cylinder 34, the relief valve 77 is opened, the selector valve 81 is pilot-operated by the hydraulic oil from the head chamber 34h of the blade cylinder 34 flowing out from the relief valve 77, and is switched to the second position P5 to allow communication between the back pressure chamber 70r2 and the oil tank 52, whereby the back pressure of the check valve 41 can be released and the poppet valve 71 can be moved in the valve opening direction, and the hydraulic oil is returned from the head chamber 34h to the oil tank 52 via the control valve 28 to release the overload.

By providing the fuse valve 84 in the balance line 83 between the pair of head chambers 34h communicating with the blade cylinder 34, when the balance line 83 is broken, for example, the front-rear pressure difference across the fuse valve 84 reaches a predetermined pressure predetermined in advance, so that the fuse valve 84 is closed, and the hydraulic oil can be prevented from flowing out from the head chambers 34h of the blade cylinder 34 via the balance line 83, and the displacement of the body 11 due to the oil outflow can be prevented.

When attempting to communicate the head chamber 34h and the rod chamber 34r with the oil tank 52 through the control valve 28, respectively, by setting the area of the power piston 43 receiving the rod chamber pressure of the blade cylinder 34 larger than the area of the poppet valve 71 of the check valve 41 receiving the head chamber pressure of the blade cylinder 34, the force that the power piston 43 receives from the rod chamber pressure exceeds the force that the poppet valve 71 of the check valve 41 receives from the head chamber pressure, and the poppet valve 71 of the check valve 41 can be moved in the valve opening direction by the power piston 43. As a result, it becomes possible to communicate both the head chamber 34h and the rod chamber 34r with the oil tank 52. Therefore, the floating function can be easily given to the blade cylinder 34.

Further, the anti-drift valve device 36 is configured such that all structures and passages are incorporated into the interior of the valve body 40, and the structures are complete in the interior of the valve body 40, and thus additional piping can be minimized, the anti-drift valve device 36 can be more easily installed on a general working machine that does not have the anti-drift valve device 36.

By attaching the anti-drift valve device 36 to the blade cylinder 34 that moves the blade 32 up and down, the blade 32 can be moved up and down, and drift of the body 11 supported by the reaction force of the blade 32 that is in contact with the ground can be prevented with a simple structure without newly adding a pilot line or the like from the control valve 28 side.

The present invention can provide a work machine 10 that can move a blade 32 up and down with a simple structure and can prevent the displacement of a machine body 11 supported by the reaction force of the blade 32 contacting the ground without adding a port such as a pilot line to a swivel joint 35, which is required when hydraulic oil is supplied from a control valve 28 located in an upper swing body 13 to a blade cylinder 34 of a blade device 31 located in a lower traveling body 12, by being provided in the work machine 10 together with the above-described blade device 31. Therefore, the work machine 10 can be manufactured at low cost without increasing the cost or changing the layout for manufacturing the dedicated rotary joint 34, and can be easily applied to a conventional work machine. Especially in the case of a lower traveling body 12 where the blade arrangement 31 is located close to the ground, it is desirable to reduce the ducting as much as possible in order to reduce the likelihood of damage caused by, for example, bouncing rock. Therefore, by applying the above-described anti-drift valve device 36 and the blade device 31, it is possible to provide the work machine 10 with high reliability, which suppresses additional piping and the like while preventing drift of the machine body 11.

In one embodiment described above, the anti-drift valve device 36 may be applied to, for example, a leg cylinder serving as a fluid pressure cylinder that actuates a leg serving as an actuating unit and stabilizes the body 11. In other words, even in the leg device as the lower support device provided in the lower traveling body 12, hydraulic oil is supplied via the rotary joint 35 similarly to the blade device 31, since there is a problem in that the body 11 is prevented from drifting without adding a new port for a separate hydraulic line or pilot line to the rotary joint 35, the above-described anti-drifting valve device 36 can be appropriately used in view of cost and layout.

Further, the anti-drift valve device 36 may be applied to a fluid pressure cylinder, such as a boom cylinder, to raise the body 11 by pressing a bucket of the work equipment 15 as an actuating unit of the work machine 10 against the ground. When raising the machine body 11 by pressing the working equipment 15 against the ground, the same interaction effect can be obtained by connecting the head chamber and the rod chamber of the fluid pressure cylinder to one embodiment in reverse with respect to the anti-drift valve device 36, since the machine body 11 may be lowered due to extension of the boom cylinder or the like. Thus, depending on the hydraulic system, the first fluid chamber may be a head chamber or a rod chamber, and the second fluid chamber may be a rod chamber or a head chamber.

Industrial applicability

The present invention provides industrial applicability primarily to operators who manufacture or sell hydraulic cylinders for blade devices used in work machines such as hydraulic excavators or work machines on which these hydraulic cylinders are mounted.