JP2001342648A - Hydraulic backhoe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic backhoe capable of preventing free drop of an arm and a bucket from occurring by insuring a holding force of a bucket cylinder and an arm cylinder and enlarging a scope of work of a work machine. SOLUTION: An arm turn prevention valve 20 preventing abrupt turn in the downward direction of the arm by holding an internal pressure of the cylinder is mounted on at least bottom side of the arm cylinder 7, and a bucket turn prevention valve 20 preventing abrupt turn in the downward direction of the bucket is mounted on at least bottom side of the bucket cylinder 9. Even if a hydraulic hose connected with a holding pressure generation side in each cylinder 7, 9 is damaged by an external force while crane work or excavation and transportation works of sediment are done, bottom side oil chambers of the cylinders 7, 9 are securely shut-off by the turn prevention valves 20 and a holding pressure on the bottom side is maintained so that the work can be done safely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shovel having a working machine such as a boom, an arm and a bucket.
The present invention relates to a hydraulic excavator that improves work efficiency and work safety.

[0002]

2. Description of the Related Art Conventionally, hydraulic excavators have been used for various operations such as excavation and transportation of earth and sand. The hydraulic excavator 1 illustrated in FIG. 7 includes a traveling body 2, a revolving body 3 mounted on the traveling body 2 so as to be rotatable around a vertical axis, and a working machine 4 mounted on the revolving body 3. ing. The working machine 4 has a boom 6 vertically raised and lowered by a boom cylinder (not shown) attached to a substantially central portion of the swing body 3.
A pair of left and right links formed by an arm 8, which is vertically oscillated with the tip of the boom 6 as a fulcrum by an arm cylinder (not shown) attached to the boom 6, and a bucket cylinder (not shown) attached to the arm 8. And a bucket 11 that swings up and down with the tip of the arm 8 as a fulcrum through the arm 10.

An engine (not shown) is mounted near the rear portion of the revolving unit 3, and a variable displacement pump (not shown) driven by the engine and a discharge pressure oil from the variable displacement pump are also provided. A plurality of operating valves (not shown) for selectively supplying and driving a plurality of operating cylinders of the working machine 4 are provided. The operating valve is connected corresponding to the working cylinder of the working machine 4. A plurality of operation levers (not shown) for independently switching the plurality of operation valves are disposed in a driver's cab 3a disposed at a position deviated leftward or rightward from the front center of the revolving structure 3.

The bottom part of the boom cylinder is a revolving unit 3
And the piston rod is attached to the boom, and the boom cylinder moves the boom 6 up and down in the vertical direction. The arm cylinder has a bottom portion attached to the boom 6 and a piston rod attached to the arm 8. The arm 8 swings vertically by the arm cylinder with the tip of the boom 6 as a fulcrum. The bottom of the bucket cylinder is attached to the arm 8, and the piston rod is attached to a link 10 between the arm 8 and the bucket 11. The bucket 11 swings vertically by the bucket cylinder via a pair of left and right links 10. The hydraulic excavator 1 excavates the ground surface to a desired depth, transports the excavated earth and sand to a dump position, and dumps it.

On the other hand, there is a hydraulic excavator 1 which enables a crane operation in addition to the excavation operation and the transport operation of earth and sand.
This type of hydraulic excavator has a bucket 1 as shown in FIG.
Arm 8 via the link fixing pin 11b.
The arm 8 has a hanging hook 12 that is swingably fixed to the rear side of the arm 8 and lifts and hangs a suspended load. At the time of crane work, in order to avoid interference between the bucket 11 and the hanging hook 12, the bucket cylinder is extended until the bucket 11 reaches the maximum excavation position, and the scooping surface side of the bucket 11 is moved toward the arm 8 side. The crane work is performed by the hanging hook 12 in the posture at the time of the stop, in the state where it is most scraped.

Another hydraulic excavator having a crane function is a hydraulic excavator in which a suspension hook fixed to one end of a wire (not shown) is suspended and supported via a pulley (not shown) attached to the tip of the arm 8. There is a shovel. At the time of crane work, in order to avoid interference between the bucket and the hanging hook, the bucket cylinder is contracted and rocked until the bucket reaches the maximum dump position, and the crane by the hanging hook is held in the dumping posture. Do the work.

[0007]

Normally, a conventional hydraulic excavator operates the boom in an upright direction by an extension operation of a boom cylinder, and operates the boom in a falling direction by a contraction operation. Even when the boom is in the upright state, the boom,
Since the center of gravity of the working machine including the arm and the bucket is located in front of the machine body, a force in the contraction direction for lowering the boom acts on the boom cylinder, and a holding pressure is constantly generated on the bottom side thereof. Therefore, if the hydraulic hose connected to the bottom side of the boom cylinder is damaged by an external force, the holding force of the boom cylinder is lost, and the boom turns rapidly in the falling direction. Usually, in order to prevent this sudden rotation, a fall prevention valve for holding the internal pressure on the bottom side of the boom cylinder is mounted.

Further, the hydraulic excavator pivots the arm downward with the connecting portion to the boom as a fulcrum by the extension operation of the arm cylinder, and pivots the arm upward by the contraction operation. For example, if the hydraulic hose connected to the oil chamber on the head side of the arm cylinder is damaged by external force during the transition to the dumping operation after the excavation, the holding force of the arm cylinder is lost and the bucket is lost. Together with the arm, the arm rapidly turns downward. In order to avoid this sudden rotation, a rotation prevention valve is mounted on the head side of the arm cylinder.

When excavating earth and sand, the boom cylinder and the arm cylinder are operated to rotate the boom and the arm up and down, respectively, and simultaneously, the bucket cylinder is operated to swing the bucket at the tip of the arm. Make it work. The operation range of the arm tip at this time is within the rotation range from the vertical posture of the arm when rotated downward to the rotation upper limit position on the front side of the fuselage. A force is always applied to the bucket cylinder in the contraction direction to generate a holding pressure on the bottom side. When transporting the excavated earth and sand to the dump position, the bucket cylinder is extended and transported to the dump position in a posture (maximum excavation posture) when the bucket is stopped with the bucket scraped into the arm side. In this case, the holding pressure becomes maximum in the initial stage of transportation, and the holding pressure gradually decreases while reaching the dump position.

During the excavation, for example, if the hydraulic hose connected to the oil chamber on the bottom side of the bucket cylinder is damaged by an external force, the bucket itself does not fall.
It is not necessary to provide an anti-rotation valve on the bottom side. Further, even if the hydraulic hose is damaged during the transportation to the dump position, the soil in the bucket falls at most, and the influence on the surroundings is extremely small. Therefore, it is not usually necessary to provide a rotation prevention valve in the oil chamber on the bottom side of the bucket cylinder.

At the dump position, during the transition from the maximum excavation posture of the bucket to the dump posture, the bucket cylinder is operated in the contraction direction, so that a holding pressure is generated on the head side by the weight of the bucket. For example, when a hydraulic hose connected to an oil chamber on the head side of the bucket cylinder is broken by an external force, the holding pressure of the bucket cylinder is instantaneously lost, and the bucket rapidly turns downward. However, the conventional bucket cylinder is not provided with a rotation preventing valve for avoiding this sudden rotation.

By the way, in the model of the hydraulic excavator to which the crane function is added, the operating range of the arm tip when lifting the suspended load is, as described above, that the arm of the hydraulic excavator is moved from the vertical posture to the forward side of the machine body. The rotation range is limited to the rotation upper limit position. Therefore, similarly to the excavation work and the transport work, the holding pressure is always generated on the head side of the arm cylinder during the crane work.

In the course of lifting the suspended load within the rotation range from the vertical posture of the arm to the rotation upper limit position on the front side of the fuselage,
To move the arm cylinder upward by operating the arm cylinder in the contraction direction, for example, when a hydraulic hose connected to the oil chamber on the head side of the arm cylinder is broken by external force, The holding pressure is instantaneously lost, and the arm rapidly turns downward. Following this, the lifted suspended load swings greatly around the tip of the arm.

Further, when lifting a suspended load, especially when a lifting hook is provided on the back side of the arm, the bucket cylinder is extended to the extension limit in order to avoid interference between the bucket and the lifting wire. Hold in the scraped position. Therefore, the maximum holding pressure is generated on the bottom side of the bucket cylinder.

When the hydraulic hose connected to the oil chamber on the bottom side of the bucket cylinder breaks, the holding pressure on the bottom side is instantaneously lost similarly to the arm, and the bucket rotates rapidly downward. As described above, the bucket cylinder is not provided with a rotation preventing valve for avoiding this sudden rotation.

On the other hand, if it is possible to perform excavation and crane operations by rotating the arm to a position immediately in front of the body,
Work can be performed in front of the operator, which is more preferable in terms of work efficiency. However, at present, since the downward rotation of the arm is limited to the position where the arm is in the vertical posture as described above, the arm cannot be rotated to a position immediately in front of the fuselage, and the excavation work efficiency is improved. It is difficult. In particular, when lifting suspended loads,
Since the rotation range of the arm is limited, the hanging hook must be moved within the rotation range of the arm.
For this reason, the crane operation is performed at a position distant from the airframe due to the small rotation range of the arm, and the efficiency of the crane operation is significantly reduced.

The present invention has been made to solve such a conventional problem, and a specific object of the present invention is to secure a holding force of an arm cylinder or a bucket cylinder to prevent a free fall of an arm or a bucket. It is another object of the present invention to provide a hydraulic shovel capable of expanding a working range of a working machine.

[0018]

As described above, the reason that the limit of the downward rotation of the arm is limited to the vertical position is that the arm is rotated to a position immediately in front of the body. In this case, the arm pivots downward to the vertical position, and then pivots upward again toward the front. At this time, it is necessary to maintain the holding pressure on the bottom side of the arm cylinder. However, at present, the holding pressure of the arm cylinder is guaranteed only on the head side as described above.

However, in the case of a hydraulic excavator having a crane function, it is preferable that not only excavation work and transport work as described above, but also work can be performed particularly at the position closest to the machine body during crane work. Even when the maximum holding pressure is applied to each cylinder of the arm and the bucket, the holding pressure is surely maintained, and
When the hydraulic hose breaks, it is desirable to provide a boom, an arm, and a bucket for preventing rotation of the boom, the arm, and the bucket on the corresponding oil chamber side in order to maintain the holding pressure.

According to the first aspect of the present invention, there is provided a boom that rises and falls on a revolving structure, an arm that is connected to a tip of the boom, and that is attached to the tip of the arm, and that is attached to the tip of the arm, and that is also swingable in the vertical direction. A hydraulic excavator provided with a bucket, wherein the boom, the arm, and the bucket are each independently operated by an operation cylinder, and a bottom side of the cylinder for the arm maintains a holding pressure on the bottom side, An excavator is provided with an arm rotation preventing means for preventing the arm from freely falling.

Until the arm rotates downward and reaches the vertical position, the arm cylinder extends. At this time, the holding pressure of the arm is constantly generated on the head side of the arm cylinder. Therefore, conventionally, an anti-rotation valve is mounted on the head side of the arm cylinder. However, in the case of excavation work or crane work, when the arm is turned from the vertical posture to the upper rotation limit position on the rear side of the fuselage,
While the arm cylinder continues to extend, the holding pressure of the arm shifts to the bottom side. Therefore, in order to rotate the arm to the rotation upper limit position on the rear side of the fuselage and hold the same, the rotation prevention means is provided on the bottom side of the arm cylinder as in the present invention, similarly to the head side. Must be worn.

In the present invention, the arm rotation preventing means is directly attached to the bottom side of the arm cylinder, and while the arm is being rotated to the maximum rotation position on the rear side of the body, Even if the hydraulic hose connected to the bottom side of the arm cylinder breaks and the hydraulic pressure on the bottom side tries to escape, the arm rotation preventing means completely shuts off the bottom oil chamber of the cylinder and the external oil passage. The holding pressure of the bottom oil chamber is maintained. Further, when the operation valve is operated, for example, it is possible to detect that a hydraulic hose or the like connected to the bottom side oil chamber is broken, and to automatically return the operation valve to the inoperative position. In this case as well, the holding pressure on the bottom side is reliably maintained by the arm rotation preventing means, and the supply and discharge of the pressure oil are automatically stopped.

Based on the above configuration, it is not necessary to set the limit working range of the arm as in the prior art, and the operation of the arm cylinder allows the arm to freely move within the rotation limits on the front side and the rear side including the vertical position of the arm. Can be rotated. As a result, safety can be ensured and the work range can be expanded, so that efficient earth and sand excavation and transport work can be performed.

In the case where the rotation preventing means is provided on both the head side and the bottom side of the arm cylinder, the holding pressure in the cylinder extension direction and the contraction direction due to the load of the arm, excavated earth and the like is reduced by the rotation preventing means. Since the arm is supported instantaneously, the arm can be prevented from suddenly turning downward, and safety can be ensured in the entire expanded working range.

According to a second aspect of the present invention, in addition to the arm cylinder, at least on the bottom side of the bucket cylinder, there is provided a bucket rotation preventing means for maintaining a holding pressure on the bottom side to prevent free fall of the bucket. Have.

When the excavated earth and sand is transported to the dumping position, the bucket cylinder is extended to maintain the maximum excavation posture in which the bucket is stopped while the bucket is scraped to the lower surface of the arm. In this case, a force in the cylinder contraction direction always acts on the bucket to generate a holding pressure on the bottom side of the bucket cylinder. At that dump location,
The arm cylinder is contracted to rotate the arm upward, and the bucket cylinder is contracted to shift the bucket from the maximum excavation position to the maximum dump position. When in the dumping posture, a force in the extension direction is constantly applied to the bucket cylinder, and a holding pressure is generated on the head side of the bucket cylinder.

According to the present invention, similarly to the arm, the bucket rotation preventing means is directly attached to the bottom side of the desired cylinder oil chamber, so that the cylinder extends or contracts due to its own weight or the like. In addition to supporting the force in the direction, the bucket can be prevented from dropping sharply.

For example, when excavating and transporting earth and sand, the arm is rotated not only within the working range on the front side of the fuselage but also in the entire rotation range including the rear side of the fuselage by operating the arm cylinder. On the other hand, the bucket is swung up and down by the operation of the bucket cylinder.
Compared to the conventional case where the work is performed only within the turning range where the arm is turned from the vertical posture to the front side of the fuselage,
With the above configuration, the excavation rotation range of the bucket can be increased, and the excavation range is also increased, in conjunction with the enlargement of the rotation range of the arm. At the same time, in addition to the functions and effects described in the first aspect, the earth and sand excavation and transportation operations can be performed more reliably and efficiently, and the safety of the operations can be further improved.

In the invention according to claim 3, the hanging hook is rotatably supported between a pair of left and right bucket school bags projecting outward from the rear wall of the bucket. Stipulates.

Even in the present invention, the functions at the time of excavation and transportation work are substantially the same as those described above. However, in order to avoid interference between the bucket and the hanging hook during the crane operation, it is necessary to extend the bucket cylinder to a position (maximum excavation position) where the bucket is most squeezed to the lower surface of the arm. The crane operation using the hanging hooks is performed with the scooping surface side facing upward. When the suspended load is lifted, the holding pressure due to the suspended load, the weight of the bucket, and the like is generated on the bottom side of the bucket cylinder in most of the rotation range of the boom and the arm.

For example, even if the hydraulic hose connected to the bottom side of the bucket cylinder breaks during crane operation, the above-described bucket rotation preventing means functions instantaneously, and the bottom side oil chamber and the external oil path are connected. Is completely shut off,
The holding pressure on the cylinder bottom side is reliably maintained, and a sudden downward rotation of the bucket is prevented. This means that the crane operation can be performed not only on the front side of the fuselage including the vertical posture of the arm due to the operation of the arm cylinder, but also on the rear side of the fuselage and in the immediate vicinity of the fuselage. Since the crane operation can be performed in the vicinity of the machine body, the positional relationship between the hanging hook and the suspended load can be visually confirmed, and the working efficiency can be significantly improved. At the same time, the range of the crane operation is widened, and the crane operation on a small site can be performed effectively and safely.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is an overall view schematically showing an example of a hydraulic excavator having a suspension hook according to a first embodiment of the present invention, FIG. 2 is a hydraulic circuit diagram of the hydraulic excavator, and FIG. FIG. 4 is an overall view schematically illustrating an operation mode of a working machine in the shovel. In the present embodiment, members that are substantially the same as those of the above-described conventional technology are given the same member names and reference numerals.

In FIG. 1, a hydraulic excavator 1 according to the first embodiment includes a traveling body 2, a revolving body 3 mounted on the traveling body 2 so as to be pivotable about a vertical axis, and a cab mounted on the revolving body 3. A fuselage 13 having a 3a, an engine 3c, and the like;
And a work machine 4 attached to the airframe 13.
The work machine 4 includes a boom 6 that rises from substantially the center of the body 13, an arm 8 that is pivotally supported at a free end of the boom and swings vertically, and is supported by an arm top pin 8 a at the tip of the arm 8. And a bucket 11 that swings up and down.

The boom 6 is moved up and down by a pair of boom cylinders 5 and 5 provided between the revolving structure 3 and the revolving structure 3. The arm 8 is mounted between the boom 6 and the boom 6. The arm cylinder 7 swings vertically about the tip of the boom 6 as a fulcrum, and the bucket 11 is moved by the bucket cylinder 9 attached between the arm 8 via a pair of left and right two-joint links 10 and 10. The arm 8 is vertically swung with the tip of the arm 8 as a fulcrum.

On the left and right sides of the rear wall of the bucket 11, bucket school bags 11a are provided. One end of the bucket school bag 11a is swingably supported via the arm top pin 8a of the arm 8, and the other end is swingable to the rod end of the bucket cylinder 9 via the left and right links 10, 10. It is supported by.

Base 1 of hanging hook 12 for crane operation
2a is rotatably supported by a fixed pin 11b connecting the first link 10a and the bucket 11 on the front side.
When the hanging hook 12 is not used, the left and right links 10, 10
The hook portion 12b of the hanging hook 12 is hooked and locked by a not-shown insertion / removal pin which can be inserted / removed into a not-shown through hole formed in the links 10 and 10 and which is bored in the links 10 and 10.

As shown in FIG. 2, the hydraulic excavator 1 selectively supplies the variable displacement pump 24 and the pressure oil discharged from the variable displacement pump 24 to each of the cylinders 5, 7, 9 of the working machine 4. It is provided with three operation valves 25 to 27 to be supplied and three manual operation units 28 to 30 for independently switching the operation valves 25 to 27.

The hydraulic excavator 1 further includes an electromagnetic switching valve 3 for prohibiting the dumping operation (cylinder contraction operation) of the bucket 11 when the hanging hook 12 is not stored between the links 10, 10, ie, during crane operation.
1 and a pressure sensor 32 for detecting the oil pressure on the bottom side of the boom cylinder 5 for checking the safety load.

The variable displacement pump 24 is composed of a swash plate type pump, and controls the discharge oil amount by changing the inclination angle of the swash plate 24a by a displacement control member (not shown). The pressure oil discharged from the variable displacement pump 24 is selectively supplied to the operation valves 25 to 27 via an output circuit 33, and return oil from each of the cylinders 5, 7, 9 is supplied to the oil via a drain circuit 34. Reflux to the tank 35.

The operation valves 25 to 27 are constituted by a boom operation valve 25 corresponding to the boom cylinder 5, an arm operation valve 26 corresponding to the arm cylinder 7, and a bucket operation valve 27 corresponding to the bucket cylinder 9. I have. These operation valves 25 to 27 are four-port three-position closed center type flow control valves which are switched to a bottom side, a head side, or an inoperative position (neutral position) depending on the operation position.

The manual operation units 28 to 30 include a boom operation unit 28 corresponding to the boom operation valve 25, an arm operation unit 29 corresponding to the arm operation valve 26, and a bucket operation unit 30 corresponding to the bucket operation valve 27. Consists of Each of the operation units 28 to 30 has the same structure and function. The operation units 28 to 30 include an operation lever 36,
It has first and second pilot proportional control valves (not shown) that output pilot hydraulic pressure in accordance with the operation amount (angle) of the operation lever 36. Each of the operation units 28 to 30 operates a first and second pilot circuits 37 and 3 by operating a sensor (not shown).
The supply of pilot pressure oil to the pump 8 is cut off.

The operating lever 36 is disposed in the operator's cab 3a, which is disposed at a position deviated leftward or rightward from the center of the front part of the revolving unit 3. The pilot oil supplied to the pilot proportional control valve from a pilot pump, also not shown, increases in accordance with the operation amount of the operation lever 36, and the opening degree of the spools of the operation valves 25 to 27 is increased by the pilot pressure of the increased pilot flow. Increases, and the flow rate of the discharge pressure oil supplied to each of the cylinders 5, 7, 9 increases according to the opening degree.

The pilot pressure oil from the first pilot proportional control valve of the boom operating section 28 is supplied to the first pilot circuit 3
7, a first pressure receiving portion 25a of the boom operation valve 25
(Lower side). The pilot pressure oil from the second pilot proportional control valve is passed through a second pilot circuit 38 to a second pressure receiving portion 25b (upward side) of the boom operation valve 25.
Act on.

The pilot pressure oil from the first pilot proportional control valve of the arm operating section 29 is supplied to the first pilot circuit 3
7, the first pressure receiving portion 26a of the arm operation valve 26
(Dump side). The pilot pressure oil from the second pilot proportional control valve acts on the second pressure receiving portion 26b (excavation side) of the arm operation valve 26 via the second pilot circuit 38.

The pilot pressure oil from the first pilot proportional control valve of the bucket operating section 30 is supplied to the first pressure receiving section 27 of the bucket operating valve 27 through the first pilot circuit 37.
a (Excavation side). The pilot pressure oil from the second pilot proportional control valve acts on the second pressure receiving portion 27b (dump side) of the bucket operation valve 27 from the second pilot circuit 38 via the electromagnetic switching valve 31.

The solenoid 31a of the electromagnetic switching valve 31 for inhibiting the dumping operation of the bucket 11 includes the pressure sensor 32 for detecting the oil pressure on the bottom side of the boom 6, a boom angle sensor (not shown), and an arm angle sensor (not shown). A control signal is generated based on output signals from a hook switch detection switch (not shown) provided between the left and right links 10 and 10 and a crane mode switch (not shown) disposed on the cab 3a. The output is also electrically connected to a controller (not shown).

The controller is electrically connected to a monitor 3b in the cab 3a, an alarm display device (not shown) such as a buzzer and a lamp. The controller calculates the actual load based on each output signal of the pressure sensor 32, the boom angle sensor, and the like, compares the calculated value with a predetermined rated load value, and monitors the load state by the suspended load. I have. When it is determined that the suspended load is in the overload state, the alarm display device operates.

The controller stores information such as the ON / OFF combination of crane mode switches and limit switches (not shown). By inputting these signals, the electromagnetic switching valve 3 is controlled based on a command of the control program.
Energize or demagnetize one solenoid 31a.

When the solenoid of the solenoid-operated switching valve 31 is energized, the solenoid-operated switching valve 31 is switched to a position opposite to the position shown in FIG. 2, and a second pilot which connects the bucket operating valve 27 and the bucket operating unit 30 to each other. The circuit 38 is closed. The pilot pressure oil in the second pilot circuit 38 returns to the oil tank 35 via the electromagnetic switching valve 31. Even if the bucket operating section 30 is operated on the dump side of the bucket operating valve 27, no pilot pressure acts on the dump side of the bucket operating valve 27. This allows the bucket 1
1 does not move to the dump side.

Further, in the hydraulic excavator 1, the rotation preventing means 20, which is a characteristic part of the present invention, is directly attached to the cylinders of the cylinders 5, 7, and 9. The rotation preventing means 20 is connected to hydraulic hoses having tubes (not shown) for supplying pressure oil from operating valves 25 to 27 for driving the cylinders 5, 7, 9 respectively. The rotation preventing means 20 has a function of preventing the free fall of the working machine 4 by holding the cylinder internal pressure. In this embodiment, as shown in FIG. 1, the rotation preventing means 20 is directly attached to the bottom side of the boom cylinder 5, the bottom side and the head side of the arm cylinder 7, and the bottom side of the bucket cylinder 9, respectively. Have been.

As shown in FIG. 2, the rotation preventing means 20 in this embodiment is provided with a switching valve 41 having a throttle 41c for shutting off or discharging the pressure oil in each of the cylinders 5, 7, 9 to the outside.
A check valve 42 for connecting the front and rear of the switching valve 41 to supply pressure oil from the variable displacement pump 24 to the cylinders 5, 7, 9; And a safety valve 43 for assuring. Each cylinder 5,
Each of the rotation preventing means 20 directly attached to 7, 9 has substantially the same structure and function. Therefore, the same members and the same reference numerals are given to the same members of the rotation preventing means (hereinafter referred to as the rotation preventing valve) 20 described below.

A first oil passage 39 and a second oil passage 4 for connecting the arm cylinder 7 and a connection port of the arm operation valve 26.
Numeral 0 connects the switching valve 41. The first oil passage 39
The first pressure receiving portion 41a of the switching valve 41 is connected to a second pilot circuit 38 which is communicated with the arm operating portion 29 (digging side). The second pressure receiving portion 41b is connected to the drain circuit 34.

The first pressure receiving portion 41a of the switching valve 41 in the second oil passage 40 is connected to a first pilot circuit 37 which communicates with the arm operating portion 29 (dump side). The pressure receiving portion 41b is connected to the drain circuit 34. The switching valve 41 is always held at the closed position, and is switched to the open position by the pilot pressure oil supplied by operating the arm operating section 29.

A passage 44 connecting the front and rear of the switching valve 41
Is connected to the check valve 42. By operating the arm operating section 29, the variable displacement pump 24
The oil discharged from the cylinder flows into the arm cylinder 7 via the check valve 42. The intersection of the passage 44 on the output side of the check valve 42 and the first oil passage 39 or the intersection of the passage 44 and the second oil passage 40 connects the safety valve 43. The output side of the safety valve 43 is connected to the drain circuit 34. The safety valve 43 is always kept at the closed position. The safety valve 43 is provided with the cylinders 5, 7, 9
Is maintained at a preset set pressure.

When the arm operation valve 26 is in the neutral position (inactive state), the safety valve 43 and the check valve 4
2. First and second oil passages 39, 4 connected to the head side and the bottom side of the arm cylinder 7 by the switching valve 41.
0 is closed, and the flow of pressurized oil from the head side and bottom side oil chambers to the outside is shut off.

When the arm operating section 29 is operated to the dump side, the pilot pressure oil is supplied via the first pilot circuit 37 to the switching valve 41 on the arm cylinder bottom side.
And the first pressure receiving portion 41a of the arm operation valve 26. The arm operation valve 26 is switched to the dump side, and the switching valve 41 is switched to the open position. The oil discharged from the variable displacement pump 24 is supplied to the arm operation valve 26 through the first oil passage 39 and the passage 44.
Is supplied to the head side of the arm cylinder 7 through the check valve 42 from the connection port. The flow rate of the pressure oil in the oil chamber on the bottom side of the arm cylinder 7 is adjusted by the throttle 41c of the switching valve 41 on the bottom side, and the oil tank passes through the drain circuit 34 from the connection port of the arm operation valve 26. Return to 35. Since the flow rate of the return oil is adjusted by the throttle 41c, the arm cylinder 7 can be operated at a very low speed.

On the contrary, the arm operation unit 2
9 is operated to the excavation side, the second pilot circuit 38
The pilot pressure oil acts on the first pressure receiving portion 41a of the switching valve 41 and the second pressure receiving portion 26b of the arm operation valve 26 connected to the head side of the arm cylinder 7 via It is switched to the side. The switching valve 41 on the head side is switched to the open position. Discharge oil from the variable displacement pump 24 is supplied to the bottom side of the arm cylinder 7 via the second oil passage 40 and the passage 44. Pressure oil on the head side of the arm cylinder 7 is supplied from the switching valve 41 on the head side to the arm operation valve 2.
6 and return to the oil tank 35 through the drain circuit 34.

On the other hand, a pair of left and right boom cylinders 5,
The second oil passage 40 that connects each bottom side of the boom 5 and the single boom operation valve 25 connects the boom rotation prevention valve 20. A first oil passage 39 connecting the bottom side of the bucket cylinder 9 connects the bucket rotation preventing valve 20.

The first oil passage 39 communicating with the connection port of the boom operation valve 25 branches at an intermediate portion thereof and is connected to the head side of the boom cylinder 5. One of the second oil passages 40 branches at an intermediate portion thereof and is connected to the bottom side of the boom cylinder 5 via the boom rotation prevention valve 20.

When the operating lever 36 of the boom operating section 28 is operated upward, the pilot pressure oil from the boom operating section 28 receives the second pressure of the boom operating valve 25 via the second pilot circuit 38. Acts on the part 25b to switch the boom operation valve 25 to the up position. The discharge oil from the variable displacement pump 24 is diverted in the middle of the second oil passage 40 and supplied to the bottom side of each boom cylinder 5 via the check valve 42 of the boom rotation prevention valve 20. The pressure oil on one head side joins at an intermediate portion of the first oil passage 39 and the drain circuit 34 is connected via the boom operation valve 25.
And returns to the oil tank 35.

When the operating lever 36 of the boom operating section 28 is operated to the lower side, the pilot pressure oil from the boom operating section 28 is supplied to the first pressure receiving section 25a of the boom operating valve 25 via the first pilot circuit 37. Acts on
It acts on the first pressure receiving portion 41a of each switching valve 41 via the first pilot circuit 37 branched at the intermediate portion. The boom operation valve 25 is switched to the lower side, and each switching valve 41 is switched to the open position. The discharge oil from the variable displacement pump 24 is diverted at an intermediate portion of the first oil passage 39 and supplied to the head side of each boom cylinder 5. The pressure oil on one bottom side joins the intermediate portion of the second oil passage 40 via the switching valve 41 and returns to the oil tank 35 through the drain circuit 34 via the boom operation valve 25.

The first pressure receiving portion 4 of the switching valve 41 connected to the first oil passage 39 communicating with the connection port of the bucket operation valve 27
1a is a second pilot circuit 3 connected to the bucket operating unit 30 (dump side) via the electromagnetic switching valve 31.
8 and a second pressure receiving portion 41 b thereof is connected to the drain circuit 34.

When the operation lever 36 of the bucket operation unit 30 is operated to the dump side while the electromagnetic switching valve 31 is in the inoperative state shown in FIG. 2, the pilot pressure is transmitted through the second pilot circuit 38. The oil acts on the first pressure receiving portion 41a of the switching valve 41 and the dump side of the bucket operation valve 27. As described above, when the electromagnetic switching valve 31 is switched in response to an erroneous operation of the crane mode switch during a crane operation, the second pilot circuit 38 is closed. Therefore, the pilot pressure does not act on the bucket operation valve 27 and the bucket operation unit 3
Disables 0 dump side operations. Bucket operation unit 30
Operating lever 36 and arm operating unit 26 operating lever 36
Are operated in opposite directions, the bucket cylinder 9
And the arm cylinder 7 extend and contract in substantially the same direction.

In the hydraulic excavator 1 of the present embodiment, the base of the boom 6 is mounted on the body 13 in the standing posture in which the boom cylinder 5 is extended, and the boom cylinder 5 is extended and retracted by moving the boom cylinder 5 up and down. Raised in the direction. For this reason, a force in the contraction direction always acts on the boom cylinder 5 due to its own weight of the working machine 4 or the like, thereby generating a holding pressure on the bottom side. However, the arm 8 and the bucket 11 generate a holding pressure for holding a force acting in the extension direction or the contraction direction of the arm cylinder 7 or the bucket cylinder 9 depending on the working posture of the working machine 4.

As shown in FIG. 3, a support shaft 8 of the arm 8 is provided.
b and a fixing pin 11b for linking the bucket 11
The angle of inclination θ formed by a straight line α connecting the vertical axis and a line β perpendicular to the ground surface starting from the support shaft 8b is within a range from the vertical posture of the arm 8 to the forward side of the fuselage (θ1> 180 °). In other words, within the rotation range from the vertical posture of the arm 8 to the rotation upper limit position on the front side of the fuselage, the arm 8
, A force in the direction of cylinder extension always acts to generate a holding pressure on the head side.

When the inclination angle θ is within the range from the vertical position of the arm to the rear side of the fuselage (θ2 <180 °),
That is, when the arm 8 is rotated so as to be squeezed from the vertical posture to the rotation upper limit position on the rear side of the fuselage, the arm cylinder 7 continues the extension operation while the arm 8 is moved.
The holding pressure moves to the bottom side. Therefore, a force in the cylinder contraction direction is constantly applied to the arm 8, and a holding pressure is generated on the bottom side.

On the other hand, when the bucket cylinder 9 is extended to maintain the maximum excavation posture in which the bucket 11 is stopped with the bucket 11 scraped to the underside of the arm, regardless of the inclination angle θ of the arm 8, Within the entire rotation range, a force in the direction of cylinder contraction always acts on the bucket 11 to generate a holding pressure on the bottom side of the bucket cylinder 9. On the other hand, when the bucket 11 is moved from the maximum excavation position to the maximum dump position by contracting the bucket cylinder 9, regardless of the inclination angle θ of the arm 8, A force in the extension direction is always applied to the bucket cylinder 9, and a holding pressure is generated on the head side of the bucket cylinder 9.

The present invention resides in that the anti-rotation valve 20 is directly attached to a holding pressure generating portion of a desired cylinder which differs depending on the structure and operation mode of the work machine 4 and the like. The anti-rotation valve 20 is provided at least on the bottom side and at least the bottom side of the bucket cylinder 9.
Is the most important configuration. By adopting these configurations, the operation of the arm cylinder 7 ensures the safety of the arm 8 within the entire rotation range including the vertical posture of the arm and the entire front and rear sides of the body.
Can be rotated in the vertical direction, and safety can be ensured when the bucket cylinder 9 is operated, and the bucket 11 can be swung up and down.

During the excavation or transportation of earth and sand, the hydraulic hose connected to the bottom side of the arm cylinder 7 breaks during the rotation of the arm 8 to the maximum rotation position on the rear side of the fuselage. Even if the oil pressure on the bottom side is about to escape, the arm rotation prevention valve 20 acts instantaneously to completely shut off the cylinder bottom oil chamber and the external oil passage, and the holding pressure of the bottom oil chamber. Is maintained. For this reason, it is possible to avoid a sudden turning of the arm 8 downward. An anti-rotation valve 20 is provided on the head side of the arm cylinder 7 as in the related art.

Therefore, in this embodiment, the working range of the arm can be expanded to the maximum swing limit position in the front-rear direction including the vertical posture. That is, the holding pressure in the cylinder extension direction and the contraction direction is instantaneously supported by the rotation preventing valve 20 by the load of the arm 8 and excavated earth and sand, so that the arm 8 can turn suddenly downward. Can be prevented and safety is ensured throughout the extended working range.

Therefore, it is no longer necessary to set the limit working range of the arm 8 as in the prior art, and by operating the arm cylinder 7, the entire working range including the vertical position of the arm and the front and rear sides of the body (shown in FIG. 3). A, B) can be freely rotated. Such expansion of the working range leads to efficient earth and sand excavation and transportation operations.

On the other hand, when the excavated soil is transported to the dump position, the bucket cylinder 9 is extended to maintain the bucket 11 in the maximum excavation posture. Similarly to the arm 8, the bucket rotation preventing valve 2 is provided in the bottom oil chamber of the cylinder 9.
0 is directly attached, so that in addition to supporting the own weight of the bucket 11 and the force in the cylinder extension direction acting due to excavated earth and sand, the hydraulic hose connected to the bottom side oil chamber is broken. However, the holding pressure in the bottom-side oil chamber is maintained by the bucket rotation prevention valve 20, and the bucket 1
1 can be prevented from suddenly turning downward. Therefore, in combination with the expansion of the rotation range of the arm 8, the excavation rotation range of the bucket 11 can be increased, and the excavation range also increases.

During the crane operation, the links 10, 1
0, the not-shown insertion / removal pin attached to the link 10,
Then, the suspension hook 12 stored between the links 10 and 10 is rotated to expose the space between the links 10 and 10 to the outside. At this time, in order to avoid interference between the bucket 11 and the hanging hook 12, the bucket 1
It is necessary to extend the bucket cylinder 9 to the position where 1 is scraped to the lower side of the arm. When the bucket cylinder 9 is extended to the maximum, the maximum holding pressure is always generated on the bottom side of the bucket cylinder 9 by the weight of the bucket 11. The crane operation using the hanging hooks 12 is performed while maintaining the posture in which the scooping surface side of the bucket 11 faces upward.

When lifting the suspended load, for example, even if the hydraulic hose connected to the bottom side of the bucket cylinder 9 is broken, the bucket rotation preventing valve 20 functions instantaneously, and the bottom side oil chamber and the external Completely shut off the oil passage,
The holding pressure on the cylinder bottom side is reliably maintained, the sudden downward rotation of the bucket 11 is prevented, and the drop of the suspended load is also prevented. By expanding the working range of the arm 8, a crane operation can be performed in the vicinity of the fuselage. Therefore, the positional relationship between the hanging hook 12 and the suspended load can be visually checked, thereby significantly improving the working efficiency. Can be done. At the same time, since the working area of the crane work is expanded, the crane work in a small site can be performed efficiently and safely.

FIG. 4 shows another hydraulic circuit for driving the arm cylinder 7. In the second embodiment, the bottom side of the arm cylinder 7 will be described as an example, but the present invention is not limited to this.
The same applies to the head side of the arm cylinder 7 and the other boom cylinders 5 and bucket cylinders 9. In the figure, the same members as those of the hydraulic circuit for the arm cylinder 7 shown in FIG. Therefore, a detailed description of these members will be omitted.

As shown in FIG.
A pressure sensor 45 for detecting the oil pressure of the second oil passage 40 connecting the connection port of the arm cylinder 7 and the bottom side of the arm cylinder 7 is provided. A first pilot circuit 37 for connecting the arm operation valve 26 (dump side) with the arm operation section 29;
Is connected to an electromagnetic switching valve 46 for automatically returning the operating arm operation valve 26 to the inoperative position.

When the bucket cylinder 9 is contracted by operating the operation lever 36 to the dump side, the output circuit 33 is connected to the head side of the bucket cylinder 9.
Discharge oil from the variable displacement pump 24 is supplied through the arm operation valve 26, the first oil passage 39, and the check valve 42. The pressure oil on one cylinder bottom side returns to the oil tank 35 via the switching valve 41 switched to the open position by the pilot pressure, the second oil passage 40, the arm operation valve 26, and the drain circuit 34. At this time, if the hydraulic hose connected to the bottom-side oil chamber is broken and the hydraulic pressure in the second hydraulic passage 40 fluctuates, the pressure sensor 45 detects the pressure of the leakage, and the hydraulic pressure detection signal is output. Output to controller not shown.

This controller is connected to the above-mentioned alarm display device in order to monitor the oil pressure abnormality. The controller compares the detected oil pressure value output from the pressure sensor 45 with a predetermined normal oil pressure value to determine whether the oil pressure in the second oil passage 40 is a normal oil pressure value. Is done. When a hydraulic pressure exceeding a predetermined hydraulic pressure is generated in the second oil passage 40, the controller outputs a switching signal to the electromagnetic switching valve 46. When the solenoid 46a of the electromagnetic switching valve 46 is energized by a switching signal from the controller, the electromagnetic switching valve 46 is switched to a position opposite to the position shown in FIG. 4 and closes the first pilot circuit 37. The pilot oil in the first pilot circuit 37 returns to the oil tank 35 via the drain circuit 34.

Thus, the arm operation valve 26 automatically returns to the inoperative position shown in FIG. 4, and stops the oil from flowing out of the hydraulic hose. At the same time, the switching valve 41 of the arm rotation preventing valve 20 on the cylinder bottom side returns to the closed position shown in FIG. 4, and closes the second oil passage 40 connecting the bottom side of the arm cylinder 7. The flow of the pressure oil from the bottom side to the outside is completely shut off. On the other hand, the pressure oil on the cylinder head side is also used for the arm rotation prevention valve 20 on the head side.
This completely shuts off the flow of pressure oil to the outside. Therefore, even when the arm operating section 29 is operating, the arm rotation preventing valve 20 can be reliably and quickly operated to the closed position, and the operation of the hydraulic excavator 1 is efficient and safe. Is made.

FIGS. 5 and 6 show essential parts of a hydraulic excavator having a swing type and an offset type boom.
As shown in FIG. 5, the swing boom 51 is connected to the revolving unit 3.
Swivelly supported at the rear. Swing boom 5
1 swings left and right by the operation of a swing boom cylinder 50 attached to the rear part of the swing body 3. Same cylinder 5
The boom rotation prevention valve 20 having the same structure as that of the first embodiment is directly attached to the head side and the bottom side of the zero.

Further, as shown in FIG. 6, an offset boom 61 having a base portion attached to the revolving structure 3 has a middle portion supported rotatably. Offset boom 61
An offset boom cylinder 60 is attached to an intermediate portion of the cylinder. The arm 8 has an offset boom cylinder 60
With the operation described above, the offset boom 61 swings in the left-right direction with the distal end portion as a fulcrum. The same boom rotation prevention valve 20 as in the first embodiment is directly attached to the head side and the bottom side of the offset boom cylinder 60.

Since the boom rotation prevention valves 20 are directly attached to the head side and the bottom side of each of the cylinders 50 and 60, when the tip of the swing boom 51 and the end of the offset boom 61 are rotated, the head is temporarily stopped. Even if the hydraulic hose connected to the side or the bottom side is broken, the boom rotation preventing valve 20 fixes the hydraulic hose at its rotation position, thereby preventing unnecessary swing.

As is clear from the above description, according to the hydraulic excavator 1 provided with the suspension hook 20 according to the present invention, each of the cylinders 5, 7,. Since the anti-rotation valve 20 is directly attached to the desired holding pressure generating position of 9, 50, 60, the holding pressure on the cylinder head side or the bottom side, which is always generated by excavated earth and sand or a suspended load, is reliably maintained. And sufficient and effective earth and sand excavation, transportation work and crane work can be performed effectively, and work safety can be enhanced. It should be noted that the present invention is not limited to the above-described embodiments, but naturally includes a technical range that can be easily changed by those skilled in the art from those embodiments.

[Brief description of the drawings]

FIG. 1 is an overall view schematically showing an example of a hydraulic excavator having a suspension hook as a typical embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram of the hydraulic excavator.

FIG. 3 is an overall view schematically showing an operation mode of a working machine in the excavator.

FIG. 4 is another hydraulic circuit diagram applied to the working machine.

FIG. 5 is a partially enlarged view schematically showing a main part of a hydraulic excavator provided with a swing type boom.

FIG. 6 is a partially enlarged view schematically showing a main part of a hydraulic excavator provided with an offset boom.

FIG. 7 is an overall view schematically showing an example of a conventional hydraulic excavator provided with a hanging hook.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic excavator 2 Traveling body 3 Revolving structure 3a Cab 3b Monitor 3c Engine 4 Work implement 5 Boom cylinder 6 Boom 7 Arm cylinder 8 Arm 8a Arm top pin 8b Support shaft 9 Bucket cylinder 10 Link 10a, 10b First-second link 11 Bucket 11a Bucket school bag 11b Fixing pin 12 Hanging hook 12a Base 12b Hook section 13 Body 20 Anti-rotation valve 24 Variable displacement pump 24a Swash plate 25 Boom operating valve 25a-27a, 41a First pressure receiving section 25b-27b, 41b Second Pressure receiving part 26 Arm operating valve 27 Bucket operating valve 28 Boom operating part 29 Arm operating part 30 Bucket operating part 31, 46 Electromagnetic switching valve 31a, 46a Solenoid 32, 45 Pressure sensor 33 Output circuit 34 Drain circuit 35 Oil tank 36 Operating lever 37 , 3 The first and second pilot circuits 39 and 40 the first and second oil passage 41 switching valve 41c throttle 42 check valve 43 safety valve 44 passage 50 swing boom cylinder 51 swing boom 60 offset boom cylinder 61 offset boom

Continued on the front page F term (reference) 2D003 AA01 AB03 AB04 AC07 AC11 BA02 BA07 CA03 DA03 DA04 DB02 DB04 DB05 2D015 GA02 GB04 GB06 GB07 3F204 AA09 BA02 CA05 FA07 FB12 FC08 FD06

Claims (3)

[Claims] 1. A boom that rises and falls on a revolving structure, an arm that is connected to a tip of the boom and swings vertically, and a hydraulic shovel that is attached to the tip of the arm and that also has a bucket that swings vertically. Wherein each of the boom, arm and bucket is independently operated by an operation cylinder, and a holding pressure on a bottom side of the cylinder for the arm is maintained to prevent free fall of the arm. A hydraulic shovel comprising an arm rotation preventing means. 2. The hydraulic shovel according to claim 1, further comprising a bucket rotation preventing means at least on a bottom side of the bucket cylinder for maintaining a holding pressure on the bottom side and preventing free fall of the bucket. 3. The hydraulic excavator according to claim 1, wherein the suspension hook is rotatably supported between a pair of left and right bucket school bags projecting outward from a rear wall of the bucket.