JP2003056507A - Hydraulic circuit of work machine with telescopic arm - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the operating speed of an arm expandable cylinder and a bucket closing cylinder from slowing, because of the pressure loss of the oil path connected between a telescopic arm and a machine body and achieve proper pressure setting of a relief valve for preventing the expandable cylinder from buckling in a work machine the equipped with a telescopic arm. SOLUTION: The machine includes a bottom oil path connected between a bottom chamber of the arm expandable cylinder and the arm control valve of the machine body, and a opening/closing valve. The opening/closing valve which opens the tank oil path connected between the bottom chamber and a tank of the machine body, when the expandable cylinder is contracted is provided in the connecting part between the tank oil path and the bottom chamber in paralle to the bttom oil path.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for a working machine with a telescopic arm.

[0002]

2. Description of the Related Art A work machine with a telescopic arm equipped with a clamshell bucket at the end of the telescopic arm is used for digging vertical shafts in foundation excavation work, water and sewer work, manhole work, and the like. Explaining with reference to FIG. 5, the work machine with the telescopic arm includes a lower traveling body 1, an upper revolving body 2 mounted on the lower traveling body 1 so as to be horizontally rotatable, and an upper revolving body 2 in a vertical direction. A boom 3 swingably attached to
Telescopic arm 4 attached to the tip of boom 3
A clamshell bucket 5 attached to the lower end of the telescopic arm 4, a boom swing cylinder 3a interposed between the upper swing body 2 and the boom 3, and an arm interposed between the boom 3 and the telescopic arm 4. The rocking cylinder 4a is provided. The upper swing body 2 includes a driver's cab 2a.

The telescopic arm 4 is formed in a multi-stage box shape and is telescopically operated by an arm telescopic cylinder 10 which is a one-rod hydraulic cylinder arranged therein and a wire. The clamshell bucket 5 is a bucket opening / closing cylinder 2 in which a pair of buckets are double rod hydraulic cylinders.
8 is opened and closed, one end of the cylinder rod is rotatably attached to the telescopic arm 4 at the other end around the opening / closing center of the pair of buckets, and the cylinder body and the pair of buckets are connected by links. In the pit digging work, the arm telescopic cylinder 10 and the bucket opening / closing cylinder 28 are operated by a steering operation in the cab 2a,
The clamshell bucket 5 that has been opened is extended to the bottom of the vertical hole H by extending the telescopic arm 4, and the bottom of the hole is excavated while closing the bucket to store the earth and sand in the bucket. Pull it outside and discharge the soil in the bucket to a dump truck.

The hydraulic circuit of the working machine with the retractable arm described above will be described with reference to FIG. This hydraulic circuit supplies the arm telescopic cylinder 10 and the bucket opening / closing cylinder 28 provided on the telescopic arm side, and the discharge oil of the main pump 7 provided on the machine body side to the arm telescopic cylinder 10 and the bucket opening / closing cylinder 28, respectively. The arm control valve 9 and the bucket control valve 27, the arm operation pilot valve 15 and the bucket operation pilot valve 30 that operate these control valves by the oil discharged from the pilot pump 8, and connect the telescopic arm side and the machine body side. , Arm control valve 9 and arm telescopic cylinder 1
Bottom oil passage Y1 and rod chamber R
Rod oil passage Y2 between and bucket control valve 27
Oil passage S1 between the oil chamber O and the open side oil chamber O of the bucket opening / closing cylinder 28, and a cylinder oil passage S2 between the close side oil chamber C.
It has and. The main pump 7 and the pilot pump 8 are driven by the prime mover 6. The main pump 7 includes a variable displacement mechanism 7 a, and the maximum discharge pressure of the main pump 7 is defined by the main relief valve 12.

The hydraulic circuit further includes a drop prevention valve 11 for preventing the telescopic arm 4 from falling and a slow return valve 14 for limiting the extension speed of the arm telescopic cylinder 10 in the rod oil passage Y2 on the telescopic arm side. . The bottom oil passage Y1 on the telescopic arm side is provided with a buckling prevention relief valve 13 that limits the hydraulic pressure in the bottom chamber B to prevent the arm telescopic cylinder 10 from buckling. A relief oil passage D1 for flowing the released oil is provided between the relief valve 13 and the tank 40 on the machine body side.

[0006]

The hydraulic circuit of the conventional working machine with a telescopic arm having the above-mentioned configuration has the following problems to be solved.

(1) Delay in cylinder operating speed: Oil passages Y1, Y2, S1, S connecting the telescopic arm side and the machine body side
2, D1 has a large pressure loss in the oil passage because it is long due to the structure of the working machine. For example, the tank 4 from the telescopic arm side to the machine body side.
There is a problem that the pressure loss of the return oil to 0 becomes large and the contraction speed of the arm extension / contraction cylinder 10 and the opening / closing speed of the bucket opening / closing cylinder 28 become slow. Since this pressure loss also increases the discharge pressure of the main pump 7, as shown in FIG. 7, the flow rate decreases with the increase in pressure, which also slows the operating speed of the cylinder. Then, work efficiency is deteriorated, and problems such as heat generation of hydraulic oil and energy loss occur. Especially the arm extension cylinder 10
Requires a relatively large working stroke because of the telescopic arm 4 that deeply digs a vertical hole, so that a large amount of oil is required during operation, and the amount of oil supplied to the rod chamber during contraction is lower than that of the bottom chamber. The amount of returned oil is amplified, and the above-mentioned problems are likely to occur.

(2) Vacuum phenomenon in the bottom chamber of the telescopic cylinder: Since the relief oil passage D1 connecting the relief valve 13 for preventing buckling to the tank 40 is also long, the back pressure of the relief valve increases due to the pressure loss. Therefore, as shown in FIG. 8, a pressure loss in the relief oil passage D1 indicated by the characteristic line b occurs with respect to the relationship between the relief pressure and the flow rate of the single relief valve indicated by the characteristic line a. The relationship between the pressure and the relief flow rate is shown by the characteristic line c,
When the pressure for preventing buckling is set to a predetermined value at a predetermined flow rate, the pressure oil will escape from the relief valve 13 at a low pressure. Therefore, when pressure oil is supplied to the bottom oil passage Y1 and the arm telescopic cylinder 10 is extended, the relief valve 13 opens at a low pressure, and a part of the flow rate supplied from the main pump 7 is a bottom chamber B of the arm telescopic cylinder 10. And the arm telescopic cylinder 10 is pulled in the extension direction due to the weight of the clamshell bucket 5 and the like, so that a vacuum phenomenon occurs in the bottom chamber B, and the controllability of the arm telescopic cylinder 10 deteriorates. Furthermore, if this vacuum phenomenon occurs frequently, the arm telescopic cylinder 10
Deteriorate the seal, etc.

The present invention has been made in view of the above facts, and its technical problem is, in a working machine with a telescopic arm equipped with a telescopic arm, due to a pressure loss of an oil passage connecting the telescopic arm and the machine body. An object of the present invention is to provide a hydraulic circuit that solves the problem that the operating speed of the arm extension cylinder, the bucket opening / closing cylinder, etc. becomes slow. Another object of the present invention is to provide a hydraulic circuit capable of appropriately setting the pressure of the relief valve that prevents the arm telescopic cylinder from buckling and eliminating the vacuum phenomenon.

[0010]

According to a first aspect of the present invention, in a working machine with a telescopic arm equipped with a telescopic arm, a bottom chamber of an arm telescopic cylinder that extends and retracts the arm and an arm control valve of a main body of the work machine. A tank oil passage that connects the bottom chamber and the tank of the working machine main body is provided in parallel with the bottom oil passage that connects to the tank. The tank oil passage is opened at the connecting portion between the tank oil passage and the bottom chamber when the arm telescopic cylinder is contracted. It is a hydraulic circuit of a working machine with a telescopic arm characterized by comprising an on-off valve.

In addition to the bottom oil passage connecting the bottom chamber of the arm telescopic cylinder and the arm control valve, a tank oil passage connected in parallel to the tank is provided to reduce pressure loss by forming two oil passages.

According to a second aspect of the present invention, in the hydraulic circuit for a working machine with a telescopic arm according to the first aspect, a clamshell bucket is attached to a tip of the telescopic arm, and a pair of bucket opening / closing cylinders for opening and closing the bucket are provided. A switching valve is provided which branches each of the cylinder oil passages and connects the other oil passage to the tank oil passage when pressure oil is supplied to one of the oil passages.

Then, the return oil passage of the opening / closing cylinder of the clamshell bucket attached to the telescopic arm is connected to the tank oil passage to reduce the pressure loss by forming two oil passages.

According to a third aspect of the present invention, in a work machine equipped with a telescopic arm equipped with a telescopic arm, a bottom oil passage connecting a bottom chamber of an arm telescopic cylinder for telescopically extending the arm and an arm control valve of the working machine body. An additional bottom oil passage that connects the bottom chamber and the arm control valve is provided in parallel, and the opening and closing that opens to the tank of the work machine body when the arm expansion cylinder is contracted at the connection between the additional bottom oil passage and the arm control valve. It is a hydraulic circuit of a working machine with a telescopic arm, which is equipped with a valve.

In addition to the bottom oil passage connecting the bottom chamber of the arm telescopic cylinder and the arm control valve, an additional bottom oil passage is provided in parallel to reduce the pressure loss by forming two oil passages.

According to a fourth aspect of the present invention, in a hydraulic circuit for a working machine with a telescopic arm according to the third aspect, a clamshell bucket is attached to a tip of the telescopic arm, and a pair of bucket opening / closing cylinders for opening and closing the bucket are provided. A switching valve is provided which branches each of the cylinder oil passages and connects the other oil passage to the additional bottom oil passage when the pressure oil is supplied to one of the oil passages.

Then, the return oil passage of the opening / closing cylinder of the clamshell bucket attached to the telescopic arm is connected to the additional bottom oil passage to reduce the pressure loss by forming two oil passages.

According to a fifth aspect of the present invention, in the hydraulic circuit of the working machine with the telescopic arm according to any one of the first to fourth aspects, the buckling for releasing the bottom chamber of the arm telescopic cylinder at a predetermined pressure. An anti-relief valve for prevention of buckling is provided, and the set pressure of the anti-buckling relief valve is changed to a pressure higher than a predetermined buckling prevention pressure when the arm expanding / contracting cylinder is extended.

When the arm expanding / contracting cylinder is extended, the set pressure is increased to prevent pressure oil from escaping from the buckling prevention relief valve to prevent the vacuum phenomenon.

According to a sixth aspect of the invention, in the hydraulic circuit of the working machine with the telescopic arm according to any one of the first to fifth aspects, the arm is provided between the bottom chamber and the rod chamber of the arm telescopic cylinder. When extending the telescopic cylinder,
The regeneration chamber is provided with a regeneration valve that allows the rod chamber to communicate by allowing only the flow in the direction of the bottom chamber.

Then, during the extension operation of the arm expanding / contracting cylinder, the exhaust oil from the rod oil chamber is replenished to the bottom chamber side by the regeneration valve to prevent the vacuum phenomenon in the bottom chamber.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a hydraulic circuit of a working machine with a telescopic arm constructed according to the present invention will be described in more detail with reference to the accompanying drawings illustrating preferred embodiments.

The first embodiment will be described with reference to FIG. Note that, in FIG. 1, substantially the same parts as those in FIG. 6 are denoted by the same reference numerals.

This hydraulic circuit includes an arm telescopic cylinder 10 provided on the side of the telescopic arm and an oil telescopic cylinder 10 provided on the side of the machine body for discharging oil from the main pump 7.
Arm control valve 9 to be supplied to the arm control valve 9 and the arm control pilot valve 15 for operating the arm control valve 9 by the discharge oil of the pilot pump 8, and the arm telescopic cylinder 1.
Bottom oil passage Y1 connecting the bottom chamber B of 0 and the arm control valve 9, and a rod oil passage Y2 connecting the rod chamber R of the arm telescopic cylinder 10 and the arm control valve 9, and the bottom oil passage Y1 in parallel with the bottom oil passage Y1. And a tank oil passage T that connects the tank to the tank 40 on the machine body side. At the connecting portion between the tank oil passage T and the bottom chamber B, the arm telescopic cylinder 1
An on-off valve 18 that is opened when the contraction operation is 0 is provided.

On the telescopic arm side, a buckling prevention relief valve 20 for releasing the bottom chamber B of the arm telescopic cylinder 10 at a predetermined pressure, and between the bottom chamber B and the rod chamber R, the arm telescopic cylinder 10 is provided. Is provided with a regeneration valve 17 which allows the rod chamber R to communicate with each other while allowing only the flow in the direction of the bottom chamber B during the extension operation.

On the side of the telescopic arm, the rod oil passage Y2 is further provided.
In addition, the fall prevention valve 11 of the telescopic arm 4 and the slow return valve 14 that limits the extension speed of the arm telescopic cylinder 10
Is equipped with. Fall prevention valve 11 and slow return valve 1
Since No. 4 is a well-known one that has been conventionally used, the description thereof will be omitted unless necessary.

The open / close valve 18 includes a bottom chamber B and a tank oil passage T.
It is provided with a logic valve 18a which opens and closes the communication by the pilot circuit 18b. Pilot oil is supplied to and discharged from the pilot circuit 18b by an electromagnetic switching valve 19 which is switched by an extension operation signal of the arm telescopic cylinder 10. The electromagnetic switching valve 19 is an arm operation pilot valve 1 on the machine body side.
When the valve 15a on the extension side of No. 5 is operated, the pressure switch 25 provided in the pilot oil passage operates to operate the relay 2
It is located in the actuated position "A" by an electrical signal via 6 as an extension operation signal. The electromagnetic switching valve 19 connects the pilot circuit 18b to the bottom oil passage Y1 connected to the bottom chamber B in the non-actuated position "N", and the actuated position "A".
In the above, it is released to the tank 40 via the drain oil passage D2. In the non-operating position "N" where the pilot oil is not supplied to the pilot circuit 18b, the communication between the bottom chamber B and the tank oil passage T is closed, and when the pilot circuit 18b is supplied with the pressure oil from the cylinder oil passage Y1, the logic valve is closed. The spring chamber 18a is released to the drain oil passage D2 so that the bottom chamber B and the tank oil passage T communicate with each other.

The buckling prevention relief valve 20 has a bottom chamber B
Provided to the tank oil passage T at a predetermined pressure, a relief valve 20b for vent connected to the vent port of the relief valve body 20a, and provided between the vent port and the relief valve 20b for vent. Open / close valve 20c
It has and. The on-off valve 20c is switched by pilot oil, and its pilot port is connected between the orifices 23 and 24 of the oil passage connecting the rod oil passage Y2 of the arm extension / contraction cylinder 10 to the drain oil passage D2. The on-off valve 20c is positioned in the open state in the non-operating position "N" where the pilot pressure oil is not supplied. During the expansion / contraction operation of the arm expansion / contraction cylinder 10, the rod oil passage Y2
When pressure oil is introduced from the nozzle through the orifice 23 to reach a predetermined pressure, it is switched to the operating position "A" and the relief valve body 20
Close the vent port of a.

The set pressure of the relief valve body 20a is
When the open / close valve 20c is in the operating position "A" and the vent port is closed, the pressure is higher than a predetermined buckling prevention set pressure,
Moreover, when the pressure oil is set to a pressure that does not escape during the operation of the arm telescopic cylinder 10 and the opening / closing valve 20c is in the non-operating position "N" and the vent port is opened, the vent port of the relief valve body 20a is for venting. The pressure of the relief valve main body 20a connected to the relief valve 20b is set to the buckling prevention set pressure by the vent relief valve 20b.

The regeneration valve 17 is formed by a normally closed switching valve which is interposed between the rod oil passage Y2 and the head oil passage Y1 and which is opened by pilot oil. The head oil passage is provided on the rod oil passage Y2 side. Check valve 1 that allows only the flow to the Y1 side
7a is provided. Pilot oil is supplied and discharged by an electromagnetic switching valve 16 that is switched by an extension operation signal of the arm telescopic cylinder 10. The electromagnetic switching valve 16 releases the pilot circuit of the regeneration valve 17 to the tank 40 via the drain oil passage D2 at the non-operating position "N", and the bottom oil passage Y1 connected to the bottom chamber B at the operating position "A".
Connect to.

The electromagnetic switching valve 16 is provided with a pressure switch 25 provided in the pilot oil passage when the valve 15a on the extension side of the arm operation pilot valve 15 on the machine body side is operated.
Is activated and is positioned at the operating position “A” by an electric signal as an extension operation signal via the relay 26. Therefore, the regeneration valve 17 is in the non-operating position “N” of the electromagnetic switching valve 19.
Closed in and open in the operating position "A".

The operation of the first embodiment as described above will be described with reference to FIG.

(1) Contraction operation of the arm expansion / contraction cylinder: When the arm control valve 9 is switched to the chamber "B" by operating the valve 15b of the arm operation pilot valve 15, the discharge oil of the main pump 7 is discharged from the rod oil passage. It flows through Y2, and is led from the check valve 14a of the slow return valve 14 to the rod chamber R of the arm telescopic cylinder 10 through the check valve 11b of the fall prevention valve 11. On the other hand, since the pressure oil in the bottom chamber B is guided to the pilot circuit 18b of the opening / closing valve 18 via the electromagnetic switching valve 19 in the non-operating position "N", the spring chamber of the opening / closing valve 18 is released to the drain oil passage D2. Then, the opening / closing valve 18 is opened, and the oil discharged from the bottom chamber B of the arm telescopic cylinder 10 flows from the bottom oil passage Y1 to the arm control valve 9 and from the opening / closing valve 18 to the tank oil passage T. It flows through two systems of flow and returns to the tank 40 of the body of the machine.

Then, the pressure loss between the bottom chamber B and the tank 40 is reduced as compared with the case of only the conventional rod oil passage Y1. Further, since the pressure in the bottom chamber B when the arm extending / contracting cylinder 10 contracts decreases, the discharge pressure of the main pump 7 becomes lower than in the conventional case, and as a result, the pump flow rate increases due to the pump characteristic (FIG. 7). Therefore, the contraction speed of the arm telescopic cylinder 10 can be increased, and the work efficiency can be improved.

(2) Relief valve for preventing expansion and buckling of the arm expansion / contraction cylinder: The valve 15a of the arm operation pilot valve 15 is operated to move the arm control valve 9 to the chamber "A".
When switched to, the discharge oil of the main pump 7 is guided to the bottom chamber B of the arm telescopic cylinder 10 through the bottom oil passage Y1. The pilot circuit 18b of the on-off valve 18 is the relay 2
Since it is connected to the drain oil passage D2 via the electromagnetic switching valve 19 which is switched to the operating position "A" by the electric signal from 6, the on-off valve 18 is closed, and the bottom oil passage Y1.
And the communication between the tank oil passage T is cut off.

During the extension operation of the arm telescopic cylinder 10,
To the pilot circuit of the on-off valve 20c of the buckling prevention relief valve 20, the pressure oil of the rod oil passage Y2 connected to the rod chamber R of the arm telescopic cylinder 10 is introduced through the orifice 23, and the on-off valve 20c operates at the operating position ". Switch to "A". Then, since the vent port of the relief valve main body 20a is closed, the relief valve main body 20a becomes the set pressure of itself. This set pressure is higher than the buckling prevention set pressure, and is set to a pressure at which the pressure oil does not escape during the operation of the arm telescopic cylinder 10, so the pressure oil supplied to the bottom chamber B does not escape.

When the arm telescopic cylinder 10 extends and the clamshell bucket 5 (FIG. 5) at the tip of the arm 4 comes into contact with the ground, the operation of the arm telescopic cylinder 10 is stopped. Along with that, the pressure in the rod chamber R decreases, and the on-off valve 20c returns to the non-operating position "N" because the pressure in the pilot circuit decreases. As a result, the vent port of the relief valve body 20a is connected to the vent relief valve 20b, and the pressure of the relief valve body 20a is set by the vent relief valve 20c. Since the vent relief valve 20c sets the buckling prevention relief valve 20 to the buckling prevention set pressure, the set pressure of the buckling prevention relief valve 20 is automatically set to the buckling prevention when the clamshell bucket 5 is grounded. The pressure can be reduced and the boom telescopic cylinder 10 can be prevented from buckling.

(3) Arm expansion / contraction cylinder expansion operation, regeneration valve: When the arm expansion / contraction cylinder 10 expansion operation, the pressure switch 25 provided on the valve 15a of the arm operation pilot valve 15 is operated and the relay 26 is operated. The electromagnetic switching valve 16 is switched from the non-operating position “N” to the operating position “A”, and the pressure in the bottom chamber B of the boom telescopic cylinder 10 is supplied to the pilot circuits of the regeneration valve 17 and the fall prevention valve 11. Then, the regeneration valve 17 is switched to the operating position "A" by the pressure oil guided to the pilot circuit via the operating position "A" of the electromagnetic switching valve 16. On the other hand, the pressure oil in the rod chamber R of the arm telescopic cylinder 10 opens the poppet valve 11 a of the fall prevention valve 11 and opens the throttle valve 14 of the slow return valve 14.
It is guided to the regeneration valve 17 and the arm control valve 9 via b and the rod oil passage Y2. Since the regeneration valve 17 is switched to the operating position "A", most of the pressure oil discharged from the rod chamber R of the arm telescopic cylinder 10 is regenerated from the regeneration valve 17 to the bottom chamber B side, and the rest is from the arm control valve 9. Return to tank 40. At this time, the electromagnetic switching valve 19
Is switched to the operating position "A" by an electric signal from the relay 26, and the on-off valve 18 is in the closed state with the pilot circuit 18b in the non-operating position "N". Therefore, the bottom chamber B of the arm telescopic cylinder 10 is supplied with a sufficient flow rate, which is the discharge flow rate of the main pump 7 plus the flow rate regenerated from the rod chamber R.

Thus, when the arm telescopic cylinder 10 is extended, the escape of pressure oil from the conventional buckling prevention relief valve is prevented, and the flow rate of the main pump 7 and the flow rate regenerated from the regeneration valve 17 are reduced. All arm telescopic cylinder 1
Since it is supplied to 0, a sufficient flow rate is supplied to the bottom chamber B even when the arm telescopic cylinder 10 is extended at high speed. Then, the vacuum phenomenon is less likely to occur, the operation controllability is improved, the deterioration of the seal and the like is prevented, and the extension speed of the telescopic arm 4 can be increased as compared with the conventional case.

The second embodiment will be described with reference to FIG. In FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted unless necessary.

This hydraulic circuit is different from the above-described first embodiment (FIG. 1) in that it further includes a bucket opening / closing cylinder 28 of the clamshell bucket 5 on the telescopic arm side and a bucket opening / closing cylinder 28 on the machine body side. Bucket control valve 27 for supplying the discharge oil of the main pump 7 to 28
And the bucket control valve 27 to the pilot pump 8
Bucket operation pilot valve 30 operated by the discharge oil of
And a cylinder oil passage S1 between the bucket control valve 27 and the opening side oil chamber O of the bucket opening / closing cylinder 28, and a cylinder oil passage S2 between the closing side oil chamber C. Further, a switching valve 29 is provided that branches each of the cylinder oil passages S1 and S2 and connects the other oil passage to the tank oil passage T when the pressure oil is supplied to one of the oil passages.

The switching valve 29 is a three-position valve that is held in a neutral position that normally closes the communication between the cylinder oil passages S1 and S2 and the tank oil passage T, and pressure oil is supplied to the cylinder oil passage S1. To the operating position “A” to connect the cylinder oil passage S2 to the tank oil passage T, and when pressure oil is supplied to the cylinder oil passage S2, the cylinder oil passage S1 is switched to the operating position “B” to change the cylinder oil passage S1 to the tank oil passage. Connect to T.

The operation of the second embodiment as described above will be described. The operations of the arm expansion cylinder, the buckling prevention relief valve, the regeneration valve, and the like described in the first embodiment will be omitted except when necessary to avoid duplication.

(1) Single operation of bucket opening / closing cylinder:
By operating the valve 30a of the bucket operation pilot valve 30,
When the bucket control valve 27 is switched to the chamber "A",
The oil discharged from the main pump 7 passes through the cylinder oil passage S2,
It is guided to the chamber C of the bucket opening / closing cylinder 28. At this time, the switching valve 29 is switched to the operating position "B" by introducing this pressure oil to its pilot circuit, and the branched oil passage of the cylinder oil passage S1 connected to the chamber O communicates with the tank oil passage T. Conversely, when the valve 30b of the bucket operation pilot valve 30 is operated to switch the bucket control valve 27 to the chamber "B", the discharge oil of the main pump 7 passes through the cylinder oil passage S1 and the chamber O of the bucket opening / closing cylinder 28. Be led to. At this time, the switching valve 29 is switched to the operating position "A" by introducing this pressure oil into its pilot circuit, and the branched oil passage of the cylinder oil passage S2 connected to the chamber C communicates with the tank oil passage T. Thus, the oil discharged from the bucket opening / closing cylinder 28 flows through two systems, that is, the flow from the cylinder oil passage S1 or S2 to the bucket control valve 27, and the flow from the switching valve 29 to the tank oil passage T. Return to 40.

Therefore, as compared with the conventional case, the tank 40
Since the pressure loss of the return oil is reduced, the discharge pressure of the main pump 7 becomes lower than the conventional one, and the discharge flow rate increases.
The operating speed of the bucket opening / closing cylinder 28 can be increased.

(2) Interlocking operation of the arm telescopic cylinder and bucket opening / closing cylinder: When the extension operation of the arm telescopic cylinder 10 and the operation of the bucket opening / closing cylinder 28 are interlocked,
Since there is no oil flow from the arm telescopic cylinder 10 in the tank oil passage T connected to the switching valve 29, the return oil of the bucket opening / closing cylinder 28 is transferred to the tank oil passage T via the switching valve 29 and transferred to the bucket opening / closing cylinder 10. The flow is the same as in the single operation of 28. Therefore, the return oil of the bucket opening / closing cylinder 28 returns to the tank 40 from both the switching valve 29 and the bucket control valve 27, so that the arm expanding / contracting cylinder 10
When the bucket opening / closing cylinder 28 is interlocked with the extending operation of the bucket opening / closing operation, the same opening / closing speed as that of the bucket opening / closing cylinder 28 alone operation can be obtained.

On the other hand, when the contraction operation of the arm expanding / contracting cylinder 10 and the operation of the bucket opening / closing cylinder 28 are interlocked with each other, the return oil from the bottom chamber B of the arm expanding / contracting cylinder 10 is divided into two systems of a bottom oil passage Y1 and a tank oil passage T. Since it flows through the oil passage, the pressure loss during this period is reduced as compared with the conventional single oil passage. Further, since a part of the return oil of the bucket opening / closing cylinder 28 flows into the tank oil passage T via the switching valve 29, the speed of the bucket opening / closing cylinder 28 can be made higher than that in the case of interlocking operation in the conventional technique. .

By the above operation, the arm telescopic cylinder 1
Even in the interlocking operation of 0 and the bucket opening / closing cylinder 28,
Since the speed of the arm telescopic cylinder 10 can be increased and the bucket opening / closing speed can be increased, the work cycle time can be shortened and the work efficiency can be improved.

The third embodiment will be described with reference to FIG. In FIG. 3, the same parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted except when necessary.

This hydraulic circuit corresponds to the bottom chamber B of the arm telescopic cylinder 10 in the above-described first embodiment (FIG. 1).
In place of the tank oil passage T connecting the tank 40 with the tank 40 and the opening / closing valve 18 at the connecting portion between the bottom chamber B and the tank oil passage T, a bottom oil passage Y1 connecting the bottom chamber B and the arm control valve 9 is provided.
An additional bottom oil passage Y3 connecting the bottom chamber B and the arm control valve 9 is provided in parallel with the above, and a connection portion between the additional bottom oil passage Y3 and the arm control valve 9 is provided with a work for contracting the arm telescopic cylinder 10. An on-off valve 31 that opens to a tank 40 of the machine body is provided. A buckling prevention relief valve 20 that releases the bottom chamber B of the arm telescopic cylinder 10 at a predetermined pressure is provided on the working machine body side.

The on-off valve 31 is provided with a logic valve 31a for opening and closing the communication between the additional bottom oil passage Y3 and the tank 40 by the pilot circuit 31b. The pilot circuit 31b is supplied with pilot oil from the valve 15b of the arm operation pilot valve 15 when the arm extension cylinder 10 is contracted. The logic valve 31a has its pilot circuit 31
At the non-acting position "N" where the pilot oil is not supplied to b, the communication between the additional bottom oil passage Y3 connected to the bottom chamber B of the arm telescopic cylinder 10 and the tank 40 is closed, and the pilot oil is supplied to the pilot circuit 31b. Then, the spring chamber of the logic valve 31a is released to the drain oil passage D2, and the additional bottom oil passage Y3 communicates with the tank 40. When the valve 15a on the extension side of the arm operation pilot valve 15 is operated, pilot oil is not supplied to the opening / closing valve 31,
The spring chamber of the logic valve 31a is not released to the drain, and the communication between the additional bottom oil passage Y3 and the tank 40 is closed.

The structure of the buckling prevention relief valve 20 is as described above, but the relief valve main body 20a has the bottom oil passage Y1.
To the tank 40 at a predetermined pressure. Further, the vent port of the relief valve body 20a and the vent relief valve 20
The method of supplying pilot oil to the on-off valve 20c provided between b is different. That is, in the third embodiment, the pilot pressure oil supplied to the on-off valve 20c is supplied from between the orifices 23 and 24 provided in the oil passage that branches the rod oil passage Y2 and connects to the drain oil passage D2. Be guided.

The operation of the third embodiment as described above will be described.

(1) Contraction operation of the arm expansion / contraction cylinder: When the arm control valve 9 is switched to the chamber "B" by operating the valve 15b of the arm operation pilot valve 15, the main pump 7 discharges oil from the rod oil passage. It flows through Y2, and is led from the check valve 14a of the slow return valve 14 to the rod chamber R of the arm telescopic cylinder 10 through the check valve 11b of the fall prevention valve 11. On the other hand, since the pilot oil of the valve 15b is branched and guided to the pilot circuit 31b of the on-off valve 31, the spring chamber of the on-off valve 31 is released to the drain oil passage D2, the on-off valve 31 is opened, and the arm expands and contracts. The return oil discharged from the bottom chamber B of the cylinder 10 flows through two systems, that is, a flow that flows from the bottom oil passage Y1 to the arm control valve 9 and a flow that flows through the additional bottom oil passage Y3 to the opening / closing valve 31. Return to tank 40.

Then, the pressure loss between the bottom chamber B and the tank 40 is reduced as compared with the case of only the conventional rod oil passage Y1. Further, since the pressure in the bottom chamber B when the arm telescopic cylinder 10 is contracted is reduced, the discharge pressure of the main pump 7 is lower than in the conventional case, and as a result, the pump flow rate is increased due to the pump characteristic (FIG. 7). Therefore, the contraction speed of the arm telescopic cylinder 10 becomes faster.

(2) Extension operation of the arm telescopic cylinder, regeneration valve: When the valve 15a of the arm operation pilot valve 15 is operated to switch the arm control valve 9 to the chamber "A",
Since the on-off valve 31 is in the closed state, the discharge oil of the main pump 7 is guided to the bottom chamber B of the arm telescopic cylinder 10 through two oil passages, the bottom oil passage Y1 and the additional bottom oil passage Y3. Further, the pressure switch 25 provided on the valve 15a operates, the electromagnetic switching valve 16 is switched from the non-operating position "N" to the operating position "A" via the relay 26, and the regeneration valve 17 and the fall prevention valve 11 The pressure in the bottom chamber B of the boom telescopic cylinder 10 is supplied to the pilot circuit of. The pressure oil in the rod chamber R of the arm extension / contraction cylinder 10 is introduced to the regeneration valve 17 and the arm control valve 9 via the throttle valve 14b of the slow return valve 14 and the rod oil passage Y2 by opening the poppet valve 11a of the fall prevention valve 11. Get burned. The regeneration valve 17
Since it is switched to the operating position “A” by the pressure oil guided to the pilot circuit via the electromagnetic switching valve 16, most of the pressure oil discharged from the rod chamber R of the arm telescopic cylinder 10 is discharged from the regeneration valve 17 to the bottom chamber B. Side, and the rest returns from the arm control valve 9 to the tank 40. Therefore,
The flow rate regenerated from the rod chamber R is added to the discharge flow rate of the main pump 7, and a sufficient flow rate is supplied to the bottom chamber B of the arm telescopic cylinder 10.

(3) Relief valve for extending and retracting the arm expanding / contracting cylinder: During the extending operation of the arm expanding / contracting cylinder 10, the orifice 23 is provided in the pilot circuit of the opening / closing valve 20c of the buckling preventing relief valve 20. The pressure oil in the rod oil passage Y2 connected to the rod chamber R of the arm extension / contraction cylinder 10 is guided through the opening / closing valve 20c to the operating position "A". Then, the vent port of the relief valve main body 20a is closed, and the relief valve main body 20a becomes the set pressure of itself. This set pressure is higher than the buckling prevention set pressure,
Moreover, since the pressure oil is set to a pressure at which the pressure oil does not escape during the operation of the arm extension cylinder 10, the supplied pressure oil does not escape.

Therefore, since the pressure oil does not escape from the buckling prevention relief valve 20 during the extension operation of the arm expanding / contracting cylinder 10, the supply flow rate of the main pump 7 and the flow rate regenerated from the regenerating valve 17 are all. , And the pressure oil supply oil passage from the arm control valve 9 to the arm telescopic cylinder 10 is a bottom oil passage Y1 and an additional bottom oil passage Y3. The discharge flow rate of the main pump 7 increases as compared with the embodiment. As a result, a sufficient flow rate can be supplied to the bottom chamber B even when the arm telescopic cylinder 10 is extended at a high speed, so that the vacuum phenomenon is less likely to occur and the extension speed of the telescopic arm 4 can be further increased as compared with the first embodiment. it can.

When the arm telescopic cylinder 10 extends and the clamshell bucket 5 attached to the tip of the arm 4 comes into contact with the ground, the operation of the arm telescopic cylinder 10 is stopped. Along with that, the pressure in the rod chamber R decreases, and the on-off valve 20c returns to the non-operating position "N" because the pressure in the pilot circuit decreases. As a result, the vent port of the relief valve body 20a is connected to the vent relief valve 20b, and the pressure of the relief valve body 20a is set by the vent relief valve 20c. Since the vent relief valve 20c sets the buckling prevention relief valve 20 to the buckling prevention set pressure, the set pressure of the buckling prevention relief valve 20 is automatically set to the buckling prevention when the clamshell bucket 5 is grounded. The pressure can be reduced and the boom telescopic cylinder 10 can be prevented from buckling.

With the above operation, the extension speed of the telescopic arm 4 can be made faster than in the first embodiment, so that the working efficiency can be further improved. Further, in the present embodiment, since the on-off valve 31 and the buckling prevention relief valve 20 are provided on the machine body side, the piping on the telescopic arm side can be simplified and the telescopic arm of the telescopic arm can be simplified as compared with the first embodiment. The weight can be reduced.

A fourth embodiment will be described with reference to FIG. In FIG. 4, the same parts as those in FIGS. 2 and 3 are designated by the same reference numerals, and the description thereof will be omitted unless necessary.

This hydraulic circuit is different from the above third embodiment (FIG. 3) in that the bucket of the clamshell bucket 5 is further used on the telescopic arm side used in the second embodiment (FIG. 2). A bucket control valve 27 that is provided with an opening / closing cylinder 28 and that supplies the discharge oil of the main pump 7 to the bucket opening / closing cylinder 28, and a bucket operation pilot valve that operates the bucket control valve 27 with the discharge oil of the pilot pump 8. 30, a cylinder oil passage S1 between the bucket control valve 27 and the open side oil chamber O of the bucket opening / closing cylinder 28, and a close side oil chamber C.
And a cylinder oil passage S2 between and. Further, a switching valve 29 is provided which branches each of the cylinder oil passages S1 and S2 and connects the other oil passage to the additional bottom oil passage Y3 when the pressure oil is supplied to one of the oil passages.

Further, in this embodiment, a connecting portion between the additional bottom oil passage Y3 and the arm control valve 9 serves as an opening / closing valve which opens to the tank 40 of the working machine body when the arm expanding / contracting cylinder 10 is contracted. , An on-off valve 32 in place of the on-off valve 31 in the third embodiment (FIG. 3)
Is equipped with.

The on-off valve 32 includes a logic valve 32a and a pilot circuit 32b, and is the same as the on-off valve 31 except for the pilot circuit 32b. The pilot circuit 32b is supplied with pilot oil from the valve 15a of the arm operation pilot valve 15 when the arm extension cylinder 10 is extended. The logic valve 32a is connected to the pilot circuit 32b.
In the operating position "A" where the pilot oil is supplied to the tank, that is, during the extension operation of the arm telescopic cylinder 10, the communication between the additional bottom oil passage Y3 and the tank 40 is closed, and the non-operating position "N" where the pilot oil is not supplied is supplied. In other words, when the arm telescopic cylinder 10 is not extended, for example, when the arm telescopic cylinder 10 is contracted, the spring chamber is released to the drain oil passage D2 and the additional bottom oil passage Y3 connected to the bottom chamber B of the arm telescopic cylinder 10 communicates with the tank 40. To do.

The operation of the fourth embodiment as described above will be described. The operations of the arm expansion cylinder, the buckling prevention relief valve, the regeneration valve, and the like described in the third embodiment will be omitted except when necessary to avoid duplication.

(1) Single operation of bucket opening / closing cylinder:
By operating the valve 30a of the bucket operation pilot valve 30,
When the bucket control valve 27 is switched to the chamber "A",
The oil discharged from the main pump 7 is introduced into the chamber C of the bucket opening / closing cylinder 28 via the cylinder oil passage S2. At this time, the switching valve 29 is switched to the operating position "B" by introducing this pressure oil to its pilot circuit, and the oil passage branched from the cylinder oil passage S1 connected to the chamber O communicates with the additional bottom oil passage Y3. Conversely, when the valve 30b of the bucket operation pilot valve 30 is operated to switch the bucket control valve 27 to the chamber "B", the oil discharged from the main pump 7 is the cylinder oil passage S1.
And is guided to the chamber O of the bucket opening / closing cylinder 28.
At this time, the switching valve 29 is switched to the operating position “A” by introducing this pressure oil to its pilot circuit, and the oil passage branched from the cylinder oil passage S2 connected to the chamber C is the additional bottom oil passage Y3.
Communicate with. Thus, the oil discharged from the bucket opening / closing cylinder 28 flows from the cylinder oil passage S1 or S2 to the bucket control valve 27 and the switching valve 29.
To the additional bottom oil passage Y3 and then return to the tank 40 of the machine body.

Therefore, as compared with the conventional case, the tank 40
Since the pressure loss of the return oil to the main pump 7 decreases, the discharge pressure of the main pump 7 becomes lower than in the conventional case, and the pump flow rate increases, so that the operating speed of the bucket opening / closing cylinder 28 can be increased.

(2) Interlocking operation of arm telescopic cylinder and bucket opening / closing cylinder: When the extension operation of the arm telescopic cylinder 10 and the operation of the bucket opening / closing cylinder 28 are interlocked,
The pressure oil supply oil passage of the arm telescopic cylinder 10 is the bottom oil passage Y.
Since there are two systems, the first and the additional bottom oil passage Y3, the pressure loss during this period is lower than that in the first embodiment (FIG. 1). Further, since the return oil of the bucket opening / closing cylinder 28 is supplied to the additional bottom oil passage Y3 connected to the bottom chamber B of the arm expanding / contracting cylinder 10 via the switching valve 29, the extension operation of the arm expanding / contracting cylinder 10 and the operation of the bucket opening / closing cylinder 28 are performed. In the case of interlocking, a large amount of oil is supplied to the bottom chamber B of the arm expanding / contracting cylinder 10, a further flow rate can be supplied to the arm expanding / contracting cylinder 10 at the time of interlocking, and the vacuum phenomenon is less likely to occur.

When the contraction operation of the arm expanding / contracting cylinder 10 and the operation of the bucket opening / closing cylinder 28 are interlocked with each other, the return oil from the bottom chamber B of the arm expanding / contracting cylinder 10 becomes the two systems of the bottom oil passage Y1 and the additional bottom oil passage Y3. Therefore, the pressure loss during this period is reduced. Therefore, a part of the return oil of the bucket opening / closing cylinder 28 flows to the additional bottom oil passage Y3 connected to the bottom chamber B of the arm extension / contraction cylinder 10 via the switching valve 29. It can be faster than the operation.

Further, in this embodiment, since the opening / closing valve 32 is open to the tank 40 except when the arm expanding / contracting cylinder 10 is extended, an oil passage connecting the additional bottom oil passage Y3 to the tank 40 is secured. Embodiment 3
The opening / closing speed of the bucket is further improved as compared with (FIG. 3).

With the above operation, the arm telescopic cylinder 1
Since the speed of the arm telescopic cylinder 10 can be secured and the bucket opening / closing speed can be increased even in the interlocking operation of 0 and the bucket opening / closing cylinder 28, the work cycle time can be shortened and the work efficiency can be improved.

Although the present invention has been described in detail above based on the embodiments, the present invention is not limited to the above embodiments, and various modifications are possible within the scope of the present invention, for example, as described below. It can be transformed or modified.

(1) Clamshell bucket: In the present embodiment, the clamshell bucket 5 is attached to the tip of the telescopic arm 4, but the telescopic arm is limited to the clamshell bucket 5. Not a thing.

(2) Open / close valve: In the present embodiment,
As the opening / closing valve 18 provided at the connection between the bottom chamber B of the arm extension / contraction cylinder 10 and the tank oil passage T, the electromagnetic switching valve 1 is used.
It has a logic valve 18a which is opened and closed by 9
If there is no problem with the capacity and pressure loss of the on-off valve, it may be an electromagnetic on-off valve that can be directly switched by an electric signal. Similarly, the on-off valve 31 at the connecting portion between the additional bottom oil passage and the tank may be a pilot-operated on-off valve that can be directly switched by pilot oil.

(3) Regeneration valve: In the present embodiment, the regeneration valve 17 is a hydraulic pilot operated switching valve which is switched by the pilot oil of the electromagnetic switching valve 16, but the capacity of the regeneration valve is If there is no problem with pressure loss or the like, this may be an electromagnetic opening / closing valve that can be directly switched by an electric signal.

[0076]

According to the hydraulic circuit of the working machine with the telescopic arm constructed according to the present invention, in the working machine with the telescopic arm equipped with the telescopic arm, the pressure loss of the oil passage connecting the telescopic arm and the machine body is reduced. There is provided a hydraulic circuit that solves the problem that the operation speed of the arm extension cylinder, the bucket opening / closing cylinder, etc. becomes slow. Further, there is provided a hydraulic circuit capable of appropriately setting the pressure of the relief valve that prevents the arm telescopic cylinder from buckling and eliminating the vacuum phenomenon.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a hydraulic circuit of a work machine with a telescopic arm constructed according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of a hydraulic circuit of a working machine with a telescopic arm configured according to the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of a hydraulic circuit of a working machine with a telescopic arm configured according to the present invention.

FIG. 4 is a circuit diagram showing a fourth embodiment of a hydraulic circuit of a work machine with a telescopic arm constructed according to the present invention.

FIG. 5 is a side view of a work machine with a telescopic arm.

FIG. 6 is a conventional hydraulic circuit diagram of a work machine with a telescopic arm.

FIG. 7 is a characteristic diagram showing the relationship between the discharge pressure of the main pump and the flow rate.

FIG. 8 is a characteristic diagram of a conventional buckling prevention relief valve.

[Explanation of symbols]

4: Telescopic arm 5: Clamshell bucket 9: Arm control valve 10: Arm telescopic cylinder 11: Fall prevention valve 13: Buckling prevention relief valve 14: Slow return valve 15: Arm operation pilot valve 17: Regeneration valve 18: Open / close valve 20: Buckling prevention relief valve 27: Bucket control valve 28: Bucket open / close cylinder 29: Switching valve 30: Bucket operation pilot valve 31: Open / close valve 32: Open / close valve 40: Tank B: Bottom room D1: Relief oil passage D2: Drain oil passage R: Rod room S1: Cylinder oil passage S2: Cylinder oil passage T: Tank oil passage Y1: Bottom oil passage Y2: Rod oil passage Y3: Additional bottom oil passage

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nobuaki Matoba             2-5-3 Marunouchi, Chiyoda-ku, Tokyo             Hishi Heavy Industries Ltd. (72) Inventor Shinya Nozaki             7-14 Wadamiyadori, Hyogo-ku, Kobe-shi, Hyogo             Issue Nishiryo Engineering Co., Ltd. F-term (reference) 2D003 AA01 AB03 AB05 BA01 BA02                       BB03 CA02 DA03 DA04                 3H089 AA25 BB02 BB11 BB14 CC01                       DA03 DB03 DB47 DB49 DB68                       EE17 EE22 GG02 JJ01

Claims (6)

[Claims] 1. In a working machine with a telescopic arm equipped with a telescopic arm, the bottom chamber is provided in parallel with a bottom oil passage that connects a bottom chamber of an arm telescopic cylinder that extends and retracts the arm and an arm control valve of a working machine body. A telescopic arm comprising a tank oil passage connecting the tank of the working machine main body, and an opening / closing valve opening at the connecting portion between the tank oil passage and the bottom chamber when the arm telescopic cylinder is contracted. Hydraulic circuit of the working machine. 2. A clamshell bucket is attached to the end of the telescopic arm, each of a pair of cylinder oil passages of a bucket opening / closing cylinder that opens and closes the bucket is branched, and pressure oil is supplied to one of the oil passages. The hydraulic circuit for a working machine with a telescopic arm according to claim 1, further comprising a switching valve that allows the other oil passage to communicate with the tank oil passage. 3. A work machine equipped with a telescopic arm equipped with a telescopic arm, wherein the bottom chamber and the arm are provided in parallel with a bottom oil passage that connects the bottom chamber of the arm telescopic cylinder that extends and contracts the arm and the arm control valve of the working machine body. An additional bottom oil passage connecting the control valve is provided, and an opening / closing valve that opens to the tank of the working machine body is provided at the connection between the additional bottom oil passage and the arm control valve when the arm telescopic cylinder is contracted. Hydraulic circuit for work machines with telescopic arms. 4. A clamshell bucket is attached to the end of the telescopic arm, each of a pair of cylinder oil passages of a bucket opening / closing cylinder that opens and closes the bucket is branched, and pressure oil is supplied to one of the oil passages. The hydraulic circuit for a working machine with a telescopic arm according to claim 3, further comprising a switching valve that allows the other oil passage to communicate with the additional bottom oil passage. 5. A buckling prevention relief valve for releasing the bottom chamber of the arm telescopic cylinder at a predetermined pressure, wherein the set pressure of the buckling prevention relief valve is a predetermined buckling when the arm telescopic cylinder is extended. The hydraulic circuit for a working machine with a telescopic arm according to any one of claims 1 to 4, wherein the hydraulic pressure is changed to a pressure higher than the prevention pressure. 6. An extension operation of the arm telescopic cylinder between the bottom chamber of the arm telescopic cylinder and the rod chamber,
The hydraulic circuit for a working machine with a telescopic arm according to any one of claims 1 to 5, further comprising a regeneration valve that allows the rod chamber to communicate by allowing only the flow in the direction of the bottom chamber.