JP2001040713A - Construction machine with crane function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve workability and operability by controlling the cylinder operating speed of at least part of hydraulic cylinders via pressure oil discharge quantity control, and providing a discharge quantity adjustment section on a pressure oil discharge path. SOLUTION: Discharge quantities of first and second main pumps 9, 10 are reduced by selecting the crane work mode with a work mode selector switch 37, thereby the pressure oil feed quantities to hydraulic actuators 14-18 are reduced. When a boom and an arm are operated to the descent side while the crane work mode is selected, the pilot pressures fed to boom and arm control valves 21, 22 and boom and arm descent preventing valves 40, 47 are reduced by third solenoid proportional pressure reducing valves 41, 48, thereby the discharging speed of the oil discharged into an oil tank 12 from a boom cylinder 16 and an arm cylinder 17 via the valves 21, 22, 40, 47 is slowed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a construction machine with a crane function used for various construction work and civil engineering work.

[0002]

2. Description of the Related Art In general, in a construction machine, a front attachment composed of a boom, an arm, a bucket, and the like is mounted on an upper revolving structure that is rotatably supported by a lower traveling structure, such as a hydraulic shovel. In addition, a hook for suspending a suspended load is attached to the bucket, and a crane operation using the hook is performed in addition to a normal operation such as digging and loading by the bucket. 2. Description of the Related Art A hydraulic excavator with a crane function configured so as to be able to carry out an operation is known. In this case, when the operating speed for the operating tool operation amount of each actuator such as a turning motor, a boom cylinder, and an arm cylinder is set to be suitable for performing a normal operation such as excavation and loading,
When a crane operation is performed, there is a problem that the operation is too fast and a stable operation cannot be performed, or the operability is poor. Therefore, when performing a crane operation, it is proposed to reduce the discharge amount of the hydraulic pump that supplies the pressure oil to each of the actuators, thereby reducing the operation speed.

[0003]

Since the boom and the arm are loaded on the descending side by the weight of the front attachment and the weight of the luggage, the boom cylinder and the arm cylinder are moved when the boom and the arm are lowered. The operating speed is controlled by meter-out control by the boom control valve and the arm control valve, that is, the flow rate of pressurized oil discharged from the boom cylinder and the arm cylinder to the oil tank. For this reason, the operation speed cannot be reduced too much when the boom and the arm are lowered only by the control of reducing the discharge amount of the hydraulic pump to reduce the supply amount of the pressurized oil to the boom cylinder and the arm cylinder. However, there is a problem to be solved by the present invention.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has been created for the purpose of solving these problems, and includes a crane operation and a normal operation other than the crane operation. In the construction machine with a crane function configured so that both operations can be performed based on the expansion and contraction operation of the hydraulic cylinder, at least a part of the hydraulic cylinder is operated at a cylinder operating speed by controlling hydraulic oil discharge from the hydraulic cylinder. The hydraulic cylinder is configured to perform control, and further provided in the hydraulic oil discharge path of the hydraulic cylinder is a discharge amount adjusting means that operates to reduce the amount of pressurized oil discharged. By doing so, the cylinder operating speed of the hydraulic cylinder, which controls the cylinder operating speed by controlling the amount of hydraulic oil discharged from the hydraulic cylinder, can be reduced, thereby improving workability and operability during crane work. Is improved. Further, the construction machine with the crane function is provided with a work mode selection means for selectively setting the crane work mode and the normal work mode, while the discharge amount adjusting means is configured to control the hydraulic oil discharge amount of the hydraulic cylinder when the crane work mode is set. , The discharge amount adjusting means can be operated based on the setting of the work mode selecting means. In this device, the discharge of oil from the hydraulic cylinder is prevented in the pressure oil discharge path of the hydraulic cylinder whose hydraulic oil discharge amount is controlled, when the operation tool operation for the hydraulic cylinder is not performed, and based on the operation of the operation tool, In the meantime, while providing a drip-prevention valve that allows the discharge of oil, the discharge amount adjusting means adjusts the discharge amount of the pressurized oil from the drip-prevention valve. It can be carried out. In this case, the discharge amount adjusting means can be configured using a pressure reducing valve provided in the pilot oil passage for switching the descent prevention valve to the pressure oil discharge allowable state.
Further, the discharge amount adjusting means adjusts the discharge amount of the hydraulic oil from the control valve which operates to control the supply and discharge of the hydraulic oil of the hydraulic cylinder, thereby controlling the discharge amount using the control valve. Can be. In this case, the discharge amount adjusting means can be configured using a pressure reducing valve provided in a pilot oil passage for switching the control valve to a pressure oil discharging state. The present invention can be applied to a construction machine with a crane function, such as a hydraulic shovel, including, for example, a boom swingably supported by an airframe and an arm swingably supported at a tip end of the boom. In this case, the discharge amount adjusting means is provided in at least one of a pressure oil discharge circuit on the reduction side of the boom cylinder for rocking the boom and a pressure oil discharge circuit on the extension side of the arm cylinder for rocking the arm. With this arrangement, the operating speed of the boom cylinder contraction and the arm cylinder extension during the crane operation can be reduced.

[0005]

Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a hydraulic shovel having a crane function.
It comprises a crawler-type lower traveling body 2, an upper revolving body 3 rotatably supported by the lower traveling body 2, a front attachment 4 mounted on the upper revolving body 3, and the like. Reference numeral 4 denotes a boom 5 whose base end is vertically swingably supported by the upper swing body 3, an arm 6 which is supported by the front end of the boom 5 so as to be able to swing back and forth,
The basic structure is the same as that of the conventional structure, such as being composed of various members such as a bucket 7 supported at the tip end of the arm 6 so as to be able to swing back and forth. A hook 8 for lowering is attached, so that a crane operation using the hook 8 can be performed in addition to a normal operation such as excavation and loading by the bucket 7.

FIG. 2 shows a schematic hydraulic circuit of the hydraulic shovel 1. In FIG. 2, reference numerals 9 and 10 denote first and second main pumps driven by an engine, 11 a pilot pump, 12 an oil tank, 13 is a control valve unit, 14 is a turning motor for turning the upper turning body 2, 15L and 15R are left and right running motors, 16 is a boom cylinder for rocking the boom 5, and 17 is a rocking arm. An arm cylinder 18 for moving the bucket 7 is a bucket cylinder for swinging the bucket 7. Further, 9a and 10a are the first and second main pumps 9,
This is a flow rate control device for controlling each of the ten discharge amounts.

The control valve unit 13 includes a turning motor 14, left and right traveling motors 15L,
5R, for turning, for left and right traveling, for controlling the supply and discharge of hydraulic oil to each hydraulic actuator of the boom cylinder 16, the arm cylinder 17, and the bucket cylinder 18, respectively.
Each control valve 19 for boom, arm, and bucket,
20L, 20R, 21, 22, and 23 are incorporated. Each of these control valves 19 to 23 is a pilot-operated three-position switching valve, and a neutral position N in which hydraulic oil is not supplied to the hydraulic actuators 14 to 18 in a state where pilot pressure is not supplied from the corresponding pilot valve.
However, when the pilot pressure is supplied from each pilot valve based on the operation of the operating tool, the pressure is switched to the pressure oil supply position X or Y for supplying the pressure oil to the hydraulic actuators 14 to 18, respectively. (In FIG. 2, the oil passage for pilot pressure is omitted.) The control of the supply and discharge of the pressure oil to the boom cylinder 16 will be described later in detail.

Further, the control valve unit 13 receives the control oil 20L, left turning, and arm control valves 20L, 1H for supplying the hydraulic oil supplied from the first main pump 9 to the left.
9, a first center bypass oil passage A that flows to the oil tank 12 via a boom merge valve 24 and a first negative control relief valve (hereinafter, referred to as a first negative control valve) 25; Hydraulic oil from the first main pump 9 is provided in parallel with the bypass oil passage A, and is supplied to the control valves 20L, 19, and 22 for the left traveling, turning, and arm of the hydraulic oil supply position X or Y, respectively. Tandem parallel oil passage B and second main pump 1
The control oil 20R, 23, 21 for the right running, the bucket, and the boom, the merging valve 26 for the arm, and the second negative control relief valve (hereinafter, referred to as a second negative control valve) are supplied with the pressure oil supplied from 0. The second center bypass oil passage C that flows to the oil tank 12 via 27
And provided in parallel with the second center bypass oil passage C,
A second tandem parallel oil passage D for supplying the hydraulic oil from the second main pump 10 to the control valves 20R, 23, and 21 for the right running, bucket, and boom at the hydraulic oil supply position X or Y is formed. ing. The boom merge valve 24 is a valve that operates to supply the pressure oil in the first center bypass oil passage A to the oil chamber 16a on the extension side (boom rise side) of the boom cylinder 16, and also includes a joint for the arm. The valve 26 is a valve that operates to supply the pressure oil in the second center bypass oil passage C to the arm control valve 22 at the pressure oil supply position X or Y. Further, the control valve unit 13 is also provided with a pump merging valve 28 that operates to merge the pressure oils of the first and second main pumps 9, 10.
8 operates according to the work performed by the hydraulic excavator 1 and the like, but the detailed description thereof is omitted.

On the other hand, E and F are first and second negative control oil passages (hereinafter, referred to as first and second negative control oil passages) which are led from oil passages upstream of the first and second negative control valves 25 and 27, respectively. ), The signal pressures of the first and second negative control oil passages E and F (hereinafter, referred to as first and second negative control pressures) are input to the first and second shuttle valves 29 and 30, respectively. . Here, the first and second negative control pressures are supplied to the first and second negative control valves 25 and 27, respectively.
The higher the flow rate of the second center bypass oil passages A and C, that is, the smaller the amount of pressurized oil supplied to the hydraulic actuators 14 to 18, the higher the pressure, and the lower the flow rates of the first and second center bypass oil passages A and C. As the pressure oil supply amount to the hydraulic actuators 14 to 18 increases, the pressure decreases.

The first and second shuttle valves 29, 3
0 denotes first and second electromagnetic proportional pressure reducing valves 31 and 32 to be described later.
Output pressure, and the first and second negative control pressures,
High pressure side is selected and the first and second main pumps 9, 10
To the flow control devices 9a and 10a. The flow control devices 9a and 10a are provided with the first and second shuttle valves 2
When the signal pressures input from 9 and 30 are high, the discharge amounts of the first and second main pumps 9 and 10 are reduced, and when the signal pressure is low, the discharge amounts of the first and second main pumps 9 and 10 are increased. The discharge amount is controlled as follows.

The first and second electromagnetic proportional pressure reducing valves 31,
32 outputs a signal pressure to each of the first and second shuttle valves 29 and 30 based on a control command from the control unit 33.
The control unit 33 is constituted by a microcomputer or the like, which controls the first and second electromagnetic proportional pressure reducing valves 31 and 32 and third electromagnetic proportional pressure reducing valves 41 and 48 described later. First, control of the first and second electromagnetic proportional pressure reducing valves 31 and 32 will be described with reference to a block diagram shown in FIG. FIG. 3
In the above, 34 is a crane operation signal setting device, which sets a signal for the first and second electromagnetic proportional pressure reducing valves 31 and 32 to output a signal pressure suitable for crane operation, which will be described later. Output to the signal switch 35. Here, the signal pressure suitable for crane operation output from the first and second electromagnetic proportional pressure reducing valves 31 and 32 is defined as the discharge amount of the first and second main pumps 9 and 10 which is used for normal operation such as excavation operation. Is performed to reduce the discharge amount to, for example, about half of the maximum discharge amount in the case of performing the above operation. This signal pressure is hereinafter referred to as a crane signal pressure. Reference numeral 36 denotes a minimum signal setting device, which is a first and second electromagnetic proportional pressure reducing valve 31,
A signal for minimizing the signal pressure output from the signal switch 32 is set and output to the signal switch 35. On the other hand, reference numeral 37 denotes a work mode selection switch provided on the driver's seat portion. In the present embodiment, the work mode selection switch 37 includes a "crane work mode" for performing a crane work using the hook 8; The “normal operation mode” when performing normal operations such as excavation and loading using the bucket 7 can be selectively set. The signal selected by the operation mode selection switch 37 is Signal switch 3
5 is input. When the signal of the “crane operation mode” is input from the operation mode selection switch 37, the signal switch 35 selects the signal set by the crane operation signal setting device 34 and sends the signal to the valve drive signal setting device 38. Output. When the signal of the “normal operation mode” is input, the signal set by the minimum signal setting device 36 is selected and output to the valve drive signal setting device 38. Further, based on the signal selected by the signal switch 35, the valve drive signal setting device 38 controls the first and second electromagnetic proportional pressure reducing valves 3
Drive signals for the first and second electromagnetic pressure reducing valves 31 and 32 are set and output to the first and second electromagnetic proportional pressure reducing valves 31 and 32.

That is, when the "normal operation mode" is selected by the operation mode selection switch 37, the first and second electromagnetic proportional pressure reducing valves 31, 32 are driven based on the signal of the minimum signal setting device 36. As a result, the first and second electromagnetic proportional pressure reducing valves 31 and 32 output the minimum signal pressure to the first and second shuttles 29 and 30. And first,
The second shuttle valves 29 and 30 select the output signal pressure from the first and second electromagnetic proportional pressure reducing valves 31 and 32 and the high pressure side of the first and second negative control pressures. Since the minimum signal pressure is output from the first and second electromagnetic proportional pressure reducing valves 31, 32, the first and second shuttle valves 29,
Reference numeral 30 selects the first and second negative control pressures on the high pressure side and outputs them to the flow control devices 9a and 10a. Thus, when the "normal operation mode" is selected, the flow control device 9a,
10a controls the discharge amounts of the first and second main pumps 9, 10 based on the first and second negative control pressures, as shown by the solid line in FIG.

On the other hand, when the "crane operation mode" is selected, the first and second electromagnetic proportional pressure reducing valves 31, 32 are driven based on the signal of the crane operation signal setting device 34. The first and second electromagnetic proportional pressure reducing valves 31 and 32 output the crane signal pressure to the first and second shuttle valves 29 and 30. And the first and second shuttle valve 2
9 and 30, when the first and second negative control pressures are higher than the crane signal pressure, the first and second negative control pressures are selected, and the crane signal pressure is higher than the first and second negative control pressures. If it is high, the crane signal pressure is selected and output to the flow control devices 9a and 10a. Thereby, the flow control device 9
No signal lower than the crane signal pressure is input to the a and 10a. Thus, when the “crane operation mode” is selected, as shown by the dotted line in FIG. Even if the second negative control pressure is low, the discharge amounts of the first and second main pumps 9 and 10 are controlled so as to decrease to a flow rate suitable for crane work (for example, a flow rate about half of the maximum flow rate).

Next, control of supply and discharge of pressurized oil from the boom cylinder 16 will be described with reference to FIG. FIG. 5
2 shows a portion related to the boom cylinder 16 in FIG. 2 and shows a pilot oil passage, where 10 is a second main pump, 11 is a pilot pump, 12 is an oil tank, and 21 is a boom control. It is a valve. Reference numeral 39 denotes a boom pilot valve,
The boom pilot valve 39 includes an extension-side pilot valve 39A and a reduction-side pilot valve 39B. These extension-side and reduction-side pilot valves 39A and 39B are provided with boom operating tools (not shown).
Is operated to the extension side and the reduction side, respectively, to output the pilot pressure oil.

The boom control valve 21 is a pilot-operated three-position switching valve as described above, and when the boom control valve 21 is located at the neutral position N, the hydraulic oil from the second main pump 10 The oil chamber 16a on the extension side (boom raising side) of the boom cylinder 16 and the contraction side (boom lowering side)
Not supplied to the oil chamber 16b and both oil chambers 16a and 16b
Is not discharged to the oil tank 12, but the pilot pressure oil output from the expansion-side pilot valve 39A is supplied to the expansion-side pilot port 21a, so that the pressure oil from the second main pump 10 drops The position is switched to the extension position X where the oil is supplied to the extension oil chamber 16a via the prevention valve 40 and the oil from the reduction oil chamber 16b is discharged to the oil tank 12. The pilot pressure output from 39B is supplied to the contraction-side pilot port 21b via a third electromagnetic proportional pressure-reducing valve 41 described later, so that the pressure oil from the second main pump 10 is supplied to the contraction-side oil chamber 16b. on the other hand,
It is configured to switch to the contraction side position Y where the oil from the extension side oil chamber 16a is discharged to the oil tank 12 via the descent prevention valve 40. The boom control valve 21
Is switched to the extension side position X, the boom cylinder 1
When the boom control valve 6 is extended and the boom 5 is raised, the boom control valve 21 is switched to the reduction side position Y, so that the boom cylinder 16 is contracted and the boom 5 is lowered. Is the front attachment 4
Since the load is applied to the descending side due to its own weight and the weight of luggage, the operating speed of the boom cylinder 16 at the time of boom lowering is controlled by meter-out control, that is, from the boom cylinder 16 of the boom control valve 21 at the reduction side position Y It is controlled by the degree of opening of the discharge path to the oil tank 12. The operating speed of the boom cylinder 16 when the boom is raised is meter-in controlled.

The lowering prevention valve 40 is mounted directly on the boom cylinder 16, and is a two-position switching valve having a pilot port 40a. In a state where the oil is not supplied, the oil flow from the boom control valve 21 to the boom cylinder extension side oil chamber 16a is allowed, but the flow in the opposite direction is located at the first position X where the check valve 40b prevents the flow. . On the other hand, pilot port 40
a is supplied with pilot pressure,
Reduces the oil in the boom cylinder extension side oil chamber 16a by a throttle valve 40.
c, the switch is switched to the second position Y for discharging to the boom control valve 21. In this case, the opening degree of the throttle valve 40c,
That is, the discharge path from the boom cylinder extension side oil chamber 16a is controlled to increase as the pilot pressure supplied to the pilot port 40a increases, and decrease as the pilot pressure decreases. Further, the lowering prevention valve 40
The pilot pressure output from the reduction-side pilot valve 39B is supplied to the pilot port 40a via the third electromagnetic proportional pressure-reducing valve 41. Thus, the descent prevention valve 40 is switched to the second position Y only when the boom operating tool is operated on the descent side to allow the discharge of the oil from the extension-side oil chamber 16a. Thereby, it is possible to prevent the boom 5 from dropping under its own weight due to the weight of the front attachment 4 or the weight of luggage.

The third electromagnetic proportional pressure reducing valve 41
Is provided in a pilot oil passage from the boom reduction side pilot valve 39B to the boom control valve reduction side pilot port 21b and the descent prevention valve pilot port 40a. The third electromagnetic proportional pressure-reducing valve 41 operates based on a control command from the control unit 33. Control of the third electromagnetic proportional pressure-reducing valve 41 will be described with reference to the block diagram of FIG. In FIG. 6, reference numeral 42 denotes a crane operation signal setting device, which receives a signal from a pressure detector 43 for detecting the output pilot pressure of the reducing pilot valve 39B and outputs the inputted output pilot pressure. A signal for reducing the output pressure of the third electromagnetic proportional pressure reducing valve 41 is set for
The signal is output to a signal switch 44 described later. Reference numeral 45 denotes a maximum pressure signal setting device. The signal pressure output from the third electromagnetic proportional pressure reducing valve 41 is the maximum pressure, that is, without reducing the output pilot pressure from the reduction side pilot valve 39B. A signal to be output is set and output to the signal switch 44. And this signal switch 44
When the signal from the work mode selection switch 37 described above is input and the signal of the "crane work mode" is input, the signal set by the crane work signal setting device 42 is selected and the valve drive signal setting device 46 is set. Output to Also,
When the signal of the “normal operation mode” is input, the signal set by the maximum pressure signal setting device 45 is selected and output to the valve drive signal setting device 46. Further, the valve drive signal setting device 46 sets a drive signal for the third electromagnetic proportional pressure reducing valve 41 based on the signal selected by the signal switch 44 and outputs the signal to the third electromagnetic proportional pressure reducing valve 41.

That is, when the "normal operation mode" is selected by the operation mode selection switch 37, the third electromagnetic proportional pressure reducing valve 41 is driven based on the signal of the maximum pressure signal setting device 36. Thus, the third electromagnetic proportional pressure reducing valve 41 outputs the output pilot pressure from the reduction side pilot valve 39B to the boom control valve reduction side pilot port 21b and the descent prevention valve pilot port 40a without reducing the pressure. When the boom operating tool is operated in the downward direction while the "normal operation mode" is selected, the pilot pressure corresponding to the operation amount of the operating tool is increased as shown by the solid line in FIG. The boom cylinder 16 is supplied to the control valve reduction side pilot port 21b and the descent prevention valve pilot port 40a, and performs the reduction (boom lowering) operation at a speed corresponding to the operation amount of the operating tool.

On the other hand, when the "crane operation mode" is selected, the third electromagnetic proportional pressure reducing valve 41 is driven based on the signal of the crane operation signal setting device 42, and the third electromagnetic proportional pressure reducing valve 41 is driven. The pressure reducing valve 41 reduces the output pilot pressure from the reduction side pilot valve 39B and outputs the reduced pressure to the boom control valve reduction side pilot port 21b and the descent prevention valve pilot port 40a.
Here, the boom control valve 21 and the descent prevention valve 40 are controlled so that the opening degree of the discharge passage from the boom cylinder extension side oil chamber 16a decreases as the pilot pressure supplied to the pilot ports 21b and 40a decreases. Therefore, when the pilot pressure is reduced, the discharge speed of the oil from the boom cylinder extension side oil chamber 16a is reduced. When the operation tool for the boom is operated in the descending side while the "crane operation mode" is selected, the pilot pressure reduced with respect to the operation amount of the operation tool as shown by a dotted line in FIG. Is the boom control valve contraction side pilot port 21
As a result, the operation speed of the boom cylinder 16 is reduced. In addition, a descent prevention valve 47 is also provided for the oil passage on the descent side (extension side) of the arm cylinder 17, and a third electromagnetic proportional pressure reducing valve 48 that operates to reduce the arm descent speed during crane operation is provided. Although they are provided, these operations are the same as those of the boom cylinder 16 described above, and therefore, the details are omitted.

In the construction as described above, the hydraulic excavator 1 can perform a crane operation using the hook 8 in addition to a normal operation such as digging and loading by the bucket 7. Is performed, by selecting the "crane operation mode" with the operation mode selection switch 37, the discharge amounts of the first and second main pumps 9, 10 are controlled to be reduced as described above. As a result, the amount of pressure oil supplied to each of the hydraulic actuators 14 to 18 decreases, and the operating speed of the hydraulic actuators 14 to 18 with respect to the operation amount of the operating tool decreases. Further, in this apparatus, when the boom 5 and the arm 6 are operated to be lowered when the "crane operation mode" is selected, the boom and arm control valves 21 and 22 and the third electromagnetic proportional pressure reducing valves 41 and 48 are used. The pilot pressure output to the boom and arm descent prevention valves 40 and 47 is reduced, whereby the boom cylinder 16 and the arm cylinder 17 are discharged to the oil tank 12 via the valves 21, 22, 40 and 47. The operating speed of the boom cylinder 16 and the arm cylinder 17 on the descending side is reduced. As a result, the front attachment 4
The boom cylinder 16, which is meter-out controlled because the load is applied on the descending side due to the weight of its own weight or the weight of luggage,
The operation speed of the lower side of the arm cylinder 17 can also be reduced, and workability and operability during crane operation are improved.

It is needless to say that the present invention is not limited to the above-described embodiment, and may be configured as in the second embodiment shown in FIG. In the second embodiment, the same components as those in the first embodiment are not described, and are denoted by the same reference numerals.
In other words, FIG. 8 shows a pressure oil supply / discharge circuit of the boom cylinder 16, in which a pilot oil passage from the reduction side pilot valve 39B to the boom control valve reduction side pilot port 21b is provided. No electromagnetic proportional pressure reducing valve is provided, and the pilot pressure output from the reduction side pilot valve 39B is directly input to the boom control valve reduction side pilot port 21b. On the other hand, the pilot port 4 of the lowering prevention valve 40
Pilot pressure is supplied to Oa from a fourth electromagnetic proportional pressure reducing valve 49 using the pilot pump 11 as a hydraulic pressure source. And, the fourth electromagnetic proportional pressure reducing valve 49
Operates based on a control command from the control unit 33, and the control is substantially the same as that of the third electromagnetic proportional pressure-reducing valve 41 of the first embodiment described above. Is operated, the pilot pressure from the pilot pump 11 is output to the descent prevention valve pilot port 40a without reducing the pressure, and the "crane operation mode" is selected. When the boom is moved down in the boom lowering state, the pilot pressure from the pilot pump 11 is reduced in accordance with the operation amount of the operating tool and output to the descent prevention valve pilot port 40a. That is, in the second embodiment, when the operation is performed on the boom lowering side while the “normal operation mode” is selected, the pilot pressure from the pilot pump 11 is reduced without being reduced. The opening of the throttle valve 40c of the descent prevention valve 40 is maximized by being supplied to the prevention valve pilot port 40a. For this reason, the boom cylinder extension side oil chamber 16b
Will be guided to the boom control valve 21 with almost no pressure loss by the descent prevention valve 40. As a result, the boom cylinder 16 is meter-out controlled only by the boom control valve 21 that is operated by the pilot pressure output from the reduction side pilot valve 39B based on the operation of the operating tool. If the crane operation mode is selected and the boom is lowered, the reduced pilot pressure is supplied to the descent prevention valve pilot port 40a.
The opening degree of the throttle valve 40c of the descent prevention valve 40 is reduced. As a result, the speed at which the oil is discharged from the boom cylinder extension side oil chamber 16a is reduced, and this oil is guided to the boom control valve 21.
Is reduced. In the second embodiment, the hydraulic supply / discharge circuit of the arm cylinder 17 is also configured in the same manner as in the case of the boom cylinder 16 described above, and the same as in the first embodiment. The second main pumps 9 and 10 are configured to control the discharge amount. In the second embodiment, the same operation and effect as those of the first embodiment are obtained, and the workability and operability at the time of crane work are improved. In the “normal operation mode”, the boom lowering and the arm lowering control are performed with almost no pressure loss by the lowering prevention valves 40 and 47, which can contribute to the improvement of the operation speed during the normal operation such as excavation and loading.

Further, according to the present invention, as in the third embodiment shown in FIG. 9, the pilot pressure reduced by the fifth electromagnetic proportional pressure reducing valve 50 operated to reduce the pressure based on the control command from the control unit 33 is reduced. The guide valve may be configured to be guided only to the boom control valve descending side pilot port 21b without being guided to the prevention valve pilot port 40a (FIG. 9).
Shows a hydraulic supply / discharge circuit for the boom cylinder 16, but the circuit for the arm cylinder is similarly configured. And also in the third embodiment,
The same operation and effect as those of the first embodiment can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a hydraulic excavator.

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

FIG. 3 is a block diagram showing discharge amount control of a main pump.

FIG. 4 is a graph showing control of a discharge amount of a main pump.

FIG. 5 is a hydraulic supply and discharge circuit diagram of a boom cylinder.

FIG. 6 is a block diagram illustrating lowering-side control of a boom cylinder.

FIG. 7 is a graph showing lowering-side control of a boom cylinder.

FIG. 8 is a circuit diagram of a hydraulic pressure supply / discharge circuit of a boom cylinder according to a second embodiment.

FIG. 9 is a circuit diagram of a hydraulic pressure supply / discharge circuit of a boom cylinder according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic excavator 5 Boom 6 Arm 16 Boom cylinder 17 Arm cylinder 21 Boom control valve 22 Arm control valve 37 Work mode selection switch 40 Descent prevention valve 41 Third electromagnetic proportional pressure reducing valve 47 Lowering prevention valve 48 Third electromagnetic proportional pressure reducing valve 49 4th electromagnetic proportional pressure reducing valve 50 5th electromagnetic proportional pressure reducing valve

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Nobuaki Matoba 2-5-1 Marunouchi, Chiyoda-ku, Tokyo F-term in Sanishi Heavy Industries, Ltd. (Reference) 2D003 AA01 AB03 AB04 AC11 BA01 BA02 BB02 CA04 CA07 CA08 DA03 DA04 FA02 5H307 AA06 AA18 BB07 CC03 DD15 EE02 EE07 EE09 ES02 FF02 FF12 GG06 GG09 HH04 HH11 JJ01

Claims (7)

[Claims] 1. A construction machine with a crane function configured to perform both a crane operation and a normal operation other than the crane operation based on the expansion and contraction operation of a hydraulic cylinder, wherein at least one of the hydraulic cylinders is provided. The hydraulic cylinder is configured to control the cylinder operating speed by controlling the amount of hydraulic oil discharged from the hydraulic cylinder, and the hydraulic oil discharge passage of the hydraulic cylinder is further provided with a discharge amount adjusting means that operates to reduce the amount of hydraulic oil discharged. A construction machine with a crane function. 2. The construction machine with a crane function according to claim 1, wherein the construction machine with a crane function is provided with a work mode selection means for selectively setting a crane work mode and a normal work mode, while the discharge amount adjusting means is configured to set the crane work mode. A construction machine with a crane function that sometimes operates to reduce the amount of hydraulic oil discharged from a hydraulic cylinder. 3. The hydraulic cylinder according to claim 1, wherein the hydraulic oil is discharged from the hydraulic cylinder to a hydraulic oil discharge passage of the hydraulic cylinder whose hydraulic oil discharge amount is controlled when the operating tool for the hydraulic cylinder is not operated. A crane for preventing the oil from being discharged based on the operation of the operating tool; and a discharge amount adjusting means for adjusting the amount of pressurized oil discharged from the drip prevention valve. Construction machinery with functions. 4. The discharge amount adjusting means according to claim 3,
A construction machine with a crane function, comprising a pressure reducing valve provided in a pilot oil passage for switching a descent prevention valve to a pressure oil discharge allowable state. 5. The discharge amount adjusting means according to claim 1, wherein the discharge amount adjusting means adjusts a discharge amount of the hydraulic oil from a control valve which operates to perform a supply and discharge control of the hydraulic oil of the hydraulic cylinder. Construction machine with crane function. 6. The discharge amount adjusting means according to claim 5,
A construction machine with a crane function comprising a pressure reducing valve provided in a pilot oil passage for switching a control valve to a pressure oil discharging state. 7. The construction machine with a crane function according to claim 1, wherein the boom is swingably supported by the body.
A hydraulic excavator having an arm swingably supported at a tip end of the boom, and a discharge amount adjusting means, a pressure oil discharge circuit on a reduction side of a boom cylinder for swinging the boom, and an arm. A construction machine with a crane function, provided in at least one of the pressure oil discharge circuits on the extension side of the arm cylinder for swinging the arm cylinder.