JP2716607B2 - Hydraulic circuit of construction machinery - Google Patents

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 construction machine such as a hydraulic shovel, to which a work tool such as a crusher can be attached as required and work can be performed using the work tool.

[0002]

2. Description of the Related Art In recent years, construction machines, for example, hydraulic shovels and hydraulic loader shovels, perform a combined operation of a traveling actuator and other actuators and a high-speed driving of an arm cylinder in order to facilitate work. On the other hand, it has been desired to be able to freely attach various working tools to the tip of the working link in order to diversify the work. A hydraulic circuit of a construction machine that meets such a demand will be described with reference to FIG. FIG. 2 is a circuit diagram showing a hydraulic circuit of a conventional construction machine. In the drawing, reference numeral 1 denotes a first variable displacement hydraulic pump (hereinafter, simply referred to as a hydraulic pump), and 2 denotes first displacement control means (hereinafter, referred to as a regulator) for controlling the displacement of the first hydraulic pump 1. Reference numeral 3 denotes a first valve group including a plurality of directional control valves connected to the first hydraulic pump 1 and the center bypass circuit 4. In the case shown, the first valve group 3 comprises a first traveling direction switching valve 5, a first arm direction switching valve 6, and other actuator direction switching valves 7, 8. 9 is a center bypass circuit 4 at a position downstream of the first valve group 3.
The throttle 10, which is a flow resistance means interposed between the throttle valve 10 and the first valve group 3, is located downstream of the first valve group 3, and a pressure value generated in the center bypass circuit 4 upstream of the throttle 9 is used as a negative control signal as a first control signal. A first pilot circuit 11 for transmitting a signal to the regulator 2 is a first relief valve as pressure control means for regulating the maximum value of the pressure of the first pilot circuit 10 so as not to exceed a predetermined set value. is there. These constitute a first hydraulic circuit. In the first valve group 3, the first traveling direction switching valve 5 is arranged at the most upstream position of the center bypass circuit 4, and can receive the hydraulic oil from the first hydraulic pump 1 preferentially. I have. The other directional control valves 7 and 8 for the actuator and the directional control valve 6 for the first arm are connected to the center bypass circuit 4, respectively, and the first hydraulic pump is disposed at a position downstream of the first directional control valve 5 for traveling. 1 are connected in parallel. First traveling direction switching valve 5
Is connected to a right traveling motor (not shown), that is, a first traveling motor, and the other actuator direction switching valves 7, 8
Are respectively connected to other actuators not shown. In the first arm direction switching valve 6, one of the two output ports is connected to the bottom side of the arm cylinder 35 via the pipe 14A, and the other output port is interposed with the check valve 15. Through an additional conduit 14B, which is connected to an input port of a direction switching valve 25 for an additional actuator described later. When the first arm direction switching valve 6 is switched to the left side position in the figure by the operation valve 48 operated by the operation lever, the arm cylinder 35 is connected via the line 14A.
And a function of discharging return oil from the bottom side to the tank side, and when switched to the right position in the figure, pressurized oil from the first hydraulic pump 1 through the pipe line 14B to the direction switching valve 25 for the additional actuator. It has the function to supply to the input port of.

Reference numeral 18 denotes a second variable displacement hydraulic pump (hereinafter simply referred to as a hydraulic pump). Reference numeral 19 denotes second displacement control means (hereinafter referred to as a regulator) for controlling the displacement of the second hydraulic pump 18. Representative), 20
Denotes a second valve group including a plurality of directional control valves connected to the second hydraulic pump 18 and the center bypass circuit 21. In the case shown, the second valve group 20 includes a directional control valve 22 for a specific actuator, a directional control valve 23 for a second arm, and a directional control valve 2 for another actuator.
4, a direction switching valve 25 for additional actuators and a second direction switching valve 26 for traveling. Reference numeral 27 denotes a throttle which is a flow resistance means interposed in the center bypass circuit 21 located at a position downstream of the second valve group 20, and reference numeral 28 denotes a first throttle.
At a position downstream of the valve group 20 and the throttle 27
A second pilot circuit for transmitting a pressure value generated in the center bypass circuit 21 on the upstream side of the second pilot circuit 21 to the second regulator 19 as a negative control signal, and 29 has a predetermined maximum value of the pressure of the second pilot circuit 28. The second relief valve 30 is a pressure control means for regulating the pressure so as not to exceed the set value.
A first bypass circuit 31 for connecting the input port of the traveling direction switching valve 26 is an opening / closing valve interposed in the first bypass circuit 30. These constitute a second hydraulic circuit. Reference numeral 32 denotes a shuttle valve that selects the high pressure side of the hydraulic oil discharged from the first and second hydraulic pumps 1 and 18 in the first and second hydraulic circuits.
Is a relief valve for regulating the maximum pressure of the selected hydraulic oil to a predetermined set value, and 34 is a tank. In the second valve group 20, the specific directional control valve 22 for the specific actuator, the second directional directional control valve for the arm 23, and the directional directional control valve for the other actuators 24 are respectively provided in parallel with the second hydraulic pump 18. It is connected. The additional actuator direction switching valve 25 and the second traveling direction switching valve 26 are tandemly connected to the second hydraulic pump 18 at positions downstream of the other actuator direction switching valves 24, respectively.

[0004] 40 is a pilot pump, and 41 is a pilot circuit branched from a pilot circuit 42 connected to the pilot pump 40. The pilot circuit 41 is divided into a pilot circuit 43 and a pilot circuit 44.
One pilot circuit 43 is connected to the pilot port of the on-off valve 31, and the other pilot circuit 44 is connected to each directional switching valve 7, 8, 6 of the first valve group 3 and each directional switching of the second valve group 20. It is connected to the tank 34 via the valves 22, 23, 24, 25 sequentially. In each of the pilot circuits 41, 43, and 44, any one of the directional control valves 7, 8, 6, 22, 23, 24, and 25 through which the pilot circuit 44 passes is switched to shut off the circuit to the tank 34. When this occurs, pressure is generated, and the on-off valve 31 is switched to the open position against the spring. Reference numeral 45 denotes a throttle interposed in the pilot circuit 41, and reference numeral 46 denotes a relief valve that regulates the discharge pressure of the pilot pump 40 to a predetermined set value. 47 transmits the pilot pressure supplied from the pilot circuit 42 to the pilot port on the illustrated a side or the b side of the directional control valve 25 for the additional actuator according to the operation of the operation lever as described above, Switching valve 25
The operation valve for switching the operation lever 48 according to the operation of the operation lever,
The pilot pressure supplied from the pilot circuit 42 is
Of the arm directional switching valve 6 and the second arm directional switching valve 23 on the illustrated c-side or the illustrated d-side pilot port.
23 is an operation valve that switches simultaneously. 49 is an operation valve 47
A shuttle valve 50 for selecting the pressure on the high pressure side of the a side and the b side, a switching valve 50 having two positions which are switched against a spring when a pilot pressure is generated on the c side of the operation valve 48;
1 is a pilot pressure generated on the d side of the operation valve 48 and the switching valve 5
This is a shuttle valve that selects the high pressure side of the pressure output from 0. The pilot pressure selected by the shuttle valve 51 is transmitted to a pilot port on the illustrated d side of the first arm direction switching valve 6.

Next, the operation of the hydraulic circuit shown in FIG. 2 will be described. When only the first and second traveling direction switching valves 5 and 26 are operated by the operation of operation means (not shown), the first traveling motor (not shown) is supplied from the first hydraulic pump 1 via the center bypass circuit 4. Driven by pressure oil,
A second traveling motor (not shown) is driven by pressure oil from the second hydraulic pump 18 via the center bypass circuit 21. At this time, since the center bypass circuits 4 and 21 are cut off, the first and second pilot circuits 10 and 28 are turned off.
, The negative control pressure decreases, and the displacement volumes of the first and second hydraulic pumps 1 and 18 are increased by the first and second regulators 2 and 19. When only the additional actuator 36 is driven, when the operation valve 47 is operated, for example, to the side a in the figure, the direction switching valve 25 for the additional actuator is switched to the side a by the pilot pressure, and the pilot pressure is changed to the shuttle valve 49, Switching valve 5
0, transmitted to the d-side pilot port of the first arm direction switching valve 6 via the shuttle valve 51 and switched to the d-side. Thereby, the hydraulic fluid of the second hydraulic pump 18 supplied through the center bypass circuit 21 and the center bypass circuit 4, the first arm direction switching valve 6, the pipe The pressure oil of the first hydraulic pump 1 supplied via the passage 14B and the check valve 15 is combined and supplied, and drives the additional actuator 36 at a high speed in the contraction direction. Conversely, when the operation valve 47 is operated to the side b in the figure, the direction switching valve 25 for the additional actuator becomes b
Side, the first arm direction switching valve 6 is switched to the d side similarly to the above, and the first hydraulic pump 1 and the second hydraulic pump 18
Are supplied together and drive the additional actuator 36 in the extension direction at high speed. Also, the arm cylinder 35
When only the operation is performed, when the operation valve 48 is operated, for example, to the side c in the figure, the first and second direction switching valves 6 and 23 are switched to the side c, and the pressure oil of the second hydraulic pump 18 is discharged to the second side. 2
Arm cylinder 35 through the arm directional control valve 23
And the pressure oil on the bottom side of the arm cylinder 35 branches to both the second arm directional switching valve 23 and the first arm directional switching valve 6 and is supplied to the tank 34.
, The arm cylinder 35 is driven at a high speed in the contraction direction. In this case, the switching valve 50 is switched, and the d-side pilot port of the first arm direction switching valve 6 has the tank pressure, so that the switching operation of the first arm direction switching valve 6 is hindered. Absent. When the operation valve 48 is operated to the d side in the opposite manner to the above, the first arm direction switching valve 6
Are switched via the shuttle valve 51, and the second arm direction switching valve 23 is switched directly to the d side. In this case, the first arm direction switching valve 6 is connected to the arm cylinder 3
The arm cylinder 35 is driven in the extension direction at a normal speed by the pressure oil of the second hydraulic pump 18 without contributing to the drive of the arm 5. Next, a combined operation of the traveling motor and the additional actuator 36 will be described. In this case, the first traveling direction switching valve 5 and the second traveling direction switching valve 26 are switched, and the switching of the first traveling direction switching valve 5 causes the first traveling direction switching valve 5 to switch to the first traveling direction switching valve 5. The supply of the pressure oil from the hydraulic pump 1 to another directional control valve is shut off. On the other hand, since the operation valve 47 is operated, as described above, the first arm direction switching valve 6 is switched to the d side, and the additional actuator direction switching valve 25 is switched to either the a side or the b side. . By these switching, the circuit of the tank 34 via the pilot circuit 44 is cut off, so that the pilot pressure of the pilot circuits 41, 43, 44 increases, and the on-off valve 31
Is switched to the open state against the spring. In the above state, the pressure oil of the first hydraulic pump 1 is supplied to the second traveling direction switching valve 26 via the first traveling direction switching valve 5, the on-off valve 31, and the first bypass circuit 30. Then, traveling is performed. The pressure oil of the second hydraulic pump 18 is supplied to the additional actuator direction switching valve 25 to drive the additional actuator 36. Next, a combined operation of the traveling motor and the arm cylinder 35 will be described. In this case, the second operation differs from the combined operation of the traveling motor and the additional actuator 36 in that the second arm direction switching valve 23 is switched instead of the additional actuator direction switching valve 25 in the second valve group 20; The only difference is that the first arm direction switching valve 6 is also switched to the c side in the first valve group 3. As a result, the hydraulic oil of the first hydraulic pump 1 is supplied to the first and second traveling direction switching valves 5 and 26, and traveling is performed. The pressure oil of the second hydraulic pump 18 is supplied to the second arm direction switching valve 23, and the arm cylinder 35 extends. This arm cylinder 35
When operating in the contraction direction that is switched to the c side, the discharge of the bottom side pressure oil is performed by the first and second arm direction switching valves 6 and 2.
Since the flow is divided into three, the speed becomes high.

[0006]

In the above-mentioned conventional hydraulic circuit, the combined operation of the traveling motor and the additional actuator 36 and the combined operation of the traveling motor and the arm cylinder 35 can be performed by switching the open / close valve 31 without any trouble. When the 35 is operated alone or in combination with a hydraulic motor, there is a problem that high-speed driving is possible in the contraction direction but high-speed driving is not possible in the extension direction. The arm cylinder 35 and the additional actuator 3
When it is necessary to perform the combined operation of the control valve 6 and the control valve 47,
48, the second arm directional control valve 2
3 is connected to the second hydraulic pump 18 so that the arm cylinder 35 can be driven, but the second arm direction switching valve 23 is switched and the center bypass circuit 21 is shut off, so the additional actuator direction switching valve The pressure oil of the second hydraulic pump 18 is not supplied to 25 and the first arm direction switching valve 6 is switched to the d side only when the first arm direction switching valve 6 is switched to the d side.
Pressure oil of the hydraulic pump 1 is supplied.
When the second arm direction switching valves 6 and 23 are switched to the c side to drive the arm cylinder 35 in the contraction direction, the additional actuator 36 cannot be driven. Further, the traveling motor, the arm cylinder 35 and the additional actuator 3
Even when the three members 6 are operated in a combined manner, the additional actuator 36 cannot be driven because the center bypass circuit 4 is shut off by switching the first traveling direction switching valve 5. That is, the combined operation of the arm cylinder 35 and the additional actuator 36 may or may not be able to drive the additional actuator 36 depending on the switching state of the first and second arm direction switching valves 6 and 23.
In addition, the combined operation of these three members and the traveling motor becomes impossible because the additional actuator 36 cannot be driven.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to improve the rotational speed of the arm without affecting the combined operation of traveling and other actuators, and An object of the present invention is to provide a hydraulic circuit of a construction machine capable of improving a combined operation of the arm and the additional actuator.

[0008]

In order to achieve the above object, the present invention includes at least first and second hydraulic circuits for driving a plurality of actuators, wherein the first hydraulic circuit comprises a first hydraulic circuit. Variable displacement hydraulic pump, and a first valve group including a first traveling direction switching valve and a first arm direction switching valve respectively connected to the first variable displacement hydraulic pump through a center bypass circuit The flow resistance means interposed in the center bypass circuit located downstream of the first valve group, and the discharge oil from the first variable displacement hydraulic pump passing through the flow resistance means via the center bypass circuit. , The pressure value generated in the center bypass circuit located downstream of the first valve group and upstream of the flow resistance means is displaced by the first variable displacement hydraulic pump. A first transmitting means for transmitting a signal to the first displacement control means to be controlled, and a maximum pressure generated in a center bypass circuit located downstream of the first valve group and upstream of the flow resistance means. Pressure control means for regulating the value to a preset value, wherein the first traveling directional control valve has a first variable displacement type in the first hydraulic circuit with priority over the first arm directional control valve. The first arm direction switching valve is connected to the first variable displacement hydraulic pump at a downstream position with respect to the first traveling direction switching valve so as to receive the pressure oil from the hydraulic pump. , The first directional control valve for the arm has two output ports,
One of them is connected to the bottom side of the arm cylinder, and the first displacement control means presets the displacement of the first variable displacement hydraulic pump based on a signal from the first transmission means. The second hydraulic circuit includes a second variable displacement hydraulic pump and a second variable displacement hydraulic pump connected to the second variable displacement hydraulic pump through a center bypass circuit. 2
A second valve group including the arm direction switching valve, the additional actuator direction switching valve, and the second traveling direction switching valve, and the first variable displacement hydraulic pump and the second traveling direction switching valve. An on-off valve interposed in a first bypass circuit for connecting an input port, wherein the second arm direction switching valve is a second actuator direction switching valve and a second traveling direction switching valve in a second hydraulic circuit. Priority over the second
The directional control valve for the additional actuator is connected to the second variable displacement hydraulic pump at a position downstream of the directional control valve for the second arm so as to receive the pressure oil from the variable displacement hydraulic pump. A second traveling direction switching valve is connected to the second variable displacement hydraulic pump at a downstream position with respect to the additional actuator direction switching valve, and the first and second arm direction switching valves are connected to each other. And a hydraulic circuit for a construction machine having operating means for controlling the switching of the on-off valve from a closed position to an open position in response to at least one of the direction switching valves for the additional actuator being operated,
The first arm direction switching valve has the other of the two output ports connected to the piston rod side of the arm cylinder, and the second hydraulic circuit has the first hydraulic control circuit connected to the first hydraulic valve downstream of the on-off valve. A second bypass circuit is provided for connecting the bypass circuit and the input port side of the additional actuator directional switching valve. The second bypass circuit is connected to the first transmission means based on the switching of the additional actuator directional switching valve. 1
Control means for interrupting the signal transmission to the displacement control means and changing the maximum value of the pressure defined by the pressure control means to a preset high value which is sufficient to drive the additional actuator. It is characterized by having.

[0009]

When only the arm cylinder is driven to contract, the first and second arm direction switching valves are switched in accordance with the operation of the operating means, and the first arm direction switching is provided at the bottom side of the arm cylinder. The pressure oil from the first hydraulic pump is supplied via the valve, and the pressure oil from the second hydraulic pump is supplied via the second arm direction switching valve. At this time, the return oil from the rod side of the arm cylinder is diverted to both the first and second arm direction switching valves and discharged to the tank. Therefore, the arm cylinder is driven to extend at high speed. On the other hand, when the arm cylinder is contracted, the first and second arm direction switching valves are switched in accordance with the operation of the operating means, and the first and second arm direction switching valves are also provided on the rod side of the arm cylinder. Pressure oils from the first and second hydraulic pumps are combined and supplied via the direction switching valve,
The return oil from the bottom side of the arm cylinder is
And is discharged to the tank. Therefore, the arm cylinder is driven to contract at high speed.
Further, when performing a combined operation of the arm cylinder and the additional actuator, regardless of whether the drive is performed in either the contraction direction or the extension direction, the first and second arm The directional control valve and the directional control valve for the additional actuator are switched, the on-off valve is switched to the open position, and the control means operates in response to the switching of the directional control valve for the additional actuator.
Is interrupted, and the pressure of the pressure control means is changed to a predetermined set value which is sufficient to drive the additional actuator. For this reason, the pressurized oil from the first and second hydraulic pumps is combined and supplied to the arm cylinder via the first and second directional switching valves for the arm, and the first bypass is supplied to the additional actuator. Pressure oil is supplied from the first hydraulic pump via the circuit, the on-off valve, and the second bypass circuit. Therefore, a combined operation of the high-speed driving of the arm cylinder and the normal driving of the additional actuator is performed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to one embodiment shown in the drawings. FIG. 1 is a circuit diagram showing a hydraulic circuit of a construction machine according to one embodiment of the present invention. In the figure, the same or equivalent parts as those shown in FIG. Reference numeral 54 denotes a first arm direction switching valve, which has the same structure as the other direction switching valves 5, 7, and 8 of the first valve group 3 as shown in FIG. The port is connected to the bottom side of the arm cylinder 35 via the pipe 14A, and the other output port is connected to the rod side of the arm cylinder 35 via the pipe 14C. Further, a pilot port on the illustrated side of the first arm direction switching valve 54 is connected to the illustrated side d of the operation valve 48. 55 denotes a downstream side of the on-off valve 31 and the first bypass circuit 30 and the directional control valve 2 for the additional actuator.
A second bypass circuit for connecting the input port 5 to the input port 5;
6 is a check valve interposed in the second bypass circuit 55.
Reference numeral 57 denotes a switching valve interposed in the first pilot circuit 10. Usually, the switching valve 57 is located on the left side in the drawing by the spring force of the spring 58 and has a first pressure of the upstream pressure of the throttle 9 by the first pilot circuit 10. When the signal transmission to the regulator 2 is maintained and the position is switched to the position on the right side in the figure, the first regulator 2 side of the pilot circuit 10 is connected to the tank 34, and the throttle 9 side of the pilot circuit 10 is shut off. A pilot circuit 59 transmits the pilot pressure selected by the shuttle valve 49 to the pilot port of the switching valve 57 and the spring chamber side of the relief valve 11. When the pilot pressure is transmitted by the pilot circuit 59, the switching valve 57 is switched to the right position in the figure, and the relief valve 1
The set pressure of 1 is increased.

Next, the operation of the hydraulic circuit shown in FIG. 1 will be described. When only the first and second traveling direction switching valves 5 and 26 are operated by operating the operation means (not shown), both traveling motors are driven by the same operation as the conventional hydraulic circuit shown in FIG. When only the additional actuator 36 is driven, when the operation valve 47 is operated, for example, to the side a in the figure,
The direction switching valve 25 for the additional actuator is switched to the side a by the pilot pressure. At the same time, the switching valve 57 is switched to the right position in the figure to reduce the negative control pressure, the first regulator 2 increases the displacement volume of the first hydraulic pump 1, and the pilot valve is moved to the spring chamber side of the relief valve 11. The pressure is applied to increase the set pressure of the relief valve 11. This prevents the relief valve 11 from operating at a high pressure generated upstream of the throttle 9 due to an increase in the displacement volume of the hydraulic pump 1, and as a result, is sufficient to drive the additional actuator 36 upstream of the throttle 9. Pressure rises. Also, a directional control valve 2 for an additional actuator.
5 through the pilot circuit 44
4 is interrupted, the pilot circuits 41 and 4
The pilot pressures of the valves 3 and 44 rise, and the on-off valve 31 is switched to the open state against the spring. As a result, the additional actuator direction switching valve 25 has the first bypass circuit 3
0, pressure oil of the first hydraulic pump 1 supplied via the on-off valve 31, the second bypass circuit 55, and the check valve 56;
The pressure oil of the second hydraulic pump 18 supplied via the center bypass circuit 21 is supplied in a combined manner, and drives the additional actuator 36 in the contracting direction at high speed. Conversely, when the operation valve 47 is operated to the side b in the figure, the additional actuator 36 is driven in the extension direction at high speed by the same operation. When only the arm cylinder is driven, when the operation valve 48 is operated to the c side, the first and second arm direction switching valves 5 are operated.
4 and 23 are switched to the c side. On the rod side of the arm cylinder 35, the pressure from the first hydraulic pump 1 via the center bypass circuit 4, the first arm direction switching valve 54, and the pipeline 14C is provided. The oil is supplied, and the pressure oil from the second hydraulic pump 18 is joined and supplied via the second arm direction switching valve 23. At this time, arm cylinder 3
The return oil from the bottom side of 5 is diverted to both the second arm direction switching valve 23 and the first arm direction switching valve 54 via the pipe 14A, and is discharged to the tank 34. Accordingly, the arm cylinder contracts at a high speed. When the operation valve 48 is operated to the side d in the figure, the first and second direction switching valves 54 and 23 for the arm are switched to the side d, and the center bypass circuit 4 , The pressure oil from the first hydraulic pump 1 is supplied via the first arm direction switching valve 54 and the pipe line 14A, and the second oil pressure is supplied via the second arm direction switching valve 23. The pressure oil from the pump 18 is combined and supplied. At this time, the return oil from the rod side of the arm cylinder 35 is transferred to the first arm directional switching valve 23 and the first oil via the pipe 14C.
Diverted to both the arm direction switching valve 54 and the tank 3
It is discharged to 4. Therefore, even when the arm cylinder 35 is driven in the extension direction, the extension operation is performed at a high speed unlike the conventional hydraulic circuit. Next, a combined operation of the traveling motor and the additional actuator 36 will be described. Since the second bypass circuit 55 exists, the pressure oil of the hydraulic pump 1 also joins the direction switching valve 25 for the additional actuator via the on-off valve 31, and the pressure oil of the first and second hydraulic pumps 1 and 18 Thus, the additional actuator 36 can be driven at high speed during the combined operation. Next, a combined operation of the traveling motor and the arm cylinder 35 will be described. In this case, the first hydraulic pump 1
Is supplied to the first and second traveling direction switching valves 5 and 26 and traveling is performed. At the same time, the second arm direction switching valve 23 is switched by the operation valve 48, and the second hydraulic pressure is changed. The pressure oil of the pump 18 is supplied to the second arm direction switching valve 23, and the arm cylinder 35 is driven. Next, the combined operation of traveling and the additional actuator 36 and the arm cylinder 35 will be described. Also in this case, since the first and second traveling direction switching valves 5, 26 are switched, the supply of the pressure oil to the other direction switching valves 7, 8, 54 in the first valve group 3 is shut off. . On the other hand, the operating valve 47 and the operating valve 4
8 is operated, the above-described second arm direction switching valve 23 is switched to either the c side or d side, and the additional actuator direction switching valve 25 is switched to either the a side or b side. . By these switching, the on-off valve 31 is switched to the open state against the spring. In the above state, the pressure oil of the first hydraulic pump 1 is supplied to the first traveling direction switching valve 5 and the second traveling direction switching valve 26 to travel. At the same time, the pressure oil of the first hydraulic pump 1 is supplied to the additional actuator direction switching valve 25 via the on-off valve 31, the second bypass circuit 55, and the check valve 56, and drives the additional actuator 36, The pressure oil of the second hydraulic pump 18 is supplied to the second hydraulic pump 18 via the center bypass circuit 21.
Is supplied to the arm direction switching valve 23 to drive the arm cylinder 35.

As described above, in the present embodiment, one output port side of the first arm direction switching valve 54 and the rod side of the arm cylinder 35 are connected by the conduit 14C, and the first bypass circuit 30 The downstream side of the on-off valve 31 and the input port side of the additional actuator direction switching valve 25 are connected by the second bypass circuit 55, so that the contraction side and the extension side of the arm cylinder 35 affect the other. And can be driven at high speed. In addition, the arm cylinder 35 and the additional actuator 36 are always
And a composite operation with. This makes it possible to increase the speed of the arm operation and improve the combined operation of the arm cylinder and the additional actuator. Further, in this embodiment, in addition to the above configuration, a switching valve 57 having a function of reducing the negative control pressure transmitted by the first pilot circuit 10 when the additional actuator is driven, and an operating valve A pilot circuit 5 that switches when operating the 47 and switches the first relief valve 11 to the spring chamber side to change the maximum value of the prescribed pressure to a value high enough to drive the additional actuator 36.
9, it is possible to obtain a sufficient driving pressure for operating the additional actuator 36. Furthermore, the additional actuator 36 can be driven by the combined hydraulic oil from the first and second variable displacement hydraulic pumps 1 and 15 during the traveling operation.
5 can be accelerated to the contraction side and the extension side. In addition, a combined operation of the three components of the traveling motor, the arm cylinder 35 and the additional actuator 36 can be performed.
In this embodiment, as a means for operating the on-off valve 31, a pilot circuit 41 via the directional control valves 6, 7, 8, 22, 23, 24, 25 in the first and second valve groups 3, 20 is used. Is described as an example, but the present invention is not limited to this. For example, the direction switching valves 6, 7, 8, 22,
Hydraulic type that guides pilot pressure signal when operating the operating means (operating valve) for operating 23, 24, 25, electric type that guides electric signal, mechanical type that guides mechanical displacement signal, etc. are adopted. The switching valve 57,
As an example, a case in which a hydraulic type that guides a pilot pressure signal when operating the operation valve 47 is employed as the signal transmission means 59 to the relief valve 11 has been described, but this is also an electric type or a mechanical type as described above. Equations and the like can be adopted. In addition, as the additional actuator 36, a hydraulic motor or the like can be used in addition to the hydraulic cylinder as shown in the figure.

[0013]

As described above, according to the present invention, the driving speed of the arm cylinder can be increased without affecting the combined operation of the traveling motor and the other actuators by the above configuration, and The combined operation of the arm cylinder and the additional actuator can be performed without any trouble. Further, it is possible to reliably cope with an increase in the load of the additional actuator. In addition, a combined operation of the three components, that is, the traveling motor, the arm cylinder, and the additional actuator can be performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a hydraulic circuit of a construction machine according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a hydraulic circuit of a conventional construction machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st variable displacement hydraulic pump 2 1st displacement control means (regulator) 3 1st valve group 4 Center bypass circuit 5 1st directional control valve for running 9 Flow resistance means (throttle) 10 1st Transmission means (pilot circuit) 11 Pressure control means (relief valve) 14A line 14C line 15 Second variable displacement hydraulic pump (regulator) 20 Second valve group 21 Center bypass circuit 23 Second arm direction switch Valve 25 Direction switching valve for additional actuator 26 Second direction switching valve for traveling 30 First bypass circuit 31 Open / close valve 35 Arm cylinder 36 Additional actuator 54 First direction switching valve for arm 55 Second bypass circuit 57 Switching valve 59 Operating means (pilot circuit)

Claims (1)

(57) [Claims] 1. A system comprising at least first and second hydraulic circuits for driving a plurality of actuators, wherein the first hydraulic circuit comprises a first variable displacement hydraulic pump and a first variable displacement hydraulic pump. A first valve group including a first traveling direction switching valve and a first arm direction switching valve respectively connected to the pump through a center bypass circuit; and a center bypass circuit at a position downstream of the first valve group. The interposed flow resistance means and the discharge oil from the first variable displacement hydraulic pump pass through the flow resistance means via the center bypass circuit, so that the oil is located downstream of the first valve group, and the flow resistance is reduced. A pressure value generated in the center bypass circuit on the upstream side of the means is transmitted to first displacement control means for controlling displacement of the first variable displacement hydraulic pump; 1 transmission means and pressure control means for regulating the maximum value of the pressure generated in the center bypass circuit located downstream of the first valve group and upstream of the flow resistance means to a preset value. The first traveling directional switching valve includes a first traveling direction switching valve that receives the pressure oil from the first variable displacement hydraulic pump in the first hydraulic circuit more preferentially than the first arm directional switching valve. The first arm direction switching valve is connected to the first variable displacement hydraulic pump at a downstream position with respect to the traveling direction switching valve, and the first arm direction switching valve has two output ports. One of which is connected to the bottom side of the arm cylinder, wherein the first displacement control means is configured to control the first variable displacement hydraulic pump based on a signal from the first transmission means. Set the displacement volume to a preset value. The second hydraulic circuit includes a second variable displacement hydraulic pump and a second arm connected to the second variable displacement hydraulic pump through a center bypass circuit. A second valve group including a direction switching valve, a direction switching valve for an additional actuator, and a second traveling direction switching valve, and input ports of the first variable displacement hydraulic pump and the second traveling direction switching valve. An on-off valve interposed in a first bypass circuit to be connected, wherein the second arm direction switching valve has priority over the additional actuator direction switching valve and the second traveling direction switching valve in the second hydraulic circuit. Second
To receive the pressure oil from the variable displacement hydraulic pump
The additional actuator direction switching valve is connected to the second variable displacement hydraulic pump at a downstream position with respect to the second arm direction switching valve, and the second travel is performed with respect to the additional actuator direction switching valve. The directional control valve is connected to the second variable displacement hydraulic pump at a downstream position.
A construction machine having an operating means for switching the open / close valve from a closed position to an open position in response to operation of at least one of the arm direction switching valve and the additional actuator direction switching valve. In the hydraulic circuit of the first aspect, the first arm direction switching valve connects the other of the two output ports to the piston rod side of the arm cylinder, and the second hydraulic circuit includes a downstream side of the on-off valve. A second bypass circuit for connecting the first bypass circuit to the input port side of the directional control valve for the additional actuator on the side thereof, and the first bypass circuit is connected to the first directional control valve based on the switching of the directional control valve for the additional actuator. The signal transmission from the transmission means to the first displacement volume control means is cut off, and the maximum value of the pressure defined by the pressure control means is set to the additional actuator. The hydraulic circuit for a construction machine characterized in that a control means for changing to a higher preset value is sufficient for moving.