JPS5985046A - Oil-pressure circuit of oil-pressure shovel - Google Patents

Abstract

PURPOSE:To obtain optimum pressure and flow rate characteristics for slewing by preventing the loss of pressure by reliefing by using a system in which a turning pump is controlled in terms of (fixed pressure)X(flow rate) basis in the oil-pressure circuit of three variable pumps having an exclusive variable pump for slewing. CONSTITUTION:In three pumps oil-pressure circuit having the first and second variable pumps 1 and 2 to supply pressure oil to an exclusive variable pump 3 for slewing, left and right-side running oil-pressure motors, a boom cylinder, a bucket cylinder and an arm cylinder, a serbo valve 84 operating by secondary pressure A3 from a remote control valve 6 to operate the switch valve for slewing is provided to the exclusive variable pump 3 for slewing. A pressure-cut off control valve 86 operating by the discharge pressure of the pump 3 is also provided, and a serbo valve 84 and a regulator 81 to control the discharge amount of the pump 3 by introducing pressure oil controlled by the pressure- cut off control valve 86 are provided.

Description

[Detailed description of the invention] The present invention is a hydraulic circuit for a hydraulic excavator with independent swing.

It is related to.

A hydraulic excavator is equipped with six hydraulic actuators: a left and right travel motor, a swing motor, a boom cylinder, an arm cylinder, and a packet cylinder.To operate these actuators, a 2-pump system or a 3-pump system hydraulic system is used. circuit is used.

However, in a two-pump type hydraulic circuit, the swing and arm
Since each circuit for the two-speed boom and one traveling circuit is connected in parallel to one pump, there is a problem that they interfere with each other during combined work with the swing and the arm or boom, resulting in poor workability.

Therefore, in order to improve workability during complex work, a constant displacement type sixth pump is used for turning, and a variable displacement type first pump is used for other actuators. A six-pump hydraulic circuit using a second pump is known. However, if the sixth pump is a fixed displacement type, high pressure and large flow output can be obtained for swinging, so workability is good during swinging work alone, but when starting swinging during combined work with swinging and other actuators. ,
The sixth pump outputs high pressure, large flow horsepower, and based on this horsepower, the first pump. Since the horsepower of the second pump is controlled, the horsepower of the second pump is controlled. The horsepower of the second pump is greatly reduced, and the workability of other actuators becomes worse. Moreover, when starting the swing, the swing motor requires high pressure, but the inflow flow rate is small, so the sixth
A large part of the pump (maximum output) is relieved by the relief valve, and this relief causes a large loss in engine power. In order to prevent output loss due to this relief, there is a circuit in which excess oil from the fifth pump's rotation flows into the second gear of the boom, but according to this circuit, the rotation is not affected by the load pressure of the boom. , The workability (matching) of swing and boom is poor.Furthermore, in order to prevent the output loss of the engine, there is a system in which the sixth pump is a variable pump and constant horsepower control is performed, but in this case,
Even when turning alone, the third pump cannot output high pressure and large flow, making it difficult to turn on slopes.

Moreover, when starting the rotation, the pressure is IJ IJ-fu pressure (high pressure)
Therefore, almost no flow rate is required, but after that, the pressure is almost constant and the flow rate gradually increases until steady rotation is achieved.However, according to the constant horsepower control of this sixth pump, the required flow rate until steady rotation is achieved. There is a problem in that it is not possible to follow and flow the flow, and it is not compatible with the characteristics of turning work.

The present invention was developed to solve these conventional problems, and is characterized by the use of a variable pump exclusively for swinging and a variable pump for other actuators. The regulator is controlled by a servo valve operated by the secondary pressure from the swing remote control valve that switches the directional control valve, and a pressure cut-off control valve (hereinafter referred to as PC control valve) operated by the discharge pressure of the swing-specific variable pump. Variable only for turning by controlling the pressure oil that leads to 5
- Control the discharge flow rate of the pump and perform pressure cut-off control (hereinafter referred to as PC control) of the swing-only variable pump without constant horsepower control to minimize engine output loss, and reduce the output of the swing-only pump. The main feature is that it allows smooth turning even on sloping ground, improving the workability of turning.

A second feature is that the regulator is provided with a stopper to compensate for the required minimum flow rate of the variable pump exclusively for swinging, thereby ensuring reliable swing operation.

Furthermore, the sixth characteristic point is that the swing-only variable pump and the other actuator variable pumps are controlled in relation to each other, and when the swing-only operation is performed, the setting value of the PC control valve is set to the highest value to achieve high pressure and large flow rate. When the swing is combined with other actuators, the set value of the PC control valve is lowered to lower the discharge pressure of the variable pump for swing, and the discharge flow rate of the variable pump for other actuators is reduced. 6- Thus, the sum of the output horsepower of each pump is controlled to be equal to or less than a predetermined value, and the workability during the complex work can be improved while effectively utilizing the output of the engine.

The present invention will be explained below based on embodiments shown in the drawings.

Figure 1 shows the overall hydraulic circuit diagram of a hydraulic excavator 1.2.
3 is the first. Second. Each sixth variable pump is driven by the engine 4. The discharge circuit 11 of the first pump 1 has an I
The arm cylinder 15 and the left traveling motor 16 are connected via the J IJ valve 12 and the direction control valve 13.14, and the second
The discharge circuit 21 of the pump 2 is connected to a boom cylinder 26. The packet cylinder 27 and the right travel motor 28 are connected, and the sixth
A swing motor 34 is connected to the discharge circuit 31 of the pump 6 via an IJ-F valve 62 and a direction control valve 66, so that the sixth pump 6 is dedicated to swing, and the first... 2nd pump 1,
2 is for other actuators. 35 and 36 are swing brake valves.

Each direction control valve 13. 14. 23. 24°25
．． Reference numerals 33 denote pilot type switching valves which are switched by the secondary pressure from the remote control valves, and in the drawing, only the swing remote control valve 6 and the boom remote control valve 7 are shown, and the other remote control valves are omitted. The remote control valves 6 and 7 introduce primary pressure from the pilot pump 5 to their primary sides, and control the secondary circuit 6 according to the operating angle of the levers 61 and 71.
2.66 and 72.75, and the secondary pressure leads to the direction control valve 65.
．． Switch between 2:6.

The horsepower and the like of each of the pumps 1t2, 3 are controlled by control circuits 8, 9, and a specific example of the control circuit 8.9 is shown in FIG.

In FIG. 2, 81 is a regulator for the sixth pump;
2 is its piston, 83 is a stopper for compensating the minimum discharge flow rate, 84 is a servo valve, 85 is its sleeve, 86 is a PC control valve, 87 is its pressure setting valve, 88 is a variable pressure reducing valve for flow rate command, 89 is a pilot switch Valve 91 is the first valve. The regulator for the second pump, 92 indicates its piston, and 96 indicates a pilot piston.

The piston 82 of the regulator 81 is connected to the swash plate (or slant shaft) of the sixth pump 3 and the sleeve 85 of the servo valve 84.
The discharge oil of the sixth pump 6 is connected to the discharge circuit 31 of the sixth pump 6 and guided to the small diameter side oil chamber by the pilot circuits 37, 37a, and the discharge oil of the third pump 6 is guided to the circuit 37b. The oil is controlled by the servo valve 84 and the PC control valve 86, and the pressure oil is guided to the large-diameter oil chamber.This operation controls the tilting angle of the sixth pump 6, and the discharge of the sixth pump 6 is controlled. The flow rate Q3 is controlled, the movement of the piston 82 of the regulator 81 is regulated by the stopper 86, and the minimum tilt angle of the sixth port/pro, that is, the minimum discharge flow rate Q3min is compensated.

The servo valve 84 is connected to the secondary circuit 62 of the swing remote control valve B.
Switching is controlled by secondary pressure selected from 63 to high pressure by shuttle valve 64 and led to circuit 65.

The PC control valve 86 converts the pressure oil controlled by the servo valve 84 and guided from the discharge circuit 9-61 of the sixth pump 6 to the circuit 86a to the discharge pressure P3 of the sixth pump B guided by the circuit 370. controlled accordingly and guided to the circuit 86b,
It controls the pressure oil led to the large-diameter side oil chamber of the regulator 81, and PC-controls the sixth pump 6. In addition, the pressure setting valve 87 is connected to the secondary circuit 72 and 73 of the boom remote control valve 7.
It is controlled by the secondary pressure selected by the shuttle valve 74 and guided to the circuit 75, and the setting value Pb of the PC control valve 86 is controlled in the range from the maximum value P-σ to the minimum value Pbmin.

The flow rate command pressure reducing valve 88 transfers the pressure introduced into the primary side from the pilot pump 5 to the piston 8 of the regulator 81.
The secondary pressure is controlled according to the movement amount of the pump 2, that is, the tilt angle of the sixth pump 5, and is guided to the secondary side circuit 88a, and the secondary pressure is selectively guided to the circuits 89a and 89b by the pilot switching valve 89, and the pilot The pilot piston 96 is actuated by selectively guiding it to the large diameter side and the small diameter side of the piston 96. The switching valve 89 is the secondary side circuit-1 of the boom remote control valve 7.
〇- 72. The high pressure is selected by the shuttle valve 74 from 73 and switched by the secondary pressure led to the circuit 75.

1st. The regulator 91 of the second pump 1, 2 is operated by the discharge pressure P, p2 led from the discharge circuit 21.31 of the pump 1, 2 by the circuit 17, "29, and the pressing force by the pilot piston 93, The piston 92 controls the tilt angle of the swash plate (i!, or oblique shaft) of the first and second pumps 1 and 2, and the output (discharge flow rate Q1゜Q2) of the first and second pumps 1 and 2 is controlled. ).

Next, the operation of the above hydraulic circuit will be explained.

(3) When the lever 61 of the remote control valve 6 for swing is tilted in the direction of arrow A, secondary pressure is led to the secondary circuit 62, and the secondary pressure is guided in the direction of arrow A1, and the directional control valve 66 is switched to the right position in the figure, and the oil discharged from the sixth pump filter is guided in the direction of arrow A2 and flows into the swing motor 64.

At this time, in FIG. 2, the secondary pressure of the rotary remote controller is guided in the direction of arrow A3 through the shuttle valve 64, and the servo valve 84 is switched to the lower position in the figure.

On the other hand, during this single swing operation, the boom remote control valve 7
Since the lever 71 is in the neutral position and no secondary pressure is introduced into the circuit 75, the PC control valve 86 is set at the maximum setting value P.
b maX and is held in the position originally shown. Therefore, initially, the oil discharged from the sixth pump O is guided in the direction of arrow A4 by the circuit 67, and from the circuit 37a to the regulator 81.
The oil flows into the small diameter oil chamber of the regulator 81 from the circuit 37b, passes through the lower position of the servo valve 84, passes through the upper position of the PC control valve 86, and flows into the large diameter oil chamber of the regulator 81, pushing up the piston 82. The tilt angle of the sixth pump 6 is increased to increase its discharge flow rate Q5.

However, at the time of starting this swing, the swing motor 64 is initially stopped due to inertia load, so when the oil discharged from the sixth pump 6 flows into the suction side of the swing motor 64, the pressure on the suction side immediately rises. Along with this, the discharge pressure P6 of the third pump 6 increases to the brake valve 35. The pressure rises rapidly at 1 corresponding to the set value Pa of '36, becomes higher than the maximum set value Pbmax of the PC control valve 86, and the discharge pressure P3
(== pa) is guided to the pilot boat of the PC control valve 86 by the circuit 370, the PC control valve 86 is immediately switched to the lower position in the drawing, and the servo valve 84 is connected to the large diameter side oil chamber of the regulator 81. The inflow of pressure oil is blocked, and the oil in the large-diameter oil chamber flows out into the tank via the lower position of the PC control valve 86.

Therefore, the oil discharged from the sixth pump 6 flowing into the small diameter side oil chamber by the circuit 37a causes the leg □Slater 8
The first piston 82 is pushed down, the tilt angle of the sixth pump 6 becomes smaller, and the discharge flow rate Q3 of the sixth pump 6 is reduced. In this case, when the piston 82 is pushed down to a predetermined position, it is stopped by the stopper 86, and the required minimum tilt angle of the sixth pump B, that is, the required minimum flow rate Q3min is compensated.

In this way, at the start of the swing alone, the discharge pressure P3 of the sixth pump B becomes the maximum pressure corresponding to the set value Pa of the brake valves 35 and 36, and the discharge flow rate Q3 becomes the required minimum flow rate Q316-m1n compensated by the stopper 83. The rotation is started from point A in Fig. 6.

Next, when the swing motor 64 starts to start, the motor 64
A flow rate commensurate with the rotation flows into the suction side of the pump B, and the pressure on the suction side, that is, the discharge pressure of the sixth pump B, decreases. When the discharge pressure P3 becomes equal to or lower than the maximum setting value Pbmax of the PC control valve 86, the PC control valve 86 is returned to the lower position in the drawing by its pressure setting valve 87, and the discharge oil of the sixth pump 6 is supplied from the circuit 57b. It flows into the large diameter side oil chamber of the regulator 81 via the lower position of the servo valve 84 and the upper position of the PC control valve 84 . At this time, the oil discharged from the sixth pump 6 is flowing into the small diameter side oil chamber, but since the pressure receiving area of the large diameter side oil chamber of the piston 82 is large, the piston 82 is pushed up. The tilting angle of the sixth pump 6 is controlled to be large, that is, the discharge flow rate Q6 is increased.

In such a case, the secondary pressure of the rotary remote controller is controlled by the lever 61.
The spool opening area of the direction control valve 66 is controlled according to the secondary pressure, the flow rate 14- flowing into the swing motor 64 is controlled according to the secondary pressure, and the spool opening area of the direction control valve 66 is controlled according to the secondary pressure. The spool opening area of the servo valve 84 is controlled by the regulator 810.
The flow rate flowing into the large-diameter oil chamber is controlled, and thus the tilt angle and discharge flow rate Q6 of the third pump 3 are controlled.

In other words, the sixth pump 6 is not of a constant horsepower control in which the flow rate is controlled only by its own discharge pressure as in the past, but is of a so-called positive control type in which the discharge flow rate Q3 is controlled according to the operating angle of the swing lever 61. At the time of starting the swing, the maximum pressure corresponding to the set value Pa of the brake valves 65 and 66 and the required minimum flow rate Q, reversely compensated by the stopper 81 of the regulator 81, are set at 3 min, and the swing is started from point A in Fig. 6. , when the rotation starts, the rotation is accelerated at a high pressure corresponding to the maximum setting of the PC control valve 81, P bma, It is possible to turn with high pressure and large flow rate within the range of point A, and a large output can be obtained from the constant horsepower control curve (thin line) based on point A in Fig. 6, and smooth turning acceleration can be achieved even on slopes.

■ Mass during combined operation of swing and boom In Fig. 1, when the lever 71 of the boom remote control valve 7 is tilted in the direction of arrow B, secondary pressure is led to the secondary side circuit 72; is guided in the direction of arrow B1, the direction control valve 26 is switched to the position shown in the drawing, and the second pump 2
The discharged oil is guided in the direction of arrow B2 to the boom cylinder 26.
into the suppression oil chamber.

Therefore, when the boom is working alone, the discharge pressure P2 of the second pump 2 increases in accordance with the boom load pressure, and the pressure P2 is guided in the direction of arrow B3 and flows into the regulator 91 shown in FIG. 2, The movement of the piston 92 is controlled, and the tilting angle of the second pump 2, that is, the discharge flow rate Q2, is controlled.Therefore, the second pump 2 is controlled by the regulator 91 according to its own discharge pressure P2, as in the conventional case, as shown in FIG. The discharge flow rate Q2 is controlled along the constant horsepower control curve shown by the solid line, the boom raising operation is performed at the maximum output, and the output of the engine 4 is utilized to the maximum.

Next, when the lever 61 of the remote control valve for rotation 6 is tilted in the direction of arrow A, the direction control valve 33 is switched by the secondary pressure of the remote control valve 6, as in the operation I above, and the discharge of the sixth pump 6 is Oil flows into the swing motor 34 and a swing operation is performed. However, during this combined work of boom and swing, the secondary pressure led out to the secondary circuit 72 of the boom remote control valve 7 is led in the direction of arrow B4 via the shuttle valve 74,
Flows into the pressure setting valve 87 and sets the set value Pb of the PC control valve 86
Therefore, the output of the third pump 6 (discharge pressure P3) is controlled to be smaller than when the rotation is performed alone.

When the discharge pressure of the sixth pump B becomes higher than the set value Pb of the PC control valve 86 controlled by the secondary pressure of the boom remote control valve 7, the PC control valve 86 moves to the lower position in the drawing. Thereafter, the piston 82 of the regulator 81 is pushed down in the same way as in the operation I above, and the discharge flow rate Q3 of the third pump 6 becomes the minimum flow rate Q3min compensated by the stopper 83, so that the brake The rotation is started at a pressure corresponding to the set value Pa of the valves 35, 36 or the set value of the PC control valve 86-17=P'bK and the minimum flow rate Jmin compensated by the stopper 83. After that,
When the rotation starts, the discharge pressure P6 of the sixth pump B becomes the above p.
When the set value pIJ of the c control valve 86 falls below, the PC control valve 8
6 returns to the upper position shown in the figure, and the servo valve 84 is controlled in a positive control manner according to the operating angle of the lever 61 of the remote control valve 6 by the same action as in the operation of step 1 above, and the regulator is 81 is controlled, and the discharge flow rate Q6 of the sixth pump B is controlled, so that the sixth pump 6
The pressure corresponding to the set value Pb of the p, c control valve 86 controlled by the boom remote control valve 7 and the swing remote control valve 6 is controlled along the control curve shown by the broken line in the figure.
The rotation is accelerated by the flow rate controlled in a positive control manner.

On the other hand, during this complex work, the regulator 81
The variable pressure reducing valve 88 is controlled in conjunction with the control of the tilting angle (discharge flow rate Q5) of the sixth pump 3, and the secondary side circuit 8
8a is controlled, the secondary pressure is guided in the direction of arrow B5, flows into the pilot piston 96 through the piston 18-rot switching valve 89, presses down the piston 96, and presses down the piston 96. The regulator 91 is controlled by the force and the discharge pressure P2 of the second pump 2, and the discharge flow rate Q2 of the second pump 2 is controlled.
The output of the pump 2 is controlled along the control curve shown by the broken line in FIG. 4, and the boom raising operation is performed using the pressure P2 and flow rate Q2 along this control curve.

Furthermore, in this case, when the amount of work of the boom is small and the operation angle of the lever 71 of the boom remote control valve 7 is reduced to reduce the secondary pressure of the remote control valve 7 for switching the boom directional control valve 26. Since the secondary pressure guided to the circuit 75 also decreases, the set value P of the PC control valve 86 decreases;
When the output of the sixth pump 6 is high and the pilot switching valve 89 is in the position shown, the secondary pressure of the variable pressure reducing valve 88 is guided to the large diameter side of the pilot piston 96, and the output of the sixth pump 6 is large. The control amount is too small, the second
The discharge flow rate Q2 of the pump 2 is significantly reduced. In addition, when the work load of the boom is large and the operating angle of the lever 71 is increased to increase the secondary pressure of the boom remote control valve 7, the secondary pressure led to the circuit 75 also increases and the PC The set value Pb of the control valve 86 becomes low, the output of the sixth pump 6 becomes small, and the pilot switching valve 89
is switched to the right position in the figure, the secondary pressure of the variable pressure reducing valve 88 is guided to the small diameter side of the pilot piston 96, the control amount of the regulator 91 becomes small, and the amount of decrease in the discharge flow rate Q2 of the second pump 2 is reduced. becomes smaller.

In this way, during complex work, the boom remote control valve 7 controls the setting value Pb of the PC control valve 86 to control the two discharge pressure ports of the sixth pump B, and the swing remote control valve 6 controls the sixth pump 6. The discharge flow rate Qsk of the second pump 2 is controlled according to the discharge flow rate Qsk of the sixth pump 6.
control the discharge flow rate Q2 of the sixth pump 6 and the second pump 2.
By mutually controlling the outputs of the two, the engine 4 will not be overloaded, and the output of the engine 4 will be effectively utilized to efficiently perform the combined work of turning and raising the boom.

FIG. 5 shows another embodiment of the control circuit 8 of the sixth pump 3 shown in FIGS. 1 and 2. In this embodiment, the piston 82 of the regulator 81 of the third pump 6 is The pressure oil from the pilot pump 5 is guided to the large diameter side oil chamber of the regulator 81 via the servo valve 84, and the secondary pressure led out from the swing remote control valve 6 to the circuit 65 is transferred to the PC. The oil is led to the pilot port of the servo valve 84 via the control valve 86, the discharge oil of the sixth pump B is led to the pilot port of the PC control valve 86 by the circuit 57C, and the oil from the boom remote control valve 7 is led to the pressure setting valve 87. A secondary pressure is introduced into the regulator 81 from the servo valve 84.
From the circuit 84a that leads pressure oil to the large diameter side oil chamber of the same circuit 84a
The pressure of the pressure oil inside is taken out and guided from the circuit 84b to the circuit 89a or circuit 89b via the pilot switching valve 89, and the pilot piston 96 is controlled. The regulator 91 of the second pumps 1 and 2 is configured to be controlled.

According to the control circuit shown in FIG. 5, during the single swing operation, the PC control valve 86 is maintained at its highest setting value, and the control circuit 65 is connected to the swing remote control valve 6. The secondary pressure led to the servo valve 84 through the PC control valve 86 is increased to increase the switching amount of the servo valve 85, and the pressure oil led from the pump 5 to the large diameter side oil chamber of the regulator 81 through the servo valve 85 is increased. The amount of movement of the comb and piston 82 is increased, and the tilt angle of the sixth pump 3 is increased.
The discharge flow rate Q3 is increased, and the switching amount of the servo valve 84, the movement i of the piston 82 of the regulator 81, and the discharge flow rate Q3 of the third pump 6 are controlled in a positive control manner by operating the t/bar 61 of the remote control valve for rotation 6. and the PC
It is possible to rotate at a high pressure corresponding to the maximum setting value of the control valve 86 and a large flow rate.

In addition, during combined work of swinging and boom raising, the set value of the PC control valve 86 is controlled by the secondary pressure of the boom remote control valve 7, and the secondary pressure guided from the swing remote control valve 6 to the servo valve 84 is controlled. , the switching amount of the servo valve 84, the amount of pressure oil flowing from the pump 5 into the large diameter side oil chamber of the regulator 81, the amount of movement of the piston 82, and the tilting angle of the sixth pump 3 are sequentially controlled = 22-. In addition to controlling the maximum discharge pressure and flow rate of the second pump 6, the pressure in the circuit 84a is guided to the pilot piston 96 via the pilot switching valve 89, and the regulator 91 is controlled to control the discharge flow rate of the second pump 2. ,
Therefore, as with the control circuits shown in FIGS. 1 and 2, the combined work of turning and raising the boom can be efficiently performed by effectively utilizing the engine output while preventing overload of the engine 4. .

Alternatively, a PC control valve 86' having the structure shown in FIG. 6 may be used in place of the PC control valve 86 in the control circuit shown in FIG. This PC control valve 86' is controlled by the pilot valve 8 by the secondary pressure from the boom remote control valve 7 led to the circuit 75.
7' leads to the sixth circuit 37C.
The discharge pressure of the pump 3 is guided to the large diameter side or the small diameter side of the pilot piston 86〃, and this piston 86#
By switching the control valve 86', the secondary pressure from the boom remote control valve 6 led to the circuit 65 is controlled and guided to the pilot port of the servo valve 84. The same effects as the PC control valve 86 shown in FIG. 5 can be achieved.

In addition, in each of the above embodiments/examples, the first. Although a common regulator 91 was used to control the discharge flow rate of the second pumps 1 and 2, as shown in FIG. The flow rate command pressure introduced from the circuit 88a shown in the figure or the circuit 84b shown in FIG. Each pump 1 is guided by the command pressure and the discharge pressure of each pump 1, 2.
, 2 may be controlled.

In each of the above-mentioned embodiments, description has been given of the combined operation of turning and raising the boom, but it goes without saying that the circuit of the present invention can also be applied to the combined operation of turning and actuators such as arms and packets.

As explained above, according to the present invention, while using a variable pump exclusively for turning, the pump is controlled by PC instead of constant horsepower control, thereby preventing output loss due to relief as in the conventional case, and By using the servo valve controlled by the swing remote control valve and the PC control valve, the discharge flow rate is controlled in a positive control manner as a high pressure corresponding to the output i of the swing-only variable pump and the set value of the PC control valve. Although it is a variable pump, it produces the same high pressure and large flow rate as a fixed pump, and can turn smoothly even on slopes. Moreover, the horsepower control of the swing-only variable pump uses a "pressure camera constant flow rate" like the conventional swing pump.
Alternatively, instead of "constant horsepower" control, it is controlled as "constant pressure and large flow rate", so it is possible to obtain the optimal pressure-flow characteristics for turning, and the engine horsepower is effectively used for the entire hydraulic system. Available.

Further, according to the second invention, the minimum discharge flow rate at high pressure controlled by the PC control valve of the swing-only variable pump can be compensated by a stopper provided on the regulator,
Rotation start can be performed reliably.

Furthermore, according to the third aspect of the present invention, during the single swing work, the setting value of the PC control valve is set to the maximum value to allow the swing to be performed at high pressure and large flow rate. Sometimes, the set value of the PC control valve is lowered to lower the output of the variable swing pump, and the output (discharge flow rate) of the variable pump for other actuators is lowered, so that the sum of the output horsepower of each pump becomes less than a predetermined value. By mutually controlling each other, the engine's output can be used effectively, and the swing and other actuators can be operated efficiently together.
This makes it possible to improve work efficiency during complex tasks.

[Brief explanation of drawings]

Fig. 1 is an overall hydraulic circuit diagram showing an embodiment of the present invention, Fig. 2 is a hydraulic circuit diagram of main parts showing a specific example of the control circuit of each pump, and Fig. 5 is a hydraulic circuit diagram of the sixth pump dedicated to swinging. Figure 4 is an output control characteristic diagram of the second pump for use with other actuators, Figure 5 is a diagram equivalent to Figure 2 showing another example of the control circuit for each pump, and Figure 6 is A hydraulic circuit diagram showing another embodiment of the PC control valve, FIG. 2 is a hydraulic circuit diagram showing another embodiment of the regulator of the second pump.
6. 1... 1st pump, 2... 2nd pump, 6... 6th pump (swing only), 4... engine, 5... pilot pump, 6... remote control valve for swing ,7...
・Remote control valve for boom, 8, 9...control circuit, 131
14... Directional control valve, 15... Arm cylinder, 1
6...Left travel motor, 23.24.25...Direction control valve, 26...Boom cylinder, 27...Packet cylinder, 28.Right travel motor, 66...Direction control valve, 34. ...Swivel motor, 35.36...Brake valve, 81...Regulator, 86...Minimum flow rate compensation stopper, 84...Servo valve, 86...Pressure cut-off control valve, 87... Pressure setting valve, 88... Variable pressure reducing valve for flow rate command, 89... Pilot switching valve, 9
1...Regulator, 93...Pilot piston. Patent Applicant: Kobe Steel, Ltd. Agent Patent Attorney: Etsushi Kotani 27- 2nd Figure 37 F Vertical 1- =-1 1. 1? / 1, etλ 1 straight 1 1; 1"""-□ i34 1 1 y 11 8f+ ・ p,, 11tr ・ 1 "- 1 → 5 Jaw A=shiβ 14 open nU39-8504G (10) Figure 3" ``Slap f boar ■: No -+ l +-111, -4.74 17i'' ladle 2f +, l 4th
figure

Claims (1)

[Claims] 1. It has a swing-only variable pump and another actuator variable pump, and the swing-only variable pump is operated by secondary pressure from a swing remote control valve that switches the swing direction control valve. A servo valve operated by the discharge pressure of the swing-only variable pump, and a pressure oil controlled by the servo valve and the pressure cut-off control valve are introduced to control the discharge flow rate of the swing-only variable pump. A hydraulic circuit for a hydraulic excavator, characterized in that it is connected to a regulator that controls the hydraulic excavator. 2. It has a swing-only variable pump and a variable pump for other actuators, and the swing-only variable pump has a servo valve operated by the secondary pressure from the swing remote control valve that switches the swing direction control valve, and a swing a pressure cut-off control valve operated by the discharge pressure of a dedicated variable pump;
The servo valve is connected to a regulator that controls the discharge flow rate of the swing-only variable pump by introducing pressure oil controlled by a pressure cut-off control valve, and the minimum discharge flow rate of the swing-only variable pump is connected to the regulator. A hydraulic circuit for a hydraulic excavator characterized by a compensation stopper. 6. A servo valve that has a swing-only variable pump and a variable pump for other actuators, and is operated by secondary pressure from a swing-use remote control valve that switches the swing-direction control valve to the swing-only variable pump, and a swing-only variable pump. It was controlled by a pressure cutoff control valve operated by the discharge pressure of the variable pump, the servo valve, and the pressure cutoff control valve. A regulator that controls the discharge flow rate of the swing-only variable pump is connected by introducing pressure oil, and a pressure signal is introduced from another actuator circuit to the pressure cut-off control valve to set the set value of the pressure cut-off control valve. At the same time, the output horsepower of each of the pumps is controlled by controlling the discharge flow rate of the variable pump for the other actuator according to the discharge flow rate control signal sent to the regulator in the variable pump for the other actuator. A hydraulic circuit for a hydraulic excavator, comprising a control circuit that controls the sum to be equal to or less than a predetermined value.