JPH02256902A - Hydraulic drive equipment for civil engineering and construction machinery - Google Patents

Abstract

PURPOSE:To prevent the occurrence of hunting by providing a control-force adding means by which, when the demand flow rate of a flow control valve is less than the maximum possible discharge quantity of a main hydraulic pump, a prescribed control force is applied to the driving parts of split-flow compensating valves, while when the former is greater than the latter, another control force is added to the above driving part. CONSTITUTION:A control-force adding means 27 is provided, by which when the demand flow rate of flow control valves, a boom direction control valve 5 and a bucket direction control valve 7, is less than the maximum possible discharge quantity of a main hydraulic pump 2, a prescribed control force is applied to the driving parts 6b, 8b of split-flow compensating valves 6, 8; while when the former is greater than the latter, another control force is added to the driving parts 6b, 8b of the valves 6, 8 so as to operate in the closing direction. Thus, the valves 5, 7 are controlled independently of whether or not the split-flow compensating valves 6, 8 are operated by a disturbance. In other words, since the system for controlling the differential pressures between the front and rear of the respective valves 5, 7 does not constitute a feedback system, the hunting of the split-flow compensating valves 6, 8 due to a disturbance can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is provided in a civil engineering/construction machine such as a hydraulic excavator, and is directed to a plurality of actuators that handle pressure oil from a main hydraulic pump via a plurality of branch compensating valves. This relates to a hydraulic drive device that can divide and supply water to each of the actuators and drive these actuators in a combined manner to perform a desired combined operation.

[Conventional technology]

FIG. 11 is a circuit diagram showing a hydraulic drive system for a hydraulic excavator as an example of this type of conventional hydraulic drive system.

The hydraulic drive device shown in FIG. 11 includes a prime mover 1, a variable displacement hydraulic pump, that is, a main hydraulic pump 2, which is driven by the prime mover 1, and a boom (not shown) that is driven by pressure oil discharged from the main hydraulic pump 2. The actuator includes a boom cylinder 3 that rotates a packet, and a packet cylinder 4 that rotates a packet (not shown).

In addition, there is also a flow control valve that controls the flow of pressure oil supplied from the main hydraulic pump 2 to the boom cylinder 3, that is, a boom directional control valve 5, and a shunt compensation that controls the differential pressure across the boom directional control valve 5. A valve 6, a flow rate control valve that controls the flow of pressure oil supplied from the main hydraulic pump 2 to the packet cylinder 4, that is, a packet directional control valve 7, and a pressure difference across the packet directional control valve 7. A branch compensating valve 8 is provided.

A control force Fa due to the pressure on the upstream side of the branch flow compensation valve 6 and the load pressure is applied to one drive part 6a of the branch flow compensation valve 6 so as to open the branch flow compensation valve 6, and the other drive part 6b
The pressure on the downstream side of this branch compensation valve 6 and the shuttle valve 9 are
．． A control force Fa due to the maximum load pressure of the circuit led through the circuit 10 is applied to close the branch compensating valve 6, and similarly, one driving portion 8a of the branch compensating valve 8 is supplied with the branch compensating valve 1M. Control force F due to pressure on the upstream side of valve 8 and load pressure
b is applied to the other drive unit 8b so that the branch flow compensation valve 8 opens, and a control force Fbz due to the downstream pressure of the branch flow compensation valve 8 and the maximum load pressure of the circuit is applied to the other drive unit 8b to open the branch flow compensation valve 8. 8 is given to close. In addition, the main hydraulic pump 2
The displacement volume is controlled by a control actuator 12 driven by a flow N regulating valve 11 that is switched according to the magnitude of the differential pressure between the pump pressure Ps of the main hydraulic pump 2 and the maximum load pressure Pamax of the circuit. Further, the maximum pressure of the pressure oil discharged from the main hydraulic pump 2, that is, the relief pressure is regulated by the main relief valve 13.

For example, when a boom cylinder 3 and a packet cylinder 4 having different driving pressures are combinedly driven, the pressure on the upstream side of the boom directional control valve 5 is Pz, and the pressure on the downstream side is PLI+ of the packet directional control valve 7. The upstream pressure is P
z2. The pressure on the downstream side is Ptz+, the pump pressure is Ps, the maximum load pressure in the circuit is Pamax+, the differential pressure between pump pressure Ps and the maximum load pressure PamaX, that is, the load sensing differential pressure is ΔPLSr, and the drive section on which the pressure PCI of the flow compensation valve 6 acts. The pressure receiving area of is al, and the pressure receiving area of the drive section on which 1 pressure Pz acts is aZ.

The pressure receiving area of the drive part on which the pump pressure Ps acts is as.The pressure receiving area of the drive part on which the maximum load pressure P amax acts is aml.
, the pressure-receiving area of the drive section on which the pressures P, , 2 of the branch compensating valve 8 act are a, 2 . The pressure-receiving area of the drive unit on which the pressure Pzz acts is aZz, the pressure-receiving area of the drive unit on which the pump pressure Ps acts is ash, the pressure-receiving area of the drive unit on which the maximum load pressure P amax acts is am2, and for convenience, a( , I=a ZI=aL+=a Zz=a Sl=
When am1=a SZ=amz, from the balance of forces acting on the driving part of the shunt compensating valve 6, PLI-at++Ps-a S+=Pz ゝa z, +Pamax-aml
(DHere, a14=a 5I=a ZI=aff
l+, pump pressure Ps and maximum load pressure P amax
Since the differential pressure between the boom directional control valve 5 and
PLS (2).

Similarly, from the balance of forces acting on the drive part of the shunt compensation valve 8, PLI-aLZ+P S-a 5z = P 22 1a Z2 + Pamax・amZ
(3) Here, aLz=a Sz=a Zz=a
mz, the differential pressure PzzPL2 across the packet directional control valve 7 is as follows: PZ2-PL2=Ps-Pamax=Δ
PL! (4) becomes.

As can be seen from equations (2) and (4) above, the boom cylinder 3. Even if the load pressure of each packet cylinder 4 changes individually, the influence of the change in load pressure does not affect other actuators, and as a result, the differential pressure across the boom directional control valve 5 and the packet directional control The differential pressure across the valve 7 is maintained at the same value of ΔPLS. Therefore, the boom cylinder 3. of the pressure oil discharged from the main hydraulic pump 2. The diversion ratio to the packet cylinder 4 is kept constant, and the pressure oil of the main hydraulic pump 2 is transferred to the boom cylinder 3. Each of the packet cylinders 4 has a boom directional control valve 5. A flow rate can be supplied according to the operation amount of each of the packet directional control valves 7, and work by combined operation of the boom and the packet, such as excavation work of earth and sand, can be performed.

[Problem to be solved by the invention]

By the way, in the conventional hydraulic drive device configured as described above, the system for controlling the differential pressure before and after the flow control valve forms a feedback system, so that disturbances acting on the flow control valve may cause the flow flow compensation valve to be affected. Easy to hunt. For example, suppose that when the boom cylinder 3 is driven by operating the boom directional control valve 5, a disturbance is applied to the diversion compensation valve 6, and the diversion compensation valve 6 moves slightly from its balanced position in the direction of closing. . In this case, since the response speed of the main hydraulic pump 2 is not so fast, the discharge flow rate of the main hydraulic pump 2 does not change instantaneously. Therefore, as mentioned above, when the branch compensating valve 6 closes slightly, the pump pressure Ps increases,
A force acting in the opening direction acts on the driving portion 6a of the branch compensating valve 6, and the branch compensating valve 6 is operated in the opening direction. If the amount of change in the differential pressure across the boom directional control valve 5 caused by the operation in the opening direction of the shunt flow compensation valve 6 is larger than the minute amount caused by the above-mentioned disturbance, the force balance point will be exceeded, and this shunt flow compensation will occur. The valve 6 becomes too open and now tries to close. By repeating such an operation, the shunt compensation valve 6 causes oscillation, that is, hunting.

There is a concern that control accuracy may deteriorate due to this hunting.

From the above, in the conventional hydraulic drive system shown in Fig. 11, it takes a great deal of time and effort to prevent hunting caused by disturbances in the shunt compensating valve and improve control accuracy. Therefore, piping design, etc. must be done based on the design, which tends to increase manufacturing man-hours.

Furthermore, even if the product is manufactured as described above, if, for example, another attachment with a different weight is attached instead of the packet, the natural frequency of the vibration system will change, causing hunting and reducing control accuracy. There are concerns that this will decline.

Although it does not have the branch compensation valve that is the premise of the present application, an electronically controlled hydraulic drive device has been proposed in Japanese Patent Application Laid-Open No. 75107/1983 as a device that can distribute and supply the discharge flow rate of a pump to a plurality of actuators. ing. this is,
When the total required flow rate of each actuator is about to exceed the pump's possible discharge flow rate, the controller outputs an operation signal to the flow control valve, that is, the solenoid valve, that controls the drive of the actuator, and the required flow rate of each actuator is proportionally adjusted. The idea is to distribute the flow rate of the pump in accordance with the possible discharge flow rate of the pump and perform composite driving of the actuator. In such conventional hydraulic drive devices, the drive of the solenoid valve is not controlled by feeding back the differential pressure across the solenoid valve. However, on the other hand, the control method of the flow control valve is limited to an electronic control type, and it is not possible to install a manual flow control valve or a pilot type flow control valve, and the circuit design In other words, there is a problem in terms of the degree of freedom in design.

The present invention has been made in view of the above-mentioned actual situation in the prior art, and its purpose is to prevent hunting of the branch flow compensation valve due to disturbances, and to use a pilot type flow control valve as a flow control valve for controlling the drive of an actuator. An object of the present invention is to provide a hydraulic drive device for civil engineering and construction machinery that can be equipped with a manual flow control valve.

[Means to solve the problem]

To achieve this objective, the present invention includes a prime mover, a main hydraulic pump driven by the prime mover, a plurality of actuators driven by pressure oil supplied from the main hydraulic pump, and a plurality of actuators driven by pressure oil supplied to these actuators. The main hydraulic pump is equipped with a flow control valve that controls the flow of pressure oil, and a diversion compensation valve that controls the differential pressure across these flow control valves. In hydraulic drive systems for civil engineering and construction machinery that are capable of combined drive of these actuators by supplying power to each of the actuators via A configuration comprising a control pressure generating means for supplying a predetermined control force to the drive part of the valve, and adding another control force to the drive part of the shunt compensating valve so that the shunt compensating valve operates in the direction of closing when the pressure is large. It's Nishide.

[Effect]

Since the present invention is configured as described above, the differential pressure across the flow control valve basically depends on the control pressure generation means. When the flow rate is smaller than the maximum possible discharge flow rate, a predetermined control force is applied to the driving part of the branch compensation valve, and the flow rate discharged from the main hydraulic pump is supplied to the corresponding actuator via the branch compensation valve and the flow control valve. , a combined drive of these actuators can be realized, and when the required flow rate of the flow control valve is larger than the maximum possible discharge flow rate of the main hydraulic pump, another control force different from the above-mentioned predetermined control force is applied to the branch flow compensation valve. The drive section of the flow control valve is forcibly applied to operate in the direction in which the branch compensation valve closes.
The required flow rate is reduced and a combined actuation of the actuator can be realized within a range that does not exceed the maximum possible delivery flow rate of the main hydraulic pump. Therefore, the flow control valve can be controlled regardless of whether or not the shunt compensating valve operates due to a disturbance.In other words, the system that controls the differential pressure across the flow control valve does not constitute a feedback system, so the shunting compensating valve Hunting can be prevented, and there are no restrictions on the operation method of the flow control valve, so that the pilot type flow control valve 2 manual type flow control valve can be provided.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydraulic drive system for civil engineering and construction machinery according to the present invention will be described below with reference to the drawings.

FIG. 1 is a 1% diagram showing one embodiment of the present invention, and this embodiment also shows, for example, a hydraulic drive device for a hydraulic excavator.

The hydraulic drive device shown in FIG.
A prime mover l equivalent to that shown in Figure 1, a main hydraulic pump 2 consisting of a variable displacement hydraulic pump, a boom cylinder 3 which is an actuator, a packet cylinder 4, and a pilot type flow control valve that controls the drive of the boom cylinder 3. That is, a boom directional control valve 5, a pilot type flow control valve that controls the drive of the packet cylinder 4, that is, a packet directional control valve 7, a branch flow compensation valve 6 that controls the differential pressure across the boom directional control valve 5, A branch compensating valve 8 is provided to control the differential pressure across the packet directional control valve 7. In addition, 20.
21 are respectively bum directional control valves 5. This is a pilot operating valve that generates pilot pressure to drive the packet directional control valve 7, and each pilot pipe line 22.23 and 24.25 is a driving part of the boom directional control valve 5 and the bucket 1 to directional control valve. 7 drive units, respectively. Further, 26 is a flow rate side 1111 means for controlling the flow rate of the main hydraulic pump 2, for example, a control actuator for controlling the displacement of the main hydraulic pump 2, and a control actuator for controlling the displacement volume of the main hydraulic pump 2, and It consists of a flow rate adjustment valve that operates and controls the drive of this control actuator.

In this embodiment, a flow control valve, that is, a boom directional control valve 5. When the required flow rate of the packet directional control valve 7 is smaller than the maximum possible discharge flow rate of the main hydraulic pump 2, the drive part 6b of the diverting compensation valve 6.8.

A predetermined control force is supplied to the branch flow compensation valve 6.8b so that the branch flow compensation valve 6.8 operates in the closing direction when the control force is large.
, 8 drive units 6b, 8b are provided with control pressure generating means 27 for applying another control force.

This control pressure generating means 27 includes a first means for determining the total value of the required flow rate of the flow rate control valve, that is, the required flow rate of the boom directional control valve 5 and the required flow rate of the head and head directional control valve 7, and a main hydraulic pressure It includes a second means for determining the maximum possible discharge flow rate of the pump 2, and a comparison means for comparing the magnitude of the total value determined by the first means and the maximum possible discharge flow rate determined by the second means. Depending on the comparison result of the means, the shunt compensation valve 6,
The driving portions 6b and 8b of 8 include a control pressure generating means 37 for generating a control pressure for driving these branch compensating valves 6 and 8.

Further, in this embodiment, a pilot pressure sensor 28 that detects the magnitude of the pilot pressure generated by the pilot operation valve 20, a pilot pressure sensor 29 that detects the magnitude of the pilot pressure generated by the pilot operation valve 21, and a main From a pump pressure sensor 30 that detects the discharge pressure of the hydraulic pump 2, a rotation speed detection sensor 31 that detects the rotation speed of the prime mover 1, for example, the target rotation speed, and these pilot pressure sensors 28 and 29. Performs arithmetic processing according to the output pilot pressure signal Pi, the pump pressure signal pp output from the pump pressure sensor 30, and the target rotation speed signal N output from the rotation speed detection sensor 31, and outputs a control force signal, Input section 32. Storage unit 33. Arithmetic unit 34. A controller 36 having an output section 35 is provided.

The first means constituting the above-mentioned control no. , pump pressure detection sensor 30
, a rotation speed detection sensor 31, and the above-mentioned controller 36
The comparison means described above is included in the calculation section 34 of the controller 36. The control pressure generating means 37 described above is composed of a solenoid valve 38 connected to each of the driving parts 6b and 8b of the branch compensation valve 6.8, and a pilot oil pressure rA39 connected to the solenoid valve 38. .

Further, the storage unit 33 of the controller 36 described above stores the functional relationship between the discharge pressure of the main hydraulic pump 2 and the displacement volume of the main hydraulic pump 2, and also stores the functional relationship between the discharge pressure of the main hydraulic pump 2 and the displacement of the main hydraulic pump 2. As shown in FIG. The pilot pressure Pi generated by .21 and the boom directional control valve5. The functional relationship between the packet directional control valve 7 and the required flow rate gi, and the third
As shown in the figure, boom directional control valve 5. Set differential pressure ΔP that is set corresponding to the differential pressure across the packet directional control valve 7
The functional relationship between the control force F and the control force F that drives the solenoid valve 38 is stored. In addition, P and P2 shown in the above-mentioned FIG. 2 indicate pilot pressures generated by the pilot operating valves 20 and 21, respectively. #.

Numeral 2 is a boom directional control valve 5 which is operated by pilot operating valves 20 and 21. Each required flow rate of the packet directional control valve 7 is shown. In addition, f in Fig. 3 is the branch compensating valve 6.
, 8 shows the force of the springs 6c, 8c that bias the drive parts 6a, 8a. Further, ΔPM and ΔP indicate a target differential pressure and a controlled differential pressure, which will be described later, and F indicates a control force corresponding to the controlled differential pressure ΔP7.

Further, the calculation unit 34 of the controller 36 described above performs calculations for determining the required flow rate of the flow rate control valve based on the pilot pressure signal Pi output from the pilot pressure detection sensors 2B and 29 and the functional relationship shown in FIG. The functional relationship between the pump pressure signal pp output from the pressure detection sensor 30, the target rotation speed signal N output from the rotation speed detection sensor 31, the discharge pressure of the main hydraulic pump 2, and the displacement volume of the main hydraulic pump 2. Based on this, calculation is performed to determine the maximum possible discharge flow rate of the main hydraulic pump 2, and the boom directional control valve 5. When the required flow rate of the packet directional control valve 7 is smaller than the maximum possible discharge flow rate of the main hydraulic pump 2, a predetermined target differential pressure ΔPX that is desirable on the circuit is set to these boom directional control valves 5. a first setting means for setting a set differential pressure ΔP corresponding to the differential pressure across the packet directional control valve 7; and a boom directional control valve 5. When the required flow rate of the packet directional control valve 7 is larger than the maximum possible discharge flow rate of the main hydraulic pump 2, the control differential pressure ΔP is smaller than the above-mentioned target differential pressure ΔPx.
, the directional control valve for the boom 5. It includes a second setting means for setting a set differential pressure ΔP corresponding to the differential pressure across the packet directional control valve 7, and sets the set differential pressure ΔP set by the first setting means and the second setting means. Calculation is performed to obtain the corresponding control force F.

The operation of the embodiment configured as described above is as follows.

Suppose now that a combined boom and bucket operation is intended for excavating earth and sand, etc., and the main hydraulic pump 2 is driven by the operation of the original machine 1, and each of the pilot operating valves 20 and 21 is operated. It is assumed that the boom directional control valve 5 and the packet circumferential directional control valve 7 are each switched to one of the positions. At this time, the controller 36 performs arithmetic processing according to the procedure 1fh'j shown in FIG.

That is, first, as shown in step S1, the controller 3
The pilot pressure signal Pi output from the pilot pressure sensors 2B and 29 is input to the calculation unit 34 via the input unit 32 of 6.
and the pump pressure signal p output from the pump pressure sensor 30.
p and the target rotational speed signal N output from the rotational speed detection sensor 31 are read. Next, the process moves to step S2, and calculations are performed to determine the required flow rate of each directional control valve 5.7 based on the pilot pressure signal Pi. At this time, the calculation unit 3
4, the functional relationship shown in FIG. 2 stored in the storage unit 33 is read out, and the required flow rate of the boom directional control valve 5 is determined from the pilot pressure P i =P of the pi-four-operated valve 20. From the pilot pressure Pi of the pilot operated valve 21 = P2, the required flow rate of the packet directional control valve 7 is determined as 11=Si2. Then step S
Moving on to step 3, a calculation is performed to obtain the total value Qv of the required flow rates of the directional control valves 5 and 7, that is, Qv=excess+#2 (5).

Next, the process moves to step S4, where calculation is performed to determine the maximum possible discharge flow rate Qp of the pump. At this time, pump pressure sensor 3
From the pump pressure signal Pp output from 0 and the known functional relationship stored in the storage unit 33, that is, the functional relationship between the discharge pressure of the main hydraulic pump 2 and the displacement of the main hydraulic pump 2, the The displacement volume is calculated as l (Pp), and from the target rotation speed signal N output from the rotation speed detection sensor 31 and the above displacement volume # (Pp), the maximum possible discharge flow rate Qp is calculated as follows: Qp=N-multi( P p ) (6) is obtained.

Next, moving to step 11iS5, the comparison means included in the calculating section 34 compares the total value Qv of the directional control valve required flow rate obtained in step 1+ll'is3 and the pump maximum possible discharge flow rate Qp. As a result of this comparison, the total required flow rate Q
When it is determined that V is smaller than the pump maximum possible discharge flow rate Qp, the process moves to Hand+1LITs6. In step S6, the first setting means included in the arithmetic unit 34 performs a setting, that is, a process of setting the target differential pressure ΔPX, which has the functional relationship shown in FIG. 3, to the set differential pressure P. Then hand 11q S
Move on to 7. In this step S7, a calculation is performed to obtain the control force F corresponding to the set differential pressure ΔP from the functional relationship shown in FIG. In this case, according to the functional relationship shown in Figure 3, the set differential pressure ΔP
- The control force F is determined to be 0 when the target differential pressure ΔPX is reached.

Next, the process moves to step S8, and the control surface signal (F=O) obtained in step S7 is outputted from the output section 35 of the controller 36 to the drive section of the electromagnetic valve 38.

In this case, since the value of the control force signal is O, no control pressure is generated in the solenoid valve 3 days. At this time, since the force of the spring 6c is f, the balance of forces acting on the driving part of the shunt compensating valve 6 is PLI ・aL++ f = P
z+ ・a ZI (7) Here, aLI=az
, so the differential pressure Pz before and after the boom directional control valve 5,
-PL, is P z HPLI= f/ aLI
(s). Similarly, since the force of the spring 8c is f, the balance of forces acting on the drive part of the shunt compensating valve 8 is as follows: PLz・aLz+f=P Zz −a Zz
(9) Here, since aL2-azz-aLI, the differential pressure Pzz between the front and rear direction control valves 7
Ptz is: PZ2 Ptz=f/aLt 00
). Since f+''Ll in (8) and (9) above are constants, their respective right sides are constant and tend to be equal to each other.

In general, if the flow rate passing through a directional control valve is Q, its opening area is A, the differential pressure across this directional control valve is ΔP, and the proportionality constant is K, then there is a relationship of Q = K - A - (ΔP (I+)). From this, the through flow of the boom directional control valve 5 and the bucket directional control valve 7 shown in Fig. 1 above is Q+, Qz, and their opening areas are A, , A2.
, the proportionality constant to 5. Kz, for the boom directional control valve 5, Q+ = + ・At ・I−P
ZI PLI α2) holds, and the above (8)
From 2, Q, = to, -AI -f/a, (13)
It can be expressed as Regarding the packet directional control valve 4, Q2=2 ・A2 ・%l”P Zz ' PL2
04) holds, and from the above equation 00), this round equation can be expressed as Q2 = 2 ・A2 ・f completion fuwa meeting, 05).

Therefore, the flow division ratio 0- + /Q 2 of the boom directional control valve 5 and the bucket directional control valve 7 is 03 as described above.
), 05) From the formula, Q I / Q 2 - K l - A 1
・4-1cho--Len' 8 1bu/K Z
・A2 ・rm knee, ・A I/K 2 ・A 2 (I
It becomes Q. Here, K, 2. △1. Since A2 is a constant, the right side of the above 0(i)2 is constant.

That is, the directional control valve 5 for the boom and the directional control valve 7 for the bucket are each QfJl, and the meteors Q, , Q-
The ratio of boom cylinders 3 and 2 remains constant regardless of variations in the load pressures of other actuators. The packet cylinder 4 has a boom directional control valve 5. A flow rate corresponding to the opening area corresponding to the operation amount of the packet directional control valve 7 is supplied, and a desired composite drive can be realized.

Further, when the determination in step S5 of FIG. 4 described above is satisfied, that is, when the total value Qv of the required flow rates of the directional control valves 5.7 is larger than the maximum possible discharge flow rate Qp of the pump, the process moves to step S9. In this step S9, the control differential pressure ΔP is calculated, for example, using the following calculation formula.

ΔPv=ΔPX −h (Qp/Qv) Q7
) Here, h (Qp/Qv) represents a function of Qp/Qv. Next, move to hand t+lN5IO and set the set differential pressure Δ
A setting is made in which P is the control differential pressure ΔP obtained in step S9. This set differential pressure ΔP=ΔPy is smaller than the target differential pressure ΔP, for example, as shown in FIG. Next, the process moves to step S7, where the functional relationship shown in FIG. 3 stored in the storage section 33 is read out to the calculation section 34, and the control force F corresponding to the set differential pressure ΔP is determined. In this case, set differential pressure ΔP=ΔP
The control force F corresponding to v becomes Fy, which is larger than 0.

Next, the process moves to step S8, and a control force signal (F=FY) is output from the output section 35 of the controller 36 to the drive section of the solenoid valve 38. As a result, the solenoid valve 38 is opened as appropriate, and the pilot pressure of the pilot hydraulic pressure source 39 is applied to the branch compensation valve 6 as a control pressure corresponding to the above-mentioned control force Fv via the solenoid valve 38.
, 8 to the drive unit 6b 8b. At this time, the balance of forces acting on the drive part of the shunt compensating valve 6 is as follows: PLt・aL++f=PZ1 +Fv (1B
) Here, since all=azl, the differential pressure Pz, -P, across the boom directional control valve 5 is: P ZIPt+= (f Fy )/at+ 0
9). Similarly, the balance of forces acting on the driving part of the shunt compensating valve 8 is as follows: PI3-aLzf = P Z2 ・82g + F
Y C2 [1) Here, ;3Lz=a Zz =at
+, so the differential pressure Pz across the packet directional control valve 7
2 PL2 is P Z2 -PL2=Cf-Fy)
/at+ (21). By the way, the characteristic line in Figure 3 can be expressed as F = f - α · ΔP (22), where α is the proportionality constant, and since F = Fv and ΔP = ΔP7, these can be expressed as (22 ), F, f=f−α
・ΔP? (23), and this (2
3) Modifying the equation, f-FV=cr-ΔP v
(24). This equation (24) is converted into the above (
19), Substituting into formula (21), PZI PLI=α・ΔP y / a Ll
(25) P Zz −P,, 2=a ・ΔP v /
a t+ (26). Therefore, the flow rate Ql passing through the boom directional control valve 5 and the flow rate Q2 passing through the packet directional control valve 7 are respectively Q+= + ・A1 ・Ji−Fukoko (27)
Q2 = 2 ・A2 ・ α・Δ YaLl (28), and the current division ratio Q, /Q, is Q+ /Qt = + ・AH−Cl−APy /
a1/2 ・A2 ・Fi・ΔP v / a Ll
= 1 ・A l /K Z ・A2 (29), which is constant. Therefore, in this case as well, the boom directional control valve 5. The flow rate corresponding to the operation amount of each of the packet directional control valves 7 is controlled by the boom cylinder 3. The water can be divided and supplied to each of the packet cylinders 4, and stable composite driving can be realized.

In the embodiment configured in this way, as described above, the control pressure generating means 27 drives the branch compensating valves 6 and 8.
It depends on the target differential pressure ΔPX set by the first setting means of the calculation unit 34 of the controller 36 or the control differential pressure P Y set by the second setting means, that is, the set differential pressure ΔP, Moreover, this set differential pressure ΔP does not feed back the fluctuation in the differential pressure across the directional control valves 5 and 7 due to the operation of the branch compensating valves 6 and 8, so if a disturbance is applied to each of the branch compensating valves 6 and 8, stable control accuracy is obtained without causing hunting even when
Even if another attachment with a different weight is attached instead of the packet, stable control accuracy can be obtained without any influence.

Further, in this embodiment, hydraulic pilot type flow control valves can be provided as the boom directional control valve 5 and the packet directional control valve 7, and these flow control valves are not limited to electromagnetic valves.

FIGS. 5 and 6 are circuit diagrams showing other embodiments of the present invention.

The embodiment shown in FIG.
0. A packet directional control valve 41 is provided, and
These boom directional control valves 40. The first means for determining the required flow rate of the packet directional control valve 41 is a stroke detection sensor 42 that detects the operating stroke of the boom directional control valve 4o, and a stroke detection sensor that detects the operating stroke of the packet directional control valve 41. 43, a storage section 33 of a controller 36, and a calculation section 34. Although not shown in the storage unit 33 of the controller 36, the boom directional control valve 40 ensures excellent control accuracy, and the flow control valve is not limited to a solenoid valve, but also a pilot flow control valve or a manual flow control valve. This has the effect of increasing the degree of freedom in design compared to the conventional method.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the hydraulic drive system for civil engineering and construction machinery of the present invention, and FIGS. 2 and 3 show functional relationships stored in the storage section of the controller shown in FIG. 1, respectively. 4 are flowcharts showing the procedure of processing performed by the controller shown in FIG. 1, FIGS. 5 and 6 are circuit diagrams showing other embodiments of the present invention, and FIGS. 7 and 9. FIG. 10 is a diagram showing another example of the shunt compensation valve, respectively.
Fig. 8 shows the controller 1-- corresponding to the shunt compensation valve shown in Fig. 7.
---- Prime mover, 2---Main hydraulic pump, 3-boom cylinder, 4-1111--Packet cylinder, 5-boom directional control valve, 6---Diversion compensation valve, 7. -Packet directional control valve, 8-...-Diversion compensation valve, 20.21
-・----Pilot operated valve, 22, 23゜24,
25-----Pilot pipe line, 27--Control pressure generation means, 28, 29--Pilot pressure sensor, 30-----Pump pressure sensor, 31--
-Rotation speed detection sensor, 32--...input section, 33--
---1 storage section, 34--calculation section, 35---output section, 36--controller, 37-------
Control pressure generation means, 38--Solenoid valve, 39--Pilot oil pressure source, 40--Boom directional control valve, 4 L
--------Packet directional control valve, 42, 43-
1111...Stroke detection sensor, 44°45-
------1 drive device, 4-6.47・----1 branch flow compensation valve, 48-・-・・-relief valve, 49-・-・
-・Hydraulic pressure source, 50-・Diversion compensation valve, 50 c------
--Spring, 50 d---- Set force variable means. Figure 1

Claims (9)

[Claims] (1) A prime mover, a main hydraulic pump driven by the prime mover, a plurality of actuators driven by pressure oil supplied from the main hydraulic pump, and the flow of pressure oil supplied to these actuators. The actuator is equipped with a flow rate control valve that controls the flow rate control valve, and a branch flow compensation valve that controls the differential pressure between the front and rear flow rate control valves. Hydraulic drive systems for civil engineering and construction machinery that can supply each of these actuators and drive these actuators in combination,
When the required flow rate of the flow rate control valve is smaller than the maximum possible discharge flow rate of the main hydraulic pump, a predetermined control force is supplied to the drive section of the branch flow compensation valve, and when the flow rate is larger than the maximum possible discharge flow rate of the main hydraulic pump, the flow rate control valve operates in the closing direction. 1. A hydraulic drive device for civil engineering and construction machinery, comprising control force adding means for adding another control force to the drive section of the shunt compensating valve. (2) The control force adding means includes a first means for determining the required flow rate of the flow control valve, a second means for determining the maximum possible discharge flow rate of the main hydraulic pump, and the required flow rate determined by the first means. The hydraulic drive system for civil engineering and construction machinery according to claim 1, further comprising comparison means for comparing the maximum possible discharge flow rate determined by the second means. (3) The second means includes a pump pressure detection sensor that detects the discharge pressure of the main hydraulic pump, a rotation speed detection sensor that detects the rotation speed of the prime mover, and the discharge pressure of the main hydraulic pump and the displacement of the main hydraulic pump. a storage unit that stores the functional relationship between
and calculating the maximum possible discharge flow rate of the main hydraulic pump based on the pump pressure signal output from the pump pressure detection sensor, the rotation speed signal output from the rotation speed detection sensor, and the functional relationship stored in the storage section. 3. The hydraulic drive system for civil engineering and construction machinery according to claim 2, further comprising a controller having an arithmetic unit that performs the following operations. (4) The flow control valve is a pilot type flow control valve driven by pilot pressure, and the first means includes a pilot pressure detection sensor that detects the pilot pressure, and a sensor that detects the pilot pressure and the required flow rate of the flow control valve. The controller includes a storage section that stores a functional relationship, and a calculation section that calculates a required flow rate based on the pilot pressure signal output from the pilot pressure detection sensor and the functional relationship stored in the storage section. Claim (3)
Hydraulic drive system for the civil engineering and construction machinery described. (5) The flow control valve is a manual flow control valve that is driven by manual operation, and the first means includes a stroke detection sensor that detects the operating stroke of the manual flow control valve; The controller includes a storage unit that stores a functional relationship of the required flow rate, and a calculation unit that calculates the required flow rate based on the operational stroke output from the stroke detection sensor and the functional relationship stored in the storage unit. Civil engineering as described in claim (3)
Hydraulic drive system for construction machinery. (6) The hydraulic drive system for civil engineering/construction machinery according to claim (3), wherein the comparison means is included in the calculation section of the controller. (7) When the required flow rate of the flow control valve is smaller than the maximum possible discharge flow rate of the main hydraulic pump, the calculation unit of the controller sets a predetermined target pressure differential that is desirable on the circuit to the differential pressure across the flow control valve. a first setting means for setting a set differential pressure; and a first setting means for setting a control differential pressure that is a value smaller than the target differential pressure when the required flow rate of the flow control valve is larger than the maximum possible discharge flow rate of the main hydraulic pump. 4. The hydraulic drive system for civil engineering and construction machinery according to claim 3, further comprising a second setting means for setting a set differential pressure corresponding to a differential pressure across the flow control valve. (8) Claim (7) characterized in that the control force adding means includes a control pressure generating means that generates a control pressure corresponding to the control force calculated by the calculation section of the controller and applies it to the drive section of the branch compensation valve. ) Hydraulic drive system for civil engineering and construction machinery. (9) Claim (9) characterized in that the control force adding means includes a drive device that operates in accordance with the control force calculated by the calculation unit of the controller and applies the corresponding control force to the drive unit of the shunt compensation valve. 7) Hydraulic drive device for the civil engineering/construction machinery described above.