JPH06123302A - Oil pressure controller of construction machine - Google Patents

Abstract

PURPOSE:To provide control valves CV in respective circuit systems connected to a pair of variable pump P1, P2, and accurately control the rate of flow which passes through the control valves CV and pressure, etc., downstream from the control valve, and enable any control with abundant variation such as confluence control CONSTITUTION:Each control valve CV is provided with a servo mechanism, and can be servo-controlled by an electric signal. The opening of the control valve CV is detected by each stroke sensor 16, and differential pressure between pressures in front and rear of the control valve CV is detected by firs and second pressure sensors 17, 18. Signals detected by respective sensors 16, 17, 18 are inputted in each valve controller CV, and the control valves CV and a confluence/separation valve D are controlled by valve controllers and a main controller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device most suitable for use in a power shovel which is a construction vehicle.

[0002]

2. Description of the Related Art The conventional hydraulic control system shown in FIG.
A plurality of actuators a ₁ and a ₂ are driven by one variable pump P, and a flow control valve with pressure compensation 1 for each of these actuator circuits and a variable throttle 2 which is functionally held by a spool valve (not shown). Is equipped with. The tilting angle of the variable pump P, that is, the discharge amount is controlled by the regulator 3. The regulator 3 is divided into a bottom side chamber 3b and a rod side chamber 3c by a piston 3a, and a spring 3d is interposed in the rod side chamber 3c. The bottom side chamber 3b is connected to the shuttle valve 4, and the shuttle valve 4 selects the higher load pressure of both actuators a ₁ and a ₂ . Therefore, the maximum pressure of each actuator is introduced to the bottom side chamber 3b. Further, the rod side chamber 3c is configured to guide the discharge pressure of the variable pump P, which is the pressure between the variable pump P and the flow control valve with pressure compensation 1. The regulator 3 thus configured reduces the discharge amount of the variable pump P when the piston 3a moves in the direction of the arrow 5 against the spring 3d, and changes when the piston 3a moves in the direction opposite to the arrow 5. The discharge amount of the pump P is increased.

The flow control valve with pressure compensation 1 has one pilot chamber 1a connected to the upstream side of the variable throttle 2 and the other pilot chamber 1b connected to the downstream side of the variable throttle 2. Then, in addition to the pressure acting on the pilot chamber 1b, the spring force of the spring 6 also acts on the other pilot chamber 1b. Also, one pilot room 1
The control pilot chamber 1 on which the pilot pressure from the control mechanism that controls the flow rate distribution of each actuator acts on the a side
c is also provided.

A flow control valve 1 with pressure compensation as described above
Controls the differential pressure before and after the variable orifice 2 to be equal to the spring force of the spring 6 according to the opening degree of the variable orifice 2.
In other words, regardless of the load pressure of the actuator,
The supply flow rate is kept constant depending on the opening of the variable orifice 2. Further, the discharge pressure of the variable pump P is controlled to be higher than the load pressure by the pressure difference determined by the spring 3d of the regulator 3. As a result, the flow rate to the actuator is
Since it is determined by the differential pressure due to d and the opening of the variable throttle 2, it is not affected by the magnitude of the load, and so-called load sensing control becomes possible.

[0005]

When the hydraulic circuit as described above is used in a power shovel, there are the following problems. That is, when the arm is swung down to the vertical position in order to lower the bucket to the ground, a counter load due to its own weight drop acts on the arm cylinder of the power shovel. However, when the bucket is scraped inward from this vertical posture, a forward load acts on this arm cylinder. Therefore, in the arm cylinder of this power shovel, when the arm is swung down to the vertical posture as described above, it is necessary to perform meter-out flow rate control to throttle the flow rate on the return side of the arm cylinder. When the bucket is scraped inward, meter-in flow rate control for controlling the supply flow rate is required. In order to deal with this, in the above-mentioned conventional hydraulic circuit, the throttle is provided on the meter-out side and the opening of the variable throttle 2 is reduced to prevent the bucket from running out.

However, if the opening of the variable throttle 2 is too small, the supply flow rate cannot keep up with the extension speed of the arm cylinder, causing a problem of cavitation. Therefore, if the opening of the variable throttle 2 is increased, another problem will occur when the load is small. That is, if only the opening of the variable throttle is increased while keeping the same throttle opening on the meter-out side, the throttle resistance on the return side becomes too large with respect to the supply amount when the load is small. Therefore, there is a problem that the pushing pressure from the supply side becomes too large, resulting in energy loss.

In this conventional hydraulic circuit, for example,
I cannot do so-called rolling work while pressing the back of the bucket of the power shovel against the ground. That is, in this conventional hydraulic circuit, since the flow rate proportional to the opening degree of the variable throttle 2 is tried to flow, the circuit pressure rises to the relief pressure when the actuator cannot move, for example, when the rolling operation is performed. Resulting in. Therefore, there is also a problem that pressure control cannot be performed during rolling work.

Further, when it is attempted to drive all actuators with one pump as in the conventional case,
For example, if there is an actuator with a low load pressure and an actuator with a high load pressure, the pump discharge pressure will be the pressure with the higher load pressure. If the pump discharge pressure is high as described above, the opening degree of the variable throttle 2 must be extremely reduced in order to prevent an unnecessary flow rate from being supplied to the actuator having the lower load pressure. However, if the opening of the variable throttle 2 is made extremely small, the pressure loss due to the throttle becomes energy loss and the efficiency becomes poor, and the sound of fluid passing through the throttle becomes loud and the operator feels uncomfortable. . Further, when the horsepower constant control of the pump is performed, the higher the load pressure is, the more the discharge amount is reduced, but as a result, the required flow rate cannot be satisfied. An object of the present invention is to provide a hydraulic circuit capable of preventing cavitation during meter-out, reducing energy loss, and enabling pressure control regardless of the load.

[0009]

SUMMARY OF THE INVENTION According to the present invention, there is provided a variable pump in which a tilt angle is controlled by an output of a regulator to make a discharge amount variable, a spool valve connected between the variable pump and an actuator, and It is premised on a hydraulic circuit of a construction machine having an operation valve for controlling pilot pressure of a spool valve. Based on the above hydraulic circuit, the present invention provides a control valve having a servo valve mechanism connected to each circuit system between a variable pump and a spool valve and controlling a throttle opening degree according to a pilot signal. And a stroke sensor for electrically detecting the switching stroke of the control valve, and a first for electrically detecting the pressure on the upstream side of the control valve.
A pressure sensor, a second pressure sensor that electrically detects the pressure on the downstream side of the control valve, and the opening degree of the control valve is electrically controlled based on signals from the stroke sensor and the first and second pressure sensors. And a valve controller for.

Further, a merging / branching valve for merging or disconnecting both circuit systems is provided on the upstream side of the control valve, and a signal input to the valve controller and a control signal for the spool valve are input. In addition, it is equipped with a main controller that electrically controls the regulator of the variable pump based on a command signal input in advance and a signal from the valve controller, and outputs a signal to the valve controller. The valve is provided with a bleed-off throttle which maintains its maximum opening when it is in the neutral position and whose opening decreases during this switching process and closes at least in the complete switching position.

[0011]

Since the present invention is configured as described above, the opening of the control valve of each circuit system can be freely set according to the signals from the first and second pressure sensors and the stroke sensor. For example, when the second pressure sensor detects that the pressure on the downstream side of the control valve has become equal to or lower than the set pressure, it is determined that the counter load is acting on the actuator,
The opening degree of the control valve can be slightly increased. Further, the pressure difference before and after the control valve can be sensed to perform the same flow rate control as in the conventional case, and the load sensing control similar to the conventional case can be performed by combining the regulator and the control valve.

Further, when the output signal from the operating means is small, the switching amount of the spool valve is small and the bleed-off throttle is open, for example, the main controller is arranged so that the discharge amount of the variable pump maintains the minimum set flow rate. To issue a command. With this configuration, when the output signal of the operating means becomes large and the opening of the bleed-off throttle of the spool valve becomes small, the pressure on the upstream side of the bleed-off throttle increases. When the pressure on the upstream side of the bleed-off throttle becomes higher than the load pressure, the hydraulic oil on the upstream side starts to flow to the actuator side, that is, in this case, the higher the load pressure, the more the flow rate supplied to the actuator. The lower the load pressure, the higher the supply flow rate. This enables so-called rolling work by pressure control. Furthermore, in the case where the flow rate becomes insufficient with only the variable pump of one circuit system, the main controller outputs a switching signal to the merging / branching valve to merge both pumps.

[0013]

According to the hydraulic circuit of the present invention, the opening of the control valve can be freely set by electrically detecting the switching stroke of the control valve and the differential pressure before and after the switching stroke. When the counter load is acting, the opening degree of the control valve can be slightly increased to prevent the occurrence of cavitation. Moreover, when the load is small,
The opening of this control valve can be made sufficiently small to keep the pushing pressure against the actuator low, and the energy loss can be reduced. Further, since the spool valve is provided with the bleed-off throttle, pressure control can be performed while keeping the flow rate small, so that so-called rolling operation can be performed while pressing the back surface of the power shovel against the ground. Further, since the variable pumps are separately connected to the two circuit systems, there is no problem that energy loss becomes large or fluid noise is generated due to the pressure difference between the circuit systems. Moreover, even if the flow rate becomes insufficient with one variable pump, both pumps can be joined by switching the merging / branching valve, so that the flow rate will not be insufficient.

[0014]

[First Embodiment] In the first embodiment shown in FIGS. 1 and 2, one circuit system is constituted by a right traveling motor MR, a boom cylinder BM, and a bucket cylinder BK, and a variable pump P is provided in this one circuit system. ₁ is connected. The left traveling motor ML, the arm cylinder A, and the swing motor TN constitute the other circuit system, and the variable pump P ₂ is connected to the other circuit system. All the actuators of these two circuit systems are all connected in parallel via the parallel passage 11.

A control valve CV and a spool valve SV are connected to all the parallel passages 11. Moreover, in both of these circuit systems, the merging passage 12 is connected to the upstream side of the control valve CV, and the merging / dividing valve D is provided in the merging passage 12. The merging / branching valve D is configured to shut off the merging passage 12 when it is in the normal position shown in the figure, and to communicate the merging passage 12 when it is in the switching position. The tilting angle, that is, the discharge amount of both the variable pumps P ₁ and P ₂ is controlled by the regulator 13. The regulator 13 is electrically controlled by the pump controller PC shown in FIG.

The control valve CV has a servo valve mechanism and has a spring 14 on one side thereof and an electromagnetic control section 15 on the other side thereof. This electromagnetic control unit 1
As shown in FIG. 2, 5 is proportional to the output signal from the valve controller VC connected to each control valve CV,
The control valve CV is operated against the spring 14 to control its opening. However, the control valve CV is designed to have the maximum opening when in the normal position shown in the figure.
Further, the stroke sensor 16 is connected to the control valve CV, the first pressure sensor 17 common to each control valve CV is connected to the upstream side of the control valve CV, and each control valve CV is connected to the downstream side thereof. A separate second pressure sensor 18 is connected. And each of these sensors 16-18 is connected to the valve controller VC, as shown in FIG.

The stroke sensor 16 is a control valve CV.
Is detected, the valve controller VC calculates the opening degree of the control valve CV based on the stroke signal.
The first pressure sensor 17 detects the pressure on the upstream side of the control valve CV, and the second pressure sensor 18 detects the pressure on the downstream side. In this way, the sensors 16-18
As shown in FIG. 2, the valve controller VC that receives a signal from the control valve CV is individually connected to each control valve CV. The main controller MC issues a command to the valve controller CV or the pump controller PC. is there.
In addition, the valve controller VC is a control valve as described above.
It controls the opening of CV and feeds back the signals from these sensors to the main controller MC. The pump controller PC also operates according to a command from the main controller MC, and feeds back the operation status of the regulator 13 to the main controller MC.

In the spool valve SV, the pilot chambers 19 and 20 provided on both sides of the spool valve SV are connected to the pilot operating valve 21 shown in FIG. 2, and are switched in accordance with the pressure signal from the pilot operating valve 21. ing. Further, centering springs 22 and 23 are provided in the pilot chambers 19 and 20, respectively, so that the neutral position shown in the figure is normally maintained. A meter-out throttle 24 is provided in the return passage of the spool valve SV thus configured. The higher pressure of the pilot chamber 19 or 20 is selected by the shuttle valve 25 shown in FIG. 2, and the selected pressure is electrically detected by the third pressure sensor 26. Input to the main controller MC.

Further, the spool valve SV connected to the traveling motors MR and ML is provided with a bleed-off throttle 27 which maximizes the opening at the neutral position shown in the figure. The bleed-off throttle 27 is connected to the parallel passage 1 via the branch passage 28.
It communicates with 1. When the spool valve SV is in the neutral position, the bleed-off throttle 27 configured as described above maintains its opening to the maximum and returns the fluid that has passed through the branch passage 28 to the tank T. Then, as the spool valve SV is switched from the neutral position, the opening degree of the bleed-off throttle 27 becomes smaller.
And communicate with both.

However, the minute switching range differs depending on the type of actuator. For example, in the case of a swing motor TN of a power shovel having a large inertial force, the bleed-off throttle 27 is opened even when the spool valve SV is switched by 80%. On the contrary, in the case of the bucket cylinder BK having a small inertial force, the bleed-off throttle 27 is closed even when the spool valve SV is slightly switched. In FIG. 1, reference numeral 29 is a counterbalance valve provided between the traveling motors MR and ML and the spool valve SV, 30 is a brake valve provided between the swing motor TN and the spool valve SV, and 31 is both traveling. A traveling straight valve that connects the motors MR and ML, and reference numeral 32 in FIG. 2 is a mode setter connected to the main controller MC for setting the flow rate distribution when the antisaturation function is exerted.

Next, the operation of the first embodiment will be described. First, individual control of individual circuit systems will be described, and then composite control for combining pump discharge amounts of both circuit systems will be described. . First, pilot operated valve 2
The pilot pressure of 1 is input to the main controller MC, and the magnitude of this pilot pressure is proportional to the switching amount of the spool valve SV, that is, the required flow rate of the actuator. Then, the main controller MC calculates the total of the required flow rate of each actuator in each circuit system, outputs a flow rate command corresponding to the total flow rate to the pump controller PC, and the variable pumps P ₁ and P ₂ issue the commanded flow rate. The respective regulators 13 are controlled so as to discharge.

Further, the valve controller VC operates by the command signal of the main controller MC to control the control valve CV. The specific control mode is as follows. That is, the valve controller VC includes the stroke sensor 16
The opening degree of the control valve CV is calculated by the signal from, and the first and second pressure sensors 17 and 18 detect the differential pressure before and after the control valve CV. Then, based on this differential pressure signal and the calculated opening value, the flow rate passing through the control valve CV is calculated, and the deviation between the passing flow rate and the command flow rate value from the main controller MC is calculated. , Servo-control the control valve CV so that the deviation becomes zero. In other words, if the calculated flow rate at that time is less than the command flow rate value, the control valve CV
The opening is increased, and in the opposite case, the opening is decreased.

Normally, the meter-in flow rate control is performed as described above, but the valve controller VC constantly monitors the pressure on the downstream side of the control valve CV based on the signal from the second pressure sensor 18. . Then, when the pressure on the downstream side becomes equal to or lower than the set pressure, it is determined that the counter load has acted, and the opening of the control valve CV is commanded from the main controller MC so that the pressure does not drop further. Greater than the value. If the opening of the control valve CV is increased in this way, the control at that time is the meter-out flow rate control by the meter-out throttle 24. That is, in this case, the meter-in flow rate control and the meter-out flow rate control are automatically switched based on the predetermined reference pressure.

Further, in this case, the actual opening area of the control valve CV becomes larger than the flow control command value of the main controller MC, and as a matter of course, the flow rate passing therethrough is also
Since it is larger than the command value, the valve controller VC determines the actual flow rate depending on the opening area of the main controller.
It feeds back to MC and prompts to change the command value of the main controller MC. At this time, if in the anti-saturation state, the main controller MC changes the command value for the other control valve CV in order to prioritize the flow rate supplied to the control valve CV having a large opening area.

Further, when the bleed-off control is performed, the spool valve SV connected to the traveling motors MR and ML is slightly switched. At this time, as a matter of course, the output signal from the pilot operated valve 21 becomes small, but this output signal is detected by the third pressure sensor 26 and input to the main controller MC. The main controller MC that receives the signal from the third pressure sensor 26 sends a signal to the valve controller VC of the traveling system to set the opening of the control valve CV of the traveling system to the minimum set flow rate of the variable pumps P ₁ and P _2. Control to flow. When the pilot operated valve 21 is operated from this state to stroke the spool valve SV of the traveling system, the opening of the bleed-off throttle 27 becomes smaller, and the spool valve SV connected to the traveling motors MR and ML is connected to the input port side of the spool valve SV. The opening becomes large. However, the flow rate supplied to the spool valve SV is maintained at the minimum set flow rate controlled by the control valve CV.

As described above, when the opening of the bleed-off throttle 27 becomes small while keeping the supply flow rate constant, the pressure on the upstream side thereof rises. When the increased upstream pressure becomes higher than the load pressure on the actuator side, the pressure oil in the parallel passage 11 starts to flow to the actuator side. In other words, the higher the load pressure on the actuator, the lower the flow rate supplied to the actuator and the higher the bleed-off flow rate. Therefore, during the so-called rolling operation in which the back surface of the bucket of the power shovel is pressed against the ground, the pressing force of the bucket can be controlled while controlling the pressure.

When the output signal of the pilot operated valve 21 is small and the spool valve SV is in the neutral position, the opening of the bleed-off throttle 27 is kept at the maximum, so that the system pressure of the actuator becomes low. Therefore, if the load pressure on the actuator side is high, the load check valve that receives the pressure remains closed and the flow rate is not supplied to the actuator. Further, in this embodiment, the bleed-off throttle 27 is provided only on the spool valve SV of the traveling system, but with this configuration, bleed-off control of actuators other than the traveling system is also possible. Because both circuit systems are parallel circuits, if the bleed-off flow rate is controlled at one place, the actuator of the circuit system is controlled by the bleed-off flow rate at this one place. However, it is natural that each spool valve SV may be provided with a bleed-off throttle, if necessary.

Next, a composite control for combining the pump discharge amounts of both circuit systems will be described. Now, it is assumed that only a specific actuator of one circuit system, for example, the boom cylinder BM is used, and the required flow rate of the boom cylinder BM exceeds the maximum discharge amount of the variable pump P ₁ .
In such a situation, first, a signal that the required flow rate of the boom cylinder BM exceeds the maximum discharge amount of the variable pump P ₁ is input to the main controller MC. When this signal is input, the main controller MC operates the pump controller PC on the variable pump P ₂ side, and the boom cylinder
The regulator 13 is operated so as to discharge the insufficient flow rate required by the BM.

At the same time, the main controller MC
The diverter valve D is opened to connect both circuit systems. However, at this time, if the control valve CV of the traveling system is opened even a little, the bleed-off throttle 27 operates and the bleed-off control is performed. Therefore, the control valve CV of the traveling system is completely closed. , The main controller MC outputs a signal to the valve controller VC. By setting in this way, the discharge oil of the variable pump P ₂ joins the circuit system on the variable pump P ₁ side via the joining passage 12,
Make up for the insufficient flow rate of the boom cylinder BM. At this time, if the actuators other than the boom cylinder BM are simultaneously operated, the flow rate is naturally controlled within the range of the maximum total flow rate of the variable pumps P ₁ and P _{2 in} the same manner as described above. Moreover, when the total required flow rate of each actuator exceeds the maximum total flow rate of both pumps, the main controller MC
While functioning, controls the control valve CV to exert the anti-saturation function.

Further, when the actuators of both circuit systems are simultaneously operated and the flow rate is insufficient in one circuit system and the flow rate is insufficient in the other circuit system, for example, a boom cylinder of one circuit system is used. A case where the raising operation of the BM and the start of the swing motor TN of the other circuit system are simultaneously performed will be described. In this case, since the swing motor TN has a large inertia, a large pressure is required at the time of starting the swing motor TN, but the flow rate is not so large. Therefore, when the swing motor TN is started, bleed-off control is performed using the control valve CV and the spool valve SV connected to the left traveling motor ML, and the flow rate control is performed by the control valve CV connected to the swing motor TN.

On the other hand, during the raising operation of the boom cylinder BM, a large flow rate is often required although it does not require as much pressure as when the swing motor TN is started. Therefore, in such a situation, the main controller MC opens the merging / branching valve D to merge both variable pumps P ₁ and P ₂ . Further, specifically, the required flow rate from the pilot operation valve 21 connected to the boom cylinder BM is the variable pump P.
_When the maximum discharge amount of ₁ is exceeded, the main controller MC issues an open command to the merge / divide valve D. Variable pump P ₂
On the side, in order to supply the flow rate returned to the tank from the bleed-off throttle 27 to the swing motor TN, a command is issued to close the control valve CV connected to the left travel motor ML. As a result, the circuit pressures of both circuit systems become the same.

At this time, the sum of the required flow rate based on the signal from the pilot operation valve 21 for controlling the swing motor TN and the required flow rate based on the signal from the pilot operation valve 21 for controlling the boom cylinder BM becomes Pump P ₁ ,
Even if the total maximum flow rate of P ₂ is exceeded, the flow rate that actually flows into the swing motor TN at the time of start-up becomes less than the required flow rate. Therefore, the valve controller VC controlling the swing motor TN calculates the flow rate actually supplied to the swing motor TN at this time, and feeds back the actual flow rate signal to the main controller MC. Main controller MC
Is the sum of the above actual flow rate and the required flow rate of the boom cylinder BM. If it is less than the total maximum discharge amount of both pumps P ₁ and P ₂ , the discharge amounts of both pumps are combined within the range of the maximum discharge amount. To compensate for the insufficient flow rate of the boom cylinder BM. If the total of the above actual flow rate and the required flow rate of the boom cylinder BM exceeds the total maximum discharge rate of both pumps,
The antisaturation function is exerted based on the flow rate distribution determined by the mode setter 32.

According to the hydraulic circuit of the first embodiment as described above, when the counter load acts on the actuator, the opening degree of the control valve CV is made larger than the command value to automatically perform the meter-out flow rate control. Since it is switched to, it is possible to reliably prevent the occurrence of cavitation and the like. Further, during the meter-out flow rate control, the main controller MC functions to secure the flow rate required for the pressure control, and the anti-saturation control that appropriately distributes the flow rate to other actuators can be performed.

Further, during the meter-in flow rate control, the control valve CV can perform accurate control and the opening thereof can be appropriately maintained, so that the opening of the control valve CV is not too large and the pushing pressure does not become high. Therefore, unlike the conventional case, the problem that the energy loss increases due to the unnecessary pushing pressure does not occur. When the output signal of the pilot operated valve 21 is small and the switching amount of the spool valve SV is small, pressure control is possible while performing bleed-off control. Therefore, a so-called rolling operation in which the back surface of the bucket of the power shovel is pressed against the ground is also possible. Furthermore, while combining both circuit systems, the most appropriate flow rate control is possible within the range of the total maximum discharge flow rate of both pumps, even if the required flow rate exceeds the total maximum discharge flow rate of both pumps. It is possible to control according to the situation.

The second embodiment shown in FIG. 3 is characterized in that an electric operating device 33 is used in place of the pilot operated valve 21 of the first embodiment. That is, in the second embodiment, as shown in FIG. 4, the operating device 33 is directly connected to the main controller MC, and the spool valve SV is switched by an electric signal according to the operation amount of the operating device 33. It is a thing. By using the operation device 33 in this manner, the signal system can be entirely controlled by electricity. When electrical control is possible in this way, for example, during meter-out flow rate control, the opening of the meter-out throttle 24 of the spool valve SV can be positively reduced to prevent the actuator from running away. In any case, it is possible to increase the variation of the control by electrically controlling everything.

The third embodiment shown in FIG.
Is characterized in that it has three positions of a closed position, a fully open position and a diaphragm position, and the other points are the same as in the first embodiment. Further, in the third embodiment, when the pressure difference between the two circuit systems is large, if the merging / dividing valve D is switched to the throttle position, the pump pressure of the circuit system having the lower pressure will not be increased more than necessary. There is an advantage that energy loss can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment.

FIG. 2 is a circuit diagram of an electric system of the first embodiment.

FIG. 3 is a circuit diagram of a second embodiment.

FIG. 4 is a circuit diagram of an electric system of a second embodiment.

FIG. 5 is a circuit diagram of a third embodiment.

FIG. 6 is a conventional circuit diagram.

[Code] P ₁ variable pump P ₂ variable pump CV control valve SV spool valve 13 regulator D merge / divide valve MC main controller VC valve controller 16 stroke sensor 17 first pressure sensor 18 second pressure sensor 21 as means for operating spool valve Pilot operated valve 27 Bleed-off throttle 33 Similarly, operating device as operating means for spool valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Ozeki 8-7-24 Tsuji, Urawa-shi, Saitama Kayaba Industrial Co., Ltd. Urawa factory (72) Inventor Takahashi Yoneaki 8-7-24 Tsuji, Urawa-shi, Saitama Prefecture Kayaba Industrial Co., Ltd. Urawa Factory (72) Inventor Atsushi Fujii 8-7-24 Tsuji, Urawa-shi, Saitama Kayaba Industrial Co., Ltd. Urawa Factory

Claims (1)

[Claims] 1. A variable pump having two circuit systems, each of which is connected to a variable pump whose displacement is controlled by controlling a tilt angle by an output of a regulator, between the variable pump and an actuator. In a hydraulic control device for a construction machine, in which a spool valve is connected and an operating means for controlling the switching of the spool valve is provided, each circuit system is connected between the variable pump and the spool valve, and a pilot signal is transmitted. A control valve having a servo valve mechanism that controls the throttle opening accordingly, a stroke sensor that electrically detects a switching stroke of the control valve, and a first valve that electrically detects pressure on the upstream side of the control valve. A pressure sensor and a second pressure sensor for electrically detecting the pressure on the downstream side of the control valve,
A valve controller for electrically controlling the opening of the control valve based on signals from the stroke sensor and the first and second pressure sensors is provided, and both circuit systems are joined upstream of the control valve. , Or with a merging / dividing valve that divides them, the signal input to the valve controller and the control signal of the spool valve are input, and based on the command signal input in advance and the signal from the valve controller. Is equipped with a main controller that electrically controls the regulator of the variable pump and outputs a signal to the valve controller. Moreover, the spool valve maintains the maximum opening when it is in the neutral position. , The opening is reduced during this switching process and the bleed is closed at least at the complete switching position. Hydraulic control system for a construction machine, characterized in that a full stop.