JPH06116986A - Hydraulic controller of construction machine - Google Patents

Abstract

PURPOSE:To control pressure of a circuit and flow while controlling electrically the opening of a controlling valve CV equipped with a servo mechanism with a main controller MC and, at the same time, to make it possible to control combined flow of a pair of variable pumps P1 and P2 connected separately to a pair of circuit systems. CONSTITUTION:Independent circuit systems are connected to a pair of variable pumps P1 and P2 and, at the same time, connection between parallel passages 11 of actuators connected to the circuit systems is made through a first confluent valve D1, or such connection can be disconnected. One variable pump P1 is joined to an arm cylinder A side, the other variable pump P2 is joined to a boom cylinder BM side and, at the same time, the first confluent valve D1 and a third confluent valve D3 are provided to those confluent courses.

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.

BACKGROUND OF THE INVENTION In particular, a feature of the present invention is that the pressure and flow rate of the circuit can be controlled while electrically controlling the opening of a control valve having a servo mechanism by a controller. There has never been a hydraulic control device for a construction machine using such a control valve.

SUMMARY OF THE INVENTION The present invention has a pair of circuit systems, and each of the circuit systems is connected with a separate variable pump, and the variable pumps are combined to control the operation of the actuator to be optimum. Is intended for.

[0002]

SUMMARY OF THE INVENTION According to the present invention, two circuit systems in which a plurality of actuators are connected in parallel are individually connected to the respective circuit systems, and the tilt angle is controlled by the output of the regulator to discharge. A pair of variable pumps with variable amounts, a spool valve connected between the actuators and the variable pump and switched by operating means such as a pilot operated valve, and electrically connected upstream of the spool valve. A control valve having a controlled servo mechanism, a stroke sensor for electrically detecting a switching stroke of the control valve, a first pressure sensor for electrically detecting a pressure on an upstream side of the control valve, and a control valve Pressure sensor for electrically detecting the pressure on the downstream side of the control valve, and a control valve based on signals from the stroke sensor and the first and second pressure sensors And a valve controller for electrically controlling the opening.

Further, the signal input to the valve controller and the control signal for the spool valve are input, and the regulator of the variable pump is electrically controlled based on the command signal input in advance and the signal from the valve controller. And a main controller that outputs a signal to the valve controller, a first merging passage that connects one circuit system and the other circuit system, and a first merging valve that blocks or connects the merging passage. When,
A second merging passage that connects the variable pump of one circuit system to the light load actuator side of the other circuit system, and a second merging passage that is provided in this second merging passage, from the variable pump of one circuit system to the above of the other circuit system. A check valve that allows only flow to the light load actuator, a second merging valve that is provided on the upstream side of the check valve and can switch between a throttle position and a free flow position, and the light load actuator of the other circuit system. The priority valve provided upstream of the confluence point of the second confluence passage with respect to, and capable of switching between the free flow position and the throttle position according to the signal from the main controller, and the variable pump of the other circuit system, A third merging passage for communicating with a specific actuator of the circuit system;
A third merging valve provided in the merging passage and capable of switching between the throttle position and the free flow position is provided.

[0004]

Since the present invention is configured as described above, the discharge oil of the variable pump of one circuit system is constantly joined to the light load actuator of the other circuit system via the second joining passage. Further, by opening the first merging valve and merging both variable pumps, it is possible to operate each actuator within the range of the maximum total discharge amount of both pumps. Further, if the priority valve is switched to the throttle position, another actuator having a large load can be preferentially operated.

[0005]

According to the hydraulic control device of the present invention, the first
If you open the confluence valve, each actuator can be operated within the maximum total discharge amount of the variable pumps of both circuit systems. For example, when the required flow rate is insufficient with only one pump, the total of both pumps Maximum flow rate can be used. Since one variable pump is made to communicate with the other light load actuator via the second merging passage, even if this light load actuator becomes runaway,
The supply flow rate is not short enough to cause cavitation. Moreover, since the second merging valve is provided in the second merging passage, it is possible to distinguish between the free flow and the flow imparting throttling resistance. Therefore, if the priority valve is switched to the throttle position, the actuator with a large load can be preferentially operated.

[0006]

In the illustrated embodiment, 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 _{1 is connected} to this one circuit system.
Are connected. The left traveling motor ML, the arm cylinder A, and the turning 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 first merging passage 12 is connected to the upstream side of the control valve CV and the first merging passage 12 is connected.
Is provided with a first merging valve D ₁ . This first merging valve D ₁
Has a configuration in which the first merging passage 12 is shut off when in the normal position shown and the first merging passage 12 is communicated when 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 portion 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 controller is individually connected to each control valve CV. The main controller MC issues a command to the valve controller VC 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, 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 a 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 has a bleed-off throttle 2 which maximizes the opening at the neutral position shown in the figure.
7 is provided. The bleed-off throttle 27 communicates with the parallel passage 11 via a branch passage 28. 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 of the bleed-off throttle 27 becomes smaller. However, in the range where the switching amount is very small, the parallel passage 11 is provided on both the actuator side and the bleed-off throttle 27. Communicate with.

However, the above-mentioned 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. Reference numeral 29 in FIG. 1 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 in FIG. Reference numeral 31 is a mode setting device connected to the main controller MC for setting the flow rate distribution when the antisaturation function is exerted.

Variable pump P _{1 of the} above one circuit system
Is connected to the upstream side of the control valve CV connected to the arm cylinder A via the second merging passage 32. Then, in the second merging passage 32, the check valve 3 which allows only the flow from the variable pump P ₁ to the control valve CV of the arm cylinder A is provided.
3 is provided, and a second merging valve D ₂ is provided on the upstream side of the check valve 33. This second merging valve D ₂ is controlled by the main controller MC, maintains the throttle position in the normal state shown, and maintains the free flow position when switching the throttle position. Further, a priority valve 34 is provided in the parallel passage 11 on the upstream side of the confluence point of the second confluence passage 32. This priority valve 34 is a main controller MC
The free-flow position is maintained in the normal state shown in the figure, and the throttle position is maintained when it is switched. The first pressure sensor 17 is connected to the downstream side of the priority valve 34.

Further, the variable pump P of the other circuit system mentioned above.
₂ is connected to the upstream side of the control valve CV connected to the boom cylinder BM via the third merging passage 35. A check valve 36 that allows only the flow from the variable pump P ₂ to the boom cylinder BM is provided in the third merging passage 35, and a third merging valve D ₃ is provided on the upstream side of the check valve 36. There is. This third merging valve D ₃ is also controlled by the main controller MC, maintains the throttle position in the normal state shown in the figure, and maintains the free flow position by switching it. Further, a check valve 37 is provided on the parallel passage 11 connected to the boom cylinder BM and on the upstream side of the confluence point with the third confluence passage 35. The check valve 37 is configured to allow only the flow to the boom cylinder BM.

Next, the operation of this 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, the pilot pressure of the pilot operation valve 21 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.

Furthermore, when the bleed-off control is performed, the output signal from the pilot operated valve 21 naturally becomes small. However, this output signal is detected by the third pressure sensor 26, and this is output to the main controller MC. input. The main controller MC receiving the signal from the third pressure sensor 26 sends a signal to the valve controller VC of the target actuator, and the minimum set flow rate of the variable pumps P ₁ and P ₂ flows through the opening of the control valve CV. To control. When the pilot operated valve 21 is operated from this state to stroke the spool valve SV of the target actuator, the opening of the bleed-off throttle 27 becomes smaller and the opening of the spool valve SV at the input port side becomes larger. 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 is reduced while keeping the supply flow rate constant, the pressure on the upstream side thereof is increased. 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 degree of the bleed-off throttle 27 is kept at the maximum, so 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.

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.

As a result, the oil discharged from the variable pump P ₂ joins the circuit system on the variable pump P ₁ side via the third joining passage 35, the third joining valve D ₃ and the check valve 36,
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 total maximum flow rate of both pumps, the main controller MC
While functioning, controls the control valve CV to exert the anti-saturation function.

Further, as described above, in the third merging passage 35,
The reason why the third merging valve D ₃ is provided is as follows. For example, one variable pump P _1
When the discharge pressure of ₂ is high, this third merging valve D ₃ maintains the throttle position. If the third merging passage 35 is allowed to flow freely in such a case, the discharge pressure of _one variable pump P ₁ also becomes
The discharge pressure of the other pump P ₂ rises, and the energy loss increases accordingly. Therefore, in order to reduce such energy loss, the third merging valve D ₃ is kept at the throttle position. However, both pumps P
When the discharge pressures of ₁ and P ₂ are equal, there is no energy loss as described above, so the third merging valve D ₃ is switched to the free flow position to eliminate the pressure loss due to the throttle. Further, the check valve 36 is provided in order to prevent the flow rate from flowing backward when the discharge pressure of the one variable pump P ₁ is higher than the discharge pressure of the other pump P ₂ contrary to the above. Is.

Furthermore, when the actuators of both circuit systems are simultaneously operated, and the flow rate of one circuit system is insufficient and the flow rate of the other circuit system is insufficient, 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, it requires a large pressure at the time of starting, but does not require such a large flow rate.
Therefore, when the swing motor TN is activated, the pressure of the swing motor TN is controlled while bleed-off control is performed using the control valve CV and the spool valve SV connected thereto.

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 circumstance, the main controller MC opens the first merging valve D ₁ to merge both variable pumps P ₁ and P ₂ . Further, specifically, when the required flow rate from the pilot operated valve 21 connected to the boom cylinder BM exceeds the maximum discharge amount of the variable pump P ₁ , the main controller MC
Issues an open command to the first merging valve D ₁ and prompts an increase in the discharge amount so that the other variable pump P ₂ can cover the shortage of the required flow rate of the boom cylinder BM. As a result, the boom cylinder BM and the swing motor TN are controlled by the total discharge amount of both pumps P ₁ and P ₂ , and the insufficient flow rate of the boom cylinder BM is also compensated.

At this time, the total 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 that controls 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 actual flow rate and the required flow rate of the boom cylinder BM exceeds the total maximum flow rate of both pumps, the antisaturation function is exerted based on the flow rate distribution determined by the mode setter 31. If the discharge pressures of the two variable pumps P ₁ and P ₂ detected by the first pressure sensor 17 are equal, the first discharge valve D ₁ is opened to merge them, and the total discharge amount of both variable pumps is increased. Each actuator can be operated while being used.

Further, the variable pump P of the above one circuit system
_{Since 1} is always supplied to the arm cylinder A through the second merging passage 32, even if the arm cylinder A becomes a runaway, the supply shortage does not occur. Moreover, since the second merging valve D ₂ is provided in the second merging passage 32, the pressure on the variable pump P ₁ side of _one circuit system does not become extremely low. That is, no matter what the condition of the arm cylinder A is, each actuator of one circuit system can be operated.

If the second merging valve D ₂ is kept at the throttle position, which is the normal position shown in the figure, the discharge pressure of _one variable pump P ₁ can be maintained, so that the actuator of each actuator of the one circuit system can be maintained. Does not affect operation. Also, when one of the actuators is not operating,
If this second merging valve D ₂ is switched to the free flow position, pressure loss due to the restriction can be prevented. The main controller MC controls all the operations of the second merging valve D ₂ . Further, when the arm cylinder A and the swing motor TN are simultaneously operated and the load pressure of the arm cylinder A is high, the priority valve 34 is maintained at the illustrated free flow position. When the second pressure sensor 18 detects that the load pressure of the arm cylinder A has decreased, the main controller
The MC operates to switch the priority valve 34 to the throttle flow position.
As a result, the swing motor TN can be driven preferentially.

According to the hydraulic circuit of the first embodiment as described above, when the counter load acts on the actuator, the opening of the control valve CV is made larger than the command value, and the meter-out flow rate control is automatically performed. Since it switches to, it is possible to reliably prevent the occurrence of cavitation. 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. Also, while merging both circuit systems,
The most appropriate flow rate control is possible within the range of the total maximum discharge flow rate of both pumps, and even if the required flow rate exceeds the total maximum discharge flow rate of both pumps, control that is in the actual situation becomes possible.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment.

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

[Code]

P ₁ variable pump P ₂ variable pump CV control valve SV spool valve 12 1st confluence passage D ₁ 1st confluence valve 13 regulator MC main controller VC valve controller 16 stroke sensor 17 1st pressure sensor 18 2nd pressure sensor 21 spool valve Pilot operated valve as operating means 27 Bleed-off throttle 32 Second merging passage D ₂ Second merging valve 33 Check valve 34 Priority valve 35 Third merging passage D ₃ Third merging 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 two circuit system in which a plurality of actuators are connected in parallel, and a pair of variable circuits that are individually connected to each circuit system and that control the tilt angle by the output of a regulator to make the discharge amount variable. A pump, a spool valve connected between each actuator and the variable pump and switched by operating means such as a pilot operated valve, and a servo mechanism upstream of the spool valve and electrically controlled A control valve, a stroke sensor that electrically detects the switching stroke of this control valve, a first pressure sensor that electrically detects the pressure on the upstream side of this control valve, and an electrical pressure sensor that detects the pressure on the downstream side of this control valve. The second pressure sensor that detects the pressure and the opening of the control valve is electrically controlled based on the signals from the stroke sensor and the first and second pressure sensors. And a signal input to the valve controller and a control signal for the spool valve are input, and the regulator of the variable pump is electrically operated based on the command signal input in advance and the signal from the valve controller. A main controller that controls or outputs a signal to a valve controller, a first merging passage that connects one circuit system and the other circuit system, and a first merging unit that blocks or connects the merging passage. A valve and a second merging passage that connects the variable pump of one circuit system to the light load actuator side of the other circuit system; and a second merging passage that is provided in this second merging passage so that the variable pump of one circuit system is connected to the other circuit A check valve that allows only flow to the above light load actuator of the system, and a check valve installed upstream of this check valve In addition, it is provided on the upstream side of the confluence point of the second confluence passage of the second confluence valve that can switch between the throttle position and the free flow position and the light load actuator of the other circuit system. A priority valve that can be switched between a free flow position and a throttle position according to the above, a third merging passage for connecting the variable pump of the other circuit system to a specific actuator of one circuit system, A hydraulic control device for a construction machine, comprising a third merging valve which is provided in a merging passage and is capable of switching between a throttle position and a free flow position.