JPS595166B2 - Control method of pump control hydraulic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pump control hydraulic circuit, and particularly to a method of controlling a pump control hydraulic circuit in which a hydraulic pump and a plurality of actuators are connected in a closed circuit.

In construction machines such as hydraulic excavators, movable members such as arms and arm buckets are operated by hydraulic actuators.

In order to save energy, the operating hydraulic circuit for this actuator is increasingly used in which one or two hydraulic actuators are each connected in a closed circuit to a plurality of double rotary hydraulic pumps via switching valves.

This type of hydraulic circuit switches the switching valve using a control lever corresponding to each actuator, controls the amount of tilting of the swash plate of the hydraulic pump, and supplies pressure oil from the hydraulic pump to a predetermined actuator. However, if the operating lever is operated rapidly, the swash plate tilting speed of the hydraulic pump will also operate rapidly.

Such rapid changes in the speed of the actuator, for example, when driving and stopping a movable member with large inertia, act on the movable member as acceleration and deceleration, making it difficult for the movable member to operate smoothly. It causes shock.

As a result, there was a drawback that the operability was not good.

The present invention has been made based on the above-mentioned problems, and an object of the present invention is to provide a method for controlling a pump control hydraulic circuit with good operability.

A feature of the present invention is that a dual-rotating hydraulic pump is connected in a closed circuit to a plurality of actuators via a switching valve, and the switching valve can be switched and reversed by operating a control lever corresponding to each actuator. In a pump control hydraulic circuit that controls the amount of forward rotation of the swash plate of a hydraulic pump, the maximum value of the swash plate tilt speed of the pump due to the operation of the operating lever is set to a swash plate tilt speed that is suitable for the operation of each actuator. It is determined at each sampling period whether or not the swash plate tilting speed is within the range of .

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 is a diagram showing the overall configuration of a pump control hydraulic circuit to which an example of the control method of the present invention is applied.

In the figure, 1 and 2 are hydraulic cylinders, 3 is a double rotary hydraulic pump, 4 is a swash plate sequential control device for the hydraulic pump 3, and 5 is a closed circuit connecting the hydraulic pump 3 and the hydraulic cylinders 1 and 2. The switching valves provided, 6 is the operating lever of the hydraulic cylinder 1, 7 is the operating amount detector of the operating lever 6, 8 is the operating lever of the hydraulic cylinder 2, 9 is the operating amount detector of the operating lever 8, 10 is the hydraulic pump 3 11 is a switching valve control circuit that determines the priority order of connection with the hydraulic cylinders 1 and 2, and outputs a position switching signal to the switching valve 5 based on this determination.

In this example, a high priority is given to the coupling relationship between the hydraulic pump 3 and the hydraulic cylinder 1.

12 is a pump control circuit that calculates a swash plate tilting speed suitable for each hydraulic cylinder 1, 2 based on the lever operation amount, the output of the switching valve control circuit 11 and the displacement meter 10, and applies this calculated value in the order of the swash plate. output to the rotation control device 4.

The switching valve control circuit 11 and the pump control circuit 12 execute arithmetic processing according to the flowcharts shown in FIGS. 2 and 3.

This calculation process will be described later.

13 is a charge pump, 14 is a relief valve 15 of the charge pump 13, a check valve provided on the outlet side of the charge pump 13, 16 is a flushing valve, 17 is a relief valve provided at the return port of the flushing valve 16, 18 is a hydraulic pump 3 relief valve.

Next, a method of controlling the above-described configuration will be explained using the arithmetic processing flowcharts shown in FIGS. 2 and 3 and the timing chart shown in FIG. 4.

Hydraulic pump 3 when the control method of the present invention is first applied
The operation of the switching valve 5 will be explained with reference to the timing chart shown in FIG.

In FIG. 4, A is the amount of operation of the operating lever 8, B is the amount of operation of the operating lever 6, C is the amount of forward rotation of the swash plate of the hydraulic pump 3, and D is the amount of operation of the operating lever 6.
is the switching signal to the b position of the switching valve 5, and E is the switching signal to the a position of the switching valve 5.
Indicates a switching signal to the position.

The time chart in FIG. 4 shows that at time t1, the operating lever 8 is pulled from neutral to the maximum operating amount in a short period of time, then at time t2, the operating lever 6 is pulled from neutral to the maximum operating amount in a short period of time, and at time t3, the operating lever 6 is pulled from neutral to the maximum operating amount in a short period of time. Operation lever 6
The figure shows the case where the control lever 8 is returned to the neutral position in a short period of time, and the operating lever 8 is returned to the neutral position in a short period of time at time t4.

First, when control is started before time t1, both the operating lever 6 and the operating lever 8 are in the neutral position, so the hydraulic pump 3
The swash plate of is in the neutral position (C), and the position of the switching valve 5 is also in the neutral position (D and E).

Next, at time t1, when the operating lever 8 is suddenly pulled to the maximum operating amount, the switching valve 5 is switched to the a position shown in FIG.
Hydraulic pump 3 and hydraulic cylinder 2 are coupled.

Then, the amount of forward rotation of the swash plate of the hydraulic pump 3 increases at a maximum speed suitable for the operation of the hydraulic cylinder 2.

At this time, the swash plate tilting speed of the hydraulic pump 3 corresponds to the acceleration of the hydraulic cylinder 2, and if the inertia of the load driven by the hydraulic cylinder 2 is small, the maximum value of the swash plate tilting speed is set high. The hydraulic cylinder 1 is accelerated at an appropriate acceleration in response to the operation of the operating lever 8.

Next, when the operating lever 6 is operated at time t2, the connection between the hydraulic pump 3 and the hydraulic cylinder 2 is released, and the hydraulic pressure is Pump 3 must be connected to hydraulic cylinder 1.

However, if the switching is done immediately, a severe shock will occur.

For this reason, first, while maintaining the switching position of the switching valve 5 at the a position, the amount of forward rotation of the swash plate of the hydraulic pump 3 is reduced to return it to neutral.

Since the decreasing speed of the swash plate tilt at this time corresponds to the deceleration of the hydraulic cylinder 2, the hydraulic pump 3 is activated at the swash plate rotation speed corresponding to the appropriate deceleration of the hydraulic cylinder 2, as in the case of acceleration. Return the swash plate to neutral.

Then, after the swash plate returns to neutral, the switching valve 5 is switched to the b position, and the hydraulic pump 3 is coupled to the hydraulic cylinder 1.

Next, in order to accelerate the hydraulic cylinder 1, the amount of tilting of the swash plate of the hydraulic pump 3 is increased.

Since the swash plate tilting speed at this time corresponds to the acceleration of the hydraulic cylinder 1, the appropriate value of the maximum swash plate tilting speed is different from that when the hydraulic cylinder 2 is accelerated.

That is, when the inertia of the load driven by the hydraulic cylinder 1 is larger than that of the hydraulic cylinder 2, the maximum swash plate tilting speed must be set lower.

Even when the operating lever 6 is suddenly returned to neutral at time t3, the rate of decrease in the amount of tilting of the swash plate of the hydraulic pump 3 is controlled to an appropriate maximum value corresponding to the deceleration of the hydraulic cylinder 1.

Then, since the swash plate of the hydraulic pump 3 returns to the neutral state and the wipe operation lever 8 remains pulled, the switching valve 5 switches to the a position, the connection between the hydraulic pump 3 and the hydraulic cylinder 2 is restored, and the hydraulic pressure is restored again. Cylinder 2 is accelerated at an appropriate acceleration.

At time t4, the operating lever 8 is suddenly returned to the neutral position, and even in the case of 1-, the hydraulic cylinder 2 decelerates at an appropriate deceleration, and after the hydraulic pump 3 returns to neutral, the switching valve 5 also returns to the n position (neutral position). return.

The operation of the hydraulic pump 3 and the switching valve 5 when the control method of the present invention is applied has been described above, taking as an example the case where the operating levers 6 and 8 are suddenly operated.
It goes without saying that when the operation lever 8 is operated slowly, the amount of tilting of the swash plate of the hydraulic pump 3 follows the operation amount of the operation lever 6 and the operation lever 8, and changes gradually. .

Next, a control method for realizing the above-mentioned operation will be explained using the flowcharts of FIGS. 2 and 3.

In FIG. 2, the routine on the right side indicated by the dashed line is the same as the routine on the left side, except that the execution procedure inside the broken line is replaced by the switching valve 5a ON, so it can be omitted. be.

First, when control is started before time t1 shown in FIG.
2 starts execution of arithmetic processing according to the routine on the left.

First, initialize this routine.

This is because, in the control method of the present invention, the switching of the switching valve 5 is performed after the swash plate of the hydraulic pump 3 is returned to the neutral position, as described above.

For this reason, a procedure for determining whether the swash plate rotation is neutral is provided at the later stage, and when the swash plate rotation becomes neutral, a flag indicating completion of determination of forward neutrality is set.

Initial setting means that when entering the left-hand routine from the right-hand routine, the order/neutral judgment completion flag is cleared, and if the left-hand routine is to be executed repeatedly, this step is necessary. Skip this and move on to the next step.

The next step is to determine the neutrality of the swash plate rotation.

Since the swash plate rotation is neutral before time t1 in Fig. 4,
Set the completion judgment flag for forward neutral.

Next, the neutral state of the swash plate rotation is determined again, but since the swash plate is naturally in the neutral position, a signal is output to set the switching valve 5 to the neutral position (n position).

Therefore, the hydraulic pump 3 is not coupled to the hydraulic cylinder 1 or the hydraulic cylinder 2.

Next, a temporary tilting command corresponding to the amount of operation of the operating lever 8 is output, but since the operating lever 8 is in the neutral position, the swashplate tilting command is sent to the swashplate control device 4 through the swashplate maximum speed limit control. A rotation speed command is output.

This series of arithmetic processing is performed once at a certain sampling time ΔT.
It is repeated on a number of occasions.

Next, at the time t□ shown in Fig. 4, when the control lever 8 is suddenly operated from neutral to the maximum operation amount, the arithmetic processing moves to the routine on the right side shown in Fig. 2 and is executed according to the priority order determination procedure. .

That is, the initial setting of this routine and the neutral determination procedure for forward rotation of the swash plate are performed, and a signal for switching the switching valve 5 to the a position is output to the switching valve 5.

Next, the operating amount of the operating lever 8 is set as a temporary forward rotation command amount X,
Output to swash plate maximum speed limit control routine.

The calculation process for this swash plate maximum speed limit control is executed according to the flowchart shown in FIG.

In FIG. 3, the provisional forward rotation command amount X based on the lever operation amount described above is compared with the forward rotation command amount Y output to the swash plate control device 4 in the calculation process executed one time before. The deviation Z (=X-Y) is determined.

On the other hand, the position of the switching valve 5 is determined and the appropriate maximum increment ΔY of the swash plate tilting amount per sampling time is selected.

That is, when the switching valve 5 is in the b position, the appropriate value ΔY1 for the hydraulic cylinder 1 is selected as the appropriate maximum increment ΔY, and otherwise, the appropriate value ΔY2 for the hydraulic cylinder 2 is selected as ΔY.

This time, the switching valve 5 is switched to the a position, so ΔY2
is selected and set as the appropriate maximum increment amount ΔY.

Next, the absolute value of the previously calculated deviation Z and the appropriate maximum increment amount ΔY
If I21≦ΔY, the tentative forward rotation command amount X is directly output to the swash plate control device 4 as the swash plate forward rotation command amount Y.

If Z>ΔY, then the sign of Z is determined, and if 2>0, ΔY is added to the forward rotation command amount Y output to the swash plate control device 4 as the result of the previous calculation process.

It is output to the swash plate control device 4 as a new forward rotation command amount Y.

In addition, in the case of ZkuO, the calculation of Y=Y-ΔY is executed and a new forward rotation command amount Y is output to the swash plate control device 4.

In the example of the timing chart in FIG. 4, the operation lever 8 is suddenly operated at time t□, so lzl>Δ
Since Y and Z>0, the new forward rotation command amount Y is the appropriate maximum increment amount ΔY−ΔY for the previous rotation command amount Y.
It is output as a value with 2 added.

Since this calculation is executed once every sampling time ΔT, the amount of forward rotation of the swash plate of the hydraulic pump 3 increases by ΔY2 at time intervals of ΔT.

Therefore, the maximum rotation speed of the swash plate is limited to ΔY2/AT.

When Z-0, that is, the temporary forward rotation command amount X based on the lever operation amount and the forward rotation command amount Y output to the swash plate control device 4 match, the swash plate forward rotation amount is maintained at a constant value.

Next, time t2 in the timing chart of FIG.
By determining the payout priority order by operating the operating lever 6, the arithmetic processing moves to the routine on the left side of FIG.

Then, following the initial settings, a neutral judgment of the swash plate is performed.
If the swash plate tilts, it is at its maximum value and of course it is not in neutral, so first output X-0 to the swash plate maximum speed limit control routine as a temporary rotation command to return the swash plate to neutral. .

At this time, since the switching valve 5 is still held at the a position, the value ΔY2 corresponding to the hydraulic cylinder 2 is selected as the appropriate maximum increment amount ΔY.

And since IZ1 n ΔY and Z ku O, Y
= Y - ΔY is calculated and a forward rotation command amount Y is output to the swash plate control device 4 .

As mentioned before, this process is performed using the sampling time ΔT
Since the rotation is executed once every 20 days, the amount of forward rotation of the swash plate of the hydraulic pump decreases by ΔY2 at time intervals of ΔT.

Therefore, at this time, the swash plate rotation speed iu-ΔY2/ΔT
limited to.

Then, when Z=O, that is, the swash plate returns to neutral, a tilting neutral determination completion flag is set, and the switching valve is temporarily returned to the neutral position.

Subsequently, a temporary forward rotation command X by the operating lever 6 is output to the swash plate maximum speed limit control routine.

In the swash plate maximum speed limit control routine shown in FIG. 3, the calculation of Z=X-Y is performed as before, and then the position of the switching valve 5 is determined.

At this time, since the switching valve 5 has not yet been switched to the b position, the appropriate maximum increment ΔY of the swash plate forward rotation amount is set as ΔY2.
is selected for the time being, and the forward rotation command amount Y=ΔY2 is output to the swash plate control device 4 via the route lzl>ΔY, Z>0.

In the next arithmetic processing cycle, the initial setting and neutral determination completion steps of the routine on the left side of FIG. 2 are skipped and the process moves to the steps surrounded by broken lines.

At this point, the neutral state of the swash plate is determined again, but since Y-ΔY2 was output in the previous cycle, it is not neutral, so an output is output to switch the switching valve 5 to position b, and the hydraulic pump 3 and hydraulic cylinder Combine with 1.

Then, the operation amount of the operation lever 6 is outputted as a temporary forward rotation command amount X to the swash plate maximum speed limit control routine.

In the swash plate maximum speed limit control routine shown in FIG. 3, the deviation Z is calculated in the same manner as before.

Next, since the switching valve 5 has already been switched to the b position, the hydraulic cylinder 1
Select ΔY1 set corresponding to .

Then, through the route lzl>Δy, z>o, Y=
It calculates Y+ΔY and outputs a forward rotation command amount Y to the swash plate control device 4.

Therefore, in each subsequent calculation processing cycle, the amount of forward rotation of the swash plate of the hydraulic pump 3 increases by ΔY1, and the swash plate tilting speed increases by ΔY1.
It is limited to Y1/ΔT.

If ΔY2>ΔY1 is set at this time, the swash plate tilting speed will be smaller than when the hydraulic cylinder 2 is driven.

Then, similarly to when the hydraulic cylinder 2 was accelerated from time t□, Z=0, that is, the swash plate forward rotation command amount Y is
The amount of forward rotation of the swash plate of the hydraulic pump 3 increases until it becomes equal to the temporary forward rotation command amount X corresponding to the operation amount.

Next, when the operating lever 6 is abruptly returned to the neutral position at time t3, the arithmetic processing returns to the routine on the right side according to the priority order determination in the flowchart of FIG.

At this time, initial settings and swash plate neutral judgment are performed first.
Since the swash plate forward rotation amount Y of the hydraulic pump 3 is the maximum value, in order to return the swash plate to neutral, the temporary forward rotation command amount is set as X=O.
is output to the swashplate maximum speed limit control routine.

In this routine, the same control as when the swash plate was returned to neutral at time t2 is performed, but since the switching valve 5 has been switched to the b position, ΔY1 is set as the appropriate maximum increment ΔY of the forward rotation amount.
is selected, and the swash plate forward rotation speed is controlled to -ΔY1/AT.

When the swash plate of the hydraulic pump 3 returns to neutral, a swash plate sequential neutral determination completion flag is set, and then the switching valve 5 is temporarily returned to the n position.

After that, a temporary forward rotation command amount X based on the operating amount of the operating lever 8 is output to the swash plate maximum speed limit control routine, and is again set as the appropriate maximum increment value ΔY of the swash plate forward rotation amount in accordance with the hydraulic cylinder 2. ΔY2 is selected.

Then, the forward rotation amount Y=ΔY2 is output to the swash plate control device 4 through the route lzl>ΔY:2>0.

In the next arithmetic processing cycle, we skip the initial setting of the routine on the right side of Fig. 2 and the neutral judgment completion procedure, and move on to the procedure enclosed by the broken line.This time, we switch the switching valve 5 to position a, and then switch the hydraulic pump 3 and the hydraulic pressure. Connect cylinder 2.

After that, while controlling the swash plate forward rotation speed to ΔY2/AT in the same way as when accelerating the hydraulic cylinder 2 from time t1,
Increase the amount of forward rotation of the swash plate.

At time t4, when the operating lever 8 is abruptly returned to the neutral position, the calculation process moves to the routine on the left side according to the priority determination in the flowchart of FIG.

In this case as well, the initial setting and forward rotation are determined to be neutral, and X=0 is output to the swash plate maximum speed limit control routine as a temporary forward rotation command amount to return the swash plate forward rotation to neutral.

At this time, since the switching valve 5 is in position a, ΔY2 is selected as the appropriate maximum increment amount ΔY, and lzl>Δ
y, z<.

The forward rotation speed of the swash plate of the hydraulic pump 3 is set to -Δ
While controlling to the value of Y2/ΔT, the amount of forward rotation of the swash plate is decreased to neutral.

When the swash plate of the hydraulic pump 3 returns to neutral, the switching valve 5 is switched to the n position to disconnect the hydraulic pump 3 and the hydraulic cylinder 2.

In the above embodiment, the maximum value ΔY/ΔT of the swash plate forward rotation speed was adjusted by keeping ΔT constant and changing ΔY, or conversely, by setting ΔY as a constant unit increment amount and adjusting ΔY.
It can also be implemented by changing T.

The passage of time can be determined by the number of cycles of arithmetic processing.

That is, if a counter is provided that is incremented by 1 each time arithmetic processing is performed, when the content of the counter reaches R, it can be seen that the time ΔT=R·Δt has elapsed.

Here, Δt is the cycle time of arithmetic processing.

Therefore, by comparing the content R of the counter with a constant value N, R
If the swash plate forward rotation command amount Y is increased or decreased when =N, the maximum value of the swash plate forward rotation speed can be controlled.

FIG. 5 shows a flowchart of swash plate maximum speed limit control based on the above-mentioned concept.

In contrast to the method shown in Fig. 3, where 2 types of appropriate maximum increment amount ΔY of the swash plate tilting amount were prepared depending on the position of the switching valve 5,
Here, two types of numerical values N to be compared with the contents of the counter R are prepared in correspondence with the position of the switching valve 5.

That is, when the switching valve 5 is in the b position, the increase timing of the swash plate forward rotation amount is ΔT1=N1Δt, and when the switching valve 5 is in the a position, the increase timing is ΔT2−N2Δt.

Therefore, if N1>N2, the maximum swash plate rotation speed of the hydraulic pump 3 when connected to the hydraulic cylinder 1 will be smaller than when connected to the hydraulic cylinder 2.

The method for controlling a pump control hydraulic circuit according to the present invention is effective when applied to a hydraulic circuit that operates a boom and a packet in a construction machine such as a hydraulic excavator.

In other words, when the hydraulic cylinder 1 shown in Fig. 1 is used as a hydraulic cylinder for boom operation, and the hydraulic cylinder 2 is used as a hydraulic cylinder for packet operation, the packet can be operated rapidly, so the efficiency of processing thousands of packets can be increased. can be increased.

Furthermore, since the boom can be operated at a slow speed when starting and stopping the boom, it is possible to prevent shocks that occur when starting and stopping the boom, which has a large inertia.

Furthermore, in the above embodiment, two hydraulic cylinders are connected to one hydraulic pump in a closed circuit via a switching valve, but a plurality of hydraulic actuators are connected to a plurality of hydraulic pumps in a closed circuit via a switching valve. It is possible to implement this even if

Furthermore, it is also possible to implement the switching valve control circuit and pump control circuit in the above-described embodiments by a microcomputer.

As detailed above, according to the control method of the present invention, the maximum speed of the swash plate rotation of the hydraulic pump can be controlled in accordance with the operating acceleration suitable for each actuator.
High hydraulic pressure is not generated in each actuator even if the operating lever is operated rapidly.

As a result, it is not necessary to consume energy through the relief valve, so energy savings can be achieved, and the shock that occurs when driving and stopping movable members with large inertia can be reduced, so the actuator The operability and work performance of the driven movable member can be improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the overall configuration of a pump control hydraulic circuit to which an example of the control method of the present invention is applied, and FIG. 2 is a diagram showing the processing performed by the priority determination circuit and the swash plate tilting amount calculation circuit shown in FIG. FIG. 3 is a flowchart showing an example of the process performed in the swash plate maximum speed limit control in the flowchart shown in FIG. 2, and FIG. 4 is a flowchart showing the process shown in FIGS. 2 and 3. FIG. 5 is a time chart for explaining the operation when carried out, and is a flowchart showing another example of the processing performed in the swash plate maximum speed limit control in the flowchart shown in FIG. 2. 1.2... Hydraulic cylinder, 3... Double rotary hydraulic pump, 4... Swash plate sequential control device, 5...
...Switching valve, 6...Operating lever for hydraulic cylinder 1, 8...Operating lever for hydraulic cylinder 2,
10...Displacement meter, 11...Switching valve control circuit, 12...Pump control circuit.

Claims (1)

[Scope of Claims] 1. A double rotary hydraulic pump is connected in a closed circuit to a plurality of actuators via a switching valve, and by operating a control lever corresponding to each actuator, the switching valve is switched and the double rotary hydraulic pump is switched. In the pump control hydraulic circuit that controls the amount of tilting of the swashplate of the pump, the maximum value of the swashplate tilting speed of the pump due to the operation of the operating lever is set within a swashplate tilting speed range that is set to be suitable for the operation of each actuator. A control method for a pump control hydraulic circuit, characterized in that it is determined at each sampling period whether or not the maximum value of the swash plate tilting speed is within the set swash plate tilting speed. 2. The maximum value of the swash plate tilting speed is adjusted by keeping a preset sampling period ΔT of the swash plate tilting speed constant and changing its allowable increment amount ΔY. A method for controlling a pump control hydraulic circuit according to scope 1. 3 The maximum value of the swash plate tilting speed is determined by changing the preset sampling period ΔT of the swash plate tilting speed, and determining its allowable increment ΔY.
2. A method for controlling a pump control hydraulic circuit according to claim 1, wherein the adjustment is made by keeping .