JPH04370404A - Hydraulic cylinder controller - Google Patents

Abstract

PURPOSE:To stably control the action of a hydraulic cylinder. CONSTITUTION:A pressure compensation circuit 16 outputs control signals to control a serve valve 13 so that a load pressure may become equal to the objective pressure value. A speed compensation circuit 17 outputs control signals to control the servo valve 13 so that a cylinder speed may become equal to the objective speed value. A determination circuit 21 determines to control either loading pressure or cylinder speed based on a pressure comparing signal from a pressure comparing circuit 22 and a speed comparing signal from a speed comparing circuit 23 in the case where either the load pressure or cylinder speed reaches its objective value so as to output determination signal. A change- over switch 18 switches and selects a control signal based on the one mentioned above according to the determination signal from the determination circuit 21 and outputs the signal to the servo valve 13. The action of the hydraulic cylinder is stably controlled by thus always monitoring the load pressure and the cylinder speed and automatically switching pressure control and speed control according to the loading state.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to improvements in hydraulic cylinder control devices.

0002

[Prior Art] Conventionally, hydraulic cylinder control devices for controlling the operation of hydraulic cylinders used in injection molding machines, etc.
There is one as shown in FIG. This hydraulic cylinder control device uses a pressure detector 4 to detect the operating pressure (corresponding to load pressure; hereinafter referred to as load pressure) of pressure oil that operates the hydraulic cylinder 1 . On the other hand, the operating speed of the hydraulic cylinder 1 (hereinafter simply referred to as cylinder speed) is detected by a speed detector 5. The pressure signal representing the load pressure detected by the pressure detector 4 and the speed signal representing the cylinder speed detected by the speed detector 5 are sent to the control section 2, which controls the pressure compensation. It has a circuit 6 and a speed compensation circuit 7. Then, the pressure compensation circuit 6 controls the servo valve 3 based on the pressure signal from the pressure detector 4 and the pressure command signal input from the outside.
Outputs a control signal for feedback control of the operation. On the other hand, the speed compensation circuit 7 outputs a control signal for feedback controlling the operation of the servo valve 3 based on the speed signal from the speed detector 5 and the speed command signal input from the outside.

When the pressure control selection signal is output from the input circuit 9, the changeover switch 8 selects the pressure compensation circuit 6 side and sends the control signal from the pressure compensation circuit 6 to the servo valve 3. . On the other hand, when the speed control selection signal is output from the input circuit 9, the speed compensation circuit 7 side is switched and selected, and the control signal from the speed compensation circuit 7 is sent to the servo valve 3. In this way, when the pressure compensation circuit 6 side is selected by the changeover switch 8, feedback control based on the load pressure (hereinafter simply referred to as pressure control) is performed, while when the speed compensation circuit 7 side is selected. Feedback control (hereinafter simply referred to as speed control) based on cylinder speed is performed.

[0004] The changeover switch 8 by the input circuit 9
The control is performed, for example, as follows. That is,
A proximity switch 10 is installed to detect that the piston rod of the hydraulic cylinder 1 has moved by a predetermined length, and a detection signal from the proximity switch 10 is input to an input circuit 9. The input circuit 9 outputs a speed control selection signal when the detection signal from the proximity switch 10 is not active, and outputs a pressure control selection signal when the detection signal from the proximity switch 10 is active.

[0005]

As described above, the control of the hydraulic cylinder 1 in the conventional hydraulic cylinder control device described above is based on the pressure control selection signal and the speed control selection signal from the input circuit 9 based on the position of the piston rod. Either control or speed control is selected and executed. Therefore, when the above speed control is being carried out, it is completely impossible to carry out pressure control.

Therefore, for example, if the load pressure increases and the cylinder speed decreases during speed control,
The control unit 2 attempts to return the reduced cylinder speed to the target value based on the speed command signal, ignoring fluctuations in the load pressure. Then, a control signal to increase the opening degree of the servo valve 3 is output. As a result, the oil pressure applied to the piston of the hydraulic cylinder 1 further increases, and the load pressure further increases. In this way, this state continues until the pressure control selection signal is input from the input circuit 9 and the pressure compensation circuit 6 side is selected, causing the load pressure to rise abnormally.

Furthermore, when the detection signal from the proximity switch 10 becomes active and switches to pressure control after the load pressure has abnormally increased as described above, the pressure control for the hydraulic cylinder 1 suddenly stops. will enter the controlled state from the non-controlled state. Therefore, as shown in FIG. 6, there is a problem that oscillation and dead time occur in the control operation of the hydraulic cylinder 1.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a hydraulic cylinder control device that can stably control the operation of a hydraulic cylinder by automatically switching between the pressure control and speed control according to the load condition. be.

[0009]

[Means for Solving the Problems] In order to achieve the above object, a hydraulic cylinder control device of the invention according to claim 1 is provided.
As illustrated in FIG.
a control signal for feedback-controlling the operation of the servo valve 13 so that the operating pressure becomes the pressure target value based on the operating pressure of the pressure oil that operates the hydraulic cylinder 11 detected by and the pressure target value; pressure feedback control means 16 and 19 that output
speed feedback for outputting a control signal for feedback controlling the operation of the servo valve 13 so that the operating speed becomes the speed target value based on the operating speed of the hydraulic cylinder 11 and the speed target value detected by the control means 17 and 20; and switching means 1 for switching and selecting control signals from the pressure feedback control means 16 and 19 or the speed feedback control means 17 and 20 and outputting the selected control signals to the servo valve 13;
8, and the speed detection means 1 determines whether the operating pressure detected by the pressure detection means 14 has reached the pressure target value.
It monitors whether the operating speed detected by step 5 has reached the speed target value, and determines that if either the detected operating pressure or the operating speed reaches the target value, one of the above is to be controlled. and outputs to the switching means 18 a determination signal for switching and selecting a control signal based on one of the control signals from the pressure feedback control means 16 and 19 or the control signals from the speed feedback control means 17 and 20. Judgment means 2
1, 22, and 23.

Further, the hydraulic cylinder control device of the invention according to claim 2, as illustrated in FIGS. 1 and 3, includes a servo valve 13 that controls the amount of pressure oil supplied to the hydraulic cylinder 11; Feedback control of the operation of the servo valve 13 so that the operating pressure becomes the pressure target value based on the operating pressure of the pressure oil for operating the hydraulic cylinder 11 detected by the detection means 14 and the pressure target value. pressure feedback control means 16 for outputting a control signal of
, 19, and for feedback controlling the operation of the servo valve 13 so that the operating speed becomes the speed target value based on the operating speed of the hydraulic cylinder 11 detected by the speed detecting means 15 and the speed target value. speed feedback control means 17, 20 that output control signals of the pressure feedback control means 16, 19, and control signals from the pressure feedback control means 16, 19 or the speed feedback control means 17, 20.
a switching means 18 for switching and selecting a control signal from the servo valve 13 and outputting the selected control signal to the servo valve 13; and the pressure detecting means 1.
4 has reached a first dummy pressure target value that is lower than the pressure target value by a predetermined value;
Whether or not the detected operating pressure has reached a second dummy pressure target value that is lower than the first dummy pressure target value by a predetermined value, the operating speed detected by the speed detection means 15 has reached the speed target value. If the detected operating pressure reaches the first dummy pressure target value from the low pressure side, the pressure is increased until the operating pressure reaches the second dummy pressure target value from the high pressure side. It is determined that feedback control is to be performed, and a determination signal for switching and selecting the control signals from the pressure feedback control means 16 and 19 is output to the switching means 18, while the detected operating speed is set to the speed target value. determining means 23, 31 for determining that speed feedback control is to be performed when the speed feedback control is reached, and outputting a determination signal to the switching means 18 for switching and selecting the control signals from the speed feedback control means 17, 20; 32,
It is characterized by having 33.

[0011]

In the invention according to claim 1, the operating pressure of the pressure oil for operating the hydraulic cylinder 11 is detected by the pressure detecting means 14, while the operating speed of the hydraulic cylinder 11 is detected by the speed detecting means 15. Then, the determining means 21, 22, and 23 monitor whether the detected operating pressure has reached the pressure target value and whether the detected operating speed has reached the speed target value. If either the detected operating pressure or the operating speed has reached the target value, it is determined that one of the operating pressures or operating speeds is to be controlled, and a control signal from the pressure feedback control means 16, 19 or speed feedback control is output. Means 17,
A determination signal for switching and selecting a control signal based on one of the control signals from 20 is output to the switching means 18.

According to the determination signals from the determination means 21, 22, 23, the switching means 18 controls the control signals from the pressure feedback control means 16, 19 or the speed feedback control means 17,
The control signal based on one of the control signals from 20 is switched and selected. Thus, based on the control signal selected by the switching means 18, the servo valve 1
The operation of step 3 is feedback-controlled to control either the operating pressure or the operating speed. As a result, even when either the operating pressure or the operating speed is being controlled, it is constantly monitored whether the other has reached the target value. If one of the above values becomes lower than the target value and the other value reaches the target value, the control signal based on the other value is automatically switched and selected to control the other value. Therefore, the hydraulic cylinder 11
operation is controlled stably.

In the invention according to claim 2, the hydraulic cylinder 1
The operating pressure of the pressure oil that operates the hydraulic cylinder 11 is detected by the pressure detection means 14, while the operating speed of the hydraulic cylinder 11 is detected by the speed detection means 15.

[0014] Then, the determining means 23, 31, 32,
33, whether or not the detected operating pressure has reached a first dummy pressure target value that is lower than the pressure target value by a predetermined value, the detected operating pressure is further determined by a predetermined value than the first dummy pressure target value. It is monitored whether the lower second dummy pressure target value has been reached and whether the detected operating speed has reached the speed target value. When the detected operating pressure reaches the first dummy pressure target value from the low pressure side, it is determined that pressure control is to be performed until the operating pressure reaches the second dummy pressure target value from the high pressure side. . and,
A determination signal for switching and selecting control signals from the pressure feedback control means 16 and 19 is output to the switching means 18. Then, the determination means 23, 3
According to determination signals from pressure feedback control means 1, 32, and 33, control signals from pressure feedback control means 16 and 19 are switched and selected by switching means 18. In this way, the operation of the servo valve 13 is feedback-controlled based on the control signals from the pressure feedback control means 16 and 19 selected by the switching means 18, and the operating pressure is controlled.

On the other hand, the determination means 23, 31, 32, 3
3, it is determined that speed control is to be performed when the detected operating speed reaches the speed target value. Then, a determination signal for switching and selecting the control signals from the speed feedback control means 17 and 20 is output to the switching means 18. The determination means 23,
According to the determination signals from 31, 32, 33, the switching means 18 switches and selects the control signals from the speed feedback control means 17, 20. In this way, the operation of the servo valve 13 is feedback-controlled based on the control signals from the selected speed feedback control means 17, 20, and the operating speed is controlled.

[0016] In this way, when either the operating pressure or the operating speed is monitored and the other is controlled, when the operating pressure reaches the first dummy pressure target value that is lower than the pressure target value, the system switches to pressure control. This allows for smooth switching to pressure control with little overshoot. In addition, when switching the pressure control, when the operating pressure reaches the first dummy pressure target value from the low pressure side, pressure control is entered, while when the second dummy pressure target value is reached from the high pressure side, pressure control is exited. It has hysteresis so that Therefore, even if the operating pressure and operating speed are both approximately at the target values, the pressure control and the speed control are not alternately switched, and more stable control of the hydraulic cylinder is performed.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to illustrated embodiments. FIG. 1 is a block diagram of a hydraulic cylinder control device in this embodiment. This hydraulic cylinder control device is generally composed of a control section 12, a servo valve 13, a pressure detector 14, and a speed detector 15. A pressure signal representing the load pressure of the hydraulic cylinder 11 detected by the pressure detector 14 and a speed signal representing the cylinder speed of the hydraulic cylinder 11 detected by the speed detector 15 are sent to the control section 12. be done.

The pressure compensation circuit 16 in the control section 12 calculates the load pressure based on the pressure signal calculated by the subtractor 19 and the target value (hereinafter referred to as pressure target value) P of the load pressure based on the pressure command signal. Based on the value of the difference between the two, a control signal for feedback controlling the operation of the servo valve 13 that controls the amount of pressure oil supplied to the hydraulic cylinder 11 is output. Similarly, speed compensation circuit 1
7 is a servo valve based on the value of the difference between the cylinder speed based on the speed signal calculated by the subtractor 20 and the cylinder speed target value (hereinafter referred to as speed target value) S based on the speed command signal. A control signal for feedback control of the operation of step 3 is output.

The changeover switch 18 operates based on a determination signal outputted from the determination circuit 21 as will be described in detail later.
The control signal from the pressure compensation circuit 16 or the control signal from the speed compensation circuit 17 is selected and outputted to the servo valve 13. A pressure comparison signal from a pressure comparison circuit 22 and a speed comparison signal from a speed comparison circuit 23 are input to the determination circuit 21 . A pressure command signal from the outside and a pressure signal from the pressure detector 14 are input to the pressure comparison circuit 22 . Then, the pressure target value P based on the pressure command signal and the load pressure based on the pressure signal are compared, and the pressure comparison signal indicating whether the load pressure has reached the pressure target value P is output. On the other hand, a speed command signal from the outside and a speed signal from the speed detector 15 are input to the speed comparison circuit 23. Then, the speed target value S based on the speed command signal and the cylinder speed based on the speed signal are compared, and the speed comparison signal indicating whether the cylinder speed has reached the speed target value S is output.

That is, in this embodiment, the above-mentioned determination means is composed of a determination circuit 21, a pressure comparison circuit 22, and a speed comparison circuit 23.

The determination circuit 21 determines whether to perform pressure control or speed control according to the following determination criteria, and outputs a determination signal representing the determination result. <State A> At the start of operation in a state where cylinder speed = 0 and load pressure = 0, it is determined that it is necessary to implement speed control to prevent the piston of the hydraulic cylinder 11 from jumping out, and the speed compensation circuit 17 side A determination signal for selecting the speed control determination signal (hereinafter referred to as speed control determination signal) is output as the determination signal. <State B> A state in which cylinder speed < S and load pressure < P. It is determined that speed control needs to be performed until the cylinder speed reaches the speed target value S, and the speed control determination signal is Output as a judgment signal. <Status C> Cylinder speed≧S or load pressure≧
State P If the cylinder speed has reached the speed target value S, it is determined that speed control needs to be performed, and the speed control determination signal is output as the determination signal. Alternatively, if the load pressure has reached the pressure target value P, it is determined that pressure control needs to be performed, and the pressure compensation circuit 16
A determination signal for selecting the side (hereinafter referred to as a pressure control determination signal) is output as the determination signal.

FIG. 2 shows the relationship between the cylinder speed and the load pressure when the operation of the hydraulic cylinder 11 is controlled by the hydraulic cylinder control device configured as described above. Below, Figure 2
Accordingly, the operation of the hydraulic cylinder control device in this embodiment will be described in detail. Here, control section 1
It is assumed that a speed command signal representing the speed target value "S1" and a pressure command signal representing the pressure target value "P" are input to 2. Since both the load pressure and the cylinder speed are "0" at time point A, the determination circuit 21 determines that the state is in the state A (that is, the initial state) and outputs the speed control determination signal. Then, the changeover switch 18
switches to select the speed compensation circuit 17. Thereafter, the servo valve 13 is switched to the supply side and driving of the hydraulic cylinder 11 is started. And the pressure detector 14
until the load pressure based on the pressure signal from the speed detector 15 reaches the pressure target value "P" or the cylinder speed based on the speed signal from the speed detector 15 reaches the speed target value "S1".
The determination circuit 21 determines that the state B is present and continues to output the speed control determination signal. Then, the changeover switch 18
outputs a control signal to the servo valve 13 for adjusting the cylinder speed from the speed compensation circuit 17 to the speed target value "S1". As a result, the speed control is executed, and the cylinder speed increases to the speed target value "S1" as shown in FIG. 2(a).
”.In this way, speed control continues until the point RO is reached.

At time point 0, the cylinder speed has reached the speed target value "S1", so the determination circuit 21 determines that the state C has been entered and continues outputting the speed control determination signal. As a result, the speed control is further continued, and the cylinder speed is maintained at the speed target value "S1" as shown in FIG. 2(a). In this way, the cylinder speed reaches the speed target value "S1"
The piston rod continues to move forward until reaching point C. At time point C, the speed target value changes from “S1” to “
S2''. Then, since the speed target value is set to a high value, the cylinder speed becomes lower than the speed target value again, and the determination circuit 21 determines that the state has returned to state B and outputs a speed control determination signal. As a result,
Furthermore, the speed control continues, the cylinder speed increases, and the load pressure also increases accordingly. Then, we reach point 2.

At time d, the cylinder speed reaches the speed target value “S”.
2". Then, the determination circuit 21 determines that the state has entered state C again and outputs a speed control determination signal to continue speed control. At this point, the load pressure is also close to the pressure target value "P". Therefore, from now on, if either the load pressure or the cylinder speed is greater than or equal to the target value, the determination circuit 21 determines that it is necessary to control one of the above, and A determination signal is output.As a result, pressure control and speed control are executed alternately, and as shown in FIG. 2, the cylinder speed is approximately equal to the speed target value "S2" and the load pressure is the pressure target value "S2". P” is maintained approximately equal to P”.

Assume that the load pressure decreases for some reason at time e. Then, the determination circuit 21 will output only the speed control determination signal. As a result, only the cylinder speed is controlled to the speed target value "S2". Thereafter, the operation of the hydraulic cylinder 11 is controlled in the same manner by determining which of the above-mentioned states the load is in.

As described above, this embodiment is provided with a determination circuit 21 that controls the operation of the selector switch 18 for selecting either the pressure control or the speed control. The determination circuit 21 receives a pressure comparison signal from the pressure comparison circuit 22 indicating whether the load pressure has reached the pressure target value P, and a pressure comparison signal from the speed comparison circuit 23 indicating whether the cylinder speed has reached the speed target value S. In response to the speed comparison signal representing
If it is determined that pressure control needs to be performed, a pressure control determination signal is output. On the other hand, if it is determined that speed control needs to be performed, a speed control determination signal is output.

When the content of the judgment signal inputted from the judgment circuit 21 is a speed control judgment signal, the changeover switch 18 switches and selects the speed compensation circuit 17 side;
In the case of a pressure control determination signal, the pressure compensation circuit 16 side is switched and selected. Then, based on the control signal from the pressure compensation circuit 16 or the control signal from the speed compensation circuit 17 which is switched and selected by the changeover switch 18, the operation of the servo valve 13 is feedback-controlled to implement pressure control or speed control. It is.

At this time, the determination circuit 21 outputs a pressure control determination signal if the load pressure has reached the pressure target value P. Alternatively, if the cylinder speed has reached the speed target signal S, a speed control determination signal is output. Therefore, according to the present embodiment, based on the pressure comparison signal and the speed comparison signal, one of the pressure control and speed control is performed while monitoring the detected value related to the other control, and When the detected value related to the control becomes lower than the target value and the detected value related to the other control reaches the target value, it is possible to switch to the other control. In other words, it is possible to automatically switch between pressure control and speed control depending on the load condition to obtain stable operation of the hydraulic cylinder.

In the embodiment described above, pressure control is carried out when the load pressure reaches the pressure target value P. or,
When the cylinder speed reaches the speed target value S, speed control is performed. For this reason, as shown in Fig. 2, during a period when both the load pressure and cylinder speed are approximately equal to the target values, pressure control and speed control are performed alternately, and the waveforms of the load pressure and cylinder speed both oscillate. Stable hydraulic cylinder operation cannot be obtained. Therefore, in the next embodiment, in order to obtain more stable operation of the hydraulic cylinder, the hydraulic cylinder control device is configured as follows.

In the hydraulic cylinder control device of this embodiment, the above-mentioned determination means is constructed as shown in FIG. below,
The hydraulic cylinder control device of this embodiment will be explained with reference to FIG.

In FIG. 3, the determination circuit 31 includes a speed comparison signal from the speed comparison circuit 23 and a first pressure comparison circuit 32.
A first pressure comparison signal from the pressure comparison circuit 33 and a second pressure comparison signal from the second pressure comparison circuit 33 are input. The speed comparison circuit 23 receives an external speed command signal and a speed signal from the speed detector 15 as in the above embodiment. Then, the speed target value S based on the speed command signal is compared with the cylinder speed based on the speed signal, and a speed comparison signal indicating whether the cylinder speed has reached the speed target value S is output.

The first pressure comparison circuit 32 includes a first pressure target signal obtained by lowering the voltage of an external pressure command signal representing the pressure target value P1 by a predetermined value by a variable resistor 34, and the pressure detector 14. The pressure signal from Then, a target value based on the first pressure target signal (hereinafter, the first
The dummy pressure target value P2 is compared with the load pressure based on the pressure signal, and the first pressure comparison signal indicating whether the load pressure has reached the first dummy pressure target value P2 is output. Hereinafter, the actual pressure target value P1 represented by the pressure command signal will be referred to as the actual pressure target value. Further, the second pressure comparison circuit 33 receives a second pressure target signal obtained by lowering the voltage of the first pressure target signal by a predetermined value using a variable resistor 35, and the pressure signal. Then, a target value P3 (hereinafter referred to as the second dummy pressure target value) lower than the first dummy pressure target value P2 based on the second pressure target signal is compared with the load pressure based on the pressure signal, and the load pressure is determined. The second pressure comparison signal indicating whether the second dummy pressure target value P3 has been reached is output.

The determination circuit 31 determines whether speed control or pressure control should be performed according to the following determination criteria, and outputs a determination signal representing the determination result. <State D> A state in which cylinder speed = 0 and load = 0. This is the same as state A in the above embodiment, and a speed control determination signal is output. <State E> Cylinder speed <S and load pressure <P2
This state is the same as state B in the above-described embodiment, and a speed control determination signal is output. <State F> Cylinder speed≧S and load pressure<P3
In this state, since the cylinder speed has reached the speed target value S and the load pressure has not yet reached the second dummy pressure target value P3, it is determined that speed control needs to be performed, and the speed control determination signal is sent. Output. <State G> A state where cylinder speed≧S and P3≦load pressure (increase)<P2 The above cylinder speed has reached the speed target value S, and the increasing load pressure is still at the first dummy pressure target value P2. Since the speed has not been reached, it is determined that speed control needs to be performed, and a speed control determination signal is output.

<State H> State where load pressure≧P2 Since the load pressure has reached the first dummy pressure target value P2, it is determined that pressure control needs to be performed, and a pressure control determination signal is output. <State I> Cylinder speed≧S and P3≦Load pressure (decrease)<P2 The above cylinder speed has reached the speed target value S, but the decreasing load pressure has still reached the second dummy pressure target value P3. Since it is not, it is determined that pressure control needs to be performed, and a pressure control determination signal is output.

Here, an actual pressure target value P1 based on the pressure command signal, a first dummy pressure target value P2 based on the first pressure target signal, and a second dummy pressure target value P3 based on the second pressure target signal. As mentioned above, the relationship is P1>
It is set so that P2>P3. In this way, the comparison reference values in the first pressure comparison circuit 32 and the second pressure comparison circuit 33 are set lower than the actual pressure target value P1 based on the pressure command signal, and the load pressure reaches the actual pressure target value P1. The pressure control is started from the front. By doing this, when switching from speed control to pressure control, the control can be switched smoothly with little overshoot.

[0036] Furthermore, as shown in the above states G to I,
Pressure control is entered when the load pressure reaches the first dummy pressure target value P2 from the low pressure side, and further reaches the second dummy pressure target value P3 (lower pressure than the first dummy pressure target value P2) from the high pressure side. to escape from pressure control. In other words, pressure control switching is provided with hysteresis. By doing so, once the load pressure reaches the first dummy pressure target value P2, speed control is not performed until the load pressure decreases to the second dummy pressure target value P3 or less.

FIG. 4 shows the relationship between the cylinder speed and the load pressure when the operation of the hydraulic cylinder 11 is controlled by the hydraulic cylinder control device configured as described above. Hereinafter, the operation of the hydraulic cylinder control device in this embodiment will be explained in detail according to FIG. 4. Here, the control section 12
It is assumed that a speed command signal representing the speed target value "S1" and a pressure command signal representing the actual pressure target value "P1" are input to the. At the point in time, the determination circuit 31 determines that the state is D, and outputs the speed control determination signal. In this way, speed control is implemented and driving of the hydraulic cylinder 11 is started. Then, the load pressure is set to the first dummy pressure target value “
Until the cylinder speed reaches the speed target value "S1" or the cylinder speed reaches the speed target value "S1", it is determined that the state is E, and speed control is implemented until the cylinder speed reaches the target speed value "S1".

At time point 3, the cylinder speed has reached the speed target value "S1" and the load pressure has not yet reached the second dummy pressure target value "P3", so the determination circuit 31 is in the above-mentioned state F. It determines that this is the case and outputs a speed control determination signal. As a result, the speed control described above is continued, and the cylinder speed is maintained at the speed target value "S1" as shown in FIG. 4(a) until time point N is reached. At time 0, the cylinder speed has reached the speed target value "S1", and the increasing load pressure has reached the second dummy pressure target value "P3", but the first dummy pressure target value "P2" is still not reached. '' has not been reached, the determination circuit 31 determines that the state is in the above-mentioned state G and outputs a speed control determination signal. As a result, the speed control is continued until the time point is reached.

At the point in time, the load pressure reaches the first pressure target value "
Then, the determination circuit 31 determines that the above-mentioned state H has entered and outputs the pressure control determination signal.As a result, the pressure control is started before the load pressure reaches the actual pressure target value "P1". is started, and the load pressure is controlled so as to reach the actual pressure target value "P1" with a small overshoot.In this case, as described above, the load pressure is controlled to become the second dummy pressure target value "P3". Pressure control continues until the pressure becomes lower than .At that point, the speed target value becomes “
Suppose that the load pressure is changed from "S1" to "S2".While the load pressure is being controlled to the actual pressure target value "P1", suppose that the load pressure decreases for some reason. reach.

At time O, the cylinder speed has reached the speed target value "S2", and the decreasing load pressure has reached the first dummy pressure target value "P2", but is still below the second dummy pressure target value. Since the value "P3" has not been reached, the judgment circuit 3
1 determines that the state is in the above-mentioned state I and outputs a pressure control determination signal. As a result, the pressure control described above is continued until the point in time is reached. At the point in time, the cylinder speed reaches the speed target value "S2"
The load pressure has reached the second dummy pressure target value "P3"
Since the speed has become lower, the determination circuit 31 determines that the state has returned to the above-mentioned state F and outputs a speed control determination signal. As a result, the speed control is switched to the above speed control and the cylinder speed is controlled to reach the speed target value "S2".

As described above, in this embodiment, since the pressure control is switched to the first dummy pressure target value P2 which is lower than the actual pressure target value P1, it is possible to smoothly switch to the pressure control with little overshoot. Further, in this embodiment, since the switching of pressure control is provided with hysteresis as described above, only pressure control is executed during the period from the above-mentioned time point 1 to time point wa. Therefore, pressure control and speed control are alternately switched as in the case of the above embodiment, and the cylinder speed and load pressure do not pulsate, and the load pressure is changed to the actual pressure target value "P1" as shown in FIG. ” is controlled stably so that

[0042] The configuration of the determination means in this invention is as follows:
The present invention is not limited to the block diagrams shown in FIGS. 1 and 3.

[0043]

As is clear from the above, the hydraulic cylinder control device of the invention according to claim 1 has the following advantages: Based on the speed, the determining means determines that if either the detected operating pressure or the operating speed reaches the target value, one of them is to be controlled, and a control signal or speed from the pressure feedback control means is determined. A determination signal is output for switching and selecting a control signal based on one of the control signals from the feedback control means, and the switching means outputs the selected control signal to the servo valve according to this determination signal. When controlling one of the operating pressure or operating speed, always monitor the other,
When one of the above values falls below the target value and the other reaches the target value, the other value can be automatically controlled. Therefore, by automatically switching between pressure control and speed control according to the load condition, the operation of the hydraulic cylinder can be stably controlled.

In the hydraulic cylinder control device of the invention according to claim 2, based on the operating pressure of the hydraulic cylinder detected by the pressure detecting means and the operating speed of the hydraulic cylinder detected by the speed detecting means, the determining means performs the following: When the detected operating pressure reaches the first dummy pressure target value from the low pressure side, pressure control is performed until the operating pressure reaches the second dummy pressure target value from the high pressure side, which is lower than the first dummy pressure target value. It determines that the speed control will be performed and outputs a determination signal for switching and selecting the control signal from the pressure feedback control means, while determining that the speed control will be performed when the detected operating speed reaches the speed target value. A judgment signal is output for switching and selecting the control signal from the speed feedback control means, and the switching means outputs the selected control signal to the servo valve according to each of the above judgment signals, so that the operating pressure is not the actual pressure. When the first dummy pressure target value, which is lower than the target value, is reached, the pressure control is started. Therefore, when automatically switching to the pressure control according to the load condition, it is possible to smoothly switch with little overshoot, and to control the operation of the hydraulic cylinder more stably.

Furthermore, when the operating pressure reaches the first dummy pressure target value from the low pressure side, pressure control is entered, and furthermore, when the operating pressure reaches the second dummy pressure target value lower than the first dummy pressure target value from the high pressure side. When the above pressure control is reached, the pressure control is exited and the pressure control switching has hysteresis. Once switched, the speed control will not be switched to the speed control until the operating pressure falls to the second dummy pressure target value. Therefore, when both the operating pressure and the operating speed have approximately reached the target values, the operating pressure and the operating speed do not pulsate, and the operation of the hydraulic cylinder can be controlled more stably.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a hydraulic cylinder control device of the present invention.

FIG. 2 is a diagram showing the relationship between cylinder speed and load pressure when the operation of a hydraulic cylinder is controlled by the hydraulic cylinder control device of FIG. 1;

FIG. 3 is a block diagram of main parts of a hydraulic cylinder control device different from that in FIG. 1;

4 is a diagram showing the relationship between cylinder speed and load pressure when the operation of a hydraulic cylinder is controlled by the hydraulic cylinder control device of FIG. 3; FIG.

FIG. 5 is a block diagram of a conventional hydraulic cylinder control device.

6 is a diagram showing the relationship between cylinder speed and load pressure in control by the conventional hydraulic cylinder control device shown in FIG. 5. FIG.

[Explanation of symbols]

11... Hydraulic cylinder,
12...Control unit, 13...Servo valve,
14...Pressure detector, 1
5...speed detector,
16...Pressure compensation circuit, 17...Speed compensation circuit,
18... changeover switch, 21,
31...determination circuit, 22
...Pressure comparison circuit, 23...Speed comparison circuit,
32...first pressure comparison circuit, 33...second pressure comparison circuit.

Claims (2)

[Claims] 1. A servo valve (13) that controls the amount of pressure oil supplied to the hydraulic cylinder (11), and a pressure detection means (14) that detects the amount of pressure oil supplied to the hydraulic cylinder (11).
) for outputting a control signal for feedback controlling the operation of the servo valve (13) so that the operating pressure becomes the pressure target value based on the operating pressure of the pressure oil that operates the pressure oil and the pressure target value. Feedback control means (16,1
9), and the servo valve (13) so that the operating speed becomes the speed target value based on the operating speed of the hydraulic cylinder (11) detected by the speed detecting means (15) and the speed target value. Speed feedback control means (1) outputting a control signal for feedback controlling the operation of the
7, 20) and the pressure feedback control means (16
, 19) or the speed feedback control means (17, 20) and outputs the selected control signal to the servo valve (13); and the pressure detection means (14). ) monitors whether the operating pressure detected by the speed detecting means (15) has reached the pressure target value and whether the operating speed detected by the speed detecting means (15) has reached the speed target value. When either the operating pressure or the operating speed reaches the target value, it is determined that one of the above is to be controlled, and the control signal from the pressure feedback control means (16, 19) or the speed feedback control means (17, 2) is determined to be controlled.
0) and determining means (21, 22, 23) for outputting a determination signal for switching and selecting a control signal based on one of the control signals from the switching means (18) to the switching means (18). Cylinder control device. 2. A servo valve (13) that controls the amount of pressure oil supplied to the hydraulic cylinder (11), and a pressure detection means (14) that detects the amount of pressure oil supplied to the hydraulic cylinder (11).
) for outputting a control signal for feedback controlling the operation of the servo valve (13) so that the operating pressure becomes the pressure target value based on the operating pressure of the pressure oil that operates the pressure oil and the pressure target value. Feedback control means (16,1
9), and the servo valve (13) so that the operating speed becomes the speed target value based on the operating speed of the hydraulic cylinder (11) detected by the speed detecting means (15) and the speed target value. Speed feedback control means (1) outputting a control signal for feedback controlling the operation of the
7, 20) and the pressure feedback control means (16
, 19) or the speed feedback control means (17, 20) and outputs the selected control signal to the servo valve (13); and the pressure detection means (14). ) has reached a first dummy pressure target value that is lower than the pressure target value by a predetermined value, and whether the detected operating pressure is further lower than the first dummy pressure target value by a predetermined value. It monitors whether the second dummy pressure target value has been reached and whether the operating speed detected by the speed detection means (15) has reached the speed target value, and the detected operating pressure is on the low pressure side. If the operating pressure reaches the first dummy pressure target value from
A determination signal for switching and selecting the control signal from 6, 19) is output to the switching means (18), and when the detected operating speed reaches the speed target value, speed feedback control is performed. Then, it is determined that
Determination means (23, 31) outputting a determination signal for switching and selecting the control signal from the speed feedback control means (17, 20) to the switching means (18).
, 32, 33).