JPH05106607A - Speed/thrust control device for hydraulic actuator - Google Patents

Abstract

PURPOSE:To prevent the occurrence of hunting and enhance the efficiency in the speed/thrust device for a hydraulic cylinder or the like, by inputting each of the deviation between the instructed speed and the detected speed and the deviation between the instructed thrust and the detected thrust into compensating element, and inputting into an amplifier a smaller one of the outputs from the elements so as to control the speed or the thrust. CONSTITUTION:The speed and pressure of a hydraulic cylinder 21 are sensed by a speed sensor 24 and a pressure sensor 25, respectively. The sensed speed Vf/b is inputted into a deviation detection section 31 wherein a deviation DELTAV between this sensed speed and a speed instruction value Vc is calculated. A deviation detection section 32 calculates a deviation 6F between a sensed thrust Ff/b and a thrust instruction value Fc. A first and a second compensating element 33, 34 produce a speed operation amount Vs and a thrust operation amount Fs on the basis of the speed deviation DELTAV and the thrust deviation DELTAF, which are inputted into a control system switching circuit 35. The switching circuit 35 outputs to an amplifier 23 a smaller operation amount S of Vs and Fs to thereby drive a three-way valve 22 and control the operating speed and thrust of the hydraulic cylinder 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control system having a speed control system for maintaining the operating speed of hydraulic actuators such as hydraulic cylinders and hydraulic motors at a speed command value, and a thrust control system for maintaining its thrust at a thrust command value. The present invention relates to a speed / thrust control device for an actuator.

[0002]

2. Description of the Related Art Speed of such a hydraulic actuator
As a conventional device similar to the thrust control device, there is, for example, a flow rate / pressure control device for a fluid pump as described in JP-A-64-32082.

The basic structure thereof is configured as shown in FIG. 16, and the switch 4 is switched to the A side during normal flow rate control, and a variable displacement hydraulic pump section (a variable displacement hydraulic pressure pump which is a fluid pump) is used. (Including means for controlling a variable capacity mechanism such as a pump and its swash plate and an amplifier for driving the same) 1) For example, an angle sensor attached to the swash plate detects a swash plate angle θ, that is, a discharge flow rate Q, and a flow rate instruction value. The deviation from Qc is input to the servo amplifier 2 which is a correction element, and the output thereof controls the swash plate angle of the variable displacement hydraulic pump unit 1 so that the discharge flow rate Q matches the flow rate instruction value Qc. As a result, the cylinder 6 is driven at a constant moving speed.

When the cylinder 6 reaches the stroke end or hits the object 10 and is mechanically stopped, the pressure in the cylinder 6 starts to rise rapidly. The detected pressure value P is the difference (Pc-α; Pc) between the pressure command value Pc and the predetermined value α.
(Slightly lower value), the output of the comparator 5 is inverted and the switch 4 is switched to the B side, the deviation between the pressure instruction value Pc and the pressure detection value P is input to the servo amplifier 3, and the output causes pressure difference. Pressure control is performed by feedback-controlling the swash plate angle of the variable displacement hydraulic pump unit 1 so that the detected value P matches the pressure instruction value Pc.

[0005]

In this case, the switching between the flow rate control state and the pressure control state is performed only by (Pc-α) -P as described below. Note that Gp and Gq are amplification factors of the servo amplifiers 3 and 2, respectively. (Pc-α) -P SW4 Hydraulic pump operation amount ≤0 B (Pc-P) Gp> 0 A (Qc-Q) Gq

Here, when the control state is switched, that is, when (Pc-α) -P = 0, (Pc-P) Gp and (Qc-Q) Gq are usually not equal (may be equal). However, it is generally not equal because it changes depending on the state). Therefore, the discharge load circuit pressure increases (Pc
When -α) -P = 0, a jump occurs in the hydraulic pump operation amount. That is, from (Qc-Q) Gq to (Pc-
P) The signal drops to Gp, which causes the load pressure to drop instantaneously to (Pc-α) -P> 0, and the manipulated variable jumps again. This is repeated to enter the hunting state.

In order to solve such a problem, Japanese Patent Application Laid-Open No. 64-32082 proposes a flow rate / pressure control device constructed as shown in FIGS. 17 (A) and 17 (B). In these figures, the parts corresponding to those in FIG. 16 are designated by the same reference numerals. In addition, 11 is a directional control valve, 12
Is an output voltage upper limit circuit.

According to these configurations, the servo amplifier 2,
When the amplification factors of 3 are Gq and Gp, the gain of the flow rate control is determined by Gq, the gain of the pressure control is determined by Gp × Gq, and the flow rate control / pressure control switching characteristic (cutoff width)
Is determined by Gp. According to these, the jump of the hydraulic pump operation amount at the time of control switching as in the case described above does not occur, and the hunting phenomenon at the switching point is improved.

However, since the pressure control generally has a higher feedback gain than the flow rate control, the control gain must be kept low. Therefore, it is desired to lower Gp × Gq, but since Gq is high, Gp must be extremely low, resulting in a large cutoff width, which causes a problem that the maximum power point of the pump cannot be used. If Gp is increased for the purpose of improving this, Gq must be lowered,
Then, there arises a problem that the responsiveness during the flow rate control is lowered. Such a problem similarly occurs in a speed / thrust control device for a hydraulic actuator in which the hydraulic pump described above is replaced with a hydraulic actuator, and the operating speed and thrust are detected to perform feedback control.

The present invention has been made in view of the above problems, and in a speed / thrust control device for a hydraulic actuator, switching is smoothly performed without causing a hunting phenomenon at the time of control switching, and each compensation element The purpose of the present invention is to improve the efficiency by allowing the gain to be optimally selected, and to improve the static control accuracy without impairing the dynamic characteristics.

[0011]

In order to achieve the above-mentioned object, a speed / thrust control device for a hydraulic actuator according to the present invention supplies a hydraulic actuator such as a hydraulic cylinder, a hydraulic motor or the like, and a pressure oil to the hydraulic actuator. Control valve for controlling the operating speed and thrust of the hydraulic actuator, an amplifier for driving the control valve, speed detecting means for detecting the operating speed of the hydraulic actuator, and thrust detecting means for detecting the thrust. A first closed loop system for performing speed control by inputting the deviation between the value and the speed detection value by the speed detection means to the amplifier via the first compensation element, the thrust command value and the thrust detection by the thrust detection means. A deviation from the value is input to the amplifier via the second compensation element to form a second closed loop system for thrust control, and the output of the first compensation element is generated. And a control system switching means for switching between the first closed loop system and the second closed loop system by inputting the smaller one of the outputs of the second compensation element and the second compensation element to the amplifier. ..

[0012]

According to the present invention, the speed command value is Vc, the speed detection value is V, the thrust command value is Fc, the pressure detection value is F, the gain of the first compensating element is Gv, and the gain of the second compensating element. To G
When f is (Vc-V) Gv <(Fc-F) Gf, the manipulated variable (Vc-V) Gv is input to the amplifier, and the speed control is performed by the first closed loop system. When −V) Gv ≧ (Fc−F) Gf, the manipulated variable (Fc−F) Gf is input to the amplifier, and thrust control is performed by the second closed loop system.

Therefore, at the control switching point, (Vc-
V) Gv = (Fc−F) Gf, and the operation amount is (Vc−
A jump does not occur even if V) Gv changes to (Fc-F) Gf, and a hunting phenomenon does not occur when the control system is switched. Further, since the gains Gv and Gf of each compensation element can be individually set to optimum values, the characteristics of each control can be made good and efficient, and the static control accuracy can be improved without impairing the dynamic characteristics. If Gf is subjected to integral compensation or the like, a very sharp cutoff characteristic can be realized.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An actual embodiment of the present invention will be specifically described below with reference to the drawings. 1 is a block diagram showing the configuration of a speed / thrust control device for a hydraulic actuator according to an embodiment of the present invention, and FIG. 2 is a diagram showing a specific mechanism and circuit example thereof.

First, the structure of this embodiment will be described with reference to FIG. 1. Reference numeral 20 is a hydraulic actuator portion, and a hydraulic cylinder 21 which is a hydraulic actuator, and pressure oil is supplied to the hydraulic cylinder 21 to determine its operating speed and thrust. A three-way valve 22 that is a control valve for controlling, an amplifier 23 that drives this three-way valve 22, a speed sensor 24 (speed detection means) that detects the operating speed of the hydraulic cylinder 21, and a hydraulic cylinder 21.
And a pressure sensor 25 (thrust force detecting means) for detecting the thrust force.

On the other hand, 30 is a speed / thrust compensating section, which is a deviation detecting section 31, 32, a first compensating element 33 and a second compensating element 34 by a servo amplifier and a control system switching circuit 35.
(Control system switching means).

Then, the deviation detector 31 detects the deviation ΔV between the speed command value Vc and the speed detection value Vf / b detected by the speed sensor 24, and inputs it to the amplifier 23 via the first compensation element 33. The deviation ΔF between the thrust command value Fc and the thrust detection value Ff / b detected by the pressure sensor 25 is detected by the deviation detection unit 32 and the first closed loop system for speed control, and the deviation ΔF is detected by the second compensation element 34. A second closed loop system for inputting to the amplifier 23 to perform thrust control is formed, and the control system switching circuit 35 selects one of the output of the first compensation element 33 and the output of the second compensation element 34, whichever has the smaller value. The output is input to the amplifier 23 to switch between the first closed loop system and the second closed loop system.

More specifically, referring to FIG. 2A, the three-way valve 22 is a spring offset type electromagnetic three-way valve, and is a spool 2 slidable in the cylinder 22a.
2b is urged to the right in the figure by the spring 22c, and when the solenoid 22d is urged by the output current Is of the amplifier 23, it is pushed back to the left by the push rod 22e operated by its electromagnetic force.

In the neutral state shown in the figure, the directional control valve 2
Although the port C connected to the cylinder 21 via 7 is closed, when the output current Is of the amplifier 23 increases, the electromagnetic force of the solenoid 22d increases, so the spool 22b resists the urging force of the spring 22c to the left. Then, the port C is connected to the port P connected to the pressure oil supply line from the hydraulic pump 28. As a result, pressure oil is supplied to the cylinder 21 to operate its piston. The operating speed increases as the output current Is of the amplifier 23 increases and the amount of oil supplied increases.

On the contrary, when the output current Is of the amplifier 23 decreases, the electromagnetic force of the solenoid 22d weakens, so that the spool 22b moves to the right due to the urging force of the spring 22c, and the port C is connected to the port T connected to the tank 26. Connect to. As a result, the hydraulic pressure in the cylinder 21 is reduced and the operation of the piston is stopped. As the output current Is of the amplifier 23 decreases, the outflow amount of the pressure oil to the tank increases, so that the thrust of the piston decreases. Direction switching valve 2
When 7 is switched, the moving direction of the piston of the hydraulic cylinder 21 is reversed.

The speed sensor 24 is, for example, the hydraulic cylinder 2.
An encoder attached to the piston rod 21a of No. 1 and an F / V converter that converts the frequency of the pulse generated by the encoder according to the movement of the piston rod 21a into a voltage signal, and detects the operating speed of the hydraulic cylinder 21. Then, the detected value Vf / b is fed back to the speed / thrust compensation unit 30.

The pressure sensor 25 detects the pressure of the pressure oil supply line from the three-way valve 22 to the hydraulic cylinder 21 and converts it into a voltage signal, and the speed / thrust compensator 30 as the thrust detection value Ff / b of the hydraulic cylinder 21. Feed back. A load cell may be used as the thrust detecting means.

The first compensation element 3 of the speed / thrust compensation unit 30
3 is composed of a parallel circuit of a proportional amplification section 33a, an integral amplification section 33b, and a differential amplification section 33c, and depending on the case, one or two of them may be used in combination. The second compensation element 34 is also composed of a parallel circuit of a proportional amplification section 34a, an integral amplification section 34b, and a differential amplification section 34c, and depending on the case, one or two of them may be used in combination.

The control system switching circuit 35 includes the first compensation element 3
Comparator 36 that compares the output value Vs (speed operation amount) of No. 3 and the output value Fs (thrust operation amount) of the second compensation element 34.
And a switch circuit 37 whose switching is controlled by its output.
When Vs <Fs, the output of the comparator 36 is at the low level “L”, the switch circuit 37 is set to the A side, and the output value Vs of the first compensation element 33 is set as the manipulated variable S. When input to the amplifier 23 and Vs ≧ Fs, the output of the comparator 36 becomes a high level “H”, the switch circuit 37 is switched to the B side, and the output value Fs of the second compensation element 34 is changed to the manipulated variable S. As an input to the amplifier 23.

Alternatively, instead of the control system switching circuit 35, as shown in FIG. 2B, the output value Vs of the first compensation element 33 and the output value Fs of the second compensation element 34 are inverted. Two operational amplifiers 39a and 39b to be input,
Two diodes Da and Db each having its output terminal connected to its cathode side and its non-inverted input terminal connected to its anode side are combined, and the signal having the smaller value of the inputs Vs and Fs is input to the amplifier 23 as the manipulated variable S. You may make it input.

In this embodiment, as the three-way valve 22,
Since the spring offset type electromagnetic three-way valve is used, when the output from the control system switching circuit 35 is zero, the adding circuit 38 is arranged so that the three-way valve 22 is in the neutral position shown in FIG. Thus, the bias voltage Eb is added to the output from the control system switching circuit 35, and the bias voltage Eb is input to the amplifier 23.

Next, the operation of this embodiment will be described with reference to the diagrams of FIGS. 3 to 5 are diagrams showing static characteristics of this embodiment, and FIG. 3 shows a speed command value Vc at the time of a cylinder stroke for speed control of the hydraulic cylinder 21.
And the cylinder speed V (detected as Vf / b) are shown.

FIG. 4 shows a thrust command value Fc and a cylinder thrust F (Ff / b) detected when the cylinder is stopped to control the thrust of the hydraulic cylinder 21 (when a large load is applied to the piston lot 21a or the cylinder end is reached). ) Shows the relationship with. FIG. 5 shows the relationship between the cylinder speed and the thrust command value at the time of speed / thrust switching, and the static characteristic of the conventional device of this type is shown by the broken line, but according to this embodiment, it is shown by the solid line. As shown, the static characteristics are improved.

6 to 8 are diagrams showing dynamic characteristics (transient characteristics), respectively. FIG. 6 shows a cylinder stroke,
FIG. 7 shows the cylinder stop, and FIG. 8 shows the speed command Vc, the detected speed Vf / b and the thrust command Fc at the time of speed / thrust switching.
And the detected thrust Ff / b are shown respectively.

FIG. 9 is a diagram showing the output characteristic of each part of FIG. 2A, and FIG. 9A shows the deviation ΔV = Vc−Vf / b which is the error of the cylinder speed and the deviation which is the error of the thrust force. ΔF = F
Each change of c-Ff / b is shown. When it reaches the cylinder end,
Since the thrust F rapidly increases and approaches the command value Fc, the deviation Δ
F decreases sharply and the output Fs of the second compensation element 34 decreases. Then, since this value is lower than the output Vs of the first compensation element 33 that has controlled the speed V so far, the speed decreases and approaches zero. At this time, the amplifier 23 has Fs
Is received, the three-way valve 22 adjusts the supply hydraulic pressure so that the detected thrust Ff / b maintains the value of the thrust command Fc.

(B) is the output value Pf (proportional component), If (integral component), Df (differential component) of each of the proportional amplification component 34a, integral amplification component 34b, and differential amplification component 34c in the second compensation element 34. ) Is shown, and the total thrust operation amount Fs is shown in (c). This is sent to the fixed terminal B of the switch circuit 37 as the output value of the second compensation element 34.

(D) is the output value Pv (proportional component), Iv (integral component), Dv (differential component) of each of the proportional amplification unit 33a, integral amplification unit 33b, and differential amplification unit 33c in the first compensation element 33. ) Is shown, and the speed operation amount Vs which is the sum thereof is shown in (e). This is sent to the fixed terminal A of the switch circuit 37 as the output value of the first compensation element 33. The smaller one of the manipulated variables Vs and Fs is the control system switching circuit 3
5 is input to the amplifier 23 as the manipulated variable S shown in (f).

In this way, when the operation amount is Vs <Fs, the speed control is performed by the speed operation amount Vs, and Vs ≧ F
When s is reached, thrust control is performed by the thrust manipulated variable Fs, so Vs = Fs at the switching point, and the manipulated variable S is Vs.
No jump occurs even when the switching is made from Fs to Fs, and the hunting phenomenon does not occur at the time of switching.

When the total gain of the first compensating element 33 is Gv and the total gain of the second compensating element 34 is Gf, the manipulated variables Vs and Fs are calculated by the following equations. Vs = Pv + Iv + Dv = (Vc−Vf / b) Gv Fs = Pf + If + Df = (Fc−Ff / b) Gf And (Vc−Vf / b) Gv <(Fc−Ff / b) Gf
When, the speed control by the first closed loop system is performed,
When (Vc−Vf / b) Gv ≧ (Fc−Ff / b) Gf, thrust control is performed by the second closed loop system.

There are various forms of the first and second compensating elements 33 and 34, and according to this configuration, it is easy to deal with them. Here, the PID compensation is used as a typical example. In this case, the gain Gv of each compensation element (the proportional amplification unit 33a, the integral amplification unit 33
b, and each gain of the differential amplification section 33c), Gf (proportional amplification section 34a, integral amplification section 34b, and differential amplification section 34c).
Each gain) can be independently set to the optimum value, so the characteristics of each control can be good and efficient,
Since integral compensation is used for Gf, a very sharp cutoff characteristic can be realized.

Next, the operation of controlling the process of the injection cylinder of the injection molding machine according to this embodiment will be described with reference to FIG.
This will be described with reference to FIGS. 10 to 12, parts corresponding to those in (A) of FIGS. 1 and 2 are designated by the same reference numerals. 40 is a fixed die 40a and a movable die 40b
The mold is composed of a cavity 40c corresponding to the shape of the article to be molded and a gate 40d communicating therewith.

Reference numeral 41 denotes a heating cylinder having a nozzle 41a at its tip, which has a screw 42 capable of rotating and sliding inside, and when a resin material is supplied from a hopper (not shown), it is heated and melted by a heater (not shown). Let And
When the screw 42 is rotated by a hydraulic motor (not shown) and pushed by the injection cylinder 21 in the direction of the arrow, the molten resin 43 is pushed out and injected from the nozzle 41a into the gate 40d of the mold 40. These are the configurations of known injection molding machines.

The injection molding process is controlled by introducing pressure oil from the hydraulic pump 28 into the rear chamber 21a or the front chamber 21b of the injection cylinder 21 via the direction switching valve 27 and the three-way valve 22. The movement of the injection cylinder 21 is such that at first, the resin 43 is injected from the nozzle 41a at the head of the heating cylinder 41 and moves quickly to a gate 40d of the mold 40 with a light load, and then to the cavity 40c of the mold 40. When the resin 43 is injected, the resin pressure in the heating cylinder 41 increases by the amount of pressure loss when passing through the gate. At the same time, injection cylinder 2
The hydraulic pressure, that is, the thrust force of the rear chamber 21a of No. 1 increases. When this value approaches the thrust command value Fc, the speed V is reduced, and "pressure injection" is performed to compensate for the pressure loss of the gate portion of the resin 43, resulting in a low speed stroke.

Next, the thrust command value Fc is increased to perform high-speed injection again, and the cavity 4 of the die 40 is
When 0c is filled, the resin pressure further rises, and approaches the thrust specification value Pc again, so the speed V decreases and the thrust control is performed to the "pressure-holding stroke". FIG. 10 shows the heating cylinder 4
The process from when the first nozzle 41a reaches the mold 40 and when the resin 43 begins to be injected into the gate 40d is shown. In this step, since the injection cylinder 21 pushes the screw 42 at a high speed, the load pressure is light and the flow rate supplied to the injection cylinder 21 is large, so the speed control shown in FIG. 6 is performed. This is a portion A-B in FIG. 5, which is a control region where the cylinder speed is constant.

That is, the speed detection value Vf / b approaches the speed command value Vc, and the thrust detection value Ff / b is considerably smaller than the thrust command value Fc. Therefore, when the speed deviation ΔV and the thrust deviation ΔF are compared, ΔV <ΔF. , The operation amount Vs output by the first compensating element 33 and the operation amount Fs output by the second compensating element 34 are also Vs <Fs. Therefore, the control system switching circuit 35 is as shown by the solid line with arrow in FIG. The smaller manipulated variable Vs is selected and input to the amplifier 23 as the manipulated variable S. As a result, the amplifier 23 increases or decreases the output current Is, that is, the current flowing to the solenoid of the three-way valve 22 according to the input operation amount S to control the amount of pressure oil supplied from the hydraulic pump 28 to the injection cylinder 21.

FIG. 11 shows the nozzle 41 of the heating cylinder 41.
The process of injecting the resin 43 injected from a into the mold chamber 40c through the gate hole of the mold 40 is shown. In this step, the resin 43 passes through the gate 40d to generate a pressure loss, and the hydraulic pressure supplied to the injection cylinder 21 is increased to compensate for this, whereby Ff / b approaches Fc.
Therefore, the value of Fs decreases and becomes lower than the value of Vs, so that the pump 28 decreases the discharge flow rate and the injection cylinder 2
The speed of 1 becomes slow.

Until Vs = Fs, the control system switching circuit 35 selects the manipulated variable Vs output from the first compensating element 33 as indicated by the broken line with an arrow and outputs it to the amplifier 23 as the manipulated variable S. I am inputting and controlling the speed,
When Vs = Fs, as shown by a solid line with an arrow, the operation amount Fs output by the second compensating element 34 is selected and the operation amount S is selected.
As a result, the control system is switched so as to be input to the amplifier 23, and thereafter, thrust control as shown in FIG. 7 is performed while Vs ≧ Fs. This is a portion B-C in FIG. 5, which is a control region where the cylinder thrust is constant.

FIG. 12 shows a pressure-holding step after the resin 43 is filled in the mold chamber 40c of the mold 40. In this step, the cylinder speed becomes zero because the piston of the injection cylinder 21 stops, but the thrust control described above is continued because it is necessary to maintain a constant pressure. This is a control point indicated by B in FIG. 5 where the cylinder speed is zero and the thrust is constant. in this way,
By using the apparatus of this embodiment, the step of performing speed / thrust control in the injection molding machine can be realized by a combination of a single hydraulic pump and injection cylinder. Moreover, the cost increase for that can be suppressed to the minimum.

In the above-described embodiment, when the speed / thrust control is switched, some overshoot occurs as shown in the thrust characteristic curve of FIG. 8, but the overshoot of the present invention is reduced. FIG. 1 shows another embodiment.
This will be described with reference to FIGS. FIG. 13 is a circuit diagram showing only the main part of this embodiment, and the other parts are the same as those of the above-mentioned embodiment shown in FIG.

In this embodiment, the second compensating element 34 'is slightly different from the second compensating element 34 of FIG. 2A, and the characteristic of the proportional amplification section 34a' is a nonlinear characteristic as shown in FIG. To Further, the proportional amplification section 34a 'and the integral amplification section 3
4b, the outputs of the differential amplification section 34c are summed, and then output through the correction amplification section 34d.
By making the characteristic of 4d non-linear (not necessarily non-linear) as shown in FIG. 15, the overshoot can be further suppressed. However, the characteristic of the proportional amplification section 34a 'is not provided without the correction amplification section 34d. It is also effective to make the non-linear characteristic as shown in FIG.

As described above, by suppressing the overshoot (pressure peak) at the time of control switching, it is possible to enhance the safety when using this device and reduce the shock (noise and vibration). Can be protected.
For example, when controlling the tension of the cable, there is no risk of the cable being cut due to overshoot. In addition, shock reduction is to suppress structural vibration, and in industrial machines such as machine tools and injection molding machines,
In addition to the effect of reducing pollution, it is believed to contribute to the improvement of dimensional accuracy of products.

In each of the above-described embodiments, the case where the present invention is applied to the speed / thrust force control device of the hydraulic cylinder has been described, but the present invention is applied to the speed / thrust force control device of another hydraulic actuator such as a hydraulic motor. Can be similarly applied to. In that case, it goes without saying that the operating speed of the hydraulic actuator may be detected by detecting the rotational speed.

[0048]

As described above, the speed / thrust control device for a hydraulic actuator according to the present invention can be smoothly switched without causing a hunting phenomenon during control switching, and the gain of each compensating element can be optimally selected. Therefore, the efficiency is high, and the static control accuracy can be improved without impairing the dynamic characteristics.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a specific mechanism and circuit example of the same.

FIG. 3 is a diagram similarly showing static characteristics at the time of the cylinder stroke.

FIG. 4 is a diagram showing static characteristics when the cylinder is stopped.

FIG. 5 is a diagram similarly showing static characteristics at the time of speed / thrust switching.

FIG. 6 is a diagram showing a dynamic characteristic of the same cylinder stroke.

FIG. 7 is a diagram similarly showing the dynamic characteristics when the cylinder is stopped.

FIG. 8 is a diagram showing a dynamic characteristic when switching between speed and thrust.

FIG. 9 is a diagram showing output characteristics of respective parts of the apparatus shown in FIG. 2 at the time of control switching.

FIG. 10 is a diagram showing an initial process until the injection of resin into the mold is started when the process of the injection cylinder of the injection molding machine is controlled by the embodiment shown in FIG.

FIG. 11 is a diagram showing a medium-term process after the resin injection is started.

FIG. 12 is a diagram showing a pressure-holding step after the mold is similarly filled with resin.

FIG. 13 is a circuit diagram showing only a main part of another embodiment of the present invention for suppressing overshoot that occurs at the time of control switching.

14 is a diagram showing a characteristic example of a proportional amplification section 34a 'in FIG.

FIG. 15 is a diagram similarly showing a characteristic example of the correction amplification unit 34d in FIG.

FIG. 16 is a block diagram showing an example of a flow rate / pressure control device using a conventional variable displacement hydraulic pump.

FIG. 17 is a block diagram showing a different example of a conventional flow rate / pressure control device which is also an improved version thereof.

[Explanation of symbols]

20 hydraulic actuator part 21 hydraulic cylinder, injection cylinder 22 three-way valve (control valve) 23 amplifier 24 speed sensor (speed detecting means) 25 pressure sensor (thrust detecting means) 26 tank 27 directional valve 28 hydraulic pump 30 speed / thrust compensating part 31, 32 Deviation detection section 33 First compensation element 34, 34 'Second compensation element 33a, 34a, 34a' Proportional amplification section 33b, 34b Integration amplification section 33c, 34c Differential amplification section 34d Correction amplification section 35 Control system switching Circuit 36 Comparator 37 Switch circuit 38 Addition circuit 40 Mold 41 Heating cylinder 42 Screw 43 Resin 45 Directional switching valve 51, 52 Wind comparator circuit Vc Speed command value Fc Thrust command value V Cylinder speed F Cylinder thrust Vf / b Speed detection value Ff / b Thrust detection value ΔV Speed deviation ΔF Thrust deviation Difference Vs Speed operation amount Fs Thrust operation amount S Operation amount Is Output current of amplifier 23

Claims (1)

[Claims] 1. A hydraulic actuator such as a hydraulic cylinder and a hydraulic motor, a control valve for supplying pressure oil to the hydraulic actuator to control its operating speed and thrust, an amplifier for driving the control valve, and the hydraulic actuator. And a thrust detecting means for detecting the thrust of the hydraulic actuator. The deviation between the speed command value and the speed detected value by the speed detecting means is passed through the first compensating element. A first closed loop system for inputting speed to the amplifier for speed control and a deviation between a thrust command value and a thrust detection value by the thrust detecting means are input to the amplifier via a second compensating element for thrust control. And a second closed loop system to be performed, and the output of the output of the first compensation element or the output of the second compensation element having a smaller value is input to the amplifier. The Te Unishi first closed-loop system and speed-thrust control apparatus for a hydraulic actuator, characterized in that a control system switching means for switching a second closed loop system.