JPH0238020A - Apparatus and method for electrically controlling liquid pressure of plastic molding machine - Google Patents

Abstract

PURPOSE:To improve the energy efficiency as high as is equal to that achieved by a purely electrically controlling system, by allowing a controller to receive a position signal from a projecting position sensor indicative of the projecting position of a pressuring shaft such as a rod or the like and a pressure signal from a pressure sensor which detects a speed signal from a pressuring shaft projecting speed sensor and an output liquid pressure from a liquid pressure pump, thereby to generate a control signal. CONSTITUTION:A controller 1 indicates a servo amplifier 2 to control the rotating speed and torque of a servo motor 5. At the same time, the controller 1 also controls the discharge amount of a variable capacity pump 4 of a two-way type. Detectors 9, 10 detect the liquid pressure of an A boat of a cylinder 8 and the projecting degree and speed of a rod 12 of a cylinder 6, respectively. The detected values are fed back to the controller 1. By the above circuit structure, the projecting shift of the cylinder rod 12 can be controlled by time and also the projecting speed and projecting force (pressure) can be controlled corresponding to the shift by a program loaded in advance into the controller 1. Therefore, the protruding volume and pressure of a material can be freely controlled if the material is protruded by this rod 12.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention broadly relates to a control i & II device and control method for a plastic molding machine, and in particular to an electric control system for a plastic molding machine in which a hydraulic pump is electrically controlled. The present invention relates to a hydraulic control device and method.

Particularly, the first invention is one in which the hydraulic pump, the rotation means for rotating it, and the electric rotation controller for controlling the same are widened without being limited, and the second invention provides for each of these. The contents are made clear by limiting the scope to bidirectional hydraulic pumps, servo motors, and servo amplifiers.

A third aspect of the invention is an electrical hydraulic pressure control device for a plastic molding machine in which pressure control by a controller is exponential.

Roughly speaking, the fourth invention relates to an electrical hydraulic pressure control method for a plastic molding machine that incorporates the first invention as a method.

[Conventional technology] The manufacturing process of injection molding machines, which are typical processing and manufacturing equipment for plastic products, ranges from a simple molding method using constant pressure to complex changes in filling speed when filling a mold with molten resin. This is a very wide range of advanced molding methods that require multi-stage speed control, multi-stage pressure control that changes the pressurizing force in multiple stages at the end of filling, or mold internal pressure control that controls the internal pressure of the mold according to an ideal pattern.

An injection molding machine is composed of various hydraulic pumps, directional control valves, hydraulic motors, cylinders, pressure control valves, flow rate control valves, etc., and is an assembly of hydraulic press elements.

In addition, some devices use a servo valve and a microcomputer to perform closed-loop control in order to obtain more advanced controllability. Recently, some models have been introduced that replace hydraulic equipment with electric servo motors.

In addition, in connection with the claimed invention, the patent application filed by the company of which the applicant of the claimed invention is the representative @ 1984-16556
4 (hydraulic power servo system) and patent application No. 62-067777 (fluid pressure supply device) filed by the same applicant as the present invention.

[Problem to be solved by the invention] As mentioned above, injection molding machines are driven by hydraulic pressure,
Some are pneumatic, some are pure electric power sources, but most are hydraulic. This is because injection molding machines require unimaginably large forces, speeds, and complex controls due to the thickness of the molded product; for example, to obtain an IJ molded product. Some machines are equipped with a power source of 50 to 60 HP and a mold clamping force of 300 tons (cited in the Hydraulic Technology Handbook published by Nikkan Kogyo Shimbun). Therefore, it can be said that the hydraulic system is optimal in order to satisfy these requirements.

However, this hydraulic system also has many problems, as the efficiency is low at about 20% when using a servo valve, and the loss due to the low efficiency is used to increase the oil temperature. Therefore, there is a waste of money in cooling the oil. Furthermore, when a servo valve is used, extreme oil cleanliness (contamination) is required (contamination control level NAS class 7), and flushing work is indispensable. This problem exists not only in injection molding, but also in molding methods belonging to the same family, such as extrusion molding, blow molding (L+low molding), and stamping molding.

As explained above, there are many problems with hydraulic control, and there is a movement to avoid hydraulic systems as much as possible and perform molding with pure electric power alone, but in the case of high output, it is superior to hydraulic systems. There's nothing. Therefore, if this problem of hydraulic pressure control can be solved, it will bring great news to the field of plastic molding.

[Means for Solving the Problems] In view of the above problems, the electrical hydraulic pressure control device and method for a plastic molding machine according to the present invention electrically controls a liquid pressure pump such as a hydraulic pump. .

In particular, unlike the invention of the above-mentioned patent application, the present invention has a controller having a programmed basic control signal, which is a position signal from a pressure shaft protrusion position sensor such as a rod, and a pressure shaft protrusion speed of the rod etc. It is configured to input a speed signal from a sensor and a pressure signal from a pressure sensor that detects the output liquid pressure of a liquid pressure pump, and output a control signal based on these signals. In particular, the third invention is characterized in that the pressurization control is increased exponentially.

The specific structure of the electric hydraulic pressure control device and method for a plastic molding machine according to the present invention will be described in detail below.

First, the configuration of the electric hydraulic pressure control device for a plastic molding machine, which is the first invention, will be described. First of all, there is a controller. This controller inputs a position signal from a pressure shaft protrusion position sensor such as a rod, which will be described later, a speed signal from a pressure shaft protrusion speed sensor such as a rod, and a pressure signal from a pressure sensor. Next, this controller has a programmed basic control signal and outputs the control signal as the above-mentioned signal.

Then there is the electrical rotation controller. This electrical rotation side
The wJ device inputs the output from the above controller. Additionally, there is a rotational drive source.

This rotation drive source is controlled by the above-mentioned electric rotation controller. Then there are bidirectional hydraulic pumps. This bidirectional liquid pressure pump is rotated by the above-mentioned rotational drive source.

Instead of this bidirectional liquid pressure pump, a one-way liquid pressure pump and a liquid flow direction switching valve may be used, which are controlled by the above-mentioned electric rotation controller.

Additionally, there are actuators. This actuator is driven by the liquid flow from the above liquid flow switching valve or the above bidirectional liquid pressure pump. There is also a pressure shaft protrusion position sensor such as a rod. This pressure shaft protrusion position sensor is provided in the above-mentioned actuator. Furthermore, there is a pressure shaft protrusion speed sensor such as a rod. This pressure shaft protrusion speed sensor is provided in the actuator described above.

Finally, there is the pressure sensor. This pressure sensor detects the output liquid pressure of the above-mentioned liquid pressure pump.

Next, the configuration of the second invention will be described. This is because the above-mentioned electric rotation controller is first limited to a servo amplifier. Next, the above rotational drive source is limited to a servo motor.

Furthermore, the above-mentioned pump is limited to a directional type α body pressure pump and a liquid flow direction switching valve, which are controlled by the above-mentioned electric rotation controller. Finally, the actuators described above are limited to cylinders.

The rest of the structure is the same as the structure of the first invention described above, so the description of the structure will be referred to.

Then, the configuration of the third invention will be described. First, the above controller issues a control signal that exponentially increases the pressurization control of the output pressure of the actuator. The other aspects are the same as the configurations of the first invention or the second invention described above, and therefore the descriptions of those configurations are incorporated herein.

Finally, the configuration of the electrical hydraulic pressure control method for a plastic molding machine, which is the fourth invention, will be described. First, a position signal from a rod protrusion position sensor provided in the actuator, which will be described later, a speed signal from a rod protrusion speed sensor, and a pressure signal from a pressure sensor that detects the output liquid pressure of a liquid pressure pump, which will be described later. input to the controller. Next, a control signal is output based on the basic control signal programmed therein and the above-mentioned signal.

Then, this output signal controls a bidirectional liquid pressure pump rotated by a rotary drive source through an electric rotation controller. Instead of this bidirectional liquid pressure pump, a one-way liquid pressure pump and a liquid flow direction switching valve controlled by the above controller may be used.

In the above manner, the driving speed and pressing force driving range of the actuator are controlled.

[Function] Since the electrical hydraulic pressure control method and apparatus for a plastic molding machine according to the present invention have the above-described configuration, the following effects are produced.

First, the operation of the first invention, an electric night pressure control device for a plastic molding machine, will be described. First, the controller inputs a position signal from a pressure shaft protrusion position sensor such as a rod, which will be described later, a speed signal from a pressure shaft protrusion speed sensor such as a rod, and one pressure word from a pressure sensor. This controller then has a programmed basic control signal and outputs a control signal as one word above.

Then, the output from the above-mentioned electric rotation controller or the above-mentioned controller I/roller is input. Furthermore, the rotary drive l source is
The above electric rotation control 'Pr: is controlled by this. Further, a bidirectional liquid pressure pump is rotated by the rotational drive source described above. This bidirectional type α body pressure pump; instead,
A one-way type/α body pressure pump and an α flow direction switching valve may be included and controlled by the above-mentioned electric rotation controller.

Then, the actuator is driven to flow the liquid from the liquid flow LJJ switching valve or the bidirectional IF body pressure pump. Further, a pressure shaft protrusion position sensor such as a rod is provided on the actuator to detect the pressure shaft protrusion position. In general, a pressure shaft protrusion speed sensor such as a rod provided in the actuator detects the pressure shaft protrusion speed. Finally, a pressure sensor detects the output liquid pressure of the liquid pressure pump.

Next, the second invention will be described. This is because, first, the above-mentioned electric rotation controller is limited to a servo amplifier, so that it functions as a servo amplifier. and,
Since the above-mentioned rotational drive is originally limited to a servo motor, this works as a servo motor.

Furthermore, since the above-mentioned pump is limited to a one-way type liquid pressure pump and a liquid flow direction switching valve controlled by the above-mentioned electric rotation controller, this is a one-way type liquid pressure pump and a liquid flow direction switching valve. The U body pressure pump produces a unidirectional liquid flow, and the liquid flow direction switching valve is controlled by the electrical rotation controller described above to switch the direction of the liquid flow. Finally, since the actuator described above is limited to a cylinder, it functions as a cylinder.

Since the other functions are the same as those of the first invention described above, the explanation of the functions is incorporated herein.

Then, the operation of the third invention will be described. This causes the controller to issue a control signal that exponentially increases the pressurization control of the output pressure of that actuator.

The other functions are the same as those of the first invention or the second invention described above, so the explanations of those functions are incorporated herein.

Finally, the operation of the fourth invention, the electrical hydraulic pressure control method for a plastic molding machine, will be described. First, a position signal from a rod protrusion position sensor provided in the actuator, which will be described later, a speed signal from a rod protrusion speed sensor, and a pressure signal from a pressure sensor that detects the output liquid pressure of a liquid pressure pump, which will be described later. When input to the controller, it outputs a control signal based on the basic control signal programmed therein and the above-mentioned signal.

Next, this output signal is passed through an electric rotation controller to control a bidirectional liquid pressure pump rotated by a rotary drive source. In place of this bidirectional liquid pressure pump, a unidirectional (α) body pressure pump and a liquid flow direction switching valve controlled by the above-mentioned controller may be used to produce the same effect.

In the above manner, the driving speed and pressing force driving range of the actuator are controlled.

[Example] Hereinafter, the electric hydraulic pressure control device and method for a plastic molding machine according to the present invention will be explained in detail using an example thereof with reference to the accompanying drawings.

FIG. 1 shows a 7M plastic molding machine according to the present invention.
It is a block diagram of a pneumatic hydraulic pressure control device.

As shown in Fig. 1, a controller 1, a servo amplifier 2, a servo motor 3, a bidirectional variable displacement pump 4, a tank 5, a check valve 6, an unload valve or external pilot type relief valve 7, a single-rod double-acting cylinder 8, and a displacement In a circuit consisting of a detector 9, a speed detector 10, and a pressure detector 11, the controller 1 gives commands to the servo amplifier 2 to control the rotational speed and torque of the servo motor 3. The discharge ff1Qs of the bidirectional variable displacement pump 4 is also controlled at the same time. At the same time, the above cylinder 8
Of A boat? The α pressure, the amount of protrusion (displacement) and the protrusion speed of the rod 12 of the cylinder 6 are detected by the respective detectors 9 and 1.
0 is detected, and the controller is fully bent back to 1.

The above-mentioned check valve 6 is for replenishing the insufficient liquid from the above-mentioned tank 5 by the rod volume when the above-mentioned rod 12 protrudes, and the above-mentioned unload valve or external bi-rod type relief valve 7 is for the above-mentioned This is for discharging iα corresponding to the volume when the rod 12 is drawn into the tank 5.

With such a circuit (iξ configuration), according to the program installed inside the controller 1 described above,
It is possible to temporally control the protrusion displacement of the cylinder rod 12 described above, and to control the protrusion speed and ejection force (pressure) according to each displacement.

That is, by determining the rotation speed or torque of the servo motor 4 and the capacity of the pump ↓, the output oil ff1Qs and the oil pressure Ps from the pump 4 can be freely controlled. It should be easy to understand that this is directly converted into the above-mentioned ejection speed and ejection force of the cylinder rod 12. Therefore, this rod 1
If the material is extruded in step 2, it is possible to freely control the amount of material extruded and the extrusion pressure.

Further, even after extrusion is completed, the volume of the material contracts as it cools within the mold, and in order to compensate for this, it is necessary to control the extrusion pressure of the rod 12 over time. In this case, the oil amount Qs is almost zero and only the oil pressure P8 has to be controlled over time.

The present invention can exhibit sufficient controllability even in this case, and the 40 rotations of the servo motor described above are mostly in a stopped state and only stall torque is generated. That is, this means that the hydraulic part functions in the same way as a continuously variable transmission having a variable reduction ratio of 0 to 1.0, and contributes only to power transmission. All of the control is performed by the servo motor 4 that receives commands from the controller 1. Further, by using a servo valve or the like, the oil amount Q8 and the oil pressure ps that occur at the turning angle are no longer leaked, resulting in a dramatic improvement in efficiency.

As shown in FIG. 2, the hydraulic pump 4 is driven by the electric motor 3a, and the hydraulic pumps 4 and 7 are connected to
The force t-1 that has been explained using the method in which the two pipes are connected is shown in the basic form, and the operation is the same even in the form shown below.

That is, as shown in FIG. 3, a one-way discharge hydraulic pump 4a and a directional switching valve 4C are combined and a tank 5a).
The direction may be determined by the amount of oil proportional to the rotational speed of the hydraulic pump 4a and the switching valve 4C. In this way, the one-way discharge variable displacement pump 4a and the directional switching valve 4C
With this combination, the check valve 6 and unload valve or relief valve 7 shown in FIG. 1 become unnecessary, and only the actuator switching valve 4C for each process is required, resulting in the most simplified hydraulic circuit.

The above explanation was given using an injection molding machine as an example. A. Control of the extrusion amount and extrusion pressure of the extrusion molding machine. B. Control of the extrusion amount and extrusion pressure of the blow molding machine. C. Control of the extrusion amount and extrusion pressure of the standby pull molding machine. It can also be applied to

Therefore, the above hydraulic pump may be of a constant displacement type or a variable displacement type. If a variable capacity type is used, the fluctuation range of the oil amount can be expanded beyond the rotational speed range of the power source. Regarding electric motors, the combination of a servo amplifier and a servo motor is the basic type of method for controlling the rotational speed and direction of the motor. However, the same thing will happen if this is replaced with an inverter and an AC induction motor. Further, instead of the electric motor, a power source such as an internal combustion engine or an external combustion engine may be used. At this time, the momentum (displacement, rotation angle, speed, acceleration, etc.) of the mechanical output P0 of the actuator is detected by a sensor and fed back to the controller, thereby controlling the rotation speed, output, etc. of the power source. .

In the method of the present invention, one actuator is used per pump.
It is not possible to operate multiple actuators at the same time.

However, if we consider the case of an injection molding machine, the processes proceed in the order of mold clamping process, injection process, cooling process, and intermediate process, and each process does not overlap. If you prepare one pump and switch the actuator for each process with a switching valve, you can do it with minimal cost and space.

Regarding the third invention, in the prior art, the pressure was controlled stepwise after the filling of the material into the mold was completed, as shown in the table in Figure 4, but the temperature of the material inside the mold was As shown in the table in Figure 5, it is normal for prices to decline exponentially. Therefore, it is natural to increase the pressure exponentially as shown in the table in Figure 6, which also leads to improved quality. In the present invention, such control is performed by the above program. In addition, in FIG. 4, filling of the t-hole is completed at the point indicated by the arrow, and the pressure rises rapidly.

Finally, the fourth invention, a method for controlling electrical hydraulic pressure for plastic molding, will be described using one embodiment thereof.

First, a position signal from the rod protrusion position sensor 9 provided in the cylinder 1, a speed signal from the rod protrusion speed sensor 10, and a pressure sensor 11 that detects the output liquid pressure of the hydraulic pump 4, which will be described later, are detected. The pressure signal is input to the controller 1 described above. Next, a control signal is output based on the basic control signal programmed therein and the above-mentioned signal. This program increases the pressure control exponentially as shown in the table of FIG.

Then, this output signal is passed through the servo amplifier 2,
The bidirectional hydraulic pump 4 rotated by the above-mentioned servo motor is controlled.

In the above manner, the drive speed and pressure force drive range of the actuator are controlled.

[Effects of the Invention] As explained above, when compared with a conventional hydraulic control system using servo valves, proportional control valves, etc., A. Energy efficiency is improved to a level comparable to that of a pure electric control system. Approximately 2
0%→approximately 80%B, the rise in oil temperature decreases rapidly, making an oil cooler unnecessary. Alternatively, the volume of the tank can be made extremely small.

It operates satisfactorily when the contamination level of C0 oil is about NAS class 9. Therefore, flushing work after the device is completed can also be omitted.

D. Since it is a pure electric servo control, the disturbance phenomenon that occurs when using a servo valve is drastically reduced (adjustment after the device is completed is easier).

Benefits such as this will come to fruition.

For reference, FIG. 7 shows an example of the circuit of a conventional injection molding machine.

This circuit is for a small machine, but compared to this,
It can be seen that the circuit of the invention is highly simplified. In other words, at the same time as the servo valve and the proportional control valve are removed, the crest valve,
There will also be no need to switch between low-capacity and high-capacity pumps.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an electrical hydraulic control device for a plastic molding machine according to the present invention. FIG. 2 is a block diagram of an embodiment near the hydraulic pump. FIG. 3 is a block diagram of an alternative embodiment of that of FIG. FIG. 4 is a table showing pressure versus time for pressurization of a prior art actuator. FIG. 5 is a table showing the temperature change of the material inside the mold. FIG. 6 is a table showing pressure versus time for pressurization of the actuator according to an embodiment of the third aspect of the present invention. FIG. 7 shows a circuit example of a conventional injection molding machine. 1... Controller 2... Servo amplifier 3
...Servo motor 4...Hydraulic pump 5...
・Tank 6...Check valve 7...Unload valve 8...Cylinder 9...Rod protrusion position sensor 10...Rod protrusion speed sensor

Claims (4)

[Claims] (1) It is programmed to input a position signal from a pressure shaft protrusion position sensor such as a rod, a speed signal from a pressure shaft protrusion speed sensor such as a rod, and a pressure signal from a pressure sensor, which will be described later. A controller that has basic control signals and outputs control signals based on these, an electric rotation controller that inputs the output from the controller, a rotation drive source controlled by the electric rotation controller, and the rotation drive source. A bidirectional liquid pressure pump or a one-way liquid pressure pump rotated by a liquid flow switching valve and a liquid flow direction switching valve controlled by the above-mentioned electric rotation controller, the liquid flow switching valve or the above two-way liquid An actuator driven by a liquid flow from a pressure pump, a pressurizing shaft protrusion position sensor such as a rod provided on the actuator, a pressurizing shaft protruding speed sensor such as a rod also provided on the actuator, and the above liquid pressure An electrical hydraulic pressure control device for a plastic molding machine, comprising a pressure sensor that detects the output liquid pressure of a pump. (2) It inputs a position signal from a rod protrusion position sensor, a speed signal from a rod protrusion speed sensor, and a pressure signal from a pressure sensor, which will be described later, and has a programmed basic control signal. a controller that outputs a control signal, a servo amplifier that inputs the output from the controller, a servo motor that is controlled by the servo amplifier, a one-way liquid pressure pump and a liquid flow direction switching valve that are rotated by the servo motor. A cylinder driven by the liquid flow from the bidirectional liquid pressure pump, a rod protrusion position sensor provided on the cylinder, and a rod also provided on the cylinder. An electrical hydraulic pressure control device for a plastic molding machine, comprising: an ejection speed sensor; and a pressure sensor that detects the output liquid pressure of the above-mentioned liquid pressure pump. (3) The plastic molding according to claim 1 or 2, wherein the controller issues a control signal that exponentially increases the pressure control of the output pressure of the actuator. Machine electrical hydraulic control device. (4) A position signal from a rod protrusion position sensor provided on the actuator, a speed signal from a rod protrusion speed sensor, and a pressure signal from a pressure sensor that detects the output liquid pressure of a liquid pressure pump, which will be described later, are sent to the controller. A bi-directional liquid pressure pump or a one-way liquid pressure pump which is rotated by a rotary drive source through an electric rotation controller using this output signal and outputs a control signal according to a basic control signal programmed therein and a basic control signal programmed therein. An electrical hydraulic pressure control method for a plastic molding machine, comprising controlling a liquid flow direction switching valve controlled by a controller, thereby controlling the drive speed and pressure force drive range of an actuator.