JPH06335946A - High-speed, low-pressure molding control device of injection molding machine - Google Patents

Abstract

PURPOSE:To simplify the structure, improve the operability, miniaturize the hydraulic pump and reduce piping diameters. CONSTITUTION:Control of injection speeds of a screw 2 is done by controlling number of revolutions of a servo motor 6 which actuates a hydraulic pump 4, and control of injection pressure is done by solenoid proportional pressure control valve 9. Therefore, a plurality of injection cylinders is obviated, resulting in a simple structure, and nonstep control of injection speed and pressure is feasible. If solenoid change-over valves 31 and 32 are turned on and a differential circuit 30c is actuated, flow rate of the hydraulic oil of the hydraulic pump 4 can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed low-pressure molding controller for controlling the injection process of a hydraulic injection molding machine.

[0002]

2. Description of the Related Art In order to improve warpage and twist of plastic molded products, improve transferability of grain, prevent damage to pins such as connectors, and extend life, a plurality of filling processes and pressure-holding processes of injection process are performed. The high-speed low-pressure molding method in which the screw thrust (injection pressure) is regulated for each section to advance the screw and the plastic is filled into the mold at low speed at high speed is widely adopted.

As an injection molding machine that realizes this molding method,
Equipped with a plurality of injection cylinders, one or more injection cylinders are selected for each section of the injection process to perform high-speed low-pressure molding (Japanese Utility Model Laid-Open No. 2-146017), injection cylinders, and a plurality of cylinders. There is known a multi-stage hydraulic cylinder that is combined in multiple stages and performs high-speed low-pressure molding in the same manner as described above (Japanese Patent Publication No. 59-15295).

[0004]

However, the above-mentioned conventional hydraulic injection molding machine for performing high-speed and low-pressure molding has many problems as follows. (1) During the injection process, the selection switching of the injection cylinder is performed by the electromagnetic switching valve, so that a shock noise is generated and discontinuous operation is performed at the time of switching. (2) Although the injection cylinder is selected to determine the maximum injection speed and the pressure, setting is difficult because the set values of the injection speed and the pressure differ depending on the cylinder selection. (3) Since the maximum injection speed and pressure are determined by the structure of the injection cylinder and stepless selection is not possible, the degree of freedom is low. (4) Since the hydraulic pump is constantly rotated by the electric motor to discharge the hydraulic oil, the energy loss is large. (5) Since the method uses multiple injection cylinders,
It has a complicated structure, is not economical, and is disadvantageous in terms of maintenance.

It is an object of the present invention to provide a high-speed low-pressure control which is excellent in operability and operation, does not generate a shock noise, has a simple structure, and is economical in producing energy without waste of energy. It is to provide a device.

Another object of the present invention is to provide a high-speed low-pressure molding control device for an injection molding machine, which can downsize the hydraulic pump and reduce the diameter of the pipe.

[0007]

In order to achieve the above object, a high-speed low-pressure control device in an injection molding machine according to a first aspect of the present invention uses a hydraulic pump which is rotated by an electric motor, by a hydraulic oil sent from the hydraulic pump. An injection cylinder that is operated to move the screw in the heating cylinder back and forth is connected, and in the hydraulic circuit between the hydraulic pump and the injection cylinder,
In an injection molding machine provided with a pressure control valve, the electric motor is a variable speed electric motor, the pressure control valve is an electromagnetic proportional pressure control valve, and the screw is a position sensor for detecting the forward movement position of the screw. , A sequence man-machine program control unit that outputs a screw forward command and receives the output signal of the position sensor, a speed setting unit that sets the moving speed of each forward stage of the screw, and the sequence man-machine. The output signals from the program control unit and the position sensor are output to the speed setting unit, and the speed switching control unit outputs the speed command signal corresponding to the screw position from the speed setting unit and the speed setting unit. When the speed command signal is received, the variable speed motor is moved so that the screw moves forward at the moving speed that matches the speed command signal. It has a servo motor driver to control, a pressure setting unit that sets the pressure in each forward stage or time zone of the screw, and a timer function, and receives the output signals of the sequence man-machine program control unit and the position sensor, and A configuration including a pressure switching control unit that outputs a signal to the pressure setting unit and outputs a pressure command signal corresponding to the screw position or time zone from the pressure setting unit to the electromagnetic proportional pressure control valve to control the hydraulic oil pressure. And

According to a second aspect of the present invention, in the first aspect of the present invention, the sequence man-machine program control section calculates the maximum moving speed of the screw for each pressure set value set in the pressure setting section, and the speed is calculated. When the speed set value set in the setting unit exceeds the maximum moving speed in the speed setting unit, the function is limited to the maximum moving speed.

According to a third aspect of the present invention, in the first or second aspect of the invention, a hydraulic circuit between the hydraulic pump and the injection cylinder includes:
The configuration is such that the differential circuits are switchably connected.

[0010]

The forward movement speed of the screw is changed by changing the rotation speed of the variable speed electric motor, and the injection pressure is changed by changing the hydraulic oil pressure by the electromagnetic proportional pressure control valve.
Therefore, the injection speed and the pressure can be controlled steplessly without depending on the cylinder selection, and there is no shock noise and discontinuous operation can be prevented. In addition, the injection speed and pressure can be easily set. Moreover, since the hydraulic pump is driven by the variable speed electric motor and only the necessary hydraulic oil is discharged, there is no energy loss. Simple structure and easy maintenance.

The sequence man-machine program control unit calculates the maximum moving speed of the screw for each pressure set value set in the pressure setting unit, and when the injection speed set value in the speed setting unit exceeds the maximum moving speed. Limits its maximum movement speed. Therefore, even when a high-capacity hydraulic pump is used to obtain a high injection speed, it is not necessary to use a large-capacity variable speed electric motor matching the capacity of the hydraulic pump.

When the differential circuit is used, the injection cylinder can be operated quickly with a small hydraulic oil flow rate, so that the hydraulic pump can be downsized and the diameter of the hydraulic pipe to the injection cylinder can be reduced. You can

[0013]

FIG. 1 shows an embodiment of a high-speed low-pressure molding control device in an injection molding machine according to the present invention. Reference numeral 1 in this figure
Is a heating cylinder. A screw 2 is inserted into the heating cylinder 1 so as to be movable in the axial direction and rotatable in the circumferential direction. The screw 2 is moved forward by the injection cylinder 3 to the left in the figure, and the resin in the heating cylinder 1 is injected into a mold (not shown). A hydraulic pump 4 is connected to the injection cylinder 3 via an electromagnetic switching valve 5. The above basic structure of the injection molding machine is well known.

Reference numeral 6 is a servo motor (variable speed electric motor) for operating the hydraulic pump 4. The screw 2 is provided with a position sensor 7 such as a pulse encoder, and the servo motor 6 is provided with a speed sensor 8 such as a pulse generator.
Is provided. The position sensor 7 detects the forward movement position of the screw 2, and the speed sensor 8 detects the servo motor 6
Detects the rotation speed of. Hydraulic pump 4 and solenoid switching valve 5
An electromagnetic proportional pressure control valve (proportional valve) 9 is provided in the hydraulic circuit between and.

Reference numeral 11 is a molding machine controller.
The molding machine control device 11 mainly includes a sequence / man-machine program control unit 12, a speed setting unit 13, a speed switching control unit 14, a pressure setting unit 15, and a pressure switching control unit 16. The sequence man-machine program control unit 12 includes an electromagnetic switching valve 5, a speed setting unit 13, a speed switching control unit 14, a pressure setting unit 15, and a pressure switching control unit 16.
Etc. are connected to and control them.

The speed setting unit 13 is divided into five stages as shown in FIG. 2, and each section S ₁ in the filling process of the injection process is divided into five stages.
And _{-S 2, S 2 -S 3,} S 3 -S 4, S 4 -S 5, S 5 -S 6,
The forward movement speeds V ₁ , V ₂ of the screw 2 in the pressure holding process,
It is for setting the ~V ₆ individually. The speed switching control unit 14 includes a sequence man-machine program control unit 12
And the interface 17 together with the pressure switching control unit 16.
Is connected to the position sensor 7 via
It has a function of receiving a screw position signal output from the speed setting unit 13 and selecting the speed setting values V ₁ , V ₂ , to V ₆ suitable for the screw position.

The speed setting values V ₁ , V ₂ , to V ₆ selected by the speed switching control unit 14 are converted into analog values by the D / A conversion unit 18 and input to the servo motor driver 20 through the amplifier 19. Servo motor driver 20
Is configured to perform feedback control of the rotation speed of the servo motor 6 according to the speed command signal output from the speed setting unit 13 and the speed signal of the speed sensor 8.

Further, the pressure setting unit 15 sets the injection pressures P ₁ , P ₂ , to P ₅ in the three stages of the pressure-holding process and the sections S ₁ -S ₂ , S ₂ -S ₆ of the filling process. To do. The pressure switching control unit 16 has a timer function, and the pressure setting unit 15 selects a pressure setting value that matches the position of the screw 2 output from the position sensor 7 and the timer setting value.

The pressure setting values P ₁ , P ₂ , ... P ₅ selected by the pressure switching control unit 16 are converted into analog values by the D / A conversion unit 21 and the electromagnetic proportional pressure control valve 9 via the amplifier 22. And the electromagnetic proportional pressure control valve 9 is controlled so that the injection pressure becomes the pressure set value.

By the way, the maximum value of the product of the injection speed Vp of the screw 2 and the pressure P is constant (see FIG. 3). The sequence man-machine program control unit 12, the injection pressure setting value P _1, P _2, calculates the maximum moving speed Vp for to P _5, the speed setting value V _1, V _2, ~V ₆ the highest moving speed V
p _1, Vp _2, ~Vp ₅ For numeric exceeding (see FIG. 2), the maximum moving speed the speed of the screw 2 Vp _1, V
A function of limiting to p ₂ , ~ Vp ₅ is provided.

Next, the operation of the high-speed low-pressure molding control device in the injection molding machine of the present invention having the above structure will be described with reference to the flow charts of FIGS. When the injection command is issued (step S1), the sequence man-machine program control unit 12 along with the solenoid b of the solenoid switching valve 5 is energized calculates a maximum moving speed Vp ₁ ~Vp ₅ (step S2), the timer T Starts timing (step S3). Next, it is determined whether or not the timer T has timed (step S4).

In the case of N in step S4, it is judged whether or not the internal latch relay is ON (step S6), and in the case of Y, the process proceeds to step S39. In the case of N, it is determined whether or not the screw 2 is between the positions S ₁ and S ₂ (step S7). If Y, the process proceeds to step S8, and if N, the process proceeds to step S13.

In step S8, it is determined whether or not the set speed V ₁ is smaller than the maximum moving speed Vp ₁ , and if Y, the set speed V ₁ is output to the servo motor driver 20 as a speed command signal (step S9). In the case of N, the maximum speed Vp ₁ is output as the speed command signal (step S10).

The servo motor driver 20 receiving the speed command signal controls the servo motor 6 so that the screw speed becomes the set speed V ₁ (or the maximum moving speed VP ₁ ) (step S11). At this time, the set pressure P ₁ of the pressure setting unit 15 is output to the electromagnetic proportional pressure control valve 9 as a pressure command signal (step S12). The above control is performed in step S
It continues until it becomes N in 7.

In step S13, the screw 2 is in the section S.
Whether the ₂ -S ₃ is determined, in the case of Y step S
14, and in the case of N, the process proceeds to step S19, but steps S13 to S18, steps S19 to S24, steps S25 to S30, and steps S31 to S36 are the above steps S7 to S36.
Since the contents are the same as those in step S12 except for the numerical values to be judged or controlled, the description thereof will be omitted.

If N in step S31, step S3
In 7, it is determined whether the screw 2 has passed the position S ₆ , and when it becomes Y, the internal latch relay is set (step S38), and the timer T ₁ starts counting (step S39). Then, in the next step S40, the timer T
_It is determined whether or not ₁ is counted up. If Y, the process proceeds to step S46, and if N, the process proceeds to step S41.

In step S41, it is determined whether or not the set speed V ₆ is smaller than the maximum moving speed Vp ₃ , and if Y, the set speed V ₆ is output (step S42), and if N, the maximum moving speed Vp ₃ Is output (step 43).
The servo motor driver 20 controls the servo motor 6 so as to attain the set speed V ₆ (or the maximum moving speed Vp ₃ ) (step S44), and the set pressure P ₃ becomes a pressure command signal from the pressure setting section 15. Electromagnetic proportional pressure control valve 9
Is output (step S45). This is step S4
Continue until 0 at Y.

In step S46, the timer T ₂ starts counting. The following steps S47 to S52 and steps S53 to S57 are the same as the above step S40.
~ Since the content is the same as step S45, its description is omitted. Step S53 to step S57 are step S
It continues until it becomes Y in 4. When the result is Y in step S4, the internal latch relay is reset (step S5), and the process is ended.

The injection rate in FIG. 3 is injection rate = cross sectional area of screw × injection speed, and in the case of FIG. 3, 1 cm ³ / S
(Injection rate) ≈1.4138 mm / S (injection speed). It is needless to say that the division of the injection process and the control of the injection speed and the pressure are examples and can be variously changed.

FIG. 9 shows another embodiment of the present invention. In this high-speed low-pressure molding control device, the differential circuit 30c is connected to the hydraulic circuits 30a and 30b between the hydraulic pump 4 and the injection cylinder 3, and more specifically between the electromagnetic switching valve 5 and the injection cylinder 3. At the same time, the differential circuit 30c is provided with an electromagnetic switching valve 31, and the hydraulic circuit 30a between the differential circuit 30c and the electromagnetic switching valve 5 is provided with an electromagnetic switching valve 32. The electromagnetic switching valves 31 and 32 are switched by a switching signal of the sequence man-machine program control unit 12. Since the other construction is the same as that of the high-speed low-pressure molding control device of FIG. 1, the same reference numerals are given and detailed description thereof is omitted.

In the high-speed low-pressure molding control device of FIG. 9, when the electromagnetic switching valves 31, 32 are turned off, the operation is exactly the same as that of the high-speed low-pressure molding control device of FIG. When the electromagnetic switching valves 31 and 32 are turned on, the differential circuit 30c operates, so that the diameter of the piston 3a of the injection cylinder 3 is D and the diameter of the piston rod 3b is D (1/5 ^1/2 ) ^1/2. In this case, when the solenoid b of the electromagnetic switching valve 5 is excited, the injection cylinder 3 becomes 5 ^1/2 when the electromagnetic switching valves 31 and 32 are off and the differential circuit 30c does not work.
The piston pin rod 3b is extended to the left in FIG. 9 at double speed and 1/5 ^1/2 pressure.

The high-speed low-pressure molding control device equipped with the differential circuit 30c controls the pressure and speed as follows, for example. Figure 1
2500 kg / cm ^{2 at} 0> injection pressure ≧ 2500/5 ^1/2
When the pressure is set in the range of (= 1118) kg / cm ² , the electromagnetic switching valves 31 and 32 are turned off. Injection pressure <2500
In the range of / 5 ^1/2 kg / cm ² , the electromagnetic switching valves 31 and 32 are turned on to activate the differential circuit 30c.

This control is performed by the sequence man machine pro
Gram control unit 12 to output the solenoid valve switching signal.
Then, the electromagnetic switching valves 31 and 32 are turned on and off. Injection
Pressure P₁, P₂, ~ P_FiveThe setting value of (Fig. 2) is the pressure setting value.
<2500/5^1/2kg / cm ²At the time, Sequence Man
P in the machine program control unit 12₁, ~ P_FiveEach setting value of
To 5^1/2Doubled and output to pressure setting unit 15, speed V₁〜〜
V₆About 1/5^1/2Doubled and output to speed setting unit 13
Let Also, the maximum moving speed VP₁, ~ VP_FiveAlso about
1/5^1/2Multiply this to the maximum speed, speed V₁, ~ V₆ 
To compare with.

After all, when the differential circuit 30c is operated, the capacity of the servo motor 6 may be selected to include the shaded area in FIG. If the differential circuit 30c is not used, 82
Whereas the hydraulic pump 4 capable of producing a speed of 0 mm / sec is required, when the differential circuit 30c is used, it is 820/5.
^The hydraulic pump 4 capable of obtaining a speed of ^1/2 (= 367) mm / sec is sufficient. Therefore, the hydraulic pump 4 can be downsized. When the differential circuit 30c is operated, the flow rate for obtaining the maximum speed is 1/5 ^1/2 as compared with the case without the differential circuit, and the diameter of the hydraulic circuit to the injection cylinder 3 can be reduced. it can.

[0035]

As described above, according to the first aspect of the present invention, the hydraulic pump rotated by the electric motor is operated by the hydraulic oil sent from the hydraulic pump to advance and retreat the screw in the heating cylinder. A cylinder is connected to the hydraulic circuit between the hydraulic pump and the injection cylinder,
In an injection molding machine provided with a pressure control valve, the electric motor is a variable speed electric motor, the pressure control valve is an electromagnetic proportional pressure control valve, and the forward movement position of the screw is detected in the screw. While the position sensor is attached, a sequence man-machine program control unit that outputs a screw forward command and receives the output signal of the position sensor, a speed setting unit that sets the moving speed of each forward stage of the screw, and A speed switching control unit for receiving a signal output from the sequence / man-machine program control unit and the position sensor, outputting a signal to the speed setting unit, and outputting a speed command signal corresponding to the screw position from the speed setting unit, and a speed setting unit. The speed command signal output from the variable speed controller is set so that the screw moves forward at a moving speed that matches the speed command signal. It has a servo motor driver that controls the motive, a pressure setting unit that sets the pressure in each forward stage or time zone of the screw, and a timer function, and receives the output signals of the sequence man-machine program control unit and the position sensor. And a pressure switching control unit for controlling the hydraulic fluid pressure by outputting a pressure command signal corresponding to the screw position or time zone from the pressure setting unit to the electromagnetic proportional pressure control valve. It is configured as
According to the invention of claim 2, in the invention of claim 1, the sequence man-machine program control unit calculates the maximum moving speed of the screw for each pressure set value set in the pressure setting unit, and the speed setting unit When the set speed setting value exceeds the maximum moving speed in the speed setting unit, the function of limiting the maximum moving speed is added, and the following effects are obtained.

(A) There is little shock noise or noise because it is not necessary to select the injection cylinder during the injection process. Further, since the injection cylinder is not switched, discontinuous operation can be prevented. (B) Since the injection speed is controlled by controlling the rotation speed of the variable speed motor, and the pressure is controlled by the electromagnetic proportional pressure control valve, the setting is easy. (C) The hydraulic pump is driven by a variable speed electric motor, and energy is saved because it is a system that discharges only necessary operating oil. (D) The structure is simple and economical, and the maintenance is easy. (E) The maximum moving speed of the screw for each pressure setting value is calculated, and if the speed setting value exceeds the maximum moving speed, it is limited to the maximum moving speed. Even when the injection speed is obtained, it is not necessary to increase the capacity of the variable speed motor, which is economical in this respect.

The invention of claim 3 is the same as claim 1 or 2.
In the invention described above, since the differential circuit is switchably connected to the hydraulic circuit between the hydraulic pump and the injection cylinder, the hydraulic pump can be downsized and the diameter of the hydraulic circuit can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a high-speed low-pressure molding control device in an injection molding machine of the present invention.

FIG. 2 is a diagram showing an example of setting an injection speed and a pressure in an injection process.

FIG. 3 is a diagram showing a relationship between an injection pressure and an injection speed (injection rate).

FIG. 4 is a flowchart showing a part of the operation of the high-speed low-pressure molding control device according to the present invention.

FIG. 5 is a flowchart showing a part of the operation of the high-speed low-pressure molding control device according to the present invention.

FIG. 6 is a flowchart showing a part of the operation of the high-speed low-pressure molding control device according to the present invention.

FIG. 7 is a flowchart showing a part of the operation of the high-speed low-pressure molding control device according to the present invention.

FIG. 8 is a flowchart showing a part of the operation of the high-speed low-pressure molding control device according to the present invention.

FIG. 9 is a block diagram showing another embodiment of the present invention.

FIG. 10 is a diagram showing a relationship between an injection pressure and an injection speed (emission rate).

[Explanation of symbols]

 1 Heating Cylinder 2 Screw 3 Injection Cylinder 4 Hydraulic Pump 6 Servo Motor (Variable Speed Electric Motor) 7 Position Sensor 9 Electromagnetic Proportional Pressure Control Valve 12 Sequence / Man-Machine Program Control Section 13 Speed Setting Section 14 Speed Switching Control Section 15 Pressure Setting Section 16 Pressure switching control unit 20 Servo motor driver 30a, 30b Hydraulic circuit 30c Differential circuit 31, 32 Electromagnetic switching valve

Claims (3)

[Claims] 1. A hydraulic pump rotated by an electric motor is connected to an injection cylinder which is operated by hydraulic oil sent from the hydraulic pump to move a screw in a heating cylinder forward and backward, and between the hydraulic pump and the injection cylinder. In an injection molding machine in which a hydraulic circuit is provided with a pressure control valve, the electric motor is a variable speed electric motor, the pressure control valve is an electromagnetic proportional pressure control valve, and the screw is forwardly moved to the screw. A sequence man-machine program control unit that outputs a screw forward command and receives the output signal of the position sensor while a position sensor that detects the moving position is attached, and a speed setting that sets the moving speed of each forward stage of the screw. Section, the sequence man-machine program control section, and the position sensor output signal to the speed setting section. A speed switching control unit that outputs a signal and outputs a speed command signal corresponding to the position of the screw from the speed setting unit, and a screw at a moving speed that receives the speed command signal output from the speed setting unit and matches the speed command signal. Has a servo motor driver for controlling the variable speed electric motor so as to move forward, a pressure setting unit for setting the pressure in each forward stage or time zone of the screw, and a timer function, and the sequence man-machine program control unit. And output a signal from the position sensor to the pressure setting unit, and control the hydraulic oil pressure by outputting a pressure command signal matching the screw position or time zone from the pressure setting unit to the electromagnetic proportional pressure control valve. A high-speed low-pressure molding control device in an injection molding machine, comprising: 2. The sequence man-machine program control unit calculates the maximum moving speed of the screw for each pressure setting value set in the pressure setting unit, and the speed setting value set in the speed setting unit is set to that speed setting value. 2. The high-speed low-pressure molding control device for an injection molding machine according to claim 1, wherein a function of limiting the maximum moving speed when the maximum moving speed is exceeded is provided. 3. A high-speed low-pressure molding control device for an injection molding machine according to claim 1, wherein a differential circuit is switchably connected to a hydraulic circuit between the hydraulic pump and the injection cylinder.