JPH11188763A - Method for controlling injection unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent overshoot of a forward movement speed of a plunger and its vibration by a method wherein an acceleration is reduced by each specific value from a point of time in reaching a speed represented by the specific formula so that the acceleration becomes zero at a point of time when a command speed reaches a set speed. SOLUTION: When a forward movement speed of a plunger is accelerated toward a speed V by an acceleration (a), it is accelerated decreasing the acceleration (a) by Δa per a specific time from a point of time when the forward movement speed of the plunger reaches a speed Vch calculated by the formula (:Vch=V-ΔV, ΔV=Δa.n+v/2, n=a/Δa,). Then, at a point of time when the forward movement speed of the plunger reaches the speed V, the acceleration (a) is made zero. When decelerated, the speed is reduced decreasing the acceleration (a) by Δa per specific time from a point of time when the forward movement speed of the plunger reaches the speed Vch. Then, the acceleration (a) is made zero at a point of time when the forward movement speed of the plunger reaches the speed V.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an injection device in a synthetic resin injection molding machine.

[0002]

2. Description of the Related Art Conventionally, as an injection device of an injection molding machine, a cylinder having an injection port at one end, a plunger sliding in an axial direction at a position facing the injection port inside the cylinder, and a driving means for moving the plunger forward and backward. The cylinder has a supply port for molding material between the sliding position of the plunger and the injection port, and pressurizes the molding material supplied to the inside of the cylinder by advance of the plunger to connect to the injection port. It is known that a molding material is configured to be injected into a cavity of a mold. This injection device includes a plunger type in which unmelted molding material is supplied into the cylinder and plasticized by a heater or the like, and is injected. A pre-plasticizer type in which a screw for melting the molding material is provided outside the cylinder is provided. There is an in-line screw type integrally provided on the tip side of the plunger. In some cases, a cylinder internal pressure detecting device is provided at the rear of the plunger or at the cylinder.

In the above-described conventional injection device, injection control is performed as follows. In the injection process of injecting molding material into the mold cavity by moving the plunger forward, measures such as balancing the flow in the runner and preventing gas generation and jetting failure in the gate part Therefore, the speed command is switched according to the information of the plunger position or the pressure, and as shown in FIG.
The plunger is advanced at multiple speeds. Immediately before the molding material is completely filled in the cavity of the mold, the speed is reduced to reduce the impact. Recently, as shown in FIG. 11, there is a type in which the speed can be changed at an arbitrary acceleration.

Further, in the injection process, a large pressing force is applied to a molding material due to clogging of a gate or the like, so that a certain limit is given to the injection power so as not to damage a mold or the like.

In the process of injecting and injecting the molding material into the cavity of the mold by advancing the plunger, the pressure is switched to a pressure-holding step of keeping the pressure constant by detecting the cylinder internal pressure or the position of the plunger. When performing injection molding, in order to inject at high speed, the injection pressure during injection is higher than the holding pressure, and the injection speed is reduced just before filling to complete filling at low speed, or the holding pressure is set to multiple stages The pressure is reduced until the filling is completed.

Also, the pressure F of the plunger during the pressure holding process is
Is, when the command pressure is Pp, the actual cylinder pressure is P ', and the cross-sectional area of the plunger is A, the pressing force F of the plunger is
It is defined by the following equation (6) or the following equation (7).

[0007]

(Equation 3)

[0008]

(Equation 4)

[0009]

However, the above conventional control method has the following problems.

When the forward speed of the plunger is accelerated, a large ejection power is required, but when the acceleration is stopped, almost no ejection power is required. However, there is a problem that an overshoot or vibration of the speed occurs as shown in FIG. 1, and also in the case of deceleration, an undershoot or vibration of the speed similarly occurs.

Further, as shown in FIG. 13, the acceleration is limited by giving a limit to the pressure of the plunger, so that rapid acceleration cannot be performed, and high-speed and low-pressure molding cannot be performed.

If the gate is clogged when the plunger is driven at a high speed, as shown in FIG. 14, even after the cylinder internal pressure sharply rises and the injection power reaches the limit, the driving means is stopped. Due to the inertia, a large pressing force was applied to the molding material, and the internal pressure of the cylinder greatly overshot, causing damage to the mold and the product and causing a product defect.

Further, since the molten molding material is a viscous fluid and a compressed fluid, a change in the cylinder internal pressure is accompanied by a time lag with respect to the movement of the plunger. Therefore, the driving of the plunger is controlled by the pressure information. If there is a sudden change in pressure, a large change in pressure occurs as shown in FIG. If the driving speed of the plunger is high, the fluctuation of the pressure due to the time delay becomes larger, so that when the thin part is injection molded, the holding pressure is set in multiple stages,
When the method of reducing the pressure by the time the filling is completed is used, there is a problem that the pressure and the speed tend to vibrate because the plunger advances at a high speed. Further, in the method in which the injection speed is reduced immediately before filling to complete the filling at a low speed, there is a problem that short shots are likely to occur because the region where the speed is low before filling is increased.

Further, when the pressure is switched to the pressure-holding step with the plunger moving forward at a high speed, there is a problem that the pressure oscillation as shown in FIG. 16 occurs due to the time delay of the change in the cylinder internal pressure.

Further, the pressure pattern of the holding pressure is accompanied by a pressure reduction,
Also, when the pressure command is small, the plunger may not return even if the plunger pressure is reduced to zero due to the sliding resistance of the plunger and the frictional resistance of the driving means, and the cylinder internal pressure may not drop. there were.

In view of the above-mentioned conventional problems, the present invention eliminates fluctuations in speed during the injection step and fluctuations in pressure during the pressure-holding step, enables high-speed injection during low-pressure molding, and causes gate clogging and the like. It is an object of the present invention to provide a method of controlling an injection device that can reduce pressure overshoot and enable lower pressure molding.

[0017]

According to the first aspect of the present invention, there is provided a cylinder having an injection port at one end, a plunger sliding in an axial direction at a position facing the injection port inside the cylinder,
Drive means for moving the plunger forward and backward, and pressurizing the molding material supplied to the inside of the cylinder by advancement of the plunger to inject the molding material into the cavity of the mold connected to the injection port. In the injection device, when the driving speed of the plunger is controlled in multiple stages and continuously by accelerating or decelerating at an arbitrarily set acceleration toward an arbitrarily set speed, the command speed of the plunger becomes the set speed. Before reaching the speed, the acceleration is reduced by a constant value so that the acceleration becomes zero when the commanded speed reaches the set speed, and the speed Vch at which the acceleration change is started.
Let a be the set acceleration, V be the set speed, Δa be the decrease in acceleration per fixed time, ΔV be the difference between V and Vch, n = a / Δa ΔV = Δa · n (n + 1) / 2 Vch = V-ΔV (1) The acceleration is reduced by a constant value so that the acceleration becomes zero when the command speed reaches the set speed before the command speed of the plunger reaches the set value. Thus, the forward speed of the plunger can be controlled without generating overshoot or vibration.

According to a second aspect of the present invention, in the above-described injection device having means for detecting the cylinder internal pressure, when a pressure lower than a preset cylinder internal pressure limit Pmax by ΔP1 is set to P1, the cylinder internal pressure becomes P1. When the pressure is lower than the maximum, the pressure limit of the plunger is maximized. When the cylinder internal pressure becomes P1 or more, the pressure limit Flim of the plunger is set to A, the cross-sectional area of the plunger is set to P, the actual internal pressure is set to P ', and an arbitrary constant Is defined by the following equation (2), (3), or (4) as kp and ki. High acceleration molding can be performed while maintaining a low pressure limit, and pressure feedback control is performed. Even when gate clogging or the like occurs, pressure overshoot can be kept small, and pressure oscillation can be prevented.

Flim = A · Pmax (2)

[0020]

(Equation 1)

[0021]

(Equation 2)

According to a fifth aspect of the present invention, in the above injection apparatus, the holding pressure for maintaining the pressure Pp constant after reducing the pressure to a pressure Pp lower than the Pch from the time when the cylinder internal pressure reaches the preset pressure Pch. When performing control, the forward speed of the plunger is reduced by a preset acceleration, and pressure feedback control is performed so that the cylinder internal pressure is maintained at Pp from the time when the cylinder internal pressure becomes equal to or lower than Pp.

When the forward speed of the plunger is reduced at a constant acceleration, if the forward speed of the plunger reaches an arbitrarily set lower limit value Vlow before the cylinder internal pressure becomes equal to or less than the pressure Pp, the speed is reduced. Is terminated, and the undershoot of the pressure can be suppressed by keeping the forward speed of the plunger at a constant Vlow until the cylinder internal pressure becomes equal to or lower than the pressure Pp. This lower limit value Vlow may be a negative value.

When the lower limit value Vlow of the forward speed of the plunger is a positive value, the pressure in the cylinder may start to increase before the pressure becomes equal to or lower than the pressure Pp. If the cylinder internal pressure does not fall below the arbitrarily set pressure within the arbitrarily set time, Vlow is changed to a negative value to newly decelerate. Further, when performing pressure feedback control so as to maintain the cylinder internal pressure at Pp, the speed limit value can be set arbitrarily, so that pressure oscillation is less likely to occur and the amount of pressure downshoot increases. Or the downshooting occurrence time can be prevented from becoming long.

According to an eleventh aspect of the present invention, in the above injection device, when the pressure of the plunger is controlled according to a preset pressure pattern from the time when the cylinder internal pressure reaches a preset pressure Pvp, When the difference between the command pressure Pp and the actual cylinder pressure P ′ is larger than the specified value ΔP2, the pressing force F is defined as F = A {Pp + kp · (Pp−P ′)} (5). When the difference between Pp and the actual cylinder pressure P 'is less than the specified value ΔP2

[0026]

(Equation 4)

When the difference between the command pressure and the actual pressure is large, the pressure fluctuation during the pressure-holding step can be prevented by setting the integral value of the pressure deviation to zero.

A method of controlling the injection device.

According to a twelfth aspect of the present invention, in the above injection apparatus, when the pressure of the plunger is controlled according to a preset pressure pattern from the time when the cylinder internal pressure reaches a preset pressure Pvp, When the internal pressure is larger than the command pressure and the difference becomes equal to or more than the allowable value ΔP3,
To change the speed limit to a sufficiently low value,
By reducing the speed command value when the pressure overshoot amount is large, it is possible to prevent pressure oscillation during the pressure holding step.

According to a thirteenth aspect of the present invention, in the above injection device, when the pressure of the plunger is controlled according to a preset pressure pattern from the time when the cylinder internal pressure reaches a preset pressure Pvp, Pressing force F,

[0031]

(Equation 3)

Alternatively,

[0033]

(Equation 4)

When the pressure F becomes equal to or less than zero, the plunger is commanded to move in the retreating direction, thereby enabling ultra-low pressure molding.

The type of the injection apparatus of the present invention may be any of a plunger type, a pre-plasticizer type and an in-line screw type.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a control method for an injection molding machine according to the present invention will be described below with reference to FIGS.

The injection molding machine according to the present embodiment shown in FIG. 1 is a screw pre-plastic injection molding machine.
And a preliminary plasticizing device 200 for supplying the plasticized molding material to the injection device 100, and a mold 300 into which the plasticized molding material is injected from the injection device 100.

The injection device 100 has a cylinder 1 having an injection port 7 at one end, a plunger 2 which slides in the axial direction of the cylinder 1 at a position facing the injection port 7 inside the cylinder 1, and moves the plunger 2 forward and backward. And a driving unit 3. In the cylinder 1, a supply port 8 for supplying a molding material into the liquid storage portion 9 in the cylinder 1 is formed between the sliding position of the plunger 2 and the injection port 7. Further, in order to detect the pressure of the molding material supplied to the liquid storage portion 9, a pressure detecting device 6 for the plunger 2 is connected to a rear portion of the plunger 2. A backflow prevention valve 4 for preventing backflow of the resin is provided at the tip of the plunger 2.

As shown in FIG. 1, the driving means 3 comprises a servomotor 33, and has an encoder 51 for detecting the rotation angle of the servomotor 33. The encoder 51 detects the position of the plunger 2 in the cylinder 1 from the detected rotation angle. The driving means 3 includes a control means 5 for controlling the driving thereof.
, A forward speed of the plunger 2 is detected from a change amount of the rotation angle obtained from the encoder 51. The control means 5 is connected with a pressure detecting device 6 for the plunger 2 and has a built-in torque detecting device for the servomotor 33. The control means 5 controls the driving of the servo motor 33 based on these detection signals.

The pre-plasticizing apparatus 200 includes a hopper 201
The molding material plasticized by the screw portion 202 is fed into the cylinder 1 through the supply port 8 of the cylinder 1 and stored in the liquid storage portion 9 in the cylinder 1.

After the plunger 2 advances, the molding material stored in the liquid storage portion 9 in the cylinder 1 is pressurized to inject the molding material into the cavity 301 of the mold 300 connected to the injection port 7 and then melt. The molded material is completed by being cooled and solidified in the cavity 301.

In the injection step in which the plunger 2 is advanced to inject and inject the molding material into the cavity 301 of the mold 300, as shown in FIG. When the plunger 2 is accelerated, the plunger 2 is accelerated while decreasing the acceleration by Δa per fixed time from the time when the forward speed of the plunger 2 becomes equal to or higher than the speed Vch calculated by the following equation (1).
When the forward speed of the vehicle reaches the speed V, the acceleration becomes zero. Also in the case of deceleration, as shown in FIG. 2 (b), as in the case of acceleration, from the time when the forward speed of the plunger 2 becomes equal to or lower than the speed Vch, the plunger 2 is decelerated while decreasing the acceleration by Δa per fixed time Go, plunger 2
When the forward speed of the vehicle reaches the speed V, the acceleration becomes zero.

N = a / Δa Δv = Δa · n (n + 1) / 2 vch = v−Δv (1) As shown in FIG. 3, the internal pressure limit Pmax of the cylinder 1 is lower by ΔP1. The pressure is P1, the actual cylinder pressure is P ', the cross-sectional area of the plunger 2 is A, and an arbitrary constant is k.
When p and ki are set, the cylinder internal pressure becomes P1 during the injection process.
When the pressure is lower than P1, the pressure limit of the plunger 2 is maximized, and when the cylinder internal pressure is equal to or higher than P1, the pressure limit Flim of the plunger 2 is set by the following pressure equation (2), (3) or (4) Control the pressure.

Flim = A · Pmax (2)

[0045]

(Equation 1)

[0046]

(Equation 2)

In particular, when the pressure is controlled by the pressing force defined by the expression (4), overshoot and vibration of the pressure are further reduced. When the plunger 2 is driven by the servo motor 33, the pressing force of the plunger 2 is converted into a torque value of the servo motor 33 in the forward direction of the plunger 2 and output as a torque limit.

When the molding material is injected into the cavity 301 of the mold 300 by advancing the plunger 2, the pressure of the cylinder 1 is increased from the time when the internal pressure of the cylinder 1 reaches a preset pressure Pch.
When performing pressure-holding control to maintain the pressure Pp constant after reducing the pressure to a pressure Pp lower than the channel, as shown in FIG.
The forward speed of the plunger 2 is reduced by the acceleration a1,
From the point in time when the cylinder internal pressure falls below Pp, pressure feedback control is performed so that the cylinder internal pressure maintains Pp.

If the forward speed of the plunger 2 reaches the lower limit value Vlow of the arbitrarily set speed before the cylinder internal pressure becomes equal to or lower than the pressure Pp, the deceleration is terminated, and until the cylinder internal pressure becomes lower than the pressure Pp. The forward speed of the plunger 2 is maintained at a constant Vlow. At this time, V
low may be a negative value. When Vlow is a positive value, the pressure in the cylinder may start to increase before it becomes equal to or lower than the pressure Pp. At that time, as shown in FIG. 5, a rise in the pressure is detected, or as shown in FIG. Then, from the time point when it is detected that the cylinder internal pressure does not become lower than the pressure Pgn within the time tgn, Vlow is changed to a negative value to newly decelerate.

When pressure feedback control is performed so that the cylinder internal pressure maintains Pp from the point in time when the cylinder internal pressure becomes equal to or lower than Pp, an arbitrary dwelling speed limit value Vp is set. However, if it is too small, the amount of pressure downshoot is large,
In addition, since the time during which the downshoot occurs is long, an optimal value is set for the molding.

Further, the plunger 2 is advanced and the mold 30 is moved.
When the pressure of the plunger 2 is controlled by the pressure pattern shown in FIG. 7 from the time when the molding material is injected into the cavity 301 of 0 and the pressure in the cylinder reaches Pvp, the cross-sectional area of the plunger 2 is A. If the difference between the command pressure Pp and the actual cylinder pressure P 'is larger than the specified value ΔP2, the pressing force F of the plunger 2 is defined by the following equation (5), and the difference between the command pressure Pp and the actual cylinder pressure P' becomes When the value is not more than the specified value ΔP2, the pressing force F is specified by the following equation (7).

F = A {Pp + kp · (Pp−P ′)} (5)

[0053]

(Equation 4)

After the pressure holding control is started by the above equation (5), (7) or the following equation (6), the actual cylinder pressure P 'is larger than the command pressure Pp, If it is equal to or more than ΔP3, the speed command value is changed to a sufficiently low Vp as shown in FIG. It is desirable that Vp be equal to or less than 1/2 of the dwell start speed Vps.

[0055]

(Equation 3)

When the calculated value of the pressing force F of the plunger 2 becomes equal to or less than zero, the speed command value is changed to a negative value Vpm as shown in FIG. Return the value to the original Vp. When the absolute values of Vpm and Vp are large, pressure oscillation occurs in a low pressure region. Vpm
= -3mm / s, Vp = 5mm / s, maximum pressure capacity 15
15kgf in the injection apparatus of 00kgf / cm ² / cm ²
Vibration does not occur at the above pressure.

[0057]

According to the control method of the injection molding machine of the present invention, the following effects are obtained.

According to the first aspect of the present invention, the acceleration is decreased by a constant value so that the acceleration becomes zero when the command speed reaches the set speed before the command speed of the plunger reaches the set value. Can be controlled without generating overshoot or vibration.

According to the second, third or fourth aspect of the present invention, when the cylinder internal pressure is lower than the pressure P1 lower by ΔP than the pressure limit, the pressure limit of the plunger is maximized to maintain the low pressure limit. High acceleration molding is possible.

Further, according to the third and fourth aspects of the present invention, the pressure overshoot can be suppressed even when the gate is clogged by performing the pressure feedback control when the cylinder internal pressure is equal to or higher than the pressure P1. In particular, in claim 4, pressure control can be performed with higher accuracy, and pressure vibration can be prevented by the combination of claim 4 and claim 11.

According to the fifth to tenth aspects of the present invention, the decompression process immediately before filling is controlled by the deceleration pattern of the forward speed of the plunger, so that a free decompression curve can be realized without generating vibration.

According to the eleventh or twelfth aspect of the present invention, the integral value of the pressure deviation is set to zero when the difference between the command pressure and the actual pressure is large, and the speed command value is reduced when the pressure overshoot amount is large. Thereby, pressure oscillation during the pressure holding step can be prevented.

According to the thirteenth aspect of the present invention, when the pressure of the plunger is equal to or less than zero, a negative speed command is issued, so that ultra-low pressure molding can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an overall configuration of an injection molding machine to which a control method for an injection molding machine of the present invention is applied.

FIG. 2 is an explanatory diagram of a control method of a plunger acceleration in the embodiment.

FIG. 3 is an explanatory diagram of a control method of a plunger pressing force in the embodiment.

FIG. 4 is an explanatory diagram of a method for controlling a pressure reduction pattern of an internal cylinder pressure by deceleration control of a plunger in the embodiment.

FIG. 5 is an explanatory diagram of a method of controlling a pressure-reducing pattern of an internal cylinder pressure by a plunger deceleration control in the embodiment.

FIG. 6 is an explanatory diagram of a method of controlling a pressure-reducing pattern of an internal cylinder pressure by deceleration control of a plunger in the embodiment.

FIG. 7 is an explanatory diagram of a pressure oscillation prevention control method by turning on and off a pressure deviation integrated value in a pressure holding step in the embodiment.

FIG. 8 is an explanatory diagram of a pressure vibration prevention control method by changing a pressure holding speed in a pressure holding step in the embodiment.

FIG. 9 is an explanatory diagram of a control method for realizing low-pressure molding in the embodiment.

FIG. 10 is an explanatory diagram of a conventional plunger speed control method.

FIG. 11 is an explanatory diagram of a conventional plunger speed control method.

FIG. 12 is an explanatory diagram of a pressure fluctuation generated by a control method of a conventional example.

FIG. 13 is an explanatory diagram of a decrease in acceleration generated by a conventional control method.

FIG. 14 is an explanatory diagram of pressure overshoot and pressure vibration generated by a control method of a conventional example.

FIG. 15 is an explanatory diagram of pressure oscillation due to a time delay of pressure in a conventional control method.

FIG. 16 is an explanatory diagram of pressure oscillation due to a time delay of pressure in a conventional control method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Plunger 3 Driving means 5 Control means 6 Pressure detection means 7 Injection port 100 Injection device 300 Mold 301 Cavity

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Ryoma Murase 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (13)

[Claims] 1. A cylinder having an injection port at one end, a plunger sliding in an axial direction at a position facing the injection port inside the cylinder, and driving means for moving the plunger forward and backward, wherein the plunger advances to move the inside of the cylinder. In the injection device configured to inject the molding material into the cavity of the mold connected to the injection port by pressing the molding material supplied to the injection port, an arbitrarily set speed at an arbitrarily set acceleration When the drive speed of the plunger is controlled in multiple stages and continuously by accelerating or decelerating toward the point, the acceleration becomes zero at the time when the command speed reaches the set speed before the command speed of the plunger reaches the set speed. The acceleration is decreased by a constant value so that the speed vch at which the acceleration change starts is represented by a, a set acceleration, v is a set speed,
Δa is the decrease value of acceleration per fixed time, Δv is v and v
A method for controlling an injection device, characterized in that the difference from ch is defined by the following equation (1). n = a / Δa Δv = Δa · n (n + 1) / 2 vch = v−Δv (1) 2. A cylinder having an injection port at one end, a plunger sliding in an axial direction at a position facing the injection port inside the cylinder, driving means for moving the plunger forward and backward, and means for detecting a cylinder internal pressure. In an injection apparatus, which is configured to pressurize the molding material supplied to the inside of the cylinder by advance of the plunger and to inject the molding material into the cavity of the mold connected to the injection port, advance the plunger. When the molding material is injected into the mold cavity, a preset cylinder pressure limit Pma
Assuming that the pressure lower than x by ΔP1 is P1, when the cylinder internal pressure is lower than P1, the pressing force of the plunger is maximized, and if the cylinder internal pressure becomes P1 or more,
A control method for an injection device, characterized in that when the pressure Flim of the plunger is defined as Flim and the cross-sectional area of the plunger is defined as A, the following formula (2) is used. Flim = A · Pmax (2) 3. When the cylinder internal pressure is equal to or higher than P1, the plunger pressing force limit Flim is set such that the actual cylinder internal pressure is P ', the cross-sectional area of the plunger is A, and arbitrary constants are kp and k.
3. The control method according to claim 2, wherein i is defined by the following equation (3). (Equation 1) 4. When the cylinder internal pressure is equal to or higher than P1, the plunger pressing force limit Flim is set such that the actual cylinder internal pressure is P ', the cross-sectional area of the plunger is A, and arbitrary constants are kp and k.
The control method for an injection device according to claim 2, wherein i is defined by the following equation (4). (Equation 2) 5. A cylinder having an injection port at one end, a plunger sliding in an axial direction at a position facing the injection port inside the cylinder, driving means for moving the plunger forward and backward, and means for detecting a cylinder internal pressure. In an injection apparatus, which is configured to pressurize the molding material supplied to the inside of the cylinder by advance of the plunger and to inject the molding material into the cavity of the mold connected to the injection port, advance the plunger. When injecting the molding material into the cavity of the mold, from the point in time when the cylinder internal pressure reaches a preset pressure Pch, the pressure is reduced to a pressure Pp lower than Pch, and then a pressure holding control for maintaining the pressure Pp constant is performed. In this case, the forward speed of the plunger is reduced by a preset acceleration, and the cylinder internal pressure is maintained at Pp from the time when the cylinder internal pressure becomes equal to or less than Pp. A method for controlling an injection device, characterized by performing pressure feedback control as described above. 6. When the forward speed of the plunger is reduced by a constant acceleration, if the forward speed of the plunger reaches an arbitrarily set lower limit value Vlow before the cylinder internal pressure becomes equal to or lower than the pressure Pp, the speed is reduced. 6. The control method for an injection apparatus according to claim 5, further comprising: maintaining the forward speed of the plunger at a constant Vlow until the cylinder internal pressure becomes equal to or lower than the pressure Pp. 7. The lower limit value Vlow of the forward speed of the plunger is a negative value.
The control method of the injection device described in the above. 8. When the lower limit value Vlow of the forward speed of the plunger is a positive value, the cylinder pressure becomes equal to the pressure P.
7. The control method according to claim 6, wherein Vlow is changed to a negative value when the voltage starts rising before reaching p or less. 9. When the lower limit value Vlow of the forward speed of the plunger is a positive value, if the cylinder internal pressure does not become lower than an arbitrarily set pressure within an arbitrarily set time, Vlow is set to a negative value. 7. The method for controlling an injection device according to claim 6, wherein the method is changed. 10. The system according to claim 5, wherein a speed limit value can be arbitrarily set when performing pressure feedback control so as to maintain the cylinder internal pressure at Pp. Control method of the injection device. 11. A cylinder having an injection port at one end, a plunger that slides in an axial direction at a position facing the injection port inside the cylinder, driving means for moving the plunger forward and backward, and means for detecting cylinder internal pressure. In an injection apparatus, which is configured to pressurize the molding material supplied to the inside of the cylinder by advance of the plunger and to inject the molding material into the cavity of the mold connected to the injection port, advance the plunger. When the molding material is injected into the cavity of the mold, and when the pressure inside the cylinder reaches a preset pressure Pvp, the pressure of the plunger is controlled according to a preset pressure pattern, the command pressure is set to Pp, Assuming that the actual cylinder pressure is P 'and the cross-sectional area of the plunger is A, the pressure F of the plunger is determined by the difference between the command pressure Pp and the actual cylinder pressure P' is a specified value ΔP2 If the difference between the command pressure Pp and the actual cylinder internal pressure P 'is equal to or less than the specified value ΔP2, the value is specified by the following expression (5). . F = A {Pp + kp. (Pp-P ')} (5) 12. A cylinder having an injection port at one end, a plunger that slides in an axial direction at a position facing the injection port inside the cylinder, driving means for moving the plunger forward and backward, and means for detecting the cylinder internal pressure. In an injection apparatus, which is configured to pressurize the molding material supplied to the inside of the cylinder by advance of the plunger and to inject the molding material into the cavity of the mold connected to the injection port, advance the plunger. When the molding material is injected into the cavity of the mold and the pressure of the plunger is controlled in a preset pressure pattern from the time when the pressure in the cylinder reaches a preset pressure Pvp, the actual cylinder pressure is commanded. The injection limiter is characterized in that when the pressure is larger than the pressure and the difference becomes equal to or more than the allowable value ΔP3, the speed limit value is changed to a sufficiently low value. Method. 13. A cylinder having an injection port at one end, a plunger sliding in an axial direction at a position facing the injection port inside the cylinder, driving means for moving the plunger forward and backward, and means for detecting a cylinder internal pressure. In an injection apparatus, which is configured to pressurize the molding material supplied to the inside of the cylinder by advance of the plunger and to inject the molding material into the cavity of the mold connected to the injection port, advance the plunger. When the molding material is injected into the cavity of the mold, and when the pressure inside the cylinder reaches a preset pressure Pvp, the pressure of the plunger is controlled according to a preset pressure pattern, the command pressure is set to Pp, When the actual cylinder pressure is P 'and the cross-sectional area of the plunger is A, the pressing force F of the plunger is defined by the following equation (6) or (7). Control method for but an injection apparatus characterized by commanding the speed of the backward direction of the plunger when it becomes less than zero. (Equation 3) (Equation 4)