JP2971284B2 - Control method and control device for electric injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method and a control apparatus for an electric injection device for injecting a resin into a molding die of an injection molding machine.

[0002]

2. Description of the Related Art Conventionally, as an injection device mounted on an injection molding machine to melt a raw material resin and inject it into a molding die, an electric servo is applied to a drive source for applying an injection pressure, a holding pressure and a back pressure to an injection screw. An electric injection device using a motor has been known.

The control method of the electric servomotor for applying the set back pressure to the injection screw during plasticization of the resin in the electric injection device is as follows: (1) The direction in which the injection screw is moved forward by the electric servomotor. (2) a method of feedback control by matching a torque command value with an actual measured value of torque or resin pressure.

[0004]

However, when there is no resin in front of the injection screw, for example, at the time of the first plasticization, any of the above-mentioned methods (1) and (2) can prevent the injection screw from moving forward. There was no resistance and the injection screw could run out of control.

[0005] Usually, the injection device is provided with a stopper for restricting the advance of the injection screw to a set limit to prevent a collision between the tip end portion of the injection screw and the heating cylinder.
For this reason, the forward runaway of the injection screw as described above is stopped by the action of the stopper, but since the stop is abrupt, the rotational movement of the electric servomotor is converted into a linear movement to move the injection screw back and forth. In some cases, the ball screw mechanism was damaged.

The present invention provides a control method and a control apparatus for an electric injection device which can prevent the above-mentioned runaway of the injection screw and prevent the ball screw mechanism and the like from being damaged due to this. .

[0007]

In order to solve this problem, the present invention employs the following configuration. That is, the control method of the electric injection device according to the first aspect controls the rotation speed and the rotation torque of the electric servomotor that drives the injection screw forward and backward, thereby injecting the resin stored in front of the injection screw into the resin. An injection-filling step of applying pressure, a pressure-holding step of applying a predetermined holding pressure to the stored resin subsequent to the injection-filling step, and applying a back pressure according to the plasticizing condition of the resin to the injection screw. In the control method of the electric injection device for sequentially performing each step of the back pressure step, the torque limit value of the electric servomotor is continuously set from the end of the pressure holding step to the start of the back pressure step. The electric servomotor is set to a zero speed state from the end of the pressure-holding step to the end of the back-pressure step.

A control device for an electric injection device according to a second aspect of the present invention includes an injection screw and an electric servomotor for driving the injection screw back and forth, as shown in FIG. An injection filling step of injecting and filling the resin stored in the mold into a molding die, a pressure holding step of applying a predetermined holding pressure to the stored resin subsequent to the injection filling step, and an injection screw for plasticizing the resin. What is claimed is: 1. A control device mounted on an electric injection device for sequentially performing a plasticizing step of storing in front, comprising: a rotation speed detecting means for outputting a rotation speed detection signal according to a rotation speed of the electric servomotor; Torque detection means for outputting a torque detection signal corresponding to the rotation torque of the motor;
Command signal output means for outputting a rotational speed command signal and a torque command signal of the electric servomotor according to a signal output pattern preset for each stage of pressure holding and plasticization,
Current value signal output means for outputting a current value signal according to the rotation speed command signal and the rotation speed detection signal; and a torque signal determined according to both the torque command signal or both the torque command signal and the torque detection signal. Signal limiting means for limiting the current value signal within a range of the upper limit value and outputting the torque value signal, and power control means for controlling power supplied to the electric servomotor in accordance with the torque value signal. In the control device of the electric injection device, the command signal output unit may be configured to set the rotational torque of the electric servomotor in a predetermined period from the end of the pressure-holding stage to the start of the plasticizing stage. Outputs a torque command signal that is equal to or greater than the torque set value of the electric servomotor at the start, and continues from the end of the pressure-holding stage to the end of the plasticizing stage Characterized in that it is a command signal output means for outputting the rotational speed command signal to zero the rotational speed of the electric servo motor Te.

[0009]

In the control method of the electric injection device having the above structure, in the injection filling step of applying an injection pressure to the resin stored in front of the injection screw, a predetermined amount of resin is stored following the injection filling step. Each step of the holding pressure step of applying the holding pressure and the back pressure step of applying the back pressure according to the plasticizing condition of the resin to the injection screw is sequentially performed. Speed state. Therefore, the injection screw does not move forward, and even if there is no resin in front of the injection screw, the injection screw does not run out of control. Note that the zero speed state means that unless an external force exceeding the set rotational torque is applied,
This is the state of the electric servomotor that maintains the stopped state, and does not mean that it is stopped stationary.

At the same time, the torque limit value of the electric servomotor is set to be equal to or greater than the preset torque limit value at the start of the back pressure step, so that the rotation torque of the electric servomotor is held at the torque limit value. You. Therefore, it is possible to prevent the injection screw from retreating abruptly due to the pressure of the resin in front of the injection screw, and no air is sucked into the heating cylinder due to such retraction of the injection screw.

Since the torque limit value of the electric servomotor is maintained until the start of the back pressure step and the process continuously shifts to the back pressure step, there is no shortage of the back pressure at the start of the plasticization. Therefore, retreat of the injection screw caused by the screw effect of the resin in the heating cylinder is prevented.

Further, since the zero-speed state of the electric servomotor is continued until the end of the back pressure process, the injection screw may run out of control even if there is no resistance to the advancement of the injection screw for some reason. There is no. On the other hand, according to the control device for the electric injection device having the above configuration, the control method can be effectively implemented, and the above-described effects can be obtained in the electric injection device.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment will be described with reference to the drawings to further clarify the present invention. First, the configuration of the control device 10 mounted on a known electric injection device (not shown) will be described.

As shown in FIG. 1, a pulley 14 which rotates integrally with the injection screw 12 is externally fitted to an injection screw 12 rotatably and forwardly and backwardly inserted into a heating cylinder (not shown). . The pulley 14 is connected to a rotation servomotor 20 via a timing belt 16, and the rotation of the injection screw 12 can be driven by the rotation servomotor 20. At the rear end 12a of the injection screw 12, a bearing box 22 is provided.
The injection screw 12 and the bearing box 22 are connected so as to be able to move forward and backward integrally along the axial direction of the injection screw 12 and to be relatively rotatable along the circumferential direction of the injection screw 12. A ball screw nut 24 substantially coaxial with the injection screw 12 is fixed to the bearing box 22.

A male screw member 26 having a structure matching with the ball screw nut 24 is screwed to the ball screw nut 24, and the ball screw nut 24 can be moved forward and backward in the axial direction in accordance with the rotation of the male screw member 26. . The proximal end 26a of the male screw member 26 is supported by a housing (not shown) so as to be rotatable and immovable in the axial direction. Also, a force sensor 28 capable of detecting an axial load acting on the male screw member 26 and outputting a signal corresponding to the load is interposed between the base end 26a of the male screw member 26 and the housing. Have been.

Further, a pulley 30 that rotates integrally with the male screw member 26 is fitted around the proximal end portion 26a of the male screw member 26. The pulley 30 is connected via a timing belt 32 to a forward / reverse servomotor 34 as an electric servomotor of the present invention, and the male screw member 26 can be rotationally driven by the forward / backward servomotor 34. The forward / backward traveling servomotor 34 is provided with a rotary encoder 36 that detects the rotational speed of the forward / backward traveling servomotor 34 and outputs a signal corresponding to the rotational speed.

With such a configuration, the rotational force of the forward / reverse servomotor 34 is converted into a linear motion via the male screw member 26 and the ball screw nut 24, and the injection screw 12 can be driven forward and backward. Therefore, the injection screw 12 is driven to rotate forward and backward by the forward / backward servomotor 34 while being driven to rotate by the rotary servomotor 20. Further, since the rotational torque of the forward / backward servomotor 34 corresponds to the axial load of the male screw member 26, the axial load detected by the force sensor 28 is the rotational torque of the forward / backward servomotor 34. Is a value corresponding to. Therefore, the force sensor 28 corresponds to a torque detecting unit that outputs a torque detection signal in the present invention, and the output signal of the force sensor 28 is hereinafter referred to as a torque detection signal KT.

Next, a control section provided for controlling the operation of the rotation servomotor 20 and the forward / backward movement servomotor 34 will be described. The above-described force sensor 28 and rotary encoder 36 are constituent elements of a control unit. The controller 40 shown on the left side in FIG. 1 incorporates a well-known microcomputer (not shown), and performs control processing according to various instructions input via the operation panel 42 and programs stored in the microcomputer in advance. Can be executed, and input contents, execution contents, and data from instruments such as the force sensor 28 can be displayed on the display panel 44.

The controller 40 includes a screw rotation command signal SR for commanding the rotation speed of the rotation servomotor 20, a torque command signal CT for commanding the upper limit value of the rotational torque of the forward / backward movement servomotor 34, The controller 40 outputs a rotation speed command signal CS for instructing the rotation speed of the advance servomotor 34 and other signals. Hereinafter, various control signals output from the controller 40 and transmission and processing of the control signals will be described. The elements will be described.

The screw rotation command signal SR output from the controller 40 is input to a motor drive amplifier 46, where it is amplified and supplied to the rotation servomotor 20. Therefore, the rotation servomotor 20 operates at a rotation speed corresponding to the screw rotation command signal SR.

The torque command signal CT is branched into two lines,
One is input to a subtractor 48. The torque command signal CT input to the subtractor 48 is subjected to a subtraction process by a signal obtained by amplifying the torque detection signal KT by the force sensor 28 by the amplifier 50, and is output as a torque feedback signal FT. The torque feedback signal FT is output from the controller 4
When the open / close switch 52 is closed by the switching signal CC from 0, it is input to the adder 56 via the compensator 54. The adder 56 receives the torque command signal CT branched on the upstream side of the subtractor 48, performs an addition process with the torque feedback signal FT, and outputs the result as the torque upper limit signal LT. This torque upper limit signal LT is input to the torque limiter 58, and the torque signal upper limit value TMAX is determined according to the torque upper limit signal LT. However, when the open / close switch 52 is opened by the switching signal CC from the controller 40, the input of the torque feedback signal FT to the adder 56 is not performed, and the torque signal upper limit value TMAX
Is determined only by the torque command signal CT.

On the other hand, a rotation speed command signal CS is also output from the controller 40, and is input to the subtractor 62 via the open / close switch 60. However, the open / close switch 60 forms a pair with the open / close switch 64. When the plasticization signal CM from the controller 40 is input, the open / close switch 64 closes and the open / close switch 60 opens, and the input of the plasticization signal CM is changed. When there is no switch, the open / close switch 60 is closed, and the open / close switch 64 is opened.
Operated. For this reason, when the open / close switch 60 is closed (the open / close switch 64 is open), the rotation speed command signal CS from the controller 40 is input to the subtractor 62.
When the open / close switch 64 is closed (the open / close switch 60 is open), the rotation speed command signal C input to the subtractor 62 is output.
S becomes zero. That is, the controller 40 and the open / close switches 60 and 64 constitute a command signal output unit of the present invention.

The rotational speed command signal CS input to the subtractor 62 is subjected to a subtraction process by a signal obtained by converting the rotational speed detection signal KK from the rotary encoder 36 by the F / V converter 66, and the current is passed through a compensator 68. The command signal FS is input to the torque limiter 58. The current command signal FS input to the torque limiter 58 is output as a torque value signal ST limited within a range not exceeding the torque signal upper limit TMAX. However, in the F / V converter 66 and the compensator 68,
When the plasticizing signal CM is input, gain switching is performed so as to increase the proportional gain. As described above, even if the rotational speed command signal CS input to the subtractor 62 becomes zero, the current command signal FS maintains the torque. The signal level exceeds the signal upper limit value TMAX.

This torque value signal ST is input to a subtractor 70. The subtractor 70 is connected to a power amplifier 74 via a compensator 72, and a current sensor 76 is provided downstream of the power amplifier 74. The current detection signal KI of the current sensor 76 is input to the subtractor 70. For this reason, the torque value signal ST is subjected to a subtraction process by the current detection signal KI of the current sensor 76 in the subtractor 70, and is further input to the power amplifier 74 as the power command signal CP via the compensator 72. The power amplifier 74 supplies power to the forward / reverse servomotor 34 according to the input power command signal CP.

Next, control processing executed by the control device 10 when the electric injection device is operated will be described with reference to FIGS. Prior to the operation of the electric injection device, the stroke S0 of the injection screw 12 during injection filling, the dwell time Th, the plasticization delay time Tc by the plasticization delay timer, the rotation speed of the injection screw 12 during plasticization, and the injection. A setting process for inputting and storing the signal output pattern, the number of cycles, and the like at each stage of filling, holding pressure, and back pressure to the controller 40 is performed by the operator. Among the signal output patterns set here, the pattern related to the torque command signal of the forward / reverse servomotor 34 includes the torque limit values T1, T2, and T1 at the injection filling stage, the dwell stage, and the back pressure stage shown in FIG. This is in accordance with T3.

After the various settings have been made, when the operation of the electric injection device is started by the operation of the operator, FIG.
The control routine according to the flowchart shown in FIG. In the control routine, first, plasticization of the resin is performed (step 210). In this step 210, the controller 40 outputs the plasticizing signal CM, opens the open / close switch 60, closes the open / close switch 64, sets the rotational speed command signal CS to zero, and outputs the F / V converter 66 and the compensator. The gain is switched to increase the proportional gain of 68. Thus, the rotation speed command signal C input to the subtractor 62
Even if S becomes zero, the current command signal FS has a signal level exceeding the torque signal upper limit TMAX.

Next, the switching signal CC is output to close the open / close switch 52. Further, a torque command signal CT set in the plasticizing stage is output. Thus, the torque signal upper limit value TMAX in the torque limiter 58 becomes the torque limit value T3 corresponding to the set back pressure in the plasticizing stage. In addition, since the current command signal FS is sufficiently large and has a signal level exceeding the torque signal upper limit value TMAX, the torque signal upper limit value TMAX is output as the torque value signal ST. Therefore, the power command signal CP has a value corresponding to the torque signal upper limit value TMAX, and the power supplied to the forward / reverse servomotor 34 in accordance with the power command signal CP is equal to the torque signal upper value TMAX, that is, the value of the plasticization stage. The electric power is in accordance with the torque limit value T3 corresponding to the pressure.

As a result, the forward / reverse servomotor 34
Becomes the torque limit value T3, and the rotation speed becomes zero. Here, the controller 40 outputs the screw rotation command signal SR, and rotates the injection screw 12 at the set rotation speed. As a result, the injection screw 12 plasticizes and feeds the supplied raw resin to the front and stores it. As the plasticization of the resin progresses and the amount of resin stored in front of the injection screw 12 increases, the injection screw 12 retreats.

At this time, since the rotational torque of the forward / backward traveling servomotor 34 maintains the torque limit value T3, the retreat of the injection screw 12 due to the screw effect is prevented. As a result, no silver streaks due to the suction of air due to the retreat of the injection screw 12 occur. In addition, since the forward / reverse servomotor 34 is set to the zero speed state, the injection screw 12 is not driven forward. For this reason, even if there is no resin in front of the injection screw 12, the injection screw 1
2 does not occur, and damage to the ball screw mechanism and the like due to this is prevented.

In the following step 220, the injection screw 1
It is determined whether or not the retreat amount S1 of 2 is equivalent to the stroke S0 of the injection screw 12 at the time of injection filling. Here, if S1 = S0, the process proceeds to the next step 230, where S1 <
If so, the process returns to step 210. At this time, if the difference between S1 and S0 is within the set tolerance, S
It is assumed that 1 = S0.

In step 230, the output of the screw rotation command signal SR is set to 0, and the rotation of the injection screw 12 is stopped. Subsequently, the plasticization signal CM is turned off, the open / close switch 60 is closed, and the open / close switch 64 is opened.
Gain switching is performed to reduce the proportional gain of the / V converter 66 and the compensator 68 (step 240). Further, the torque command signal CT is set as a signal corresponding to the torque signal upper limit value TMAX = 0, the rotational torque of the forward / reverse servomotor 34 is set to 0, and the back pressure on the injection screw 12 is eliminated (step 250).

In the next step 260, the mold is opened, closed, and pressurized by a mold clamping device (not shown). When the mold is opened, the molded product is taken out. However, in the case of the first time, since there is no product in the molding die, the actual product is not taken out. Therefore,
In this step 260, the injection device is virtually in a standby state.

In step 270, the resin stored in front of the injection screw 12 is injected and filled into the molding die. Here, first, the controller 40 opens the open / close switch 52 by the switching signal CC. Thus, the torque signal upper limit value TMAX is determined only by the torque command signal CT, and corresponds to the torque limit value T1 in the injection filling stage. Subsequently, the controller 40 outputs the rotation speed command signal CS set in the injection filling stage. As a result, the forward-reverse servomotor 34 rotates at a high speed to advance the injection screw 12, thereby injecting the resin stored in front of the injection screw 12 into the molding die. This injection filling is continued until the next step 280 determines that the advance amount S2 of the injection screw 12 has reached the set injection stroke S4.

In the next step 290, a dwell stage is performed. Here, first, the controller 40 closes the open / close switch 52 by the switching signal CC. Thus, the torque signal upper limit value TMAX is determined according to the torque command signal CT and the torque feedback signal FT, and corresponds to the torque limit value T2 in the pressure holding stage. Subsequently, the controller 40 outputs a torque command signal CT set in the pressure holding stage, and further outputs a rotation speed command signal CS set in the pressure holding stage. As a result, the forward / reverse servomotor 34 drives the injection screw 12 with the rotation torque (= torque limit value T2) corresponding to the set holding pressure. This dwell stage is the next step 3
At 00, the operation is continued until it is determined that the dwelling time Th has elapsed by counting up the Th timer. When it is determined that the dwelling stage is completed, the process proceeds to step 310.

In step 310, the controller 40
Outputs the plasticizing signal CM, opens the open / close switch 60, closes the open / close switch 64, sets the rotational speed command signal CS to zero, and increases the proportional gain of the F / V converter 66 and the compensator 68. Change the gain. As a result, even if the rotational speed command signal CS input to the subtractor 62 becomes zero, the current command signal FS remains at the torque signal upper limit TMAX.
The signal level exceeds.

Subsequently, a torque command signal CT corresponding to the torque limit value T3 in the plasticizing stage is output (step 32).
0). Thus, the torque signal upper limit value TMAX in the torque limiter 58 becomes the torque limit value T3 corresponding to the set back pressure in the plasticizing stage. Moreover, step 310
As a result, since the current command signal FS is sufficiently large and has a signal level exceeding the torque signal upper limit value TMAX, the torque signal upper limit value TMAX is output as the torque value signal ST. Therefore, the power command signal CP has a value corresponding to the torque signal upper limit TMAX, and the power supplied to the forward / reverse servomotor 34 according to the power command signal CP is:
The electric power corresponds to the torque signal upper limit value TMAX, that is, the torque limit value T3 corresponding to the back pressure in the plasticizing stage.

These steps 310 and 32
By executing 0, the rotational torque of the forward / reverse servomotor 34 becomes the torque limit value T3, and the rotational speed is brought to the zero speed state. This state is continued in the next step 330 until it is determined that the plasticization delay time Tc has elapsed by counting up of the plasticization delay timer, and when it is determined that the plasticization delay time Tc has elapsed, step 210 is performed. Return to.

Simultaneously with the end of the pressure-holding stage, the forward / backward traveling servomotor 34 is brought to the zero speed state with the rotation torque (= torque limit value T3) corresponding to the back pressure. The rise is good. Further, since the back pressure does not become insufficient, the retreat of the injection screw 12 due to the screw effect is prevented, and no silver streak due to the suction of air due to the retreat of the injection screw 12 occurs.

In step 210, a plasticizing step of a new resin is performed. However, as a result of the above steps 310 and 320, the forward / backward traveling servomotor 34 is in the zero speed state with the rotational torque corresponding to the set back pressure, so that the processing for creating this state is not performed again. The controller 40 only outputs the screw rotation command signal SR and rotates the injection screw 12 at the set rotation speed. Thereby, the injection screw 12 sends the newly supplied raw material resin forward while storing it, and stores it. Thereafter, the above processing is repeated until the set number of cycles is reached, and the operation is stopped.

By executing the above control routine, the torque limit value T at each stage of injection filling, holding pressure and back pressure is set.
1, T2, T3 and the actual rotational torque of the forward / reverse servomotor 34 are as shown in FIG. As is apparent from FIG. 3, the shortage of the torque of the forward / reverse servomotor 34 does not occur from the end of the pressure holding stage to the end of the back pressure stage.

As described above, the forward / reverse servomotor 34
At the beginning of the plasticization stage, the rotational torque corresponding to the back pressure is already held, so that the injection screw 1
2 retraction is prevented. Thereby, the injection screw 12
There is no silver streak due to the inhalation of air due to the retreat. Similarly, at the start of the plasticizing stage, the forward / reverse servomotor 34 is brought to the zero speed state, which is maintained until the end of the plasticizing stage, so that the injection screw 12 is not driven forward in the plasticizing stage. For this reason, even when there is no resin in front of the injection screw 12, the runaway of the injection screw 12 does not occur, and damage to the ball screw mechanism and the like due to this is prevented. In addition, at the same time as the end of the pressure-holding stage, the forward / backward traveling servomotor 34 is brought into the zero-speed state with the rotational torque corresponding to the back pressure, so that the rise of the back pressure at the start of the plasticizing stage is good.

Although an embodiment embodying the present invention has been described above, the present invention is not limited by such an embodiment, and the present invention can be carried out in various ways within the scope of the present invention. It is. For example, in the present embodiment, the gain is switched by the plasticizing signal CM so as to increase the proportional gain of the F / V converter 66 and the compensator 68, but in a control system having a sufficient proportional gain in this portion. if there is,
Such a gain switching operation is unnecessary.

In the case of an injection cycle in which plasticization is performed subsequent to the end of the pressure-holding stage, the plasticization delay time is set to 0.
Therefore, the plasticization delay timer becomes unnecessary, and the control related thereto is not performed.

[0044]

As described above, according to the control method of the electric injection device of the present invention, during plasticization, even if there is no resistance to the advancement of the injection screw, the runaway of the injection screw can be prevented. Is prevented. Damage to the ball screw mechanism and the like due to the sudden stop of the forward runaway does not occur.

According to the control device of the present invention, the control method of the present invention can be effectively implemented, and the above-described effects can be obtained in the electric injection device.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a configuration of a control device of an electric injection device of an embodiment.

FIG. 2 is a flowchart illustrating an example of a control routine executed by a control device of the electric injection device of the embodiment.

FIG. 3 is a graph showing a relationship between a torque limit value and an actual torque of a forward / reverse servomotor in the control device of the electric injection device of the embodiment.

FIG. 4 is a block diagram illustrating a control device of the electric injection device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Control device, 12 ... Injection screw, 28 ... Force sensor (torque detecting means), 34 ... Forward / backward traveling servomotor (Electric servomotor), 36 ... Rotary encoder (Rotation speed) Detecting means), 40: controller (command signal output means), 58: torque limiter (signal limiting means), 60: open / close switch (command signal output means), 62: subtractor (current) Command signal output means), 64 open / close switch (command signal output means), 70 subtractor (power control means), 72 compensator (power control means), 74 power amplifier ( Power control means) 76 current sensor (power control means).

Claims (2)

(57) [Claims] 1. An injection filling step of applying an injection pressure to a resin stored in front of an injection screw by controlling a rotation speed and a rotation torque of an electric servomotor for driving the injection screw back and forth. Subsequent to the step, an electric motor for sequentially performing each step of a pressure holding step of applying a predetermined holding pressure to the stored resin and a back pressure step of applying a back pressure to the injection screw according to the plasticizing conditions of the resin to the injection screw. In the method for controlling an injection-type injection device, the torque limit value of the electric servomotor is continuously equal to or greater than the torque limit value at the start of the back pressure process from the end of the pressure holding process to the start of the back pressure process. A method for controlling an electric injection device, wherein the electric servomotor is set to a zero speed state from the end of a process to the end of the back pressure process. 2. An injection filling step, comprising: an injection screw; and an electric servomotor for driving the injection screw forward and backward, wherein the resin stored in front of the injection screw is injected and filled into a molding die. The control device is mounted on an electric injection device that sequentially performs a pressure holding step of applying a predetermined holding pressure to the stored resin and a plasticizing step of plasticizing the resin and storing the resin in front of the injection screw. A rotation speed detection unit that outputs a rotation speed detection signal according to the rotation speed of the electric servomotor; a torque detection unit that outputs a torque detection signal according to the rotation torque of the electric servomotor; A command signal for outputting a rotation speed command signal and a torque command signal of the electric servomotor in accordance with a signal output pattern preset for each stage of pressure holding and plasticization. Signal output means, current command signal output means for outputting a current command signal in accordance with the rotation speed command signal and the rotation speed detection signal, and in response to the torque command signal or both of the torque command signal and the torque detection signal Signal limiting means for limiting the current command signal within a range of the determined torque signal upper limit value and outputting the same as a torque value signal; and power control for controlling power supplied to the electric servomotor in accordance with the torque value signal. In the control device of the electric injection device provided with the means, the command signal output means is configured to preset a rotational torque of the electric servomotor from the end of the pressure-holding step to the start of the plasticizing step. Output a torque command signal that is equal to or greater than the torque set value of the electric servomotor at the start of the plasticizing step, and Control device for an electric injection unit, characterized in that the command signal output means for outputting the rotational speed command signal to zero the rotational speed of the electric servo motor continues to plasticize stage ends.