JP3026153B2 - Speed control method of electric injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric injection molding machine having a drive system using a servomotor, and more particularly to a speed control system for a servomotor.

[0002]

2. Description of the Related Art An example of a speed control system of a conventional injection device will be described with reference to FIG. The speed of the servomotor 20 is detected by a speed detector 21, and the detected value _Vf is fed back to a subtractor 22. The subtractor 22 outputs the difference between the speed command value _Vr and the detection value _Vf of the speed detector 21 to the speed amplifier 23. The motor driver 24 is a speed amplifier 2
The servo motor 20 is controlled on the basis of the output of (3).

[0003] By the way, this type of servomotor has applications from low speed to high speed, and a speed pattern generator is usually used for its control, and the following two types of speed patterns are generated. is there.

The first speed pattern is a pattern in which the start-up time of the servomotor, that is, the acceleration time becomes a constant value regardless of the level of the target speed. As shown in FIG. 5, different target speed _{V 22, V 23 (V 23} > V
Even ₂₂₎ is given, the acceleration time speed pattern VP _22, V ₂₃ as is always constant at T20 is generated.

[0005] The second speed pattern is a pattern in which the acceleration of the servomotor has a constant value regardless of the target speed. That is, as shown in FIG. 6, even when different target speeds V ₃₂ and V ₃₃ (V ₃₃ > V ₃₂ ) are given, the speed pattern V is such that the acceleration is always constant.
P ₃₂ and VP ₃₃ are generated.

[0006]

In the case of the first speed pattern, the following operation becomes easy at a low speed, but the maximum acceleration capability of the servo motor is the maximum speed speed pattern VP _24.
Therefore, there is a disadvantage that the acceleration capability of the servo motor becomes more useless as the speed becomes lower.

On the other hand, in the case of the second speed pattern, the acceleration capability of the servomotor can be used regardless of whether the speed is low or high. However, since the acceleration time becomes shorter as the speed becomes lower, the following operation becomes difficult, and there is a drawback that the actual speed exceeds the target speed, that is, so-called overshoot occurs.

Accordingly, an object of the present invention is to provide an injection molding machine having a drive system using a servomotor with a speed pattern that has good followability from low to high speeds and that can effectively use the response of the drive system without waste. An object of the present invention is to provide a speed control method of an electric injection molding machine capable of speed control.

[0009]

A speed control system according to the present invention comprises a drive system using a servomotor, and generates a speed pattern based on a set value set by an operator. In the electric injection molding machine for controlling the speed of the servo motor, the speed pattern generating means includes a target speed V> V determined by the set value at a predetermined speed V _0.
If ₀ generates a speed pattern, such as acceleration of the servo motor startup is always a constant value A _0, the target speed V
If <V ₀ , the acceleration when the servo motor starts up is A ₀
A feature is that a speed pattern is generated such that the rise time is always constant at V / V ₀ .

[0010]

FIG. 1 shows a configuration for realizing a speed control system according to the present invention. A speed setting unit 11, a multi-stage speed generator 12, an acceleration / deceleration calculation unit 13, a pattern generator 1 are shown.
4 and the output of the pattern generator 14 is the speed command value _Vr
Is given to the subtractor 22 shown in FIG.

The case where the present invention is applied to an injection device will be described. In the speed setting device 11, a speed set value is given by an operator. This speed set value is one or more types of target speeds and durations required from the start to the end of injection. The multi-stage speed generator 12 sequentially switches the speed setting value based on the screw position, the elapsed time from the start of injection, and the like based on the speed setting value, and outputs a speed signal V that changes stepwise according to the switching timing.

The acceleration / deceleration calculation unit 13 includes a multi-stage speed generator 1
2 is sampled every unit time, and this is set as V _(n) . Further, the acceleration / deceleration calculation unit 13 calculates a predetermined speed V ₀ (usually 25% of the maximum speed V _max ).
Degree), and parameter information indicating the acceleration A ₀ are given, and the following calculations and determination operations are executed from the target velocities V _(n) and V _(n-1) . That is, ΔV = | V _(n) −V
_(n-1) | is calculated, and if ΔV> V ₀ , the acceleration a = A ₀ is fixed for this ΔV, and if ΔV <V ₀ , the acceleration a = A ₀ · ΔV / V ₀ and ΔV And the target velocities V _(n) and V _(n-1)
Is output.

The pattern generator 14 includes an acceleration / deceleration calculation unit 1
Receiving the acceleration a from 3 and the target speeds V _(n) and V _(n-1) ,
A speed pattern is created based on the flowchart shown in FIG. 2, and a command signal indicating a speed command value _Vr is output. However, the flowchart shown in FIG. 2 is an example on the premise that it is started every time ΔT (sec) sufficiently shorter than T10 (see FIG. 3). Therefore, the acceleration a is calculated as the speed change Va per time ΔT. Therefore, the acceleration / deceleration calculation unit 13 and the pattern generator 14 function as a speed pattern generation unit. In FIG. 2, steps S2 and S3 define the operation at the time of acceleration, that is, the startup of the servomotor, and steps S4 and S5 define the operation at the time of deceleration.

FIG. 3 shows a plurality of examples of speed patterns during acceleration. For example, if the operator has a set of at time t1 by the speed setter 11 is switched from the target speed 0 to the target speed V _13, pattern generator 14 creates a speed pattern VP _13. Similarly, if the setting is made to switch from the target speed 0 to the target speed V ₁₆ at time t1, the pattern generator 14 sets the speed pattern VP ₁₆
Create

The case of creating the speed pattern VP ₁₃ will be described with reference to FIG. In this case, the target speed V
_(n) = V _13, the target speed V _(n-1) = a _0, ΔV <V 0
Therefore, the acceleration a = A _0.
ΔV / V ₀ is output. The operation of the flowchart of FIG. 2 is performed at every time ΔT which is sufficiently shorter than the time T10 as described above.

In step S1, it is determined whether or not the condition of V _(n) > V _(n-1) is satisfied. Since this condition is satisfied, the flow shifts to step S2. In step S2, and outputs a speed obtained by adding the acceleration _{a = A 0 · ΔV / V} 0 velocity increment V _a per time ΔT defined by a velocity command value V _r. In step S3, the speed command value V _r is the target speed V _(n), i.e., do the determination if it has reached V _13, if it has not reached the process moves to operation of the next [Delta] T V _r =
Step S1~S3 are repeated until V _13. If velocity command value V _r has reached the target speed V _13, the speed command value in step _{S6 V r = V 13 (=} V (n)) as follows Δ
The operation shifts to the operation of T.

Next, a case where the speed pattern VP ₁₆ is created will be described. In this case, the target speed V _(n) = V ₁₆ ,
Since the target speed V _(n-1) = 0 and ΔV> V ₀ , the acceleration a outputs a constant value A ₀ from the acceleration / deceleration calculation unit 13. In step S1, since V _(n) > V _(n-1) , the process proceeds to step S2. In step S2, the acceleration a =
And it outputs a speed obtained by adding the velocity increment V _a per time ΔT defined by A ₀ as the speed command value V _r.

[0018] In step S3, a judgment velocity command value V _r of whether reaches the target speed V _(n) = V _16, steps S1~S3 until unless reached repeated, if reached the speed command value in step S6 V _r = V ₁₆
By setting (= V _(n) ), the speed is thereafter maintained at the target speed V ₁₆ .

The deceleration operation in steps S4 and S5 differs from the acceleration operation in the following points. That is, by subtracting the speed decrease amount V _a per time ΔT defined by There A ₀ · ΔV / V ₀ in the acceleration a = A ₀ In step S4, the speed command value in step S5 V _r is the target speed V _{(n )} Is determined. Except for this, the deceleration operation is the same as the acceleration operation.

This control method can be applied to any of an injection device using a servo motor as a drive source, a mold clamping device, and an ejector mechanism in an electric injection molding machine.

[0021]

As described above, according to the present invention, in particular, during the start-up operation of the servo motor, a speed pattern that keeps the acceleration constant when the speed is higher than a certain speed is generated according to the level of the target speed. Thus, the acceleration capability of the servomotor is effectively utilized, and when the speed is lower than a certain speed, a speed pattern in which the acceleration time is constant is generated, so that the acceleration time becomes longer, so that occurrence of overshoot can be prevented. Thus, a stable acceleration / deceleration operation can be performed while effectively utilizing the capability of the servomotor over the entire range from low speed to high speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a control system for realizing a speed control system according to the present invention.

FIG. 2 is a flowchart illustrating the operation of the speed pattern generator shown in FIG. 1;

FIG. 3 is a diagram showing an example of a speed pattern created by the speed pattern generator shown in FIG. 1;

FIG. 4 is a block diagram showing a configuration of a speed control system of a conventional injection device.

FIG. 5 is a diagram showing a first example of a conventional speed pattern.

FIG. 6 is a diagram showing a second example of a conventional speed pattern.

[Explanation of symbols]

 Reference Signs List 20 servo motor 21 speed detector 22 subtractor 23 speed amplifier 24 motor driver

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI H02P 5/00 H02P 5/00 Q (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 45/76-45 / 80 B29C 45/40-45/68 B22D 17/32

Claims (1)

(57) [Claims] 1. An electric injection molding machine having a drive system by a servomotor and controlling the speed of the servomotor by a speed pattern from a speed pattern generating means for generating a speed pattern based on a set value set by an operator. When the target speed V> V ₀ determined by the set value from the predetermined speed V ₀ , the speed pattern generating means always keeps the acceleration at the time of starting the servo motor at a constant value A _0. A speed pattern is generated, and if the target speed V <V ₀ , a speed pattern in which the acceleration at the time of starting the servo motor is A ₀ · V / V ₀ and the starting time is always constant is generated. Speed control method of electric injection molding machine.