JPH11221841A - Injection controlling method and electric injection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a free injection velocity pattern and to adjust injection force easily by transmitting the straight-ahead movement of a ball screw mechanism to an injection plunger or screw by using a toggle link mechanism, and controlling the speed of a motor. SOLUTION: When a screw 10 is advanced by transmitting the straight-ahead movement of a ball screw 38 to a toggle link mechanism 30, the properties of the mechanism 30 determined by the arm lengths of links 31, 32, the number of revolution of a motor 40 driven by the mechanism 30, and others regulate the variation of injection speed which changes with the advance of the screw 10 to a given pattern. The injection speed becomes maximum at an injection start position and decreases with the progress, of an injection process. When the injection process approaches the end, although the injection speed decreases remarkably, injection force increases rapidly. Therefore, the variation pattern of the injection speed can be changed in accordance with an injection stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection control method and an electric injection apparatus, and more particularly to an injection control method and an injection apparatus capable of adjusting an injection speed and an injection power in an injection process without being restricted by a mechanical limitation of a toggle link mechanism. The present invention relates to an injection control method and an electric injection device.

[0002]

2. Description of the Related Art Conventionally, an electric injection device used in an injection molding machine converts a rotary motion of an electric motor into a linear motion of a screw or an injection plunger for injecting molten resin into a mold by a transmission mechanism such as a ball screw. doing.

In injection molding, it is necessary to adjust injection speed, injection power, injection amount, and the like to appropriate values according to the type of a product or resin to be molded. For example, in thin molding, the resin is injected at a relatively high pressure at a high speed, and in thick molding, the resin is injected at a low pressure at a low speed.

[0004] In the linear motion type in which the output of the motor is converted into a linear motion by a ball screw or the like, since the linear motion is transmitted to a screw or an injection plunger as it is, the injection speed or the injection speed is controlled by controlling the speed and torque of the motor. Controlling output. Therefore, in order to respond to various patterns of changes in the injection speed and the injection power, the electric motor needs to have a servo motor as large as possible.

On the other hand, the motor is rotated at a constant speed and a constant torque, and the injection speed, the injection pressure and the like are changed in a constant pattern by mechanical means by applying a link mechanism such as a toggle mechanism or a crank. There is a motorized injection device. In such a link mechanism, utilizing the characteristic that the speed and force change depending on the position of the link, the injection is started at a high injection speed with a small injection power immediately after the start of the injection in the injection process, and with the progress of the injection process. In addition, it is possible to easily obtain a constant pattern of the injection speed and the injection pressure such that a large injection power is obtained at the time of the completion of the injection while reducing the injection speed.

However, in the case of the link mechanism, the pattern of the change in the injection speed and the obtained output power are uniquely determined by mechanical dimensions such as the length of the arm of the link, and the pattern of the speed change is changed as necessary. There is a problem that can not be. For this reason, an electric injection mechanism of this type, which has been improved so that the injection speed and the injection power can be adjusted, has been proposed, and examples thereof include the one disclosed in Japanese Patent Publication No. 2631576.

[0007]

However, in the prior art, when the injection speed and the injection power are adjusted, the injection amount of the resin is controlled under a constant condition while the injection speed and the injection speed during the injection process are adjusted.
In addition to being able to adjust the firing power, the injection speed pattern and firing power can be set and adjusted freely due to the mechanical dimensions of the link mechanism.
I cannot make adjustments. In particular, it has been difficult to set an appropriate injection speed pattern and adjust the injection power when the injection stroke is changed by molding with different injection amounts.

Accordingly, an object of the present invention is to solve the problems of the prior art, and to solve the problem that the injection speed pattern and the injection power during the injection process are determined by the mechanical characteristics of the link mechanism. It is another object of the present invention to provide an injection control method and an electric injection device which are capable of freely setting an injection speed pattern and easily adjusting an injection output.

[0009]

In order to achieve the above-mentioned object, the present invention provides an injection method for converting a rotary motion of an electric motor into a linear motion by a ball screw mechanism to advance an injection plunger or a screw to inject molten resin. In the above, by transmitting the linear motion of the ball screw mechanism to the injection plunger or screw using a toggle link mechanism and controlling the speed of the electric motor, the injection speed of the injection speed defined by the mechanical characteristics of the toggle link mechanism is controlled. The change pattern is changed according to the injection start position of the injection plunger or screw.

Further, according to the present invention, the injection at the start of injection in an injection speed change pattern in which an arbitrary position is an injection start position at a predetermined ratio with respect to the maximum injection speed based on the maximum injection speed in the maximum injection stroke. The speed is set.

According to the present invention, when the injection amount changes, the injection stroke changes. However, since the change pattern of the injection speed can be changed according to the injection stroke without being restricted by the mechanical limitation of the toggle link mechanism, the injection stroke can be changed. High-speed injection filling is possible even with a small amount.

Further, in the present invention, a link portion having a variable link length is incorporated in a part of the toggle link mechanism, and by adjusting the link length, the injection speed is increased or decreased to obtain a required injection power. Can be.

According to this, when a larger injection power is required from the beginning of the injection even at the same injection stroke due to the structure of the mold, the required injection power can be obtained by adjusting the link length.

According to the present invention, there is provided an injection method for converting the rotational motion of an electric motor into a linear motion by a ball screw mechanism to advance an injection plunger or a screw to inject molten resin, wherein the linear motion of the ball screw mechanism is controlled by using a toggle link mechanism. Transmitting to the injection plunger or screw,
Regardless of the change pattern of the injection speed defined by the mechanical characteristics of the toggle link mechanism, an arbitrary pattern in which the injection speed is a function of the position is set, and the motor is driven in accordance with the set injection speed pattern. The speed is controlled.

Further, the present invention relates to an electric injection device for performing an injection operation in which a rotary motion of an electric motor is converted into a linear motion by a ball screw mechanism to advance an injection plunger or a screw, wherein the linear motion of the ball screw mechanism is controlled by the injection plunger. Alternatively, a toggle link mechanism for transmitting to a screw is provided, and a length adjusting device for adjusting the link length is provided in a link portion constituting the toggle link mechanism.

According to a preferred embodiment of the present invention, the length adjusting device comprises: a link member in which male screws having different torsion directions are formed on the dividing portion; and female screws having different left and right screwing with the male screws. It has a geared socket formed at both ends and an electric motor for rotating the geared socket.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an electric injection device according to an embodiment in which the present invention is applied to a screw-in type injection device. Reference numeral 10 denotes a screw. This screw 10 is used for plasticizing and measuring resin.
A screw that also works as an injection plunger. The screw 10 is inserted into the barrel 11 so as to be rotatable and capable of moving forward and backward in the axial direction. A heater 12 for heating the barrel 11 is provided on an outer peripheral portion of the barrel 11. The resin of the molding material is supplied from the hopper 13 to the barrel 11.
It is put inside and plasticized by the rotation of the screw 10.

Reference numeral 14 denotes a rotary drive of the screw 10. The screw 10 is connected to a drive shaft 16 via a joint 15. Inside the housing 17, a radial bearing 18 for rotatably supporting the drive shaft 16 and a thrust bearing 19 for receiving a reaction force of the radiating power are incorporated. The housing 17 is attached to the front side of a moving plate 21 provided on the upper surface of the base 20 so as to be movable.

Reference numeral 22 denotes a motor for driving the drive shaft 16. A gear 23 is attached to an output shaft of the electric motor 22, and a gear 24 provided on the drive shaft 16 meshes with the gear 23. Therefore, the rotational power of the electric motor 16 is reduced through the gears 23 and 24 and
It is transmitted to.

On the base 20, a front plate 25 and a rear plate 26 are fixed to the screw side and the end opposite to the screw side, respectively. This front plate 25
A guide bar 27 that guides the movement of the movable plate 21 is extended between the and the rear plate 26 in parallel.

The toggle link mechanism 30 includes the movable plate 2
1 and a rear plate 26 as a fixed plate. Toggle link mechanism 30
Is a toggle link consisting of link 31 and link 32,
And a length adjusting device 34 for adjusting the link length of the link 32.

One end of the link 31 is rotatably connected to the back of the movable plate 21 via a pin 35, and the other end of the link 31 is connected to one end of the link 32 via a pin 36 and a ball screw. 38 is connected to the connecting member 37 at the distal end. The other end of the link 32 is rotatably connected to the front surface of the rear plate 26 via a pin 39.

Links 31 and 32 forming a toggle link
The ball screw 38 connected to the connecting portion of the motor constitutes a ball screw mechanism 46 that changes the rotational motion of the drive shaft of the electric motor 40 into a linear motion and transmits the linear motion to the toggle link. The gear case 41 is a case for housing gears 42 and 43 for transmitting the rotation of the motor 40 at a reduced speed and a nut 44, and is swingably attached to the base 20 via a pin 45. The nut 44 is connected to the ball screw 38
The ball screw 38 is moved forward and backward in the vertical direction. Accordingly, when the ball screw 38 is driven downward by the electric motor 40 in FIG.
Toggle link consisting of 1 and 32 is extended and screw is 10
Is performed so as not to perform an injection operation for moving On the other hand, when the ball screw 38 retreats upward in FIG.
The toggle link is folded to perform a weighing operation. A servo motor is used for the electric motor 40, and a precise position, such that the injection speed changes according to a predetermined injection speed change pattern by a numerical control device (not shown),
Speed feedback control is performed.

Next, FIG. 2 is a view showing the structure of a length adjusting device 34 for adjusting the link length of the toggle link. The link 32 forming a part of the toggle link is divided into link members 32a and 32b. Among the divided portions of the link member 32a, a male screw 50a of a right-hand thread is formed, and the other link member 32 is divided. A left-handed male screw 50b is formed in the portion. These link members 32
a and 32b are connected by a socket 51,
Each of the inner diameter portions at both ends of the cylindrical socket 51 has a female screw of a reverse screw, that is, a male screw 50a of a right screw.
Are formed, and a female screw 52b to which the left-handed male screw 50b is screwed is formed.

A ring gear 53 is fixed to the outer periphery of the socket 51, and a pinion 54 connected to an electric motor 56 meshes with the ring gear 53. In this case, when the socket 51 is driven by the electric motor 56 to rotate forward, the link members 32a and 32b move in the separating direction and the link length of the link 32 as a whole increases. Has become shorter in length. Further, the amount of expansion and contraction of the link length is directly or indirectly detected by a detection unit (not shown). The position of the electric motor 56 is controlled by a numerical controller (not shown) so that the detected amount matches the target value.

Next, an injection control method performed by the above-described electric injection device will be described. FIG. 3 is a diagram showing the relationship between the position of the screw 10 and the injection speed, that is, the forward speed of the screw 10 in the injection process. FIG.
FIG. 2 is a diagram schematically illustrating a main part of the electric injection device of FIG. 1.

When the linear motion of the ball screw 38 is transmitted to the toggle link mechanism 30 and the screw 10 is moved forward, the toggle determined by the length of the arms of the links 31 and 32 and the rotation speed of the electric motor 40 for driving the toggle link mechanism 30 is performed. The mechanical characteristics of the link mechanism 30 define a change in the injection speed Vc that changes as the screw 10 advances in a fixed pattern. In FIG. 3, the position of the screw 10 at the end of the injection is set to the origin 0.

In FIG. 3, a curve 60 represents the electric motor 4
0 shows a change pattern of the injection speed Vc in the case of the maximum injection stroke S1 in this injection device when 0 is rotated at a constant rotation speed. As shown by the curve 60, the injection speed Vc
Becomes maximum at the injection start position x1, and decreases as the injection process proceeds. As the injection process approaches the end, the injection speed Vc becomes extremely low, but the injection power sharply increases. This is the characteristic of the toggle link mechanism 30.

Such a change in the injection speed Vc is generally preferable in the injection step in which the molten resin is filled at a high speed and the filling is surely completed. However, the injection amount of molten resin is
It depends on the product. For example, in an injection step where the injection stroke is S2 and the injection amount is small,
Even if the injection start position changes to, for example, x2, if the rotation speed of the electric motor 40 is the same, the change in the injection speed Vc does not change and changes as shown by the curve 60 due to the characteristics of the toggle link mechanism 30. However, the injection speed at the injection start position x2 decreases to Vc2.

Although a high injection speed is originally required at the injection start position, such a decrease in the injection speed is not preferable. Therefore, even if the injection start position changes due to the difference in injection amount, a high injection speed Vc1 at the injection start position is secured by changing the change pattern of the injection speed Vc as shown by the curves 62 and 64 as follows. I do.

A curve 62 is an example of the injection speed change pattern when the injection start position is x2 and the injection stroke is S2, and a curve 64 is an injection speed change pattern when the injection start position is x3 and the injection stroke is shorter S3. It is a change pattern.

In the toggle link mechanism 30 shown in FIG. 4, L1: the arm length of the link 32 L2: the arm length of the link 31 α: the angle between the link 32 and the axis of the screw 10 β: the angle between the link 31 and the screw 10 The angle between the axes γ: the angle between the ball screw 38 and the direction of the speed v of the link 32 VE: the forward speed of the ball screw 38, the speed of the screw 10, that is, the injection speed V
c is given by the following equation.

[0033]

(Equation 1) When the injection stroke is determined as S2, the links 31, 32 and the ball screw 38 at the injection start position x2
Correspond one-to-one, so the values of α, β, and γ are also determined. The speed VE of the ball screw 38 for setting the injection speed at the injection start position x2 to Vc1 can be calculated from equation (1). Accordingly, if the speed of the electric motor 40 is controlled by a numerical controller (not shown) and the ball screw 38 is moved at the obtained speed to start the injection process, the injection speed Vc
Changes as shown by a curve 62. Injection stroke is S
The same applies to the case of No. 3.

As described above, in the injection step in which the injection amount is changed, the injection step proceeds according to the injection speed change pattern represented by the curves 62 and 64. For this reason, since the change pattern of the injection speed can be changed according to the injection stroke without being restricted by the mechanical limitations of the toggle link mechanism, high-speed injection filling can be performed even if the injection amount is small.

The above is an example in which the injection speed change pattern is changed based on the maximum injection speed Vc1 at the maximum stroke S1 so as to maintain the same injection speed even if the injection stroke changes. , A pattern such as an injection speed of 95%, for example, may be used. This can be set freely depending on the product.

By the way, the firing force is determined by the toggle link mechanism 3
From the characteristic of 0, in FIG. 3, it changes like the curve 66 in inverse proportion to the injection speed Vc. Generally, in injection molding, since the resin is not filled in the mold at the beginning of injection, the resistance to resin flow is small, so that the injection power at the start of injection is small and a large injection power is required at the completion of injection. Depending on the structure of the mold, a larger injection power may be required from the start of injection even for the same injection stroke. In such a case, by changing the length of the link 32 of the toggle link mechanism 30, it is possible to obtain a necessary firing power as follows.

In FIG. 3, for example, in the case where the injection stroke is S1, 66 is a curve showing the change in the injection power. It is assumed that the firing output at the start of injection is P1. Therefore, if you want to increase the firing power even more,
, The socket 51 is driven by the electric motor 56 of the length adjusting device 34 to bring the link members 32a and 32b closer to each other by a predetermined amount. Thereby, the length of the entire link 32 is reduced. When the arm length of the link 32 of the toggle link mechanism 30 is shortened, the mechanical characteristics change, and the speed change pattern thereof becomes, for example, a curve 68. At this time, the change in the firing power changes as indicated by the curve 70, so that at the start of injection, a firing power P2 greater than P1 can be obtained. If the length of the link 32 is increased,
Conversely, the firing power can be reduced.

FIG. 5 shows an injection speed change setting pattern different from that of FIG. FIG. 5A shows an example of an injection speed change pattern in which the injection process proceeds while the maximum injection speed is kept constant after the start of injection, and the injection speed gradually decreases as the injection process approaches completion. is there. FIG.
(B), after starting the injection at a low speed, increasing the injection speed,
This is an example of a pattern in which the injection speed is gradually reduced as the time nears completion.

These injection speed change patterns are set in advance irrespective of the characteristics of the toggle link mechanism 30, and are set in accordance with molding conditions such as the shape of a molded product with the injection speed as a function of position. In an actual injection process, a numerical controller (not shown) executes position control and speed control of the electric motor 40 so that the injection speed changes according to the set injection speed change pattern based on the relationship of the above-described equation (1). I do.

Although the present invention has been described above with reference to the embodiment in which the present invention is applied to a screw-in-line type injection device, the present invention is not limited to an injection plunger, such as a screw prepeller type or plunger type injection device. The present invention can also be applied to an injection device that injects resin by moving forward. In this case, the toggle link mechanism may be connected to the injection plunger.

[0041]

As is apparent from the above description, according to the present invention, the problem that the injection speed change pattern and the injection power during the injection process are determined by the mechanical restriction of the link mechanism is solved, and the present invention is free. The setting of the ejection pattern and the easy adjustment of the ejection power can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an electric injection device according to the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of an adjusting device that adjusts the length of a link of a toggle link mechanism.

FIG. 3 is a diagram showing changes in screw position, injection speed, and injection power in an injection process.

FIG. 4 is a diagram schematically illustrating a main part of the electric injection device of FIG. 1;

FIG. 5 is a diagram showing a setting pattern of a change in an injection speed according to another embodiment.

[Explanation of symbols]

 Reference Signs List 10 screw 11 barrel 16 drive shaft 21 moving plate 22 electric motor 27 guide bar 30 toggle link mechanism 34 length adjusting device 38 ball screw 40 electric motor 44 nut 46 ball screw mechanism 51 socket

Claims (7)

[Claims] 1. An injection method for converting a rotary motion of an electric motor into a linear motion by a ball screw mechanism to advance an injection plunger or a screw to inject molten resin, wherein the linear motion of the ball screw mechanism is injected by using a toggle link mechanism. By transmitting to the plunger or screw and controlling the speed of the electric motor, the pattern of the change of the injection speed defined by the mechanical characteristics of the toggle link mechanism is changed according to the injection start position of the injection plunger or screw. An injection control method, characterized in that: 2. A method according to claim 1, wherein a maximum ratio of the injection speed to a maximum injection speed is determined based on a maximum injection speed.
2. The injection control method according to claim 1, wherein an injection speed at the start of injection in an injection speed change pattern in which an arbitrary position is set as an injection start position is set. 3. A part of the toggle link mechanism is provided with a link portion having a variable link length, and by adjusting the link length, the injection speed is increased or decreased to obtain a required injection power. The injection control method according to claim 1. 4. An injection method for converting a rotary motion of an electric motor into a linear motion by a ball screw mechanism to advance an injection plunger or a screw to inject molten resin, wherein the linear motion of the ball screw mechanism is injected by using a toggle link mechanism. Transmitting to the plunger or screw, setting an arbitrary pattern in which the injection speed is a function of the position regardless of the injection speed change pattern defined by the mechanical characteristics of the toggle link mechanism; An injection control method, wherein the speed of the electric motor is controlled according to a pattern. 5. An electric injection device for performing an injection operation for advancing an injection plunger or a screw by converting a rotational movement of an electric motor into a linear movement by a ball screw mechanism, wherein the linear movement of the ball screw mechanism is transmitted to the injection plunger or the screw. A motor-driven injection device, comprising: a toggle link mechanism for adjusting a length of a link portion of the toggle link mechanism; 6. The length adjusting device according to claim 1, wherein a male screw having a right-left twisting direction and a male screw having a right-left direction are formed at the divided portion, and a female screw having left and right different threads screwed to the male screw are formed at both ends. The electric injection device according to claim 5, further comprising: a motor that rotationally drives the geared socket. 7. A control for controlling a speed of the electric motor so that a pattern of a change in an injection speed defined by a mechanical characteristic of the toggle link mechanism can be changed according to an injection start position of the injection plunger or screw. The electric injection device according to claim 5 or 6, further comprising a unit.