JPH053815B2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to an injection molding machine, and particularly to an injection molding machine in which the temperature or viscosity of a resin material injected through a nozzle at the tip can be precisely controlled according to molding conditions. It's about machines.

(Prior art and its problems) In an injection molding machine, a predetermined heated and fluidized resin material is injected through a nozzle at the tip and filled into the product cavity of a predetermined mold. It is desirable to accurately match the temperature or viscosity of the injected resin material to the temperature or viscosity depending on the molding conditions. Therefore, conventionally, the temperature or viscosity of the resin material has been adjusted to a desired temperature or viscosity (hereinafter referred to as
Various techniques have been proposed for adjusting and controlling the temperature (generally referred to as temperature).

By the way, the resin material is heated and fluidized (plasticized) based on the rotational operation of the injection screw inserted into the injection cylinder, and the resin material is injected based on the forward movement of the injection screw. In a so-called in-line screw type injection molding machine, generally, by controlling the rotational speed of the injection screw during plasticization of the resin material, the resin material is adjust the temperature to the desired temperature,
control is being carried out. However, with this temperature control method, the actual L/
Due to the change in D, it is inevitable that the temperature of the resin material in the injection cylinder and, ultimately, the temperature of the resin material injected into the product cavity of the mold through the nozzle section will be uneven. There was a problem that molding defects were likely to occur.

In addition, in conventional in-line screw injection molding machines, as mentioned above, the temperature of the resin material in the injection cylinder before injection was only adjusted and controlled, so that the resin material could not reach the nozzle. Due to temperature changes during passing through the product cavity, the temperature difference between the actual temperature of the resin material injected into the product cavity and the target temperature tends to be relatively large.
There is a limit to accurately controlling the temperature of the resin material to a desired temperature.

Furthermore, in an in-line screw type injection molding machine, although it is possible to make the resin material inside the injection cylinder uniform as described above, the heat capacity of the injection cylinder is large, and the temperature of the resin material cannot be increased by ordinary external heating means. Because it is difficult to quickly change the temperature of the injected resin material during the injection process, there is a problem that it is not possible to quickly change and control the temperature of the injected resin material according to the temperature gradient of the resin material, the shape of the product cavity, etc. Ta.

(Solution Means) The present invention has been made in view of the above circumstances, and its gist is that, as described above, a predetermined resin material heated and fluidized in an injection cylinder is heated and fluidized in an injection cylinder. In an injection molding machine in which the injection screw inserted into the injection cylinder is moved forward to inject through the nozzle at the tip and fill the product cavity of a predetermined mold,
(a) disposed in the injection resin passage of the nozzle part so as to be movable in the front and rear direction, and changing the cross-sectional area of the injection resin passage by forward or backward operation;
(b) a calorific value control member that changes the calorific value of the resin material passing through the cross-sectional area changing portion of the injection resin passage; (b) located at a portion downstream of the cross-sectional area changing portion of the injection resin passage; a temperature/viscosity detection means for detecting the temperature or viscosity of the resin material; (c) the temperature or viscosity of the injection resin material detected by the temperature/viscosity detection means; the movement position of the injection screw or the injection operation; (d) a comparator that compares a target resin temperature or resin viscosity and outputs a deviation signal representing the comparison difference, which is set in relation to the elapsed time after the start; (e) driving means that is driven so that the deviation signal becomes zero based on the deviation signal, and moves the heat generation control member forward or backward to change the cross-sectional area of the injection resin passage;
Based on a position signal from a position sensor that detects the movement position of the heat generation amount control member, while the heat generation amount control member is within the allowable stroke range between its forward limit position and backward limit position, the comparator While supplying the deviation signal from (f) a stroke limiter that outputs an injection speed correction signal in accordance with the magnitude of the deviation signal; and (f) within the allowable stroke range of the heat generation control member, the heat generation value control of the resin material by the heat generation control member is independent. The injection speed of the resin material is controlled according to a predetermined injection speed setting value, while when the heat generation control member is about to move outside the allowable stroke range, the injection speed from the stroke limiter is controlled. Based on the correction signal, the injection speed of the resin material is adjusted to increase or decrease the calorific value of the resin material at the cross-sectional area changing portion of the injection resin passage, and the temperature or viscosity of the resin material approaches the target temperature or viscosity. The invention also includes an injection speed control means for controlling the injection speed.

(Function/Effect) According to such an injection molding machine, it is possible to rapidly and continuously control increase/decrease in the calorific value of the resin material passing through the cross-sectional area changing part of the injection resin passage in the nozzle part. Furthermore, the amount of heat generated can be increased or decreased based on the temperature or viscosity of the resin material injected into the product cavity of the mold through the nozzle. Therefore, even if the temperature or viscosity of the resin material in the injection cylinder is slightly uneven, the temperature or viscosity of the resin material injected into the product cavity can be maintained with good responsiveness to the desired target temperature or viscosity. It is possible to match with high precision, and therefore, variations in the temperature or viscosity of the resin material can be greatly suppressed.
This makes it possible to significantly reduce the occurrence of molding defects caused by variations in temperature or viscosity of the resin material.

Furthermore, within the allowable stroke range of the calorific value control member, the injection speed is controlled independently of the calorific value control of the injected resin material by the calorific value control member. When it becomes necessary to control the temperature or viscosity of the resin material (when the stroke of the heat generation control member can no longer control the temperature or viscosity), the injection speed of the resin material can be adjusted using the injection speed correction signal from the stroke limiter. The temperature or viscosity of the injected resin material can be controlled over a wider temperature or viscosity range because the amount of heat generated by the resin material at the cross-sectional area changing portion of the injection resin passage is controlled to increase or decrease. This can be done effectively, making it possible to optimize a wider range of changes in resin temperature or viscosity.

Further, according to such an injection molding machine, for the same reason as mentioned above, it is possible to optimally control the temperature or viscosity of the resin material injected into the product cavity during the injection process according to the shape of the molded product. Therefore, there is an advantage that the quality of the molded product can be further improved.

(Example) Hereinafter, in order to clarify the present invention more specifically, one example thereof will be described in detail based on the drawings.

Although an example in which the present invention is applied to an in-line screw type injection molding machine will be described here, it goes without saying that the present invention can also be applied to injection molding machines other than the in-line screw type, such as a plunger type. .

First, FIG. 1 schematically shows essential parts of an in-line screw injection molding machine according to the present invention. There, 10 is a fixed platen of the mold clamping device, and a movable platen 12 approaches and approaches the fixed platen 10.
supported in a separable manner. A fixed mold 14 and a movable mold 16 are disposed on the fixed platen 10 and the movable platen 12, respectively, and a product cavity 18 of a predetermined shape is formed between the molds 14 and 16. It's summery.

On the other hand, in the figure, 20 is a heating cylinder (injection cylinder) of an injection device, and a nozzle 22 is attached to its tip, and a plurality of band heaters 24 are attached to its outer circumference. Also,
Although not shown, a material supply port is provided at the rear end of the heating cylinder 20, and as is well known, a predetermined resin material is supplied into the heating cylinder 20 from the material supply port. It's getting old.

An injection screw 26 is fitted into the heating cylinder 20 so as to be rotatable and movable in the front-rear direction, and the resin material supplied into the heating cylinder 20 from the material supply port causes the injection screw 26 to rotate. Based on this, the material is plasticized (heated, fluidized) and guided to the front of the screw 26.
After plasticizing and metering the resin material based on the rotational operation of the injection screw 26, the injection screw 26 is moved forward, so that the resin material guided forward of the screw 26 is transferred to the nozzle 22.
The liquid is injected through the mold clamping device and filled into the product cavity 18 of the mold clamping device.

Here, as shown in detail in FIG. 2, in the nozzle 22, a needle plunger 30, which also has a longitudinal shape, is accommodated in a longitudinal cylindrical nozzle body 28 so as to be movable a predetermined distance in the longitudinal direction. The needle plunger 30
As the nozzle body 28 moves in the longitudinal direction, the cross-sectional area of the injection resin passage within the nozzle body 28 can be continuously changed.

More specifically, the nozzle body 28
The nozzle base 32 is made up of a relatively large diameter longitudinal cylindrical nozzle base 32 fixed to the tip of the nozzle base 32, and a relatively small diameter longitudinal cylindrical nozzle head 34 fixed to the tip of the nozzle base 32. A through hole 36 serving as an injection resin passage is formed so as to penetrate in the axial direction. Here, the through holes 36 of the nozzle body 28 are arranged in order from the base end side of the nozzle body 28, that is, from the upstream side of the injection resin passage.
The resin material formed into a tapered portion 38, a large diameter portion 40, a medium diameter portion 42, and a small diameter portion 44, which is heated and fluidized in the heating cylinder 10, is formed into the tapered portion 38, a large diameter portion 40, a medium diameter portion 42, and a small diameter portion 44. 38, a large diameter part 40, and a medium diameter part 42, and are guided to a small diameter part 44 at the tip of the nozzle body 28, and are injected into the product cavity 18 from this small diameter part 44. .

In addition, as is clear from FIG. 2, the taper portion 3
8 and the large diameter portion 40 are connected by a small diameter portion 46 having the same diameter as the small diameter side of the tapered portion 38, and an annular stepped surface 4 is provided between the small diameter portion 46 and the large diameter portion 40.
8 is formed. Further, the large diameter portion 40 and the medium diameter portion 42 and the medium diameter portion 42 and the small diameter portion 44 are continuously connected by tapered portions 50 and 52, respectively. Furthermore, a plurality of band heaters 24 for heating the nozzle body 28 are arranged around the outer circumference of the nozzle body 28.

On the other hand, as shown in FIG. 2, the needle plunger 30 extends from the bottom wall of the bottomed cylindrical plunger body 54 by a predetermined length having a diameter slightly larger than the small diameter portion 44 of the through hole 36. needle 5
6 has a concentrically extending structure. Here, the needle plunger 30 is shown with the needle 56 pushed into the medium diameter portion 42 and slidably fitted into the large diameter portion 40 of the plunger body 54. It is disposed within the through hole 36 so as to be movable a predetermined distance between a position where the tip end of the plunger body 56 closes the small diameter portion 44 and a position where the open end surface of the plunger body 54 abuts the stepped surface 48. The axial direction (longitudinal direction) of the needle plunger 30
As the needle 56 moves, the cross-sectional area between the tip of the needle 56 and the inner surface of the tapered part 52 of the through hole 36 is continuously changed.

That is, in this embodiment, the needle plunger 3
By controlling the movement position of 0 in the axial direction,
The size of the cross-sectional area of the through hole 36 at the tapered portion 52 portion can be continuously controlled, thereby reducing the shearing effect, etc. of the resin material passing through the tapered portion 52 portion of the through hole 36. This makes it possible to quickly and continuously control the amount of heat generated based on the amount of heat generated, and thus the temperature (viscosity) of the resin material injected into the product cavity 18 through the small diameter portion 44. As is clear from this, in this embodiment, the needle plunger 30 constitutes a heat generation control member, and the tapered portion 52 of the through hole 36 is a portion where the cross-sectional area of the injection resin passage changes. .

The needle plunger 30 is provided with a communication hole 58 that is located in the bottom wall of the plunger body 54 and communicates the inside and outside spaces of the plunger body 54. As is clear from FIG. The resin material introduced into the large diameter portion 40 of the through hole 36 is guided to the medium diameter portion 42 side through the communication hole 58.

By the way, as shown in FIG. 2, the nozzle base 32 of the nozzle main body 28 is formed with a through hole 60 that extends a predetermined length in the longitudinal direction of the nozzle 22, penetrating the side wall of the nozzle base 32 from inside to outside. has been done. An arm 62 of a predetermined length is extended from the plunger body 54 of the needle plunger 30 in a state of protruding from the through hole 60 to the outside of the nozzle body 28 . Note that the through hole 60 is formed with a length sufficient to allow movement of the needle plunger 30 in the axial direction.

A ball screw nut 64 is fixed to the tip of an arm 62 extending from the plunger body 54 of the needle plunger 30.
For this ball screw nut 64, the nozzle 22
A ball screw 66 is screwed together in parallel with the longitudinal direction. This ball screw 66 is connected to the heating cylinder 2.
It is designed to be rotationally driven by a motor 68 which is disposed in a fixed position with respect to zero.

By rotationally driving the ball screw 66 by the motor 68, the moving position of the needle plunger 30 in the axial direction can be continuously changed, thereby causing a change in the cross-sectional area of the through hole 36. Part (tapered part 52 part)
It is possible to continuously increase or decrease the cross-sectional area of the cross-sectional area, and thus the calorific value of the resin material passing through the cross-sectional area changing portion. As is clear from this, in this embodiment, the driving means is composed of the motor 68, the ball screw 66, the ball screw nut 64, and the like.

On the other hand, the nozzle head 34 of the nozzle body 28
, a temperature sensor 70 serving as a temperature/viscosity detection means for detecting the temperature of the resin material in the small diameter portion 44 facing the small diameter portion 44 of the through hole 36 is provided.
A temperature signal S indicating the temperature of the resin material in the small diameter portion 44 is sent from the temperature sensor 70.
1 is now output. A temperature signal S1 output from the temperature sensor 70 is supplied to a comparator 76 via an analog input card 72 and an A/D converter 74.

Further, a resin temperature setting pattern memory 78 is connected to this comparator 76, and based on a preset resin temperature setting pattern, the movement position of the injection screw 26 or A target temperature signal S2 representing the target resin temperature is supplied in relation to the elapsed time after the start of the injection operation. Then, the comparator 76 compares the target temperature signal S2 and the temperature signal S1 supplied from the temperature sensor 70, and generates a deviation signal S3 representing the comparison difference.
is now output. Here, the deviation signal S3 output from this comparator 76 is
is supplied to a stroke limiter 82 via a PID control circuit 80, and further supplied from this stroke limiter 82 to a motor driver 88 via a D/A converter 84 and an analog output card 86. Accordingly, the motor 68 is adjusted such that the deviation signal S3 becomes zero.
can be driven in forward and reverse rotation.

In other words, when the actual temperature of the resin material in the small diameter portion 44 represented by the temperature signal S1 is lower than the target temperature represented by the target temperature signal S2, the motor 68 is driven in normal rotation and the needle plunger 30 adjusts to the temperature difference. The cross-sectional area of the cross-sectional area changing portion of the through hole 36 is made smaller in accordance with the temperature difference. As a result, the through hole 3
The calorific value of the resin material passing through the cross-sectional area changing portion 6 is increased, and the temperature of the resin material in the small diameter portion 44 is increased, so that the temperature of the resin material in the small diameter portion 44 matches the target temperature. It has become like being forced to do something.

Further, when the actual temperature of the resin material in the small diameter portion 44 represented by the temperature signal S1 is higher than the target temperature, the motor 68 is driven in the reverse direction and the needle plunger 30 is driven to compensate for the temperature difference. The cross-sectional area of the cross-sectional area changing portion of the through-hole 36 is increased in accordance with the temperature difference.
The amount of heat generated by the resin material passing through the cross-sectional area changing portion is reduced, and the temperature of the resin material within the small diameter portion 44 is made to match the target temperature.

The stroke limiter 82 detects that the needle plunger 30 has reached a preset forward limit position (minimum cross-sectional area setting position) and a backward limit position (maximum cross-sectional area setting position), and then stops the needle plunger 30. This is to restrict movement forward of the forward limit position and backward movement of the needle plunger 30 beyond the forward limit position and backward limit position of the needle plunger 30. For a while, as described above, the deviation signal S3 from the comparator 76 is supplied to the motor driver 88 to allow movement of the needle plunger 30, but the needle plunger 30 attempts to move out of its allowable stroke range. In this case, the deviation signal S3 to the motor driver 88
is stopped to prevent the cross-sectional area of the through-hole 36 from becoming smaller than a preset minimum cross-sectional area and larger than a maximum cross-sectional area.

That is, the stroke limiter 82 is connected to the analog input card 9 from the position sensor 90.
2 and the A/D converter 94, a position signal S4 representing the movement position of the needle plunger 30 is transmitted.
The stroke limiter 82 detects whether the needle plunger 30 has reached the forward limit position or the backward limit position based on the position signal S4 from the position sensor 90. It's getting old. Based on the detection result, as described above, when the deviation signal S3 that causes the needle plunger 30 to deviate from the allowable stroke range is input, the supply of the deviation signal S3 to the motor driver 88 is stopped. It's getting old. The stroke limiter 82 is configured to output a resin passage closing signal to the motor driver 88 when the resin material is not injected, and moves the needle plunger 30 to its forward position.
The through hole 36 is closed by the tip of the needle 56.

In addition, when a deviation signal S3 that moves the needle plunger 30 outside the allowable stroke range is input, the stroke limiter 88 generates an injection speed correction signal S5 according to the magnitude of the deviation signal S3. By closing the switch 96, the injection speed correction signal S5 is supplied to an injection speed setting device (not shown), and the injection speed setting value of the resin material, that is, the injection speed correction signal S5 of the injection screw 26 is outputted. The forward speed setting value can be modified according to the content of the deviation signal S3. In other words, by closing the switch 96 as necessary, the injection speed of the resin material can be adjusted to increase or decrease the amount of heat generated by the resin material at the portion where the cross-sectional area of the through hole 36 changes. This makes it possible to bring the temperature of the resin material within the small diameter portion 44 closer to the target temperature corresponding to the target temperature signal S2. In addition, the injection speed control of the above resin material is as follows:
Except when the switch 96 is closed, the movement position control of the needle plunger 30 (control of the amount of heat generated from the resin material) is performed independently. Therefore, here, an injection speed setting device (not shown) together with the switch 96 constitutes injection speed control means.

According to the injection molding machine having such a configuration, as described above, the resin material of the small diameter portion 44 of the through hole 36 is controlled by controlling the movement of the needle plunger 30 in the longitudinal direction of the nozzle 22 by the motor 68. The temperature can be quickly and accurately matched to the target temperature represented by the target temperature signal S2, and the temperature of the resin material injected into the product cavity 18 of the mold clamping device can be set by the resin temperature setting pattern memory 78. It is possible to control the resin temperature with high precision and good responsiveness according to the resin temperature setting pattern.

Therefore, if the resin temperature setting pattern is set to a constant temperature, even if the injection screw 26
During plasticization of the resin material based on the rotational operation of the machine, the temperature of the resin material injected into the product cavity 18 is made to match the set temperature with extremely good accuracy even if the temperature of the resin material varies to some extent. Therefore, molding defects caused by variations in the temperature of the resin material can be significantly reduced, and the quality of the molded product can be significantly improved compared to the conventional method.

Furthermore, if the resin temperature setting pattern is set to the optimum pattern according to the molding conditions such as the shape of the product cavity 18, the temperature of the resin material injected into the product cavity 18 can be optimally controlled according to the molding conditions. This makes it possible to further improve the quality of molded products.

Furthermore, even if the temperature of the resin material to be injected cannot be controlled by moving the needle plunger 30 within the allowable stroke range, the injection speed of the resin material is adjusted based on the injection speed correction signal, Since the amount of heat generated by the resin material at the cross-sectional area changing portion of the through hole 36 can be controlled to increase or decrease, optimization of the temperature of the resin material can be achieved even more advantageously in a wide temperature change range.

Although one embodiment of the present invention has been described in detail above,
This is a literal example, and it goes without saying that the present invention should not be construed as being limited to this specific example.

For example, in the embodiment described above, the target temperature compared with the comparator 76 was set as a temperature pattern, but if the set temperature is constant,
The target temperature does not necessarily have to be set as a temperature pattern, but can simply be set as a signal of a constant magnitude.

Further, in the embodiment, the temperature sensor 70 is employed as the temperature/viscosity detection means, and the temperature sensor 70 is used to detect the temperature of the resin material in the small diameter portion 44 of the through hole 36, that is, the temperature of the resin material downstream of the cross-sectional area change portion of the injection resin passage. The temperature of the resin is controlled according to a preset resin temperature setting pattern, but a viscosity sensor is used instead of the temperature sensor 70, and the temperature of the resin downstream of the cross-sectional area changing part of the injection resin passage is It is also possible for the viscosity of the material to be controlled according to a predetermined resin viscosity setting pattern.

In addition, although it is omitted to list specific examples one by one, the present invention can be implemented with various changes, modifications, improvements, etc. based on the knowledge of those skilled in the art without departing from the spirit thereof. It goes without saying that.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part schematically showing an example of an in-line screw type injection molding machine according to the present invention, and FIG. 2 shows a nozzle portion of the injection molding machine shown in FIG. FIG. 18... Product cavity, 20... Heating tube (injection cylinder), 22... Nozzle, 26... Injection screw, 28... Nozzle body, 30... Needle plunger (heat amount control member), 36... Through hole (injection resin passage), 54... plunger body, 56
... Needle, 64 ... Ball screw nut, 66
... Ball screw, 68 ... Motor, 70 ... Temperature sensor (temperature/viscosity detection means), 76 ... Comparator,
78...Resin temperature setting pattern memory.

Claims (1)

[Scope of Claims] 1. A predetermined resin material heated and fluidized in an injection cylinder is injected through a nozzle portion at the tip by forward movement of an injection screw fitted into the injection cylinder. In an injection molding machine configured to fill a product cavity in a mold, the nozzle is disposed in the injection resin passage of the nozzle part so as to be movable in the front and back direction, and the injection resin passage is cut off by its forward or backward operation. By changing the area,
a calorific value control member that changes the calorific value of the resin material passing through the cross-sectional area changing portion of the injection resin passage; temperature/viscosity detection means for detecting the temperature or viscosity of the injection resin material; and the temperature or viscosity of the injection resin material detected by the temperature/viscosity detection means, and the movement position of the injection screw or the elapsed time after the start of the injection operation. a comparator that compares the target resin temperature or resin viscosity and outputs a deviation signal representing the comparison difference; a driving means that is driven such that the heating value control member becomes zero and moves the heating value control member forward or backward to change the cross-sectional area of the injection resin passage; and a position for detecting the movement position of the heating value controlling member. Based on the position signal from the sensor, a deviation signal from the comparator is supplied to the drive means while the heat generation control member is within an allowable stroke range between its forward limit position and backward limit position. If the heat generation control member is about to move outside the permissible stroke range, the supply of the deviation signal to the driving means is stopped, and the injection speed correction signal is adjusted according to the magnitude of the deviation signal. a stroke limiter that outputs a stroke limiter that outputs a While controlling the injection speed, when the heat generation control member is about to move out of the allowable stroke range, the injection speed of the resin material is adjusted based on the injection speed correction signal from the stroke limiter. , further comprising an injection speed control means for increasing or decreasing the calorific value of the resin material at the cross-sectional area changing portion of the injection resin passage so as to bring the temperature or viscosity of the resin material closer to the target temperature or viscosity. injection molding machine. 2. The calorific value control member is a needle plunger that is disposed to be movable a predetermined distance in the longitudinal direction of the nozzle portion and has a needle extending in the longitudinal direction of the nozzle portion on the distal end side, and the needle plunger is provided with a needle that extends in the longitudinal direction of the nozzle portion. The cross-sectional area between the tip of the needle and the inner wall of the injection resin passage is changed by moving the nozzle in the longitudinal direction by a driving means. The injection molding machine according to item 1.