JP2002059458A - Injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve yield of molding and quality of molding by decreasing difference in temperature hysteresis between injection nozzles in an injection molding machine with a plurality of injection nozzles. SOLUTION: Temperatures of the injection nozzles 210A and 210B are controlled by means of temperature controllers 230A and 230B. A temperature difference operating circuit 280 obtains temperature difference ΔT in detected temperatures of both nozzles and forwards a difference between this and an offset value ΔT0 as a temperature difference data DT to a main controller 240. The main controller 240 is constituted in such a way that it outputs temperature commands SA and SB modified in accordance with the temperature difference data DT to the temperature controllers 230A and 230B and the temperatures in both nozzles are elevated under a condition where the temperatures correspond to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nozzle structure for injection molding and an injection molding machine provided with the same, and more particularly to a nozzle structure suitable for performing molten metal injection molding.

[0002]

2. Description of the Related Art In general, an injection molding machine has an open structure in which the tip opening of an injection nozzle is kept open. After the molding material is injected from the injection nozzle, the molding material is solidified in the vicinity of the tip opening of the injection nozzle. There is a configuration in which a so-called cold plug is formed, and thereafter, a molded product is taken out. In such an injection molding machine, usually, a heater is arranged around an injection nozzle,
At the time of injection, the temperature of the nozzle tip of the injection nozzle is raised, while after the injection is completed, the temperature of the nozzle tip is lowered to form the cold plug, and the molding material from the tip opening of the injection nozzle is formed. To prevent leakage. Such an injection nozzle is generally used as a hot runner nozzle for eliminating a runner portion adhering to a molded product.

FIG. 9 shows a structure in the vicinity of an injection nozzle in the injection molding machine 100. The injection nozzle 110 has a nozzle cylinder 111, a nozzle tip 112 provided on the tip side of the nozzle cylinder 111, and a nozzle base having an outer diameter larger than that of the nozzle cylinder 111 and connected to an injection cylinder (not shown). 113, a tip side heater 114 arranged on the outer periphery of the nozzle cylinder 111 and the nozzle tip 112,
And a base-side heater 115 arranged on the outer periphery of the nozzle base 113. The tip opening of the nozzle tip 112 is configured to face the cavity 120 a of the mold 120. The mold 120 includes a fixed mold 121 and a movable mold 122.
And the outer peripheral surface near the tip of the nozzle tip 112 is in contact with the fixed die 121.

In FIG. 9A, when an injection screw (not shown) is driven in an injection cylinder (not shown) in the axial direction, a molding material 3 such as a low melting point metal in the injection cylinder flows through the nozzle flow channel 110a in a molten state. After that, it is extruded from the tip opening of the nozzle tip 112 into the cavity 120a. At this time, the distal heater 114 and the proximal heater 115 are connected to the nozzle cylinder 11 of the injection nozzle 110.
1 and the nozzle tip 112 are heated and the molding material 3 inside is heated.
Is guided into the cavity 120a in a molten state.

After the injection, the molding material 3 in the cavity 120a gradually decreases in temperature and gradually solidifies. At this time, by lowering the control temperature of the front heater 114, the vicinity of the front opening of the nozzle front section 112 is reduced. Is also solidified. Thereafter, as shown in FIG. 9B, the movable mold 122 is opened and the molded product 4 is moved to the nozzle tip 11.
Separate from 2 and remove. When the molded product 4 separates from the nozzle tip 112 in this way, a cold plug including the solid portion 5 and the semi-solid portion 6 in which the molding material 3 is solidified is left in the nozzle tip 112.

[0009] The solidified region of the molding material 3 shown in FIG. 9 (a) gradually extends toward the inside of the nozzle from the tip opening after the molding material 3 is injected, and eventually the smallest region formed in the nozzle tip 112. It is formed up to the inside of the tapered portion 12b beyond the narrowed portion (notch) having an inner diameter. And FIG.
As shown in (b), when the molded product is separated from the nozzle tip portion 112, the solidified region is usually divided near the narrowed portion, and the solidified region on the deeper side of the nozzle than the narrowed portion is cold. It is designed to remain in the nozzle as a plug.

In the injection molding machine 100, in order to improve the filling property of the molten metal into the cavity 120a, a multipoint gate type mold structure having a plurality of injection nozzles 110 communicating with the cavity 120a is provided (multiple gate type). Point gate structure). Further, a plurality of cavities 120a are formed in the mold 120, and the plurality of cavities 120a are formed.
Injection nozzles 11 for injecting molten metal into
In some cases, 0 is provided (a multi-cavity structure). As described above, in the injection molding machine including the plurality of injection nozzles 110, it is necessary to perform control for adjusting the injection timing and the like between the injection nozzles.

FIG. 8 shows a plurality of injection nozzles 1 as described above.
1 shows a schematic configuration of a nozzle temperature control system of an injection molding machine including 10A and 110B. Injection nozzle 110A,
Tip-side heater 114A, 11 provided in 110B
4B is configured to generate heat by receiving power supply from the temperature controllers 130A and 130B, respectively, and a temperature sensor provided at the nozzle tip sends outputs TA and TB to the temperature controllers 130A and 130B. These outputs TA and TB are also sent to the main controller 140.

The main controller 140 exchanges signals with a molding machine controller (not shown) via an input / output circuit 150. The molding machine control device controls the injection operation of the injection cylinder and the opening / closing operation of the mold, and the injection nozzles 110A and 110A are controlled in accordance with this operation.
In order to control the temperature state of 0B, the main controller 140 sends out temperature commands SA and SB to the temperature controllers 130A and 130B, and sends out a start / stop control signal S / S for starting and stopping heating. It has become.

[0010]

However, in the above-described injection molding machine, the difference in the thermal environment between the injection nozzles 110A and 110B and the difference between the thermal environment of the injection nozzles 110A and 110B and the front-end side heaters 114A and 114B.
4B, the injection nozzle 11
Even if 0A and 110B are controlled in the same way, as shown in FIG.
A temperature difference may occur between A and 110B. Therefore, the temperatures of both the injection nozzles 110A and 110B are adjusted by, for example, waiting until the temperatures of both the injection nozzles 110A and 110B reach the same temperature, or by delaying the start of heating of one of the nozzles, and proceed to the next step (for example, injection operation). It has become.

However, even if the temperature of the plurality of injection nozzles is adjusted to proceed to the next step as described above, the temperature histories of the two nozzles are different from each other, so that the molding material 3 inside the injection nozzles 110A and 110B is also different. For example, since the molten metal starts to flow out of one nozzle earlier than the injection timing, and the molten metal is solidified, the molten metal can be filled in the mold at the time of injection. There is a problem that, due to the disappearance or a difference in the formation state of the cold plug after the injection, a cold plug molding defect and a variation in the next injection amount occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to reduce the difference in temperature history between injection nozzles in an injection molding machine having a plurality of injection nozzles, thereby improving the molding yield. And to improve the molding quality.

[0013]

In order to solve the above-mentioned problems, an injection molding machine according to the present invention is an injection molding machine having a plurality of injection nozzles for injecting a molding material from a nozzle flow path into a molding die. And raising and lowering the temperature of each of the injection nozzles provided for each of the injection nozzles in order to enable the injection operation of the molding material and to form cold plugs at the tips of the plurality of injection nozzles after the injection. Heating means, a heating control means for controlling a heating state of the heating means, and a temperature detection means for detecting a temperature of a region heated by the heating means, wherein the heating control means includes a plurality of In the process of increasing or decreasing the temperature of the injection nozzle, the heating means is controlled so that the temperature difference between the plurality of injection nozzles becomes a predetermined value according to the output of the temperature detection means. And controlling.

According to the present invention, since the heating means is controlled by the heating control means so that the temperature difference between the plurality of injection nozzles becomes a predetermined value in the process of raising or lowering the temperature. Since the relationship of the temperature history between the nozzles can be controlled, it is possible to reduce problems caused by the mutual relationship between the injection state between the injection nozzles and the cold plug formation state. Specifically, for example, by setting the predetermined value to approximately 0, the difference in the temperature history between the injection nozzles can be reduced, so that the state of the molding material between the injection nozzles can be made equal, and the injection state can be reduced. In addition, it is possible to reduce the variation in the formation state of the cold plug.

Here, it is preferable that the predetermined value of the temperature difference between the injection nozzles is determined so that the difference between the injection state between the injection nozzles and the formation state of the cold plug is reduced. That is, among a plurality of injection nozzles, the thermal characteristics of the nozzles themselves (heat capacity and temperature rise / fall characteristics, etc.) and the thermal characteristics between the nozzles and the mold (the state of heat transfer between the nozzle and the mold) In many cases, there is a variation in the temperature difference between the injection nozzles in order to eliminate the difference in the injection state between the injection nozzles and the formation state of the cold plug in consideration of these variations. It is desired to perform control so as to be a predetermined value. However, if there is no significant difference in the thermal characteristics among the plurality of injection nozzles, the predetermined value may be set to substantially zero. Further, for example, when a molding material is injected from a plurality of injection nozzles into a cavity in a mold, when a temperature difference is intentionally provided between the plurality of injection nozzles in order to enhance filling property of the molding material into the cavity. Is also conceivable. In this case, the predetermined value is determined in order to intentionally cause a difference in thermal state between the plurality of injection nozzles.

In the present invention, in the process of increasing the temperatures of the plurality of injection nozzles by the heating means, the temperatures of the plurality of injection nozzles each reach a predetermined temperature based on the output of the temperature detection means. At this time, it is preferable that the apparatus is configured to perform the injection operation of the molding material. According to this means, when each of the plurality of injection nozzles reaches a predetermined temperature (the temperature may be the same or different for each injection nozzle), the molding material is injected. Is performed, the state of the molding material inside each of the injection nozzles can be in a fixed relation to each other, and a good injection state can be obtained. In particular, by making the rising mode of the set temperature of the heating means constant at each injection nozzle, reproducibility of the injection state can be ensured. Here, it is desirable that the predetermined temperatures are equal to each other in the plurality of injection nozzles.

In the present invention, the temperature of each of the plurality of injection nozzles is set to a predetermined temperature based on the output of the temperature detection means in the process of lowering the temperature of the plurality of injection nozzles after the injection of the molding material. , It is preferable to start the operation of taking out the molded article when reaching. According to this means, when each of the plurality of injection nozzles reaches a predetermined temperature (the temperature of each injection nozzle may be the same or different), the molded product is taken out. Since the operation is started (that is, the mold opening is performed), the state of the molding material inside each injection nozzle can be made to have a constant relationship with each other, and the cold plugs corresponding to each other in the plurality of injection nozzles can be set. Can be obtained. In particular, the reproducibility of the cold plug formation state can be ensured by always keeping the mode of decreasing the set temperature of the heating means constant at each injection nozzle. Here, in the plurality of injection nozzles, it is preferable that the predetermined temperatures are equal to each other.

In the present invention, the heating control means includes a temperature control section provided for each of the heating means, and a temperature difference deriving section for obtaining a temperature difference between a plurality of injection nozzles based on an output of the temperature detecting means. And a temperature command sending unit that changes a temperature command based on the temperature difference and outputs a temperature command adjusted so that the temperature difference becomes the predetermined value to the temperature control unit.

In the present invention, a plurality of heating means are arranged in the axial direction of each injection nozzle, and the temperature target value of the heating means at the most distal end of the nozzle repeatedly rises and falls according to the molding cycle. It is preferable that the temperature target value of the heating means is configured to be substantially constant.

In the present invention, a first region which is set near the tip opening of the injection nozzle and in which the solid-phase molding material is present at the time of starting the removal of the molded product, and which is closer to the nozzle base end than the first region. A second region in which the liquid-phase molding material is present at the time of starting the removal of the molded product;
An intermediate region, which is set between the region and the second region, where the solid-liquid coexisting phase of the molding material is present at the start of removal of the molded article, and when the temperature of the intermediate region reaches a predetermined temperature It is preferable that the apparatus is configured to start taking out the molded article.

Here, it is preferable that the predetermined temperature is a temperature of a solid-liquid coexisting phase of the molding material. Here, the predetermined temperature is desirably in a temperature range where the solid fraction of the solid-liquid coexisting phase is about 50 to 90%. In particular, in the case of a magnesium alloy of AZ91D, it is desirable that the angle be about 520 to 575 degrees.

In each of the above-mentioned means, it is preferable that a throttle (notch) having a minimum opening area facing the nozzle flow path is provided in the tip of the nozzle. Further, it is desirable to provide a tapered portion on the nozzle base end side of the throttle portion. In these cases, the intermediate region is a throttle section, or
This is a region inside the narrowed portion and the tapered portion.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of an injection molding nozzle structure and an injection molding machine using the same according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating a schematic configuration of a temperature control system of an injection nozzle in an injection molding machine 200 according to an embodiment of the present invention. In the injection molding machine 200 of the present embodiment, a pair of injection nozzles (hot runner nozzles) 210A and 21 used in a so-called hot runner type mold structure similar to the conventional example.
0B. FIG. 2 shows injection nozzles 210A and 210 in the injection molding machine 200 of the present embodiment.
B and a schematic perspective view showing the shape of a molded product formed by these components. FIG. 3 is a cross-sectional view showing the relationship between the injection nozzle 210A and the mold structure.

As shown in FIG. 3, in this embodiment,
The nozzle tip 212 of the injection nozzle 210A is provided with a tip opening 212a, and the fixed die 221 of the mold 220 is in contact with the tip outer surface, which is the outer surface of the opening edge of the tip opening 212a. Inside the tip opening 212a, there is provided an opening taper portion that expands in diameter toward the tip opening 212a, and on the back side (nozzle base end side) of the opening taper portion, a throttle portion (notch) having the smallest inner diameter is provided. ) 212e are formed. A tapered portion 212b whose diameter increases toward the nozzle base end side is further formed on the nozzle base end side of the throttle section 212e. The nozzle flow path 210a on the nozzle base end side of the tapered portion 212b has a substantially constant inner diameter.

A first heater 215A of an induction heating type comprising a high-frequency coil or the like is arranged around the nozzle tip 212, and a resistance heater having a heating wire or the like is provided on the base end side of the first heater 215A. A second heater 216 of the type is arranged. Further, a third heater 217 of a resistance heating type is arranged on the base end side of the nozzle of the second heater 216.

The first heater 215A is configured to heat the portion from the distal end opening 212a to the portion further advanced to the nozzle base end side through the opening tapered portion, the throttle portion 212e and the tapered portion 212b. The first heater 215A has a tip opening 2 at the nozzle tip 212.
The winding pitch of the coil may gradually increase as it moves toward the 12a side (that is, toward the nozzle tip).

At the nozzle tip 212, the throttle 21
A temperature sensor 218 such as a thermocouple for detecting the temperature of the molding material 3 (the molding material 3 in the intermediate region) in the tapered portion 212b is provided. Here, a temperature sensor for detecting the temperature of the molding material 3 (the molding material 3 in the first region) existing inside the opening tapered portion, and a temperature sensor disposed closer to the nozzle than the temperature sensor 218. In addition, a temperature sensor for detecting the temperature of the molding material 3 (the molding material 3 in the second region) closer to the nozzle base end than the tapered portion 212b may be provided.

The temperature sensor 218 outputs a feedback signal for controlling the nozzle tip 212 to a set temperature (a target temperature) by the first heater 215A. Although not shown, a temperature sensor for outputting a feedback signal for controlling the respective heating regions to the set temperature by the second heater 216 and the third heater 217 is provided in the same manner as described above.

In the present embodiment, the molding material 3 is
20 when the first heater 215A
Raise the temperature inside the nozzle tip by raising the set temperature of
Further, after the injection of the molding material 3, while maintaining the pressure of the molding material 3 (holding pressure), the set temperature of the first heater 215A is lowered to lower the nozzle temperature, and a cold plug described later is formed.

Here, in the present embodiment, the set temperatures of the second heater 216 and the third heater 217 are kept constant throughout the molding cycle, and as a result, as shown in FIG. Detection temperature T2
T3 is also substantially constant. On the other hand, the set temperature of the first heater is raised and lowered as described above, and accordingly, the detected temperature T1 at the nozzle tip (the temperature corresponding to the output of the temperature sensor 218) T1 is raised and lowered for each molding cycle. The setting temperature of the second heater 216 is such that the molding material 3 is always in the heating area of the second heater 216 in consideration of the inflow of heat from the nozzle base end side and the release of heat to the nozzle end side. The lowest temperature at which the liquid phase can be maintained, for example, a temperature near the liquidus line of the molding material 3. Further, the set temperature of the third heater 217 is higher than the set temperature of the second heater 216, and is set to a temperature at which the liquid phase state of the molding material 3 can be more stably maintained.

In this embodiment, the molding material on the base end side of the nozzle is maintained in a liquid phase by the third heater 217, and the nozzle tip 2 is maintained by the first heater 215A.
The temperature of the molding material in 12 rises and falls, and a cold plug is formed according to a molding cycle.
Here, due to the presence of the second heater 216, the volume of the nozzle region for raising and lowering the temperature by the first heater 215A is reduced, and the set temperature of the second heater 216 is set within a range that does not affect the injection of the molding material. By setting the temperature lower than that of the third heater 215, it is possible to shorten the temperature lowering time for forming the cold plug in the temperature raising / lowering cycle of the nozzle tip 212 by the first heater 215A than before.

In particular, at the nozzle tip 212, the first
When the heater 215A is configured so that the winding pitch of the heating coil gradually increases toward the distal end opening 212a,
Since the amount of heat emitted by the first heater 215A to the nozzle tip 212 gradually decreases toward the tip opening 212a, a large temperature gradient is intended even in the region of the nozzle tip 212 heated by the first heater 215A. The formation of the cold plug can be further accelerated.

Further, in the present embodiment, the injection nozzle 210 is set so as to have a substantially constant set temperature as described later.
The second heater 216 and the third heater 216A for heating the heater A are of a resistance heating type, and the first heater 215A for repeatedly raising and lowering the set temperature is of an induction heating type. Heater 2
17 can be configured at a low cost and a stable temperature environment can be configured, and the first heater 215A can be quickly raised and lowered in temperature.

The second heater 216 and the third heater 217 may be of an induction heating type. In this case, when the mold replacement is frequently performed, it is possible to quickly raise the temperature of the nozzle portion after the mold replacement.

In the present embodiment, the nozzle flow path in the nozzle tip 212 is defined as a first area on the nozzle tip side (the area where the solid phase molding material 3 exists at the time of starting the removal of the molded article 4, that is, the opening taper section). Inner area) and the second on the base end side of the nozzle.
A region (a region where the liquid-phase molding material 3 exists at the start of removing the molded product 4, that is, a region closer to the nozzle base end than the tapered portion 212 b), and an intermediate region between the first region and the second region (A region where the molding material 3 of the solid-liquid coexisting phase exists at the start of the removal of the molded product 4, that is, a region inside the narrowed portion 212 e and the tapered portion 212 b).

Here, while the molding material 3 in the first region is solidified at the solidus temperature, while the molding material 3 in the second region is maintained at the liquidus temperature, the molding material 3 in the intermediate region is solidified. It is preferable that the temperature is controlled so as to be the temperature of the solid-liquid coexistence phase, and the molded product 4 is separated from the nozzle tip 32 at this time. As a method of determining the start time of removal of the molded article in this way, there is also a method of determining the time of the molding cycle so that the removal of the molded article is started at an appropriate time in advance, and as described later. There is also a method in which the removal of the molded article is started when the temperature detected by the temperature sensor drops to a predetermined value.

In the present embodiment, when the injection of the molding material 3 into the mold 220 is completed and the molding material in the mold 220 solidifies to form the molded product 4, the vicinity of the tip opening 212a is formed. The molding material is also solidified, and the solidified region is at the tip opening 212
a gradually spreads toward the nozzle base end side. The expansion of the solidified region is caused by heat radiation through the front end outer surface portion in contact with the molding material already solidified in the mold 220 or the fixed mold 221 and the first heater 215.
It is facilitated by the lowering of the set temperature of A.

When the movable mold 222 is opened, the molded product 4
As shown in the figure, the solidification region of the molding material 3 spreads to the inside of the narrowed portion 212e and further reaches the inside of the tapered portion 212b, as shown in FIG. It is most preferable to match the semi-solid region formed of the solid-liquid coexisting phase before that. In the state shown in the figure, when the movable mold 222 is opened and the molded product 4 is separated from the nozzle tip 212,
Tapered portion 212b of nozzle tip 212 and throttle portion 2
A cold plug including the solid portion 5 and the semi-solid portion 6 is left inside 12e.

The structure of the injection nozzle 210B is exactly the same as the structure of the injection nozzle 210A.

In this embodiment, as shown in FIG. 1, the outputs TA and TB of the temperature sensors 218 provided in the injection nozzles 210A and 210B are output from the temperature controller 230.
A, 230B and comparators 260A, 260B. The temperature controllers 230A and 230B supply electric power to the first heaters 215A and 215B provided in the injection nozzles 210A and 210B, respectively, and according to the respective temperature set values, the injection nozzles 210A and 21B.
Heat OB. Temperature controller 230A, 230B
Are the temperature commands S from the main controller 240, respectively.
A, SB, the outputs TA, T of the temperature sensor 218
The first heaters 215A, 215B are set so that the detected temperature corresponding to B becomes a set temperature according to the temperature commands SA, SB.
Feedback control.

The comparators 260A and 260B are provided with the temperature threshold TL sent from the main controller 240 and the temperature controllers 230A and 230B, respectively.
Are compared with the outputs TA and TB, and the result is compared with the AND circuit 2
Send to 70. AND circuit 270 sends to main controller 240 a satisfying signal TX indicating that both outputs TA and TB of temperature controller have reached temperature threshold value TL.

On the other hand, the output T of the temperature sensor 218
A and TB are also input to a temperature difference calculation circuit 280. The temperature difference calculation circuit 280 generates temperature difference data DT corresponding to a temperature difference ΔT between the detected temperature corresponding to the output TA and the detected temperature corresponding to the output TB. Is calculated and sent to the main controller 240. The main controller 240, based on the temperature difference data DT,
A, the temperature commands SA and SB sent to 230B are corrected. Specifically, as the temperature difference data DT increases, the difference between the temperature commands SA and SB increases, and the output T
The temperature commands SA and SB are corrected so that the difference between the detected temperature corresponding to A and the detected temperature corresponding to the output TB becomes a predetermined value (an offset value described later).

The temperature difference calculation circuit 280 is set in advance.
Offset value ΔT₀From the main controller 240
Has been entered. The temperature data DT corresponds to the output TA.
Temperature between corresponding detected temperature and detected temperature corresponding to output TB
Difference ΔT and offset value ΔT ₀(ΔT−ΔT₀)When
Is required.

The offset value ΔT ₀ is, for example, due to the difference in thermal characteristics between the injection nozzles 210A and 210B, the output T
When there is a mutual difference between the temperature difference between the detected temperature corresponding to A and the temperature in the actual nozzle and the temperature difference between the detected temperature corresponding to the output TB and the temperature in the actual nozzle, Alternatively, it is set appropriately when it is desired to intentionally provide a temperature difference between the injection nozzles 210A and 210B.

The main controller 240 exchanges signals with a molding machine control device (not shown) via an input / output circuit 250, and performs a molding cycle of the injection molding machine, ie, injection, pressure holding, mold opening (molding of a molded product). Steps of starting take-out), spraying the release agent, and clamping the mold, and the injection nozzle 210
A and the temperature control state of 210B are matched.

In the present embodiment, based on the above configuration, for example, when the mold 220 is closed, the main controller 2 is transmitted from the molding machine control device via the input / output circuit 250.
40, a signal is sent to the temperature controller 230A, 230 by the main controller 240 by increasing the temperature commands SA, SB with time.
The set temperature (temperature target value) of B is increased, and as shown in FIG. 4, the first heater 215A, 215B raises the temperature T1 of the tip of the injection nozzle 210A, 210B. At this time, similarly to the one shown in FIG.
When a temperature difference ΔT occurs between 10A and 210B, the temperature difference calculation circuit 280 outputs temperature difference data DT to the main controller 240 from the temperature difference ΔT and the offset value ΔT ₀ . Then, the temperature commands SA and SB corrected based on the temperature difference data DT are sent to the temperature controllers 230A and 230B (for example, when the offset value ΔT ₀ is 0, the temperature of the injection nozzle 210A is reduced). Is lower than the injection nozzle 210B, the temperature command SA gives a higher temperature target value than the temperature command SB to the temperature controllers 230A and 230B.
Injection nozzle 2)
The temperature of 10A and the temperature of injection nozzle 210B approach offset value ΔT ₀ . Of course, if the offset value is 0, the temperature difference ΔT between both nozzles approaches 0.

As a result, the injection nozzle 210A and the injection nozzle 210B raise the temperature while keeping the temperature difference corresponding to the offset value constant (or, if the offset value is 0, the temperature is controlled to be the same as each other). When the detected temperatures of both nozzles reach the above-mentioned temperature threshold value TL, a sufficient signal TX is sent from the AND circuit 270 to the main controller 240. When the satisfaction signal TX is transmitted, the main controller 240
And a signal is sent to the molding machine control device via the controller, whereby the injection cylinder of the molding machine performs an injection operation.

After the injection operation is completed, the temperature command S
A and SB lower the set temperature of the temperature controllers 230A and 230B or set them to 0, and gradually lower the detected temperature T1 at the nozzle tip as shown in FIG. In this case, as described above, if there is a difference between the temperature drop rate of the injection nozzle 210A and the temperature drop rate of the injection nozzle 210B, in order to make the drop rates of both nozzles constant,
Based on the temperature difference data DT output from the temperature difference calculation circuit 280, the temperature commands SA and SB may be corrected so that the processes of lowering the temperature of both nozzles have a predetermined relationship with each other. Also in this case, the offset value ΔT ₀ performs the same function as described above.

In the process of lowering the nozzle temperature after the injection operation, it is difficult to control the temperature drop state of both nozzles by correcting the temperature commands SA and SB. The SB need not be modified.

At this time, when the temperature data detected by the temperature sensor 218 installed in the intermediate area decreases to a predetermined value, the satisfaction signal TX output from the AND circuit 270 is output to the main controller 240 in the same manner as described above. From the main controller 240 to the input / output circuit 25
It is preferable that a control signal is sent to the molding machine control device via the control signal 0 to start the removal of the molded product 4. In this case, the cold plug formation state can be grasped more accurately than by controlling the molding cycle determined in advance by time or starting the removal of the molded article by the temperature of the first area or the second area. Therefore, it is possible to stabilize the formation state of the cold plug, and to reduce the outflow of molten metal and the occurrence of molding defects.

The injection nozzles 210A, 210 of the present embodiment
In the injection molding machine using B, the temperature threshold value (the predetermined value of the temperature detected by the temperature sensor 218) that determines the start time of the removal of the molded product 4 is set inside the narrowed portion 212e and the tapered portion 212b (that is, the tapered portion 212b). It is preferable to set the value to a value corresponding to a state in which the molding material 3 in the (intermediate region) has dropped to the temperature of the solid-liquid coexisting phase. For example, the temperature sensor 218
If the detected temperature detected by the temperature sensor 218 is very close to the actual temperature of the molding material 3, the separation timing of the molded product 4 is determined by the time when the temperature detected by the temperature sensor 218 reaches the temperature of the solid-liquid coexisting phase of the molding material 3. It is desirable to set at the start of removal of the molded article.

Using the injection molding machine of the present embodiment, a molded article was molded using an Al—Mg based magnesium alloy AZ91D as the molding material 3. Specifically, in the case of the magnesium alloy AZ91D, as shown by a dashed line in the phase diagram (equilibrium diagram) of FIG. 6, a solid phase is formed at about 500 ° C. or less, and a liquid phase is formed at about 600 ° C. or more. 500-600 ° C
Becomes a solid-liquid coexisting phase. Here, a region surrounded by the liquidus line L and the solidus line S indicates a solid-liquid coexisting phase. In the case of the present embodiment, the molded product is taken out when the molding material in the intermediate region becomes a solid-liquid coexistence phase by the temperature sensor 218.

In the present embodiment, the set temperature of the third heater 217 is set to about 620 ° C., and the set temperature of the second heater 216 is set to about 600 ° C., so that the temperatures in the heating regions of both heaters become substantially constant. Under the control, the set temperature of the first heater 215A was repeatedly raised and lowered between about 500 ° C. (at the time of starting the removal of the molded product) and about 580 ° C. (at the time of injection) in the molding cycle. FIG. 5 shows an axial temperature profile of the injection nozzles 210A and 210B at the start of removal of the molded product.

In particular, the solid phase ratio (the ratio of the solid phase portion in the solid-liquid coexisting phase) of the intermediate region at the time of starting the removal of the molded product is about 5%.
It is preferable to set it in the range of 0 to 90%. If the solid phase ratio is lower than this range, the possibility that the molten metal will flow out due to poor formation of the cold plug increases.If the solid phase ratio is higher than this range, the molding cycle becomes longer and the inside of the nozzle becomes longer. The load applied to the constricted portion increases, which causes abnormal wear inside the nozzle tip and shortens the life of the nozzle. The temperature range of the magnesium alloy AZ91D corresponding to the range of the solid phase ratio is about 520 to 575 ° C.
It is.

A molded product 4 having a weight of about 190 g, a size of about 270.times.200.times.30 mm, and a thickness of 1 mm as shown in FIG. 2 was formed of a magnesium alloy AZ91D at the above temperature setting. The injection molding machine used for this molding is a multi-point gate type having a mold clamping capacity of 650 tons and the above two injection nozzles. As shown in FIG.
And a nozzle receiver 202 for receiving the molding machine nozzle 201
And the above-described injection nozzle 21 together with the nozzle receiver 202.
0A, 210B.

As a result of molding by the above-described injection molding machine, the temperature histories of the plurality of injection nozzles during the temperature rising process almost coincide with each other, and the injection timings of the injection nozzles 210A and 210B are almost always the same. An injection operation can now be performed. As a result, almost no defective products such as defective filling of the molten metal due to outflow of the molten metal or the like before injection are found, and it has become possible to manufacture molded products of extremely high quality.

Further, since the time lag of the injection timing in the plurality of injection nozzles is reduced as described above, the cold plug formation state due to the subsequent temperature drop of the injection nozzles becomes similar to each other. It was possible to suppress the variation in the injection amount of the molding material and the decrease in the molding quality due to the variation in the forming state.

Further, when the temperature histories of the plurality of injection nozzles during the temperature lowering process are controlled so as to be substantially the same, the identity of the cold plug formation state between the injection nozzles 210A and 210B is further improved. As a result, a more stable operation state can be obtained, and an accident of molten metal spill can be eliminated.

Although the above embodiment has been described with a mold having a so-called multipoint gate mold structure, a so-called multi-cavity mold capable of molding a plurality of molded products with a plurality of injection nozzles is also used. By synchronizing the timing, it is possible to reduce the variation in molding conditions between molded products, and thus, it is possible to reduce the variation in molding quality.

It should be noted that the injection molding nozzle structure and the injection molding machine of the present invention are not limited to the above-described illustrated examples, and various modifications can be made without departing from the scope of the present invention. It is.

[0061]

As described above, according to the present invention,
Since the relationship of the temperature history between the injection nozzles can be controlled, it is possible to reduce problems caused by the mutual relationship between the injection state between the injection nozzles and the cold plug formation state.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram showing a schematic configuration of a temperature control system of an injection nozzle in an embodiment of an injection molding machine according to the present invention.

FIG. 2 is a schematic perspective view showing an injection path and a structure of a molded product in the embodiment.

FIG. 3 is a cross-sectional view illustrating a structure of an injection nozzle according to the embodiment.

FIG. 4 is a graph showing detected temperatures of respective heating regions by a first heater, a second heater, and a third heater of the embodiment.

FIG. 5 is a graph showing a temperature profile in the axial direction of the injection nozzle of the embodiment.

FIG. 6 is an equilibrium diagram of a molding material used in the embodiment.

FIG. 7 is a graph showing a process of increasing the temperature of an injection nozzle in a conventional injection molding machine having a multipoint gate mold structure.

FIG. 8 is a configuration block diagram showing a schematic configuration of a temperature control system of an injection nozzle in a conventional injection molding machine.

FIG. 9 is a cross-sectional view showing a state at the time of injection (a) and at the time of removal of a molded product (b) in a conventional injection molding machine.

[Explanation of symbols]

 100, 200 Injection molding machine 210A, 210B Injection nozzle 210a Nozzle flow path 212 Nozzle tip 212a Tip opening 215A, 215B First heater 216 Second heater 217 Third heater 218 Temperature sensor 220 Mold 221 Fixed mold 222 Movable Type 230A, 230B Temperature controller 240 Main controller 250 Input / output circuit 260A, 260B Comparator 270 AND circuit 280 Temperature difference calculation circuit

Claims (4)

[Claims] 1. An injection molding machine having a plurality of injection nozzles for injecting a molding material from a nozzle flow path into a molding die, wherein the injection molding machine enables an injection operation of the molding material and a plurality of injection nozzles after the injection. Heating means for increasing and decreasing the temperature of the injection nozzle, provided for each injection nozzle to form a cold plug at the tip of the injection nozzle, heating control means for controlling the heating state of the heating means, Temperature detecting means for detecting the temperature of the region heated by the heating means, wherein the heating control means, in the process of increasing or decreasing the temperature of the plurality of injection nozzles, of the temperature detecting means An injection molding machine, wherein the heating means is controlled so that a temperature difference between the plurality of injection nozzles becomes a predetermined value according to an output. 2. The process according to claim 1, wherein the temperature of the plurality of injection nozzles is increased by the heating means.
An injection molding machine configured to perform an injection operation of the molding material when a plurality of injection nozzles reach respective predetermined temperatures based on an output of the temperature detection means. 3. The method according to claim 1, wherein the temperature of the plurality of injection nozzles decreases after the injection of the molding material, based on an output of the temperature detection means. An injection molding machine characterized in that when a temperature of each nozzle reaches a predetermined temperature, a removal operation of a molded product is started. 4. The heating control device according to claim 1, wherein the heating control unit includes a temperature control unit provided for each of the heating units, and a plurality of injection units based on an output of the temperature detection unit. A temperature difference deriving unit for obtaining a temperature difference between the nozzles,
A temperature command sending unit that changes a temperature command based on the temperature difference and outputs a temperature command adjusted so that the temperature difference becomes the predetermined value to the temperature control unit. Machine.