JPH054990Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heating cylinder temperature control device for an injection molding machine.

[Prior Art] Generally, in an injection molding machine, as shown in FIG. 5, resin is plasticized by rotating a screw (not shown) disposed in a heating cylinder 1.
This plasticized resin is extruded into a mold (not shown) by the movement of a screw, thereby performing molding. Then, on the outer periphery of the heating cylinder 1,
From the tip, the first heater H1, the second heater H
An injection nozzle heater NH is wound around the injection nozzle 2 provided at the tip of the heating cylinder 1, and the first heater H1, the second heater H2, Third heater H
3 and the injection nozzle heater NH, the first heating cylinder position 1a and the second heating cylinder position correspond to the axial center position of each
A temperature sensor (not shown) is provided at each of the heating cylinder position 1b, the third heating cylinder position 1c, and the injection nozzle position 2a.

When molding with ordinary resin, the temperature of the heating cylinder 1 and injection nozzle 2 should be set at 200°C to 300°C.
, and if you want to interrupt the molding operation,
The temperature of the heating cylinder 1 is lowered by directly turning off the power to each heater or lowering the set temperature to stop or weaken the heating by each heater (Utility Model Publication No. 54-21574). , see Utility Model Application No. 61-40221). This is to prevent property changes such as carbonization and decomposition caused by the resin staying at a high temperature for a long time. For example, in the case of carbonization, there is a problem in that the carbide adhering to the screw etc. sometimes comes off during the molding operation and mixes with the resin, appearing as black spots in the molded product.

[Problem to be solved by the invention] However, simply stopping heating by each heater as described above has the disadvantage that the temperature of the heating cylinder 1 does not come down easily because the heat capacity of the heating cylinder 1 etc. is large. .

According to experiments, as shown in FIG. 6, the temperature at the third heating cylinder position 1c and the injection nozzle position 2a decreases relatively quickly, and the temperature at the first heating cylinder position 1a and the second heating cylinder position 1b decreases relatively quickly. For example, if the limit temperature at which carbonization is unlikely to occur is 150°C, it will take about 2 hours for the temperature to drop from 230°C to 150°C at the first heating cylinder position 1a, and at the second heating cylinder position 1b was also found to take about 2 hours to drop from 215°C to 150°C. However, in this experiment, the reason why the temperature at the third heating cylinder position 1c decreased relatively quickly was because the heating cylinder was located at the lower part of the hopper 3.
This is because the cooling water is guided so that heat does not move from the hopper 3 side to the hopper 3 side, and the base end side of the heating cylinder 1 is cooled by the cooling water, and the temperature of the injection nozzle 2a decreases relatively quickly. This is because the injection nozzle 2 has a small mass and a small heat capacity. On the other hand, the first heating cylinder position 1a and the second heating cylinder position 1b
The reason why the temperature decreases slowly is because the heating cylinder 1 has a thick wall and a large heat capacity, and because the lower part of the hopper 3 is not easily affected by the cooling water.

Therefore, in the conventional method of lowering the temperature of the heating tube 1 or the injection nozzle 2 by stopping heating with each heater, the resin inevitably stays at a high temperature for a long time when the molding operation is interrupted, and the resin It was unavoidable that some of the carbonization would occur and appear as black spots on the molded product.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a heating barrel temperature control device for an injection molding machine that can prevent property changes such as carbonization.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a heater provided in a heating cylinder, an air nozzle provided around the heating cylinder and spouting cooling air toward the heating cylinder, and the above-mentioned. A heater power ON/OFF circuit that supplies and stops current to the heater, a switching valve that supplies and stops cooling air to the air nozzle, and a solenoid power supply that excites the switching valve's solenoid and opens the switching valve. The ON/OFF circuit, the molding temperature setting device that sets the molding temperature, the warming temperature setting device that sets the warming temperature, and keeping either the set temperature of the molding temperature setting device or the setting temperature of the warming temperature setting device above warm. The molding/warming switching circuit is selected by the selection switch, and when the setting temperature of the molding temperature setting device is selected in this molding/warming switching circuit, the temperature of the heating cylinder is set to the setting temperature of the molding temperature setting device. Controls the above heater power ON/OFF circuit, and also controls the above molding and
When the set temperature of the heat retention temperature setting device is selected in the heat retention switching circuit, a command is output to the above solenoid power ON/OFF circuit to open the above switching valve, supply cooling air to the air nozzle, and set the heat retention temperature of the heating tube. After lowering the temperature to the set temperature of the heater, the switching valve is closed and the temperature controller is equipped to control the heater power ON/OFF circuit so that the temperature of the heating cylinder remains at the set temperature of the heat retention temperature setting device. .

[Function] In the present invention, when the set temperature of the heat retention temperature setting device is selected by operating the heat retention selection switch,
The switching valve is controlled to the air supply state, and air is ejected from the air nozzle toward the heating cylinder. Then, the temperature of the heating cylinder rapidly decreases, and the temperature of the resin within the heating cylinder decreases in a short period of time to a temperature at which changes in properties are unlikely to occur.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 3. However, the same elements as those shown in FIG. 5 are denoted by the same reference numerals, and the explanation thereof will be omitted.

As shown in FIGS. 1 and 2, a heating cylinder 1
is horizontally attached via an adapter 5 to an injection cylinder 4 for moving a screw (not shown) in the heating cylinder 1, and the adapter 5 includes:
A resin supply hole (not shown) communicating from the inside of the hopper 3 attached to the top surface of the heating cylinder 1 is formed. The adapter 5 is provided with a heat insulating cover 6 extending from its distal end toward the distal end side of the heating cylinder 1.

The heat insulation cover 6 includes a top plate part 6a that covers the upper part of the heating cylinder 1, and side plate parts 6b, 6 that hang down from the left and right side edges of the top plate part 6a and cover the left and right sides of the heating cylinder 1.
b, and the top plate portion 6a includes:
first air nozzle 7, second air nozzle 8,
A third air nozzle 9 and a fourth air nozzle 10 are attached.

The first air nozzle 7 is an injection nozzle heater NH
and the first heater H1, the second air nozzle 8 is located between the first heater H1 and the second heater H2, and the third air nozzle 9 is located between the second heater H2 and the second heater H2. The fourth air nozzle 10 is located between the third heater H3 and the tip end surface of the adapter 5, and each of these air nozzles has its ejection port extending around the circumference of the heating cylinder 1. oriented perpendicular to the plane. The first air nozzle 7 is connected to the first solenoid valve (switching valve) 11, the second air nozzle 8 is connected to the second solenoid valve (switching valve) 12, and the third air nozzle
The air nozzle 9 is a third solenoid valve (switching valve) 13
, and the fourth air nozzle 10 connects the cooling air supply source 1 through a fourth solenoid valve (switching valve) 14.
It is connected to 5.

When the first solenoid valve 11 is neutral, the P port and the A port are in a blocked state, and the solenoid 11a
When power is applied to 2, the P port and A port are connected.
This is a solenoid valve with port 2 position. Other second solenoid valves 12, third solenoid valves 13, and fourth solenoid valves 14
The solenoid valve 12 has the same structure as the first electromagnetic valve 11, and the solenoids 12a and 1 provided respectively.
3a and 14a. Then, the first solenoid valve 11 to the fourth solenoid valve 14, the injection nozzle heater NH, and the first
The heater H1 to the third heater H3 are controlled by a control circuit (control means) 21 shown in FIG.

The control circuit 21 includes a molding/warming switching circuit 21a that selects either the set temperature of the molding temperature setter 22 or the set temperature of the warmer temperature setter 23;
A temperature controller 21b controls the temperature of the heating cylinder 1 or the injection nozzle 2 based on the set temperature selected by the molding/warming switching circuit 21a, and the injection nozzle heater NH and the first heater H1 to 3rd
A heater power ON/OFF circuit 21c supplies and stops current to each of the heaters H3, and a first solenoid valve 1 according to a command from the temperature controller 21b.
Turns on and off the solenoid power supply that supplies and stops current to each solenoid of the first to fourth solenoid valves 14
It is composed of a circuit 21d. Here, the molding temperature setting device 22 is the injection nozzle position temperature setting device 2.
2a, a first heating cylinder position temperature setting device 22b,
It is composed of a second heating cylinder position temperature setting device 22c and a third heating cylinder position temperature setting device 22d, and the injection nozzle position 2a during molding and the first
The temperatures of the heating cylinder position 1a to the third heating cylinder position 1c are individually set. Further, the heat retention temperature setting device 23 sets the temperature of the injection nozzle 2 and the heating cylinder 1 to a temperature at which carbonization of the resin is difficult to occur when the molding operation is interrupted, etc. The temperatures of the heating cylinder position 1a to the third heating cylinder position 1c are collectively set to the same temperature.

The molding/warming temperature setting device 22 or the warming temperature setting device 23 is selected in the molding/warming temperature setting device 21a by a heating selection switch 24.
When the heat retention selection switch 24 is turned on, it gives a command to the molding/warm retention switching circuit 21a to select the heat retention temperature setter 23.

The temperature controller 21b controls the injection nozzle position 1.
a, and the heater power ON/OFF circuit 21c so that the temperature at the first heating cylinder position 1a to the third heating cylinder position 1c becomes the temperature set by the molding temperature setting device 22 or the heat retention temperature setting device 23. At the same time, the temperature at the injection nozzle position 2a and the first to third heating cylinder positions 1a to 1c is set to the temperature set by the insulation temperature setting device 23 when the insulation temperature setting device 23 is selected. Turn on the switches leading to each solenoid in the solenoid power ON/OFF circuit 21d until the first
The fourth electromagnetic valve 11 to the fourth electromagnetic valve 14 are switched.

Next, the operation of the device configured as described above will be explained.

When the molding operation is interrupted, when the heat retention selection switch 24 is turned on to keep the heating cylinder 1 warm,
The heat retention temperature setting device 23 is set by the molding/heat retention switching circuit 21a.
is selected, and the temperatures of the injection nozzle 2 and the heating cylinder 1 are controlled by the temperature controller 21b based on the set temperature of the heat retention temperature setting device 23. Immediately after switching to keep warm, keep warm temperature setting device 2
From the set temperature of 3, the injection nozzle position 2a, and the first heating cylinder position 1a to the third heating cylinder position 1c
Since the temperature of
The switches leading to each heater in the ON/OFF circuit 21c are turned OFF and heating of the injection nozzle 2 and heating tube 1 are stopped, and the switches leading to each solenoid in the solenoid power ON/OFF circuit 21d are turned ON. Then, the first solenoid valve 11 to the fourth solenoid valve 14 are switched, and air is ejected from the first nozzle 7 to the fourth nozzle 10 toward the injection nozzle 2 and the heating cylinder 1. Then, the temperature at the injection nozzle position 2a, which has a small heat capacity, decreases rapidly and reaches the set temperature of the heat retention temperature setting device 23. Therefore, when the solenoid power is turned on and
The switch leading to the solenoid 11a of the OFF circuit 21d is turned OFF, the air jetting from the first nozzle 7 is stopped, and the heater power is turned off.
The switch connected to the injection nozzle heater NH of the ON/OFF circuit 21c is repeatedly turned ON and OFF, and the temperature at the injection nozzle position 2a is adjusted to the temperature setting device 23.
The temperature will be maintained at the set temperature. In this way, the jetting of air from the air nozzles is stopped in the order in which the set temperature of the heat retention temperature setter 23 is reached, and the temperature is maintained at the set temperature of the heat retention temperature setter 23.

In the apparatus configured as described above, the first
air nozzle 7 to fourth air nozzle 10
Since the heating cylinder 1 and the injection nozzle 2 can be cooled by blowing out air from the heating cylinder 1 and the injection nozzle 2, the heating cylinder 1 and the injection nozzle 2 can be cooled quickly by
The temperature can be lowered to a set value.
Therefore, when the molding operation is interrupted, the time during which the resin remains in a high temperature state becomes extremely short, which is extremely effective in preventing changes in the properties of the resin such as carbonization.

Further, each air nozzle from the first air nozzle 7 to the fourth air nozzle 10 is located at a position where the outer peripheral surface of the injection nozzle 2 or the heating cylinder 1 is exposed from the heater, such as between the injection nozzle heater NH and the first heater H1. Since the air nozzles are arranged in
The injection nozzle 2 and heating cylinder 1 can be efficiently cooled.

[Example] Regarding the above-mentioned example, an experiment was conducted to determine the temperature drop state of the injection nozzle 2 and the heating cylinder 1 when switching to heat retention, and the experimental results will be described below.

FIG. 4 shows the temperature measurement results of the injection nozzle 2 and the heating cylinder 1 when air was ejected from the first air nozzle 7 to the fourth air nozzle 10 by switching to heat retention. As is clear from this figure, the temperature drop of the injection nozzle 2 with a small heat capacity is the fastest, and the temperature drop of the first heating cylinder position 1a and the second heating cylinder position 1b is slightly slower, and this tendency is as follows. This is consistent with the experimental results for the conventional example shown in FIG. However, the first heating cylinder position 1
The heat retention setting temperature of 100°C was reached in about 30 minutes at the a and second heating cylinder positions 1b as well.
It also takes about 15 minutes to reach 150℃. In the conventional example, it took about 2 hours to reach 150°C, so it was confirmed that the heat retention setting temperature was reached in about 1/8 of the time compared to the conventional example.

[Effects of the invention] As explained above, the present invention includes a heater provided in a heating cylinder, an air nozzle provided around the heating cylinder that spouts cooling air toward the heating cylinder, and a current flow to the heater. Heater power supply to supply/stop
ON/OFF circuit, switching valve that supplies and stops cooling air to the air nozzle, solenoid power ON/OFF circuit that excites the solenoid of this switching valve to open the switching valve, and molding that sets the molding temperature. A temperature setting device, a heating temperature setting device that sets the heating temperature, and a molding/warming switching circuit that selects either the set temperature of the molding temperature setting device or the temperature setting of the heating temperature setting device using a heating selection switch. Then, when the set temperature of the molding temperature setting device is selected by this molding/warming switching circuit, the heater power ON/OFF circuit is controlled so that the temperature of the heating cylinder becomes the set temperature of the molding temperature setting device, and When the set temperature of the heat retention temperature setting device is selected in the molding/heat retention switching circuit, a command is output to the solenoid power ON/OFF circuit to open the switching valve, supply cooling air to the air nozzle, and turn on the heating cylinder. Equipped with a temperature control controller that controls the heater power ON/OFF circuit so that the temperature of the heating cylinder is maintained at the set temperature of the heat retention temperature setter by closing the switching valve after the temperature has been lowered to the set temperature of the heat retention temperature setter. With this structure, when the heat retention temperature setter is selected by operating the heat retention selection switch, air is ejected from the air nozzle toward the heating cylinder, reducing the temperature of the heating cylinder in a short time. Therefore, changes in properties such as carbonization of the resin in the heating cylinder can be completely prevented, and a molded product of good quality can be obtained.

In addition, after the temperature of the heating cylinder rapidly drops to the temperature set on the heat retention temperature setting device, the jet of cooling air from the air nozzle stops and the heating cylinder is maintained at the set temperature, so that the heating cylinder does not exceed the required temperature. Therefore, the interrupted molding operation can be resumed quickly.

[Brief explanation of the drawing]

1 to 3 are diagrams showing one embodiment of the present invention, in which FIG. 1 is an overview of the heating cylinder temperature control device, FIG. 2 is a view taken in the direction of the arrow in FIG. 1, and FIG. A block diagram showing a control circuit, FIG. 4 is a diagram showing experimental results of a heating cylinder temperature control device shown as an embodiment of the present invention, and FIG. 5 is an overview diagram of a heating cylinder temperature control device shown as a conventional example. FIG. 6 is a diagram showing the experimental results of the heating cylinder control device. 1... Heating tube, 7... First air nozzle, 8
...Second air nozzle, 9...Third air nozzle, 10...Fourth air nozzle, 11...First solenoid valve (switching valve), 12...Second solenoid valve (switching valve), 13 ...Third solenoid valve (switching valve), 1
4... Fourth solenoid valve (switching valve), 21... Control circuit (control means).

Claims (1)

[Scope of utility model registration request] Heaters H1, H2, H3 provided in heating cylinder 1
and air nozzles 7, 8, 9, 1 provided around the heating cylinder 1 and jetting cooling air toward the heating cylinder 1.
0, and a heater power ON/OFF circuit 21c that supplies and stops current to the heaters H1, H2, and H3.
and switching valves 11, 12, 1 for supplying and stopping cooling air to the air nozzles 7, 8, 9, 10.
3, 14 and this switching valve 11, 12, 13, 14
A solenoid power ON/OFF circuit 21d that excites the solenoids 11a, 12a, 13a, and 14a to open the switching valves 11, 12, 13, and 14, a molding temperature setting device 22 that sets the molding temperature, and a molding temperature setting device 22 that sets the heat retention temperature. and the temperature setting of the molding temperature setting device 22 or the warming temperature setting device 23.
Keep warm selection switch 2 for one of the set temperatures.
Molding/thermal insulation switching circuit 21a selected by 4
When the set temperature of the molding temperature setter 22 is selected in the molding/warming switching circuit 21a, the heating cylinder 1
The heater power supply ON/OFF circuit 21c is controlled so that the temperature becomes the set temperature of the molding temperature setting device 22, and when the temperature setting of the warming temperature setting device 23 is selected by the molding/warming switching circuit 21a, A command is output to the solenoid power ON/OFF circuit 21d to open the switching valves 11, 12, 13, and 14, and cooling air is supplied to the air nozzles 7, 8, 9, and 10 to keep the heating cylinder 1 warm. After lowering the temperature to the set temperature of 23, the switching valves 11, 12, 13, 14
is closed and the temperature of the heating cylinder 1 is set to the heat retention temperature setting device 23.
1. A heating cylinder temperature control device for an injection molding machine, comprising: a temperature control controller 21b that controls a heater power ON/OFF circuit 21c so as to maintain a set temperature.