JPH054207B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a temperature control device that can be used in injection molding machines and extrusion molding machines.

(Prior art) The conventional injection molding machine shown in FIG.
Nozzle 2 is installed on the left side of cylinder 1.
The right side is inserted into the hot spring jacket 3 and fixed with a two-piece retainer ring 4 and bolts 5. A heater 12 is provided on the outer periphery of the cylinder 1 in front of the retainer ring 4, and a thermocouple 11
The temperature is controlled to an appropriate temperature using a temperature controller 10 as a detector. The heater 18 on the outer periphery of the cylinder in front of the heater 12 and the heater 19 on the outer periphery of the nozzle are each controlled at appropriate temperatures by a temperature controller (not shown).

Next, to explain the relationship between the resin plasticization process and temperature control, the screw 6 in the cylinder 1 (the illustrated one shows only a part of the flight) has a supply part 7 having a deep and constant groove depth, It is composed of a compression section 8 whose groove depth gradually becomes shallower and a measuring section 9 whose groove depth is shallow and constant. When pellet-like (or powder) resin is supplied from the hopper 13, in the supply section 7,
The friction force is the product of the friction coefficient between the resin and the inner surface of the cylinder 1, the cylinder internal pressure, and the surface area of the cylinder inner surface, and the product of the friction coefficient between the resin and the bottom surface of the supply section 7, the cylinder internal pressure, and the screw bottom surface area. Due to the difference in frictional force, as the screw 6 rotates,
The resin is transported forward, and at the same time, the resin is preheated by heat transfer from the cylinder 1.

In addition, due to heat transfer from the heater 12, the hopper hole 17
When the temperature around the area rises (generally above 90°C to 100°C), the surface of the pellet-like resin melts and becomes rough, making it difficult for it to fall into the screw supply section 7. Cooling water is passed through. The cooling water flow rate is determined by the manually operated valve 16.
It is adjusted based on the operator's experience and intuition.
Note that the cooling water flows from the inlet pipe 14 through the passage 20 in the hopper jacket 3 to the outlet pipe 15. The range of the cylinder 1 that comes into contact with the screw supply section 7 is the part from the hopper hole 17 to the heater 12. Here, the cylinder portion after the heater 12 will be referred to as a cylinder base portion 1a. The temperature of the cylinder base 1a is determined by the balance between heat transfer from the heater 12, heat absorption by the cooling water in the hopper jacket 3, and heat transfer to the resin.

Next, the resin conveyed by the supply section 7 is melted by the compression section 8 by shearing and compression by mechanical energy and heat transfer from the heater 18 . The molten resin passes through the check valve 10 and is stored at the tip of the screw.

The quality of the molten resin, particularly the uniformity of the resin temperature, is closely related to the quality of the molded product. That is,
Burning due to overheating of a part of the resin temperature, short shot due to too low temperature, delamination due to resins with uneven temperature not bonding systematically when cooled, uneven resin temperature layer on the surface This causes molding defects such as flow marks. Therefore, in order to achieve uniform resin temperature, attempts have been made to improve the screw shape, screw rotation speed, feedback control and program control of the screw rotation speed, back pressure, and PID control of the cylinder heater, and some results have been obtained.

However, there are generally two types of relationships between the friction coefficient of resin and temperature, as shown in FIG. This is shown by solid and dotted lines. In particular, for resins having the characteristics shown by the solid line, the coefficient of friction changes significantly depending on the temperature of the cylinder base 1a corresponding to the screw supply section 7, and the conveying force fluctuates. For this reason, the amount of resin passing through the compression section 8, which is the next step, changes, so even if the rotation speed and back pressure are the same, the shear force and compression force change, and the resin temperature fluctuates. By the way, the resins with the characteristics shown in the solid line are ABS,
These are PMMA, PA66, and PET, and the resins with the characteristics indicated by the dotted line are PP and LDPE. Recently, resins having the characteristics shown in the solid line have been used for precision optical parts such as lenses and industrial parts, and in order to stabilize molding quality, a high level of resin temperature uniformity is required.

However, since the conventional cylinder base 1a interferes with the retainer ring 4 and the bolts 5, there is a portion of the cylinder outer periphery below the retainer ring where the heater cannot be attached. Temperature fluctuations occur due to disturbances such as heat radiation there. Furthermore, since the passage of cooling water through the hot spring jacket 3 is adjusted by the operator's intuition, there is no control to suppress temperature fluctuations, which deteriorates the uniformity of resin temperature.

Another drawback is that by continuing to flow cooling water through the hot pad jacket 3, the hot pad jacket 3 may become too cool. As an example of this, the cylinder base temperature distribution in an actual machine is shown by the solid line in FIG. As you can see, the temperature drops rapidly after passing thermocouple 11. Even with the heater 12, the temperature decreases rapidly like this because the hot spring jacket 3 is supercooled by the cooling water flowing through it, which deprives the heater 12 of heat transfer.

In such a case, preheating of the resin in the supply section 7 becomes insufficient. When the cold resin is conveyed to the compression section 8, it becomes insufficient for the mechanical energy supplied and the heat transfer of the cylinder, resulting in unmelted resin and uneven resin temperature. At the same time, the melting cannot follow the decrease in the groove depth of the compressed portion 8, clogging of the solid resin occurs, and the screw driving force increases. Therefore, when transporting the resin, the compression section 8
It is necessary to preheat to a temperature just before melting. As described above, the conventional cylinder base 1a dissipates heat from the outer periphery of the cylinder under the retainer ring 4 and overcools the hot spring jacket 3, resulting in insufficient preheating of the resin, resulting in uneven resin temperature and screw drive. It was causing an increase in power.

(Problems to be Solved by the Invention) The present invention attempts to solve problems in conventional injection molding machines, such as uneven resin temperature and increased screw driving force.

(Means for Solving the Problems) Therefore, the present invention provides an injection system in which the temperature of the cylinder base in the range from the hopper hole to the screw supply section is controlled by cooling the hopper jacket and heating from the heater on the outer circumference of the cylinder. In a temperature control device for a cylinder of a molding machine, etc., a heating device is provided at the bottom of a retainer ring for fixing the hopper jacket and the cylinder, a temperature control device for the heating device is provided, and the temperature of the cylinder in the hopper jacket is detected. It is equipped with a thermocouple and a solenoid valve that adjusts the flow rate of cooling water passed through the hopper jacket, and the solenoid valve is controlled by the signal from the thermocouple to control the resin temperature in the hopper hole. It is intended as a means to solve problems.

(Function) When the area around the hopper hole is about to become overheated due to heat transfer from the cylinder, the controller that detects the temperature using the second thermocouple issues a signal, operates the solenoid valve, and causes the flow of water from the inlet pipe into the hopper jacket. The temperature near the hopper hole is controlled to an appropriate temperature by adjusting the flow rate of cooling water. Next, the temperature of the heating device is controlled by a temperature controller having a first thermocouple as a detector installed in the cylinder at the bottom of the retainer ring, so that the cylinder temperature in this part is controlled to an appropriate temperature.

(Example) Examples of the present invention will be described below with reference to the drawings. FIGS. 1 to 3 show examples of the present invention. First, the embodiment shown in FIGS. 1 and 2 will be explained.
A cartridge heater 23 is installed in the cylinder 1 from the cylinder hopper hole 17 to the mounting position of the heater 12, which is controlled by a temperature controller 22 having a thermocouple 21 as a detector. A thermocouple 24 inserted into the cylinder 1 at the bottom of the hopper hole 17 is used as a detector, and a controller 26 of an electromagnetic proportional flow valve (or electromagnetic switching valve) 25 for controlling the amount of cooling water is installed. The structure of each part other than the above structure is the same as that shown in FIG. 4 above.

Next, the operation of the embodiment configured as above will be explained. First, when the vicinity of the hopper hole 17 is about to become overheated due to heat transfer from the cylinder 1, the controller 26, which detects the temperature using the thermocouple 24, outputs a signal, operates the electromagnetic proportional flow valve 25, and closes the inlet pipe 14. The temperature near the hopper hole 17 is controlled to an appropriate temperature by adjusting the flow rate of cooling water flowing into the hopper jacket 3 from the hopper jacket 3. Therefore, the resin in the hopper hole 17 is
Moderate preheating (below 80℃) is possible without causing overheating.

Next, a temperature controller 2 is used as a detector for a thermocouple 21 installed in the cylinder at the bottom of the retainer ring 4.
2, the temperature of the cartridge heater 23 is controlled, so the cylinder temperature in this area is controlled to an appropriate temperature. Furthermore, by controlling both, an ideal temperature distribution at the cylinder base can be achieved. An example of this is shown by the dotted line in FIG. This temperature distribution is set at 80° C., which is a temperature at which the position of the hopper hole 17 can be sufficiently preheated without causing the resin to rise. Since the resin is sufficiently preheated to the thermocouple 11 position, the temperature at the lower part of the retainer ring 4, that is, the thermocouple 21 position, is 140°C, and the temperature at the thermocouple 11 position is 140°C.
This is an example where the temperature is set to 180℃. In addition, temperature control allows
This temperature distribution becomes stable.

Next, another embodiment shown in FIG. 3 will be described. As shown in FIG. 32, the cylinder base 1a is heated by flowing high temperature oil. Note that 33 is a controller that uses the thermocouple 24 as a detector to control the temperature and flow rate of oil, and 34 is a seal that prevents oil from leaking into the hopper hole 17.

(Effects of the Invention) Since the present invention is configured as described above in detail, the temperature at the base of the cylinder is stabilized, and the friction coefficient of the resin is stabilized, so that fluctuations in conveying capacity are reduced. This makes the resin temperature uniform and reduces molded product defects. Further, since the cylinder corresponding to the screw compression part from the hopper hole is controlled to have an appropriate temperature distribution without overheating or overcooling, the resin can be preheated during transportation. This makes it possible to equalize the resin temperature and reduce the driving force of the screw.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a temperature control device in an injection molding machine showing an embodiment of the present invention, and FIG.
3 is a side sectional view of a temperature control device showing an embodiment different from that shown in FIG. 1, FIG. 4 is a side sectional view of a conventional injection molding machine, and FIG. Diagram showing the relationship. FIG. 6 is a diagram showing the relationship between position and cylinder temperature in the conventional method and the present invention. Explanation of main parts of the diagram 1...Cylinder, 3...
Hot spring jacket, 4... Retainer ring, 17
... Hopper hole, 21 ... Thermocouple (first thermocouple),
22... Temperature controller, 23... Cartridge heater (heating device), 24... Thermocouple (second thermocouple), 2
5... Solenoid proportional flow valve (electromagnetic valve), 26... Controller.

Claims (1)

[Claims] In a temperature control device for a cylinder such as an injection molding machine, the temperature of the cylinder head in the range from the hopper hole to the screw supply section is controlled by cooling the hopper jacket and heating from a heater around the cylinder. A heating device is installed at the bottom of the retainer ring for fixing, and a temperature control device is installed for the heating device, and a thermocouple is installed to detect the cylinder temperature in the hot spring jacket, and the flow rate of cooling water passing through the hot spring jacket is adjusted. 1. A temperature control device comprising a solenoid valve for controlling the resin temperature in the hopper hole by controlling the solenoid valve by a signal from the thermocouple.