JP2016087977A - Thermo-forming apparatus, thermo-forming method, heater temperature control method, heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermo-forming apparatus in which, in thermo-forming, while the heating time for a heating object is shortened, the temperature of the heating object is properly controlled.SOLUTION: The thermo-forming apparatus includes a heater for heating a heating object, a temperature measurement unit for measuring the surface temperature of the heating object, and a control unit for controlling the temperature of the heater, and in which, when heating the heating object, the control unit sequentially lowers the temperature of the heater, and when the surface temperature of the heating object reaches the target temperature, the control unit controls the temperature of the heater such that the surface temperature approaches the target temperature.SELECTED DRAWING: Figure 2

Description

  The present invention relates to temperature control of a heater used for thermoforming.

  In thermoforming, the object to be heated such as plastic is softened by applying heat, and then molding is performed. A thermoforming apparatus used for this thermoforming has a heater for applying heat to an object to be heated. The temperature of the heater is controlled by a control unit such as a microcomputer and the object to be heated is heated to a predetermined temperature.

  Cited Document 1 discloses a thermoforming apparatus that controls the temperature of a heater for the purpose of shortening the heating time for an object to be heated. In this thermoforming apparatus, first, the control unit sets the temperature of the heater so that the temperature increase rate of the object to be heated is increased, and raises the object to be heated to a predetermined temperature. Next, when the object to be heated reaches a certain temperature, the control unit decreases the temperature of the heater to decrease the rate of temperature increase of the object to be heated. The temperature drop of the heater is repeated in stages according to the temperature of the object to be heated, and the object to be heated is heated.

JP 2000-317967 A

  Since the invention disclosed in the cited document 1 only controls the temperature of the heater in steps, the amount of heat from the heater does not affect the temperature change of the object to be heated when the temperature of the heater falls below a certain value. There is. For example, the temperature of the inside of the object to be heated is slower than that of the surface, and if the temperature of the heater falls below a certain temperature, the internal temperature may not be controlled.

  The present invention has been made in view of the above problems. A heating device capable of appropriately managing the temperature of the object to be heated while shortening the heating time for the object to be heated, a temperature control method for the heater, and this It aims at providing a thermoforming apparatus provided with a heating apparatus, and a thermoforming method.

  In order to solve the above problems, according to one aspect of the present invention, there is provided a thermoforming apparatus that heats and shapes a heated object, and measures a surface temperature of the heated object and a heater that heats the heated object. When heating the object to be heated, the temperature of the heater is sequentially lowered, and when the measured surface temperature of the object to be heated reaches the target temperature, the surface temperature is set to the target temperature. And a controller that controls the temperature of the heater so as to approach the vicinity.

The “heater” may be anything such as an infrared or far infrared heater as long as the amount of heat applied to the object to be heated can be varied.
“Substance to be heated” is a material to be thermoformed, and can be thermoformed, such as plastics such as thermoplastic resins and thermosetting resins, and mixed materials obtained by mixing plastics with other physical properties. Anything is acceptable.
The “temperature measurement unit” may be any device that can measure the surface temperature of the object to be heated, such as a thermocouple, a thermistor, a contact thermometer such as a thermopile or a radiation thermometer. It may be a thing.
“Sequentially lowering the heater temperature” includes not only continuously lowering the heater temperature, but also lowering the heater temperature step by step while repeating lowering and holding the temperature.
The “target temperature” is a target temperature when the object to be heated is heated, and is a value set as appropriate according to the environment in which the thermoforming apparatus is installed and the characteristics of the object to be heated.
“When the target temperature is reached” means not only the time when the surface temperature measured by the temperature measurement unit becomes the target temperature in a strict sense, but also the error of the temperature measured by the temperature measurement unit or a certain amount of time. It is a concept that includes the case where the temperature approaches the target temperature including the range.

In the invention configured as described above, the control unit heats the object to be heated while sequentially decreasing the temperature of the heater from a certain temperature in order to shorten the heating time of the object to be heated. In this process, when the surface temperature of the object to be heated reaches the target temperature, the control unit switches temperature control for the heater in order to control the temperature of the object to be heated. In the temperature control after switching, the control unit controls the temperature of the heater based on the surface temperature measured by the temperature measurement unit so that the surface temperature approaches the target temperature.
For this reason, it is possible to appropriately manage the temperature of the object to be heated while utilizing the temperature control for shortening the heating time.

  Further, the present invention can also be understood as a heat forming method, a heating apparatus, and a heater temperature control method using the same invention specific matters.

The figure explaining the structure of a thermoforming apparatus. The figure explaining the principle of the temperature control of a heater. The block diagram explaining the structure of the heating apparatus 30. FIG. FIG. 4 is a diagram illustrating the configuration of the heater unit 10 included in the heating device 30. The figure explaining the electric energy of the heater unit 10 which produces | generates arbitrary calorific values. The figure explaining control of the electric energy of the heater unit 10 by the operating device 35. FIG. The flowchart explaining control of the heater unit 10 performed by PLC31 as an example. The figure which shows the temperature change (FIG.8 (b)) of the sheet | seat S1 which changes according to the change of this heater temperature (FIG.8 (a)) and this heater temperature change. The figure explaining the structure of the heating apparatus 30 in 2nd Embodiment. The figure which shows the change of the heater temperature controlled by the heating apparatus 110, and the temperature change of the sheet | seat S1 which changes according to a heater temperature. The figure explaining the structure of the thermoforming apparatus 110 concerning 3rd Embodiment. The figure explaining the structure of the heating apparatus 30 concerning 3rd Embodiment. The figure explaining the change of heater temperature and the temperature change of sheet | seat S1.

Hereinafter, embodiments of the present invention will be described in the following order.
1. First embodiment:
(1) Schematic configuration of thermoforming device (2) Principle of temperature control of heater (3) Configuration of heating device (4) Temperature control method of heater (5) Action and effect of thermoforming device (6) Modification 2. Second embodiment:
3. Third embodiment:
4). Other embodiments:

1. First embodiment:
(1) Schematic configuration of thermoforming apparatus A thermoforming apparatus as an example of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration of a thermoforming apparatus. The thermoforming device 100 includes a heating device 30, a forming device 40, and a control device 50. In FIG. 1, in addition to the thermoforming device 100, a sheet supply device 98 and a sheet holding unit 99 are provided as auxiliary. The thermoforming apparatus 100 shown in the first embodiment manufactures a molded product S2 by heating and molding a sheet S1 (object to be heated). Note that the direction from the left to the right in the drawing is also referred to as the sheet conveyance direction.

  The sheet S1 thermoformed by the thermoforming apparatus 100 will be described as an example of a cut shape. However, the sheet S1 is not limited to this, and the sheet S1 is not limited to this. May be used. The material of the sheet S1 is plastic, and in particular, it will be described as a thermoplastic resin, but may be a thermosetting resin. The material of the sheet S1 may be a carbon fiber thermoplastic composite material in which carbon fiber is contained in plastic, or a material in which glass or aramid is contained in plastic (so-called composite material).

  When the user operates the control device 50 to start thermoforming the sheet S1, the sheet supply device 98 takes out the sheet S1 stocked at the sheet stock position LS and supplies it to the sheet holding means 99. The sheet holding unit 99 supplies the sheet S <b> 1 supplied from the sheet supply device 98 to the heating device 30.

  The heating device 30 heats and softens the supplied sheet S <b> 1 using the heater unit 10. The heater unit 10 functions as a heater of the present invention, and its temperature is controlled by the control device 50. The heater unit 10 includes an upper heater (first heating unit) 11 positioned above the supplied sheet S1 and a lower heater (second heating unit) 12 positioned below the sheet S2. Yes. The upper heater 11 applies heat to the sheet S1 from above, and the lower heater 12 applies heat to the sheet S1 from below. A specific configuration of the heater unit 10 will be described later.

The forming device 40 forms the sheet S <b> 1 that has been softened by the heating device 30. Although the forming apparatus 40 will be described as an apparatus corresponding to vacuum forming, it may be an apparatus compatible with compressed air forming. The molding apparatus 40 includes an upper mold 41 in which a cavity corresponding to the molded product S2 is formed, a clamp 42, an upper table (not shown) that holds the upper mold, and a lower table (not shown) that holds the clamp. A molding table drive mechanism (not shown) that holds the upper table and the lower table so as to be movable up and down, and a differential pressure supply mechanism (not shown) that generates a differential pressure in the cavity of the upper mold are provided.
First, the softened sheet S <b> 1 is carried between the upper mold 41 and the clamp 42. Next, the upper die 41 and the clamp 42 are changed from the separated position to the close position by the molding table driving mechanism. The separation position is a position where the distance between the upper die 41 and the clamp 42 is the longest. The proximity position is a position between the upper mold 41 and the clamp 42 where the sheet S1 is formed. Next, the differential pressure supply mechanism generates a differential pressure in the cavity of the upper mold 41 to bring the sheet S1 into close contact with the upper mold 41. Therefore, the shape of the sheet S1 changes to a shape corresponding to the cavity. Next, the molding table drive mechanism changes the upper mold 41 and the clamp 42 to the separated position, and the molded product S2 is taken out.

  The control device 50 controls a series of processes performed by the heating device 30 and the molding device 40. The control device 50 includes a programmable controller (described later), a control board, and the like. The I / O port of the programmable controller is connected to the heating device 30 and the molding device 40, and the control device 50 can control the driving of the heating device 30 and the molding device 40.

(2) Principle of heater temperature control FIG. 2 is a diagram for explaining the principle of heater temperature control. Fig.2 (a) is a figure which shows the temperature change of a heater unit. FIG. 2B is a diagram illustrating a temperature change of the sheet S1. FIG. 2B shows a change in the temperature of the surface and the inside of the sheet S1 that changes according to the time t (horizontal axis).
In the heating of the sheet S1 by the heating device 30, a process of rapidly increasing the sheet S1 to a certain temperature and a process of absorbing the difference in temperature change between the surface and the inside of the sheet S1 to make the sheet S1 uniform temperature are performed. Is called. Hereinafter, for the heater unit 10, temperature control performed to raise the temperature of the sheet S1 to a constant temperature is referred to as heating control, and temperature control performed to maintain the temperature of the sheet S1 at a constant temperature is Also described as temperature hold control.

  The heating control controls the temperature rise curve of the sheet S1 to heat the sheet S1 to a certain temperature (target temperature Td) (FIG. 2A). In order to realize this, after raising the heater temperature to the initial set temperature (initial temperature), the heater temperature is sequentially lowered according to the temperature of the sheet S1 (FIG. 2A). Therefore, the temperature of the sheet S1 can be quickly raised, and the time required for heating can be shortened.

  In the temperature holding control, as shown in FIG. 2B, after the surface temperature of the sheet S1 reaches the target temperature Td, the surface temperature of the sheet S1 is maintained at a constant temperature. Here, the time until the internal temperature of the sheet S1 reaches the target temperature Td is slower than the time until the surface temperature reaches the target temperature Td. The target temperature Td is, for example, a temperature set as a target value for the sheet S1 supplied to the forming apparatus 40, and is a temperature that does not exceed the melting point of the sheet S1. In the temperature holding control, the heater unit is controlled so as to maintain the surface temperature of the sheet S1 in the vicinity of the target temperature Td, thereby increasing the internal temperature, so that the surface and the inside of the sheet S1 are kept at a uniform temperature (target temperature Td). To do.

(3) Configuration of Heating Device Next, the configuration of the heating device 30 as an example of the present invention will be described.
FIG. 3 is a block diagram illustrating the configuration of the heating device 30. FIG. 4 is a diagram illustrating the configuration of the heater unit 10 included in the heating device 30.

As shown in FIG. 3, in addition to the heater unit 10 (upper heater 11 and lower heater 12), the heating device 30 includes a programmable controller (hereinafter also referred to as PLC: programmable logic controller) 31, a user interface 32, A radiation thermometer (temperature measurement unit) 33, a thermocouple thermometer 34, and an operating device 35 are provided.
In the first embodiment, the PLC 31, the user interface 32, and the operation device 35 constitute a part of the control device 50, but may be separate from the control device 50.

First, the configuration of the heater unit 10 will be described with reference to FIG.
FIG. 4A is a view as seen from the heating side that radiates heat in the heater unit 10.
FIG. 4B is an enlarged view of a heater element that is a part of the heater unit 10.

  A heater unit 10 shown in FIG. 4A includes heater elements H3 (a main heater H1 and a sub heater H2) arranged in the x direction and the y direction in the drawing. The heater element H3 is a general term for the main heater H1 and the sub heater H2. The main heater H1 is disposed substantially at the center of the heating side surface. A thermocouple thermometer 34 is attached to the main heater H1, and the temperature of the main heater H1 is measured as the heater measurement temperature Dhm. A radiation thermometer 33 is located near the main heater H1 and detects the surface temperature of the sheet S1 supplied to the heating device 30 as the sheet surface temperature Dss. A plurality of sub heaters H2 are arranged in the x direction and the y direction so as to surround the main heater H1.

The heater element H3 shown in FIG. 4 (b) is a high-speed follow-up type heater capable of rapid response with a temperature rising rate of 60 [° C./second] or more at the rated voltage, and is formed in a meandering shape having a turn-up portion. A heater element H32 is disposed on one surface of an approximately octagonal insulating plate H31. The heater element H32 includes a plurality of belt-like heat generating plates H33 and a plurality of connecting plates H34 that alternately connect the end portions of the adjacent heat generating plates H33. Each heat generating plate H33 is mountain-folded on the side away from the insulating plate H31 along the longitudinal direction, and is arranged spaced apart in parallel with the longitudinal direction. Each connecting plate H34 is folded in the opposite direction to the heat generating plate H33. As a result, the inclined surface of the connecting plate H34 and the inclined surface of the adjacent heat generating plate H33 are in contact with each other, and the power supply terminals H36 and H36 are formed as one electric heating alloy strip. The edge in the width direction of each heat generating plate H33 is held by a plurality of substantially cylindrical support bases H35 protruding from the insulating plate H31.
For the heater element, an alloy wire or band for electric heating such as nickel chrome wire or band, iron chrome wire or band, or the like can be used. Further, the shape of the heater element H3 is not limited to the shape shown in FIG.

  The amount of heat generated by each heater element H3 is controlled by the amount of power supplied. If the amount of power supplied to a certain heater element H3 increases, the amount of heat generated by the heater element H3 increases, and if the amount of power supplied decreases, the amount of heat generated by the heater element H3 decreases. By changing the combination of the amount of power supplied to each heater element H3, the amount of heat generated in the entire heater unit 10 can be defined.

  FIG. 5 is a diagram illustrating the amount of power of the heater unit 10 that generates an arbitrary amount of heat generation as an example. In FIG. 5, the position of the heater element H3 constituting the heater unit 10 is schematically shown by grids specified by coordinates in the x direction and the y direction, and the amount of power (power ratio) corresponding to each heater element H3 is represented by a square. It is shown as the value shown in the eye. In FIG. 5, the amount of power supplied to the heater element H3 is shown as a power ratio. The power ratio is, for example, a value representing the amount of power supplied to the heater element H3 between the maximum power amount (100 [%]) and the minimum power amount (0 [%]). For example, the power ratio of the sub heater H2 is set based on the value of the main heater H1. In FIG. 5, the power ratio of the main heater H1 is set to 50 [%], and the power ratio of the sub heater H2 is set to increase from the inner cell to the outer cell.

  Returning to FIG. 3, the user interface 32 inputs various types of information to the PLC 31. The user interface 32 includes a touch panel, operation keys, and the like. When the user operates the user interface 32 to input information for identifying the sheet S1 to be supplied to the thermoforming apparatus 100, the PLC 31 can identify the type of the sheet S1 to be heated.

  The PLC 31 controls the heater temperature according to the internal program. The PLC 31 receives the sheet surface temperature Dss from the radiation thermometer 33 and the heater measurement temperature Dhm from the thermocouple thermometer 34 through the A / D converter 36. The PLC 31 is connected to the operation device 35, processes information (Dss, Dhm) input by the program, and outputs an ON ratio RL to the operation device 35. The ON ratio RL is a signal indicating a ratio between a period during which power is supplied to the heater element H3 per unit time (ON period) and a period during which power is not supplied (OFF period). Used to control the power ratio.

  The PLC 31 includes a memory 311 constituted by a ROM and a RAM, a first temperature control means 312 functionally realized by a CPU (not shown) executing a program recorded in the memory 311, a second temperature Control means 313 and switching means 314 are provided.

  The first temperature control unit 312 performs heating control on the heater unit 10. In the heating control, the first temperature control means 312 changes the heater temperature setting information Ihd read from the memory 311 in accordance with the comparison result between the sheet surface temperature Dss and the target sheet temperature information Its, and changes the heater temperature stepwise. To lower. The target sheet temperature information Its is a condition for the PLC 31 to change the heater temperature setting information Ihd in the heating control, and is information indicating the target surface temperature of the sheet S1. The heater temperature setting information Ihd is information used by the PLC 31 to set the heater temperature in the heating control.

  The switching unit 314 compares the sheet surface temperature Dss with the target temperature Td, and when the sheet surface temperature Dss reaches the target temperature Td, the temperature control for the heater unit 10 performed by the PLC 31 is switched from heating control to temperature holding control.

  The second temperature control means 313 performs temperature holding control on the heater unit 10. In the temperature holding control, the heater temperature is controlled based on the sheet surface temperature Dss so that the temperature of the sheet S1 approaches the target temperature Td. The second temperature control means 313 controls the temperature of the sheet S1 by feedback control such as PID control and PI control. For example, in the feedback control, the sampling time of the sheet surface temperature Dss is set to 1 [sec].

  The controller 35 controls the amount of power supplied to the heater unit 10 based on the ON ratio RL output from the PLC 31. The operating device 35 is connected between the AC power source and the heater element H3. Although not shown in the figure, the operation device 35 is connected to each of the heater elements H3 constituting the heater unit 10. As an example of the operation device 35, it is configured to include an SSR (Solid State Relay) in which the contact is switched on / off according to the ON ratio RL, and a thyristor.

FIG. 6 is a diagram for explaining the control of the electric energy of the heater unit 10 by the operation device 35. 6A to 6C, the horizontal axis represents time [t], and the vertical axis represents voltage E.
In FIG. 6A, the half cycle of the AC voltage supplied from the AC power source is evenly sampled with a value of 0-255. 255 is assigned to the period starting from the voltage E = 0, and 0 is assigned to the period ending at E = 0.
The electric energy can be shown as an integral value (time t × voltage E) in the graph shown in FIG. FIG. 6B shows an example in which the power ratio of AC power is 50 [%]. In this case, by turning off the power supply to the heater element H3 in the period of 255 to 128 in the half cycle of the AC voltage and turning on the power supply to the heater element H3 in the period of 129 to 0, the heater element The power ratio with respect to H3 can be set to 50 [%].

  Therefore, the amount of power supplied to the heater element H3 is changed by switching on / off of the AC voltage by the operating device 35 based on the ON ratio RL output from the PLC 31, and as a result, the amount of power in the heater unit 10 is changed. Can be controlled. As shown in FIG. 6C, when the half wavelength of the AC voltage is evenly sampled with a value of 0 to 255, the ON ratio RL can be shown as the ON ratio in the period of 0 to 255.

(4) Heater Temperature Control Method Next, a heater temperature control method performed by the heating device 30 will be described.
FIG. 7 is a flowchart illustrating the control of the heater unit 10 executed by the PLC 31 as an example. FIG. 8 is a diagram showing a change in heater temperature (FIG. 8A) and a change in the temperature of the sheet S1 that changes in accordance with the change in heater temperature (FIG. 8B).
The PLC 31 executes the processing shown in the flowchart shown in FIG. 7, whereby the temperatures of the heater unit 10 and the sheet S1 shown in FIG. 8 are controlled. Steps S1 to S6 correspond to the heating control, and steps S11 to S15 correspond to the temperature holding control.

  In step S1 of FIG. 7, the first temperature control means 312 sets heater temperature setting information Ihd1 and target sheet temperature information Its1 as initial values, and starts heating control. By the process of step S1, the ON ratio RL corresponding to the heater temperature setting information Ihd is output from the PLC 31 to the operation device 35.

  In step S2, the first temperature control means 312 keeps the heater unit (main heater H1) 10 at the temperature set by the heater temperature setting information Ihd. For example, the first temperature control unit 312 compares the heater measured temperature Dhm with the current heater temperature setting information Ihd, and changes the ON ratio RL according to the comparison result.

  In step S3, the first temperature control means 312 acquires the sheet surface temperature Dss. The sheet surface temperature Dss acquired in step S3 is the surface temperature of the sheet S1 heated at the heater temperature corresponding to the heater temperature setting information Ihd.

  In step S4, the first temperature control unit 312 compares the sheet surface temperature Dss with the target temperature Td. When the sheet surface temperature Dss is lower than the target temperature Td (step S4: NO), the sheet S1 is not at a sufficient temperature. Therefore, the first temperature control unit 312 proceeds to step S5.

In step S5, if the sheet surface temperature Dss is lower than the target sheet temperature information Its (step S5: NO), the first temperature control unit 312 returns to step S2. That is, the heating of the sheet S1 at the heater temperature set by the heater temperature setting information Ihd is continued.
On the other hand, if the sheet surface temperature Dss is higher than the target sheet temperature information Its (step S5: YES), the first temperature control means 312 proceeds to step S6, and the heater temperature setting information Ihd and the target sheet temperature information Its To change. Then, the first temperature control means 312 returns to step S2. The heater temperature setting information Ihd (for example, Ihd2) after the change is a lower value than the heater temperature setting information Ihd (for example, Ihd1) before the change, and the target sheet temperature information Its is a higher value. By repeating the processes in steps S2 to S6, the heater temperature setting information Ihd changes to a low value as the sheet surface temperature Dss increases (in FIG. 8, in order of Ihd1, Ihd2, and Ihd3). That is, the heater temperature is lowered (FIGS. 8A and 8B).

  On the other hand, when the sheet surface temperature Dss becomes higher than the target temperature Td (step S4: YES), the switching unit 314 switches the temperature control of the PLC 31 to the temperature holding control. In the temperature holding control shown in FIG. 8A, it is described that the heater temperature is lowered, but this is only an example.

  In step S11, the second temperature control unit 313 acquires the sheet surface temperature Dss. The sheet surface temperature Dss is increased to near the target temperature Td by heating control.

  In step S12, the second temperature control unit 313 calculates a comparison amount between the sheet surface temperature Dss acquired in step S11 and the target temperature Td. The comparison amount is calculated based on, for example, the difference between the sheet surface temperature Dss and the target temperature Td.

  In step S13, the second temperature control means 313 corrects the ON ratio RL output to the operation device 35 according to the comparison amount calculated in step S12. Feedback control for bringing the sheet surface temperature Dss closer to the target temperature Td is performed by the controller 35 controlling the amount of electric power according to the corrected ON ratio RL.

  In step S14, the second temperature control means 313 waits for a predetermined time (for example, 1 [sec]). The standby period in step S14 may be any value, but the shorter the standby period, the more detailed the temperature management of the sheet S1.

In step S15, the second temperature control unit 313 returns to step S11 and repeats the processes from step S11 to S14 if the condition for terminating the temperature holding control is not satisfied (step S15: NO). Therefore, unless the condition is satisfied, the temperature holding control is continued. By continuing the temperature holding control, as indicated by a dotted line in FIG. 8B, the internal temperature of the sheet S1 increases, and becomes a surface temperature and a uniform temperature.
On the other hand, if the condition for ending the second temperature control is satisfied (step S15: YES), the second temperature control means 313 ends the temperature holding control.

  An example of a condition for ending the temperature holding control is a time required for the internal temperature of the sheet S1 to reach the target temperature Td (hereinafter also simply referred to as a duration). The “continuation period” is set in the PLC 31 according to, for example, the characteristics of the sheet S1 identified by the input from the user interface 32. The duration is a value obtained experimentally according to the characteristics of the sheet S1. By setting the continuation period, which is a condition for ending the temperature holding control, according to the characteristics of the sheet S1, the optimum temperature corresponding to the sheet S1 can be changed only by changing this period according to the type of the sheet S1 to be thermoformed. Control can be performed.

(5) Operation and effect of thermoforming apparatus As described above, in the thermoforming apparatus 100 according to the present invention, the surface temperature of the sheet S1 is heated to the target temperature Td by the heating control for reducing the heater temperature, and then the heater temperature. The temperature holding control is performed so that the temperature approaches the target temperature Td. Therefore, the time required for heating the sheet S1 can be shortened by heating control. Further, the internal temperature can be brought close to the surface temperature and the uniform temperature by the temperature holding control.
In particular, the present invention is effective in the case of thermoforming an object to be heated whose surface and interior have different temperature changes, such as a sheet having a thickness of a predetermined amount or more, or a so-called composite material in which different materials are mixed with plastic.

On the other hand, unlike the present invention, when the amount of heat applied from the heater unit 10 to the sheet S1 is increased to rapidly increase the interior of the sheet S1 to the target temperature Td, the process of increasing the interior of the sheet S1 to the target temperature Td. Thus, it is assumed that the surface of the sheet S1 exceeds the melting temperature. As a result, the surface of the sheet S1 is burnt, resulting in deterioration of the appearance of the molded product and reduction in strength.
On the other hand, in the present invention, since the temperature change curve of the surface of the sheet S1 is changed within a range not exceeding the melting temperature, the surface of the sheet S1 is not burnt and the quality of the molded product S2 can be maintained. .

The heater is not limited to the heater unit shown in the first embodiment, and any heater such as a ceramic heater may be used. On the other hand, the heater temperature is raised to the temperature set by the heater temperature setting information in the heating control by using a heater having high responsiveness to the input from the control unit (PLC 31 in the present embodiment). Time can be shortened. As a result, the time for heating the sheet S1 to the target temperature Td can be shortened. Further, by using the heater unit 10 having high responsiveness corresponding to the input, in the temperature holding control, the followability of the heater temperature with respect to the feedback control becomes high, and the surface temperature of the sheet S1 is easily held at the target temperature Td. be able to.
As an example of a heater having high responsiveness to input, a heater having a temperature rising rate at a rated voltage of 40 [° C./second] or more can be used, more preferably 60 [° C./second] or more. it can.

(6) Modified Example As another example of the condition for ending the temperature holding control, the PLC 31 may detect that the forming of the sheet S1 in the forming device 40 performed in the previous stage of the heating device 30 is completed. . In this case, the PLC 31 converts the flag (for example, changes from 0 to 1) when the forming of the sheet S1 by the forming apparatus 40 is completed. The second temperature control means 313 ends the temperature holding control when detecting that the flag has been changed by the interrupt control during the temperature holding control. By setting the end of the process by the former forming apparatus 40 as the condition for the end of the temperature holding control, the temperature management of the sheet S1 can be continued until the process by the forming apparatus 40 is completed. For example, the heating device 30 can continue the temperature management of the sheet S1 even if a problem occurs in the molding process by the thermoforming device 40 and time is required for the molding. Therefore, the sheet S1 can be quickly removed after the molding device 40 is restored. It becomes possible to supply.

2. Second embodiment:
In the second embodiment, the heating device 30 is different from the first embodiment in the configuration in which the upper heater 11 and the lower heater 12 are individually controlled so as to approach the target temperature Td.

FIG. 9 is a diagram illustrating the configuration of the heating device 30 according to the second embodiment.
Also in the second embodiment, in addition to the heater unit 10 (upper heater 11, lower heater 12), the heating device 30 includes a PLC 31, a user interface 32, a radiation thermometer 33, a thermocouple thermometer 34, an operating device. 35.

  On the other hand, the radiation thermometer 33 includes a first radiation thermometer 331 that detects the sheet surface temperature Dss1 of the sheet S1 from above (one surface) of the sheet S1, and a sheet S1 from below (second side) of the sheet S1. And a second radiation thermometer 332 for detecting the sheet surface temperature Dss. In FIG. 9, a thermocouple thermometer 341 that measures the heater measurement temperature Dhm is attached only to the upper heater 11.

  In addition to the first temperature control unit 312 and the switching unit 314 that perform heating control, the PLC 31 supplies a third temperature control unit 315 that performs feedback control of the upper heater 11 based on the sheet surface temperature Dss1, and a sheet surface temperature Dss2. 4th temperature control means 316 which feedback-controls the lower heater 12 based on. That is, the third temperature control unit 315 and the fourth temperature control unit 316 individually connect the upper heater 11 and the lower heater 12 based on the surface temperatures (Dss1, Dss2) of the respective surfaces of the sheet S1. Feedback control.

  FIG. 10 is a diagram illustrating a temperature change of the heater unit controlled by the heating device 30 and a temperature change of the sheet S1 that changes according to the temperature of the heater unit. FIG. 10A is a diagram showing a temperature change of the upper heater 11. FIG. 10B is a diagram showing a temperature change of the lower heater 12. FIG. 10C is a diagram showing a temperature change of the sheet S1. In FIG. 10C, for easy explanation, the temperature change (indicated by the dotted line) on the lower surface of the sheet S1 is shown larger than the temperature change on the upper surface.

  Also in the second embodiment, first, the heating control by the first temperature control means 312 is performed on the sheet S1. As shown in FIGS. 10A and 10B, the first temperature control means 312 lowers the temperatures of the upper heater 11 and the lower heater 12 in a stepwise manner.

  When the surface temperature of the sheet reaches the target temperature Td, the third temperature control unit 315 and the fourth temperature control unit 316 perform individual temperature holding control on the upper heater 11 and the lower heater 12, respectively. . The third temperature control means 315 performs feedback control so that the sheet surface temperature Dss1 indicating the temperature of the upper surface of the sheet S1 approaches the target temperature Td. The fourth temperature control unit 316 performs feedback control so that the sheet surface temperature Dss2 indicating the temperature of the lower surface of the sheet S1 approaches the target temperature Td. For example, when the temperature change of the lower surface of the sheet S1 is larger than the temperature change of the upper surface due to the shape of the sheet S1 and environmental conditions, the change in the ON ratio RL output from the fourth temperature control unit 316 is the first. This is larger than the change in the ON ratio RL output from the third temperature control means 315.

  As described above, the second embodiment has the following effects in addition to the effects of the first embodiment. Depending on the temperature of each surface of the sheet S1, the heater temperature facing each surface can be individually controlled, and the temperature of the sheet S1 is kept uniform without depending on the shape, material, environmental conditions, etc. of the sheet. It becomes possible. In particular, the present invention is effective in the case where the thickness of the sheet S1 is equal to or greater than a certain value and the object to be heated has a large temperature change on the respective sides.

3. Third embodiment:
In the third embodiment, a configuration in which a plurality of heater units 10 are provided along the conveyance path of the sheet S1 and the temperature control for each heater unit 10 is different is different from the other embodiments.

FIG. 11 is a diagram illustrating the configuration of the thermoforming apparatus 100 according to the third embodiment.
The heating device 30 which is a part of the thermoforming device 100 includes a first heater unit 110 and a second heater unit 120 located on the downstream side of the first heater unit 110 in the conveying direction of the sheet S1. ,have. That is, the sheet S1 passing through the heating device 30 is heated by the first heater unit 110 and then heated by the second heater unit 120.

FIG. 12 is a diagram illustrating the configuration of the heating device 30 according to the third embodiment.
The heating device 30 includes a PLC 31, a user interface 32, radiation thermometers 333 and 334, a thermocouple thermometer 34, and an operating device 35 in addition to the first heater unit 110 and the second heater unit 120.

  Also in the third embodiment, the PLC 31 functionally includes the first temperature control means 312 and the second temperature control means 313. On the other hand, in the third embodiment, the first temperature control unit 312 controls the heating of the first heater unit 110, and the second temperature control unit 313 controls the second heater unit 10. To maintain the temperature. That is, in the third embodiment, the heater units to be controlled by the first temperature control means 312 and the second temperature control means 313 are separate.

The surface temperature of the sheet S1 used by the first temperature control means 312 is measured by the radiation thermometer 333 as the sheet surface temperature Dss3. The surface temperature of the sheet S1 used by the second temperature control means 313 is measured by the radiation thermometer 334 as the sheet surface temperature Dss4.

FIG. 13 is a diagram for explaining a change in heater temperature and a change in temperature of the sheet S1.
FIG. 13A is a diagram illustrating a temperature change of the first heater unit 110. FIG. 13B is a diagram showing a temperature change of the second heater unit 120. FIG. 13C is a diagram illustrating a temperature change of the sheet S1.

  In the heating device 30 configured as described above, first, when the sheet S <b> 1 is supplied to the heating device 30, the first temperature control unit 312 performs heating control on the first heater unit 110. In the heating control performed by the first temperature control unit 312, the heater temperature of the first heater unit 110 is decreased stepwise to heat the sheet S <b> 1 to the target temperature Td (FIG. 13A).

  When the sheet S1 passes through the first heater unit 110 in a state where the surface temperature Dss of the sheet S1 has reached the target temperature Td, the second temperature control unit 313 controls the temperature of the second heater unit 120 to maintain the temperature. I do. In the temperature holding control performed by the second temperature control unit 313, the heater temperature of the second heater unit 120 is feedback-controlled so that the surface temperature Dss of the sheet S1 approaches the target temperature Td (FIG. 13B). Therefore, the internal temperature of the sheet S1 approaches the target temperature Td and becomes a surface temperature and a uniform temperature.

  As described above, the third embodiment has the following effects in addition to the first embodiment. Even for the sheet S1 having a long heating time until the target temperature Td is reached, the heating process can be divided into two, and the heating time of the sheet S1 in total can be shortened.

4). Other embodiments:
There are various embodiments of the present invention.
In the heating control performed by the control unit, the heater temperature is decreased only in one step. For example, in the heating control, the heater temperature may be continuously decreased.

  As a method for controlling the heater temperature, controlling the amount of electric power is only an example, and any method that can control the heater temperature, such as changing the relative distance between the heater and the object to be heated, can be used. There may be.

  In the third embodiment, providing two heaters in the conveyance direction of the sheet S1 is merely an example, and two or more heaters may be provided. In this case, the first temperature control means performs heating control on the first heater on the upstream side in the transport direction, and the second temperature control means performs temperature holding control on the heater on the downstream side with respect to this heater. Do.

Needless to say, the present invention is not limited to the above embodiments. It goes without saying for those skilled in the art,
・ Applying mutually interchangeable members and configurations disclosed in the above embodiments by appropriately changing the combination thereof.− Although not disclosed in the above embodiments, it is a publicly known technique and the above embodiments. The members and configurations that can be mutually replaced with the members and configurations disclosed in the above are appropriately replaced, and the combination is changed and applied. It is an embodiment of the present invention that a person skilled in the art can appropriately replace the members and configurations that can be assumed as substitutes for the members and configurations disclosed in the above-described embodiments, and change the combinations and apply them. It is disclosed as.

DESCRIPTION OF SYMBOLS 10 ... Heater unit, 11 ... Upper heater (first heating part), 12 ... Lower heater (second heating part), 30 ... Heating device, 31 ... Programmable controller (control part), 32 ... User interface, 33 ... Radiation thermometer (temperature measurement unit), 34 ... thermocouple thermometer, 35 ... operator, 36 ... AD converter, 40 ... molding device, 41 ... upper die, 42 ... clamp, 50 ... control device, 98 DESCRIPTION OF SYMBOLS ... Sheet supply apparatus, 99 ... Sheet holding means, 100 ... Thermoforming apparatus, 110 ... Heater unit, 120 ... Heater unit, 311 ... Memory, 312 ... First temperature control means, 313 ... Second temperature control means

Claims (11)

A thermoforming apparatus for heating and molding an object to be heated,
A heater for heating the object to be heated;
A temperature measuring unit for measuring the surface temperature of the object to be heated;
When heating the object to be heated, the temperature of the heater is sequentially decreased, and when the measured surface temperature of the object to be heated reaches a target temperature, the surface temperature is brought close to the target temperature, And a controller for controlling the temperature of the heater. The control unit, according to the surface temperature to be measured, a first temperature control means for controlling the temperature of the heater to be lowered stepwise from an initial temperature,
Second temperature control means for feedback-controlling the temperature of the heater so that the measured surface temperature approaches the target temperature when the measured surface temperature reaches the target temperature. The thermoforming apparatus according to claim 1, which is characterized by:  3. The thermoforming apparatus according to claim 2, wherein the second temperature control unit continues the feedback control until an internal temperature of the object to be heated becomes a temperature close to a surface temperature. 4.   3. The heat according to claim 2, wherein the period during which the feedback control is continued is a period until the molding of another object to be heated that has been molded before the object to be heated is completed. Molding equipment.   5. The operation device according to claim 1, further comprising an operation device configured to control an amount of electric power of the heater according to a control amount of the temperature of the heater output from the control unit. Thermoforming equipment. The heater includes a first heating unit located on a first side of the article to be heated, and a second heating unit located on a second side facing the first side across the article to be heated. Have
The temperature measurement unit includes a first temperature measurement unit that measures the surface temperature of the heated object on the first side, and a second temperature that measures the surface temperature of the heated object on the second side. A measuring unit,
The control unit, based on the surface temperature measured by the first temperature measurement unit, third temperature control means for controlling the temperature of the first heating unit,
The heat according to claim 1, further comprising: a fourth temperature control unit that controls the temperature of the second heating unit based on the surface temperature measured by the second temperature measurement unit. Molding equipment. The heater has a first heater and a second heater located downstream of the first heater in the transport direction of the object to be heated,
The first temperature control means controls the temperature of the first heater,
The thermoforming apparatus according to claim 2, wherein the second temperature control unit controls the temperature of the second heater.   The thermoforming apparatus according to any one of claims 1 to 7, wherein the heater has high temperature change responsiveness to an input from the control unit. A thermoforming method for heating and molding an object to be heated,
While gradually lowering the temperature of the heater, the heated object is heated,
When the measured surface temperature of the object to be heated reaches a target temperature, the temperature of the heater is controlled so that the surface temperature approaches the target temperature,
A thermoforming method, wherein the heated object to be heated is formed. A heating device used for thermoforming,
A heater for heating an object to be heated;
A temperature measuring unit for measuring the surface temperature of the object to be heated;
When heating the object to be heated, the temperature of the heater is sequentially decreased, and when the measured surface temperature of the object to be heated reaches a target temperature, the heater is brought close to the target temperature. And a controller for controlling the temperature of the heating device. A temperature control method for a heater used in thermoforming,
While gradually lowering the temperature of the heater, the heated object is heated,
A heater temperature control method, comprising: controlling a temperature of the heater so that the surface temperature approaches a target temperature when the measured surface temperature of the object to be heated reaches a target temperature.

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