JPH05337954A - Resin sheet heating apparatus - Google Patents

Abstract

PURPOSE:To simplify a process uniformizing the temp. distribution of a heated resin sheet. CONSTITUTION:The surface heating part and rear heating part opposed to the surface and rear of a resin sheet S are constituted as the aggregates of unit heaters and a distance sensor 40 is provided to the heater element 22 of each of the unit heaters. The heater elements 22 of the respective unit heaters are allowed to advance and retreat with respect to the resin sheet S corresponding to the spaced-apart distances of the heaters (intervals between the resin sheet S and the respective unit heaters) detected by the distance sensors 40. By this constitution, even when the resin sheet S is bent to be drawn down, the spaced-apart distances of the heaters are kept almost uniform over a heating period regardless of the place of the resin sheet S and the emission of heat to the resin sheet S from the heater elements 22 of the unit heaters is made uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin sheet heating device for heating a resin sheet by a heater arranged so as to face the resin sheet.

[0002]

2. Description of the Related Art Conventionally, a resin sheet heating device of this type is
It is used for heating a sheet material formed of a thermoplastic resin, that is, a resin sheet, by shaping it by an appropriate method such as vacuum molding to obtain a molded body. The heating temperature at this time is appropriately determined according to the thermoplastic resin used, and it is required to heat the entire surface of the resin sheet as uniformly as possible in order to ensure the quality of the molded body. That is, if the temperature distribution of the resin sheet is non-uniform, the degree of softening also becomes non-uniform, so that there is a difference in the elongation of the resin sheet during molding, and the thickness of the molded body becomes non-uniform. In particular,
The thickness of the corners of the deep drawn part becomes thinner than other places.

Therefore, in the conventional resin sheet heating apparatus, by controlling the temperature of the heater, for example, the temperature of the resin sheet is controlled to be different depending on the heating location of the resin sheet, and the temperature of the resin sheet is spread over the entire surface of the sheet. I am trying to make it as uniform as possible.

[0004]

However, even if the temperature of the heater is controlled as described above, the temperature of the resin sheet may not be uniformized in some cases. When controlling the temperature of the heater, the target temperature can be controlled within a relatively short time when the temperature is increased, but the target temperature is set when the temperature is decreased. It takes a long time. In addition, undershoot or overshoot occurs in the behavior of the control temperature when the target temperature is set.
Due to these factors, excessive heating or the like may occur, and the temperature distribution of the resin sheet may become uneven.

Further, the following problems have been pointed out. Since the resin sheet is softened by heating, if the resin sheet is held horizontally, for example, the resin sheet is bent by its own weight, so-called drawdown occurs. This drawdown occurs to some extent, regardless of the type of resin sheet, sheet thickness, heating temperature, etc.

Since drawdown occurs even during heating,
The distance between the heater and the resin sheet is not uniform, and the state of heat radiation from the heater to the resin sheet is different. Therefore, the temperature distribution of the resin sheet becomes non-uniform. In order to avoid such a situation, the temperature control of the heater as described above requires complicated temperature control in consideration of the degree of drawdown, that is, the type of resin sheet, the sheet thickness, etc., which is complicated. .. Further, as described above, it is difficult to make the temperature distribution of the resin sheet uniform because the temperature control is likely to have a long control time and excessive heating.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a resin sheet heating apparatus which can easily uniformize the temperature distribution in the resin sheet when heating the resin sheet.

[0008]

Means for Solving the Problems The means adopted by the present invention in order to achieve such an object is a resin sheet heating device having a heater arranged so as to face a resin sheet and heating the resin sheet. Then, the heater is configured as a heater group in which unit heating units that individually generate heat are collected, and each unit heating unit in the heater group is provided so as to be movable back and forth with respect to the resin sheet, and The gist is to individually advance and retreat the unit heating unit by following the bending.

[0009]

In the resin sheet heating apparatus having the above structure, the unit heating section in the heater group constituting the heater is individually advanced and retracted in accordance with the bending of the resin sheet due to heating, so that the heating of the resin sheet can be achieved. The distance between each unit heating unit and the resin sheet is kept constant.

In individually advancing and retracting the unit heating unit by following the bending of the resin sheet due to heating, the distance between each unit heating unit and the resin sheet is detected, and each unit heating unit is advanced or retracted according to the detection result. You can do it. Further, it is only necessary to experimentally grasp beforehand how the resin sheet is bent by heating, and based on the result, move each of the unit heating portions forward and backward.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the resin sheet heating apparatus according to the present invention will be described with reference to the drawings. First, a schematic configuration of a resin sheet heating apparatus 10 of an example will be described with reference to FIG. 1 that schematically shows a side surface of a main part and FIG. 2 that schematically shows a plane of a main part.

As shown, the resin sheet heating device 10
Is for heating the resin sheet S whose sides are clamped and held horizontally by a holding mechanism (not shown) from the front and back sides thereof, and has the following configuration. The resin sheet heating device 10 includes a front surface heating unit 12 located above the resin sheet S and heating the front surface thereof, and a back surface heating unit 14 located below the resin sheet S and heating the back surface thereof.

The front surface heating section 12 and the back surface heating section 14 are
The heater unit 16 in which the seven unit heaters 20 are arranged is 5
The unit heaters 20 are arranged in rows and are configured as a 5 × 7 matrix heater group. It should be noted that the front surface heating unit 12 and the back surface heating unit 14 are different from each other only in the heating direction, and are composed of the same unit heater 20.

In this embodiment, the resin sheet S is a two-layer sheet material in which a skin sheet made of a thermoplastic resin PVC and a PP foam are laminated, and the front and back sides of the sheet are 150-150.
The purpose is to heat to 200 degrees. Therefore, the capacity of each unit heater 20 and the distance (heater separation distance) between the surface of the resin sheet S and the heating surface of the unit heater 20 in a state of being held horizontally are determined as follows. Unit heater capacity: 300 to 500 degrees Heater separation distance: 300 to 400 mm Note that these values are predetermined according to the desired resin sheet temperature prior to the heat treatment, and the heating temperature of the unit heater 20 and the heater separation distance are Adjusted.

As shown in FIG. 3, the unit heater 20 includes a heater body 22 having a heating element such as a heating wire on its surface, and a heater elevating mechanism 30 for elevating the heater body 22 with respect to a fixed plate 24. .. The fixing plate 24 is vertically movable and is provided so as to be fixed at an arbitrary position.
Therefore, by moving the fixed plate 24 up and down, it is possible to adjust the initial value of the heater separation distance. That is, the initial heater separation distance before heating can be adjusted according to the properties of the resin sheet to be heated.

The heater raising / lowering mechanism 30 has a link 32 connecting the heater body 22 to a fixed plate 24 so as to be able to move up and down, a penetrating through the fixed plate 24 and erected on the upper surface of the heater body 22, and a rack is formed on the upper end. An elevating shaft 34, a pinion 36 for vertically moving the elevating shaft 34 that meshes with the rack, and a motor 38 that is a drive source thereof are provided. A distance sensor 40 that detects the distance to the detection target is embedded in the center of the surface of the unit heater 20 so as to be insulated.

Starting with the distance sensor 40, the heater body 22
The heating element and the motor 38 are connected to a control device (not shown) and controlled by this control device. Specifically, the distance to the detection target detected by the distance sensor 40 (the distance to the resin sheet S in the case of the present embodiment).
Is converted into an electric signal for a predetermined time (for example, 100 mse
Output to the control device for each c). Upon receipt of this, the control device drives the motor 38 according to the above distance, and the vertical movement of the lifting shaft 34 by the pinion and the rack causes
The unit heater 20 is moved up and down. Thus, the unit heater 2
0 goes back and forth with respect to the resin sheet S. on the other hand,
The heater body 22 is controlled so that its heating element generates heat at a constant temperature.

Next, how the resin sheet S is heated by the resin sheet heating device 10 having the above-described structure will be described. The heating of the resin sheet S is started from the time when the heater body 22 of each unit heater 20 in the front surface heating unit 12 and the back surface heating unit 14 generates heat to a predetermined temperature and the temperature becomes uniform. That is, the front surface heating unit 12 and the back surface heating unit 14
After the temperature becomes constant, the resin sheet S is separated from the surface of each unit heater 20 by a predetermined heater separation distance L (for example, 3
20 mm) apart and the heating is started.

When the set resin sheet S receives heat radiated from each unit heater 20 and the temperature of the resin sheet S rises, the resin sheet S gradually softens. As a result, the resin sheet that was held horizontally before heating (see FIG. 1) gradually bends due to its own weight, and drawdown occurs in the resin sheet S as shown in FIG.

The amount of bending in this drawdown increases with the passage of heating time up to a predetermined amount of bending which is determined by the material and thickness of the resin sheet S, the heat generation temperature of the unit heater 20, and the like. That is, the distance between the unit heater 20 and the resin sheet S changes as the heating time elapses, and the resin sheet S
Separates from the unit heater 20 in the front surface heating unit 12 and approaches the unit heater 20 in the back surface heating unit 14.

As described above, the resin sheet heating apparatus 10 of this embodiment has the distance sensor 40 in each unit heater 20.
Heater lifting mechanism 3 according to the heater separation distance detected by
The unit heater 20 is moved back and forth with respect to the resin sheet S via 0. Therefore, by moving the unit heater 20 forward and backward so that the heater separation distance detected by the distance sensor 40 becomes a predetermined heater separation distance L, as shown in FIG. 4, the drawn-down resin sheet S and each unit heater 20 are separated from each other. The distance between the two is kept substantially uniform regardless of the location of the resin sheet S over the heating period.

As a result, the resin sheet heating apparatus 1 of the embodiment
According to 0, the heat radiation from the unit heaters 20 constituting the front surface heating section 12 and the back surface heating section 14 to the resin sheet S becomes uniform, so that the temperature distribution on the front surface and the back surface of the resin sheet S is It can be uniform.

Moreover, in order to make the temperature distribution of the resin sheet S uniform, it is only necessary to move the unit heaters 20 back and forth while keeping the control temperature constant.
The temperature distribution in the resin sheet S can be easily made uniform.

The resin sheet heating apparatus 10 of this embodiment is also used.
Then, the distance sensor 40 is provided in each unit heater 20 in the front surface heating unit 12 and each unit heater 20 in the back surface heating unit 14. Therefore, the temperature distribution on the front surface and the back surface of the resin sheet S can be made uniform at a predetermined temperature determined by each surface without being influenced by the thickness of the resin sheet S. Further, even when the front surface (skin sheet made of PVC) and the back surface (PP foam) of the resin sheet S are heated to different temperatures, the unit heater 20 is used according to the sheet separation distance between the front and back surfaces of the resin sheet S. To move back and forth. Then, through this, each sheet on the front surface or the back surface can be heated to a desired temperature for each sheet, and the temperature distribution can be made uniform.

Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment and can be implemented in various modes without departing from the scope of the present invention. Of course. The modification will be described below. In the above embodiment, the distance sensor 40 is provided at the center of the unit heater 20. However, the distance sensor 40 may be provided at the left and right ends of the heater body 22 of the unit heater 20 as shown in FIG. In this case, the heater lifting mechanism 30 of the unit heater 20 is configured as follows. That is, the heater body 22 is connected to the elevating shaft 34 by a universal joint or the like so that the heater body 22 can be swung, and a cylinder or the like for swinging the heater body 22 is provided between the heater body 22 and the fixed plate 24.

The detection distances from the left and right distance sensors 40 can be used for calculating the advance / retreat amount of the unit heater 20 and the swinging amount of the heater body 22 according to the bending of the resin sheet S. By doing so, not only can the unit heater 20 be advanced and retracted in accordance with the bending of the resin sheet S, but the heater body 22 can be tilted in accordance with the bending of the resin sheet S as shown in FIG. .. Therefore, the heater separation distance between the unit heater 20 and the resin sheet S is
It is possible to make it uniform over almost the entire surface of the heater body 22,
The temperature distribution on the front and back surfaces of the resin sheet S can be made more uniform.

In the above embodiment, the distance sensor 4 is provided for each unit heater 20 in the front surface heating section 12 and the back surface heating section 14.
Although 0 is provided, the distance sensor 40 may be provided in each unit heater 20 of either the front surface heating unit 12 or the back surface heating unit 14. In this case, the thickness of the resin sheet S may be taken into consideration when applying the heater separation distance detected on one heating unit side to the other heating unit side. If the distance sensor 40 is provided only on the heating section on one side as described above, the cost can be reduced due to the reduction in the number of sensors installed.

In the above embodiment, the unit heater 20 is provided with the distance sensor 40, and the unit heater 20 is provided in accordance with the detected distance.
, But you can also do the following: That is, in consideration of the desired temperature of the resin sheet S, the heat generation temperature in the front surface heating section 12 and the back surface heating section 14 (ambient temperature of the place where the resin sheet S is heated), the material and thickness of the resin sheet S, the heating time is considered. The correlation between the occurrence of the flexure of the resin sheet S (the appearance of drawdown) is experimentally grasped in advance, and this relationship is stored in the memory of the control device. Then, the stored correlation is read every time the heating time elapses, and each unit heater 20 may be moved back and forth.

With this structure, the distance sensor 40 is provided in each unit heater 20 of the front surface heating section 12 and the rear surface heating section 14.
Is not required at all, and the configuration can be simplified and the cost can be reduced. Further, since the distance sensor 40 is not required, the unit heater is used as a unit heater having a small heating area and the front surface heating unit 12 and the back surface heating unit 14 are arranged in a matrix to form a unit heater array. The number and the number of columns can be increased. Therefore, when maintaining the heater separation distance between the unit heater and the resin sheet S, the heater separation distance is set to the resin sheet S for each heating area of the small resin sheet per unit heater.
Can be made uniform over the entire surface. As a result, the temperature distribution of the resin sheet S can be made more uniform.

Although the pinion and the rack are used for the heater elevating mechanism 30 for moving the unit heater 20 forward and backward, an appropriate mechanical element such as a cylinder or a ball screw can be used. Further, the resin sheet to be heated is not limited to the two-layer resin sheet shown in the above embodiment, and it goes without saying that it may be a sheet molded from a single resin. Further, although the distance sensor 40 is provided on the heater body 22, it may be provided on the fixed plate 24. At this time, the distance from the space between the adjacent heater bodies 22 to the seat surface may be measured. If the distance sensor 40 is provided on the fixed plate 24 in this way, the distance sensor 40 can be separated from the heater body 22 that is a heating element, so that the distance sensor can be protected from heat.

[0031]

As described above in detail, in the resin sheet heating apparatus of the present invention, the distance between each unit heating section and the resin sheet is set by moving each unit heating section in the heater group constituting the heater back and forth. Keep constant throughout the heating of the. As a result, according to the resin sheet heating device of the present invention,
By uniformly radiating the heat from each unit heating unit to the resin sheet, the temperature distribution of the resin sheet can be made uniform. Moreover, in order to make the temperature distribution uniform, it is only necessary to keep the heating temperature by the heater constant and move the unit heating unit forward and backward, so that the temperature distribution in the resin sheet can be easily made uniform.

[Brief description of drawings]

FIG. 1 is a schematic diagram schematically showing a side surface of a main part of the resin sheet heating apparatus 10 according to an embodiment for explaining a schematic configuration thereof.

FIG. 2 is a schematic view schematically showing a plane of a main part of a resin sheet heating device 10 according to an embodiment.

FIG. 3 is a unit heater 2 in a resin sheet heating device 10.
Explanatory drawing for demonstrating the structure of 0.

FIG. 4 is an explanatory diagram for explaining how the resin sheet S is heated by the resin sheet heating device 10.

FIG. 5 is an explanatory diagram for explaining a configuration of a heater body 22 in a modified example.

FIG. 6 is an explanatory diagram illustrating a heating state of a resin sheet S in a modified example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Resin sheet heating device 12 ... Front surface heating part 14 ... Back surface heating part 16 ... Heater unit 20 ... Unit heater 22 ... Heater body 30 ... Heater lifting mechanism 40 ... Distance sensor S ... Resin sheet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Furuta Kenichi Furuta Nishiokasugai-gun, Aichi 1 Ochiai, Ochiai, Nagahata No. 1 Toyoda Gosei Co., Ltd. Address inside Toyota Gosei Co., Ltd.

Claims (1)

[Claims] 1. A resin sheet heating device having a heater arranged to face a resin sheet and heating the resin sheet, wherein the heater group is a group of heaters that individually generate heat. Each unit heating unit of the heater group is provided so as to be movable back and forth with respect to the resin sheet, and the unit heating unit is individually moved back and forth by following the bending of the resin sheet due to heating. A resin sheet heating device.