JP2023065178A - Heating apparatus and heating method - Google Patents

Abstract

To provide a heating apparatus equipped with a radiation thermometer capable of being automatically controlled using the radiation thermometer and capable of uniformly heating a workpiece in a short time, and a heating method.SOLUTION: A heating apparatus 1 includes an infrared heater 2 that heats a workpiece W, a control unit 5 that controls the output of the infrared heater 2, and a radiation thermometer 4 that measures the surface temperature of the workpiece W, and the infrared heater 2 can arbitrarily change the output between a first output for rapidly raising the temperature of the workpiece W until the surface temperature of the workpiece W reaches a predetermined target temperature, and a second output that emits mid-infrared to far-infrared rays at a lower output than the first output and maintains the surface temperature of the workpiece W until the internal temperature of the workpiece W reaches the target temperature. The second output is controlled by the control unit 5 according to the surface temperature of the workpiece W measured by the radiation thermometer 4.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a heating apparatus and a heating method capable of heating an object to be heated evenly to the inside in a short period of time.

Conventionally, when a work (object to be heated) such as a resin containing CFRP (carbon fiber reinforced composite material) or GFRP (glass fiber reinforced composite material) is rapidly heated using infrared rays, the surface of the object to be heated has priority. Therefore, a temperature difference occurs between the surface and the center of the object to be heated, and it is difficult to heat the entire object to be heated uniformly. Furthermore, due to the temperature control during heating, even if you try to measure the temperature with a radiation thermometer, the scattered infrared light overlaps the measurement area (infrared region) of the radiation thermometer, making it impossible to accurately measure the temperature. I didn't. In particular, when an object to be heated, which is generally called a thick object having a thickness of 2 mm or more, is rapidly heated, a large temperature difference of several tens of degrees Celsius or more occurs between the surface and the center of the object to be heated. This temperature difference has been one of the causes of deterioration in quality in processes such as press molding that are performed after heating. For this reason, until now, the heating of a thick sample has been dealt with by slowly heating over time to reduce the temperature difference between the surface and the center of the sample, resulting in poor productivity.

Under such circumstances, in Patent Document 1, while conveying the work by a conveyor in the heating furnace, in the upstream first heating zone, the surface temperature of the work is rapidly raised to the target temperature, and the temperature of the first heating zone In the downstream soaking zone, the heating temperature is limited to an extent that suppresses a sudden drop in the surface layer temperature of the work, and the internal temperature of the work is increased by heat transfer from the surface layer side to the inside of the work. In the heating zone, the surface layer temperature is raised to the target temperature again, and the surface layer temperature and the internal temperature of the work are heated so that they are within the target temperature range, so that the temperature difference between the surface layer and the inside of the work becomes small. Techniques for heating are disclosed.

Japanese Patent No. 5547940

However, the heating method disclosed in Patent Literature 1 merely heats by setting the temperature and heating time (conveyor speed) in each heating zone of the heating furnace. Therefore, it is necessary to consider the optimum heating conditions every time the conditions such as the shape of the workpiece change, and it must be said that the automatic control of the heating device is far from being achieved. In addition, since the heating zones with different temperature zones need to be arranged side by side from upstream to downstream, the furnace length must be long, and a large-sized heating device is required.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heating apparatus and a heating method capable of automatically controlling the heating temperature using a radiation thermometer and heating the workpiece uniformly in a short period of time.

In order to achieve the above object, the invention according to claim 1 is a heating apparatus comprising an infrared heater for heating an object to be heated, a control section for controlling the output of the infrared heater, and an object to be heated. a radiation thermometer for measuring surface temperature, the infrared heater has a first output for raising the temperature of the object to be heated until the surface temperature of the object to be heated reaches a predetermined target temperature, and an output lower than the first output. emits mid-infrared to far-infrared rays, and maintains the surface temperature of the object to be heated until the internal temperature of the object to be heated reaches the target temperature. is controlled by the controller according to the surface temperature of the object to be heated measured by the radiation thermometer.
According to a second aspect of the present invention, in the configuration described above, the radiation thermometer is provided with a radiation exclusion tube the inside of which is coated with an infrared-absorbing material.
According to a third aspect of the present invention, in the above configuration, the first output is the maximum output of the infrared heater.
The invention according to claim 4 is a heating method using a heating device equipped with the radiation thermometer according to any one of claims 1 to 3, wherein until the surface temperature of the object to be heated reaches a predetermined target temperature, A heating turn that raises the temperature of an object to be heated by an infrared heater with a first output, and a heat retention turn that maintains the surface temperature of the object until the internal temperature of the object reaches a target temperature by an infrared heater with a second output. and the second output is controlled by the controller according to the surface temperature of the object to be heated measured by the radiation thermometer during the heat retention turn.
The invention according to claim 5 has an infrared heater for heating an object to be heated, a control section for controlling the output of the infrared heater, and a radiation exclusion tube the inside of which is coated with an infrared absorbing material. , and a radiation thermometer for measuring the surface temperature of the object to be heated, the infrared heater radiates mid-infrared to far infrared rays, and the output of the infrared heater corresponds to the surface temperature of the object to be heated measured by the radiation thermometer. It is characterized by being controlled by the control unit accordingly.
The invention according to claim 6 is a heating method using the heating device according to claim 5, wherein the object to be heated is heated by an infrared heater until the surface temperature and internal temperature of the object to be heated reach predetermined target temperatures. The output of the infrared heater is controlled by the controller according to the surface temperature of the object to be heated measured by the radiation thermometer when the temperature of the object to be heated is raised.

The main effect of the present invention is to provide a heating apparatus and a heating method equipped with a radiation thermometer capable of automatically controlling the heating temperature using the radiation thermometer and heating the workpiece uniformly in a short period of time. is.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows the heating apparatus of this invention, (a) is a top view, (b) is a sectional view on the AA line of (a). It is an explanatory view showing a radiation thermometer of the present invention. 4 is a graph showing transition images of the output of an infrared heater and the surface and cross-sectional center temperatures of a workpiece in a heating process. It is a graph which shows a heating test result. 5 is a graph showing the relationship between the difference between the work surface temperature measured using a thermocouple and the work surface temperature measured using a radiation thermometer, and the output of an infrared heater.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.
1A and 1B are explanatory diagrams showing a heating apparatus of the present invention, in which FIG. 1A is a plan view and FIG.
As shown in FIGS. 1(a) and 1(b), the heating device 1 is capable of loading a plurality of straight pipe infrared heaters 2 and a workpiece W to be heated such as CFRP. A movable stage 3 that advances in a predetermined direction, a radiation thermometer 4 for measuring the surface temperature of the workpiece W, and a control unit 5 that controls the output of the infrared heater 2 are provided.
In this embodiment, the stage 3 moves on two rails R installed along two opposite sides of the heating device 1, and the moving mechanism of the stage 3 at that time is a known moving mechanism. applies.
The controller 5 may be individually connected to each infrared heater 2 to control each infrared heater 2 individually, or may uniformly control all the infrared heaters 2 . The control unit 5 is also connected to a radiation thermometer 4 so that the output of the infrared heater 2 can be adjusted according to the temperature measured by the radiation thermometer 4 . The output of the infrared heater 2 can be adjusted to any value between 0%, which is the stopped state, and 100%, which is the maximum output.
The work W is heated by the heating device 1 to eliminate latent stress, and after heating, is subjected to deformation processing such as press molding, lamination and compositing processing, and the like.

As shown in FIG. 1(b), the infrared heaters 2 are arranged in an upper heater unit 2a and a lower heater unit 2b with the stage 3 sandwiched therebetween. Reflection units 6 are provided above the upper heater 2a and below the lower heater 2b in order to improve heating efficiency. Furthermore, heat insulating materials 7 are arranged above and below the reflecting unit 6 to prevent heat transfer to the outside of the heating device 1 . By providing the upper heater 2a and the lower heater 2b, the work W can be heated simultaneously from both sides in the vertical direction.

FIG. 2 is an explanatory diagram showing the radiation thermometer of the present invention.
The radiation thermometer 4, as shown in FIG. 2, includes a detector 4a, a lens 4b, and a cylindrical radiation exclusion tube 8 having a predetermined length.
The radiation thermometer 4 measures the surface temperature of the workpiece W by detecting infrared rays radiated from the surface of the workpiece W to be measured by the detector 4a via the lens 4b and converting them into electric signals. is. The radiation exclusion cylinder 8 is coated with a black paint having infrared absorption properties on the inside. Since the infrared rays entering the radiation exclusion tube 8 are absorbed by the black paint, the influence of the infrared rays scattered between the upper heater unit 2a and the lower heater unit 2b is suppressed, and the workpiece W is detected by the radiation thermometer 4. A more accurate measurement of surface temperature is possible. It is desirable that the radiation exclusion cylinder 8 be formed in a shape that does not block the incidence of radiant light (infrared rays) to the lens 4b. If the diameter of the radiation exclusion tube 8 is too large, the amount of scattered light incident on the lens 4b increases, possibly degrading the measurement accuracy. On the other hand, if the diameter of the radiation exclusion tube 8 is too small, the amount of radiant light incident on the lens 4b is reduced, which may reduce the measurement accuracy. Moreover, the radiation exclusion tube 8 has a length such that the tip thereof is arranged between the infrared heater 2 (upper heater unit 2a) and the work W, as shown in FIG. 1(b). As a result, the scattered light emitted from the upper heater unit 2a is prevented from entering the radiation exclusion tube 8. FIG. That is, by using the radiation exclusion cylinder 8 having a shape having an appropriate diameter and length, it becomes possible to measure the surface temperature of the workpiece W with the radiation thermometer 4 more accurately.

Next, a method for heating the workpiece W using the heating device 1 will be described.
FIG. 3 is a graph showing transition images of the output of the infrared heater and the surface and cross-sectional center temperatures of the workpiece in the heating process.
First, after the workpiece W is placed on the stage 3, the stage 3 is moved. As the stage 3 moves, the workpiece W moves inside the heating device 1 .
After the work W has moved into the heating device 1, as shown in FIG. , the workpiece W is rapidly heated by the infrared heater 2 (heating turn H). In the heating turn H, high-power near-infrared rays are emitted from the infrared heater 2 . The internal temperature of the work W is lower than the target temperature because it is heated from the surface with a high output. Since the near-infrared wavelength region overlaps the measurement region of the radiation thermometer 4, the radiation thermometer 4 detects the scattered light from the infrared heater 2 in the heating turn H, and the surface temperature of the workpiece W cannot be measured accurately. Cannot measure. Therefore, in the heating turn H, it is necessary to rapidly raise the temperature of the work W to near the target temperature in a short time according to a predetermined temperature pattern confirmed in advance. In the present application, near-infrared rays refer to infrared rays in the wavelength range of 0.7 μm to 1.5 μm. In addition, mid-infrared rays refer to infrared rays in the wavelength region of 1.5 μm to 4.0 μm, and far infrared rays refer to infrared rays in the wavelength region of 4.0 μm to 1000 μm.

After the surface temperature of the workpiece W reaches around the target temperature, the controller 5 changes the output of the infrared heater 2 to the second output (10% output here). Then, while maintaining the surface temperature of the work W around the target temperature, the internal temperature of the work W is raised to around the target temperature (warming turn K). In the heat-retaining turn K, the infrared heater 2 radiates low-output infrared rays, ie, middle infrared rays to far infrared rays. The wavelength region from mid-infrared rays to far-infrared rays does not overlap with the measurement region of the radiation thermometer 4 . Therefore, it is possible to measure the surface temperature of the workpiece W with a predetermined accuracy or higher using the radiation thermometer 4 . At this time, it is conceivable that a certain amount of measurement error may occur due to scattered light. The measurement error is almost suppressed, the measurement target is narrowed down to the infrared rays from the surface of the work W, and accurate temperature measurement of the work W (measurement at the normal set value of emissivity 0.9 to 0.95) is possible. . Since the radiation thermometer 4 can accurately measure the surface temperature of the workpiece W, the controller 5 automatically controls the output of the infrared heater 2 according to the measured temperature in the heat retention turn K. there is As a result, the heating device 1 maintains the surface temperature of the work W and performs an appropriate heat treatment until the internal temperature of the work W reaches the target temperature.
In this way, the heating turn H and the heat retaining turn K are performed by changing the output of the infrared heater 2, so that the heating device 1 can be designed to be smaller than a large-sized conventional heating device that requires a long furnace length. .
In the heat-retaining turn K, the output of the infrared heater 2 is reduced to change the radiated infrared rays from mid-infrared rays to far-infrared rays. Therefore, the control unit 5 can automatically control the output of the infrared heater 2, that is, the heating temperature, based on the measured temperature. As a result, while preventing the surface temperature of the work W from deviating from the target temperature, the work W can be appropriately heated until the internal temperature reaches the target temperature.

Next, the results of a heating test using the heating device 1 of the present invention are shown.
FIG. 4 is a graph showing the heating test results.
In the heating test, using the heating device 1, a work W made of CFRP with a thickness of 4 mm and 100 mm square was heated for 30 seconds, and the surface and inside of the center of the work, the surface and inside of the point 30 mm from the center of the work, and the point of 45 mm from the center of the work. Temperature measurements were taken at each measurement point on the surface and inside. The temperature measurement at each measurement point on the surface and inside of the work W was performed using a thermocouple. The internal temperature is the temperature at a depth of 2 mm from the surface.

FIG. 4 shows the results of the heating test. The graph of FIG. 4 shows transitions of the surface temperature of the work W detected by the radiation thermometer 4 and the power (output of the infrared heater 2) in addition to the temperature measured at each of the measurement points described above. The radiation thermometer 4 measured the surface temperature at the center of the work.
First, as the heating turn H, the power is set to 90 kW (the output of the infrared heater 2 is 100%, which is the first output), and heating is performed until the surface temperature of the work W reaches the target temperature of 200°C. gone.
With the passage of time, the surface temperature of the work W rapidly increased almost uniformly from the start of heating at any of the center of the work W, the point 30 mm from the center, and the point 45 mm from the center, reaching the target temperature in about 10 seconds. reached. On the other hand, the internal temperature of each part of the work W is about 120° C. even after 10 seconds have passed, and it can be seen that there is a large difference from the surface temperature of the work W.
Also, at this time, it can be seen that the radiation thermometer 4 cannot accurately measure the temperature due to the scattered light from the infrared heater 2 .

After the surface temperature of the workpiece W reaches the target temperature, switch to the heat insulation turn K, reduce the power to about 10 kW (the output of the infrared heater 2 is about 10%, which is the second output), and Heating was performed until the internal temperature reached the target temperature of 200°C.
In addition, in the heat-retaining turn K, the electric power is finely adjusted by the control unit 5 . As the overshooting surface temperature of the work W changes toward the target temperature, the internal temperature of the work W rises gently, and in about 30 seconds from the start of heating, the surface temperature and the inside of the work W All of the temperatures reached the target temperature at all measurement points.
By performing the heating turn H and the heat-retaining turn K in this way, a 4 mm thick object can be uniformly heated even in a short time of 30 seconds.
At this time, it can be seen that the radiation thermometer 4 can accurately measure the surface temperature of the workpiece W as the output of the infrared heater 2 approaches about 10%. This is because the output of the infrared heater 2 is reduced, so that the infrared heater 2 emits mid- to far-infrared rays that do not overlap the measurement area of the radiation thermometer 4 , and the scattered light is detected by the radiation thermometer 4 . It can be seen that the radiation thermometer 4 can accurately measure the surface temperature of the work W by excluding the radiation with the radiation exclusion tube 8 .

FIG. 5 is a graph showing the relationship between the difference between the workpiece surface temperature measured using a thermocouple and the workpiece surface temperature measured using a radiation thermometer, and the output of the infrared heater.
FIG. 5 is a graph showing the relationship between the difference between the surface temperature of the work W measured using the thermocouple and the surface temperature of the work W measured using the radiation thermometer 4, and the output of the infrared heater 2. show.
When the output of the infrared heater 2 is 100%, that is, the first output, the difference between the surface temperature of the work W measured using the thermocouple and the surface temperature of the work W measured using the radiation thermometer 4 is , approximately Δ60°C. Therefore, it can be seen that the radiation thermometer 4 cannot accurately measure the surface temperature of the workpiece W in the case of the first output.
Assuming that the output of the infrared heater 2 is 50%, the difference between the surface temperature of the work W measured using the thermocouple and the surface temperature of the work W measured using the radiation thermometer 4 is approximately Δ20°C. rice field.
Furthermore, when the output of the infrared heater 2 is reduced and the output is set to 10%, that is, the second output, the surface temperature of the work W measured using the thermocouple and the surface temperature of the work W measured using the radiation thermometer 4 The difference from the surface temperature was approximately Δ0°C. Therefore, when the second output is selected, the radiation thermometer 4 can accurately measure the surface temperature of the workpiece W. FIG.

The heating device 1 configured as described above includes an infrared heater 2 for heating the workpiece W, a controller 5 for controlling the output of the infrared heater 2, and a radiation thermometer 4 for measuring the surface temperature of the workpiece W. The infrared heater 2 has a first output that rapidly heats the workpiece W until the surface temperature of the workpiece W reaches a predetermined target temperature, and a lower output than the first output to radiate middle infrared to far infrared rays. The output can be arbitrarily changed between a second output that maintains the surface temperature of the work W until the internal temperature of the work W reaches the target temperature, and the second output is measured by the radiation thermometer 4 It is controlled by the controller 5 according to the surface temperature of the work W to be applied.
Therefore, by making the output of the infrared heater 2 variable, the heating device 1 can be designed to be smaller than a conventional large-sized heating device that requires a long furnace length.
In addition, by reducing the output of the infrared heater 2 and changing the radiated infrared rays from middle infrared rays to far infrared rays, it becomes possible to measure the surface temperature of the workpiece W with the radiation thermometer 4. Therefore, based on the measured temperature, The output of the infrared heater 2 by the controller 5, that is, the heating temperature can be automatically controlled. As a result, while preventing the surface temperature of the work W from deviating from the target temperature, the work W can be appropriately heated until the internal temperature reaches the target temperature.

In addition, the radiation thermometer includes a radiation exclusion tube the inside of which is coated with an infrared-absorbing material.
Therefore, the infrared rays that have entered the radiation exclusion cylinder 8 are absorbed by the black paint as they proceed, so that the influence of the scattered infrared rays emitted from the surface of the work W is suppressed, and the surface temperature of the work W measured by the radiation thermometer 4 is reduced. More accurate measurement becomes possible.

The present invention has been described above based on the illustrated examples, and the technical scope thereof is not limited thereto. For example, the first output and the second output can be arbitrarily set as long as the object to be heated can be heated to the target temperature in a desired time.
Moreover, the shape and the number of installation of the infrared heater are not limited as long as the infrared heater can heat the object to be heated, and any shape and number of installation may be used. Furthermore, it may be installed only above or below the object to be heated.
Also, a plurality of radiation thermometers may be provided, and the installation position is not limited.
Also, the radiation exclusion tube can be arbitrarily designed in length, shape, etc., as long as the surface temperature of the object to be heated can be accurately measured.
Further, the control section only needs to be able to change the output of the infrared heater, and the control section may automatically control the output of the infrared heater or artificially change the output of the infrared heater via the control section.
Further, the stage is not limited to one that moves on rails by a well-known drive mechanism, and the stage itself may be formed by a belt conveyor, for example.
In addition, the heating device includes a heating area for heating the surface of the object to be heated to a target temperature by an infrared heater with a first output, and a control unit that adjusts the second output to uniformly heat the inside of the object to the target temperature. A heat insulating area for heating may be provided in the heating area, and the object to be heated may be heated by moving a stage on which the object to be heated is placed from the heating area to the heat insulating area.
In addition, the heating of the object to be heated includes an infrared heater that emits mid-infrared to far infrared rays to heat the object to be heated, a control unit that controls the output of the infrared heater, and an interior that is coated with a material that absorbs infrared rays. Using a heating device that has a radiation exclusion cylinder and a radiation thermometer that measures the surface temperature of the object to be heated, the infrared heater is heated until the surface temperature and internal temperature of the object to be heated reach a predetermined target temperature. may be controlled by the controller in accordance with the surface temperature of the object to be heated measured by the radiation thermometer.

DESCRIPTION OF SYMBOLS 1... Heating apparatus, 2... Infrared heater, 4... Radiation thermometer, 5... Control part, 8... Radiation exclusion cylinder, W... Work (object to be heated).

Claims (6)

An infrared heater for heating an object to be heated, a control unit for controlling the output of the infrared heater, and a radiation thermometer for measuring the surface temperature of the object to be heated,
The infrared heater has a first output for raising the temperature of the object to be heated until the surface temperature of the object to be heated reaches a predetermined target temperature, and a lower output than the first output for radiating mid-infrared to far-infrared rays. and a second output that maintains the surface temperature of the object to be heated until the internal temperature of the object to be heated reaches the target temperature,
The heating device, wherein the second output is controlled by the controller according to the surface temperature of the object to be heated measured by the radiation thermometer. 2. The heating device according to claim 1, wherein the radiation thermometer has a radiation exclusion tube the inside of which is coated with an infrared-absorbing material. 3. The heating device according to claim 1, wherein said first output is the maximum output of said infrared heater. Using the heating device according to any one of claims 1 to 3,
a heating turn for raising the temperature of the object to be heated by the infrared heater with the first output until the surface temperature of the object to be heated reaches a predetermined target temperature;
a heat-retaining turn of maintaining the surface temperature of the object to be heated until the internal temperature of the object to be heated reaches the target temperature with the infrared heater of the second output;
A heating method, wherein the controller controls the second output in the heat retaining turn according to the surface temperature of the object to be heated measured by the radiation thermometer. An infrared heater for heating an object to be heated, a control unit for controlling the output of the infrared heater, and a radiation exclusion cylinder the inside of which is coated with a material having infrared absorption properties, the surface temperature of the object to be heated and a radiation thermometer for measuring
The infrared heater radiates mid-infrared to far-infrared rays,
The heating device, wherein the output of the infrared heater is controlled by the controller in accordance with the surface temperature of the object to be heated measured by the radiation thermometer. Using the heating device according to claim 5,
raising the temperature of the object to be heated by the infrared heater until the surface temperature and internal temperature of the object to be heated reach predetermined target temperatures;
A heating method, wherein the output of the infrared heater is controlled by the controller according to the surface temperature of the object to be heated measured by the radiation thermometer when the temperature of the object to be heated is raised.

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