JP3091900B2 - Drying furnace operation control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the operation of a coated product drying oven, in particular an oven used for the drying of surface coatings on painted automobile bodies and the like. In particular, the invention relates to such a drying oven,
The present invention relates to an improvement in a control method when shifting from a so-called empty furnace operation to a drying process operation.

[0002]

2. Description of the Related Art In an automobile factory, an automobile body or the like which has been subjected to electrodeposition coating or electrostatic coating is thereafter passed through a drying oven, and heat treatment is performed in a radiant heating area and a convection heating area subsequent thereto. By doing so, the surface coating is dried.

[0003] In order to achieve proper coating drying, such drying ovens are usually equipped with a temperature sensor, for example in the area of the radiant heating panel (usually in the center of the panel), whereby the detected temperature is detected. By controlling the operation of the burner and the fan in the hot air circulation path based on the signal, the supply amount and the temperature of the heating air to the radiant heating panel are adjusted, and the temperature in the area of the radiant heating panel is always preferred. An operation control to keep the temperature within a range (for example, about 200 ± 5 ° C.) is generally performed.

[0004]

However, despite the operation control based on the above-mentioned detected temperature, there has hitherto been a problem of drying called "baked sweet" due to insufficient radiant heating of the coated product. In some cases, defects occurred. Such drying failure is caused when a large number of coated articles are sequentially conveyed through a passage in a drying oven and processed (so-called,
In the case of continuous drying), when the coating products to be treated are hardly found, but after the state of a so-called empty furnace where the coating products to be processed are not present in the drying furnace, the next group of coating products is transported to the drying furnace and processed. In particular, it is sometimes found for the second to third paint products from the head of the column of the next group. That is, when the operation levels of the radiant heating fan and the burner of the drying oven are at a high level during continuous drying, poor drying does not occur. When the level returns from the low level in (1) to the high level in the drying process, poor drying occurs. The condition of the empty furnace occurs when the number of painted products is reduced due to production adjustment or when the product specifications of painted products are changed to new ones. Since a control method of increasing the operation level is generally adopted, poor drying called "baked sweet" may frequently occur.

In view of such circumstances, the present inventors have studied and studied a method for preventing the occurrence of the above-mentioned poor drying. Then, in the course of the research, when the next group of coated articles were carried into the drying furnace in the state of the empty furnace, the temperature inside the drying furnace was not kept uniform over the entire furnace. It has been found that a certain degree of temperature distribution occurs (usually in the range of about ± 20 ° C.). For example, at the time of the next loading of the coated product, the temperature at the position near the furnace entrance in the area of the radiant heating panel is about more than the temperature at the center position of the area where the temperature sensor is usually provided. It was found that the temperature was lower by about 10 to 20 ° C.

[0006] Accordingly, from the above fact, the above-mentioned poor drying (baked sweet) causes the next group of coated articles to be treated in the drying furnace when the operation is shifted from the operation in the empty furnace to the operation in the drying process. Even if the temperature at the central position in the area of the radiant heating panel is maintained at a temperature in a range suitable for the drying process, the temperature at the position near the furnace entrance in the area is It is presumed that this occurs because the temperature remains low enough to perform the treatment, which results in insufficient heating of the coated article. From this, it is conceivable to move the mounting position of the temperature sensor from the central position in the area of the radiant heating panel to a position closer to the furnace entrance. However, if the position of the temperature sensor is changed in such a manner. If
Since the operation of the burner and the fan is controlled based on the temperature detected by the temperature sensor at the position near the furnace entrance, the temperature in the area of the radiant heating panel as a whole tends to reach a high temperature exceeding an appropriate range. Since it is predicted that poor drying due to overheating will often occur in the coated product, the above-mentioned means cannot be adopted immediately.

As described above, the object of the present invention is not only in the case where the drying process is continuously performed, but also in the case where the coated products are dried in groups and the state of the empty furnace is generated during the drying process. Drying of a coated product that can effectively prevent the occurrence of poor drying such as sweetness, and thus can achieve appropriate and economical film drying in the drying process of a coated product such as a painted automobile body. An object of the present invention is to provide a furnace operation control method.

[0008]

SUMMARY OF THE INVENTION The present invention provides at least two
Temperature sensors are provided in the coating product drying oven, particularly at a position near the center of the area of the radiant heating panel and a position near the furnace entrance, and based on the detected temperatures of these temperature sensors, the heating air is supplied to the radiant heating panel. The present invention relates to an operation control method for controlling the operation of a burner and a fan to be supplied to a furnace, thereby adjusting a furnace temperature in an area of a radiant heating panel.

In operation control using a plurality of temperature sensors, there is a problem as to which of the plurality of detected temperatures obtained from each temperature sensor is used to control the operation of the burner and the fan. The method of the present invention comprises:
One solution to this problem is proposed in controlling the operation of the drying furnace, when the high-level operation is continuously performed, the temperature in the entire area of the radiant heating panel is within an appropriate range. When the coated product enters the area of the radiant heating panel, the position of the radiant heating panel near the furnace entrance when the paint enters the area of the radiant heating panel The temperature sensor which is given priority as the source of the temperature information is determined such that "the temperature at is already kept within an appropriate range".

Specifically, the method of controlling the operation of a coated article drying oven according to the present invention includes the steps of: providing a plurality of temperature sensors in the coated article drying oven; and placing at least a first temperature sensor in a position near the center of the area of the radiant heating panel. A second temperature sensor is provided at a position near the furnace entrance in the area of the panel, and the operation of the burner and the fan is controlled based on the temperature detected by these temperature sensors, so that the temperature of the furnace in the area of the radiant heating panel is controlled. A method of performing the adjustment: 1) when the temperature detected by one of the first and second temperature sensors falls below the lower limit of the set furnace temperature range, The temperature of the burner is determined based on the temperature detected by the temperature sensor until the temperature detected by the temperature sensor exceeds the lower limit of the set furnace temperature range. And 2) control the operation of the fan. However, 2) even when the detected temperature of the second temperature sensor falls below the lower limit of the set furnace temperature range, the detected temperature of the first temperature sensor is When the temperature exceeds the upper limit of the set furnace temperature range, the first temperature sensor has priority over the second temperature sensor, and controls the operation of the burner and the fan based on the temperature detected by the first temperature sensor. It is characterized by the following.

As the first temperature sensor and the second temperature sensor used in the present invention, a temperature sensor capable of measuring a temperature in a range from about room temperature to a temperature range suitable for drying a coated article to be treated is used. Applied, for example,
In ovens for drying electrodeposited automobile bodies and the like, a temperature sensor sensitively sensitive over a range from room temperature to about 250 ° C. is suitable.

[0012]

According to the present invention, when the detected temperatures of the plurality of provided temperature sensors, particularly the first and second temperature sensors, are within the set furnace temperature range (for example, 200 ± 5 ° C.). The operation control of the burner and the fan is performed based on the detected temperatures of these temperature sensors, particularly the detected temperatures of the first temperature sensor near the center of the area of the radiant heating panel, and, of the first and second temperature sensors, If the detected temperature of any of the temperature sensors falls below the lower limit of the set furnace temperature range, the detected temperature is determined based on the detected temperature of the temperature sensor at which the temperature has dropped, that is, the temperature sensor is set to another temperature. The operation control of the burner and the fan is performed with priority over the temperature sensor of (1). Then, the control in the latter case is continued until the temperature detected by the temperature sensor exceeds the lower limit of the set furnace temperature range.

Accordingly, by such operation control, the furnace temperature in the area of the radiant heating panel is always kept at a temperature suitable for the drying treatment by the radiant heating, both at a position near the center of the area and at a position near the furnace entrance of the area. Adjusted to be maintained. Therefore, for example, even when a large number of coated articles are continuously transferred to a drying oven (at the time of continuous drying), it is possible to perform radiant heating at an appropriate temperature on each coated article, and to perform appropriate drying treatment. Can be achieved.

The above-described operation control is described below, particularly when the drying process of the coating products of a certain group is completed and the drying process is performed after the next group of coating products arrives after the drying process of the group is completed and the next group of coating products arrives. Is meaningful. When the drying process of one coating product group is completed and it is in the state of an empty furnace, since there is no coating product that takes heat in the drying furnace,
Based on the temperature detected by the first temperature sensor, operation control is performed to reduce the operation levels of the fan and the burner. Then, when the next group of coated products arrives at the drying oven and enters the oven, heat is taken away by the coated products, so the furnace temperature in the area of the radiant heating panel near the furnace entrance decreases. Therefore, the temperature detected by the second temperature sensor also decreases. At this point, the furnace temperature has not yet dropped near the center of the area of the radiant heating panel,
The temperature detected by the temperature sensor of FIG. Then, slightly later than the temperature decrease at the position near the furnace entrance, the furnace temperature near the center of the area of the radiant heating panel decreases, and the temperature detected by the first temperature sensor also decreases. Thus, the temperature detected by the second temperature sensor is the first temperature.
Prior to the temperature detected by the temperature sensor, the temperature falls below the lower limit of the set furnace temperature range. However, in the present invention, the temperature detected by the second temperature sensor falls below the lower limit of the set furnace temperature range. At this point, the priority temperature sensor is replaced with the second temperature sensor from the first temperature sensor, and thereafter, the operation is controlled based on the detected temperature of the second temperature sensor, and thereby the operation level of the fan and the burner is controlled. Is rapidly increased. Then, such an increase in the driving level will be
Until the detected temperature of the temperature sensor exceeds the lower limit of the set furnace temperature range. After the temperature detected by the second temperature sensor exceeds the lower limit of the range of the set furnace temperature,
The operation returns to the operation control based on the temperature detected by the first temperature sensor.
Therefore, when the next group of painted products enters the area of the radiant heating panel, even if the temperature at the location near the furnace entrance in the same area temporarily drops, the temperature is immediately reduced (the next painted product It is possible to return to the range of the furnace temperature suitable for the drying process (while it is near the furnace inlet), so that the radiant heating at the appropriate temperature is satisfactorily performed from the first coated product in the next group of coated products. And a suitable drying treatment can be achieved for each coating in the population. Therefore, even if the process of returning from the operation at the time of the drying process to the operation at the time of the drying process again after the operation at the time of the empty furnace is frequently performed, with respect to the coated product subjected to the drying process,
Defects such as roasted sweet do not occur.

In addition, in the present invention, when the detected temperature of the first temperature sensor exceeds the upper limit of the set furnace temperature range, based on the detected temperature of the first temperature sensor,
Control is performed to reduce the operating levels of the burner and the fan. Such operation control always gives priority to the first temperature sensor over the second temperature sensor. When the next group of coated articles enters the drying furnace through the state of the empty furnace, the second temperature sensor has the second temperature sensor. In the process where the operation control to increase the operation level of the burner and the fan is performed based on the temperature detected by the temperature sensor, the temperature detected by the first temperature sensor exceeded the upper limit of the set furnace temperature range. Occasionally, it is immediately converted to operation control based on the temperature detected by the first temperature sensor, and an excessive rise in temperature in the area of the radiant heating panel is prevented. Accordingly, excessive radiant heating of the painted product is suppressed, and the occurrence of defective drying due to excessive heating can be prevented.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be clarified below by describing embodiments thereof with reference to the drawings. FIG. 1 shows a coated article drying furnace 1 for performing a drying process on an electrodeposition-coated automobile body or the like in an automobile factory. The drying furnace 1 is composed of a radiant heating zone 2 and a convection heating zone 3 following the radiant heating zone 2.
Are provided on the left and right side walls in the furnace and the like, and the fan 5 and the burner 6 are installed outside the furnace, and these are connected to form one circulation path 7, and the heating generated by the combustion of the burner 6 The air is circulated by the rotation of the fan 5
By continuously circulating through the heating panel 4 and supplying it to the heating panel 4, the passage 14 in the furnace,
Radiant heating is applied to the coated article 10 to be conveyed, and the initial drying of the surface coating film can be performed. In the figure, the arrow f indicates the flow of the heated air in the panel 4. On the other hand, the convection heating zone 3 has a structure in which the radiantly heated coated product can be completely dried by convection heating thereafter.

The control device for the above operation in the area of the radiant heating panel 4 includes an inverter controller 8 for the fan 5 and a valve opening control motor 9 for the burner 6.
The controller 8 controls the rotation speed of the fan 5, and the motor 9 supplies the fuel to the burner 6.
The degree of opening / closing of a valve to be supplied to the vehicle can be controlled.

In this embodiment, the first temperature sensor 1
1 is provided at a position near the center of the area of the radiant heating panel 4, and a second temperature sensor 12 is provided at a position near the furnace entrance in the area of the panel 4; Is output to the temperature controller 13. The temperature controller 13 is connected to the inverter controller 8 and the control motor 9, and when receiving a temperature detection signal p from the temperature sensors 11 and 12, a control signal corresponding to the detected temperatures of the temperature sensors 11 and 12. q is sent to the controller 8 and the motor 9. The inverter controller 8 and the control motor 9 increase or decrease the rotation speed of the fan 5 and increase or decrease the combustion of the burner 6 based on the content of the input control signal q.
Accordingly, the supply amount and the temperature of the heated air to the radiant heating panel 4 are adjusted by such control, and the level of the temperature in the area of the panel 4 can be controlled.

In this embodiment, the following operation control in which a specific temperature sensor is given priority in some cases is performed. 1) The range of the furnace temperature in which the detection temperatures of the first temperature sensor 11 and the second temperature sensor 12 are both set (for example, 20
If it is within the range of 0 ± 5 ° C.), the operation control of the fan 5 and the burner 6 is performed based on the temperature detected by the first temperature sensor 11. 2) When the temperature detected by the first temperature sensor 11 falls below the lower limit of the set furnace temperature range, the first temperature sensor 1
1 is prioritized, the operation control of the fan 5 and the burner 6 is performed based on the temperature detected by the temperature sensor 11, and the operation control is thereafter performed at the lower limit of the furnace temperature range in which the temperature detected by the temperature sensor 11 is set. It is continued until it exceeds. 3) If the temperature detected by the second temperature sensor 12 falls below the lower limit of the set furnace temperature range, the second temperature sensor 1
2 is prioritized, the operation control of the fan 5 and the burner 6 is performed based on the temperature detected by the temperature sensor 12, and the operation control is thereafter performed at the lower limit of the furnace temperature range in which the temperature detected by the temperature sensor 12 is set. It is continued until it exceeds. 4) If the temperature detected by the first temperature sensor 11 exceeds the upper limit of the set furnace temperature range, the first temperature sensor 11
Is given priority, and based on the detected temperature of the first temperature sensor 11, the operation control of the fan 5 and the burner 6 is performed, and the operation control is thereafter performed within the range of the furnace temperature in which the detected temperature of the temperature sensor 11 is set. Until it falls below the upper limit,
You can continue.

Next, an operation control method for the radiant heating zone 2 in the drying furnace 1 having the above configuration will be described.
When the detected temperatures of the first temperature sensor 11 and the second temperature sensor 12 are within the set furnace temperature range, the operation control of the fan 5 and the burner 6 is performed based on the detected temperatures of the first temperature sensor 11. When the detected temperature of one of the temperature sensors 11 and 12 falls below the lower limit of the set furnace temperature range, the temperature sensor at which the detected temperature has dropped so Based on the detected temperature, operation control for increasing the operation levels of the fan 5 and the burner 6 is performed until the detected temperature exceeds the lower limit of the set furnace temperature range.
When the detected temperature of the first temperature sensor 11 exceeds the upper limit of the set furnace temperature range, the fan 5 and the burner 6 are controlled based on the detected temperature of the first temperature sensor 11.
Operation control is performed to lower the operation level of the vehicle. Therefore, the furnace temperature in the area of the radiant heating panel 4 is
Is adjusted so that the temperature is always maintained at a temperature suitable for the drying treatment by radiant heating at the position near the center of the furnace and at the position near the furnace entrance in the same area 4. Therefore,
At the time of continuous drying, radiant heating at an appropriate temperature could be performed on each of the coated articles 10, appropriate drying treatment was stably achieved, and no defective drying due to excessive heating occurred.

Further, the drying process of the coating products 10 of a certain group is completed and the state of the furnace becomes an empty furnace.
When 0 .. arrives and the drying process is performed, the following operation control is performed. When the state of the empty furnace is reached, since the coated article 10 does not exist in the furnace, the fan 5
Operation control for lowering the operation level of the fan (or the fan 5 and the burner 6) is performed based on the temperature detected by the first temperature sensor. After that, the next group of painted products 10
Arrives at the drying furnace 1 and enters the furnace, the furnace temperature in the area of the radiant heating panel 4 begins to gradually decrease from a position closer to the furnace inlet than a position near the center of the furnace. Therefore, as shown in FIG. 2, before the detected temperature curve a of the first temperature sensor, the detected temperature curve b of the second temperature sensor falls below the lower limit of the set furnace temperature range. Therefore, when the detected temperature curve b of the second temperature sensor falls below the lower limit of the set furnace temperature range, the priority temperature sensor is switched from the first temperature sensor 11 to the second temperature sensor 1.
After that, operation control is performed such that the operation level of the fan 5 (or the fan 5 and the burner 6) is rapidly increased to a high level during the drying process based on the temperature detected by the second temperature sensor 12. You. This operation control is continued until the detected temperature curve b of the second temperature sensor exceeds the lower limit of the set furnace temperature range, and the detected temperature curve b exceeds the lower limit of the set furnace temperature range. Thereafter, the operation returns to the operation control based on the temperature detected by the first temperature sensor 11.

Accordingly, when the next group of painted articles 10 enters the area of the radiant heating panel 4, the temperature at the position near the furnace entrance in the area 4 is immediately restored even if there is a temporary drop. Thus, the temperature can be maintained within the range of the set furnace temperature. Therefore, radiant heating at an appropriate temperature can be satisfactorily performed from the first coated product in the next row of the coated product group, and an appropriate drying process can be performed for each of the coated products 10 in the group. There were no defects such as roasted sweets on the product.

Further, as shown in FIG. 3, when the next group of coated articles 10... Enters the drying furnace 1 through the state of the empty furnace, based on the temperature detected by the second temperature sensor 12, In the process in which the operation control for increasing the operation level of the fan 5 (or the fan 5 and the burner 6) is performed,
If the detected temperature curve a of the first temperature sensor 11 exceeds the upper limit of the set furnace temperature range, it is immediately converted to operation control based on the detected temperature of the first temperature sensor 11. Thereafter, based on the temperature detected by the temperature sensor 11, an operation control for lowering the operation level of the fan 5 (or the fan 5 and the burner 6) is performed until the detected temperature curve a falls below the upper limit of the set furnace temperature range. Be done for a while.
Therefore, an excessive rise in temperature in the area of the radiant heating panel 4 did not occur, and generation of defective products due to excessive heating could be prevented.

[0024]

As described above, according to the operation control method of the present invention, not only in the case of continuous drying, but also in the case where the coated articles are dried in groups (the state of the empty furnace occurs). In this case, it is possible to effectively prevent the occurrence of poor drying such as baking sweets, and therefore, it is possible to achieve appropriate and economical coating film drying in the drying treatment of an electrodeposited automobile body or the like. The effect that it can be obtained is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a coated article drying furnace suitable for carrying out an operation control method of the present invention, in particular, an area of a radiant heating panel.

FIG. 2 is a diagram illustrating a method of controlling the operation of the area of the radiant heating panel of the drying furnace of FIG. 1;

FIG. 3 is a diagram for explaining a method of controlling the operation of the area of the radiant heating panel of the drying furnace of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paint drying oven 2 Radiation heating area 3 Convection heating area 4 Radiation heating panel 5 Fan 6 Burner 7 Circulation path 8 Inverter controller 9 Control motor 10 Painted automobile body 11 First temperature sensor 12 Second temperature sensor 13 Temperature controller f Flow of heated air p Temperature detection signal q Control signal a Temperature curve detected by the first temperature sensor b Temperature curve detected by the second temperature sensor

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ identification code FI // B05C 9/14 B05C 9/14 (58) Field surveyed (Int. Cl. ⁷ , DB name) F26B 21/10-21 /twenty two

Claims (1)

(57) [Claims] 1. A plurality of temperature sensors in a paint drying oven, at least a first temperature sensor at a position near the center of the area of the radiant heating panel and a second temperature sensor near the furnace entrance in the area of the panel. A method for controlling the temperature of the furnace in the area of the radiant heating panel by controlling the operation of the burner and the fan based on the temperatures detected by the temperature sensors, wherein the method comprises the steps of: If the detected temperature of any of the temperature sensors falls below the lower limit of the set furnace temperature range, the temperature sensor has priority over the other temperature sensors, and then the detected temperature of the temperature sensor Until the temperature exceeds the lower limit of the set furnace temperature range, the operation control of the burner and the fan is performed based on the temperature detected by the temperature sensor. Even when the detected temperature of the sensor is lower than the lower limit of the set furnace temperature range, if the detected temperature of the first temperature sensor exceeds the upper limit of the set furnace temperature range, An operation control method for a coated article drying furnace, wherein the first temperature sensor is prioritized over the second temperature sensor, and the operation of the burner and the fan is controlled based on the temperature detected by the first temperature sensor.