Transport heating device and temperature control method

Abstract

To provide a conveyance heating device capable of reducing a temperature of each furnace body in a short time upon a type change.SOLUTION: A conveyance heating device comprises: a plurality of connected furnace bodies; an air blower and a heating part respectively provided at each furnace body; conveyance means conveying an object to be heated in each furnace body; a gas introduction part and a gas lead-out part respectively provided at each furnace body: a common pipe connected with the gas introduction part and the gas lead-out part; an inverter controlling a motor of each air blower; and a control apparatus controlling the inverter. The control device reduces a temperature of each furnace body having a high actual temperature compared with a set temperature by controlling the engine speed of the motor through the inverter upon a type change.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a transport and heating device and a temperature control method that are applied to, for example, a reflow device. [Background technology]

[0002] A reflow apparatus is used in which a solder composition is supplied to an electronic component or a printed wiring board in advance, and the board is transported into a reflow furnace by a transport conveyor. In the heating zone of the reflow apparatus, hot air is blown onto the board, melting the solder in the solder composition and soldering the electrodes of the board to the electronic component. In the reflow apparatus, the surface temperature of the object to be heated, for example, the board, is controlled according to a desired temperature profile, so that the desired soldering can be performed. When the production conditions are changed, for example, when the type of solder alloy composition used is changed, it is required to reduce the temperature in the furnace in a short time in order to set a temperature profile corresponding to the changed solder alloy composition, in order to improve workability.

[0003] In order to lower the temperature inside the furnace of the reflow device, it takes time to lower the temperature by stopping heating and allowing the temperature to drop naturally. To solve this problem, it has been proposed to inject an inert gas at room temperature into the furnace whose temperature is to be lowered (see Patent Document 1). In Patent Document 1, when changing the set temperature among multiple zones of the reflow device, a gas inlet section is provided for one or multiple zones where the change in the set temperature is large, to introduce a gas that is lower in temperature than the gas in the zone. The device described in Patent Document 1 is configured to introduce an inert gas, for example nitrogen gas, into the furnace by utilizing the pressure of a nitrogen gas generator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-246515 A Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, in order to introduce nitrogen gas into the desired zone, it is necessary to operate a nitrogen gas generator and control the introduction of nitrogen gas by a valve, which results in a complex configuration and high energy consumption.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a conveying and heating device and a temperature control method capable of lowering the temperature inside a furnace in a short period of time without using a separate pressure source such as a nitrogen gas generator. [Means for solving the problem]

[0007] The present invention relates to a furnace having a plurality of connected furnace bodies and A blower and a heating unit are provided in the furnace body, A conveying means for conveying the object to be heated within the furnace body; A gas inlet and a gas outlet are provided in the furnace body, a common pipe connected to the gas inlet and the gas outlet; An inverter that controls each of the blower motors; A control device is provided for controlling each of the inverters, The control device is a conveying and heating device that controls the motor rotation speed via an inverter when changing the type of material, thereby lowering the temperature of the furnace body whose actual temperature is higher than the set temperature. The present invention also provides a temperature control method for a conveying and heating device including a plurality of connected furnace bodies, blowers and heating units each provided in the furnace bodies, a conveying means for conveying an object to be heated within the furnace bodies, a gas inlet and a gas outlet each provided in the furnace bodies, a common pipe connected to the gas inlet and the gas outlet, inverters each controlling a blower motor, and a control device each controlling the inverter, This is a temperature control method in which the control device controls the motor rotation speed via an inverter when switching between different types of products, thereby lowering the temperature of the furnace body that is higher than the set temperature. Effect of the Invention

[0008] According to at least one embodiment, the temperature inside the furnace body can be reduced to a desired value by controlling the rotation speed of the blower motor. Therefore, a simple and energy-saving configuration can be achieved. Note that the effects described here are not necessarily limited, and may be any of the effects described in the present invention. In addition, the contents of the present invention should not be interpreted as being limited to the effects exemplified in the following description. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of a reflow apparatus to which the present invention can be applied. [Diagram 2] FIG. 2 is a schematic diagram showing a schematic configuration of one embodiment of the present invention. [Diagram 3] FIG. 3 is a cross-sectional view showing an example of the configuration of the furnace body. [Figure 4] FIG. 4 is a block diagram showing a system configuration according to an embodiment of the present invention. [Diagram 5] FIG. 5 is a flowchart showing a process flow according to an embodiment of the present invention. [Figure 6] FIG. 6 is a graph showing the experimental results. BEST MODE FOR CARRYING OUT THEINVENTION

[0010] The present invention will be described below with reference to the embodiments. Note that the embodiment described below is a preferred specific example of the present invention, and various technically preferable limitations are attached, but the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description to the effect that the present invention is limited.

[0011] Fig. 1 shows a schematic configuration of a conventional reflow apparatus 101 to which the present invention can be applied. The reflow apparatus 101 includes a reflow furnace 102, a conveyor chain 103 as a conveying means for passing an object to be heated, for example a printed circuit board (hereinafter referred to as a workpiece) W having surface-mount electronic components mounted on both sides, through the reflow furnace 102, rotors (idlers, sprockets, etc.) 105a, 105b, 105c, 105d that define the movement path of the conveyor chain 103, and an outer plate 106. Note that Fig. 1 shows only one of two parallel conveyor chains, conveyor chain 103.

[0012] The reflow furnace 102 heats the workpiece W from above and below, and then cools it after heating. The conveyor chain 103 is one of two conveyor chains arranged parallel to the conveying direction. For example, a roller chain is used as the conveyor chain 103. The outer plate 106 is a case that covers the entire structure.

[0013] The workpiece W is carried into the reflow furnace 102 from the carry-in entrance 107, then transported by the transport chain 103 in the direction of the arrow (from left to right in FIG. 1) at a predetermined speed, and finally removed from the carry-out exit 108. Although not shown, a workpiece carry-in device for carrying in the workpiece W is provided in front of the carry-in entrance 107, and a workpiece unloading device for sending the workpiece W to the outside is disposed in the rear of the carry-out exit 108.

[0014] The reflow furnace 102 has nine upper furnace bodies Z1 to Z9 that are located above the conveying path of the conveying chain 103 and are connected to be arranged in line, and nine lower furnace bodies Z11 to Z19 that are located below the conveying path of the conveying chain 103 and are connected to be arranged in line. When there is no need to particularly distinguish between the upper furnace body and the lower furnace body, they are simply referred to as furnace bodies. The eight furnace bodies Z1, Z11 to Z8, Z18 from the entrance 107 side are furnace bodies in the heating zone, and the furnace bodies Z9 and Z19 on the exit 108 side are furnace bodies in the cooling zone. The furnace bodies ZZ9 and Z19 in the cooling zone are provided with forced cooling units (not shown). The number of furnace bodies is an example, and other numbers of furnace bodies may be provided. The multiple furnace bodies Z1 to Z19 control the temperature of the workpiece W according to the temperature profile during reflow.

[0015] Each furnace body is provided with a blower (e.g., a turbo fan) and a temperature detector (e.g., a thermocouple) that detects the temperature inside the furnace. The furnace bodies Z11 to Z8, Z18 in the heating zone are provided with heaters as heating means. M1 and M11 are the blower motors of the furnace bodies Z1 and Z11, respectively. M2 to M9 and M12 to M19 also indicate the blower motors of each furnace body.

[0016] The above-mentioned multiple furnace bodies Z1, Z11 to Z9, Z19 control the temperature of the workpiece W in accordance with a temperature profile during reflow. For example, the temperature profile includes a preheat zone for heating the workpiece W, for example a printed wiring board on which electronic components are mounted, a reflow zone following the preheat zone, and a final cooling zone.

[0017] The preheat zone is a section where the board is heated from room temperature. The preheat zone is a section for activating the flux, removing the oxide film on the surface of the electrodes and solder powder, and eliminating uneven heating of the printed wiring board. The reflow zone is a section where the solder melts and the joint is completed. Even after passing the preheat zone, there is unevenness in the temperature rise in the reflow zone, so heating to a temperature exceeding the melting temperature of the solder is required. The final cooling zone is a section where the printed wiring board is rapidly cooled and the solder composition is formed. In the case of lead-free solder, the temperature in the reflow section is higher than that of eutectic solder (for example, 240°C to 260°C).

[0018] In the reflow soldering equipment shown in Figure 1, the temperature control of the preheat zone is mainly performed by the furnaces Z1, Z11 to Z5, and Z15. The temperature control of the reflow zone is performed by the furnaces Z6, Z16 to Z8, and Z18. The temperature control of the cooling zone is performed by the furnaces Z9 and Z19.

[0019] In one embodiment of the present invention, as shown in FIG. 2, each of the upper furnace bodies Z1 to Z9 is provided with a gas inlet and a gas outlet, and a common pipe 201 connected to the gas inlet and the gas outlet is provided. Similarly, each of the lower furnace bodies Z11 to Z19 is provided with a gas inlet and a gas outlet, and a common pipe 211 connected to the gas inlet and the gas outlet is provided. The gas outlet is provided at a location where the pressure is increased by the blower of each furnace body, and the gas inlet is provided at a location where the pressure is low in each furnace body. It is to be noted that the gas inlet and the gas outlet may not be provided for all furnace bodies, and the gas inlet and the gas outlet may be provided for some of the furnace bodies. For example, the gas inlet and the gas outlet may not be provided for the furnace bodies Z9 and Z19 in the cooling zone. The reason is that the oxygen concentration of the atmosphere inside the furnace bodies Z9 and Z19 is high because they are close to the discharge port 108. Furthermore, valves for controlling the inflow and outflow of gas may be provided in association with the gas inlet and gas outlet as necessary.

[0020] With reference to Fig. 3, an example of the configuration of the furnace bodies Z5 and Z15 will be described. In the gap between the upper furnace body Z5 and the lower furnace body Z15, a workpiece W having surface-mount electronic components mounted on both sides of a printed wiring board is placed on a transport conveyor 21 and transported. The furnace bodies Z5 and Z15 are filled with atmospheric gas, such as nitrogen (N2) gas. The furnace bodies Z5 and Z15 blow hot air (heated atmospheric gas) onto the workpiece W to heat it. Infrared rays may be irradiated together with the hot air.

[0021] The furnace body Z5 is composed of a main heating source 2, a sub-heating source 3, a blower 4, a heat storage member 5, a hot air circulation duct 6, an opening 7, etc. The furnace body Z15 is, for example, almost similar to the furnace body Z5 described above, and is equipped with a main heating source 12, a sub-heating source 13, a blower 14, a heat storage member 15, a hot air circulation duct 16, an opening 17, etc. The blower 4 has a motor M5, a motor mounting plate 8, and a rotating blade 9. Similarly, the blower 14 has a motor M15, a motor mounting plate 18, and a rotating blade 19. As the blower, a centrifugal fan such as a turbo fan or a sirocco fan, an axial blower, etc. may be used. Other furnace bodies have the same configuration as that shown in FIG. 3. The configuration of the furnace body shown in FIG. 3 is an example, and other configurations may be used.

[0022] Hot air is blown onto the workpiece W through the openings 7 and 17. The main heating source 2, the main heating source 12, the auxiliary heating source 3 and the auxiliary heating source 13 are composed of, for example, electric heaters. The heat storage members 5 and 15 are made of, for example, aluminum and have a large number of holes through which the hot air passes and is blown onto the workpiece W.

[0023] For example, in the furnace body Z5, hot air is circulated by the blower 4. That is, the hot air circulates through the route (main heating source 2 → heat storage member 5 → opening 7 → workpiece W → hot air circulation duct 6 → auxiliary heating source 3 → hot air circulation duct 6 → blower 4 → main heating source 2). Similarly, in the furnace body Z15, hot air circulates through the route (main heating source 12 → heat storage member 15 → opening 17 → workpiece W → hot air circulation duct 16 → auxiliary heating source 13 → hot air circulation duct 16 → blower 14 → main heating source 12).

[0024] In the furnace body Z5, as described above, the gas circulates, so that the area from the peripheral surface of the rotary blade 9 to the outlet of the opening 7 is a high pressure area, and the area from the hot air circulation duct 6 to the suction port of the rotary blade 9 is a low pressure area. The blower 4 provides a gas outlet 22 in the high pressure area, and a gas inlet 23 in the low pressure area. The pipes attached to the gas outlet 22 and the gas inlet 23 are connected to the pipe 201. As in the furnace body Z5, in the furnace body Z15, the blower 14 provides a gas outlet 24 in the high pressure area, and a gas inlet 25 in the low pressure area. The pipes attached to the gas outlet 24 and the gas inlet 25 are connected to the pipe 211. As in the furnace bodies Z5 and Z15, the gas outlet and gas inlet connected to the pipe 201 and the pipe 211 are provided for the other furnace bodies.

[0025] The structure of the furnace body is different from the example shown in Fig. 3 in that the blower sucks in the atmosphere from a position between the motor and the rotating blades and blows out the atmosphere from the circumferential surface of the rotating blades. In this case, the position of the circumferential surface of the rotating blades becomes a high-pressure area, and it is necessary to extend the piping for gas discharge to the back of the furnace body. As a result, the structure for maintaining the airtightness of the furnace body becomes complicated. In the configuration of Fig. 3, the rotating blades 9 and 19 are structured to suck in the atmosphere from the sides facing the main heating sources 2 and 12, respectively, so the distance between the rotating blades and the motor is smaller, and it is not necessary to extend the piping for gas discharge to the back of the furnace body, and the structure can be simplified.

[0026] One embodiment of the present invention includes an inverter provided for the motors M1 to M19 of the blower of the reflow soldering device described above, and a control device that controls the motors M1 to M19 by the inverter. The control device controls the rotation speed of the motors M1 to M19 through the inverter to lower the temperature inside the furnace body that has been set. The control device also includes a temperature detector that detects the temperature inside the furnace, and temperature information detected by the temperature detector is supplied to the control device.

[0027] Fig. 4 shows a system configuration of an embodiment of the present invention. Fig. 4 shows a control signal system, and the power system is omitted. M1 to M19 indicate motors of the blowers of the reflow device shown in Fig. 1, and INV1 to INV19 are inverters that drive and control each motor. Furthermore, TH1 to TH19 are heat detectors (for example, thermocouples) for detecting the internal temperatures of the furnace bodies. For example, the furnace body Z5 is provided with a motor M5 for rotating the rotary blades of the blower and a heat detector TH5, and the furnace body Z15 is provided with a motor M15 for rotating the rotary blades of the blower and a heat detector TH15.

[0028] The inverters INV1 to INV19 are connected to a control device, for example, a programmable logic controller (referred to as PLC in FIG. 4 and in the following description) 31 via a network 32. The PLC 31 supplies each of the inverters INV1 to INV19 with a control signal instructing the number of rotations, and the inverters INV1 to INV19 supply monitor signals, alarm signals, and the like to the PLC 31. The monitor signals are signals that indicate the magnitude of the loads on the motors M1 to M19.

[0029] The temperatures detected by the thermal detectors TH1 to TH19 are supplied to the PLC 31 via the network 33. A personal computer 34 is connected to the PLC 31. The personal computer 34 functions as a user interface. For example, the personal computer 34 issues rotation speed commands to the PLC 31 and displays an alarm screen. Note that a control device other than a PLC may be used to control the inverters INV1 to INV19.

[0030] The temperature control method performed by the PLC 31 will be described with reference to the flow chart of Fig. 5 and Table 1. The temperature control method according to the present invention reduces the temperature of the furnace body to a set temperature in a short time when the production item is changed. Since the temperature setting and temperature change control for each of the two furnace bodies (e.g. Z1 and Z11) located above and below are the same, only the temperature of one furnace body, e.g. the upper furnace body, and the control of the blower motor of that furnace body will be described. Also, an example in which the temperature is set for the furnace bodies Z1 to Z8 included in the preheat zone and the reflow zone will be described.

[0031] [Table 1]

[0032] A case where a product type is changed from a certain production item A to a production item B will be described. Table 1 shows the set temperatures of these production items and the difference in set temperatures between these production items. The PLC 31 controls the motor speed of the first furnace body, which is the target for lowering the temperature, to be lowered, and the motor speed of the second furnace body, which is lower in temperature than the first furnace body, to be increased, so that the atmosphere of the second furnace body is fed into the first furnace body to lower the temperature of the first furnace body. The motor speed is controlled to one of three levels, for example, low (denoted as LOW), medium (denoted as MID), and high (denoted as HIGH). The rotation speeds of the production items A and B during operation (during operation) are set to be equal to each other (for example, MID).

[0033] The rotation speeds (LOW, MID, HIGH) of the motors M1 to M19 (blower) correspond to the frequencies of the drive signals from the inverters INV1 to INV19, and an example of the pressure (closed state) in the pipe 201 (and pipe 211) in this case is shown in Table 2. The pressure is lowest when the rotation speed is LOW, the pressure is highest when the rotation speed is HIGH, and the pressure is intermediate when the rotation speed is MID.

[0034] [Table 2]

[0035] An example of control by the PLC 31 will be described with reference to the flow chart of FIG. Step ST1: The process of changing the temperature settings is started. A changeover from production item A to production item B is started, and a change from the temperature setting conditions of production item A to the temperature setting conditions of production item B is started. Table 1 shows the difference between the respective set temperatures of the two items A and B.

[0036] Step ST2: The temperature drop of the furnace body is confirmed. For example, the actual temperature of each furnace body in the reflow zone 5 minutes after the start is detected, and it is confirmed that the temperature has dropped since the start. At this time, the rotation speed setting (frequency) of all the furnace bodies is set to the same (for example, MID). Therefore, there is no pressure difference between the furnace bodies.

[0037] Step ST3: Identify the first furnace body X, the target of which is to lower the temperature. Compare the set temperature and the actual temperature of the production item B, and identify the furnace body with the largest difference between the set temperature and the actual temperature as the first furnace body. Usually, the first furnace body X is a furnace body included in the reflow zone. In this example, the furnace body Z6 is identified as the first furnace body.

[0038] Step ST4: The second furnace body, that is, the furnace body Y from which the atmosphere is moved, is identified. The set temperature and actual temperature of production item B are compared to identify the furnace body with the smallest value of (set temperature - actual temperature). Usually, this is the furnace body in the preheat zone with a low temperature setting. In this example, furnace body Z2 is identified.

[0039] Step ST5: The setting of the fan speed is changed. The fan speed of furnace body Z2 in the preheat zone, which has a low temperature atmosphere and is identified as the source furnace, is increased. As a result, the pressure in furnace body Z2 increases. At the same time, the speed of furnace body Z6 in the reflow zone, which has a high temperature atmosphere and is identified as the target furnace whose temperature is to be reduced, is decreased. As a result, the pressure in furnace body Z6 decreases. Due to the pressure difference between furnace body Z2 and furnace body Z6, the atmosphere in the preheat zone moves to the reflow zone through pipe 201.

[0040] Step ST6: It is determined whether the temperature of a specific furnace body Z6 has reached (set temperature + / - 5°C). 5°C is an example of an allowable temperature error value, and may be set to another value. The process of step ST6 is repeated until the temperature of the furnace body Z6 falls within this range. When it is detected in step ST6 that the temperature of the furnace body Z6 in the reflow zone has reached (set temperature + / - 5°C), the rotation speeds of both furnace bodies Z2 and Z6 are set to MID to prevent a pressure difference from occurring. Then, the process proceeds to the next step ST7.

[0041] Step ST7: With the rotational speed setting (frequency) of all the furnace bodies set to the same (for example, MID), it is determined whether the temperatures of all the other furnace bodies Z7, Z8 included in the reflow zone, for example, have reached (set temperature + / - 5°C). Since the actual temperature of the furnace body Z6 has reached (set temperature + / - 5°C) by the processing of step ST6, the difference between the set temperature and the actual temperature of the other furnace bodies (furnace bodies Z7, Z8) in the reflow zone is checked. If the difference regarding these furnace bodies is not within (set temperature + / - 5°C), that furnace body is identified, and the processing returns to step ST3. The identified furnace body is subjected to a process to lower the temperature in the same manner as described above. Then, when it is detected in step ST7 that the temperatures of all the furnace bodies in the reflow zone have reached (set temperature + / - 5°C), the processing proceeds to the next step ST8 (temperature setting change completion). If the temperature of the furnace body has dropped too much, the heater of that furnace body may be turned on to control the temperature to be raised.

[0042] FIG. 6 shows the result of temperature measurement of the furnace body Z6 of the embodiment of the present invention described above. When the atmosphere of the furnace body Z2 moves to the furnace body Z6 through the pipe 201 due to the pressure difference between the furnace body Z2 and the furnace body Z6, an atmosphere of about 128°C flows at about 650L / min, and the temperature of the furnace body Z6 drops as shown in the graph of FIG. 6. As a result, the temperature drops from 240°C to 220°C in about 2 minutes. Furthermore, the temperature drops from 220°C to 210°C in about 2 minutes. Such a temperature drop occurs in a short time compared to the temperature drop due to natural heat dissipation, and the efficiency of the product type changeover work can be improved.

[0043] The embodiment of the present invention described above can shorten the time required for temperature control when switching between different types of products by controlling the rotation speed of an existing blower without providing a pressure generating source, thereby simplifying the configuration and achieving energy savings.

[0044] Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-mentioned embodiments, and various modifications based on the technical concept of the present invention are possible. The present invention is not limited to printed circuit boards, but can also be applied to reflow of flexible boards, boards in which rigid boards and flexible boards are bonded together, and rigid-flex boards that are a combination of these. The present invention can also be applied to a reflow device with a single heating furnace (one zone). Furthermore, the present invention can also be applied to heating devices for curing resin, etc., in addition to reflow devices. The configurations, methods, steps, shapes, materials, and values ​​given in the above-mentioned embodiments are merely examples, and different configurations, methods, steps, shapes, materials, and values ​​may be used as necessary. The configurations, methods, steps, shapes, materials, and values ​​of the above-mentioned embodiments can be combined with each other as long as they do not deviate from the gist of the present invention. [Explanation of symbols]

[0045] 101: Reflow device, 103: Conveyor chain, W: Work, 4, 14... blower, 9, 19... rotating blades, 22, 24... gas outlet, 23, 25...gas inlet, 31...PLC, Z1 to Z19...furnace body, M1~M19... Blower motor, INV1~INV19... Inverter, TH1~TH19: Temperature detector, 201, 211: Piping

Claims

1. A plurality of connected furnace bodies; A blower and a heating unit respectively provided in the furnace body; A conveying means for conveying an object to be heated within the furnace body; A gas inlet and a gas outlet are provided in the furnace body, a common pipe connected to the gas inlet and the gas outlet; An inverter that controls each of the motors of the blowers; A control device is provided to control each of the inverters, The control device controls the number of revolutions of the motor through the inverter when switching between different types of materials, thereby lowering the temperature of the furnace body whose actual temperature is higher than the set temperature.

2. 2. The conveying and heating device according to claim 1, further comprising temperature detectors for detecting temperatures inside the plurality of furnace bodies, and temperature information detected by the temperature detectors is supplied to the control device.

3. By the control device, Detecting a first furnace body whose temperature is to be reduced using the temperature information and a second furnace body whose internal temperature is lower than that of the first furnace body; The rotation speed of the motor of the first furnace body is reduced, and the rotation speed of the motor of the second furnace body having a lower furnace temperature than the first furnace body is increased; 3. The transporting and heating device according to claim 2, wherein an atmosphere is caused to flow from said second furnace body to said first furnace body through said piping.

4. 4. The transporting and heating device according to claim 3, wherein the control device performs control to repeat the process according to claim 3 so that the temperatures of the plurality of furnace bodies included in the reflow zone are within a predetermined range with respect to a set temperature.

5. 5. The conveying and heating device according to claim 1, wherein the control device sets the rotation speed of the motor of the first furnace body, the temperature of which is to be reduced, to the lowest rotation speed, and sets the rotation speed of the motor of the second furnace body, the temperature of which is lower than that of the first furnace body, to the highest rotation speed.

6. A temperature control method for a conveying and heating device including a plurality of connected furnace bodies, blowers and heating units provided in each of the furnace bodies, a conveying means for conveying an object to be heated within the furnace bodies, a gas inlet and a gas outlet provided in each of the furnace bodies, a common pipe connected to the gas inlet and the gas outlet, inverters for controlling motors of the blowers, and a control device for controlling the inverters, A temperature control method in which the control device controls the rotation speed of the motor via the inverter when changing the type of product, thereby lowering the temperature of the furnace body that is higher than a set temperature.

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