JP2008196756A - Heating furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating furnace adaptable to various types of workpiece while reducing heating time. <P>SOLUTION: The workpiece is heated in a first heating chamber 2 set at a first set temperature T1 lower than a target temperature, and the workpiece is heated in a second heating chamber 3 positioned in a downstream side of the first heating chamber 2 in a conveyance route of the work and set at a second set temperature T3 higher than the target temperature. In the first heating chamber 2, the workpiece conveyed from an upstream side of the heating chamber 2 is conveyed toward the downstream side at a first conveyance speed V2. In the second heating chamber 3, the workpiece conveyed from an upstream side of the heating chamber 3 is conveyed toward a downstream side at a second conveyance speed V3 faster than the first conveyance speed V2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heating furnace that performs a process such as heat treatment or brazing on a workpiece, and more particularly, to a heating furnace that raises the workpiece to a target temperature by heating the workpiece in stages in a plurality of heating chambers.

  For example, an aluminum heat exchanger includes an evaporator, a condenser, a radiator, and the like, and these are generally manufactured by a brazing method. In this manufacturing method, after assembling various parts of a heat exchanger such as a core part made of tubes, fins, etc., a tank part made of a header plate, a tank cover member, etc., these various parts are heated in a heating furnace. It brazes integrally with the brazing material previously provided in the junction part of between.

  A heating furnace that performs such processing includes, for example, a plurality of heating chambers, and has a configuration in which workpieces are sequentially passed through individual heating chambers by a continuous conveyor. The individual heating chambers are set so that their temperatures increase sequentially from the upstream side to the downstream side of the workpiece transfer process. The workpieces are heated in stages in the individual heating chambers, for example, brazing temperature. Reach the target temperature.

Patent Document 1 discloses a roller herstep type heating furnace. In this heating furnace, a plurality of transfer rollers are provided in a single heating chamber, and after dividing the rollers into a plurality of groups, the rotation speed of the rollers is adjusted for each group, thereby transferring the workpiece. A technique for controlling speed is disclosed.
Japanese Patent No. 291366

  By the way, in this kind of heating furnace, in the heating chamber on the high temperature side where the temperature of the workpiece is close to the target temperature, the temperature difference between the temperature in the heating chamber and the temperature of the workpiece becomes small, and thus the temperature gradient of the workpiece becomes small. Therefore, a certain amount of heating time is required until the workpiece reaches the target temperature. Therefore, the heating time of the heating chamber depends on the length of the heating chamber. On the other hand, in order to shorten the heating time, it is conceivable to raise the set temperature of the heating chamber to a temperature higher than the target temperature of the workpiece so that the temperature gradient of the workpiece does not become gradual. It is necessary to increase the conveyance speed or shorten the length of the heating chamber.

  However, in the conventional heating furnace, since the work is transported by a continuous conveyor, the transport speed in each heating chamber becomes the same, and when the transport speed is increased, the transport speed in other heating chambers is also increased. As a result, the heating time may be insufficient in these heating chambers. On the other hand, when the length of the heating chamber is shortened, for example, it becomes impossible to cope with a case where another workpiece having a different heating time is desired to be heated.

  Although Patent Document 1 discloses a method for controlling the workpiece conveyance speed, the method controls the conveyance speed in a single heating chamber, and is relative in individual heating chambers having different set temperatures. It does not disclose how to control the correct conveyance speed.

  This invention is made | formed in view of such a situation, The objective is to provide the heating furnace which can be adapted with respect to a various workpiece | work, aiming at shortening of heating time.

  A heating furnace according to claim 1 of the present invention is a heating furnace that heats a workpiece to a target temperature by gradually heating the workpiece by a plurality of heating chambers, and is a first set temperature lower than the target temperature. A first heating chamber that heats the workpiece, and a chamber that is positioned downstream of the first heating chamber in the workpiece conveyance path and that is set to a second set temperature that is higher than the target temperature. In the second heating chamber for heating the workpiece and the first heating chamber, the workpiece conveyed from the upstream side of the first heating chamber to the downstream side of the first heating chamber has a first conveyance speed. In the first transfer unit and the second heating chamber, the workpiece transferred from the upstream side of the second heating chamber is moved to the downstream side of the second heating chamber than the first transfer speed. Second transport unit that transports at a fast second transport speed Having.

  The heating furnace according to claim 2 of the present invention is located in an upstream atmosphere of the first heating chamber in the workpiece transfer path, and in an indoor atmosphere set at a third set temperature lower than the first set temperature. In the third heating chamber for heating the workpiece and the third heating chamber, the workpiece conveyed from the upstream side of the third heating chamber is moved to the downstream side of the third heating chamber, and the first conveyance speed is set. And a third transport unit for transporting at a slower third transport speed.

  In the heating furnace according to claim 3 of the present invention, the second heating chamber is located on the most downstream side in the workpiece transfer path, and the length of the second heating chamber in the workpiece transfer direction is set to Longer than the length of the workpiece in the conveyance direction.

  In the heating furnace according to claim 4 of the present invention, the temperature gradient related to the temperature rise of the workpiece in the second heating chamber is set to correspond to the temperature gradient related to the temperature rise of the workpiece in the first heating chamber. The temperature of the second heating chamber is controlled based on the set temperature, and the workpiece is set to be conveyed to the outside of the second heating chamber in synchronization with the arrival timing of the workpiece at the target temperature. And a control device for controlling the second transport unit based on the second transport speed.

  According to the heating furnace according to claim 1 of the present invention, by setting the temperature of the second heating chamber to be equal to or higher than the target temperature, it is possible to suppress the gradual temperature gradient of the workpiece even near the target temperature. Further, by controlling the conveyance speed individually for each heating chamber and increasing the conveyance speed of the second heating chamber, overheating of the workpiece can be suppressed. As a result, the heating time can be shortened while effectively raising the workpiece to the target temperature. Moreover, since the conveyance speed can be set for each heating chamber, even when a workpiece having different specifications is heated, the heating time can be easily changed according to the workpiece.

  According to the heating furnace concerning Claim 2 of this invention, the workpiece | work can be heated up uniformly by heating a workpiece | work in multiple stages.

  According to the heating furnace according to claim 3 of the present invention, since the conveyance speed of the most downstream heating chamber is the fastest, it is possible to suppress problems such as a workpiece colliding or stagnation in the heating furnace. .

  According to the heating furnace of the fourth aspect of the present invention, since the temperature gradient in the vicinity of the target temperature of the work does not become gentle, it is possible to perform control that realizes shortening of the heating time.

  Drawing 1 is a mimetic diagram showing the whole heating furnace composition concerning the embodiment of the present invention. This heating furnace is mainly composed of a plurality of heating chambers (in this embodiment, three heating chambers 1 to 3), a transfer device 5, and a control device 6, and processes such as heat treatment and brazing on the workpiece. I do. The workpiece is, for example, an aluminum heat exchanger such as a radiator. In this heating furnace, the fins and headers of the radiator can be brazed.

  The plurality of heating chambers 1 to 3 are continuously arranged from upstream to downstream along the workpiece conveyance path, and each has an independent chamber (atmosphere). In each of the heating chambers 1 to 3, for example, the workpieces conveyed to the room are heated by radiant heat from an electric heater or combustion heat from a gas burner, and further by convection using a circulation fan (not shown). To do. The workpiece conveyed by the conveyance device 5 to be described later sequentially passes through these heating chambers 1 to 3, whereby the workpiece is heated in each of the heating chambers 1 to 3. In the embodiment, the temperature is raised to a brazing temperature (for example, 600 ° C.). These heating chambers 1 to 3 are made into a non-oxidizing atmosphere by an atmospheric gas, for example, nitrogen gas, and the atmosphere before and after the heating chambers 1 to 3 is sealed to seal the non-oxidizing atmosphere in the heating chambers 1 to 3 It is blocked by the atmosphere blocking chamber 4.

  The individual heating chambers 1 to 3 are individually provided with set temperatures T1 to T3, and the temperatures can be set independently in the respective heating chambers 1 to 3. In the present embodiment, these set temperatures T1 to T3 are set such that the temperatures of the heating chambers 1 to 3 are sequentially increased from the upstream side to the downstream side of the workpiece conveyance path. Specifically, the set temperature T2 of the heating chamber 2 located downstream of the heating chamber 1 at the most upstream side is set higher than the set temperature T1 of the most upstream heating chamber 1 in the workpiece transfer process. The set temperature T3 of the heating chamber 3 on the downstream side (the most downstream side in the workpiece transfer process) is set higher than the set temperature T2 of 2 (T1 <T2 <T3). By setting the stepped set temperatures T1 to T3 in this way, it is possible to raise the temperature of the workpiece stepwise through the heating chambers 1 to 3. When the temperature of the workpiece is raised stepwise, even if there is a difference in heat capacity depending on the part of the work, the part where the heat capacity is small and the temperature rises quickly does not rise above the set temperature, and the part has a large heat capacity Since the workpiece is transferred to the downstream heating chamber in a state where the temperature reaches the set temperature, the workpiece can be heated in a balanced state regardless of the heat capacity.

  As one of the features of this embodiment, the set temperature T3 of the heating chamber 3 located on the most downstream side is set to a temperature higher than the target temperature of the workpiece, and the heating on the upstream side of the heating chamber 3 is performed. The set temperatures T1 and T2 of the chambers 1 and 2 are set to a temperature lower than the target temperature of the workpiece. Further, in the heating chamber 3 at the set temperature T3, the distance L3 in the workpiece conveyance direction is longer than the distance L1, L2 in the workpiece conveyance direction with respect to the heating chambers 1 and 2 located upstream of the heating chamber 3.

  The set temperature of each of the heating chambers 1 to 3 is set by the control device 6 described later, and the temperature is adjusted by the control device 6 so that the temperature in the room becomes the set temperature.

  The conveyance device 5 has a function of conveying a workpiece along a predetermined conveyance path in a heating furnace including the heating chambers 1 to 3. For example, a conveyor device or the like can be used. The transfer device 5 passes the workpiece placed on the conveyor through the heating chambers 1 to 3 sealed by the atmosphere blocking chamber 4. At this time, the conveyed work passes through the heating chamber 1 having the lowest set temperature T1, the heating chamber 2 having the intermediate set temperature T2, and the heating chamber 3 having the highest set temperature T3 in this order.

  The conveyance apparatus 5 is divided | segmented for every heating chamber 1-3, and can set the conveyance speed of a workpiece | work independently in each heating chamber 1-3. Specifically, the transfer device 5 includes first to fifth transfer units 5a to 5e, and a series of transfer paths in the heating furnace is configured by these transfer units 5a to 5e. The 1st conveyance unit 5a is a unit which conveys a workpiece | work to the heating chamber 1 of the most upstream side, ie, the heating chamber 1 of setting temperature T1, and the 2nd conveyance unit 5b is in the heating chamber 1 of setting temperature T1, The workpiece conveyed from the upstream side (first conveyance unit 5a) of the heating chamber 1 is conveyed to the downstream side (third conveyance unit 5c) at the conveyance speed V1. The third transport unit 5c transports a workpiece transported from the upstream side (second transport unit 5b) of the heating chamber 2 to the downstream side (fourth transport unit 5d) in the heating chamber 2 at the set temperature T2. Transport with V2. In the heating chamber 3 having the set temperature T3, the fourth transport unit 5d transports a workpiece transported from the upstream side (third transport unit 5c) of the heating chamber 3 to the downstream side (fifth transport unit 5e). Transport with V3. The 5th conveyance unit 5e is a unit for conveying the workpiece | work from the heating chamber 3 (4th conveyance unit 5d) to a downstream process.

  Here, as one of the features of the present embodiment, the conveyance speeds V1 to V3 of the second to fourth conveyance units 5b to 5d are set in the heating chambers 1 to 3 from the upstream side to the downstream side of the workpiece conveyance path. The workpiece conveyance speed is set to increase sequentially. Specifically, the transport speed V2 in the third transport unit 5c is faster than the transport speed V1 in the second transport unit 5b, and the fourth transport unit 5d is faster than the transport speed V2 in the third transport unit 5c. The conveyance speed V3 at is higher (V1 <V2 <V3). At this time, the conveyance speeds V1 to V3 are in such a relationship that they sequentially increase in proportion to the increase in the set temperatures T1 to T3 of the corresponding heating chambers 1 to 3.

  Each of the transport units 5a to 5e is driven by a driving unit such as a motor for driving a conveyor, and the control of the unit including the transport speed and the like is performed by a control device 6 described later.

  The control device 6 controls the heating furnace based on a target temperature that is a target temperature increase value of the workpiece. In relation to the present embodiment, the control device 6 controls the transport device 5 based on the transport speeds V1 to V3 in the second to fourth transport units 5b to 5d. Moreover, the control apparatus 6 controls the heating chambers 1-3 based on the sensor input which is a detected value from the temperature sensor (not shown) provided in each heating chamber 1-3, and preset temperature T1-T3. Then, feedback control of the heating state is performed so that the atmosphere in each of the heating chambers 1 to 3 becomes the set temperature T1 to T3.

  Hereinafter, the brazing process using the heating furnace having such a configuration will be described. Here, a radiator will be exemplified and described as the workpiece. In the brazing process, various parts of the radiator such as the core part made of tubes and fins and the upper and lower header tank parts made of the header plate and the tank cover member are assembled and then heated in a heating furnace. It brazes integrally through the brazing material previously provided in the junction part between various components.

  The radiator is formed using parts made of aluminum, and these various parts mainly have an aluminum alloy containing pure aluminum and an element such as Mn as a core material. Therefore, in order to join components together, a brazing material of an Al—Si based alloy having a melting point lower than that of a core material containing Si or the like in aluminum is clad on the surface of the core material at the joining portion.

  Then, various parts clad with this brazing material (core part, upper and lower header tank part) are assembled, or various parts in the state of core material (core part, upper and lower header tank part) instead of clad brazing material After the brazing material foil is placed on the joints of these parts and these parts are assembled, flux is applied to the brazed joints and brazing is performed in a heating furnace.

  Specifically, in the heating furnace, the work as the assembled core part and header tank part is placed on the transfer device 5 and is first transferred to the heating chamber 1. In the heating chamber 1, the set temperature is set to the temperature T1, and the work is transported in the chamber at the transport speed V1. When the inside of the heating chamber 1 is transported, it is then transported to the heating chamber 2. The heating chamber 2 is set to a temperature T2 where the set temperature is higher than the temperature T1, and the workpiece is transported in the room at a transport speed V2 higher than the transport speed V1. In the heating chambers 1 and 2, as a preheating process, the assembled core portion and header tank portion are preheated stepwise to the set temperatures T1 and T2.

  When the preheating step is performed, the workpiece is then transferred to the heating chamber 3 by the transfer device 5. The heating chamber 3 has a set temperature set to a temperature T3 that is higher than the temperature T2, and the workpiece is transported in the room at a transport speed V3 that is faster than the transport speed V2. In the heating chamber 3, the core portion and the header tank portion are brazed as a brazing step.

  When the brazing process is performed in the heating chamber 3, it is transferred from the heating chamber 3 to the outside of the heating furnace by the transfer device 5. Then, in the slow cooling process, the heat of the brazed core part and the upper and lower header tank parts is removed, and in the cooling process, the core part and the upper and lower header tank parts that have undergone the slow cooling process are cooled to room temperature. The By sequentially performing such a series of preheating step, brazing step, slow cooling step, and cooling step, the core portion and the upper and lower header tank portions are joined to form a radiator.

  Here, with reference to FIG. 2 and FIG. 3, the concept of the heating furnace concerning this embodiment is demonstrated. FIG. 2 is a schematic diagram showing a configuration of a conventional heating furnace, and FIG. 3 shows a temperature rising state of a workpiece in the heating furnace, specifically, a temperature rising state of a portion having a large heat capacity and a temperature rising portion of a portion having a small heat capacity. It is explanatory drawing which shows a temperature state, respectively.

  As shown in FIG. 2, the conventional heating furnace includes a plurality of heating chambers 11 to 13 in which set temperatures T <b> 11 to T <b> 13 are individually set, and these heating chambers 11 to 13 are connected by a continuous conveyor 15. By conveying the workpiece, the workpiece is heated in stages. Here, the set temperature T13 of the most downstream heating chamber 13 is a temperature corresponding to the final target temperature of the workpiece, that is, the brazing temperature, and the upstream heating chamber 12 is lower than the target temperature. The set temperature T12 is set to the temperature, and the set temperature T11 is set to a lower temperature in the heating chamber 11 on the most upstream side (T11 <T12 <T13).

  As shown in FIG. 3, the workpiece heated in the heating chamber 11 is heated with a temperature gradient as shown in the region a, and the workpiece heated in the heating chamber 12 is raised with a temperature gradient as shown in the region b. Be warmed. Further, the workpiece heated in the heating chamber 13 is heated with a temperature gradient as shown in the region c.

  Here, as shown in FIG. 3, when the temperature of the workpiece rises and the temperature difference between the heating chamber and the temperature of the workpiece decreases, the temperature gradient also decreases (see region c). Therefore, in the heating chamber 13 where the temperature gradient is small, a certain amount of heating time is required until the work reaches the target temperature.

  As described above, in the heating furnace having the conventional configuration, the work is transported by the continuous conveyor 15 from the inlet of the heating chamber 11 to the outlet of the heating chamber 13, so that the transport speed in each of the heating chambers 11 to 13 is also constant. It must be. Therefore, the heating time of the workpiece in each heating chamber 13 depends on the length of the heating chamber 13, that is, the length L 13 in the conveyance direction in the heating chamber 13.

  In order to shorten the heating time, the set temperature of the heating chamber 13 is set to a value larger than the target temperature of the workpiece, the temperature difference between the temperature in the heating chamber 13 and the temperature of the workpiece is increased, and the workpiece is set to the target temperature. It is conceivable to prevent the temperature gradient from becoming gradual until the temperature is increased. However, when the set temperature of the heating chamber 13 is increased, the conveyance speed is increased or the length L3 of the heating chamber 13 is shortened by the amount corresponding to the shortening of the heating time, thereby shortening the work residence time in the heating chamber 13. It is necessary to let

  By the way, when the conveyance speed is increased, the conveyance speed in the other heating chambers 11 and 12 is also increased, so that the heating time in these heating chambers 11 and 12 may be insufficient. On the other hand, when the length L3 of the heating chamber 13 is shortened, for example, there is a possibility that it may not be possible to cope with a case where another workpiece having a different heating time is desired to be heated.

  Therefore, in the present embodiment, the set temperature T3 of the heating chamber 3 is set to a value higher than the final target temperature of the workpiece, and the temperature in the heating chamber (set temperature T3) and the temperature of the workpiece transferred into the chamber are set. The device is designed to prevent the temperature gradient from becoming gradual by increasing the difference between the two. However, since the set temperature T3 is set to a value larger than the target temperature of the workpiece, the time for the workpiece to reach the target temperature is shorter than when the set temperature T3 is set to the target temperature of the workpiece. . Therefore, in the present embodiment, the conveyance speed V3 in the heating chamber 3 is set large. Specifically, the conveyance speed V <b> 3 is set so that the workpiece comes out of the heating chamber 3 in synchronization with the timing at which the workpiece reaches the target temperature.

  The set temperature of each heating chamber and the conveyance speed in each heating chamber are such that the temperature gradient of the workpiece in the heating chamber on the downstream side substantially corresponds to the temperature gradient of the workpiece in the heating chamber on the upstream side of this heating chamber. Through experiments and simulations, the temperature is set appropriately in consideration of the target temperature of the workpiece, the set temperature of the immediately preceding heating chamber, the length in the transfer direction in the heating chamber, and the like. Specifically, the control device 6 is configured so that the temperature gradient related to the temperature increase of the workpiece in the heating chamber 3 corresponds to the temperature gradient related to the temperature increase of the workpiece in the heating chamber 2 upstream of this. The heating chamber 3 is controlled based on the set temperature T3 of 3. Further, the control device 6 is set so that the workpiece is conveyed to the downstream side of the heating chamber 3 (the outlet of the heating chamber 3) in synchronization with the arrival timing of the workpiece at the target temperature that is the target temperature rise. Based on the transport speed V3 of the fourth transport unit 5d, the fourth transport unit 5d is controlled. Synchronizing the timing not only indicates a state that exactly matches the timing, but also reaches the target temperature that is the target temperature increase value of the workpiece, and the conveyance timing of the workpiece to the outlet of the heating chamber 3. It also includes situations where are generally consistent.

  Below, the effect by embodiment of this invention is demonstrated.

  According to the configuration of the heating furnace, by setting the temperature of the heating chamber 3 to be equal to or higher than the target temperature, it is possible to suppress a gradual temperature gradient of the workpiece even near the target temperature, and to increase the conveyance speed. Overheating can be suppressed by individually controlling each chamber and increasing the conveyance speed at that time. Thereby, heating time can be shortened, raising a workpiece | work to target temperature. Moreover, since the conveyance speed can be set for each heating chamber, even when a workpiece having different specifications is heated, the heating time can be easily changed according to the workpiece.

  In addition, the heating furnace which concerns on this invention is not limited to embodiment mentioned above, A various deformation | transformation and change are possible based on the technical idea of this invention. For example, in the present embodiment, the set temperature T3 of the heating chamber 3 on the most downstream side is increased from the normal temperature and the conveyance speed V3 is increased. T2 may be increased more than usual, and the conveyance speeds V1 and V2 may be increased. According to this configuration, the heating time can be shortened in each of the heating chambers 1 to 3.

The schematic diagram which shows the whole structure of the heating furnace concerning embodiment of this invention. Schematic diagram showing the configuration of a conventional heating furnace Explanatory drawing which shows the temperature rising state of the workpiece | work in a heating furnace, specifically, the temperature rising state of a site | part with a large heat capacity, and the temperature rising state of a site | part with a small heat capacity, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating chamber 2 Heating chamber 3 Heating chamber 4 Atmosphere interruption | blocking chamber 5 Transfer apparatus 5a 1st transfer unit 5b 2nd transfer unit 5c 3rd transfer unit 5d 4th transfer unit 5e 5th transfer unit 6 Control apparatus 11 Heating chamber 12 Heating chamber 13 Heating room 15 Conveyor

Claims (4)

In a heating furnace in which the workpiece is heated to a target temperature by heating the workpiece in stages by a plurality of heating chambers (1 to 3),
A first heating chamber (2) for heating the workpiece in a room set at a first set temperature lower than the target temperature;
A second heating chamber that heats the workpiece in a chamber that is located downstream of the first heating chamber (2) in the conveyance path of the workpiece and is set to a second set temperature that is higher than the target temperature. (3) and
In the first heating chamber (2), the work conveyed from the upstream side of the first heating chamber (2) is transferred to the downstream side of the first heating chamber (2) at a first conveyance speed. A first transport section (5c) transported by
In the second heating chamber (3), the work conveyed from the upstream side of the second heating chamber (3) is moved to the downstream side of the second heating chamber (3). A heating furnace comprising: a second transport unit (5d) that transports at a second transport speed that is faster than the transport speed. The workpiece is heated in an indoor atmosphere that is positioned upstream of the first heating chamber (2) in the workpiece conveyance path and is set to a third set temperature lower than the first set temperature. A third heating chamber (1);
In the third heating chamber (1), the work transported from the upstream side of the third heating chamber (1) is transferred to the downstream side of the third heating chamber (1). The heating furnace according to claim 1, further comprising a third transport unit (5b) that transports at a third transport speed that is slower than the transport speed. The second heating chamber (3) is located on the most downstream side in the workpiece transfer path,
The length of the workpiece in the conveyance direction with respect to the second heating chamber (3) is longer than the length of the workpiece in the conveyance direction with respect to the first heating chamber (2). The heating furnace described in 1. The temperature gradient related to the temperature rise of the workpiece in the second heating chamber (3) is set to correspond to the temperature gradient related to the temperature rise of the workpiece in the first heating chamber (2). Based on the set temperature, the temperature of the second heating chamber is controlled, and the workpiece is transferred to the outside of the second heating chamber (3) in synchronization with the arrival timing of the workpiece at the target temperature. 4. The apparatus according to claim 1, further comprising a control device (6) that controls the second transport unit (5 d) based on the second transport speed set to be performed. 5. A heating furnace described in one item.

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