JP2006159228A - Brazing method for heat exchanger and preheating apparatus for brazing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brazing method or the like for a heat exchanger, a method for sure brazing even if spacing of piping is small or piping is bent. <P>SOLUTION: Heated air from a nozzle 31 is applied near a joining position W between a core 10 and piping 11, 12, preheating the joining position W prior to the brazing 9. Also, in a piping brazing apparatus, a turn table having at least three positions, i.e., an attaching/detaching, a preheating and a brazing position is used, so that operations such as setting, preheating, brazing and removing of the core 10 can be performed in parallel at each position. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat exchanger brazing method that can be used for brazing pipes or the like to a heat exchanger, and a brazing preheating device suitable for use in that case.

  For example, a heat exchanger such as an evaporator, which is a constituent part of an automotive air conditioner, joins a pipe to the core of the heat exchanger in the manufacturing process. At this time, a core constituted by a tube serving as a refrigerant passage and a fin for increasing heat exchange efficiency is formed by vacuum brazing. Thereafter, a plurality of pipes serving as refrigerant introduction paths / discharge paths with respect to the tube are joined to the predetermined positions of the core by brazing.

When brazing the pipe to the core, if the interval between the plurality of pipes is sufficiently wide, it is preferable to perform high-frequency brazing by arranging a high-frequency coil around the pipe at the joint between the pipe and the core.
However, since the core is arranged in a limited space such as an engine room of an automobile, the piping is often bent, and high-frequency brazing cannot always be used. In such a case, conventional brazing using a torch burner (hereinafter referred to as burner brazing) is used (see, for example, Patent Document 1).

JP 2000-79463 A (paragraph [0004])

  However, even in the case of burner brazing, it may be difficult to braze the entire circumference of the pipe with the torch burner at the joint between the pipe and the core. For example, as shown in FIG. 4, the pipe 2 is bent in the vicinity of the joining position with respect to the core 1, or the interval between the pipes 2 is narrow, and therefore, it interferes with the torch burner. For this reason, a brazing defect is likely to occur, which causes a defect such as refrigerant leakage. In order to avoid this, the interval and bending of the pipe 2 can be changed. However, in this case, there is a design limitation on the arrangement and handling of the pipe 2.

By the way, aluminum alloy is frequently used as the material of the core 1 of the heat exchanger such as an evaporator. When the core 1 is made of an aluminum alloy, the difference between the melting point of the base material of the core 1 (660 ° C.) and the melting point of the brazing material used for brazing the pipe 2 (600 ° C.) is, for example, that the core 1 is made of copper. It is small compared to the case of. For this reason, it is easy to exceed the melting point of the base material due to excessive heating. In particular, a brazing material for an aluminum alloy is difficult to visually recognize even when it is melted, and thus easily falls into excessive heating.
Furthermore, in order to perform brazing with a torch burner, it is natural that the joint portion between the pipe 2 and the core 1 must be heated to a temperature equal to or higher than the melting point of the brazing material.
In addition, when the plurality of pipes 2 have different diameters, the heat capacities are different. Therefore, when brazing is performed at the same time, brazing of one of the pipes is likely to be insufficient or a failure due to overheating is likely to occur.
For this reason, advanced skills are required for brazing with a torch burner.

  The present invention has been made on the basis of such a technical problem, and even when the interval between the pipes is small or the pipe is bent, the heat exchange can be performed reliably. It aims at providing the brazing method etc. of a vessel.

The present invention made for this purpose is a method of brazing a brazing object to a heat exchanger, wherein the heat exchanger and the brazing object are below the melting point of the heat exchanger and the brazing object. And a brazing process in which a preheated heat exchanger and a brazing object are brazed with a burner.
Thus, brazing can be performed quickly by preheating the heat exchanger and the brazing object. In addition, since it is easy to control the temperature of the gas, preheating can be stably performed regardless of the season. In addition, at that time, by performing preheating with a gas having a temperature lower than the melting point of the heat exchanger and the object to be brazed, even if the preheating is longer than expected, the heat exchanger or brazing It is possible to prevent the base material of the object from melting.
As such a gas, it is preferable to use air that has passed through an energized electric heating coil, and in the preheating step, the air heated by passing through the energized electric heating coil is used as a gas for the heat exchanger and Spray near the joining position of the brazing object.
At this time, in the preheating step, it is preferable to blow the gas toward a position offset from the joining position of the heat exchanger and the brazing object. This is to prevent the flux from scattering. In this preheating step, it is preferable to preheat the heat exchanger and the brazing object with gas and to evaporate moisture contained in the flux used when brazing the heat exchanger and the brazing object. This also can suppress unnecessary scattering of the flux.

  Such a heat exchanger brazing method can be effectively applied to any brazing object, but is particularly effective when the brazing object has a pitch within 50 mm with respect to the heat exchanger. This is a case where at least one of the conditions is found in the case of a plurality of pipes joined in the case of a pipe bent in the vicinity of the position joined to the heat exchanger. This is because when such a pipe is to be brazed, it is difficult to braze the entire circumference of the pipe to the heat exchanger stably.

When executing such a heat exchanger brazing method, it is suitable to use the brazing preheating device of the present invention as described below.
That is, the brazing preheating device of the present invention is provided so as to face the vicinity of a joining position of a heat source for heating air and a brazing object to be brazed to the heat exchanger and the heat exchanger. And a nozzle that blows out heated air. In such an apparatus, the joining position can be preheated by blowing air heated by a heat source from the nozzle and blowing it near the joining position of the heat exchanger and the brazing object.
Such a device may further include a shielding member that is disposed between the nozzle and the joining position and shields air blown from the nozzle from being directly blown to the joining position.
Further, a plurality of holding portions that hold the heat exchanger and the brazing object in a positioned state may be provided at equal intervals, and a turntable that is rotatable about the rotation axis may be provided. In this case, the turntable is rotationally driven by the driving device, and the plurality of holding units are attached to and detached from the holding unit with the heat exchanger and the brazing object, and the heat exchanger and brazing held by the holding unit. The position can be sequentially moved to a position where air is blown from the nozzle to the object and a position where the heat exchanger and the brazing object are brazed. Thereby, the attaching / detaching work, preheating, and brazing work can be performed in parallel with each other.
In addition, a nozzle drive mechanism that moves the nozzle and the shielding member closer to and away from the heat exchanger and the brazing object that are held by the holding unit and positioned at a position where air is blown from the nozzle can be further provided.

  According to the present invention, brazing can be performed easily and stably even when the interval between the pipes is small or the pipe is bent, and the workability, work safety, and production can be improved. Can be improved.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
As shown in FIG. 1, an evaporator core (heat exchanger) 10 includes a tube 10a serving as a refrigerant flow path and fins 10b for increasing the heat exchange efficiency of the tube 10a. The form and structure of the core 10 are not limited at all.
The core 10 is provided with a pipe (a brazing object) 11 serving as a refrigerant supply path to the tube 10a and a pipe (a wax serving as a refrigerant discharge path from the tube 10a) at a position communicating with the end of the tube 10a. (Attachment object) 12 is joined by burner brazing.

In the present invention, when joining the pipes 11 and 12 to the core 10 of the evaporator, after preheating the vicinity of the joining position, the pipes 11 and 12 are joined to the core 10 by burner brazing.
FIG. 2 is a view for explaining a pipe brazing device (brazing preheating device) 20 used when brazing the pipes 11 and 12 to the core 10 in the present embodiment.
As shown in FIG. 2, the pipe brazing device 20 can hold three or more cores 10 on a turntable 21 having a substantially circular shape in a plan view at equal intervals in the circumferential direction by a jig (holding unit) (not shown). It is like that. The turntable 21 is rotationally driven by a driving mechanism such as a motor (not shown) around a rotating shaft 21a provided at the center thereof. The turntable 21 stops for a predetermined time each time it rotates by a certain angle, and the held core 10 can be positioned at the three positions of the attaching / detaching position P1, the preheating position P2, and the brazing position P3 for a predetermined time. ing.

At the attachment / detachment position P1, the core 10 is set on the turntable 21 by the operator or a working robot, and the core 10 is removed after the brazing is completed. When the core 10 is set, the pipes 11 and 12 are positioned and fixed at predetermined positions by a jig (not shown).
In the preheating position P2, the vicinity of the position where the pipes 11 and 12 are joined to the core 10 is heated by heated air (gas) by the preheating mechanism 30 described later.
At the brazing position P3, the pipes 11 and 12 are brazed and joined to the core 10 by the operator or the working robot using the burner 40.

The preheating mechanism 30 blows heated air onto the core 10 held on the turntable 21 and located at the preheating position P2, and includes a nozzle 31 and a shielding member 32.
The nozzle 31 is supplied by a fan, a pump, or the like, and blows a gas (generally air) heated by an electric heating coil (heat source) that generates heat by energization in the vicinity of the joint position W between the core 10 and the pipes 11 and 12. As shown in FIG. 1 (b), the sprayed position of the heated air by the nozzle 31 is in the vicinity of the joint position W between the core 10 and the pipes 11 and 12 and from the joint position W between the core 10 and the pipes 11 and 12. An offset position is preferred. For example, when the pipes 11 and 12 are set on the upper surface side of the core 10 and bonding is performed, the nozzle 31 is set so that the heated air hits below the bonding position W. This is to prevent the flux applied to the joining position W between the core 10 and the pipes 11 and 12 from being blown off by the heated air.
It is also effective to provide a plurality of such nozzles 31 and increase the heating efficiency.

  The shielding member 32 covers the heated air blown from the nozzle 31 so that it does not directly hit the joining position W of the pipes 11 and 12 with respect to the core 10. This is also to prevent the flux applied to the joining position W between the core 10 and the pipes 11 and 12 from being blown off.

  As shown in FIG. 3, the nozzle 31 and the shielding member 32 are moved toward and away from the core 10 on the turntable 21 by a driving mechanism (nozzle driving mechanism) such as a guide rail and a driving cylinder (not shown). It can be done. The direction of approaching / separating may be any direction, but may be, for example, a direction that moves up and down.

Now, a method of brazing the pipes 11 and 12 to the core 10 using the pipe brazing apparatus 20 having such a configuration will be described.
First, as shown in FIG. 2, the core 10 is set on the turntable 21 at the attachment / detachment position P1. And the piping 11 and 12 which should be joined to this core 10 is positioned and set to a predetermined position with the jig which is not illustrated. At this time, the flux is applied in advance around the joint position W between the core 10 and the pipes 11 and 12. This flux is obtained by dissolving flux powder with water and can be applied with a brush or the like.

Subsequently, the turntable 21 is rotated by a predetermined angle, and the set core 10 and the pipes 11 and 12 are moved to the preheating position P2.
In the preheating position P2, first, the shielding member 32 is lowered and moved to a position that covers the joint position W between the core 10 and the pipes 11 and 12.
Subsequently, the nozzle 31 is then lowered and moved to a position that covers the joint position W between the core 10 and the pipes 11 and 12. Then, heated air is blown out from the nozzle 31 and applied to the vicinity of the joint position W between the core 10 and the pipes 11 and 12 to heat the core 10. Then, the heat is transmitted through the core 10 and the joining position W between the core 10 and the pipes 11 and 12 is heated. At this time, it is preferable to constantly blow out heated air from the nozzle 31. This is because the time required for heating the heated air itself can be omitted. In this case, the heated air blown out from the nozzle 31 strikes the flux at the joining position W between the core 10 and the pipes 11 and 12 by the shielding member 32 that has moved before the position covering the joining position W between the core 10 and the pipes 11 and 12. Can be prevented.

In this way, the joining position W between the core 10 and the pipes 11 and 12 is preheated by continuing to apply the heated air from the nozzle 31 for a predetermined time or more.
At this time, it is preferable to heat so that the temperature of the joining position W of the core 10 and the piping 11 and 12 may be 100-350 degreeC, and a more preferable temperature range is 200-250 degreeC. This is to evaporate moisture contained in the flux by setting the temperature at the joint position W between the core 10 and the pipes 11 and 12 to 100 ° C. or higher. Moreover, it is for preventing the preform | base_material of the core 10 and the piping 11 and 12 from melting by setting the temperature of the joining position W of the core 10 and the piping 11 and 12 to 350 degrees C or less. For this purpose, heated air having a temperature of 400 ° C. or higher is preferably applied to the vicinity of the joint position W between the core 10 and the pipes 11 and 12 at an air volume of 240 L (liter) / min or more for a predetermined time. By setting it as such conditions, the joining position W of the core 10 and the piping 11 and 12 can be heated to 250 degreeC (preheating) within 40 second, for example.
It is also effective to reciprocate the nozzle 31 up and down or horizontally with respect to the core 10 during heating so that heated air is applied over a wider range.

After a predetermined time has elapsed, the turntable 21 is rotated by a predetermined angle, and the preheated core 10 and the pipes 11 and 12 are moved to the brazing position P3.
At the brazing position P <b> 3, the pipes 11 and 12 are brazed and joined to the core 10 using the burner 40 by an operator or a working robot.

  After completion of brazing, the turntable 21 is rotated by a predetermined angle, and the core 10 joined with the pipes 11 and 12 is returned to the attachment / detachment position P1. Then, the core 10 is removed from the turntable 21 by the operator or the working robot, whereby the joining of the pipes 11 and 12 to the core 10 is completed.

By the way, the rotation of the turntable 21 such as the attaching / detaching position P1-preheating position P2-brazing position P3-attaching / detaching position P1 is performed every preset cycle time.
And the attaching / detaching step of the core 10 at the attaching / detaching position P1, the preheating step at the preheating position P2, and the brazing step at the brazing position P3 are performed in parallel. That is, while the core 10 is being attached / detached at the attaching / detaching position P1, the core 10 set in advance is preheated at the preheating position P2, and in the meantime, the core 10 previously preheated is brazed at the brazing position P3. It is attached. Thereby, in the pipe brazing apparatus 20, the pipes 11 and 12 can be efficiently brazed to the core 10, and such a pipe brazing apparatus 20 can be suitably used particularly in a mass production process.

  In such a pipe brazing apparatus 20, the joining position W between the core 10 and the pipes 11 and 12 is preheated by applying heated air from the nozzle 31 in the vicinity of the joining position W between the core 10 and the pipes 11 and 12. I did it. Thereby, when brazing with the burner 40 after that, the time until the brazing is completed by applying the flame of the burner 40 to the joint position W between the core 10 and the pipes 11 and 12 can be shortened compared to the conventional method. . Therefore, when the pipes 11 and 12 have different diameters and different heat capacities, or the burner 40 interferes with the pipes 11 and 12, the flame of the burner 40 can be successfully applied to the entire circumference of the joint position W between the core 10 and the pipes 11 and 12. Even if it is not a case, it can suppress that the specific site | part of the joining position W of the core 10 and the piping 11 and 12 will be heated too much. As a result, the occurrence of brazing defects can be prevented, and defects such as refrigerant leakage can be reduced. In particular, this method is particularly effective when the core 10 is made of an aluminum alloy, the melting point of the brazing material is close to the melting point of the base material, and it is difficult to visually confirm the melting of the brazing material. Yes, it is possible to facilitate and stabilize the brazing operation.

Further, by using heated air for heating the joint position W between the core 10 and the pipes 11 and 12, the joint position W between the core 10 and the pipes 11 and 12 is not heated above the temperature of the heated air. Is also a big advantage. That is, when the work is stopped due to some reason such as a failure of the apparatus in the post-process or the like, in the pipe brazing apparatus 20, the heated air continues to hit the joining position W between the core 10 and the pipes 11 and 12 from the nozzle 31. It will be. In such a case, when a heat source having a temperature higher than the melting point of the base material of the core 10 or the pipes 11 and 12 is used for preheating, if the preheating is performed for a long time, the base material temperature exceeds the melting point, May melt. On the other hand, when heated air is used, even in such a case, the joining position W between the core 10 and the pipes 11 and 12 is not heated above the temperature of the heated air, so preheating is assumed. Even if it is carried out for a long time, there is no case where the base material melts beyond the melting point.
In addition, when heated air is used, the temperature of the joint position W between the core 10 and the pipes 11 and 12 after preheating can be set within a certain range regardless of the season or the like. As a result, the subsequent brazing process can be performed stably.

  In addition, the heated air is locally applied by the nozzle 31 in the vicinity of the joint position W between the core 10 and the pipes 11 and 12. Thereby, the temperature of the other part of the core 10 (part away from the position where the heated air is applied) does not increase so much. Therefore, even when the operator removes the core 10 after the brazing is completed, the core 10 can be held with a gloved hand, and workability and work safety can be improved.

Further, if the joining position W between the core 10 and the pipes 11 and 12 is heated to 100 ° C. or higher by preheating, moisture contained in the flux can be surely blown off, and this also improves workability. it can.
Further, at this time, the heated air is not directly applied to the joining position W between the core 10 and the pipes 11 and 12, but is applied to the vicinity of the joining position W between the core 10 and the pipes 11 and 12. Since the joint position W between the pipe 10 and the pipes 11 and 12 is covered, the flux itself can be prevented from being blown off by the heated air.

  Now, in the pipe brazing device 20, since the turntable 21 having at least three positions of the attaching / detaching position P1, the preheating position P2, and the brazing position P3 is used, the core 10 is set, preheated, brazed, and the core 10 It is possible to efficiently perform operations such as removal of the battery, which can greatly improve productivity.

  In this way, according to the pipe brazing apparatus 20, even when the distance between the pipes 11 and 12 is small or the pipes 11 and 12 are bent, brazing is performed easily and stably. In addition, the workability, work safety, and productivity can be improved.

Now, since the case where it pre-heats and the case where it does not perform were compared, the result is shown.
Here, the core 10 and the pipes 11 and 12 were made of JIS A3003 alloy having a melting point of 659 ° C., and the brazing material was made of JIS BA4047 alloy having a melting point of 577 to 580 ° C.
In the pipe brazing device 20, after the core 10 was set on the turntable 21 at the attachment / detachment position P1, preheating was performed at the preheating position P2. At this time, the temperature of the heated air used for preheating at the preheating position P2 was set at two temperatures of 200 ° C. and 350 ° C., and preheating was performed for 300 seconds.
Then, after preheating, the pipes 11 and 12 are brazed at the brazing position P3, and at that time, the temperature at a plurality of locations at the joint position W (brazing part) between the core 10 and the pipes 11 and 12 was measured with a thermocouple. .
For comparison, after setting the core 10 on the turntable 21 at the attachment / detachment position P1, the pipes 11 and 12 are brazed at the brazing position P3 without preheating at the preheating position P2, and similarly, The temperature of several places of the brazing part was measured with a thermocouple.
The results are shown in Table 1.

As shown in Table 1, when brazing is performed without preheating, the temperature difference between the maximum temperature and the minimum temperature of the brazed portion is 45 ° C, and the maximum temperature is 660 ° C. When 11 and 12 were made of an aluminum alloy, there was a portion reaching the melting point. On the other hand, when preheating is performed, the temperature difference is 35 ° C. (when preheating is 200 ° C.), 20 ° C. (when preheating is 350 ° C.), and the maximum temperature is 645 ° C. (when preheating is 200 ° C.), 630 ° C. (When preheating is 350 ° C.). As a result, it can be seen that preheating can suppress an excessive rise in the temperature at a specific location during brazing. This is because the amount of heat input during brazing is smaller than when no preheating is performed, that is, brazing. It is suggested that can be done in a short time.
Further, the fluidity and gap filling property of the brazing material in the brazing process were equal or better than those without preheating.

In the above embodiment, the evaporator core 10 constituting the automobile air conditioner is taken as an example of the heat exchanger. However, other heat exchangers such as a condenser, a heater, an intercooler, an oil cooler, and the like are used. The present invention can also be applied to this. Further, the core 10 itself is not limited to any material or structure. Furthermore, the present invention can be applied not only to the pipes 11 and 12 but also to brazing various brackets or the like to the heat exchanger.
In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

It is a figure which shows the brazing method of the heat exchanger in this Embodiment, Comprising: (a) Top view and (b) Side view which show the position with respect to the heat exchanger of the nozzle in the case of preheating. It is a top view of a piping brazing apparatus. It is a perspective view which shows operation | movement of the nozzle and shielding member at the time of brazing. It is a perspective view which shows the example of the heat exchanger with which brazing is difficult.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Core (heat exchanger), 11, 12 ... Pipe (brazing object), 20 ... Pipe brazing apparatus (brazing preheating apparatus), 21 ... Turntable, 21a ... Rotary shaft, 30 ... Preheating mechanism, 31 ... nozzle, 32 ... shielding member, 40 ... burner, P1 ... attachment / detachment position, P2 ... preheating position, P3 ... brazing position, W ... joining position

Claims (9)

A method of brazing an object to be brazed to a heat exchanger,
A preheating step of preheating the heat exchanger and the brazing object with a gas having a temperature equal to or lower than a melting point of the heat exchanger and the brazing object;
A brazing step of brazing the preheated heat exchanger and the brazing object with a burner;
A brazing method for a heat exchanger, comprising:   2. The heat exchanger according to claim 1, wherein in the preheating step, the air that has passed through the energized electric heating coil is blown as the gas to the vicinity of the joining position of the heat exchanger and the brazing object. Brazing method.   3. The brazing method for a heat exchanger according to claim 1, wherein in the preheating step, the gas is blown toward a position offset from a joining position of the heat exchanger and the brazing object. 4. .   In the preheating step, the heat exchanger and the brazing object are preheated by the gas, and moisture contained in a flux used when brazing the heat exchanger and the brazing object is evaporated. 4. A heat exchanger brazing method according to claim 1, wherein the heat exchanger is brazed.   The brazing object is at least one of a plurality of pipes joined to the heat exchanger at a pitch of 50 mm or less, or a pipe bent near a position joined to the heat exchanger. The brazing method for a heat exchanger according to any one of claims 1 to 4. A heat source for heating the air;
A nozzle that blows out air heated by the heat source, provided to face the vicinity of the joining position of the brazing object to be brazed to the heat exchanger and the heat exchanger;
A brazing preheating device comprising:   The wax according to claim 6, further comprising a shielding member that is disposed between the nozzle and the joining position and shields the air blown from the nozzle from being directly blown to the joining position. Preheating device. A plurality of holding portions that hold the heat exchanger and the brazing object in a state of being positioned at equal intervals, and a turntable that can rotate around a rotation axis;
The turntable is driven to rotate, a plurality of the holding units are attached to and detached from the holding unit with the heat exchanger and the brazing object, the heat exchanger held by the holding unit, and the A position where air is blown from the nozzle to the brazing object; and a drive device which sequentially moves the heat exchanger and the brazing object to a brazing position;
The brazing preheating device according to claim 6 or 7, further comprising:   It further comprises a nozzle drive mechanism that moves the nozzle and the shielding member closer to and away from the heat exchanger and the brazing object that are held by the holding unit and positioned at a position where air is blown from the nozzle. The brazing preheating device according to claim 8.

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