JPH03169440A - Manufacture of aluminum double pipe system heat exchanger - Google Patents

Abstract

PURPOSE:To manufacture the fully jointed Al made double pipe system heat exchanger of high performance by charging the inner fin between the Al made inner pipe and the outer pipe with the separation preventing means of butt part set and brazing it after expanding inner pipe. CONSTITUTION:The Al made inner pipe 1 and the Al made outer pipe 2 are arranged coaxially. The above outer pipe 2 is formed to the cylindrical shape so that both side peripheral edge parts of Al sheet are butted, the spot welded part 27 is provided on its butt jointing part 24 to prevent separation. The Al inner fin 4 is charged in the flowing space 3 of heat exchanging medium between the above inner and outer pipes. Next, mandrel for expanding pipe 30 is inserted in the inner pipe 1, and the inner pipe 1 is expanded over the longitudinal direction and the inner fin 4 is brought into close contact with the inner pipe and the outer pipe 2. After then, this assembled body 20 is heated, the brazing material preliminarily applied to the pipe 1 and 2 is melted, and both ends of the inner and outer pipe 1, 2, and the inner and outer pipes with the inner fin 4 are joined by brazing approximately completely and sufficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to a method for manufacturing an aluminum double-tube heat exchanger used in water-cooled oil coolers for automobiles and the like.

In this specification, the term aluminum is used to include its alloys.

Conventional technology A double-tube heat exchanger made of aluminum generally has a heat exchange medium circulation space formed between an inner tube and an outer tube made of coaxially arranged aluminum, and a space for improving heat transfer efficiency in the space. It has a structure in which aluminum inner fins for use in the pipe are connected to both the inner and outer tubes. Therefore,
In order to improve the efficiency of such a double-tube heat exchanger, sufficient bonding between the inner fin and both the inner and outer tubes is essential. For this reason, the applicant uses an aluminum brazing sheet for at least one of the inner and outer tubes or the inner fin,
We have proposed a method of joining the inner and outer tubes with the inner fins by brazing (Japanese Patent Application No. 11-131845), but in order to further ensure sufficient brazing, we expanded the inner tube in the length direction before brazing. Then, a process is performed to bring the inner and outer tubes into close contact with the inner fins.

Problems to be Solved by the Invention By the way, the inner tube can be an electric resistance welded tube made by electric resistance welding of the abutting portions of both side edges of a cylindrical molded aluminum sheet, but the outer tube is large in size. Therefore, it is difficult to perform electric resistance welding of the butt parts. For this reason, a cylindrical hollow body with its abutting portions kept separated has been used as the outer tube, but this has the following drawbacks.

In other words, when the inner tube is expanded to bring the inner and outer tubes into close contact with each other as described above, if the abutting portions of both side edges of the outer tube remain separated, they will be subjected to radial force due to the tube expansion. However, since the abutting portion expands and separates, there is a drawback that sufficient adhesion between the inner and outer tubes and the inner fins cannot be obtained. However, in order to prevent this, by fitting and fixing the heat exchanger assembly (110) into the split mold (100) as shown in FIG. 112a) is restrained so that it cannot be expanded, and in this state, the tube expansion mandrel (112a) is restrained so that it cannot be expanded.
20) into the inner tube (111) to expand the tube. However, in this case, when moving on to the brazing process, it is impossible to prevent the outer tube abutment part (ll2a) from expanding due to elasticity when removed from the split mold, and the tightness between the inner and outer tubes and the inner fins is still affected. There was a problem with it being damaged. Even if brazing is performed in such a state, the bonding rate of the inner fins is only about 90%, and as a result, sufficient heat exchange efficiency cannot be obtained.

The present invention was made in view of the above technical background, and enables brazing to be performed while ensuring sufficient adhesion between the inner and outer tubes and the inner fins, thereby achieving excellent heat exchange efficiency. The purpose is to manufacture and provide aluminum double-tube heat exchangers.

Means for Solving the Problems In order to achieve the above object, the present invention includes an inner tube (1) made of aluminum and an outer tube formed by forming an aluminum sheet into a cylindrical shape so that both side edges thereof are abutted. pipe (2)
are arranged coaxially, and an aluminum inner fin is installed in the heat exchange medium circulation space (3) between both the inner and outer tubes, and then the inner tube (1) is expanded in the length direction,
A method for manufacturing an aluminum double-tube heat exchanger in which the inner and outer tubes (1) and (2) and the inner fins (4) are then joined by brazing, the method comprising at least the steps from tube expansion to brazing as described above. The abutting portion (24) is attached to the outer tube (2).
) is characterized in that it is carried out with separation prevention means provided.

The inner and outer tubes (1) and (2) and the inner fins (4) come into close contact with each other due to the expansion process of the working inner tube (1), but this close contact is maintained by the separation prevention means until the end of the brazing process. The inner fin (4) and the inner and outer tubes (1) and (2) are then brazed together. As a result, poor bonding between the inner fin and the inner and outer tubes due to the expansion of the abutting portion (24) of the outer tube (2) is prevented.

Embodiment Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 14. The embodiments show the case where the present invention is applied to a method of manufacturing a water-cooled oil cooler for an automobile.

First, as shown in FIGS. 1 to 5, an inner tube (1), an outer tube (2), and an aluminum offset inner fin (4) as heat exchanger components are prepared. Inner tube (1)
is an electric resistance welded aluminum brazing sheet whose outer surface or both inner and outer surfaces of the core material ({l) (shown in Fig. 5) are coated with brazing filler metal (12), and the abutting portions (14) on both sides of the aluminum brazing sheet are electrically welded. Use a tube. In addition, both ends of the inner tube (1) are flared to have enlarged tube portions (1) with an outer diameter approximately equal to the inner diameter of the outer tube.
3) Form (13) in advance.

On the other hand, the outer tube (2) is manufactured as follows.

That is, as shown in FIGS. 6 and 7, first, a plating sheet (23) of a predetermined size is coated with a brazing metal layer (22) on the inner or outer surfaces of a core material (2l) made of aluminum. prepare.

The brazing material layer (22) generally has a Si content of about 6 to
An AΩ-Si alloy of about 13 wt% is used. Next, both ends of the praising sheet (23) in the width direction are struck in the thickness direction with a hammer or a press. By performing this blow on the lower surface of one end and the upper surface of the other end, as shown in Fig. 8, one side end is gradually thinned from the lower edge to the upper edge. At the other side end, an inclined surface (23b) which becomes gradually thinner from the upper edge to the lower edge is formed. Furthermore, the brazing material i (22) is present on both slopes. By forming both end portions of the praising sheet (23) in this manner, when the both side edges are abutted as shown in FIG. Accordingly, a brazing material layer (22) can be interposed on the abutting surface, and sufficient bonding of the abutting portion (24) can be ensured by subsequent brazing. Next, as shown in FIG. 9, the central part of the praising sheet (23) in the width direction is pressed along the length direction to form a bulge into a semicircular cross section to form a bulge (25). There is. Next, as shown in FIG.
and outlet pipe attachment holes (6) are bored at both ends of the bulge (25) in the length direction. Incidentally, if necessary, the peripheral ends of these mounting holes are drawn in advance to form outwardly projecting bosses.

The above-mentioned hole-drilling was performed by pressing a mold having a shape that matches the shape of the bulging portion (25) from the lower surface side. By doing so, it is possible to prevent the bulge (25) from being crushed or deformed, and it is possible to drill a mounting hole with high dimensional accuracy at an appropriate position. Of course, the holes may be made by milling or the like. Subsequently, after performing surface punching as necessary, the horizontal portions (26) on both sides of the plating sheet (23) excluding the bulging portion (25) are pressed into a U-shaped cross section as shown in Fig. 11. After cutting it into an oval shape, it is molded into a round vibrator shape while applying an external force by pressing so that both edges are abutted. Then, the first
As shown in Figure 2, multiple spots of the butt part (24) are spot welded using argon welding.
A separation prevention means is provided to obtain the desired outer tube (2). Note that (27) in Fig. 2 is a spot welded portion as a means for preventing separation.

A heat exchanger is assembled using the outer tube (2), inner tube (1), and inner fin (4) thus manufactured. Assembly is performed as follows. That is, as shown in Fig. 2, first the inner fins (4) are curved in the direction of the arrow (A) and placed along the outer peripheral surface of the inner tube (1), and then the inner fins (4) are The inner fins (4) are pushed into the outer tube (2) to form a heat exchanger assembly (20).

Next, as shown in Fig. 1, a tube expansion mandrel (30
) is inserted into the inner tube (1) to expand the inner tube (1) in the length direction. During tube expansion, radial pressure is applied to the outer tube (2), but the abutting portion (24) of the outer tube (2)
) are spot welded, so the butt area will not expand. Due to this tube expansion, the heat exchange medium circulation space (3) is narrowed, and the inner fin (4) comes into close contact with the inner tube (1) and the outer tube (2).

Next, the heat exchanger assembly subjected to the above-mentioned tube expansion is heated to melt the brazing filler metal of the inner and outer tubes (1) and (2).
2) are brazed at both ends in the longitudinal direction, and the inner and outer tubes (1) and (2) and the inner fins (4) are brazed and joined to form a heat exchanger as shown in FIGS. 3 to 5. Finished product and eggplant. Any brazing method including vacuum brazing may be used as the brazing method. The butt part of the outer tube (2) (
24) is prevented from expanding by the spot welds not only after expansion but also during the brazing process, so the inner fin (4) remains in close contact with the inner and outer tubes (1) and (2), and this state It is brazed as it is. As a result, a bonding rate of approximately 100% or close to it is achieved. In addition, the non-welded parts of the outer tube (2) other than the spot welded portions of the abutting portions (24) are necessarily joined in this brazing process, but the outer tube (2) has a brazing seat at the manufacturing stage. Since both end portions (23a) and (23b) of (23) are crushed into a gradually thinner state by hitting, the abutting portions (24) match the overlapping state after forming into a cylinder, and the abutting surfaces are mutually Since the brazing material layer is present in between, the joining of the abutting portions (24) can be more reliably and sufficiently guaranteed. Note that (7) and (8) shown in FIGS. 3 and 4 are an oil inlet pipe and an oil outlet pipe that were joined at the same time as the above-mentioned brazing or separately welded after brazing.

The heat exchanger manufactured as described above is used by being incorporated into a tank part of an automobile radiator. The oil flowing into the oil distribution space (3) from the inlet pipe (7) flows around the outer tube (2) and the inner tube (1) in the process of flowing through the oil distribution space (3) including the inner fins (4). ) It exchanges heat with the water flowing inside, is cooled, and flows out of the vessel from the outlet pipe (8).

In the above embodiment, from the tube expansion process of the inner tube until the heat exchanger assembly is brazed, the abutting portion (2) of the outer tube (2)
As a means for preventing separation in 4), a case has been shown in which several locations of the abutting portions are metallically joined by spot welding, but the means for preventing separation is not limited to this. For example, as shown in Fig. 13, the outer circumference of the outer tube (2') is mechanically fixed at multiple points by fastening with wire (40), etc., and the inner tube is expanded and brazed in this state. , the wire (40) may be removed after brazing if necessary. In addition, as shown in Fig. 14, wedge-shaped protrusions (4t) and notches (42) that can be fitted into each other are provided alternately on both sides of the abutting portion of the outer tube (2''), and these are fitted into each other. Alternatively, various other means can be employed as long as they can prevent the abutting portions from separating from each other from the tube expansion process until the brazing process.

Effects of the Invention As explained above, in the present invention, the outer tube made of an aluminum sheet is provided with means for preventing the abutting portions from separating, and the tube expansion step and the brazing step are carried out in this state. Therefore, brazing can be performed while maintaining the close contact between the inner and outer tubes and the inner fins after the tube expansion process, and the parts to be joined can be almost completely and sufficiently joined without causing any separation. As a result, it becomes possible to manufacture and provide a high-performance heat exchanger with excellent heat exchange efficiency.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway vertical sectional view showing a state before pipe expansion of an oil cooler heat exchanger assembly according to an embodiment of the present invention;
Figure 2 is a perspective view showing the state before inserting the inner tube and inner fin into the outer tube, Figure 3 is a front view of the completed heat exchanger, and Figure 4 is the heat exchanger seen from the oil pipe side. A side view of the completed product, Fig. 5 is a sectional view taken along the line ■-■ in Fig. 3, Fig. 6 is a perspective view of the plating sheet for the outer pipe structure, and Fig. 7 is a cross-sectional view taken along the line -■ in Fig. 6.
-■ line sectional view, Figure 8 is a sectional view after hitting both ends of the praising seat, Figure 9 is a perspective view of the shape of the bulge on the praising seat, and Figure 10 is the oil inlet/outlet. A perspective view after drilling the pipe attachment hole, Figure 1 is a perspective view after forming into a U-shaped cross section, Figure 12 is a perspective view after forming into a cylindrical shape, Figure 13
FIG. 14 is a perspective view showing another modification of the separation preventing means for the outer tube abutting portion, and FIG. 15 is a conventional manufacturing method. FIG. (1) Inner tube, (2) Outer tube, (3) Heat exchange medium (oil) circulation space, (4) Inner fin, (24) (24') ( 24”)... Butt part, (27)... Spot welding part, (40)
... wire - (41) ... wedge-shaped projection piece, (42)
... Wedge-shaped notch ( (27) (40) (41
) (42) is separation prevention means). Figure 14 above

Claims (1)

[Claims] An inner tube (1) made of aluminum and an outer tube (2) made of an aluminum sheet formed into a cylindrical shape so that both edges are abutted are arranged coaxially, and the heat between the inner and outer tubes is After loading an aluminum inner fin into the exchange medium circulation space (3), the inner tube (1) is expanded in the length direction, and then the inner and outer tubes (1) and (2) and the inner fin (4) are connected by brazing. ), wherein at least the steps from tube expansion to brazing are performed by attaching separation prevention means to the outer tube (2) at the abutting portion (24). A method for manufacturing an aluminum double-tube heat exchanger, characterized in that the manufacturing method is carried out in a state where a