Heat exchanger

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger, and more particularly to a heat exchanger for vehicles that prevents filler metal, for bonding header pipes and porous smoothing tubes, from flowing from the header pipes along scratches or die lines formed in the porous smoothing tubes and melting corrugated pins, thereby improving efficiency in brazing.

2. Description of the Related Art

Generally, a heat exchanger for vehicles, as shown in FIG. 1, comprises a plurality of porous smoothing tubes 2, obtained by extruding a material made of aluminum or aluminum alloy and arranged in parallel; a pair of header pipes 1 bonded to the porous smoothing tubes 2; and a plurality of corrugated pins 3 interposed between the porous smoothing tubes 2.

Here, the header pipes 1 and the pins 3 are obtained by cladding the surfaces of base materials with filler metal. Since the filler metal has a melting point lower than that of the base material of the header pipes 1 and the pins 3, when a brazing process is performed at a temperature in the range between the melting point of the base material and the melting point of the filler metal, the filler metals of the header pipes 1 and the pins 3 are melted at their bonding portions, thereby bonding the header pipes 1, the porous smoothing tubes 2 and the pins 3.

Here, since the porous smoothing tubes 2 are obtained by extruding the material made of aluminum or aluminum alloy, scratches or die lines are formed on the surfaces of the porous smoothing tubes 2 in an extruding direction.

Since the scratches or die lines provide routes, through which the molten filler metal from the header pipes 1 flows in the direction toward the pins 3 by capillary action or surface tension, the pins 3 are not brazed to correct positions of the porous smoothing tubes 2 due to the excessive molten filler metal, but the pins 2 adjacent to the header pipes 1 are melted.

Accordingly, in order to prevent the filler metal from flowing down along the external surfaces of the porous smoothing tubes 2 between the header pipes 1 and the pins 3, there is proposed a method for placing at least one cutoff means on the surfaces of the porous smoothing tubes 2 in a transverse direction of the porous smoothing tubes 2.

However, the above conventional method is disadvantageous in that the cutoff means mars the external appearance of the heat exchanger after the brazing process for bonding components is finished.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a heat exchanger for vehicles that prevents filler metal (for bonding header pipes, porous smoothing tubes, and pins) from flowing along scratches or die lines formed in the porous smoothing tubes and melting corrugated pins.

In accordance with the present invention, the above and other objects can be accomplished by the provision of a heat exchanger comprising: a plurality of porous smoothing tubes obtained by extruding a material made of aluminum or aluminum alloy and arranged in parallel; a pair of header pipes bonded to the porous smoothing tubes; and a plurality of pins interposed between the porous smoothing tubes, wherein a plurality of filler metal absorption means are formed in parallel on portions of the porous smoothing tubes, which are bonded to the heater pipes and inserted into the header pipes, so that the filler metal absorption means absorb molten filler metal and prevent the molten filler metal from leaking to the outside, to prevent pin-melting when the header pipes, the porous smoothing tubes, and the pins are bonded by brazing.

Preferably, the filler metal absorption means may be dented grooves formed in the external surfaces of the porous smoothing tubes, and have a depth of 5% to 10% of the wall thickness of the porous smoothing tubes.

Further, preferably, the number of the filler metal absorption means formed at one edge of one surface of each of the porous smoothing tubes may be from two to six, and the filler metal absorption means may be symmetrically formed at both surfaces of the porous smoothing tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view of a conventional heat exchanger for vehicles;

FIG. 2 is a cross-sectional view of a portion of a heat exchanger, in which a header pipe and a porous smoothing tube are bonded, in accordance with the present invention; and

FIG. 3 is a cross-sectional view taken along the line A-A of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, a preferred embodiment of the present invention will be described in detail with reference to the annexed drawings.

The following description made in conjunction with the preferred embodiment of the present invention has been made only for a better understanding of the present invention. Some parts in this embodiment are substantially the same as those in the prior art and thus are denoted by the same reference numerals, even though they are depicted in different drawings.

FIG. 2 is a cross-sectional view of a portion of a heat exchanger, in which a header pipe and a porous smoothing tube are bonded, in accordance with the present invention, and FIG. 3 is a cross-sectional view taken along the line A-A of FIG. 2.

With reference to FIGS. 2 and 3, the heat exchanger of the present invention, similarly to the conventional heat exchanger, comprises a plurality of porous smoothing tubes 2 obtained by extruding a material made of aluminum or aluminum alloy and arranged in parallel, a pair of header pipes 1 bonded to the porous smoothing tubes 2, and a plurality of corrugated pins 3 interposed between the porous smoothing tubes 2.

Here, a plurality of filler metal absorption means are formed on the surface of a portion of each porous smoothing tube 2, which is inserted into the header pipe 1 in a longitudinal direction.

Preferably, the filler metal absorption means 4 are dented grooves formed in the external surfaces of the porous smoothing tubes 2, and are obtained by pressure.

Further, preferably, the filler metal absorption means 4 are formed in both surfaces of each of the porous smoothing tubes 2.

The number of the filler metal absorption means 4 is at least two to six on one edge of one surface of each of the porous smoothing tubes 2. Preferably, the filler metal absorption means 4 has a depth greater than 5% of the wall thickness of the porous smoothing tube 2 but not more than 10% of the wall thickness of the porous smoothing tube 2.

In the embodiment of the present invention, the filler metal absorption means 4 has a depth of 10 μm to 50 μm, and a width of 50 μm to 200 μm and preferably 100 μm to 200 μm.

That is, in case that scratches or die lines having a depth of 12 μm are formed on the surface of the porous smoothing tube 2, the probability of melting the pins 3 of a heat exchanger, which dose not comprise any filler metal absorption means 4, is approximately 15%, the probability of melting the pins 3 of the heat exchanger of the present invention, which comprises two filler metal absorption means 4, is 8.3%, and the probability of melting the pins 3 of the heat exchanger of the present invention, which comprises four filler metal absorption means 4, is 2.8%.

In case that the number of the filler metal absorption means 4 is less than two, the filler metal absorption means 4 have almost no effect upon the heat exchanger. Accordingly, it is preferable that the number of the filler metal absorption means 4 is two or more.

On the other hand, in case that the number of the filler metal absorption means 4 is more than six, an excessively large quantity of the filler metal for bonding the porous smoothing tubes 2 and the header pipes 1 is removed by the filler metal absorption means 4, thereby causing difficulty in obtaining a stable bonding portion. Accordingly, it is preferable that the number of the filler metal absorption means 4 is six or less.

In case that the depth of the filler metal absorption means 4 is less than 5% of the wall thickness of the porous smoothing tubes 2, the filler metal absorption means 4 has little effect in preventing the leakage of the filler metal by absorbing the filler metal. On the other hand, in case that the depth of the filler metal absorption means 4 is more than 10% of the wall thickness of the porous smoothing tubes 2, the filler metal absorption means 4 generates structural problems.

The filler metal absorption means 4 are spaced from each other at designated intervals in parallel with the longitudinal direction of the tube 2. The length of the filler metal absorption means 4 is limited to an area stretching from the wall of the header pipe 1 to an area of 1 mm to 2 mm before the tip of the porous smoothing tube 2, and is preferably 6 mm to 8 mm long.

The filler metal absorption means 4 are formed prior to a step of cutting each of the porous smoothing tubes 2 into pieces having a designated length.

In this case, preferably, the filler metal absorption means 4 are formed at both sides of the porous smoothing tubes 2, while leaving cutting positions, by a pressure sufficiently low so as to not be deformed by being pressed by the holes of the porous smoothing tubes 2.

Accordingly, the filler metal absorption means 4, which are formed at both sides of each of the porous smoothing tubes 2 of the heat exchanger of the present invention, absorb molten filler metal generated during brazing, thereby preventing the generation of pin-melting.

As a result of experimentation, none of a total of twenty heat exchangers exhibited pin-melting.

Since the filler metal absorption means 4 of the heat exchanger of the present invention are inserted into the inside of the header pipe 1 and sealed, a hole, which may be formed in a portion of the tube 2 adjacent to the filler metal absorption means 4, does not damage the filler metal absorption means 4, and so the heat exchanger has an improved external appearance compared to the conventional heat exchanger comprising additional cutoff means.

As apparent from the above description, the present invention provides a heat exchanger that comprises a plurality of filler metal absorption means, formed on both sides of each of porous smoothing tubes, provided with both ends bonded to header pipes so as to prevent filler metal from flowing from the header pipes along scratches or die lines formed in the porous smoothing tubes and melting corrugated pins, thereby remarkably reducing failures generated by the melting of the pins and having an improved external appearance compared to conventional heat exchangers having additional cutoff means.

Although the preferred embodiment of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.