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Heat exchanger

Heat exchanger description/claims

The present application is a Divisional of U.S. application Ser. No. 11/037,467, filed Jan. 19, 2005, which is based upon and claims the benefit of priority from the prior Japanese Patent Applications Nos. 2004-011689, 2004-015959 and 2004-021566 filed on Jan. 20, 2004, Jan. 23, 2004 and Jan. 29, 2004, respectively; the entire contents of which are incorporated herein by reference.

1. Field of the Invention

The present invention relates to a heat exchanger for use in automotive air-conditioning systems and the like.

2. Description of the Related Art

A conventional heat exchanger includes flat tubes arranged in multiple stages as heat transfer tubes, corrugated outer fins each arranged between the adjacent multistage flat tubes, and a pair of header tanks connected to opposite open ends of the flat tubes for communication. A corrugated inner fin is inserted in each tube.

The header tanks each include a pipe, lids closing opposite open ends of the pipe, and a partition plate partitioning a passage extending longitudinally through the pipe. The pipe has a plurality of multistage tube insertion slots into which the tubes are inserted.

In this heat exchanger, a refrigerant introduced into one of the header tanks through a refrigerant inlet connector flows through the tubes between the header tanks in a zigzag path, and finally is discharged through a refrigerant outlet connector fixed to either of the header tanks. During that time, the refrigerant flowing through the heat exchanger exchanges heat with air passing through spaces in the outer fins between the tubes. For example, when the heat exchanger is used as a radiator or a condenser, the refrigerant is cooled and the air is heated. When the heat exchanger is used as an evaporator, the refrigerant is heated and the air is cooled.

In the manufacturing method of the heat exchanger, with the tubes and the outer fins arranged alternately, the tubes are inserted into the tube insertion slots in the header tanks to form a temporary assembly. Next, the temporary assembly is heated to a predetermined temperature to melt brazing material on a surface of each component, and then cooled. As a result, the components are bonded (joined) to each other by the cooled brazing material so as to form the heat exchanger.

In the above-described related art, the components constituting the heat exchanger each have a brazing material layer on a peripheral surface thereof. Therefore, during brazing, molten brazing material flows all over the heat exchanger. Much of the molten brazing material flows into joint surfaces by capillarity flow. Generally, a core of the heat exchanger, in which the tubes are joined to the outer fins, has a much greater total joint area (total contact area) than the header tanks. Therefore, brazing material of the header tanks flows out to the core of the heat exchanger during brazing. As a result, the header tanks are short of brazing material, so that (i) brazing between members constituting the header tanks have reduced stability; (ii) brazing between the header tanks and the tubes has reduced stability; and (iii) brazing between the header tanks and piping connectors have reduced stability.

In the above-described art, each tube may be formed by bending a single metal plate into a tubular shape, or may be formed by combining two metal plates in a tubular shape. The tube in either form includes a metal plate joint (seam). With this tube structure including a seam, during brazing, a molten brazing material in a brazing material layer on the inner surface of the tube and a molten brazing material in a brazing material layer on the outer surface of the tube flow into or out of the tube through the seam of the tube. At that time, the brazing material is absorbed into one of the inner side and the outer side of the tube which has a larger total joint area, and the other side of the tube becomes short of brazing material. Generally, the total area of inner joint surfaces of the tube (joint surfaces between the inner peripheral surface of the tube and the inner fin) is larger than the total area of outer joint surfaces of the tube (joint surfaces between the outer peripheral surface of the tube and the outer fins). Therefore, the outer joint surfaces of the tube (joint surfaces between the outer peripheral surface of the tube and the outer fins) tend to be short of brazing material.

It is an object of the present invention to prevent molten brazing material from flowing between a core of a heat exchanger and header tanks during brazing. It is another object of the present invention to prevent molten brazing material from flowing from the inside of tubes to the outside of the tubes or from the outside of the tubes to the inside of the tubes during brazing.

The inventors of the present invention have noted that a portion of a tube having no brazing material layer thereon can prevent flow of brazing material.

A heat exchanger according to one aspect of the present invention comprises outer fins; a plurality of tubes arranged alternately with the outer fins; and header tanks receiving open ends of the tubes for communication with the tubes. The header tanks each comprise a first member and a second member which are combined with each other. The first member has tube insertion slots into which the open ends of the tubes are inserted, while the second member does not have tube insertion slots. The first member is either a core material which does not have brazing material layers on outer and inner peripheral surfaces thereof, or a core material having a brazing material layer on an outer peripheral surface thereof but not having a brazing material layer on an inner peripheral surface thereof. The second member is brazed to the outer or inner peripheral surface of the first member which does not have brazing material layers thereon.

A heat exchanger according to another aspect of the present invention comprises tubes; outer fins brazed to outer surfaces of the tubes; and inner fins brazed inside the tubes. Each of the tubes has a seam and does not have a brazing material layer on an inner peripheral surface thereof but has a brazing material layer on an outer peripheral surface thereof. Each of the inner fins has brazing material layers on both surfaces of a core material, and is brazed to the inner peripheral surface of the tube, avoiding contact with the seam of the tube.

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