JPH09253775A - Method for expanding tube with inner fin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the outside shape of a tube from being distorted after tube expansion and to prevent an inner fin from being crushed. SOLUTION: This is a method of expanding a tube 1 having plural inner fins 2, 3 which is extended in the longitudinal direction and different in projecting height, arranged at intervals in the circumference direction on the inner circumference surface of the tube 1. A tube expanding member 4 is used, wherein a max. outside diameter is larger than the inside diameter of the tube 1, on the outside circumference face, plural recessed grooves 5, 6 extended in the axial direction and fitted with inner fins 2, 3 of the tube 1 are formed at intervals in the circumference direction, and the width and depth of the recessed grooves 2, 3 are larger than the width and depth of the inner fins 2, 3. In the state of fitting the inner fins 2, 3 in the recessed grooves 5, 6, the tube expanding member 4 is passed through the inside of the tube 1, a part without the inner fins 2, 3 on the inside face of the tube 1 is pressed and expanded with a part between adjoining recessed groove, 5, 6 on the outside circumference face of the tube expanding member 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for expanding a pipe with an inner fin when manufacturing an oil cooler used in, for example, a hydraulic power steering device for automobiles, an automatic transmission, or the like.

In the following description, the term "aluminum" includes aluminum alloy in addition to pure aluminum.

[0003]

2. Description of the Related Art As the oil cooler described above, a U-shaped aluminum pipe made of an aluminum extruded profile having a circular cross section and having two straight pipe portions extending in parallel to each other, and an aluminum pipe. Equipped with a large number of parallel plate fins made of aluminum, which are bridged over both straight pipe parts, and on the inner peripheral surface of the aluminum pipe,
It is known that a plurality of inner fins extending in the length direction and having the same protrusion height from the inner circumferential surface of the pipe are integrally formed at intervals in the circumferential direction.

Such an oil cooler was manufactured as follows. That is, an aluminum tube with a U-shaped inner fin and a plate fin having two circular through holes are prepared, and first, the straight tube portion of the aluminum tube is passed through the through hole of the plate fin. Then, by expanding the straight pipe portion of the aluminum pipe, the outer diameter of the straight pipe portion is brought into close contact with the outer peripheral surface of the straight pipe portion of the product aluminum pipe to the peripheral edge of the through hole in the plate fin. Then, the aluminum tube and the plate fin are brazed. Thus, the oil cooler was manufactured. The pipe expansion of the aluminum pipe in the above method uses a pipe expansion member having a maximum outer diameter slightly larger than the diameter of the virtual circle where the tip of the inner fin is located, and the pipe expansion member is passed through the pipe to form an outer peripheral surface of the pipe expansion member. Then, the tip of the inner fin is pushed outward in the radial direction to expand the aluminum tube.

By the way, recently, in order to further improve the cooling efficiency of the oil cooler, a plurality of inner fins extending in the length direction and having different projecting heights are circumferentially arranged on the inner peripheral surface of the aluminum pipe. It has been proposed that the device be provided in advance (see Japanese Patent Laid-Open No. 6-331294).

By the way, when the conventional pipe expanding method is applied, the pipe expanding of the aluminum pipe for manufacturing such an oil cooler is larger than the diameter of the virtual circle in which the tips of the inner fins having a high protruding height are located. By using a pipe expanding member with the maximum outer diameter and passing the pipe expanding member inside the pipe, the tip of the inner fin with a high protruding height is pushed radially outward by the outer peripheral surface of the pipe expanding member to expand the aluminum pipe. Will be seen.

However, in this case, since the pitch between the inner fins having a high protruding height becomes considerably large, the outer shape of the aluminum tube after expansion becomes distorted, and as a result, the outer peripheral surface of the aluminum tube and the plate fin penetrate. There is a problem that a gap is formed between the holes and the peripheral edge of the holes, and the heat transfer efficiency between the aluminum tube and the fins deteriorates. Also,
The tip of the inner fin having a high protruding height may be crushed.

An object of the present invention is to provide a method for expanding a tube with an inner fin that solves the above problems.

[0009]

In the method for expanding a pipe with an inner fin according to the present invention, a plurality of inner fins extending in the length direction and having different projecting heights are circumferentially spaced on the inner peripheral surface. A method for expanding a pipe with an inner fin, which has a maximum outer diameter larger than the inner diameter of the pipe, and has a plurality of recessed grooves extending in the axial direction on the outer peripheral surface and into which the inner fin of the pipe fits. Are formed at intervals in the circumferential direction, and the width and depth of the concave groove are larger than the width and height of the inner fin, and the inner fin is fitted into the concave groove. By passing the member through the pipe, the portion of the outer peripheral surface of the pipe expanding member between the adjacent concave grooves presses the portion of the inner surface of the pipe where the inner fin does not exist to expand the pipe.

According to the pipe expanding method of the present invention, since the portion of the outer peripheral surface of the pipe expanding member between the adjacent concave grooves presses the portion of the inner surface of the pipe where the inner fin does not exist to expand the pipe, the outer shape of the expanded pipe. There is no need to worry. Further, since the inner fin is formed on the outer peripheral surface of the pipe expanding member, and the width and depth of the inner fin are fitted into the concave grooves which are larger than the width and height of the inner fin, the pipe expanding member is passed through the pipe. The inner fins are prevented from being crushed when the pipe is expanded.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
This will be described with reference to the drawings. In this embodiment, the method of the present invention is applied to the expansion of an aluminum pipe in the production of an oil cooler. In the following description, the right side of FIG. 2 is referred to as the front and the opposite side is referred to as the rear.

On the inner peripheral surface of the aluminum tube (1) with inner fins to be expanded, two kinds of inner fins (2) (3) extending in the length direction and having different projecting heights are circumferentially spaced. Are alternately provided. The expansion member (4)
The outer diameter gradually increases from the front end toward the rear, and the maximum outer diameter is slightly larger than the inner diameter of the pipe (1) to be expanded, and the pipe to be expanded and expanded in the axial direction on the outer peripheral surface.
Multiple grooves for loosely fitting the inner fins (2) and (3) of (1)
(5) and (6) are formed alternately at intervals in the circumferential direction. The width and depth of the grooves (5) (6) are the inner fins (2) (3).
It is slightly larger than the width and height of.

First, the aluminum tube with inner fins (1) to be expanded is passed through circular through holes (8) formed in a large number of parallel plate fins (7) made of aluminum. The diameter of the through hole (8) of the plate fin (7) is slightly larger than the outer diameter of the aluminum pipe (1) to be expanded, and a cylindrical shape around the plate fin (7) is used to maintain the space between the adjacent plate fins (7). The part (9) is integrally formed. An outward flange (10) is integrally formed at the tip of the tubular portion (9).

Next, the tube expanding member (4) is detachably attached to the tip of the pushing member (11), and the inner fins (2) and (3) are recessed.
(5) Fit the aluminum tube from its front end so that it fits into (6).
(1) Insert inside and move forward. Then, the portion of the outer peripheral surface of the pipe expanding member (4) between the adjacent concave grooves (5) and (6) is pressed radially outward by the portion of the inner surface of the pipe (1) where the inner fins (2) and (3) are not present. As a result, the aluminum tube (1) is expanded. Then, the outer peripheral surface of the aluminum tube (1) is brought into close contact with the peripheral edge of the through hole (8) of the plate fin (7) and the inner peripheral surface of the tubular portion (9). After that, the aluminum tube (1) and the plate fins (7) are brazed.

In the above description, the case where the pipe expanding method of the present invention is applied to the pipe expanding of the aluminum pipe in the production of the oil cooler has been described.
The present invention can be applied to other than expansion of such an aluminum tube. Further, it goes without saying that it can be applied to the expansion of a tube made of a material other than aluminum.

[0016]

As described above, according to the pipe expanding method of the present invention, the outer shape of the expanded pipe is not distorted, so that the present invention is applied to the pipe expanding for fixing the heat exchange pipe and the fin. In this case, the heat transfer efficiency between the heat exchange tube and the fin becomes excellent. Moreover, the inner fins are prevented from being crushed.

[Brief description of drawings]

FIG. 1 is a transverse cross-sectional view of a maximum outer diameter portion of a pipe expanding member used in a pipe expanding method of the present invention.

FIG. 2 is a vertical sectional view showing a tube expanding method of the present invention.

FIG. 3 is an enlarged sectional view taken along line III-III of FIG. 2;

FIG. 4 is an enlarged sectional view taken along line IV-IV of FIG. 2;

[Explanation of symbols]

 (1) Aluminum tube with inner fin (2) (3) Inner fin (4) Expansion member (5) (6) Groove

Claims (1)

[Claims] 1. A method for expanding a pipe with inner fins, wherein a plurality of inner fins extending in the longitudinal direction and having different projecting heights are provided on an inner peripheral surface at intervals in the circumferential direction. , Having a maximum outer diameter that is larger than the inner diameter of the pipe, and having a plurality of recessed grooves that extend in the axial direction and that fit the inner fins of the pipe on the outer peripheral surface at intervals in the circumferential direction. By using a pipe expanding member whose width and depth are larger than the width and height of the inner fin, and by inserting the pipe expanding member into the pipe with the inner fin fitted in the concave groove, the adjacent concaves on the outer peripheral surface of the pipe expanding member are A pipe expanding method for a pipe with an inner fin, comprising: pressing a portion of the inner surface of the pipe where the inner fin does not exist between the grooves to expand the pipe.