JPH04284929A - Method and device for expanding fine diameter tube - Google Patents

Abstract

PURPOSE:To reduce a force for pushing mandrel and to prevent the generation of deflective deformation of mandrel due to a reaction force at the time of expanding tube. CONSTITUTION:A mandrel 3 is pushed into the inside of a long size fine diameter tube 1 for refrigerant tube of heat exchanger or the like which is expanded for fixing cooling fins 2 on the outer periphery. A punch part 4 for expanding tube is mounted at the tip of the mandrel 3 and an ultrasonic vibrator transducer 5 is connected with a horn 7 and cone 6 at the rear end of the man-drel. Ultrasonic frequency vibration which is generated with the vibrator transducer 5 is converged with the cone 6 and horn 7, transmitted to the punch part 4 at the tip of the mandrel 3 and the coefficient of friction between the punch part and the inside surface of tube can be reduced by obtaining amplitude of about several tens mum in the punch part. By lowering the mandrel 3, a supporting plate 8 is pushed down with a supporting bar 12 which is mounted on the uppermost part supporting plate 8, lowered together with a rod 10 and the expansion of the tube 1 is executed.

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 small diameter long tubes such as heat exchangers, and an apparatus used therefor.

0002

[Prior Art] Fig. 3 shows a conventional tube expansion technique for small diameter pipes. From the viewpoint of conduction, the refrigerant pipe 1 is often expanded and fixed to the cooling fins 2. The tube expansion method involves fixing the tube 1 and the cooling fins 2 together while pushing the mandrel 3 having the tip punch portion 4 into the tube 1.

In this case, the outer diameter of the punch portion 4 is the same as that of the tube 1.
It is set to take a value slightly larger than the inner diameter dimension of. (Usually, the increase rate of the diameter is about several percent to several tens of percent.)

[0004] When this mandrel 3 is pushed into the tube 1, a pushing reaction force is generated. Oil 14 is supplied in liquid or mist form to reduce friction between the punch section 4 and the inner surface of the tube 1 and reduce the pushing force.

[0005] Pipe 1 and cooling fins 2 used in a heat exchanger
In order to reduce weight, there is a tendency for smaller diameter ones to be used. Further, the inner surface of the tube 1 is often provided with several grooves to improve heat transfer performance.

[0006]

[Problem to be Solved by the Invention] By the way, when expanding a small diameter tube (such as when the inner diameter of the tube is 5 mm or less), the outer diameter of the mandrel 3 needs to be smaller than the inner diameter of the tube 1. The diameter will be small. However, the reaction force during tube expansion may cause the mandrel 3 to bend, making it impossible to smoothly push it into the tube 1. Further, the tube 1 may be buckled and deformed due to the tube expansion reaction force. (The tube 1 is often made of copper or aluminum alloy, which has good thermal conductivity, and has a low yield stress, so it is easily deformed.)

[0007] In order to eliminate such troubles, conventionally, in order to reduce the tube expansion reaction force, as shown in FIG.
Oil 14 is used between the inner surface of the tube and the punch 4, but this must be cleaned in a post-process after pipe expansion, which requires a large number of man-hours.

As described above, there are the following problems to be solved in the conventional expansion of small diameter tubes. (1) Reduction of mandrel pushing force during tube expansion. (2) Prevention of bending and deformation of the mandrel. (3) Abolition of oil for pipe expansion (practical use of oil-less pipe expansion)
.

[0009]

[Means for Solving the Problems] In order to solve the above problems, in the method for expanding a small diameter tube of the present invention, a small diameter tube used for a heat exchanger, etc. is expanded, and a large number of heat dissipation fins are installed around the outer circumference of the small diameter tube. When fixing the tube, the tube expansion mandrel is pushed into the small diameter tube while applying ultrasonic vibrations to reduce the pushing force during tube expansion.

[0010] As a tube expansion device for carrying out such a tube expansion method, an ultrasonic vibrator is connected to the rear end of a mandrel having a punch portion at the tip for pushing into a small diameter tube and expanding the tube, and the A mandrel passage hole is bored, and a support member that moves together with the mandrel when it moves is disposed around the outer periphery of the tube expanding mandrel to prevent excessive deflection of the mandrel.

[0011]

[Operation] According to the above-mentioned method and apparatus for expanding a small diameter tube of the present invention, by applying ultrasonic vibration to the mandrel, an amplitude of approximately several tens of micrometers (amplitude in the axial direction of the mandrel) can be obtained at the tip punch portion. As a result, the coefficient of friction between the punch portion and the inner surface of the tube can be reduced.

[0012] Furthermore, by providing a hole slightly larger than the outer diameter of the punch portion in the mandrel passage portion of the support member, deflection of the mandrel is prevented.

[0013] When the mandrel is pushed in, the support member also moves downward in the same way, and always guides the mandrel during the pipe expansion operation.

[0014]

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a schematic diagram showing the method and device for expanding a small diameter tube of the present invention using ultrasonic waves, and Fig. 2 is a schematic diagram showing the method of the present invention and a conventional method. FIG. 2 is a comparison diagram showing the relationship between mandrel pushing force and pushing speed.

In FIG. 1, numeral 1 denotes a long thin tube such as a refrigerant tube of a heat exchanger, 2 a cooling fin fixed to the outer periphery of the tube, 3 a mandrel pushed into the thin tube 1, and a mandrel at its tip. A punch section 4 for pipe expansion is attached.

An ultrasonic vibrator 5 is connected to the rear end of the mandrel 3 via a horn 7 and a cone 6.
The ultrasonic vibrations generated by this are focused by the cone 6 and horn 7 and transmitted to the tip punch portion 4 of the mandrel 3.

The cooling fins 2 are lowered by lowering the mandrel 3.
The tube is expanded by pushing it into the tube 1 supported by the tube.

[0018] When the reaction force during tube expansion is large, the mandrel 3
In order to prevent this, the present invention provides a support plate 8 that is guided by a bearing 11 supported by a pedestal 13 and supported by a rod 10 that moves up and down. A hole slightly larger than the outer diameter of the punch portion 4 is provided in the central portion of the support plate 8 through which the mandrel 3 passes, to prevent the mandrel 3 from being deformed. A plurality of support plates 8 are fitted into the rod 10, and a coil spring 9 is provided between the support plates.

When the mandrel 3 is lowered (the vibrator 5, cone 6, and horn 7 are integrated), the support plate 8 is pushed down by the support rod 12 attached to the uppermost support plate 8, and is lowered together with the rod 10. Expand tube 1. In addition,
The bearings 11 are supported by a pedestal 13, and two bearings are provided on each side.

FIG. 2 shows the effect of the present invention in comparison with the conventional method, and shows the tube expansion results when the mandrel diameter is about 3 mm and the mandrel length is about 300 mm. In the conventional method that does not use ultrasonic vibration, when the mandrel pushing speed is gradually increased, buckling occurs in the mandrel, resulting in large bending and deformation, making it impossible to expand the tube. When the method of the present invention was used, the pushing force during tube expansion could be reduced to about 20% or less compared to the conventional method. Furthermore, even if the mandrel pushing speed increased, the rate at which the pushing force increased also became smaller. Furthermore, it was confirmed that the effect of reducing the mandrel pushing force was sufficient even when no tube expansion oil was used.

[0021]

As described above, according to the present invention, the following effects can be obtained. (1) By expanding the tube while applying ultrasonic vibration to the mandrel, the coefficient of friction between the punch portion and the inner surface of the tube can be reduced, and the mandrel pushing force can be reduced. (2) Since the mandrel support member is disposed around the outer periphery of the mandrel passage portion, it is possible to prevent the mandrel from being bent or deformed due to reaction force during pipe expansion. (3) Since it has become possible to put oil-less pipe expansion into practical use, it is no longer necessary to clean the pipe in the post-process after the pipe expansion is completed, and the number of man-hours can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a tube expansion situation by an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram comparing the relationship between the mandrel pushing force and pushing speed of the present invention and the conventional method.

FIG. 3 is an explanatory diagram of a state of tube expansion according to a conventional method.

[Explanation of symbols]

1 pipe 2 Finn 3 Mandrel 4 Punch part 5. Oscillator 6 Cone 7 Horn 8 Support plate 9 Coil spring 10 Rod 11 Bearing 12 Support rod 13 Mount 14 Oil

Claims (2)

[Claims] [Claim 1] When expanding a small-diameter tube used in a heat exchanger or the like and fixing a large number of heat dissipation fins to the outer periphery of the tube, a mandrel for expanding the tube is pushed into the narrow-diameter tube while applying ultrasonic vibration. A method for expanding small diameter pipes, which is characterized by reducing the pushing force during expansion. [Claim 2] An ultrasonic vibrator is connected to the rear end of a mandrel, which has a punch portion at the tip for pushing into a small diameter tube and expanding the tube, and a hole for passing through the mandrel is bored in the center, so that when the mandrel is moved, A tube expansion device for a small diameter tube, characterized in that a support member that moves integrally is arranged around the outer periphery of a tube expansion mandrel.