JPH04339521A - Hair pin bending method for coolant pipe or the like - Google Patents

Abstract

PURPOSE:To improve slidability between a pipe and a mandrel, to reduce bending moment and to prevent dent, etc., by adding ultrasonic oscillation to the mandrel. CONSTITUTION:One side of a half of the coolant pipe 5 is held with a bending die 2 and a clamping die 3 therebetween and by moving an arm 4, the bending die 2, clamping die 3 and the coolant pipe 5 are integrally turned while making the center axis of the bending die 2 as a center. The ultrasonic wave generated from an oscillator 8 is transmitted to the mandrel 6 through a horn 9 and a mandrel holding bar 7. This ultrasonic oscillation improves the slidability between the coolant pipe 5 and the mandrel 6 at the time of hair pin bending. By this method, lubricativity at the time of hair pin bending is improved and the use of an oil is eliminated. Further, the moment at the time of bending is reduced and the dent, etc., at the inside of the bending part in the coolant pipe can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for hairpin bending refrigerant pipes of heat exchangers for air conditioners.

0002

2. Description of the Related Art FIG. 4 is a plan view showing a conventional hairpin bending method for refrigerant pipes. In the figure, 1 is a pressure mold, 2 is a bending mold that can rotate around its central axis, 3 is a clamp mold, 4 is an arm attached to the clamp mold, and 5 is a pressure mold that is connected to the bending mold and the clamp mold. A refrigerant pipe is held between the refrigerant pipes, a mandrel 6 is inserted into the refrigerant pipe, and a mandrel holding rod 7 is attached to the mandrel and holds the mandrel from a fixed part (not shown). The refrigerant pipe 5 is thin-walled and small-diameter, with a diameter of about 10 mm or less and a thickness of 0.4 mm.
It is of a certain degree.

This device bends one half of the refrigerant pipe 5 into a mold 2.
and the clamp mold 5, and move the arm 4 to bend the mold 2.
, the clamp mold 3, and the refrigerant pipe 5 are rotated integrally around the central axis of the bending mold 2. At this time, since the lateral movement of the other half of the refrigerant pipe 5 is restrained by the pressure mold 1, the refrigerant pipe 5 bends into a hairpin shape. The refrigerant pipe 5 is bent in the direction of coming out of the mandrel 6 at the bend while sliding against the mandrel. Oil is used to smooth the sliding movement between the inner surface of the refrigerant tube and the mandrel.

0004

[Problems to be Solved by the Invention] In the conventional technology, oil is used to improve the sliding property between the mandrel and the inner surface of the refrigerant tube during bending, but the bending moment is large, and for this reason, the hairpin Conventionally, during bending, deformation such as a dent as shown in FIG. 5 may occur inside the bent portion of the refrigerant pipe. Furthermore, the oil needs to be washed in the final process, which is time-consuming.

The present invention eliminates the drawbacks of the prior art described above, improves the sliding properties without using oil, does not cause deformation such as dents in the refrigerant pipe, and does not require cleaning in the final process. The present invention aims to provide a method for hairpin bending of refrigerant pipes.

[0006]

[Means for Solving the Problems] The present invention solves the above-mentioned problems by restraining the lateral movement of about half of the tube, inserting a mandrel from the end of that portion of the tube,
The mandrel is held at a fixed part outside the pipe, and the other half of the pipe is sandwiched between a bending die and a clamping die along the bending die, and the part of the tube sandwiched between the bending die, clamping die, and these is In a hairpin bending method for refrigerant pipes, etc., in which the tube is bent along the bending die while sliding against the mandrel by rotating the tube as a unit around the center of the bending die,
The present invention relates to a hairpin bending method for refrigerant pipes, etc., characterized by applying ultrasonic vibration to the mandrel.

[0007]

[Operation] By applying ultrasonic vibration to the mandrel, the lubricity of the sliding part between the pipe and the mandrel during bending is improved and the bending moment is reduced. Also, with this,
The occurrence of dents inside the bends of the pipe is prevented. Furthermore, the oil conventionally used in the sliding portion is no longer necessary.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view of an embodiment of the present invention. In the figure, 8 is an ultrasonic oscillator provided on the fixed part, and 9 is a horn whose one end is connected to the oscillator and the other end is connected to the mandrel holding rod 7. In this embodiment, the oil conventionally used between the refrigerant pipe and the mandrel is not used. The parts other than the above are the same as the conventional technology.

In this embodiment, the ultrasonic waves generated from the oscillator 8 are transmitted to the mandrel 6 via the horn 9 and the mandrel holding rod 7. This ultrasonic vibration has the effect of improving the slidability between the refrigerant pipe 5 and the mandrel 6 during hairpin bending.

FIG. 2 is a diagram showing the results of an experiment comparing the bending moments of the prior art and this embodiment in hairpin bending. Point A in the figure shows the conventional technology, with no vibration,
The bending moment in the presence of oil, point B, shows this example, and shows the bending moment in the state with vibration and without oil. From these results, it can be seen that in this example, the bending moment during bending is smaller than in the prior art, and the slidability between the refrigerant pipe and the mandrel is further improved. FIG. 3 is a cross-sectional view of a hairpin-shaped refrigerant tube made by the method of this example, and shows that there are no dents or the like.

The method of this embodiment described in detail above provides the following effects. (1) Adding ultrasonic vibration improves lubricity during hairpin bending, eliminating the need for oil. (2) The moment during bending is reduced, and dents on the inside of the bent portion of the refrigerant pipe can be prevented. (3) Since no oil is used, the cleaning process can be omitted, resulting in cost reduction.

0012

Effects of the Invention: In the hairpin bending method for refrigerant pipes, etc. of the present invention, ultrasonic vibrations are applied to the mandrel, so the sliding properties between the pipe and the mandrel during bending are improved, and oil is removed. There is no need to use it, the bending moment is reduced, and dents, etc. that conventionally occur inside the bent portion of the pipe are prevented. Furthermore, since no oil is used, the cleaning process after bending can be omitted, resulting in cost reduction.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment of the present invention.

FIG. 2 is an experimental result diagram comparing the bending moment between the above embodiment and the prior art.

FIG. 3 is a cross-sectional view of a hairpin-shaped refrigerant tube manufactured according to the above embodiment.

FIG. 4 is a plan view showing conventional hairpin processing.

FIG. 5 is a cross-sectional view of a hairpin-shaped refrigerant tube manufactured by a conventional method.

[Explanation of symbols]

1 Pressure type 2 Bending mold 3 Clamp type 4 Arm 5 Refrigerant pipe 6 Mandrel 7 Mandrel holding rod 8 Oscillator 9 Horn

Claims (1)

[Claims] 1. Restraining the lateral movement of about half of the tube, inserting a mandrel through the end of that section of the tube, holding the mandrel in a fixed position outside the tube, and restraining the other half of the tube. The half part is sandwiched between a bending die and a clamp die that follows the same bending die, and the bending die, clamp die, and the part of the tube sandwiched between these are rotated as one body around the center of the bending die, and the tube is placed on a mandrel. 1. A hairpin bending method for refrigerant pipes, etc., in which refrigerant pipes, etc., are bent along a bending die while sliding against the mandrel, the method comprising applying ultrasonic vibration to the mandrel.