JP2756194B2 - Method for manufacturing inner double grooved pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a grooved tube used in a heat exchanger such as a refrigerator or an air conditioner.

[0002]

2. Description of the Related Art Generally, a heat transfer tube used for a heat exchanger of an air conditioner or a refrigerator is a device in which chlorofluorocarbon or the like is flown as a refrigerant in a tube to perform heat exchange with outside air conditioning of the tube. The use of internally grooved tubes having triangular or trapezoidal grooves of .53 and 7.0 mm has led to higher efficiency and more compact heat exchangers. However, since there is a strong demand for more compact and higher efficiency, an inner surface double grooved tube in which spiral grooves cross each other instead of the conventional inner surface grooved tube and a method of manufacturing the same have been developed. By forming a groove twice on the inner surface of the tube, the inner surface double grooved tube makes the groove shape more complicated, activates the turbulent flow effect, and increases the heat transfer area as compared with the conventional single groove. In addition, a cavity can be formed on the inner surface of the tube in order to promote boiling, and the heat transfer performance can be greatly improved (Japanese Patent Application Laid-Open Nos. 57-150799 and 1-317637). As its manufacturing method, rolling rollers for diameter reduction processing are arranged in two stages coaxially with the drawing die, plugs for groove processing connected to floating plugs are arranged at positions corresponding to each roller, and doubled. There is known a method of forming a groove. However, such a high performance pipe is not used in a small air conditioner which is particularly required to be compact and highly efficient. One of the problems is that a small diameter of 8 to 4 mmφ used in such a small air conditioner is used. When the inner surface double grooved pipe is manufactured by the conventional method, the friction resistance and plastic deformation resistance at the grooved part are doubled because double groove processing is performed compared to single groove processing. If the speed exceeds a certain value during continuous drawing groove processing, the tensile strength of the pipe exceeds the resistance applied to the pipe, and the pipe breaks. In particular, this tendency becomes remarkable as the pipe becomes smaller in diameter, and the processing speed is greatly reduced as compared with the conventional single-sided grooved pipe.
For this reason, a method of providing a continuous pipe drawing device between the first inner groove processing portion and the second inner groove processing portion has been devised as in JP-A-60-15015. However, if such a method is used in actual production, the size of the apparatus is inevitably increased.

[0003]

DISCLOSURE OF THE INVENTION As a result of studying the above problems, the present invention has developed a method of manufacturing an inner double grooved pipe having a superior performance without reducing the processing speed by a relatively simple method. It was done.

[0004]

According to the present invention, a rolling tool for reducing the diameter while rotating in a planetary manner on a plane perpendicular to the tube axis coaxially with the drawing die is arranged in two stages. A grooved plug connected to a drawing plug is arranged at a corresponding position of a forming tool, and after a grooved plug having an outer diameter of 7.5 mm or more is formed in a manufacturing method of continuously forming a groove in a pipe continuously, the grooved plug is set to 1 This is a method for producing a double-grooved tube with an inner surface, characterized in that a small diameter processing of 10 to 50% is performed by drawing or drawing twice or more times to finish the outer diameter to 8 to 4 mm. That is, the present invention is to produce a double-grooved tube on the inner surface by an apparatus as shown in FIG. 1, for example. In this apparatus, a floating plug 2, a first grooved plug 3 for grooved processing, and a second grooved plug 4 are connected by a tie rod 5 inside a drawing die 22.
A first rolling roller 6 and a second rolling roller 7 are provided outside the grooved plug. The base tube 1 is reduced in diameter by a floating plug and a drawing die, forms a groove inclined or not inclined in one direction on an inner surface by a first grooved plug and a first rolling roller, and forms a second grooved plug and a second By forming a groove crossing the above groove by a rolling roller, for example, an inner surface double having a groove 9 and a peak 10 as shown in FIG. 2 and forming a cross groove 11 crossing the groove 9 is formed. A grooved tube 8 is manufactured. Further, the present invention can also produce an inner surface double grooved tube 8 having a groove portion 9 and a peak portion 10 having a cross portion 11 at a cross groove 11 as shown in FIG. In the grooved tube, the flow of the refrigerant liquid in the groove changes due to the presence of the above-mentioned misalignment, and the heat transfer performance is improved.

[0005]

According to the manufacturing method of the present invention, a double-grooved tube which could not be subjected to high-speed groove processing in the past, in particular, a small-diameter inner-surface double-grooved tube is replaced with a conventional single-inner-groove tube. It can be manufactured at a high speed. In the present invention, the outer diameter of the grooved plug is 7.5.
The reason why the diameter is not less than mm is that when the diameter is less than the above value, the outer diameter of the raw tube becomes thin, and it becomes impossible to form a double groove at high speed. The reason why the emptying rate after the groove processing is set to 10% to 50% is that when the airtightness exceeds 50%, the scraping 13 frequently occurs on the outer surface of the tube as shown in FIG. 4 during emptying. On the other hand, if it is less than 10%, the conventional method cannot be used, and the processing speed at the time of forming a small-diameter pipe groove cannot be increased.

[0006]

An embodiment of the present invention will be described below.
Using an apparatus as shown in FIG. 1, an outer diameter of 12.7 was used as a raw tube.
Although not shown, a phosphoric acid deoxidized copper tube of mm × 0.45 mm in thickness is pulled in the direction of the arrow A by a pulling device such as a continuous drawing machine. In this pipe, a floating plug 2 and a first grooved plug 3 for groove processing have an outer diameter φ9.9.
mm and a second grooved plug 4 having a diameter of 9.5 mm is inserted into a floating plug and revolved from the outer surface of the tube to reduce the diameter of the copper tube. The groove was reduced to form a double groove on the inner surface of the tube. Here, a large number of fine first grooves having 90 grooves, a lead angle (left-handed twist) of 18 °, and a groove depth of 0.10 mm were formed on the heat transfer surface by the first grooved plug 3 and the first rolling roller 6. Formed, and then the number of grooves is 60, the lead angle (right-hand twist) is 18 °, and the groove depth is 0.16 by the second grooved plug 4 and the second rolling roller 7.
mm groove is formed so as to crush the first groove, and the second groove 9 as shown in FIG. 2 crushes the first groove 11 to form the cross groove 11 and forms an inner surface with an outer diameter of 10 mm. A double grooved tube was formed. After that, when winding into a coil by a winder, the drawing is performed by a die and the drawing rate is 3
At 0%, the product was finished with an outer diameter of 7.00 mm.

[0007] In comparison with the conventional method, when the same product is double-grooved and finished with a drawing rate of 10% or less, for example, the base tube is 9.53 mm x 0.40 mm thick. Then, using a first grooved plug outer diameter of 7.5 mm and a second grooved plug outer diameter of 7 mm, a grooved outer diameter of 7.
Compared to a case where a 5 mm grooved tube was wound around a coil (drawing ratio: 7%) while finishing the outer diameter to 7.00 mm, the production amount per unit time was 7.30% by the drawing ratio of 30% according to the present invention. The case finished to 00 mm is about 2.8 times, which is almost the same as the case of the conventional single inner grooved tube. One of the reasons is that the outer diameter of the tube is large when grooved, so the weight per unit length is heavy, and even if grooved at the same processing speed, the production volume per unit time increases. It is. On the other hand, if you want to make a double groove on the inner surface,
The frictional resistance and plastic deformation resistance in the grooved part take twice as much as that with a single groove, and the narrower the raw tube, the lower the speed limit for continuous drawing groove processing, inevitably per unit time This is because the production amount decreases. However, if the drawing rate is set too large during the drawing drawing after such groove formation, (5)
(0% is the limit) Insufficient mark-to-claw frequent, and conversely, the amount of non-defective products per unit time is drastically reduced. Next, in the production of the inner surface double grooved tube in which the cut-shaped cross groove 11 having the deviation portion 12 as shown in FIG. 3 is formed, the groove is shifted along the cross groove when drawing by drawing. By forming the deviation portion 12, the flow of the refrigerant liquid in the groove collides with one side of the mountain portion 10 to disturb the flow, and the flow of the liquid is A stagnation holding section is formed, and a liquid film distribution is formed in the groove to improve heat transfer performance. In addition, due to the turbulent flow action of such a deviation portion, there is also an effect of removing refrigerating machine oil and dirt which adhere to the inside of the cross groove 11 and cause deterioration in performance. The thus-obtained double-grooved tube was assembled in a double-type heat exchanger, a refrigerant was flowed in the tube, water was flowed in the annular portion to perform heat exchange, and evaporation heat transfer was obtained. Table 1 shows the experimental conditions at that time.

[0008]

[Table 1]

FIG. 5 shows the heat transfer coefficient in the tube during the evaporation. FIG. 6 shows a conventional 7.00 mm as shown in FIG.
The results are also shown for a single inner grooved tube (number of grooves 60, twist angle 18 °, groove depth 0.15 mm). According to this, the inner surface double grooved tube according to the production method of the present invention showed twice as high evaporation performance as the conventional inner surface grooved tube.

[0010]

As described above, according to the method for manufacturing the inner surface double grooved tube of the present invention, the inner surface grooved tube is about two times smaller than the conventional inner surface grooved tube.
An inner double grooved tube having twice the evaporation performance can be manufactured at approximately the same weight per unit time as a conventional single inner grooved tube.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an apparatus used for manufacturing an inner surface double grooved tube of the present invention.

FIG. 2 is a perspective view of an essential part showing an example of an inner double grooved tube manufactured according to the present invention.

FIG. 3 is a perspective view of an essential part showing an example of an inner surface double grooved tube manufactured according to the present invention.

FIG. 4 is a cross-sectional view of a grooved tube having a mark portion generated during manufacturing of an inner surface double grooved tube.

FIG. 5 is a diagram showing the relationship between the evaporation heat transfer coefficient and the refrigerant flow rate of the inner double-grooved tube manufactured according to the present invention.

FIG. 6 is a perspective view of a main part of a conventional inner grooved pipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base tube 2 Floating plug 3 First grooved plug 4 Second grooved plug

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-42112 (JP, A) JP-A-4-266417 (JP, A) JP-A-2-197551 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) B21C 1/00

Claims (1)

(57) [Claims] 1. A rolling tool for reducing the diameter while rotating in a planetary manner on a plane perpendicular to the tube axis coaxially with a drawing die is arranged in two stages, and a drawing plug is provided at a position corresponding to each rolling tool. In the manufacturing method of arranging a grooved plug connected to the pipe and doubling the groove continuously in the pipe, after grooving with a grooved plug having an outer diameter of 7.5 mm or more, once or twice or more emptying is performed. A method for producing a double-grooved tube with an inner surface, characterized in that a small-diameter processing of 10 to 50% is performed by drawing and finishing to an outer diameter of 8 to 4 mm.