JP3337880B2 - Manufacturing method of heat transfer tube with double groove - 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 drawing a double grooved heat transfer tube used for a heat exchanger of a refrigerator or an air conditioner at a high speed.

[0002]

2. Description of the Related Art A heat transfer tube used in a heat exchanger for an air conditioner such as a refrigerator or a room air conditioner is provided with a refrigerant such as freon gas (Freon is a trade name of DuPont for fluorochloro-substituted hydrocarbons). And evaporates or condenses the refrigerant to exchange heat with the fluid flowing outside the tube. As the heat transfer tube, as shown in FIG. 6, a heat transfer tube with an inner surface groove having a large number of fine grooves 27 formed on the inner surface to improve heat transfer characteristics is frequently used. By the way, Freon R22 and R12 have been conventionally used as the refrigerant, but since these destroy the ozone layer, a plan to completely eliminate them from the viewpoint of environmental conservation is being advanced. Alternatives to Freon R22, R12 include Freon R32, R134a, R12, which do not affect the ozone layer.
5 and so on. In particular, these refrigerants were mixed [R
32 / R134a / R125] and mixed refrigerants such as [R32 / R125]
It has a cooling capacity close to that of conventional Freon R22 and the like, and is highly evaluated as a substitute because of its nonflammability.

The above-mentioned mixed refrigerants include an azeotropic refrigerant and a non-azeotropic refrigerant, and the above-mentioned [R32 / R134a / R125] and [R32 /
R125] and the like are non-azeotropic refrigerants. An azeotropic refrigerant is
Although the liquefaction start temperature (dew point) and the liquefaction end temperature (boiling point) are the same and show the same behavior as a single refrigerant, there is no particular problem,
Since the non-azeotropic refrigerant has a different liquefaction start temperature and liquefaction end temperature, when the refrigerant evaporates or condenses, the high-boiling components concentrate on the liquid phase side and the low-boiling components concentrate on the gas phase side. This concentration difference causes diffusion resistance and heat resistance, and lowers the heat transfer coefficient in evaporation or condensation. For this reason, in a boiling heat transfer tube using a non-azeotropic refrigerant, as shown in FIG.
25, 26 (cavity structure), a turbulent flow effect of the refrigerant was activated to promote the boiling, and a double grooved heat transfer tube was developed (Japanese Patent Application Laid-Open No. 1-317637).

[0004] By the way, the heat transfer tube with a double groove has a double groove, so that the friction resistance and the plastic deformation resistance at the time of drawing are twice as large as those of a single groove (FIG. 6). Therefore, there is a problem that the drawing cannot be performed at a high speed. As a countermeasure, there is a method of reducing the resistance applied to the tube by changing the spiral projections provided on the two grooved plugs so that the inclination with respect to the axis is different in the same direction and the pressing member is changed from a roll to a ball. 57-36016) Applied. In this method, as shown in FIG. 8, a metal tube 10 is reduced in diameter by a die 11 and a floating plug 12, and then two plugs having a spiral groove formed in the outer periphery are formed in the reduced diameter metal tube 20. 21,22
The balls 31 and 32 are pressed from the outside while pulling the planets while rotating in a planetary manner, and are pulled out, and finally processed into the double grooved heat transfer tube 28 through the finishing die 59. The method of gripping the balls 31 and 32 in the above method is as shown in FIG.
The conical surfaces of the members 71 to 73 each having a conical surface are pressed against the balls 31 and 32 whose distance is defined by 70 from the outside.

[0005]

However, in the above-described method of manufacturing a heat transfer tube with a double groove, the metal tube 20 is hardened by the first groove processing, and a trace of the ball 31 remains on the surface. For this reason, in the second groove processing, the ball 32 rolls irregularly on the surface of the metal tube 20 and starts to run out. This run-out cannot be suppressed only by the conical surfaces of the members 71 to 73, and therefore, the inner surface formed The shape of the grooves became non-uniform, and the heat transfer characteristics deteriorated. In addition, if the ball is accelerated in planetary rotation (revolution) and high-speed withdrawal is performed, the centrifugal force acting on the ball increases and the ball ramps up more and more. There was a problem of doing. An object of the present invention is to provide a method for manufacturing a heat transfer tube with a double groove which can be drawn at a high speed.

[0006]

According to the present invention, two grooved plugs provided with a large number of grooves on the outer peripheral surface thereof are rotatably held in a drawing direction in a metal tube drawn in a predetermined direction. The first and second rows of balls are arranged on two outer peripheral surfaces of the metal tube holding the plug, respectively.
The method of forming a double groove in the inner surface of the metal tube by pressing the balls in the second and second columns against the outer peripheral surface of the metal tube while rotating the planets, wherein the balls in the first and second columns are formed. Are defined on the outer sides of the balls in the first and second rows, respectively, and the distance between the balls in the circumferential direction is defined.
While gripped by the ball cage for each row, machining f
One row by a ball retainer rotatably mounted on a pad
Do not move the ball in the eye and the second row in the pull-out direction
A method for manufacturing a heat transfer tube with double grooves, characterized in that the heat transfer tube is positioned in a tube axis direction .

In the present invention, the balls in the first and second rows are
Since the ball is held by the flanges arranged on the outer sides of the balls in the first and second rows and the ball retainer that defines the distance between the balls, the ball can be sufficiently prevented from ramping up.
Therefore, a double groove having different directions with respect to the tube axis can be formed at a high speed. Further, in the present invention, the force applied in the pulling-out direction of the first row of balls and the second row of balls is received by one ball holder, so that the processing head can be reduced in size and weight, and a drive motor for rotating the processing head can be obtained. Power consumption can be reduced.

In the present invention, the angle θ of the holes 62 of the second row of balls formed in the ball retainer is set to 40 to 90 degrees,
By increasing the thickness of the inner surface or the end of the surface of the wall portion, the damage can be reliably prevented. By setting the clearance C between the ball 32 and the hole 62 to 0.50 mm or less, it is possible to more reliably prevent the ball 32 from running out (see FIG. 2).

[0009] In order to press the ball firmly against the ball retainer and to prevent the ball from running out, the force in the pulling direction applied to one ball at the time of grooving is made sufficiently larger than the centrifugal force applied per ball in the radial direction. There is a need. When a double grooved heat transfer tube having an outer diameter of 10 to 6 mm commonly used in an air conditioner or the like is manufactured at a high speed according to the present invention, the first row and the second row are used.
The total number of balls in the row is 4-6, the ball diameter is 6-15mm,
Outer diameter of grooved plug is 5 to 12 mm, groove depth is 0.1 to 0.3 m
m is appropriate.

In the present invention, if the total number of balls in the first row and the second row is less than 4, the axis of the metal tube swings during the drawing process, making it difficult to form grooves. On the other hand, the balls are gripped by the ball retainer by the pulling force. When the number of balls is too large, the pulling stress applied per ball decreases,
When the centrifugal force exceeds this, the ball starts to rampage. Therefore, the total number of balls in the first and second rows is preferably 4 to 6. It is effective to increase the number of balls to be distributed in the first row and the second row to the greater groove processing force. The grooving force depends on the depth, number, etc. of the groves. When the total number of balls is four, there are two ways of distributing them, two each, and one and three. There is an advantage that the shaft is less likely to run out during the drawing process while being held.

[0011]

The present invention will be described below in detail with reference to examples. Example 1 FIG. 1A is an explanatory view showing an example of a method for manufacturing a heat transfer tube with double grooves according to the present invention. A copper tube 10 having an outer diameter of 13 mm is reduced in diameter by a die 11 and a floating plug 12, and first and second two outer peripheral grooved plugs (hereinafter referred to as plugs) are provided inside the reduced diameter copper tube 20. Abbreviations) 21 and 22 are arranged, and the first row of balls 31 and the second row of balls 32, which rotate in a planetary manner, are pressed from the outside to form a double groove on the inner surface of the copper tube. (Not shown) to finish to a predetermined outer diameter. The first and second two plugs 21 and 22 were integrally connected to and supported by the mandrel 13 at the end of the floating plug 12. The balls 31 and 32 in the first and second rows are loosely fitted in the holes of the ball holders 51 and 52, respectively. The ball retainer 52 is rotatably mounted on the processing head 53 via a bearing 54. The first end of the processing head 53
And two second cylindrical flanges 54 and 55 are attached, and the first and second rows of balls 31 and 32 are in contact with the inner surfaces of the cylindrical flanges 54 and 55, respectively. Is suppressed. The movement of the balls 31 and 32 in the first and second rows in the pulling-out direction is suppressed by the ball holder 52.

Here, the inner peripheral surfaces of the cylindrical flanges 54, 55 are slightly reduced in diameter in the pull-out direction.
Is moved in the axial direction to finely adjust the distance between the flanges 54 and 55 and the copper tube 20 to adjust the pressing force of the balls 31 and 32 on the copper tube 20. To move the flanges 54 and 55 in the axial direction, the thickness of the liners 56 and 57 is changed. FIG. 1B is a view taken in the direction of the arrow AA. The two balls 32 in the second row are the second
The copper tube fits into the hole 62
They are arranged to face each other with 20 therebetween. The configuration of the ball portion in the first row is the same as that of the ball portion in the second row, and a description thereof will be omitted.

When the processing head 53 is rotated, the balls 31 and 32 rotate around the copper tube 20 in a planetary rotation. When the copper tube 20 is pulled out in this state, a first groove is formed by the balls 31 in the first row, and a second groove is formed by the balls 32 in the second row.

According to the method shown in FIG. 1, a double grooved heat transfer tube having an outer diameter of 9.53 mm was manufactured. The first plug has an outer diameter of 9.8
mm, the number of grooves was 70, the twist angle was 25 degrees (the twist direction was left), and the groove depth was 0.10 mm. The second plug has an outer diameter
9.5 mm, the number of grooves was 50, the twist angle was 10 degrees (the twist direction was right), and the groove depth was 0.20 mm. Outer diameter for ball
The clearance C between the ball in the second row during the groove processing and the hole of the second cage was 0.1 mm, and the hole angle θ was 60 degrees (see FIG. 2). The number of balls in the first and second rows was varied.

As shown in FIG. 4, the shape of the inner surface groove of the manufactured heat transfer tube is such that the direction of the grooves 25 and 26 is different from the tube axis. Fins 24 and grooves 25 with a height of 0.20 mm in the first groove processing
The fins 24 were intermittently crushed by the second groove processing to form the grooves 26. The force required for the groove processing was larger in the first groove processing than in the second groove processing.

(Embodiment 2) FIG. 3 is an explanatory view of a ball holding method according to a second embodiment of the present invention. In this method, the ball 31 in the first row and the ball 32 in the second row are held by one ball holder 58, and the balls 31 and 32 in the drawing direction are held by the ball holder 58.
The movement of is suppressed. Others are the same as FIG.

The ball was gripped by the method shown in FIG. 3 to produce a double grooved heat transfer tube having an outer diameter of 6.5 mmφ. A copper tube having an outer diameter of 10 mm was used. In the first plug,
The outer diameter is 7.6mm, the number of grooves is 50, the torsion angle is 20 degrees (the torsion direction is right), and the groove depth is 0.20mm.
The outer diameter was 7.2 mm, the number of grooves was 20, the twist angle was 20 degrees (the twist direction was left), and the groove depth was 0.30 mm. The ball diameter was 7.0 mm for the first row and 6.5 mm for the second row.

Comparative Example 1 A ball was gripped by the conventional method shown in FIG.
A double grooved heat transfer tube was manufactured in the same manner as in Example 1.

The inner groove shape and appearance of the double grooved heat transfer tube manufactured by each of the above methods were examined. Table 1 shows the results.

[0020]

[Table 1]

As is clear from Table 1, the products of the present invention (N
o.1 to 5) all had good inner groove shape and appearance. Regarding the number of balls arranged in the first and second rows, 4-2 (No. 1), in which a larger number of balls are arranged in the first row having a greater groove processing force,
Pulling was performed more stably than 2-4 (No. 2). The same production was performed with the total number of balls being 7 (4-3). However, since the drawing stress applied per ball was reduced, the appearance and the drawing stability were slightly reduced. On the other hand, the conventional product has a low revolving speed of 20,000 rpm and a low drawing speed of 40 m / min. (No. 6)
However, the inner groove shape and appearance were slightly poor, and when the revolving speed and pulling speed of the ball were increased to 30,000 rpm and 50 m / min, respectively (No. 7), the ball in the second row became severer. Both the inner groove shape and the appearance were poor. Further, when the number of balls was reduced (No. 8), the metal tube was broken. still,
In the present invention, the force applied in the pulling-out direction of the first row of balls and the second row of balls is received by one ball holder, so that the processing head is reduced in size and weight, and the power consumption of the processing head rotating motor is reduced. Savings.

Example 3 In Example 1, a heat transfer tube with double grooves was manufactured by changing the shape of the hole of the ball cage in various ways. Table 2 shows the results.

[0023]

[Table 2]

As is clear from Table 2, when the hole angle of the ball cage is 40 to 90 degrees and the clearance is 0.1 to 0.5 mm (Nos. 10 to 13, 15), the hole wall ends may be damaged. Without the ball, the ball also rotated well. However, in Nos. 9 and 14, the hole angle θ was too small or too large, so the inner or inner side of the hole wall became thin and partially damaged, and in No. 16 the clearance was narrow and the ball rotated. Was slightly hindered, and in No. 17, the clearance was too large and the ball was slightly hit. However, there was no practical problem in the quality of the obtained heat transfer tubes.

A non-azeotropic refrigerant [R32 / R134a / R125] was placed in the No. 1 double grooved heat transfer tube manufactured by the method of the present invention, and the evaporative heat transfer coefficient in the tube was measured. As a result, as shown in FIG. 5, the heat transfer characteristic was higher than that of a conventional single grooved inner grooved tube with R-22.

[0026]

As described above, according to the present invention, a double grooved heat transfer tube suitable for accelerating the boiling of a non-azeotropic refrigerant can be produced at a high speed, which has a remarkable industrial effect.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a first embodiment of a method for manufacturing a heat transfer tube with double grooves according to the present invention.

FIG. 2 is an explanatory diagram of a contact portion between a hole of a ball retainer and a ball.

FIG. 3 is an explanatory view of a ball holding method showing a second embodiment of the method of manufacturing a double grooved heat transfer tube of the present invention.

FIG. 4 is a perspective view of an inner surface groove in which the direction of the groove of the double grooved heat transfer tube is different from the tube axis.

FIG. 5 is a diagram showing the relationship between the heat transfer coefficient of refrigerant and the flow rate of refrigerant in a double-groove heat transfer tube manufactured by the method of the present invention.

FIG. 6 is a perspective view of an inner surface groove of the heat transfer tube with a single groove.

FIG. 7 is a perspective view of a heat transfer tube with double grooves.

FIG. 8 is an explanatory diagram of a conventional method for manufacturing a double grooved heat transfer tube.

FIG. 9 is an explanatory view of a ball portion in a conventional method for manufacturing a heat transfer tube with double grooves.

[Explanation of symbols]

 10 Metal tube 11 Die 12 Floating plug 13 Mandrel 20 Reduced metal tube 21,22 Plug with outer circumferential groove 24 ... Fins 25, 26, 27 ... Groove 28 ... Heat transfer tube with double grooves 31 ... Balls in first row 32 ... Balls in second row 51, 52, 58 ... Ball retainer 53 ……… Working head 54,55… Flange 56,57… Liner 59 ……… Finishing dies 61,62… Holes opened in the ball cage 70 ………… Spacers 71,72,73… Member having a conical surface

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-6016 (JP, A) JP-A-60-15015 (JP, A) JP-A-62-263820 (JP, A) JP-A-6-263820 134515 (JP, A) Japanese Utility Model Hei 5-39710 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21C 1/00-19/00 B21D 17/00 B21D 53/06 F28F 1/40

Claims (3)

(57) [Claims] 1. A metal pipe drawn in a predetermined direction,
Two grooved plugs provided with a large number of grooves on the outer peripheral surface are rotatably held in the pulling direction in order, and the first row is provided on each of the two outer peripheral surfaces of the metal tube holding the plug. 2
Arrange the balls in the first row and the balls in the first and second rows,
Pressing the outer peripheral surface of the metal tube while rotating the planet,
In the method of forming a double groove in the inner surface of the metal tube, a flange in which the first and second rows of balls are disposed outside the first and second rows of balls, respectively , It is gripped by the ball holders in each row that defines the spacing between the balls, and is rotatably attached to the processing head.
Pull out the first and second rows of balls using a ball holder
A method for manufacturing a heat transfer tube with a double groove, characterized in that the tube is positioned in the tube axis direction so as not to move in the tube direction . 2. Using two ball retainers, the first ball retainer defines the distance between the balls in the first row, and the second ball retainer defines the distance between the balls in the second row. Prescribe and pull out the first and second rows of balls
2. The method for manufacturing a double grooved heat transfer tube according to claim 1, wherein the tube is positioned in the tube axis direction so as not to move in the direction . 3. The total number of balls in the first and second rows is 4 to
The method according to claim 1 or 2, wherein the number of the heat transfer tubes is six.