JP2003062608A - Machining method for inner grooved tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a machining method for an inner grooved tube, which enables reduction of localized wear of a grooved plug and manufacturing an inner grooved tube with uniformly high fins in the longitudinal direction inside the tube material. SOLUTION: A floating plug and a grooved plug connected to the floating plug in a relatively rotatable manner via a connecting shaft are inserted into a tube material, and while the tube material is subjected to a successive reducing work by a holding die and plural pieces of rolling balls, the floating plug is connected to the holding die so as to position the grooved plug at a position arranged for the rolling balls, and a groove profile of the grooved plug is transferred onto the inside surface of the tube material by pressing the inside surface of the tube material on the grooved plug with the rolling balls. In the machining method for the inner grooved tube, the profile of the groove is transferred to the inside surface of the tube material by rotational driving of the rolling balls around a central axis intersecting the axis of the tube at an angle θ.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing an inner grooved pipe in which a groove is formed on the inner surface of the pipe, and more specifically, an inner surface used in air-cooled heat exchangers for home and commercial air conditioners. The present invention relates to a method for processing a grooved heat transfer tube.

[0002]

2. Description of the Related Art An inner grooved tube in which a spiral groove is formed on the inner surface of the tube to improve heat transfer efficiency is used for a condenser and an evaporator of an air-cooled heat exchanger. FIG. 8 is a schematic cross-sectional view in the direction of a pipe central axis (hereinafter referred to as a pipe axis) showing a conventional processing apparatus for an inner grooved pipe. A conventional apparatus and method for processing an inner grooved tube will be described with reference to FIG.

A floating plug 2 is provided inside the tube 8.
Has been inserted. The floating plug 2 has an outer diameter on the pipe supply side (the left side is the supply side and the right side is the drawing side in the drawing) slightly smaller than the inner diameter of the raw pipe 8, and the outer diameter on the pipe drawing side is that on the pipe supply side. It has a smaller truncated cone shape. On the outer surface of the base pipe 8 at a position corresponding to the floating plug 2, the base pipe 8 together with the floating plug 2 is attached.
The holding die 1 for reducing the diameter is arranged.

A substantially cylindrical grooved plug 3 is connected to the floating plug 2 via a connecting shaft 4.
A groove having a shape to be formed on the inner peripheral surface of the shell 8 is formed on the outer peripheral surface of the grooved plug 3. Further, the grooved plug 3 can freely rotate about the connecting shaft 4.
A plurality of rolling balls 5 are arranged side by side in the pipe circumferential direction on the outer surface of the shell 8 at a position corresponding to the grooved plug 3. The rolling balls 5 are accommodated in the processing ring 21 and are arranged at appropriate intervals with respect to each other, and the processing balls 21 hold the rolling balls 5 at predetermined positions in the tube axis direction.

The processing ring 21 is the drive shaft 2 of the motor 9.
Connected to 2. The motor 9 has a cylindrical drive shaft 22.
And a coil 23 for rotating the drive shaft 22 by a magnetic field
And has a drive shaft 22 by supplying power to the coil 23.
Is driven to rotate, and the processing ring 21 is driven to rotate coaxially with the pipe axis. Due to the rotation of the processing ring 21, the compaction balls 5 rotate in the circumferential direction around the pipe axis. The tube 8 passes through the center of the motor 9. Also, rolling balls 5
On the downstream side of the tube drawing direction, a finishing die 7 for contracting the outer diameter of the tube 8 having fins on its inner surface to a predetermined size is provided in contact with the tube 8.

The conventional processing method using the internal grooved pipe processing apparatus configured as described above is as follows. The floating plug 2 is inserted into the tip of the raw tube 8 and its position is held by mechanical or magnetic means.
Then, from this state, the tip of the raw pipe 8 is supplied to the finishing die 7 through the holding die 1, and the holding of the floating plug 2 is released. After that, the floating plug 2 moves to a position corresponding to the holding die 1 with the movement of the drawing of the raw tube 8. Then, by pulling out thereafter, the raw tube 8 is contracted by the floating plug 2 and the holding die 1, further contracted by the rolling balls 5 which follow, and receives the rolling force by the rolling balls 5. It is pressed by the grooved plug 3 arranged inside the tube 8.

The grooved plug 3 is connected to the floating plug 2 via a connecting shaft 4, and the floating plug 2 is connected to the holding die 1 by the frictional force caused by pulling out the raw tube 8 and the reaction force from the holding die 1. Since it is stationary at the corresponding position, the grooved plug 3 also remains at the position corresponding to the rolling ball 5. Therefore, the ball compaction ball 5
When the outer peripheral surface of the grooved plug 3 is rotatably driven to rotate in the circumferential direction, the groove shape formed on the outer peripheral surface of the grooved plug 3 is transferred to the inner peripheral surface of the shell 8 by the synergistic action with the grooved plug 3. Thus, the fin 6 is formed. At this time, the grooved plug 3 is rotated by the groove formed on the peripheral surface of the grooved plug 3 by pulling out the raw pipe 8. Further, the raw pipe 8 having the fins 6 formed on its inner surface is subjected to a contracting process by a finishing die 7 to manufacture an inner grooved pipe having a desired outer diameter.

By the way, when the inner grooved pipe is machined by the above-described conventional inner grooved pipe machining method, although the grooved plug 3 is generally made of a super hard material having wear resistance, it is machined. When the length of the raw tube 8 is as long as several thousand meters, even if a cemented carbide material is used as the grooved plug 3, the surface of the grooved portion of the grooved plug 3 (the area pressed by the rolling balls 5) Wears locally. For this reason, if the rolling is continuously performed, for example, the height of the fins 6 may be sequentially lowered. In addition, there is a problem that the tool life of the grooved plug 3 is short.

Moreover, in recent years, further downsizing of the inner grooved tube has been required due to the downsizing of the equipment used. For example, copper pipes with internal grooves for heat exchangers such as air conditioners are dominated by ultra-small diameter pipes with an outer diameter of 6 to 8 mm. In the future, switching to new refrigerants that comply with CFC regulations will lead to smaller and thinner walls. Tend to be. With this,
In order to maintain or improve the performance of the inner grooved tube itself such as heat transfer characteristics, the groove tends to become deeper and higher fin. The fins formed by these small diameter inner surface grooved pipes are high fins having a ratio of 0.025 or more with respect to the outer diameter of the pipe, and in the extremely small diameter copper pipe, for example, the outer diameter of the pipe is 7.0 m.
The height of the crest of the fin is increased to 0.18 mm or more with respect to m. In particular, such a high fin shape causes remarkable wear on the grooved plug surface.

Therefore, in order to solve the above-mentioned problem of wear of the grooved plug, the present applicant has firstly pressed the raw pipe against the grooved plug with a rolling ball to form an inner groove on the inner face of the raw pipe. When transferring and forming, a processing method of an inner grooved tube in which a compaction ball is moved continuously or intermittently in the tube axis direction to process is proposed (JP-A-11-19711).

In the processing method of the inner grooved tube proposed above,
Since the groove processing position of the grooved plug changes, local wear of the grooved plug can be reduced and an inner grooved pipe having uniformly high fins in the longitudinal direction of the inner surface of the raw pipe can be manufactured. A mechanical or electrical device is required to move the pressure ball or the grooved plug in the tube axis direction of the blank tube.

Then, in the course of subsequent development, local wear of the grooved plug can be reduced and an inner grooved pipe having high fins uniformly in the longitudinal direction of the inner surface of the blank can be manufactured. We have developed a processing method for inner grooved pipes with various configurations.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to reduce local wear of a grooved plug and to make uniform in the longitudinal direction of the inner surface of the blank tube. It is intended to provide a method for processing an inner grooved tube which can produce an inner grooved tube having extremely high fins.

[0014]

In order to achieve the above-mentioned object, a method of working an inner grooved pipe according to the present invention (claim 1) is such that a floating plug is provided in a raw pipe and a connecting shaft is connected to the floating plug. A grooved plug that is relatively rotatably connected to each other, and the diameter of the element pipe is sequentially reduced by a holding die and a plurality of rolling balls, and the floating plug is engaged with the holding die to form a groove. Of the inner grooved pipe that transfers the groove shape of the grooved plug to the inner surface of the raw tube by locating the attached plug at the position where the rolling balls are placed and pressing the inner surface of the raw tube against the grooved plug with the rolling balls. In the processing method, the groove shape is transferred to the inner surface of the raw pipe by rotating the compaction ball about a central axis that intersects the pipe axis at an intersecting angle θ. In this case, it is desirable that the intersection angle θ is 1 to 20 degrees (claim 2).

In the above-mentioned structure, the groove is formed on the inner surface of the pipe by rotationally driving the compaction ball about the central axis that intersects the pipe axis at the intersecting angle θ. Therefore, the rolling trajectory of the compaction ball during the groove machining. Is continuously passed through different surfaces of the grooved plug in the tube axis direction, and the different pressure balls press the different surfaces. Therefore, unlike the conventional case where the crossing angle θ = 0 degree, The surface to be pressed is also pressed by the surface that has a width in the tube axis direction, and as a result, local wear of the grooved plug can be reduced compared to the past, and the life of the grooved plug as a whole can be improved, It is possible to manufacture an inner grooved tube having fins that are uniformly tall in the longitudinal direction of the surface. In this case, the range of the intersection angle θ is preferably 1 to 20 degrees. If the intersecting angle θ is less than 1 degree, the local abrasion of the grooved plug cannot be expected to be reduced, which is the same as the conventional method for processing the inner grooved pipe. When the crossing angle θ exceeds 20 degrees and is large, the gap between the grooved plug and the rolling ball fluctuates in the circumferential direction, which causes vibration and causes excessive machining on the groove processing side (narrower clearance side), which causes Breakage occurs.

In order to achieve the above-mentioned object, a method for processing an inner grooved pipe according to the present invention (claim 3) is such that a floating plug is provided inside the raw pipe and the floating plug is relatively disposed via a connecting shaft. Insert the rotatably connected grooved plug, and gradually reduce the diameter of the raw pipe with the holding die and the plurality of rolling balls, and engage the floating plug with the holding die to roll the grooved plug. In the method for processing the inner grooved pipe, which is located at the position where the pressure balls are arranged, and the groove shape of the grooved plug is transferred to the inner surface of the raw pipe by pressing the inner surface of the raw pipe against the grooved plug by the rolling balls, By arranging the pressure balls in the pipe circumferential direction at different positions in the pipe axis direction, and by rotating the pressure balls around the pipe axis, the groove shape is transferred to the inner surface of the raw pipe. is there.

In the above construction, the rolling balls are arranged in the circumferential direction of the pipe at different positions in the pipe axial direction, and the rolling balls are driven to rotate about the pipe axis to form grooves on the inner surface of the pipe. Since the machining is performed, the respective rolling balls during the grooving pass and press on different rotation trajectories, that is, different surfaces in the tube axis direction of the grooved plug. Therefore, the pressed surface of the grooved plug is also pressed by the surface having a width in the tube axis direction, and the groove is transferred with that width, so that local wear of the grooved plug can be reduced as compared with the prior art, and the grooved plug can be reduced. It is possible to improve the life as a whole and manufacture an inner grooved pipe having uniformly high fins in the inner pipe longitudinal direction.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional explanatory diagram of an inner surface grooved portion for explaining a method for processing an inner surface grooved pipe according to the present invention (claim 1), and the basic configuration of the entire inner surface grooved pipe processing apparatus is as follows. The structure is the same as that of the conventional inner grooved pipe processing apparatus shown in FIG. In the following description, the same components as those of the conventional device are designated by the same reference numerals.

The inner surface grooved portion shows only the compaction balls 5 and the grooved plugs 3, but a machining ring 21 accommodating the compaction balls 5 and a coil for rotating a cylindrical drive shaft 22 by a magnetic field as in the conventional case. Motor 9 having 23 and grooved plug 3
And is configured. Then, in the inner groove processing portion in this example, the central axis 10 of the rotation trajectory of the compaction ball 5 is
The processing ring 21 and the motor 9 are held so as to intersect with the tube axis 11 at the intersection angle θ in the central portion of the grooved plug 3.

In the processing method using the apparatus for processing the inner surface grooved tube having the above-described structure, the rotational trajectory of the compaction balls 5 is an elliptical trajectory when viewed in the axial direction of the tube. The rolling ball 5 rotating to the upper side in the figure corresponds to the inner surface of the raw tube 8 on the upper surface 12 of the grooved plug 3, and the rolling ball 5 rotating to the lower side in the figure corresponds to the inner surface of the raw tube 8. The grooves are transferred and formed by pressing on the lower surface 13 of the grooved plug 3. Therefore, as shown in FIG. 2, assuming that the crossing angle is θ and the pipe outer diameter 2R is after groove machining, the surface of the grooved plug 3 against which the raw pipe 8 is pressed is the same as in the conventional machining shown in FIG. 2B. It is expanded by about R · tan θ in the tube axis direction as compared with the method, local wear of the grooved plug 3 can be reduced as compared with the conventional method, the life of the grooved plug 3 as a whole can be improved, and the raw pipe 8 It is possible to manufacture an inner surface grooved tube having fins that are uniformly high in the inner surface longitudinal direction. In addition,
The major axis of the central part in the figure corresponding to the major axis side of the ellipse is the tube 8
Since it is configured to be larger than the outer diameter of the hollow tube, the inner surface of the raw tube 8 is not pressed against the grooved plug 3. Further, reference numeral 3A indicates a region on the surface of the grooved plug 3 which is pressed by the rolling balls 5, and reference numeral 5A indicates a rotation trajectory of the rolling balls 5.

Incidentally, the inner surface grooved processing under the following conditions can be exemplified. (1) Conditions for raw tube Material: Copper Dimensions: Outer diameter 8.0 mm, Tube wall thickness 0.3 mm (2) Conditions for grooved plug 3 Outer diameter: 7.2 mm, Number of grooves: 50, Lead angle: 18 ° ( 3) Processing conditions Drawing speed: 50 m / min Rolled ball rotation speed: 20000 r. p. m. Number of balls: 4 Crossing angle: θ = 15 degrees

In machining the inner grooved pipe under the above conditions, the surface area of the grooved plug against which the blank pipe is pressed is about three times that of the conventional case, and the tool life of the grooved plug is about three times that of the conventional case. In addition, it is possible to continue the processing of the inner surface grooved tube having the fins which are uniformly high in the longitudinal direction of the inner surface of the blank tube.

FIG. 3 is a cross sectional explanatory view of an inner surface grooved portion for explaining the inner surface grooved tube processing method (claim 3) according to the present invention. The inner surface grooved tube shown in FIG. 3 is processed. The basic configuration of the entire apparatus is the same as that of the conventional apparatus for processing the inner grooved tube shown in FIG. 8 as in FIG. In the following description, the same components as those of the conventional device are designated by the same reference numerals.

The inner groove processing portion, like FIG. 1, shows only the rolling balls 5 and the grooved plugs 3, but the processing ring 21 containing the rolling balls 5 and the cylindrical drive shaft 22 are formed by a magnetic field. It has a motor 9 having a coil 23 for rotation and a grooved plug 3. Then, the inner groove processing portion in this example has a cylindrical ball holder 14 for holding the rolling balls 5 at predetermined intervals in the circumferential direction, and the accommodating holes 15 for the rolling balls 5 are formed on the tube shaft as shown in FIG. It is provided so as to be shifted in the direction, the rolling balls 5 are housed in the housing holes 15 and set in the processing ring 21, and the rotation center shaft 16 of the cylindrical ball holder 14 and the tube shaft 11 are concentrically arranged. It was done. Although not shown in the drawings, a cylindrical ball holder is also used in the conventional configuration, and in this case, the accommodating holes are provided at predetermined intervals on the same circumference.

In the processing method using the inner grooved pipe processing apparatus having the above-described structure, since the four rolling balls 5 are provided with a predetermined gap in the pipe axial direction, the rolling balls 5
As shown in FIG. 5, the rotation orbits of each of the rolling balls are also formed at four positions.
The groove is transferred and formed by pressing on the surface of. Therefore, the surface of the grooved plug 3 against which the raw pipe 8 is pressed is enlarged as compared with the conventional processing method shown in comparison with FIG. 2B, and local wear of the grooved plug 3 can be reduced as compared with the conventional method. It is possible to improve the life of the attached plug 3 as a whole and manufacture an inner grooved tube having fins that are uniformly high in the longitudinal direction of the inner surface of the shell 8.

FIG. 6 is an explanatory view showing another example of attachment of the compaction balls according to the present invention to the cylindrical ball holder.
Even if the accommodating holes 15 of the compaction balls 5 are provided in a zigzag manner as in the present example, the same operational effect as the example of FIG. 3 can be obtained.

Although the example shown in FIGS. 3 and 6 has four rolling balls, the present invention is not limited to this example, and a ball holder for rolling balls can be used. It is desirable to determine the number in the range of, for example, about 2 to 6 depending on the mounting space. When three or more balls are provided, two rolling balls 5 may be provided on one rotation track. Furthermore, in the above example, the interval of the rolling balls of the rolling balls in the axial direction of the tube is 0.5 mm at the center of the ball. However, it is preferably within 1 mm at the maximum. Becomes rough,
There is a concern that the inner fins will not be sufficiently formed.

Incidentally, the inner surface grooved processing under the following conditions can be exemplified. (1) Conditions for raw tube Material: Copper Dimensions: Outer diameter 8.0 mm, Tube wall thickness 0.3 mm (2) Conditions for grooved plug 3 Outer diameter: 7.2 mm, Number of grooves: 50, Lead angle: 18 ° ( 3) Processing conditions Drawing speed: 50 m / min Rolled ball rotation speed: 20000 r. p. m. Number of balls: 4 Cylindrical ball holder for rolling balls: Figure 7

In the processing of the inner grooved pipe under the above conditions, since the raw pipe being processed can be pressed at four positions of the grooved plug, the tool life of the grooved plug can be increased to about four times that of the conventional one, and It is possible to continue the processing of an inner grooved pipe having fins that are uniformly high in the longitudinal direction of the inner surface of the pipe.

[0030]

As described above, according to the inner grooved pipe processing method of the present invention, the local wear of the grooved plug can be reduced, and the life of the grooved plug as a whole can be improved. As a result, it is possible to manufacture an inner grooved tube having fins that are uniformly high in the longitudinal direction of the inner surface of the blank tube.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of an inner surface groove processing portion of an apparatus for carrying out an inner surface grooved pipe processing method according to the present invention.

FIG. 2 is a cross-sectional explanatory view of an inner surface grooved portion for explaining a surface state of a grooved plug which is used by pressing a raw pipe during processing of an inner surface grooved pipe, wherein a is an example of the present invention, b shows a conventional example.

FIG. 3 is a cross-sectional explanatory view of an inner surface groove processing portion of another embodiment for carrying out the inner surface grooved pipe processing method according to the present invention.

4A and 4B are explanatory views of a ball holder provided in the inner groove processing portion shown in FIG. 3, in which a is a perspective view and b is a developed view.

5 is a cross-sectional explanatory view of an inner groove processing portion for explaining a surface state of a grooved plug which is used by pressing a raw pipe during processing of an inner grooved pipe according to the embodiment shown in FIG. 3; .

6A and 6B are explanatory views of another ball holder according to the present invention which is provided in the inner groove processing portion shown in FIG. 3, in which a is a perspective view and b is a developed view.

7A and 7B are explanatory views of a ball holder provided in the inner surface groove processing portion used in the inner surface grooved tube processing method according to the present invention, in which a is a perspective view and b is a developed view.

FIG. 8 is a schematic cross-sectional view in the tube central axis direction showing a conventional apparatus for processing a grooved tube on the inner surface.

[Explanation of symbols]

3: Plug with groove 5: Rolled ball
8: Tube 9: Motor 10: Central axis 1
1: Pipe shaft 12: Upper surface of grooved plug 13:
Lower surface 14 of grooved plug: Cylindrical ball holder 15:
Rolling ball accommodating hole 16: central axis of rotation of ball holder 21:
Processing ring 22: Drive shaft 23: Coil θ:
Crossing angle

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) F28F 1/40 F28F 1/40 DF term (reference) 4E028 HA03 HA07 4E096 EA18 FA02 FA04 FA18 FA23 FA24 FA26 FA32 HA15

Claims (3)

[Claims] 1. A floating plug and a grooved plug which is rotatably connected to the floating plug via a connecting shaft are inserted into the raw pipe, and the raw pipe is held by a die and a plurality of rolling balls. By successively reducing the diameter by using, the floating plug is engaged with the holding die to position the grooved plug at the position where the rolling balls are arranged, and the inner surface of the raw pipe is pressed against the grooved plugs by the rolling balls. In a method of processing an inner grooved pipe in which the groove shape of a grooved plug is transferred to the inner surface of the raw pipe, by rotating the compaction ball about a central axis intersecting the pipe axis at a crossing angle θ,
A method for processing an inner grooved pipe, characterized in that the groove shape is transferred to the inner surface of the raw pipe. 2. The method for processing an inner grooved pipe according to claim 2, wherein the intersecting angle θ is 1 to 20 degrees. 3. A floating plug and a grooved plug which is rotatably connected to the floating plug via a connecting shaft are inserted into the raw pipe, and the raw pipe is held by a die and a plurality of rolling balls. By successively reducing the diameter by using, the floating plug is engaged with the holding die to position the grooved plug at the position where the rolling balls are arranged, and the inner surface of the raw pipe is pressed against the grooved plugs by the rolling balls. In a method of processing an inner grooved pipe in which the groove shape of a grooved plug is transferred to the inner surface of a raw pipe, rolling balls are arranged in the circumferential direction at different positions in the axial direction, and the rolling balls are A method for processing an inner surface grooved pipe, characterized in that the groove shape is transferred to the inner surface of the raw tube by rotating the tube around the tube axis.