JP4647855B2 - Internal grooved tube processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method for processing an internally grooved tube in which a groove is formed on the tube inner surface, and more specifically, a method for processing an internally grooved heat transfer tube used in an air-cooled heat exchanger such as a domestic or commercial air conditioner. It is about.
[0002]
[Prior art]
In the condenser and the evaporator of the air-cooled heat exchanger, an internally grooved tube in which a spiral groove is formed on the tube inner surface to improve heat transfer efficiency is used. FIG. 8 is a schematic cross-sectional view in the direction of the tube center axis (hereinafter referred to as the tube axis) showing a conventional processing apparatus for internally grooved tubes. A conventional processing apparatus and processing method for an internally grooved tube will be described with reference to FIG.
[0003]
A floating plug 2 is inserted into the base tube 8. This floating plug 2 has an outer diameter on the tube supply side (the left side in the drawing is the supply side and the right side is the extraction side) slightly smaller than the inner diameter of the raw tube 8, and the outer diameter on the tube extraction side is that of the tube supply side. It is a smaller truncated cone shape. A holding die 1 for reducing the diameter of the pipe 8 together with the floating plug 2 is arranged on the outer surface of the pipe 8 at a position corresponding to the floating plug 2.
[0004]
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 raw tube 8 is processed 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 raw pipe 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 an appropriate distance from each other, and the rolling balls 5 are held at predetermined positions in the tube axis direction by the processing ring 21.
[0005]
The processing ring 21 is connected to the drive shaft 22 of the motor 9. The motor 9 has a cylindrical drive shaft 22 and a coil 23 that rotates the drive shaft 22 by a magnetic field. By supplying power to the coil 23, the drive shaft 22 is rotationally driven, and the machining ring 21 is coaxial with the tube axis. Rotate on top. By the rotation of the processing ring 21, the rolling ball 5 rotates in the pipe circumferential direction around the pipe axis. Note that the raw tube 8 passes through the center of the motor 9. Further, on the downstream side of the rolling ball 5 in the tube drawing direction, a finishing die 7 for reducing the outer diameter of the raw tube 8 having fins formed on the inner surface to a predetermined size is provided in contact with the raw tube 8. Yes.
[0006]
A conventional processing method using the processing device for an internally grooved tube 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. From this state, the tip of the raw tube 8 is supplied to the finishing die 7 through the holding die 1 and the holding of the floating plug 2 is released. Thereafter, the floating plug 2 moves to a position corresponding to the holding die 1 as the raw tube 8 starts moving. Then, the tube 8 is contracted by the floating plug 2 and the holding die 1 by the subsequent drawing, and further contracted by the subsequent rolling ball 5, and receives the rolling force by the rolling ball 5 to receive the element. The grooved plug 3 disposed inside the tube 8 is pressed.
[0007]
The grooved plug 3 is connected to the floating plug 2 through a connecting shaft 4, and the floating plug 2 corresponds to the holding die 1 due to the frictional force caused by pulling out the raw tube 8 and the drag from the holding die 1. Therefore, the grooved plug 3 also stops at a position corresponding to the rolling ball 5. Therefore, when the rolling ball 5 is in rolling contact with the outer peripheral surface of the raw tube 8 and rotationally driven in the circumferential direction, the outer periphery of the grooved plug 3 is formed on the inner peripheral surface of the raw tube 8 by the cooperative action with the grooved plug 3. The fin shape is formed by transferring the groove shape formed on the surface. At this time, the grooved plug 3 is rotated by a groove carved in the peripheral surface of the grooved plug 3 by pulling out the raw tube 8. Further, the raw tube 8 having the fins 6 formed on the inner surface thereof is subjected to contraction processing with a finishing die 7 to produce an inner grooved tube having a desired outer diameter.
[0008]
By the way, when machining an internally grooved tube by the above-described conventional method of machining an internally grooved tube, the grooved plug 3 is generally made of a hard metal having wear resistance, but is processed. When the length of the groove is as long as several thousand meters, even if a cemented carbide is used as the grooved plug 3, the surface of the groove processing portion (the area pressed by the rolling ball 5) of the grooved plug 3 is locally To wear. For this reason, if rolling is performed continuously, for example, problems such as the height of the fins 6 sequentially decreasing occur. In addition there is a problem that in turn the tool life of the grooved plug 3 is short.
[0009]
Moreover, in recent years, the inner grooved tube has been required to be further compacted due to the compactness of the equipment or equipment used. For example, inner grooved copper pipes for heat exchangers such as air conditioners are mainly used for extremely small diameter pipes with an outer diameter of 6 to 8 mm. Tend to be. Along with this, in order to maintain the performance of the internally grooved tube itself such as heat transfer characteristics or improve the performance, the grooves tend to become deeper and higher fins. The fins formed by these small-diameter inner-grooved pipes are high fins having a ratio of 0.025 or more with respect to the pipe outer diameter. In the extremely small copper pipe, for example, the pipe outer diameter is 7.0 mm. The height of the fin peak is increased to 0.18 mm or more. In particular, the wear on the grooved plug surface is remarkable with such a high fin shape.
[0010]
Therefore, the problems relating to the wear of the grooved plug as described above are improved, and the applicant first presses the element tube against the grooved plug with a rolling ball to transfer and form the inner groove on the inner surface of the element tube. At the same time, a processing method of an internally grooved tube was proposed in which a rolling ball is processed by moving it continuously or intermittently in the tube axis direction (Japanese Patent Laid-Open No. 11-19711).
[0011]
In the above-described method for machining an internally grooved pipe, the groove machining position of the grooved plug changes, so that local wear of the grooved plug can be reduced and the inner pipe has an evenly high fin in the longitudinal direction of the inner surface. Although an internally grooved tube can be manufactured, a mechanical or electrical device for moving the rolling ball or the grooved plug in the tube axis direction of the raw tube is required.
[0012]
And in the process of proceeding with subsequent development, it is now possible to reduce the local wear of the grooved plug, and to produce an internally grooved tube having fins that are uniformly high in the longitudinal direction of the inner surface of the tube. A processing method for internally grooved tubes has been developed.
[0013]
[Problems to be solved by the invention]
The present invention has been made against the background described above, and its purpose is to reduce the local wear of the grooved plug and to provide an internally grooved tube having uniformly high fins in the longitudinal direction of the inside surface of the tube. A method for processing an internally grooved tube is provided.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a method for processing an internally grooved pipe according to the present invention (Claim 1) is connected to a floating plug in a raw pipe and to the floating plug so as to be relatively rotatable via a connecting shaft. The grooved plug is inserted into the grooved tube, and the tube is successively reduced in diameter by a holding die and a plurality of rolling balls, and the floating plug is engaged with the holding die and the grooved plug is disposed on the rolling ball. In a processing method of an internally grooved tube in which the groove shape of the grooved plug is transferred to the inner surface of the raw tube by pressing the inner surface of the raw tube against the grooved plug with the rolling ball. The groove shape is transferred to the inner surface of the raw tube by being rotationally driven about a central axis that intersects the axis at an intersection angle θ. In this case, the intersection angle θ is preferably 1 to 20 degrees (claim 2).
[0015]
In the above configuration, the rolling ball is grooved on the inner surface of the tube by rotationally driving the rolling ball around the central axis that intersects the tube axis at an intersecting angle θ. Unlike the conventional case where the crossing angle θ = 0 degrees, the pressed surface of the grooved plug is different because the rolling ball continuously passes through different surfaces of the plug in the tube axis direction and presses the different surfaces. Is pressed on the surface with a width in the tube axis direction. As a result, the local wear of the grooved plug can be reduced as compared with the conventional case, and the life of the grooved plug as a whole can be improved. An internally grooved tube having uniformly high fins can be produced. In this case, the range of the intersection angle θ is preferably in the range of 1 to 20 degrees. If the crossing angle θ is less than 1 degree, local wear reduction of the grooved plug cannot be expected, which is the same as the conventional method of processing an internally grooved tube. Also, when the crossing angle θ exceeds 20 degrees, the gap between the grooved plug and the rolling ball fluctuates in the circumferential direction, so that vibration occurs, and the raw tube is not processed due to excessive machining on the grooving side (narrow gap side). Breakage or the like occurs.
[0016]
In order to achieve the above object, a method of processing an internally grooved tube according to the present invention (Claim 3) is capable of rotating relative to a floating plug in the raw tube via a connecting shaft. The connected grooved plug is inserted, and the raw tube is sequentially reduced in diameter by a holding die and a plurality of rolling balls, and the floating plug is engaged with the holding die to insert the grooved plug into the rolling ball. In a processing method of an inner surface grooved tube, the inner surface of the grooved plug is transferred to the inner surface of the raw tube by pressing the inner surface of the raw tube against the grooved plug by the rolling ball. Are arranged in the pipe circumferential direction with different arrangement positions in the pipe axis direction, and the rolling ball is rotated around the pipe axis to transfer the groove shape to the inner surface of the raw pipe.
[0017]
In the above-described configuration, the rolling ball is disposed in the pipe circumferential direction with a different arrangement position in the pipe axis direction, and the inner surface of the pipe is grooved by rotationally driving the rolling ball around the pipe axis. Therefore, each rolling ball during grooving passes through and presses on different rotation tracks, 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 the width, so that the local wear of the grooved plug can be reduced as compared with the conventional grooved plug. The overall life can be improved, and an internally grooved tube having uniformly high fins in the longitudinal direction of the inside surface of the raw tube can be manufactured.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional explanatory view of an inner surface grooved portion for explaining an inner surface grooved tube processing method according to the present invention (Claim 1). It is the same structure as the processing apparatus of the conventional internal grooved pipe shown in the said FIG. In the following description, the same components as those of the conventional apparatus are denoted by the same reference numerals.
[0019]
The inner surface grooving portion shows only the rolling ball 5 and the grooved plug 3, but has a machining ring 21 that houses the rolling ball 5 and a coil 23 that rotates the cylindrical drive shaft 22 by a magnetic field as in the prior art. The motor 9 and the grooved plug 3 are provided. The inner surface groove machining portion in this example includes the machining ring 21 and the motor 9 so that the central axis 10 of the rotation track of the rolling ball 5 intersects the tube shaft 11 at the intersection angle θ in the central portion of the grooved plug 3. It is set as the structure which hold | maintains.
[0020]
In the processing method using the internal grooved tube processing apparatus having the above-described configuration, the rotation trajectory of the rolling ball 5 is an elliptical trajectory when viewed from the tube axis direction. The rolling ball 5 rotating upward is the inner surface of the raw tube 8 on the upper surface 12 of the grooved plug 3, and the rolling ball 5 rotating downward in the figure is the grooved plug of the inner surface of the raw tube 8. 3 are respectively pressed against the lower surface 13 to form grooves. Therefore, as shown in FIG. 2, if the crossing angle θ and the tube outer diameter 2R after grooving are set, the surface of the grooved plug 3 against which the raw tube 8 is pressed is compared with the conventional processing shown in FIG. 2b. As compared with the conventional method, it is enlarged by about R · tan θ in the tube axis direction, so that local wear of the grooved plug 3 can be reduced as compared with the conventional method, and the life of the grooved plug 3 as a whole can be improved. An internally grooved tube having uniformly high fins in the longitudinal direction of the inner surface can be produced. In addition, since the major axis of the central portion in the figure corresponding to the major axis side of the ellipse is configured to be larger than the outer diameter of the element tube 8, the inner surface of the element tube 8 is not pressed against the grooved plug 3. Reference numeral 3A denotes a region on the surface of the grooved plug 3 pressed by the rolling ball 5, and reference numeral 5A denotes a rotation trajectory of the rolling ball 5.
[0021]
Incidentally, inner surface grooving can be exemplified under the following conditions.
(1) Material condition of raw pipe: Copper Dimensions: Outer diameter 8.0mm, Pipe thickness 0.3mm
(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 Rolling ball rotation speed: 20000 r. p. m.
Number of balls: 4 Crossing angle: θ = 15 degrees
In the processing of internally grooved pipes under the above conditions, the surface area of the grooved plug against which the raw pipe being processed is pressed is about three times that of the conventional case, and the tool life of the grooved plug can be about three times that of the conventional, Processing of the internally grooved tube having uniformly high fins in the longitudinal direction of the inner surface of the raw tube can be continued for a long time.
[0023]
FIG. 3 is a cross-sectional explanatory view of an inner surface grooved portion for explaining the inner surface grooved tube processing method according to the present invention (Claim 3), and shows the entire inner surface grooved tube processing apparatus shown in FIG. The basic configuration is the same as the conventional grooved tube processing apparatus shown in FIG. In the following description, the same components as those of the conventional apparatus are denoted by the same reference numerals.
[0024]
As shown in FIG. 1, the inner surface groove processing portion shows only the rolling ball 5 and the grooved plug 3, but a coil for rotating the processing ring 21 containing the rolling ball 5 and the cylindrical drive shaft 22 by a magnetic field. The motor 9 having 23 and the grooved plug 3 are provided. And the inner surface groove processing part in this example is a tube shaft as shown in FIG. 4 in which the accommodation hole 15 of the rolling ball 5 of the cylindrical ball holder 14 that holds the rolling ball 5 at a predetermined interval in the circumferential direction. The rolling ball 5 is accommodated in the accommodation hole 15 and set in the processing ring 21, and the rotation center shaft 16 and the tube shaft 11 of the cylindrical ball holder 14 are provided concentrically. It is a thing. Although not shown in the conventional configuration, a cylindrical ball holder is used. In this case, the accommodation holes are provided at predetermined intervals on the same circumference.
[0025]
In the processing method using the internal grooved tube processing apparatus having the above-described configuration, the four rolling balls 5 are provided at predetermined intervals in the tube axis direction. As shown in FIG. 5, four locations are formed, whereby the inner surface of the raw tube 8 is pressed against the surface of the grooved plug 3 for each rolling ball 5 to transfer and form the groove. Therefore, the surface of the grooved plug 3 against which the raw tube 8 is pressed is enlarged as compared with the conventional processing method shown in FIG. 2b, and the local wear of the grooved plug 3 can be reduced as compared with the conventional method. The life of the attached plug 3 as a whole can be improved, and an internally grooved tube having uniformly high fins in the longitudinal direction of the inside surface of the base tube 8 can be manufactured.
[0026]
FIG. 6 is an explanatory view showing another example of attaching the rolling ball to the cylindrical ball holder according to the present invention, and the accommodation holes 15 of the rolling ball 5 are provided in a staggered manner as in this example. Even so, the same effects as the example of FIG. 3 can be obtained.
[0027]
In the examples shown in FIGS. 3 and 6, the case of four rolling balls is taken as an example, but the present invention is not limited to this example, and the space for mounting the rolling balls to the ball holder is not limited to this example. Therefore, it is desirable to determine the number in the range of about 2 to 6, for example. When three or more balls are provided, two rolling balls 5 may be provided on one rotating track. Furthermore, in the above example, the spacing in the tube axis direction of each rolling track of the rolling ball is 0.5 mm at the center of the ball, but is preferably within 1 mm at the maximum. There is a concern that the surface roughness becomes rough and the inner fins are not sufficiently formed.
[0028]
Incidentally, inner surface grooving can be exemplified under the following conditions.
(1) Material condition of raw pipe: Copper Dimensions: Outer diameter 8.0mm, Pipe thickness 0.3mm
(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 Rolling ball rotation speed: 20000 r. p. m.
Number of balls: 4 Rolling ball cylindrical ball holder: Fig. 7
[0029]
In the processing of internally grooved pipes under the above conditions, the tool tube of the grooved plug can be about four times longer than the conventional one because the raw pipe being processed can be pressed at four locations on the grooved plug. Processing of the internally grooved tube having fins that are uniformly high in the longitudinal direction can be continued for a long time.
[0030]
【The invention's effect】
As described above, according to the processing method of inner grooved tubes according to the present invention, it can be reduced localized wear of the grooved plug, and thus it is possible to achieve the life improvement of the entire grooved plug, containing tube An internally grooved tube having uniformly high fins in the longitudinal direction of the surface can be produced.
[Brief description of the 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 tube processing method according to the present invention.
FIG. 2 is a cross-sectional explanatory view of an inner surface groove processing portion for explaining a surface state of a grooved plug used by pressing an element tube during processing of an inner surface grooved tube, where a is an example of the present invention; b shows a conventional example.
FIG. 3 is a cross-sectional explanatory view of an internal groove processing portion of another embodiment for carrying out the internal grooved tube processing method according to the present invention.
4A and 4B are explanatory views of a ball holder provided in the inner surface groove processing portion shown in FIG. 3, wherein a is a perspective view and b is a development view.
FIG. 5 is a cross-sectional explanatory view of the inner surface groove processing portion for explaining the surface state of the grooved plug used by pressing the base tube during the processing of the inner surface grooved tube according to the embodiment shown in FIG. 3; .
6A and 6B are explanatory views of another ball holder according to the present invention provided in the inner surface groove machining portion shown in FIG. 3, wherein a is a perspective view and b is a developed view.
FIGS. 7A and 7B are explanatory views of a ball holder provided in an internal groove processing portion used in the method for processing an internal groove tube according to the present invention, wherein a is a perspective view and b is a development view.
FIG. 8 is a schematic cross-sectional view in the tube central axis direction showing a conventional processing apparatus for internally grooved tubes.
[Explanation of symbols]
3: Slotted plug 5: Rolling ball 8: Elementary tube 9: Motor 10: Center shaft 11: Tube shaft 12: Upper surface of the grooved plug 13: Lower surface of the grooved plug 14: Cylindrical ball holder 15: Rolling ball accommodation hole 16: Center axis of rotation of ball holder 21: Processing ring 22: Drive shaft 23: Coil θ: Crossing angle

Claims (3)

A floating plug and a grooved plug that is rotatably connected to the floating plug via a connecting shaft are inserted into the raw pipe, and the raw pipe is sequentially reduced in diameter by a holding die and a plurality of rolling balls. At the same time, the grooved plug is positioned at the position where the rolling ball is disposed by engaging the floating plug with the holding die, and the inner surface of the tube is pressed against the grooved plug by the rolling ball. In the processing method of an internally grooved tube that transfers the groove shape of the grooved plug, the groove shape is transferred to the inner surface of the raw tube by rotating the rolling ball around a central axis that intersects the tube axis at an intersecting angle θ. A method for processing an internally grooved tube. The method for processing an internally grooved tube according to claim 1 , wherein the intersecting angle θ is 1 to 20 degrees. A floating plug and a grooved plug that is rotatably connected to the floating plug via a connecting shaft are inserted into the raw pipe, and the raw pipe is sequentially reduced in diameter by a holding die and a plurality of rolling balls. At the same time, the grooved plug is positioned at the position where the rolling ball is disposed by engaging the floating plug with the holding die, and the inner surface of the tube is pressed against the grooved plug by the rolling ball. In a processing method of an internally grooved tube for transferring a groove shape of a grooved plug, a rolling ball is arranged in a pipe circumferential direction with a different arrangement position in the tube axis direction, and the rolling ball is centered on the tube axis. A method for processing an internally grooved tube, wherein the groove shape is transferred to the inner surface of the raw tube by being rotationally driven.

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