JP4588267B2 - 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. 20 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. With reference to this FIG. 20, the conventional processing apparatus and processing method of an internally grooved pipe will be described.
[0003]
A floating plug 12 is inserted into the raw tube 18. This floating plug 12 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 18, 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 11 for reducing the diameter of the pipe 18 together with the floating plug 12 is disposed on the outer surface of the pipe 18 at a position corresponding to the floating plug 12.
[0004]
A substantially cylindrical grooved plug 13 is connected to the floating plug 12 via a connecting shaft 14. A groove having a shape to be formed on the inner peripheral surface of the raw tube 18 is processed on the outer peripheral surface of the grooved plug 13. Further, the grooved plug 13 can freely rotate about the connecting shaft 14. A plurality of rolling balls 15 are arranged in the pipe circumferential direction on the outer surface of the raw pipe 18 at a position corresponding to the grooved plug 13. The rolling balls 15 are accommodated in the processing ring 31 and arranged at an appropriate distance from each other. The processing balls 31 hold the rolling balls 15 at predetermined positions in the tube axis direction.
[0005]
The processing ring 31 is connected to the drive shaft 32 of the motor 19. The motor 19 has a cylindrical drive shaft 32 and a coil 33 that rotates the drive shaft 32 by a magnetic field. By supplying power to the coil 33, the drive shaft 32 is rotationally driven, and the machining ring 31 is coaxial with the tube axis. Rotate on top. By the rotation of the processing ring 31, the rolling ball 15 rotates in the pipe circumferential direction around the pipe axis. Note that the raw tube 18 passes through the center of the motor 19. Further, on the downstream side of the rolling ball 15 in the tube drawing direction, a finishing die 17 for reducing the outer diameter of the raw tube 18 having fins formed on the inner surface to a predetermined dimension is provided in contact with the raw tube 18. 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 12 is inserted into the tip of the raw tube 18 and the position thereof is held by mechanical or magnetic means. From this state, the tip of the raw tube 18 is supplied to the finishing die 17 through the holding die 11 and the holding of the floating plug 12 is released. Thereafter, the floating plug 12 moves to a position corresponding to the holding die 11 as the raw tube 18 starts moving. Then, the tube 18 is contracted by the floating plug 12 and the holding die 11 by the subsequent drawing, and further contracted by the subsequent rolling ball 15, and receives the rolling force by the rolling ball 15 to receive the element. The grooved plug 13 disposed inside the tube 18 is pressed.
[0007]
The grooved plug 13 is connected to the floating plug 12 via a connecting shaft 14, and the floating plug 12 corresponds to the holding die 11 due to the frictional force caused by pulling out the raw tube 18 and the drag from the holding die 11. Therefore, the grooved plug 13 also stops at a position corresponding to the rolling ball 15. Therefore, when the rolling ball 15 is in rolling contact with the outer peripheral surface of the raw tube 18 and rotationally driven in the circumferential direction, the outer periphery of the grooved plug 13 is formed on the inner peripheral surface of the raw tube 18 by the cooperative action with the grooved plug 13. The fins 16 are formed by transferring the groove shape formed on the surface. At this time, the grooved plug 13 is rotated by a groove carved in the peripheral surface of the grooved plug 13 by pulling out the raw tube 18. In addition, the raw tube 18 having the fins 16 formed on the inner surface thereof is subjected to contraction processing by a finishing die 17 to produce an inner grooved tube having a desired outer diameter.
[0008]
By the way, in recent years, heat transfer tubes used in heat exchangers for air conditioners such as refrigerators and room air conditioners have a large number of fine spiral grooves formed on the inner surface as described above in order to improve heat transfer performance. Heat tubes are used. On the other hand, Freon R22, R21 and the like that have been conventionally used as refrigerants to be circulated in the heat transfer tubes are in the direction of being totally abolished because they destroy the ozone layer of the earth. Freons R32, R134a, which do not destroy the ozone layer, It is replacing alternatives such as R125. In particular, mixed refrigerants such as “R32 / R134a / R125” and “R32 / R125” mixed with these refrigerants have characteristics close to those of conventional Freon R22, etc., and are nonflammable, so they are highly suitable as alternatives. It is evaluated.
[0009]
However, since the mixed refrigerants such as “R32 / R134a / R125” and “R32 / R125” are non-azeotropic refrigerants and have different liquefaction start temperature (dew point) and vaporization start temperature (boiling point), evaporation or When condensing, high-boiling components concentrate on the liquid phase side and low-boiling components concentrate on the gas phase side. This difference in density causes diffusion resistance and thermal resistance, and reduces the heat transfer coefficient during evaporation or condensation. Therefore, in order to maintain or improve the heat transfer performance of the refrigerant as described above, JP-A-10-211537 and JP-A-10-238984 propose heat transfer tubes having inner grooves with different lead angles. Yes.
[0010]
Further, as described in Japanese Patent Laid-Open No. 10-238984, a so-called seam pipe manufactured by pipe welding a metal strip can also be used as a heat transfer pipe, and is described in the same publication. As described above, in this method by tube-forming welding, a groove pattern is formed on the inner surface side of the band plate, and an inner-grooved tube is obtained by performing tube-forming welding later. In this case, a groove pattern having a plurality of types of patterns in the circumferential direction can be formed on the inner surface of the metal tube. For example, a plurality of virtual boundary lines along the axial direction can be set on the inner surface of the metal tube, and oblique groove patterns with different directions can be alternately arranged so as to be symmetric with respect to the virtual boundary line. . That is, a groove pattern having a shape like a pine needle (hereinafter referred to as a pine needle groove) can be formed by oblique grooves that intersect with each other across a virtual boundary line.
[0011]
Further, as described in the publication, when a pine needle groove is formed in the heat transfer tube, the refrigerant flowing along the groove collides on the virtual boundary line, which can improve the heat exchange efficiency satisfactorily. it can. Furthermore, in recent years, use of alternative refrigerants for CFCs has been studied in various heat exchangers. In connection with this, the request | requirement which uses the inner surface grooved tube in which the above special groove patterns were formed as a heat exchanger tube, and improves the heat exchange efficiency of a heat exchanger is also increasing.
[0012]
[Problems to be solved by the invention]
However, as pointed out in the above publication, a welded part is formed over the entire length of the internally grooved pipe manufactured by the above pipe making welding, and refrigerant leakage may occur in this welded part. However, since it is higher than other parts, there is a concern that the reliability and durability are slightly lowered.
[0013]
On the other hand, JP-A-10-211537 proposes a method for manufacturing a heat transfer tube having the following configuration. That is, the second grooved plug and the first grooved plug have a groove on the outer periphery that has a different lead angle, groove shape, groove pitch, or groove dimension with respect to the axis. A step of inserting a grooved plug into the metal tube at a predetermined interval and rotatably, and an appropriate number of first-stage processed balls around the first grooved plug while pulling out the metal tube in a certain direction. The metal tube is pressed against the first grooved plug by the first-stage processed ball while rotating the planets, and the inner surface of the metal tube is not pressed by the first-stage processed ball with a predetermined width of the spiral smooth A plurality of small first length grooves of a predetermined length that are discontinuous in the tube axis direction are formed in a spiral shape, and then an appropriate number of second-stage processes are made around the second grooved plug. While the ball is rotating on a planetary plane, Pressing the tube against the second grooved plug and forming a plurality of small second-type grooves of a predetermined length that are discontinuous in the tube axis direction on the spiral smooth portion of the inner surface of the metal tube, It is a manufacturing method of a heat exchanger tube.
[0014]
However, in the above proposed manufacturing method, although there is no welded portion and a heat transfer tube without fear of refrigerant leakage at the welded portion can be manufactured, a spiral smooth portion having a predetermined width is left on the inner surface of the metal tube, and the tube axis direction After the first type grooves having a plurality of small predetermined lengths that are discontinuous are formed in a spiral shape, the second type of the second type having a plurality of small predetermined lengths that are discontinuous in the tube axis direction to the remaining spiral smooth portion. Since the groove is formed, it is necessary to accurately control the drawing speed and the number of revolutions of the ball in order to leave the spiral smooth portion and form the second kind of groove pattern there. When the ratio of the numbers (drawing speed / ball rotation speed) exceeds the tube axis length of the first type groove pattern, the spiral smooth portion does not remain and the second type groove pattern is the first type groove. It will be formed overlapping the pattern, and depending on the control, the first type Or groove pattern and the second type of groove pattern is formed to overlap with either one or both ends in the width direction, or the smooth portion either one or both ends can remain remained a concern.
[0015]
In Japanese Patent Laid-Open No. 10-238984, a grooved plug is inserted into a metal tube, and a plurality of balls whose rotational trajectories are determined on the inner peripheral surface of the outer race while moving the metal tube in the axial direction are attached to the metal tube. In the manufacturing method of an inner surface grooved tube in which the diameter of the metal tube is reduced and a groove is formed in the inner surface of the metal tube by a rolling method in which the planetary rotation is performed while being in contact with the outer surface of the tube, the inner surface of the outer race A curved surface whose radius from the center of rotation changes smoothly along the circumferential direction, and adjusts the pressing amount applied from the ball to the outer peripheral surface of the metal tube to a predetermined value to form a groove by the rolling method, Before or after the step of forming the groove, the grooved plug outer peripheral pattern is different from the outer race rotational phase or inner peripheral surface shape to form another groove by the rolling method. By A plurality of groove patterns different inner surface circumferential direction is formed into a spiral across the tubes overall length, the production method of the inner grooved tube has been proposed.
[0016]
However, in the manufacturing method proposed in Japanese Patent Laid-Open No. 10-238984, there is no joint anywhere on the entire circumference of the tube, and the groove pattern on the inner surface of the tube has a plurality of types of patterns in the circumferential direction. Although the inner grooved tube can be easily manufactured, since the groove processing is performed twice before and after the drawing direction, the groove processing apparatus including the outer race is compared with the case of performing the single groove processing as in the prior art. The length in the drawing direction increases. Therefore, in order to prevent the device eccentricity and vibration, and to form a grooved tube with less fluctuation in the wall thickness of the tube, the device rigidity is larger than when the groove is processed once as in the prior art. Necessary. On the other hand, since the rolling ball rolls at high speed on the inner peripheral surface of the outer race, which has an elliptical cross section, it reciprocates in the radial direction of the metal tube during the rotary motion during grooving, and returns to the base tube. Since the amount of pressing also fluctuates, it is easy to cause vibration of the processing device and the groove plug, and further rigidity is required to prevent vibration.
[0017]
The present invention is based on the technical background as described above, and the object thereof is an inner surface groove having a relatively simple structure and having a plurality of different groove patterns in the tube axis direction on the tube inner surface, Alternatively, the present invention provides a method for processing an internally grooved tube that can form an internally grooved groove having a continuously changed groove pattern, and that allows for greater groove change and more active turbulent refrigerant flow.
[0018]
[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 plug, the diameter of the base tube is successively reduced by a holding die and a plurality of rolling balls, and the floating plug is engaged with the holding die so that the grooved plug is disposed on the rolling ball. As a grooved plug in a processing method of an inner surface grooved tube in which the grooved shape of the grooved plug is transferred to the inner surface of the elemental tube by pressing the inner surface of the elemental tube against the grooved plug with a rolling ball. , Grooved plugs with multiple groove patterns with different groove shapes such as lead angle, groove depth, groove width, number of grooves in the tube axis direction or groove shapes such as lead angle, groove depth, groove width, number of grooves, etc. Continuously changing With use of the grooved plug, and performs grooving the inner surface while continuously or intermittently reciprocated grooved plug or compacting ball tube axis direction.
[0019]
In the above configuration, by reciprocating the grooved plug or the rolling ball in the tube axis direction of the raw tube, the position of the groove plug surface where the inner surface groove processing is performed is changed. Here, since the grooved plug has a different groove pattern in the tube axis direction, the formed inner surface groove has an inner surface groove having a plurality of different groove patterns in the tube axis direction, or a groove pattern that is continuously changed. An internal groove can be formed. Further, the length of the groove pattern in the tube axis direction can be freely controlled by controlling the period of the reciprocating motion of the grooved plug or the rolling ball. Further, except for changing the position of the groove plug surface where the inner surface groove processing is performed, the configuration of the processing device such as the rolling ball and the rotational drive is basically the same as the device configuration illustrated and described in the prior art. The inner surface groove can be processed with a relatively simple configuration without generating vibration more than necessary.
[0020]
In order to achieve the above object, a method for processing an internally grooved tube according to the present invention (Claim 2) is capable of relatively rotating in a raw tube via a floating plug and a connecting shaft connected to the floating plug. The grooved plug is inserted into the connected grooved plug, and the base 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 roll the grooved plug into the rolling ball. In the processing method of an internally grooved tube, the grooved plug shape is transferred to the inner surface of the raw tube by pressing the inner surface of the raw tube against the grooved plug with a rolling ball. As a plug, a grooved plug having a plurality of groove patterns with different groove shapes such as lead angle, groove depth, groove width, and number of grooves in the tube axis direction or grooves such as lead angle, groove depth, groove width, number of grooves, etc. Shape is continuous The inner surface of the pipe is grooved by rotating the rolling ball around the central axis that intersects the pipe axis at the crossing angle θ at the boundary position of the groove pattern of the grooved plug. Is. In this case, the crossing angle θ is preferably 1 to 20 degrees.
[0021]
In the above configuration, the inner surface of the tube is grooved by rotating the rolling ball around the central axis intersecting the tube axis at the intersection angle θ at the boundary position of the groove pattern of the grooved plug. The rolling ball of the inside of the rolling ball continuously passes through different surfaces of the grooved plug in the tube axis direction. At this time, the grooved plug surface has a different groove pattern in the tube axis direction. A plurality of groove patterns having different directions can be formed in a spiral shape over the entire length of the tube. If the crossing angle θ is too large at that time, the gap between the grooved plug and the rolling ball fluctuates in the circumferential direction, and vibration occurs due to excessive machining on the narrow gap side. To do. Therefore, the range of the intersection angle θ is preferably about 1 to 20 degrees.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of an apparatus for carrying out the inner grooved tube processing method (claim 1) according to the present invention. In the figure, 8 is an elementary tube, and 9 is a motor.
[0023]
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.
[0024]
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 machined on the outer peripheral surface of the grooved plug 3, and in this example, as shown in FIG. Different groove patterns 3A and 3B are formed. 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.
[0025]
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, and is reciprocated in the tube axis direction by reciprocating drive means 10 provided on a gantry (not shown). By driving, the rolling ball 5 is held so as to be reciprocally movable at a predetermined position on the outer periphery of one of the groove patterns 3A and 3B of the grooved plug 3 together with the processing ring 21. Further, by supplying power to the coil 23, the drive shaft 22 is rotationally driven, and the machining ring 21 is rotationally driven coaxially with the tube axis. 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.
[0026]
The processing method using the internal grooved tube processing apparatus having the above-described configuration 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.
[0027]
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. On the other hand, the rolling ball 5 is reciprocally driven in the tube axis direction by the reciprocating drive means 10 and is held so as to be reciprocally movable at a predetermined position on the outer periphery of the groove pattern 3A, 3B of the grooved plug 3 together with the processing ring 21. Yes.
[0028]
Therefore, when the rolling ball 5 is held at a predetermined position of the groove pattern 3A of the grooved plug 3 and is brought into rolling contact with the outer peripheral surface of the base tube 8 and rotated in the circumferential direction, the cooperating action with the grooved plug 3 is caused. The groove shape of the groove pattern 3A formed on the outer peripheral surface of the grooved plug 3 is transferred to the inner peripheral surface of the raw tube 8 to form the fin 6A, and then the rolling ball 5 is moved to move the grooved plug. 3 is held at a predetermined position of the groove pattern 3B and is rotationally driven in rolling contact with the outer peripheral surface of the raw tube 8 to rotate in the circumferential direction, a groove is formed on the inner peripheral surface of the raw tube 8 by the cooperative action with the grooved plug 3. The groove shape of the groove pattern 3B formed on the outer peripheral surface of the attached plug 3 is transferred to form the fin 6B. Thereafter, by repeatedly reciprocating the rolling ball 5, fins 6A and 6B are alternately formed on the inner surface of the raw tube 8 as shown in FIG. At the time of the rotational drive, 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. The base tube 8 having the fins 6A and 6B alternately formed on the inner surface is subjected to contraction processing by a finishing die 7 to produce an inner grooved tube having a desired outer diameter.
[0029]
In the above example, the groove pattern formed on the outer peripheral surface of the grooved plug 3 is an example in which two groove patterns are formed in a pine needle shape at the front and rear, but the lead angle is different as shown in FIG. A continuous groove pattern may be used, or a flat portion may be formed in a pine needle shape before and after the smooth portion at the center portion as shown in FIG. 5, or four groove patterns may be formed as shown in FIG. May be formed continuously.
[0030]
In the above example, the grooved plug 3 is fixed in position, and the rolling ball 5 side is reciprocated in the tube axis direction. However, as shown in FIG. 7, the rolling ball 5 is fixed in position, A die holder (not shown) that accommodates and holds the holding die 1 may be reciprocally moved in the tube axis direction so that the grooved plug 3 side is reciprocated in the tube axis direction. Examples of movement of the grooved plug 3 in this case are shown in FIGS. 8 is an example in which the first and second groove patterns are formed at equal intervals in the tube axis direction, and the movement example in FIG. 9 is the first groove pattern in the tube axis direction from the second groove pattern. The example in the case of forming at a long interval, the movement example in FIG. 10 is an example in the case of forming the first to fourth groove patterns formed on the grooved plug 3.
[0031]
Incidentally, inner surface grooving can be exemplified under the following conditions.
(1) Raw tube conditions
Material: Copper
Dimensions: Outer diameter 8.0mm, tube thickness 0.3mm
(2) Conditions for grooved plug 3 (in the case of the three groove patterns in FIG. 11)
Groove pattern A: outer diameter 7.2 mm, number of grooves 50, lead angle 15 °, length 7 mm
Groove pattern B: outer diameter 7.2 mm, number of grooves 50, lead angle 5 °, length 2 mm
Groove pattern C: outer diameter 7.2 mm, number of grooves 50, lead angle -15 °, length 7 mm
The lead angles of the groove pattern A and the groove pattern C are reversed.
(3) Processing conditions
Drawing speed: 50m / min
Rolling ball rotation speed: 20000 r. p. m.
Number of balls: 4
[0032]
Under the above conditions, the axially central portion of the grooved plug 3 shown in FIG. 11 is set as the initial rolling ball position (reciprocating reference position of the rolling ball), and the rolling ball position is moved after the base tube is pulled out 400 mm. At the same time as shown in FIG. 12, grooving was performed. As a result, as shown in FIG. 13, an internally grooved tube whose internal groove shape was alternately changed continuously in the tube axis direction was obtained. In addition, the position of the code | symbol 1 in the vertical axis | shaft of FIG. 12 shows the boundary position of the groove pattern C and the groove pattern B, and the position of the code | symbol -1 shows the boundary position of the groove pattern B and the groove pattern A, respectively.
[0033]
FIG. 14 is a cross-sectional explanatory view of an inner surface groove machining portion for explaining a method for machining an internally grooved tube according to the present invention (Claim 2). The basic configuration of the entire apparatus excluding the internal groove processing portion shown in this figure is the same as that of the internal grooved tube processing apparatus shown in FIG.
[0034]
The inner groove processing portion in the inner grooved tube processing apparatus shown in FIG. 1 includes a processing ring 21 that accommodates the rolling ball 5, a motor 9 having a coil 23 that rotates a cylindrical drive shaft 22 by a magnetic field, A grooved plug 3 in which groove patterns 3A and 3B are formed, the grooved plug 3 in the raw pipe 8 is fixed in position, and the processing ring 21 and the motor 9 on the outer peripheral side of the raw pipe 8 are moved in the pipe axis direction. Although the inner groove processing portion in this example is configured to be reciprocally movable, the grooved plug 3 in the raw tube 8 is similarly fixed in position, and the processing ring 21 on the outer peripheral side of the raw tube 8 and the motor 9 are also fixed. Is fixed in position, and at the same time, the processing ring 21 and the motor are arranged such that the central axis 24 of the rotating track of the rolling ball 5 intersects the tube axis 25 at the crossing angle θ at the boundary between the groove patterns 3A and 3B of the grooved plug 3. 9 is held.
[0035]
In the processing method using the internal grooved tube processing apparatus having the above-described configuration, the rotation track of the rolling ball 5 is an elliptical track when viewed from the tube axis direction, and this corresponds to the short axis side of the ellipse. The rolling ball 5 that rotates upward is formed by pressing the inner surface of the base tube 8 against the groove pattern 3A of the grooved plug 3 to transfer the groove pattern 3A, and the rolling pressure that rotates downward in the figure. The ball 5 is formed by pressing the inner surface of the base tube 8 against the groove pattern 3B of the grooved plug 3 to transfer the groove pattern 3B. On the other hand, since the major axis of the central portion in the drawing 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.
[0036]
The groove shape of the inner surface of the raw tube 8 formed as described above is as shown in FIG. 15, and the groove shape of the groove pattern 3A and the groove shape of the groove pattern 3B are spirally adjacent to each other with the same width. The transferred groove shape is obtained.
[0037]
In the above example, when the crossing position of the rolling ball 5 is positioned near the groove pattern B as shown in FIG. 16, the groove shape width to which the groove pattern A is transferred is narrow as shown in FIG. The groove shape width to which the pattern B is transferred can be formed wide, and by fixing the crossing position of the rolling ball 5 at an appropriate position across the groove patterns A and B of the grooved plug 3, an appropriate combination of the groove shape widths can be obtained. An internally grooved tube can be manufactured. Further, as the grooved plug 3, the one shown in FIGS. 4 to 6 can be used.
[0038]
Incidentally, inner surface grooving can be exemplified under the following conditions.
(1) Raw tube conditions
Material: Copper
Dimensions: Outer diameter 8.0mm, tube thickness 0.3mm
(2) Conditions for grooved plug 3 (in the case of two groove patterns in FIG. 18)
Groove pattern A: outer diameter 7.2 mm, number of grooves 50, lead angle 15 °, length 8 mm
Groove pattern B: outer diameter 7.2 mm, number of grooves 50, lead angle -15 °, length 8 mm
The lead angles of the groove pattern A and the groove pattern B are reversed.
(3) Processing conditions
Drawing speed: 50m / min
Rolling ball rotation speed: 20000 r. p. m.
Number of balls: 4
Crossing angle θ: 15 °
[0039]
FIG. 19 shows the inner surface groove shape of the raw tube 8 formed under the above conditions. The groove shapes of the groove pattern A and the groove pattern B are spirally transferred with the same width.
[0040]
【The invention's effect】
As described above, according to the method for processing an internally grooved tube according to the present invention, an inner surface groove having a plurality of different groove patterns in the tube axial direction or a continuous groove on the inner surface of the tube with a relatively simple structure. It is possible to transfer and form the inner surface groove having the groove pattern changed to the above, and the groove formed by the transfer has a large groove change and can activate the turbulent flow of the refrigerant more. Further, the groove pattern that can be selected also has a higher degree of freedom than the conventional one.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of an apparatus for carrying out a method for processing an internally grooved tube according to the present invention.
FIG. 2 is a front view of a grooved plug used in the method for processing an internally grooved tube according to the present invention.
FIGS. 3A and 3B are explanatory views of the groove shape of the inner surface of the raw tube formed by the processing method of the inner surface grooved pipe according to the present invention, where a is when the groove width is changed, and b is when the groove width is made equal. FIG.
FIG. 4 is a front view of another embodiment of the grooved plug used in the method for processing an internally grooved tube according to the present invention.
FIG. 5 is a front view of another embodiment of the grooved plug used in the method for processing an internally grooved tube according to the present invention.
FIG. 6 is a front view of another embodiment of the grooved plug used in the method of processing an internally grooved tube according to the present invention.
FIG. 7 is a schematic cross-sectional view showing an example of an apparatus according to another embodiment for carrying out the method for processing an internally grooved tube according to the present invention.
8 is an explanatory diagram of a grooved plug movement pattern applied to the method of processing an internally grooved tube by the apparatus shown in FIG.
9 is an explanatory diagram of a movement pattern of a grooved plug according to another embodiment, which is applied to the method of processing an internally grooved tube by the apparatus shown in FIG.
10 is an explanatory view of a movement pattern of a grooved plug according to another embodiment, which is applied to the method of processing an internally grooved tube by the apparatus shown in FIG. 7;
FIG. 11 is a front view of another embodiment of the grooved plug used in the method for processing an internally grooved tube according to the present invention.
12 is an explanatory view of a movement pattern of the grooved plug when the grooved plug of FIG. 11 is applied to the method of processing the internally grooved tube by the apparatus shown in FIG. 7;
13 is an explanatory view of the groove shape of the inner surface of the raw tube when the grooved plug of FIG. 11 is applied to the method of processing the internally grooved tube by the apparatus shown in FIG.
FIG. 14 is a cross-sectional explanatory view of an internal groove processing portion for explaining a method of processing an internal groove tube according to the present invention.
15 is an explanatory view of the groove shape of the inner surface of the raw tube formed by the processing method of the inner surface grooved tube by the apparatus shown in FIG. 14;
FIG. 16 is a cross-sectional explanatory view of an inner surface groove machining portion of another embodiment for explaining a method of machining an inner surface grooved tube according to the present invention.
17 is an explanatory view of the groove shape of the inner surface of the raw tube formed by the processing method of the inner grooved tube by the apparatus shown in FIG.
18 is a front view of a grooved plug applied to the method of processing an internally grooved tube by the apparatus shown in FIG.
19 is an explanatory view of the groove shape on the inner surface of the raw tube when the grooved plug of FIG. 18 is applied to the method of processing the internally grooved tube by the apparatus shown in FIG.
FIG. 20 is a schematic cross-sectional view in the tube central axis direction showing a conventional processing apparatus for internally grooved tubes.
[Explanation of symbols]
1: Holding die 2: Floating plug
3: Plug with groove 3A, 3B: Groove pattern 4: Connection shaft
5: Rolling ball 6A, 6B: Fin 7: Finishing die
8: Elementary tube 9: Motor 10: Reciprocating drive means
21: Processing ring 22: Drive shaft 23: Coil
24: Center axis 25: Pipe axis θ: Crossing angle
A, B, C: Groove pattern

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 arrangement position of the rolling ball by engaging the floating plug with the holding die, and the inner surface of the blank 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, as the grooved plug, a plurality of groove patterns having different groove shapes such as lead angle, groove depth, groove width, and number of grooves in the tube axis direction Grooved plugs or grooved plugs whose groove shape such as lead angle, groove depth, groove width, number of grooves, etc. are continuously changed, and grooved plugs or rolling balls are continuously used in the tube axis direction. Some Method of processing an inner grooved tube, characterized in that to perform a groove on the tube surface while intermittently reciprocated. 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 arrangement position of the rolling ball by engaging the floating plug with the holding die, and the inner surface of the blank 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, as the grooved plug, a plurality of groove patterns having different groove shapes such as lead angle, groove depth, groove width, and number of grooves in the tube axis direction Or a grooved plug whose groove shape such as lead angle, groove depth, groove width, and number of grooves is continuously changed, and a rolling ball at the boundary of the groove pattern of the grooved plug. Method of processing an inner grooved tube and performing groove on the tube surface by the rotary drive about a central axis which intersects with the tube axis intersection angle theta. The method for processing an internally grooved tube according to claim 2, wherein the intersection angle θ is 1 to 20 degrees.

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