JP2007218566A - Tube with grooves on inner surface and its manufacturing method, and fluted plug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent cracking in a groove or a fin during manufacturing. <P>SOLUTION: The ratio (R/δ) of the circular radius R mm of a bottom angular part (2b) of a groove (2) for the bottom width δ mm of the groove (2) is 0.10-0.25, and the ratio (r/δ) of the circular radius r mm at the tip of a fin (3) for the bottom width δ mm of the groove (2) is 0.14-0.20. Thereby, when rolling-machining, tubing materials (copper materials) can easily flow into the groove of a fluted plug. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

    The present invention relates to an internally grooved tube, a manufacturing method thereof, and a grooved plug used in the manufacture thereof, and particularly relates to prevention of cracking and breakage during the manufacture of an internally grooved tube.

2. Description of the Related Art In recent years, an internally grooved tube having a large number of grooves formed on the inner surface of a tube to improve heat transfer performance is often used as a heat transfer tube of a heat exchanger such as a refrigeration apparatus (so-called finned tube heat exchanger). For example, a large number of fins extending spirally in the tube axis direction are formed on the inner surface of the internally grooved tube of Patent Document 1, and grooves are formed between these fins. In this internally grooved tube, the cross section of the fin is formed in a tapered mountain shape, and the cross section of the groove is formed in an inverted trapezoidal shape.
JP-A-8-174044

    However, in a conventional internally grooved tube, if the shape of the fin or groove is simply determined based on the design conditions for heat transfer performance, there is a problem that the fin is chipped during manufacturing or the bottom of the groove is cracked. (See FIG. 8). Furthermore, in the assembly of the heat exchanger, when the inner grooved tube penetrated through the plurality of fin plates is expanded and brought into close contact with the through hole, if the above-described chipping or cracking is present in the fin on the inner surface of the tube, the crack is caused. In the worst case, there was a problem that the fins dropped off or the tube itself was broken.

    Here, the principle that chips and cracks are generated in the fins and the like during the production of the internally grooved tube will be described. In general, an internally grooved tube is a state in which a grooved plug having a groove formed on the outer peripheral surface is inserted into the raw tube, and the outer surface of the raw tube is pressed to transfer the groove shape of the grooved plug to the inner surface of the raw tube. Manufactured. That is, when the raw tube is pressed, the inner wall of the raw tube is deformed so as to flow into the groove of the grooved plug, and fins and grooves are formed on the inner surface of the raw tube. At that time, depending on the shape of the fin or groove to be formed, that is, the groove shape of the grooved plug, the raw tube material becomes difficult to flow. As the fluidity of the raw pipe material is deteriorated, the fins and the like are chipped and cracked.

    The present invention has been made in view of such points, and the object of the present invention is to prevent the occurrence of chipping and cracking of fins and the like during manufacturing by devising the shape of the fins and grooves. It is to provide a highly internally grooved tube and to provide a manufacturing method thereof and a grooved plug used therein.

    The first invention presupposes an internally grooved tube having a plurality of grooves formed on the inside surface. The groove has an inverted trapezoidal cross section and an arc shape at the bottom corner, and a ratio (R / δ) of the arc radius Rmm of the bottom corner to the bottom width δmm of the groove. ) Is 0.10 or more and 0.25 or less.

    In the above invention, the groove shape of the grooved plug is transferred to the inner surface of the raw tube by inserting the grooved plug having the protrusions and grooves formed on the outer peripheral surface thereof and pressing the outer surface of the raw tube. Let Specifically, when the blank tube is pressed, the inner wall surface of the blank tube is plastically deformed along the groove shape of the grooved plug, and the blank tube material flows into the groove from the ridge tip of the grooved plug. A plurality of grooves are formed on the inner surface of the raw tube. That is, the protrusion of the grooved plug corresponds to the groove of the tube.

    Here, for example, when the bottom width δ of the groove of the tube (the width of the tip of the ridge of the grooved plug) increases, it becomes difficult for the raw tube material to flow into the groove from the tip of the ridge in the grooved plug. As a result, defects such as cracks occur in the groove of the tube. However, in the present invention, in the tube, the arc radius R of the bottom corner of the groove is set appropriately with respect to the bottom width δ of the groove. That is, in the grooved plug, the tip corner of the ridge is appropriately set with respect to the tip width of the ridge, so that the raw tube material can easily flow into the groove from the tip of the ridge. As a result, the raw tube material surely flows into the groove of the grooved plug.

    According to a second aspect of the present invention, in the first aspect of the present invention, the protrusion formed tapered adjacent to the groove has a top portion formed in an arc shape, an arc radius rmm of the top portion, and a bottom width δmm of the groove. (R / δ) is 0.14 or more and 0.20 or less.

    In the above invention, the arc radius r of the top of the ridge is defined in relation to the bottom width δ of the groove in the pipe. That is, in the grooved plug, the arc radius at the bottom of the groove is defined in relation to the tip width of the protrusion. Here, when the bottom width δ of the groove increases in the pipe, the raw pipe material becomes difficult to flow into the groove in the grooved plug and hardly reaches the bottom of the groove, but the arc radius of this bottom (the top of the top of the ridge of the pipe). Since the arc radius r) is set appropriately, the raw tube material flows reliably to the bottom of the groove.

    The third invention is premised on an internally grooved tube having a plurality of grooves formed on the inner surface. The groove has an inverted trapezoidal cross section, and the bottom corner is formed in an arc shape. The bottom corner has an arc radius Rmm, and a taper formed adjacent to the groove. The ratio (R / θ) to the apex angle θ ° is 0.0006 or more and 0.0014 or less.

    In the above invention, the arc radius R of the bottom corner of the groove in the pipe is defined by the relationship with the apex angle θ of the ridge, so that the raw pipe material can easily flow from the ridge tip into the groove in the grooved plug. That is, for example, if the apex angle θ of the ridge in the pipe (the apex angle of the groove of the grooved plug) is small, the angle of the tip corner of the ridge is steep in the grooved plug, and the flow of the raw tube material is disturbed. Since the arc radius of the tip corner (arc radius R of the bottom corner of the tube groove) is appropriately set, the flow of the raw tube material becomes smooth. As a result, the raw tube material flows reliably into the groove.

    In a fourth aspect based on the third aspect, the top of the protrusion is formed in an arc shape, and a ratio (r / θ) between the arc radius rmm of the top and the apex angle θ ° of the protrusion. Is 0.0008 or more and 0.0012 or less.

    In the above invention, the arc radius r of the top of the ridge is defined in relation to the vertex angle θ of the ridge in the pipe. That is, in the grooved plug, the arc radius at the bottom of the groove is defined in relation to the apex angle of the groove. For example, when the apex angle θ of the ridge in the tube (the apex angle of the groove of the grooved plug) becomes small, the bottom of the groove becomes narrow in the grooved plug, and the raw tube material becomes difficult to reach the bottom. Since the arc radius (the arc radius r of the top of the ridge of the tube) is appropriately set, the raw tube material surely flows into the bottom of the groove.

    The fifth invention presupposes an internally grooved tube having a plurality of grooves formed on the inside surface. The groove has an inverted trapezoidal cross section, and the bottom corner is formed in an arc shape. The bottom corner has an arc radius Rmm, and a taper formed adjacent to the groove. The ratio (R / h) to the height hmm is 0.13 or more and 0.32 or less.

    In the above-described invention, the arc radius R of the bottom corner of the groove is defined in relation to the height h of the ridge in the pipe, so that the raw pipe material can easily flow from the ridge tip into the groove in the grooved plug. In other words, for example, if the height h of the ridge in the pipe (the depth of the groove of the grooved plug) increases, the raw tube material does not sufficiently flow from the tip of the ridge into the groove in the grooved plug. Since the arc radius of the corner portion at the tip of the strip (the bottom corner portion R of the groove of the tube) is appropriately set, the raw pipe material easily flows into the groove.

    In a sixth aspect based on the fifth aspect, the top of the protrusion is formed in an arc shape, and a ratio (r / h) between the arc radius rmm of the top and the height hmm of the protrusion is It is 0.18 or more and 0.26 or less.

    In the above invention, the arc radius r of the top of the ridge is defined in relation to the height h of the ridge in the pipe. That is, in the grooved plug, the arc radius of the bottom of the groove is defined in relation to the depth of the groove. For example, when the height h of the ridge (the groove depth of the grooved plug) increases in the pipe, the raw tube material becomes difficult to reach the bottom of the groove in the grooved plug. Since the arc radius r) of the top of the ridge is appropriately set, the raw tube material flows reliably to the bottom of the groove.

    According to a seventh invention, in the second invention, the arc radius r of the top of the protrusion is 0.04 mm, the arc radius R of the bottom corner of the groove is 0.05 mm, and the bottom width δ of the groove Is 0.23 mm.

    In the above-described invention, in the grooved plug, the shape of the tip corner portion of the ridge and the shape of the bottom portion of the groove are optimal with respect to the tip width of the ridge. Therefore, the fluidity of the raw pipe material is optimized, and the raw pipe material flows smoothly and reliably into the groove.

    8th invention presupposes the grooved plug used in order to form a some groove | channel on the inner surface of a raw tube by a rolling process in which a some protrusion is formed in an outer peripheral surface. The protrusion is formed in a trapezoidal shape with a tapered cross section and the tip corner is formed in an arc shape. The ratio of the arc radius Rmm of the tip corner to the tip width δmm of the protrusion ( R / δ) is from 0.10 to 0.25.

    In the above invention, a grooved plug having a plurality of protrusions and grooves formed on the outer peripheral surface is inserted into the raw tube, and the outer surface of the raw tube is pressed, so that the groove shape of the grooved plug is changed to the inner surface of the raw tube. Let them transcribe. Specifically, when the blank tube is pressed, the inner wall surface of the blank tube is plastically deformed along the groove shape of the grooved plug, and the blank tube material flows into the groove from the ridge tip of the grooved plug. A spiral groove is formed on the inner surface of the raw tube. That is, the protrusion of the grooved plug corresponds to the groove of the tube.

    Here, in the grooved plug, for example, when the tip width δ of the ridge increases, the raw tube material hardly flows from the ridge tip into the groove. Thereby, defects, such as a crack, generate | occur | produce in the groove | channel and protrusion of a pipe | tube. However, in the present invention, since the arc radius R of the tip corner of the ridge is appropriately set with respect to the tip width δ of the ridge, the raw tube material can easily flow into the groove from the tip of the ridge. That is, the fluidity of the raw tube material is improved, and the raw tube material surely flows into the groove of the grooved plug.

    In a ninth aspect of the present invention based on the eighth aspect, the substantially V-shaped groove formed between the protrusions has an arcuate bottom portion, an arc radius rmm of the bottom portion, and The ratio (r / δ) to the tip width δmm is 0.14 or more and 0.20 or less.

    In the above invention, the arc radius r of the groove bottom is defined in relation to the tip width δ of the ridge. Here, when the tip width δ of the ridge increases, the raw tube material does not easily flow into the groove and reaches the bottom of the groove, but since the arc radius r of this bottom is appropriately set, The tube material that has flowed into the groove reliably flows to the bottom of the groove.

    A tenth aspect of the invention is based on a grooved plug having a plurality of ridges formed on the outer peripheral surface and used for forming a plurality of grooves on the inner surface of the raw tube by rolling. The protrusion is formed in a trapezoidal shape with a tapered cross section and the tip corner is formed in an arc shape. The arc radius Rmm of the tip corner is substantially V formed between the protrusions. The ratio (R / θ) to the apex angle θ ° of the letter-shaped groove is 0.0006 or more and 0.0014 or less.

    In the above invention, since the arc radius R of the tip corner portion of the ridge is defined by the relationship with the apex angle θ of the groove, the raw tube material can easily flow into the groove from the tip of the ridge. That is, for example, when the apex angle θ of the groove is reduced, the angle of the tip corner of the ridge is steep and the flow of the raw material is disturbed. However, since the arc radius R of the tip corner is appropriately set, The flow of pipe material is smooth. As a result, the raw tube material flows reliably into the groove.

    In an eleventh aspect based on the tenth aspect, the groove formed between the protrusions has a bottom formed in an arc shape, and a ratio between the arc radius rmm of the bottom and the apex angle θ ° of the groove. (R / θ) is 0.0008 or more and 0.0012 or less.

    In the above invention, the arc radius r of the groove bottom is defined in relation to the apex angle θ of the groove. For example, when the apex angle θ of the groove is reduced, the bottom of the groove is narrowed and the raw tube material is difficult to reach the bottom. However, since the arc radius r of the bottom is appropriately set, The raw pipe material that has flown into the groove surely flows to the bottom of the groove.

    The twelfth invention is premised on a grooved plug having a plurality of protrusions formed on the outer peripheral surface and used for forming a plurality of grooves on the inner surface of the raw tube by rolling. The protrusion is formed in a trapezoidal shape with a tapered cross section and the tip corner is formed in an arc shape. The arc radius Rmm of the tip corner is substantially V formed between the protrusions. The ratio (R / h) to the depth hmm of the letter-shaped groove is 0.13 or more and 0.32 or less.

    In the above invention, since the arc radius R of the tip corner of the ridge is defined in relation to the depth h of the groove, the raw tube material can easily flow into the groove from the ridge tip. That is, for example, when the depth h of the groove increases, the raw tube material does not sufficiently flow into the groove from the tip of the ridge, but the arc radius R of the tip corner of the ridge is appropriately set. It becomes easy for the pipe material to flow into the groove.

    In a thirteenth aspect based on the twelfth aspect, the groove formed between the protrusions has a bottom portion formed in an arc shape, and a ratio of an arc radius rmm of the bottom portion to a depth hmm of the groove ( r / h) is from 0.18 to 0.26.

    In the above invention, the arc radius r of the groove bottom is defined by the relationship with the groove depth h. For example, when the depth h of the groove increases, the raw tube material becomes difficult to reach the bottom of the groove, but the arc radius r of the bottom is set appropriately, so that the raw material that has flowed into the groove from the tip of the ridge Surely flows into the bottom of the groove.

    In a fourteenth aspect based on the ninth aspect, the arc radius r of the bottom of the groove is 0.04 mm, the arc radius R of the tip corner of the ridge is 0.05 mm, and the tip of the ridge is The width δ is 0.23 mm.

    In the above invention, the shape of the tip corner of the ridge and the shape of the bottom of the groove are optimal with respect to the tip width of the ridge. Therefore, the fluidity of the raw pipe material is optimized, and the raw pipe material flows smoothly and reliably into the groove.

    According to a fifteenth aspect, the grooved plug (20) according to any one of claims 8 to 14 is inserted into the raw pipe (P), and the outer surface of the raw pipe (P) corresponding to the insertion position is pressed. A groove shape corresponding to the protrusion shape of the grooved plug (20) is formed on the inner surface of the raw pipe (P) by a manufacturing process.

    In the above invention, the groove shape of the grooved plug is transferred to the inner surface of the element tube by pressing the outer surface of the element tube into which the grooved plug is inserted (rolling step). Here, in the grooved plug, the arc radius R at the tip corner of the ridge and the arc radius r at the bottom of the groove are defined so that the raw tube material can easily flow into the groove. Cracks and the like are prevented.

    In a sixteenth aspect based on the fifteenth aspect, the raw pipe (P) is reduced in diameter before the rolling step.

    In the above invention, a plurality of grooves are formed on the inner surface of the reduced diameter pipe.

    Therefore, according to the first to seventh inventions, the valley bottom R and the fin tip r of the internally grooved tube are defined in relation to the bottom width δ of the groove, the apex angle θ of the ridge, or the height h of the ridge. As a result, the raw pipe material can smoothly flow into the groove. That is, it is possible to suppress a decrease in the fluidity of the raw tube material due to the bottom width δ of the groove, the apex angle θ of the ridge, and the like. Therefore, it is possible to prevent protrusions and groove cracks that occur during manufacturing. As a result, a highly reliable inner grooved tube can be provided.

    Further, according to the eighth to fourteenth inventions, the fin tip R and bottom r of the grooved plug are defined in relation to the tip width δ of the ridge, the apex angle θ of the groove, or the depth h of the groove. As a result, the tube material can flow smoothly into the groove. Therefore, it is possible to prevent protrusions and grooves from cracking in the manufacture of the inner surface grooved tube. As a result, a highly reliable grooved plug can be provided.

    In addition, according to the fifteenth or sixteenth invention, it is possible to provide a method for manufacturing an internally grooved tube that can prevent protrusions and grooves from cracking.

    Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

    The inner grooved tube of the present embodiment is used as a heat transfer tube of a heat exchanger (so-called fin-and-tube heat exchanger) provided in a refrigeration apparatus or the like, and the refrigerant flows through the inside. The refrigerant flowing through the inner grooved tube evaporates or condenses by exchanging heat with air and water circulating around the tube. The internally grooved tube of the present embodiment (hereinafter referred to as heat transfer tube (1)) is made of copper or a copper alloy. The material is not limited to this, and may be aluminum or the like.

    As shown in FIGS. 1 to 3, a plurality of fins (3) extending spirally in the tube axis direction are formed on the inner surface of the heat transfer tube (1). This fin (3) comprises the protrusion formed in the mountain shape with a tapered cross section. Adjacent grooves (2) are formed between the fins (3). The groove (2) is formed in an inverted trapezoidal cross section. These grooves (2) and fins (3) are formed in parallel and are inclined by a predetermined angle α (hereinafter referred to as a lead angle α) with respect to the tube axis direction.

    The fin (3) has a tip portion (3a) formed in an arc shape, and a linear inclined portion (3b) is formed continuously to the tip portion (3a). A bottom flat portion (2a) is formed at the bottom of the groove (2). At both ends of the bottom flat portion (2a), bottom corner portions (2b) that are continuous with the inclined portions (3b) of the fins (3) are formed. The bottom corner (2b) is formed in an arc shape. That is, the inclined part (3b) and a part of the tip part (3a) of the fin (3), the bottom flat part (2a) and the bottom corner part (2b) constitute the groove (2). .

    In addition, the groove (2) and the fin (3) are characterized in that the arc radius R (hereinafter referred to as the valley bottom R) of the bottom corner (2b) is a feature of the present invention so that defects such as chipping and cracking do not occur during manufacturing. .) And the arc radius r (hereinafter referred to as fin tip r) of the tip (3a) are set.

    Specifically, the ratio (R / δ) between the valley bottom R and the bottom width δ of the groove (2) is set to 0.10 or more and 0.25 or less. The ratio (R / δ) is preferably 0.20 or more and 0.23 or less. Further, the ratio (r / δ) between the fin tip r and the bottom width δ of the groove (2) is set to 0.14 or more and 0.20 or less. The ratio (r / δ) is preferably 0.16 or more and 0.19 or less. Here, the bottom width δ of the groove (2) indicates the distance connecting the intersection of the extended line of the inclined part (3b) and the extended line of the bottom flat part (2a).

    The heat transfer tube (1) of the present embodiment has a fin tip r of 0.04 mm, a valley bottom R of 0.05 mm, a groove bottom width δ of 0.23 mm, a fin apex angle θ of 40 °, a fin The height h is set to 0.18 mm. As for other dimensions and angles, the outer diameter of the tube is 7 mm, the number N of grooves (2) is 50, the lead angle α of the grooves (2) is 18 °, and the bottom wall thickness t is 0.25 mm. Is set.

    In the present invention, the valley bottom R and the fin tip r may be defined in relation to the fin apex angle θ °, instead of being defined in relation to the groove bottom width δ. Specifically, the ratio (R / θ) between the valley bottom R and the fin apex angle θ ° is defined as 0.0006 or more and 0.0014 or less. The ratio (R / θ) is preferably 0.0011 or more and 0.0014 or less. The ratio (r / θ) between the fin tip r and the fin apex angle θ ° is defined as 0.0008 or more and 0.0012 or less. The ratio (r / θ) is preferably 0.0009 or more and 0.0011 or less.

    Further, the valley bottom R and the fin tip r may be defined in relation to the fin height h. Specifically, the ratio (R / h) between the valley bottom R and the fin height h is defined as 0.13 or more and 0.32 or less. The ratio (R / h) is preferably 0.25 or more and 0.31 or less. A ratio (r / h) between the fin tip r and the fin height h is defined as 0.18 or more and 0.26 or less. The ratio (r / h) is preferably 0.20 or more and 0.25 or less.

<Method for manufacturing heat transfer tube>
Next, the manufacturing method of the said heat exchanger tube (1) is demonstrated, referring FIGS. 4-6. As shown in FIG. 4, the heat transfer tube manufacturing apparatus (10) of the present embodiment includes a rolled ball (11), a holding die (12), a holding plug (13), a connecting shaft (14), And a slotted plug (20).

    The holding die (12) is formed in an annular shape and is disposed so as to be in contact with the outer surface of the raw pipe (P). The holding plug (13) is configured to be inserted into the raw tube (P) and sandwich the raw tube (P) with the holding die (12). The rolling ball (11) is disposed downstream of the holding die (12) (on the right side in FIG. 4), and rotates planetarily to press the raw tube (P) while contacting the outer surface of the raw tube (P). It is configured as follows. The grooved plug (20) is inserted into a position corresponding to the rolling ball (11) of the raw pipe (P). The grooved plug (20) is rotatably connected to the holding plug (13) by a connecting shaft (14).

    As shown in FIGS. 5 and 6, the grooved plug (20) is formed in a cylindrical shape, and a plurality of spiral fins (22) are formed on the outer peripheral surface. A spiral groove (21) is formed between the fins (22). These grooves (21) and ridges (22) are formed in parallel and are inclined by a predetermined angle with respect to the axial direction.

    The fin (22) of the grooved plug (20) constitutes a ridge having a trapezoidal shape with a tapered cross section. In the fin (22), a tip corner (22b) that is both ends of the tip (22a) is formed in an arc shape, and a linear inclined portion (22c) is formed continuously to the tip corner (22b). Has been. The groove (21) of the grooved plug (20) has a bottom (21a) formed in an arc shape and is continuous with the inclined portion (22c) of the fin (22). That is, the inclined portion (22c) and the tip corner portion (22b) of the fin (22) and the bottom portion (21a) constitute the groove (21). The groove (21) and the fin (22) of the grooved plug (20) are formed to correspond to the fin (3) and the groove (2) of the heat transfer tube (1), respectively.

    In addition, the grooved plug (20) also prevents the occurrence of defects such as cracks in the fin (3) of the heat transfer tube (1) during manufacturing, that is, the fin (3) of the heat transfer tube (1) described above. The arc radius R (hereinafter referred to as fin tip R) of the tip corner portion (22b) and the arc radius r (hereinafter referred to as valley bottom r) of the bottom portion (21a) are set so that the groove (2) can be processed. Has been.

    That is, the ratio (R / δ) between the fin tip R and the fin tip width δ is set to 0.10 or more and 0.25 or less. The ratio (r / δ) between the valley bottom r and the fin tip width δ is set to 0.14 or more and 0.20 or less. Here, the fin tip width δ indicates the distance connecting the intersection of the extension line of the tip part (22a) and the extension line of the inclined part (22c). Specifically, in the grooved plug (20) of the present embodiment, the valley bottom r is 0.04 mm, the fin tip R is 0.05 mm, the fin tip width δ is 0.23 mm, and the apex angle θ of the groove (21) is 40. The groove depth h is set to 0.18 mm.

    Also in this grooved plug (20), the present invention is defined by the relationship with the apex angle θ ° of the groove (21) instead of the relationship with the fin tip width δ for the fin tip R and the valley bottom r. You may make it do. That is, the ratio (R / θ) between the fin tip R and the apex angle θ ° of the groove (21) is defined to be 0.0006 or more and 0.0014 or less. A ratio (r / θ) between the valley bottom r and the apex angle θ ° of the groove (21) is defined to be 0.0008 or more and 0.0012 or less.

    Further, the fin tip R and the valley bottom r may be defined in relation to the fin height h. That is, the ratio (R / h) between the fin tip R and the fin height h is defined as 0.13 or more and 0.32 or less. A ratio (r / h) between the valley bottom r and the fin height h is defined as 0.18 or more and 0.26 or less.

    In the grooved plug (20), the range of desirable values of the above-mentioned ratios (R / δ, r / δ, R / θ, r / θ, R / h, r / h) is as follows. This is the same as the value range described in 1).

    In the manufacturing apparatus (10) of this embodiment, the 1st process of diameter-reducing the pipe (P) and the 2nd process of rolling the diameter-reduced pipe (P) are performed.

    In the first step, the raw tube (P), which is a smooth tube, is inserted through the holding die (12). Rolling lubricating oil is injected into the raw pipe (P), and the holding plug (13) and the grooved plug (20) connected by the connecting shaft (14) are inserted. Thereafter, the raw tube (P) is pulled out in the drawing direction (the direction indicated by the arrow in FIG. 4). Then, the raw tube (P) is reduced in diameter between the holding die (12) and the holding plug (13) (diameter reduction processing).

    In the second step, the raw pipe (P) whose diameter has been reduced in the first step is further pulled out and passes through the rolled ball (11). During this passage, the raw tube (P) is pressed against the grooved plug (20) by the rolled ball (11). Then, the inner wall surface of the raw pipe (P) is plastically deformed along the groove (21) shape of the grooved plug (20). Specifically, as shown in FIG. 6, the raw tube material (copper material or copper alloy material) is formed from the tip (22a) of the grooved plug (20) to the groove (21) along the inclined portion (22c). Flows into the bottom (21a). As a result, the shape of the groove (21) of the grooved plug (20) is transferred to the inner surface of the raw pipe (P) (rolling process).

    By the way, the heat transfer tube (1) has a groove (2) and a groove (2) so that the liquid refrigerant has an annular flow that reaches the top of the tube along the groove (2) so that the inner surface area based on the required heat transfer amount can be secured. The shape of the fin (3) is designed. That is, the larger the inner surface area, the greater the amount of heat exchange between the refrigerant and the air, and the entire inside of the tube can be used for heat transfer by forming an annular flow. As a result, the heat transfer performance of the heat transfer tube (1) can be enhanced. Specifically, the number N of grooves (2), the lead angle α of the grooves (2), the fin apex angle θ, and the fin height h are set based on the above design conditions. When the above four numerical values are determined, the valley width δ of the groove (2) is naturally determined. Moreover, the valley bottom wall thickness t is set based on the refrigerant | coolant pressure in a pipe | tube, and the required intensity | strength of a heat exchanger tube (1) is ensured.

    Here, for example, when the valley width δ of the groove (2) of the heat transfer tube (1) is increased depending on the design conditions, the raw tube material is transferred from the tip (22a) to the inclined portion (22c) in the grooved plug (20). It becomes difficult to flow. However, in this embodiment, as described above, the fin tip R and bottom r of the grooved plug (20) are defined in relation to the fin tip width δ (the valley width δ of the heat transfer tube (1)). That is, in the grooved plug (20), the fin tip R and the bottom r are set according to the fin tip width δ so that the raw tube material can easily flow into the groove (21). As a result, the raw tube material easily flows from the tip end portion (22a) along the tip corner portion (22b) to the inclined portion (22c), and further from the inclined portion (22c) to the bottom portion (21a). Therefore, the raw tube material can surely flow into the groove (21) of the grooved plug (20). As a result, defects such as chipping and cracking in the grooves (2) and fins (3) of the heat transfer tube (1) can be avoided.

    In addition, when the apex angle θ of the fin (3) of the heat transfer tube (1) (the apex angle θ of the groove (21) of the grooved plug (20)) becomes small depending on the design conditions, in the grooved plug (20), It becomes difficult for the material to flow from the front end portion (22a) to the inclined portion (22c). That is, since the flow angle of the raw material from the tip (22a) to the inclined part (22c) becomes steep, the flow of the raw material is disturbed, and the flow of the raw material into the groove (21) is insufficient. Become. However, as described above, if the fin tip R and bottom r of the grooved plug (20) are appropriately set in relation to the apex angle θ of the groove (21) (fin apex angle θ of the heat transfer tube (1)). The shape of the groove (21) is such that the raw pipe material easily flows in accordance with the apex angle θ. Therefore, the raw tube material can surely flow into the groove (21) of the grooved plug (20).

    In addition, when the fin height h of the heat transfer tube (1) is increased depending on the design conditions, in the grooved plug (20), it is difficult for the raw material to reach the bottom (21a) of the groove (21). However, as described above, if the fin tip R and bottom r of the grooved plug (20) are appropriately set in relation to the depth h of the groove (21) (fin height h of the heat transfer tube (1)). The shape of the groove (21) is such that the raw tube material flows into the bottom (21a) reliably according to the depth h. Therefore, the raw tube material can surely flow into the groove (21) of the grooved plug (20).

    Here, in any of the above cases, the larger the fin tip R and the bottom r, the greater the inflow of the raw tube material into the groove (21), but the smaller the inner surface area of the heat transfer tube (1) becomes. Thermal performance will decrease. Therefore, the upper limit values of the fin tip R and the bottom r are set within a range in which the necessary heat transfer amount can be secured.

    Thus, in the present embodiment, the valley bottom R and the fin tip r of the heat transfer tube (1), that is, the fin tip R and the bottom r of the grooved plug (20) are set according to the numerical values of various parameters set according to the design conditions. It was made to prescribe. Therefore, it is possible to improve the workability while ensuring the functionality (heat transfer performance, etc.) of the heat transfer tube (1). As a result, a highly reliable heat transfer tube (1) can be provided.

<Evaluation results>
Next, evaluation test results such as cracks during production of the heat transfer tube (1) will be described with reference to FIG. In all cases (cases 1 to 3), the outer diameter of the heat transfer tube is 7 mm, the number N of the grooves (2) is 50, the lead angle α of the grooves (2) is 18 °, and the bottom of the valley. The thickness t was 0.25 mm.

    As shown in FIG. 7, in case 1 and case 3, chipping or cracking occurred in the fin (3) or groove (2), and no cracking or the like occurred in case 2 at all. Thus, it can be seen that Case 2 satisfies the specified numerical range of the ratio of the valley bottom R and the fin tip r to the valley bottom width δ and the like described above. On the other hand, it can be seen that Case 1 and Case 3 are out of the specified numerical value range.

<< Other Embodiments >>
For example, in the said embodiment, although the copper heat-transfer tube used for a heat exchanger was made into object, it is good also as object about pipes for another use, such as a water pipe.

    Further, the shape of the groove (2) of the heat transfer tube (1) is not limited to a spiral shape, and may be, for example, a linear groove extending along the axial direction.

    In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or its use.

    As described above, the present invention is useful as an internally grooved tube having a spiral groove on its inner surface, a manufacturing method thereof, and a grooved plug used in the manufacture thereof.

It is a longitudinal cross-sectional view which shows the heat exchanger tube which concerns on embodiment. It is a cross-sectional view which shows the heat exchanger tube which concerns on embodiment. It is a cross-sectional view which shows the principal part of the heat exchanger tube which concerns on embodiment. It is a block diagram which shows the manufacturing apparatus which concerns on embodiment. It is a perspective view which shows the plug with a groove | channel which concerns on embodiment. It is a cross-sectional view which shows the principal part of the plug with a groove | channel which concerns on embodiment. It is a table | surface which shows the result of an evaluation test. It is a cross-sectional view which shows the crack of a groove | channel, a fin, etc.

Explanation of symbols

1 Heat transfer tube (inner grooved tube)
2 groove
2b Bottom corner
3 Fins
3a Tip
10 Production equipment
11 Rolled balls
12 Holding dies
13 Retaining plug
20 Slotted plug
21 groove
21a Bottom
22 Fins
22b Tip corner
P tube

Claims (16)

An internally grooved tube having a plurality of grooves formed on the inner surface,
The groove has an inverted trapezoidal cross section and the bottom corner is arcuate, and the ratio (R / δ) between the arc radius Rmm of the bottom corner and the bottom width δmm of the groove is An internally grooved tube characterized by being 0.10 or more and 0.25 or less. In claim 1,
The tapered ridge formed adjacent to the groove has an arcuate top, and the ratio (r / δ) between the arc radius rmm of the apex and the bottom width δmm of the groove is 0.14 or more. An internally grooved tube characterized by being 0.20 or less. An internally grooved tube having a plurality of grooves formed on the inner surface,
The groove has an inverted trapezoidal cross section, and the bottom corner is formed in an arc shape. The bottom corner has an arc radius Rmm, and the top of a tapering ridge formed adjacent to the groove. An internally grooved tube having a ratio (R / θ) to the angle θ ° of 0.0006 or more and 0.0014 or less. In claim 3,
The ridge is formed such that the apex is formed in an arc shape, and the ratio (r / θ) between the arc radius rmm of the apex and the apex angle θ ° of the ridge is 0.0008 or more and 0.0012 or less. Features an internally grooved tube. An internally grooved tube having a plurality of grooves formed on the inner surface,
The groove is formed in an inverted trapezoidal cross section and the bottom corner is formed in an arc shape. The arc radius Rmm of the bottom corner and the height of the taper formed adjacent to the groove are tapered. An inner grooved tube having a ratio (R / h) with respect to the height hmm of 0.13 or more and 0.32 or less. In claim 5,
The top of the protrusion is formed in an arc shape, and the ratio (r / h) between the arc radius rmm of the top and the height hmm of the protrusion is 0.18 or more and 0.26 or less. An internally grooved tube. In claim 2,
An inner surface groove characterized in that the arc radius r of the top of the ridge is 0.04 mm, the arc radius R of the bottom corner of the groove is 0.05 mm, and the bottom width δ of the groove is 0.23 mm. Tube. A plurality of protrusions are formed on the outer peripheral surface, and the grooved plug is used to form a plurality of grooves on the inner surface of the raw tube by rolling,
The protrusion is formed in a trapezoidal shape with a tapered cross section, and the tip corner is formed in an arc shape. The ratio of the arc radius Rmm of the tip corner to the tip width δmm of the protrusion (R / A grooved plug, wherein δ) is 0.10 or more and 0.25 or less. In claim 8,
The substantially V-shaped groove formed between the protrusions has an arcuate bottom, and the ratio (r / δ) between the arc radius rmm of the bottom and the tip width δmm of the protrusion is 0. A grooved plug characterized by being in the range of 14 to 0.20. A plurality of protrusions are formed on the outer peripheral surface, and the grooved plug is used to form a plurality of grooves on the inner surface of the raw tube by rolling,
The protrusion is formed in a trapezoidal shape with a tapered cross section, and the tip corner is formed in an arc shape. The arc radius Rmm of the tip corner and a substantially V-shape formed between the protrusions. A grooved plug, characterized in that the ratio (R / θ) to the apex angle θ ° of the groove is 0.0006 or more and 0.0014 or less. In claim 10,
The groove formed between the protrusions has an arcuate bottom, and the ratio (r / θ) between the arc radius rmm of the bottom and the apex angle θ ° of the groove is 0.0008 or more and 0.0012. A grooved plug characterized by: A plurality of protrusions are formed on the outer peripheral surface, and the grooved plug is used to form a plurality of grooves on the inner surface of the raw tube by rolling,
The protrusion is formed in a trapezoidal shape with a tapered cross section, and the tip corner is formed in an arc shape. The arc radius Rmm of the tip corner and a substantially V-shape formed between the protrusions. A grooved plug, characterized in that the ratio (R / h) to the groove depth hmm is 0.13 or more and 0.32 or less. In claim 12,
The groove formed between the protrusions has an arcuate bottom, and the ratio (r / h) between the arc radius rmm of the bottom and the depth hmm of the groove is 0.18 or more and 0.26 or less. A grooved plug characterized by being. In claim 9,
The arc radius r of the bottom of the groove is 0.04 mm, the arc radius R of the tip corner of the ridge is 0.05 mm, and the width δ of the tip of the ridge is 0.23 mm. Slotted plug. The grooved plug (20) according to any one of claims 8 to 14 is inserted into the element pipe (P), and the element is subjected to a rolling step of pressing the outer surface of the element pipe (P) corresponding to the insertion position. A method for producing an internally grooved tube, wherein a groove shape corresponding to the protruding shape of the grooved plug (20) is formed on the inner surface of the tube (P). In claim 15,
A method of manufacturing an internally grooved tube, wherein the diameter of the raw tube (P) is reduced before the rolling step.

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