JP7636050B2 - Tube expansion tool and tube expansion method - Google Patents

Description

The present invention relates to a tube expansion tool and method used to expand heat exchanger tubes.

When manufacturing heat exchangers used in home room coolers, etc., a tube expansion tool is used to expand a copper heat exchange tube that penetrates a fin layer in which multiple heat dissipation fins are stacked, and to integrate the heat dissipation fins and the heat exchange tube. When expanding the heat exchange tube using the tube expansion tool, the avec phenomenon, in which the fins stick to each other, may occur due to the longitudinal shrinkage of the heat exchange tube that occurs with the tube expansion.
Recently, in order to improve the thermal properties of heat exchangers and reduce their weight for energy saving and other reasons, there has been a demand for thinner copper heat exchange tubes. When thin-walled copper heat exchange tubes are expanded, they shrink more in the longitudinal direction than when normal-thickness heat exchange tubes are expanded. In addition, to reduce the weight of heat exchangers, it is desirable to use aluminum heat exchange tubes instead of copper heat exchange tubes. However, since aluminum has a lower thermal conductivity than copper, there is a demand for further thinning in order to improve the thermal properties of aluminum heat exchange tubes.

When expanding the thinned heat exchange tube in this way, shrinkage of the heat exchange tube due to expansion can be prevented by grasping and expanding the upper end of the heat exchange tube protruding from the top plate of the fin layer and the lower end of the heat exchange tube protruding from the bottom plate. However, since the lower end of the heat exchange tube is not expanded, it can be easily grasped with a grasping tool such as a receiver. However, it is difficult to grasp and expand the tip of the heat exchange tube that is to be expanded. An expansion tool that can grasp the tip of such a heat exchange tube and expand it is proposed in the following Patent Document 1.

Patent Document 1 describes a heat transfer tube fixing device having a gripping part that grips one axial end of a plurality of heat transfer tubes that are inserted into the insertion holes of a plurality of heat transfer fins that are stacked at a predetermined interval, and a moving part that moves in the axial direction of the heat transfer tube to switch between a first state in which the gripping part is covered and a second state in which the gripping part is not covered, and a mandrel device having a mandrel that is inserted into the heat transfer tube from one axial end side of the heat transfer tube, the moving part being a plate-shaped A heat transfer tube expanding device has been proposed, in which the mandrel is inserted into the heat transfer tube to expand the heat transfer tube while the moving part is in the first state, the gripping part fixes the heat transfer tube so that it does not move in the axial direction, and the heat transfer fin and the heat transfer tube are fixed. The member provided with the gripping part is a collet chuck in which the tip of a cylindrical body is divided into a plurality of gripping pieces, which are curved radially outward from the cylindrical body along the way, and a fan-shaped slit is opened on the tip surface between the gripping pieces, which gradually widen in the tip direction, and the gripping pieces are the gripping part.

According to this heat transfer tube expanding device, a single plate-like member can simultaneously grip and expand the tips of many heat transfer tubes (referred to as heat exchange tubes). However, in recent years, room coolers and the like have been shifting to high-mix low-volume production, and the arrangement and arrangement density of the heat exchange tubes inserted into the fin layers of the heat exchanger are frequently changed. Every time the arrangement and arrangement density of the heat exchange tubes are changed, the plate-like member must be changed to one that matches the arrangement and density of the changed heat exchange tubes, which requires a complicated replacement work.
In contrast to the tube expansion tool proposed in Patent Document 1, which uses a single plate-shaped member to simultaneously grip and expand the tip ends of multiple heat exchange tubes, Patent Documents 2 and 3 listed below propose tube expansion tools that can grip and expand the tip end of each heat exchange tube used in a heat exchanger.

A schematic diagram of an example of the tube expansion tool proposed in Patent Document 2 is shown in Fig. 9. The target to be expanded by the tube expansion tool 100 shown in Fig. 9 is a heat exchange tube 104 that is inserted into a collared through-hole in a fin layer in which a plurality of heat dissipation fins 102 having collared through-holes of a predetermined height are stacked, and a tip portion 104a of the heat exchange tube 104 protrudes from a top plate 106 of the fin layer.
The lower ends of the heat exchange tubes 104 protruding from the bottom plate of the fin layer are held by a holding jig (not shown) such as a receiver.

This tube expansion tool 100 is an expansion mandrel 108 having a mandrel 108b at the front end of which is attached an expansion billet 108a that expands the heat exchange tube 104 and integrates it with each of the heat dissipation fins 102, and a rear end of which is connected to a pressing means (not shown) that is provided so as to be movable in the direction of inserting and removing the expansion billet 108a into and from the heat exchange tube 104, and a cylindrical body 112a that is slidably inserted onto the expansion mandrel 108, and multiple gripping pieces 112b that are formed by dividing the tip of the cylindrical body 112a are inserted in the middle of the tube 104. The slit 112c formed between the gripping pieces 112b, 112b is curved radially outward from the cylindrical body 112a, and is formed into a fan-shaped slit section that gradually widens toward the tip while leaving a narrow slit section 112 of a certain length at the rear end of the cylindrical body 112a. The gripping body 112 has an inclined surface 112e on the outer surface of the part corresponding to the protrusion 112d that protrudes inward from the cylindrical body 112a formed on the inner wall surface of the gripping piece 112b, and is composed of a cylindrical body 114 that is inserted outside the gripping body 112 so as to be slidable in the longitudinal direction.

In the method of expanding the heat exchange tube 104 using the expansion tool 100 shown in FIG. 9, the gripper 112 located above the tip 104a of the heat exchange tube 104 protruding from the top plate 106 shown in FIG. 10(a) is lowered so that its tip surface abuts against the top plate 106 as shown in FIG. 10(b), and the tip 104a of the heat exchange tube 104 is surrounded by the multiple gripping pieces 112b of the gripper 112. Next, as shown in FIG. 10(c), the expansion mandrel 108 is lowered to expand the part including the tip 104a of the heat exchange tube 104 with the expansion billet 108a to form the expanded part 104b, and the descent of the expansion mandrel 108 is stopped. The expanded expanded part 104b and the top plate 106 are integrated. Furthermore, as shown in FIG. 10(d), the cylindrical body 114 is lowered along the gripping body 112, and its tip portion rides on the inclined surface 112e of the gripping body 112, reducing the width of the fan-shaped slit portion of the slit 112c to approximately the same width as the remaining narrow slit portion. At that time, the protruding portion 112d on the inner wall surface of the gripping piece 112b presses the expanding portion 104b to form a crimped portion 104c with a reduced diameter. The protruding portion 112d and the crimped portion 104c become the gripping portion of the heat exchange tube 104 when the descent of the tube expansion mandrel 108 is resumed to expand the heat exchange tube 104 to the lower end protruding from the fin layer of the heat exchange tube 104, and together with a gripping tool such as a receiver that grips the lower end of the heat exchange tube 104, it is possible to prevent the heat exchange tube 104 from shrinking due to tube expansion.

A schematic diagram of an example of the tube expansion tool proposed in Patent Document 3 is shown in FIG. 11(a). The object to be expanded by the tube expansion tool 200 in FIG. 11(a) is, like the tube expansion tool 100 in Patent Document 2, a heat exchange tube 204 that is inserted into a collared through hole in a fin layer in which heat dissipation fins 202 having a plurality of collared through holes of a predetermined height are stacked, and whose tip 204a protrudes from the top plate 206 of the fin layer. The lower end of the heat exchange tube 204 protruding from the bottom plate of the fin layer is held by a holding tool (not shown) such as a receiver.

The tube expansion tool 200 is inserted from the tip 204a of the heat exchange tube 204 that penetrates the fin layer and protrudes from the top plate 206, and directly contacts the outer peripheral surface of the expansion billet 208a, which is the maximum outer diameter, with the inner wall surface of the heat exchange tube 204, expanding the heat exchange tube 204 and integrating it with the heat dissipation fin 202. This tube expansion tool 200 is capable of reducing its diameter by tightening force, and is equipped with a chuck sleeve 212a in which the inner wall surface 212d of the tip protrudes inward more than the inner wall surface of the other parts and is formed in a thick portion 212b, and a clamp bush 214 that is slidably provided along the outer peripheral surface of the chuck sleeve 212a in the direction of tightening or releasing the tightening of the chuck sleeve 212a, and a recessed groove 212c is formed on the inner wall surface of the thick portion 212b of the chuck sleeve 212a. Furthermore, within the chuck sleeve 212a, a guide portion 216a is formed at the tip to be inserted into the tip of the expanded heat exchange tube 204, and a flare punch 216 is formed in the middle to further expand the tip of the expanded tube to form a flare portion. The flare punch 216 is mounted so as to be slidable in the vertical direction along a mandrel 208b, the tip of which is fitted with an expansion billet 208a.

When expanding the heat exchange tube 204 as shown in Fig. 11(b) using the tube expansion tool 200 shown in Fig. 11(a), first, the tip 204a of the heat exchange tube 204, whose rear end is held by a holding tool (not shown), which protrudes after penetrating the fin layer, is inserted into the thick part 212b formed at the tip of the chuck sleeve 212a, and the clamp bush 214 is lowered to tighten the chuck sleeve 212a including the thick part 212b. At this time, the thick part 212b of the chuck sleeve 212a is also reduced in diameter, and the tip 204a of the heat exchange tube 204 is adjusted in a direction in which the axis of the tube expansion billet 208a coincides with that of the tube expansion billet 208a. At this time, the tip 204a of the heat exchange tube 204 is not gripped by the thick portion 212b of the chuck sleeve 212a, and by pressing the top plate 206 with the tip surface of the chuck sleeve 212a, the length of the tip 204a of the heat exchange tube 204 protruding from the top plate 206 can be adjusted.
Next, the expanded billet 208a is inserted into the tip 204a of the heat exchange tube 204 to expand it, and the outer circumferential surface of the expanded portion 204b is pressed against the inner wall surface 212d of the thick portion 212b of the chuck sleeve 212a to generate a gripping force to grip it, and then the insertion of the expanded billet 208a into the heat exchange tube 204 is temporarily stopped, and the guide portion 216a of the flare punch 216 is inserted into the expanded portion 204b. By inserting this guide portion 216a, a decrease in the gripping force caused by the diameter reduction due to the springback phenomenon of the expanded portion 204b after the passage of the expanded billet 208a is prevented.
Furthermore, the expansion billet 208 a is inserted again in the direction toward the rear end of the heat exchange tube 204 to expand the tube, and the heat exchange tube 204 and the heat dissipation fin 202 are integrated together.
Thereafter, after the expansion of the heat exchange tube 204 is completed, the clamp bush 214 is raised to release the grip of the expanded portion 204b of the heat exchange tube by the thick portion 212b of the chuck sleeve 212a, and the chuck sleeve 212a is further raised, after which the flare punch 216 is lowered along the mandrel 208b to form a flare portion at the tip portion of the expanded portion 204b, and the expansion billet 208a is pulled out of the expanded heat exchange tube 204.

Patent No. 5696745 Patent No. 5870418 JP 2010-247190 A

According to the tube expansion tool 100 of Patent Document 2, the tip of each heat exchange tube 104 can be grasped to expand the heat exchange tube 104, and it is possible to prevent as much as possible the shrinkage of the heat exchange tube 104 due to tube expansion. Furthermore, since the tube expansion tool 100 is provided for each heat exchange tube 104, it is possible to respond to changes in the arrangement and arrangement density of the heat exchange tubes 104 inserted into the fin layer for each changed heat exchange tube 104, and therefore it is possible to quickly respond even if the arrangement and arrangement density of the heat exchange tubes 104 are frequently changed.
However, as shown in Fig. 10C, the tube expansion jig 100 expands the tip 104a of the heat exchange tube 104 that is not fixed to the top plate 106 of the fin layer by lowering the tube expansion mandrel 108 and inserting the tube expansion billet 108a. The tip 104a of the heat exchange tube 104 that is not fixed to the top plate 106 of the fin layer, which protrudes from the top plate 106, may be inclined. The axis of the tip 104a of the heat exchange tube 104 in this inclined state and the axis of the tube expansion mandrel 108 do not coincide, and when the tube expansion mandrel 108 is lowered and the tube expansion billet 108a is inserted into the tip 104a of the heat exchange tube 104, the tip 104a of the heat exchange tube 104 may buckle. Even if the axial center of the tip 104a of the heat exchange tube 104 and the expanding mandrel 108 are aligned, if the tip 104a of the heat exchange tube 104 is expanded in an unfixed state, shrinkage occurs in the tip 104a.
Furthermore, when the expansion billet 108a expanding the tip 104a of the heat exchange tube 104 reaches a predetermined position, the descent of the expansion mandrel 108 is temporarily stopped, the gripping body 112 is lowered to form the crimped portion 104c in the expanded portion 104b, and then the descent of the expansion mandrel 108 is resumed to resume expansion by the expansion billet 108a. In this manner, while the expansion billet 108a is expanding the heat exchange tube 104, controlling the drive means of the expansion mandrel 108 so that the descent of the expansion mandrel 108 can be stopped and resumed when the expansion billet 108a reaches a predetermined position requires a complex control means. Furthermore, when the expansion of the heat exchange tube 104 is completed and the expansion billet 108a is removed, the crimped portion 104c, which has undergone work hardening, must be re-expanded with the expansion billet 108a, which places an excessive load on the gripping means, such as a receiver, that grips the rear end of the heat exchange tube 104, and there is a risk that the gripping means, such as a receiver, and/or the rear end of the heat exchange tube 104 may be damaged.

The slit 112c formed in the gripping body 112 of the tube expansion jig 100 is a fan-shaped slit portion that is gradually widened toward the tip while leaving a narrow slit portion of a predetermined length. This slit 112c is intended to expand and contract only the fan-shaped slit portion. If the narrow slit portion is also expanded or contracted, the expansion and contraction stress will be concentrated on the rear end portion 115 of the narrow slit portion, and there is a risk of cracks occurring in the rear end portion 115. When using a tube expansion jig 100 having a gripping body 112 in which such a slit 112c is formed, it is necessary to minimize the variation in the outer diameter of the expanded portion 104b of the heat exchange tube 104. However, in the expanded portion 104b of the heat exchange tube 104, in addition to variations in the outer diameter of the heat exchange tube 104 itself, there is also variation in the expansion, and when the fan-shaped slit portion is expanded and contracted by the multiple gripping pieces 112b of the gripping body 112 to grip the expanded portion 104b with such variations, the narrow slit portion following the fan-shaped slit portion may also expand and contract, and the expansion and contraction stress may concentrate on the rear end portion 115 of the narrow slit portion, causing it to break. This is also the case with the collet chuck with a fan-shaped slit opening at the tip surface, which is used as a member with a gripping portion formed in the heat transfer tube expansion device of Patent Document 1.

According to the tube expansion tool 200 of Patent Document 3, when the tube expansion billet 208a is inserted into the tip 204a of the heat exchange tube 204, the tip 204a of the heat exchange tube 204 is adjusted by the chuck sleeve 212a in a direction in which the axis of the tip 204a coincides with that of the tube expansion billet 208a. This prevents the tube expansion tool 100 of Patent Document 2 from inserting the tube expansion billet 208a into the tip 204a of the heat exchange tube 204, which is in an inclined state. In addition, since the inner wall surface of the heat exchange tube after expansion is smooth, the tube expansion billet 208a can be easily pulled out of the expanded heat exchange tube.

In the tube expansion jig 200, similarly to the tube expansion jig 100, when the tip portion 204a of the heat exchange tube 204 is expanded, the insertion of the tube expansion billet 208a into the heat exchange tube 203 is temporarily stopped, and the guide portion 216a of the flare punch 216 is inserted into the expanded portion 204b, and then the insertion of the tube expansion billet 208a is resumed. In this manner, while the tube expansion billet 208a is expanding the heat exchange tube 104, it is necessary to control the drive means of the tube expansion mandrel 208 so that the descent of the tube expansion mandrel 208 can be stopped and resumed when the tube expansion billet 208a reaches a predetermined position, which requires a complex control means.
In addition, the expansion jig 200 grips the expansion section 204b of the heat exchange tube 204 by the thick portion 212b of the chuck sleeve 212a due to a gripping force generated when the outer circumferential surface of the expansion billet 208a presses the outer circumferential surface of the expansion section 204b against the inner wall surface 212d of the chuck sleeve 212a when the gap between the outer circumferential surface of the expansion billet 208a and the inner wall surface 212d of the thick portion 212b of the chuck sleeve 212a becomes minimum, as described below. In other words, the expansion of the heat exchange tube 204 by the tube expansion billet 208a is an operation of expanding the inner diameter while reducing the tube wall as the tube expansion billet 208a advances, and even if the expanded tube portion 204b has a reduced tube thickness, if the tube thickness is a predetermined thickness, the expanded tube portion 204b is pressed against the inner wall surface 212d of the chuck sleeve 212a with a predetermined pressing force from the tube expansion billet 208a to exert a predetermined gripping force in the minimum gap between the outer circumferential surface of the tube expansion billet 208a and the inner wall surface 212d of the chuck sleeve 212a. Since the inner wall surface 212d of the chuck sleeve 212a is pressed by the tube expansion billet 208a in this way, it is necessary for the inner wall surface 212d of the chuck sleeve 212a to have a strength capable of resisting the pressing force of the tube expansion billet 208a. In addition, the heat exchange tube 204 to be expanded usually has variations in tube thickness and/or outer diameter, and when expanding an expansion billet 204 in which the tube thickness is thinner and/or the outer diameter is shifted in the direction of smaller diameter, the tube thickness of the expanded portion 204b which has been expanded and reduced in thickness and reaches the minimum gap between the expansion billet 208a and the inner wall surface 212d of the chuck sleeve 212a may become less than a predetermined thickness, and the gripping force of the expanded portion 204b may suddenly decrease. For this reason, the range in which the expansion tool 200 can accommodate variations in the tube thickness and/or outer diameter of the heat exchange tube 204 is narrow.
Incidentally, the groove 212c formed on the inner wall surface 212d of the chuck sleeve 212a is a clearance for the excess tube wall of the expanded portion 204b generated in the minimum gap between the outer circumferential surface of the expansion billet 208a and the inner wall surface 212d of the chuck sleeve 212a during expansion of the expansion billet 204 whose tube thickness is thick and/or whose outer diameter has shifted in the direction of a larger diameter, as described below, and is intended to prevent damage to the chuck sleeve 212a and deformation of the expanded heat exchange tube. Therefore, in the expansion of the heat exchange tube 204 having a tube thickness and/or outer diameter that does not generate excess tube wall in the minimum gap between the expansion billet 208a and the chuck sleeve 212a, the original space is preserved in the groove 212c, and the gripping force of the expanded portion 204b is generated only by the pressing force of the expansion billet 208a against the inner wall surface 212d of the chuck sleeve 212a.

The present invention has been made to solve the above problems, and aims to provide an expanding tool and method that uses an expanding tool having a chuck sleeve with a slit formed therein, and can expand the tip of the heat exchange tube in a direction that coincides with the axis of the expanding billet, even if the tip of the unexpanded heat exchange tube is inclined against the top plate of the fin layer, and can insert the expanding billet continuously into the heat exchange tube without stopping the insertion of the billet into the heat exchange tube, and can easily remove the expanded billet from the heat exchange tube without damaging the gripping means for gripping the rear end of the heat exchange tube and the rear end of the heat exchange tube, can easily and reliably grip the tip of a heat exchange tube having variations in tube thickness and/or outer diameter with the chuck sleeve, and can distribute the stress associated with the expansion and contraction of the slit in the chuck sleeve.

The tube expansion tool made to achieve the above object is a tube expansion tool that expands a heat exchange tube, which penetrates a fin layer in which a plurality of heat dissipation fins are laminated, and whose front and rear ends protrude from the fin layer by gripping the front and rear ends so as to prevent longitudinal contraction of the tube, and integrates the tube with each of the heat dissipation fins. The tube expansion tool includes a mandrel that is inserted from the front end of the gripped heat exchange tube at its rear end, and to which an expansion billet that expands the heat exchange tube is connected to the front end, and whose rear end is connected to a press-fitting means that is provided so as to be movable in a direction in which the expansion billet is inserted into and removed from the heat exchange tube, and a press-fitting means that is inserted slidably around the mandrel. a chuck sleeve having a ridge formed on the inner wall of the chuck sleeve, the ridge being inserted into the heat exchange tube, and a plurality of gripping pieces formed by dividing the tip of the chuck sleeve into which the tip of the heat exchange tube is inserted are curved in a bow shape toward the outer surface of the chuck sleeve due to their spring force, and slits between the gripping pieces are formed of a hole having a curved inner wall that opens into the circumferential surface of the rear end side of the chuck sleeve, and a fan-shaped slit portion that gradually widens from an opening narrower than the width of the hole toward the tip of the chuck sleeve, and a ridge formed as a protrusion protruding inward from each of the inner wall surfaces of the gripping pieces; and and a slide sleeve which slides each of the gripping pieces against the spring force in a direction to fasten the gripping pieces or in a direction to release the restraint so as to compress the entire slit and restrain each of the gripping pieces into a cylindrical shape, the cross-sectional shape of the convex strip is a trapezoid or a triangle which gradually narrows from the base toward the tip, and the protruding length of the convex strip from the inner wall surface of the gripping pieces is such that each of the gripping pieces of the chuck sleeve into which the tip of the heat exchange tube is inserted is restrained into a cylindrical shape by the sliding of the slide sleeve, and the expanded billet is inserted into the tip of the heat exchange tube which is positioned in a direction to coincide with the axis of the expanded billet. When each tip of the ridges bites into the outer peripheral surface of the expanded portion that has been inserted and expanded without reducing the inner diameter of the expanded portion, and a gripping portion is formed that grips the expanded portion of the heat exchange tube, a space is formed between the entire inner wall surface of each of the gripping pieces, excluding the ridges, and the outer peripheral surface of the expanded portion , and when the slide sleeve slides in the direction in which the restraint by the chuck sleeve is released, each of the gripping pieces bends in a bow shape toward the outer surface of the cylindrical body due to the spring force, so that the tip of each of the ridges disengages from the bite into the outer peripheral surface of the expanded portion and the gripping by the gripping portion is released .

The hole constituting the slit of the chuck sleeve is an elongated hole, the opening of the fan-shaped slit formed at the tip of the elongated hole is narrower than the width of the elongated hole, and when the gripping part is released from restraint, the width of the elongated hole gradually expands in the direction of the opening, so that the stress caused by the expansion and contraction of the slit can be sufficiently distributed by the curved inner wall surface of the elongated hole, which is preferable.

The portion of the gripping piece of the chuck sleeve where the convex rib is formed is formed in a thick section that is thicker in the outer surface direction than the other parts of the cylindrical body , an inclined surface is connected to the rear end of the thick section, and the entire body including the inclined surface and the thick section is bowed in the outer surface direction of the cylindrical body due to its spring force, so that when the slide sleeve rides up on the thick section, each of the gripping pieces can be strongly restrained into a cylindrical shape, which is preferable.

When each of the gripping pieces is constrained into a cylindrical shape by the sliding sleeve, an annular ridge is formed from the ridges, and the tip of the annular ridge bites into the outer peripheral surface of the expanded portion at the tip of the heat exchange tube in an annular shape, which is preferable because it ensures a secure grip.

By forming multiple annular ridges, the tips of the multiple annular ridges can be inserted into the outer peripheral surface of the expanded portion at the tip of the heat exchange tube, which is preferable as it provides a more secure grip.

It is preferable that the height of the ridge from the inner wall surface is 0.5 to 0.8 mm, and the bite width of the tip of the ridge is 0.01 to 0.07 mm .

The tube expansion method achieved to achieve the above object is a method for expanding a heat exchange tube, which penetrates a fin layer in which multiple fins are stacked, and whose leading and trailing ends protrude from the fin layer, by gripping and expanding the leading end of the heat exchange tube, whose trailing end is gripped, with the above-mentioned tube expansion tool so as to prevent longitudinal contraction, and integrating it with each of the fins. The method includes inserting the leading end of the heat exchange tube into the multiple gripping pieces that form the leading end of the chuck sleeve constituting the tube expansion tool, and sliding the slide sleeve against the spring force of the multiple gripping pieces of the chuck sleeve to the upper surface side of the gripping pieces. The method is characterized in that the heat exchange tube is inserted into the tip of the heat exchange tube, the entire slit is narrowed and constrained into a cylindrical shape, the heat exchange tube is adjusted in a direction in which the axis of the heat exchange tube coincides with that of the expansion billet, and the tip of the ridge is inserted into the outer circumferential surface of the expanded portion without narrowing the inner diameter of the expanded portion, forming a gripping portion in which a space is formed between the entire surface of the inner wall surface of each gripping piece, excluding the ridge, and the outer circumferential surface of the expanded portion, and then, without stopping the expansion billet, the expansion of the heat exchange tube with the tip gripped by the gripping portion is continued in the direction of the rear end side of the heat exchange tube.

After the expansion of the heat exchange tube is completed, the expansion billet is pulled out from the expanded heat exchange tube held by the gripping portion, and then the slide sleeve is slid from the upper side of the multiple gripping pieces of the chuck sleeve, releasing the cylindrical restraint state of the multiple gripping pieces, and the spring force of each of the gripping pieces causes them to bend in a bow shape toward the outside of the cylindrical body , releasing the engagement of the tip of the convex rib with the outer peripheral surface of the expanded portion , thereby easily releasing the gripping by the gripping portion.

According to the expansion tool of the present invention, the tip of an unexpanded heat exchange tube can be expanded while being positioned in a direction so that its axis coincides with that of the expansion billet, thereby preventing buckling or other problems from occurring at the tip of the heat exchange tube.
In addition, since only the tip of the convex rib of the chuck sleeve bites into the outer peripheral surface to form a gripping portion without reducing the inner diameter of the expanded portion of the heat exchange tube, the heat exchange tube can be expanded continuously without stopping the expanded billet once, and once expansion is completed, the expanded billet can be easily removed from the heat exchange tube without damaging the gripping means that grips the rear end of the heat exchange tube or the rear end of the heat exchange tube.
Within this gripping portion, a gap is formed between the entire inner wall surface excluding the convex ribs of the chuck sleeve and the outer peripheral surface of the expanded portion, so that even if there is variation in the tube thickness and/or outer diameter of the unexpanded heat exchange tube, this can be accommodated by the width at which the tip of the convex ribs of the chuck sleeve bites into the outer peripheral surface of the expanded portion of the heat exchange tube, making it possible to easily accommodate variations in the tube thickness and/or outer diameter of the heat exchange tube.
In this way, the entire inner wall surface of the chuck sleeve, excluding the convex ribs, is not in direct contact with the outer peripheral surface of the expanded portion of the heat exchange tube, and the pressing force of the expansion billet is not received through the outer peripheral surface of the expanded portion of the heat exchange tube, making it possible to eliminate the need for solidification measures such as thickening the chuck sleeve and to reduce the weight of the chuck sleeve.
Furthermore, when the gripping pieces of the chuck sleeve are constrained into a cylindrical shape by the slide sleeve or released from the constrained state, the expansion/contraction stress applied to the rear end of the slit formed between the gripping pieces of the chuck sleeve due to the expansion/contraction of the slit can be dispersed, thereby preventing the occurrence of cracks, etc. due to the concentration of the expansion/contraction stress at the rear end of the slit.

FIG. 2 is a partial cross-sectional view for explaining an example of a tube expansion jig to which the present invention is applied. 2 is a partial cross-sectional view illustrating a state in which a tip portion of an unexpanded heat exchange tube is inserted into a tip portion of a chuck sleeve of the tube expansion jig shown in FIG. 1 . 2 is a partial cross-sectional view illustrating a state in which the tip portion of the chuck sleeve is converged into a cylindrical shape by the slide sleeve of the tube expansion jig shown in FIG. 1 . This is a partial cross-sectional view explaining that when the tip of an unexpanded heat exchange tube inserted into the tip of the chuck sleeve of the expansion jig shown in Figure 1 is in an inclined state and the axis of the tip does not coincide with the axis of the expansion billet, the position of the tip of the heat exchange tube is adjusted. 2 is a partial cross-sectional view illustrating a state in which a portion including a tip portion of an unexpanded heat exchange tube inserted into the tip portion of the chuck sleeve of the expansion jig shown in FIG. 1 is expanded by an expansion billet. 4 is a partial cross-sectional view illustrating a state in which a portion including a tip portion of a heat exchange tube is expanded by a tube expansion billet. FIG. FIG. 4 is a partial cross-sectional view illustrating a state in which a flare portion is formed at the tip end of the expanded heat exchange tube. FIG. 11 is a partial front view illustrating another example of a slide sleeve to which the present invention is applied. FIG. 11 is a partial cross-sectional view illustrating a conventional pipe expansion jig. FIG. 10 is a partial cross-sectional view illustrating a pipe expanding method using the conventional pipe expanding jig shown in FIG. 9 . FIG. 11 is a partial cross-sectional view illustrating a conventional pipe expansion jig. FIG. 12 is a partial cross-sectional view illustrating a gripping portion formed by the conventional pipe expanding jig shown in FIG. 11 .

The present invention is described in detail below, but the scope of the present invention is not limited to these.

An example of a tube expansion tool to which the present invention is applied is shown in FIG. 1(a). The tube expansion tool 10 shown in FIG. 1(a) is attached to a tube expansion machine dedicated to expanding heat exchange tubes. The object to be expanded by this tube expansion tool 10 is a heat exchange tube 14 that is inserted into a collared through hole in a fin layer 17 in which a plurality of heat dissipation fins 12 having collared through holes of a predetermined height are stacked, and the tip 14a protrudes from the top plate 16 of the fin layer 17. The heat exchange tube 14 is usually a straight tube or a hairpin tube. In the case of a straight tube, the lower end protrudes from the bottom plate of the fin layer 17, and in the case of a hairpin tube, the U-shaped part protrudes from the bottom plate of the fin layer. The protruding part protruding from the bottom plate of the fin layer 17 is held by a holding tool (not shown) such as a receiver.

The tube expansion tool 10 is composed of an expansion mandrel 18 having a mandrel 18b connected to a pressing means (not shown) that is movable in the direction of inserting and removing the expansion billet 18a from the tip of the heat exchange tube 14, an expansion billet 18a is inserted from the tip of the heat exchange tube 14 to expand the heat exchange tube 14 and integrate it with each of the heat dissipation fins 12, a chuck sleeve 20 that is slidably inserted around the expansion mandrel 18, and a slide sleeve 22 that is slidably inserted around the chuck sleeve 20. FIG. 1(b) shows an enlarged partial cross-sectional view of the chuck sleeve 20. The chuck sleeve 20 is a cylindrical body 20a that is slidably inserted around the mandrel 18b of the expansion mandrel 18, and the tip of the cylindrical body 20a is divided into equal parts to form a plurality of gripping pieces 20b. The grip piece 20b has a thick portion 20c at its tip that bulges outward from the cylindrical body 20a and is thicker than the other portions, and an inclined surface 20d is formed between the main body side of the grip piece 20b and the thick portion 20c. The grip piece 20b, including the thick portion 20c and the inclined surface 20d, is curved in a bow shape toward the outer surface of the cylindrical body 20a due to its spring force. The spring force of the grip piece 20b is obtained by heat treatment of the grip piece 20b, as described below.

Between the gripping pieces 20b, 20b that are bowed toward the outer surface of the cylindrical body 20a, a slit 21 is formed on the circumferential surface of the cylindrical body 20a, which consists of a long hole portion 20e with a curved inner wall that opens in the longitudinal direction of the cylindrical body 20a, an opening portion 20f formed at the tip of the long hole portion 20e that is narrower than the width of the long hole portion 20e, and a fan-shaped slit portion 20g that gradually widens from the opening portion 20f toward the tip of the cylindrical body 20a. The long hole portion 20e also gradually widens in width toward the opening portion 20f, but the width is narrow at the opening portion 20f. Furthermore, a plurality of protrusions 20h that protrude inward of the cylindrical body 20a are formed on each inner wall surface 20ci corresponding to the thick portion 20c of the gripping piece 20b. As shown in the partially enlarged cross-sectional view of FIG. 1(b), the cross-sectional shape of the protrusion 20h is a trapezoid or triangle that gradually narrows from the base toward the tip, and the height of the protrusion 20h from the inner wall surface 20ci is preferably 0.5 to 0.8 mm.

A slide sleeve 22 is inserted around the chuck sleeve 20 so as to slide freely along its outer periphery. When the slide sleeve 22 slides downward and rides up on the thick portions 20c of the gripping pieces 20b of the chuck sleeve 20 against the spring forces of the gripping pieces 20b of the chuck sleeve 20 as shown in FIG. 1(c), the entire slit 21 consisting of the long hole portion 20e, the opening 20f, and the sectorial slit portion 20g including the long hole portion 20e is contracted to clamp each of the gripping pieces 20b into a cylindrical shape. When each of the gripping pieces 20b is clamped into a cylindrical shape, the long hole portion 20e is contracted to become a long hole slit portion 23a with a constant width, and the opening 20f and the sectorial slit portion 20g are also reduced to become a narrow slit portion 23c with the same width as the narrow opening portion 23b, which is narrower than the width of the long hole slit portion 23a. The long hole slit portion 23a and the narrow slit portion 23c, which has the same width as the narrow opening portion 23b, form the slit 23. In addition, the multiple ridges 20h formed on the inner wall surface of each gripping piece 20b form multiple annular ridges 20H. The cross-sectional shape of these annular ridges 20H is also trapezoidal or triangular, with the width gradually narrowing from the base to the tip.

When the slide sleeve 22, which has been constraining each of the gripping pieces 20b into a cylindrical shape as shown in FIG. 1(c), is slid upward as shown in FIG. 1(b), the state in which each of the gripping pieces 20b is constrained into a cylindrical shape is released, and as shown in FIG. 1(b), each of the gripping pieces 20b is warped toward the outer surface of the cylindrical body 20a due to its spring force, and the elongated slit portion 23a, narrow opening portion 23b, and narrow slit portion 23c that constitute the slit 23 shown in FIG. 1(c) are each widened, and the elongated hole portion 20e, whose width is gradually widened toward the opening 20f shown in FIG. 1(b), the opening 20f that is wider than the narrow opening portion 23b, and the narrow slit portion 23c become the fan-shaped slit portion 20g that gradually widens from the opening 20f toward the tip of the cylindrical body 20a, thereby forming the slit 21.

When the gripping pieces 20b of the chuck sleeve 20 are constrained into a cylindrical shape by the slide sleeve 22, the slit 21 between the gripping pieces 20b of the chuck sleeve 20 is in a state consisting of the long hole slit portion 23a, the narrow opening portion 23b, and the narrow slit portion 23c as shown in Fig. 1(c), and when this constrain is released, it is in a state consisting of the long hole portion 20e, the opening portion 20f, and the fan-shaped slit portion 20g as shown in Fig. 1(b). In this way, the entire slit 21 formed between the gripping pieces 20b expands and contracts when the gripping pieces 20b are constrained into a cylindrical shape and when the constrain is released. Therefore, the expansion and contraction stress accompanying the expansion and contraction of the entire slit 21 is applied to the rear end of the long hole portion 20e (long hole slit portion 23a), but the expansion and contraction stress is dispersed by the curved inner wall at the rear end of the long hole portion 20e (long hole slit portion 23a), and the risk of cracks occurring due to stress concentration as in the collet chuck of Patent Document 1 and the gripping body of Patent Document 2 in which only fan-shaped slits are formed can be eliminated.
The chuck sleeve 20 of the tube expansion jig 10 shown in Fig. 1 can be manufactured by grinding, and the gripping piece 20b formed by grinding is given springiness by applying heat treatment, and the gripping piece 20b can be warped outward from the cylindrical body 20a by its own spring force. This spring force can be made large by forming the long hole slit portion 23a.

Using the tube expansion tool 10 shown in FIG. 1, the heat exchange tube 14 is inserted into the through-hole formed by the collar in the fin layer 17 in which the heat dissipation fins 12 having a plurality of collared through-holes of a predetermined height are stacked, and the tip 14a of the heat exchange tube 14 protruding from the top plate 16 of the fin layer 17 is expanded. First, as shown in FIG. 2(a), the tip surface of the gripping piece 20b of the chuck sleeve 20, in which the tip 14a of the heat exchange tube 14 is inserted into the gripping piece 20b, is abutted against the top plate 16 of the fin layer 17, and the tip 14a of the heat exchange tube 14 protrudes from the top plate 16 by a predetermined length. This is because the heat exchange tube 14 inserted into the collared through-hole in the fin layer 17 is not integrated with the top plate 16 and the heat dissipation fin 12 as shown in FIG. 2(b), and the tip 14a of the heat exchange tube 14 may not protrude from the top plate 16 by a predetermined length.

Next, as shown in FIG. 3(a), the slide sleeve 22 slides over the inclined surface 20d against the spring force of each of the arched gripping pieces 20b of the chuck sleeve 20 and onto the thick-walled portion 20c, thereby constraining each of the gripping pieces 20b into a cylindrical shape. The slits 21 between the cylindrically constrained gripping pieces 20b are entirely narrowed, the fan-shaped slit portion 20g becomes a narrow slit portion 23c, and the ridges 20h formed on the inner wall surfaces of the gripping pieces 20b form annular ridges 20H as shown in FIG. 3(b). The multiple annular ridges 20H are located near the tip of the tip portion 14a of the heat exchange tube 14, and when the axis of the tip portion 14a of the heat exchange tube 14 and the axis of the expanded billet 18a are aligned, the tip of the annular ridge 20H is close to the outer circumferential surface of the tip portion 14a as shown in FIG. 3(b).

However, as shown in FIG. 2, when the tip 14a of the heat exchange tube 14 is inserted into the gripping piece 20b of the chuck sleeve 20, the heat exchange tube 14 is not fixed to the top plate 16 of the fin layer 17 and the heat dissipation fin 12, and as shown in FIG. 4(a), the tip 14a of the heat exchange tube 14 inserted into the gripping piece 20b is inclined, and the axis of the tip 14a and the expanded billet 18a may not be aligned. If the expanded billet 18a is inserted into the tip 14a of the heat exchange tube 14 in this state, the tip 14a may buckle. In this regard, according to the expanding jig 10 shown in FIG. 1, the gripping piece 20b of the chuck sleeve 20 is constrained into a cylindrical shape by the slide sleeve 22, as shown in FIG. 4(b), so that the inclined tip 14a can be adjusted to match the axis of the expanded billet 18a.

In this way, with the axis of the tip 14a of the heat exchange tube 14 and the expansion billet 18a aligned, the expansion billet 18a is inserted into the tip 14a as shown in Figure 5 to start expansion. As shown in Figure 6, which is a partially enlarged view, the outer peripheral surface of the expansion portion 14b immediately after the start of expansion is pressed against the inner wall surface of the through hole of the top plate 16 forming the fin layer 17 and the collared through hole of the heat dissipation fin 12, and is integrated. Furthermore, at the tip of the expansion portion 14b of the heat exchange tube 14, as shown in the partially enlarged cross-sectional view, the tip portions of the multiple annular ridges 20H formed on each inner wall surface 20ci corresponding to the thick portion 20c of the gripping piece 20b bite into the outer peripheral surface of the expansion portion 14b without reducing the inner diameter of the expansion portion 14b, forming a gripping portion. In this way, the gripping piece 20b of the chuck sleeve 20 only has the tip of its annular ridge 20H biting into the outer circumferential surface of the expanded tube portion 14b, and the inner wall surface 20ci of the thick-walled portion 20c excluding the annular ridge 20H is not in contact with the outer circumferential surface of the expanded tube portion 14b, and a space 20k is formed between the inner wall surface 20ci and the outer circumferential surface of the expanded tube portion 14b. The distance L between the point where the tip of the most distal annular ridge 20H bites into and the tip of the expanded tube portion 14b is preferably about 2 to 3 mm. In addition, the biting width t of the tip of the annular ridge 20H is preferably adjusted to be 0.01 mm or more, about 0.05 to 0.07 mm. If the bite width t of the tip of the annular ridge 20H is less than 0.01 mm, the expansion tends to be insufficient due to the springback phenomenon of the expanded portion 14b after the expansion billet 18a passes through, and if the bite width t exceeds 0.07 mm, the insertion pressure of the expansion billet 18a into the tip 14a tends to increase rapidly. This gripping portion can be formed while the heat exchange tube 14 is being expanded continuously without stopping the expansion billet 18a inserted into the tip 14a of the heat exchange tube 14, preventing the heat exchange tube 14 from shrinking due to expansion.

As shown in FIG. 6, the inner wall surface 20ci of the gripping piece 20b of the chuck sleeve 20 is not in contact with the outer peripheral surface of the expanded tube portion 14b, and a space 20k is formed between the inner wall surface 20ci and the outer peripheral surface of the expanded tube portion 14b. Therefore, even if there is variation in the tube wall thickness and/or outer diameter of the heat exchange tube 14 to be expanded, it can be easily dealt with by increasing or decreasing the bite width t of the tip of the annular ridge 20H. For example, even if the tube wall thickness and/or outer diameter of the heat exchange tube 14 varies in a direction thicker than the median value of the variation and/or in a direction larger than the median value of the variation, it can be dealt with by increasing the bite width t of the tip of the annular ridge 20H to t', as shown in the partially enlarged view of FIG. 6. On the other hand, even if the tube wall thickness and/or outer diameter of the heat exchange tube 14 varies in a direction thinner than the median value of the variation and/or in a direction smaller than the median value of the variation, it can be dealt with by decreasing the bite width t of the tip of the annular ridge 20H.

When the tube expansion billet 18a reaches the lower end protruding portion of the heat exchange tube 14 protruding from the lowest plate of the fin layer 17, the tube expansion by the tube expansion billet 18a ends. In this way, the tube expansion tool 10 shown in Figures 1 to 6 allows the heat exchange tube 14 to be continuously expanded without stopping the tube expansion billet 18a. Furthermore, when the expanded tube billet 18a is extracted from the expanded heat exchange tube 14, the inner diameter of the gripping portion of the heat exchange tube 14 is not reduced, so the expanded tube billet 18a can be extracted smoothly, and excessive load is not applied to the gripping tool such as a receiver that grips the expanded tube billet 18a and the lower end of the heat exchange tube 14. This also eliminates the risk of damage to the holding jig, such as a receiver, and/or the lower end of the heat exchange tube 14, which may occur when excessive load is placed on the holding jig, such as a receiver, that holds the lower end of the heat exchange tube 14 when the expanded billet 18a is removed from the expanded heat exchange tube 14.
Then, the slide sleeve 22 is slid to release the cylindrical constraint on the gripping piece 20b of the chuck sleeve 20, and the spring force of the gripping piece 20b causes it to bend in a bow shape outwardly from the cylindrical body 20a, releasing the engagement of the expansion portion 14b at the tip of the annular ridge 20H with the outer circumferential surface, allowing the expansion tool 10 to be moved upward from the fin layer 17.

After the tube expansion is completed, the fin layer 17 integrated with the expanded heat exchange tube is removed from the tube expansion machine, and a flare portion forming device forms a flare portion 15a at the tip of the expanded heat exchange tube 15 protruding from the top plate 16 of the fin layer 17 of the expanded heat exchange tube 15 as shown in FIG. 7. The end of a connecting tube 30 that is connected to another expanded heat exchange tube 15 is inserted into the flare portion 15a and brazed 31 is performed. On the outer peripheral surface corresponding to the brazing 31 of the flare portion 15a, a biting groove 24 is formed at the tip of the annular ridge 20H formed on the gripping piece 20b of the chuck sleeve 20, but it is reinforced by the brazing 31, and the strength of the flare portion 15a is not reduced by the biting groove 24.

In recent years, in the production of heat exchangers such as room coolers, which are produced in small quantities and in a wide variety of products, it is desirable to improve production efficiency by minimizing the need for part replacement in the tube expansion machine. There is also a demand for tube expansion tools that can handle the expansion of heat exchanger tubes with slightly different tube diameters or walls.
When the tube expanding tool 10 shown in Fig. 1 to Fig. 7 is used to hold and expand heat exchange tubes having different tube diameters or walls, when the gripping pieces 20b of the chuck sleeve 20 into which the tip ends of the heat exchange tubes having different tube diameters or walls are inserted are constrained into a cylindrical shape as shown in Fig. 5 and Fig. 6, an excessive force may act on the slide sleeve 22, causing the slide sleeve 22 to deform. Such a risk can be eliminated by forming a round hole 22a, which is a hole with a curved inner wall surface and is opened in the middle of the chuck sleeve 20 as shown in Fig. 8, and a narrow slit portion 22b, which is narrower than the round hole 22a, in the direction from the opening formed in the round hole 22a toward the tip end, thereby adding springiness to the chuck sleeve 20. The tube expanding tool using the chuck sleeve 20 shown in Fig. 8 can also be used to expand heat exchange tubes having large variations in tube wall thickness and/or outer diameter.

1 to 7, multiple annular ridges 20H are formed on the expanded portion 14b of the heat exchange tube 14, but a single annular ridge 20H may be used. Alternatively, one or multiple projections may be formed on each inner wall surface of the gripping pieces 20b of the chuck sleeve 20, and the projection tips may be configured to bite into the outer circumferential surface of the expanded portion 14b. In addition, the flared portion 15a of the expanded heat exchange tube 15 is formed by a flare forming device separate from the tube expanding machine, but a flare punch may be provided in the tube expanding machine that expands the heat exchange tube 14, and the flare portion 15a may be formed at the tip of the expanded heat exchange tube 15 after the tube expansion is completed.
Furthermore, although the tube expansion tool shown in Figures 1 to 7 is used to expand a heat exchange tube inserted into a vertical fin layer, it may also be used to expand a heat exchange tube inserted into a horizontal fin layer.

Now, the expansion of the heat exchange tube 204 when using the chuck sleeve 212a in which a groove 212c is formed on the inner wall surface 212d of the thick portion 212b, which constitutes the tube expansion jig 200 shown in FIG. 11, instead of the chuck sleeve 20 in which multiple annular ridges 20H are formed on the inner wall surface corresponding to the thick portion 20c of the gripping piece 20b shown in FIG. 1, is described with reference to FIG. 12. In the tube expansion billet 208a and chuck sleeve 212a shown in FIG. 12, the minimum gap D between the outer peripheral surface that is the maximum outer diameter R of the tube expansion billet 208a and the inner wall surface 212d of the thick portion 212b of the chuck sleeve 212a is usually adjusted based on the median value of the variation in the tube thickness and/or outer diameter of the heat exchange tube 204 to be expanded.

Fig. 12(a) shows a case where a heat exchange tube 204 having a wall thickness and/or an outer diameter close to the center of variation is expanded. As shown in Fig. 12(a1), the heat exchange tube 204 is inserted into a chuck sleeve 212a, and the outer circumferential surface of the heat exchange tube 204 is close to the inner wall surface 212d of the thick-walled portion 212b. As the expansion billet 208a, which is inserted as shown in Fig. 12(a2) into the tip 204a of the heat exchange tube 204, advances, the tip 204a reduces in wall thickness and the inner diameter is expanded. However, before being pressed by the outer circumferential surface of the maximum outer diameter R of the expansion billet 208a, the outer circumferential surface of the expanded portion 204b does not come into contact with the inner wall surface 212d of the chuck sleeve 212a. As the insertion of the expanded billet 208a progresses, when the expanded billet 208a reaches the minimum gap D between the outer peripheral surface of the maximum outer diameter R and the inner wall surface 212d of the chuck sleeve 212a as shown in the enlarged partial cross-sectional view of Fig. 12(a3), the outer peripheral surface of the expanded billet 208a with the maximum outer diameter R abuts the outer peripheral surface of the expanded portion 204b against the inner wall surface 212d of the chuck sleeve 212a and is pressed and gripped with a predetermined pressing force. At this time, the minimum gap D between the outer peripheral surface of the maximum outer diameter R of the expanded billet 208a and the inner wall surface 212d of the chuck sleeve 212a becomes approximately equal to the pipe wall thickness of the expanded portion 204b that has been expanded and reduced in thickness, so that no excess pipe wall is generated in the expanded portion 204b and the space of the recessed groove 212c is maintained as it is.
Here, when expanding a heat exchange tube 204 that has shifted from the median of the variation in the direction of thinner tube thickness and/or smaller outer diameter, when the expanded billet 208a reaches the minimum gap D between the outer circumferential surface of its maximum outer diameter R and the inner wall surface 212d of the chuck sleeve 212a, the thickness of the expanded portion 204b may be reduced below a predetermined thickness. In such a case, the pressing force of the outer circumferential surface of the maximum outer diameter R of the expanded billet 208a pressing the inner wall surface 212d of the chuck sleeve 212a via the outer circumferential surface of the expanded portion 204b may decrease, resulting in a decrease in gripping force. Therefore, when a chuck sleeve 212a having a groove 212c formed on an inner wall surface 212d of a thick-walled portion 212b shown in FIG. 11 is adopted instead of the chuck sleeve 20 shown in FIG. 1, the range that can be accommodated for heat exchanger tubes whose wall thickness has shifted from the median value of variation toward a thinner tube thickness and/or a smaller outer diameter is narrow.

On the other hand, FIG. 12(b) shows the case of expanding a heat exchange tube 204 having a wall thickness thicker than the median of the variation. As shown in FIG. 12(b1), the expansion billet 208a inserted into the tip 204a of the heat exchange tube 204 inserted into the chuck sleeve 212a expands the inner diameter while reducing the wall thickness of the tip 204a as shown in FIG. 12(b2). The outer peripheral surface of the expanded expanded portion 204b is abutted against the inner wall surface 212d of the chuck sleeve 212a and pressed against it, further reducing the wall thickness toward the minimum gap D before the outer peripheral surface of the maximum outer diameter R of the expansion billet 208a reaches the minimum gap D with the inner wall surface 212d of the chuck sleeve 212a. The reduced tube wall is at the tip side of the expansion billet 208a, and a tube wall surplus 204c is generated between the heat exchange tube 204 and the inner wall surface 212d of the chuck sleeve 212a. If the tube expansion is continued while leaving this tube wall surplus 204c, there is a risk that the chuck sleeve 212a will be damaged by excessive pressure and/or the heat exchange tube 204 will be deformed near the lower end surface of the chuck sleeve 212a. For this reason, as shown in FIG. 12(b3) and its enlarged partial cross-sectional view, the tube wall surplus 204c is released into the recessed groove 212c to prevent excessive pressure from being applied to the chuck sleeve 212a and to prevent deformation of the heat exchange tube 204.

As shown in Fig. 12(b3), when the excess tube wall 204c is released into the groove 212c, a protrusion is formed on the outer circumferential surface of the expanded tube portion 204b, which, together with the pressing force against the inner wall surface 212d of the chuck sleeve 212a, allows the expanded tube portion 204b to be securely held against tension. For this reason, even in the case of expanding a heat exchange tube 204 in which the tube wall thickness is thinner and/or the outer diameter is shifted in a direction to be smaller than the median value of the center value of the variation, it is considered that forming a protrusion on the outer circumferential surface of the expanded tube portion 204b by releasing the excess tube wall 204c into the groove 212c as shown in Fig. 12(b3) may be effective in holding the expanded tube portion 204b against tension.
However, if the minimum gap D between the maximum outer diameter R of the expansion billet 208a and the inner wall surface 212d of the chuck sleeve 212a is adjusted so that a tube wall excess 204c occurs even when expanding a heat exchange tube 204 whose tube wall thickness is thinner and/or whose outer diameter is shifted in the direction toward a smaller diameter than the median of variation, when a heat exchange tube 204 whose tube wall thickness is thicker and/or whose outer diameter is shifted in the direction toward a larger diameter is expanded, excessive tube wall excess 204c occurs near the minimum gap D, and therefore excessive tube wall excess 204c occurs on the inner wall surface 212d of the chuck sleeve 212a. If a large groove 212c is formed as an allowance for such excessive pipe wall excess 204c, the strength of the chuck sleeve 212a will decrease, and therefore it will be necessary to thicken the chuck sleeve 212a and the clamp bush 214 in order to maintain the strength, which may result in the pipe expansion jig becoming larger and heavier.

The tube expansion tool of the present invention can be used to manufacture heat exchangers used in home room coolers, etc.

10, 100, 200: tube expansion tool, 12, 102, 202: heat dissipation fin, 14, 104, 204: heat exchange tube, 14a, 104a, 204a: tip, 14b, 104b, 204b: tube expansion section, 15: tube expansion heat exchange tube, 15a: flare section, 16, 106, 206: top plate, 17: fin layer, 18, 108: tube expansion mandrel , 18a, 108a, 208a: tube expansion billet, 18b, 108b, 208b: mandrel, 20: chuck sleeve, 20h: ridge, 20H: annular ridge, 20a, 112a: cylindrical body, 20b: gripping piece, 20c: thick portion, 20ci: inner wall surface, 20d: inclined surface, 20e: long hole portion, 20f: opening, 20g: sector-shaped slit portion, 20k: space portion , 21, 23, 112c: slit, 22: slide sleeve, 22a: round hole, 22b: narrow slit section, 23a: long hole slit section, 23b: narrow opening, 23c: narrow slit section, 24: biting groove, 30: connecting tube, 31: brazing, 104c: crimping section, 112: gripping body, 112b: gripping piece, 112d: protruding section, 112e: inclined surface, 114: cylindrical body, 115: rear end of the narrow slit section constituting the slit 112c, 204c: excess material, 212a: chuck sleeve, 212b: thick section, 212c: concave groove, 212d: inner wall surface of the thick section 212b, 214: clamp bush, 216: flare punch, t, t': biting width, D: minimum gap, L: distance, R: maximum outer diameter

Claims (8)

A tube expansion tool for a heat exchange tube that penetrates a fin layer in which a plurality of heat dissipation fins are laminated, and whose front and rear ends protrude from the fin layer, is gripped and expanded by the front and rear ends so as to prevent the tube from shrinking in the longitudinal direction, and is integrated with each of the heat dissipation fins,
a mandrel having a rear end connected to a press-fitting means provided so as to be movable in a direction for inserting and removing the expansion billet into and from the heat exchange tube;
a chuck sleeve comprising a cylindrical body slidably fitted onto the mandrel, a plurality of gripping pieces formed by dividing a tip end of the cylindrical body into which the tip ends of the heat exchange tubes are inserted, the gripping pieces being curved in a bow shape toward the outer surface of the cylindrical body due to their spring force, slits between the gripping pieces being formed with a hole portion having a curved inner wall opening onto the circumferential surface of the rear end side of the cylindrical body, and a fan-shaped slit portion which gradually widens from an opening narrower than the width of the hole toward the tip end of the cylindrical body, and a protrusion formed as a protrusion protruding inwardly from each of the inner wall surfaces of the gripping pieces;
A slide sleeve is slidably inserted along the outer circumferential surface of the chuck sleeve, and slides in a direction to fasten each of the gripping pieces against the spring force so as to narrow the entire slit between the gripping pieces of the chuck sleeve and to restrain each of the gripping pieces into a cylindrical shape, or slides in a direction to release the restraint,
The cross-sectional shape of the convex strip is a trapezoid or a triangle that gradually narrows from the base toward the tip,
a protruding length of the ridge from the inner wall surface of the gripping piece such that, when each of the gripping pieces of the chuck sleeve into which the tip of the heat exchange tube is inserted is restrained into a cylindrical shape by the sliding of the slide sleeve, and the expansion billet is inserted into the tip of the heat exchange tube positioned in a direction aligned with the axis of the expansion billet, each of the tip of the ridge bites into the outer peripheral surface of the expanded portion without reducing the inner diameter of the expanded portion, forming a gripping portion that grips the expanded portion of the heat exchange tube, a space is formed between the entire surface of each inner wall surface of the gripping pieces excluding the ridge and the outer peripheral surface of the expanded portion , and when the slide sleeve slides in a direction that releases the restraint by the chuck sleeve, each of the gripping pieces bends in a bow shape toward the outer surface of the cylindrical body due to the spring force, so that the tip of each of the ridges disengages from the bite into the outer peripheral surface of the expanded portion and the gripping by the gripping portion is released . The tube expansion jig according to claim 1, characterized in that the hole constituting the slit of the chuck sleeve is an elongated hole, the opening of the fan-shaped slit formed at the tip of the elongated hole is narrower than the width of the elongated hole, and when the gripping part is released from restraint, the width of the elongated hole is gradually expanded in the direction of the opening. The tube expansion jig described in claim 1, characterized in that the portion of the gripping piece of the chuck sleeve on which the convex rib is formed is formed in a thick portion that is thicker than other portions of the cylindrical body in the outer surface direction, an inclined surface is connected to the rear end of the thick portion, and the entire portion including the inclined surface and the thick portion is bow-shaped toward the outer surface direction of the cylindrical body due to its spring force. The tube expansion tool according to claim 1, characterized in that when each of the gripping pieces is constrained into a cylindrical shape by the sliding sleeve, an annular ridge is formed from the ridges. The pipe expansion jig according to claim 4 , characterized in that a plurality of the annular ridges are formed. The tube expansion jig according to claim 1, characterized in that the height of the ridge from the inner wall surface is 0.5 to 0.8 mm, and the bite width of the tip of the ridge is 0.01 to 0.07 mm. A method for expanding a heat exchange tube, the heat exchange tube penetrating a fin layer in which a plurality of fins are stacked, the front end and the rear end protruding from the fin layer, the rear end of the heat exchange tube being gripped so as to prevent the heat exchange tube from shrinking in the longitudinal direction, the front end of the heat exchange tube being gripped and expanded by the tube expansion tool according to claim 1, and the heat exchange tube being integrated with each of the fins,
inserting a tip end of the heat exchange tube into a plurality of gripping pieces that form a tip end of the chuck sleeve constituting the tube expansion jig;
The slide sleeve is slid toward the upper surface of the gripping pieces against the spring force of the multiple gripping pieces of the chuck sleeve, the entire slit is contracted in width and constrained into a cylindrical shape, and the heat exchange tube is positioned in a direction in which the axis of the heat exchange tube coincides with that of the expanded billet.
the tip end of the ridge is inserted into the outer circumferential surface of the expanded portion by inserting the expansion billet into the tip end of the heat exchange tube to expand the tube, without reducing the inner diameter of the expanded portion, thereby forming a gripping portion in which a space is formed between the entire surface of each inner wall surface of the gripping pieces excluding the ridge and the outer circumferential surface of the expanded portion;
A method for expanding a heat exchange tube, characterized in that the expansion of the heat exchange tube, the tip portion of which is held by the holding portion, is continued in the direction toward the rear end portion of the heat exchange tube without stopping the expansion billet. After the expansion of the heat exchange tube is completed, the expanded billet is pulled out from the expanded heat exchange tube held by the holding portion.
Next, the slide sleeve is slid from the upper surface side of the multiple gripping pieces of the chuck sleeve to release the cylindrical restraint state of the multiple gripping pieces, and the spring force of each of the gripping pieces causes them to bend in a bow shape toward the outside of the cylindrical body , thereby releasing the gripping by the gripping portions by releasing the engagement of the tip ends of the convex ribs with the outer peripheral surface of the expansion portion.

Images