JPS63188433A - Method for pipe expansion of cross fin coil - Google Patents

Abstract

PURPOSE:To prevent a buckling by eliminating the compression force in the pipe axial direction and to improve the yield by reducing the shrinking allowance by performing a pipe expansion by constraining the opening end side of a heat transfer pipe so as not to move to the communicating end side in the case of the pipe expansion. CONSTITUTION:The opening end side part of a heat transfer pipe 4 is inserted into the through holes 9, 9... of the clamp body 8 having through holes 9, 9... and to be bisected and pinched by a clamp body 8. In the case of pipe expansion, a mandrel 6 is inserted into each heat transfer pipe 4 and after expanding the open side end part the pipe expansion of the remaining part is continued by constraining the heat transfer pipe 4 so as not to move to the communicating end side by the clamp body 8. as a result, no compression stress in the pipe axial direction is applied on the heat transfer pipe 4 and there is no danger at all of the scrapping due to the buckling. The shrinking allowance in the pipe axial direction can drastically be reduced as well and the material yield can be improved remarkably.

Description

[Detailed Description of the Invention] [Industrial Application Field] When manufacturing a cross-fin coil, which is a type of heat exchanger, the present invention applies heat exchanger tubes to a coil to be processed in the assembly stage during manufacturing. The present invention relates to a method for expanding a cross-fin coil by mechanically expanding the tube by inserting a mandrel and crimping and fixing it to a fin.

[Conventional technology]

Conventionally, such pipe expansion has been carried out by a method as described in Japanese Patent Application Laid-Open No. 60-27428.

The principle will be explained with reference to FIG.

The coil l to be processed is made by stacking a large number of fins 3.3 between tube sheets 2 at predetermined intervals, and placing a large number of heat transfer tubes 4.4 at right angles thereto. It is constructed by inserting a skewer.

Two heat exchanger tubes 4.4... are connected in a U-shape at one end,
At this stage, the container tube has a tube plate 2.2 and fins 3.3...
・Not completely fixed.

For tube expansion, the coil l to be processed is placed on the support stand 5 with the heat exchanger tube connection end facing down, and in this state the heat exchanger tube 4.4
Mandrels arranged corresponding to the containers 6.6.
This is done by inserting the ... all at once from the open end side.

When the mandrel 6 is inserted, a tube expansion door provided at the tip of the mandrel 6 expands the heat transfer tube 4 from the inside and presses it onto the fins 3, 3, . . . .

The above is a pipe expansion method for a vertical type, but it is also carried out based on the same principle in a horizontal type.

(Problems to be Solved by the Invention) In such a conventional pipe expansion method, during pipe expansion, the coil 1 to be processed is supported by work supports from all four circumferences in addition to the support stand 5. It is the support 5 that receives the force.For this reason, the heat exchanger tube 4 is subjected to a strong compressive force in the tube axial direction due to the insertion of the mandrel 6, and as a result, the heat exchanger tube 4 often buckles. .

If buckling occurs in the heat exchanger tube 4, not only will the processed coil 1 be scrapped, but the tube expander such as the mandrel 6 will be damaged, resulting in a large economic loss.

Further, the heat exchanger tube 4 shrinks in the tube axis direction as the tube expands, and the compressive force applied to the heat exchanger tube 4 in the tube axis direction increases this shrinkage.

Conventionally, this shrinkage allowance was 4% or more relative to the pipe length, and when expanding the pipe, a material with a length that took into account this shrinkage allowance was required, which was a factor that lowered the manufacturing yield.

Furthermore, this shrinkage caused large variations due to wall thickness deviations of the heat exchanger tubes 4, 4, etc.

The open end of the heat exchanger tube 4 is flared after expansion, and a U-tube is inserted therein and connected by brazing.
As mentioned above, if there is variation in the shrinkage margin of the heat exchanger tubes 4,
The amount of protrusion from the tube plate 2 differs depending on the container tube, and there are cases where the fitting allowance for the U tube is insufficient.

If the fitting allowance for the U-tube is insufficient, a joint failure will occur during brazing, causing a major problem in terms of coil quality.

The present invention provides a novel tube expansion method that solves all of these problems.

[Means for solving problems]

The principle of the tube expansion method of the present invention will be explained with reference to FIGS. 1 and 2 using representative examples.

FIG. 1 shows a first method of the present invention, and FIG. 2 shows a second method of the present invention, and both figures show the coil 1 to be processed placed in a predetermined position of a tube expander.

In both figures, reference numeral 8 denotes a clamp body having through holes 9, 9, . . . at corresponding positions of the heat exchanger tubes 4, 4, . (plate),
The open end portions of the heat exchanger tubes 4, 4, . . . are inserted into the through holes 9, 9, . The diameter of the i3 holes 9.9... is larger than the outer diameter of the heat exchanger tube 4 before expansion, and smaller than the outer diameter of the heat exchanger tube 4 after expansion.

In addition, in FIG. 2, lO is a hook body, and heat exchanger tube 4.
This is to lock the connecting end of No. 4 so that it does not move toward the open end during pipe expansion.

In the method of the present invention, the mandrel 6.
6... are inserted into the heat exchanger tubes 4, 4... all at once from the open end side.

When the tube expansion head 7 at the tip of the mandrel 6 passes the clamp body 8 as the mandrel 6 is inserted, the open end of the heat transfer tube 4 is expanded and fixed to the clamp body 8 by pressure. Subsequent tube expansion is performed with the open end of the heat transfer tube 4 immovably restrained toward the connecting end.

In this way, the method of the present invention inserts the mandrel 6.6... into each heat exchanger tube 4.4... from the open end side, and at the stage of expanding the open end, the expanded portion is removed. The heat exchanger tubes are restrained without moving toward the connecting ends, and the mandrels 6, 6, and so on are continued to be inserted with the open ends of the heat exchanger tubes 4, 4, and so on in the restrained state.

In addition, in the second method, in addition to restraining the open end of the heat exchanger tube, the connecting end of the heat exchanger tube is restrained by the hook body IO so as not to move toward the open end during tube expansion.

(Function) In the first method shown in FIG. 1, after the open end of the heat exchanger tube 4 is restrained by the clamp body 8, until the insertion of the mandrel 6 is completed, the heat exchanger tube 4 is expanded. This causes shrinkage in the tube axis direction, but since the open end is supported by the clamp body 8 without moving toward the connecting end, the shrinkage occurs toward the open end.

Therefore, even if the heat exchanger tube 4 is initially supported on the stand 5, during the actual expansion period 1jW, the support rises from the stand 5, and the tube is expanded without being subjected to compressive force in the tube axis direction. move on.

As a result, there is no risk of buckling in the heat exchanger tube 4, shrinkage in the tube axis direction is greatly reduced, and the amount of protrusion of the open end is kept constant, eliminating the possibility of tube end irregularities. .

In the second method shown in FIG. 2, after the open end of the heat exchanger tube 4 is restrained by the clamp body 8, the heat exchanger tube 4
After all, it tries to contract in the direction of the tube axis. However, since the open end is restrained by the clamp body 8, the compressive force in the pipe axial direction is not applied, and contraction in the pipe axial direction is prevented by the restraint of the connecting end by the hook body 10. Absorbed as a decrease.

As a result, it is possible to use the same length of material as the product length without changing the pipe length.

〔Example〕

Hereinafter, variations in implementing the method of the present invention will be explained in detail regarding the clamp body that is the restraining means for the open end of the heat exchanger tube and the hook body that is the restraining means for the connecting end, and furthermore, the implementation procedure using an actual machine and the The implementation results will also be explained.

○ Clamp body The clamp body 8 is used in common in the first method and the second method.

The clamp body 8 shown in FIG. 3 is a plate having through holes 9 provided corresponding to the arrangement positions of the mandrels 6.

This plate has a split structure so that all the through holes 9 are divided into two in order to facilitate the removal of the open end of the heat exchanger tube after the tube expansion is completed. FIG. 3(a) shows the assembled state of the plates, and FIG. 3(b) shows the disassembled state.

The effective diameter d of the through hole 9 must be larger than the outer diameter of the tube before expansion because it is necessary to pass the open end of the heat transfer tube before expansion. Because it needs to be fixed, it must be smaller than the outer diameter of the tube after expansion. If the outer diameter of the heat exchanger tube 4 after expansion is X (ms),
The effective part diameter d (base layer) is preferably in the range of x-o, os to x-0,3.

When actually performing tube expansion, consideration must be given to retracting the clamp body 8 so that it does not get in the way when the coil 1 to be processed is attached to and removed from the tube expander.

In the clamp body 8 of FIG. 3, in order to smoothly insert the open end of the heat exchanger tube into the through hole 9, it is preferable that the peripheral edge of the through hole 7L9 is tapered outward on one surface.

The material and thickness of the clamp body 8 must be selected so that it can withstand the tube expansion load applied to the coil 1 to be processed.

4 to 6 show other variations of the clamp body 8.

The clamp body 8 in FIG. 4 is a plate-shaped clamp body 8 as shown in FIG. 3, and the diameter of the through hole 9 can be changed mechanically by a throttle mechanism.

In this clamp body 8, after the mandrel 6 has passed through the clamp body 8, the diameter of the through hole 9 can be reduced to forcibly fix the open end of the heat exchanger tube to the clamp body 8, Moreover, the work when removing the open end of the heat transfer tube from the clamp body 8 after tube expansion becomes easier.

The clamp body 8 in FIG. 5 uses the tube plate 2 as a part of the clamp body 8, and clamps the tube plate 2 at the open end of the heat exchanger tube of the processed coil l set in a tube expander to a clamper 80.
80, and the heat transfer tubes 4 are fixed to the tube plate 2 for subsequent tube expansion.

The clamp body 8 shown in FIG. 6 uses the fins 3 as a part of the clamp body 8, and a large number of sheet metal sheets 81, 81...・
are inserted in multiple stages, and after the heat transfer tube 4 is fixed to the fin 3 at this portion by expanding the sheet metal insertion portion, the fin 3 is supported by the sheet metal 81 for subsequent tube expansion.

Here, to briefly touch on the holder 5 for the processed coil 1, in the method of the present invention, the holder is placed on the pedestal during substantial tube expansion after the open end of the heat exchanger tube is fixed to the clamp body 8. However, until the open end is fixed to the clamp body 8, the receiver requires a means such as a stand 5 to receive the tube expansion load.

Since this is a short period of time at the initial stage of pipe expansion, if the workpiece support or the support stand 5 can receive the tube expansion load by means other than the support stand 5, the support stand 5 can be omitted.

O-hook body The hook body lO is used to carry out the second method of the present invention, and is used to prevent the U-shaped connecting part on the heat exchanger tube connecting end side from shifting toward the open side end during tube expansion. belongs to.

The hook body lO shown in FIG.
The character-shaped connecting portion is locked with a pin.

It is desirable that the pin be tiltable so that it can be easily locked into the U-shaped connecting portion. The base of the pin also serves as a stand 5.

The hook body lO shown in FIG. 8 uses the tube plate 2 on the heat exchanger tube connecting end side as a part of the hook body lO, and clamps the tube plate 2 with clampers 101, 101 to prevent it from moving toward the open end side of the heat exchanger tubes. This is how it was done.

The hook body 10 in FIG. 9 is attached to the U-shaped connecting portion of the heat exchanger tube connecting end example. A round rod is inserted through the heat exchanger tube, and the round rod is fixed so as not to move toward the open end of the heat exchanger tube during tube expansion, thereby preventing the heat exchanger tube from shrinking. Although this hook body 10 cannot be applied to a processed coil l in which the heat exchanger tubes 4 are arranged in a staggered manner with respect to the fins 3,
The coil 1 to be processed, in which the heat transfer tubes 4 are arranged on the base surface, is easy to install and has high utility value.

These hook bodies 1O are desirably designed to contact the inner periphery of the U-shaped connecting portion over a wide range in order to suppress deformation of the U-shaped connecting portion on the heat exchanger tube connecting end side. It has been confirmed that no problematic deformation of the U-shaped connection occurs when the U-shaped connection is secured with a round bar whose cross section is an arc that is virtually the same as the inner periphery of the U-shaped connection.

○ Implementation procedure in an actual machine FIGS. 10 and 11 are a front view and a side view showing the structure of an example of an actual machine used to implement the method of the present invention.

According to both figures, four guide posts 12 are erected at the four corners of the base 11, a mandrel guide body 13 is provided in the middle part thereof, and the upper part is connected and fixed with an upper frame 14 to form a frame. There is.

A main cylinder 15 is fixed downwardly to the upper frame 14, and a pressurizing frame 16 that is slidably supported by a guide boss l-12 is connected to the rond tip of the main cylinder 15.

A surface pressure plate 17 is attached to the pressure frame 16, to which a predetermined number of mandrels 6 are attached downwardly at predetermined intervals, and a tube expansion head 7 is provided at the tip of the mandrel 6.

Between the pressure frame 16 and the mandrel guide 13, a plurality of intermediate plates 18 are slidably supported on the guide post 12.
Equipped with The mandrel guide 13 and the intermediate plate 18 are
A mandrel passage hole is provided at a location corresponding to the mandrel 6, and the descending mandrel 6 is supported. The intermediate plates 18 are connected to each other, to the pressurizing frame 16, and to the mandrel guide 13 by rods 19.

A clamp body 8 is fixed horizontally below the mandrel guide 13. The clamp body 8 is a plate having a structure as shown in FIG. 3, and the clamp body 8 is a plate having a structure as shown in FIG.
It has a through hole 9 (FIG. 3) for pushing the open end of the heat exchanger tube through at a location corresponding to , and is provided so as to be openable and closable in the opposite direction.

The dimensions of the through hole provided in the clamp body 8 are as described above.

A stand 5 is provided on the base 1 of the frame for placing the coil to be processed l at a predetermined position of the tube expander, and the holder supports the coil to be processed l placed on the stand 5 from all four sides. A workpiece holder 21 for this purpose is attached to the guide post 12.

The first method of the present invention is implemented with the above configuration, but the second method
In order to carry out the method described above, the receiver is further provided with a hook body 10 as shown in FIG. 7 at the stand 5.

To carry out the method of the present invention using such a tube expander, first, the pressurizing frame 16 is raised to the upper limit position with respect to the upper frame 14, and the clamp body 8 is opened.

Next, in this state, the coil 1 to be processed is placed on the support stand 5 with the open end of the heat exchanger tube facing upward, and is fixed with the workpiece support 21 from all four sides. At this time, it goes without saying that the coil 1 to be processed is centered such that the heat exchanger tube 4 is positioned coaxially with the mandrel 6 on the extension line of the mandrel 6.

When the coil 1 to be processed is finished centrifuging, the clamp body 8 is then closed with the open end of the heat exchanger tube inserted into its through hole.

Next, the main cylinder 15 on the upper frame 14 is driven to lower the pressurizing frame 16. As the pressure frame 16 descends, the mandrel 6 descends and is inserted into the heat exchanger tube 4 of the coil 1 to be processed.

As mentioned above, the through hole of the clamp body 8 is set to a diameter smaller than the outer diameter of the heat exchanger tube 4 when expanded without restraint, so that the tube expansion head 7 inserted into the heat exchanger tube 4 from the open end side When it passes the clamp body 8, the open end portion is fixed to the clamp body 8.

Even after the open end is fixed to the clamp body 8, the mandrel 6 continues to descend and expand the tube, but during this tube expansion period,
The open end of the heat transfer tube 4, which is about to contract in the axial direction due to tube expansion, is supported by the clamp body without moving up and down, and is in a so-called suspended state, so that it is not subjected to compressive force in the tube axial direction. Prevented.

The shrinkage force in the tube axis direction of the heat exchanger tubes 4 is such that in the first method, the receiver at the connecting end rises from the stand 5, but in the second method, the connecting end is restrained by a hook body. Now, heat transfer tube 4
It does not reduce the length of the wall, but is absorbed as a reduction in wall thickness.

As the pressure frame 16 descends, the intermediate plate 18 also descends; however, due to the magnitude of friction, the pressure frame 16 first descends to the upper intermediate plate 18, and then the pressure frame 1
6 and the upper intermediate plate 18 descend to the lower intermediate plate 18, and finally the pressurizing frame 16 and the upper and lower intermediate plates 18 descend to the mandrel support frame 13 to complete the pipe expansion.

When the tube expansion is completed, the pressurizing frame 16 is raised to remove the mandrel 6 from the heat exchanger tube 4, and then the clamp body 8 is disassembled and separated from the heat exchanger tube 4.

When the separation of the clamp body 8 is completed, the workpiece receiver 21 is removed and the expanded coil 1 to be processed is removed from the tube expanding machine.

Although the above is a case where the pipe expander is a vertical type, the method of the present invention is similarly carried out in the case of a horizontal pipe expander.

Results When a 2.5/8-inch tube (outer diameter 8゜0m5) to be processed coil whose specifications are shown in Table 1 was expanded using the conventional method whose principle is shown in Fig. 12, the tube axis of heat transfer tube 4 was The shrinkage in the direction is 4
．． 0 to 4.5%, and the amount of protrusion from the tube sheet 2 at the open end also varied by a maximum of 5%.

Furthermore, buckling of the heat exchanger tubes 4 also occurred at a rate of about 0.2%.

The specifications of the pipe expander are shown in Table 2.

In addition, the heat transfer tube 4 is a 3.0/8 inch tube (outside diameter 9.5
In the case of Ryu), the shrinkage was 4.2 to 4.7%.

Table 1 Table 2 Therefore, the first method of the present invention was applied to this tube expansion. The clamp body 8 used was of the split plate type shown in FIG. 3, and the effective diameter of the through hole 9 was 8.50 l. Incidentally, the outer diameter of the heat transfer tube 4 after expansion is 8.65mm.

As a result of applying this property, the shrinkage of the heat exchanger tube 4 in the tube axis direction is 2.5
/ 2.0 to 2.1% in the case of 8 inch pipe, and 3
, respectively decreased to 2.0-2.2% in case of 0/8 inch tube. Further, there was no variation in the amount of protrusion of the open end, and buckling of the heat exchanger tube 4 was completely prevented.

Furthermore, as a result of applying the second method of the present invention using the hook body lO shown in FIG. 7, shrinkage in the tube axis direction is completely prevented for any tube, and The decrease in wall thickness due to prevention of shrinkage was about 6%, which was not a particular problem. Further, there was no variation in the amount of protrusion of the open end, and no buckling occurred in the heat exchanger tube 4.

〔Effect of the invention〕

As is clear from the above description, in the method of the present invention, when expanding the heat transfer tube 4 of the coil to be processed, the open end is restrained from moving toward the communicating end. The heat exchanger tube 4, which tends to contract in the tube axial direction as the tube expands, is not subjected to a compressive force in the tube axial direction, although it receives a strong force toward the connecting end due to the insertion of the mandrel 6.

As a result, the contraction of the heat exchanger tube 4 in the tube axis direction is largely alleviated or prevented, and the length of the heat exchanger tube to be subjected to tube expansion can be shortened by that much, thereby making it possible to reduce the material cost. Also,
Since the heat exchanger tube 4 is not subjected to compressive force in the tube axis direction, buckling of the heat exchanger tube 4 is also prevented, and scrapping of the processed coil 1 due to buckling is eliminated. By preventing this scrapping and reducing the material costs mentioned above, manufacturing costs can be significantly reduced.

Moreover, by preventing buckling, the tube expander is protected and its durability is increased.

Furthermore, according to the method of the present invention, the protrusion amount of the open end of the heat exchanger tube 4 from the tube plate 2 is uniform, and the U-tube brazing after expansion ensures the joining in the process, and the product quality is improved. It is also possible to improve quality.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic diagrams showing the principle of the method of the present invention, Figures 3 to 6 are perspective views showing variations of the clamp body, and Figures 7 to 9 show variations of the hook body. A perspective view, FIG. 1O, and FIG. 11 are front and side views showing the structure of an example of an actual machine suitable for carrying out the method of the present invention, and FIG. 12 is a schematic diagram showing the principle of the conventional method. Inside, l: coil to be processed, 2: tube sheet, 3: fin, 4: heat transfer tube, 5! The receiver is a stand, 6: Mandrel, 7: Tube expansion head, 8: Clamp body, 9: Through hole, l5 ji.・ )-to 8 ξ4

Claims (2)

[Claims] (1) A large number of fins (3
), (3)..., a coil to be processed ( 1), each heat exchanger tube (
4), (4)... insert the connecting end side hemandrels (6), (6)... from the open end side of each heat exchanger tube (4).
, (4)... simultaneously expand the fins (3), (3)...
When expanding the cross-fin coil to be fixed to..., insert the mandrels (6), (6)... into each heat transfer tube (4), (4)... from the open end side, and At the stage where the end portions are expanded, the expanded portions are restrained without moving toward the connecting end of the heat exchanger tubes, and the open end portions of the heat exchanger tubes (4), (4), etc. are placed on a mandrel (6) in the restrained state. ), (6)...
A method for expanding a cross-fin coil, characterized by continuing insertion of the cross-fin coil. (2) A large number of fins (3
), (3)..., a coil to be processed is constructed by inserting a large number of heat transfer tubes (4), (4)..., two of which are connected in a U-shape at one end, through a skewer. For (1), each heat exchanger tube (
4), (4)... insert the connecting end side hemandrels (6), (6)... from the open end side of each heat exchanger tube (4).
, (4)... simultaneously expand the fins (3), (3)...
When expanding the cross-fin coil to be fixed to..., each heat transfer tube (4), (4)... is restrained at its connecting end without moving toward the open end, and in this state, each heat transfer tube (4), (4)...
4), (4)... from the open end of the mandrel (6
), (6)... are inserted, and at the stage of expanding the open end, the expanded portion is further restrained without moving toward the connecting end of the heat exchanger tubes, and each heat exchanger tube (4), (4), With the open end and the connecting end of the mandrels (6) and (6) in the restrained state,
)... A cross-fin coil expansion method characterized by continuing insertion of...