JPH0477238B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heat exchanger for air conditioning equipment using an internally grooved tube as the main heat exchange tube, and a method for manufacturing the same.
In particular, the inner groove in the part of the inner grooved pipe opposite to the part into which the return bend pipe is inserted is crushed by plastic working means, making it possible to perform reliable brazing joints while suppressing the consumption of brazing material. The present invention relates to a heat exchanger for air conditioners using attached tubes and a method for manufacturing the same.

[Conventional technology]

As a conventional heat exchanger for air conditioning equipment, Fig. 6a,
There is one shown in b. Generally, one or both ends of the main heat exchange tube 13, which is a smooth tube or a tube with internal grooves, is expanded into a bell mouth shape, and the return bend tube 14 is inserted into this portion, and then the brazing material 15 is heated and melted. to seal the refrigerant gas inside the pipe. The flared portion 16 of the main heat exchange tube 13 is designed so that the brazing material 15 can effectively enter the tube.
The main heat exchange tube 13
and the parallel gap portion 17 of the return bend pipe 14 are usually 0.1 mm in order to ensure a strong connection between the two, and in consideration of the workability of charging the return bend pipe 14.
It has a gap of about 0.15 mm and a length of about 5 to 10 mm. The bell mouth end part 18 is made of brazing material 1
5 is stopped from flowing out to areas other than the brazed parts. As mentioned above, smooth tubes or tubes with internal grooves can be used as heat exchange tubes in heat exchangers for air conditioning equipment, but internally grooved tubes have fine spiral grooves that prevent the evaporation of the refrigerant. Its application is rapidly expanding because it significantly promotes condensation and heat transfer, and can be processed in almost the same way as smooth tubes in the manufacture of heat exchangers. Note that 19 is a fin member bridging the main heat exchange tubes 13.

[Problem that the invention seeks to solve]

However, according to the conventional heat exchanger for air conditioning equipment using internally grooved tubes and its manufacturing method, when expanding the main heat exchange tube 13 made of an internally grooved tube into a bell mouth shape, it is different from expanding a smooth tube. Similarly, since we use a tube expansion method in which a jig is forcibly inserted into the main heat exchange tube 13 to expand it, the following three disadvantages inherent to internally grooved tubes are avoided, which are not problems when expanding a smooth tube into a bellmouth shape. be.

(1) The amount of decrease in the depth of the internal groove of an internally grooved tube due to bellmouth expansion is approximately 0.01 mm to 0.03 mm, and the initial groove depth of approximately 0.1 mm to 0.2 mm is effective for improving heat transfer performance. For internally grooved tubes, for example, as shown in the diagrams before and after the bellmouth-shaped tube expansion in Figures 7a and b, it is unlikely that the groove depth and groove cross-sectional area will be reduced by the bellmouth-shaped tube expansion. Compared to a smooth tube, the gap will definitely increase by an amount corresponding to the groove volume of the internally grooved tube, and the consumption of expensive brazing material will increase. In addition, if the amount of brazing material is not increased reliably, it may cause refrigerant leakage due to poor brazing.
According to a trial calculation example for a pipe with internal grooves of 60, the increase in brazing material consumption due to the groove volume is about 60% compared to a smooth pipe.
It even reaches an increase.

(2) Since a groove remains at the bell mouth end, brazing material is likely to flow out through this groove to the non-bell mouth portion, which may lead to leak failure due to lack of brazing material.

(3) Internally grooved tubes have internal grooves compared to smooth tubes with the same outer diameter, so the minimum inner diameter is smaller by twice the groove depth. On the other hand, the return bend pipe cannot be made much smaller than the main heat exchange pipe in order to avoid increasing the pressure loss of the refrigerant inside the pipe.
Heat exchangers for air conditioners that use tubes with inner grooves usually use the same return bend tubes as when smooth tubes are used. Therefore, from the viewpoint of insertability of the return bend pipe, the minimum internal diameter of the bell mouth part is set to be the same as that of the smooth pipe, and from the consideration of strength, the bottom wall thickness of the bell mouth end part is also set to be the same as that of the smooth pipe. The outer diameter of the bell mouth portion is expanded by twice the groove depth compared to a smooth tube.
Similarly, the tube expansion magnification for the flared portion also increases. For example, the flare diameter for a smooth tube is
Assuming 12mmφ, in the case of an internally grooved pipe with a groove depth of 0.2mm, the flare diameter will be 12.4mmφ, which means that the tube expansion magnification will increase from 1.26 times to 1.30 times. Originally, this is an even more disadvantageous condition for inner-grooved tubes, which have a notch effect and are more susceptible to cracking during expansion than smooth tubes, and cracks at flared portions, etc. Outflow of brazing material outside the pipe also causes a shortage of brazing material.

[Means for solving problems]

The present invention has been made in view of the above, and solves the problem of the increase in brazing material consumption, which is a problem inherent to internally grooved tubes in heat exchangers for air conditioners using internally grooved tubes and in the method for manufacturing the same. In order to prevent brazing material from flowing out at the bellmouth end and to prevent cracks in the bellmouth-shaped tube expansion, the inner groove of the part where the return bend tube is inserted and brazed is made after the inner groove forming process and , a heat exchanger for air conditioning equipment using an internally grooved tube that is made to practically resemble a smooth tube by forcibly crushing it through a plastic deformation process in the process before charging the return bend tube, and a method for manufacturing the same. It provides:

That is, in the heat exchanger for air conditioning equipment using the internally grooved pipe of the present invention, the internal groove in the part where the return bend pipe is inserted and brazed is crushed and smoothed, and the wall thickness is equal to the original bottom. It is larger than the thickness.

Further, the method for manufacturing a heat exchanger for air conditioning equipment using the internally grooved tube of the present invention includes the following plastic deformation step.

In other words, an external restraint type is placed around the outer circumference of a pipe with internal grooves, a processing member is inserted into the inner circumference, and the return bend pipe is inserted and the internal groove of the part to be brazed is forcibly flattened and smoothed. become This results in the part having a smooth inner surface similar to a smooth tube. The plastic deformation process is provided after the inner groove forming process and before the return bend pipe charging process. The plastic deformation process is performed after the internal groove forming process because it is generally essential for manufacturing efficiency to form internal grooves continuously, and the plastic deformation process is used as a method to flatten and smooth the internal grooves. To use
For example, there is a limit to the improvement of work efficiency in the cutting method, and removal of cutting waste and lubricating oil tends to lead to secondary cost increases. On the other hand, according to the plastic deformation processing method, the wall thickness after crushing is greater than the original bottom wall thickness, so the strength is also improved.

Hereinafter, a heat exchanger for air conditioning equipment using the internally grooved tube of the present invention and a method for manufacturing the same will be explained in detail.

〔Example〕

FIG. 1 shows a first embodiment of the present invention, and shows a plastic deformation process in which only the inner groove is crushed without changing the outer diameter of the tube. It consists of a mandrel 2 having a diameter of _{1.5 mm} and a holding die 3 having a circular groove having a predetermined inner diameter D ₀ in half to support the strong stress in the tube axis direction applied to the inner grooved tube 1.
As shown in FIGS. 2a and 2b, the outer diameter D _n of the mandrel 2 is the outer diameter D ₀ , the minimum inner diameter D i , and the outer diameter D _n of the inner grooved tube 1 when the peak portion 1 a is crushed and the groove portion 1 b is filled. The inner diameter is made to match the inner diameter of the inner grooved tube 1.

In the above configuration, after the straight internally grooved tube 1 cut to the length for final use is placed and fixed in the holding die 3, the mandrel 2 having the aforementioned outer diameter D _n is pushed into the tube. At this time, the internally grooved tube 1 is fixed by the holding die 3, and the peak portion 1a is crushed. As a result, the inside is
D _n , and the tube outside diameter does not change. The internally grooved tube 1 whose predetermined portions have been smoothed in this manner is then processed by a conventional bellmouth-shaped tube expansion method.
In this example, a plastic deformation process was adopted in which the inner surface of the straight pipe is crushed when it is cut to the final length, but in a machine that bends a coiled material while continuously cutting it, the material may still be exposed to the bending tool immediately after bending. You may do so while being restrained.

Figures 3a and 3b show a second embodiment of the invention,
In this embodiment, instead of inserting the mandrel 2 in the first embodiment, a roller expansion method is used. By rotating the tapered mandrel 4, a plurality of tapered rollers 5 arranged around the outer periphery of the mandrel 4 at a certain angle with the axis of the mandrel 4 revolve around the mandrel 4 while rotating on their own axis, thereby forming an inner groove. This is to crush and smooth the inner groove of the attached tube 1. Although the roller tube expansion method has the advantage of generating large tube radial stress without applying tube axial force, it also has the disadvantage of slow tube expansion speed.

FIG. 4 shows a third embodiment of the present invention, in which the plastic deformation step of crushing and smoothing the inner surface is performed simultaneously with the bellmouth-shaped tube expansion step. A tube expansion head 9 attached to the tip of a rod 8 that expands almost the entire length of the straight portion of the internally grooved tube 1 formed into a predetermined U-shape (primary tube expansion) and a hairpin bent portion of the internally grooved tube 1 A receiver 10 for holding, a roller tube expansion tool 11 that includes a tapered mandrel 11a, a roller 11b, and a roller 11c and simultaneously smooths the inner surface of the internally grooved tube 1 and expands it into a bell mouth shape; It consists of a restraint die 12 that restrains the inner grooved tube 1 during the process.
The roller 11b of the roller tube expansion tool 11 revolves around the tapered mandrel 11a while rotating itself as the tapered mandrel 11a rotates, thereby smoothing the inner surface and performing parallel tube expansion. Similarly, the roller 11c revolves around the tapered mandrel 11a while rotating, but the roller 11c also revolves around the tapered mandrel 11a.
It contacts the internally grooved tube 1 at a predetermined angle different from that of 1b to perform flare expansion of the bell mouth portion. If the rod 8 and the tapered mandrel 11a are spline-coupled, the rotation of the rod 8 can be transmitted to the tapered mandrel 11a, and the rod 8,
The tube expansion head 9 and the tapered mandrel 11a are free to move in the vertical direction. On the other hand, the tapered mandrel 11a may be rotated from another drive source.

In the above configuration, the tube expansion head 9 is inserted into the internally grooved tube 1 and the rod 8 is lowered to perform primary expansion and bring it into close contact with the iron plate 6 and aluminum fin 7. At this time, the roller tube expansion tool 11 is lowered to a predetermined position due to its own weight. After that, the tapered mandrel 11a of the roller tube expansion tool 11
Rotate and insert. Tapered mandrel 1
As the tube 1a rotates, the rollers 11b and 11c revolve around the tapered mandrel 11a while rotating, and the roller 11b crushes the inner surface of the internally grooved tube 1 to expand it to a predetermined diameter, and the roller 11c
flares the tip at a predetermined angle.

Figures 5a to 5d show how the inner groove of the inner grooved tube 1 is crushed and smoothed by the roller tube expansion tool 11, and the machining progresses from Figure 5b to Figure 5c. In Fig. 5d, it can be seen that the inner groove has been almost completely flattened and smoothed. This allows it to be handled in the same way as a smooth tube in brazing joints. In this embodiment, since the plastic deformation for crushing the inner groove and the bellmouth-shaped tube expansion are performed at the same time, there is no need to newly install a special plastic deformation process, which is economical. It is also possible to replace the roller tube expansion tool 11 with a mandrel having a similar shape to the tapered mandrel 11a and push it in to expand the tube into a bell mouth shape. When an attempt is made to crush the hairpin, a large axial force is applied to the lower hairpin bending portion, and since this portion can only be restrained by the receiver 10 on the outside of the hairpin bending portion, the unrestrained inner portion will buckle. Therefore, when performing plastic deformation to crush the inner groove and bellmouth-like tube expansion at the same time, the roller tube expansion method is essential.

〔Effect of the invention〕

As explained above, according to the heat exchanger for air conditioning equipment using the internally grooved tube of the present invention and the manufacturing method thereof, the internal groove in the part of the internally grooved tube into which the return bend pipe is inserted and brazed. In the process after forming the inner groove and before inserting the return bend pipe, this part was forcibly crushed by plastic deformation to make this part practically similar to a smooth tube. It is possible to suppress the increase in the tube size, and furthermore, it is possible to avoid cracking caused by the inner groove when expanding the tube into a bell mouth shape.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention,
FIGS. 2a and 2b are explanatory diagrams of an internally grooved tube before and after expansion.
FIGS. 3a and 3b are explanatory diagrams showing a second embodiment of the present invention. FIG. 4 is an explanatory diagram showing a third embodiment of the present invention. FIGS. 5a to 5d are explanatory diagrams showing changes in the inner groove due to tube expansion in the third embodiment. FIGS. 6a and 6b are explanatory diagrams of a conventional heat exchanger for air conditioning equipment. FIGS. 7a and 7b are explanatory diagrams showing the state of inner grooves in the bell mouth portion of a conventional heat exchanger for air conditioning equipment. Explanation of symbols 1... Internally grooved tube, 2... Mandrel, 3... Pressed type, 4... Tapered mandrel, 5...
Roller, 6... Iron plate, 7... Aluminum fin, 8
... Rod, 9... Tube expansion head, 10... Receiver,
11...Roller tube expansion tool, 12...Restriction type.

Claims (1)

[Claims] 1. A refrigerant circuit is constructed by arranging a plurality of internally grooved tubes in parallel, and brazing and joining a U-shaped return bend tube inserted into one or both ends of the internally grooved tubes. In the heat exchanger for air conditioning equipment, the inner groove of the inner grooved tube at the portion opposite to the portion where the return bend tube is inserted is flattened and smoothed to have a wall thickness greater than the bottom wall thickness. A heat exchanger for air conditioning equipment that uses internally grooved tubes. 2. A heat exchanger for air conditioning equipment in which a plurality of internally grooved tubes are arranged in parallel, and a U-shaped return bend tube inserted into one or both ends of the internally grooved tube is joined by brazing to form a refrigerant circuit. In the method for manufacturing a vessel, an extra-tube restraint mold having a predetermined inner diameter is placed on the outer periphery of a portion of the internally grooved tube into which the return bend tube is inserted, and a processed member is placed on the inner periphery of the portion facing the portion. A heating device for air conditioning equipment using an internally grooved tube, characterized in that the inner surface of the internally grooved tube is smoothed by plastic deformation based on the cooperative action of the processed member and the externally restrained type. Method of manufacturing an exchanger.