U.S. patent application number 10/528705 was filed with the patent office on 2007-03-08 for semifinished flat tube, process for producing same, flat tube, heat exchanger comprising the flat tube and process for fabricating the heat exchanger.
Invention is credited to Satoru Kaimura, Takashi Tamura.
Application Number | 20070051499 10/528705 |
Document ID | / |
Family ID | 35581808 |
Filed Date | 2007-03-08 |
United States Patent
Application |
20070051499 |
Kind Code |
A1 |
Kaimura; Satoru ; et
al. |
March 8, 2007 |
Semifinished flat tube, process for producing same, flat tube, heat
exchanger comprising the flat tube and process for fabricating the
heat exchanger
Abstract
A semifinished flat tube 30 is for use in producing a flat tube
1 comprising an upper and a lower wall 2, 3 opposed to each other,
and left and right opposite side walls 4, 5 interconnecting the
upper and lower walls 2, 3 at opposite side edges thereof. The
semifinished flat tube is produced from a metal plate 15 having two
flat first portions 17, 18 for making the upper and lower walls 2,
3, a second portion 16 interconnecting the two first portions 17,
18 integrally for forming the right side wall 5, and two third
portions 9, 10 projecting upward from the respective first portions
17, 18 integrally with the first portion each at a side edge
thereof opposite to the second portion 16 for making the left side
wall 4, by bending the metal plate 15 to the shape of a hairpin at
the second portion 16 to cause the third portions 9, 10 to butt
against each other. The two third portions 9, 10 arc joined to each
other by laser welding intermittently from outside at a plurality
of portions spaced apart longitudinally thereof.
Inventors: |
Kaimura; Satoru; (Tochigi,
JP) ; Tamura; Takashi; (Tochigi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
35581808 |
Appl. No.: |
10/528705 |
Filed: |
October 23, 2003 |
PCT Filed: |
October 23, 2003 |
PCT NO: |
PCT/JP03/13523 |
371 Date: |
March 22, 2005 |
Current U.S.
Class: |
165/104.19 |
Current CPC
Class: |
F28D 1/0391 20130101;
B21C 37/151 20130101; F28F 2275/067 20130101; F28F 1/022
20130101 |
Class at
Publication: |
165/104.19 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 30, 2002 |
JP |
2002-315134 |
Nov 26, 2002 |
US |
60428922 |
Claims
1. A semifinished flat tube comprising a pair of flat walls opposed
to each other, and two side walls interconnecting the flat walls at
opposite side edges thereof for use in producing a flat tube, the
semifinished flat tube being produced from a metal plate having two
first portions for making the flat walls, a second portion
interconnecting the first portions for forming one of the side
walls, and two third portions projecting from the respective first
portions and each formed on the first portion at a side edge
thereof opposite to the second portion for making the other side
wall, by bending the metal plate to the shape of a hairpin at the
second portion to cause the third portions to butt against each
other and welding the two third portions to each other at least at
longitudinal opposite end portions thereof from outside.
2. A semifinished flat tube according to claim 1 wherein the two
third portions are joined to each other by laser welding.
3. A semifinished flat tube according to claim 1 wherein the third
portions of the metal plate protrude from and are made integral
with the respective first portions.
4. A semifinished flat tube according to claim 1 wherein the third
portions of the metal plate are each formed by bending a side edge
portion of the first portion.
5. A semifinished flat tube according to claim 1 wherein the two
third portions are welded to each other intermittently at a spacing
longitudinally thereof.
6. A semifinished flat tube according to claim 5 wherein the weld
positioned at each of opposite end portions is at a distance of up
to 10 mm from the longitudinal end of the third portion.
7. A semifinished flat tube according to claim 5 wherein the weld
positioned at each of opposite end portions is at a distance of up
to 5 mm from the longitudinal end of the third portion.
8. A semifinished flat tube according to claim 5 wherein the pitch
P of all the welds is up to 100 mm.
9. A semifinished flat tube according to claim 5 wherein assuming
that the welds have a nugget diameter D and that the two third
portions have a combined height H, D/H is at least 0.18.
10. A semifinished flat tube according to claim 5 wherein assuming
that the welds have a depth of penetration d and that each of the
third portions has a thickness t, d/t is at least 0.25.
11. A semifinished flat tube according to claim 1 wherein the two
third portions are welded to each other continuously over the
entire length thereof.
12. A semifinished flat tube according to claim 11 wherein assuming
that the continuous weld has a width W and that the two third
portions have a combined height H, W/H is at least 0.18.
13. A semifinished flat tube according to claim 11 wherein assuming
that the weld has a depth of penetration d and that each of the
third portions has a thickness t, d/t is at least 0.25.
14. A semifinished flat tube according to claim 1 wherein the metal
plate comprises an aluminum brazing sheet, and a brazing material
layer is formed at a top end of each of the third portions.
15. A semifinished flat tube comprising a pair of flat walls
opposed to each other, and two side walls interconnecting the flat
walls at opposite side edges thereof for use in producing a flat
tube, the semifinished flat tube being produced from a metal plate
having a first portion for making one of the flat walls, two second
portions having an approximately one-half the width of the first
portion for making the other flat wall, two third portions
connecting the first portion to the respective two second portions,
and two fourth portions extending upright from the respective
second portions and each formed on the second portion at a side
edge thereof opposite to the third portion, by bending the metal
plate at the third portions to cause the side edges to butt against
each other, with top ends of the two fourth portions in bearing
contact with the first portion and welding the two second portions
to each other at least at longitudinal opposite end portions
thereof from outside.
16. A semifinished flat tube according to claim 15 wherein the two
second portions are joined to each other by laser welding.
17. A semifinished flat tube according to claim 15 wherein the two
second portions are welded to each other intermittently at a
spacing longitudinally thereof.
18. A semifinished flat tube according to claim 15 wherein the two
second portions are welded to each other continuously over the
entire length thereof.
19. A semifinished flat tube according to claim 15 wherein the
metal plate comprises an aluminum brazing sheet having a brazing
material layer over opposite surfaces thereof.
20. A process for producing a semifinished flat tube comprising a
pair of flat walls opposed to each other, and two side walls
interconnecting the flat walls at opposite side edges thereof for
use in producing a flat tube, the process being characterized by
preparing a metal plate having two first portions for making the
flat walls, a second portion interconnecting the first portions for
forming one of the side walls, and two third portions projecting
from the respective first portions and each formed on the first
portion at a side edge thereof opposite to the second portion for
making the other side wall, bending the metal plate by the roll
forming process to the shape of a hairpin at the second portion to
cause the third portions to butt against each other, welding the
two third portions to each other intermittently at a spacing
longitudinally thereof from outside to make a semifinished
continuous body and thereafter cutting the semifinished continuous
body into semifinished flat tubes each having a weld at each of
longitudinal opposite end portions thereof.
21. A process for producing a semifinished flat tube comprising a
pair of flat walls opposed to each other, and two side walls
interconnecting the flat walls at opposite side edges thereof for
use in producing a flat tube, the process being characterized by
preparing a metal plate having two first portions for making the
flat walls, a second portion interconnecting the first portions for
forming one of the side walls, and two third portions projecting
from the respective first portions and each formed on the first
portion at a side edge thereof opposite to the second portion for
making the other side wall, bending the metal plate by the roll
forming process to the shape of a hairpin at the second portion to
cause the third portions to butt against each other, welding the
two third portions to each other continuously over the entire
length thereof from outside to make a semifinished continuous body
and thereafter cutting the semifinished continuous body.
22. A process for producing a semifinished flat tube according to
claim 20 wherein the two third portions are joined to each other by
laser welding.
23. An apparatus for producing a semifinished flat tube comprising
a pair of flat walls opposed to each other, and two side walls
interconnecting the flat walls at opposite side edges thereof for
use in producing a flat tube, the apparatus comprising a roll
forming device for bending a metal plate having two first portions
for making the flat walls, a second portion interconnecting the
first portions for forming one of the side walls, and two third
portions projecting from the respective first portions and each
formed on the first portion at a side edge thereof opposite to the
second portion for making the other side wall, to the shape of a
hairpin at the second portion to cause the third portions to butt
against each other, a welding device disposed downstream from the
roll forming device for welding the two third portions to each
other from outside and a cutting device disposed downstream from
the welding device.
24. An apparatus for producing a semifinished flat tube according
to claim 23 wherein the welding device is a laser welding
device.
25. A flat tube comprising a semifinished flat tube according to
claim 1 wherein the two third portions are brazed to each
other.
26. A heat exchanger comprising a pair of headers arranged in
parallel and spaced apart from each other, a plurality of parallel
heat exchange tubes each comprising a flat tube according to claim
25 and each joined at opposite ends thereof to the two headers,
fins each disposed in an air flow clearance between each pair of
adjacent heat exchange tubes and brazed to the adjacent tubes.
27. A process for fabricating a heat exchanger characterized by
preparing a plurality of semifinished flat tubes according to claim
1, preparing a pair of headers each having semifinished tube
inserting holes equal in number to the number of semifinished flat
tubes and formed at a spacing and a plurality of fins, arranging
the pair of headers as spaced apart and arranging the semifinished
flat tubes and the fins alternately, inserting opposite ends of the
semifinished flat tubes into the respective tube inserting holes of
the headers, and brazing the two third portions of each of the
semifinished flat tubes to each other, the semifinished flat tubes
to the headers, and each of the fins to the adjacent semifinished
flat tubes on opposite sides thereof at the same time.
28. A vehicle comprising a refrigeration cycle having a compressor,
a condenser and an evaporator, the condenser being a heat exchanger
according to claim 26.
29. A process for producing a semifinished flat tube according to
claim 21 wherein the two third portions are joined to each other by
laser welding.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is an application filed under 35 U.S.C.
.sctn.111 (a) claiming the benefit pursuant to 35 U.S.C.
.sctn.119(e) (1) of the filing data of Provisional Application No.
60/428,922 filed Nov. 26, 2002 pursuant to 35 U.S.C.
.sctn.111(b).
TECHNICAL FIELD
[0002] The present invention relates to semifinished flat tubes
useful for producing flat tubes for use as heat exchange tubes for
heat exchangers, such as refrigerant tubes in condensers or
evaporators for motor vehicle air conditioners, oil tubes for motor
vehicle oil coolers, water tubes for motor vehicle radiators and
heat medium tubes for heater cores, a process for producing the
same, flat tubes, heat exchangers comprising such flat tubes and a
process for fabricating the exchanger.
[0003] The term "aluminum" as used herein and in the appended
claims includes aluminum alloys in addition to pure aluminum.
BACKGROUND ART
[0004] In recent years, widely used in motor vehicle air
conditioners in place of conventional serpentine condensers are
condensers which comprise, as shown in FIG. 15, a pair of headers
100, 101 arranged in parallel and spaced apart from each other,
parallel flat refrigerant tubes 102 made of aluminum and each
joined at its opposite ends to the two headers 100, 101, corrugated
aluminum fins 103 each disposed in an air flow clearance between
the adjacent refrigerant tubes 102 and brazed to the adjacent tubes
102, an inlet pipe 104 connected to the upper end of peripheral
wall of the first 100 of the headers, an outlet pipe 105 connected
to the lower end of peripheral wall of the second 101 of the
headers, a first partition 106 provided inside the first header 100
and positioned above the midportion thereof, and a second partition
107 provided inside the second header 101 and positioned below the
midportion thereof, the number of refrigerant tubes 102 between the
inlet pipe 104 and the first partition 106, the number of
refrigerant tubes 102 between the first partition 106 and the
second partition 107 and the number of refrigerant tubes 102
between the second partition 107 and the outlet pipe 105 decreasing
from above downward to provide groups of channels. A refrigerant
flowing into the inlet pipe 104 in a vapor phase flows zigzag
through units of channel groups in the condenser before flowing out
from the outlet pipe 105 in a liquid phase. The condensers of the
construction described are called multiflow condensers, and realize
high efficiencies, lower pressure losses and supercompactness.
[0005] It is required that the refrigerant tube 102 of the
condenser described be excellent in heat exchange efficiency and
have pressure resistance to the high-pressure gaseous refrigerant
to be introduced thereinto. Moreover, the tube needs to be small in
wall thickness and low in height so as to make the condenser
compact.
[0006] The publication of Japanese Patent No. 2915660 discloses a
known flat tube which is excellent in heat exchange efficiency for
use as such a refrigerant tube 102. The flat tube disclosed in the
above publication comprises an upper wall, a lower wall, a right
and a left side wall interconnecting the upper and lower walls at
the respective right and left side edges thereof, and a plurality
of reinforcing walls interconnecting the upper and lower walls,
extending longitudinally of the tube and spaced apart from one
another as positioned between the right and left side walls, the
tube having parallel fluid channels formed inside thereof. Each of
the reinforcing walls is provided by forming a ridge projecting
inward from at least one of the upper and lower walls integrally
therewith and brazing the ridge to the inner surface of the other
wall which is flat. Alternatively, the reinforcing wall is provided
by forming a downward ridge projecting downward from the upper wall
integrally therewith, forming an upward ridge projecting upward
from the lower wall integrally therewith and brazing the ridges to
each other end to end.
[0007] Such a flat tube is fabricated from a metal plate having two
first portions for making the upper and lower walls, a second
portion interconnecting the first portions, and two projecting
third portions formed on the respective first portions integrally
therewith each at a side edge thereof opposite to the second
portion, by a process including bending the metal plate to the
shape of a hairpin at the second portion and brazing the third
portions to each other end to end. In the case where the
reinforcing walls are to be made by the first-mentioned method, the
ridges formed on at least one of the first portions are brazed to
the other first portion simultaneously when the third portions are
brazed to each other. In the case where the reinforcing walls are
to be made by the second-mentioned method, the ridges formed on one
of the first portions and the ridges formed on the other first
portion are brazed simultaneously when the third portions are
brazed to each other.
[0008] Such flat tubes are produced in the following manner
simultaneously when a condenser is fabricated. A condenser and flat
tubes are fabricated at the same time by bending an aluminum plate
having two first portions for making the upper and lower walls, a
second portion interconnecting the first portions, and two
projecting third portions formed on the respective first portions
integrally therewith each at a side edge thereof opposite to the
second portion, to the shape of a hairpin at the second portion by
the roll forming process to cause the third portions to butt
against each other and to make a semifinished continuous body,
thereafter cutting the continuous body into predetermined lengths
to prepare a plurality of semifinished flat tubes, preparing a pair
of aluminum headers each having semifinished flat tube inserting
holes equal in number to the number of the semifinished flat tubes
and arranged at a spacing and a plurality of corrugated aluminum
fins, arranging the pair of headers as spaced apart and arranging
the semifinished flat tubes and the corrugated fins alternately,
inserting opposite ends of the semifinished flat tubes into the
respective holes of the headers, and simultaneously brazing the
third portions of each of the semifinished flat tubes to each
other, the flat tubes to the headers and the flat tubes to the
corrugated fins.
[0009] However, we have found that the semifinished flat tube has
the following problems. When the semifinished continuous body is
cut into semifinished flat tubes, opposite ends of the flat tube
open to entail the likelihood that the tube opposite ends can not
be inserted into the corresponding holes of the headers in
fabricating the condenser. The aluminum plate for use in making the
semifinished flat tubes is given a reduced thickness recently to
obtain a condenser of reduced weight, with the result the
semifinished flat tubes are insufficient in rigidity. This results
in the likelihood that the tubes will deform when the tubes are
assembled into a condenser or otherwise handled.
[0010] An object of the present invention is to resolve the above
problems and to provide a semifinished flat tube which can be
prevented from opening at its opposite ends and which has higher
rigidity than those of the prior art.
DISCLOSURE OF THE INVENTION
[0011] The present invention provides a first semifinished flat
tube comprising a pair of flat walls opposed to each other, and two
side walls interconnecting the flat walls at opposite side edges
thereof for use in producing a flat tube, the semifinished flat
tube being produced from a metal plate having two first portions
for making the flat walls, a second portion interconnecting the
first portions for forming one of the side walls, and two third
portions projecting from the respective first portions and each
formed on the first portion at a side edge thereof opposite to the
second portion for making the other side wall, by bending the metal
plate to the shape of a hairpin at the second portion to cause the
third portions to butt against each other and welding the two third
portions to each other at least at longitudinal opposite end
portions thereof from outside.
[0012] With the first semifinished flat tube of the invention, the
two third portions are welded to each other at least at
longitudinal opposite end portions thereof from outside. This
prevents the semifinished flat tube from opening at its opposite
ends, and the opposite ends of the tubes to be used for fabricating
a heat exchanger can be reliably inserted into the respective tube
inserting holes of the headers. Further the third portions of each
of the semifinished tubes can be brazed subsequently in the
fabrication process without producing any fault. Moreover, the
semifinished tube of the invention has higher rigidity than those
of the prior art, and such tubes can be assembled into the heat
exchanger or otherwise handled free of deformation.
[0013] In the first semifinished flat tube of the invention, the
two third portions may be joined to each other by laser welding. In
this case, the third portions can be welded to each other from
outside relatively easily.
[0014] In the first semifinished flat tube of the invention, the
third portions of the metal plate may protrude from and be made
integral with the respective first portions. Alternatively, the
third portions of the metal plate may each be formed by bending a
side edge portion of the first portion.
[0015] In the first semifinished flat tube of the invention, the
two third portions may be welded to each other intermittently at a
spacing longitudinally thereof. This gives higher rigidity to the
semifinished flat tube than conventionally, and such tubes can be
prevented from deforming when to be assembled into a heat exchanger
or otherwise handled.
[0016] With the first semifinished flat tube wherein the third
portions are welded to each other intermittently, the weld
positioned at each of opposite end portions may be at a distance of
up to 10 mm from the longitudinal end of the third portion. This
prevents the opposite ends of the semifinished tube from opening
with improved effectiveness.
[0017] With the first semifinished flat tube wherein the third
portions are welded to each other intermittently, the weld
positioned at each of opposite end portions may be at a distance of
up to 5 mm from the longitudinal end of the third portion. This
prevents the opposite ends of the semifinished tube from opening
with further improved effectiveness.
[0018] With the first semifinished flat tube wherein the third
portions are welded to each other intermittently, the pitch P of
all the welds may be up to 100 mm. The semifinished tube is then
reliably given higher rigidity than in the prior art, and such
tubes can be prevented from deforming reliably when to be assembled
into a heat exchanger or otherwise handled.
[0019] With the first semifinished flat tube wherein the third
portions are welded to each other intermittently, it is assumed
that the welds have a nugget diameter D and that the two third
portions have a combined height H. The ratio D/H may then be at
least 0.18. Further assuming that the welds have a depth of
penetration d and that each of the third portions has a thickness
t, d/t may be at least 0.25. In these cases, the welds can be
prevented from cracking. This eliminates the likelihood that the
brazing operation subsequently conducted will produce a faulty
brazed joint.
[0020] With the first semifinished flat tube of the invention, the
two third portions may be welded to each other continuously over
the entire length thereof. The tube is then given higher rigidity
than the first semifinished tube wherein the third portions are
welded to each other intermittently, and such tubes are reliably
prevented from deforming when to be assembled into a heat exchanger
or to be otherwise handled. However, the semifinished tube wherein
the third portions are welded to each other intermittently can be
produced at a higher speed than the one where the third portions
are welded continuously.
[0021] With the first semifinished flat tube wherein the third
portions are welded to each other continuously, it is assumed that
the continuous weld has a width W and that the two third portions
have a combined height H. The ratio W/H may then be at least 0.18.
Further assuming that the weld has a depth of penetration d and
that each of the third portions has a thickness t, d/t may be at
least 0.25. In these cases, the weld can be prevented from
cracking. This eliminates the likelihood that the brazing operation
subsequently conducted will produce a faulty brazed joint.
[0022] With the first semifinished flat tube of the invention, the
metal plate may comprise an aluminum brazing sheet, with a brazing
material layer formed at the top end of each of the third portions.
When the third portions are to be brazed to each other
subsequently, the brazing material layer at the top ends is usable
for brazing, consequently eliminating the time and labor needed for
applying a brazing material separately.
[0023] The present invention provides a second semifinished flat
tube comprising a pair of flat walls opposed to each other, and two
side walls interconnecting the flat walls at opposite side edges
thereof for use in producing a flat tube, the semifinished flat
tube being produced from a metal plate having a first portion for
making one of the flat walls, two second portions having an
approximately one-half the width of the first portion for making
the other flat wall, two third portions connecting the first
portion to the respective two second portions, and two fourth
portions extending upright from the respective second portions and
each formed on the second portion at a side edge thereof opposite
to the third portion, by bending the metal plate at the third
portions to cause the side edges to butt against each other, with
top ends of the two fourth portions in bearing contact with the
first portion and welding the two second portions to each other at
least at longitudinal opposite end portions thereof from
outside.
[0024] With the second semifinished flat tube of the invention, the
two second portions are welded to each other at least at
longitudinal opposite end portions thereof from outside. This
prevents the semifinished flat tube from opening at its opposite
ends. When such tubes are to be used for fabricating a heat
exchanger, the tube opposite ends can be reliably inserted into the
respective tube inserting holes of the headers. Further the fourth
portions of each of the semifinished tubes can be brazed
subsequently in the fabrication process without producing any
fault. Moreover, the semifinished tube of the invention has higher
rigidity than those of the prior art. When to be assembled into the
heat exchanger or otherwise handled, such tubes can be prevented
from deforming.
[0025] In the second semifinished flat tube of the invention, the
two second portions may be joined to each other by laser welding.
In this case, the second portions can be welded to each other from
outside relatively easily.
[0026] With the second semifinished flat tube of the invention, the
two second portions may be welded to each other intermittently at a
spacing longitudinally thereof. Alternatively, the two second
portions may be welded to each other continuously over the entire
length thereof. In these cases, the semifinished tube is given
higher rigidity than conventionally, and when to be assembled into
a heat exchanger or otherwise handled, such tubes can be prevented
from deforming.
[0027] With the second semifinished flat tube of the invention, the
metal plate may comprise an aluminum brazing sheet having a brazing
material layer over opposite surfaces thereof. When the second
portions, as well as the fourth portions, are to be subsequently
brazed, the brazing material layer of the metal plate is usable for
brazing. This eliminates the time and labor needed for applying a
brazing material separately.
[0028] The present invention provides a process for producing a
semifinished flat tube comprising a pair of flat walls opposed to
each other, and two side walls interconnecting the flat walls at
opposite side edges thereof for use in producing a flat tube, the
process being characterized by preparing a metal plate having two
first portions for making the flat walls, a second portion
interconnecting the first portions for forming one of the side
walls, and two third portions projecting from the respective first
portions and each formed on the first portion at a side edge
thereof opposite to the second portion for making the other side
wall, bending the metal plate by the roll forming process to the
shape of a hairpin at the second portion to cause the third
portions to butt against each other, welding the two third portions
to each other intermittently at a spacing longitudinally thereof
from outside to make a semifinished continuous body and thereafter
cutting the semifinished continuous body into semifinished flat
tubes each having a weld at each of longitudinal opposite end
portions thereof.
[0029] The present invention provides another process for producing
a semifinished flat tube comprising a pair of flat walls opposed to
each other, and two side walls interconnecting the flat walls at
opposite side edges thereof for use in producing a flat tube, the
process being characterized by preparing a metal plate having two
first portions for making the flat walls, a second portion
interconnecting the first portions for forming one of the side
walls, and two third portions projecting from the respective first
portions and each formed on the first portion at a side edge
thereof opposite to the second portion for making the other side
wall, bending the metal plate by the roll forming process to the
shape of a hairpin at the second portion to cause the third
portions to butt against each other, welding the two third portions
to each other continuously over the entire length thereof from
outside to make a semifinished continuous body and thereafter
cutting the semifinished continuous body.
[0030] With these processes for producing a semifinished flat tube,
the two third portions are preferably joined to each other from
outside by laser welding.
[0031] The present invention provides an apparatus for producing a
semifinished flat tube comprising a pair of flat walls opposed to
each other, and two side walls interconnecting the flat walls at
opposite side edges thereof for use in producing a flat tube, the
apparatus comprising a roll forming device for bending a metal
plate having two first portions for making the flat walls, a second
portion interconnecting the first portions for forming one of the
side walls, and two third portions projecting from the respective
first portions and each formed on the first portion at a side edge
thereof opposite to the second portion for making the other side
wall, to the shape of a hairpin at the second portion to cause the
third portions to butt against each other, a welding device
disposed downstream from the roll forming device for welding the
two third portions to each other from outside and a cutting device
disposed downstream from the welding device.
[0032] With the apparatus of the invention for producing a
semifinished flat tube, the welding device is preferably a laser
welding device.
[0033] The present invention provides a flat tube which comprises
the first semifinished flat tube described above wherein the two
third portions are brazed to each other. In this case, the two
third portions are brazed to each other as temporarily held
together by the welds at least at respective opposite end portions,
so that the brazed portions are free of faults over the entire
length thereof.
[0034] The present invention provides a heat exchanger comprising a
pair of headers arranged in parallel and spaced apart from each
other, a plurality of parallel heat exchange tubes each comprising
the flat tube described above and each joined at opposite ends
thereof to the two headers, fins each disposed in an air flow
clearance between each pair of adjacent heat exchange tubes and
brazed to the adjacent tubes.
[0035] The present invention provides a process for fabricating a
heat exchanger characterized by preparing a plurality of
semifinished flat tubes described above, preparing a pair of
headers each having semifinished tube inserting holes equal in
number to the number of semifinished flat tubes and formed at a
spacing and a plurality of fins, arranging the pair of headers as
spaced apart and arranging the semifinished flat tubes and the fins
alternately, inserting opposite ends of the semifinished flat tubes
into the respective tube inserting holes of the headers, and
brazing the two third portions of each of the semifinished flat
tubes to each other, the semifinished flat tubes to the headers,
and each of the fins to the adjacent semifinished flat tubes on
opposite sides thereof at the same time.
[0036] The present invention provides a vehicle comprising a
refrigeration cycle having a compressor, a condenser and an
evaporator, the condenser being the heat exchanger described
above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 is a cross sectional view showing a flat tube
produced from a first embodiment of semifinished flat tube shown in
FIGS. 4 to 6.
[0038] FIG. 2 is a diagram schematically showing an apparatus for
fabricating the first embodiment of semifinished flat tube.
[0039] FIG. 3 includes views showing some steps of a process for
fabricating the first embodiment of the semifinished flat tube.
[0040] FIG. 4 is a perspective view partly broken away and showing
the first embodiment of semifinished flat tube.
[0041] FIG. 5 is a fragmentary plan view showing the first
embodiment of the semifinished flat tube.
[0042] FIG. 6 is an enlarged view in section taken along the line
VI-VI in FIG. 5.
[0043] FIG. 7 is a perspective view partly broken away and showing
a second embodiment of semifinished flat tube.
[0044] FIG. 8 is a cross sectional view showing a flat tube
produced from a third embodiment of semifinished flat tube shown in
FIG. 10.
[0045] FIG. 9 includes views showing some steps of a process for
fabricating the third embodiment of the semifinished flat tube.
[0046] FIG. 10 is a perspective view partly broken away and showing
the third embodiment of semifinished flat tube.
[0047] FIG. 11 is a perspective view partly broken away and showing
a fourth embodiment of semifinished flat tube.
[0048] FIG. 12 is a cross sectional view showing a flat tube
produced from a fifth embodiment of semifinished flat tube shown in
FIG. 10.
[0049] FIG. 13 includes views showing some steps of a process for
fabricating the fifth embodiment of the semifinished flat tube.
[0050] FIG. 14 is a perspective view partly broken away and showing
a fifth embodiment of semifinished flat tube.
[0051] FIG. 15 is a perspective view showing a condenser for use in
a motor vehicle air conditioner.
BEST MODE OF CARRYING OUT THE INVENTION
[0052] Embodiments of the present invention will be described below
with reference to the drawings. In the following description, the
upper and lower sides, and the left- and right-hand sides of FIGS.
1, 8 and 12 will be referred to as "upper," "lower," "left" and
"right," respectively. Throughout the drawings, like parts will be
designated by like reference numerals.
[0053] FIG. 1 shows a flat tube, FIG. 2 shows an apparatus for
producing semifinished flat tubes, FIG. 3 shows some steps of a
process for producing the semifinished flat tube, and FIGS. 4 to 6
show the semifinished flat tube.
[0054] With reference to FIG. 1, the flat tube 1 is made of
aluminum and comprises an upper and a lower flat wall 2, 3 (a pair
of flat walls) opposed to each other, left and right opposite side
walls 4, 5 interconnecting the upper and lower walls 2, 3 at left
and right opposite side edges thereof, and a plurality of
reinforcing walls 6 interconnecting the upper and lower walls 2, 3,
extending longitudinally of the tube and spaced apart from one
another as positioned between the right and left side walls 4, 5,
the tube having parallel fluid channels 7 formed inside thereof.
Although not shown, each of the reinforcing walls 7 is provided
with communication holes for causing the adjacent fluid channels 7
to communicate with each other therethrough, the communication
holes in the entire tube being in a staggered arrangement when seen
from above.
[0055] The left side wall 4 comprises a portion 9 projecting
downward from the left side edge of the upper wall 2 integrally
therewith and a portion 10 projecting upward from the left side
edge of the lower wall 3 integrally therewith, and is formed by
causing these portions 9, 10 to butt against each other and brazing
these portions in this state. The right side wall 5 is made
integral with the upper and lower walls 2, 3.
[0056] Each of the reinforcing walls 6 comprises a downward ridge
11 projecting downward from the upper wall 2 integrally therewith
and an upward ridge 12 projecting upward from the lower wall 3
integrally therewith, and is formed by causing these ridges 11, 12
to butt against each other and brazing the ridges 11, 12 in this
state.
[0057] The flat tube 1 is produced by making a semifinished flat
tube first, and brazing the semifinished flat tube at the required
portions.
[0058] The semifinished flat tube is produced by the process to be
described below using a production apparatus shown in FIG. 2.
[0059] First, an aluminum brazing sheet clad with a brazing
material over opposite surfaces thereof is passed between rolling
rolls to prepare a metal plate 15 as shown in FIG. 3(a) for making
flat tubes. The metal plate 15 comprises two flat first portions
17, 18 for making the upper and lower walls 2, 3, a second portion
16 interconnecting the two first portions 17, 18 integrally for
forming the right side wall 5, two third portions 9, 10 projecting
upward from the respective first portions 17, 18 integrally with
the first portion each at a side edge thereof opposite to the
second portion 16 for making the left side wall 4, and ridges 11,
12 projecting upward from the respective first portions 17, 18
integrally therewith and arranged at a predetermining spacing
leftward or rightward. The ridges 11 on one of the first portions,
17, and the ridges 12 on the other first portion 18 are positioned
symmetrically about a center line with respect to the widthwise
direction. The second portion 16 has a larger thickness than the
two first portions 17, 18. Further the two third portions 9, 10
have a larger thickness than the ridges 11, 12. The height of the
projecting third portions 9, 10 is approximately one-half the width
of the second portion 16. By forming the third portions 9, 10 and
the ridges 11, 12 on one surface of the aluminum brazing sheet
integrally therewith which sheet is clad with the brazing material
over opposite surfaces thereof, a brazing material layer (not
shown) is formed on opposite side faces and the top faces of the
third portions 9, 10 and the ridges 11, 12 and on the upper and
lower surfaces of the two first portions 17, 18. The brazing
material layer on the top faces of the third portions 9, 10 and the
ridges 11, 12 has a larger thickness than the brazing material
layer on the other portions. The third portion 10 on the first
portion 18 for making the lower wall 3 is integrally provided, on
the top face thereof, with a ridge 19 extending longitudinally of
the third portion 10. On the other hand, the third portion 9 on the
first portion 17 for making the upper wall 2 has formed in its top
face a groove 20 extending longitudinally of the third portion 9
for the ridge 19 to be forced in by a press fit. The ridge 19 and
the groove 20 are formed when the aluminum brazing sheet is formed
by rolling, and a brazing material layer is present on the top face
and opposite side faces of the ridge 19 and on the bottom face and
opposite side faces which define the groove 20. The metal plate 15
is prepared in the form of a coil with the third portions 9, 10 and
ridges 11, 12 facing radially inward.
[0060] The production apparatus shown in FIG. 2 comprises a supply
roll 21 for placing the coil 15A of metal plate 15 thereon, a
straightening device 22 for correcting the distortion of the metal
plate 15 paid out from the roll 21, a roll forming device 23
disposed downstream from the straightening device 22 for bending
the metal plate 15 at the second portion 16 to the shape of a
hairpin to cause the two third portions 9, 10, as well as the
opposed ridges 11, 12 in each pair, to butt against each other, a
laser welding device 25 disposed downstream from the roll forming
device 23 for joining the butting third portions 9, 10 to each
other by laser welding from outside to make a semifinished
continuous body 24, a straightening device 26 disposed downstream
from the welding device 25 for correcting the distortion of the
continuous body 24, and a cutting device 27 disposed downstream
from the correcting device 26 for cutting the continuous body
24.
[0061] To produce the semifinished flat tube using the production
apparatus described, the metal plate 15 paid out from the coil 15A
on the supply roll 21 is treated by the straightening device 22 for
the removal of distortion, and thereafter fed to the roll forming
device 23, by which the metal plate 15 is progressively bent at
opposite side edges of the second portion 16 by the roll forming
process [see FIG. 3, (b), (c)] and finally bent to the shape of a
hairpin to cause the two third portions 9, 10, as well as the
ridges 11, 12 in each pair, to butt against each other and to force
the ridge 19 into the groove 20 by a press fit, whereby a bent body
28 is obtained [see FIG. 3, (d)]. At this time, the right side wall
5 is formed by the second portion 16, the upper wall 2 by the first
portion 17 and the lower wall 3 by the other first portion 18.
[0062] The bent body 28 is then fed to the laser welding device 25,
by which the butting parts of the two third portions 9, 10 are
joined by laser welding intermittently at a spacing along the
length thereof from outside to make a semifinished continuous body
24. Subsequently, the semifinished continuous body 24 has its
distortion corrected by the straightening device 26 and is
thereafter cut into semifinished flat tubes each having two welds
31 respectively at longitudinal opposite end portions of the third
portions 9, 10. FIGS. 4 to 6 show the semifinished flat tube 30
thus produced.
[0063] As shown in FIGS. 4 to 6, the semifinished flat tube 30 is
obtained by intermittently welding the two third portions 9, 10 to
each other at the butting ends thereof at a spacing longitudinally
of these portions by laser welding, and has a plurality of laser
welds 31 formed at a spacing along the longitudinal direction. It
is desired that the laser weld 31 and positioned at each of
opposite end portions be at a distance L of up to 10 mm, preferably
up to 5 mm, from the longitudinal end of the third portion 9 or 10.
It is also desired that the pitch P of all the laser welds 31 be up
to 100 mm, preferably up to 60 mm, more preferably up to 30 mm.
Assuming that the laser welds 31 have a nugget diameter D and that
the two third portions 9, 10 have a combined height H, D/H is
preferably at least 0.18. Further assuming that the laser welds 31
have a depth of penetration d and that each of the third portions
9, 10 has a thickness t, d/t is preferably at least 0.25.
[0064] A flat tube is produced from the semifinished flat tube 30
by heating the tube 30 at a predetermined temperature to braze the
two third portions 9, 10, as well as the correspond ridges 11, 12
in each pair, to each other utilizing the brazing material layer on
the metal plate 15, whereby the left side wall 4 and each
reinforcing wall 6 are formed. Thus, the flat tube 1 is
produced.
[0065] When the flat tube 1 is to be used, for example, as the
refrigerant tube 102 of the condenser shown in FIG. 15, such a
depth of penetration d and that each of the third portions 9, 10
has a thickness t, d/t is preferably at least 0.25. With the
exception of these features, the flat tube 40 is the same as the
semifinished flat tube 30 shown in FIGS. 4 to 6.
[0066] The semifinished flat tube 40 is produced by a process
similar to the process for producing the flat tube 30 shown in
FIGS. 4 to 6, using the apparatus shown in FIG. 2. However, the
process differs from the process for the tube 30 in that the two
third portions 9, 10 are welded by the laser welding device 25 to
each other continuously over the entire length thereof from
outside.
[0067] The heat exchanger comprising flat tubes which are produced
from semifinished flat tubes of either one of the two types
described is used in vehicles comprising a refrigeration cycle
having a compressor, a condenser and an evaporator, as the
condenser of the refrigeration cycle. Alternatively, the heat
exchanger is used as the evaporator of the refrigeration cycle.
Further alternatively, the heat exchanger may be installed in motor
vehicles to serve as an oil cooler or radiator.
[0068] The present invention will be described below with reference
to specific examples.
EXAMPLE 1
[0069] An aluminum brazing sheet made from JIS BAS211P was rolled
into a metal plate 15 shown in FIG. 3, (a). The metal plate was
then made into a semifinished flat tube 40 wherein two third
portions 9, 10 were continuously joined to each other over the
entire length thereof by laser welding as shown in FIG. 7. The
laser welding conditions were: pulse width, 0.5 flat tubes 1 may be
produced simultaneously with the fabrication of the condenser. More
specifically, the condenser is fabricated in the following manner.
First prepared are a plurality of semifinished flat tubes 30. Also
prepared are a pair of aluminum headers 100, 101 each having
semifinished tube inserting holes equal in number to the number of
semifinished flat tubes 30, and a plurality of corrugated aluminum
fins 103. The pair of headers 100, 101 are then arranged as spaced
apart, the semifinished flat tubes 30 and the fins 103 are arranged
alternately, and opposite ends of the semifinished flat tubes 30
are inserted into the respective tube inserting holes of the
headers 100, 101. The resulting assembly is thereafter heated at a
predetermined temperature to braze the two third portions 9, 10.,
as well as the corresponding ridges 11, 12 in each pair, of each
semifinished flat tube to each other, the flat tubes 30 to the
headers 100, 101, and each of the corrugated fins 103 to the
adjacent flat tubes 30 on opposite sides thereof at the same time
utilizing the brazing material layer of the metal plate 15. In this
way, the condenser is fabricated.
[0070] FIG. 7 shows a second embodiment of semifinished flat tube
for use in producing the flat tube of FIG. 1.
[0071] The semifinished flat tube 40 shown in FIG. 7 has two third
portions 9, 10 which are continuously welded by laser welding over
the entire length thereof. Suppose the continuous laser weld 41 has
a width W, and the two third portions 9, 10 have a combined height
H. The ratio W/H is then preferably at least 0.18. Further assuming
that the laser weld 41 has ms; frequency, 66.7 Hz; pulse energy, 3
J; assist gas, none; work moving velocity, 30 m/min. The continuous
laser weld 41 was 0.6 mm in width W and 0.2 mm in the depth of
penetration d. The semifinished flat tube 40 was 1.1 mm in the
combined height H of the two third portions 9, 10, 0.4 mm in the
thickness t of each of the third portions 9, 10, and 16 mm in the
overall width.
EXAMPLES 2-9
[0072] An aluminum brazing sheet made from JIS BAS211P was rolled
into a metal plate 15 shown in FIG. 3, (a). The metal plate was
then made into a semifinished flat tube 30 wherein two third
portions 9, 10 were intermittently joined to each other at a
spacing longitudinally thereof by laser welding as shown in FIGS. 4
to 6. The laser welding conditions were: pulse width, 0.5 ms;
frequency, 66.7 Hz; pulse energy, 3 J; assist gas, none; work
moving velocity, 200 m/min. The laser welds were 0.6 mm in nugget
diameter D and 0.2 mm in the depth of penetration d. The weld laser
31 positioned at each of opposite end portions of the third
portions 9, 10 was at a distance L of 15 mm from the longitudinal
end of the third portion. The tubes 30 of the examples were
produced with varying weld pitches P. The semifinished flat tubes
30 were 1.1 mm in the combined height H of the two third portions
9, 10, 0.4 mm in the thickness t of each of the third portions 9,
10, and 16 mm in the overall width.
Evaluation Test 1
[0073] The welds 41, 30 produced in the semifinished flat tubes 40,
30 of Examples 1 to 9 by laser welding were observed. These
semifinished flat tubes 40, 30 of Examples 1 to 9 were also
assembled through the steps preceding the brazing step in
fabricating condensers like the one shown in FIG. 15 and were
checked for handleability for assembling. Table 1 shows the
results. TABLE-US-00001 TABLE 1 Example Pitch P (mm) Evaluation 1
-- A 2 10 A 3 20 A 4 30 A 5 40 B 6 50 B 7 60 B 8 70 C 9 80 C
[0074] With reference to Table 1, the column of "Evaluation," "A"
indicates that the tube has no cracks in the laser weld, has high
rigidity and is reliably insertable into the tube inserting hole of
the header in assembling the condenser; "B" indicates that fine
cracks, although found in the laser weld, cause no trouble in
brazing the two third portions to each other, and that the tube is
reliably insertable into the tube hole of the header in assembling
the condenser, and "C" indicates that fine cracks, although found
in the laser weld, cause no trouble in brazing the two third
portions to each other, and that the tube has slightly open ends
such that about 2 to 3% of all the tubes used for assembling the
condenser are not insertable into the tube hole of the header.
EXAMPLES 10-15
[0075] An aluminum brazing sheet made from JIS BAS211P was rolled
into a metal plate 15 shown in FIG. 3, (a). The metal plate was
then made into a semifinished flat tube 30 wherein two third
portions 9, 10 were intermittently joined to each other at a
spacing longitudinally thereof by laser welding as shown in FIGS. 4
to 6. The laser welding conditions were: pulse width, 0.5 ms;
frequency, 66.7 Hz; pulse energy, 3 J; assist gas, none; work
moving velocity, 200. m/min. The laser weld 31 positioned at each
of opposite end portions of the third portions 9, 10 was at a
distance L of 15 mm from the longitudinal end of the third portion.
The pitch P of all the welds was 30 mm. The tubes 30 of the
examples were produced with varying values for D/H ahd for d/t
wherein D is the nugget diameter of laser the welds 31, H is the
combined height of the two third portions 9, 10, d is the depth of
penetration of the laser welds 31, and t is the thickness of each
of the third portions 9, 10. The semifinished flat tubes 30 were
1.1 mm in the combined height H of the two third portions 9, 10,
0.4 mm in the thickness t of each of the third portions 9, 10, and
16 mm in the overall width.
Evaluation Test 2
[0076] The welds 30 produced in the semifinished flat tubes 30 of
Examples 10 to 15 by laser welding were observed. Table 2 shows the
results. TABLE-US-00002 TABLE 2 Results of observation of laser
welds d/t Example D/H 0.25 0.5 0.75 1 10 0.18 Y Y Y 11 0.27 Y X X
12 0.36 Y X 13 0.45 Y X X 14 0.55 X X X X 15 0.64 X X X
[0077] With reference to Table 2, the columns of "Results of
observation of laser welds," "X" indicates that no cracks are found
in the laser welds, and "Y" indicates that fine cracks, although
found, cause no trouble in brazing the two third portions to each
other.
[0078] Tables 1 and 2 reveal that the laser welds in the
semifinished flat tubes of the present invention develop no cracks
that would produce faults in the subsequent step of brazing,
further indicating that the tubes are highly handleable in
assembling the condenser.
[0079] FIG. 8 shows another embodiment of flat tube.
[0080] With reference to FIG. 8, a flat tube 50 has a left side
wall 4, which is formed by downwardly folding over the left side
edge of an upper wall 2 to form a portion 51, folding back the left
side edge of a lower wall 3 to form a portion 52 and brazing the
two portions 51, 52 to each other in a butting relation.
[0081] Each of reinforcing walls 6 is formed by bending the upper
wall 2 downward to form a downward ridge 53, brazing the lower edge
of the ridge 53 to the lower wall 3, bending the lower wall 3
upward to form an upward ridge 54 and brazing the upper edge of the
ridge 54 to the upper wall 2. The downward edges 53 and the upward
edges 54 are arranged alternately leftward or rightward.
[0082] The flat tube 50 is produced by making a semifinished flat
tube first, and brazing the required portions of the tube.
[0083] The semifinished flat tube is produced in the manner shown
in FIG. 9.
[0084] Prepared first from an aluminum brazing sheet clad with a
brazing material over opposite surfaces is a metal plate 55 as
shown in FIG. 9, (a) for use in producing the semifinished flat
tube. The metal plate 55 comprises two flat first portions 56, 57
for making the upper and lower walls 2, 3, and a second portion 58
connecting the two first portions 56, 57 to each other integrally
for making a right side wall 5. The first portions 56, 57 have
upwardly projecting bent portions 59, 60 extending longitudinally
of the metal plate 55 and arranged at a spacing leftward or
rightward. Each bent portion 59 (60) comprises a vertical upright
part 59a (60a) which is perpendicular or substantially
perpendicular to the metal plate 55, and a slanting upright part
59b (60b) which is inclined at predetermined angles with respect to
the metal plate 55 and the vertical upright part 59a (60a). There
is a clearance between the two upright parts 59a, 59b (60a, 60b).
The bent portions 59 of the first portion 51 for making the upper
wall 2 and the bent portions 60 of the other first portion 52 for
making the lower wall 3 are positioned asymmetrically about the
widthwise center line of the metal plate 55.
[0085] The metal plate 55 is then contracted in the widthwise
direction, whereby the upright portions 59a, 59b (60a, 60b) of each
bent portion 59 (60) are brought into intimate contact with each
other to make the upwardly projecting ridge 53 (54). The first
portions 56, 57 are bent upward each at a side edge portion thereof
opposite to the second portion 58, whereby upwardly projecting
third portions 51, 52 are formed for making the left side wall 4
[see FIG. 9, (b)].
[0086] The metal plate 55 is then wound into a coil with the third
portions 51, 52 and the ridges 53, 54 facing radially inward, and
the coil is placed on the supply roll 21 of the production
apparatus shown in FIG. 2 to produce a semifinished flat tube using
the apparatus.
[0087] Stated more specifically, the metal plate 55 paid out from
the coil on the supply roll 21 is treated by the straightening
device 22 for the removal of distortion, and thereafter fed to the
roll forming device 23, by which the metal plate 55 is
progressively bent at opposite side edges of the second portion 58
by the roll forming process [see FIG. 9, (c)] and finally bent into
the shape of a hairpin to cause the two third portions 51, 52 to
butt against each other, to contact the ridges 53 of the first
portion 56 with the other first portion 57, and to contact the
ridges 54 of the other first portion 57 with the first portion 56,
whereby a bent body 61 is obtained [see FIG. 9, (d)]. At this time,
the right side wall 5 is formed by the second portion 58, the upper
wall 2 by the first portion 56 and the lower wall 3 by the other
first portion 57.
[0088] The bent body 61 is then fed to the laser welding device 25,
by which the butting parts of the two third portions 51, 52 are
joined by laser welding intermittently at a spacing along the
length thereof from outside to make a semifinished continuous body.
Subsequently, the semifinished continuous body has its distortion
corrected by the straightening device 26 and is thereafter cut into
semifinished flat tubes each having two laser welds respectively at
longitudinal opposite end portions of the third portions 51, 52.
FIG. 10 shows the semifinished flat tube 65 thus produced.
[0089] As shown in FIG. 10, the semifinished flat tube 65 is
obtained by intermittently welding the two third portions 51, 52 to
each other at the butting ends thereof at a spacing longitudinally
of these portions by laser welding, and has a plurality of welds 66
formed at a spacing along the longitudinal direction. The
semifinished flat tube 65 is the same as the semifinished flat tube
shown in FIGS. 4 to 6 with respect to the distance L of the laser
weld 66 and positioned at each of opposite end portions from the
longitudinal end of the third portion 51 or 52, the pitch P of all
the laser welds 66, the relationship D/H between the nugget
diameter D of the laser welds 66 and the combined height H of the
third portions 51, 52, and the relationship d/t between the depth
of penetration d of the laser welds 66 and the thickness t of each
of the third portions 51, 52.
[0090] To produce a flat tube from the semifinished flat tube 65,
the tube 65 is heated at a predetermined temperature to braze the
two third portions 51, 52 to each other, the ridges 53 of the first
portion 56 to the other first portion 57, and the ridges 54 of the
other first portion 57 to the first portion 56, utilizing the
brazing material layer on the metal plate 55, whereby the left side
wall 4 and each reinforcing wall 6 are formed. Thus, the flat tube
50 is produced.
[0091] When the flat tube 50 is to be used, for example, as the
refrigerant tube 102 of the condenser shown in FIG. 15, such flat
tubes 50 may be produced by the foregoing process simultaneously
with the fabrication of the condenser as in the case where flat
tubes 1 are used.
[0092] FIG. 11 shows another embodiment of semifinished flat tube
for use in producing the flat tube 50 of FIG. 8.
[0093] FIG. 11 shows a semifinished flat tube 70 having two third
portions 51, 52 which are joined to each other continuously by
laser welding over the entire length thereof. The semifinished flat
tube 70 is the same as the semifinished flat tube 65 shown in FIG.
10 with respect to the relationship W/H between the width W of the
continuous laser weld 71 formed by laser welding and the combined
height H of the third portions 51, 52, and the relationship d/t
between the depth of penetration d of the laser weld 71 and the
thickness t of each of the third portions 51, 52.
[0094] Using the apparatus shown in FIG. 2, the semifinished flat
tube 70 is produced by the same process as the semifinished flat
tube 65 shown in FIG. 10, whereas the process differs from the
process for the tube 65 in that the welding operation to be
conducted by the laser welding device 25 is performed continuously
to join the two third portions 51, 52 over the entire length
thereof from outside.
[0095] The heat exchanger comprising flat tubes 50 which are
produced from semifinished flat tubes of either one of the two
types 65, 70 described is used in vehicles comprising a
refrigeration cycle having a compressor, a condenser and an
evaporator, as the condenser of the refrigeration cycle.
Alternatively, the heat exchanger is used as the evaporator of the
refrigeration cycle. Further alternatively, the heat exchanger may
be installed in motor vehicles to serve as an oil cooler or
radiator.
[0096] FIG. 12 shows still another embodiment of flat tube.
[0097] With reference to FIG. 12, a flat tube 80 has an upper wall
2 comprising left and right two portions 81, 82, and left and right
opposite side walls 4, 5 integral with the upper and lower walls 2,
3. A reinforcing wall 6 is provided by bending the two portions 81,
82 of the upper wall 2 vertically downward each at a side edge
portion opposite to the side wall 4 or 5 to form portions 83, 84,
brazing the lower edges of the portions 83, 84 to the lower wall 3
in contact therewith, and brazing the portions 81, 82 to each other
and the portions 83, 84 to each other.
[0098] The flat tube 80 is produced by making a semifinished flat
tube first, and brazing the required portions of the tube.
[0099] The semifinished flat tube is produced in the manner shown
in FIG. 13.
[0100] Prepared first from an aluminum brazing sheet clad with a
brazing material over opposite surfaces is a metal plate 85 as
shown in FIG. 13, (a) for use in producing the semifinished flat
tube. The metal plate 85 comprises a first portion 86 for making
the lower wall 3, two second portions 81, 82 having an
approximately one-half the width of the first portion 86 for making
the upper wall 2, two third portions 87, 88 connecting the first
portion 86 to the respective two second portions 81, 82 for making
the left and right side walls 4, 5, and two fourth portions 83, 84
extending upright from the respective second portions 81, 82 and
each formed on the second portion 81 or 82 at a side edge thereof
opposite to the third portion 87 or 88.
[0101] Subsequently, the metal plate 85 are bent at the two third
portions 87, 88 [see FIG. 13, (b) and (c)] to cause the side edges
of the second portions 81, 82 where the fourth portions 83, 84 are
formed to butt against each other, to bring the fourth portions 83,
84 into intimate contact with each other and to bring the lower
ends of the fourth portions 83, 84 into contact with the first
portion 86, whereby a bent body 89 is obtained [see FIG. 13,
(d)].
[0102] The butting portions of two second portions 81, 82 of the
bent body 89 are thereafter joined to each other intermittently at
a spacing longitudinally thereof by laser welding from outside to
make a semifinished continuous body. Subsequently, the continuous
body is cut into semifinished flat tubes so that two welds are
positioned at longitudinal opposite end portions of the second
portions 81, 82. In this way, the semifinished flat tube 90 shown
in FIG. 14 is produced.
[0103] The semifinished flat tube thus obtained is the same as the
semifinished flat tube shown in FIGS. 4 to 6 with respect to the
distance L of the laser welds 91 positioned at opposite end
portions from the respective longitudinal ends of the second
portions 81, 82, and the pitch P of all laser welds 91.
[0104] Incidentally with the semifinished flat tube shown in FIG.
14, the two second portions 81, 82 may be joined to each other
continuously over the entire length thereof by laser welding
instead of intermittently welding the second portions 81, 82.
[0105] A flat tube 80 is produced from the semifinished flat tube
90 by heating the tube 90 at a predetermined temperature to braze
the lower edges of the fourth portions 83, 84 to the first portion
86 utilizing the brazing material layer of the metal plate 85 and
to braze the two second portions 81, 82 to each other and the two
fourth portions 83, 84 to each other utilizing the brazing material
layer on the metal plate 85, whereby the upper wall 2 and the
reinforcing wall 6 are formed. Thus, the flat tube 80 is
produced.
[0106] A heat exchanger comprising such flat tubes 80 is used in
vehicles, such as motor vehicles, as a heater core.
INDUSTRIAL APPLICABILITY
[0107] The semifinished flat tubes are suitable for producing flat
tubes for use as heat exchange tubes for heat exchangers, such as
refrigerant tubes in condensers or evaporators for motor vehicle
air conditioners, oil tubes for motor vehicle oil coolers, water
tubes for motor vehicle radiators and heat medium tubes for heater
cores.
* * * * *