U.S. patent application number 11/547796 was filed with the patent office on 2009-01-08 for heat exchanger tube, heat exchanger, and manufacturing method thereof.
This patent application is currently assigned to SHOWA DENKO K.K. Invention is credited to Takenori Hashimoto, Kazuhiko Minami, Tomoaki Yamanoi.
Application Number | 20090008068 11/547796 |
Document ID | / |
Family ID | 35124905 |
Filed Date | 2009-01-08 |
United States Patent
Application |
20090008068 |
Kind Code |
A1 |
Minami; Kazuhiko ; et
al. |
January 8, 2009 |
Heat Exchanger Tube, Heat Exchanger, and Manufacturing Method
Thereof
Abstract
This invention relates to a method of manufacturing an aluminum
heat exchanger tube. In forming a thermally sprayed layer 21 on a
surface of an aluminum flat tube by thermally spraying Al--Si alloy
thermal-spraying particles, quenching the thermally sprayed
thermal-spraying particles in a molten state to make them adhere to
the tube core 2a. The surface of the thermally sprayed layer 21 is
smoothed with, e.g., reduction rolls to form a brazing layer 20.
With this method, brazing defects due to fin detachment, erosion to
the tube of the brazing material, etc., can be prevented, resulting
in good brazing performance.
Inventors: |
Minami; Kazuhiko; (Tochigi,
JP) ; Yamanoi; Tomoaki; (Tochigi, JP) ;
Hashimoto; Takenori; (Tochigi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
SHOWA DENKO K.K
Tokyo
JP
|
Family ID: |
35124905 |
Appl. No.: |
11/547796 |
Filed: |
April 8, 2005 |
PCT Filed: |
April 8, 2005 |
PCT NO: |
PCT/JP2005/007288 |
371 Date: |
March 4, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60561903 |
Apr 14, 2004 |
|
|
|
Current U.S.
Class: |
165/133 ;
427/452 |
Current CPC
Class: |
F28F 13/18 20130101;
B23K 1/008 20130101; B23K 2101/14 20180801; F28F 1/126 20130101;
F28D 1/05391 20130101; B23K 1/0012 20130101; B23K 35/286 20130101;
F28F 21/084 20130101 |
Class at
Publication: |
165/133 ;
427/452 |
International
Class: |
F28F 19/06 20060101
F28F019/06 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 8, 2004 |
JP |
204-113784 |
Claims
1. A method of manufacturing an aluminum heat exchanger tube, the
method comprising the steps of: in forming a thermally sprayed
layer on a surface of an aluminum flat tube by thermally spraying
Al--Si alloy thermal-spraying particles, quenching the thermally
sprayed thermal-spraying particles in a molten state to make them
adhere to a tube core; and smoothing a surface of the thermally
sprayed layer to form a brazing layer.
2. The method of manufacturing an aluminum heat exchanger tube as
recited in claim 1, wherein surface roughness (Ry) of the tube core
is adjusted to less than 10 .mu.m.
3. The method of manufacturing an aluminum heat exchanger tube as
recited in claim 1 or 2, wherein surface roughness (Ry) of the
brazing layer is adjusted to less than 50 .mu.m.
4. The method of manufacturing an aluminum heat exchanger tube as
recited in any one of claims 1 to 3, wherein a thermal-spraying
temperature of the thermal-spraying particles is adjusted to
3,000.degree. C. or above.
5. The method of manufacturing an aluminum heat exchanger tube as
recited in any one of claims 1 to 4, wherein the thermal-spraying
particles are cooled to 800.degree. C. or below after reaching the
tube core.
6. The method of manufacturing an aluminum heat exchanger tube as
recited in any one of claims 1 to 5, wherein in thermally spraying
the thermal-spraying particles, a temperature difference between
the thermal-spraying particles in a molten state and the
thermal-spraying particles reached the tube core in a cooled state
is adjusted to 2500.degree. C. or more.
7. The method of manufacturing an aluminum heat exchanger tube as
recited in any one of claims 1 to 6, wherein in thermally spraying
the thermal-spraying particles, the thermal-spraying particles
reached the tube core are cooled by releasing the heat to the tube
core.
8. The method of manufacturing an aluminum heat exchanger tube as
recited in any one of claims 1 to 7, wherein an average equivalent
diameter of Si crystallization particles in the thermally sprayed
layer is adjusted to 1 .mu.m or less.
9. The method of manufacturing an aluminum heat exchanger tube as
recited in any one of claims 1 to 8, wherein an apparent volume
rate (filling rate) of the brazing material in the brazing layer is
adjusted to 40% or more.
10. The method of manufacturing an aluminum heart exchanger tube as
recited in any one of claims 1 to 9, wherein in thermally spraying
the thermal-spraying particles, a thermal-spraying distance from a
spraying position of the thermal-spraying particles to an adhering
position on the tube core is adjusted to 30 to 150 mm.
11. The method of manufacturing an aluminum heart exchanger tube as
recited in any one of claims 1 to 10, wherein thermal spraying of
the thermal-spraying particles is performed by an arc spraying
method.
12. The method of manufacturing an aluminum heat exchanger tube as
recited in any one of claims 1 to 11, wherein a Si content in the
thermally sprayed layer is adjusted to 6 to 15 mass %.
13. The method of manufacturing an aluminum heart exchanger tube as
recited in any one of claims 1 to 12, wherein an average thickness
of the brazing layer is adjusted to 3 to 50 .mu.m.
14. The method of manufacturing an aluminum heart exchanger tube as
recited in any one of claims 1 to 13, wherein the surface of the
thermally sprayed layer is pressed with reduction rolls to smooth
the surface.
15. The method of manufacturing an aluminum heat exchanger tube as
recited in any one of claims 1 to 14, wherein Zn is contained to
the thermally sprayed layer.
16. The method of manufacturing an aluminum heat exchanger tube as
recited in any one of claims 1 to 15, wherein Zn and Cu are
contained to the thermally sprayed layer.
17. The method of manufacturing an aluminum heat exchanger tube as
recited in any one of claims 1 to 16, wherein the tube core is
formed by extrusion, and the thermal-spraying particles are
thermally sprayed to the tube core immediately after the
extrusion.
18. The method of manufacturing an aluminum heat exchanger tube as
recited in any one of claims 1 to 17, wherein each thermal-spraying
particle adheres to the surface of the tube core in a flat
state.
19. The method of manufacturing an aluminum heat exchanger tube as
recited in any one of claims 1 to 18, wherein the thermal-spraying
particles are thermally sprayed under a non-oxidizing
atmosphere.
20. A method of manufacturing an aluminum heat exchanger tube, the
method comprising the steps of: in forming a thermally sprayed
layer on a surface of an aluminum flat tube by thermally spraying
Al--Si alloy thermal-spraying particles, thermally spraying the
thermal-spraying particles to a tube core by an arc spraying
method, and quenching the thermally sprayed thermal-spraying
particles to 800.degree. C. or below; and smoothing a surface of
the thermally sprayed layer to form a brazing layer.
21. A method of manufacturing an aluminum heat exchanger tube, the
method comprising the steps of: in forming a thermally sprayed
layer on a surf ace of an aluminum flat tube by thermally spraying
Al--Si alloy thermal-spraying particles, performing the thermal
spraying by arc spraying in which a thermal-spraying distance from
a spraying position of the thermal-spraying particles to an
adhering position of the tube core is adjusted to 30 to 150 mm; and
smoothing a surface of the thermally sprayed layer to form a
brazing layer.
22. A method of manufacturing an aluminum ha at exchanger tube, the
method comprising the steps of: in forming a thermally sprayed
layer on a surface of an aluminum flat tube by thermally spraying
Al--Si alloy thermal-spraying particles, thermally spraying the
thermal-spraying particles with a thermal-spraying temperature of
3,000.degree. C. or above and cooling them to 800.degree. C. or
below to make them adhere to a tube core; and smoothing a surface
of the thermally sprayed layer to form a brazing layer.
23. A method of manufacturing an aluminum heat exchanger tube, the
method comprising the steps of: in forming a thermally sprayed
layer on a surf ace of an aluminum flat tube by thermally spraying
Al--Si alloy thermal-spraying particles, thermally spraying the
thermal-spraying particles in a molten state and cooling to make
them adhere to a tube core, and adjusting a temperature difference
between the thermal-spraying particles in a molten state and the
thermal-spraying particles after the cooling is adjusted to
2,500.degree. C. or more; and smoothing a surface of the thermally
sprayed layer to form a brazing layer.
24. An aluminum heat exchanger tube manufactured by the method as
recited in any one of the claims 1 to 23.
25. An aluminum heat exchanger tube, comprising: an aluminum flat
tube core; and a thermally sprayed layer formed on a surface of the
tube core by thermally spraying thermal-spraying particles of
molten Al--Si alloy, wherein a surface of the thermally sprayed
layer is smoothed to form a brazing layer, and wherein an average
equivalent diameter of Si crystallization particles in the
thermally sprayed layer is adjusted to 1 .mu.m or less.
26. The aluminum heat exchanger tube as recited in claim 25,
wherein an apparent volume rate (filling rate) of the brazing
material in the brazing layer is adjusted to 40% or more.
27. An aluminum heat exchanger including aluminum heat exchanger
tubes and aluminum fins brazed to the tubes in an assembled state,
wherein the heat exchanger tubes are manufactured by the method as
recited in any one of claims 1 to 23.
28. An aluminum heat exchanger including a pair of aluminum headers
and a plurality of heat exchanger tubes arranged in a longitudinal
direction of the header with a fin interposed therebetween, end
portions of the heat exchanger tubes being communicated with the
headers, wherein the heat exchanger tubes are manufactured by the
method as recited in any one of claims 1 to 23.
29. A method of manufacturing an aluminum heat exchanger, the
method comprising: a step of preparing an aluminum heat exchanger
tube manufactured by the method as recited in any one of claims 1
to 23; a step of preparing an aluminum fin; and a step of brazing
the heat exchanger tube and the fin in an assembled state.
30. A method of manufacturing an aluminum heat exchanger, the
method comprising: a step of preparing a plurality of aluminum heat
exchanger tubes manufactured by the method as recited in any one of
claims 1 to 23; a step of preparing a plurality of aluminum fins; a
step of preparing a pair of headers; a step of obtaining a
provisional assembly in which the plurality of heat exchanger tubes
arranged in a longitudinal direction of the header with the fin
interposed therebetween are assembled with the headers with end
portions of each heat exchanging tube communicated with the
headers; a step of integrally brazing adjacent heat exchanger tubes
and the fins by simultaneously brazing the provisional
assembly.
31. A refrigeration cycle in which refrigerant compressed by a
compressor is condensed with a condensed, and the condensed
refrigerant is decompressed by passing through a decompressor, and
the decompressed refrigerant is evaporated with an evaporator and
returned to the compressor, wherein the condenser is constituted by
the aluminum heat exchanger as recited in claim 28.
Description
[0001] This application claims priority under 35 U.S.C. .sctn.119
to Japanese Patent Application No. 2004-113784 filed on Apr. 8,
2004 and U.S. Provisional Application No. 60/561,903 filed on Apr.
14, 2004, the entire disclosures of which are incorporated herein
by reference in their entireties.
CROSS REFERENCE TO RELATED APPLICATIONS
[0002] 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 date of U.S. Provisional Application
No. 60/561,903 filed on Apr. 14, 2004, pursuant to 35 U.S.C.
.sctn.111(b).
TECHNICAL FIELD
[0003] The present invention relates to an aluminum heat exchanger
used for, for example, a refrigeration cycle for car
air-conditioners, a tube for such heat exchangers, and a method of
manufacturing the same.
[0004] In this disclosure including claims, the wording of
"aluminum" denotes aluminum and its alloy.
BACKGROUND ART
[0005] The following description sets forth the inventor's
knowledge of related art and problems therein and should not be
construed as an admission of knowledge in the prior art.
[0006] As an aluminum heat exchanger for use in a refrigeration
cycle for car air-conditioners, the so-called multi-flow type or
parallel flow type heat exchanger 51 as shown in FIG. 5 is
well-known. In this heat exchanger, a plurality of flat tubes 52
are arranged in the thickness direction with a corrugated fin 53
interposed therebetween, and hollow headers 54 are connected to the
ends of the tubes 52 in fluid communication.
[0007] In manufacturing such a heat exchanger 51, commonly, heat
exchanger components are fabricated into a provisional assembly,
and then the assembly is integrally brazed in a furnace. As a
method of forming a brazing layer, as disclosed by Patent Document
1 (Japanese Unexamined Laid-open Patent Publication No. S59-10467)
for example, it is well-known that brazing alloy is thermally
sprayed onto a surface of an aluminum heat exchanger tube.
[0008] In cases where a brazing alloy is thermally sprayed onto a
surface of a heat exchanger tube 52 to form a brazing material
layer, however, unevenness of the brazing material layer is large,
and therefore a brazing layer contracts after the brazing. As a
result, as exaggeratingly shown in FIG. 5, some joining scheduled
portions between the heat exchanger tube 52 and the fin 53 may
become un-joined continuously along the longitudinal direction of
the tube 52, which may cause a poor brazed portion such as the
so-called fin detachment.
[0009] To solve the problem, conventionally, various technique have
been proposed. For example, Patent document 2 (JP, H11-33709,A)
discloses a technique in which a brazing alloy is thermally sprayed
onto a streaked surface of a heat exchanger tube (tube core) to
thereby form a brazing layer. Patent document 3 (JP, H06-200344,A)
discloses a technique in which at the time of thermally spraying
brazing alloy powder the brazing powder is thermally sprayed on a
surface of a heat exchanger tube in a state in which non-fused
structure remains partially without completely fusing the alloy
powder.
[0010] In the technique in which streaked irregularities are formed
on the surface of the tube core, however, capillary force will be
generated along the streaked irregularity portions causing an easy
flow of the fused brazing material on the tube surface during the
brazing. This in turn generates erosion of the tube by the brazing
material, resulting in poor brazing.
[0011] In the technique in which the brazing alloy powder is
thermally sprayed in a state in which non-fused structure remains
partially, in cases where, for example, the thermally spraying
particle size is large, a cavity will be formed between particles
thermally sprayed on the tube surface. This causes deteriorated
volume rate (filling rate) of the substantial brazing material (net
thermally sprayed layer) in the entire thermally sprayed layer
(apparent thermally sprayed layer) including the cavity. As a
result, the actual amount of brazing material tends to decrease.
Thus, there is a room to be improved.
[0012] The description herein of advantages and disadvantages of
various features, embodiments, methods, and apparatus disclosed in
other publications is in no way intended to limit the present
invention. Indeed, certain features of the invention may be capable
of overcoming certain disadvantages, while still retaining some or
all of the features, embodiments, methods, and apparatus disclosed
therein.
[0013] Other objects and advantages of the present invention will
be apparent from the following preferred embodiments.
DISCLOSURE OF INVENTION
[0014] The preferred embodiments of the present invention have been
developed in view of the above-mentioned and/or other problems in
the related art. The preferred embodiments of the present invention
can significantly improve upon existing methods and/or
apparatuses.
[0015] The present invention was made in view of the aforementioned
conventional technology, and aims to provide a heat exchanger tube
capable of preventing occurrence of poor brazing due to fin
detachment or erosion of a tube by brazing material and attaining
good brazing, a heat exchanger and a method of manufacturing
them.
[0016] To attain the aforementioned objects, the structure of the
present invention can be summarized as follows.
[0017] [1] A method of manufacturing an aluminum heat exchanger
tube, the method comprising the steps of:
[0018] in forming a thermally sprayed layer on a surface of an
aluminum flat tube by thermally spraying Al--Si alloy
thermal-spraying particles, quenching the thermally sprayed
thermal-spraying particles in a molten state to make them adhere to
the tube core; and
[0019] smoothing a surface of the thermally sprayed layer to form a
brazing layer.
[0020] The aluminum heat exchanger tube obtained by the
manufacturing method of this invention will be combined with and
brazed to, for example, an aluminum fin. At this time, good brazing
performance can be secured.
[0021] That is, in the heat exchanger tube obtained by the
manufacturing method of this invention, the surface of the
thermally sprayed layer formed by thermally spraying alloy is
smoothed to obtain a brazing layer. Therefore, a fin can be joined
in a balanced manner over the entire surface of the brazing layer,
which assuredly prevents poor joining such as fin detachment.
[0022] Furthermore, in this invention, since the thermally sprayed
layer is smoothed to form the brazing layer, the smoothing enhances
the brazing material filling rate of the brazing layer, resulting
in a sufficient amount of the brazing material as the brazing
layer, which can assuredly prevent poor brazing due to shortage of
brazing material.
[0023] Furthermore, in this invention, since the molten
thermal-spraying particles are quenched, moderate brittleness can
be given to the thermally sprayed layer as compared with the case
where thermal spraying is performed in a state in which the
thermal-spraying particles are partially in a non-molten state and
where the thermal-spraying particles are not quenched but gradually
cooled. For this reason, when the thermally sprayed layer is formed
into the brazing layer by smoothing the thermally sprayed layer,
only the thermally sprayed layer can be assuredly formed into a
desired state. Thus, for example, the deformation of the tube core
can be prevented effectively, resulting in high quality.
[0024] In this invention, "melting" of the thermal-spraying
particles can be performed by adjusting the thermal-spraying
temperature to 3,000.degree. C. or above, preferably 3,500.degree.
C. or above, more preferably 4,000.degree. C. or above, still more
preferably 4,500.degree. C. or above. In cases where an arc
spraying method is employed, "melting" of the thermal spraying
particles can be performed more assuredly. In this invention,
especially in cases where the thermal-spraying temperature is set
to a high temperature, it is considered that smoothing of the
thermally sprayed layer can be executed effectively. That is, in
the case of high temperature thermal spraying, it is considered
that the thermal-spraying particles decrease in size, the cooling
rate increases, the quickly cooled small sized thermal-spraying
particles accumulate on the tube surface to form a desired brittle
structure as the thermally sprayed layer, which enables effective
smoothing of the thermally sprayed layer.
[0025] Moreover, in this invention, by adjusting the temperature
difference between the thermal-spraying particles in a molten state
and the thermal-spraying particles reached the tube core in a
cooled state to 2,500.degree. C. or more, preferably 3,000.degree.
C. or more, more preferably 3,500.degree. C. or more, and/or by
performing the thermal spraying at the thermal-spraying distance of
30 to 150 mm by an arc thermal spraying method, "quenching" of the
thermal-spraying particles can be performed.
[0026] [2] The method of manufacturing an aluminum heat exchanger
tube as recited in the aforementioned Item 1, wherein surface
roughness (Ry) of the tube core is adjusted to less than 10
.mu.m.
[0027] In this invention, since the surface of the tube core is
formed into a smooth surface, the brazing layer can be stably
secured to a wide surface area of the tube core. Thus, it is
possible to effectively prevent unexpected flow of the molten
brazing material on the surface of the tube core during the
brazing, which can assuredly prevent defects, such as erosion to
the tube core of the brazing material.
[0028] [3] The method of manufacturing an aluminum heat exchanger
tube as recited in the aforementioned Item 1 or 2, wherein surface
roughness (Ry) of the brazing layer is adjusted to less than 50
.mu.m.
[0029] In this invention, since the surface of the brazing layer is
smoothed, a fin can be brazed to the brazing layer assuredly, which
more assuredly prevents occurrence of brazing defects such as fin
detachment.
[0030] [4] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 3,
wherein a thermal-spraying temperature of the thermal-spraying
particles is adjusted to 3,000.degree. C. or above.
[0031] In this invention, melting of the thermal-spraying particles
can be assuredly attained in the thermal spraying processing.
[0032] [5] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 4,
wherein the thermal-spraying particles are cooled to 800.degree. C.
or below after reaching the tube core.
[0033] In this invention, quenching of the thermal-spraying
particles can be smoothly performed at the time of the thermal
spraying.
[0034] [6] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 5,
wherein in thermally spraying the thermal-spraying particles, a
temperature difference between the thermal-spraying particles in a
molten state and the thermal-spraying particles reached the tube
core in a cooled state is adjusted to 2500.degree. C. or more.
[0035] In this invention, quenching of the thermal-spraying
particles can be assuredly performed at the time of the thermal
spraying.
[0036] [7] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 6,
wherein in thermally spraying the thermal-spraying particles, the
thermal-spraying particles reached the tube core is cooled by
releasing the heat to the tube core.
[0037] In this invention, quenching of the thermal-spraying
particles can be more smoothly performed at the time of the thermal
spraying.
[0038] [8] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 7,
wherein an average equivalent diameter of Si crystallization
particles in the thermally sprayed layer is adjusted to 1 .mu.m or
less.
[0039] In this invention, melting and quenching of the
thermal-spraying particles are assuredly performed at the time of
the thermal spraying.
[0040] [9] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 8,
wherein an apparent volume rate (filling rate) of the brazing
material in the brazing layer is adjusted to 40% or more.
[0041] In this invention, a sufficient amount of the brazing
material can be secured in the brazing layer, which in turn can
assuredly prevent occurrence of brazing defects due to shortage of
brazing material.
[0042] [10] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 9,
wherein in thermally spraying the thermal-spraying particles, a
thermal-spraying distance from a spraying position of the
thermal-spraying particles to an adhering position on the tube core
is adjusted to 30 to 150 mm.
[0043] In this invention, quenching, etc., of thermal-spraying
particles can be performed more assuredly.
[0044] [11] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 10,
wherein thermal spraying of the thermal-spraying particles is
performed by an arc spraying method.
[0045] In this invention, melting, etc., of the thermal-spraying
particles can be performed more assuredly.
[0046] [12] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 11,
wherein a Si content in the thermally sprayed layer is adjusted to
6 to 15 mass %.
[0047] In this invention, a brazing layer further improved in
brazing performance can be formed.
[0048] [13] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 12,
wherein an average thickness of the brazing layer is adjusted to 3
to 50 .mu.m.
[0049] In this invention, a stable brazing layer can be formed.
[0050] [14] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 13,
wherein the surface of the thermally sprayed layer is pressed with
reduction rolls to smooth the surface.
[0051] In this invention, smoothing of the thermally sprayed layer
can be performed continuously, improving the working
efficiency.
[0052] [15] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 14,
wherein Zn is contained to the thermally sprayed layer.
[0053] In this invention, a sacrificial protection layer can be
formed on the tube surface.
[0054] [16] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 15,
wherein Zn and Cu are contained to the thermally sprayed layer.
[0055] In this invention, a sacrificial protection layer can be
formed on the tube surface, and the potential of the tube surface
can also be adjusted.
[0056] [17] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 16,
wherein the tube core is formed by extrusion, and the
thermal-spraying particles are thermally sprayed to the tube core
immediately after the extrusion.
[0057] In this invention, a desired thermally sprayed layer can be
formed assuredly in an efficient manner, which in turn can form a
desired brazing layer assuredly and efficiently.
[0058] [18] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 17,
wherein each thermal-spraying particle adheres to the surface of
the tube core in a flat state.
[0059] In this invention, quenching of the thermal-spraying
particles can be performed efficiently.
[0060] [19] The method of manufacturing an aluminum heat exchanger
tube as recited in any one of the aforementioned Items 1 to 18,
wherein the thermal-spraying particles are thermally sprayed under
a non-oxidizing atmosphere.
[0061] In this invention, forming of an oxide film on the
thermal-spraying particles can be prevented, which enables
formation of a stable thermally sprayed layer.
[0062] [20] A method of manufacturing an aluminum heat exchanger
tube, the method comprising the steps of:
[0063] in forming a thermally sprayed layer on a surface of an
aluminum flat tube by thermally spraying Al--Si alloy
thermal-spraying particles, thermally spraying the thermal-spraying
particles to a tube core by an arc spraying method, and quenching
the thermally sprayed thermal-spraying particles to 800.degree. C.
or below; and
[0064] smoothing a surface of the thermally sprayed layer to form a
brazing layer.
[0065] In the heat exchanger tube obtained by the manufacturing
method of this invention, in the same manner as mentioned above,
the brazing layer is obtained by smoothing the surface of the
thermally sprayed layer obtained by the thermal spraying of brazing
alloy. A fin can be brazed to the brazing layer assuredly, which
more assuredly prevents occurrence of brazing defects such as fin
detachment.
[0066] Furthermore, in this invention, since the brazing layer is
formed by smoothing the thermally sprayed layer, the smoothing can
increase the brazing material filling rate of the brazing layer, a
sufficient amount of brazing material in the brazing layer can be
secured, which assuredly can prevent brazing defects due to
shortage of brazing material.
[0067] Furthermore, in this invention, molten thermal-spraying
particles are thermally sprayed on the tube core by an arc spraying
method and the sprayed thermal-spraying particles are quenched to a
predetermined temperature or below. Therefore, moderate brittleness
can be given to the thermally sprayed layer as compared with the
case where thermal spraying is performed in a state in which the
thermal-spraying particles are partially in a non-molten state and
where the thermal-spraying particles are not quenched but gradually
cooled. For this reason, when the thermally sprayed layer is formed
into the brazing layer by smoothing the thermally sprayed layer,
only the thermally sprayed layer can be assuredly formed in a
desired state. Thus, for example, the deformation of the tube core
can be prevented effectively, resulting in high quality.
[0068] [21] A method of manufacturing an aluminum heat exchanger
tube, the method comprising the steps of:
[0069] in forming a thermally sprayed layer on a surface of an
aluminum flat tube by thermally spraying Al--Si alloy
thermal-spraying particles, performing the thermal spraying by an
arc spraying method in which a thermal-spraying distance from a
spraying position of the thermal-spraying particles to an adhering
position on the tube core is adjusted to 30 to 150 mm; and
[0070] smoothing a surface of the thermally sprayed layer to form a
brazing layer.
[0071] In the heat exchanger tube obtained by the manufacturing
method of this invention, good brazing performance can be secured
in the same manner as mentioned above.
[0072] Furthermore, in this invention, molten thermal-spraying
particles are thermally sprayed to the tube core by an arc spraying
method, and the thermal-spraying particles are sprayed to tube core
with high kinetic energy to thereby be deformed into a flat shape
and quenched. Therefore, in the same manner as in the
above-mentioned case, a heat exchanger tube of high quality can be
secured.
[0073] [22] A method of manufacturing an aluminum heat exchanger
tube, the method comprising the steps of:
[0074] in forming a thermally sprayed layer on a surface of an
aluminum flat tube by thermally spraying Al--Si alloy
thermal-spraying particles, thermally spraying the thermal-spraying
particles with a thermal-spraying temperature of 3,000.degree. C.
or above and cooling them to 800.degree. C. or below to make them
adhere to a tube core; and
[0075] smoothing a surface of the thermally sprayed layer to form a
brazing layer.
[0076] In the heat exchanger tube obtained by the manufacturing
method of this invention, in the same manner as mentioned above,
good brazing performance can be secured.
[0077] Furthermore, in this invention, molten thermal-spraying
particles are sprayed to the tube core at a high temperature, and
the sprayed thermal-spraying particles are quenched at a
temperature below a predetermined temperature. Therefore, in the
same manner as mentioned above, high quality heat exchanger tube
can be provided.
[0078] [23] A method of manufacturing an aluminum heat exchanger
tube, the method comprising the steps of:
[0079] in forming a thermally sprayed layer on a surf ace of an
aluminum flat tube by thermally spraying Al--Si alloy
thermal-spraying particles, thermally spraying the thermal-spraying
particles in a molten state and cooling to make them adhere to a
tube core, and adjusting a temperature difference between the
thermal-spraying particles in a molten state and the
thermal-spraying particles after the cooling is adjusted to
2,500.degree. C. or more; and
[0080] smoothing a surface of the thermally sprayed layer to form a
brazing layer.
[0081] In the heat exchanger tube obtained by the manufacturing
method of this invention, in the same manner as mentioned above,
good brazing performance can be secured.
[0082] Furthermore, in this invention, since molten
thermal-spraying particles are sprayed to the tube core and the
sprayed thermal-spraying particles are quenched, in the same manner
as mentioned above, high quality heat exchanger tube can be
provided.
[0083] [24] An aluminum heat exchanger tube manufactured by the
method as recited in any one of the aforementioned Items 1 to
23.
[0084] The heat exchanger tube of this invention is obtained by the
aforementioned manufacturing method of this invention, and
therefore in the same manner as mentioned above, good brazing
performance and high quality can be secured.
[0085] [25] An aluminum heat exchanger tube, comprising:
[0086] an aluminum flat tube core; and
[0087] a thermally sprayed layer formed on a surface of the tube
core by thermally spraying thermal-spraying particles of molten
Al--Si alloy,
[0088] wherein a surface of the thermally sprayed layer is smoothed
to form a brazing layer, and
[0089] wherein an average equivalent diameter of Si crystallization
particles in the thermally sprayed layer is adjusted to 1 .mu.m or
less.
[0090] In the heat exchanger tube of this invention, since the
brazing layer is formed by smoothing the thermally sprayed layer,
in the same manner as mentioned above, good brazing performance can
be secured.
[0091] Moreover, since the Si crystallization in the thermally
sprayed layer is small, it is possible to confirm the melting and
quenching of the thermal-spraying particles at the time of the
thermal spraying, and therefore a heat exchanger tube of high
quality can be obtained.
[0092] [26] The aluminum heat exchanger tube as recited in the
aforementioned Item 25, wherein an apparent volume rate (filling
rate) of the brazing material in the brazing layer is adjusted to
40% or more.
[0093] In the heat exchanger tube of this invention, since the
filling rate of the brazing material in the brazing layer is high,
a sufficient amount of brazing material can be secured, and further
improved brazing performance can be secured.
[0094] [27] An aluminum heat exchanger including aluminum heat
exchanger tubes and aluminum fins brazed to the tubes in an
assembled state, wherein the heat exchanger tubes are manufactured
by the method as recited in any one of the aforementioned Items 1
to 23.
[0095] Since this specifies a heat exchanger equipped with a heat
exchanger tube as a main component obtained by the aforementioned
method of the invention, in the same manner as mentioned above, the
same functions and results can be secured.
[0096] [28] An aluminum heat exchanger including a pair of aluminum
headers and a plurality of heat exchanger tubes arranged in a
longitudinal direction of the header with a fin interposed
therebetween, end portions of the heat exchanger tubes being
communicated with the headers,
[0097] wherein the heat exchanger tubes are manufactured by the
method as recited in any one of the aforementioned Items 1 to
23.
[0098] This invention specifies the so-called parallel-flow type or
multi-flow type heat exchanger equipped with the heat exchanger
tubes obtained by the aforementioned manufacturing method of the
invention as main components. Therefore, in the same manner as
mentioned above, the same functions and results can be secured.
[0099] [29] A method of manufacturing an aluminum heat exchanger,
the method comprising:
[0100] a step of preparing an aluminum heat exchanger tube
manufactured by the method as recited in any one of the
aforementioned Items 1 to 23;
[0101] a step of preparing an aluminum fin; and
[0102] a step of brazing the heat exchanger tube and the fin in an
assembled state.
[0103] In this invention, since the heat exchanger is manufactured
using the heat exchanger tube obtained by the aforementioned
manufacturing method of the invention, in the same manner as
mentioned above, the same functions and results can be secured.
[0104] [30] A method of manufacturing an aluminum heat exchanger,
the method comprising:
[0105] a step of preparing a plurality of aluminum heat exchanger
tubes manufactured by the method as recited in any one of the
aforementioned Items 1 to 23;
[0106] a step of preparing a plurality of aluminum fins;
[0107] a step of preparing a pair of headers;
[0108] a step of obtaining a provisional assembly in which the
plurality of heat exchanger tubes arranged in a longitudinal
direction of the header with the fin interposed therebetween are
assembled with the headers with end portions of each heat
exchanging tube communicated with the headers;
[0109] a step of integrally brazing adjacent heat exchanger tubes
and the fins by simultaneously brazing the provisional
assembly.
[0110] In this invention, the so-called parallel-f low type or
multi-flow type heat exchanger is manufactured by using the heat
exchanger tubes obtained by the aforementioned manufacturing method
of the invention. Therefore, in the same manner as mentioned above,
the same functions and results can be secured.
[0111] [31] A refrigeration cycle in which refrigerant compressed
by a compressor is condensed with a condenser, and the condensed
refrigerant is decompressed by passing through a decompressor, and
the decompressed refrigerant is evaporated with an evaporator and
returned to the compressor,
[0112] wherein the condenser is constituted by the aluminum heat
exchanger as recited in the aforementioned Item 28.
[0113] In the refrigeration cycle of this invention, the same
effects can be demonstrated.
EFFECTS OF THE INVENTION
[0114] As mentioned above, according to the present invention,
brazing defects due to fin detachment, erosion to the tube of
brazing material, etc., can be prevented, and therefore good
brazing performance can be secured.
[0115] The above and/or other aspects, features and/or advantages
of various embodiments will be further appreciated in view of the
following description in conjunction with the accompanying figures.
Various embodiments can include and/or exclude different aspects,
features and/or advantages where applicable. In addition, various
embodiments can combine one or more aspect or feature of other
embodiments where applicable. The descriptions of aspects, features
and/or advantages of particular embodiments should not be construed
as limiting other embodiments or the claims.
BRIEF DESCRIPTION OF DRAWINGS
[0116] The preferred embodiments of the present invention are shown
by way of example, and not limitation, in the accompanying figures,
in which:
[0117] FIG. 1 is a front view showing an aluminum heat exchanger
according to an embodiment of this intention;
[0118] FIG. 2 is an enlarged perspective view showing joined
portions of the tubes and fins in the heat exchanger of the
aforementioned embodiment;
[0119] FIG. 3A is an enlarged cross-sectional view showing a tube
core immediately after thermal spraying during a manufacturing
process of the heat exchanger tube according to the embodiment, and
FIG. 3B is an enlarged cross-sectional view showing the tube core
immediately after smoothing of the thermally sprayed brazing
material;
[0120] FIG. 4A is an enlarged cross-sectional view showing a tube
core immediately after thermal spraying in a manufacturing process
of the heat exchanger tube, which is an example outside the scope
of the invention, and FIG. 4B is an enlarged cross-sectional view
showing the tube core immediately after smoothing of the tube core;
and
[0121] FIG. 5 is a front view showing a conventional heat exchanger
in which fin detachment occurred due to brazing.
BEST MODE FOR CARRYING OUT THE INVENTION
[0122] In the following paragraphs, some preferred embodiments of
the invention will be described by way of example and not
limitation. It should be understood based on this disclosure that
various other modifications can be made by those in the art based
on these illustrated embodiments.
[0123] FIG. 1 is a front view showing an aluminum heat exchanger 1
which is an embodiment of this invention. As shown in this figure,
this heat exchanger 1 is used as a condenser for use in a
refrigeration cycle of a car air-conditioner, and constitutes a
multi-flow type heat exchanger.
[0124] In this heat exchanger 1, a plurality of flat heat
exchanging tubes 2 arranged horizontally are disposed between a
pair of vertical hollow headers 4 and 4 arranged in parallel with
each other with the ends of the tubes communicated with the hollow
headers 4 and 4. Between the adjacent tubes 2 and outside the
outermost tubes, a corrugated fin 3 is disposed, and a side plate
10 is disposed outside the outermost corrugated fin 3.
[0125] In this heat exchanger 1, as the tube 2, a tube made of
aluminum (including its alloy, hereinafter simply referred to as
"aluminum") is used, and brazing material is covered on
predetermined portions of each component. The tubes 2, fins 3,
headers 4 and side plates 10 are provisionally assembled into a
provisional heat exchanger assembly, and the assembly is integrally
brazed in a furnace, whereby the entire assembly is integrally
brazed.
[0126] As shown in FIG. 2, the tube 2 includes a tube core 2a which
is an aluminum extruded member and a brazing layer 20 of an Al--Si
alloy as brazing alloy formed on at least one surface of the tube
core.
[0127] As the core 2a of the tube 2, an Al--Mn alloy with high
pressure resistance (high strength) and high heat resistance, such
as a JIS3003 alloy, can be preferably used.
[0128] In this embodiment, by extruding this alloy, the tube core
2a is formed.
[0129] It is preferable that the surface roughness Ry of the tube
core 2a is adjusted to less than 10 .mu.m. That is, if the surface
roughness Ry exceeds 10 .mu.m, capillary attraction occurs on the
surface of the tube core 2a, resulting in easy flow of brazing
material, which in turn causes erosion to the tube by the brazing
material. Thus, there is a possibility that brazing defects
occur.
[0130] In this embodiment, the brazing layer 20 on the tube core 2a
is formed by forming a thermally sprayed layer 21 by making Al--Si
alloy adhere to the tube core by a thermal spraying method as shown
in FIG. 3A, and then smoothing the surface of the thermally sprayed
layer 21 by compressing the surface as shown in FIG. 3B.
[0131] In this embodiment, although a method of carrying out
thermal spraying of the Al--Si alloy as a brazing alloy to the
surface of the tube core 2a is not limited to a specific one, in
performing the thermal spraying, the thermal-spraying particles are
sprayed to the tube core 2a and quenched. In other words, the
thermal spraying method of this invention is not specifically
limited so long as the aforementioned quenching can be
performed.
[0132] In this embodiment, in order to melt the thermal-spraying
particles, the thermal-spraying temperature can be set to
3,000.degree. C. or above, or any known means including a means
using arc spraying can be adopted.
[0133] As a means for quenching the thermal-spraying particles, for
example, it is preferable to employ a method in which the
thermal-spraying temperature of the brazing alloy at the time of
thermal spraying is adjusted to high, the hot thermal-spraying
particles are sprayed on the tube core 2a, and the heat of the
thermal-spraying particles is made to emit to the tube core 2a
immediately after the reaching of the thermal-spraying particles to
the core member 2a to thereby quickly cool the thermal-spraying
particles to a temperature of the tube core member 2a. For example,
a means for cooling the thermal-spraying particles whose
thermal-spraying temperature is 3,000.degree. C. or above to
800.degree. C. or below by making them adhere the tube core 2a can
be employed.
[0134] Concretely, in this embodiment, it is preferable to employ a
means for quenching the thermally sprayed particles whose
thermal-spraying temperature is high (4,500 to 5,500.degree. C.) to
the tube core temperature (400 to 500.degree. C.) immediately after
the extrusion by using an arc spraying method. In cases of flame
spraying or high velocity flame spraying, since the
thermal-spraying temperature is low (2,000 to 3,000.degree. C.) as
compared with arc spraying, there are possibilities that melting of
the thermal-spraying particles cannot fully be performed, or
increasing of the cooling rate is difficult and therefore quenching
cannot fully be performed. Furthermore, since they use brazing
alloy powder, there is a possibility that the filling rate may
deteriorate and therefore it is not always suitable.
[0135] In this invention, however, if quenching can be performed
irrespective of the thermal-spraying temperature and/or the tube
core temperature, any kind of thermal spraying method can be
employed. For example, the quenching of the thermal-spraying
particles can be performed by controlling the thermal-spraying
distance which will be explained below.
[0136] In this embodiment, in performing thermal-spraying, it is
preferable to adjust the thermal-spraying distance from the
spraying portion (spraying position) of the thermal spraying gun to
the tube core surface (adhering position) to 30 to 150 mm. That is,
in cases where the thermal-spraying distance is within the
aforementioned specified range, the speed of thermal-spraying
particles is high, and therefore the kinetic energy of the
thermal-spraying particles is high. For this reason, since the
thermal spraying particles change into a flat shape and adhere to
the tube core surface when the thermal spraying particles are
sprayed on the tube core surface, the filling rate becomes high and
the heat release performance of the thermal spraying particles to
the tube core 2a is also improved, which enables sufficient
quenching. Furthermore, the thermal-spraying distance is relatively
short, i.e., 30 to 150 mm, resulting in a shorter arriving time of
the thermal-spraying particles to the tube core 2a, or a shorter
time from the thermal-spraying of the thermal-spraying particles to
the cooling initiation, which in turn can perform the quenching
more assuredly. In other words, in cases where the thermal-spraying
distance is less than 30 mm or exceeds 150 mm, the speed of the
thermal-spraying particles becomes slower and therefore sufficient
kinetic energy cannot be secured, causing a smaller amount of
deformation of the thermal-spraying particles when the
thermal-spraying particles adhere to the tube core, resulting in
low filling rate. Furthermore, the heat releasing performance of
the thermal-spraying particles to the tube core deteriorates,
resulting in a failure of quenching. Especially in cases where the
thermal-spraying distance exceeds 150 mm, during the flying of the
thermal-spraying particles, the thermal-spraying particles
different in flying speed may aggregate. For example, large
particles and small particles will aggregate to become large
particles to be deposited. As a result, the thermally sprayed layer
21 becomes hard and moderate brittleness cannot be secured. Thus,
as will be detailed below, there is a possibility that smoothing of
the thermally sprayed layer 21 cannot be attained effectively, and
therefore it is not preferable.
[0137] In cases where a brazing alloy is sprayed by an arc spraying
method, for example, a method of scanning a thermal spraying gun of
an arc spraying machine with respect to the tube core 2a or a
method of carrying out thermal spraying while rewinding the core
member 2a rolled into a coiled form can be adopted. Furthermore, in
cases where the tube core 2a is an extruded member, a method in
which extrusion and thermal spraying are performed continuously
while placing a thermal spraying gun arranged immediately after an
extrusion die can be employed. Especially in cases where extrusion
and thermal spraying are performed continuously, productive
efficiency can be improved.
[0138] Furthermore, if an oxide film is formed on thermal-spraying
particles at the time of thermal spraying processing, the surface
of the thermal-spraying particle hardens, resulting in decreased
deformation of the thermal-spraying particle to be caused by
colliding against the tube core 2a, which may cause deterioration
of the filling rate. For this reason, in order to prevent the
formation of an oxide film on thermal-spraying particles, it is
preferable to perform the thermal spraying processing in a
non-oxidizing atmosphere, such as a nitrogen atmosphere or an argon
atmosphere. From the economical view point, it is preferable to
perform the thermal spraying in a nitrogen atmosphere.
[0139] The thermally sprayed layer 21 can be formed only on one
surface of the tube core 2a, and also can be formed on both
surfaces. Needless to say, in cases where the thermally sprayed
layer 21 is formed on both surfaces of the tube core, it is
preferable to arrange thermal spraying guns at upper and lower
sides of the tube core 2a.
[0140] In this embodiment, although the content of Si in the
thermally sprayed layer 21 is not specifically limited, in order to
secure good brazing performance, it is preferable to adjust the Si
content to 6 to 15 mass %.
[0141] It is preferable that the thermally sprayed layer 21
contains Zn in order to form a sacrificial protection layer on the
surface of the tube. The Zn content in the thermally sprayed layer
21 is preferably adjusted to 1 to 30 mass %.
[0142] Furthermore, it is preferable that the thermally sprayed
layer 21 contains Cu within the range of 0.1 to 1 mass % for the
purpose of potential adjustment, etc.
[0143] Furthermore, in this embodiment, the thermally sprayed layer
21 may contain other elements, such as Fe, Mn, In, Sn, Ni, Ti, and
Cr, as long as it is within the range that affects neither brazing
performance nor corrosion resistance.
[0144] In this embodiment, after forming a thermally sprayed layer
21 on the tube core 2a as shown in FIG. 3A, the surface of the
thermally sprayed layer 21 is smoothed to form a brazing layer 20
as shown in FIG. 3B. Thus, a heat exchanger tube 2 is obtained.
[0145] Although the method of smoothing the surface of the
thermally sprayed layer 2 is not specifically limited, a pressing
method using reduction rolls and a cutting method such as scalping
(trimming) can be exemplified. Among other things, a method of
smoothing using reduction rolls is preferably employed since the
method can improve the productivity by consecutive operation.
[0146] This smoothing processing is preferably performed at the
tube correcting step. That is, as described above, in cases where
the extrusion step of extruding the tube core 2a and the thermal
spraying step of thermally spraying the brazing material to the
extruded tube member (tube core) are performed continuously, it is
usually performed that the extruded tube member after the brazing
material thermal spraying is rolled into a coiled form and
thereafter the thermally sprayed tube is cut into a predetermined
size while being unwinding in the following tube correcting step to
thereby manufacture heat exchanger tubes 2. At the tube correcting
step, by performing the smoothing processing using reduction rolls,
smoothing processing can be performed simultaneously with the tube
correcting processing.
[0147] In this embodiment, the surface roughness Ry of the smoothed
brazing layer 20 is preferably adjusted to 50 .mu.m or less, more
preferably to 40 .mu.m or less. That is, in cases where the surface
roughness falls within the specified range, the fin 3 can be brazed
to the brazing layer 20 in a balanced manner, which can prevent
occurrence of brazing defects such as fin detachment.
[0148] In this embodiment, since the thermal-spraying particles are
sprayed in a molten state and then quenched at the aforementioned
thermal spraying processing, moderate brittleness can be given to
the thermally sprayed layer 21. Therefore, as shown in FIG. 3B, the
crushing of the brittle peak portions of the thermally sprayed
layer 21 can be evenly performed over the entire region with
rollers, etc. Thus, the surface of the thermally sprayed layer 21
(surface of the brazing layer) can be assuredly formed to have a
desired smooth surface. Furthermore, since compressive deformation
of only the thermally sprayed layer 21 can be performed
appropriately, the volume rate (filling rate) of the brazing
material in the entire brazing layer (apparent brazing layer)
containing voids can be improved, resulting in a sufficient amount
of brazing material on the tube required to perform brazing.
[0149] In this embodiment, the filling rate of the brazing material
in the brazing layer 20 is preferably adjusted to 40% or more, more
preferably 60% or more. Securing the filling rate within the
aforementioned range secures a sufficient amount of the brazing
material, which effectively prevents occurrence of brazing defects
such as fin detachment.
[0150] In cases where quenching of the thermal-spraying particles
is inadequate or a part of the thermal-spraying particles
(thermal-spraying powder) is in a non-molten state at the time of
thermal spraying processing, the rigidity of the thermally sprayed
layer 121 becomes high excessively as shown in FIG. 4A. As a
result, even if the tube core 2a having the thermally sprayed layer
121 of high rigidity is rolled with reduction rollers, as shown in
this FIG. 4B, the tube core 2a is deformed without causing any
deformation of the thermally sprayed layer 121, which may cause
deteriorated quality. Furthermore, since the thermally sprayed
layer 121 is not compressed, the filling rate of the brazing
material in the thermally sprayed layer 121 cannot be improved,
which may make it difficult to secure the necessary amount of
brazing material required for brazing.
[0151] In this embodiment, it is preferable to adjust the average
equivalent diameter of the Si crystallization in the brazing layer
20 to 1 .mu.m or less. That is, in cases where the dispersibility
of Si in the brazing layer 20 is good and the brazing performance
is good, Si crystallization becomes small. Also in cases where the
brazing alloy is fully molten at the thermal spraying step and
quenching is fully made and therefore the thermal-spraying
particles has moderate brittleness, the crystallization of Si
becomes small. Accordingly, in this embodiment, the particle
diameter of Si crystallization is preferable small. Concretely, it
is preferable to adjust the average equivalent diameter of Si
crystallization to 1 .mu.m or less.
[0152] Although the thickness (average thickness) of the brazing
layer 20 is not specifically limited, it is preferable to adjust
the thickness to 3 to 50 .mu.m. More preferably, the lower limit is
adjusted to 5 .mu.m or more and the upper limit to 30 .mu.m or
less. That is, in cases where the thickness of the brazing layer 20
is adjusted within the aforementioned range, the joining of the
tube 2 and the fin 3 can be performed assuredly, and fin
detachment, etc., can be prevented effectively.
[0153] The heat exchanger tube 2 of this embodiment is used
together with other heat exchanger components, such as hollow
headers 4 and 4, corrugated fins 3 and side plates 10, and is
assembled into a provisional heat exchanger assembly. Thereafter,
flux is applied to this assembly and dried. Then, the assembly is
heated in a furnace of a nitrogen gas atmosphere to thereby
integrally braze the components. Thus, a heat exchanger 1 is
manufactured.
[0154] The obtained heat exchanger 1 is free from brazing defects
such as fin detachment, and is excellent in joined strength.
[0155] That is, in the heat exchanger tube 2 of this embodiment,
since the brazing layer 20 is obtained by smoothing the surface of
the thermally sprayed layer 21 formed by the thermal spraying of
brazing alloy, the fin 3 can be joined to the entire surface of the
brazing layer 20 in a balanced manner, which in turn can assuredly
prevent brazing defects such as fin detachment.
[0156] Especially in this embodiment, if the surface roughness Ry
of the tube core 2a is adjusted to less than 10 .mu.m, the brazing
layer 20 is secured to the entire surface of the tube core 2a in a
stable manner. Therefore, unexpected flowing of the molten brazing
material during the brazing can be effectively prevented, which can
assuredly prevent occurrence of defects such as erosion to the tube
of the brazing material.
[0157] Moreover, in this embodiment, since the brazing layer 20 is
formed by compressing the thermally sprayed layer 21, the brazing
material filling rate of the brazing layer 20 can be improved.
Therefore, sufficient amount of brazing material for the brazing
layer 20 can be secured, which can assuredly prevent occurrence of
brazing defects due to shortage of brazing material.
[0158] Furthermore, in this embodiment, since fully molten thermal
spraying particles are quenched, moderate brittleness can be given
to the thermally sprayed layer 21. Therefore, at the time of
smoothing the thermally sprayed layer 21 with reduction rollers,
etc., only the thermally sprayed layer 21 can be compressed into a
desired compressed shape. Thus, crush deformation of the tube core
2a can be prevented effectively, resulting in high quality.
[0159] In addition, in this embodiment, in cases where the surface
roughness Ry of the brazing layer 20 is adjusted to below the
specific value, the fin 3 can be brazed to the brazing layer 20 in
a balanced manner, which can more assuredly prevent occurrence of
brazing defects such a fin detachment.
EXAMPLE
[0160] Hereafter, examples related to the present invention and
comparative examples for verifying the effects of the invention
will be explained.
TABLE-US-00001 TABLE 1 Surface Thermal spraying processing
roughness Thermal Thermal-spraying Smoothing of Filling Average of
core Thermal spraying Thermal Thermal particles brazing layer rate
of equivalent member spraying tempera- spraying spraying Molten
Cooling (surface brazing diameter of Si (Ry) method ture distance
environment state.sup.*1 rate.sup.*2 roughness Ry) material
crystallization Example 1 10 .mu.m Arc thermal 5,000.degree. C. 120
mm Air Molten Quenching Smoothed 50% 0.7 .mu.m spraying (40 .mu.m)
Example 2 8 .mu.m Arc thermal 5,500.degree. C. 60 mm Nitrogen
Molten Quenching Smoothed 50% 0.1 .mu.m spraying (37 .mu.m) Example
3 7 .mu.m Arc thermal 4,800.degree. C. 60 mm Nitrogen Molten
Quenching Smoothed 60% 0.5 .mu.m spraying (35 .mu.m) Example 4 8
.mu.m Arc thermal 5,000.degree. C. 80 mm Air Molten Quenching
Smoothed 50% 0.4 .mu.m spraying (40 .mu.m) Example 5 8 .mu.m Arc
thermal 4,800.degree. C. 120 mm Nitrogen Molten Quenching Smoothed
40% 0.8 .mu.m spraying (40 .mu.m) Example 6 8 .mu.m Arc thermal
5000.degree. C. 100 mm Nitrogen Molten Quenching Smoothed 50% 0.6
.mu.m spraying (42 .mu.m) Com. Ex. 1 8 .mu.m Arc thermal
5,000.degree. C. 150 mm Air Molten Quenching Non-smoothed 30% 0.9
.mu.m spraying (60 .mu.m) Com. Ex. 2 15 .mu.m Flame thermal
2,800.degree. C. 150 mm Air Partially Non- Smoothed 30% 1.5 .mu.m
spraying not molten quenching (40 .mu.m) Com. Ex. 3 10 .mu.m Flame
thermal 2,500.degree. C. 200 mm Air Partially Non- Non-smoothed 20%
2 .mu.m spraying not molten quenching (60 .mu.m) Com. Ex. 4 40
.mu.m Arc thermal 5,000.degree. C. 120 mm Air Molten Quenching
Non-smoothed 20% 0.7 .mu.m spraying (60 .mu.m) Com. Ex. 5 30 .mu.m
Flame thermal 3,000.degree. C. 250 mm Air Molten Non- Smoothed 40%
1.8 .mu.m spraying quenching (60 .mu.m) Com. Ex. 6 8 .mu.m HVOF
thermal 2,600.degree. C. 100 mm Air Partially Quenching Smoothed
50% 2 .mu.m spraying not molten (65 .mu.m) .sup.*1"Molten": the
thermal spraying temperature is 3,000.degree. C. or above;
"Partially not molten": below 3,000.degree. C. .sup.*2"Quenching":
the temperature difference between the thermal-spraying particles
and the extruded tube material is 2,500.degree. C. or above;
"Non-quenching": below 2,500.degree. C.
Example 1
[0161] As shown in Table 1, a flat multi-bored extruded tube (tube
core) 16 mm width, 3 mm height and 0.5 mm wall thickness was
extruded with an extruder using extrusion material of an Al alloy
(Cu: 0.4 mass %, Mn: 0.21 mass %; Al: balance). The surface
roughness Ry of the obtained tube core was 10 .mu.m.
[0162] An Al--Si alloy was thermally sprayed to the upper and lower
surfaces of the extruded tube through thermal spraying guns of an
arc spraying machine arranged at the upper and lower sides of the
outlet of the extruder, to thereby form a thermally sprayed layer.
In this thermal spraying processing, the thermal-spraying distance
was adjusted to 120 mm in the atmosphere.
[0163] The molten thermal-spraying particles to be sprayed against
the tube core adhered to the tube core by being cooled from the
thermal-spraying temperature to a temperature of the tube core by
being absorbed in heat by the tube core when they reached the tube
core.
[0164] In Table 1, as for the cooling degree of the
thermal-spraying particles, in cases where the difference between
the thermal-spraying temperature of the thermal-spraying particles
and the temperature of the tube core was 2,500.degree. C. or more,
it was denoted as "quenching", and in cases where it was less than
2,500.degree. C., it was denoted as "non-quenching." In the case of
Example 1, the thermal-spraying temperature of the thermal-spraying
particles was 5,000.degree. C., the temperature of the tube core
was 400.degree. C., and those temperature difference was
4,600.degree. C. Accordingly, the cooling degree in Example was
quenching.
[0165] After performing the thermal spraying, the aforementioned
extruded tube with a thermally sprayed layer was immersed in a
cooling bath to be cooled, and then continuously rolled into a coil
form.
[0166] Thereafter, while recoiling, the coil foamed tube was
pressed with reduction rollers to compress the thermally sprayed
layer to smooth the surface, thereby forming a brazing layer 50% in
net filling rate of the brazing material (apparent filling rate of
the brazing material to the brazing layer), 20 .mu.m in thickness,
and 40 .mu.m in surface roughness (Ry), and then cut into a
predetermined length to obtain heat exchanger tubes. In these
tubes, the average equivalent diameter of Si crystallization was
0.7 .mu.m.
[0167] Then, using the aforementioned heat exchanger tubes, the
so-called multi-flow type aluminum heat exchanger (see FIG. 1) was
provisionally assembled. Slurry in which non-corrosive flux was
suspended in water was sprayed to the heat exchanger provisional
assembly and then dried. Then, the assembly was heated at
600.degree. C. for 10 minutes in a nitrogen gas atmosphere furnace
to integrally braze the components to thereby obtain the heat
exchanger in Example 1.
Example 2
[0168] As shown in table 1, against the extruded tube 8 .mu.m in
surface roughness Ry, thermal spraying was performed by an arc
spraying method at the thermal-spraying temperature of
5,500.degree. C. and the thermal-spraying distance of 60 mm in a
nitrogen atmosphere. The tube member with the thermally sprayed
layer was pressed with reduction rollers to form a brazing layer
50% in brazing material filling rate, 15 .mu.m in thickness, 37
.mu.m in surface roughness Ry. Thus, the heat exchanger tube was
manufactured in the same manner as mentioned above. In this tube,
the average equivalent diameter of Si crystallization was 0.1
.mu.m.
[0169] Then, a heat exchanger was manufactured using the heat
exchanger tubes in the same manner as in the aforementioned
Example.
Example 3
[0170] As shown in table 1, against the extruded tube 7 .mu.m in
surface roughness Ry, thermal spraying was performed by an arc
spraying method at the thermal-spraying temperature of
4,800.degree. C. and the thermal-spraying distance of 60 mm in a
nitrogen atmosphere. The tube member with the thermally sprayed
layer was pressed with reduction rollers to form a brazing layer
60% in brazing material filling rate, 20 .mu.m in thickness, 35
.mu.m in surface roughness Ry. Thus, the heat exchanger tube was
manufactured in the same manner as mentioned above. In this tube,
the average equivalent diameter of Si crystallization was 0.5
.mu.m.
[0171] Then, a heat exchanger was manufactured using the heat
exchanger tubes in the same manner as in the aforementioned
Example.
Example 4
[0172] As shown in table 1, against the extruded tube 8 .mu.m in
surface roughness Ry, thermal spraying was performed by an arc
spraying method at the thermal-spraying temperature of
5,000.degree. C. and the thermal-spraying distance of 80 mm in an
atmosphere. The tube member with the thermally sprayed layer was
pressed with reduction rollers to form a brazing layer 50% in
brazing material filling rate, 30 .mu.m in thickness, 40 .mu.m in
surface roughness Ry. Thus, the heat exchanger tube was
manufactured in the same manner as mentioned above. In this tube,
the average equivalent diameter of Si crystallization was 0.4
.mu.m.
[0173] Then, a heat exchanger was manufactured using the heat
exchanger tubes in the same manner as in the aforementioned
Example.
Example 5
[0174] As shown in table 1, against the extruded tube 8 .mu.m in
surface roughness Ry, thermal spraying was performed by an arc
spraying method at the thermal-spraying temperature of
4,800.degree. C. and the thermal-spraying distance of 120 mm in a
nitrogen atmosphere. The tube member with the thermally sprayed
layer was pressed with reduction rollers to form a brazing layer
40% in brazing material filling rate, 20 .mu.m in thickness, 40
.mu.m in surface roughness Ry. Thus, the heat exchanger tube was
manufactured in the same manner as mentioned above. In this tube,
the average equivalent diameter of Si crystallization was 0.8
.mu.m.
[0175] Then, a heat exchanger was manufactured using the heat
exchanger tubes in the same manner as in the aforementioned
Example.
Example 6
[0176] As shown in table 1, against the extruded tube 8 .mu.m in
surface roughness Ry, thermal spraying was performed by an arc
spraying method at the thermal-spraying temperature of
5,000.degree. C. and the thermal-spraying distance of 100 mm in a
nitrogen atmosphere. The tube member with the thermally sprayed
layer was pressed with reduction rollers to form a brazing layer
50% in brazing material filling rate, 25 .mu.m in thickness, 42
.mu.m in surface roughness Ry. Thus, the heat exchanger tube was
manufactured in the same manner as mentioned above. In this tube,
the average equivalent diameter of Si crystallization was 0.6
.mu.m.
[0177] Then, a heat exchanger was manufactured using the heat
exchanger tubes in the same manner as in the aforementioned
Example.
Comparative Example 1
[0178] As shown in table 1, against the extruded tube 8 .mu.m in
surface roughness Ry, thermal spraying was performed by an arc
spraying method at the thermal-spraying temperature of
5,000.degree. C. and the thermal-spraying distance of 150 mm in an
atmosphere. Without performing the smoothing of the thermally
sprayed layer, the brazing layer 30% in brazing material filling
rate, 60 .mu.m in thickness, 60 .mu.m in surface roughness Ry was
formed. Thus, the heat exchanger tube was manufactured in the same
manner as mentioned above. In this tube, the average equivalent
diameter of Si crystallization was 0.9 .mu.m.
[0179] Then, a heat exchanger was manufactured using the heat
exchanger tubes in the same manner as in the aforementioned
Example.
Comparative Example 2
[0180] As shown in table 1, against the extruded tube 15 .mu.m in
surface roughness Ry, thermal spraying was performed by a flame
spraying method at the thermal-spraying temperature of
2,800.degree. C. and the thermal-spraying distance of 150 mm in an
atmosphere. The tube member with the thermally sprayed layer was
pressed with reduction rollers to form a brazing layer 30% in
brazing material filling rate, 40 .mu.m in thickness, 40 .mu.m in
surface roughness Ry. Thus, the heat exchanger tube was
manufactured in the same manner as mentioned above. In this tube,
the average equivalent diameter of Si crystallization was 1.5
.mu.m.
[0181] Then, a heat exchanger was manufactured using the heat
exchanger tubes in the same manner as in the aforementioned
Example.
Comparative Example 3
[0182] As shown in table 1, against the extruded tube 10 .mu.m in
surface roughness Ry, thermal spraying was performed by a flame
spraying method at the thermal-spraying temperature of
2,500.degree. C. and the thermal-spraying distance of 200 mm in an
atmosphere. Without performing the smoothing of the thermally
sprayed layer, the brazing layer 20% in brazing material filling
rate, 40 .mu.m in thickness, 60 .mu.m in surface roughness Ry was
formed. Thus, the heat exchanger tube was manufactured in the same
manner as mentioned above. In this tube, the average equivalent
diameter of Si crystallization was 2 .mu.m.
[0183] Then, a heat exchanger was manufactured using the heat
exchanger tubes in the same manner as in the aforementioned
Example.
Comparative Example 4
[0184] As shown in table 1, against the extruded tube 40 .mu.m in
surface roughness Ry, thermal spraying was performed by an arc
spraying method at the thermal-spraying temperature of
5,000.degree. C. and the thermal-spraying distance of 120 mm in an
atmosphere. Without performing the smoothing of the thermally
sprayed layer, the brazing layer 20% in brazing material filling
rate, 40 .mu.m in thickness, 60 .mu.m in surface roughness Ry was
formed. Thus, the heat exchanger tube was manufactured in the same
manner as mentioned above. In this tube, the average equivalent
diameter of Si crystallization was 0.7 .mu.m.
[0185] Then, a heat exchanger was manufactured using the heat
exchanger tubes in the same manner as in the aforementioned
Example.
Comparative Example 5
[0186] As shown in table 1, against the extruded tube 30 .mu.m in
surface roughness Ry, thermal spraying was performed by a flame
spraying method at the thermal-spraying temperature of
3,000.degree. C. and the thermal-spraying distance of 250 mm in an
atmosphere. Without performing the smoothing of the thermally
sprayed layer, the brazing layer 40% in brazing material filling
rate, 80 .mu.m in thickness, 60 .mu.m in surface roughness Ry was
formed. Thus, the heat exchanger tube was manufactured in the same
manner as mentioned above. In this tube, the average equivalent
diameter of Si crystallization was 1.8 .mu.m.
[0187] Then, a heat exchanger was manufactured using the heat
exchanger tubes in the same manner as in the aforementioned
Example.
Comparative Example 6
[0188] As shown in table 1, against the extruded tube 8 .mu.m in
surface roughness Ry, thermal spraying was performed by a HVOF
(high-speed flame) splaying method at the thermal-spraying
temperature of 2,600.degree. C. and the thermal-spraying distance
of 100 mm in an atmosphere. Without performing the smoothing of the
thermally sprayed layer, the brazing layer 50% in brazing material
filling rate, 80 .mu.m in thickness, 65 .mu.m in surface roughness
Ry was formed. Thus, the heat exchanger tube was manufactured in
the same manner as mentioned above. In this tube, the average
equivalent diameter of Si crystallization was 2 .mu.m.
[0189] Then, a heat exchanger was manufactured using the heat
exchanger tubes in the same manner as in the aforementioned
Example.
<Evaluation>
[0190] As for each heat exchanger of the aforementioned Examples
and Comparative Examples, the joining rate between the fin and the
tube was measured. In the evaluation, ".circleincircle." denotes
that the joining rate between the fin and the tube was 95% or more;
".smallcircle." denotes that the joining rate between the fin and
the tube was 90% or more but less than 95%; ".DELTA." denotes that
the joining rate between the fin and the tube was 60% or more but
less than 90%; "X" denotes that the joining rate between the fin
and the tube was less than 60% or fin detachment was occurred. The
evaluation results are collectively shown in the following Table
2.
TABLE-US-00002 TABLE 2 Evaluation Fin/tube joining rate Remarks
Example 1 .circleincircle. -- Example 2 .circleincircle. -- Example
3 .circleincircle. -- Example 4 .circleincircle. -- Example 5
.largecircle. -- Example 6 .circleincircle. -- Com. Example 1 X --
(fin detachment) Com. Example 2 .largecircle. Deformed in
cross-section of tube core Com. Example 3 X -- (fin detachment)
Com. Example 4 X Erosion of tube core by (fin detachment) brazing
material Com. Example 5 .largecircle. Deformed in cross-section of
tube core Com. Example 6 .largecircle. Deformed in cross-section of
tube core
[0191] As will be clear from Table 2, in Examples 1 to 6 satisfying
the requirements of this invention, brazing defects such as fin
detachment was prevented, and good brazing performance was secured.
Furthermore, in Examples 1 to 6, tube deformation due to the
smoothing was assuredly prevented, resulting in high quality.
[0192] To the contrary, in Comparative Examples deviating from the
requirements of this invention, good performance was not secured.
For example, like in Comparative Examples 1, 3 or 4 in which
smoothing of the thermally sprayed layer was not performed and the
brazing material filling rate was low, fin detachment occurred and
good brazing performance was not secured. Furthermore, in cases
where melting of the thermal-spraying particles at the time of
thermal spraying was inadequate like in Comparative Examples 2, 5
and 6, or in cases where quenching was inadequate, the tube itself
was crushed at the time of smoothing the thermally sprayed layer,
causing deterioration of quality.
INDUSTRIAL APPLICABILITY
[0193] This invention can be applied to an aluminum heat exchanger
for use in a car air-conditioning refrigeration cycle, a heat
exchanger tube used for such a heat exchanger, and a manufacturing
method thereof.
[0194] While the present invention may be embodied in many
different forms, a number of illustrative embodiments are described
herein with the understanding that the present disclosure as to be
considered as providing examples of the principles of the invention
and such examples are not intended to limit the invention to
preferred embodiments described herein and/or illustrated
herein.
[0195] While illustrative embodiments of the intention have been
described herein, the present invention is not limited to the
various preferred embodiments described herein, but includes any
and all embodiments having equivalent elements, modifications,
omissions, combinations (e.g., of aspects across various
embodiments), adaptations and/or alterations as would be
appreciated by those in the art based on the present disclosure.
The limitations in the claims are to be interpreted broadly based
on the language employed in the claims and not limited to examples
described in the present specification or during the prosecution of
the application, which examples are to be construed as
non-exclusive. For example, in the present disclosure, the term
"preferably" is non-exclusive and means "preferably, but not
limited to." In this disclosure and during the prosecution of this
application, means-plus-function or step-plus-function limitations
will only be employed where for a specific claim limitation all of
the following conditions are present in that limitation: a) "means
for" or "step for" is expressly recited; b) a corresponding
function is expressly recited; and c) structure, material or acts
that support that structure are not recited. In this disclosure and
during the prosecution of this application, the terminology
"present invention" or "invention" may be used as a reference to
one or more aspect within the present disclosure. The language
present invention or invention should not be improperly interpreted
as an identification of criticality, should not be improperly
interpreted as applying across all aspects or embodiments (i.e., it
should be understood that the present invention has a number of
aspects and embodiments), and should not be improperly interpreted
as limiting the scope of the application or claims. In this
disclosure and during the prosecution of this application, the
terminology "embodiment" can be used to describe any aspect,
feature, process or step, any combination thereof, and/or any
portion thereof, etc. In some examples, various embodiments may
include overlapping features. In this disclosure and during the
prosecution of this case, the following abbreviated terminology may
be employed: "e.g." which means "for example;" and "NB" which means
"note well."
* * * * *