U.S. patent application number 14/099303 was filed with the patent office on 2014-08-07 for method and apparatus for manufacturing fin-integrated tube for use in heat exchanger.
This patent application is currently assigned to DENSO CORPORATION. The applicant listed for this patent is DENSO CORPORATION. Invention is credited to Yoshinobu FURUKAWA, Takeshi ITOH.
Application Number | 20140215825 14/099303 |
Document ID | / |
Family ID | 51257998 |
Filed Date | 2014-08-07 |
United States Patent
Application |
20140215825 |
Kind Code |
A1 |
FURUKAWA; Yoshinobu ; et
al. |
August 7, 2014 |
METHOD AND APPARATUS FOR MANUFACTURING FIN-INTEGRATED TUBE FOR USE
IN HEAT EXCHANGER
Abstract
The method of manufacturing a fin-integrated tube for a heat
exchanger includes step of disposing a rolling roller group
including rolling rollers so as to surround the periphery of a
tube, each of the roller crests of the rolling rollers being
rounded at an end thereof into an R-shape, widths of the R-shaped
ends being gradually increased from one axial end to the other
axial end for each of the rolling rollers, and step of causing the
roller crests to press the periphery of the tube from the one axial
end to the other axial end by axially moving and rotating the
rolling roller group relative to the tube so as to deform a part of
the periphery of the tube into a spirally projecting portion while
shaping it into a spiral fin by gradually squeezing the part of the
periphery of the tube using the R-shaped end portions.
Inventors: |
FURUKAWA; Yoshinobu;
(Okazaki-shi, JP) ; ITOH; Takeshi; (Anjo-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DENSO CORPORATION |
Kariya-city |
|
JP |
|
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
51257998 |
Appl. No.: |
14/099303 |
Filed: |
December 6, 2013 |
Current U.S.
Class: |
29/890.046 ;
29/727 |
Current CPC
Class: |
B21C 37/26 20130101;
Y10T 29/53122 20150115; Y10T 29/49378 20150115 |
Class at
Publication: |
29/890.046 ;
29/727 |
International
Class: |
B21D 53/06 20060101
B21D053/06 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 1, 2013 |
JP |
2013-018326 |
Claims
1. A method of manufacturing a fin-integrated tube for a heat
exchanger, the fin-integrated tube including a cylindrical tube and
a spiral fin integrally formed in a periphery of the tube,
comprising the steps of: disposing a rolling roller group including
a plurality of rolling rollers each having a plurality of roller
crests on a periphery thereof so as to surround the periphery of
the tube with a predetermined lead angle, each of the roller crests
being rounded at an end thereof into an R-shape to be an R-shaped
end, widths of the R-shaped ends of the roller crests being
gradually increased from one axial end to the other axial end for
each of the rolling rollers, so that each of the rolling rollers
serves as a gradual roller; and causing the roller crests of the
rolling rollers to press the periphery of the tube from the one
axial end to the other axial end by axially moving and rotating the
rolling roller group relative to the tube so as to deform a part of
the periphery of the tube into a spirally projecting portion while
shaping the spirally projecting portion into the spiral fin by
gradually squeezing the part of the periphery of the tube using the
R-shaped end portions of the roller crests of the rolling
rollers.
2. The method of manufacturing a fin-integrated tube for a heat
exchanger according to claim 1, wherein the fin-integrated tube is
made of stainless steel.
3. A manufacturing apparatus for manufacturing a fin-integrated
tube for a heat exchanger, the fin-integrated tube including a
cylindrical tube and a spiral fin integrally formed in a periphery
of the tube, comprising: a tube holding part for holding a proximal
end portion of the tube so as to be rotatable together with the
tube; and a rolling roller head disposed coaxially with the tube so
as to be axially movable relative to the tube; the rolling roller
head having a rolling roller group including a plurality of rolling
rollers each having a plurality of roller crests on a periphery
thereof, said rolling roller group being configured to surround the
periphery of the tube with a predetermined lead angle, each of the
roller crests being rounded at an end thereof into an R-shape to be
an R-shaped end, widths of the R-shaped ends of the roller crests
being gradually increased from one axial end to the other axial end
for each of the rolling rollers, so that each of the rolling
rollers serves as a gradual roller, wherein the rolling roller head
is configured to be driven to axially move in a direction from a
distal end to a proximal end of the tube and rotate relative to the
tube so as to cause the roller crests of the rolling rollers to
press the periphery of the tube in the direction from the distal
end to the proximal end so as to deform a part of the periphery of
the tube into a spirally projecting portion while shaping the
spirally projecting portion into the spiral fin by gradually
squeezing the part of the periphery of the tube using the R-shaped
end portions of the roller crests of the rolling rollers.
4. The manufacturing apparatus for manufacturing a fin-integrated
tube for a heat exchanger according to claim 3, wherein heights of
the roller crests of each of the rolling rollers increase stepwise
in a direction from one axial end to the other axial end
thereof.
5. The manufacturing apparatus for manufacturing a fin-integrated
tube for a heat exchanger according to claim 3, further comprising:
a rolling head holder holding the rolling roller head such that the
rolling roller head is opposed to the tube holding part on a
processing bench, the rolling head holder being formed with a slide
hole which opens to an end thereof facing the tube holding part; a
movable sleeve slidably held inside the slide hole and supporting a
periphery of a proximal end portion of the rolling roller head; and
a biasing means for biasing the movable sleeve in a direction in
which the rolling roller head advances; the slide hole, the movable
sleeve and the biasing means serving as an extension absorbing
mechanism for absorbing extension of the tube being form-processed
by the manufacturing apparatus.
6. The manufacturing apparatus for manufacturing a fin-integrated
tube for a heat exchanger according to claim 3, wherein the
fin-integrated tube is made of stainless steel.
Description
[0001] This application claims priority to Japanese Patent
Application No. 2013-18326 filed on Feb. 1, 2013, the entire
contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method and an apparatus
for manufacturing a high temperature-resistant fin-integrated tube
for use in a heat-exchanger mountable on a vehicle.
[0004] 2. Description of Related Art
[0005] There are known various heat exchangers which can be used in
a cooling system, a driving system and an air-conditioning system
of a vehicle. FIG. 19 shows a common fin-integrated tube for use in
a heat exchanger. This fin-integrated tube includes a tube 200
through which heat-exchanging medium flows and a plurality of
hat-shaped rings 201 brazed to the tube 200 such that the tube 200
passes through a stack of the hat-shaped rings 201 as fins 202.
[0006] It is known to form a plurality of fins integrally with a
tube serving as a radiator to provide a compact and
highly-efficient heat exchanger. For example, refer to Japanese
Patent Application Laid-open No. 2001-332666. This patent document
describes carving the outer or inner wall of a tube to form a
plurality of fins which are integrally connected to the tube at
their thick proximal end portions. The plurality of the fins are
formed using a carving knife such that they become thinner from
their proximal end portions to their distal end portions to
increase their surface area to thereby increase the heat
dissipation effect.
[0007] As a heat exchanger mountable on a vehicle, the exhaust heat
recovery device is receiving attention. The exhaust heat recovery
device recovers exhaust heat emitted from an engine. The exhaust
heat recovery device includes a fin-integrated tube which contains
pure water and is mounted in the exhaust passage of the engine for
recovering the exhaust heat. Since this fin-integrated tube is
exposed to exhaust gas, it is made of heat-resistant and
corrosion-resistant stainless steel and their fins are joined to
the tube using a nickel-based brazing material, for example.
[0008] However, it turned out that the fins of such a
fin-integrated tube may be deformed due to a linear expansion
difference in the dissimilar metal joint by the brazing material in
a case of a high-efficiency engine that emits high-temperature
exhaust gas (900.degree. C., for example). Further, if the number
of the fins is increased to increase the heat exchange efficiency,
manufacturing time and cost increase greatly because the fins have
to be joined one by one to the tube.
[0009] The inventors of the present invention studied a possibility
of adoption of a fin-integrated tube which does not include any
brazing material, and can be manufactured by the method described
in the above patent document. However, the method of carving the
tube surface to form fins as described in the above patent
document, which is suitable for the case where the tube is made of
metal easy to carve such as aluminum, is difficult to use in the
case where the tube is made of stainless steel. Further, the wall
thickness and the rigidity of the tube have to be sufficiently
large, while on the other hand, the shapes of the fins formed by
carving the outer or inner surface of the tube along its axis and
the wall thickness after the carving of the tube are likely to be
non-uniform. Hence, it is difficult to reduce individual difference
in the radiation performance. As explained above, it has been
difficult so far to achieve both reducing the manufacturing cost
and increasing the heat exchange efficiency.
SUMMARY
[0010] An exemplary embodiment provides a method of manufacturing a
fin-integrated tube for a heat exchanger, the fin-integrated tube
including a cylindrical tube and a spiral fin integrally formed in
a periphery of the tube, including the steps of:
[0011] disposing a rolling roller group including a plurality of
rolling rollers each having a plurality of roller crests on a
periphery thereof so as to surround the periphery of the tube with
a predetermined lead angle, each of the roller crests being rounded
at an end thereof into an R-shape to be an R-shaped end, widths of
the R-shaped ends of the roller crests being gradually increased
from one axial end to the other axial end for each of the rolling
rollers, so that each of the rolling rollers serves as a gradual
roller; and
[0012] causing the roller crests of the rolling rollers to press
the periphery of the tube from the one axial end to the other axial
end by axially moving and rotating the rolling roller group
relative to the tube so as to deform a part of the periphery of the
tube into a spirally projecting portion while shaping the spirally
projecting portion into the spiral fin by gradually squeezing the
part of the periphery of the tube using the R-shaped end portions
of the roller crests of the rolling rollers.
[0013] The exemplary embodiment provides also a manufacturing
apparatus for manufacturing a fin-integrated tube for a heat
exchanger, the fin-integrated tube including a cylindrical tube and
a spiral fin integrally formed in a periphery of the tube,
including:
[0014] a tube holding part for holding a proximal end portion of
the tube so as to be rotatable together with the tube; and
[0015] a rolling roller head disposed coaxially with the tube so as
to be axially movable relative to the tube;
[0016] the rolling roller head having a rolling roller group
including a plurality of rolling rollers each having a plurality of
roller crests on a periphery thereof, said rolling roller group
being configured to surround the periphery of the tube with a
predetermined lead angle,
[0017] each of the roller crests being rounded at an end thereof
into an R-shape to be an R-shaped end, widths of the R-shaped ends
of the roller crests being gradually increased from one axial end
to the other axial end for each of the rolling rollers, so that
each of the rolling rollers serves as a gradual roller,
[0018] wherein
[0019] the rolling roller head is configured to be driven to
axially move in a direction from a distal end to a proximal end of
the tube and rotate relative to the tube so as to cause the roller
crests of the rolling rollers to press the periphery of the tube in
the direction from the distal end to the proximal end so as to
deform a part of the periphery of the tube into a spirally
projecting portion while shaping the spirally projecting portion
into the spiral fin by gradually squeezing the part of the
periphery of the tube using the R-shaped end portions of the roller
crests of the rolling rollers.
[0020] According to the exemplary embodiment, there is provided a
high-performance and low-cost heat exchanger for vehicle use, which
includes fin-integrate tubes manufactured without use of brazing
material.
[0021] Other advantages and features of the invention will become
apparent from the following description including the drawings and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In the accompanying drawings:
[0023] FIG. 1 is a general view of a manufacturing apparatus for
manufacturing a fin-integrated tube according to a first embodiment
of the invention;
[0024] FIG. 2 is a partially enlarged view of the fin-integrated
tube manufactured by a method performed using the manufacturing
apparatus according to the first embodiment of the invention;
[0025] FIG. 3 is a partially enlarged view of a form rolling part
of the manufacturing apparatus according to the first embodiment of
the invention;
[0026] FIG. 4 is plan and side views of a form rolling roller head
constituting the rolling part;
[0027] FIG. 5 is a partially enlarged view of an exhaust heat
recovery device including the fin-integrated tubes manufactured by
the method performed using the manufacturing apparatus according to
the first embodiment of the invention;
[0028] FIG. 6 is a cross-sectional view of the exhaust heat
recovery device;
[0029] FIG. 7 is a perspective view of the exhaust heat recovery
device;
[0030] FIG. 8 is a schematic diagram for explaining a rolling
process performed using the rolling roller head of the rolling part
of the manufacturing apparatus according to the first embodiment of
the invention;
[0031] FIG. 9 is a diagram showing an example of the shapes of the
roller crests of rolling rollers of the rolling roller head;
[0032] FIGS. 10 and 11 are schematic diagrams for explaining a fin
shaping process performed using the rolling rollers;
[0033] FIG. 12 is a schematic diagram for explaining variation of
effect of the rolling rollers depending on variation of the angles
of the roller crests of the rolling rollers;
[0034] FIG. 13 is a schematic diagram for explaining variation of
the effect of the rolling rollers depending on variation of the
R-shaped end portions of the roller crests of the rolling
rollers;
[0035] FIG. 14 is a schematic diagram for explaining a tube
extension at the time of the rolling process;
[0036] FIG. 15 is a cross-sectional view for explaining effects of
a extension absorbing mechanism of the rolling roller head;
[0037] FIG. 16 is a side view showing an example of the shapes of
the roller crests of rolling rollers of a manufacturing apparatus
according to a second embodiment of the invention;
[0038] FIG. 17 is a schematic diagram for explaining a tube forming
process performed using the rolling rollers of the manufacturing
apparatus according to the second embodiment of the invention;
[0039] FIG. 18 is a schematic diagram for explaining a method of
manufacturing a fin-integrated tube performed using a cored bar as
a third embodiment of the invention; and
[0040] FIG. 19 is a perspective view of a conventional
fin-integrated tube.
PREFERRED EMBODIMENTS OF THE INVENTION
First Embodiment
[0041] FIG. 1 is a general view of a manufacturing apparatus
according to a first embodiment of the invention, which
manufactures a fin-integrated tube 2 shown in FIG. 2. The
fin-integrated tube 2 is used for various vehicle-mounted heat
exchangers. The fin-integrated tube 2 is made from a cylindrical
tube material 2'. The tube material 2' is plastic-deformed by a
rolling roller head 4 of a form rolling part 6 to form the
fin-integrated tube 2 including a tube 21 and a fin 22 wound
spirally on the outer periphery of the tube 21 at a predetermined
pitch. FIG. 3 is a partially enlarged view of the form rolling part
6 which is a main part of the manufacturing apparatus. FIG. 4 is
plan and side views of the rolling roller head 4 of the form
rolling part 6.
[0042] FIG. 5 is a partially enlarged view of an exhaust heat
recovery device including the fin-integrated tubes 2. FIG. 6 is a
cross-sectional view of the exhaust heat recovery device. FIG. 7 is
a perspective view of the exhaust heat recovery device. The heat
recovery device is for recovering exhaust heat emitted from an
engine, and exchanging heat with engine cooling water. The exhaust
heat recovery device is used for warming the engine to increase
fuel economy. As shown in FIGS. 6 and 7, the exhaust heat recovery
device includes a heating section (heat exchanging section) 1
housing a plurality of the fin-integrated tubes 2, a heat guard 100
above which a tank is disposed, and a condensing section 101 having
a LCC pipe P through which the engine cooling water (LLC) flows.
The heating section 1 is mounted inside a duct D provided midway of
the exhaust passage of the engine. The condensing section 101 is
disposed in the upper space of the tank. The heating section 1 and
the condensing section 101 are loop-connected to each other through
a steam passage 102 and a valve 103 to constitute a loop heat pipe
(heat loop) enclosing working medium. The loop heat pipe operates
to transfer heat by evaporation and condensation of the working
medium. In this embodiment, pure water is used as the working
medium.
[0043] The heating section 1 includes a plurality of the
fin-integrated tubes 2 which are arranged in rows along the flow
direction of the exhaust gas and in rows along the direction
perpendicular to the flow direction of the exhaust gas within the
duct D. Each of the fin-integrated tubes 2 includes the tube 21
extending in the direction perpendicular to the flow direction of
the exhaust gas and the spiral fin 22 projecting radially outward
from the periphery of the tube 21. The bottom end of the tube 21 is
closed, and the top end of the tube 21 penetrates through a core
plate 3 forming the bottom plate of the tank and opens to the lower
space in the tank. The inside of the tank is partitioned into the
upper space and the lower space by a tank inner 4. The tank inner 4
is formed with the steam passage 102 projecting upward. The lower
space to which the fin-integrated tubes 2 open and the upper space
in which the condensing section 101 is disposed are in
communication through the steam passage 102.
[0044] The steam introduced from the steam passage 102 into the
condensing section 101 exchanges heat with the engine cooling water
by contacting with the LLC pipe, and becomes condensed water. The
condensed water is refluxed back to the heating section 1 by
opening or closing the valve 103 depending on the pressure inside
the tank. A partition 105 having an oxygen introducing hole 104 is
provided in the lateral direction of the steam passage 102 for
removing oxygen generated by contact between high-temperature steam
and metal, for example. A copper oxide containing case 106
containing granular copper oxide 107 is provided below the space
partitioned by the partition 105. The generated hydrogen is guided
from the hydrogen introducing hole 104 to the copper oxide
containing case 106, and reduced to be removed.
[0045] As shown in FIG. 5, the fin 22 is integrally connected to
the tube 21 at its proximal end portion, and exchanges heat with
the exhaust gas contacting the fin surface at its thin distal end
portion which is spirally joined to the tube 21 in layers at a
predetermined fin pitch (Fp) in the axial direction of the tube 21.
The fin-integrated tube 2 is exposed to high-temperature exhaust
gas in the duct D. Accordingly, the fin-integrated tube 2 is made
of a heat-resistant and oxidation-resistant metal such as stainless
steel. As described in the foregoing, conventional fin-integrated
tubes manufactured by brazing have a concern that their fins may be
deformed in a usage environment where the temperature of exhaust
gas is high (100 to 900.degree. C., for example) causing the heat
exchange efficiency to be lowered.
[0046] Hence, in this embodiment, the tube material 2' undergoes a
specific rolling process in order to form the continuous spiral fin
22 integral with the periphery of the tube 21. The tube material 2'
before the rolling process is approximately 10 mm in outer
diameter, approximately 7 mm in inner diameter, and approximately
1.5 mm in wall thickness. The fin height (Fh) and the fin thickness
(Ft) are determined so as to achieve a target heat exchange
performance and a target exhaust flow performance (exhaust flow
pressure loss). The wall thickness of a part of the peripheral
portion of the tube material 2', which is used as a fin forming
portion, is set smaller than the thickness (t) of the tube 21 (or
smaller than a half of the wall thickness of the tube material 2'),
for example, approximately 0.7 mm, to provide a thin and high fin
shape. For example, when the fin pitch is 1.5 mm, the fin forming
portion is plastic-deformed in the radial direction such that the
fin height is between 1.8 mm and 2.6 mm to achieve the target
performances.
[0047] Generally, a common rolling process is for plastic-deforming
a row material to the shape analogous to the shape of the outer
surface of a rolling roller by pressing the rolling roller to the
periphery of the row material. Accordingly, common rolling rollers
are not suitable for shaping the thin-wall tube material 2' to have
a thin-wall fin by deforming the tube material 2' to expand
radially outward. Hence, a newly developed rolling roller head 4
specialized for use in fin forming is used in this embodiment. A
manufacturing apparatus including the rolling roller head 4, and a
method of manufacturing the fin-integrated tube using this
manufacturing apparatus are explained in the following.
[0048] As shown in FIG. 1, the manufacturing apparatus for
manufacturing the fin-integrated tube 2 has a processing bench 7 on
which a tube holding part 3 for holding and fixing the tube
material 2' to be processed and the for rolling part 6 including a
rolling roller head 4 of three-roller type and a rolling head
holder 5 are mounted so as to be opposed to each other. The tube
holding part 3 includes a holding chuck 31 for holding the proximal
end portion (the left end portion in FIG. 3) of the material tube
2'. The holding chuck 31 is mounted to a rotating shaft 32 coupled
to a driving part 72. The tube material 2' can be rotated by
rotating the rotating shaft 32. The form rolling part 6 is axially
movable on the processing bench 7 by a conveying shaft 61 mounted
on a supporting table 62 supporting the rolling head holder 5 to
which the roller head 4 is mounted. The driving part 71 drives the
conveying shaft 61 in synchronism with the rotating shaft 32 to
move the rolling roller head 4 toward the end portion (the right
end portion in FIG. 1) of the tube material 2' disposed coaxially
with the rolling roller head 4 at a predetermined speed.
[0049] As shown in FIG. 3, the rolling roller head 4 includes a
flange portion 44 to which the roller group (the rollers 41, 42 and
43) is mounted and a cylindrical proximal end portion 45. The
cylindrical proximal end portion 45 of the rolling roller head 4 is
inserted and fixed to a movable sleeve 52 having a container-like
shape. The movable sleeve 52 is axially and slidably supported in a
slide hole 51 formed so as to open to one end (the left side end in
FIG. 3) of the head holder 5. The rolling head holder 5 includes an
axially elongated hole 55 penetrating through the lateral wall of
the slide hole 51. The movable sleeve 52 includes locking pins 54
formed in the periphery thereof so as to project from the elongated
hole 55 to restrict the movable sleeve 52 from moving in the
rotating direction. Between the bottom of the movable sleeve 52 and
the other end (the right side end in FIG. 3) of the rolling head
holder 5, a coil-shaped compression spring 56 is disposed as a
biasing member to bias the movable sleeve 52 toward the rolling
roller head 4.
[0050] The movable sleeve 52 and the spring 56 constitute an
extension absorbing mechanism for absorbing extension of the tube
material 2' being form-rolled. The movable sleeve 52 can move to a
distance adaptable to extension of the tube material 2'. The spring
56 is disposed in the rear of the movable sleeve 52 (opposite the
rolling roller head 4) and always biased forward (toward the tube
forming direction) at an appropriate load. The biasing force
applied to the movable sleeve 52 can be determined through pretest
to such a value that generates a pressing force enabling the roller
crests of the rolling rollers 41, 42 and 43 to bite the periphery
of the tube material 2' at the beginning of a forming process and
to retract to absorb extension of the tube material 2'. An
adjustment screw 57 is mounted to the opening formed in the other
end (the right side end in FIG. 3) of the rolling head holder 5. By
screwing in the adjustment screw 57 in the axial direction, the
compression amount of the spring 56 to which the adjustment screw
57 abuts can be adjusted.
[0051] As shown in FIG. 4, the rolling roller head 4 includes, as a
rolling roller group surrounding the periphery of the tube material
2' in three directions, the three rolling rollers 41, 42 and 43
disposed in a concentric pattern at even intervals. Each of the
rolling rollers 41, 42 and 43 includes a plurality of the roller
crests 44 at its periphery to form a desired fin shape. The rolling
rollers 41, 42 and 43 are rotatably supported by the rolling roller
head 4 such that they are inclined by a predetermined lead angle
(three degrees in this embodiment) to the center axis of the tube
material 2'.
[0052] As shown in FIG. 8, the roller crests 44 are formed of
concavo-convex portions arranged in the axial direction at even
pitch. The three rolling rollers 41, 42 and 43 are displaced by a
predetermined pitch from one another in the axial direction.
Accordingly, by sending the rolling roller head 4 in synchronism
with rotation of the tube material 2' (one pitch per one rotation),
the tube material 2' is pushed in between the rolling rollers 41,
42 and 43, and the rolling rollers 41, 42 and 43 move relative to
the tube material 2' in the axial direction while being driven to
rotate. As a result, the roller crests 44 of the rolling rollers
41, 42 and 43 move past the periphery of the tube material 2' in
succession while pressing the periphery to form the fin 22
projecting spirally.
[0053] It is not easy to form such a fin shape which is thin and
has a large heat transfer area. Hence, this embodiment uses the
three rolling rollers 41, 42 and 43 as a gradual roller whose
roller crests 44 change in shape stepwise along the axial
direction. More specifically, as shown in FIG. 9, the end portions
of the roller crests 44 of each of the rolling rollers 41, 42 and
43 are rounded so as to be R-shaped portions having a circular arch
shape (referred to as the "R-shaped end portions" hereinafter), the
sizes (widths) of the R-shaped end portions becoming gradually
larger from one axial end to the other axial end. The roller crest
44 at the one axial end has a roughly triangular-cross section as a
whole and is formed to a shape of sufficiently small "R" at its
end, so that it can bite the tube material 2' easily. The arc
diameters of the R-shaped end portions are gradually increased
along the axial direction, and accordingly, the roller crests 44
near the other axial end (near the rolling head holder 5) have an
inverted U-shaped cross-section as a whole.
[0054] The tube material 2' is not deformed easily because the
rolling roller head 4 applies load in three directions. In
addition, since the three rolling rollers 41, 42 and 43 serve as a
gradual roller, the processing load can be reduced. The roller
crests 44 of the rolling roller group constituted of the three
rolling rollers 41, 42 and 43 are shaped such that the R-shaped end
portions become gradually larger in the time order of abutment on
the tube material 2'. Some of the adjacent R-shaped end portions
may be the same in shape, if the arc diameters (R) of the R-shaped
end portions of the roller crests 44 increase stepwise in the axial
direction as a whole.
[0055] Preferably, the R-shaped end portions of the roller crests
44 of the rolling rollers 41, 42 and 43 are different from one
another in shape except those at their both ends. FIG. 9 shows an
example of this case, where each of the rolling rollers 41, 42 and
43 includes 13 rows of the roller crests 44 arranged along the
axial direction, the arc diameter R at the 1st row being a mm (R=a)
for all of the rolling rollers 41, 42 and 43, the arc diameters R
at the 12nd and 13rd rows being 6a mm (R=6a) for all of the rolling
rollers 41, 42 and 43. In this example, the arc diameter R at the
2nd row is a mm for the rolling roller 41, a+0.02 mm for the
rolling roller 42, and a+0.04 mm for the rolling roller 43. For the
3rd to 10th rows, the arc diameter R is increased with the increase
of the row number for all of the rolling rollers 41, 42 and 43. The
arc diameter R at the 11th row is 6a-0.05 mm for the rolling roller
41, 6a-0.03 mm for the rolling roller 42, and 6a-0.01 mm for the
rolling roller 43. It is possible to disperse the processing load
to thereby form the fin shape with high precision by
differentiating the roller crests 44 in shape, and to reduce
variation of the formed fin shape by equating the shapes of the
roller crests 44 of the rolling rollers 41, 42 and 43 at the
beginning and end of the fin forming process.
[0056] FIGS. 10 and 11 are schematic diagrams for explaining the
fin shaping process using the rolling rollers 41, 42 and 43 as a
gradually R-changing roller. At the beginning of the tube forming
process, the fin forming portion of thickness of t of the periphery
of the tube material 2' is pushed into the shape analogous to the
roller crests 44 at a small load. Thereafter, the R-shaped end
portions of the roller crests 44 pushing into the periphery of the
tube material 2' are gradually increased in size, as a result of
which the tube material 2' is squeezed between the lateral sides of
the roller crests 44 to be plastic-deformed so as to extend upward.
Accordingly, since the pushing force is dispersed to the lateral
sides, the fin shaping process can be smoothly performed by
squeezing up the fin forming portion so as to change from a roughly
trapezoidal shape to a desired fin shape using the roller
crests.
[0057] As shown in FIG. 10, the root portions between adjacent
roller crests are shaped such that they become gradually deeper in
the direction from the end at which the R-shaped end portion is
minimum to the end at which the R-shaped end portion is maximum. As
shown in FIG. 11, the fin height is gradually increased.
Accordingly, the depth of the root portion at the end at which the
R-shaped end portion is minimum can be made sufficiently small to
prevent the rolling rollers 41, 42 and 43 from being broken,
because it is only required to hold the fin 22 at this end. The
root portions are shaped such that their depths gradually increase
with the progress of the fin shaping process so as to provide
necessary spaces for holding the fin being formed to project
radially outward.
[0058] Next, the advantages of using the roller crests of the
rolling rollers 41, 42 and 43 are explained with reference to FIGS.
12 and 13. As shown in FIG. 12, the roller angle (the angle theta
formed by the lateral sides of adjacent roller crests 44) is
V-shaped when their R-shaped end portions are small, and becomes
gradually narrower as the R-shaped end portions become larger.
Accordingly, the pushing force is dispersed to the lateral sides to
facilitate the fin shaping. As shown in FIG. 13, the roller crests
44 are rounded at their ends, and the widths of their ends are
gradually increased (as roller crests of a totally gradually
R-changing roller). Accordingly, it is possible to prevent a
shearing stress from concentrating in their ends and to disperse
the shearing stress to the lateral sides. Further, since the arc
diameters (R) are gradually increased, most of the portion being
shaped by the following roller is limited in the area facing a
45-degree lateral sector of the circumference of the leading
roller. This makes it possible to extend the fin forming portion
upward by a large amount, because the forming load can be
sufficiently dispersed to the lateral sides while squeezing the
thick wall portion at the fin proximal end portion.
[0059] Next, effects of the extension absorbing mechanism provided
in the rolling head holder 5 are explained with reference to FIGS.
14 and 15. In this embodiment, as shown in FIG. 14, extension
toward the chuck 31 occurs in the tube material 2' when the leading
roller crest 44 (the first crest in FIG. 14) of each of the rolling
rollers 41, 42 and 43 bites the periphery of the tube material 2'.
Since this extension is accumulated for each of the roller crests
biting the periphery of the tube material 2', the tube material 2'
is likely to be axially compressed and deformed. On the other hand,
the rolling head holder 5 shown in FIG. 15 is configured such that
the proximal end portion 45 of the rolling roller head 4 is
resiliently supported by the movable sleeve 52 and the spring 56 so
as to be movable relative to the rolling head holder 5.
Accordingly, the rolling head holder 5 shown in FIG. 15 can release
the tube extension stress occurring between the tube material 2'
rotating pivoted at one end thereof and the rolling roller head 4
advancing forward at a constant speed by receiving the tube
extension stress in the movable sleeve 52 and retracting the spring
56 while compressing it. Hence, according to the rolling head
holder 5 shown in FIG. 15, it is possible to prevent the tube
material 2' from being deformed by absorbing the extension of the
tube material 2'.
Second Embodiment
[0060] FIG. 16 is a side view showing an example of the shape of
the roller crests of a modification of the rolling roller head 4
included in a manufacturing apparatus according to a second
embodiment of the invention. FIG. 17 is a schematic diagram for
explaining a tube forming process performed using the modification
of the rolling roller head 4. In the second embodiment, as shown in
FIG. 16, each of the rolling rollers 41, 42 and 43 is constituted
of a first rolling roller 4a and a second rolling roller 4b to
enable performing a two-stage rolling. The first rolling roller 4a,
which is a main part of the rolling roller head 4, is a gradually
R-changing roller whose R-shaped end portions of the roller crests
44 become larger gradually as is the case of the first embodiment.
That is, as shown in FIG. 17, the R-shaped end portions are smaller
at the forward end of the tube material 2' and larger at the
rearward end of the tube material 2' so that the fin forming
portion is squeezed radially outward (upward in FIG. 17) gradually
(Ft1). In the first rolling roller 4a, the heights (outer diameters
D1) of the roller crests 44 are the same, while the depths of the
root portions between adjacent roller crests 44 become gradually
larger so that the fin forming portion which becomes gradually
higher with the progress of the fin shaping process can be held in
the root portions securely.
[0061] In FIG. 16, the second rolling roller 4b disposed following
the first rolling roller 4a is a projecting roller configured such
that the heights (outer diameters D2) of the roller crests 44 are
higher than those of the first rolling roller 4a, and become
gradually larger toward the rear end thereof. As shown in FIG. 17,
since the tube material 2' is gradually pushed radially inward
(Fh2: downward in FIG. 17), the fin height can be more increased.
Since the tube material 2' has been made thin by the first rolling
roller 4a, the plastic deformation by the second rolling roller 4b
can be facilitated.
Third Embodiment
[0062] Next, a third embodiment of the invention is described with
reference to FIG. 18. FIG. 18 is a schematic diagram for explaining
a method of manufacturing a fin-integrated tube performed using a
cored bar as a third embodiment of the invention. As shown in FIG.
18, there is slight plastic deformation in the inner wall of the
formed tube 21 in the direction in which it was pushed by the
rolling rollers 41, 42 and 43. Such plastic deformation can be
reduced by performing the forming process using a cored bar 8
mounted to the inner wall of the tube 21. Using the cored bar 8
facilitates the roller crests 44 to bite the tube 21, and minimizes
escape of the tube 21 caused by resilient deformation of the tube
21 at the time of pushing the roller crests 44 into the tube 21, to
thereby maximize the height of the fin 22. Further, using the cored
bar 8 reinforces the thin tube 21 and makes it resistant to
bending.
[0063] The fin-integrated tube 2 of the invention underwent a heat
endurance test in a state of being mounted to the exhaust heat
recovery device shown in FIGS. 6 and 7. More specifically, the
exhaust heat recovery device was fabricated by disposing a
plurality of the fin-integrated tubes 2 inside the duct D to
constitute the heating section 1, and the temperature of the gas
flowing into the duct D was changed repeatedly (2,000 cycles)
within the range from 100 to 900.degree. C. For comparison, the
same test was performed for the conventional fin-integrated tube
shown in FIG. 19.
[0064] It was found that the fin 22 of the fin-integrated tube 2 of
the invention did not change in shape before and after the test.
Further, the heat exchange performance and the pressure loss were
found to be within a predetermined standard. On the other hand, in
the case of the conventional fin-integrated tube, the fin
deformation gradually increased with the increase of the cycles due
to difference in linear expansion coefficient in the dissimilar
metal joint thereof. After 2,000 cycles of the change of the gas
temperature, the heat exchange performance dropped by 25%, and the
pressure loss dropped by 50%. From this test, it was confirmed that
the fin-integrated tube 2 of the present invention exhibits high
durability under high temperature environment.
[0065] The manufacturing method of the present invention enables
manufacturing fin-integrated tubes integrally provided with a
spiral fin with a high degree of formability by using the
three-roller type rolling roller head including gradual rollers.
According to the manufacturing method of the present invention,
since the tube material 2' is plastic-deformed, the material is not
wasted unlike in conventional machining or cutting work, and it is
easy to adjust the heat transfer area (heat exchange performance)
of the fin by adjusting the fin pitch depending on the lead angle
of the rolling roller.
[0066] In the above embodiments, stainless steel is used as the
material of the fin-integrated tube 2. However, a metal material
having good heat conductivity such as aluminum or copper, or an
alloy of them may be used depending on the usage environment. The
material of the rolling rollers 41, 42 and 43 can be determined
depending on the material of the tube material 2'. For example,
when the tube material 2' is made of a hard material, the rolling
rollers 41, 42 and 43 may be made of a stronger material such as an
ultrahard alloy.
[0067] The fin-integrated tube manufactured by the manufacturing
method or apparatus of the present invention can be used for
various heat exchangers other than exhaust heat recover devices,
such as those used in a cooling system, a driving system or an
air-conditioning system of a vehicle.
[0068] The above explained preferred embodiments are exemplary of
the invention of the present application which is described solely
by the claims appended below. It should be understood that
modifications of the preferred embodiments may be made as would
occur to one of skill in the art.
* * * * *