U.S. patent application number 11/663448 was filed with the patent office on 2008-07-31 for louver fin and corrugation cutter.
This patent application is currently assigned to CALSONIC KANSEI CORPORATION. Invention is credited to Kenji Tochigi, Hirokazu Yaezawa.
Application Number | 20080179048 11/663448 |
Document ID | / |
Family ID | 36090137 |
Filed Date | 2008-07-31 |
United States Patent
Application |
20080179048 |
Kind Code |
A1 |
Yaezawa; Hirokazu ; et
al. |
July 31, 2008 |
Louver Fin and Corrugation Cutter
Abstract
A louver fin (11) has a corrugated shape by alternately forming
bent portions (15) and flat portions (17) in a strip thin sheet
(13). In the louver fin (11), a plurality of louvers (19, 21) cut
and bent out of the flat portions (17) along the longitudinal
direction Y of the strip thin sheet (13) are arranged parallel to
each other along the width direction X of the strip thin sheet
(13). In the louver fin (11) the louvers (18, 19) are cut and bent
at an approximately same angle with respect to the longitudinal
direction Y of the strip thin sheet (13).
Inventors: |
Yaezawa; Hirokazu; (Tochigi,
JP) ; Tochigi; Kenji; (Kanagawa, JP) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
CALSONIC KANSEI CORPORATION
|
Family ID: |
36090137 |
Appl. No.: |
11/663448 |
Filed: |
September 22, 2005 |
PCT Filed: |
September 22, 2005 |
PCT NO: |
PCT/JP2005/017455 |
371 Date: |
March 22, 2007 |
Current U.S.
Class: |
165/152 ;
72/185 |
Current CPC
Class: |
B21D 13/04 20130101;
F28F 1/128 20130101; B21D 31/046 20130101 |
Class at
Publication: |
165/152 ;
72/185 |
International
Class: |
F28F 3/02 20060101
F28F003/02; B21D 13/08 20060101 B21D013/08 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2004 |
JP |
2004-274877 |
Nov 9, 2004 |
JP |
2004-325485 |
Claims
1. A louver fin characterized by comprising: a plurality of flat
portions which are made of a strip thin sheet, and in each of which
a plurality of louvers are cut and bent along a longitudinal
direction of the strip thin sheet, are arranged parallel to each
other along a width direction of the strip thin sheet, and are
formed so that bending angles of the louvers become approximately
the same with respect to the longitudinal direction of the strip
thin sheet; and a bent portion serving as a boundary between the
flat portions and being a portion for coupling the flat portions so
that the plurality of flat portions form a corrugated shape.
2. A corrugation cutter characterized by comprising: a pair of
cutters in each of which a plurality of tooth portions are formed
along a circumferential direction, and which are combined to mesh
with each other; and characterized in that: a corrugated fin with
louvers is formed by forming alternately bent portions and flat
portions in a strip thin sheet, which is supplied between the pair
of cutters, at a predetermined pitch by using apex portions and
bottom portions of the tooth portions facing each other, and by
cutting and bending a plurality of louvers out of the flat portions
of the strip thin sheet by using a plurality of cutting and bending
edges provided on side surfaces of the tooth portions; and that an
edge angle of the cutting and bending edge provided on a side
surface of each of the tooth portions changes along a longitudinal
direction of the strip thin sheet so that the angle becomes smaller
in a cutting start portion of one of the louvers and that the angle
becomes larger in a cutting finish portion thereof.
3. A corrugation cutter characterized by comprising: a first cutter
in which a plurality of first tooth portions having triangular
shapes are formed along a circumferential direction, in which a
plurality of first cutting and bending edges for cutting and
bending louvers in a strip thin sheet are provided on side surfaces
in the circumferential direction of each of the first tooth
portions, and in which an edge angle of each of the first cutting
and bending edges gradually changes along longitudinal directions
of the first cutting and bending edges so that the angle becomes
smaller in a cutting start portion of one of the louvers, and that
the angle becomes larger in a cutting finish portions thereof; and
a second cutter which is rotationally driven in synchronization
with the first cutter so as to mesh with the first cutter; in which
a plurality of second tooth portions are formed along a
circumferential direction; in which the second tooth portions
alternately form bent portions and flat portions machine the strip
thin sheet into a corrugated shape in conjunction with the first
tooth portions by alternately forming bent portions and flat
portions of the strip thin sheet; in which a plurality of second
cutting and bending edges for cutting and bending the louvers in
the strip thin sheet in conjunction with the first tooth portions
are provided on the side surfaces in the circumferential direction
of the second tooth portions; and in which an edge angle of each of
the second cutting and bending edges gradually changes along
longitudinal directions of the cutting and bending edges so that
the angle becomes smaller in the cutting start portion of one of
the louvers, and that the angle becomes larger in the cutting
finish portion thereof.
4. A corrugation cutter characterized by comprising a pair of
cutters in each of which a plurality of tooth portions are radially
formed, and which are placed to face each other at a predetermined
distance, characterized in that: a corrugated fin with louvers is
formed by forming alternately bent portions and flat portions in a
strip thin sheet, which is supplied between the pair of cutters by
using apex portions and bottom portions of the tooth portions
facing each other, and by cutting and bending a plurality of
louvers out of the flat portions of the strip thin sheet by using a
plurality of cutting and bending edges provided on side surfaces of
the tooth portions; the cutting and bending edge provided on one
side surface of each tooth portion is formed with an edge height
which continuously increases from the apex-side edge portions
toward the bottom-side edge portions, and which becomes smallest in
an apex-side edge portion for machining a cutting start portion of
one of the louvers, and becomes largest in a bottom-side edge
portion for machining a cutting finish portion thereof, the cutting
and bending edge including an inclined edge having an edge angle
.theta. formed from the apex-side edge portions to the bottom-side
edge portions; and that the cutting and bending edge provided on
the other side surface of each tooth portion is formed with an edge
height which continuously increases from the apex-side edge
portions toward the bottom-side edge portions, and which becomes
smallest in a bottom-side edge portion for machining the cutting
start portion of the louver, and becomes largest in apex-side edge
portions for machining the cutting finish portion thereof, and the
cutting and bending edge including an inclined edge having an edge
angle .theta. formed from the bottom-side edge portions to the
apex-side edge portions.
5. A corrugation cutter characterized by comprising: a first cutter
in which a plurality of first tooth portions are formed along a
circumferential direction, in which a plurality of first cutting
and bending edges for cutting and bending louvers in a strip thin
sheet are provided on side surfaces in the circumferential
direction of each of the first tooth portions, and in which an edge
height of each of the first cutting and bending edges gradually
changes along longitudinal directions of the first cutting and
bending edges so that the height becomes smallest in a cutting
start portion of one of the louvers, and become largest in a
cutting finish portion thereof; and a second cutter which is
rotationally driven in synchronization with the first cutter so as
to mesh with the first cutter; in which a plurality of second tooth
portions are formed along a circumferential direction; in which the
second tooth portions machine the strip thin sheet into a
corrugated shape in conjunction with the first tooth portions by
alternately forming bent portions and flat portions of the strip
thin sheet; in which a plurality of second cutting and bending
edges for cutting and bending the louvers in the strip thin sheet
in conjunction with the first tooth portions are provided on the
side surfaces in the circumferential direction of the second tooth
portions; and in which an edge height of each of the second cutting
and bending edges gradually changes along longitudinal directions
of the second cutting and bending edge so that the height becomes
smallest in the cutting start portion of the louver, and becomes
largest in the cutting finish portion thereof.
6. A corrugation cutter characterized by comprising: a first cutter
in which a plurality of first tooth portions are formed along a
circumferential direction, and in which a plurality of first
cutting and bending edges for cutting and bending louvers in a
strip thin sheet are provided on side surfaces in the
circumferential direction of the first tooth portions, and in which
an edge angle e of each of the first cutting and bending edges is
constant along longitudinal directions thereof; and a second cutter
which is rotationally driven in synchronization with the first
cutter so as to mesh with the first cutter; in which a plurality of
second tooth portions are formed along a circumferential direction;
in which the second tooth portions machine the strip thin sheet
into a corrugated shape in conjunction with the first tooth
portions, by alternately forming bent portions and flat portions of
the strip thin sheet; in which a plurality of second cutting and
bending edges for cutting and bending the louvers in the strip thin
sheet in conjunction with the first tooth portions are provided on
side surfaces of the second tooth portions in the circumferential
direction; in which an edge angle .theta. of each of the second
cutting and bending edges is constant along longitudinal directions
thereof; and in which a clearance between the first cutting and
bending edge and the second cutting and bending edge gradually
changes relatively to be largest in a cutting start portion of one
of the louvers and to be smallest in a cutting finish portion
thereof.
Description
TECHNICAL FIELD
[0001] The present invention relates to a radiating louver fin used
in a heat exchanger, and a corrugation cutter for forming this
louver fin.
BACKGROUND ART
[0002] In cooling devices and air conditioners mounted on vehicles
such as automobiles, heat exchangers such as radiators, heater
cores, condensers, and evaporators are used. These heat exchangers
are configured to exchange with air via a corrugated fin that is
formed in a corrugated shape. In recent years, in order to improve
heat dissipation performance, a corrugated fin with louvers
(hereinafter referred to as a louver fin) has been developed, in
which a plurality of louvers that are obliquely open in flat
portions (sections between bent portions) of the fin are
formed.
[0003] FIG. 1 is a perspective view showing the appearance of a
typical louver fin. In a louver fin 1, a strip thin sheet 3 is
formed in a corrugated shape so that bent portions 3a and flat
portions 3b are alternately continued, and that a plurality of
louvers 5 having oblique opening directions are formed in each flat
portion 3b along the width direction.
[0004] The louver fins 1 are classified into bidirectional louver
fins and unidirectional louver fins according to the arrangement of
the louvers 5 of the flat portions 3b. The louver arrangement of a
bidirectional louver fin is shown in FIG. 2. FIG. 2 is a
cross-sectional view of the bidirectional louver fin shown in FIG.
1, when is cut in the width direction. In a bidirectional louver
fin 1A, the louvers 5 (5a and 5b) formed in one flat portion 3b are
formed to be symmetrical to each other so that the opening
directions (bending directions) thereof become opposite on the
opposite sides of a central portion Cl. Further, the louver
arrangement of a unidirectional louver fin is shown in FIG. 3. FIG.
3 is a cross-sectional view of an unillustrated unidirectional
louver fin, when is cut in the width direction. In a unidirectional
louver fin 1B, all the opening directions of the louvers 5 are
formed to be in the same direction over the entire area of one flat
portion 3b. This unidirectional louver fin 1B has advantages such
as higher heat dissipation performance and lower air-flow
resistance than those of the bidirectional louver fin 1A.
[0005] When the louvers 5 are cut and bent, the material is
stretched inward and outward in bottom portions of the louvers, and
distortion caused at this time is accumulated around side end
portions of the bent portions 3a. In the unidirectional louver fin
1B, the distortion of the louvers 5 which is caused by cutting and
bending is distributed in the same direction over the entire side
portions. Accordingly, as shown in FIG. 4, a twist occurs in the
entire fin due to the distortion, and this causes the fin to curl.
If the fin curls in this way after corrugation forming, it becomes
impossible to automate the attachment thereof to a heat exchanger
core.
[0006] Incidentally, in the bidirectional louver fin 1A, since
distortion caused when the louvers are cut and bent is brought into
balance in the central portion C1, the fin does not curl after
corrugation forming.
[0007] As a conventional technology for preventing such a
unidirectional louver fin from curling after corrugation forming, a
corrugated fin is known in which peripheral portions of a strip
metal sheet are bent to increase rigidity and to prevent the fin
from curling after shaping (JPA 2003-83691).
DISCLOSURE OF INVENTION
[0008] However, in a corrugated fin described as the conventional
technology, the process of bending peripheral portions of a strip
metal sheet is needed, and the fin width needs to be increased by a
quantity corresponding to the bending. For this reason, there has
been the problem that material yields are decreased.
[0009] To solve the above-described problem, it is desired to
develop a louver fin having such a shape in which the fin does not
curl after corrugation forming, and a corrugation cutter for
forming such a louver fin without increasing the number of
processes, and without decreasing material yields.
[0010] An object of the present invention is to provide a louver
fin which does not curl after corrugation forming, and a
corrugation cutter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a perspective view showing the appearance of a
typical louver fin.
[0012] FIG. 2 is a cross-sectional view of a bidirectional louver
fin, when is cut in the width direction.
[0013] FIG. 3 is a cross-sectional view of a unidirectional louver
fin, when is cut in the width direction.
[0014] FIG. 4 is a perspective view showing the curling state of a
unidirectional louver fin.
[0015] FIG. 5 is a perspective view showing part of a louver fin
according to a first embodiment of the present invention.
[0016] FIG. 6 is a cross-sectional view taken along line 6-6 of
FIG. 5.
[0017] FIG. 7 is an overall constitution diagram showing a process
for manufacturing the louver fin.
[0018] FIG. 8 is a perspective view showing the arrangement of a
corrugation cutter according to the first embodiment.
[0019] FIG. 9 is an enlarged partial view showing a plurality of
tooth portions shown in FIG. 8.
[0020] FIG. 10 is an exploded perspective view of a corrugation
cutter according to the first embodiment of the present
invention.
[0021] FIG. 11 is an enlarged side view of a tooth portion (for one
blade) of the corrugation cutter according to the first embodiment
of the present invention.
[0022] FIGS. 12A to 12C are cross-sectional views taken along lines
12A-12A, 12B-12B, and 12C-12C of FIG. 11.
[0023] FIG. 13 is a partial cross-sectional view showing a meshing
portion of the corrugation cutter according to the first embodiment
of the present invention.
[0024] FIG. 14 is an enlarged side view showing a tooth portion
(for one blade) of a corrugation cutter according to a second
embodiment of the present invention.
[0025] FIGS. 15A to 15C are cross-sectional views taken along lines
15A-15A, 15B-15B, and 15C-15C of FIG. 14.
[0026] FIG. 16 is a perspective view showing the arrangement of the
corrugation cutter according to the second embodiment of the
present invention.
[0027] FIG. 17 is an enlarged partial view showing a plurality of
tooth portions shown in FIG. 16.
[0028] FIG. 18 is an exploded perspective view of the corrugation
cutter according to the second embodiment of the present
invention.
[0029] FIG. 19 is a perspective view showing part of a louver fin
according to the second embodiment of the present invention.
[0030] FIG. 20 is a perspective view showing the arrangement of a
corrugation cutter according to a third embodiment of the present
invention.
[0031] FIG. 21 is an enlarged partial view of a plurality of tooth
portions shown in FIG. 20.
[0032] FIG. 22 is an exploded perspective view of the corrugation
cutter according to the third embodiment of the present
invention.
[0033] FIG. 23 is a perspective view showing part of a louver fin
according to the third embodiment of the present invention.
[0034] FIG. 24 is an enlarged side view of a tooth portion (for one
blade) of the corrugation cutter according to the third embodiment
of the present invention.
[0035] FIGS. 25A to 25C are cross-sectional views taken along lines
25A-25A, 25B-25B, and 25C-25C of FIG. 24.
[0036] FIG. 26A is an explanatory diagram showing the arrangement
of upper and lower cutters, corresponding to FIG. 25A; FIG. 26B is
an explanatory diagram showing the arrangement of the upper and
lower cutters, corresponding to FIG. 25B; and FIG. 26C is an
explanatory diagram showing the arrangement of the upper and lower
cutters, corresponding to FIG. 25C.
[0037] FIG. 27A is an explanatory cross-sectional view showing a
state in which the upper and lower cutters are cutting and bending
louvers, corresponding to FIG. 25A; FIG. 27B is an explanatory
cross-sectional view showing a state in which the upper and lower
cutters are cutting and bending the louvers, corresponding to FIG.
25B; and FIG. 27C is an explanatory cross-sectional view showing a
state in which the upper and lower cutters are cutting and bending
the louvers, corresponding to FIG. 25C.
BEST MODE FOR CARRYING OUT THE INVENTION
[0038] Hereinafter, details of louver fins and corrugation cutters
according to embodiments of the present invention will be described
with reference to drawings.
First Embodiment
[0039] FIG. 5 is a perspective view showing part (corrugated shape
for one crest) of a louver fin according to a first embodiment, and
FIG. 6 is a cross-sectional view taken along line 6-6 of FIG.
5.
[0040] A louver fin 11 described in this embodiment has a
continuous corrugated shape obtained by alternately forming bent
portions 15 and flat portions 17 in a strip thin sheet 13 made of,
for example, an aluminum member. In each flat portion 17, a
plurality of louvers 18 or 19 cut and bent along the longitudinal
direction Y of the strip thin sheet 13 are arranged parallel to
each other along the width direction X of the strip thin sheet
13.
[0041] As shown in FIG. 6, these louvers 18 and 19 are formed so
that the respective bending directions thereof are aligned with one
direction. Further, the bending directions of the louvers 18 and 19
are approximately the same angle .theta. along the longitudinal
direction Y of the strip thin sheet 13.
[0042] Here, a process for manufacturing the louver fin 11 will be
briefly described. FIG. 7 is an overall constitution diagram
showing the process for manufacturing the louver fin. When the
strip thin sheet 13 unwound from a roll 13A passes between a pair
of corrugation cutters 21A and 21B (corrugation cutter 21) placed
upper and lower positions in the traveling direction, the formation
of the bent portions 15 by corrugation forming and the cutting and
bending of the louvers 18 and 19 in the flat portions 17 by louver
forming are performed at almost the same time. Thereafter, a
resistance is applied to the feeding of a corrugated portion by
pitch adjusting rolls 23A and 23B, thus reducing the length and
adjusting the pitch of the adjacent bent portions 15. Then, the
strip thin sheet 13 is fed to a next cutting blade 25 to be cut to
a predetermined length. Thus, the louver fin 11 having a length
corresponding to the dimensions of a heat exchanger core on which
the louver fin 11 is to be mounted is completed.
[0043] Next, the structure of a corrugation cutter 21 for shaping
the louver fin 11 such as shown in FIG. 5 will be described.
[0044] FIG. 8 is a perspective view showing the arrangement of the
corrugation cutter 21 shown in FIG. 7. In the corrugation cutter 21
including the pair of (first and second) corrugation cutters 21A
and 21B, one cutter as a male cutter and the other as a female
cutter are placed so as to mesh with each other, and are
rotationally driven in the directions of arrows by an unillustrated
driving mechanism. The structure will be described below primarily
by taking the corrugation cutter 21A as an example.
[0045] In the corrugation cutter 21A, a plurality of tooth portions
31A are formed radially at a predetermined pitch along the
circumferential direction, and apex portions 33 and bottom portions
35 of the tooth portions 31A are alternately formed on the
perimeter. As shown in an enlarged partial view of FIG. 9, in each
tooth portion 31A, a plurality of cutting and bending edges 39 are
formed on one side surface 37, and a plurality of cutting and
bending edges 41 are formed on other side surface 37. Thus, the
bent portions 15 are consecutively formed in the strip thin sheet
13 at a predetermined pitch by the apex portions 33 and the bottom
portions 35 of the tooth portions 31A, and the plurality of louvers
18 and 19 such as shown in FIG. 5 are cut and bent out of the flat
portions 17 of the strip thin sheet 13 by the cutting and bending
edges 39 and 41 formed on the side surfaces 37 of the tooth
portions 31A.
[0046] FIG. 10 is an exploded perspective view of the corrugation
cutter 21A. The corrugation cutter 21A has a structure in which a
predetermined number of thin-plate blades 29 each having a
plurality of tooth portions 31A formed radially along the
circumferential direction are stacked. In each blade 29, cutting
and bending edges 39 and 41 are alternately formed at a
predetermined pitch along the circumferential direction. It should
be noted that the corrugation cutter 21A may be one formed
monolithically.
[0047] Similarly in the corrugation cutter 21B, a plurality of
tooth portions 31B are formed radially at a predetermined pitch
along the circumferential direction, a plurality of cutting and
bending edges are formed on one side surface of each tooth portion
31B, and a plurality of cutting and bending edges are formed on
other side surface thereof (reference numerals are not shown).
[0048] The corrugation cutter 21A configured as described above and
the corrugation cutter 21B pairing up therewith are placed so that
the respective tooth portions 31A and 31B thereof mesh with each
other. By the apex portions 33 of one of the corrugation cutters
21A and 21B meshing with the bottom portions 35 of the other
cutter, the bent portions 15 and the flat portions 17 are
alternately formed in the strip thin sheet 13. At the same time, by
the cutting and bending edges 39 (41) of one cutter meshing with
the cutting and bending edges 41 (39) of the other cutter, the
louvers 18 and 19 are cut and bent.
[0049] Next, the shapes of the cutting and bending edges 39 and 41
formed on the side surfaces 37 of the tooth portions 31B will be
described. FIG. 11 is an enlarged side view of the tooth portion
31B (for one blade), and FIGS. 12A to 12C are cross-sectional views
taken along lines 12A-12A, 12B-12B, and 12C-12C of FIG. 11.
[0050] In the corrugation cutter 21B of this embodiment, the edge
angles of the cutting and bending edges 39 and 41 are changed so
that the angles become smaller in cutting start portions of the
louvers 18 and 19 and that the angles become larger in cutting
finish portions.
[0051] For example, if the direction of shaping the fin is assumed
to be the direction of an arrow Z as shown in FIG. 5, the louvers
18 and 19 are cut and bent in the order from a heavy lined arrow ab
to a heavy lined arrow cd. Here, let 19a and 19b be cut and bent
portions in opposite end portions of the louver 19, and similarly
let 18c and 18d be cut and bent portions in opposite end portions
of the louver 18. The cut and bent portion 19a is the cutting start
portion of the louver 19, and the cut and bent portion 19b is the
cutting finish portion. Moreover, the cut and bent portion 18c is
the cutting start portion of the louver 18, and the cut and bent
portion 18d is the cutting finish portion.
[0052] On the other hand, in the corrugation cutter 21B, as shown
in FIGS. 11 to 12C, the edge angle of the cutting and bending edge
41 for cutting and bending the louver 19 is gradually increased so
that the edge angle becomes an edge angle of .phi.h in an edge
portion 41h for shaping the cut and bent portion 19a, an edge angle
of phi in an intermediate portion, and an edge angle of pi in an
edge portion 41i for shaping the cut and bent portion 19b. Here,
these edge angles have the relationship
.phi.i>.phi.hi>.phi.h, and the edge angle is steplessly
changed between edge angles of .phi.h and .phi.i.
[0053] Further, the edge angle of the cutting and bending edge 39
for cutting and bending the louver 18 is gradually increased so
that the edge angle becomes an edge angle of .phi.j in an edge
portion 39j for shaping the cut and bent portion 18c, an edge angle
of .phi.jk in an intermediate portion, and an edge angle of .phi.k
in an edge portion 39k for shaping the cut and bent portion 18d.
Here, these edge angles have the relationship
.phi.k>.phi.jk>.phi.j, and the edge angle is steplessly
changed between edge angles of .phi.k and .phi.j.
[0054] It should be noted that, with regard to the directions of
forming the cutting and bending edges 39 and 41, as shown in FIGS.
12A to 12C, cutting surfaces of the edges are formed to face
opposite directions on the side surfaces 37 positioned on opposite
sides of the apex portion 33 of one tooth portion 31B.
[0055] On the other hand, the corrugation cutter 21A pairing up
with the corrugation cutter 21B is also formed in about the same
shape. The edge angles of the cutting and bending edges are changed
so that the angles become smaller in cutting start portions of the
louvers 18 and 19 and that the angles become larger in cutting
finish portions. FIG. 13 is a partial cross-sectional view showing
the meshing portion between the corrugation cutters 21A and 21B.
Each cutting and bending edge of the corrugation cutter 21B is
paired with the cutting and bending edge 39 (41) of the corrugation
cutter 21A so that the directions and angles of the edges become
mirror symmetric when they are meshed with each other.
[0056] Generally, in louver forming using corrugation cutters, the
edge angles .phi. of the cutting and bending edges 39 and 41
determine the bending angles of the louvers 18 and 19. That is, the
bending angles become larger in portions in which the edge angles p
are large, and the bending angles become smaller in portions in
which the edge angles .phi. are small. In usual louver forming,
cutting and bending are neatly performed in a portion (cutting
start portion) cut and bent first. However, in a portion (cutting
finish portion) cut and bent later, cutting and bending are not
neatly performed. Accordingly, bending angles differ between cut
and bent portions at opposite ends of one louver, and distortion
occurs in the louver.
[0057] On the other hand, in the corrugation cutter 21A (21B) of
this embodiment, the edge angles of the cutting and bending edges
39 and 41 become smaller in cutting start portions of louvers, and
become larger in cutting finish portions. Accordingly, in the
cutting start portions neatly cut and bent, shaping is performed so
that the bending angles do not become larger; and, in the cutting
finish portions not neatly cut and bent, shaping is performed so
that the bending angles become larger. Accordingly, as shown in
FIG. 5, shaping can be performed so that the bending angles in the
cut and bent portions 18c, 18d, 19a, and 19b at both ends of the
louvers 18 and 19 become approximately equal. Thus, since the
bending angles in the cut and bent portions at both ends of the
louvers become approximately equal, there is no distortion in the
louvers, and a twist of the entire fin due to distortion can be
prevented. Therefore, a warp in the louver fin 11 after shaping can
be prevented.
[0058] Accordingly, in the corrugation cutter 21 described in this
embodiment, there is no need for the process of bending peripheral
portions of the strip thin sheet 13 in order to prevent a twist,
and there is also no need for increasing the fin width by a
quantity corresponding to the bending. Thus, a unidirectional
louver fin which does not warp after corrugation forming can be
obtained without increasing the number of manufacturing processes
and decreasing material utilization.
[0059] It should be noted that for the edge angles of the cutting
and bending edges 39 and 41, optimum values are individually found
according to the shape and material of the fin. These values can be
determined by performing an experiment or a simulation.
Second Embodiment
[0060] Next, a corrugation cutter according to a second embodiment
of the present invention will be described.
[0061] As a technology relating to the machining of a corrugation
cutter such as shown in the aforementioned first embodiment, a
method is known in which an inclined edge surface of a cutter is
ground at an angle so as to match the grinding surface of a
grinding stone (see JPA 1-2833). However, in the machining method
described in JPA 1-2833, since an inclined edge can be machined
only at a constant edge angle, it is technically difficult to
manufacture a corrugation cutter (gradual-change corrugation
cutter) according to the aforementioned first embodiment in which
an edge angle gradually changes. Further, a gradual-change
corrugation cutter can be machined by machining an inclined edge by
means other than a grinding process using a grinding stone, such as
a cutting process or a discharge process. However, since a cutting
process is inferior in the surface roughness of a machined surface
to a grinding process, fin shaping may be adversely affected.
Further, a discharge process takes more machining time than a
grinding process, and therefore causes an increase in cost.
[0062] In view of this, in the second embodiment, a corrugation
cutter is provided which has functions equivalent to those of the
corrugation cutter that can form the louver fin according to the
first embodiment and that have edge angles gradually changing, and
which can be manufactured by a grinding process.
[0063] First, the basic structure of the corrugation cutter
according to the second embodiment will be described using FIGS. 16
to 18. FIG. 16 is a perspective view showing the arrangement of the
corrugation cutter. FIG. 17 is an enlarged partial view of tooth
portions. FIG. 18 is an exploded perspective view of the
corrugation cutter. FIG. 19 is a perspective view showing part
(corrugated shape for one crest) of a louver fin.
[0064] As shown in FIG. 16, a corrugation cutter 121 includes a
pair of (first and second) corrugation cutters 121A and 121B. The
corrugation cutters 121A and 121B are placed so that one as a male
cutter and the other as a female cutter mesh with each other, and
are rotationally driven in the directions of arrows by an
unillustrated driving mechanism. The following description will be
given by taking the corrugation cutter 121A as an example.
[0065] In the corrugation cutter 121A, a plurality of tooth
portions 131A are formed radially at a predetermined pitch along
the circumferential direction, and apex portions 133 and bottom
portions 135 of the tooth portions 131A are alternately formed on
the perimeter. As shown in FIG. 17, in each tooth portion 131A, a
plurality of cutting and bending edges (shapes of the edges are not
shown) 139 are formed on one side surface 137a, and a plurality of
cutting and bending edges (shapes of the edges are not shown) 141
are formed on other side surface 137b.
[0066] As shown in FIG. 18, the corrugation cutter 121A has a
structure in which a predetermined number of thin-plate blades 129
each having a plurality of tooth portions 131A formed radially
along the circumferential direction are stacked. In each blade 129,
cutting and bending edges 139 and 141 are alternately formed at a
predetermined pitch along the circumferential direction. It should
be noted, however, that the corrugation cutter is not limited to a
structure in which a plurality of members are stacked, and may be
one formed monolithically.
[0067] Similarly, in the corrugation cutter 121B, a plurality of
tooth portions 131B are formed radially at a predetermined pitch
along the circumferential direction, a plurality of cutting and
bending edges are formed on one side surface of each tooth portion
131B, and a plurality of cutting and bending edges are formed on
other side surface thereof (reference numerals are not shown).
[0068] As shown in FIG. 16, when the corrugation cutter 121A having
the above-described cutting and bending edges 139 and 141 formed
therein and the corrugation cutter 121B having cutting and bending
edges formed therein which have the same structures are meshed with
each other and rotationally driven, and a strip thin sheet 113 is
supplied between these cutters, the apex portions 133 of one
corrugation cutter mesh with the bottom portions 135 of the other
corrugation cutter, and bent portions 115 and flat portions 117 are
alternately formed in the strip thin sheet 113 such as shown in
FIG. 19. At the same time, by the cutting and bending edges 139
(141) of one corrugation cutter meshing with the cutting and
bending edges 139 (141) of the other corrugation cutter, a
plurality of louvers 118 and 119 are cut and bent out of the flat
portions 117 of the strip thin sheet 113, thus obtaining a louver
fin 111.
[0069] Next, the shapes of the cutting and bending edges 139 and
141 formed on the side surfaces 137a and 137b of the tooth portions
131A (131B) will be described. FIG. 14 is an enlarged partial view
showing the shapes of side surfaces of adjacent tooth portions
131B. FIGS. 15A to 15C are cross-sectional views taken along lines
15A-15A, 15B-15B, and 15C-15C of FIG. 14, showing the mesh of
cutting and bending edges, and showing a virtual cross section at
the time when the corrugation cutters 121A and 121B mesh with each
other.
[0070] In the corrugation cutter 121B of this embodiment, as shown
in FIG. 14, the cutting and bending edge 139 provided on one side
surface 137a of the tooth portion 131B is shaped (ground down) so
that an edge height hi becomes smallest in an apex-side edge
portion 139a for machining the cutting start portion of the louver
118, that an edge height h2 becomes largest in a bottom-side edge
portion 139a for machining the cutting finish portion of the louver
118, and that the edge height continuously increases from the
apex-side edge portion 139a toward the bottom-side edge portion
139b.
[0071] Here, as shown in FIG. 19, a louver 118 is cut and bent in
the direction of an arrow from a cutting start portion 118a toward
a cutting finish portion 118b, and a louver 119 is cut and bent in
the direction of an arrow from a cutting start portion 119c toward
a cutting finish portion 119d (the direction of shaping the fin is
assumed to be the direction of an arrow a) The edge heights h1 and
h2 are represented as heights from a chain line showing the shape
of an original gear. It should be noted that a two-dot chain line
indicates an edge height before the edge heights h1 and h2 are
provided in this embodiment. That is, the two-dot chain line
indicates a shape obtained by attaching an edge to the shape of the
original gear.
[0072] Accordingly, the cross sections of the cutting and bending
edge 139 are the same from the apex-side edge portion 139a to the
bottom-side edge portion 139b. However, in this embodiment, by
continuously cutting down the edge height of the cutting and
bending edge 139 from the position of the two-dot chain line, the
thickness t (land width) of the cutting and bending edge 139 in the
width direction thereof gradually decreases from the apex-side edge
portion 139a toward the bottom-side edge portion 139b.
[0073] Further, an inclined edge 140 is shaped at the same edge
angle .theta. from the apex-side edge portion 139a to the
bottom-side edge portion 139b. The two-dot chain line shown in FIG.
14 indicates a line for the case where shaping is performed at the
edge angle .theta. from the apex-side edge portion 139a to the
bottom-side edge portion 139b. In this embodiment, since the edge
height is continuously cut down from the apex-side edge portion
139a toward the bottom-side edge portion 139b, the range outside
the solid line of the cutting and bending edge 139 indicates a
region in which the inclined edge 140 is not actually machined.
[0074] Moreover, a cutting and bending edge 141 provided on the
other side surface 137b of the tooth portion 131B is shaped (ground
down) so that the edge height h1 is smallest in a bottom-side edge
portion 141a for machining the cutting start portion 119c of the
louver 119 shown in FIG. 19, that the edge height h2 is largest in
an apex-side edge portion 141b for machining the cutting finish
portion 119d of the louver 119, and that the edge height
continuously increases from the apex-side edge portion 141a toward
the bottom-side edge portion 141b.
[0075] Accordingly, the cross section of the cutting and bending
edge 141 is the same from the bottom-side edge portion 141a to the
apex-side edge portion 141b. However, in this embodiment, by
continuously cutting down the edge height of the cutting and
bending edge 141 from the position of the two-dot chain line, the
thickness t (land width) of the cutting and bending edge 141 in the
width direction thereof gradually decreases from the bottom-side
edge portion 141a toward the apex-side edge portion 141b.
[0076] Further, an inclined edge 142 is shaped at the same edge
angle .theta. from the bottom-side edge portion 141a to the
apex-side edge portion 141b. The two-dot chain line shown in FIG.
14 indicates a line for the case where shaping is performed at the
edge angle .theta. from the bottom-side edge portion 141a to the
apex-side edge portion 141b. In this embodiment, since the edge
height is continuously cut down from the bottom-side edge portion
141a toward the apex-side edge portion 141b, the range outside the
solid line of the cutting and bending edge 141 indicates a region
in which the inclined edge 142 is not actually machined.
[0077] In the tooth portions 131A of the corrugation cutter 121A
pairing up with the above-described corrugation cutter 121B,
cutting and bending edges (hereinafter denoted by 139A and 191A)
similar to those of the tooth portions 131B are formed. Further,
when the corrugation cutters 121A and 121B are meshed with each
other, the cutting and bending edges 139 provided on the side
surfaces 137a of the tooth portions 131B of the corrugation cutter
121B face the cutting and bending edges 139A provided on the side
surfaces 137a of the tooth portions 131A of the corrugation cutter
121A, and the cutting and bending edges 141 provided on the side
surfaces 137b of the tooth portions 131B of the corrugation cutter
121B face the cutting and bending edges 141A provided on the side
surfaces 137b of the tooth portions 131A of the corrugation cutter
121A. Thus, each cutting and bending edge 139 (141) of the
corrugation cutter 121B is paired with the cutting and bending edge
139A (141A) of the corrugation cutter 121A so that the directions
and angles of the edges become mirror symmetric when they are
meshed with each other.
[0078] Next, the action of the corrugation cutter 121 according to
this embodiment will be described. Here, a description will be
given for the case where the louver 119 is cut and bent in the
direction of an arrow from the cutting start portion 119c toward
the cutting finish portion 119d in FIG. 19.
[0079] In the machining of the cutting start portion 119c of the
louver 119, as shown in FIG. 15A which is a cross section taken
along line 15A-15A of FIG. 14, the flat portion 117 of the strip
thin sheet 113 is cut and bent between the bottom-side edge portion
141a of the cutting and bending edge 141 of the corrugation cutter
121B and the apex-side edge portion 141b of the cutting and bending
edge 141A of the corrugation cutter 121A. At this time, the flat
portion 117 is cut and bent at a bending angle of .phi.a along the
line connecting a corner portion 142b of the inclined edge
(hereinafter referred to as an upper inclined edge) 142 of the
corrugation cutter 121A and a corner portion 142a of the inclined
edge (hereinafter referred to as a lower inclined edge) 142 of the
corrugation cutter 121B.
[0080] In the machining of an intermediate cut and bent portion
119cd of the louver 119, as shown in FIG. 15B which is a cross
section taken along line 15B-15B of FIG. 14, the flat portion 117
of the strip thin sheet 113 is cut and bent between an intermediate
edge portion 141ab of the cutting and bending edge 141 of the
corrugation cutter 121B and an intermediate edge portion 141a of
the corrugation cutter 121A. At this time, the flat portion 117 is
cut and bent at a bending angle of .phi.b along the line connecting
a corner portion 142ab of the upper inclined edge 142 and a corner
portion 142ab of the lower inclined edge 142.
[0081] In the machining of a cutting finish portion 119d of the
louver 119, as shown in FIG. 15C which is a cross section taken
along line 15C-15C of FIG. 14, the flat portion 117 of the strip
thin sheet 113 is cut and bent between the apex-side edge portion
141b of the cutting and bending edge 141 of the corrugation cutter
121B and the bottom-side edge portion 141a of the cutting and
bending edge 141A of the corrugation cutter 121A. At this time, the
flat portion 117 is cut and bent at a bending angle of .phi.c along
the line connecting a corner portion 141a of the upper inclined
edge 142 and a corner portion 142b of the lower inclined edge
142.
[0082] As described above, in the corrugation cutters 121A and 121B
of this embodiment, since the width-direction thicknesses t of the
cutting and bending edges 139 and 141 gradually changes from t1 to
t3 (t1>t2>t3) while the edge angles .theta. thereof are made
constant, the bending angles of the inclined edges 140 and 142 also
change continuously. Accordingly, the louvers formed in the strip
thin sheet 113 are shaped so that the bending angles .phi. become
smaller (.phi.a) in cutting start portions and that the bending
angles .phi. become larger (.phi.c) in cutting finish portions.
[0083] Generally, in louver forming using corrugation cutters, the
edge angles .phi. of the cutting and bending edges 139 and 141
determine the bending angles of louvers. That is, the bending
angles .phi. become larger when machining is performed using
portions in which the edge angles .theta. are large, and the
bending angles .phi. become smaller when machining is performed
using portions in which the edge angles .theta. are small. In usual
louver forming, cutting and bending are neatly performed in a
portion (cutting start portion) cut and bent first. However, in a
portion (cutting finish portion) cut and bent later, cutting and
bending are not neatly performed. Accordingly, bending angles
differ between opposite ends of one louver, and distortion occurs
in the louver.
[0084] On the other hand, with the corrugation cutters 121A (121B)
of this embodiment, the bending angle .phi. becomes smaller
(.phi.a) in the cutting start portion of a louver and becomes
larger (.phi.c) in the cutting finish portion. Accordingly, as in
the case where shaping is performed using a gradual-change
corrugation cutter, in the cutting start portion neatly cut and
bent originally, shaping is performed so that the bending angle
does not become larger; and, in the cutting finish portion not
neatly cut and bent, shaping is performed so that the bending angle
becomes larger. Accordingly, as shown in FIG. 19, the bending
angles .phi. in the cutting start portion 118a and the cutting
finish portion 118b of the louver 118 and those in the cutting
start portion 119c and the cutting finish portion 119d of the
louver 119 can be made approximately equal after shaping. Thus,
since the bending angles in opposite end portions of the louvers
118 and 119 shaped in one direction are made approximately equal,
there is no distortion in the louvers, and a twist of the entire
fin due to distortion can be prevented. Therefore, a warp in the
louver fin 111 after shaping can be prevented.
[0085] Moreover, in the corrugation cutters 121A and 121B of this
embodiment, since the edge angles .theta. can be made constant, a
corrugation cutter can be manufactured which has functions
equivalent to those of the gradual-change corrugation cutter
according to the aforementioned first embodiment. According to this
second embodiment, since the inclined edges 140 and 142 are
machined by not a cutting process but a grinding process, the
surface roughness of machined surfaces can be made equivalent to
that of current ones, and adverse affects on fin shaping can be
avoided. Further, unlike a discharge process, a long machining time
is not required. Therefore, an increase in cost can be avoided.
[0086] It should be noted that for the edge heights and edge angles
of the cutting and bending edges 139 and 141, optimum values are
individually found according to the shape and material of the fin.
These values can be determined by performing an experiment or a
simulation.
Third Embodiment
[0087] Next, a corrugation cutter according to a third embodiment
of the present invention will be described.
[0088] In the machining method described in the aforementioned JPA
1-2833, since an inclined edge can be machined only at a constant
edge angle, it is technically difficult to manufacture a
corrugation cutter (gradual-change corrugation cutter) according to
the aforementioned first embodiment in which an edge angle
gradually changes. Further, a gradual-change corrugation cutter can
be machined by machining an inclined edge by means other than a
grinding process using a grinding stone, such as a cutting process
or a discharge process. However, since a cutting process is
inferior in the surface roughness of a machined surface to a
grinding process, fin shaping may be adversely affected. Further, a
discharge process takes more machining time than a grinding
process, and therefore causes an increase in cost.
[0089] In view of this, in the third embodiment, a corrugation
cutter is provided which has functions equivalent to those of the
corrugation cutter according to the aforementioned first embodiment
having edge angles gradually changing, and which can be
manufactured by a grinding process.
[0090] First, the basic structure of the corrugation cutter
according to the third embodiment will be described using FIGS. 20
to 23. FIG. 20 is a perspective view showing the arrangement of the
corrugation cutter. FIG. 21 is an enlarged partial view of tooth
portions. FIG. 22 is an exploded perspective view of the
corrugation cutter. FIG. 23 is a perspective view showing part
(corrugated shape for one crest) of a louver fin.
[0091] As shown in FIG. 20, a corrugation cutter 221 includes a
pair of (first and second) corrugation cutters 221A and 221B. The
corrugation cutters 221A and 221B are placed so that one as a male
cutter and the other as a female cutter mesh with each other, and
are rotationally driven in the directions of arrows by an
unillustrated driving mechanism. The following description will be
given by taking the corrugation cutter 221A as an example.
[0092] In the corrugation cutter 221A, a plurality of tooth
portions 231A are formed radially at a predetermined pitch along
the circumferential direction, and apex portions 233 and bottom
portions 235 of the tooth portions 231A are alternately formed on
the perimeter. As shown in FIG. 21, in each tooth portion 231A, a
plurality of cutting and bending edges (shapes of the edges are not
shown) 239 are formed on one side surface 237a, and a plurality of
cutting and bending edges (shapes of the edges are not shown) 241
are formed on other side surface 237b.
[0093] As shown in FIG. 22, the corrugation cutter 221A has a
structure in which a predetermined number of thin-plate blades 229
each having a plurality of tooth portions 231A formed radially
along the circumferential direction are stacked. In each blade 229,
cutting and bending edges 239 and 241 are alternately formed at a
predetermined pitch along the circumferential direction. It should
be noted, however, that the corrugation cutter is not limited to a
structure in which a plurality of members are stacked, and may be
one formed monolithically.
[0094] Similarly, in the corrugation cutter 221B, a plurality of
tooth portions 231B are formed radially at a predetermined pitch
along the circumferential direction, a plurality of cutting and
bending edges are formed on one side surface of each tooth portion
231B, and a plurality of cutting and bending edges are formed on
other side surface thereof (reference numerals are not shown).
[0095] When the corrugation cutter 221A having the above-described
cutting and bending edges 239 and 241 formed therein and the
corrugation cutter 221B having cutting and bending edges formed
therein which have the same structures are meshed with each other
and rotationally driven, and a strip thin sheet 213 is supplied
between these cutters as shown in FIG. 20, the apex portions 233 of
one corrugation cutter mesh with the bottom portions 235 of the
other corrugation cutter, and bent portions 215 and flat portions
217 such as shown in FIG. 23 are alternately formed in the strip
thin sheet 213. At the same time, by the cutting and bending edges
239 (241) of one corrugation cutter meshing with the cutting and
bending edges 239 (241) of the other corrugation cutter, a
plurality of louvers 218 and 219 are cut and bent out of the flat
portions 217 of the strip thin sheet 213, thus obtaining a louver
fin 211.
[0096] Next, the shapes of the cutting and bending edges 239 and
241 formed on the side surfaces 237a and 237b of each tooth portion
231A (231B) will be described. FIG. 24 is an enlarged partial view
showing the shapes of side surfaces of adjacent tooth portions
231B. FIGS. 25A to 25C are cross-sectional views taken along lines
25A-25A, 25B-25B, and 25C-25C of FIG. 24, showing the mesh of
cutting and bending edges, and showing a virtual cross section at
the time when the corrugation cutters 221A and 221B mesh with each
other.
[0097] It should be noted that FIG. 26A shows a state in which
cutting and bending edges start cutting the louver 219, and a cross
section of the mesh thereof corresponds to FIG. 25A. FIG. 26B shows
a state in which the cutting and bending edges are cutting an
intermediate portion 219c d of the louver 219, and a cross section
of the mesh thereof corresponds to FIG. 25B. FIG. 26C shows a state
in which the cutting and bending edges are cutting a cutting and
bending finish portion 219d of the louver 219, and a cross section
of the mesh thereof corresponds to FIG. 25C. Moreover, FIGS. 27A to
27C are views showing the states of the flat portion 217 actually
cut and bent by the corrugation cutters 221A and 221B at mesh
positions corresponding to FIGS. 25A to 25C, respectively.
[0098] In the corrugation cutter 221B of this embodiment, as shown
in FIG. 24, the cutting and bending edge 239 provided on one side
surface 237a of the tooth portion 231B is set so that the thickness
(land width) of the edge in the width direction thereof becomes
equal between an apex-side edge portion 239a for machining a
cutting start portion 218a of the louver 218 shown in FIG. 23 and a
bottom-side edge portion 239b for machining the cutting finish
portion 218b of the louver 218. As shown in FIG. 24, the cutting
and bending edges 239 and 241 are formed so that the angles and
land widths of inclined edges are made constant from the apex-side
edge portions to the bottom-side edge portions, and the lengths
(portions denoted by ha, hb, and hc) vary by which the inclined
edges protrude from the portions indicated by chain lines.
[0099] Here, as shown in FIG. 23, the louver 218 is cut and bent in
the direction of an arrow from the cutting start portion 218a
toward the cutting finish portion 218b, and the louver 219 is cut
and bent in the direction of an arrow from the cutting start
portion 219c toward the cutting finish portion 219d (the direction
of shaping the fin is assumed to be the direction of an arrow
a).
[0100] In this embodiment, as shown in FIGS. 25A to 25C, inclined
edges 240 and 242 are formed so that the edge angles of the cutting
and bending edges 239 and 241 of the corresponding tooth portions
231A and 231B of the corrugation cutters 221A and 221B are the same
angle .theta. over the longitudinal directions of the edges. These
inclined edges 240 and 242 are formed by being ground down.
Further, the edges denoted by the same reference numeral of the
inclined edges 240 and 242 of the cutting and bending edges 239 and
241 are set so as to be parallel to each other with a predetermined
clearance c provided therebetween in a state in which they mesh
with each other.
[0101] Hereinafter, the clearance c will be described with
reference to FIGS. 24 to 27C.
[0102] This clearance c is set so that the distance between the
inclined edges 240 becomes a large clearance c1 as shown in FIG.
25A at a position (see FIG. 26A) 241a at which the louver 219
starts being cut. The flat portion 217 to be cut and bent is cut
and bent at a bending angle of .phi.a along the line connecting a
corner portion 242a of the inclined edge (hereinafter referred to
as an upper inclined edge) 242 of the corrugation cutter 221A and a
corner portion 242a of the inclined edge (hereinafter referred to
as a lower inclined edge) 242 of the corrugation cutter 221B.
[0103] Next, in the machining of the intermediate cut and bent
portion 219cd of the louver 219, as shown in FIG. 25B which is a
cross-sectional view taken along line 25B-25B at a position 241ab
of FIG. 24, an intermediate-level clearance c2 is set. Further, the
flat portion 217 of the strip thin sheet 213 is cut and bent
between an intermediate edge portion 241ab of the cutting and
bending edge 241 of the corrugation cutter 221B and an intermediate
edge portion 241ab of the corrugation cutter 221A. At this time,
the flat portion 217 is cut and bent at a bending angle of .phi.b
along the line connecting a corner portion 242ab of the upper
inclined edge 242 and a corner portion 242ab of the lower inclined
edge 242.
[0104] Next, in the machining of the cutting and bending end point
position 219d of the louver 219, as shown in FIG. 25 which is a
cross-sectional view taken along line 25C-25C at a position 241b of
FIG. 24, a small clearance c3 is set. Further, as shown in FIG.
25C, the flat portion 217 of the strip thin sheet 213 is cut and
bent between an end-point-side edge portion 241b of the cutting and
bending edge 241 of the corrugation cutter 221B and an edge portion
241a of the corrugation cutter 221A. At this time, the flat portion
217 is cut and bent at a bending angle of .phi.c along the line
connecting a corner portion 242a of the upper inclined edge 242 and
a corner portion 242b of the lower inclined edge 242. In this way,
in the cutting and bending edges of the corrugation cutter of this
embodiment, the clearances c1, c2, and c3 are determined by the
protruding quantities (ha, hb, and hc) of the inclined edges.
[0105] Next, the action of the corrugation cutter 221 according to
this embodiment will be described. Here, a description will be
given for the case where the louver 219 is cut and bent in the
direction of an arrow from the cutting start portion 219c toward
the cutting finish portion 219d in FIG. 23.
[0106] In the machining of the cutting start portion 219c of the
louver 219, as shown in FIG. 25A which is a cross section taken
along line 25A-25A of FIG. 24, the flat portion 217 of the strip
thin sheet 213 is cut and bent between the bottom-side edge portion
241a of the cutting and bending edge 241 of the corrugation cutter
221B and the edge portion 241b of the corrugation cutter 221A. At
this time, the flat portion 217 of the strip thin sheet 213 is cut
and bent at a bending angle of pa with the clearance c1 along the
line connecting the corner portion 242b of the upper inclined edge
242 and the corner portion 242a of the lower inclined edge 242.
[0107] In the machining of the intermediate cut and bent portion
219cd of the louver 219 shown in FIG. 23, as shown in FIG. 25B
which is a cross section taken along line 25B-25B of FIG. 24, the
flat portion 217 of the strip thin sheet 213 is cut and bent
between the intermediate edge portion 241ab of the cutting and
bending edge 241 of the corrugation cutter 221B and the
intermediate edge portion 241ab of the corrugation cutter 221A. At
this time, the flat portion 217 is cut and bent at a bending angle
of .phi.b with a clearance of c2 along the line connecting the
corner portion 242ab of the upper inclined edge 242 and the corner
portion 242ab of the lower inclined edge 242.
[0108] In the machining of the cutting finish portion 219d of the
louver 219, as shown in FIG. 25C which is a cross section taken
along line 25C-25C of FIG. 24, the flat portion 217 of the strip
thin sheet 213 is cut and bent between the apex-side edge portion
241b of the cutting and bending edge 241 of the corrugation cutter
221B and the edge portion 241a of the corrugation cutter 221A. At
this time, the flat portion 217 is cut and bent at a bending angle
of .phi.c with clearance c3 along the line connecting the corner
portion 242a of the upper inclined edge 242 and the corner portion
242b of the lower inclined edge 242.
[0109] As described above, in the corrugation cutters 221A and 221B
of this embodiment, since only the clearance c is gradually changed
(c3<c2<c1) while the edge angles .theta. of the cutting and
bending edges 239 and 241 are made constant as shown in FIGS. 25A
to 25C, the bending angles of the inclined edges 240 and 242 also
change continuously. Accordingly, the louvers formed in the strip
thin sheet 213 are shaped so that the bending angles .phi. become
smaller (.phi.a) in cutting start portions and that the bending
angles .phi. become larger (.phi.c) in cutting finish portions.
[0110] Generally, in louver forming using corrugation cutters, the
edge angles .theta. of the cutting and bending edges 239 and 241
determine the bending angles of louvers. That is, the bending
angles .phi. become larger when machining is performed using
portions in which the edge angles .theta. are large, and the
bending angles .phi. become smaller when machining is performed
using portions in which the edge angles .theta. are small. In usual
louver forming, cutting and bending are neatly performed in a
portion (cutting start portion) cut and bent first. However, in a
portion (cutting finish portion) cut and bent later, cutting and
bending are not neatly performed. Accordingly, bending angles
differ between opposite ends of one louver, and distortion occurs
in the louver.
[0111] On the other hand, with the corrugation cutters 221A (221B)
of this embodiment, the bending angle .phi. becomes smaller
(.phi.a) in the cutting start portion of a louver and becomes
larger (.phi.c) in the cutting finish portion. Accordingly, as in
the case where shaping is performed using a gradual-change
corrugation cutter, in the cutting start portion neatly cut and
bent performed originally, shaping is performed so that the bending
angle does not become larger; and, in the cutting finish portion
not neatly cut and bent, shaping is performed so that the bending
angle becomes larger. Accordingly, as shown in FIG. 23, the bending
angles in the cutting start portion 218a and the cutting finish
portion 218b of the louver 218 and those in the cutting start
portion 219c and the cutting finish portion 219d of the louver 219
can be made approximately equal after shaping. Thus, since the
bending angles in opposite end portions of the louvers 218 and 219
shaped in one direction are made approximately equal, there is no
distortion in the louvers, and a twist of the entire fin due to
distortion can be prevented. Therefore, a warp in the louver fin
211 after shaping can be prevented.
[0112] Moreover, in the corrugation cutters 221A and 221B of this
embodiment, since the edge angles .theta. can be made constant, a
corrugation cutter can be easily manufactured which has functions
equivalent to those of the corrugation cutter according to the
aforementioned first embodiment. According to this third
embodiment, since the inclined edges 240 and 242 are machined by
not a cutting process but a grinding process, the surface roughness
of machined surfaces can be made equivalent to that of current
ones, and adverse affects on fin shaping can be avoided. Further,
unlike a discharge process, a long machining time is not required.
Therefore, an increase in cost can be avoided.
[0113] It should be noted that for the edge heights and edge angles
of the cutting and bending edges 239 and 241, optimum values are
individually found according to the shape and material of the fin.
These values can be determined by performing an experiment or a
simulation.
INDUSTRIAL APPLICABILITY
[0114] Corrugation cutters according to the present invention can
be applied to heat exchangers including a radiator mounted on a
vehicle such as an automobile, and a heater core, a condenser, an
evaporator, and the like used in an air conditioner, and are useful
particularly in manufacturing a unidirectional louver fin suitable
for these heat exchangers.
* * * * *