U.S. patent application number 09/730800 was filed with the patent office on 2001-06-07 for ventilated disc.
This patent application is currently assigned to Akebono Brake Industry Co., Ltd. Invention is credited to Kobayashi, Tadashi.
Application Number | 20010002638 09/730800 |
Document ID | / |
Family ID | 18391626 |
Filed Date | 2001-06-07 |
United States Patent
Application |
20010002638 |
Kind Code |
A1 |
Kobayashi, Tadashi |
June 7, 2001 |
Ventilated disc
Abstract
An inner disc portion and an outer disc portion are connected
through first to fifth connecting ribs. The second and third
connecting ribs which are provided on the outer diameter side are
inclined reversely to each other so that a portion where the
distance between outer-diameter-side end portions of the second and
third connecting ribs is wider and a portion where the distance is
narrower are provided alternately. The fourth connecting ribs are
provided in the portions where the distance is wider respectively.
In addition, each of the fifth connecting ribs are provided between
the first connecting ribs and the second and third connecting ribs
respectively. The inclination angle .theta. of the second and third
connecting ribs is regulated so that the distances between the end
portions of the respective ribs are equal to one another.
Inventors: |
Kobayashi, Tadashi; (Tokyo,
JP) |
Correspondence
Address: |
MORGAN, LEWIS & BOCKIUS
1800 M STREET NW
WASHINGTON
DC
20036-5869
US
|
Assignee: |
Akebono Brake Industry Co.,
Ltd
|
Family ID: |
18391626 |
Appl. No.: |
09/730800 |
Filed: |
December 7, 2000 |
Current U.S.
Class: |
188/218XL ;
188/264AA |
Current CPC
Class: |
F16D 2065/1328 20130101;
F16D 2200/0013 20130101; F16D 65/128 20130101 |
Class at
Publication: |
188/218.0XL ;
188/264.0AA |
International
Class: |
F16D 065/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 1999 |
JP |
P.HEI. 11-347644 |
Claims
What is claimed is:
1. A ventilated disc comprising: a ring-like inner disc portion; a
ring-like outer disc portion; and connecting ribs for connecting
surfaces of said inner and outer disc portions, said connecting
ribs including: first connecting ribs provided between
inner-diameter-side portions of said inner and outer disc portions
and long in radial directions of said inner and outer disc
portions; second and third connecting ribs provided alternately
circumferentially between outer-diameter-side portions of said
inner and outer disc portions and inclined reversely to each other
with respect to radial directions of said inner and outer disc
portions, fourth connecting ribs provided at a circumferentially
central portion of a largest distance between adjacent ones of said
second and third connecting ribs and between said
outer-diameter-side portions of said inner and outer disc portions,
wherein said inner and outer disc portions are in opposite to each
other parallelly and coaxially at a predetermined distance
therebetween.
2. The ventilated disc according to claim 1, wherein the second and
third connecting ribs are provided so that a circumferential phase
of inner-diameter-side end portions of said second and third
connecting ribs coincides with that of the first connecting
ribs.
3. The ventilated disc according to claim 1, wherein said
connecting ribs further include fifth connecting ribs provided
between radially intermediate portions of said inner and outer disc
portions, and a circumferential phase of the fifth connecting ribs
is shifted by half a pitch from that of said first connecting
ribs.
4. The ventilated disc according to claim 2, wherein said
connecting ribs further include fifth connecting ribs provided
between radially intermediate portions of said inner and outer disc
portions, and a circumferential phase of the fifth connecting ribs
is shifted by half a pitch from that of said first connecting
ribs.
5. The ventilated disc according to claim 3, wherein a length of
the fifth connecting ribs is made larger than a length of each of a
radial gap located between the first connecting rib and one of the
second and third connecting ribs.
6. The ventilated disc according to claim 1, wherein the first to
fourth connecting ribs define: a first distance between
inner-diameter-side end portions of circumferentially adjacent ones
of the first connecting ribs; a second distance between
outer-diameter-side end portions of circumferentially adjacent ones
of the second and third connecting ribs and being the narrowest
one; a third distance between outer-diameter-side end portions of
circumferentially adjacent ones of the second and fourth connecting
ribs; and a fourth distance between outer-diameter-side end
portions of circumferentially adjacent ones of the third and fourth
connecting ribs, wherein the first to fourth distances are
substantially equal to one another.
7. The ventilated disc according to claim 2, wherein the first to
fourth connecting ribs define: a first distance between
inner-diameter-side end portions of circumferentially adjacent ones
of the first connecting ribs; a second distance between
outer-diameter-side end portions of circumferentially adjacent ones
of the second and third connecting ribs and being the narrowest
one; a third distance between outer-diameter-side end portions of
circumferentially adjacent ones of the second and fourth connecting
ribs; and a fourth distance between outer-diameter-side end
portions of circumferentially adjacent ones of the third and fourth
connecting ribs, wherein the first to fourth distances are
substantially equal to one another.
8. The ventilated disc according to claim 3, wherein the first to
fourth connecting ribs define: a first distance between
inner-diameter-side end portions of circumferentially adjacent ones
of the first connecting ribs; a second distance between
outer-diameter-side end portions of circumferentially adjacent ones
of the second and third connecting ribs and being the narrowest
one; a third distance between outer-diameter-side end portions of
circumferentially adjacent ones of the second and fourth connecting
ribs; and a fourth distance between outer-diameter-side end
portions of circumferentially adjacent ones of the third and fourth
connecting ribs, wherein the first to fourth distances are
substantially equal to one another.
9. The ventilated disc according to claim 6, wherein a difference
between the largest one and the smallest one among the first to
fourth distances is within 20% in view of the largest one.
10. The ventilated disc according to claim 6, wherein a difference
between the largest one and the smallest one among the first to
fourth distances is within 10% in view of the largest one.
11. The ventilated disc according to claim 1, wherein the sectional
shape of each of the second and third connecting ribs is formed as
curved line and to be symmetric with each other with respect to the
radial direction.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The ventilated disc according to the present invention is
used in the state where the ventilated disc has been incorporated
in a disc brake for braking a vehicle.
[0003] Disc brakes are hitherto used broadly as braking apparatus
for braking vehicles. FIG. 7 shows a disc brake presented in JIS D
0107. A piston 4 is fluid-tightly fitted into a cylinder 3 provided
in a cylinder body 2 supported on a stationary portion astride a
disc 1 in which the disc 1 which rotates together with a wheel is
supported. At the time of braking, pressure fluid is supplied into
the cylinder 3 so that a pair of pads 5 and 5 provided on opposite
sides of the disc 1 are pressed against the opposite sides of the
disc 1.
[0004] Other than such a solid disc 6 as shown in FIG. 8, a
ventilated disc 7 shown in FIG. 9 is hitherto used as the disc 1
forming such a disc brake. The ventilated disc 7 has a ring-like
inner disc portion 8, a ring-like outer disc portion 9, and a large
number of connecting ribs (radiator fins) 10. The inner and outer
disc portions 8 and 9 are disposed parallelly and coaxially at a
distance from each other. The connecting ribs 10 connect respective
surfaces of the disc portions 8 and 9 facing each other. Each air
channel 11 radially extending is formed between the
circumferentially adjacent connecting ribs 10. Such a ventilated
disc 7 is fixedly attached to a hub unit which supports the wheel
rotatably on the stationary portion, by an attachment portion 12
provided coaxially with the disc portions 8 and 9. When the vehicle
is running, the ventilated disc 7 rotates together with the wheel
and the air flows in the respective air channels 11 from the inner
diameter side to the outer diameter side by centrifugal force to
thereby cool the ventilated disc 7.
[0005] Such a ventilated disc 7 is employed chiefly in a
high-performance vehicle, or the like, which needs great braking
ability. Generally, in the conventional ventilated disc 7, as shown
in FIG. 10, a plurality of connecting ribs 10 are arranged
radially. However, as shown in FIG. 11, a ventilated disc in which
connecting ribs 10a are inclined in the direction of rotation of
the ventilated disc is also known conventionally.
[0006] Further, as shown in FIG. 12, a ventilated disc in which
connecting ribs 10b each bent like an arc are inclined in the
direction of rotation is also known conventionally, for example, as
disclosed in JP-A-8-164828 and JP-B-54-14710. In the ventilated
disc in which the connecting ribs 10a or 10b are inclined in the
direction of rotation as described above, the pumping effect due to
rotation becomes large. Accordingly, when a large amount of heat is
generated in braking at the time of high-speed running, a large
amount of air is made flow in the air channels 11a or 11b between
circumferentially adjacent ones of the connecting ribs 10a or 10b.
As a result, the effect of restraining the temperature rising of
the ventilated disc is remarkable. In the case of using the
ventilated disc shown in FIGS. 11 or 12, however, it is necessary
to regulate the direction of rotation of the ventilated disc (the
counterclockwise direction in FIGS. 11 or 12) in order to circulate
a large amount of air into the air channels 11a or 11b. It is
therefore impossible to standardize parts of the ventilated disc
between right and left sides of the vehicle.
[0007] In the case of such a ventilated disc 7, as shown in FIGS. 9
to 12, which is generally conventionally used, vibration called
judder is apt to be generated at the time of sudden braking or the
like in the state of running at a high speed. That is, in each of
the conventional structures shown in FIGS. 9 to 12, the distance
between circumferentially adjacent ones of the connecting ribs 10,
10a or 10b is narrower on the inner diameter side of the ventilated
disc 7 but wider on the outer diameter side thereof. On the other
hand, the rigidity of the ventilated disc 7 in its axial direction
is larger in portions corresponding to the connecting ribs 10, 10a
or 10b, but smaller in portions corresponding to the air channels
11, 11a or 11b. Therefore, a difference between the rigidity in the
portions corresponding to the connecting ribs 10, 10a or 10b and
the rigidity in the portions corresponding to the air channels 11,
11a or 11b becomes more conspicuous on the outer diameter side than
on the inner diameter side. As a result, slight circumferential
irregularities are apt to be formed on the opposite surfaces of the
ventilated disc 7 in finishing on the opposite surfaces for
flattening.
[0008] In addition, such circumferential irregularities are also
produced by the temperature rising of the ventilated disc 7 at the
time of braking. That is, at the time of braking, the pair of pads
5 (FIG. 7) press the ventilated disc 7 from the axially opposite
sides of the disc 7 strongly. Then, the temperature of the
ventilated disc 7 rises due to the friction between the opposite
surfaces of the ventilated disc 7 and the respective pads 5, so
that the ventilated disc 7 expands thermally. Such thermal
expansion due to the temperature rising becomes more conspicuous in
the portions of the connecting ribs 10, 10a or 10b having large
thermal capacity than in the portions of the air channels 11, 11a
or 11b having small thermal capacity. Thus, the portions
corresponding to the connecting ribs 10, 10a or 10b become recess
portions, and the portions corresponding to the air channels 11,
11a or 11b become protrusion portions, so that slight
irregularities are produced circumferentially. Particularly when
the distance between circumferentially adjacent ones of the
connecting ribs 10, 10a or 10b on the inner diameter side differs
largely from that on the outer diameter side as in the conventional
structures shown in FIGS. 10 to 12, the aforementioned
irregularities produced by the difference in temperature rising are
apt to be large and uneven between the inner diameter side and
outer diameter side. Thus, vibration is apt to be produced as
mentioned above.
[0009] In addition, in the case of the conventional structures
shown in FIGS. 10 to 12, it is difficult to make the saving of
weight compatible with the enhancement of heat radiation
performance. That is, in order to enhance the heat radiation
performance, it is considered that the number of the connecting
ribs 10, 10a or 10b is increased so that the heat exchange area
with the air flowing into the air channels 11, 11a or 11b is
enlarged. If the number of the connecting ribs 10, 10a or 10b is
increased, however, the weight of the ventilated disc 7 increases
correspondingly. Undesirably, the ventilated disc 7 fixed to the
wheel has a so-called unsprung load so that even a slight increase
in weight results in deterioration in the performance of the
vehicle mainly on comfortability. On the other hand, from the point
of ensuring the strength of the ventilated disc 7, it is difficult
to reduce the thickness of the connecting ribs 10, 10a or 10b so as
to restrain the increase in weight.
[0010] Taking the foregoing circumstances into consideration, the
present invention was developed to realize a ventilated disc which
can prevent its axially opposite surfaces from being deformed to
undulate circumferentially, and which is light in weight.
[0011] Like the aforementioned ventilated disc which has been
conventionally known, a ventilated disc according to the present
invention comprises a ring-like inner disc portion and a ring-like
outer disc portion which are disposed parallelly and coaxially at a
distance from each other; and a large number of connecting ribs for
connecting opposite surfaces, of the disc portions, facing each
other. The ventilated disc rotates together with a wheel while
being fixed thereto. Then, the ventilated disc is rubbed by pads
supported by the vehicle body at the time of braking.
[0012] Particularly, in the ventilated disc according to the
present invention, the connecting ribs include a large number of
first to fourth connecting ribs. Of those ribs, the first
connecting ribs are provided in the inner-diameter-side portions on
each of the opposite disc portions, and are long in the radial
direction of the opposite disc portions respectively. The second
and third connecting ribs are provided alternately
circumferentially in the outer-diameter-side portions on each of
the opposite disc portions, and are inclined reversely to each
other with respect to the radial direction of the opposite disc
portions, i.e. symmetric with respect to the radial direction. Each
of the fourth connecting ribs is provided at a circumferential
center of a portion where a distance between the second and third
connecting ribs is largest.
[0013] Preferably, the second and third connecting ribs are
provided so that a circumferential phase of inner-diameter-side end
portions of the second and third connecting ribs coincides with
that of the first connecting ribs, and a large number of fifth
connecting ribs are provided between radially intermediate portions
of the opposite disc portions so that a circumferential phase of
the fifth connecting ribs is shifted by half a pitch from that of
the first connecting ribs.
[0014] Further preferably, a distance between inner-diameter-side
end portions of circumferentially adjacent ones of the first
connecting ribs, a distance which is between outer-diameter end
portions of circumferentially adjacent ones of the second and third
connecting ribs and which is the narrowest one, a distance between
outer-diameter-side end portions of circumferentially adjacent ones
of the second and fourth connecting ribs, and a distance between
outer-diameter-side end portions of circumferentially adjacent ones
of the third and fourth connecting ribs are made substantially
equal to one another.
[0015] In the case of such a ventilated disc according to the
present invention as configured thus, a large difference in
distance can be prevented from appearing between circumferentially
adjacent ones of the connecting ribs. Accordingly, the opposite
surfaces of the ventilated disc can be prevented from being
deformed to undulate circumferentially with the finishing process
applied to the opposite surfaces or the temperature rising at the
time of braking. In addition, the first to fifth connecting ribs
which are respectively shorter than connecting ribs constituting
conventional structures are disposed radially and
circumferentially. Accordingly, the total surface area of the
connecting ribs can be enlarged without reducing the strength or
without increasing the weight. It is therefore possible to realize
a ventilated disc which is light in weight. Further, because the
second and third connecting ribs are provided to be inclined
reversely to each other, it is possible to realize a ventilated
disc which can circulate a large amount of air inside the
ventilated disc so as to exhibit an excellent cooling effect and in
which the direction of attachment is not limited.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a partially cut-away front view showing an
embodiment of the present invention.
[0017] FIG. 2 is a cut-away front view of a main portion of the
same embodiment.
[0018] FIG. 3 is a sectional view taken on line A-A in FIG. 1.
[0019] FIG. 4 is a back view from the left of FIG. 3.
[0020] FIG. 5 is a view from an arrow B in FIG. 4.
[0021] FIG. 6 is a sectional view taken on line C-C in FIG. 1.
[0022] FIG. 7 is a partially sectional view of a disc brake.
[0023] FIG. 8 is a perspective view of a solid disc.
[0024] FIG. 9 is a perspective view of a ventilated disc which has
been conventionally known.
[0025] FIG. 10 is a schematic sectional view taken on line D-D in
FIG. 9, showing a first example of the conventional structure.
[0026] FIG. 11 is a schematic sectional view taken on line D-D in
FIG. 9, showing a second example of the conventional structure.
[0027] FIG. 12 is a schematic sectional view taken on line D-D in
FIG. 9, showing a third example of the conventional structure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] FIGS. 1 to 6 show an embodiment of the present invention. In
the same manner as the aforementioned conventional ventilated disc
7 shown in FIG. 9, a ventilated disc 7a according to the present
invention is integrally made up from metal such as cast iron or the
like. The ventilated disc 7a has a ring-like inner disc portion 8a
and a ring-like outer disc portion 9a which are disposed parallelly
and coaxially at a distance from each other. Then, respective
surfaces of these disc portions 8a and 9a facing each other are
connected to each other through numbers of first to fifth
connecting ribs 13a, 13b and 14 to 17.
[0029] Of those ribs, the first connecting ribs 13a and 13b are
provided between inner-diameter-side portions of the
above-mentioned disc portions 8a and 9a respectively. Each of the
first connecting ribs 13a and 13b is formed linearly so as to long
radially. On the other hand, the second and third connecting ribs
14 and 15 are provided alternately in the circumferential direction
on outer-diameter-side portions between the disc portions 8a and 9a
respectively. The second and third connecting ribs 14 and 15 are
inclined at the same angle .theta. (for example, about 15 degrees)
with respect to the direction of diameter of the disc portions 8a
and 9a. Then, the second connecting ribs 14 are inclined reversely
to the third connecting ribs 15. That is, the second connecting
ribs 14 and the third connecting ribs 15 are symmetric with respect
to the radial direction.
[0030] In addition, the second and third connecting ribs 14 and 15
are provided in portions where the circumferential phase of their
inner-diameter-side end portions coincides with that of the first
connecting ribs 13a and 13b. To say other words, the inner end
portions of the second connecting ribs 14, 14 are located on the
outer-diameter-side extension lines of a half of the first
connecting ribs 13a disposed circumferentially alternately,
respectively. On the other hand, the inner end portions of the
third connecting ribs 15 are located on the outer-diameter-side
extension lines of the first connecting ribs 13b. which are the
other half of the first connecting ribs, respectively. Further, the
second and third connecting ribs 14 and 15 are disposed so that
circumferentially adjacent ones of them are paired to form a shape
of "truncated-V".
[0031] Although the sectional shape of each of the second and third
connecting ribs 14 and 15 is shown to be a straight line in the
embodiment of FIG. 1, the sectional shape of each of the second and
third connecting ribs 14 and 15 may be a curved line as shown in
FIG. 12 which was described previously. Then, the second and third
connecting ribs 14 and 15 are formed to be symmetric with each
other with respect to the radial direction. This is because the
ventilated discs 7a having the same shape can be used in the left
and right sides of a vehicle by eliminating limit on the direction
of rotation of the disc 7a.
[0032] On the other hand, the respective fourth connecting ribs 16
are provided radially between outer-diameter-side portions of the
opposite disc portions 8a and 9a. Each of the fourth connecting
ribs 16 is formed to have a sectional shape like a straight line
which is shorter than any of the first to third connecting ribs
13a, 13b, 14 and 15. In addition, each of the fourth connecting
ribs 16 is provided on the outer-diameter-side end portions on a
circumferentially central portion where the distance between
circumferentially adjacent ones of the second connecting ribs 14
and the third connecting ribs 15 is largest.
[0033] Further, the fifth connecting ribs 17 are provided radially
between diameter-direction intermediate portions of the opposite
disc portions 8a and 9a. Each of the fifth connecting ribs 17 is
formed to have a sectional shape like a straight line which is
shorter than any of the first to third connecting ribs 13a, 13b, 14
and 15, in the same manner as the fourth connecting ribs 16
described above. In addition, the respective fifth connecting ribs
17 are provided in portions where the circumferential phase of the
fifth connecting ribs 17 is shifted by half a pitch from that of
the first connecting ribs 13a and 13b. Therefore, the respective
fifth connecting ribs 17 are located in the central portions of the
outer-diameter-side opening portions of the air channels 11c each
of which is located between circumferentially adjacent ones of the
first connecting ribs 13a and 13b. In addition, the circumferential
phase of the fourth connecting ribs 16 coincides with that of the
fifth connecting ribs 17. To say other words, the fifth connecting
ribs 17 are located on the inner-diameter-side extension lines of
the fourth connecting ribs 16 respectively. Incidentally, each of
the lengthwise opposite edge portions of the connecting ribs 13a,
13b and 14 to 17 described above is formed to be a convex curved
surface like a semi-cylindrical surface.
[0034] In addition, length L.sub.17 of each of the fifth connecting
ribs 17 is made larger than length L.sub.18 of each of radial gaps
18 which are located between the first connecting ribs 13a and 13b
and the second and third connecting ribs 14 and 15 radially
adjacent to each other (L.sub.17>L.sub.18). Further, the
radially central positions of the respective fifth connecting ribs
17 are made to coincide with the radially central positions of the
respective radial gaps 18. Therefore, the air passing through the
radial gaps 18 in the circumferential direction collides with the
fifth connecting ribs 17. Thus, there is no fear that the air
passing through the radial gaps 18 reaches adjacent ones of the
radial gaps 18 directly (without flowing radially outward).
[0035] Further, the inclination angle .theta. of each of the second
and third connecting ribs 14 and 15 with respect to the radial
direction of the opposite disc portions 8a and 9a (and further the
width of each rib) is regulated. As a result, a distance D.sub.13
between inner-diameter-side end portions of circumferentially
adjacent ones of the first connecting ribs 13a and 13b, a distance
D.sub.14-15 between circumferentially adjacent ones of the second
connecting ribs 14 and the third connecting ribs 15 which is the
narrowest in the outer-diameter end portions, a distance
D.sub.14-16 between outer-diameter-side end portions of
circumferentially adjacent ones of the second connecting ribs 14
and the fourth connecting ribs 16, and a distance D.sub.15-16
between outer-diameter-side end portions of circumferentially
adjacent ones of the third connecting ribs 15 and the fourth
connecting ribs 16, 16. are made substantially equal to one another
(D.sub.13.apprxeq.D.sub.14-15.app-
rxeq.D.sub.14-16.apprxeq.D.sub.15-16). The statement that the
distances D.sub.13, D.sub.14-15, D.sub.14-16 and D.sub.15-16 are
substantially equal to one another means that a difference between
the largest one of the distances and the smallest one thereof is
within 20%, preferably within 10%, in view of the largest one.
[0036] In the case of the ventilated disc 7a according to the
present invention configured thus, it is possible to prevent a
large difference from appearing in distance between
circumferentially adjacent ones of the connecting ribs. That is,
the second and third connecting ribs 14 and 15 provided on the
outer-diameter side, where the distance between circumferentially
adjacent ones of the connecting ribs is apt to be large, are
inclined with respect to the radial direction. Thus, the distance
between circumferentially adjacent ones of the second and third
connecting ribs 14 and 15 at the outer-diameter-side end portions
can be made narrow alternately so as to be equal to the distance
D.sub.13 between circumferentially adjacent ones of the first
connecting ribs 13a and 13b on the inner-diameter-side end
portions. In addition, the respective fourth connecting ribs 16 are
provided in portions where the distance between circumferentially
adjacent ones of the second and third connecting ribs 14 and 15 on
the outer-diameter-side end portions is set to be large
alternately. The fourth ribs 16 are provided in those enlarged
distances between the ribs 14 and 15. Thus, each distance of this
portion can be made substantially equal to the distance D.sub.13
between the inner-diameter-side end portions of the first
connecting ribs 13a and 13b.
[0037] Thus, according to the present invention, the respective
distances D.sub.13, D.sub.14-15, D.sub.14-16 and D.sub.15-16
between circumferentially adjacent ones of the connecting ribs 13a,
13b and 14 to 16 can be made substantially equal to one another all
over the ventilated disc 7a. As a result, the opposite surfaces of
the ventilated disc 7a can be prevented from being deformed to
undulate circumferentially with the process of finishing the
opposite surfaces or the temperature rising at the time of braking.
That is, the distances D.sub.13, D.sub.14-15, D.sub.14-16 and
D.sub.15-16 are made to equal to one another so that the axial
rigidity of the ventilated disc 7a is made substantially even all
over the ventilated disc 7a. Therefore, irregularities which may
cause vibration called judder described above are difficult to be
formed with the above-mentioned finishing process (the finishing
accuracy is enhanced).
[0038] In addition, as the distances D.sub.13, D.sub.14-15,
D.sub.14-16 and D.sub.15-16 are equal to one another, there is no
fear that a difference in thermal expansion quantity between the
portion corresponding to each of the connecting ribs 13a, 13b and
14 to 17 and the portion corresponding to each of the air channels
which are provided in the portions away from the connecting ribs
13a, 13b and 14 to 17 becomes uneven over the ventilated disc 7a
due to temperature rising at the time of braking even if such a
difference appears. That is, also in the case of the present
invention, it is inevitable that there appears a difference in
thermal expansion quantity between the portion corresponding to
each of the connecting ribs 13a, 13b and 14 to 17 and the portion
corresponding to each of the air channels which are provided in the
portions away from the connecting ribs 13a, 13b and 14 to 17, so
that fine irregularities are produced on the opposite surfaces of
the ventilated disc 7a. However, there is no fear that the
distribution and height of the irregularities on the inner diameter
side differ from those on the outer diameter side. To say other
words, fine irregularities due to the temperature rising become
substantially uniform all over the opposite surfaces of the
ventilated disc 7a. Such uniform irregularities do not make the
contact surface pressure uneven between each of the opposite
surfaces of the ventilated disc 7a and each of the pads 5 (see FIG.
7) in view of the whole friction surfaces of the ventilated disc 7a
at the time of braking. Thus, such uniform irregularities hardly
cause vibration called judder described above.
[0039] Further, the connecting ribs 13a, 13b and 14 to 17, which
are shorter than the connecting ribs 10, 10a and 10b (see FIGS. 10
to 12) constituting the conventional structures, are disposed
radially and circumferentially. Accordingly, the total surface area
of the connecting ribs 13a, 13b and 14 to 17 can be enlarged
without reducing the strength or without increasing the weight.
Thus, the ventilated disc 7a can be made light in weight. Further,
because the second and third connecting ribs 14 and 15 are provided
to be inclined at the same angle .theta. reversely to each other,
it is possible to realize a ventilated disc which can circulate a
large amount of air inside the ventilated disc so as to exhibit an
excellent cooling effect, and in which the direction of attachment
is not limited.
[0040] Since a ventilated disc according to the present invention
is configured to operate thus, the ventilated disc can contribute
to realizing a disc brake which prevents vibration from being
generated at the time of braking so as not to give an unpleasant
feeling to crew members and so on. In addition, though the
ventilated disc has a structure with an excellent cooling
efficiency, the direction of rotation of the ventilated disc is not
limited. Accordingly, ventilated discs having the same shape can be
used in the left and right sides of a vehicle, so that the cost can
be reduced by the standardization of parts.
* * * * *