Ventilated disc

Details Ventilated disc Ventilated disc

2000-12-07

2002-04-09

Graham, Matthew C. (Department: 3613)

Brakes

Elements

Brake wheels

C188S2640AA

Reexamination Certificate

active

06367599

ABSTRACT:

BACKGROUND OF THE INVENTION
Field of the Invention
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.
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
.
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
.
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
10
a
are inclined in the direction of rotation of the ventilated disc is also known conventionally.
Further, as shown in
FIG. 12
, a ventilated disc in which connecting ribs
10
b
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
10
a
or
10
b
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
11
a
or
11
b
between circumferentially adjacent ones of the connecting ribs
10
a
or
10
b.
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
FIG. 11
or
12
, however, it is necessary to regulate the direction of rotation of the ventilated disc (the counterclockwise direction in
FIG. 11
or
12
) in order to circulate a large amount of air into the air channels
11
a
or
11
b.
It is therefore impossible to standardize parts of the ventilated disc between right and left sides of the vehicle.
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
,
10
a
or
10
b
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
,
10
a
or
10
b,
but smaller in portions corresponding to the air channels
11
,
11
a
or
11
b.
Therefore, a difference between the rigidity in the portions corresponding to the connecting ribs
10
,
10
a
or
10
b
and the rigidity in the portions corresponding to the air channels
11
,
11
a
or
11
b
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.
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
,
10
a
or
10
b
having large thermal capacity than in the portions of the air channels
11
,
11
a
or
11
b
having small thermal capacity. Thus, the portions corresponding to the connecting ribs
10
,
10
a
or
10
b
become recess portions, and the portions corresponding to the air channels
11
,
11
a
or
11
b
become protrusion portions, so that slight irregularities are produced circumferentially. Particularly when the distance between circumferentially adjacent ones of the connecting ribs
10
,
10
a
or
10
b
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.
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
,
10
a
or
10
b
is increased so that the heat exchange area with the air flowing into the air channels
11
,
11
a
or
11
b
is enlarged. If the number of the connecting ribs
10
,
10
a
or
10
b
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
,
10
a
or
10
b
so as to restrain the increase in weight.
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.
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.

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