Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
2000-07-06
2002-04-09
Schwartz, Christopher P. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S073470, C188S072400
Reexamination Certificate
active
06367595
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a disk brake for use in motor vehicles such as automobiles, and particularly of a type having a one-piece caliper with opposed pistons.
A typical conventional opposed-piston type disk brake has a caliper
50
comprising separate inner and outer portions
51
and
52
as shown in
FIGS. 8 and 9
. The inner and outer portions
51
,
52
are secured together by bolts
54
with their flat surfaces
53
in close contact with each other. Each of the inner and outer portions
51
,
52
are formed with a pair of close-bottomed cylinders
55
. A piston
59
is received in each cylinder
55
with the gap between the piston and the cylinder liquid-tightly sealed by a piston seal
58
. The caliper is formed with a groove
61
in which is received a disk rotor such that the rotor rotates with a predetermined clearance left between its outer perimeter and the inner wall of the caliper.
Friction pads
60
are disposed between the disk rotor and the pistons
59
on both sides while hanging from pad pins
66
inserted through pin holes
65
formed in the pads and secured to the caliper
50
. When fluid pressure is applied from an external fluid supply source, the pistons
59
on both sides are moved toward each other to press the pads
60
against the rotor, thereby applying braking force to the wheel. The caliper
50
is formed with torque bearing surfaces
62
at both ends of the pads
60
to bear braking torque.
With this type of caliper, since the inner and outer portions are strongly joined together by the bolts
54
, they are less likely to deflect at a portion near the groove
61
when the pads are pressed against the disk rotor for braking. But the bolts
54
necessarily increase the thickness of the bridge portion
110
of the caliper. This in turn reduces the radius R
1
(
FIG. 9
) of the disk rotor and thus the effective braking radius R
2
, which is the radius of the circle that passes the centers of the pistons
59
.
One way to increase the effective braking radius R
2
without increasing the wheel inner radius R
0
is to form the caliper as a one-piece member and thus to omit the bolts
54
. But if the thickness of the bridge portion of such a one-piece caliper is reduced to increase the effective braking thickness R
2
, the outer portion of the caliper tends to bend outwardly due to stress concentration on the inner corner of the outer portion of the caliper, especially if the caliper is made of a aluminum alloy for reduced weight.
One possible solution to this problem would be to provide reinforcing ribs
118
as used in a floating-caliper type disk brake shown in FIG.
10
. The ribs
118
are formed to extend across the inner corner X of the outer jaw
114
. But actually, it would be impossible to use such ribs in a one-piece, opposed-piston type caliper because with this type of caliper the inner corners of the caliper are located much closer to the disk rotor than with the floating caliper because the opposed-piston type caliper needs torque bearing portions
62
(FIG.
8
). Thus, if such ribs were provided along the inner corner of the outer portion of the caliper, they would interfere with the rotor.
An object of the invention is to provide an opposed-piston type disk brake having a one-piece caliper and provided with a means for preventing the outer portion of the caliper from bending outwardly during braking.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a disk brake comprising a one-piece caliper comprising an inner portion formed with a first cylinder and fastened to a stationary part of a vehicle, an outer portion formed with a second cylinder, and a bridge portion connecting the inner and outer portions together and having an annular inner surface defining a corner, pistons each received in one of the first and second cylinders, a disk rotor fastened to a wheel of the vehicle and disposed between the pistons, and friction pads disposed between the disk rotor and the pistons so as to be movable toward and away from the disk rotor, characterised in that the caliper is formed with a recess having an arcuate cross-section having a predetermined radius of curvature in the inner surface of the outer portion along the corner to extend in a direction in which the pistons are moved so as not to protrude radially inwardly of the annular inner surface of the bridge portion.
Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which:
REFERENCES:
patent: 4494630 (1985-01-01), Stoka et al.
patent: 5150772 (1992-09-01), Pantale et al.
patent: 5558183 (1996-09-01), Way
patent: 5660251 (1997-08-01), Nishizawa et al.
patent: 5687818 (1997-11-01), Nishizawa et al.
patent: 5860494 (1999-01-01), Nishizawa et al.
patent: 6000506 (1999-12-01), Warwick
patent: 11-63041 (1999-03-01), None
Matsuzaki Yoshiki
Mori Koji
Greenblum & Bernstein P.L.C.
Siconolfi Robert A.
Sumitomo Electric Industries Ltd.
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