Brakes – Elements – Brake wheels
Reexamination Certificate
1999-07-20
2001-12-04
DePumpo, Daniel G. (Department: 3611)
Brakes
Elements
Brake wheels
C188S2640AA
Reexamination Certificate
active
06325185
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a brake disc rotor of a disc brake device for a vehicle. More particularly, the invention relates to a ventilated type brake disc rotor in which fins are radially provided between opposed disc plates and ventilation holes are opened between the fins.
Society of Mechanical Engineers paper (Vol. 55, 122nd issue, No. 88-0622A) and Japanese Patent Application Laid-Open No. 9-280278 disclose conventional ventilated type brake disc rotors.
SUMMARY OF THE INVENTION
The inventors of the present invention have analyzed a ventilated type brake disc rotor as illustrated in
FIGS. 9 and 10
.
In
FIGS. 9 and 10
, a brake disc rotor comprises a disc plate
1
on the outer side of a vehicle, a disc plate
2
on the inner side which is opposed to the disc plate
1
, and a plurality of fins
3
disposed between the plates
1
and
2
. The plurality of fins
3
are arranged at intervals in the circumferential direction of the rotor. Radially extending a ventilator hole passages or
4
are defined between the fins
3
. Each ventilator hole
4
is a hole or passage communicating the opening portions at the inner and outer ends in the radial direction of the rotor. A part
3
a
of the plurality of fins
3
is widened by bridging neighboring fins.
With this construction, when the brake disc rotor rotates, a cooling air passes from the inner periphery of the rotor toward the outer periphery of the rotor along each ventilator hole
4
, thereby cooling the brake disc rotor. During braking, both of the disc plates
1
and
2
are tightly sandwiched by sliding pads (not shown) from the right and left sides, that is, from the outer and inner sides of the vehicle.
In the construction, however, since the part
3
a
of fins is formed in wide, the cooling performance tends to deteriorate as compared with the fins which are not wide. In addition, a thermal non-uniformity occurs in the circumferential direction of the rotor, so that it is not preferable from the viewpoint of thermal deformation strength.
The inventors have consequently further analyzed a ventilated type brake disc rotor in which such an aspect is taken into account as shown in
FIGS. 11 and 12
.
The basic construction of the ventilated type brake disk rotor is similar to that shown in
FIGS. 9 and 10
. As will be understood from
FIGS. 11 and 12
, a plurality of long fins
3
A having the long fin length and short fins
3
B having the short fin length are alternately arranged in the circumferential direction of the rotor. The periphery side of each long fin
3
A in the circumferential direction has a wide expanded part
5
.
In the construction, the number and area of the ventilation holes
4
are larger than those of the above construction, so that the cooling performance is improved. Since the fins
3
A and
3
B are not widened extremely, the thermal non-uniformity in the circumferential direction of the rotor is corrected and the thermal deformation strength is also improved.
In the ventilated type brake disc rotor, however, it is considered that there is room for improvement in suppression of brake noise, that is, typically brake squeal.
More specifically, in case of suppressing brake squeal in the frequency band of 5 to 10 kHz, since a brake disc rotor in which the long fins
3
A and the short fins
3
B are alternately arranged can produce an effect on brake squeal in a higher frequency band, the brake squeal in the frequency band of 5 to 10 kHz can not be sufficiently suppressed. There is consequently the possibility that unpleasant noises occur.
It is also considered that there is room to improve suppression of a so called groan sound caused by thermal deformation of the brake disc rotor.
More specifically, as illustrated in
FIG. 13A
for example, when the fins
3
A and
3
B of the brake disc rotor are arranged in the circumferential direction of the rotor, it is considered that thermal deformation occurs in such a manner that, as shown in
FIG. 13B
, parts having the fins
3
A and
3
B are thick so as to have thickness of t
3A
and t
3B
, respectively, and a part having the ventilation hole
4
is relatively thin due to influence of heat generated during braking so as to have thickness of t
4
. In such a case, a vibratory force is created due to the thermal deformation, that is, variation in the thickness of the brake disc rotor. Due to the vibratory force, an uncomfortable noise, that is, the groan sound may occur in the cabin of the vehicle. The thermal deformation basically depends on the number of fins
3
A and
3
B and their lengths and widths, that is, the rigidity of the disc plates
1
and
2
. For example, in a case where the brake disc rotor has 48 fins of the same length, the groan sound appears as the 48th vibration component caused by the thermal deformation. As shown in
FIG. 13A
, in the construction that the brake disc rotor has the long fins
3
A and the short fins
3
B, in addition to the 48th vibration component, the 24th vibration component also appear as shown in
FIG. 14
where the amplitude of vibration with respect to the order of vibration which is caused by thermal deformation is shown.
The present invention has been achieved based on the analysis above mentioned and it is an object of the present invention to provide a brake disc rotor which can effectively suppress both of brake squeal and groan sound while assuring sufficient cooling performance.
In order to achieve the object, a brake disc rotor of the present invention has a fundamental construction comprising: a first disc plate: a second disc plate facing the first disc plate; a plurality of fins arranged in the radial direction of the brake disc rotor between the first and second disc plates; and a plurality of ventilation holes each of which is positioned between neighboring fins of the plurality of fins and communicates a space on the inner circumferential side and a space on the outer circumferential side in the radial direction of the brake disc rotor. The plurality of fins have a plurality of sets each including two long fins and two short fins, one of the two long fins has an expanded part which is expanded in its width direction, the long fins and the short fins are alternately arranged in the circumferential direction of the brake disc rotor in each of the plurality of sets, and the plurality of sets are arranged at equal intervals in the circumferential direction of the brake disc rotor.
With the construction, both the mass and the rigidity of the portion of the expanded part increase, so that diametral nodal mode (eigermode) of the characteristic vibration of the brake disc rotor which occurs when a vibratory force during braking is applied, that is, the multiple root mode having a quarter wavelength phase difference such that the position of the long fin having the expanded part corresponds to the node position in one of vibration modes and corresponds to the loop position in the other of the vibration modes is separated, and vibrations are not accordingly coupled. The brake squeal can be therefore effectively suppressed.
Further, the four fins constructing one set of fins can employ three kinds regarding the lengths and widths contributing to the rigidity of the disc plates. The vibration energy of the vibratory force can be therefore effectively dispersed into three orders and the groan sound can be effectively suppressed.
And further, since the long fins extending to the inner side of the brake disc rotor and short fins are alternately arranged, the entrance area of the cooling air is enlarged. Also, since the long fins each having the expanded part are included, the flow velocity of the cooling air increases. Thus, the cooling efficiency can be improved, the thermal nonuniformity in the circumferential direction of the brake disc rotor is not substantial, and the thermal deformation strength can be improved.
REFERENCES:
patent: 3809192 (1974-05-01), Stehle
patent: 4132294 (1979-01-01), Poli
patent: 4379501 (1983-04-01), Hagiwara
patent: 4523666 (1985-06-01), Murray
patent: 55
Doi Kazuhiro
Hamabe Tsutomu
Kubota Masahiro
Matsubara Takashi
DePumpo Daniel G.
Divine David
Foley & Lardner
Nissan Motor Co,. Ltd.
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