Bevel gear

Details Bevel gear Bevel gear

2002-03-06

2004-05-11

Joyce, William C. (Department: 3682)

Machine element or mechanism

Gearing

Teeth

C074S457000

Reexamination Certificate

active

06732605

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a bevel gear for use in power transmission devices in a variety of machinery, and more particularly, to a bevel gear suited for use in automotive differential gearing.
Straight bevel gears and spiral bevel gears are generally manufactured by preparing a gear material
100
as shown in
FIG. 1A
by forging or machining, and then forming a tooth
101
in the material
100
by cutting as shown in
FIG. 1B
, resulting in a bevel gear
102
as shown in FIG.
1
C. These bevel gears can also be produced by electric discharge machining (not shown) as disclosed in Japanese Patent Laid-Open Publication No. HEI-9-323219. The tooth
101
of the bevel gear
102
is shaped to gradually increase in dimensions from a small-diameter end to a large-diameter end. However, a fillet curve between a tooth flank A of the tooth
101
and a bottom land B has a radius of curvature R being identical from the small-diameter end to the large-diameter end (See cross-sectional views of FIG.
1
D and
FIG. 1E
, illustrating the small-diameter end and the large-diameter end, respectively). A radius of curvature R of the fillet curve depends on a radius of curvature R at the small-diameter end for providing good meshing with a mating gear.
SUMMARY OF THE INVENTION
This kind of related bevel gear faces, however, a problem described below when used in automotive differential gearing. That is, the bevel gear used in automotive differential gearing is adjusted to contact at its teeth a mating gear at a position close to the large-diameter end with a larger tooth width, so as to deal with the power transmission load. This causes the gear to be likely to break at the dedendum of the large-diameter end because of the small radius of curvature of the fillet curve depending on that of the small-diameter end. To prevent such breakage, it is necessary to disadvantageously use a large-sized bevel gear for obtaining required strength. This has been a problem to be solved.
This invention was made with the above problem in mind, and has an object of providing a bevel gear having sufficient strength from a small-diameter end to a large-diameter end.
In order to achieve the above object, a bevel gear according to this invention has a radius of curvature of a fillet curve between a tooth flank and a bottom land at a large-diameter end made greater than that at a small-diameter end.
According to this invention, a radius of curvature at a large-diameter end is made greater than that at a small-diameter end, increasing the strength of the large-diameter end which is otherwise likely to be broken, and thereby achieving sufficient, even strength from the small-diameter end to the large-diameter end. This enables reduction in size of the bevel gear and thus the reduction in size of a transmission device including the bevel gear, leading to reduction in cost thereof.


REFERENCES:
patent: 2285575 (1942-06-01), Elbertz
patent: 2436276 (1948-02-01), Whildhaber
patent: 2778240 (1957-01-01), Prester
patent: 6129793 (2000-10-01), Tan et al.
patent: 6324931 (2001-12-01), Tsung
patent: 706 080 (1954-03-01), None
patent: 9-323219 (1997-12-01), None
Katsuo, “Webbed Bevel Gear,” Patent Abstracts of Japan, vol. 012, No. 495, Dec. 23, 1988, JP 63 215329, Sep. 7, 1988, 1 Sheet, Abstract.

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