Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling accommodates drive between members having... – Coupling transmits torque via radially spaced ball
Reexamination Certificate
1998-09-21
2001-08-28
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Coupling accommodates drive between members having...
Coupling transmits torque via radially spaced ball
C464S906000
Reexamination Certificate
active
06280336
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a hub unit incorporated in the drive wheel side of a vehicle, etc.
Since it is necessary that a power transmission device which transmits the power of engine of an automobile, etc., to wheels matches angular and axial displacement resulting from changes in the relative positional relationship between engine and wheels, for example, one end of a drive shaft intervening between the engine side and the drive wheel side is connected to differential gears via a plunging type constant velocity universal joint while the other end is connected to drive wheel via a hub unit including a fixed type constant velocity universal joint. The hub unit comprises an axle hub connected to drive wheel along with brake rotor, an axle bearing which rotatably supports the axle hub with respect to body side supporting member (knuckle portion, etc.), and a constant velocity universal joint for transmitting power of the drive shaft to the axle hub. As a constant velocity universal joint of the hub unit, such a structure (ball fixed joint) has generally been known, in which torque transmitting balls are, respectively, disposed in six ball tracks opened to be like a wedge in one axial direction.
As regards the hub unit, such a structure (hereinafter called a “compact type hub unit”) has been developed, in which an axle hub, axle bearing and constant velocity universal joint are assembled with each other, and various types thereof have been proposed, in view of decreasing the production costs, number of assembling steps, lightening the weight, widening the operating angle in line with movements of the joint center, and improving the steering performance. However, conventional compact type hub units have problems as described below, which become obstacles in practical applications.
(1) The design of tire size, wheel rim and brake rotor is determined in order, depending on the output of engine, and the diameter of a shaft portion of the constant velocity universal joint is also determined on the basis of the engine output. The compact type hub unit is constructed so that the axle bearing intervenes between the brake rotor and an outer joint member (also acting as the axle hub) of the constant velocity universal joint. Actually however, since the outer diameter of the axle bearing is made too large, it is difficult to accommodate the hub unit at the bore side of the brake rotor.
(2) Since the axle bearing and the constant velocity universal joint are very close to each other, the internal exothermic reaction of the constant velocity universal joint is transmitted to the axle bearing, and there is a possibility that the service life of the bearing is decreased.
(3) Since on the bore side of the brake rotor the empty space is small heat collects therein resulting in a temperature rise of the axle bearing and the exothermic reaction of the brake.
(4) In comparison with a case where the respective members are independently disposed, the total weight is decreased. However, the hub unit itself is made heavy and its scale is increased. Thus, it is difficult to handle the hub unit.
SUMMARY OF THE INVENTION
The present invention has an object to solve the abovementioned problems inherent to the conventional compact type hub units.
In order to solve the abovementioned problems, the invention provides a hub unit comprising an axle hub connected to a drive wheel; an axle bearing disposed on the outer circumferential surface of the axle hub, which rotatably supports the axle hub with respect to a body side supporting member; and a constant velocity universal joint for transmitting the power of the drive shaft to the axle hub, wherein the constant velocity universal joint comprises the axle hub acting as an outer joint member having eight curved outside guide grooves formed on a spherical inner circumferential surface thereof in the axial direction; an inner joint member having eight curved inside guide grooves formed on a spherical outer circumferential surface thereof in the axial direction and a fitting portion having tooth profile for connecting the drive shaft formed on an inner circumferential surface thereof; eight torque transmitting balls disposed in eight ball tracks respectively, the ball tracks being formed by cooperation of the outside guide grooves of the axle hub and the inside guide grooves of the inner joint member corresponding to each other and are opened to be wedge-like in one axial direction; and a cage for retaining the torque transmitting balls,
and wherein the ratio r2 (D
OUTER
/PCD
SERR
) of the outer diameter (D
OUTER
) of the axle hub to the pitch circle diameter (PCD
SERR
) of the tooth profile of the fitting portion of the inner joint member is 2.5≦r2<3.2.
The reason why 2.5≦r2<3.2 is employed resides in the following. That is, the pitch circle diameter (PCD
SERR
) of the tooth profile of the fitting portion of the inner joint member can not be greatly changed due to the relationship with the strength of the drive shaft or the like. Therefore, the value of r2 mainly depends on the outer diameter (D
OUTER
) of the axle hub (outer joint member). If r2<2.5 (mainly in a case where the outer diameter D
OUTER
is smaller), the thickness of the respective parts (outer joint member, inner joint members, etc.) is made too thin, there remains a worry in view of the strength. On the other hand, if r2 ≧3.2 (mainly in a case where the outer diameter D
OUTER
is greater), there is a case where a problem arises in practical applications in the dimensional aspect, and an object to make the unit compact can not be achieved. In addition, the general value of r
2
of a six-ball constant velocity universal joint is r2≧3.2.
By employing 2.5≦r2<3.2, it is possible to secure the strength of the axle hub (outer joint member), etc., and the durability of the joint equivalent to or greater than a comparative joint (six-ball constant velocity universal joint), and it is possible to make the outer diameter (
DOUTER
) of the axle hub compact.
The invention has the following effects and advantages.
(1) Since the outer diameter (D
OUTER
) of the axle hub (concurrently acting as the outer joint member of the constant velocity universal joint) can be made smaller than ever, it becomes easy to make a design of accommodating the axle bearing on the bore side of the brake rotor.
(2) Since the constant velocity universal joint is heated less than a comparative joint (a six-ball constant velocity universal joint), the adverse influence on the temperature rise of the axle bearing and the exothermic reaction of the brake due is suppressed, so that the service life of the bearing or brake is further improved.
(3) Since the outer diameter (D
OUTER
) of the axle hub is made small, the entire unit can be made light and compact, and its handling made easy.
REFERENCES:
patent: 4424047 (1984-01-01), Welschof et al.
patent: 5975767 (1999-11-01), Mizukoshi et al.
patent: 802341 (1997-10-01), None
patent: 97/24538 (1997-07-01), None
Sone Keisuke
Wakita Akira
Arent Fox Kintner & Plotkin & Kahn, PLLC
Binda Greg
Browne Lynne H.
NTN Corporation
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