Two stage torsional vibration damper

Details Two stage torsional vibration damper Two stage torsional vibration damper

1997-04-02

2001-05-01

Browne, Lynne H. (Department: 3629)

Rotary shafts, gudgeons, housings, and flexible couplings for ro

Torque transmitted via flexible element

Coil spring

C464S063100

Reexamination Certificate

active

06224487

ABSTRACT:

This invention relates generally to torsional vibration dampers and more particularly to two stage torsional vibration dampers having inner and outer annular arrays of damping springs.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,941,860 granted to Michel Graton Jul. 17, 1990 discloses a two-stage torsional vibration damper particularly for automotive vehicles having an inner annular array of damping springs partially disposed in windows of an inner drive plate and an outer annular array of damping springs partially disposed in windows of an outer drive plate. The inner and outer drive plates have notches in their adjacent peripheries that form passages. The notches of the respective drive plates are offset circumferentially with respect to each other and disposed on a pitch circle that is between the inner and outer annular arrays of damping springs. The two arrays of damping springs are retained by two retainer plates on opposite sides of the drive plates. The retainer plates are connected to each other by spacer pins that pass through passages formed by the notches in the adjacent peripheries of the inner and outer drive plates. The spacer pins serve as stops that limit the angular displacements of the inner and outer drive plates with respect to the retainer rings so that the compression of damping springs is also limited.
One drawback of the Graton torsional vibration damper is that only half of the spacer pins function as stops to limit the angular displacements of the inner and outer drive plates and compression of the damping springs. Every other spacer pin or half of the spacer pins act as stops when the damper is driven in the clockwise direction and the other half act as stops for counterclockwise drive. Another drawback is that the Graton torsional vibration damper requires very long notches in the adjacent peripheries of the drive plates so that each drive plate has very few abutments for the spacer pins to stop against. For instance, the preferred embodiment disclosed in the Graton patent has six spacer pins and only three pads on each drive plate that serve as abutments for the spacer pins to stop against.
Still another drawback is that the Graton torsional vibration damper is limited to an even number of spacer pins in order to provide a balanced stop arrangement.
A still further drawback of the Graton torsion damper is in the use of complicated friction dampers that are expensive to manufacture and difficult to assemble. One friction damper arrangement comprises two friction rings and a Belleville washers that must be shaped to accommodate the spacer pins as shown in
FIGS. 1
,
2
and
3
of the Graton patent drawing. Another Graton friction damper arrangement comprises a plurality of fiber reinforced synthetic bushes having rectangular heads that are alternately arranged as shown in
FIGS. 4 and 5
of the Graton patent drawing.
U.S. Pat. No. 5,246,399 granted to John P. Yanko et al Sep. 21, 1993 discloses a two stage torsional vibration damper that has an improved stop arrangement for limiting the angular displacements of the inner and outer drive plates and compression of the damping springs which avoids several drawbacks of the Graton torsional vibration damper discussed above.
The Yanko two stage torsional vibration damper is characterized by a ring member that is disposed between the inner and outer drive plates in the radial direction and fastened between the retainer plates in the axial direction. The ring member has circumferentially spaced enlargements that include a plurality of stop surfaces that limit the angular displacements of the inner and outer drive plates with respect to the retainer plates and the compression of the inner and outer arrays of damping springs. Each enlargement of the Yanko member acts as a stop in each drive direction thereby increasing the number of functional stops in comparison to the Graton arrangement significantly. The notches in the adjacent peripheries of the inner and outer drive plates are also relatively short in comparison to the Graton arrangement so that the number of abutments for engaging the stops is also increased significantly. For instance the preferred embodiment disclosed in the Yanko patent has eight tangs on each drive plate that serve as abutments for the stop surfaces of the ring member. Moreover the Yanko torsional vibration damper does not require an even number of tangs for a balanced stop arrangement. Hence the Yanko stop arrangement provides higher torque resistance and greater design freedom in comparison to the Graton stop arrangement.
While the Yanko arrangement is an improvement over the Graton arrangement, further improvements are possible. For instance, the Yanko ring member is a machined forging that is relatively expensive to manufacture. The Yanko ring member also requires radial space between the tangs of the inner and outer drive plates, which can reduce the number of damping springs, increase the overall diameter of the torsional vibration damper, and/or introduce weaknesses in the drive plates.
SUMMARY OF THE INVENTION
The object of this invention is to provide improvements over the two-stage torsional vibration damper disclosed in the Yanko patent and still further improvements over the two-stage torsional vibration damper disclosed in the Graton patent.
A feature of the invention is that the two stage torsional vibration damper has a plurality of individual drive blocks that are radially disposed between inner and outer drive plates that all function as stops to limit the angular displacements of the drive plates with respect to the retainer plates and compression of the damping springs in either drive direction. These individual drive blocks reduce manufacturing costs and radial space requirements significantly in comparison to the Yanko ring member.
Another feature of the invention is that the two-stage torsional vibration damper has stops in the form of individual drive blocks that are shaped and securely fastened to the retainer plates to resist shear forces.
Still another feature of the invention is that the two stage torsional vibration damper has a plurality of drive blocks that center the drive plates with respect to each other as well as act as stops for limiting the angular displacements of the drive plates with respect to the retainer plates.
Yet another feature of the invention is that the two stage torsional vibration damper has inner and outer drive plates that have confronting pairs of tangs at their adjacent peripheries that serve as abutments for the individual drive blocks that are disposed between the drive plates.
Still yet another feature of the invention is that the two stage torsional vibration damper includes a friction damper comprising an annular friction ring and Belleville washer that is economical, easily assembled and does not need to accommodate the drive blocks that hold the retainer plates together.
These and other objects, features and advantages of the invention will become apparent from the description below, which is given by way of example with reference to the accompanying drawing.


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