Arc coil spring configuration
View Patent ↗Improved performance of arc coil springs by stress reduction when they are bottomed out is achieved by forming the coil spring wire in a substantially trapezoidal or other shape such that when bottomed, the side surfaces of the coil abut and carry the bottoming load which is distributed over a comparatively large surface area. The angles of the sidewalls of the substantially trapezoidal cross section wire are preferably coincident with lines of radius when the spring is installed in an arc in a clutch, damper or flywheel. The radius of the outer surface of the arc coil spring wire is matched to the radius of the inner surface of the guide or housing so that the area of contact is large, thereby distributing the outwardly directed spring force over a large area, reducing the force per unit area and improving lubrication retention on the contacting surfaces.
1. An arc spring and housing for a rotating damper comprising, in combination,
a housing having a region for receiving an arc spring, said region having an outer, curved, spring engaged surface defining a radius from a center of rotation of said housing and a stop at each end of said spring receiving region, and
an arc spring disposed in said region between said stops, said arc spring defining a plurality of coils, said coils fabricated of substantially trapezoidal cross section spring wire having sidewalls configured to contact one another along a line when fully compressed and an outer surface of said spring wire having a radius of curvature substantially equal to said radius of said curved, spring engaged surface of said housing.
2. The arc spring and housing of claim 1 wherein said sidewalls are disposed at angles conforming to lines of radius when said plurality of coils are disposed in said housing.
3. The arc spring and housing of claim 1 wherein said housing includes a first drive portion and a second driven portion and wherein one of said stops is coupled to said first drive portion and another of said stops is coupled to said second driven portion.
4. The arc spring and housing of claim 1 wherein inner regions of said arc spring are in sidewall to sidewall contact when said arc spring is fully compressed.
5. The arc spring and housing of claim 1 wherein said sidewalls of said coils converge at an angle between approximately 2° and 10°.
6. The arc spring and housing of claim 1 wherein a pair of arc springs are disposed in said housing in diametrical opposition.
7. The arc spring and housing of claim 1 wherein an included angle between said sidewalls of said coils of said arc spring is larger when a radius of curvature of said arc spring is smaller and smaller when said radius of curvature of said arc spring is larger.
8. A flywheel assembly comprising, in combination,
a first flywheel disc having at least one first spring stop and at least a portion of a circumferential spring housing having a first inner surface of a first circumferential radius of curvature,
a second flywheel disc having a least a second spring stop,
an arc compression spring disposed between said first and said second spring stops and within said portion of said spring housing, said arc compression spring having coil wire defining a substantially trapezoidal cross section, said trapezoidal cross section having converging sidewalls conforming to lines of radius and a narrower end of said trapezoidal cross section having a second radius of curvature substantially equal to said first circumferential radius of curvature of said first inner surface of said spring housing.
9. The flywheel assembly of claim 8 wherein said flywheel is a dual mass flywheel.
10. The flywheel assembly of claim 8 wherein said first flywheel disc includes a first drive portion and said second flywheel disc includes a second driven portion.
11. The flywheel assembly of claim 8 wherein inner regions of said arc compression spring are in sidewall to sidewall contact when said arc compression spring is fully compressed.
12. The flywheel assembly of claim 8 wherein said first and second flywheel discs include a plurality of stops and a plurality of said arc compression springs disposed between said stops.
13. The flywheel assembly of claim 8 wherein said converging sidewalls define angles between approximately 2° and 10°.