V-ribbed belt having an outer surface with improved coefficient of friction
A V-ribbed belt for a mechanical power transmission is disclosed. The V-ribbed belt comprises an outer back-side surface, an inner front-side surface, and a load-carrying section disposed between the front-side and back-side surfaces. The front-side surface includes a plurality of laterally spaced longitudinally extending v-ribs. The back-side surface includes a plurality of raised features that, when running on a flat-faced, back-side pulley, form a contact patch of about 20% to about 50% of that of a traditional flat-faced belt running on a flat-faced pulley. The reduced contact patch provides increased contact pressure which in turn provides an improved effective coefficient of friction between the belt and the pulley.
1. In a V-ribbed belt pulley system comprising (a) a V-ribbed belt having an outer back-side section, an inner front-side section having a plurality of laterally spaced longitudinally extending v-ribs, and a load-carrying section disposed between said back-side and said front-side sections and coextensive with both the back-side and front-side sections, (b) a front-side driving pulley frictionally engaged with the front-side section of the V-ribbed belt, and (c) a flat-faced back-side pulley frictionally engaged with the back-side section of the V-ribbed belt, the improvement wherein the outer surface of the back-side section of the V-ribbed belt has a maximum thickness of about 1.3 mm and comprises raised features separated by low regions having a depth of 0.1 mm to 1.0 mm alternating therebetween, wherein the raised features have a uniform center-to-center distance and contact the back-side pulley forming a reduced contact patch with the back-side pulley, the reduced contact patch having an area about 20% to about 50% of the area of a full contact patch that would be formed between the back-side pulley and a flat-faced belt over the same length of engagement.
2. The V-ribbed belt pulley system of claim 1 wherein the raised features extend longitudinally along the length of the V-ribbed belt and are spaced laterally across the width of the back-side of the V-ribbed belt.
3. The V-ribbed belt pulley system of claim 2 wherein a transverse cross-section through the width of at least one of said raised features has a curved outermost pulley-contacting surface.
4. The V-ribbed belt pulley system of claim 2 wherein said raised features comprise continuous ribs extending longitudinally along the length of the back-side of the V-ribbed belt, said ribs having curved pulley-contacting surfaces.
5. The V-ribbed belt pulley system of claim 4 wherein the reduced contact patch is defined by the area of contact between the flat-faced back-side pulley and the apexes of the curved pulley-contacting surfaces of said ribs.
6. The V-ribbed belt pulley system of claim 2 wherein at least one of said raised features comprises a triangular rib having a vertex that contacts the back-side pulley.
7. The V-ribbed belt pulley system of claim 1 wherein said raised features have a width of about 0.2 mm to about 1.8 mm and the center-to-center distance is about 0.4 mm to about 3.6 mm.
8. The V-ribbed belt pulley system of claim 1 wherein the thickness of the back-side section of the belt including the raised features is about 0.76 mm to about 1.3 mm and the thickness of the front-side section of the belt is about 4.0 mm to about 6.35 mm.
9. The V-ribbed belt pulley system of claim 8 wherein the load-carrying section of the belt comprises longitudinally extending load-carrying cords.
10. The V-ribbed belt pulley system of claim 1 wherein the reduced contact patch formed by contact between the raised features and the back-side pulley has an area about 20% to about 35% of the area of a full contact patch that would be formed between the back-side pulley and a flat-faced belt over the same length of engagement.
11. A V-ribbed belt pulley system comprising:
(a) a V-ribbed belt having an outer back-side section and an inner front-side section separated from one another by a coextensive load carrying section, the front-side section having a plurality of laterally spaced longitudinally extending v-ribs;
(b) a grooved front-side driving pulley frictionally engaged with the front-side section of the V-ribbed belt; and
(c) a flat-faced back-side pulley frictionally engaged with the back-side section of the V-ribbed belt;
wherein the outer surface of the back-side section of the V-ribbed belt comprises a plurality of ribs extending longitudinally along the length of the back-side of the V-ribbed belt, the ribs having curved outer tips separated by low regions having a depth of 0.1 mm to 1.0 mm alternating therebetween, wherein the ribs contact and frictionally engage the flat-faced back-side pulley at the apexes of the ribs.
12. The V-ribbed belt pulley system of claim 11 wherein the ribs have a width of about 0.2 mm to about 1.8 mm and a center-to-center distance of about 0.4 mm to about 3.6 mm.
13. The V-ribbed belt pulley system of claim 11 wherein the thickness of the back-side section of the belt including the raised features is about 0.76 mm to about 1.3 mm and the thickness of the front-side section of the belt is about 4.0 mm to about 6.35 mm.
14. A V-ribbed belt pulley system comprising:
(a) a V-ribbed belt having an outer back-side section and an inner front-side section, the front-side section having a plurality of laterally spaced longitudinally extending v-ribs;
(b) a grooved front-side driving pulley frictionally engaged with the front-side section of the V-ribbed belt; and
(c) a flat-faced back-side pulley frictionally engaged with the back-side section of the V-ribbed belt;
wherein the outer surface of the back-side section of the V-ribbed belt comprises a plurality of raised features that contact and frictionally engage the flat-faced back-side pulley, the raised features extending longitudinally along the length of the belt and having heights of 0.1 mm to 1.0 mm.
15. The V-ribbed belt pulley system of claim 14 wherein the raised features comprise longitudinally extending ribs having curved tips that contact the flat-faced back-side pulley at the apexes of the ribs.
16. The V-ribbed belt pulley system of claim 15 wherein the ribs have heights of about 0.5 mm to about 1.0 mm.
17. The V-ribbed belt pulley system of claim 14 wherein at least one raised feature is separated from an adjacent raised feature by a longitudinally extending curved channel.
18. The V-ribbed belt pulley system of claim 14 wherein the raised features comprise longitudinally extending triangular ribs having pointed tips that contact the flat-faced back-side pulley at the vertices of the ribs.
19. A V-ribbed belt comprising:
an inner front-side section having a plurality of laterally spaced longitudinally extending V-ribs;
an outer back-side section having grooves recessed therein that create raised features in its outer surface; and
a coextensive load-carrying section disposed between said back-side and said front-side sections;
wherein the raised features have a uniform center-to-center distance and the belt is characterized by a coefficient of friction between the outer back-side section and a flat back-side pulley that increases with consecutive ten hour or twenty-four hour cycles at peak or at 10% slip under dry, dust conditions in a test chamber following SAE J2432 test conditions.