V-ribbed belt and use thereof

1. A V-ribbed belt having a plurality of V-rib portions extending along a longitudinal direction of the belt and in parallel with one another, and comprising a compression rubber layer including a frictional power transmission face at least a part of which is configured to come in contact with a V-rib groove portion of pulleys,

wherein the frictional power transmission face of the compression rubber layer is formed from a vulcanizate of a rubber composition containing a rubber component and a noise suppression improver,

wherein the noise suppression improver is at least one kind selected from the group consisting of a surfactant, a plasticizer having a larger solubility parameter than the rubber component, inorganic particles, and polyethylene resin particles,

wherein a V-rib angle of the V-rib portions is larger than a V-rib groove angle of the pulleys by 5° to 9° thereby forming a gap between an end portion of each of the V-rib portions and a corresponding one of a plurality of V-rib groove portions of the pulleys, and

wherein a torque loss of the V-ribbed belt is 0.20 N·m to 0.24 N·m when operated with the pulleys, and

wherein the torque loss is measured based on applying an initial tension to the V-ribbed belt within a range of 100 to 600 N, and rotating a driving pulley at 2,000 rpm with no load on the driving pulley.

2. The V-ribbed belt according to claim 1 , wherein the V-rib angle of the V-rib portions is 41° to 45°.

3. The V-ribbed belt according to claim 1 , wherein the pulleys include a pulley having an outer diameter of 65 mm or less.

4. The V-ribbed belt according to claim 1 ,

wherein the noise suppression improver includes a polyethylene glycol nonionic surfactant and

a ratio of the polyethylene glycol nonionic surfactant is 2 to 20 parts by mass relative to 100 parts by mass of the rubber component.

5. The V-ribbed belt according to claim 1 ,

wherein the noise suppression improver includes an ether ester plasticizer and

a ratio of the ether ester plasticizer is 5 to 15 parts by mass relative to 100 parts by mass of the rubber component.

6. The V-ribbed belt according to claim 1 , wherein the rubber component contains an ethylene-α-olefin elastomer.

7. A belt transmission apparatus comprising the V-ribbed belt according to claim 1 and the pulleys including a V-rib groove portion that can be fitted to the V-rib portions of the V-ribbed belt.

8. The belt transmission apparatus according to claim 7 , wherein the pulleys include a pulley having an outer diameter of 65 mm or less.

9. A method for reducing torque loss of a belt transmission apparatus, the method comprising winding the V-ribbed belt according to claim 1 on pulleys including a pulley having an outer diameter of 65 mm or less.