Toothed belt
A toothed belt includes a plurality of tooth parts that are disposed at predetermined intervals along the longitudinal direction and contain a rubber composition (A) as a base material and a back side that has a cord embedded therein and contains a rubber composition (B) as a base material, in which the cord contains a Lang-twisted carbon fiber and is formed in a diameter of 1.1 mm or more and 2.5 mm or less and the rubber composition (B) constituting the back side has a hardness of from 80 degrees to 89 degrees in JIS-A hardness.
1. A toothed belt comprising:
a plurality of tooth parts that are disposed at predetermined intervals along a longitudinal direction and comprise a rubber composition (A) as a base material, and
a back side that has a cord embedded therein and comprises a rubber composition (B) as a base material,
wherein the cord comprises a Lang-twisted carbon fiber and is formed in a diameter of 1.1 mm or more and 2.5 mm or less,
wherein the rubber composition (B) constituting the back side has a hardness of from 80 degrees to 89 degrees in JIS-A hardness,
wherein the rubber composition (A) constituting the tooth parts has a hardness of from 92 degrees to 96 degrees in JIS-A hardness, and
wherein the hardness of the rubber composition (A) constituting the tooth parts is different from the hardness of the rubber composition (B) constituting the back side, and
wherein the bending rigidity of the back side is from 100 to 600 N/mm 2 .
2. The toothed belt according to claim 1 , wherein a difference between the hardness of the rubber composition (A) constituting the tooth parts and the hardness of the rubber composition (B) constituting the back side is from 7 degrees to 16 degrees in JIS-A hardness.
3. The toothed belt according to claim 1 , wherein both of the rubber composition (A) constituting the tooth parts and the rubber composition (B) constituting the back side comprise a hydrogenated acrylonitrile-butadiene rubber and an unsaturated carboxylic acid metal salt.
4. The toothed belt according to claim 1 , wherein the rubber composition (B) constituting the back side comprises a hydrogenated acrylonitrile-butadiene rubber and an unsaturated carboxylic acid metal salt in a mass ratio of from 68.6:31.4 to 100:0.
5. The toothed belt according to claim 1 , wherein the rubber composition (A) constituting the tooth parts comprises a hydrogenated acrylonitrile-butadiene rubber and an unsaturated carboxylic acid metal salt in a mass ratio of from 73.8:26.2 to 47.6:52.4.
6. The toothed belt according to claim 3 , wherein the rubber composition (A) constituting the tooth parts comprises a short fiber in an amount of from 3 to 7 parts by mass based on 100 parts by mass of a total amount of a rubber component comprising the hydrogenated acrylonitrile-butadiene rubber and the unsaturated carboxylic acid metal salt.
7. The toothed belt according to claim 1 , wherein the tooth parts have a tooth pitch of from 8 mm to 14 mm.
8. The toothed belt according to claim 1 , wherein the hardness of the rubber composition (B) constituting the back side is from 80 degrees to 82 degrees.
9. The toothed belt according to claim 1 , wherein the Lang-twisted carbon fiber has a primary twist factor ranging from 0.65 to 1.61.
10. The toothed belt according to claim 1 , wherein the rubber composition (A) constituting the tooth parts has an E′ of from 200 to 300 MPa under an atmospheric temperature of 70° C. as measured according to JIS K6394 (2007) and a loss factor (Tan δ) ranging from 0.1 to 0.2.