Automatic transmission.

摘要

An automatic transmission comprising: a first frictional engagement element (2A) and a second frictional engagement element (3A) juxtaposed in the axial direction; a first hydraulic servo unit (2B) including a first cylinder (21) having a side wall portion interposed between the two frictional engagement elements (2A,2B); and a second hydraulic servo unit (3B) including a second cylinder (32) having a side wall portion interposed between the two frictional engagement elements (2A,2B). The first cylinder (21) further has a first outer circumferential cylinder portion (212) extending from the outer circumference of the side wall portion (211) thereof toward the first frictional engagement element (2A) and a first inner circumferential cylinder portion (313) extending from the inner circumference (311) thereof toward the first frictional engagement element (2A). The first hydraulic servo unit (2B) further includes: a first piston (22) having its inner and outer circumferences so slidably supported by the outer circumferential cylinder portion (212) and the first inner circumferential cylinder portion (313) of the first cylinder (21) as to slide in the axial direction thereby to push the first frictional engagement element (2A) and a first return spring (23) arranged in the inner circumference of the first frictional engagement element (2A) for pushing back the first piston (22). The second cylinder (32) further has a second outer circumferential cylinder portion (312) extending from the outer circumference of the side wall portion thereof toward the second frictional engagement element (3A), and an inner circumferential cylinder portion made common with the first inner circumferential cylinder portion (313). The second hydraulic servo unit (3B) further includes: a second piston (32) having its larger-diameter outer circumferential portion (321) and a smaller-diameter outer circumferential portion (322) so slidably supported by the inner circumference of the second outer circumferential cylinder portion (312) and the inner circumference of the first inner circumferential cylinder portion (313) as to slide in the axial direction thereby to push the second frictional engagement element (3A); and a second return spring (33) arranged in the inner circumference of the first frictional engagement (2A) element for pushing back the second piston (32).