| 摘要 |
The present invention refers to a bicycle gearshift with improved precision control, which comprises a kinematic mechanism in the form of a four-bar linkage (11) with a base body (12) and a mobile body (14) connected together through a pair of connecting rods (13,15) articulated to the base body (12) and to the mobile body (14) at four pin elements (16,17,18,19), each pair of opposite pin elements (16,19 and 17,18) of the four pin elements (16,17,18,19) defining a diagonal of the four-bar linkage-kinematic mechanism, the base body (12) comprising a first attachment group (23) to a bicycle frame (20) and the mobile body (14) being connected to a chain guide (21) at a second attachment group (34), the four-bar linkage-kinematic mechanism (11) being associated with gearshift actuation means (28) suitable for deforming the four-bar linkage-kinematic mechanism (11) so as to determine a displacement of the mobile body (14) with respect to said base body (12) and consequently a primary displacement of the chain guide (21) in the axial direction with respect to the axis (A) of a cogset (33), at least one from the first attachment group (23) and the second attachment group (34) comprising a chain tensioning spring (25,35), the chain tensioning spring (25,35) determining a set-up of the chain guide (21) when engaged with a chain (27) of a bicycle transmission, and it is characterised in that it comprises a kinematic mechanism (45) for adjusting the preload of the chain tensioning spring (25,35) as a function of the primary displacement of the chain guide (21) so as to determine a variation in the set-up of the chain guide (21). |
