Control apparatus for automatic transmission

Abstract

Abstract When a vehicle is halted with the transmission in a forward drive range, an input clutch is disengaged to enhance the fuel efficiency and, at the same times a hill-hold brake is engaged to prevent the vehicle from rolling backward on a steep up-slope. At that time, the hydraulic pressure P C-1 of the input clutch C1 is gradually reduced by ΔP CIR (P C-1 =P C-1 -ΔP CIR ) while the hydraulic pressure P B-1 of the hill-hold brake B1 is increased gradually so as to satisfy an equation P B-1 =K1+K2 X e where ΔP cir is a change in hydraulic pressure which is required for gradually disengaging the first clutch C1, K1 is a hill-hold brake pressure at which braking resistance begins, K2 is hill-hold brake pressure producing a fully braked condition, and e is the input/output rotational-speed ratio of a torque converter Subsequently during start of vehicle movement, the hydraulic pressure P C-1 of the input clutch C1 is gradually increased (P C-1 =p C-1 +ΔP C-1A ) while the hydraulic pressure P B-1 of the hill-hold brake B1 is gradually decreased (P B-1 ==P B-1- ΔP B-1 ) until the ratio of the rotational speed N C-1 of the first clutch C1 becomes less than a rotational speed N C-1E corresponding to the clutch being almost engaged ΔP C-1A and ΔP B-1 are incremental values proportional to accelerator depression so that a delay in starting is reduced in accordance with driver demand.

Inventors

• 👤 Hiroshi Tsutsui
• 👤 Kazumasa Tsukamoto
• 👤 Masahiro Hayabuchi
• 👤 Masaaki Nishida
• 👤 Yoshihisa Yamamoto
• 👤 Akitomo Suzuki

Bibliographic Details