Control apparatus for automatic transmission
First Claim
1. A control apparatus for an automatic transmission comprising:
- a transmission mechanism for providing a plurality of transmission ratios for a vehicle;
an input clutch provided between the transmission mechanism and an engine;
a hill-hold brake for preventing rotation of an output shaft of the transmission mechanism;
a neutral control for disengaging the input clutch and for engaging the hill-hold brake when the vehicle in a forward drive range is halted, said neutral control including gradual changing means for providing simultaneous gradual changes in disengaging and engaging forces of the input clutch and the hill-hold brake so that the engaging force of said input clutch in a slip region thereof is gradually changed while an engaging force of said hill-hold brake is gradually changed in a direction opposite to the direction in which said engaging force of said input clutch is changed to prevent transmission shock and vehicle roll-back on a hill incline;
a torque converter; and
means for detecting an input/output rotational-speed ratio of said torque converter, as said engaging force of said input clutch is changed, said gradual changing means changing the engaging force of said hill-hold brake in accordance with the detected input/output rotational-speed ratio.
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Accused Products
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 PC-1 of the input clutch C1 is gradually reduced by ΔPCIR (PC-1 =PC-1 -ΔPCIR) while the hydraulic pressure PB-1 of the hill-hold brake B1 is increased gradually so as to satisfy an equation PB-1 =K1+K2 X e where ΔPcir 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 PC-1 of the input clutch C1 is gradually increased (PC-1 =pC-1 +ΔPC-1A) while the hydraulic pressure PB-1 of the hill-hold brake B1 is gradually decreased (PB-1 ==PB-1-ΔPB-1) until the ratio of the rotational speed NC-1 of the first clutch C1 becomes less than a rotational speed NC-1E corresponding to the clutch being almost engaged ΔPC-1A and ΔPB-1 are incremental values proportional to accelerator depression so that a delay in starting is reduced in accordance with driver demand.
62 Citations
11 Claims
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1. A control apparatus for an automatic transmission comprising:
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a transmission mechanism for providing a plurality of transmission ratios for a vehicle; an input clutch provided between the transmission mechanism and an engine; a hill-hold brake for preventing rotation of an output shaft of the transmission mechanism; a neutral control for disengaging the input clutch and for engaging the hill-hold brake when the vehicle in a forward drive range is halted, said neutral control including gradual changing means for providing simultaneous gradual changes in disengaging and engaging forces of the input clutch and the hill-hold brake so that the engaging force of said input clutch in a slip region thereof is gradually changed while an engaging force of said hill-hold brake is gradually changed in a direction opposite to the direction in which said engaging force of said input clutch is changed to prevent transmission shock and vehicle roll-back on a hill incline; a torque converter; and means for detecting an input/output rotational-speed ratio of said torque converter, as said engaging force of said input clutch is changed, said gradual changing means changing the engaging force of said hill-hold brake in accordance with the detected input/output rotational-speed ratio. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification