| 摘要 |
PURPOSE: To prevent the worsening of the fuel consumption in the shift to the low speed stage by judging whether or not the traveling on the low speed stage after the inhibition of the traveling on the high speed stage improves the efficiency of a torque converter to perform the down shift concerning the control on an uphill road in the shift to the low speed stage on the basis of the result of the judgement. CONSTITUTION: While the efficiency of a torque converter 20 is represented as the function of a speed ratio e (= turbine rotational speed Nt/engine rotational speed Ne) with an almost rightward rising property, the property is lowered once right before it enters the fluid coupling region and then rises rightward again. Thus, whether or not the downshift to the low speed stage improves the efficiency can be perceived by observing the degree of the speed ratio e. Then when the present speed ratio e is low and thereby the efficiencyηof the torque converter 20 is also low in an ECU 84, an automatic transmission 2 is controllably shifted down to the low speed stage to lessen the slip ratio and improve the efficiency. |
