Automatic mechanical transmission control

Claim 1

An improved automatic transmission system for vehicles having a throttle-controlled engine, an operator actuated throttling control means and a transmission having a plurality of gear ratio combinations selectively engagable between a transmission input shaft and a transmission output shaft, said transmission input shaft being operatively connected to said engine, said transmission system including an information processing unit having means for receiving a plurality of input signals including (1) an input signal indicative of the position of said throttle controlling means, (2) an input signal indicative of the rotational speed of said engine, and (3) an input signal indicative of the speed of said vehicle, and (4) an input signal indicative of the direction of the last shift, said processing unit including means for processing said input signals in accordance with a program to select a desirable gear ratio for a given combination of input signals and for generating output signals whereby said transmission system is operated in accordance with said program, and means associated with said transmission effective to actuate said transmission to effect engagement of one of said gear ratio combinations in response to said output signals from said processing unit, said program having a first mode of operation and a second mode of operation, at least one of (a) the engine speeds at which said processing unit commands upshifts after a downshift being greater in said second than in said first mode of operation and (b) the engine speeds at which said processing unit commands downshifts after an upshift being less in said second mode than in said first mode of operation, said processing unit having means to set said program to said second mode of operation, the improvement characterized by: said processing unit including means for processing said input signals to provide a calculated expected engine speed value indicative of the expected rotational speed of the engine in the selected gear ratio combination at the existing vehicle speed at the time of the last shift, said means to reset said program to said first mode of operation including means to calculate a minimum reset engine speed value and a maximum reset engine speed value as a function of said expected engine speed at the time of engagement of the last engaged gear ratio, and means to reset said program to said first mode thereof in response to engine speed exceeding said maximum reset value or engine speed being less than said minimum reset value; said minimum reset engine speed value being less than said expected engine speed value and said maximum reset engine speed value being greater than said expected engine speed value.