Automatic transmission control
First Claim
1. A control system for an automatic transmission of a vehicle, said transmission having input and output shafts, a plurality of selectable drive ratios between the input and output shafts and including shifting means for changing the drive ratio, a speed signal generating means coupled with the transmission for producing a speed signal having a value corresponding to the speed of the output shaft, a shift signal generating means responsive to the speed signal for producing an upshift signal event at the upper end of each of plural speed ranges of said output shaft and a downshift signal event at the lower end of each speed range, counting means connected with the shift signal generating means and responsive to the number and sense of the upshift and downshift signal events for producing a command signal having a value corresponding to the speed range, and speed range control means connected with the counting means and responsive to said command signal for controlling said shifting means in accordance with the command signal.
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Abstract
An electronic digital control system is disclosed for vehicle power transmissions, especially adapted for off-highway earth moving vehicles. Automatic forward speed range shifting is provided in response to the vehicle speed subject to certain overriding manual control. A transmission output speed signal is applied to a shift signal generating means which has a plurality of channels each corresponding to a different forward speed range. A level detecting means in each channel produces digital upshift and downshift signals and shift signal counting means, connected with all channels, produces a net count of upshift and downshift signal events and a command signal representing the speed range into which the transmission is to be shifted. A shift control circuit responds to the command signal to effect the required ratio change in the transmission. Feedback means are provided from the counting means to the shift signal generating means to ensure that a shift signal event will not be produced for any speed range except those immediately higher or lower than the existing speed range. A manual range selector switch inhibits the automatic system from shifting to a speed range higher than that selected by the operator. The system includes means for causing lock-up of the torque converter in a predetermined speed range and for momentary unlock of the converter during shifting of the transmission. Manual control functions including reverse drive, neutral and low-low drive are provided in the control system.
35 Citations
29 Claims
- 1. A control system for an automatic transmission of a vehicle, said transmission having input and output shafts, a plurality of selectable drive ratios between the input and output shafts and including shifting means for changing the drive ratio, a speed signal generating means coupled with the transmission for producing a speed signal having a value corresponding to the speed of the output shaft, a shift signal generating means responsive to the speed signal for producing an upshift signal event at the upper end of each of plural speed ranges of said output shaft and a downshift signal event at the lower end of each speed range, counting means connected with the shift signal generating means and responsive to the number and sense of the upshift and downshift signal events for producing a command signal having a value corresponding to the speed range, and speed range control means connected with the counting means and responsive to said command signal for controlling said shifting means in accordance with the command signal.
- 8. A control system for an automatic transmission of a vehicle, said transmission having input and output shafts and a plurality of selectable drive ratios between the input and output shafts and including shifting means for changing the drive ratio, a speed signal generating means coupled with the transmission for producing a speed signal having a value corresponding to the speed of the output shaft, a shift signal generating means including a plurality of shift signal channels corresponding to a plurality of different speed ranges with adjacent ranges joined by transition zones bounded by an upshift point and a downshift point, each of said channels including level detecting means responsive to said speed signal for producing a speed logic signal which changes from a first logic state to a second logic state at the upshift point of the respective channel and which changes from the second logic state to the first logic state at the downshift point of the respective channel, each of said channels also including an upshift signal circuit and a downshift signal circuit connected with the respective level detecting means and responsive to said speed logic signal for producing upshift and downshift signal events at said upshift and downshift points respectively, counting means connected with all of said shift signal channels and responsive to said upshift and downshift signal events for producing a command signal corresponding to the difference between the count of upshift and downshift signal events, feedback means connected from the output of said counting means to the inputs of said upshift and downshift signal circuits for inhibiting generation of upshift and downshift signal events for all speed ranges except the ones immediately above and below the speed range corresponding to said command signal, and speed range control means connected with said counting means and responsive to said command signal for controlling said shifting means in accordance with said command signal.
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29. A control system for an automatic transmission of a vehicle, said transmission having input and output shafts and including shifting means for changing the drive ratio of said transmission to provide plural different speed ranges of said output shaft, a speed signal generating means coupled with one of said shafts of the transmission for producing a speed signal, a shift signal generating means connected with the speed signal generating means and responsive to the speed signal for producing an upshift signal event at the upper end of each of said plural speed ranges and a downshift signal event at the lower end of each of said speed ranges, counting means connected with the shift signal generating means and responsive to the number and sense of the upshift and downshift signal events for producing a command signal having a value corresponding to the speed range, and speed range control means connected with the counting means and responsive to said command signal for controlling the shifting means in accordance with the command signal.
Specification