Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
1999-07-26
2001-02-27
Marmor, Charles A (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S149000
Reexamination Certificate
active
06193630
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a vehicle transmission shift control system, and more particularly, to a clutch slip-based powershift transmission shift control system.
Modern agricultural powershift transmissions, such as the AG250 powershift transmission manufactured by Funk Manufacturing, contain multiple electronically controlled, hydraulically actuated wet clutches which direct the flow of power through the transmission. These clutches are grouped according to the portion of the transmission gear train section they control. The group of clutches which are connected directly to or through constantly meshing gears to the transmission output shaft are referred to as range clutches. Clutches between the transmission input and the range clutches are known as speed clutches. During shifting from one transmission input to output speed ratio to another speed ratio, the speed clutches change the flow of power through the transmission from one range clutch to another, resulting in an interim transmission ratio. This prepares the input section of the gear train for the final target transmission speed ratio. All clutch exchanges are controlled by fixed timing values based on a measured engine load. The load signal itself, however, cannot distinguish between the amount of engine power passing through the transmission and the amount absorbed by an external application, such as a power-take-off (PTO) application. It would therefore be desirable to sense only the transmission load, which would allow for precisely matched clutch engagements. When the transmission reaches the interim ratio, which is higher than the target ratio, the transmission output speed and vehicle ground speed will increase or decrease unless the torque transmitted by the off going range clutch is maintained at a constant transmission output torque. Therefore, it would be desirable for the range clutch to maintain its original static torque level in a new dynamic slip condition. Static coefficients of friction are typically different (usually larger) than dynamic coefficients of friction, and clutch torque capacity is dependent upon the coefficient of friction between the clutch discs. When the range clutch slips and transitions from static to dynamic operation, torque capacity changes, resulting in an abrupt shift which vehicle operators perceive as a bad shift.
SUMMARY OF THE INVENTION
Accordingly, an object of this invention is to provide powershift transmission control system which prevents abrupt shifts and which produces smooth shifts.
Another object of this invention is to sense the torque transmitted by an off-going clutch in order to distinguish between torque present at the transmission output shaft and torque present at an external application, such as a PTO application.
Another object of this invention is to improve transmission shifting by controlling the torque transmitted by an off-going clutch during a shift.
Another object of this invention is to control such an off-going clutch so that it transmits, during a slipping (dynamic friction) condition, the same torque that it transmitted during a locked up (static friction) condition.
This and other objects are achieved by the present invention wherein clutch slip is monitored during a shift. Shaft speeds are measured on both sides of a clutch and calculations based on gear ratios are performed during a shift to measure slip speed between the clutch friction disks and separators. The clutch control pressure is gradually reduced or ramped downward until relative rotation (slip) between the off-going clutch friction and reaction plates is detected. The pressure at which slip occurs in the off-going clutch is then used to calculate the portion of the engine load passing through the transmission. This updated engine load number is then used to set various other parameters which are essential to a smooth shift. The clutch control pressure is then increased so that the same torque is transmitted through the slipping clutch without locking up and returning to a static friction condition. Target clutch control pressures may be calculated or modeled for known or measured load conditions and known clutch friction behavior. Clutch control pressure may be held constant, stepped higher or lowered to compensate for the difference in static and dynamic coefficients of friction in the two clutch operating modes. Once clutch slip has been detected and controlled, speed clutches may be exchanged to an interim transmission gear ratio in preparation for a final exchange of two range clutches. Relative speed of the on-coming clutch friction and reaction plates may be monitored to trigger the exchange of torque transmission between the on-coming and off-going clutches with optimal timing (at or near synchronization). This results in a more constant output speed because transmitted torque delivered to the output shaft is more constant. Transmitted torque is controlled by matching clutch control pressure to the operating condition. Maintaining transmitted torque through the clutch in changing conditions minimizes accelerations of the shaft and vehicle, improving shift quality. If the clutch plate static coefficient of friction is greater than the dynamic coefficient of friction, clutch control pressure can be increased when the static to dynamic transition occurs, and this can be detected by sensing relative clutch speeds.
REFERENCES:
patent: 4989477 (1991-02-01), Hunter et al.
patent: 5012575 (1991-05-01), Fujiwara et al.
patent: 5014573 (1991-05-01), Hunter et al.
patent: 5043383 (1991-08-01), Butts et al.
patent: 5070747 (1991-12-01), Lentz et al.
patent: 5072390 (1991-12-01), Lentz et al.
patent: 5113343 (1992-05-01), Hunter et al.
patent: 5283738 (1994-02-01), Schwab et al.
patent: 5413539 (1995-05-01), Leonard et al.
patent: 5480363 (1996-01-01), Matsubara et al.
patent: 5520586 (1996-05-01), Brown et al.
patent: 5704871 (1998-01-01), Furukawa et al.
patent: 5778329 (1998-07-01), Officer et al.
patent: 5865707 (1999-02-01), Shimada et al.
patent: 6007458 (1999-12-01), Ohashi et al.
Janasek Clayton George
Sparks Richard Marvin
Deere & Company
Marmor Charles A
Pang Roger
LandOfFree
Slip-based shift control system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Slip-based shift control system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Slip-based shift control system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2559853