System and method for decreasing ratio changing time in electronically enhanced powertrain systems

Abstract

A system and method for decreasing the time required to complete a ratio change in an electronically enhanced powertrain system is provided. The powertrain system includes a number of devices for providing a retarding torque to engine rotation to increase the decay rate of the engine speed during an upshift. These devices include an engine brake and an input shaft brake. A retarding torque is also provided by increasing engine accessory load by controlling various engine accessories such as a cooling fan, an air compressor, a hydraulic pump, an air conditioning compressor, and an alternator.

What is claimed is:  
     
       1. A method for reducing a ratio changing time in a mechanical powertrain system including an engine having a device operative to retard engine rotation, the engine being coupled by a master friction clutch to a mechanical change gear transmission having a plurality of gear ratio combinations and a neutral gear state selectively engageable between a transmission input shaft and a transmission output shaft, the system also including an electronic control unit for receiving a plurality of input signals indicative of an engine speed, an output shaft speed, and a neutral gear state, the electronic control unit also being operative to generate command signals for controlling the engine retarding device, the method comprising: 
       sensing the neutral gear state which occurs after disengaging a current gear ratio and before effecting engagement of a target gear ratio; and  
       while the master friction clutch is engaged, applying a retarding torque to the engine while the engine speed is above a synchronous speed at which engagement of the target gear ratio is effected so as to increase engine deceleration and reduce ratio changing time;  
       monitoring the closure rate at which engine speed approaches the synchronous speed; and  
       
         controlling application of the retarding torque based on the closure rate.  
       
     
     
       2. The method of  claim 1  wherein the transmission further includes an input shaft brake for retarding rotation of the input shaft and wherein applying a retarding torque comprises actuating the engine retarding device in combination with actuating the input shaft brake. 
     
     
       3. The method of  claim 2  wherein the engine retarding device is an engine compression brake. 
     
     
       4. The method of  claim 1  wherein the transmission system further includes a plurality of engine accessories coupled to the engine and in communication with the electronic control unit and wherein applying a retarding torque comprises energizing at least one of the plurality of engine accessories to increase engine load. 
     
     
       5. The method of  claim 4  wherein the engine accessories include a cooling fan, an air compressor, a hydraulic pump, an air conditioning compressor, and an alternator. 
     
     
       6. The method of  claim 1  wherein the transmission system further includes a plurality of engine accessories coupled to the engine and in communication with the electronic control unit, the transmission further includes an input shaft brake for retarding rotation of the input shaft, and wherein applying a retarding torque comprises actuating a combination of devices selected from the group consisting of the plurality of engine accessories, the engine retarding device, and the input shaft brake. 
     
     
       7. The method of  claim 1  further comprising: 
       monitoring the closure rate at which the engine speed approaches the synchronous speed; and  
       controlling application of the retarding torque based on the closure rate.  
     
     
       8. The method of claim  7   1 wherein controlling application of the retarding torque includes increasing the retarding torque. 
     
     
       9. The method of claim  7   1 wherein monitoring the closure rate includes determining if the engine speed is above an engine idle reference speed. 
     
     
       10. A control system for reducing a ratio changing time of a mechanical powertrain system including an engine coupled to a mechanical change gear transmission having a plurality of gear ratio combinations and a neutral gear state selectively engageable between a transmission input shaft and a transmission output shaft, the powertrain system also including an electronic control unit for receiving a plurality of input signals indicative of an engine speed, an output shaft speed, and a neutral gear state, the electronic control unit also being operative to generate command signals for controlling the engine and the transmission, the control system comprising: 
       means for applying a retarding torque in response to a command from the electronic control unit, the retarding torque being applied to the engine while the engine speed is above a synchronous speed at which the target gear ratio is effected so as to increase engine deceleration and reduce ratio changing time;  
       means for monitoring the closure rate at which the engine speed approaches the synchronous speed; and  
       means for controlling application of the retarding torque based on the closure rate.  
     
     
       11. The control system of  claim 10  wherein the means for applying a retarding torque comprises an input shaft brake attached to the transmission and in communication with the electronic control unit for retarding rotation of the input shaft. 
     
     
       12. The control system of  claim 10  wherein the means for applying a retarding torque comprises an engine brake. 
     
     
       13. The control system of  claim 12  wherein the engine brake is an engine compression brake. 
     
     
       14. The system of  claim 10  wherein the means for applying a retarding torque comprises a plurality of engine accessories coupled to the engine for increasing a load on the engine so as to retard engine rotation. 
     
     
       15. The system of  claim 10  wherein the means for applying a retarding torque comprises an engine cooling fan for increasing a load on the engine so as to retard engine rotation. 
     
     
       16. The system of  claim 15  wherein the means for applying a retarding torque further comprises an air compressor, a hydraulic pump, an air conditioning compressor, and an alternator, all of which are coupled to the engine for increasing a load on the engine so as to retard engine rotation. 
     
     
       17. The system of  claim 10  wherein the means for monitoring the closure rate includes means for determining if the engine speed is above an engine idle reference speed. 
     
     
       18. The method of  claim 1  wherein the transmission further includes an input shaft brake for retarding rotation of the input shaft and wherein the step of applying a retarding torque comprises actuating the input shaft brake. 
     
     
       19. A method for reducing a ratio changing time in a mechanical powertrain system including an engine having a device operative to retard engine rotation, the engine being coupled by a master friction clutch to a mechanical change- gear transmission having a plurality of gear ratio combinations and a neutral gear state selectively engageable between a transmission input shaft and a transmission output shaft, the system also including an electronic control unit for receiving a plurality of input signals indicative of an engine speed, an output shaft speed, and a neutral gear state, the electronic control unit also being operative to generate command signals for controlling the engine retarding device, the method comprising:    
       
         sensing the neutral gear state which occurs after disengaging a current gear ratio and before effecting engagement of a target gear ratio;  
       
         determining a first value indicative of one of  ( i )  a current engine speed and  ( ii )  an expected engine speed;    
         determining a second value indicative of one of  ( i )  a current synchronous speed for engaging said target ratio and  ( ii )  an expected synchronous speed for engaging said target ratio;    
       
         determining a difference between said first and second values; and  
       
         while the master friction clutch is engaged, generating command signals to said engine retarding device for applying a retarding torque to the engine while the engine speed is above a synchronous speed at which engagement of the target gear ratio is effective so as to increase engine deceleration and reduce ratio changing time, said engine retarding device controlled in accordance with at least one of  ( i )  said difference and  ( ii )  a rate of change of said difference.    
     
     
       20. The method of  claim 19  wherein, if said difference is less than about 40 RPM, then the engine retarding device is not activated.  
     
     
       21. The method of  claim 19 , wherein said engine retarding device has a determined reaction time, and said engine retarding device is controlled based upon said reaction time.  
     
     
       22. A method for reducing a ratio changing time in a mechanical powertrain system including an engine having a device operative to retard engine rotation, the engine being coupled by a master friction clutch to a mechanical change- gear transmission having a plurality of gear ratio combinations and a neutral gear state selectively engageable between a transmission input shaft and a transmission output shaft, the system also including an electronic control unit for receiving a plurality of input signals indicative of an engine speed, an output shaft speed, and a neutral gear state, the electronic control unit also being operative to generate command signals for controlling the engine retarding device, the method comprising:    
       
         sensing the neutral gear state which occurs after disengaging a current gear ratio and before effecting engagement of a target gear ratio;  
       
       
         determining a value indicative of an engine speed;  
       
       
         determining a synchronous window of engine speeds for engaging said target gear ratio; and  
       
       
         while the master friction clutch is engaged, generating command signals to said engage retarding device for applying a retarding torque to the engine while the engine speed is above a synchronous speed at which engagement of the target gear ratio is effective so as to increase engine deceleration and reduce ratio changing time, said engine retarding device controlled in accordance with said value and said synchronous window.  
       
     
     
       23. The method of  claim 22  wherein said engine retarding device has a determined reaction time, and said engine retarding device is controlled based upon said reaction time.  
     
     
       24. A method for reducing a ratio changing time in a mechanical powertrain system including an engine having a device operative to retard engine rotation, the engine being coupled by a master friction clutch to a mechanical change- gear transmission having a plurality of gear ratio combinations and a neutral gear state selectively engageable between a transmission input shaft and a transmission output shaft, the system also including an electronic control unit for receiving a plurality of input signals indicative of an engine speed, an output shaft speed, and a neutral gear state, the electronic control unit also being operative to generate command signals for controlling the engine retarding device, the method comprising:    
       
         sensing the neutral gear state which occurs after disengaging a current gear ratio and before effecting engagement of a target gear ratio;  
       
       
         determining a rate of engine speed decay required for synchronous engagement of said target ratio;  
       
       
         comparing said rate to a reference value; and  
       
       
         only if said rate exceeds said reference value, while mater friction clutch is engaged, applying a retarding torque to the engine while the engine speed is above a synchronous speed at which engagement of the target gear ratio is effective so as to increase engine deceleration and reduce ratio changing time.  
       
     
     
       25. A method for reducing a ratio changing time in a mechanical powertrain system including an engine having a device operative to retard engine rotation, the engine being coupled by a master friction clutch to a mechanical change- gear transmission having a plurality of gear ratio combinations and a neutral gear state selectively engageable between a transmission input shaft and a transmission output shaft, the system also including an electronic control unit for receiving a plurality of input signals indicative of an engine speed, an output shaft speed, and a neutral gear state, the electronic control unit also being operative to generate command signals for controlling the engine retarding device, the method comprising:    
       
         determining a value indicative of a natural engine speed decay rate;  
       
       
         sensing the neutral gear state which occurs after disengaging a current gear ratio and before effecting engagement of a target gear ratio; and  
       
       
         while the master friction clutch is engaged, generating command signals to said engine retarding device for applying a retarding torque to the engine while the engine speed is above a synchronous speed at which engagement of the target gear ratio is effective so as to increase engine deceleration and reduce ratio changing time, said engine retarding device controlled in accordance with said value.  
       
     
     
       26. A method for reducing a ratio changing time in a mechanical powertrain system including an engine having a device operative to retard engine rotation, the engine being coupled by a master friction clutch to a mechanical change- gear transmission having a plurality of gear ratio combinations and a neutral gear state selectively engageable between a transmission input shaft and a transmission output shaft, the system also including an electronic control unit for receiving a plurality of input signals indicative of an engine speed, an output shaft speed, and a neutral gear state, the electronic control unit also being operative to generate command signals for controlling the engine retarding device, the method comprising:    
       
         sensing the neutral gear state which occurs after disengaging a current gear ratio and before effecting engagement of a target gear ratio; and  
       
       
         determining if engaging said target gear ratio involves a multiple ratio upshift; and  
       
       
         while the master friction clutch is engaged, generating command signals to said engine retarding device for applying a retarding torque to the engine while the engine speed is above a synchronous speed at which engagement of the target gear ratio is effective so as to increase engine deceleration and reduce ratio changing time, said engine retarding device controlled in accordance with said determination.  
       
     
     
       27. The method of  claim 26  wherein said engine retarding device is activated only during multiple ratio upshifts.