Continuously variable power split transmission (CVPST) system for use in a hybrid vehicle

Abstract

The present invention is concerned with a continuously variable power split transmission(CVPST) system for use in a hybrid vehicle. The vehicle has a first motor, such as an internal combustion (IC) engine and a second motor, such as an electric motor. The system has a step-up gearbox for providing additional fixed speed ratios to extend overall transmission conversion range (CR) of the system. The system also has a speed variator and a countershaft being operatively connected to the second motor of the vehicle so that any power input applied by the second motor to the countershaft reduces the power flowing through the speed variator Also. an adjustment of the variator speed ratio i v allows a passage from underdrive i UD to overdrive i OD range of speed ratios in the step-up gearbox to be synchronized.

What is claimed is:  
     
         1 . A continuously variable power split transmission (CVPST) system for use in a hybrid vehicle, the vehicle having a first motor power supply and a second motor power supply, the system comprising: 
 (a) a step-up gearbox having an input shaft and an output shaft, the output shaft being connected to a main ratio gear set, the gearbox providing additional fixed underdrive i UD  and overdrive i OD  speed ratios to extend overall transmission conversion range (CR) of the system; and    (b) an infinitely adjustable, power split variable speed transmission unit comprising: 
 a sun shaft operatively connected to the first motor power supply of the vehicle;  
 a planetary gear set having a sun gear fixed to the sun shaft, at least two planet gears meshed with the sun gear, a ring gear meshed with the planet gears, a control gear or control sprocket coupled to the ring gear, a planet carrier having planet axes for mounting the planet gears, the planet carrier being keyed to the input shaft of the gearbox;  
 a countershaft extending parallel to the sun shaft, the countershaft being operatively connected to the ring gear through a first clutch and an additional control gear with idler gear or an additional control sprocket with chain so that the countershaft and ring gear rotate in the same direction, the countershaft being also operatively connected to the second motor power supply of the vehicle through a second clutch; and  
 a speed variator mounted between the sun shaft and the countershaft to adjustably vary the speed of the countershaft and thereby adjusting the speed and torque of the planet carrier through an adjustment of a variator speed ratio i v ;  
 whereby, on the one hand, any power input applied by the first motor power supply to the sun shaft is split into two streams merging on the planet carrier and input shaft of the gearbox, one passing through the speed variator, countershaft and ring gear, the other directly through the sun gear, and, on the other hand, any power input applied by the second motor power supply to the countershaft reduces the power flowing through the speed variator, and  
 whereby, the adjustment of the variator speed ratio i v  allows a passage from the underdrive i UD  to overdrive i OD  fixed speed ratios in the step-up gearbox to be synchronized.  
   
     
     
         2 . The system according to  claim 1 , wherein the control gear or control sprocket of the planetary gear set is fixed on or integral with the ring gear and the first clutch is mounted on the countershaft, the first clutch coupling the countershaft with the additional control gear or additional sprocket being freely mounted on the countershaft.  
     
     
         3 . The system according to  claim 1 , wherein the step-up gearbox is an in-line or parallel step-up gearbox.  
     
     
         4 . The system according to  claim 1 , wherein the step-up gearbox comprises a synchronizer ring.  
     
     
         5 . The system according to  claim 1 , wherein the first clutch is a dry or wet multi-disc clutch.  
     
     
         6 . The system according to  claim 1 , wherein the sun shaft is coaxially journalled within the planet carrier, the sun shaft being keyed to a motor shaft, the motor shaft being operatively connected to the first motor power supply, the motor shaft extending through the input shaft of the gearbox.  
     
     
         7 . The system according to  claim 1 , wherein the speed variator comprises: 
 a pair of pulleys respectively mounted onto the sun shaft and the countershaft in such a manner as to extend in the same plane, each of the pulleys having a fixed sheave and a movable sheave;    an endless V-belt mounted onto the pulleys; and    means for adjusting a distance between the fixed and movable sheave of each pulley.    
     
     
         8 . The system according to  claim 1 , wherein the ratio of the radius of the planet gears to the radius of the sun gear is ranging between 1.8 and 2.5.  
     
     
         9 . The system according to  claim 1 , wherein the main gear ratio set comprises a first gear fixed on the output shaft and a second gear connected to a differential housing.  
     
     
         10 . A continuously variable power split transmission (CVPST) system for use in a hybrid vehicle, the vehicle having a first motor power supply and a second motor power supply, the system comprising: 
 (a) a step-up gearbox having an input shaft and an output shaft, the output shaft being connected to a main ratio gear set, the gearbox providing additional fixed underdrive i UD  and overdrive i OD  speed ratios to extend overall transmission conversion range (CR) of the system; and    (b) an infinitely adjustable, power split variable speed transmission unit comprising: 
 a sun shaft operatively connected to the first motor power supply of the vehicle;  
 a planetary gear set having a sun gear fixed to the sun shaft, at least two planet gears meshed with the sun gear, a ring gear meshed with the planet gears, a control gear or control sprocket fixed to the ring gear, a planet carrier having planet axes for mounting the planet gears, the planet carrier being keyed to the input shaft of the gearbox;  
 a countershaft extending parallel to the sun shaft, the countershaft being operatively connected to the ring gear through a first clutch and an additional ratio gear with idler gear or an additional control sprocket with chain so that the countershaft and ring gear rotate in the same direction, the first clutch being mounted on the countershaft, the first clutch coupling the countershaft with the additional control gear or sprocket, the additional control gear or sprocket being freely mounted on the countershaft, the countershaft being also operatively connected to the second motor power supply of the vehicle through a second clutch; and  
 a speed variator mounted between the sun shaft and the countershaft to adjustably vary the speed of the countershaft and thereby adjusting the speed and torque of the planet carrier through an adjustment of a variator speed ratio i v ;  
 whereby, on the one hand, any power input applied by the first motor power supply to the sun shaft is split into two streams merging on the planet carrier and input shaft of the gearbox, one passing through the speed variator, countershaft and ring gear, the other directly through the sun gear, and, on the other hand, any power input applied by the second motor power supply to the countershaft reduces the power flowing through the speed variator, and  
 whereby, the adjustment of the variator speed ratio i v  allows a passage from the underdrive i UD  to overdrive i OD  fixed speed ratios in the step-up gearbox to be synchronized.  
   
     
     
         11 . The system according to  claim 10 , wherein the step-up gearbox is an in-line or parallel step-up gearbox.  
     
     
         12 . The system according to  claim 10 , wherein the sun shaft is coaxially journalled within the planet carrier, the sun shaft being keyed to a motor shaft, the motor shaft being operatively connected to the first motor power supply, the motor shaft extending through the input shaft of the gearbox.