Methods and devices for altering the transmission ratio of a drive system

Abstract

The transmission ratio between a first motor and an output shaft is varied by changing the speed of a second motor. The first and second motors are coupled to the output shaft with a planetary gear set. The first and second motors may both add power to the drive system.

1 . A drive system for varying the transmission ratio between a first motor and an output shaft, comprising:
 a first motor;   a second motor;   an output shaft;   a control system coupled to the first and second motors, the control system controlling operation of the first and second motors; and   a planetary gear set including a ring gear, a sun gear and a carrier which supports at least one planet gear, the first motor, the second motor, and the output shaft each being coupled to at least one of the ring gear, sun gear and carrier, wherein the transmission ratio between the first motor and the output shaft is varied by varying the speed of the second motor.   
     
     
         2 . The drive system of  claim 1 , wherein:
 the output shaft speed increases when the speed of the second motor increases and the speed of the first motor is held constant.   
     
     
         3 . The drive system of  claim 1 , wherein:
 the transmission ratio is controlled by the control system so that the speed of the second motor is dependent upon an output torque demand on the output shaft.   
     
     
         4 . The drive system of  claim 1 , wherein:
 the first motor is a heat engine; and   the second motor is an electric motor.   
     
     
         5 . The drive system of  claim 4 , wherein:
 the heat engine is an internal combustion engine.   
     
     
         6 . The drive system of  claim 1 , wherein:
 the first motor is a turbine.   
     
     
         7 . The drive system of  claim 1 , wherein:
 the first motor is coupled to the sun gear;   the second motor is coupled to the ring gear; and   the output shaft is coupled to the carrier.   
     
     
         8 . The drive system of  claim 1 , wherein:
 the first motor is coupled to the sun gear;   the second motor is coupled to the carrier; and   the output shaft is coupled to the ring gear.   
     
     
         9 . The drive system of  claim 1 , further comprising:
 a synchronizer which couples rotation of the first motor and the output shaft at a fixed transmission ratio.   
     
     
         10 . The drive system of  claim 1 , wherein:
 the first motor is operated in a performance range by varying the speed of the second motor thereby varying the transmission ratio between the first motor and the output shaft to maintain operation in the performance range.   
     
     
         11 . The drive system of  claim 10 , wherein:
 the first motor is operated in the performance range with a speed in a range of less than 2000 rpm while the power output increases at least 50% of a peak power output.   
     
     
         12 . The drive system of  claim 11 , wherein:
 the first motor is operated with the speed in the performance range of less than 1000 rpm.   
     
     
         13 . The drive system of  claim 1 , wherein:
 the first and second motors both add power to the output shaft.   
     
     
         14 . The drive system of  claim 1 , further comprising the step of:
 means for stopping the second motor to provide a fixed speed ratio between the first motor and the output shaft.   
     
     
         15 . The drive system of  claim 14 , wherein:
 the first and second motors combine power in series to the output shaft.   
     
     
         16 . The drive system of  claim 1 , further comprising:
 a power storage device;   the second motor being an electric motor capable of operating as a generator, the second motor being coupled to the power storage device to generate and store electrical energy.   
     
     
         17 . A method of varying the transmission ratio between the first motor and the output shaft using a second motor, comprising the steps of:
 providing a first motor, a second motor, an output shaft and a planetary gear set including a ring gear, a sun gear and a carrier which supports at least one planet gear;   coupling the first motor, the second motor, and the output shaft each to one of the ring gear, sun gear and carrier;   producing a rotary output at the output shaft, wherein the transmission ratio between the first motor and the output shaft is varied by varying the speed of the second motor.   
     
     
         18 . The method of  claim 17 , wherein:
 the producing step is carried out with the speed of the output shaft increasing when the speed of the second motor increases when the speed of the first motor is held constant.   
     
     
         19 . The method of  claim 17 , wherein:
 the producing step is carried out with the transmission ratio being controlled by the second motor based upon an output torque demand on the engine.   
     
     
         20 . The method of  claim 17 , wherein:
 the providing step is carried out with the first motor being a heat engine and the second motor is an electric motor.   
     
     
         21 - 126 . (canceled)