Hydraulic hybrid vehicle with large-ratio shift transmission and method of operation thereof

Abstract

A vehicle includes an internal combustion engine configured to power a hydraulic pump to pressurize hydraulic fluid, which is used to power the vehicle directly or is stored in an accumulator. A drive module, including a hydraulic pump/motor and a multi-speed mechanical transmission, is operatively coupled to drive wheels of the vehicle to provide motive power to the vehicle. The drive module can also include a second hydraulic motor (or multiple hydraulic motors) configured to provide motive power. The transmission is configured to progress through its gears at ratio shifts of no less than 2:1 between adjacent gear positions. The transmission is configured to place the hydraulic motor in neutral during some portions of vehicle operation, and to engage the motor during other portions of vehicle operation.

1 . A drive module of a vehicle, comprising:
 a support frame;   a first hydraulic pump/motor coupled to the support frame and having a first driveshaft;   a second hydraulic pump/motor coupled to the support frame and having a second driveshaft rotationally coupled to the first driveshaft; and   a mechanical transmission coupled to the support frame and operatively coupled to the first and second hydraulic pump/motors for selective transmission of rotational force from the first and second driveshafts to a differential of the vehicle at a ratio that is selectable from among a plurality of ratios, no change of ratios between any two successive gear ratios of the transmission being less than 2:1.   
     
     
         2 . The module of  claim 1  wherein no change of ratios between any two successive gear ratios of the transmission is less than 3:1. 
     
     
         3 . The module of  claim 1  wherein the transmission is configured to place the first and second pump/motors in a neutral condition relative to the differential while a separate power source provides motive power to the vehicle. 
     
     
         4 . The module of  claim 3  comprising a third hydraulic pump/motor operatively coupled to the differential and configured to act as the separate power source. 
     
     
         5 . The drive module of  claim 1  wherein the drive module is integrated into a housing having separate covers for each of the first and second pump/motors and the transmission. 
     
     
         6 . The drive module of  claim 1 , comprising a differential coupled to the support frame and operatively coupled to the transmission to receive rotational force from the transmission and to distribute the rotational force to first and second wheels of the vehicle. 
     
     
         7 . A drive system for a hybrid vehicle, comprising:
 a first power source, including a first pump/motor having a first driveshaft;   a second power source, including a second pump/motor having a second driveshaft rotationally coupled to the first driveshaft so as to rotate at a common rate with the first driveshaft;   a third pump/motor configured to be powered to pressurize fluid for driving the first and second pump/motors;   a mechanical transmission having an input and an output, the input operatively coupled to the first and second driveshafts, the transmission including a neutral setting, at which the first and second pump/motors are disengaged from the output;   a third power source capable of providing motive power to the vehicle independent of the first and second power sources.   
     
     
         8 . The drive system of  claim 7  wherein the first and second pump/motors and the transmission are encased within a common housing. 
     
     
         9 . The drive system of  claim 7 , comprising an internal combustion engine configured to selectively drive the third pump/motor. 
     
     
         10 . The drive system of  claim 9  wherein a driveshaft of the third pump/motor is operatively coupled to a driveshaft of the engine. 
     
     
         11 . The drive system of  claim 7  wherein the first and second driveshafts are coupled to the input of the transmission without an intervening clutch. 
     
     
         12 . The drive system of  claim 7  wherein the third power source includes a fourth pump/motor. 
     
     
         13 . The drive system of  claim 7  wherein the output of the mechanical transmission and the third power source are both operatively coupled to a pair of drive wheels. 
     
     
         14 . The drive system of  claim 7  wherein the output of the mechanical transmission is operatively coupled to a first pair of drive wheels and the third power source is operatively coupled to a second pair of drive wheels. 
     
     
         15 . The drive system of  claim 7  wherein the transmission comprises:
 a plurality of individually selectable gear ratios; and 
 a synchronizer configured to synchronize a rotation speed of the first and second driveshafts with a rotation speed of the output of the transmission according to a ratio of one of the plurality of gear ratios. 
 
     
     
         16 . The drive system of  claim 7  wherein the transmission includes a plurality of individually selectable gear ratios between the input and the output, and wherein a difference in ratio between any one of the gear ratios and any adjacent one of the gear ratios is at least 2:1. 
     
     
         17 . The drive system of  claim 16  wherein the difference in ratio between any one of the gear ratios and any adjacent one of the gear ratios is at least 3:1. 
     
     
         18 . The drive system of  claim 7  comprising a control unit configured to control changes of displacement of the first and second pump/motors so that the respective displacements change substantially simultaneously and remain substantially equal to each other. 
     
     
         19 . The drive system of  claim 7  wherein the first and second pump/motors are positioned in opposition to each other so that axial forces acting on the driveshafts of the respective pump/motors substantially cancel. 
     
     
         20 . A method for operating a hybrid vehicle, comprising:
 accelerating the hybrid vehicle by applying high-pressure fluid to a hydraulic machine coupled to apply torque to a drive axle of the vehicle;   removing torque applied by the hydraulic machine by reducing a fluid displacement of the machine;   following the removing torque, changing from a first gear ratio to a second gear ratio of a transmission interposed between the hydraulic machine and the drive axle, a difference in ratio between the first gear ratio and the second gear ratio being at least 2:1; and   following the changing from a first gear ratio to a second gear ratio, restoring torque applied by the hydraulic machine by increasing the fluid displacement of the machine.   
     
     
         21 . The method of  claim 17  wherein the difference in ratio between the first gear ratio and the second gear ratio is at least 3:1 
     
     
         22 . The method of  claim 20  wherein the restoring torque comprises increasing torque, immediately following the changing from a first gear ratio to a second gear ratio, until an acceleration level of the vehicle is substantially equal to an acceleration level of the vehicle immediately prior to the removing torque. 
     
     
         23 . The method of  claim 20 , comprising:
 shifting the transmission to place the hydraulic machine in a neutral condition while the vehicle is traveling at a substantially constant cruising speed; and   providing motive power to the vehicle from a separate power source while the hydraulic machine is in a neutral condition.   
     
     
         24 . The method of  claim 20 , comprising:
 moving pressurized fluid to a hydraulic accumulator by operating an internal combustion engine to power a hydraulic pump.   
     
     
         25 . The method of  claim 20 , comprising:
 operating the hybrid vehicle in a reverse direction by reversing a direction of torque applied by the hydraulic motor to the drive axle.   
     
     
         26 . The method of  claim 20  wherein:
 the hydraulic machine comprises a pair of hydraulic machines coupled together and configured to rotate at an equal rate; 
 applying high-pressure fluid to the hydraulic machine comprises applying hydraulic fluid to the pair of hydraulic machines; 
 reducing the fluid displacement of the hydraulic machine comprises reducing the fluid displacement of each of the pair of hydraulic machine substantially equally; and 
 increasing the fluid displacement of the hydraulic machine comprises increasing the fluid displacement of each of the pair of hydraulic machine substantially equally. 
 
     
     
         27 . The method of  claim 20  wherein the method is a method for operating an on-road passenger hybrid vehicle.