Hybrid vehicle having electric mode simulating low gear ratio

摘要

A motor vehicle 11 has an engine 12 driving an automatic transmission 13 which in turn drives a front final drive unit 14 connected to a pair of front wheels 15 by front driveshafts 16. The front final drive unit 14 also drives a rear drive take-off unit 17 which is connected to a rear final drive unit 18 by a propshaft 19. The rear final drive unit 18 is connected to rear wheels 21 by driveshafts 22, and houses a traction motor/generator 35 which can drive the rear wheels 21 through an epicyclic reduction gear 39 a crownwheel 27 and pinion 31. The pinion 31 is also driven by the propshaft 19 through a control coupling 33. The traction motor/generator 35 and transmission 13 are controlled by an electronic control unit (ECU) 51 according to engine load and speed, road speed, etc and an input from a transmission selector 46 having a selector lever 47 controlled by the driver. The ECU 51 also has an input from a driver-controlled hill descent control switch 45. An engine motor/generator 29 is driven by the engine 12, both motor/generators 35 being connected to a traction battery 61. The transmission 13 has ratios suitable for on-road driving only. For off-road driving, the drive from the engine 12 through the transmission 13 is disconnected and the ECU 51 controls the traction motor/ generator 35 to simulate an ultra-low ratio lower than the lowest ratio in the transmission 13. The ultra-low ratio can be brought into effect by the selector lever 47 or when a hill descent control switch 45 is operated.