Vehicle shift quality using a supplemental torque source

Details Vehicle shift quality using a supplemental torque source Vehicle shift quality using a supplemental torque source

1999-08-17

2001-02-27

Wright, Dirk (Department: 3681)

Interrelated power delivery controls, including engine control

Plural engines

Electric engine

Reexamination Certificate

active

06193628

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to use of a supplemental torque source to improve shift quality in a motor vehicle.
2. Description of the Related Art
Refer first to
FIG. 1
, an illustration of typical driven wheel torques during an automatic transmission upshift event, such as from first gear to second gear. (The upshift event begins at t=1.4 seconds on the horizontal axis and is complete at about t=2.0 seconds.) The curve reflecting a system with a torque converter shows a torque “hole” at about t=1.4 seconds due to engagement of the shifting clutch and subsequent transfer of torque from the offgoing to the oncoming friction element. Shudder-like oscillations, or “shuffle” in driven wheel torque then continue during the “intertia phase” of the shift until about t=2.0 seconds.
In order to reduce cost and improve the fuel efficiency of a motor vehicle with an automatic transmission, it has been proposed to remove the vehicle's torque converter. The resulting effect of subtracting the very significant damping effect of the torque converter is also shown in FIG.
1
. The torque hole at t=1.4 seconds is larger, the oscillations up to t=2.0 seconds are larger, and very substantial oscillations in wheel torque continue beyond t=3.0 seconds. Obviously, much is lost in damping of wheel torque oscillations by removal of the torque converter.
Wheel torque oscillations are readily felt by the occupants of the vehicle. Therefore, a system which allows for removal of the torque converter for cost savings, particularly in a hybrid electric vehicle, and which can provide alternate damping for wheel torque oscillations will prove advantageous.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide damping of wheel torque in a motor vehicle, in order to improve comfort for occupants of the vehicle.
It is a further object of the present invention to facilitate removal of the torque converter of a motor vehicle without introducing objectionable wheel torque oscillations, particularly during transmission shift events.
The present invention is adapted for application in a motor vehicle comprising an engine, an electrical machine coupled to provide supplemental torque to a torque provided by the engine, a transmission having an input coupled to receive torque provided by the engine, and at least one wheel shaft driven by an output of the transmission, the wheel shaft having a driven end and an end coupled to a respective wheel of the motor vehicle.
In one embodiment, the present invention provides a method for suppressing driveline oscillations comprising: for at least one wheel shaft, sensing a difference in rotational speed between the driven end of the wheel shaft and the wheel shaft's respective wheel, and generating a torque command for the electrical machine to supply a torque which is a function of the difference.
In a second embodiment, the present invention provides a method for suppressing driveline oscillations comprising sensing a rotational speed at the output of the transmission to generate a transmission output speed signal, and generating a torque command for the electrical machine to supply a torque which is a function of the transmission output speed signal.
In a third embodiment, the present invention provides a method for suppressing driveline oscillations comprising sensing a rotational speed of the engine to generate an engine speed signal; filtering the engine speed signal to substantially eliminate at least a low-frequency range of the engine speed signal below a frequency range of the oscillations and thereby generate a second signal; and generating a torque command for the electrical machine to supply a torque which is a function of the second signal.
The present invention allows removal of a vehicle's torque converter without introduction of objectionable oscillations in the driveline of the vehicle. Cost and fuel-efficiency advantages will result.


REFERENCES:
patent: 4252208 (1981-02-01), Heidemeyer et al.
patent: 4411171 (1983-10-01), Fiala
patent: 4458156 (1984-07-01), Maucher et al.
patent: 5613920 (1997-03-01), Uno et al.
patent: 5833570 (1998-11-01), Tabata et al.

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