Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2000-05-26
2002-02-12
Wolfe, Willis R. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C701S110000, C701S111000, C123S436000
Reexamination Certificate
active
06347275
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for attenuating torsional vibration in a drive train of a vehicle, and more particular to such method and apparatus that can attenuate torsional vibration caused upon rapid acceleration and deceleration of the vehicle.
2. Description of the Related Art
When a vehicle is accelerated or decelerated quickly, an output of an engine steeply fluctuates and causes torsional vibration in a drive train between the engine and drive wheels. Such torsional vibration results in back and forth oscillation of the vehicle so that passengers in the vehicle feel uncomfortable. To suppress the torsional vibration, an engine revolution speed that changes with the torsional vibration of the drive train is detected and its change rate is calculated. Using the resulting value, an amount of fuel to be injected into the engine is sequentially modified (increased or decreased) to counterbalance the engine speed fluctuation. This technique is known in the art and disclosed, for instance, in Japanese Patent Application Laid-Open Publication Nos. 60-26242 and 7-324644.
The above mentioned conventional method will be described in detail in reference to
FIGS. 8A
to
8
E of the accompanying drawings.
When an accelerator opening APS (accel position sensor detection) is changed to “open” from “closed” (or to a certain value from zero) (FIG.
8
A), an engine output steeply increases so that torsional vibration occurs in a drive train operatively coupling an engine with drive wheels. This torsional vibration causes an engine revolution speed RPM to fluctuate (FIG.
8
B). A sensor detects the engine revolution speed RPM, and a calculator computes its change rate &Dgr;RPM (&Dgr;RPM=RPM−RPM(−1)) (
FIG. 8C
) RPM represents the current engine revolution speed, and RPM(−1) represents the engine revolutions speed obtained at previous detection. If &Dgr;RPM is positive (+), an amount of fuel injection for correction Qacl
2
(
FIG. 8D
) takes a negative value in order to suppress &Dgr;RPM. On the other hand, if &Dgr;RPM is a negative value, Qacl
2
takes a positive value to reduce &Dgr;RPM. Such correction value Qacl
2
is added to a basic amount of fuel injection Qbase, which is determined by the accelerator opening APS and the engine revolution speed RPM (FIG.
8
E). The resulting value Qfnl is the corrected amount of fuel injection (target amount of fuel injection).
The correction value Qacl
2
is continuously increased and decreased in accordance with the change of &Dgr;RPM to counterbalance &Dgr;RPM and Qfnl is also increased and decreased in the same manner. Further, the basic value Qbase of the final value Qfnl is determined by the accelerator opening and engine speed. Therefore, the fuel is injected in accordance with the accelerator opening APS and it is ensured to provide an engine output in accordance with the accelerator opening. At the same time, a torque sufficient to offset the torsional vibration in the drive train is generated. Accordingly, the torsional vibration is positively attenuated.
Incidentally, the inventor found that the magnitude of torsional vibration in the drive train caused upon change of the accelerator opening APS from “closed” to “open” in
FIG. 8A
is not determined by the difference between the current target value Qfnl (Qbase) at the time of accelerator opened and the previous target value Qfnl(−1) at the time of accelerator closed, but by the difference Qabs between the current final value Qfnl (Qbase) and the value Qbad at the time of minimum torque being required by the drive wheels (i.e., at the time of a drive force being first transmitted to the drive wheels from the engine). The inventor also found that the difference Qx between Qbad and Qfnl(−1) does not contribute to occurrence of the torsional vibration in the drive train at all.
Therefore, if the correction value Qacl
2
described in the preceding paragraphs is determined by the difference Qabs between Qfnl (Qbase) and Qbad, then it is possible to further efficiently attenuate the torsional vibration in the drive train. The value Qbad required to find out the difference Qabs varies with the engine speed RPM and temperature Tw of water flowing in the engine. Thus, if Qbad is obtained from RPM and Tw, Qabs is obtained from Qbad and Qfnl (Qbase), and Qacl
2
is determined from Qabs, then it is feasible to efficiently damp the torsional vibration concerned.
In the conventional technique for attenuating the torsional vibration, however, the correction value Qacl
2
is never obtained from the difference Qabs. Therefore, there is room for improvement in this regard.
Further, if the above described way of controlling the amount of fuel injection is executed, as illustrated in
FIGS. 8A
to
8
E, it is generally believed that the wave or oscillation of the engine revolution speed change &Dgr;RPM and the wave of the correction value Qacl
2
have reversed shapes of the same period (FIGS.
8
C and
8
D). However, if it is observed microscopically, the correction value Qacl
2
is determined after the change occurs in the engine revolution speed RPM. In actuality, therefore, the wave of the correction value Qacl
2
fluctuates at a slightly delayed phase &lgr; from the &Dgr;RPM wave. As a result, if the correction value Qacl
2
is determined solely from &Dgr;RPM as in the above described control, the correction made becomes “run after” correction having a time delay corresponding to the phase difference &lgr;. Consequently, appropriate correction cannot be expected. This results in longer time to be required in torsional vibration attenuation.
On the other hand, the change in the engine revolution speed RPM is caused by increase and decrease of the amount of fuel injection. Specifically, the difference between the amount of fuel injection before acceleration (or deceleration) and the current amount of fuel injection after acceleration/deceleration becomes the cause of fluctuation of the engine revolution speed RPM, i.e., torsional vibration in the drive train. Thus, the difference Qdelta between the last amount of fuel injection Qaclini prior to quick acceleration (or deceleration) of the vehicle and the current basic amount of fuel injection Qbase should be calculated, and then the corrected amount of fuel injection should be determined from this difference Qdelta. By dosing so, the torsional vibration can be promptly damped as compared with the technique of determining the correction value Qacl
2
solely from the engine revolution speed change &Dgr;RPM.
However, the conventional technique of damping the torsional vibration never determines the corrected value from the difference Qdelta Thus, there is also room for improvement in this regard.
SUMMARY OF THE INVENTION
An object of the present invention is to overcome the above described problems and make improvements in the above mentioned regards.
According to one aspect of the present invention, there is provided a method of attenuating torsional vibration in a drive train of a vehicle, including the step of detecting engine revolution speed fluctuation that varies with torsional vibration caused in the drive train when the vehicle is quickly accelerated/decelerated, the step of determining a basic amount of fuel injection Qbase from an accelerator opening APS and an engine revolution speed RPM, the step of determining an amount of fuel injection (minimum torque fuel injection) Qbad needed at the time of drive power being first transmitted to drive wheels from an engine based on water temperature Tw and engine revolution speed RPM, the step of calculating a difference Qabs by subtracting the minimum torque fuel injection Qbad from the basic value Qbase, the step of determining a correction value Qacl
2
to counterbalance the fluctuation of the engine revolution speed RPM based on the difference Qabs, engine revolution speed RPM, engine revolution speed change &Dgr;RPM and/or its differential value D&Dgr;RPM, and the step of sequentia
Isuzu Motors Limited
McCormick Paulding & Huber LLP
Wolfe Willis R.
LandOfFree
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