Vibration damping control device of a diesel engine vehicle

[0016]According to the control gain determining portion as described above, a control gain is decreased when a compensation component value by the vibration damping control deviates from a restriction range for variation of a fuel injection quantity, and the control gain is increased when the compensation component value does not deviate from the restriction range. That is, in this case, the control gain is set so as to increase or to decrease depending upon the relation between a restriction range for variation of a fuel injection quantity and the variation of the fuel injection quantity corresponding to the compensation component. With this manner, strictly speaking, just before the decreasing of a control gain, a compensation component value deviates from a restriction range for variation of a fuel injection quantity; however, after this, the compensation component is decreased so as not to suffer the restriction for the variation of the fuel injection quantity, so that, substantially, the wave forms of varying components corresponding to the compensation component of the vibration damping control can be reflected, with almost no deformation of the wave form (with almost no changing of the frequency characteristic and phase characteristic) and also without unnecessary decrease of the oscillational amplitude, in the requested value or execution amount of a fuel injection quantity, as a control command, given to the engine.

[0017]In this regard, as described above, preferably, the changing of a control gain is performed at a time point when the sign of a compensation component value is reversed. At the time point of the reversion of the sign of a compensation component value, the compensation component value becomes 0, and thus, advantageously, the compensation component can be smoothly varied around before and after the change of the control gain, and also the avoiding of a sudden change of a driving torque or a wheel torque corresponding to the compensation component will become easy. Accordingly, as understood from the above-mentioned structure, in the first aspect of the present invention, if a compensation component value deviates from a restriction range for variation of a fuel injection quantity, the decreasing of a control gain will be executed at the first time point of the reversion of the sign of the compensation component value after the occurrence of the deviation. And, at a time point of the reversion of the sign of a compensation component value, if the compensation component value has not deviated from a restriction range for variation of a fuel injection quantity between the present time point and the time point of the preceding reversion of the sign of the compensation component value, the increase of a control gain is executed.

[0018]Furthermore, regarding the change of a control gain in the first aspect of the present invention, while the decrease of a control gain should be quickly executed, the increase of the control gain is not needed to execute immediately after a compensation component value does not deviate from a restriction range for variation of a fuel injection quantity. Rather, if a once decreased control gain is increased immediately, a compensation component value would deviate again f

In this regard, in fuel injection quantity controls for diesel engines, there is a case in which it is required to set out a restriction for the variation width of a fuel injection quantity, and, in this case, it has been found that a variation of a fuel injection quantity (variation of a wheel torque) requested by a vibration damping control cannot be achieved, so that a vehicle body vibration cannot be well suppressed and, in some occasions, a request of a driving torque from a vibration damping control may induce an effect of amplification of a vehicle body vibration, such as