Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2002-08-15
2004-06-01
Vo, Hieu T. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C123S406510, C123S399000, C477S110000
Reexamination Certificate
active
06745119
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an ignition timing control system and method and an engine control unit for an internal combustion engine, and more particularly to an ignition timing control system and method and an engine control unit of this kind, for retarding ignition timing so as to reduce longitudinal vibrations of an automotive vehicle caused by steep changes in torque during acceleration.
2. Description of the Prior Art
When an automotive vehicle is accelerated, driving wheels cannot follow up a sudden increase in torque of an internal combustion engine, so that a drive system for transmitting torque from the engine to the driving wheels, particularly, a drive shaft, undergoes torsion. Although the displacement of the engine caused by the torsion is absorbed by a mount via which the engine is installed on the vehicle, this can bring about acceleration-caused fluctuations in the rotational speed of the engine, thereby producing longitudinal vibrations of the vehicle. Such longitudinal vibrations of the vehicle detriment the feeling of acceleration and impair running stability of the vehicle. As a solution to this problem, the technique of reducing the longitudinal vibrations of the vehicle by retardation of ignition timing has been conventionally known, and proposed e.g. in Japanese Utility Model Registration Publication No. 2548648.
The proposed ignition timing control system judges that the vehicle is in rapid acceleration when the opening degree of a throttle valve of the engine is sharply increased, and an initial value of a retard amount of ignition timing is set according to the rotational speed of the engine and the vehicle speed. The retardation of ignition timing is immediately started by the thus set initial value of the retard amount, and the retard amount is progressively decreased therefrom. Further, the retardation of ignition timing is continued over a predetermined time period, and when it is terminated, if the rotational speed of the engine is decreasing, the ignition timing is advanced, inversely. Thus, the proposed ignition timing control system suppresses the longitudinal vibrations of the vehicle by reducing steep changes in torque during acceleration, and at the same time maintains acceleration performance.
However, the conventional ignition timing control system necessarily executes the retardation of ignition timing when the opening degree of the throttle valve is sharply increased from a small opening degree condition, irrespective of whether the actual changes in torque are large or small. Therefore, for example, even when the torque of the engine does not actually change so sharply and the acceleration-caused fluctuations in the rotational speed of the engine are small, causing almost no longitudinal variations of the vehicle, the retardation of ignition timing is executed, only to degrade the acceleration performance. Further, since the ignition timing is advanced if the engine rotational speed is decreasing at the termination of the retardation, this may cause knocking, and hence damage to the engine. Further, since the retard amount is simply set according the rotational speed of the engine and the vehicle speed, this cannot set the optimum retard amount suitable for operating conditions of the engine and the vehicle.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an ignition timing control system and method and an engine control unit for an internal combustion engine, which are capable of setting optimum timing for execution of retardation of ignition timing when a vehicle on which the engine is installed is accelerated, thereby effectively reducing longitudinal vibrations of the vehicle, which might be caused by changes in torque, and maintaining acceleration performance.
To attain the above object, according to a first aspect of the present invention, there is provided an ignition timing control system for an internal combustion engine, for retarding ignition timing during acceleration,
the ignition timing control system comprising:
acceleration demand-detecting means for detecting a demand of acceleration of the engine;
rotational speed-detecting means for detecting a rotational speed of the engine;
rotational variation amount-calculating means for calculating a variation amount of the rotational speed of the engine, based on the detected rotational speed of the engine;
rotational variation amount differential value-calculating means for calculating a differential value of the variation amount of the rotational speed of the engine, based on the calculated variation amount of the rotational speed of the engine;
retard amount-calculating means for calculating a retard amount for retarding the ignition timing; and
retardation execution means for executing retardation of the ignition timing by the retard amount, on condition that the demand of the acceleration is detected, that the variation amount of the rotational speed of the engine is larger than a predetermined amount, and that the differential value of the variation amount of the rotational speed of the engine is smaller than a predetermined value.
According to this ignition timing control system, the retard amount-calculating means calculates a retard amount for retarding the ignition timing. Further, the ignition timing is retarded by the retard amount, on condition that the demand of the acceleration is detected, that the variation amount of the rotational speed of the engine is larger than a predetermined amount, and that the differential value of the variation amount of the rotational speed of the engine is smaller than a predetermined value. The timing of execution of retardation of the ignition timing is determined based on the variation amount of the rotational speed of the engine and the differential value of the variation amount of the rotational speed of the engine for the following reason:
As described hereinabove, the longitudinal vibrations of the vehicle cased by acceleration-caused fluctuations in the rotational speed of the engine during acceleration of the vehicle are due to incapability of the driving wheels following up a sudden increase in torque of the engine. This causes changes in the ratio of transmission of torque from the engine to the driving wheels, whereby periodical changes occur in the driving force acting on the driving wheels, such that the relationship between the torque of the engine and the driving wheel-driving force fluctuates with respect to the 1:1 relationship under a constant speed condition of the vehicle. More specifically, when the ratio of transmission of torque of the engine to the driving wheels lowers, a reaction occurs to the engine with a magnitude corresponding to the lowering of the ratio of torque transmission, causing a steep increase in the rotational speed of the engine, whereby the rotational variation is increased. Then, the increased rotational speed causes a rebound of an increase in the vehicle-driving force, and this causes a decrease in the engine rotational speed or the degree of increase in the same as a reaction, whereby the rotational variation is dropped. Thus, the rotational variation (variation amount of the rotational speed) of the engine changes such that it decreases with increase in the vehicle-driving force, and increases with decrease in the same, exhibiting anti-phase relationship to the vehicle-driving force. The cause of generation of the longitudinal vibrations of the vehicle is nothing other than the variation or fluctuations in the vehicle-driving force. Therefore, if the increase in the vehicle-driving force is suppressed, the decrease in the vehicle-driving force as a reaction to the increase can also be suppressed, whereby the longitudinal vibrations of the vehicle can be effectively suppressed.
From the above viewpoint, according to the present invention, when the variation amount of the rotational speed of the engine is larger than the predetermined amount, and at the same time the differential value of the variation amount of
Katagiri Yoshihiro
Ohno Tetsuya
Shiraki Tatsuya
Yatani Hiroshi
Arent & Fox PLLC
Honda Giken Kogyo Kabushiki Kaisha
Vo Hieu T.
LandOfFree
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