Power unit for motor vehicle utilizing a thermal engine down to

Prime-mover dynamo plants – Traction

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Details

290 4C, 180 65A, 318139, 320 61, B60L 1114, H02J 714

Patent

active

044554923

DESCRIPTION:

BRIEF SUMMARY
This invention relates to the propulsion of automobile vehicles or the like.
It is known that in automobile town traffic conditions the average energetic efficiency of the engines and more particularly of internal combustion engines is very poor, and this is due mainly to three reasons, the first one being linked to the frequent stops during which the engine is idling for a zero useful work, the second one being linked to the many decelerations during which the engine fuel consumption is increased for a negative work, and the third one is linked to the many accelerations and level running stretches on intermediate gear ratios while the engine operates at a relatively high speed with low or very low torques, therefore at speeds involving a high specific fuel consumption for a moderate useful work.
Regarding the first reason, it is noted that when idling the fuel consumption is roughly proportional to the engine cubic capacity and to the richness of the air-fuel mixture. Now, a very slow idling speed would require, due to the irregularity of the engine torque, a flywheel having a very high moment of inertia which would be detrimental to the efficiency at medium and high speeds. On the other hand, lean mixtures affording low consumption and pollution ensure a smooth operation only when the engine is warm. During the many cold starts the starter device must be kept in operation more or less and this in actual practice assists in contradicting the optimistic results obtained during an official approval and boasted by manufacturers.
In connection with the second reason, it is known that when decelerating the fuel consumption is proportional to the idling consumption and to the engine vacuum, the latter increasing with the engine speed. Therefore, we have the same inconveniences as those mentioned hereinabove, except that they are amplified.
In connection with the third reason, it is known that in town traffic conditions too low gear ratios (in relation to those normally required) are imposed by several factors: the necessity, in actual practice, of keeping a certain reserve of acceleration for safety reasons; the trend of the torque/engine speed characteristics showing at low engine speeds a slope promoting instability, due to an increment in the reaction torque, entails a reduction in the engine speed causing in turn a reduction in the engine torque; at very low engine speeds, the irregularity of the engine torque, thus increasing the preceding inconvenience; finally, the modern trend towards the use of low cylinder capacity and high maximum speed engines, in which the substantial lag in the inlet valve closing movement is attended by a reduction of the cylinder charge at low engine speeds and therefore by a lower engine torque.
In addition to these conventional engines, so-called "hybrid" mixed-power units are also known which comprise an internal combustion engine of relatively reduced power output coupled with a reversible electric machine cooperating with a storage battery, so that when there is an excess of engine power output the electric machine recovers the excess power and charges the battery, whereas during the periods in which the engine power output is not sufficient, the electric machine operates as an electric motor and assists the thermal engine by discharging the battery. Consequently, in such power units it is assumed that the electric machine has a power rating of same magnitude as the thermal engine and that the storage battery has a substantial capacity to deliver the same power during a period ranging from a few minutes to a few tens of minutes. Therefore, power units of this character are extremely heavy and expensive.
Finally, on motor vehicles propelled by internal combustion engines, it is also known to use a continuous speed variator coupling the engine output shaft to the shaft of an auxiliary electric machine, for example a dynamo or an alternator, this variator being responsive to means for maintaining the velocity of rotation of the auxiliary electric machine within a predetermined

REFERENCES:
patent: 3842287 (1974-10-01), Nakamura
patent: 3923115 (1975-12-01), Helling
patent: 4021677 (1977-05-01), Rosen et al.
patent: 4165795 (1979-08-01), Lynch et al.
patent: 4233858 (1980-11-01), Rowlett

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