Hybrid drive

The phrase "hybrid" means a drive that uses a combination of several sources of energy to drive a vehicle. This may include various combinations, such as the internal combustion engine - electric - battery, fuel cell - electric - battery, combustion engine - flywheel, etc. The most common concept is the combination of combustion engine - electric - battery. Now you better describe how the entire system works.

The biggest reason for the introduction of hybrid drives for cars is the low efficiency of internal combustion engines. Efficiency of today's internal combustion engines varies approximately between 30 to 40%. Petrol (gasoline) engines generally have somewhat lower efficiency at the lower limit, ignition (diesel) engines are doing a little better. The value of efficiency of combustion engines is largely determined by the effectiveness of the thermodynamic cycle, he has a clear physical limitations. In the future, it can not expect significant efficiency improvements to conventional internal combustion engines.

Another problem is that the effectiveness of the internal combustion engine reaches only in optimal conditions. Of course, in normal operation, the optimum conditions achieved only rarely and that means that the overall efficiency is even lower. An extreme case is the engine running at idle. The engine consumes fuel, but the car does not take place without any work, because standing still. In addition, the combustion engine can operate satisfactorily only in a relatively narrow band of speed. That is why a car with an internal combustion engine needs a transmission.

Use of the gearbox, however, provides additional significant losses, like every mechanical transfer. In addition, usually only a limited number of gears and this is another reason why it can not operate the engine in optimum condition (of course there are transmission with continuously variable gear ratio , but they have just got worse efficiency).

In contrast, the current electric motors have an efficiency of around 95%. In addition, this high efficiency achieved in a wide range of speeds and loads. Electric thus appears as an ideal solution. Its disadvantage is too high but the weight of batteries needed. This results in a small range per battery charge. In addition, difficult and slow pure electric vehicle recharging batteries removed from the game.

The hybrid drive (HEV - Hybrid Electric Vehicle) allows the combination of these two types of propulsion, a combustion engine and electric motor. The hybrid internal combustion engine may not be mechanically connected to the wheels. So there may be only as a power generator. The combustion engine can work undisturbed in their optimum speed, power or recharge the electric batteries. The same concept has been used for years in diesel-electric locomotives.

The advantage of ordering with no mechanical connection of the electric motor to the wheels is that there is no need for transmission. Electric traction motors are in fact capable of working in a wide speed range with high efficiency and sufficient torque from virtually zero speed. When using two engines and even eliminating the differential, as between the left and right wheels is not a mechanical bond. There is also the possibility to use four smaller engines located directly at the wheel and get a full four-wheeler, without the need for complex inter-differentials. Considering that the efficiency of each gear with helical teeth is 0.98, the effectiveness of bearing 0.995, then each such simplification is beneficial. The biggest advantage, however, remains the fact that the combustion engine works only in its optimum condition with the highest possible efficiency. If enough energy in batteries, or there is a deceleration , the motor stops completely.

By placing the motor directly to the wheels get rid of a gearbox, axle. For example we get more space for passengers and luggage, reduce losses, etc. On the other hand, significantly increase the unsprung weight of the vehicle. This affects the life of the chassis components and vehicle comfort.

Today's hybrid drive concepts still prefer rigid connection of the combustion engine and wheels. The electric motor rather assists the states in transition, where it is advantageous to turn off the internal combustion engine , such as when maneuvering in traffic or around town. Hybrid drive is relatively young and promising development industry, and therefore there are many different combinations and variations. Currently, each automaker develops the concept and philosophy.

Finally, it remains to be noted that hybrid drives due to its good performance and have a good issue . They are therefore considered a good ecological alternative to current vehicles with internal combustion engine. Their only disadvantage remains higher price for new and complicated technology. However, there are many states that sales of hybrid cars legislative favors. Also, many large cities in the desert center of high fees for cars, but hybrid cars for free.

Who introduced the first production hybrid car?
The first mass-produced hybrid car in the world is the Toyota Prius. This car won the "Car of the Year 2005". The car is powered by a combined system of an internal combustion engine and electric motor.

Are hybrid cars safer?
According to the study, " American Institute of transport safety insurance "hybrid cars are safer than vehicles with conventional propulsion. Risk of injury to the person traveling in them is lower by about 25%. The reason hybrid cars safer, according to experts, primarily higher weight hybrid vehicles, because batteries and electric motors mean additional compared to conventional drive weight gain of more than 10%. Accordingly, while hybrids are safer for passengers in this car, but logically more dangerous for drivers of light other small cars as well as for pedestrians. Hybrid cars might, due to less handling and longer braking distances cause an accident by up to 20% more often.

Text: John Sajdl
Photo: www.theautochannel.com, www.saab.com, www.evworld.com, www.nrel.gov
Keywords: hybrid, the internal combustion engine efficiency, ecology, hybrid