Everything about hybrid cars
A hybrid car is a vehicle driven by a hybrid propulsion system. A distinctive feature of the hybrid power plant is the use of two or more energy sources and their corresponding engines, which convert energy into mechanical work. Some sources use the term hybrid engine, which is technically incorrect.
Despite the variety of energy sources (thermal energy of gasoline or diesel fuel, electricity, the energy of compressed air, the energy of compressed liquefied gas, solar energy, wind energy, etc.), a combination of an internal combustion engine and an electric motor is used on an industrial scale on hybrid vehicles.
The main advantage of a hybrid car is a significant reduction in fuel consumption and emissions of harmful substances into the atmosphere, which is achieved by:
- coordinated work of the internal combustion engine and electric motor;
- the use of high-capacity batteries;
- using braking energy, the so-called regenerative braking, which converts the kinetic energy of motion into electricity.
At the same time, many other innovative developments are used in hybrid cars, which allow saving fuel and saving the atmosphere, including: a system for changing the valve timing ; stop-start system ; exhaust gas recirculation system ; exhaust gas heating system; improved aerodynamics; electric drive of auxiliary devices (water pump, air conditioning , power steering , etc.); tires with reduced rolling resistance.
It should be noted that the greater effect of hybrid cars is observed when driving in the urban cycle, which is characterized by frequent stops, idling. When driving at a constant high speed (suburban cycle) hybrids are not so effective.
Depending on the nature of the interaction between the internal combustion engine and the electric motor, the following schemes of hybrid power plants are distinguished: serial, parallel, serial-parallel.
Hybrid car serial circuit
In a sequential circuit, the car is driven by an electric motor. The internal combustion engine is connected only with a generator, which in turn feeds the electric motor and charges the battery.
In a hybrid vehicle with a sequential powerplant scheme, it is usually possible to connect to the electrical network at the end of the trip. Such cars are called Plug-in Hybrid (literally – a plug – in hybrid ). The implementation of this function involves the use of high-capacity batteries (lithium-ion batteries), which leads to a reduction in the use of internal combustion engines and, accordingly, reduction of harmful emissions.
Representatives of the Plug-in Hybrid are Chevrolet Volt, Opel Ampera cars. They are also called extended-range electric vehicles ( Extended Range Electric Vehicle, EREV ). These cars have the ability to move up to 60 km on battery power and up to 500 km on the energy of a generator driven by an internal combustion engine.
Hybrid Car Parallel Circuit
In a parallel circuit, the electric motor and internal combustion engine are installed in such a way that they can work both independently and jointly. This is achieved by connecting the internal combustion engine, electric motor and gearbox using automatically controlled clutches.
Hybrid cars using a parallel circuit are called Mild Hybrid (literally moderate or soft hybrid ). They use an electric motor of low power (about 20 kW), which provides, as a rule, additional power when accelerating a car. In most designs, the electric motor located between the engine and the gearbox also serves as a starter and alternator.
Well-known hybrid cars with a parallel circuit are Honda Insight, Honda Civic Hybrid, BMW Active Hybrid 7, Volkswagen Touareg Hybrid, Hyundai Elantra Hybrid. The pioneer in this field is Honda and its system Integrated Motor Assist, IMA (literally – integrated engine assistant).
During the operation of the IMA system, the following characteristic modes can be distinguished:
- Work from the electric motor.
- Joint operation of the internal combustion engine and the electric motor.
- Work from the internal combustion engine while charging the battery from the electric motor in generator mode.
- Charging the battery in regenerative braking mode.
Hybrid car serial-parallel circuit
In a series-parallel circuit, the internal combustion engine and the electric motor are connected through a planetary gearbox. In this case, the power of each engine can be transmitted to the drive wheels simultaneously in a ratio of 0 to 100% of the rated power. In contrast to the parallel circuit, a generator has been added to the serial-parallel circuit, providing energy to the motor.
Hybrid cars using a serial-parallel circuit are called Full Hybrid (literally – a full hybrid ). Famous full hybrids are Toyota Prius, Lexus RX 450h, Ford Escape Hybrid. Toyota and its Hybrid Synergy Drive , HSD , dominate this segment of the hybrid car market.
The power plant of the HSD system is an internal combustion engine (connected to the planet carrier of the planetary gearbox), an electric motor (connected to the ring gear of the planetary gearbox), and a generator (connected to the sun gear of the planetary gearbox).
The internal combustion engine operates according to the Atkinson cycle, in which mediocre power indicators are realized at low revs, and accordingly, greater fuel efficiency and lower harmful emissions are achieved.
The following modes are distinguished in the operation of the Hybrid Synergy Drive system:
- Electric vehicle mode, in which the internal combustion engine is turned off and the battery is powered by the electric motor.
- Driving mode with a constant (cruising) speed, at which the power from the internal combustion engine is distributed between the drive wheels and the generator. The generator, in turn, feeds an electric motor, the power of which is added to the power of the internal combustion engine. If necessary, the battery is charged.
- Forced mode, in which an electric motor powered by a battery is connected to the internal combustion engine, providing a power pulse.
- An economical mode in which the battery powers the generator. The generator converts electrical energy into mechanical energy, slowing the rotation of the internal combustion engine. At the same time, the engine torque does not decrease, but fuel efficiency is achieved.
- Braking mode, in which the electric motor works as a generator, and the electricity is used to rotate the sun gear in the opposite direction, slowing down the speed of the car.
- Battery charging mode, carried out using the internal combustion engine and generator.
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