A hybrid car is called the vehicle is driven with the hybrid power plant. A distinctive feature of the hybrid power plant is the use of two or more energy sources and their corresponding engine that converts energy into mechanical work. Some sources use the term “hybrid engine”, which from a technical point of view is incorrect.
Despite the diversity of sources of energy (thermal energy of gasoline or diesel fuel, electricity, compressed air energy, the energy of compressed liquefied gas, solar energy, wind energy and others) on an industrial scale on hybrid cars use a combination of combustion engine and electric motor.
The main advantage of the hybrid car lies in the substantial reduction of fuel consumption and emissions of harmful substances into the atmosphere, which is achieved:
- the coordinated work of the internal combustion engine and an electric motor;
- the use of high-capacity batteries;
- the use of braking energy, the so-called regenerative braking, which converts the kinetic energy of motion into electricity.
Hybrid vehicle use a lot of other innovations that save fuel and protect nature, it is:
- the system changes the valve timing;
- the start stop system;
- the EGR system;
- the heated coolant exhaust gases;
- improved aerodynamics;
- electric accessories (water pump, air conditioner, power steering and other);
- tyres with reduced rolling resistance.
It should be noted that the greater effect of the hybrid cars is observed when driving in the city, which is characterized by frequent stops, work in idle mode. When moving with a constant high speed (extra-urban) hybrids are not as effective.
Depending on the nature of the interaction of the internal combustion engine and an electric motor there are several schemes of hybrid power systems:
Serial hybrid car
The sequential scheme, the vehicle is driven by an electric motor. The internal combustion engine is connected with only a generator which in turn powers the electric motor and charge the battery.
In the hybrid vehicle with a serial circuit of the power plant, as a rule, the possibility of connection to the electrical network at the end of the trip. These cars are called Plug-in Hybrid (literally – plug-in hybrid). The realization of this function involves the use of larger capacity batteries (lithium ion batteries), leads to a reduction in the use of internal combustion engines and, consequently, reduction of harmful emissions.
Representatives of Plug-in Hybrid are the Chevrolet Volt, Opel competition. They are called electric vehicles with extended range (Extended Range Electric Vehicle, EREV). These cars have the possibility of moving up to 60 miles on battery power and up to 500 km on energy generator driven by the internal combustion engine.
Parallel hybrid vehicle
In the parallel scheme, the electric motor and the internal combustion engine are installed in such a way that can work both independently and jointly. This is achieved by connecting the internal combustion engine, electric motor and transmission with automatically controlled clutches.
Hybrid cars that use a parallel scheme, are called Mild Hybrid (literally – mild hybrid). They use the electric motor of low power (20 kW), which provides, as a rule, additional power during acceleration of the vehicle. In most constructions, the motor located between the engine and transmission, also performs the function of a starter and generator.
Known hybrid vehicles in the parallel circuit are the Honda Insight, Honda Civic Hybrid, the BMW Active Hybrid 7, the Volkswagen Touareg Hybrid, Hyundai Elantra Hybrid. A pioneer in this area is Honda and its Integrated Motor Assist IMA (literally – integrated assistant engine).
When the IMA system we can identify the following typical conditions:
- Operation of the motor.
- The joint work of the internal combustion engine and an electric motor.
- Work from internal combustion engines while also charging the battery from the electric motor in generator mode.
- Charging the battery for regenerative braking.
A series-parallel hybrid vehicle
When a series-parallel scheme, the internal combustion engine and the electric motor are connected through a planetary reducer. Thus the power of each motor can be transmitted to the drive wheels simultaneously in a ratio of from 0 to 100% of nominal power. In contrast to the parallel circuit in series-parallel scheme added a generator that provides energy to the motor.
Hybrid cars that use a series-parallel scheme, are called Full Hybrid(literally – full hybrid). Known full hybrids are the Toyota Prius, Lexus RX 450h, the Ford Escape Hybrid. In this segment of the hybrid vehicle market dominated by Toyota and its Hybrid Synergy Drive HSD.
Propulsion system HSD is an internal combustion engine (connected to the pinion carrier of the planetary gear), the motor (connected to the crown gear of the planetary gear), generator (connected to the sun gear of the planetary gear).
The internal combustion engine operates on the Atkinson cycle, which are implemented mediocre performance indicators at low rpm, respectively achieves greater fuel economy and lower emissions.
In the Hybrid Synergy Drive system there are the following modes:
- The electric mode in which the internal combustion engine is switched off and the battery powers the electric motor.
- Mode of motion with constant (cruising) speed at which power from the engine is distributed between the driving wheels and the generator. The generator in turn powers the electric motor, the power of which is summed with the power of ice. Optionally, the battery is charging.
- Forced mode in which the engine is attached an electric motor powered by rechargeable batteries, providing power pulse.
- Eco mode in which the battery powers the generator. The generator converts electrical energy into mechanical energy, slowing the rotation of the engine. When the engine torque is not reduced, and achieves fuel efficiency.
- The braking mode in which the motor operates as a generator, and electricity is used to rotate the sun gear in the opposite direction, slowing the speed of the vehicle.
- The battery charging mode, which is achieved with the help of the internal combustion engine and generator.