The recent launch of the Toyota Corolla Altis Hybrid has got people wondering how a hybrid system works – or some just really assume that they know about the system without even bothering to research.
Toyota hybrids primarily use the Atkinson cycle engine in tandem with electric motors. This type of engine has been used in other hybrid vehicles, like the Prius, and other brands as well, such as the Hyundai Ioniq Hybrid.
To give you a clear-cut view of how Toyota’s hybrid powertrains work, here’s an explanation.
The Series-Parallel Hybrid system
The all-new Toyota Corolla Altis Hybrid uses a series-parallel hybrid system. It is different from a parallel-only or series-only hybrid system.
In a parallel hybrid system, the engine is used to charge the battery, as well as power the car in tandem with the electric motor. Examples of vehicles that use the parallel hybrid systems are the supercars like the Ferrari LaFerrari. In the La Ferrari, the gasoline engine stays on and it works with the electric motors to power the car and to enhance its performance.
A series hybrid system, on the other hand, means that the vehicle only uses the gasoline engine to charge the battery, which in turn powers an electric motor. These are typically seen in all-electric vehicles with range extenders. The range extenders are usually a small displacement internal combustion engine.
Now, the Corolla Altis Hybrid’s series-parallel system can enter electric-only mode and can switch off the gasoline engine when it isn't needed. When the batteries run low and there is no chance for regenerative braking to be used, the gasoline engine comes alive and powers the car and charges the batteries at the same time. When power becomes a priority, the engine, and electric motor work together to give out maximum performance.
In the case of most of Toyota’s hybrids, the system is mated to an eCVT. The eCVT runs in tandem with an inverter, power, control unit, and the ECU to ensure that the voltage that is entering the electric motor and power splitter is correct. The power splitter distributes the power made by the engine and the regenerative braking system to either increase the power of the vehicle or to charge the batteries.
Explaining the Atkinson Cycle Engine
As we’ve mentioned, Toyota uses the Atkinson Cycle in conjunction with the electric motor. An Atkinson cycle type of engine takes in a little less fuel but utilizes the most of what the fuel can offer. It works by leaves the intake valve open slightly longer when a piston in the engine has completed its intake stroke and begins to enter the compress the fuel to air mixture. This creates a leak and effectively reduces the air-fuel charge in the cylinder. The cylinder then enters the combustion stroke or power stroke, giving the engine enough time to fully burn the remaining fuel and air mixture in the cylinder it ignited. Through this, fuel efficiency is maximized, but it isn’t without compromise.
The downside to this is that there’s less power when the fuel and air mixture ignites – proportionally less than what a conventional engine would use. What the engine lacks in power, the electric motor makes up for in Toyota’s hybrid system.
Atkinson Cycle + Hybrid System
Toyota combines the fuel efficiency of the Atkinson Cycle engine and the electric motor to deliver maximum efficiency through its series-parallel hybrid system. The combination of the two helps extend the distance the vehicle can travel through the battery and regenerative braking. It also enhances power when performance becomes prioritized.
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