Analysis of the Start-Stop System of Micro Hybrid Technology

Under the general trend of energy conservation and environmental protection, various automobile manufacturers are also constantly developing new energy conservation and environmental protection technologies to get a share of the fiercely competitive market. Start-stop technology is one of them, which is committed to minimizing the fuel loss when the engine is idling. I believe that everyone is familiar with start-stop technology, and now more and more models are equipped with this technology. Is this a new technology that has only been available in recent years? What are the differences in the implementation methods? The following is a brief introduction to start-stop technology.

● What is Start-Stop Technology?

When driving on crowded urban roads, cars always have to stop and wait for traffic lights, and the energy consumed by the engine idling is meaningless. The start-stop technology is dedicated to minimizing the fuel loss when the engine is idling, avoiding the waste of this part of energy, and at the same time has important significance for saving energy and reducing emissions.

So how does the start-stop system work? When encountering a red light or traffic jam, the driver brakes to stop the vehicle, shifts the gear into neutral and completely releases the clutch pedal. At this time, the control system automatically shuts down the engine, saving fuel wasted by idling. When the green light is released, the driver steps on the clutch and the engine automatically restarts, and the vehicle can move forward after shifting into gear.

If it is an automatic transmission model, the operation is even simpler. The driver only needs to apply the brakes to stop the vehicle, and the engine will automatically shut down. After releasing the brakes, the driver refuels and the engine will automatically start. This energy-saving driving method does not change people's daily driving habits, does not bring any trouble to the owner, but brings significant effects of fuel saving and emission reduction.

● Development history of Start-stop technology

As early as 1970, Toyota had already dabbled in start-stop technology. At that time, it tried to install an electronic device on the Toyota Crown that could shut down the engine after the car was stationary for 1.5 seconds. The test results found that in the busy traffic in Tokyo, the use of this new technology could increase fuel economy by 10%.

In 1980, this technology began to be equipped on mass-produced models for sale, including Fiat's Regata and Volkswagen's second-generation Polo.

By 1994, the third-generation Volkswagen Golf and Lupo (3L model), as well as the 1999 Audi A2 (3L model) were all equipped with start-stop technology, but these models did not sell well due to their high prices.

In addition to Toyota, Mazda has also developed an i-Stop system in Japan. When restarting from a stationary idle state, it will determine the cylinder to be operated first. The piston of the cylinder will stop in the appropriate position and the scavenging stroke will be completed in the cylinder. When the system determines that it will restart, it will inject fuel to ignite and burn quickly, and drive the starter motor at the same time. The starting process takes about 0.35 seconds and is quite smooth.

In addition, Honda's first-generation Insight model sold in the domestic market in 1999 was equipped with this technology. Since 2006, the Civic Hybrid model has also used start-stop technology. Honda has been using this technology for more than ten years.

In 2006, Citroën of the French PSA Group developed an idling shutdown system called "start-stop", which was installed on the Citroën C2 and Citroën C3. This system combines the sensodrive automatic transmission developed by the company with the electronically controlled ISG reversible generator (ISG integrates the starter motor and generator, and was jointly developed by Valeo and Denso Corporation of Japan).

This system is also installed on the 2011 facelifted Peugeot 3008 e-HDi model. Combined with the 1.6L diesel engine and brake energy recovery system, it can save fuel consumption by up to 15%.

At the end of 2008, Fiat introduced the start-stop system produced by Bosch and installed it on the Fiat 500 model. Alfa Romeo launched the MiTo model in the same year and also equipped it with the same system. In 2009, Volvo also used the start-stop technology on the DRIVe model.

BMW has applied the start-stop technology to its models for many years, including the mini series models after 2008. BMW has been committed to reducing the loss of engine power. They use Bosch's enhanced starter motor, which can withstand more starts than ordinary starter motors in the environment of frequent shutdown and start.

● Three modes of Stop-Start system

As an entry-level technology for hybrid vehicles (mild hybrid), the Stop-Start system has broad application prospects due to its low cost and significant energy-saving and emission-reduction effects. Currently, there are three main forms of the Stop-Start system:

Split starter/generator start-stop system

Start-stop systems that use a separate starter and generator are common. The starter and generator of this system are designed independently, the power required to start the engine is provided by the starter, and the generator provides electrical energy to the starter.

Bosch is the mainstream supplier of this start-stop system. This system includes a highly enhanced starter, an enhanced battery (usually an AGM battery), a controllable generator, an engine ECU with an integrated start/stop coordination program, sensors, etc.

Bosch's starter motor can automatically resume engine operation quickly and quietly, reducing fuel consumption during starting. This start-stop system has few parts and is easy to install. It can be applied to various hybrid concepts (belt drive, spur gear drive and electric shaft drive). In addition, the system components are consistent with the traditional components in size, so they can be directly equipped on various vehicles.

At present, there are many models in the world that are equipped with Bosch Stop-Start system, including BMW 1, 3, 5 Series, X3, Volkswagen Passat, Golf, Mercedes-Benz A, B, C, E Series (part), Audi A6, A8, Renault Megane, Opel Corsa, Astra, etc.

Since 2009, some Chinese automakers have also cooperated with Bosch to match the Stop-Start system. The Changan CX30 launched in the first half of 2010 is equipped with this system. Great Wall, Geely, SAIC, Chery and other domestic brands have also launched matching models one after another.

Integrated starter/generator start-stop system

The integrated starter/generator is a synchronous electric machine excited by a permanent magnet inner rotor and a single-tooth stator, which enables the drive unit to be integrated into the hybrid powertrain.

Valeo developed the i-Start system (i-Stop-Start System), which was first used in PSA (Peugeot-Citroen Group) e-HDi models. The electronic control device of the i-Start system is integrated inside the generator. When the engine stops at a red light, the car will automatically start the engine as soon as the gear is engaged or the brake pedal is released.

Valeo will equip 50 models of more than 10 automakers with the i-Start system. By 2013, 1 million PSA models will be equipped with this system. France's PSA Group, Mercedes-Benz and Smart are the main customers of Valeo's Stop-Start system.

Mazda SISS Intelligent Start-Stop System

The two start-stop systems introduced above start the engine through the starter, and the process is the same as starting the engine under normal circumstances. However, Mazda's SISS intelligent start-stop system restarts the engine through the expansion force generated by direct fuel injection in the cylinder.

Of course, in order to start the engine by igniting the force generated by the fuel, the piston must stop at the correct position to ensure smooth starting. Therefore, the engine using this technology needs to mark the position where each cylinder should be when the fuel is injected. It is reported that this method can start the engine in as short as 0.35 seconds, which is twice as fast as the system controlled by the motor.

This system has intelligent and efficient control and can achieve the start-stop function without a starter. It has been used in some Mazda 2, Mazda 3 and Mazda 6 models sold in the Japanese market.

Summary: Start-stop technology can automatically stop the engine when the vehicle stops temporarily, thereby reducing fuel consumption and emissions. This technology has a good effect on energy conservation and emission reduction, especially in large cities with congested traffic. In Europe, where fuel prices are high and emission regulations are quite strict, start-stop technology has been widely used. At present, the start-stop technology market in China is not yet mature, but with the rising oil prices and energy-saving and environmental protection environment, more cars will soon use this technology.