Gasoline Direct Injection

Gasoline Direct Injection

While the traditional method of fuel intake is port fuel injection, direct injection far surpasses that technology. Bosch’s gasoline direct injectors provide ultrahigh pressured fuel directly into the car engine’s combustion chamber, making for a more fuel efficient and more environmentally friendly engine. Older port fuel injectors spray into intake ports where the fuel mixes with air until the intake valve sucks the mixture in, leaving time for the fuel to dissipate and lose pressure. Direct fuel injectors mount on the cylinder heads and spray directly into the engine cylinder at pressures up to 15,000 pounds per square inch, enough to atomize the fuel. Once in the engine cylinder, the fuel is able to ignite immediately. This allows for much more efficient burning of fuel, which leads to optimal engine performance.

Overall Place in Fuel System and General Function

Four stainless steel injectors each are inserted into two fuel rails via rubber O-ring assembly for an air tight fit. These fuel rails are supplied by high pressure pumps, which pump gasoline from the fuel tank. The fuel then enters the injectors through the nozzle and passes through a lightweight synthetic filter to clear out engine debris and other impurities.

High Pressure Fuel Assembly
Each injector is also connected to an electrical control unit (shown right) via plastic molding plugs to provide pulses, which open and close the injector’s valve. The control unit provides current to cycle a metal solenoid via magnetic flux. This solenoid is attached to the valve needle and the needle ball. The solenoid and needle oscillate up and down in cycle with the electrical pulses to open and close the valve seat. This allows for controlled release of fuel into the combustion chamber. For lower engine speeds, the solenoid oscillates slowly, and for the highest speeds, the solenoid and valve needle leave the valve seat completely open, allowing for maximum fuel injection.

Injector Components

After passing through the filter, the fuel then passes through a 2.13 cm conductor barrel, which contains the solenoid (4) as well as the filter (1). The barrel is laser welded to a 0 .79 cm diameter stainless steel housing, the valve sleeve. The valve sleeve holds a 11 mm valve needle (6), which is laser welded to a 15 mm diameter needle ball (7) at the bottom of the valve sleeve. The bottom of the valve sleeve is laser welded to a valve seat (8), where the needle ball rests to impede the flow of fuel when the engine is not in cycle.

Fuel Injector Cross Section

Each valve seat is manufactured using an extremely refined technology, laser drilling. This manufacturing process helps originate a unique spray pattern, based on the type of injector and the injector’s location in the fuel rail assembly, in order to accurately target the combustion location. The laser drilling machines are set to drill certain angles and diameters to create spray holes with nanometer precision. This allows for a consistent spray pattern and fuel volume flow. The laser is also capable of drilling holes so small, that the fuel passing through atomizes at high pressure, optimizing fuel efficiency.

Current Customers

Bosch makes various different models and styles of gasoline direct fuel injectors, for many automotive companies’ high performance models, including:

• 
  Ferrari
  
• 
  BMW
  
• 
  Audi
  
• 
  Jaguar
  
• 
  Ford
  
• 
  GM
  
• 
  Chrysler.
  

Ferrari Engine (injectors not visible)
Each injector comes equipped with custom components to suit the customer’s needs. W1hether it is valve sleeve length, conductor barrel width, or plastic molding shape, the design will be sure to fit perfectly with the car engine model.

Manufacturing Process

Out of the hundreds of thousands of Bosch injectors produced worldwide every day, all of them are made in state of the art clean rooms. Each clean room follows strict rules on sanitation and safety, ensuring that no injectors contain any hints of impurities or deficiencies. In these clean rooms, dozens of engineers and skilled laborers work on the manufacturing of these injectors with the help of Staubi’s highly automated assembly system. Throughout the assembly process the Staubi robots continuously swap parts in and out to be laser welded, or tested for certain parameters. Each batch of parts is also tested by one of Bosch’s highly skilled and trained manufacturing workers. They are tested for dimension specifications, and functionality purposes to ensure that each customer is getting a consistently, excellent product.

Summary


Bosch High Pressure Fuel Injector
While a cycle for a fuel injector is complex, it happens very quickly. In a fraction of a second, fuel is pumped from the gas chamber to a high pressure fuel pump, where the fuel is compressed to about 17,000 PSI. The fuel then travels through the fuel rail and into the fuel injector, where it passes through the filter. The fuel then travels through the conductor barrel, around the solenoid, and into the valve sleeve. As the electric pulses lift the solenoid along with valve needle and ball, the valve seat opens. The fuel then shoots through the microscopic holes at ultrahigh pressure into the combustion chamber to ignite and drive the pistons.