ACTUATOR

FUEL FLOW REGULATOR

Role

Description

• The piston is retained at he base of its location by means of the spring
  
• The connection between the 2 pipes is open
  
• The inlet to the high pressure stage of the high pressure fuel pump is open
  
• The fuel is directed to the high pressure stage of the high pressure fuel pump
  

• The fuel flow regulator electric coil drives the magnetic core (magnetic force)
  
• The piston moves
  
• The connection between the 2 pipes is closed
  
• The fuel is directed towards the high pressure fuel regulator valve
  

Special features

• Maximum voltage Injection of expanding foam = Maximum fuel flow
  
• Minimum voltage Injection of expanding foam = Minimum fuel flow
  

HIGH PRESSURE FUEL REGURATOR

Role

Description

Control

• The fuel high pressure opposes the action of the magnetic core and ball
  
• The fuel released by the high pressure fuel regulator returns to the fuel tank
  

• The engine-ECU controls the high pressure fuel regulator by reducing the frequency of the OCR signal
  
• The coil of the high pressure fuel regulator drives the magnetic core (magnetic force)
  
• The fuel return closes
  
• The force applied to the ball and the magnetic force of the core is higher than the pressure in the fuel high pressure common injection rail
  
• The high pressure fuel regulator cut-off valve increases
  

• The engine-ECU increases the frequency of the OCR signal supplied to the high pressure fuel regulator coil
  
• The coil of the high pressure fuel regulator drives the magnetic core (magnetic force)
  
• The fuel return opens
  
• Te force applied to the ball and the magnetic force of the core is lower than the pressure in the fuel high pressure common injection rail
  
• The cut-off valve of the high pressure regulator decrease
  

Special feature

• OCR 100 %: High pressure fuel regulator open, minimum pressure
  
• OCR 0 %: High pressure fuel regulator closed, maximum pressure
  

FUEL INJECTOR

Role

• Pre-injection in order to reduce the operating noise and to diminish the polluting emissions
  
• Main injection
  
• Post-injection for heating the exhaust gases in order to enhance the filtration of the particles
  

Description

Principle of opening and closing of the diesel injector

· Opening principle of a diesel injector

• The additional supply duct opening (1) closes and the leak-off opening (2) opens
  
• The equilibrium between the pressure of the control chamber and the pressure chamber is broken
  
• The pressure present in pressure chamber lift the diesel injector needle
  
• The control piston lifts up
  
• The fuel in sent to the top of the piston
  

· Closing principle of a diesel injector

• The spring of the diesel injector needle holes the closing end pad its seat
  
• The additional supply duct opening opens and the leak-off opening closes
  
• The rise in pressure in the control chamber causes the diesel injector to close
  
• The fuel fills the chamber above the needle via the additional duct and via the conventional supply opening
  
• The equilibrium of pressure is re-established between the control chamber and the pressure chamber
  
• The diesel injector is ready for a new cycle
  

Number of injections per cycle

• 2 pilot up to 3,200 r/min (Then 1 up to 4,500 r/min)
  
• 1 Main
  
• 2 post injections depending on the vehicle load (During the regeneration phase)
  

Strategies used

• Hydraulic compensation
  


On the conventional piezo-electric diesel injectors, there is an operating clearance between the actuator and the mushroom valve, to compensate for the variations linked with the thermal expansion of the parts.
Over time, this clearance tends to increase.
When the injection ends, any clearances are compensated.
The thrust rod spring exerts a pressure which tends to increase the volume of the hydraulic chamber.
If the clearances have increased, a corresponding quantity of diesel fuel infiltrates via the internal leak-offs of the thrust rod to compensate for them.
The guarantee the operation of the diesel injector, this remains full of diesel fuel so that the hydraulic chamber of the thrust rod does not empty.
A valve incorporated in the global return pipe of the 4 diesel injectors provides this function by maintaining a pressure of 10 bars.

• Adaptation of the pilot injection for each diesel injector
  


Principle of analysis of the acceleration of the crankshaft when the pedal is released.
Individual adaptation of the pilot injection.
The engine-ECU measures the acceleration of the crankshaft obtained by injecting very small pilot quantities, each time the pedal is released.
Depending on the results, the engine-ECU increases or reduces the quantities injected (diesel injector control time) until the acceleration corresponds to a typical graph pre-recorded in the memory of the engine-ECU.
The engine-ECU analyses the corrections to be made to the control of each diesel injector.

• Regulation of the place to place flow
  


Principle of analysis of the acceleration of the crankshaft at idle.
Management of the place to place flow.
The engine-ECU measures the acceleration of the crankshaft during the pressure relief phase when the engine is at idle and at low engine speeds.
The engine-ECU then adjusts the control of the diesel injectors (main injection) to obtain identical accelerations; the aim being to obtain a great regularity of operation.

• Lowering of the fuel pressure (protection of the fuel circuit)
  


Principle of analysis of the diesel fuel temperature.
In order to protect the high pressure pump and the components of the fuel circuit, the temperature at the high pressure fuel pump inlet must remain below 70°C.
If the temperature exceeds this value, the fuel pressure is lowered to reduce the temperature of the diesel fuel.

An ID code (consisting of 10 alphanumeric characters) is stamped on the head of each injector, representing the injection characteristics of the individual injector. The engine-ECU uses this information to realize optimal injection amount control. When a new injector is used on a vehicle, its ID code must be input into the system through the use of the M.U.T.-III.

The variable geometry control motor is built in the turbocharger controller installed to the turbocharger and varies the nozzle vane angle of turbocharger. The engine-ECU controls the boost pressure by changing the electrical currents going through the variable geometry control motor coil.

The throttle valve control motor integrated into the throttle body opens and closes the throttle valve. The engine-ECU controls the throttle valve control motor by changing the electrical currents going through the motor coil. This control regulates amount of the exhaust recirculation by including the differing pressure between intake and exhaust. It is also possible to stop the engine smoothly.

The swirl control solenoid valve which is mounted at the inlet manifold side of cylinder head via the bracket is an ON/OFF control type solenoid valve. The engine-ECU turns on the solenoid valve at slow engine speeds and then closes the swirl control valve by applying the vacuum pressure to the swirl control actuator.

Refer to GROUP 17 - Emission Control <Diesel> - Exhaust Gas Recirculation (EGR) System <4HN> .

Refer to GROUP 17 - Emission Control <Diesel> - Exhaust Gas Recirculation (EGR) System <4HN> .