Hydraulic Electronic Unit Injector (HEUI) C7 and C9 - Components
HEUI Injector (Components)
The HEUI injector serves four functions. The HEUI injector pressurizes supply fuel from 450 kPa (65 psi) to 175 MPa (25382 psi). The HEUI injector functions as an atomizer by pumping high-pressure fuel through orifice holes in the unit injector tip. The HEUI injector delivers the correct amount of atomized fuel into the combustion chamber. And the HEUI injector disperses the atomized fuel evenly throughout the combustion chamber.
Cross section of HEUI injector
(40) Solenoid
(41) Armature spring
(42) Armature
(43) Seated pin
(44) Spool spring
(45) Spool valve
(46) Check ball for intensifier piston
(47) Intensifier piston
(48) Return spring
(49) Plunger
(50) Barrel
(51) Nozzle case
(52) Inlet fill check
(53) Stop
(54) Nozzle spring
(55) Check piston
(56) Sleeve
(57) Reverse flow check valve
(58) Nozzle check
(59) Nozzle tip
HEUI Fuel Injector (Operation)
The HEUI injector operates with a split injection cycle. The split injection cycle has five phases of injection:
-Pre-Injection
-Pilot injection
-Injection delay
-Main injection
-Fill
Pre-Injection
Cross section of pre-injection cycle
(41) Armature spring
(42) Armature
(43) Seated pin
(44) Spool spring
(45) Spool valve
(47) Intensifier piston
(49) Plunger
(55) Check piston
(58) Nozzle check
The injector is in the phase of pre-injection when the engine is running and the injector is between firing cycles. Plunger (49) and the intensifier piston (47) are at the top of the piston bore. The cavity below the plunger is full of fuel.
In the upper end, the armature (42) and the seated pin (43) are held down by the armature spring (41). High pressure actuation oil flows into the injector. The oil then flows around the seated pin to the top of the check piston (55) . This flow provides a positive downward force on the nozzle check (19) at all times when fuel is not being injected.
The spool valve (45) is held in the top of the bore for the spool valve by the spool spring (44) . In this
position, the spool valve blocks actuation oil from reaching the intensifier piston. Actuation pressure is felt on both the top and bottom of the spool, so hydraulic forces on the spool are balanced. The spool valve is held in the up position or the closed position by the force of the spool spring.
Pilot Injection
The HEUI injector serves four functions. The HEUI injector pressurizes supply fuel from 450 kPa (65 psi) to 175 MPa (25382 psi). The HEUI injector functions as an atomizer by pumping high-pressure fuel through orifice holes in the unit injector tip. The HEUI injector delivers the correct amount of atomized fuel into the combustion chamber. And the HEUI injector disperses the atomized fuel evenly throughout the combustion chamber.
Cross section of HEUI injector
(40) Solenoid
(41) Armature spring
(42) Armature
(43) Seated pin
(44) Spool spring
(45) Spool valve
(46) Check ball for intensifier piston
(47) Intensifier piston
(48) Return spring
(49) Plunger
(50) Barrel
(51) Nozzle case
(52) Inlet fill check
(53) Stop
(54) Nozzle spring
(55) Check piston
(56) Sleeve
(57) Reverse flow check valve
(58) Nozzle check
(59) Nozzle tip
HEUI Fuel Injector (Operation)
The HEUI injector operates with a split injection cycle. The split injection cycle has five phases of injection:
-Pre-Injection
-Pilot injection
-Injection delay
-Main injection
-Fill
Pre-Injection
Cross section of pre-injection cycle
(41) Armature spring
(42) Armature
(43) Seated pin
(44) Spool spring
(45) Spool valve
(47) Intensifier piston
(49) Plunger
(55) Check piston
(58) Nozzle check
The injector is in the phase of pre-injection when the engine is running and the injector is between firing cycles. Plunger (49) and the intensifier piston (47) are at the top of the piston bore. The cavity below the plunger is full of fuel.
In the upper end, the armature (42) and the seated pin (43) are held down by the armature spring (41). High pressure actuation oil flows into the injector. The oil then flows around the seated pin to the top of the check piston (55) . This flow provides a positive downward force on the nozzle check (19) at all times when fuel is not being injected.
The spool valve (45) is held in the top of the bore for the spool valve by the spool spring (44) . In this
position, the spool valve blocks actuation oil from reaching the intensifier piston. Actuation pressure is felt on both the top and bottom of the spool, so hydraulic forces on the spool are balanced. The spool valve is held in the up position or the closed position by the force of the spool spring.
Pilot Injection