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
Cross section of pilot injection cycle
(40) Solenoid
(42) Armature
(43) Seated pin
(45) Spool valve
(46) Check ball for intensifier piston
(47) Intensifier piston
(49) Plunger
(54) Nozzle spring
(55) Check piston
(58) Nozzle check
(60) Nozzle tip
(61) Drain
Pilot injection occurs when the ECM sends a control current to the solenoid (40). The current creates a magnetic field which lifts the armature (42) and the seated pin (43). The seated pin has a lower seat and an upper seat. When the seated pin is lifted by the armature, the upper seat closes off the flow of actuation pressure to the check. The lower seat opens, allowing the actuation oil on top of check piston (55) to flow to drain (61). Actuation oil that is trapped below spool (45) will also flow to drain (61). The actuation oil drains through a vent hole in the side of the injector.
The drop in pressure under the spool causes a hydraulic difference that acts on the spool. The spool moves into the open position when hydraulic pressure acts on the top of the spool. This hydraulic pressure forces the spool downward. The downward movement of the spool is stopped when the spool and the pin force the check ball (46) onto the ball seat. This action prevents any actuation pressure from escaping from the cavity for the intensifier piston (47). This drop in the actuation pressure also removes the downward force on the check piston.
Actuation oil now flows past the open spool and to the top of the intensifier piston. The downward movement of the piston and plunger (49) pressurizes the fuel in the plunger cavity to the nozzle tip (60). Pilot injection begins when the injection pressure increases in order to overcome the force of the nozzle spring (54) which lifts the nozzle check (58).
Pilot injection will continue if the following conditions exist:
-The solenoid is energized.
-The spool remains open.
-There is no actuation pressure on top of the check piston.
Injection Delay
Cross section of injection delay
(40) Solenoid
(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
Injection delay begins when the control current to the solenoid (40) stops and the solenoid is de-energized. The armature (42) is held in the up position by a magnetic field. When the magnetic field is de-energized, the armature spring (41) pushes the armature and the seated pin (43) downward. The seated pin closes the lower seat and the seated pin opens the upper seat. This action allows the actuation pressure to flow to the top of the check piston (55). The hydraulic force on the check piston quickly overcomes the injection pressure and the nozzle check (58) closes. Injection stops.
Actuation pressure increases under the spool valve (45) that creates the balance of hydraulic force on the top and bottom of the spool. The weak spool spring (44) now acts on the spool and closes the spool slowly. As the spool remains open, actuation pressure continues to flow past the spool to intensifier piston (47) and to plunger (49). The injection pressure in the nozzle and in the plunger cavity increases quickly when the nozzle check is held in the closed position.
Main Injection
Cross section of main injection cycle
(40) Solenoid
(42) Armature
(43) Seated pin
(45) Spool valve
(46) Check ball for intensifier piston
(55) Check piston
(58) Nozzle check
(61) Drain
Main injection begins when the solenoid (40) is re-energized. The magnetic field is instantly created and the force of the magnetic field lifts the armature (42) and the seated pin (43). The upper
seat closes off the flow of actuation pressure. The upper seat opens the check piston (55) and the bottom of the spool (6) to the drain (61). The hydraulic force that holds the nozzle check (58) closed quickly dissipates and the injection pressure opens the nozzle check. This opening pressure is the start of main injection. A difference in hydraulic forces on the spool is also created. This difference forces the spool downward. The check ball (46) for the intensifier piston is held in the closed position when the spool is in this position. Main injection continues if the solenoid remains energized.
Fill
Cross section of fill cycle
(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
(55) Check piston
(57) Reverse flow check valve
(58) Nozzle check
(61) Drain
The fill cycle begins when the solenoid (40) is de-energized. The armature (42) and the seated pin (43) are forced down by the armature spring (41). The seated pin closes the lower seat and the seated pin opens the upper seat. Actuation pressure is restored to the top of the check piston (55). This
pressure closes the nozzle check (58) and injection ends. Actuation pressure is also felt under the valve spool (45) and restores the hydraulic balance on the spool. The valve spring (44) slowly closes the spool and stops the flow of actuation oil to the intensifier piston (47).
As the spool raises, the check ball (46) for the intensifier piston is no longer held closed. Oil in the cavity for the intensifier piston lifts the check off the seat. The oil flows to the drain (61) through a vent hole in the side of the injector. The return spring (48) pushes up plunger (49) and the intensifier piston. This action pushes all of the oil out of the cavity for the intensifier piston. The check valve (45) for the fuel inlet is taken off the valve seat as the plunger lifts. This lifting allows supply fuel to flow into the plunger cavity. The fill cycle is complete when the plunger and the piston are at the top of the bore. The plunger cavity is now full of fuel.
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BLOG.TEKNISI
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
Cross section of pilot injection cycle
(40) Solenoid
(42) Armature
(43) Seated pin
(45) Spool valve
(46) Check ball for intensifier piston
(47) Intensifier piston
(49) Plunger
(54) Nozzle spring
(55) Check piston
(58) Nozzle check
(60) Nozzle tip
(61) Drain
Pilot injection occurs when the ECM sends a control current to the solenoid (40). The current creates a magnetic field which lifts the armature (42) and the seated pin (43). The seated pin has a lower seat and an upper seat. When the seated pin is lifted by the armature, the upper seat closes off the flow of actuation pressure to the check. The lower seat opens, allowing the actuation oil on top of check piston (55) to flow to drain (61). Actuation oil that is trapped below spool (45) will also flow to drain (61). The actuation oil drains through a vent hole in the side of the injector.
The drop in pressure under the spool causes a hydraulic difference that acts on the spool. The spool moves into the open position when hydraulic pressure acts on the top of the spool. This hydraulic pressure forces the spool downward. The downward movement of the spool is stopped when the spool and the pin force the check ball (46) onto the ball seat. This action prevents any actuation pressure from escaping from the cavity for the intensifier piston (47). This drop in the actuation pressure also removes the downward force on the check piston.
Actuation oil now flows past the open spool and to the top of the intensifier piston. The downward movement of the piston and plunger (49) pressurizes the fuel in the plunger cavity to the nozzle tip (60). Pilot injection begins when the injection pressure increases in order to overcome the force of the nozzle spring (54) which lifts the nozzle check (58).
Pilot injection will continue if the following conditions exist:
-The solenoid is energized.
-The spool remains open.
-There is no actuation pressure on top of the check piston.
Injection Delay
Cross section of injection delay
(40) Solenoid
(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
Injection delay begins when the control current to the solenoid (40) stops and the solenoid is de-energized. The armature (42) is held in the up position by a magnetic field. When the magnetic field is de-energized, the armature spring (41) pushes the armature and the seated pin (43) downward. The seated pin closes the lower seat and the seated pin opens the upper seat. This action allows the actuation pressure to flow to the top of the check piston (55). The hydraulic force on the check piston quickly overcomes the injection pressure and the nozzle check (58) closes. Injection stops.
Actuation pressure increases under the spool valve (45) that creates the balance of hydraulic force on the top and bottom of the spool. The weak spool spring (44) now acts on the spool and closes the spool slowly. As the spool remains open, actuation pressure continues to flow past the spool to intensifier piston (47) and to plunger (49). The injection pressure in the nozzle and in the plunger cavity increases quickly when the nozzle check is held in the closed position.
Main Injection
Cross section of main injection cycle
(40) Solenoid
(42) Armature
(43) Seated pin
(45) Spool valve
(46) Check ball for intensifier piston
(55) Check piston
(58) Nozzle check
(61) Drain
Main injection begins when the solenoid (40) is re-energized. The magnetic field is instantly created and the force of the magnetic field lifts the armature (42) and the seated pin (43). The upper
seat closes off the flow of actuation pressure. The upper seat opens the check piston (55) and the bottom of the spool (6) to the drain (61). The hydraulic force that holds the nozzle check (58) closed quickly dissipates and the injection pressure opens the nozzle check. This opening pressure is the start of main injection. A difference in hydraulic forces on the spool is also created. This difference forces the spool downward. The check ball (46) for the intensifier piston is held in the closed position when the spool is in this position. Main injection continues if the solenoid remains energized.
Fill
Cross section of fill cycle
(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
(55) Check piston
(57) Reverse flow check valve
(58) Nozzle check
(61) Drain
The fill cycle begins when the solenoid (40) is de-energized. The armature (42) and the seated pin (43) are forced down by the armature spring (41). The seated pin closes the lower seat and the seated pin opens the upper seat. Actuation pressure is restored to the top of the check piston (55). This
pressure closes the nozzle check (58) and injection ends. Actuation pressure is also felt under the valve spool (45) and restores the hydraulic balance on the spool. The valve spring (44) slowly closes the spool and stops the flow of actuation oil to the intensifier piston (47).
As the spool raises, the check ball (46) for the intensifier piston is no longer held closed. Oil in the cavity for the intensifier piston lifts the check off the seat. The oil flows to the drain (61) through a vent hole in the side of the injector. The return spring (48) pushes up plunger (49) and the intensifier piston. This action pushes all of the oil out of the cavity for the intensifier piston. The check valve (45) for the fuel inlet is taken off the valve seat as the plunger lifts. This lifting allows supply fuel to flow into the plunger cavity. The fill cycle is complete when the plunger and the piston are at the top of the bore. The plunger cavity is now full of fuel.
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BLOG.TEKNISI
Hello, I have a problem, I bought a C9 unit injection for the Claas Lexsio 550 combine and it turns out that the fuel goes to the oil, the experts say that it is the fault of the unit injectors and now I do not know what may be wrong with them, which may cause the unit injectors to leak fuel into the oil
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