Land Rover Common Rail System Crs Denso Manual
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Operation Section1–26 Fuel Discharge Quantity Control • The diagram below shows that the suction starting timing (SCV (Suction Control Valve) ON) is constant (determined by the pump speed) due to the crankshaft position sensor signal. For this reason, the fuel suction quantity is controlled by changing the suction ending timing (SCV OFF). Hence, the suction quantity decreases when the SCV is turned OFF early and the quantity increases when the SCV is turned OFF late. • During the intake stroke, the plunger receives the fuel feed pressure and descends along the cam surface. When the SCV turns OFF (suction end), the feed pressure on the plunger ends and the descent stops. Since the suction quantity varies, when suction ends (except for maximum suction) the roller separates from the cam surface. • When the drive shaft rotates and the cam peak rises and the roller comes in contact with the cam surface again, the plunger is pressed by the cam and starts pumping. Since the suction quantity = the discharge quantity, the discharge quantity is controlled by the timing with which the SCV is switched OFF (suction quantity). 0 2 4 6 8 101214 16 0 2 4 6 8 1012 14 0 2 4 6 8 101214 16 0 2 4 6 8 1012 14 Suction Suction Suction SuctionDecreased Suction Quantity Increased Suction Quantity ON OFF SCV 1 SCV 2 Suction Pumping Start of Suction End of Suction Start of Pumping End of Pumping 360 CR TDC #1TDC #3 TDC #4TDC #2 Cylinder Recognition Sensor Signal Crankshaft Position Sensor Signal ON OFF Crankshaft Angle Compression Top Dead Center Fuel ON Plunger RollerOFF Fuel OFF Fuel OFF Delivery Valve Discharge Horizontal Cam Lift Vertical Cam Lift Check Valve SCV PumpingSuction PumpingSuctionPumpingSuction PumpingSuction Delivery Valve Q000833E
Operation Section1–27 3.3 HP3 Type (1) Construction and Characteristics • The supply pump is primarily composed of the pump unit (eccentric cam, ring cam, two plungers), the SCV (suction control valve), the fuel temperature sensor and the feed pump (trochoid type), and is actuated at 1/1 or 1/2 the engine rotation. • The two compact pump unit plungers are positioned symmetrically above and below on the outside of the ring cam. • The fuel discharge quantity is controlled by the SCV, the same as for the HP2, in order to reduce the actuating load and suppress the rise in fuel temperature. In addition, there are two types of HP3 SCV: the normally open type (the suction valve opens when not energized) and the normally closed type (the suction valve is closed when not ener- gized). • With a DPNR system (Diesel Particulate NOx Reduction) system, there is also a flow damper. The purpose of this flow damper is to automatically shut off the fuel if a leak occurs in the fuel addition valve passage within the DPNR. Q000835E Suction Valve Plunger Ring Cam SCV (Suction Control Valve) Delivery ValveFeed Pump Fuel Temperature Sensor
Operation Section1–28 (2) Exploded View Q000836E Pump Housing CamshaftEccentric CamRing CamFeed Pump Plunger Element Sub-AssemblySCV (Suction Control Valve) Regulating ValveFuel Temperature Sensor Delivery Valve Delivery Valve Delivery Valve Element Sub-Assembly Plunger
Operation Section1–29 (3) Component Part Functions Feed Pump • The trochoid type feed pump, which is integrated in the supply pump, draws fuel from the fuel tank and feeds it to the two plungers via the fuel filter and the SCV (Suction Control Valve). The drive shaft actuates the outer/inner rotors of the feed pump, thus causing the rotors to start rotating. In accordance with the space that increases and decreases with the movement of the outer and inner rotors, the feed pump draws fuel into the suction port and pumps fuel out the discharge port. Regulating Valve • The regulating valve keeps the fuel feed pressure (discharge pressure) below a certain level. If the pump speed in- creases and the feed pressure exceeds the preset pressure of the regulating valve, the valve opens by overcoming the spring force in order to return the fuel to the suction side. Component PartsFunctions Feed Pump Draws fuel from the fuel tank and feeds it to the plunger. Regulating Valve Regulates the pressure of the fuel in the supply pump. SCV (Suction Control Valve) Controls the quantity of fuel that is fed to the plungers. Pump Unit Eccentric Cam Actuates the ring cam. Ring Cam Actuates the plunger. Plunger Moves reciprocally to draw and compress fuel. Delivery Valve Prevents reverse flow from the rail of the fuel pumped from the plunger. Fuel Temperature Sensor Detects the fuel temperature. To Pump Chamber From Fuel TankOuter Rotor Inner Rotor Suction PortDischarge Port Q000770E Bushing Piston Spring Plug Feed Pump SCV Pump Housing Q000837E
Operation Section1–30 Suction Control Valve (SCV) • In contrast to the HP2, the SCV for the HP3 supply pump is equipped with a linear solenoid valve. The fuel flow vol- ume supplied to the high-pressure plunger is controlled by adjusting the engine ECU supplies power to the SCV (duty ratio control). When current flows to the SCV, the internal armature moves according to the duty ratio. The armature moves the needle valve, controlling the fuel flow volume according to the amount that the valve body fuel path is blocked. Control is performed so that the supply pump suctions only the necessary fuel quantity to achieve the target rail pressure. As a result, the supply pump actuation load is reduced. • There are two types of HP3 SCV: the normally open type (the suction valve opens when not energized) and the nor- mally closed type (the suction valve is closed when not energized). The operation of each type is the reverse of that of the other. • In recent years, a compact SCV has been developed. Compared to the conventional SCV, the position of the return spring and needle valve in the compact SCV are reversed. For this reason, operation is also reversed. Normally Open Type - When the solenoid is not energized, the return spring pushes against the needle valve, completely opening the fuel passage and supplying fuel to the plungers. (Total quantity suctioned → Total quantity discharged) - When the solenoid is energized, the armature pushes the needle valve, which compresses the return spring and closes the fuel passage. In contrast, the needle valve in the compact SCV is pulled upon, which compresses the return spring and closes the fuel passage. - The solenoid ON/OFF is actuated by duty ratio control. Fuel is supplied in an amount corresponding to the open surface area of the passage, which depends on the duty ratio, and then is discharged by the plungers. Q002340E Conventional SCV External ViewReturn Spring Solenoid Valve Body Cross Section Needle Valve Q002309E Return Spring Solenoid Valve Body Needle Valve Compact SCV External View Cross Section
Operation Section1–31 Duty Ratio Control - The engine ECU outputs sawtooth wave signals with a constant frequency. The value of the current is the effective (average) value of these signals. As the effective value increases, the valve opening decreases, and as the effec- tive value decreases, the valve opening increases. When the SCV Energized Duration (Duty ON Time) is Short - When the SCV energization time is short, the average current flowing through the solenoid is small. As a result, the needle valve is returned by spring force, creating a large valve opening. Subsequently, the fuel suction quantity increases. QD0710E Average Current Difference Actuating Voltage ON OFF Current Low Suction Quantity High Suction Quantity Q002341E Needle Valve Large Valve OpeningSCV Feed Pump Conventional SCV
Operation Section1–32 When the SCV Energized Duration (Duty ON Time) is Long - When the energization time is long, the average current flowing to the solenoid is large. As a result, the needle valve is pressed out (in the compact SCV, the needle valve is pulled), creating a small valve opening. Subsequently, the fuel suction quantity decreases. Q002321E Compact SCV Needle ValveLarge OpeningFeed Pump Q002342E Needle Valve Small OpeningSCV Feed Pump Conventional SCV
Operation Section1–33 Q002322E Small Valve Opening Compact SCVNeedle ValveSCV Feed Pump
Operation Section1–34 Normally Closed Type - When the solenoid is energized, the needle valve is pressed upon (in the compact SCV, the cylinder is pulled upon) by the armature, completely opening the fuel passage and supplying fuel to the plunger. (Total quantity suctioned → Total quantity discharged) - When power is removed from the solenoid, the return spring presses the needle valve back to the original position, closing the fuel passage. - The solenoid ON/OFF is actuated by duty ratio control. Fuel is supplied in an amount corresponding to the open surface area of the passage, which depends on the duty ratio, and then is discharged by the plungers. Duty Ratio Control - The engine ECU outputs sawtooth wave signals with a constant frequency. The value of the current is the effective (average) value of these signals. As the effective value increases, the valve opening increases, and as the effective value decreases, the valve opening decreases. Q002343ECross Section External ViewReturn Spring Solenoid Valve Body Needle Valve Conventional SCV Q002323ECross Section External ViewReturn Spring Solenoid Valve Body Needle Valve Compact SCV Q000844E Average Current Difference Actuating Voltage ON OFF Current High Suction Quantity Low Suction Quantity
Operation Section1–35 When the SCV Energized Duration (Duty ON Time) is Long - When the energization time is long, the average current flowing to the solenoid is large. As a result, the needle valve is pushed out (in the compact SCV, the needle valve is pulled), creating a large valve opening. Subsequently, the fuel suction quantity increases. Q002344E Needle Va l v eLarge Opening SCV Feed Pump Conventional SCV Q002324 E Large Valve Opening Compact SCV Needle Va l v eSCV Feed Pump