Denso CRS - Page 35

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Operation Section

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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 View

Return Spring

Solenoid

Valve Body

Cross Section

Needle Valve

Q002309E