Bơm ECD-V - P - Intake Restriction Control
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"Intake Restriction Control, EGR Control and Glow Control"
ECD (Electronically Controlled Diesel): An electronically controlled system for diesel fuel injection.
Eighth SessionEighth Session
11
SERVICE TECH Vol.471 04-4
This control system adjusts the air intake volume of the engine to secure a comfortable and safe drive.
The "intake restriction valve (sub valve)" located halfway along the intake manifold opens and closes according
to the engine conditions. This reduces noise and vibration, and prevents overrun.
Main Operations Objective
When starting the engine
Fully opens the sub valve to minimize the emission of white
smoke and black smoke
When idling
Restricts the air intake volume to reduce noise
When engine is stopped
Fully closes the sub valve to reduce engine vibration and noise
During Abnormally high engine speed
Fully closes the sub valve to prevent overrun
The sub valve installed in parallel to the main valve can be moved to 3
positions, "Fully open, Half open, or Fully closed", with the 2 level
diaphragm. This is how the air intake volume is controlled.
1
1
Intake Restriction Control
1-1 Control Outline
1-2
2 Level Diaphragm Type Intake Restriction Mechanism
Sub Valve
2 Level Diaphragm
Vacuum Pump
Air
2 Level Diaphragm
Chamber B
Sub
Valve
Main
Valve
Accelerator
Pedal
Accelerator Position
Engine Speed
Key Switch
Refrigerant Temperature
Vacuum
Engine
ECU
VSV1
VSV2
Chamber A
Air
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SERVICE TECH Vol.471 04-4
This component is constructed from 2 diaphragms and springs, and a rod. Chamber A and chamber B are
separated by the diaphragms. When a vacuum or air pressure is introduced to these chambers the rod moves,
which via the link makes the sub valve move to one of the 3 positions.
This is a solenoid valve that selects the airflow ports according to the signal received from the engine ECU,
switching the pressure feed to the diaphragm chamber.
The energization of VSV1 or VSV2 is selected according to the driving and engine conditions. A vacuum or air
pressure is channeled into the diaphragm chamber, which moves the sub valve to one of 3 positions and adjusts
the intake air volume.
Active Air Flow
Port E Port F Air Port
Energized
(ON)
Not
Energized
1-3 Component Construction and Operation
2 Level Diaphragm
Vacuum
Vacuum
Vacuum
Air Pressure
Air Pressure
Air Pressure
Rod
Chamber B
Spring
Chamber A
Fully Open Half Open Fully Closed
VSV (Vacuum Switching Valve)
Air Port
E Port
F Port
Chamber A or Chamber B
Diaphragm Port
To
From
Vacuum
Port
1-4 Intake Restriction Position and Driving Conditions
Sub Valve Position
Fully Open
Half Open
Fully Closed
Actuator
VSV
VSV1
OFF
OFF
Air Pressure Air Pressure
Vacuum
Vacuum
Air Pressure
Vacuum
ON
ON
ON
OFF
VSV2
Chamber A Chamber B
Diaphragm Chamber
Driving Conditions
• When starting (starter ON)
• When idling during warm-up
• When driving
• When idling after warm-up
• When engine stalled (IG/ON)
•
When abnormally high engine speed is detected
•
For 2 seconds after stopping the engine
• When overrun is detected
• When SPV abnormality is detected
Engine Conditions
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SERVICE TECH Vol.471 04-4
Part of the exhaust gas is recirculated to the intake side, which slows combustion and controls NOx emissions.
In EGR (Exhaust Gas Recirculation) control, an amount of exhaust gas appropriate to the driving conditions is
returned to the intake manifold and reinserted in the combustion process. This system lowers the combustion
temperature and reduces nitrogen oxide (NOx) emissions.
• EGR Valve
This component is constructed from a diaphragm, spring and valve. When a vacuum is introduced to the
diaphragm chamber, a valve that is interlinked with the diaphragm opens. The exhaust gas flows from the
exhaust manifold to the intake manifold side.
• E-VRV (Electric Vacuum Regulating Valve)
This is a solenoid valve for switching the vacuum. Duty control is performed by the engine ECU. When the
solenoid valve goes on or off, the vacuum from the vacuum pump is switched, which controls the vacuum feed
to the diaphragm chamber of the EGR valve.
Duty Control
This control utilizes the duty ratio.
The duty ratio is the ratio of energized (ON)
duration to non-energized (OFF) duration. It
is calculated using the following formula, in
which the ON duration (t) is divided by the
unit of time (T).
2
2
EGR Control Outline
2-1 Control Outline
Injection Pump
Vacuum Pump
(Vacuum)
Exhaust Manifold
Engine Speed Signal
Accelerator Position Signal
Throttle Position Sensor
Diaphragm
Chamber
Air
EGR Valve
Coolant Temperature
Sensor
Engine
ECU
Component Construction and Operation
Filter
EGR Valve
Vacuum Pump
Coil
EGR Valve E-VRV
Duty Ratio = × 100 (%)
T
t
ON
t
T
OFF
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SERVICE TECH Vol.471 04-4
This control improves startability during cold weather and reduces emission gases and noise.
The heat generating part is a "ceramic glow plug" that uses a conductive ceramic heating element.
The resistance at ordinary temperatures is about 0.5 , and when current flows it rapidly generates heat.
However as the temperature increases the resistance of the control coil also increases, and the electric volume
gradually decreases. This "self control function" maintains a roughly constant temperature.
A heat source installed in the engine combustion chamber improves
startability by both warming the air inside the combustion chamber and
by acting as an ignition source for the fuel.
In addition, even after the engine is started, it generates heat for a
limited time to reduce the emission of white smoke and diesel knock
noise.
3
3
Glow Control Outline
3-1 Control Outline
Glow Plug
Auxiliary
Combustion
Chamber
Glow Relay
Glow Plug
Glow Plug
Indicator Lamp
Coolant
Temperature
Sensor
Engine
ECU
3-2 Glow Plug
Type With Control Coil
48
Energization Time (Sec.)
Self Control Function
Temperature(°C)
12
1000
Ceramic Glow PlugCeramic Glow Plug
Ceramic Heating Element
(Resistance at Ordinary Temperatures : About 0.5 )
