Denso Avance
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Transcript of Denso Avance
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8/12/2019 Denso Avance
1/4
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8/12/2019 Denso Avance
2/410SERVICE TECH Vol.469 03-12
In order to change the injection timing, the amount of fuel pressure added to the timer piston of the injection pump is
controlled, and the position of the piston is varied. The movement of the timer piston rotates the roller ring via the slide
pin. As a result, the position of the roller relative to the cam plate is changed, which varies the timing of the start of
injection.The control of injection timing when the timing control valve is ON is explained below. The control when the timing
control valve is switched between ON/OFF is explained in section 3-2 Timing Control Valve (TCV).
22 Basic Control Method for Injection Timing
When the pressure is low in the high pressure chamber side, the timer piston is pushed in the direction of
injection retard by the timer spring.
Timing Control
Valve
Roller Ring
R etard T im in g : Timing Control Valve is widely open.
Timer Piston
Timer Spring
Low Pressure
Side
High Pressure Chamber
(Inside Pump Chamber)
ON Time: Long
Retard
Slide Pin
Engine
ECU
Cam Plate
When the pressure is increased in the high pressure chamber it overcomes the strength of the spring and
moves in the advance direction.
A d vance T im ing : Timing Control Valve is almost closed.
ON Time: Short
Advance
Low Pressure
Side
Engine
ECU
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8/12/2019 Denso Avance
3/411 SERVICE TECH Vol.469 03-12
The crankshaft position sensor is an electromagnetic pick-up type sensor for detecting the crankshaft position ofthe engine. It is installed on the engine cylinder block, and through the projection installed on the crankshaft, it
generates a pulse for every revolution of the engine. This pulse is used as a "standard crankshaft position" signal
in order to control injection timing.
One pulse of the crankshaft position signal is generated for every revolution of the engine (360 CA). On the otherhand during the same period the injection pump completes 1/2 a revolution (180 PA), and if the engine has 4
cylinders a pulse equivalent to 2 cylinders is output by the engine speed sensor. (The position of the engine speed
sensor changes according to the injection timing, so the actual relative position varies with the engine conditions.)
The actual injection timing is calculated from these two signals, which the engine ECU compares with the target
injection timing.
With the crankshaft position sensor signal as a standard, the angle (CA) up to the position of the certain pulse of
the engine speed sensor signal determined by each engine is calculated as the actual injection timing.
33 Construction and Operation of Components
3-1 Crankshaft Position Sensor
Projection
Crankshaft Position
Sensor
Relationship between the crankshaft position sensor signal and the engine speed sensor signal
Engine Speed Sensor
Crankshaft Position Sensor
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8/12/2019 Denso Avance
4/412SERVICE TECH Vol.469 03-12
The timing control valve is an electromagnetic valve that opens and closes the fuel passages to the high pressure
and low pressure side of the timer piston, according to actuating signals from the engine ECU. The opening degree
of these passages is controlled by the ON/OFF rate (duty ratio) of the current energized by the coil. When the
current is ON for a long time, the open time of the TCV becomes longer. This causes a lot of fuel to leak from the
high pressure chamber side to the low pressure chamber side. The pressure of the high pressure chamber side
is reduced so the timer piston loses out to the strength of the timer spring, and it moves to the retard side.
Duty Ratio
Expresses the ratio between energized (ON) and non-
energized (OFF) electricity. The ratio is calculated
from the following formula, dividing the length of theON time (t) by the unit of time (T)..
In the figure on the left, the ON time is longer so the
TCV passage is open for a long period, and the timer
piston moves to the retard side.
3-2 Timing Control Valve (TCV)
Timer Piston
Timing Control Valve
High Pressure Chamber
Timer Spring
ON Duty Ratio: Minimum AdvanceON Duty Ratio: Maximum Retard
Coil
Low Pressure Side
Moving Core SpringHigh Pressure Chamber
(Inside Pump Chamber)
Coil
Low Pressure Side
Moving Core Spring
Fuel Valve
High Pressure Chamber
(Inside Pump Chamber)
Fuel Valve
Duty Ratio = 100 (%)t
T