Operation Section
1
–
77
To Increase the EGR Quantity
- The E-VRV duty ratio is controlled
*1
. In the stable condition shown in the bottom center diagram, an increase in the
current that is applied to the coil causes the attraction force FM in the coil to increase. When this force becomes
greater than the vacuum force FV that acts on the diaphragm, the moving core moves downward. Along with this
movement, the port from the vacuum pump to the upper chamber of the diaphragm opens. Consequently, the out-
put vacuum increases, which causes the EGR valve to open and the EGR volume to increase. Meanwhile, because
"increased output vacuum equals increased FV", the moving core moves upward with the increase in FV. When
FM and FV are equal, the port closes and the forces stabilize. Because the vacuum circuit of the EGR is a closed
loop, it maintains the vacuum in a stabilized state, provided there are no changes in the amperage.
< NOTE >
*1 : The engine ECU outputs sawtooth wave signals with a constant frequency. The value of the current is the effective (average) value of these
signals. For details, see the explanation of the HP3 supply pump and SCV.
To Decrease the EGR Volume
- A decrease in the current that is applied to the coil causes FV to become greater than FM. As a result, the dia-
phragm moves upward. The moving core also moves upward in conjunction with the movement of the diaphragm,
causing the valve that seals the upper and lower diaphragm chambers to open. Consequently, the atmospheric
pressure in the lower chamber enters the upper chamber, thus reducing the output vacuum. This causes the EGR
valve to close and the EGR volume to decrease. Because "decreased output vacuum equals decreased FV", the
moving core moves downward with the decrease in FV. When FM and FV are equal, the port closes and the forces
stabilize.
FV
FM
FM > FV
EGR Quantity Increased
FM < FV
EGR Quantity Decreased
To EGR Valve
From Vacuum Pump
Atmosphere
Valve
Spring
Coil
Stator Core
Diaphragm
Moving Core
Q000904E
To Next Page
Loading...
