Bơm ECD-V - P - ECD-V4 Outline
Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (1.86 MB, 4 trang )
"ECD-V4 System"
ECD (Electronically Controlled Diesel): An electronically controlled system for diesel fuel injection.
Final SessionFinal Session
9
SERVICE TECH Vol.472 04-6
Direct injection engines require high fuel injection pressure. In response, the ECD-V4 is a high-pressure injection
pump with improved features such as fuel pumping and distribution.
(Compared with 60MPa for the ECD-V3, the ECD-V4 has an injection pressure of 130MPa)
The final session of “Fundamentals of the ECD System” will explain the ECD-V4 injection pump, concentrating on
the differences to the ECD-V3.
An inner cam type pumping mechanism is used in the ECD-V4 to obtain the injection pressure required for a direct
injection engine (approx. 130MPa). The ECD-V3 injection pump uses a face cam type pumping mechanism.
However, in this type the cam surface and roller “slip” at high pressure, resulting in mechanical loss. In the inner cam
type this loss is minimized, so high pressure can be generated.
1
1
ECD-V4 Outline
Engine Speed Sensor
Pulsar
Feed Pump
Roller
Plunger
Cam Ring (Inner Cam)
Timer Piston
Timing Control Valve (TCV)
Rotor
ROM
Solenoid Spill Valve (SPV)
2
2
Inner Cam Mechanism
Inner Cam
Cam Ring
Roller
Plunger
Inner Cam Type Face Cam Type
Face Cam
10
SERVICE TECH Vol.472 04-6
As the engine drives the injection pump drive shaft, the built-in feed pump is also rotated. Fuel is suctioned from
the fuel tank and sent to the pump feed gallery. At this time the solenoid spill valve is open (SPV: OFF), and the
fuel pump area (rotor) is replenished with fuel.
The solenoid spill valve is closed (SPV: ON), and the inner cam and plunger pressurize the fuel trapped in the
rotor as the drive shaft rotates. At the instant when the pressure required to open the delivery valve is reached,
fuel is pumped from the high-pressure pipes to the nozzle, and injection begins.
The solenoid spill valve opens (SPV: OFF), and as pressure in the rotor reduces, the delivery valve closes and
injection ends.
3
3
Fuel Suction and Pumping
Suction
Pumping / Injection
End of Injection
Suction Pumping / Injection
Solenoid Spill Valve (SPV)
During Suction
During Spill
Cam
Roller
Plunger
Cam
Rotor
During Suction
During Pumping
Rotor Rotation
Roller
Cam Ring
Rotor
Plunger
In the inner cam, the roller and rotor rotate the inner side of the cam ring, which moves the plunger.
11
SERVICE TECH Vol.472 04-6
This solenoid spill valve instantly applies high voltage (approx. 150V) to ensure fast responsiveness. It is installed in
the fuel passage connecting the fuel pump rotor to the pump chamber. Upon receiving a signal from the engine ECU
for fuel suction or the end of injection, the solenoid spill valve opens the passage to the fuel pump area (rotor).
The solenoid spill valve in high injection pressure type injection pumps must switch OFF and ON once or twice instantly
during the period from the start to the end of fuel injection. For this reason, it must have be highly responsive. An EDU
(Electronic Driving Unit) is used for high-speed operation of the solenoid spill valve under high-pressure fuel conditions. High
voltage is applied at the instant of actuation, attracting the valve with strong magnetism to close it quickly and completely.
Upon receiving an “IJT signal” from the engine ECU, the EDU instantly applies high voltage (approx. 150V) from the
high voltage generation circuit to the solenoid spill valve. This ensures fast valve response. The valve that was
temporarily attracted is held using “current control”, and it remains closed. At this time the solenoid spill valve current
is detected by the current detection circuit. If conditions are normal, an “IJF signal” is returned to the engine ECU. If
conditions are abnormal, a malfunction is judged because the signal is not returned, and “IJT signal” output is halted.
4
4
Solenoid Spill Valve SPV (High Response Type)
Pump Chamber
OFF ON
Rotor
Passage ClosedPassage Open
Pump Chamber
Rotor
Engine
ECU
Engine
ECU
ON (Approx. 150V)
4-1
Actuation Method for the Solenoid Spill Valve (High Response Type)
4-2 Operation of the EDU
5V
0V
5V
0V
Current
Detection
Circuit
Control
Circuit
High Voltage
Generation Circuit
EDU
IJT Signal
IJF Signal
Engine
ECU
SPVD
SPVF
IJT
IJF
SPV
0V
Approx.
150V
SPV
E
2
Solenoid Spill Valve
SPV
Solenoid Spill Valve Waveform
12
SERVICE TECH Vol.472 04-6
The injection quantity control method is more or less the same as in the face cam type injection pump (ECD-V3).
One difference is that fuel is sucked into the pressure chamber, and the solenoid spill valve stays open (OFF) and
closes immediately before the start of pumping. In other words, both the start of injection and end of injection can be
controlled.
As for the ECD-V3, the ON and OFF timing of the solenoid spill valve are determined based on the signal from the
engine speed sensor. The number of pulses and intervals between the pulses are detected, enabling the calculation
of the cam angle of the inner cam.
• This concludes the “Fundamentals of the ECD System” sessions. An explanation of the common rail system
(CRS) will start in the next issue.
5
5
Method for Injection Quantity Control
Cam Ring
(Lift)
(Injection Angle)
Solenoid Spill Valve Signal
Short ON Duration (Small Injection Quantity)
(Injection Angle)
Cam Ring
(Lift)
Solenoid Spill Valve Signal
Short ON Duration (Large Injection Quantity)
Solenoid Spill Valve
(SPV)
Rotor
Engine Speed Senso
r
Cam Ring
Pulsar
Roller
Drive Shaft
Pulsar
Engine Speed Sensor
