Society of Automotive Engineers of Japan, Inc. 240 Landmarks Top JSAE HOME
240 Landmarks of Japanese Automotive Technology
left image
240 Landmarks TopDiesel Engine > Common rail ECD-U2
 Common rail ECD-U2
image
image
 
This system consists of a supply pump, common rail, injectors, an ECU that controls these components and sensors as shown in Fig. 1. The fuel pressure in the common rail is controlled by controlling the fuel injection volume from the supply pump using a solenoid valve. The fuel pressure is detected by the pressure sensor set in the common rail, and controlled to the set optimal value according to the engine speed and load by the solenoid valve in the supply pump. This greatly improved the pressure-increase performance in low engine speed regions compared with conventional in-line pumps and unit injectors. It also enabled high-pressure injection in low speed regions, allowing fuel to be atomized in all regions. Consequently, it was possible to remarkable reduce the black smoke unique to diesel engines.
In addition, the common rail fuel pressure is applied through the injector nozzle side and hydraulic piston to the nozzle rear side. The injection volume and timing are controlled by turning on and off the nozzle back pressure by a solenoid valve. When current is passed through the solenoid valve, the high-pressure fuel in the nozzle back side flows to the low-pressure side. Then the high-pressure on the nozzle side lifts a needle to start injection. When the supply of the current to the solenoid valve is stopped, high pressure is applied to the back side of the nozzle again and the nozzle is closed, stopping the injection. It is therefore possible to electronically control the injection timing and injection period by the power application timing and period of the solenoid valve respectively. Moreover, as shown in Fig. 2, adding a power pulse prior to the main injection raises the nozzle back controlled hydraulic pressure twice to obtain a pilot injection characteristic with only a very little amount of nozzle opening. This shortens ignition delay and suppresses pre-mixed combustion to counter issues such as reduction of NOx, combustion noise and vibration, as well as to improve startability and fuel efficiency.
dot
Storage location:DENSO CORPORATION, DIESEL INJECTION ENGINEERING DIV. NO. 1 (1-1 Showa-cho, Kariya-shi, Aichi 448-8661)
dot
Year manufactured:1995
dot
Manufacturer:Denso Corporation
dot
Classification:Mass-production system
dot
Current status:In use: open to the public
dot
Model / Manufacture
Company name:Denso Corporation
dot
Installation model:Hino Rising Ranger
dot
Year of manufacture:1995
dot
Designed by:Shohei Ito
dot
Specification
dot
Performance
dot
Device
dot
Points of interest, topicality:Common rails were firstly put into practical use by Denso. Due to their significance, Bosch then applied them in passenger cars.
dot
Features:Common rails greatly changed diesel engines in Europe. They are more popular than gasoline engines due to their acceleration at high speeds.
dot
Reference materials:(1) Engine Technology Vol. , No. 4, p. 46, Sep. 1999
(2)Proceedings of JSAE, "Common rail fuel injection system for improvement of engine performance and reduction of exhaust emission on heavy duty diesel engine", 1997
(3) The 14th Internal Combustion Engine Symposium Text, "Improvement of practical fuel consumption with pilot injection", 1997
dot
240 Landmarks TopDiesel Engine > Common rail ECD-U2 page top
COPYRIGHT (C) SOCIETY OF AUTOMOTIVE ENGINEERS OF JAPAN, INC. ALL RIGHTS RESERVED.