Common Rail Fuel Pressure Control for Smooth Gearshift
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Solution Overview
Problem
Common rail fuel injection systems in vehicles face challenges in achieving repeatable and smooth gearshifts, particularly when driving uphill, due to high fuel pressure leading to loud noises and torque uncertainties, as existing solutions fail to adequately lower fuel pressure in a controlled manner.
Innovation Solution
A control system that initiates a decrease in fuel pressure in the common rail fuel system before lowering engine torque during gearshift, ensuring a low fuel pressure for smooth gear release and synchronization, and raises fuel pressure only after engaging a new gear, using a command bus for efficient communication and distributed control units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If fuel pressure is maintained at high levels during uphill driving, then engine power is sufficient for climbing, but engine torque becomes unpredictable and gearshift becomes jerky
Solution Approach 1:
The control system initiates fuel pressure reduction before the gearshift command is executed. When an uphill drive is detected and a gearshift is required, the system prematurely lowers the fuel pressure in the common rail from the high level needed for climbing to a lower level suitable for smooth gear engagement, thereby ensuring repeatable engine torque at the moment of gearshift.
2Speed
If fuel pressure is reduced quickly to enable gear release, then gearshift can be performed, but opening time for fuel actuator becomes too short causing noise and knock
Solution Approach 1:
The system performs preliminary fuel pressure reduction before the gearshift event, creating a time buffer that allows the fuel actuator to maintain adequate opening time even during rapid gearshift operations. This prevents short burst fuel injection and associated noise and knock.
Solution Approach 2:
By reducing fuel pressure in advance, the system cushions against the potential harm of short opening times during gearshift. The lowered pressure acts as a protective measure that ensures sufficient fuel actuator opening time and enables pilot injections, thereby preventing noise and knock.
3Reliability
If fuel pressure is lowered before gearshift, then repeatable torque is achieved, but time is lost in pressure adjustment
Solution Approach 1:
The control system detects uphill driving conditions and impending gearshift requirements in advance, initiating fuel pressure reduction at an optimally timed moment before the gearshift command. This preliminary action ensures that the pressure adjustment is completed just in time for smooth gear engagement, minimizing any time loss while achieving repeatable torque.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables repeatable engine torque throughout the gearshift process, reduces unwanted engine sounds, and guarantees smooth gear operations by controlling fuel pressure in synchronization with torque changes, enhancing driver comfort and transmission reliability.
Implementation Method 1
a piezo based actuator
Data Source
AI summary
The present invention relates to the control of fuel pressure in a common rail engine in connection with an automatic gearshift procedure. Upon receipt of a primary gearshift command, a fuel pressure in the common rail fuel system is decreased. This decrease is initiated during a time interval prior to reducing engine torque. A gear is released after the engine torque is lowered, thereby enabling a smooth gear release.