Segmented Cam Profile for Higher Fuel Injection Pressure
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Solution Overview
Problem
In mechanical fuel injection pumps, increasing plunger speed to enhance fuel injection pressure while maintaining maximum lift amount and fuel injection capacity is challenging, often resulting in pump size increases and potential degradation of fuel injection capacity.
Innovation Solution
A cam with a first cam surface for a higher speed increase rate during the pre-stroke period and a second cam surface for a lower speed increase rate during the pressure increasing period, allowing for increased plunger speed without excessive maximum lift and maintaining fuel injection capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the cam profile is set to increase the plunger speed, then the fuel injection pressure increases, but the maximum lift amount of the cam increases causing pump size increase
Solution Approach 1:
The cam profile is segmented into two distinct cam surfaces: a first cam surface for the pre-stroke period with a higher speed increase rate, and a second cam surface for the pressure increasing period with a lower speed increase rate. This segmentation allows optimization of plunger speed without increasing maximum lift amount, thereby increasing fuel injection pressure while avoiding pump size increase.
Solution Approach 2:
The invention changes the parameter of speed increase rate between different cam surfaces. The first cam surface has a higher speed increase rate than the second cam surface, allowing the plunger to achieve higher speed for fuel injection pressure increase without proportionally increasing the maximum lift amount, thus avoiding pump size enlargement.
2Stress or pressure
If the cam profile is set to increase the plunger speed while maintaining maximum lift amount, then the fuel injection pressure increases, but the effective injection period is shortened causing fuel injection capacity degradation
Solution Approach 1:
The cam profile is divided into two cam surfaces with different speed increase rates. The first cam surface (pre-stroke period) has a higher speed increase rate to quickly build plunger speed, while the second cam surface (pressure increasing period) has a lower speed increase rate to maintain adequate injection period. This segmentation enables fuel injection pressure increase while preserving fuel injection capacity.
3Stress or pressure
If the maximum lift amount of the cam is increased to increase plunger speed, then the fuel injection pressure increases, but the pump size increases
Solution Approach 1:
Instead of increasing maximum lift amount, the invention changes the speed increase rate parameter of the cam profile. The first cam surface has a higher speed increase rate than the second cam surface, allowing plunger speed increase for fuel injection pressure improvement without increasing maximum lift amount, thus avoiding pump size increase.
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 increased fuel injection pressure while minimizing the increase in maximum lift amount and degradation of fuel injection capacity, reducing pump size and weight.
Implementation Method 1
A fuel injection pump for a diesel engine converts a rotational motion of a camshaft into a reciprocating motion by using a plunger
Implementation Method 2
The fuel injection pump increases a pressure of a fuel in a fuel supply chamber and supplies the fuel to an injector by using the reciprocating motion of the plunger
Data Source
AI summary
The purpose of the present invention is to increase the pressure of fuel while reducing an increase in the maximum lift amount of a cam and deterioration of a fuel injection ability. This cam for use in a fuel injection pump that increases the pressure of fuel supplied into a fuel supply chamber by an axial movement of a plunger. The cam includes a first cam surface that causes an increase rate of an axial speed of the plunger when the cam rotates at a constant speed, in a pre-stroke period until the plunger increases the pressure of the fuel in the fuel supply chamber, to be a first increase rate, and a second cam surface that causes the increase rate of the axial speed of the plunger when the cam rotates at the constant speed, in a pressure increasing period that is a period from a start of increasing the pressure of the fuel in the fuel supply chamber by the plunger, to be a second increase rate, wherein the first increase rate is set higher than the second increase rate.