Eccentric Cam Roller Drive for GDI Pump Durability
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Solution Overview
Problem
Existing high-pressure fuel supply pumps for direct injection gasoline engines face challenges in asynchronous actuation, leading to increased wear and complexity due to high rotational speeds and stresses on cam follower bearings, which results in reduced durability and increased costs.
Innovation Solution
A cam system with a circular cam having an offset axis, utilizing a cam roller and cam follower that rotates eccentrically, reducing contact velocity and stress on the bearings by converting sliding to rolling contact, thereby simplifying the design and increasing robustness, and potentially eliminating the need for a cam follower.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional cam and cam follower roller system is used for asynchronous actuation, then the HPP can be driven at variable speeds independent of engine speed, but the high rotational speeds and stresses on the cam follower bearing lead to increased wear and reduced durability
Solution Approach 1:
The patent employs a circular cam with an offset axis that rotates about its center, creating a sinusoidal motion profile. This curved, rotating cam surface replaces the traditional translating cam, and the circular geometry enables smooth, continuous motion with reduced impact loads on the follower bearing, thereby improving durability while maintaining variable speed capability
Solution Approach 2:
The invention transitions from a static cam profile to a dynamically rotating circular cam. The cam rotates about its own axis while the follower maintains contact through a spring-loaded mechanism. This dynamic system allows the cam to adapt its contact point continuously, distributing wear more evenly and reducing peak stresses on the follower bearing during asynchronous operation
2Strength
If the cam follower roller bearing size is increased to handle high speeds and stresses, then bearing capacity is improved, but the size and complexity of the cam follower assembly increases
Solution Approach 1:
The rotating circular cam with its smooth curved surface distributes contact forces more evenly across the follower roller bearing. This reduces peak contact stresses, allowing the use of a smaller, simpler bearing that can still handle the loads without excessive wear or failure
Solution Approach 2:
The spring-loaded follower mechanism incorporates a cushioning element that absorbs and dampens impact loads before they reach the bearing. This pre-cushioning effect protects the bearing from shock loads during asynchronous operation, enabling the use of a more compact bearing design with adequate capacity
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
The solution results in a more compact, lighter, and robust drive system with reduced vibration and noise, improved durability, and simplified lubrication, allowing for variable speed operation independent of engine speed, enhancing the reliability and efficiency of the fuel supply system.
Implementation Method 1
a circular cam roller (107) surrounding the cam (109) and a cam bearing (108) interposed between the cam roller (107) and the cam (109)... the cam roller rotates eccentrically relative to the cam shaft while maintaining contact with the follower, thereby reciprocating the follower and the piston
Implementation Method 2
The cam follower roller embodiment is sized and configured based on the rolling contact stress between the cam roller and cam follower roller... By adding the rolling function to the cam roller the bearing design (now the cam roller bearing) can be more robust
Data Source
AI summary
In a high pressure fuel supply system, a variable speed motor asynchronously actuates a pumping piston with a drive mechanism including a circular cam with cam roller, having an axis that is offset from the axis of the cam drive shaft. A rolling or sliding cam follower is rigidly connected to the piston, and a piston retainer is operatively connected among the piston, the cam follower and the cam roller. As the cam shaft rotates, the cam roller rotates eccentrically relative to the cam shaft while maintaining contact with the cam follower, thereby reciprocating the follower and the piston along the actuation axis, in corresponding charging and pumping strokes of the piston.