Variable Valve Train Control via Cam Follower Shifting
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Solution Overview
Problem
Conventional valve train systems for reciprocating piston internal combustion engines have limitations in varying valve duration and timing, leading to restricted engine performance across a wide range of speeds, with fixed duration and timing profiles resulting in compromised fuel efficiency and increased pollution at varying RPM conditions.
Innovation Solution
A valve train control device that includes a primary cam lobe and follower, with an auxiliary motion transfer device allowing the cam follower to shift relative to the cam lobe in response to engine parameters, altering valve timing and duration by using a secondary cam lobe and follower, and a controller to adjust the motion transfer, enabling continuous variable control of valve opening duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fixed duration and timing profiles are used in conventional valve train systems, then the system structure is simple, but engine performance is restricted across a wide range of speeds with compromised fuel efficiency and increased pollution
Solution Approach 1:
The cam follower is divided into a first cam follower and a second cam follower, with the ability to selectively engage different cam lobes (first cam lobe and second cam lobe) on the camshaft. This segmentation allows the valve train to switch between different cam profiles, enabling varied valve duration and timing characteristics without requiring a completely complex reconfiguration system.
Solution Approach 2:
The valve train control device incorporates dynamic switching capability between different cam followers and cam lobes based on operating conditions. The system can transition from a fixed configuration to a dynamic configuration where the cam follower position relative to the cam lobe is variable, allowing optimization of valve timing and duration across different engine speeds and loads.
2Productivity
If a single cam lobe profile is used, then the device complexity is reduced, but the engine performance cannot be optimized across a wide range of RPM conditions
Solution Approach 1:
The camshaft is designed with multiple cam lobes (first cam lobe and second cam lobe) that can be selectively engaged by different cam followers. This multi-functionality allows a single camshaft to provide multiple valve timing and duration profiles, enabling the engine to optimize performance across different RPM ranges and operating conditions without requiring multiple separate camshafts.
Solution Approach 2:
The system enables changes in valve train parameters (duration, timing, lift) by switching between different cam lobe profiles. The first cam lobe and second cam lobe have different geometric parameters, and the ability to select between them allows dynamic adjustment of valve operation characteristics to match different engine operating conditions, thereby optimizing power output and fuel efficiency.
3Ease of manufacture
If fixed valve timing and duration are maintained, then the valve train system is simple to control, but fuel efficiency deteriorates and pollution increases at varying RPM conditions
Solution Approach 1:
The valve train control device introduces dynamic adjustability to valve timing and duration through the ability to switch between different cam followers and cam lobes. This dynamic capability allows the system to adapt valve operation to optimal settings for different RPM conditions, reducing fuel consumption and emissions without requiring overly complex control mechanisms.
Solution Approach 2:
The control system monitors engine operating conditions (such as RPM, load, and throttle position) and uses this feedback to determine the optimal cam follower and cam lobe combination. Based on the feedback from sensor inputs, the system selectively engages appropriate cam profiles to minimize fuel inefficiency and pollution while maintaining acceptable system complexity.
Data Source
AI summary
A valve train control device, for use in a reciprocating piston internal combustion engine having a camshaft with a primary cam lobe, is provided herein and generally includes a primary cam follower positioned in an operational path between the primary cam lobe and a corresponding valve with the primary cam follower being constructed to follow the primary cam lobe while an auxiliary motion transfer device, having at least a portion responsive to at least one engine parameter, may be placed in a variable motion operational path including the primary cam follower to shift the primary cam follower relative to the primary cam lobe during at least a portion of the camshaft rotation to alter one or more valve operating parameters relative to a set of valve parameters defined by the primary cam lobe profile interacting with an unshifted primary cam follower.