Electric Variable Valve Timing Sprocket Guide Bosses
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Solution Overview
Problem
The existing electric variable valve timing mechanisms face challenges in preventing the sprocket unit from falling into the narrow space covered by the chain cover during removal or attachment operations, which can lead to accidental drops and complications during maintenance.
Innovation Solution
The installing structure incorporates a chain cover with multiple bosses that extend radially and are arranged to engage the sprocket unit, restricting its vertical movement and allowing it to be safely removed or attached without falling, by positioning them such that the sprocket unit contacts the bosses when moving downward, preventing it from passing through the narrow spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sprocket unit is removed from the camshaft during maintenance operations, then the sprocket unit can be accessed and serviced, but the sprocket unit may accidentally fall into the narrow space covered by the chain cover
Solution Approach 1:
The patent introduces a guide member as an intermediary component between the sprocket unit and the chain cover space. This guide member protrudes from the chain cover and guides the sprocket unit during removal and installation operations, preventing it from falling into the narrow space while still allowing access for maintenance. The guide member acts as a mediator that facilitates safe handling without blocking necessary access.
2Reliability
If the chain cover completely encloses the timing chain and sprocket unit space, then protection is improved, but access for removal and installation becomes difficult
Solution Approach 1:
The chain cover is segmented with a specific opening that provides access to the sprocket unit while maintaining protection for the timing chain. Rather than being a completely enclosed structure, the chain cover is divided to create an access pathway that allows maintenance operations while still protecting the internal components from contamination and damage.
3Reliability
If the guide member protrudes far enough to prevent falling, then safety is improved, but interference with sprocket unit movement may occur
Solution Approach 1:
The guide member is designed with specific local characteristics - it protrudes only to the necessary extent to prevent the sprocket unit from falling into the chain cover space, but not so far as to interfere with the normal movement and installation/removal operations. The guide member's dimensions and positioning are optimized locally to provide just enough guidance and protection without creating unnecessary interference.
Data Source
AI summary
An electric variable valve timing apparatus includes a sprocket unit and an electric motor. The electric motor is fixed to a chain cover with bolts. The chain cover includes plural bosses each having an internal thread to which one of the bolts is threaded. The bosses extend from the chain cover toward the sprocket unit to positions at which the bosses face an outer periphery of the sprocket unit in a radial direction. The bosses are arranged such that, when the sprocket unit moves downward from an attaching position, at which the sprocket unit is attached to the camshaft, at least two bosses are engaged with the sprocket unit to restrict downward movement of the sprocket unit, and that the sprocket unit is allowed to move between a location outside of a space covered by the chain cover and the attaching position.