Crank Web Pulsar Ring Layout for Compact Engine Angle Sensing
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Solution Overview
Problem
Existing crank angle detection devices for engines face challenges in downsizing and enhancing the appearance, as they often require larger crank cases and expose the pulsar sensor, leading to increased dimensions and a less aesthetically pleasing design.
Innovation Solution
A crank angle detection device featuring a pulsar ring with integrated weights for inertia balance, fixed to the crank web, which allows for reduced crank web thickness and maintains engine dimensions, while the pulsar sensor is positioned internally to avoid increasing the engine's size and improve appearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pulsar sensor is arranged at a position opposed to the outer circumferential face of the flywheel, then the crank angle can be detected, but the crank case and case cover become larger and the pulsar sensor exposed outside deteriorates appearance
Solution Approach 1:
The pulsar ring is moved from the flywheel (outer dimension) to the crank web (inner dimension), changing the spatial arrangement from radial to axial positioning. This allows the sensor to detect crank angle internally without requiring external space, resolving the contradiction between detection capability and compact size.
Solution Approach 2:
The pulsar ring is nested on the crank web, utilizing the existing internal structure of the crankshaft assembly. This nesting approach allows the detection mechanism to be integrated within the existing components, avoiding external expansion of the crank case.
2Measurement precision
If the pulsar ring is arranged at the end of the crank shaft, then the crank angle can be detected, but the engine dimension in the crank shaft direction increases
Solution Approach 1:
The pulsar ring is repositioned from the crank shaft end (axial extension) to the crank web (radial position). This dimensional shift moves the detection mechanism from extending the engine length to utilizing the existing radial space, thereby preventing increase in engine dimension in the crank shaft direction.
3Ease of manufacture
If the thickness of the crank web is reduced for the pulsar ring to be attached, then the pulsar ring can be mounted, but the inertia balance of the crank shaft is affected
Solution Approach 1:
A weight is added to the pulsar ring at a position opposite to the detection portions to counterbalance the inertia change caused by reducing the crank web thickness. This counterweight compensation maintains the overall inertia balance of the crankshaft while enabling the pulsar ring attachment with reduced web thickness.
Solution Approach 2:
The pulsar ring and the balancing weight are combined into a single integrated component. This merging allows the pulsar ring to serve dual functions: crank angle detection and inertia balance maintenance, eliminating the need for separate balancing weights and simplifying the manufacturing process.
Data Source
AI summary
A crank angle detection device for an engine capable of achieving downsizing and enhancing appearance of the engine is provided. A crank angle detection device for an engine that includes a pulsar ring including a plurality of detection portions and rotating coaxially with a crank shaft of the engine, and a sensor detecting a passage state of the detection portions. Here, the pulsar ring is fixed to a crank web of the crank shaft. A weight for adjusting inertia balance of the crank shaft is fixed to the crank web arranged close to an end of the crank shaft in an axial direction. The weight has a shape obtained by increasing thickness of a part of the pulsar ring.