Engine Trigger Wheel Nested in Cylinder Block
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Solution Overview
Problem
Conventional trigger wheels for reciprocating piston engines, when mounted outside the cylinder block, increase the overall engine length, which is problematic for compact vehicles and hybrid engines where space is limited and frontal collision safety is a concern.
Innovation Solution
A compact, single-piece steel trigger wheel with a central annular portion and a cylindrical rim portion, featuring circumferentially spaced trigger teeth and apertures to shift the center of mass away from the axis of rotation, allowing for mounting within the cylinder block without increasing engine length, and counterweights with recesses to maintain balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the trigger wheel is mounted outside the cylinder block, then the trigger wheel can be easily accessed and installed, but the overall engine length increases
Solution Approach 1:
The trigger wheel is nested within the cylinder block structure by mounting it on the rear end of the crankshaft that extends into the cylinder block. The trigger wheel is positioned within the space defined by the cylinder block end walls, effectively nesting the trigger wheel assembly within the existing engine structure rather than adding external length.
Solution Approach 2:
The trigger wheel is oriented with its plane perpendicular to the crankshaft axis, and the trigger teeth extend radially outward from the crankshaft centerline. This dimensional arrangement allows the sensor to be mounted on the cylinder block interior surface, utilizing the radial dimension rather than extending the engine length in the axial direction.
2Length of moving object
If the trigger wheel is mounted inside the cylinder block, then the engine length is reduced, but the trigger teeth may be damaged by the end wall
Solution Approach 1:
The trigger teeth are positioned asymmetrically relative to the cylinder block end wall. The crankshaft is offset from the centerline of the cylinder block, and the trigger wheel is mounted on the rear end of the crankshaft, creating an asymmetric arrangement where the trigger teeth clear the end wall by a safe margin while still being mounted within the cylinder block interior.
Solution Approach 2:
The design preliminarily establishes proper clearance between the trigger teeth and the cylinder block end wall through precise positioning of the crankshaft and trigger wheel. This preliminary positioning ensures that during normal operation, the trigger teeth maintain a safe distance from the end wall, preventing damage before it can occur.
3Length of moving object
If the trigger wheel is made narrow, then the engine length is reduced, but the signal reliability decreases
Solution Approach 1:
The trigger wheel features a rim portion with trigger teeth that is locally optimized for signal generation. The rim portion has a sufficient radial width to ensure reliable sensor detection, while the overall trigger wheel assembly remains compact in the axial direction. The local quality of the rim portion provides the necessary signal reliability without compromising the overall engine compactness.
4Length of moving object
If material is removed from the end counterweight to create a recess, then the trigger wheel can be mounted within the cylinder block, but the crankshaft balance is disrupted
Solution Approach 1:
The recess removed from the end counterweight creates an unbalanced condition. To compensate, additional counterweight material is added to other portions of the crankshaft counterweights, or balancing masses are added to the trigger wheel assembly itself. This anti-weight approach restores the dynamic balance of the rotating assembly despite the material removal necessary for mounting the trigger wheel within the cylinder block.
Data Source
AI summary
An engine trigger wheel is disclosed having a central annular portion and a cylindrical rim portion defining a number of trigger teeth, wherein the central annular and cylindrical rim portions are pressed from a single piece of metal. A number of balance apertures are formed in the central annular portion to move a center of mass of the trigger wheel away from an axis of rotation. The engine trigger wheel when fastened to one end of a crankshaft of an engine provides both an indication of the angular position of the crankshaft and a counterweight function.