Outboard Motor Gear Preload Stabilization
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Solution Overview
Problem
The existing shift mechanisms for outboard motors with R/R and C/R specifications face challenges in stabilizing the behavior of driven gears under large loads, leading to displacement and reduced service life due to uneven load distribution and thrust transmission, which affects the abutment of teeth between gears.
Innovation Solution
A supporting structure comprising a first and second driven gear, conical roller bearings, and a supporting member that applies preload to the bearings to stabilize the driven gear's behavior, with a tubular portion and a bearing housing configuration that includes a preload mechanism to maintain proper alignment and reduce displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the driven gear is supported by a conical roller bearing without preload, then the bearing can accommodate radial loads, but the driven gear displaces under large loads causing tooth abutment changes
Solution Approach 1:
A preload mechanism is implemented that applies a preliminary axial force to the conical roller bearing before the gear operates under load. This preload ensures the bearing is pre-compressed and maintains stable gear positioning even when large radial loads are applied during forward movement, preventing gear displacement and tooth abutment changes.
2Force
If thrust from the propeller shaft is transmitted to the driven gear, then the gear is supported axially, but the gear behavior becomes unstable due to varying thrust
Solution Approach 1:
The thrust transmission path is separated from the driven gear. Instead of transmitting propeller shaft thrust directly to the driven gear through the bearing, the thrust is extracted and handled by a dedicated thrust bearing on the propeller shaft. This isolation eliminates the instability caused by varying thrust forces affecting the gear's rotational behavior.
3Adaptability or versatility
If a single shift mechanism is used for both R/R and C/R specifications, then component versatility is improved, but the driven gear on the rear side experiences unstable behavior under large loads
Solution Approach 1:
The preload mechanism is specifically applied to the driven gear on the rear side (second driven gear) that experiences large loads during forward movement in C/R specification. This localized quality enhancement ensures that only the critical gear position receives the additional stability support needed, while maintaining the universal design for both R/R and C/R specifications.
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
This configuration stabilizes the driven gear's behavior, prevents displacement, and maintains the abutment of teeth between the driving and driven gears, enhancing the durability and service life of the gears while allowing the same shift mechanism to be used for both R/R and C/R specifications.
Implementation Method 1
The first conical roller bearing and the second conical roller bearing are disposed on outer periphery of the tubular portion of the second driven gear
Implementation Method 2
The supporting member applies a preload to the first conical roller bearing and the second conical roller bearing and holds the first conical roller bearing and the second conical roller bearing to the outer periphery of the tubular portion of the second driven gear
Data Source
AI summary
An outboard motor includes a first driven gear and a second driven gear, a first conical roller bearing and a second conical roller bearing, and a nut. The first driven gear and the second driven gear mesh with a driving gear. The driving gear rotates through transmission of a rotative power from an engine unit. The first conical roller bearing and the second conical roller bearing are disposed on an outer periphery of a tubular portion of the second driven gear. The first conical roller bearing and the second conical roller bearing are arranged in a front-rear direction in directions opposite from one another. The nut is disposed on the outer periphery of the tubular portion of the second driven gear. The nut is displaceable in an axial direction of the tubular portion. With the nut, a preload is applied to the first conical roller bearing and the second conical roller bearing to hold the first conical roller bearing and the second conical roller bearing to the outer periphery of the tubular portion of the second driven gear.