Straddled Vehicle Engine Unit Layout for Compact Starter and Balancer Integration
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Solution Overview
Problem
Existing engine units with scavenge pumps have a large dimension in the top-and-bottom direction, making it challenging to integrate a starter motor and balancer without increasing the motorcycle's size, either in height or length, which affects the overall compactness of the engine system.
Innovation Solution
The engine unit is designed with the starter motor positioned further upward and partially overlapping with the cylinder, the balancer positioned further downward and rearward, and the scavenge pump located further downward than the crankshaft, ensuring a compact configuration by optimizing the layout to avoid overlapping and maximize space usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the starter motor and balancer are provided in an engine unit having a scavenge pump, then the engine unit can perform starting and vibration reduction functions, but the dimension of the engine unit in the top-and-bottom direction is increased
Solution Approach 1:
The patent transitions from a conventional top-and-bottom stacking arrangement to a front-and-rear linear arrangement along the vehicle's length direction. The scavenge pump is positioned at the front, followed by the crankshaft, balancer, and starter motor in sequence toward the rear, utilizing the longitudinal dimension instead of the vertical dimension to accommodate all components.
Solution Approach 2:
The balancer is arranged to be surrounded by the starter motor in the top-and-bottom direction, with the balancer positioned further downward than the starter motor. This nested configuration allows both components to occupy overlapping vertical spaces efficiently, reducing the overall height requirement while maintaining both functions.
2Adaptability or versatility
If the dimension of the engine unit in the front-and-rear direction is increased, then the starter motor and balancer can be accommodated, but the size of the motorcycle is increased in the front-and-rear direction
Solution Approach 1:
The patent merges the scavenge pump and engine components into a single integrated engine unit that functions as both a power source and an oil supply system. The scavenge pump is directly incorporated within the engine unit structure, eliminating the need for separate mounting space and reducing overall motorcycle length.
Solution Approach 2:
The patent utilizes the top-and-bottom vertical dimension to arrange components (starter motor above balancer) rather than extending in the front-and-rear direction, thereby compacting the engine unit's longitudinal footprint while maintaining all necessary functions.
3Reliability
If the scavenge pump is arranged at a position further downward than the crankshaft, then the oil collection is improved, but the engine unit dimension in the top-and-bottom direction increases
Solution Approach 1:
The patent resolves the height increase issue by arranging the scavenge pump, crankshaft, balancer, and starter motor in a front-to-back sequence along the vehicle's length rather than stacking them vertically. The scavenge pump remains positioned to receive oil from the crankcase while the overall vertical dimension is controlled through the nested balancer-starter motor arrangement.
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 arrangement allows for a compact engine system that maintains the motorcycle's size without increasing the height or length, ensuring efficient lubrication and vibration reduction while allowing for a larger swing range and storage volume.
Implementation Method 1
a scavenge pump that is configured to collect oil in the crankcase of the engine
Implementation Method 2
a balancer that is configured to rotate to reduce vibration of the crankshaft
Implementation Method 3
a starter motor that is configured to rotate a crankshaft of the engine
Data Source
Figure 1
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AI summary
A center axis (C1) of a cylinder (62) is located at a position further downward than a center axis (C2) of a crankshaft (CS) in a cross section orthogonal to a vehicle front-and-rear direction. A center axis (C4) of a balancer (120) is arranged at a position further upward than the center axis (C2) of the crankshaft (CS), and a scavenge pump (131) is arranged at a position further downward than the crankshaft (CS), The balancer (120) is arranged at a position further downward than an intake pipe (74) and further rearward than a starter motor (110) in a vehicle side view. The starter motor (110) is arranged at a position further upward than the cylinder (62) in the vehicle side view, and is arranged to at least partially overlap with the cylinder (62) in a vehicle plan view. A dimension (R1) of the starter motor (110) in a top-and-bottom direction is smaller than a dimension (R2) of a rotation trajectory of the balancer (120) in the top-and-bottom direction in the vehicle side view.