Compact Engine Pump Shaft Design via Planar Rotor Arrangement
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Solution Overview
Problem
Existing internal combustion engines for saddle riding vehicles face challenges in downsizing due to the length of the pump shaft, which is required to be shortened to achieve a more compact engine body.
Innovation Solution
A single pump shaft is disposed between the crankshaft and the shift drum, with oil pumps' rotors positioned to minimize shaft length, and the rotors are arrayed to straddle the crankcase mating face, improving pump efficiency and allowing for a more compact engine design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the pump shaft length is reduced to achieve engine body downsizing, then the engine body size is reduced, but the arrangement space for oil pump rotors is limited
Solution Approach 1:
The patent transitions from a conventional linear arrangement of pump rotors along the shaft axis to a two-dimensional planar arrangement at the crankcase mating face. By positioning rotors side-by-side in the width direction rather than end-to-end in the longitudinal direction, the design achieves compact longitudinal profile while maintaining adequate rotor arrangement space.
Solution Approach 2:
The patent divides the pump rotor assembly into multiple independent rotors arranged in parallel at the crankcase mating face. This segmentation allows each rotor to be positioned independently within the available width, optimizing space utilization and enabling the shaft to be shortened in the longitudinal direction without compromising rotor arrangement.
2Productivity
If multiple oil pump rotors are arranged at the crankcase mating face, then pump efficiency is improved, but assembly precision requirements increase
Solution Approach 1:
The patent merges multiple pump rotors into a single integrated pump assembly that is mounted as one unit at the crankcase mating face. This consolidation maintains the high efficiency benefits of multiple rotors while reducing assembly complexity and precision requirements compared to installing multiple separate rotor assemblies.
Solution Approach 2:
The crankcase mating face serves multiple functions: it provides the mounting location for pump rotors, acts as a sealing surface, and facilitates modular assembly. By designing the rotor arrangement to utilize this multi-functional surface, the patent achieves efficient pump operation without imposing excessive precision requirements on the assembly process.
3Volume of moving object
If the pump shaft is shortened, then the engine body is downsized, but the structural stability of the pump shaft decreases
Solution Approach 1:
The patent applies local reinforcement at critical sections of the shortened pump shaft, particularly at the bearing support locations and rotor mounting areas. By concentrating structural strength where needed rather than uniformly increasing shaft dimensions, the design maintains stability while keeping the overall shaft length short for engine downsizing.
Solution Approach 2:
The patent incorporates preliminary structural features during shaft design, such as optimized bearing placement and integrated rotor mounting, that pre-establish stability before the shaft is installed. This preliminary structuring ensures that the shortened shaft maintains adequate stiffness and stability without requiring post-assembly modifications or excessive length.
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 reduces the engine body size by shortening the pump shaft and enhancing pump efficiency, while also improving bearing accuracy and reducing assembly errors.
Implementation Method 1
the pump gear being arranged on the pump shaft so as to transmit power from the crankshaft
Implementation Method 2
first oil pump rotors included in the first oil pump are disposed at a mating face of the pair of left and right crankcase half bodies, and a second oil pump rotor included in the second oil pump is disposed between a pump gear and the first oil pump
Data Source
AI summary
In an internal combustion engine for a saddle riding vehicle, in which a gear transmission and a shift drum of a shift change device is stored in a crankcase, the gear transmission having a plurality of transmission shafts parallel to a crankshaft extending in a vehicle width direction, a single pump shaft common to first and second oil pumps is rotatably supported by the crankcase. First oil pump rotors of the first oil pump are disposed at a mating face of a pair of left and right crankcase half bodies. A second oil pump rotor of the second oil pump is disposed between a pump gear and the first oil pump and at a side surface, on a side opposite to the mating face, of one crankcase half body out of the pair of left and right crankcase half bodies, the pump gear being arranged in the pump shaft.