In-Wheel Motor Gear Layout to Avoid Suspension Interference
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Solution Overview
Problem
Existing in-wheel motor drive devices face interference issues with vehicle bodies and suspension parts due to the large pitch circle diameter of the output gear required for high speed reduction ratios, leading to insufficient motive power and potential defects in suspension parts.
Innovation Solution
The implementation of a three-shaft two-stage parallel shaft gear speed reducer with a large-diameter intermediate gear, where the circumscribed circle of the intermediate gear is superimposed with the pitch circle of the wheel bearing, allows for a suppressed pitch circle diameter of the output gear while maintaining a high speed reduction ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the pitch circle diameter of the output gear is increased to achieve a high speed reduction ratio, then the speed reduction ratio is improved, but the in-wheel motor drive device interferes with vehicle body or suspension parts
Solution Approach 1:
The single-stage gear train is segmented into a two-stage gear train with an intermediate gear. The first gear train reduces speed from the input gear to the intermediate gear, and the second gear train reduces speed from the intermediate gear to the output gear. This segmentation allows achieving a high overall speed reduction ratio (product of both stages) while keeping the pitch circle diameter of the output gear small, thus avoiding interference with vehicle body or suspension parts.
2Power
If the pitch circle diameter of the output gear is increased to achieve a high speed reduction ratio, then the speed reduction ratio is improved, but the housing becomes larger and mounting space for lower arm ball joint is reduced
Solution Approach 1:
By dividing the gear train into two stages with an intermediate gear, the housing can be designed to accommodate the intermediate gear in the axial direction. This allows the output gear to have a smaller pitch circle diameter, reducing the radial space required and thus the overall housing volume, while still achieving the required high speed reduction ratio through the combined effect of both gear stages.
3Power
If the motor size is increased to provide sufficient motive power, then the motive power is improved, but the in-wheel motor drive device interferes with vehicle body or suspension parts
Solution Approach 1:
The intermediate gear acts as a mediator in the power transmission system. It receives power from the input gear through the first gear train and transmits it to the output gear through the second gear train. This intermediary gear train configuration allows the motor to be smaller while still delivering sufficient motive power to the wheel, as the gear trains provide the necessary torque multiplication without requiring a large motor or large output gear that would cause interference.
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 effectively prevents interference with vehicle bodies and suspension parts, allows for a more compact in-wheel motor drive device, and ensures sufficient motive power without compromising the strength or weight of the suspension parts.
Implementation Method 1
a large-diameter intermediate gear and a small-diameter intermediate gear which are provided integrally and coaxially with each other. The input gear and the large-diameter intermediate gear mesh with each other to form a gear train on an input side. The small-diameter intermediate gear and the output gear mesh with each other to form a gear train on an output side.
Data Source
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AI summary
Provided is an in-wheel motor drive device (21) including: a motor (28) ; a wheel bearing (53) ; and a speed reducer (38) . The speed reducer (38) comprises: a speed reducer input shaft (Sin) including an input gear (34); a speed reducer output shaft (Sout) including an output gear (37); and an intermediate shaft (Sm) including a small-diameter intermediate gear (36) and a large-diameter intermediate gear (35). The large-diameter intermediate gear (35) has a circumscribed circle which is superimposed with a pitch circle of a plurality of rolling elements (42) of the wheel bearing (53) when viewed from an axial direction.