Transmission Case Rib Offset Rigidity Weight Reduction
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Solution Overview
Problem
Existing transmission cases in automatic transmissions experience vibration and noise due to insufficient rigidity, which is exacerbated by attempts to reinforce them, leading to increased weight.
Innovation Solution
A transmission case design featuring a cylindrical bearing portion and an arc-shaped rib with an offset wall portion that connects the bearing and rib, increasing rigidity without increasing plate thickness, thereby reducing vibration and noise without significant weight gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the plate thickness dimension of the transmission case is increased to increase rigidity, then the rigidity is improved, but the weight of the transmission case increases significantly
Solution Approach 1:
The patent introduces a rib structure that extends in the projection direction (perpendicular to the main plate surface), transforming a two-dimensional thickness increase problem into a three-dimensional structural reinforcement solution. The rib projects from the surface to provide additional stiffness without requiring increased plate thickness, thereby avoiding weight increase while improving rigidity.
Solution Approach 2:
The rib is designed with an arc portion that has a curved cross-section, where the curvature radius is specifically set to be 0.05 to 0.15 times the outer diameter of the bearing portion. This curved geometry provides optimal stress distribution and rigidity enhancement while minimizing material usage compared to straight or angular rib designs.
2Strength
If reinforcement ribs are added to increase rigidity, then the rigidity is improved, but the weight of the transmission case increases significantly
Solution Approach 1:
The rib structure is strategically positioned and dimensioned to provide reinforcement only where needed - specifically in the region between the bearing portion and the outer peripheral side of the transmission case. The arc portion's curvature radius and projection height are optimized to deliver maximum rigidity improvement in this critical area without adding unnecessary weight throughout the entire transmission case.
3Object-affected harmful factors
If the bearing portion is made more rigid to reduce vibration, then the vibration is restrained, but the weight of the transmission case increases
Solution Approach 1:
The transmission case is segmented into functional zones: the bearing portion for shaft support, the rib structure for rigidity enhancement, and the arc portion for stress distribution. This segmentation allows each component to be optimized for its specific function - the bearing portion maintains its vibration-damping properties while the rib-arc structure provides the necessary rigidity support without adding excessive weight to the entire assembly.
Data Source
AI summary
A transmission case include: a wall portion; a bearing portion having a through-hole penetrating through the wall portion such that a power transmission shaft is inserted into the through-hole, the bearing portion projecting from the wall portion in a cylindrical shape; and a rib projected from the wall portion in the same direction as a projection direction of the bearing portion, the rib having an arc portion. When viewed from a direction along the center line of the bearing portion, the wall portion includes i) a first wall portion in a region surrounded by the bearing portion, the arc portion of the rib and two common tangent lines to the bearing portion and the arc portion of the rib, and ii) a second wall portion in another region; and the first wall portion is offset in the projection direction of the bearing portion relative to the second wall portion.