Pump Drive Wheel Centering Plate Mounting for Automatic Transmission
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Solution Overview
Problem
In off-axis pump arrangements in automatic transmissions, the press fit of the spur gear wheel on the clutch side leads to deformation, suboptimal meshing, loud gearing noises, and increased wear due to the long tolerance chain and constraining forces, which complicates assembly and reduces durability.
Innovation Solution
The pump drive wheel on the clutch side is mounted on a centering plate that also serves as the rear wall of the pump, with torque transmission via a slotted clutch hub and carrier fingers, decoupling coercive forces and using a steel sleeve with a lower coefficient of expansion to maintain a constant bearing gap despite temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the pump drive wheel is mounted on the clutch hub by press fit, then the wheel is securely fixed, but the gear wheel deforms and meshes suboptimally causing loud noises
Solution Approach 1:
The patent introduces a centering plate as an intermediary component between the clutch hub and the pump drive wheel. This centering plate serves as a mediator that properly positions and supports the pump drive wheel, preventing direct press-fit contact between the wheel and clutch hub. The centering plate with its bearing ensures the pump drive wheel is accurately centered and supported without deformation, thereby eliminating the harmful gearing noises while maintaining secure fixation.
2Power
If the pump drive wheel is mounted on the clutch hub, then torque transmission is achieved, but constraining forces from clutch imbalances are transferred to the pump causing increased wear
Solution Approach 1:
The centering plate acts as a mediator that separates the clutch assembly from the pump drive mechanism. It accepts torque transmission from the clutch hub through the pump drive wheel while isolating the pump bushings from constraining forces caused by clutch imbalances. The bearing on the centering plate supports the pump drive wheel independently, preventing force transfer to the pump and thereby improving reliability by reducing wear on pump bushings and impellers.
Solution Approach 2:
The patent segments the torque transmission path from the pump support function by introducing the centering plate as a separate component. This segmentation allows the clutch hub to transmit torque to the pump drive wheel through the centering plate without directly connecting to the pump shaft, thereby isolating the pump from harmful forces while maintaining efficient torque transmission.
3Device complexity
If the pump drive wheel is mounted on the clutch hub, then the assembly is compact, but the long tolerance chain causes suboptimal gear meshing
Solution Approach 1:
The centering plate serves as a precision intermediary component that establishes an accurate reference position for the pump drive wheel. By mounting the wheel on the centering plate rather than directly on the clutch hub, the patent creates a dedicated positioning interface that minimizes the tolerance chain. The bearing and centering features on the centering plate ensure precise gear meshing while maintaining a compact overall assembly.
4Ease of manufacture
If the pump drive wheel is preassembled with the bearing on the centering plate, then assembly is simplified, but thermal expansion differences between steel gear and aluminum plate must be accommodated
Solution Approach 1:
The patent explicitly addresses thermal expansion by selecting materials with different expansion coefficients for the steel pump drive wheel and aluminum centering plate. The design accommodates this thermal expansion difference through the bearing clearance and the compliant mounting arrangement, allowing the components to expand and contract at different rates without causing binding or distortion. This enables preassembly while maintaining proper clearances across the operating temperature range.
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 solution reduces noise, improves gear mesh durability, simplifies assembly by preassembling the pump drive wheel, and maintains consistent bearing clearance, thereby enhancing the overall performance and longevity of the transmission.
Implementation Method 1
a sleeve is pressed into the inside diameter of the aluminum centering plate, which sleeve is made of a material that has a lower coefficient of linear expansion than the centering plate, the sleeve being shaped in such a way that the outside diameter of the centering plate is at a certain distance from the outer contour the centering plate again concentrically encloses. The resulting gap between the sleeve and the outside diameter of the centering plate is designed in such a way that a gap of varying size, depending on the temperature, is maintained over the entire temperature range.
Data Source
Figure 1
Figure 2
AI summary
The present invention relates to a support of the pump drive wheel (4) on the coupling side in an automatic transmission, particularly in a dual-clutch transmission, wherein the pump drive wheel (4) on the clutch side is mounted on the centering plate (7) of the pump (2).