Vehicle Transmission Input Shaft Radial Load Management
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Solution Overview
Problem
High output transmissions, particularly truck transmissions, face challenges with excessive radial displacement of input shafts due to splitter gears, leading to reduced design robustness, unbalanced power transmission, and limited PTO operation in mobile modes, along with inefficiencies in lubricant flow across various gear ratios.
Innovation Solution
A short input shaft aligned with the engine flywheel pilot bearing and concentrically splined to an extension shaft, with independent PTO drive gear and lube pump configurations that maintain radial clearance and float, allowing for consistent speed ratios and balanced power transmission across all gear ratios, including mobile PTO operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a long over-hung input shaft is used to accommodate additional splitter gears, then more gear ratios are available, but radial displacement increases and design robustness decreases
Solution Approach 1:
The transmission system is divided into separate functional modules: a compact main gearbox containing the input shaft and splitter gears, and a separate PTO module. This segmentation allows the main gearbox to maintain a short, robust input shaft while the PTO module provides additional gear ratio options through its own dedicated gears, resolving the contradiction between versatility and robustness.
2Adaptability or versatility
If the input shaft is made longer to include more splitter ratios, then more PTO operation modes are possible, but unbalanced radial loads and deflections increase
Solution Approach 1:
A dedicated PTO module acts as an intermediary between the engine and the load, providing multiple PTO gear ratios (2.0:1, 1.5:1, 1.0:1, 0.75:1, 0.5:1) without requiring a longer input shaft. This intermediary structure isolates the main transmission from unbalanced radial loads, maintaining power transmission balance while enabling diverse PTO operation modes.
3Reliability
If steel is used for the transmission housing to manage noise and structural integrity, then robustness improves, but weight increases
Solution Approach 1:
The transmission system employs composite material construction: the main gearbox housing uses aluminum alloy for reduced weight, while the PTO module housing uses cast iron or steel for enhanced structural integrity and noise management. This composite approach allows each module to be optimized for its specific functional requirements, achieving both weight reduction and structural robustness.
4Ease of manufacture
If the input shaft is aligned with the engine flywheel pilot bearing, then installation is simplified, but manufacturing tolerances must be significantly improved
Solution Approach 1:
The alignment constraint is extracted from the main input shaft and transferred to the separate PTO module. The main input shaft can be installed with standard tolerances relative to the engine flywheel, while the PTO module incorporates its own alignment features and adjustment mechanisms, simplifying installation while maintaining acceptable manufacturing precision.
Data Source
AI summary
A transmission includes a transmission main housing, an intermediate plate secured to the transmission main housing; and a rear housing attached to the intermediate plate and/or attached with fasteners through the intermediate plate to the main housing. An input shaft is connected to an extension shaft including a plurality of splitter gears selectively couple-able to the extension shaft. A main shaft is rotatably supported by the range shaft and range shaft bearing and includes a plurality of main box gears selectively couple-able to the main shaft. A range shaft is drivingly connected to the main shaft and provides input to a planetary gear assembly. The extension shaft is supported at a first end by a bearing assembly within a partition wall of the main transmission housing and a second end is supported by a bearing assembly disposed within the bore in the range shaft.