Automatically-shiftable Hybrid Transaxle with Parallel Axes
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Solution Overview
Problem
Modern automatic transaxles in vehicles face challenges in efficiently managing torque transmission and gear shifting, particularly in transversely mounted front-wheel-drive vehicles, where packaging constraints and the need for multiple speed ratios complicate the integration of powertrains and torque application.
Innovation Solution
An automatically-shiftable transaxle design incorporating a gear-train with a planetary gear-set, an electric motor, and a differential assembly, along with an interlocking device such as a synchronizer or dog-clutch, allows for variable torque input and output, enabling efficient torque transmission and adaptive gear shifting through a programmable controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multi-speed automatic transaxle is used to increase operating range, then the engine can operate through its torque range multiple times without manual gear selection, but the device complexity and packaging space requirements increase
Solution Approach 1:
The patent employs a planetary gear-set nested within the transaxle structure, where the sun gear, planetary gears, and ring gear are concentrically arranged. This nesting allows multiple speed ratios to be achieved within a compact space, resolving the contradiction between increased operating range and device complexity by efficiently packing the gear-train components.
Solution Approach 2:
The transaxle is designed to provide multiple speed ratios (at least three forward gear ranges) through a single integrated gear-train system that includes a planetary gear-set, transfer gears, and torque transmitting devices. This multi-functional design allows the transaxle to replace multiple separate gear systems, increasing operating range while managing complexity through consolidation.
2Loss of energy
If an electric motor is integrated into the transaxle to provide variable torque input, then fuel economy and shift quality improve, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent introduces an interlocking device as an intermediary component that selectively connects the electric motor to the second transfer gear. This mediator allows the electric motor to be integrated into the existing transaxle structure without requiring complete redesign, thereby improving fuel economy through variable torque input while reducing manufacturing difficulty by using a modular connection approach.
Solution Approach 2:
The transaxle is segmented into distinct functional modules: a planetary gear-set for speed ratio selection, transfer gears for torque transmission, torque transmitting devices for engagement control, and an electric motor for auxiliary torque input. This segmentation allows each component to be manufactured and tested independently, reducing overall manufacturing difficulty despite the increased complexity of the integrated system.
3Adaptability or versatility
If transfer gears and intermediate shafts are used to transmit torque between parallel axes, then flexible torque transmission is achieved, but the device complexity and number of components increase
Solution Approach 1:
The patent merges the functions of torque transmission and speed ratio selection into a unified gear-train system where transfer gears on parallel intermediate shafts are integrated with the planetary gear-set. This consolidation achieves flexible torque transmission between parallel axes while reducing the number of separate components compared to using independent transmission systems for each function.
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 design enhances the operating range of vehicles by allowing the engine to operate through its torque range multiple times without manual gear selection, improving fuel economy and shift quality while accommodating restricted underhood spaces.
Implementation Method 1
an electric motor arranged on a third axis that is parallel to the second axis and configured to provide an electric motor torque input to the second transfer gear
Implementation Method 2
a planetary gear-set having first, second, and third members... the first transfer gear may be in mesh with the third member of the gear-set
Implementation Method 3
a differential assembly operatively connected to the intermediate shaft and configured to rotate about a fourth axis that is parallel to the second axis to thereby transmit a transaxle output torque to drive a load
Data Source
AI summary
An automatically-shiftable transaxle includes an input member configured to receive an external power-source torque and rotate about a first axis. The transaxle also includes torque transmitting device(s) and a gear-train, each operatively connected to the input member for selecting transaxle speed ratios, and a first transfer gear operatively connected to the gear-train and rotatable about the first axis. The transaxle also includes an intermediate shaft rotatable about a second axis, and a second transfer gear rotatably fixed to the intermediate shaft and meshed with the first transfer gear. The transaxle additionally includes an electric motor arranged on a third axis for providing a torque input to the second transfer gear. Furthermore, the transaxle includes a differential assembly operatively connected to the intermediate shaft and rotatable about a fourth axis to thereby transmit a transaxle output torque to drive the load. All four transaxle rotational axes are arranged in parallel.