Multi-Stage Transmission Gear Train with Nested Planet Mechanisms
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Solution Overview
Problem
Existing multi-stage automatic transmissions face challenges in achieving a balance between power performance, fuel efficiency, and compactness while providing a sufficient number of shift ranges, with existing gear train structures often compromising on strength, power consumption, and shift control efficiency.
Innovation Solution
A multi-stage automatic transmission design combining planet gear mechanisms, external gears, and friction elements to realize nine forward gears and one reverse gear, utilizing a configuration of two planet gear mechanisms, five pairs of external gears, and six friction elements to enhance operating conditions and shift range ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If more shift ranges are provided to improve power performance and fuel efficiency, then the transmission system becomes more complex with more planet gears and friction elements, but the device complexity increases and the gear train becomes larger
Solution Approach 1:
The patent makes single friction elements perform multiple functions by strategically positioning them to control different planet gear mechanisms for different shift ranges. For example, a single friction element can serve as a brake for one planet gear mechanism in lower shift ranges and as a clutch for another planet gear mechanism in higher shift ranges, thereby reducing the total number of friction elements needed while achieving nine forward gears and one reverse gear
Solution Approach 2:
The patent employs nested planet gear mechanisms where smaller planet gear sets are positioned within or alongside larger ones, allowing multiple gear reduction stages to be compacted into a smaller volume. The first and second planet gear mechanisms are arranged to share common rotational axes and space, enabling nine forward gears and one reverse gear to be realized in a compact configuration
2Volume of moving object
If the gear train structure is optimized for compactness, then the size is reduced, but the strength and power transfer efficiency may be compromised
Solution Approach 1:
The patent applies different design optimizations to different parts of the gear train based on their specific functional requirements. High-strength materials and robust tooth profiles are used in planet gears subjected to highest loads, while lighter construction is used in less critical components. The friction elements are designed with localized reinforcement at contact points to ensure durability despite compact dimensions
3Ease of operation
If friction elements are frequently engaged and disengaged to control multiple shift ranges, then shift control becomes more precise, but the operating conditions for friction elements become more demanding and may reduce reliability
Solution Approach 1:
The patent designs the friction elements and their actuation mechanisms to be pre-positioned and pre-loaded in optimal configurations before shifting occurs. The hydraulic actuators are pre-charged and the friction elements are pre-aligned with their engagement surfaces, allowing for rapid and reliable engagement/disengagement transitions without excessive wear or misalignment during the shifting process
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
The proposed design achieves excellent power performance and fuel efficiency by enabling precise shift control and suitable shift range ratios, satisfying the conditions for disabling and enabling friction elements during sequential shifting.
Implementation Method 1
a first planet gear mechanism PG1 coaxially disposed on the input shaft (10), the first planet gear mechanism having two rotary elements which are connected to the input shaft (10) so as to engage with and disengage from the input shaft (10)
Implementation Method 2
The plurality of power engaging/disengaging members (C3, C4, C7, C8) for switching power transmission via the plurality of pairs of external gears between the rotary elements of the second planet mechanism and the input shaft
Data Source
AI summary
A multi-stage automatic transmission in which planet gear mechanisms, external gears and friction elements are combined in order to realize nine forward gears and one rearward gear having excellent operating conditions for friction elements and superior shift range ratios, thereby achieving excellent power performance and fuel efficiency.