Hybrid Powertrain Planetary Gear Unit Direct Downshift
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Solution Overview
Problem
Conventional hybrid powertrains face issues with increased production cost and weight due to the inclusion of an engine clutch and external gear pairs, which also result in delayed gear shifting and reduced fuel efficiency, especially during kickdown maneuvers.
Innovation Solution
A hybrid vehicle powertrain design that removes the engine clutch and incorporates a planetary gear unit to reduce the number of gear pairs, allowing direct downshifting to a target lower gear, thereby improving gear shifting performance and reducing production costs and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an engine clutch is added to couple the engine and motor, then the hybrid powertrain can perform EV mode and HEV mode switching, but the production cost and weight of the transmission increase
Solution Approach 1:
The patent removes the engine clutch from the transmission system by integrating the motor directly to the transmission input shaft. The motor serves as the coupling mechanism between the engine and transmission, eliminating the need for a separate clutch component while maintaining mode switching capability through motor control.
Solution Approach 2:
The patent combines the motor and transmission into a more integrated assembly where the motor is directly coupled to the transmission input shaft. This merging eliminates the need for separate clutch mechanisms and reduces the overall number of components, thereby reducing weight and production cost.
2Ease of operation
If external gear pairs are provided in AMT or DCT transmissions, then manual gearbox mechanisms can be implemented, but the production cost and weight of the transmission increase
Solution Approach 1:
The patent employs a single planetary gear unit that can provide multiple gear ratios (first, second, and third gear ratios) through different engagement configurations. This multi-functional planetary gear mechanism replaces the need for separate external gear pairs for each gear stage, simplifying the overall transmission structure while maintaining manual gearbox functionality.
Solution Approach 2:
The patent changes the gear ratio parameters by engaging different elements of the planetary gear unit (sun gear, planet gears, ring gear) in various configurations. By changing which elements are engaged and which serve as input/output, the same physical gear structure can provide multiple gear ratios without requiring separate gear pairs for each ratio.
3Reliability
If gears are sequentially shifted during kickdown, then gear stages are changed step-by-step, but the gear shifting response is delayed and performance is reduced
Solution Approach 1:
The patent prepares multiple gear engagement paths in advance within the planetary gear unit structure. When kickdown is required, the system can directly engage the pre-configured lower gear ratio path (e.g., from third gear ratio to first gear ratio) without needing to pass through intermediate gear stages, enabling direct and rapid gear downshifting.
4Productivity
If the vehicle operates in EV mode at low speed, then motor power is used exclusively, but the period is short and fuel efficiency improvement is limited
Solution Approach 1:
The patent provides a wide range of gear ratios (first, second, third gear ratios with different ratios) that can be dynamically selected based on driving conditions. This enables the vehicle to operate in motor-driven modes across a broader speed range, not just at very low speeds, thereby extending the duration and effectiveness of fuel-efficient electric operation.
Data Source
AI summary
A hybrid vehicle powertrain may include input shafts, clutches, output shafts, a transmission path selector, a planetary gear unit, and a gear stage forming mechanism. The transmission path selector may bring engagement of a first input shaft with second or third input shaft. The planetary gear unit may have three rotary elements, with motor power or engine power being input via a first or second rotary element and being output with any one of two transmission gear ratios under the control of first or third rotary element in response to engagement of first and second engaging units. The gear stage forming mechanism may be formed by engagement of gear pairs having different transmission gear ratios with second and third input shafts and a first output shaft, and function to transmit the power from the second or third input shaft to the first output shaft while changing a speed by selecting a gear pair in accordance with a vehicle running speed using a gear pair selector.