Compound Planetary Gear Powertrain for Electric Vehicles
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Solution Overview
Problem
Existing powertrains for electric vehicles face challenges in achieving optimal driving characteristics and power transmission efficiency while minimizing motor capacity and power consumption during gear shifts, which affects fuel efficiency and driving range.
Innovation Solution
A powertrain configuration featuring a compound planetary gear set with three gear stages, utilizing a brake and two clutch devices to selectively engage rotation elements, allowing for efficient power transmission by minimizing power consumption during gear shifts, and including a sleeve mechanism driven by an actuator to switch between gear positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a transmission with multiple gear stages is added to reduce motor capacity, then motor capacity is reduced, but device complexity increases
Solution Approach 1:
The patent employs a compound planetary gear set where a first planetary gear set and a second planetary gear set are nested within each other. The first sun gear, first planet carrier, and first ring gear form the first planetary gear set, while the second sun gear, second planet carrier, and second ring gear form the second planetary gear set. These two gear sets are integrated such that they share common components and space, allowing three gear stages to be achieved within a compact structure without proportionally increasing overall complexity.
Solution Approach 2:
The patent designs the transmission system with multi-functional components that serve multiple purposes. The compound planetary gear set can provide three different gear stages (first, second, and third gear stages) through selective engagement of different rotation elements. The clutch devices and brake are designed to control multiple rotation elements (first through fourth rotation elements) to achieve different gear ratios, allowing a single transmission unit to perform multiple gear reduction functions that would otherwise require separate gear sets.
2Ease of operation
If clutch devices are used to switch gear stages, then gear shift capability is improved, but power consumption during gear shifts increases
Solution Approach 1:
The patent replaces traditional multi-plate clutch mechanisms with a simplified clutch device design that uses fewer friction plates and simpler actuation mechanisms. The clutch devices are designed to engage and disengage rotation elements with minimal sliding distance and lower actuation force, reducing the mechanical work required during gear shifts. The brake mechanism is also simplified to provide effective locking with minimal energy input once engaged.
Solution Approach 2:
The transmission system is designed with pre-positioned clutch devices and brake components that are already aligned with their target rotation elements before gear shifting begins. The control system anticipates gear change requirements and pre-positions the clutch plates and brake actuators in optimal locations, minimizing the time and energy required to execute the actual gear shift. This preliminary positioning reduces the power consumption associated with moving heavy clutch components during the shifting process.
Data Source
AI summary
A powertrain for a vehicle may include a compound planetary gear set configured such that, of four rotation elements, a first rotation element is connected to an input shaft and a second rotation element is connected to an output element; a brake provided to connect a rotating body to a transmission housing to be locked thereto; a first clutch device provided to switch a connection state of the rotating body between a third rotation element and a fourth rotation element of the compound planetary gear set; and a second clutch device provided to switch a connection state of the second rotation element of the compound planetary gear set to the input shaft.