EV Two-Speed Transmission with Screw Actuation for Smooth Shifting
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Solution Overview
Problem
Existing two-speed transmission systems for electric vehicles face challenges in miniaturization and power efficiency, particularly due to the use of complex mechanisms like planetary gear sets and torque-thrust converting systems, which increase size and axial length, and struggle with smooth clutch switching and regenerative control.
Innovation Solution
A two-speed transmission apparatus utilizing a torque-thrust converting mechanism with a control motor, multi-plate friction clutches, and an actuator that selectively fastens these clutches using a torque-thrust converting mechanism with a screw and nut design, allowing for miniaturization and efficient power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a planetary gear mechanism is used as the transmission mechanism, then the transmission ratio can be changed between first speed and second speed, but the device complexity increases and the axial length increases
Solution Approach 1:
The planetary gear mechanism is divided into separate functional components: sun gear, planet gears, ring gear, and carrier. Each component can independently engage or disengage through the clutch mechanism, allowing the transmission to switch between different gear ratios without requiring a completely different mechanism for each ratio.
Solution Approach 2:
The planet gears are nested within the annular space between the sun gear and ring gear, with the carrier holding the planet gears. This nested arrangement allows multiple gear elements to occupy the same axial space, reducing the overall axial length while maintaining the ability to provide multiple transmission ratios.
2Adaptability or versatility
If a planetary gear mechanism is used as the transmission mechanism, then the transmission ratio can be changed between first speed and second speed, but the device size increases
Solution Approach 1:
The planet gears are nested within the annular space between the sun gear and ring gear, with the carrier holding the planet gears. This nested arrangement allows multiple gear elements to occupy the same axial space, reducing the overall axial length while maintaining the ability to provide multiple transmission ratios.
Solution Approach 2:
The same planetary gear components (sun gear, planet gears, ring gear, carrier) serve multiple functions by engaging different clutch elements. The clutch mechanism selectively connects or disconnects these components to achieve different transmission ratios, allowing a single set of planetary gears to provide both first speed and second speed transmission.
3Use of energy by moving object
If a dog clutch is used for the first speed, then the power consumption can be saved, but the transmission shock increases during switching
Solution Approach 1:
A friction clutch is introduced as an intermediary between the input shaft and the planetary gear mechanism. This friction clutch gradually engages or disengages during switching operations, providing smooth torque transfer and preventing the sudden torque changes that cause transmission shock, while still allowing the dog clutch to remain engaged for efficient power transmission once the switch is complete.
4Ease of operation
If a friction clutch is used for the second speed, then the transmission can be switched smoothly, but the device complexity increases
Solution Approach 1:
The clutch system is segmented into two distinct types: a dog clutch for the first speed and a friction clutch for the second speed. Each clutch type is optimized for its specific function, with the dog clutch providing efficient engagement when smoothness is less critical and the friction clutch providing smooth engagement when switching quality is paramount. This segmentation allows each component to be relatively simple while the system as a whole achieves both smooth switching and efficient operation.
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 solution enables miniaturization of the transmission apparatus, reduces power consumption, and improves efficiency by allowing smooth clutch switching and regenerative control without transmission shocks, enhancing overall vehicle performance.
Implementation Method 1
an actuator comprising an armature made by soft magnetic material, a spring and an electromagnetic coil, is proposed. That is, the dog clutch is fastened by the armature under a spring force at the first speed, and the dog clutch (or the friction clutch) is not fastened by driving the armature due to the electromagnetic coil at the second speed
Implementation Method 2
an actuator comprising an armature made by soft magnetic material, a spring and an electromagnetic coil, is proposed. That is, the dog clutch is fastened by the armature under a spring force at the first speed
Implementation Method 3
an actuator comprises a control motor of electric rotation type and a torque-thrust converting mechanism including an inner diameter-side piston having outer circumference screw strips to mesh with inner circumference screw strips of a worm wheel through the worm wheel from a worm of the control motor
Data Source
AI summary
Two-speed transmission apparatus for electric vehicle comprises a planetary gear mechanism 16, friction brake 28 and friction clutch 26 in coaxial arrangement between input axis 10 and output axis 12, first speed is obtained by fastening the friction brake 28 and one-on-one second speed is obtained by fastening friction clutch 26. The electric actuator 30 to switch first speed and second speed comprises electric motor 32, a torque-thrust converting mechanism 36 and pusher 34. The torque-thrust converting mechanism 36 comprises inside cylindrical screw 40 being rotated by control motor 32 and outside cylindrical nut 42 which is screwed with cylindrical screw 40 and is connected to pusher 34 so as to integrally axis-move. The control motor 32 may include an electromagnetic brake to fasten the friction brake 28 and the friction clutch 26. Thrust of the axial direction may be transmitted by the swing of an arm 316.