Four-Speed Transaxle With Electric Caliper Brakes
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Solution Overview
Problem
Conventional electric vehicle transaxles face efficiency issues due to single-speed configurations, leading to reduced mileage and comfort due to traction force drops during shifting, and mechanical clutches suffer from heat, dust, and high maintenance costs.
Innovation Solution
A four-speed transaxle with four planetary gear sets and electric caliper brake systems that enable smooth shifting without traction interruption, using a regulatable clutch system with dry brake discs and screw-nuts for efficient power transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-speed transaxle configuration is used, then the device complexity is reduced, but the efficiency of the electric drive decreases due to covering the entire rotational speed range
Solution Approach 1:
The transaxle is segmented into multiple speed stages (first speed stage with sun gear, first carrier, first ring gear; second speed stage with second sun gear, second carrier, second ring gear) to divide the rotational speed range into discrete segments. This allows the electric drive to operate at optimal efficiency in each speed range rather than covering the entire range continuously, resolving the contradiction between simplified configuration and drive efficiency.
2Device complexity
If a sliding synchronizer sleeve is used for speed selection, then the device complexity is reduced, but the traction force drops during shifting causing comfort loss
Solution Approach 1:
The mechanical sliding synchronizer sleeve system is replaced with an electric caliper brake system that uses electromagnetic actuation. The control unit activates electric caliper brakes to selectively lock or unlock planetary gear sets, enabling smooth speed transitions without mechanical sliding contact. This substitution eliminates the traction force drop during shifting while maintaining relatively simple device complexity through electronic control.
3Ease of operation
If mechanical clutches with wet clutch plates are used, then the ease of operation is improved, but heat generation increases causing performance degradation and reduced transmission life
Solution Approach 1:
The mechanical wet clutch plate system is replaced with an electric caliper brake system that uses electromagnetic force to lock or unlock planetary gear sets. This substitution eliminates the friction-based heat generation of wet clutch plates while maintaining ease of operation through electronic control. The electric caliper brakes engage without relative sliding motion, preventing the heat and dust generation that degrades mechanical clutch performance and reduces transmission life.
4Reliability
If mechanical clutches with complex oil roads are used, then the reliability is improved, but the device complexity and manufacturing cost increase significantly
Solution Approach 1:
The complex mechanical clutch system with intricate oil roads is replaced with an electric caliper brake system controlled by a control unit. The electric calibration brakes use electromagnetic actuation to lock or unlock planetary gear sets, eliminating the need for complex lubrication pathways. This substitution maintains reliability through precise electronic control while significantly reducing device complexity and manufacturing costs associated with machining complex oil roads.
5Use of energy by moving object
If a four-speed transaxle with planetary gear sets is used, then the efficiency is improved through multiple speed stages, but the device complexity increases compared to single-speed configurations
Solution Approach 1:
Multiple planetary gear sets (first speed stage with sun gear, first carrier, first ring gear; second speed stage with second sun gear, second carrier, second ring gear) are merged into a single integrated transaxle structure. The electric caliper brake system merges the functions of speed selection and gear locking into a unified control mechanism actuated by the control unit. This merging achieves multiple speed stages for improved efficiency while managing device complexity through integrated design and common components.
6Reliability
If electric caliper brake systems are used for speed selection, then the traction force continuity is improved during shifting, but the device complexity increases compared to sliding synchronizer sleeves
Solution Approach 1:
The simple mechanical sliding synchronizer sleeve is replaced with an electric caliper brake system that uses electromagnetic actuation. Although the actuation mechanism is more complex, the overall system complexity is managed through electronic control that integrates speed selection with the existing planetary gear sets. The substitution achieves continuous traction force during shifting by eliminating mechanical sliding contact, with the control unit coordinating brake activation to maintain smooth power transmission.
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 provides high efficiency, reliability, and extended transaxle life by minimizing heat generation and maintenance needs, while maintaining traction and improving vehicle performance for passing, towing, and hauling.
Implementation Method 1
Four electric caliper brake systems are mounted on outside of the transaxle housing for selectively locking or unlocking the first, second, third and fourth planetary gear sets
Implementation Method 2
Four planetary gear sets are successively connected to one another and to the input shaft in an coaxial arrangement. Each planetary gear set has a sun gear, a ring gear, a carrier and a plurality of planet gears
Implementation Method 3
Each electric caliper brake system has a shift gear shaft with a dry brake disc secured thereto and a shift gear meshing with an external gear of the ring gear. Two pairs of independent screw-nut
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A four-speed transaxle for a high efficiency electric vehicle comprises four planetary gear sets that is operatively connected to an electric motor, four electric caliper brake systems and one stage gears. The four-speed transaxle produces its first speed ratio when a first and third electric caliper brake systems are disengaged and a second and fourth electric caliper brake systems are engaged. Second speed ratio results when the first and fourth electric caliper brake systems are engaged and the second and third electric caliper brake systems are disengaged. Third speed ratio results when the second and third electric caliper brake systems are engaged and the first and fourth electric caliper brake systems are disengaged. Fourth speed ratio is produced when the first and third electric caliper brake systems are engaged and the second and fourth electric caliper brake systems are disengaged.