Two-Speed Planetary Transmission for Low-Speed Accessory Overdrive
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Solution Overview
Problem
Rotary drive systems face limitations in driven shaft speed control due to coupling, often via an endless drive band, which restricts higher output or shaft speed at lower prime mover speeds, necessitating additional speed control for applications requiring increased performance.
Innovation Solution
A two-speed transmission system incorporating a one-way clutch, planetary gear drive, and electromagnetic brake, allowing for selective speed modes by locking or grounding components to achieve enhanced speed ratios and torque transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single-speed belt drive is used, then the system is simple and reliable, but the driven shaft speed cannot be increased at low prime mover speeds
Solution Approach 1:
The transmission system employs a planetary gear set that can dynamically shift between two speed ratios (1:1 and 2:1) based on operating conditions. The one-way clutch and electromagnetic brake enable automatic engagement/disengagement of different gear ratios, allowing the system to adapt its transmission ratio in real-time without manual intervention.
Solution Approach 2:
The planetary gear set serves multiple functions: it provides both direct drive (1:1 ratio) and overdrive (2:1 ratio) capabilities within a single transmission unit. The same gear set, when combined with the one-way clutch and electromagnetic brake, can operate in different modes (direct drive, overdrive, reverse) without requiring separate transmission systems.
2Power
If a two-speed transmission is added, then speed control and torque multiplication are improved, but the device complexity increases
Solution Approach 1:
The patent combines the one-way clutch, electromagnetic brake, and planetary gear set into a single integrated transmission assembly. These components work together as a unified system where the one-way clutch handles automatic engagement, the electromagnetic brake provides controlled grounding, and the planetary gear set delivers the speed/torque transformation, eliminating the need for separate mechanisms.
Solution Approach 2:
The electromagnetic brake replaces traditional mechanical braking mechanisms, using electromagnetic fields to ground the ring gear when needed. This substitution reduces mechanical wear and provides more precise control while maintaining the same functional outcome of locking the planetary gear set in specific ratios.
3Productivity
If higher output speed is required at low engine speeds, then accessory performance is improved, but the drive system complexity increases
Solution Approach 1:
The transmission system pre-establishes the 2:1 overdrive ratio capability through the planetary gear set configuration, allowing accessories to receive increased speed immediately when needed without requiring active control adjustments. The one-way clutch is pre-positioned to automatically engage the overdrive path when the electromagnetic brake grounds the ring gear.
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
Enables improved speed control and torque multiplication, particularly beneficial for accessory drives at low engine speeds, reducing accessory size and stress while providing overdrive capabilities and additional power transfer functionalities.
Implementation Method 1
The one-way clutch is arranged between the input and output shafts
Implementation Method 2
The electromagnetic brake is configured to selectively ground the ring gear
Implementation Method 3
The planetary gear drive includes a sun gear, carrier, ring gear, and planet gears
Implementation Method 4
A first ball bearing may be arranged between the central support shaft and the sun gear. A needle roller bearing may be arranged between the central support shaft and the output shaft
Implementation Method 5
A first dynamic seal may be arranged between the ring gear carrier and the sun gear. A third dynamic seal may be arranged between the input shaft and the output shaft
Data Source
AI summary
A two-speed transmission alternately establishes two speed ratios between a primary drive pulley and one or more accessories pulleys of an accessory drive system. The two-speed transmission includes concentric input and output shafts fixed to input and output pulleys respectively. When an actuator is disengaged, a one-way clutch transfers power between the input shaft and the output shaft. The input shaft is fixed to the planet carrier of a planetary gear set and the output shaft is fixed to the sun gear of the planetary gear set. When the actuator is engaged, the ring gear of the planetary gear set is held establishing an overdrive speed relationship between the input pulley and the output pulley.