Two-Speed Accessory Drive Pulley with Planetary Gear Speed Adjustment
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Solution Overview
Problem
Conventional motor vehicle accessory drive systems lack the ability to adjust speed dynamically, as the size of the crankshaft pulley determines the fixed speed of belt-driven accessories, limiting flexibility and efficiency.
Innovation Solution
A two-speed pulley assembly incorporating a planetary gear system with a friction clutch, one-way clutch, and torsional isolator, allowing for selective speed adjustment by engaging or disengaging the sun gear through an electromagnet and conical surfaces, while maintaining lubrication and axial stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed-size crankshaft pulley is used to drive accessories, then the structure is simple and reliable, but the speed of accessories cannot be adjusted dynamically
Solution Approach 1:
The patent applies a planetary gear system with movable components that allow the pulley to operate in two distinct speed modes. The planet carrier, planet gears, and sun gear can shift positions and engage/disengage to change the transmission ratio, enabling dynamic speed adjustment between normal and overspeed operations while maintaining structural integrity
Solution Approach 2:
The pulley is divided into multiple functional segments including the planet carrier assembly, sun gear, ring gear, and clutch mechanisms. Each segment performs a specific function in the speed variation process, allowing independent control and engagement of different speed modes through the friction clutch and one-way clutch mechanisms
2Adaptability or versatility
If a planetary gear system is added to enable speed adjustment, then speed flexibility is improved, but the device complexity increases
Solution Approach 1:
The planetary gear system is designed to provide multiple functions within a single integrated structure. The same planet carrier and gear components serve both normal speed operation and overspeed operation modes, eliminating the need for separate gear trains for each speed mode and reducing overall system complexity
Solution Approach 2:
The friction clutch and one-way clutch act as intermediary mechanisms that control the engagement and disengagement of the sun gear and planet carrier. These clutch mechanisms simplify the control logic by automatically selecting the appropriate speed mode based on operating conditions, reducing the complexity of manual or electronic control systems
3Productivity
If the sun gear is selectively engaged to change speed, then operational efficiency is improved, but the reliability of the clutch mechanism is challenged
Solution Approach 1:
The patent replaces complex multi-plate friction clutches with a simpler conical friction surface mechanism. The conical surfaces provide self-centering and automatic alignment, reducing the risk of misalignment and uneven wear that commonly plague traditional friction clutch designs, thereby improving reliability while maintaining efficient torque 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
Enables dynamic speed adjustment between normal and overspeed operations, improving the efficiency and flexibility of accessory drive systems by allowing the pulley to spin at different speeds relative to the crankshaft, enhancing performance and adaptability.
Implementation Method 1
The friction clutch is arranged to selectively prevent rotation of the sun gear
Implementation Method 2
The one-way clutch is arranged between the sun gear and the ring gear. The one-way clutch permits rotation of the sun gear relative to the ring gear in a first rotational direction, and prevents rotation of the sun gear relative to the ring gear in a second rotational direction
Implementation Method 3
The electromagnet is arranged to displace the piston in a first axial direction to frictionally engage the second conical surface with the first conical surface
Implementation Method 4
The torsional isolator is drivingly connected to the planet carrier and arranged to rotate at a same speed as the planet carrier
Data Source
AI summary
A two-speed pulley assembly for an engine accessory drive includes a planetary gear, a pulley, a friction clutch, a one-way clutch, and a torsional isolator. The planetary gear has a ring gear, a sun gear, a planet carrier and at least one planet gear. The planet carrier is arranged for driving engagement with an engine crankshaft. The pulley circumscribes the ring gear and is in driving engagement with the ring gear. The friction clutch is arranged to selectively prevent rotation of the sun gear. The one-way clutch permits rotation of the sun gear relative to the ring gear in a first rotational direction, and prevents rotation of the sun gear relative to the ring gear in a second rotational direction, opposite the first rotational direction. The torsional isolator is drivingly connected to the planet carrier and arranged to rotate at a same speed as the planet carrier.