Electromagnetic Clutch Mechanism for Automotive BAS Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing serpentine accessory drive systems in automotive vehicles face issues with high-inertia components loading the serpentine belt, leading to squealing, slipping, or vibration, and the need for an improved clutch mechanism that can lock, bypass, or transmit rotary power effectively, particularly in BAS systems where the alternator operates as a starter motor.
Innovation Solution
A clutched device comprising a pulley, shaft member, one-way clutch with a wrap spring, and an actuator with an electromagnetic coil and armature, which rotationally couples the pulley and shaft member when actuated, applying frictional force to resist rotation and engage the wrap spring with a clutch surface for power transmission in specific rotational directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an over-running decoupler is used to prevent belt squealing and vibration, then belt noise and vibration are reduced, but the ability to transmit rotary power from alternator to crankshaft in BAS systems is lost
Solution Approach 1:
The decoupler incorporates an electromagnetic actuator that can dynamically change the state of the one-way clutch from locked to unlocked, allowing the system to adapt between normal operating mode (decoupled) and BAS mode (locked), thus resolving the contradiction between preventing vibration and enabling power transmission
2Ease of operation
If a one-way clutch is used to allow free rotation in one direction, then over-running capability is achieved, but the ability to lock and transmit power in the opposite direction is limited
Solution Approach 1:
The patent replaces the purely mechanical one-way clutch with an electromagnetic-actuated one-way clutch that uses electromagnetic forces to control the engagement and disengagement of clutch surfaces, providing more reliable and controllable power transmission while maintaining over-running capability
3Power
If friction is increased to improve clutch engagement, then power transmission is enhanced, but wear on clutch surfaces increases
Solution Approach 1:
The wrap spring automatically engages the clutch surfaces when relative motion occurs between the pulley and shaft member, creating friction-based power transmission without requiring external control, and the system naturally limits wear through the elastic properties of the wrap spring
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 effectively transmits rotary power in the desired direction while preventing power transmission when not needed, reducing wear and enhancing the functionality of BAS systems by enabling idle-stop-accessory functions without significant wear on the clutching unit.
Implementation Method 1
an actuator having an electromagnetic coil and an armature
Implementation Method 2
The first wrap spring is configured to radially expand into driving engagement with a clutch surface
Implementation Method 3
A frictional force is applied to the armature when the actuator is activated. The frictional force is configured to resist rotation of the armature
Data Source
AI summary
A clutched device that includes a pulley, a shaft member, a first one-way clutch having a first wrap spring, and an actuator having an electromagnetic coil and an armature. The first one-way clutch rotationally couples the pulley and the shaft member when the actuator is actuated and rotary power is transmitted from a first one of the pulley and the shaft member to the other one of the pulley and the shaft member in a first rotational direction. A frictional force is applied to the armature when the actuator is activated. The frictional force is configured to resist rotation of the armature to cause the first wrap spring to radially expand into driving engagement with a clutch surface that is coupled to the pulley for common rotation.