Bidirectional Filtering Pulley for Start-Stop Torque Management
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Solution Overview
Problem
The introduction of start-stop systems in motor vehicles, which replace the alternator with a reversible electric machine, renders traditional filtering pulleys with freewheels ineffective, as they disengage the electric machine from the belt drive when providing power, leading to dynamic overloads on the belt.
Innovation Solution
A filtering pulley design that allows relative rotation between the hub and crown in both directions, incorporating an elastic assembly with coil springs and carriers, and a damping assembly with a friction disc and wave springs, enabling efficient torque transmission and vibration filtering without freewheel disengagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a freewheel is incorporated in the filtering unit to disengage the hub from the crown during torque reversal, then the alternator is protected during normal operation, but the electric machine is disengaged from the belt drive when providing power in start-stop systems
Solution Approach 1:
The patent removes the freewheel mechanism from the filtering unit, extracting the disengagement function that causes incompatibility with start-stop systems. This allows the electric machine to remain continuously engaged with the belt drive while providing power during starting operations.
Solution Approach 2:
The filtering unit is designed to serve multiple functions without a freewheel: it provides vibration filtering, torque transmission in both directions, and overload protection through the elastic element and damping assembly, making it compatible with both traditional alternator systems and start-stop systems with reversible electric machines.
2Ease of operation
If a freewheel mechanism is included in the filtering unit, then unidirectional motion transmission is achieved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the freewheel mechanism from the filtering unit, eliminating the complex unidirectional motion transmission system. Instead, it uses a bidirectional filtering mechanism with an elastic element and damping assembly that simplifies the overall device structure while maintaining operational effectiveness.
Solution Approach 2:
Rather than using a freewheel to allow motion in one direction only, the patent inverts the approach by designing a system that naturally accommodates bidirectional motion through the elastic and damping elements, eliminating the need for complex one-way clutch mechanisms.
3Object-affected harmful factors
If a filtering unit with spring and freewheel is used, then vibration filtering is provided, but manufacturing cost increases
Solution Approach 1:
The patent removes the freewheel component from the filtering unit, reducing the number of parts that need to be manufactured, assembled, and maintained. This extraction of the unnecessary unidirectional mechanism lowers manufacturing costs while preserving the essential vibration filtering function through the elastic element and damping assembly.
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
This design reduces dynamic overloads on the belt, allows for compact and cost-effective manufacturing, and maintains efficient torque transmission in both directions, preventing freewheel disengagement and reducing stress on the pulley components.
Implementation Method 1
The filtering unit generally comprises a spring, for example a coil spring (helical or spiral), or a plurality of springs or other elastic elements arranged circumferentially between the hub and the crown
Implementation Method 2
a damping assembly with a friction disc and wave springs
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
A filtering pulley for an accessory drive of an internal combustion engine, comprising a hub (2) suitable for being connected to an engine accessory, an annular crown (3) provided with a profile (8) configured to cooperate with a drive belt (9), externally coaxial to the hub (2) and supported in a rotationally free manner on the hub (2), a coil spring (12) able to transmit torque between the crown (3) and the hub (2), a first carrier (13) constrained to a first end (15) of the spring (12) and a second carrier (13) constrained to a second end (16) of the spring (12); each of the carriers (13, 14) is rotationally coupled to both the hub (2) and the crown (3) with a limited possibility of relative rotation with respect to each of them.