Engine Pulley Clutch Layout for Compact, Low-Noise Decoupling
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Solution Overview
Problem
Existing pulley units for motor vehicle engines face challenges in compact design due to the size of friction clutches, which also result in high noise levels, particularly when used in hybrid applications where the electric machine must drive accessories independently of the internal combustion engine.
Innovation Solution
A pulley unit with a clutch featuring an inner disc and a mobile member that can rotate axially between engagement and disengagement positions, utilizing toothing for engagement and minimizing overall dimensions, and incorporating a torsional vibration damper to reduce noise and enhance compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a friction clutch is used to decouple the pulley from the hub, then the clutch can be actuated by an electromagnetic actuator, but the overall dimensions of the pulley unit increase and noise levels rise
Solution Approach 1:
The clutch assembly is nested within the pulley structure, with the inner disc positioned inside the pulley body and the mobile member moving within the pulley's internal space. This nesting arrangement allows the clutch mechanism to be accommodated within the existing pulley footprint without significantly increasing overall dimensions.
Solution Approach 2:
The clutch mechanism transitions from a radial arrangement to an axial arrangement, with the mobile member moving axially between engagement and disengagement positions. This dimensional change allows the clutch to achieve its function within the constrained radial space of the pulley.
2Ease of operation
If a friction clutch is used to decouple the pulley from the hub, then the clutch can be actuated by an electromagnetic actuator, but noise levels increase
Solution Approach 1:
The friction-based mechanical contact is replaced with a positive engagement system using toothing on the inner disc that engages with corresponding toothing on the pulley. This substitution eliminates the sliding friction and associated noise characteristic of friction clutches.
Solution Approach 2:
The engagement mechanism changes from continuous friction contact to discrete positive engagement through toothing. This parameter change in the engagement method fundamentally alters the noise characteristics by eliminating the sliding friction noise.
3Volume of moving object
If the clutch dimensions are reduced, then the overall pulley unit becomes more compact, but the actuator dimensions must be increased to maintain transmissible torque
Solution Approach 1:
The clutch components are nested within the pulley structure, with the inner disc, mobile member, and toothing all arranged within the pulley's internal volume. This nesting allows the clutch to maintain sufficient torque transmission capability while keeping overall dimensions compact.
Solution Approach 2:
The clutch mechanism uses axial movement of the mobile member to achieve engagement and disengagement, rather than radial expansion. This dimensional change allows the clutch to maintain compact radial dimensions while providing adequate actuation space in the axial direction.
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 allows for a compact pulley unit design that maintains or slightly exceeds conventional dimensions while providing a quieter operation by using toothing for engagement, reducing noise and enabling efficient operation of accessories even when the internal combustion engine is off.
Implementation Method 1
the elastic element is subject to the thrust of at least one elastic element towards the engagement portion
Implementation Method 2
incorporating a torsional vibration damper to reduce noise and enhance compactness
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
A pulley unit comprising a hub (3) configured to be connected to a crankshaft, a pulley (7) coaxial to the hub (3) and supported in a rotationally free manner with respect thereto, a clutch (8) interposed between the hub (3) and the pulley (7), and an actuator (27) for controlling the clutch (8); the clutch (8) comprises an inner disc (12) rotationally coupled to the hub (3) and having an engagement portion (18; 64) housed inside the pulley (7), a mobile member (24) axially movable between an engagement position wherein it rotationally couples the pulley (7) to the engagement portion (18; 64) of the inner disc (12) and a disengagement portion wherein the pulley (7) is rotationally free with respect to the inner disc (12), and an elastic element (25) acting on the mobile member (24) to push it towards the engagement position.