Two-Speed Accessory Drive Clutch NVH Reduction

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Solution Overview

Problem

The engagement and disengagement of the electromagnetic clutch in current two-speed accessory drive systems generate driveline torque disturbances, leading to increased noise, vibration, and harshness (NVH), which negatively impact vehicle performance and reduce the useful life of associated components.

Innovation Solution

A method is implemented where an electric machine operates in motor mode to reduce the speed of the grounding gear of the planetary gear set when electrical demand is high, and engages the electromagnetic clutch when the speed reaches a threshold, and disengages it when demand decreases, ensuring smooth transitions and reducing NVH by matching the speed of the output and input gears.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the electromagnetic clutch is engaged and disengaged in conventional two-speed accessory drive systems, then the drive belt speed can be adjusted to meet varying electrical demands, but driveline torque disturbances occur leading to increased NVH and reduced component life

Engineering Contradiction:

Improveelectrical demand responseVSAvoidNVH and torque disturbances

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The controller pre-adjusts the drive belt speed by operating the electric machine in motor mode before clutch engagement, reducing the speed difference between engaged and disengaged states. This preliminary action minimizes the torque disturbance and NVH that would otherwise occur during clutch engagement/disengagement transitions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically changes the speed parameter of the drive belt by controlling the electric machine's motor mode operation. By adjusting the belt speed to a reduced level before clutch engagement, the system optimizes the engagement conditions to minimize harmful torque disturbances and NVH while maintaining adaptability to electrical demands.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the electromagnetic clutch is engaged frequently to meet varying electrical demands, then the system can adapt to different power requirements, but wear of the clutch and associated parts increases reducing useful life

Engineering Contradiction:

Improvepower requirement adaptationVSAvoidclutch component life

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The controller performs preliminary speed adjustment of the drive belt using the electric machine before clutch engagement. This pre-conditioning of the system reduces the shock and stress during engagement, thereby reducing wear on the clutch and associated components while maintaining the ability to adapt to varying power requirements.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses the electric machine to perform speed adjustment that would otherwise require mechanical clutch slip. By using electrical control to pre-adjust belt speed, the system reduces mechanical wear on the clutch components during engagement cycles, extending component life while maintaining adaptability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Power

If the drive belt speed is increased to meet high electrical demand, then electrical generation increases, but parasitic loss increases reducing engine efficiency

Engineering Contradiction:

Improveelectrical generationVSAvoidparasitic loss

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The system dynamically adjusts the drive belt speed based on actual electrical demand conditions. By using the electric machine to precisely control belt speed and only increasing it when necessary to meet electrical demand, the system optimizes the balance between electrical generation and parasitic losses, improving overall engine efficiency.

Inventive Principle:

Principle #15Dynamics

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 approach reduces driveline torque disturbances and NVH, enhancing the driving experience and extending the life of clutch and associated components by optimizing the engagement and disengagement of the electromagnetic clutch.

Implementation Method 1

engaging an electromagnetic clutch responsive to the speed of the grounding gear reaching a clutch engagement threshold speed

Methodology Applied

Scientific EffectElectromagnetic clutch engagement: Electromagnet

Implementation Method 2

operating an electric machine of the vehicle in a motor mode to reduce a speed of a grounding gear of a planetary gear set

Methodology Applied

Scientific EffectElectric machine motor mode operation: Linear Motor

Implementation Method 3

a planetary gear set of the two-speed accessory drive (TSAD) of the vehicle

Methodology Applied

Scientific EffectPlanetary gear mechanism: Gear

Data Source

PatentUS11623633B2Methods and systems for a two-speed accessory drive of an engine

Publication Date: 2023.04.11 FORD GLOBAL TECH LLC

AI summary

Methods and systems are provided for engaging and disengaging an electromagnetic clutch of a two-speed accessory drive of an engine of a vehicle. In one example, a method comprises, responsive to an electrical demand being higher than a threshold electrical demand, operating an electric machine of the vehicle in a motor mode to reduce a speed of a grounding gear of a planetary gear set of a two-speed accessory drive (TSAD) of the vehicle; and engaging an electromagnetic clutch responsive to the speed of the grounding gear reaching a clutch engagement threshold speed.