EV Transmission Torque Spike Control for Gear Flank Noise

Solution Overview

Problem

Electric drive machines with gearwheel mechanisms experience disruptive clicking noises during load changes due to torque zero crossings, which are difficult to mitigate without affecting drivability and require additional sealing measures.

Innovation Solution

Implementing torque spikes before flank changes in the electric drive machine's torque profile to adapt the relative speed of gearwheel flanks, reducing the impact velocity and minimizing noise by actuating retarding or accelerating torque spikes based on the type of load change.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If torque interventions are introduced to reduce noise during flank changes, then noise is reduced, but the application time is strictly limited and additional secondary measures are required

Engineering Contradiction:

ImprovenoiseVSAvoiddevice complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by introducing a torque spike before the flank change occurs. The control unit detects the flank change event and applies a torque spike that precedes the actual flank change, allowing the gearwheels to be accelerated or retarded in advance so that their flanks collide at lower relative speed, thereby reducing noise without requiring additional physical components

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the torque parameter dynamically by applying a torque spike that deviates from the normal torque profile. The control unit modifies the torque magnitude and timing parameters based on detected flank change events, creating an accelerating or retarding torque spike that reduces the relative collision speed of gearwheel flanks during the transition

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If torque gradient is decreased to reduce noise, then noise is reduced, but the influence on the cause of noise is small and additional sealing measures are required

Engineering Contradiction:

ImprovenoiseVSAvoidease of manufacture

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by introducing a torque spike before the flank change occurs. The control unit detects the flank change event and applies a torque spike that precedes the actual flank change, allowing the gearwheels to be accelerated or retarded in advance so that their flanks collide at lower relative speed, thereby reducing noise without requiring additional physical components

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces mechanical noise reduction measures (such as sealing elements, foam parts, and encapsulation measures) with a control-based approach. Instead of modifying the mechanical structure to reduce noise, the system uses electronic control to apply torque spikes that reduce the relative collision speed of gearwheel flanks, achieving noise reduction without additional mechanical components

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If torque spike is applied to adapt circumferential speed of gearwheels, then relative speed at flank collision is reduced and noise is quieter, but torque intervention must be precisely timed

Engineering Contradiction:

ImprovenoiseVSAvoidtiming precision

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent applies feedback by using a control unit that detects flank change events in real-time and responds by applying a torque spike. The control unit monitors the operational state of the gearwheel mechanism and triggers the torque intervention based on detected flank changes, ensuring the torque spike is applied at the appropriate moment to reduce relative collision speed without requiring pre-programmed timing

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies preliminary action by introducing a torque spike before the flank change occurs. The control unit detects the flank change event and applies a torque spike that precedes the actual flank change, allowing the gearwheels to be accelerated or retarded in advance so that their flanks collide at lower relative speed

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12485769B2Noise reduction in a transmission of an electric vehicle drive

Publication Date: 2025.12.02 BAYERISCHE MOTOREN WERKE AG

AI summary

A method and a device for controlling an electric driving machine of a motor vehicle are provided. A rotor shaft of the electric driving machine is connected to an output shaft of the motor vehicle via a geared transmission. During a load alteration of the driving machine, a shock torque load is applied by the driving machine prior to a changeover from one flank to another in the geared transmission in order to adjust the rotation of the gears of the geared transmission.