Multi-Axle Hill Hold Torque Blending to Prevent Creak and Jerks

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Solution Overview

Problem

In vehicles with separately driven axles, the transition to a stationary position on a hill often results in creaking noises and slight jerks due to the mismatch between drive and brake torque distributions, particularly when using a hill hold assist, leading to inefficient operation and potential overheating of electric drive units.

Innovation Solution

A method and drive arrangement that adapt the torque distribution by initially applying drive compensation torque according to a predetermined brake torque distribution, transitioning to brake compensation torque during a blending process, maintaining consistent torque ratios to minimize creaking and settling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the compensation torque is initially applied by the electric drive units and then transferred to the mechanical brake system, then the electric drive units can be terminated from static operation and overheating is avoided, but creaking noises and jerks occur due to mismatch between drive and brake torque distributions

Engineering Contradiction:

Improveprevention of electric drive unit overheatingVSAvoidcreaking noises and jerks during torque transition

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by pre-adapting the drive torque distribution to match the brake torque distribution before the transition occurs. The control unit calculates and applies a adapted drive torque distribution that corresponds to the predetermined brake torque distribution, so that when the torque is transferred from drive to brake, there is no sudden change or mismatch, thus avoiding creaking noises and jerks while still allowing the electric drive units to be terminated

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the torque distribution parameters by adapting the drive torque distribution to match the brake torque distribution. Instead of using a fixed drive torque distribution, the control unit dynamically adjusts the torque distribution parameters to correspond to the brake system's predetermined distribution, ensuring smooth transition and eliminating harmful creaking noises during the handover from electric drive to mechanical brake

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the electric drive units are used for hill hold compensation, then hill hold function is achieved, but energy efficiency deteriorates due to static operation and overheating risk

Engineering Contradiction:

Improvehill hold functionVSAvoidenergy efficiency during static operation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The control unit performs preliminary calculation and adaptation of the drive torque distribution to match the brake torque distribution before the transition. This preliminary action ensures that when the electric drive units are terminated and the brake system takes over, the hill hold function is maintained without energy loss, and the smooth transition avoids creaking noises

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the continuous operation of electric drive units with the mechanical brake system for maintaining hill hold. By adapting the torque distribution, the mechanical brake system can take over the hill hold function more efficiently, terminating the static operation of electric drive units and avoiding their overheating and energy consumption while maintaining the same hill hold performance

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If the brake torque distribution is predetermined and fixed, then the brake system has simple control, but the torque distribution does not match the drive torque distribution causing creaking during transition

Engineering Contradiction:

Improvebrake control simplicityVSAvoidcreaking noises during torque transition

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The control unit dynamically changes the drive torque distribution parameters to match the predetermined brake torque distribution. By adapting the drive torque distribution to correspond to the brake torque distribution, the system maintains the simplicity of predetermined brake control while eliminating the mismatch that causes creaking noises during transition

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12397793B2Hill hold function for a motor vehicle comprising a plurality of driven axles

Publication Date: 2025.08.26 BAYERISCHE MOTOREN WERKE AG

AI summary

A method is provided for operating a motor vehicle including a first driven axle, with which a first electric drive unit and a first brake mechanism are associated, and a second driven axle, with which a second electric drive unit and a second brake mechanism are associated, in a hill hold operating mode, in which the brake mechanisms are configured to brake the two axles with a predetermined brake torque distribution. According to the method, a hill hold requirement for the motor vehicle is identified and a compensation torque distribution to the two axles, provided in relation to the hill hold requirement, in accordance with the predetermined brake torque distribution is determined. The compensation torque is applied in accordance with the compensation torque distribution, and the compensation torque applied by the respectively associated drive unit is replaced with compensation torque applied by the brake mechanism of the respective axle.