Hybrid Powertrain Lash Removal During Engine Start

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Solution Overview

Problem

Hybrid vehicles without a mechanical neutral in their powertrain systems experience undesirable noise and vibration due to continuous engine connection, which causes sudden torque loading and lash take-up when the engine starts.

Innovation Solution

A method that detects a request to start the engine, senses the lash state, and applies incremental torque against a static member to remove lash before engine startup, ensuring the lash is cleared before engine torque is applied, thereby preventing sudden loading and associated noise and vibration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the engine is continuously connected to the powertrain system without a mechanical neutral, then the engine can continuously transmit torque to the wheels, but when the engine starts it suddenly loads the powertrain system and causes undesirable noise and vibration

Engineering Contradiction:

Improvecontinuous torque transmissionVSAvoidnoise and vibration during engine start

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The control system applies torque to the driveline components (such as the electric motor or transmission) before engine startup to take up lash in the powertrain system. This preliminary action pre-loads the mechanical connections, ensuring that when the engine starts and applies torque, there is no sudden movement or impact that would cause noise and vibration. The lash is removed in advance, smoothing the transition during engine start.

Inventive Principle:

Principle #10Preliminary action

2Object-affected harmful factors

If a mechanical neutral is added to disconnect the transmission output from the engine, then noise and vibration during engine start can be eliminated, but the device complexity increases

Engineering Contradiction:

Improvenoise and vibration during engine startVSAvoidtransmission system complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

Instead of adding a mechanical neutral mechanism to physically disconnect the transmission from the engine, the invention uses a control system that applies torque through existing electrical or mechanical actuators (such as an electric motor or clutch actuator). This substitutes a complex mechanical disconnection system with a controlled torque application system, achieving the same noise and vibration reduction effect without increasing mechanical complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Speed

If torque is immediately applied during engine start, then the engine can start quickly, but the sudden torque loading causes lash to be taken up and creates noise and vibration

Engineering Contradiction:

Improveengine start speedVSAvoidnoise and vibration from sudden torque

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

Torque is applied to the driveline components before engine startup to pre-load the powertrain system and remove lash. This preliminary torque application ensures that when the engine starts at full speed, the mechanical connections are already engaged and there is no sudden movement or impact. The sequence is reversed from conventional systems: instead of starting the engine first and then applying torque, the torque is applied first to prepare the system, then the engine starts smoothly.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9108620B2Method to reduce powertrain noise and vibration during engine start in hybrid vehicle

Publication Date: 2015.08.18 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A method of controlling a powertrain system of a hybrid vehicle includes detecting a request to start an engine, incrementally applying torque to the powertrain system, and biasing the torque against a static member of the powertrain system, such as a parking pawl of a transmission when the transmission is disposed in a parking position, to remove lash from the powertrain system prior to starting the engine.