Variable Valve Timing Electric Motor Actuator Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing variable valve timing systems face challenges in accurately changing valve timing after an engine stop command, particularly in cold environments or during engine starting, due to insufficient hydraulic pressure and slow camshaft response, leading to potential collisions and inaccurate valve timing settings for subsequent engine starts.

Innovation Solution

A variable valve timing system utilizing an electric motor as an actuator, with a stop-time phase control unit that includes a mode changeover condition setting unit and a mode changeover determination unit to switch between high-speed and feedback control modes based on rotational speed and deviation from target valve timing, ensuring accurate valve timing setting when the engine is stopped.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If hydraulic pressure is used to drive the camshaft, then the variable valve timing system can operate during engine operation, but the response is slow and inaccurate in cold environments or at engine starting due to insufficient hydraulic pressure

Engineering Contradiction:

Improvevalve timing control reliabilityVSAvoidcamshaft response speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent replaces the hydraulic drive system with an electric motor drive system. The electric motor directly drives the camshaft to change valve timing, eliminating the response delays and inaccuracies caused by insufficient hydraulic pressure in cold environments or during engine starting. This substitution enables reliable and rapid valve timing control across all operating conditions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If the valve timing is changed to a value at or around the limit valve, then the valve timing control range is maximized, but the movable part may collide with the stopper portion at high speed causing damage

Engineering Contradiction:

Improvevalve timing control rangeVSAvoidcollision damage to movable part

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements dynamic control of the valve timing change rate based on the current valve timing position. When approaching the limit valve position, the control unit automatically reduces the rate of change to prevent high-speed collision between the movable part and stopper portion. This dynamic adjustment maintains the full control range while preventing damage through speed modulation near boundaries.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control unit continuously monitors the valve timing position and adjusts the drive speed accordingly. When the valve timing approaches the limit position, the feedback mechanism reduces the drive speed to prevent collision, while maintaining high speed during normal operation to ensure rapid response. This closed-loop control achieves both full range adaptability and collision prevention.

Inventive Principle:

Principle #23Feedback

3Ease of operation

If the valve timing is not adjusted after engine stop command, then the system remains simple, but the subsequent engine starting may be difficult due to inappropriate valve timing

Engineering Contradiction:

Improveease of engine startingVSAvoidvalve timing control system complexity

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent executes preliminary valve timing adjustment after the engine stop command to prepare the camshaft in an angular position appropriate for subsequent engine starting. This preliminary action ensures optimal starting conditions are established before the engine actually stops, facilitating easier restart while maintaining straightforward control logic.

Inventive Principle:

Principle #10Preliminary action

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 system reliably changes valve timing by a required amount and accurately sets the valve timing to the target phase when the engine is stopped, preventing collisions and ensuring proper engine starting conditions.

Implementation Method 1

a variable valve timing system that uses an electric motor as an actuator

Methodology Applied

Scientific EffectElectromagnetic conversion: Electromagnetic Induction

Data Source

PatentUS7909008B2Variable valve timing system and method for controlling the same

Publication Date: 2011.03.22 TOYOTA JIDOSHA KK

AI summary

In an intake valve phase control after an engine stop command is issued, a stop-time phase is used as a target value. In the intake valve phase control, when the mode changeover condition is not satisfied, and an electric motor that serves as an actuator is not in a locked-state, the highest-speed mode, in which the amount of electric power supplied to the electric motor is fixed to the maximum value, is selected to reliably change the intake valve phase by a required amount. Then, the intake valve phase comes close to the stop-time phase and the mode changeover condition is satisfied, the control mode is changed from the highest-speed mode to the normal mode to set the control phase to the stop-time phase with higher accuracy, and the feedback control over the intake valve phase is executed.