Variable Valve Timing Controller Motor Current Restriction

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Solution Overview

Problem

Variable valve timing controllers with electric motors face durability issues and malfunctions due to excessive coil temperature rise during frequent transient operating conditions, leading to heat value and temperature-related deterioration.

Innovation Solution

A variable valve timing controller that computes a target motor speed based on engine rotation speed and camshaft phase deviation, with feedback control to adjust motor current, estimating and restricting it when it exceeds a predetermined value to prevent excessive heat generation and maintain within safe temperature limits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If motor current is increased to improve response speed of variable valve timing control, then the speed of response is improved, but motor coil temperature exceeds allowable limits causing durability deterioration

Engineering Contradiction:

Improvespeed of responseVSAvoidmotor coil temperature

Core Design Contradiction:

SpeedVSTemperature

Solution Approach 1:

The control device predicts future motor current values before they occur by using estimated current trends. This preliminary prediction allows the system to take preventive action by restricting current before temperature exceeds safe limits, rather than reacting after damage occurs. The prediction mechanism calculates future current based on current motor speed, acceleration, and deceleration rates.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control device continuously monitors actual motor current, compares it with predicted future current values, and adjusts motor current restriction accordingly. This closed-loop feedback ensures that motor current is kept within safe operating ranges while maintaining optimal valve timing control performance. The feedback mechanism dynamically adjusts the restriction level based on real-time operating conditions.

Inventive Principle:

Principle #23Feedback

2Reliability

If motor current is restricted to prevent overheating, then motor durability is improved, but the speed of response of variable valve timing control becomes slow

Engineering Contradiction:

Improvemotor durabilityVSAvoidspeed of response

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The motor current restriction level is not fixed but dynamically adjusted based on predicted future current values and actual operating conditions. The control device increases restriction when predicted current exceeds safe levels and reduces restriction when conditions allow, creating a dynamic balance between protecting the motor and maintaining control responsiveness. This dynamic adjustment adapts to changing engine operating conditions in real-time.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control device changes the motor current parameter dynamically based on predicted future current values. By adjusting the current restriction level according to predicted operating conditions, the system optimizes both motor protection and control performance. The parameter change mechanism allows the system to operate at different current levels depending on the predicted thermal state of the motor.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If transient operating condition with frequent target motor speed changes continues, then valve timing adjustment flexibility is improved, but motor coil temperature exceeds allowable temperature

Engineering Contradiction:

Improvevalve timing adjustment flexibilityVSAvoidmotor coil temperature

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

The control device predicts future motor current values that will result from frequent target speed changes before they occur. By predicting the thermal impact of upcoming valve timing adjustments, the system can prevent excessive temperature accumulation by restricting current in advance, allowing flexible valve timing control without exceeding motor temperature limits.

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

Prevents motor coil temperature from exceeding safe limits, thereby preventing durability deterioration and failure, while ensuring the variable valve timing control maintains responsiveness by restricting motor current when necessary.

Implementation Method 1

a variable valve timing controller which includes an electric motor as a driving source

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Implementation Method 2

as a driving current of the motor ('motor current') increases during the variable valve timing control, the heat value of the motor increases and a coil temperature rises

Methodology Applied

Scientific EffectHeat generation: Joule Heating

Data Source

PatentUS7762222B2Variable valve timing controller for internal combustion engine

Publication Date: 2010.07.27 DENSO CORP

AI summary

A motor current (driving current of motor) is estimated based on a target motor speed, an actual motor speed, and an engine speed. When the estimated motor current exceeds the upper limit value equivalent to a heat generation limiting current, the motor current is restricted by restricting a variation (motor speed F/B amount) in target motor speed outputted to an EDU from an ECU. Thereby, the heat value of motor may not exceed the heat generation limit, and it can be prevented that the coil temperature of motor exceeds an allowable temperature range. A durability deterioration and failure of motor can be prevented.