Engine Valve Timing Control Intermediate Lock State

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Solution Overview

Problem

The existing variable valve timing mechanism and intermediate lock mechanism face challenges in ensuring the engine is stopped in the correct intermediate lock state before engine shutdown, leading to potential engine startability issues and increased fuel consumption due to delayed engine stopping processes.

Innovation Solution

The engine valve timing control apparatus detects and confirms the intermediate lock state upon an engine stop request, executing the stopping process within a predetermined time frame to ensure the engine is stopped in the correct state, and continues monitoring the lock state after shutdown to improve detection accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the engine stop request is detected and the stopping process is executed immediately, then the responsiveness is improved, but the engine may stop at an incorrect rotation phase leading to poor startability

Engineering Contradiction:

Improveresponsiveness of engine stopVSAvoidengine startability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The intermediate lock mechanism is activated in advance before the engine stop request is executed. The lock piece is positioned to engage with the engaged groove at the intermediate lock position, preparing the rotor assembly to be restrained at the correct rotation phase. This preliminary locking action ensures that when the engine stops, it does so at the intermediate lock position suitable for starting, thereby improving engine startability without delaying the stop response.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the intermediate lock state is monitored and confirmed before executing engine stop, then engine startability is improved, but the time delay increases causing driver discomfort

Engineering Contradiction:

Improveengine startabilityVSAvoidtime delay in engine stop

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the variable valve timing mechanism and intermediate lock mechanism are driven closer to intermediate lock state before engine stop, then engine startability is improved, but hydraulic pressure may be insufficient leading to incomplete positioning

Engineering Contradiction:

Improveengine startabilityVSAvoidpositioning accuracy of valve timing

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The intermediate lock mechanism acts as an intermediary device that mechanically restrains the rotor assembly at the intermediate lock position using a lock piece and engaged groove. This mechanical locking provides a reliable position reference that does not depend on hydraulic pressure, ensuring accurate positioning even when hydraulic pressure is insufficient during engine stop.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Manufacturing precision

If the engine stop request is detected and the stopping process is delayed to ensure intermediate lock state, then positioning accuracy is improved, but fuel consumption increases due to unnecessary engine running

Engineering Contradiction:

Improvepositioning accuracy of valve timingVSAvoidfuel consumption

Core Design Contradiction:

Manufacturing precisionVSUse of energy by moving object

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP2743479B1Engine valve timing control apparatus

Publication Date: 2015.09.23 NISSAN MOTOR CO LTD

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Figure 2(A)~2(D)
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AI summary

In order to achieve an intermediate lock state in a short period when an engine is stopped and improve the accuracy of confirmation of the intermediate lock state, an engine valve timing control apparatus includes a variable valve timing mechanism capable of varying valve timing of an intake/exhaust valve, and an intermediate lock mechanism capable of restricting relative rotation positions of a first and a second rotor of the variable valve timing mechanism at an intermediate lock position for starting the engine. When an engine stop request is detected, the variable valve timing mechanism and the intermediate lock mechanism are driven and controlled such that an intermediate lock state is established before the engine is stopped (S12). When the intermediate lock state is detected within a predetermined period from the detection of the engine stop request, or when the predetermined period has expired from the detection of the engine stop request, an engine stopping process is performed (S13 to S16). Even after the engine stopping process is performed, monitoring of the intermediate lock state is continued, until the engine speed is less than a predetermined value NEmin (S17 to S19).