Crank Angle Calculation for Engine Rotation Direction Detection

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Solution Overview

Problem

Existing engine rotation direction detection methods using crank angle sensors are prone to erroneous detection due to mounting errors, machining errors, and measurement errors, leading to potential engine damage and reduced restartability.

Innovation Solution

A control apparatus utilizing two crank angle sensors with a predetermined phase difference, incorporating crank angle calculation and engine-rotation-direction detection inhibit means to accurately detect engine rotation direction and inhibit controls when errors are detected, ensuring precise detection and preventing malcontrol.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the output pattern of crank angle sensors is used to detect engine rotation direction changes, then the detection frequency is high, but mounting errors and measurement errors cause erroneous detection

Engineering Contradiction:

Improvedetection frequencyVSAvoiddetection accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the detection parameter from simple output pattern recognition to crank angle calculation based on time intervals between sensor signals. By calculating the actual crank angle using the time difference between corresponding signals from two sensors, the system achieves both high detection frequency and high accuracy, eliminating erroneous detection caused by mounting errors.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical approach of direct output pattern comparison with a computational approach using time interval measurement and angle calculation. This substitution of mechanical signal interpretation with mathematical processing enables precise rotation direction detection while maintaining high response frequency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If crank angle sensors are mounted with predetermined phase difference for rotation direction detection, then the detection capability is improved, but mounting errors and component errors lead to detection inaccuracies

Engineering Contradiction:

Improverotation direction detection precisionVSAvoidsensor mounting and component tolerance

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent uses feedback by continuously monitoring the time interval between corresponding signals from two phase-differentiated sensors and calculating the crank angle in real-time. This feedback mechanism allows the system to dynamically determine rotation direction based on actual measured intervals rather than relying on fixed mounting precision, thereby compensating for manufacturing tolerances.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent performs preliminary action by pre-calculating the expected time interval for normal rotation and comparing it with actual measured intervals. This allows the system to proactively identify rotation direction changes and detect anomalies before they lead to erroneous detection or engine damage.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If rotation direction detection is performed continuously, then the restartability is enhanced, but erroneous detection may cause malcontrol and engine damage

Engineering Contradiction:

Improveengine restartabilityVSAvoidengine damage from malcontrol

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies beforehand cushioning by implementing a validation mechanism that checks whether calculated crank angles fall within expected ranges before acting on rotation direction detection results. This protective measure prevents erroneous detection from triggering incorrect control actions that could damage the engine, while still maintaining continuous monitoring for legitimate restart conditions.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS7363143B2Control apparatus for internal combustion engine

Publication Date: 2008.04.22 MITSUBISHI ELECTRIC MOBILITY CORP

AI summary

A control apparatus for an internal combustion engine, comprising crank angle calculation means for calculating a crank angle between edges which are detected by a first crank angle sensor and a second crank angle sensor, on the basis of a crank cycle between the edges, and engine-rotation-direction detection inhibit means for inhibiting detection of an engine rotation direction on the basis of the calculated crank angle, wherein the engine-rotation-direction detection inhibit means inhibits the detection of the engine rotation direction in a case where the crank angle calculated by the crank angle calculation means has satisfied a predetermined inhibit decision condition.