Engine Control Device Hunting Prevention

Solution Overview

Problem

Existing engine control devices experience frequent hunting between fuel cut-off and fuel cut-off recovery during downhill coasting, as the techniques currently available are insufficient to prevent this repetition effectively.

Innovation Solution

An engine control device with a sensor system and controller that sets a hunting-preventing fuel cut-off rotational speed higher than the standard cut-off speed but lower than or equal to the transmission input shaft rotational speed, allowing for controlled stop and restart of fuel injection based on vehicle operating conditions, thereby preventing engine rotational speed from exceeding the cut-off threshold.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the fuel cut-off rotational speed is increased to suppress hunting between fuel cut-off and recovery, then the hunting frequency is reduced, but the fuel economy deteriorates due to repeated fuel injection and cutoff cycles

Engineering Contradiction:

Improvestability of fuel cut-off controlVSAvoidfuel economy

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The fuel cut-off rotational speed is made dynamic rather than fixed. The controller adjusts the fuel cut-off rotational speed based on the relationship between engine rotational speed and transmission input shaft rotational speed. When the engine speed approaches the transmission input shaft speed (indicating steep downhill coasting), the fuel cut-off rotational speed is increased to prevent hunting. This dynamic adjustment resolves the contradiction by adapting the control parameter to operating conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the parameter of fuel cut-off rotational speed based on the ratio between engine rotational speed and transmission input shaft rotational speed. By monitoring this ratio and adjusting the fuel cut-off threshold accordingly, the system prevents hunting on steep downhills while maintaining normal fuel economy characteristics during regular coasting operations.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the fuel cut-off rotational speed is set high to prevent hunting on steep downhill, then the hunting is prevented, but the engine rotational speed may exceed the cut-off threshold causing instability

Engineering Contradiction:

Improveprevention of huntingVSAvoidengine operational stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The controller continuously monitors the relationship between engine rotational speed and transmission input shaft rotational speed, and uses this feedback to dynamically adjust the fuel cut-off rotational speed. This feedback mechanism ensures that the fuel cut-off threshold is appropriately set to prevent hunting while maintaining engine stability, resolving the contradiction between preventing hunting and maintaining operational stability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The fuel cut-off rotational speed is made dynamic rather than fixed. The controller adjusts the fuel cut-off rotational speed based on the relationship between engine rotational speed and transmission input shaft rotational speed. When the engine speed approaches the transmission input shaft speed (indicating steep downhill coasting), the fuel cut-off rotational speed is increased to prevent hunting. This dynamic adjustment resolves the contradiction by adapting the control parameter to operating conditions.

Inventive Principle:

Principle #15Dynamics

3Productivity

If the standard fuel cut-off control is used during downhill coasting, then the fuel injection is stopped at the preset speed, but the hunting between fuel cut-off and recovery repeats frequently

Engineering Contradiction:

Improvefuel cut-off control efficiencyVSAvoidstability of engine operation

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The fuel cut-off rotational speed is made dynamic rather than fixed. The controller adjusts the fuel cut-off rotational speed based on the relationship between engine rotational speed and transmission input shaft rotational speed. When the engine speed approaches the transmission input shaft speed (indicating steep downhill coasting), the fuel cut-off rotational speed is increased to prevent hunting. This dynamic adjustment resolves the contradiction by adapting the control parameter to operating conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The transmission input shaft rotational speed serves as an intermediary parameter to detect the coasting condition and steepness of the downhill. By using this intermediary measurement, the controller can indirectly determine when hunting is likely to occur and adjust the fuel cut-off control accordingly, improving both stability and control efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP2290214B1Engine control device

Publication Date: 2019.01.16 NISSAN MOTOR CO LTD

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AI summary

In a vehicle in which an output of an engine is transmitted to a driving wheel through a transmission, an engine control device stops fuel injection of the engine, when engine rotational speed is above a preset specific fuel cut-off rotational speed while the vehicle is coasting; and restarts the fuel injection, when the engine rotational speed falls below a recovery rotational speed while the fuel injection is stopped, wherein the recovery rotational speed is below the specific fuel cut-off rotational speed. When determining that an operating state allows the stop and restart of fuel injection to be repeated, the engine control device sets a hunting-preventing fuel cut-off rotational speed based on an input shaft rotational speed of the transmission, wherein the hunting-preventing fuel cut-off rotational speed replaces the specific fuel cut-off rotational speed.