Carburetor Roller Control Contour for Precise Position Detection

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Solution Overview

Problem

Existing carburetors for hand-held internal combustion engines lack precise detection of rotational positions, leading to inefficiencies in fuel metering and engine control.

Innovation Solution

A carburetor design featuring a control contour on the carburetor cylinder that interacts with a detection means, generating an electrical signal for precise rotational position detection, allowing for accurate fuel supply and engine control through an evaluation unit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a rotational position sensor is arranged at one end of the carburetor cylinder, then the rotational position can be detected, but the construction becomes complex and tolerances between the sensor and carburetor cylinder increase

Engineering Contradiction:
Improverotational position detection precisionVSAvoidcarburetor construction complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The control contour is integrated directly into the carburetor cylinder body, merging the detection feature with the structural component. This eliminates the need for separate sensors and reduces assembly complexity while maintaining detection precision through direct mechanical interaction.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The control contour acts as an intermediary element that translates rotational position into a detectable mechanical signal. By forming the contour directly on the carburetor cylinder, it serves as both a structural feature and a detection interface, eliminating the need for additional sensing components.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Manufacturing precision

If the control contour is formed directly on the carburetor cylinder, then tolerances between the control contour and carburetor cylinder are minimized, but the manufacturing precision requirements increase

Engineering Contradiction:
Improvetolerance between control contour and carburetor cylinderVSAvoidcarburetor cylinder manufacturing complexity
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The carburetor cylinder is segmented into functional zones, with the control contour formed as a distinct feature on the cylinder body. This segmentation allows the contour to be optimized for detection while the rest of the cylinder maintains standard manufacturing tolerances, balancing precision requirements with manufacturability.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The control contour is created with high precision only in the specific local area where detection is required, while the rest of the carburetor cylinder can be manufactured with standard tolerances. This localized approach to precision reduces overall manufacturing complexity while ensuring accurate detection performance.

Inventive Principle:
Principle #3Local quality

3Measurement precision

If the detection means scans the control contour, then rotational position can be detected with high accuracy, but the device complexity increases

Engineering Contradiction:
Improverotational position detection accuracyVSAvoiddetection device complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The control contour is designed to be self-detecting through its geometric configuration. The contour's shape and position encode the rotational information directly, allowing simple mechanical or optical scanning to read the position without complex electronic sensors or processing systems.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The control contour is designed so that the detection means can scan it with constant, simple geometry throughout the rotation cycle. This equipotential design ensures that the detection process remains equally simple at all rotational positions, avoiding the need for complex variable-geometry sensing systems.

Inventive Principle:
Principle #12Equipotentiality

Data Source

PatentEP3511552B1Carburator for the combustion engine in a hand-held work device, combustion engine with a carburator and method for operating a combustion engine
Publication Date: 2021.03.31 ANDREAS STIHL AG & CO KG
  • EP3511552B1 patent drawingFigure 1~2
  • EP3511552B1 patent drawingFigure 3~5
  • EP3511552B1 patent drawingFigure 6~8

AI summary

A carburetor (18) for the internal combustion engine (1) in a hand-held implement has a carburetor housing (19) in which a carburetor roller (20) is rotatably mounted about a pivot axis (35). The carburetor roller (20) has a roller body (54) which has at least one channel (33, 34) extending transversely to the pivot axis (35), forming an intake channel section. A detection device (55) is provided for detecting at least one rotational position of the carburetor roller (20). The detection device (55) comprises a control contour (57) and a detection means (56) that interacts with the control contour (57). The control contour (57) is formed on the carburetor roller (20). A method for operating an internal combustion engine (19) provides that the control device (45) controls the amount of fuel supplied depending on the rotational position of the carburetor roller (20) detected by the detection device (55).