Hybrid Throttle Valve Control for Low-Emission Engine Speed Limiting
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Solution Overview
Problem
Existing methods for controlling two-stroke combustion engine speed in handheld power tools, such as ignition cut-out, result in increased emissions and vibrations, necessitating alternative speed control mechanisms.
Innovation Solution
A throttle valve arrangement with a first electrically operated actuator and a second manually operated actuator, allowing for automated engine speed restriction without ignition cut-out, where the first actuator biases the valve shaft towards a configurable angle and the second actuator resists rotation past that angle, enabling hybrid control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If ignition cut-out is used to limit engine speed, then engine speed is restricted below maximum speed, but emissions increase and vibrations occur
Solution Approach 1:
The patent replaces the ignition cut-out method (electrical/engine control) with a mechanical throttle valve control system. The automated electrically operated actuator mechanically adjusts the throttle valve position to limit engine speed by restricting air intake, rather than cutting out ignition. This mechanical substitution eliminates the harmful effects of ignition cut-out while achieving the same speed limitation goal.
Solution Approach 2:
The patent introduces a throttle valve as an intermediary mechanism between the operator/automated system and the engine. The throttle valve, controlled by actuators, mediates the air intake to the engine, providing a smooth and gradual speed control mechanism that avoids the abrupt cutoff and associated harmful effects of direct ignition cut-out.
2Object-generated harmful factors
If automated electrically operated actuator is used to control throttle valve, then engine speed restriction is achieved without ignition cut-out, but device complexity increases
Solution Approach 1:
The patent designs the throttle valve control system to perform multiple functions: it can be manually operated by the user, automatically controlled by an electrically operated actuator, or have both modes combined. This multi-functionality allows the same hardware system to achieve speed restriction without ignition cut-out while providing operational flexibility, thereby justifying the increased complexity through enhanced capability.
Solution Approach 2:
The patent implements a dynamic control system where the throttle valve position can be adjusted in real-time based on operational requirements. The automated actuator can dynamically modify the throttle opening to maintain optimal engine speed, and the system can transition between manual and automated control modes, making the complexity worthwhile through adaptive performance.
3Extent of automation
If first actuator biases valve shaft towards configurable angle, then automated throttle restriction is enabled, but ease of operation is reduced
Solution Approach 1:
The patent segments the control authority between two actuators: the first actuator (automated electrically operated) controls the biasing torque towards a configurable angle, while the second actuator (manual) provides resistance or assistance as needed. This segmentation allows automated speed restriction while preserving manual override capability, dividing the control function to maintain ease of operation despite automation.
Solution Approach 2:
The patent applies different control qualities to different aspects of throttle operation. The automated first actuator provides precise control for speed restriction at the configurable angle, while the manual second actuator maintains direct operator control for immediate responses. This local differentiation of control quality ensures both automation benefits and operational ease are preserved in their respective domains.
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
Provides robust and efficient engine speed regulation, reducing emissions and vibrations by allowing manual and automated throttle control, ensuring engine speed can be safely reduced to idle even if the automated actuator malfunctions.
Implementation Method 1
The first actuator comprises a first actuator member that is arranged to engage a first torsion spring. The first torsion spring is configured to apply a biasing torque to a first shaft lever attached to the valve shaft.
Implementation Method 2
A second torsion spring is arranged to urge rotation of the second actuator member towards engagement with the second shaft lever
Data Source
AI summary
A throttle valve arrangement for a handheld power tool, the throttle valve arrangement comprising a valve plate attached to a valve shaft, the valve shaft being arranged to rotate about a valve shaft axis from an idle throttle position to a wide open throttle, WOT, position, wherein the rotation of the valve shaft about the valve shaft axis is arranged to be biased towards a configurable valve shaft angle by a first actuator, wherein a second actuator of the throttle arrangement is arranged to resist rotation of the valve shaft about the valve shaft axis towards the WOT position, past an angle determined by a state of the second actuator.