Asymmetrical Fuel Retainer for Tilted Hand-Held Engine
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Solution Overview
Problem
Hand-held power tools with internal combustion engines face issues when tilted, as fuel can accumulate and flow into the overflow channel, leading to an excessive fuel/air mixture and engine malfunction, existing solutions like slat-shaped fuel retainers are inadequate as they collect fuel without controlled drainage.
Innovation Solution
Asymmetrical fuel retention devices with specific angular configurations prevent fuel from entering the overflow channel while allowing it to flow freely in the opposite direction, ensuring reliable engine operation regardless of tool position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If slat-shaped fuel retainers with rectangular cross-section are arranged on the crankcase wall, then fuel flow towards the inlet window is inhibited, but fuel accumulates on the retainers and eventually flows into the overflow channel uncontrolled
Solution Approach 1:
The fuel retainer is designed with an asymmetrical cross-section where one flank (facing away from inlet window) has a smaller angle to the radial direction than the other flank (facing inlet window). This asymmetry creates directional control: the steeper first flank effectively blocks fuel flow towards the inlet window, while the flatter second flank allows accumulated fuel to drain controlledly away from the overflow channel
Solution Approach 2:
Different flanks of the fuel retainer have different geometric properties tailored to specific functions: the first flank is designed with a smaller angle (steeper) for effective fuel blocking, while the second flank has a larger angle (flatter) for controlled drainage. This local differentiation of geometric quality enables the retainer to simultaneously perform retention and controlled release functions
2Adaptability or versatility
If the hand-held device is tilted out of working position, then fuel accumulates at the lowest point of the crankcase, but fuel flows through the inlet window into the overflow channel causing engine malfunction
Solution Approach 1:
The asymmetrical cross-section of the fuel retainer, with its differently angled flanks, provides position-independent fuel control. The geometric design ensures that regardless of device orientation, fuel is blocked from entering the overflow channel while maintaining proper fuel/air mixture supply to the combustion chamber
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
The asymmetrical design effectively inhibits fuel entry into the overflow channel, maintaining desired atomization and preventing engine stoppages, even when the tool is tilted, thus ensuring operational safety and efficient engine performance.
Implementation Method 1
Under certain operating conditions, fuel may separate from the finely atomized fuel/air mixture and collect at the bottom of the crankcase. In such a tilted position, it can happen that fuel that has accumulated at the lowest point of the crankcase flows through the inlet window into the overflow channel.
Data Source
AI summary
The invention relates to an internal combustion engine (2) of a hand-held power tool (1) and to a hand-held power tool with such an internal combustion engine (2). The internal combustion engine (2) has a crankcase (4), a crankshaft (5) rotatably mounted in the crankcase (4) about an axis of rotation (D), a combustion chamber (6), and at least one transfer port (7) leading from the crankcase (4) to the combustion chamber (6). The transfer port (7) opens into the crankcase (4) by means of an inlet window (8). The crankcase (4) has a circumferential wall (9) extending in a circumferential direction (U), the circumferential wall (9) being provided with at least one fuel retention device (10). A radial direction (R) extends from the axis of rotation (D) through the fuel retention device (10). The fuel retention device (10) extends in the radial direction (R) and in the circumferential direction (U).The fuel retention device (10) has a cross-section that is asymmetrical in the circumferential direction (U) with respect to the radial direction (R).