Membrane Carburetor Acceleration Pump Hydraulic Actuation
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Solution Overview
Problem
Existing membrane carburetors for portable handheld work apparatuses, such as chain saws and brushcutters, experience instability and increased exhaust-gas values due to air bubbles collecting in the acceleration pump chamber, leading to inconsistent engine performance over longer operating times.
Innovation Solution
The membrane carburetor design includes an acceleration pump that operates hydraulically on an actuating member within the control chamber, preventing air bubbles from entering the intake channel and ensuring stable fuel supply by using a scavenging pump to fill the pump chamber with fuel before engine start and a check valve for rapid scavenging during deceleration, thus avoiding air bubble introduction and maintaining consistent fuel delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the acceleration pump pumps fuel directly into the control chamber or fuel openings, then acceleration enrichment is achieved, but air bubbles collect in the pump chamber and are moved into the intake channel during acceleration operations, causing instability in engine running performance and increased exhaust-gas values
Solution Approach 1:
The invention introduces an intermediary actuating member (piston or diaphragm) in the control chamber that is actuated by the acceleration pump. The pump chamber connects to the control chamber via a control line, and the actuating member transmits the hydraulic action to the inlet valve or control membrane. This intermediary system prevents direct pumping of fuel (and air bubbles) into the control chamber while still achieving acceleration enrichment through the actuation of the inlet valve.
2Device complexity
If the pump chamber volume remains unchanged during constant operation, then the acceleration pump structure is simple, but air bubbles collect in the pump chamber during longer operating times and cause instability
Solution Approach 1:
The invention extracts the air bubble problem from the fuel supply system by providing a separate venting path. The control line connecting the pump chamber to the control chamber includes a vent opening that allows air bubbles to escape from the pump chamber without being pumped into the intake channel. This maintains the simple pump chamber structure while eliminating the reliability issue caused by air bubble accumulation.
3Ease of operation
If the acceleration pump acts directly on fuel in the control chamber, then fuel quantity control is direct, but the pump chamber becomes a dead space where air bubbles accumulate and cannot be removed
Solution Approach 1:
The invention segments the system into distinct functional zones: the pump chamber for generating hydraulic pressure, the control line for transmitting pressure, and the control chamber for fuel metering. The actuating member is positioned in the control chamber but is actuated through the control line from the pump chamber. This segmentation allows the pump chamber to serve as a pressure source without being a fuel storage space, enabling air bubbles to vent while maintaining direct fuel quantity control through the actuating member's influence on the inlet valve.
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
This design stabilizes engine performance by preventing air bubble-induced instability and ensuring consistent fuel supply, reducing exhaust-gas values and maintaining efficient operation over extended periods.
Implementation Method 1
the accelerator pump being hydraulically connected to the actuating member in the control chamber so as to be able to act hydraulically on the actuating member
Implementation Method 2
a deflectable control membrane delimiting the control chamber; the control membrane being operatively connected to the inlet valve so as to open in dependence upon deflections of the control membrane
Implementation Method 3
the pump chamber being connected via a first suction line to a scavenging pump
Implementation Method 4
In the second suction line, a check valve is mounted which opens in the flow direction toward the pump chamber
Data Source
AI summary
A membrane carburetor (1) has a control chamber (13) which is connected via at least one fuel opening (9, 10) to an intake channel (3). The control chamber (13) is delimited by a control membrane (14). A fuel line (54) opens into the control chamber (13) via an inlet valve (15). The inlet valve (15) opens in dependence upon the deflection of the control membrane (14). The membrane carburetor (1) has an acceleration pump (30) which is actuated in dependence upon the position of a throttle element held in the intake channel (3). A good acceleration enrichment and a stable running of the internal combustion engine are achieved when the acceleration pump (30) operates hydraulically on at least one actuating member in the control chamber (13).