Cam-Actuated Carburetor Starting System for Internal Combustion Engines
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Solution Overview
Problem
Existing starting systems for internal combustion engines, particularly those in outdoor power equipment, require manual actuation of the carburetor's starting feature, which can complicate the starting process and reduce efficiency.
Innovation Solution
A starting system that automatically actuates the carburetor's starting feature using a cam with a sealed ball bearing mounted on the crankshaft, a spring-loaded pawl, a rocker arm, and a throttle cable, allowing the system to engage and disengage the carburetor's choke valve based on engine RPMs to facilitate easier engine starting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual actuation of the carburetor's starting feature is required, then the structure remains simple, but the starting process becomes complicated and efficiency reduces
Solution Approach 1:
The system uses the engine's own rotational motion to automatically actuate the starting feature. The cam mechanism converts the crankshaft rotation into the necessary motion to open and close the choke valve, eliminating the need for manual intervention while using the engine's inherent energy.
Solution Approach 2:
The cam mechanism is pre-configured with bosses and lobes that automatically perform the choke valve actuation before the engine reaches full operating speed. The spring-loaded pawl ensures the valve is opened in advance during the starting sequence, preparing the fuel mixture before the engine is fully running.
2Productivity
If a cam mechanism with pawl is used to automatically actuate the starting feature, then the starting efficiency improves, but the device complexity increases
Solution Approach 1:
The cam mechanism serves multiple functions: it acts as a starting feature actuator, a speed regulator during starting, and a mechanical linkage between the crankshaft and throttle cable. This multi-functionality reduces the need for separate components, offsetting the added complexity.
Solution Approach 2:
The cam mechanism acts as an intermediary between the crankshaft rotation and the throttle cable actuation. It translates the rotational motion into the specific motion required for the starting feature, providing a mechanical bridge that improves control and efficiency.
3Reliability
If the choke valve is manually controlled, then the system remains simple, but the fuel mixture consistency during starting becomes unreliable
Solution Approach 1:
The cam mechanism provides automatic feedback based on the engine's rotational position and speed. The spring-loaded pawl and cam lobes ensure the choke valve opens and closes at the appropriate moments during the starting sequence, maintaining consistent fuel mixture ratios without manual intervention.
Solution Approach 2:
The system dynamically adjusts the choke valve position based on the engine's starting conditions. The cam mechanism responds to the changing rotational speed and position during starting, automatically optimizing the fuel mixture consistency throughout the starting process.
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
Automatically actuates the carburetor's starting feature, reducing the effort required to start the engine and ensuring a consistent fuel mixture is drawn in during the starting process, improving the engine's start-up efficiency and reliability.
Implementation Method 1
A spring-loaded pawl is mounted on the flywheel. The pawl is biased radially inward and configured to engage a cam boss when in an inwardly biased position so as to cause the cam to rotate with the crankshaft.
Implementation Method 2
A rocker arm is pivotally mounted adjacent the cam. The rocker arm has a spring loaded roller assembly configured to ride on the outer surface of the cam. As the cam rotates, the roller assembly riding on the cam surface is pushed outward by the cam lobe.
Data Source
AI summary
A starting system for an internal combustion engine automatically operates a starting feature on a carburetor associated with the engine. The starting system includes a cam with a bearing mounted on the crankshaft. The bearing is secured so that its inner race will always rotate with the crankshaft. The cam has bosses on one side and is shaped such that it includes a base and a lobe with an outer surface surrounding the cam. At least one spring-loaded pawl is mounted on the flywheel. The pawl is biased to engage a cam boss so as to cause the cam to rotate with the crankshaft during a start-up process. A spring loaded rocker arm is pivotally mounted adjacent the cam. The rocker arm has a roller assembly configured to ride on the outer surface of the cam. As the cam rotates, the roller assembly riding on the cam surface is pushed outward by the cam lobe. A throttle cable is attached at a first end to the rocker arm and at its opposite end to the starting feature on the carburetor. When the roller assembly ramps up the lobe, the throttle cable is pulled into an extended position to actuate the starting feature of the carburetor.