Dual-Spring Governor Control for Low-Speed Engine Noise
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Solution Overview
Problem
Conventional engine control systems for small displacement engines face challenges in starting and under-load operation at low speeds, leading to noise and increased fuel consumption, particularly due to difficulties in controlling the air/fuel ratio across varying temperatures.
Innovation Solution
An engine control system with a governor lever, control lever, governor spring, and automatic choke device, where a subsidiary spring with a smaller spring constant than the governor spring allows for adjustable throttle control, enabling low-speed starting and operation, and precise air/fuel ratio management through the automatic choke device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a relatively large spring constant is imparted to the governor spring to bring the engine into a high-speed operation state from start, then the engine can start and operate at high speeds, but the engine rotational speed cannot be set low during starting and under-load operation, leading to increased noise
Solution Approach 1:
The patent divides the single governor spring function into two separate springs: a governor spring for high-speed operation and a subsidiary spring for low-speed operation. This segmentation allows independent control of spring constants for different operating conditions, enabling low-speed starting (reducing noise) while maintaining high-speed capability when needed.
Solution Approach 2:
The patent makes the spring constant dynamically adjustable by providing two different springs that can be selected based on operating conditions. The control lever can switch between connecting to the governor spring alone (high-speed mode) or the subsidiary spring alone (low-speed mode), allowing the engine speed to be dynamically adapted to minimize noise during starting and under-load operation.
2Reliability
If the air/fuel ratio is set low (rich) by carburetor adjustment to obtain excellent low-temperature starting performance, then the engine starts well at low temperatures, but the air/fuel ratio becomes excessively low in high-temperature operation, leading to operational disorder and increased fuel consumption
Solution Approach 1:
The patent dynamically adjusts the air/fuel ratio by switching between two spring configurations. During cold starting, the subsidiary spring maintains a low air/fuel ratio for reliable starting. As temperature increases, the system can switch to the governor spring configuration that allows the automatic choke device to progressively enrich the mixture, preventing excessively lean conditions at high temperatures and reducing fuel consumption.
Solution Approach 2:
The patent introduces the automatic choke device as an intermediary mechanism that works in conjunction with the dual-spring system. The choke device provides fine-adjustment control of the air/fuel ratio based on temperature changes, mediating between the coarse adjustments provided by the two spring configurations to achieve optimal air/fuel ratio across the entire temperature range.
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
Enables smooth low-speed starting and under-load operation, stabilizes engine speed, and reduces fuel consumption by adjusting the air/fuel ratio in response to temperature changes, maintaining silencing performance and promoting efficient engine operation.
Implementation Method 1
a governor spring which is expandedly provided between the control lever and the governor lever, and which increases an urging force for rotating the governor lever in a direction to open the throttle valve; a subsidiary spring is provided between the fixed structure and the governor lever so as to constantly urge the governor lever in a direction to open the throttle valve
Implementation Method 2
a governor which increases a thrust for rotating the governor lever in a direction to close the throttle valve in accordance with an increase in an engine rotational speed
Data Source
AI summary
An engine control device includes a governor lever, a centrifugal governor, a control lever operated to oscillate between a low-speed position and a high-speed position, and a governor spring expandedly provided between the control lever and the governor lever. An automatic choke device is connected to a choke valve of a carburetor. A play is provided between the governor lever and the governor spring. The play holds the governor spring in a free state during rotation of the control lever from the low-speed position to the high-speed position by a predetermined angle. A subsidiary spring is provided between a fixed structure and the governor lever so as to constantly urge the governor lever in a direction to open the throttle valve. A spring constant of the subsidiary spring is smaller than that of the governor spring. Thus, there is provided the engine control system with the automatic choke device, which can meticulously control an air/fuel ratio from start of an engine to under-load operation of the engine in accordance with increase and decrease in temperature of the engine.