Electronic Throttle RPM Control for Spark-Ignition Engines
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Solution Overview
Problem
Spark-ignition engines used as general-purpose engines face challenges in achieving output characteristics similar to diesel engines and maintaining operational feel without discomfort, especially in controlling engine rpm accurately, as conventional mechanical governors compromise responsiveness and stability.
Innovation Solution
An rpm control device for spark-ignition engines using an electronic throttle to control intake air, incorporating sensors for rpm, intake air temperature, and pressure, along with an engine load detection system, calculates a target rpm decrease rate to perform pseudo-droop control through isochronous control, ensuring accurate rpm reduction with increasing load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a mechanical governor mechanism is used for rpm control in spark-ignition engines, then steady stability is improved, but responsiveness is degraded
Solution Approach 1:
The patent replaces the mechanical governor mechanism with an electronic control system that uses sensors to detect engine parameters (intake air amount, rpm, engine load) and an electronic control unit to calculate and control the throttle valve opening degree. This substitution eliminates the mechanical linkage delays while maintaining stable control through electronic feedback, thereby improving responsiveness without sacrificing steady stability.
2Speed
If responsiveness is prioritized in rpm control, then acceleration response is improved, but steady stability is lowered
Solution Approach 1:
The patent implements a feedback control system where sensors continuously monitor engine parameters (intake air amount, rpm, engine load) and feed this information to the electronic control unit. The ECU calculates the optimal throttle opening degree based on this feedback and adjusts the throttle valve accordingly. This closed-loop feedback mechanism enables the system to respond quickly to changes while maintaining steady stability through continuous correction, resolving the contradiction between responsiveness and stability.
3Measurement precision
If isochronous control is used to maintain target rpm accurately, then rpm control accuracy is improved, but operational comfort is degraded due to sudden acceleration or deceleration
Solution Approach 1:
The patent introduces a target decrease rate parameter that modifies the target rpm based on engine load conditions. Instead of maintaining a fixed target rpm, the system dynamically adjusts the target rpm downward according to the calculated engine load and predetermined target decrease rates. This parameter change allows the engine to operate at slightly lower speeds under load, reducing the harshness of acceleration and deceleration while maintaining accurate control, thereby improving operational comfort without sacrificing control accuracy.
Data Source
AI summary
Provided is an rpm control device for a general-purpose engine, which is capable of realizing droop control in a spark-ignition engine only by the adaptation of isochronous control. When the droop control is selected, a rotation decrease rate (K) (value equal to or smaller than 1) is obtained from an engine rpm and a load. The result of multiplication of a basic target rpm (Nb) requested by a driver by the rotation decrease rate (K) is obtained as a target rpm (No). By setting the rotation decrease rate to a smaller value as the load becomes higher, the target rpm (No) is set smaller than the basic target rpm (Nb). The isochronous control is performed by using an electronic throttle so as to achieve the obtained target rpm (No) to realize the droop control in a pseudo-manner.