Crankshaft Position Control for Straddled Vehicle Engine Restart

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Straddled vehicles equipped with four-stroke single-cylinder engines face challenges in reducing the time period to restart after combustion stop while minimizing starter motor power consumption, due to variations in crankshaft stop position caused by engine temperature and atmospheric pressure changes.

Innovation Solution

A straddled vehicle engine unit incorporating a permanent magnet type rotary electric machine and an inverter with a control device that adjusts the braking force based on both the position and instantaneous speed of the crankshaft, allowing precise control to maintain a low rotational load, thus reducing power consumption and restart time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the output torque of the starter motor is increased to cover the torque variation, then the engine can be restarted regardless of crankshaft stop position, but the power consumption of the starter motor increases

Engineering Contradiction:

Improveengine restart capabilityVSAvoidpower consumption of starter motor

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The control device performs preliminary action by detecting the crankshaft stop position before engine restart and actively controlling the crankshaft to move to a predetermined position (where rotational load is low) before the actual restart operation. This preliminary repositioning avoids the need for excessive torque capacity and reduces starter motor power consumption during restart.

Inventive Principle:

Principle #10Preliminary action

2Use of energy by moving object

If the crankshaft is driven in reverse rotation to a position with low rotational load, then the power consumption of the starter motor is reduced, but the time period until engine restart is prolonged

Engineering Contradiction:

Improvepower consumption of starter motorVSAvoidtime period until engine restart

Core Design Contradiction:

Use of energy by moving objectVSLoss of time

Solution Approach 1:

The control device applies dynamic control by continuously monitoring the crankshaft position and rotation speed, and adjusting the starter motor output in real-time. The braking force is dynamically changed based on detected position and speed to achieve precise control of the crankshaft stop position, optimizing both time and energy efficiency.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control device uses feedback from position detection means and rotation speed detection to actively control the crankshaft movement. The detected crankshaft position and rotation speed are fed back to the control device, which adjusts the starter motor operation accordingly to achieve precise positioning while minimizing time and energy consumption.

Inventive Principle:

Principle #23Feedback

3Stability of the object's composition

If the braking force is changed based on crankshaft position and rotation speed, then the crankshaft stop position variation is suppressed, but the control system complexity increases

Engineering Contradiction:

Improvecrankshaft stop position consistencyVSAvoidcontrol system complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces complex mechanical positioning mechanisms with an electronic control system that uses sensors (position detection means, rotation speed detection) and electronic control to achieve precise crankshaft positioning. This substitution of mechanical systems with electronic control and sensing reduces overall system complexity while improving precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 configuration effectively suppresses variations in the crankshaft stop position, reducing the time to restart the engine while minimizing power consumption, by applying a braking force that reflects the engine's state, thereby optimizing the restart process.

Implementation Method 1

a permanent magnet type rotary electric machine including a permanent magnet, a rotor, and a stator, the rotor connected to the crankshaft so as to be rotatable with its speed ratio fixed relative to the crankshaft

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Data Source

PatentEP3315764B1Straddled vehicle mounting an engine unit

Publication Date: 2021.04.07 YAMAHA MOTOR CO LTD

Figure 1
Figure 2
Figure 3

AI summary

An engine unit includes a four-stroke single-cylinder engine body, a permanent magnet type rotary electric machine, an inverter including switching parts, and a control device. The control device configured to: perform a stop control of controlling the plurality of switching parts such that a braking force is applied to forward rotation of a crankshaft in at least part of a time period during which the crankshaft continues forward rotation after stop of a combustion operation and until the crankshaft stops the forward rotation; and change the braking force at least once during the stop control, by changing an operation timing of the plurality of switching parts based on both a position of the crankshaft and an instantaneous value of the rotation speed of the crankshaft at the position.