Outboard Motor Shift Unit Actuator Positioning
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Solution Overview
Problem
In outboard motors, the positioning of the clutch body and actuator far from each other leads to reduced accuracy and responsiveness due to rattling, deflection, or torsion in the link mechanism, resulting in a loss of driving force and difficulty in shifting the clutch body with high precision.
Innovation Solution
The outboard motor design includes a shift unit with a clutch body that reciprocates parallel to the drive shaft, a shift fork member engaged with the clutch body, and an actuator that makes a linear motion parallel to the drive shaft, with a ball screw mechanism converting rotational power into linear motion, positioning the actuator near the clutch body to minimize mechanical deviations and losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the actuator is positioned far from the clutch body to accommodate the engine layout, then the engine installation is simplified, but the link mechanism suffers from rattling, deflection, and torsion that reduce shift accuracy and responsiveness
Solution Approach 1:
The patent introduces a link mechanism comprising a shift rod and shift fork as intermediaries to transmit the actuator's driving force to the clutch body. The shift rod connects the actuator to the shift fork, which then engages with the clutch body's shift groove. This intermediary system enables flexible actuator positioning while maintaining reliable force transmission, resolving the contradiction between ease of engine installation and shift accuracy.
2Device complexity
If the link mechanism is used to transmit driving force over a long distance, then the actuator can be positioned away from the clutch body, but rattling, deflection, and torsion occur reducing responsiveness and generating friction losses
Solution Approach 1:
The patent employs a dynamic link mechanism where the shift rod and shift fork can adapt their positions and orientations during operation. The shift fork's engagement with the clutch body's shift groove allows for dynamic force transmission that compensates for potential deflections and rattling, maintaining reliability and responsiveness despite the extended transmission distance.
3Reliability
If the actuator driving force is increased to overcome link mechanism friction and reliably shift the clutch body, then shift reliability improves, but the actuator size and power requirements increase
Solution Approach 1:
The patent utilizes the curved geometry of the shift groove in the clutch body and the corresponding engagement surfaces of the shift fork to optimize force transmission. The curved engagement allows for smooth force application that minimizes friction losses and mechanical binding, enabling reliable clutch shifting with reduced actuator power requirements.
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 improves the accuracy and responsiveness of the clutch body operation, reduces the need for increased actuator force, and miniaturizes the actuator while maintaining effective force transmission, thereby enhancing the overall shifting performance.
Implementation Method 1
a ball screw mechanism that has a ball screw nut and a screw shaft and converts rotational power generated from the motor into a rectilinear motion
Data Source
AI summary
An outboard motor includes a drive shaft that transmits rotational power from the engine, and a shift unit provided in the middle of the drive shaft. The shift unit has a dog clutch that reciprocates in parallel with the drive shaft, a shift fork member that reciprocates the dog clutch in parallel with the drive shaft, and a linear motion type actuator that reciprocates the shift fork member in parallel with the drive shaft. The actuator is arranged in the vicinity of the front side of the dog clutch such that the direction of the rectilinear motion of the screw shaft is in parallel with the axial line of the drive shaft, and the shift fork member is connected to the screw shaft.