Boat Drive Unit Axial Oil Distribution for Seal Reliability
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Solution Overview
Problem
The existing drive units for stern-drive boats face seal problems due to high-pressure pressurized oil used in clutch engagement mechanisms, which overheats mechanical seals when the engine shaft rotates at high speeds, making radial connectors unsuitable for oil distribution.
Innovation Solution
A single axial pipe introduces pressurized oil into the engine shaft, with a rotating distributor directing it alternately to separate pipes for the two clutches, minimizing relative speed and allowing for low-speed axial connection despite high pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radial connectors are used to convey pressurized oil to clutches, then oil distribution is achieved, but mechanical seals overheat due to high slide speed at engine shaft rotation
Solution Approach 1:
A rotating distributor acts as an intermediary component between the stationary oil supply and the moving clutches. The distributor rotates with the engine shaft and contains internal passages that direct pressurized oil to the appropriate clutch, eliminating the need for mechanical seals at high-speed interfaces.
Solution Approach 2:
The oil distribution problem is solved by transitioning from a radial connection approach to an axial connection approach. The single axial pipe connects to the rotating distributor, which then distributes oil radially to clutches through internal passages, effectively changing the dimensional approach to oil delivery.
2Adaptability or versatility
If multiple oil feed pipes are provided at the shaft head, then all oil inlets are accommodated, but the complexity of oil distribution system increases
Solution Approach 1:
Multiple oil feed functions are merged into a single axial pipe that supplies oil to the rotating distributor. The distributor then performs the function of distributing oil to multiple clutches through its internal passages, consolidating what would otherwise require multiple separate connection points.
Solution Approach 2:
The rotating distributor serves multiple functions: it rotates with the engine shaft, receives pressurized oil through a single axial connection, stores oil in its internal passages, and distributes oil to both clutches. This multi-functional component eliminates the need for separate specialized connections for each oil inlet.
3Reliability
If a single axial pipe is used to introduce pressurized oil, then seal problems are eliminated, but the distribution of oil to rotating clutches becomes more complex
Solution Approach 1:
The distributor is designed to rotate dynamically with the engine shaft, maintaining continuous oil supply to the clutches regardless of their rotational position. The internal passages of the distributor are positioned and sized to ensure proper oil flow dynamics during rotation, accounting for centrifugal forces and pressure gradients.
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 solution effectively addresses seal issues by reducing the relative speed at the oil input point, enabling reliable oil distribution and clutch engagement without overheating, thus enhancing the operational efficiency and compactness of the drive unit.
Implementation Method 1
a distributor formed on said shaft rotates together with the shaft and directs oil alternately towards two separate pipes leading to the control systems of the two clutches
Data Source
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AI summary
This invention relates to a drive unit of the type comprising a transmission with two coaxial bevel gears (11, 12) fitted opposite one another on the same engine shaft (10), which engage a bevel gear (13) fitted to a shaft (14) perpendicular to the preceding one, and means designed to mesh said engine shaft with one or other of said bevel gears, constituted by clutches (20, 21) housed in the body of said bevel gears (12, 11) and controlled by a pressurised fluid, wherein pipes (24, 25), designed to convey said pressurised fluid, are formed in said engine shaft (10), characterised in that, in order to supply pressurised oil to said pipes (24, 25), an axial inlet pipe (34) is formed in the head of said engine shaft (10), which said axial pipe (34) feeds a distributor (35) constituted by a valve that slides on said engine shaft, which said slide valve (35) can move between two positions in which it places said input pipe (34) in communication with one of said pipes (24, 25).