Engine Oil Seal Cooling via Rotor-Driven Airflow
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Solution Overview
Problem
The oil seal on the drive-side shaft of an engine unit in engine-driven working machines is difficult to cool, especially when covered, leading to high temperatures and potential deformation, which can cause engine stall due to inadequate airflow reaching the seal.
Innovation Solution
An air passage system is created using a vaned rotor to generate negative pressure, directing airflow from an inlet opening near the oil seal on the drive-side shaft through a rib-guided air passage to an outlet opening, enhancing cooling by utilizing the pressure difference between external air and negative pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the crankcase around the oil seal on the drive-side shaft is covered by a cover, then the engine unit is protected, but the cooling of the oil seal becomes difficult and temperature increases
Solution Approach 1:
The housing is divided into multiple walls (first wall, second wall, third wall) with a dedicated air passage system. The air passage is segmented into inlet opening, passage section, and outlet opening, allowing targeted cooling airflow to be directed specifically to the drive-side shaft oil seal area without requiring the entire crankcase to be uncovered.
Solution Approach 2:
A rib structure is introduced as an intermediary element within the air passage to guide and concentrate the cooling airflow toward the oil seal. The rib acts as a flow director, ensuring that the airflow generated by the vaned rotor is effectively channeled to the target area for cooling the oil seal.
2Adaptability or versatility
If an oil pump or recoil case is attached onto the drive-side shaft, then the engine functionality is enhanced, but the cooling of the oil seal on the drive-side shaft becomes more difficult
Solution Approach 1:
The air passage system provides localized cooling specifically at the drive-side shaft oil seal area, rather than attempting to cool the entire engine unit. The inlet opening is positioned to direct airflow precisely where needed, ensuring that the oil seal receives adequate cooling even when other components are attached to the drive-side shaft.
3Temperature
If the airflow from vaned rotor is used to cool the magnet-side shaft oil seal, then cooling is effective, but the airflow cannot reach the drive-side shaft oil seal
Solution Approach 1:
The air passage system introduces a new spatial dimension for airflow distribution by creating a dedicated passage that extends from the inlet opening through the housing to the outlet opening near the drive-side shaft. This allows the cooling airflow to reach areas that would otherwise be inaccessible from the vaned rotor location.
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 cools the oil seal on the drive-side shaft, maintaining airtightness and preventing engine stall, even when external air contact is limited, such as when an oil pump or recoil case is attached.
Implementation Method 1
the rotations of the vaned rotor cause a negative pressure near the outlet opening, and due to a pressure difference between the external air and the negative pressure, can airflow is caused from the inlet opening in the first wall through the air passage to the outlet opening
Implementation Method 2
the airflow flows along the crankcase around the oil seal on the drive-side shaft so that the oil seal can be cooled
Data Source
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AI summary
An engine-driven working machine (1) has an engine unit (2), a housing (4), and a vaned rotor (6). An air passage (24) is defined between a crankcase (10) of the engine unit (2) and a bottom wall (20) of the housing (4). The air passage (24) has an inlet opening (32) provided near an oil seal (18a) on a drive-side shaft (16a), and an outlet opening (34) provided in a magnet-side wall (22b) so as to face the vaned rotor (6). Rotations of the vaned rotor (6) cause airflow from the inlet opening (32) through the air passage (24) to the outlet opening (34).