Sensor Housing for Hand-Guided Work Apparatus
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Solution Overview
Problem
Hand-guided work apparatuses face challenges in ensuring safe operation due to contamination accumulation at pressure sensors when arranged below the crankshaft axis, leading to inaccurate measurements and potential mechanical damage.
Innovation Solution
A common sensor housing with a funnel-shaped connecting channel and a sealing ring configuration that slopes downward, ensuring contaminants flow off and providing mechanical protection, while a cylindrical section with a rod-shaped temperature sensor aids gas exchange and prevents pressure waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the pressure sensor and temperature sensor are arranged below the level of the crankshaft axis to save space, then the device complexity is reduced and space is saved, but contaminants and oil accumulate on the pressure sensor leading to unreliable operation
Solution Approach 1:
The pressure sensor is extracted from the direct crankcase interior environment by placing it in a sensor housing connected via a connecting channel. This allows the sensor to be positioned below the crankshaft axis for space savings while preventing direct contamination accumulation on the sensor surface, as the channel geometry (sloping base, funnel-shaped widening) enables contaminants to flow away from the sensor area.
2Ease of manufacture
If a cylindrical connecting channel configuration is used, then the manufacturing is simpler, but a standing pressure wave forms that falsifies measurement results
Solution Approach 1:
The connecting channel transitions from a cylindrical cross-section to a funnel-shaped cross-section that widens toward the crankcase interior. This asymmetric geometry change prevents standing pressure waves by creating a non-uniform flow path, while the sloping base ensures contaminants drain away. The asymmetry in channel geometry resolves the measurement precision issue while maintaining manufacturing feasibility through standard molding techniques.
3Measurement precision
If the temperature sensor projects into the crankcase interior, then the temperature measurement is more direct, but the temperature sensor obstructs gas exchange in the connecting channel area
Solution Approach 1:
The temperature sensor is positioned in the connecting channel rather than projecting into the crankcase interior. The sensor measures temperature through the channel wall or via a sensing element that contacts the gas flow path without physically blocking the channel. This dimensional repositioning allows the sensor to remain in the measurement zone while maintaining unobstructed gas exchange between the crankcase interior and the sensor housing.
4Ease of manufacture
If the pressure sensor is exposed during assembly and servicing, then the assembly process is simpler, but the pressure sensor is vulnerable to mechanical damage
Solution Approach 1:
The pressure sensor is nested within the sensor housing, which serves as a protective outer shell. The sensor housing is connected to the crankcase interior through the connecting channel, creating a nested structure where the fragile pressure sensor membrane is shielded by the robust housing. This nesting provides mechanical protection during assembly, servicing, and operation while maintaining sensor functionality through the connecting channel interface.
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 ensures durable and accurate sensor operation by preventing contamination accumulation and mechanical damage, maintaining reliable measurements and reducing the risk of sensor failure.
Implementation Method 1
the connecting channel widens at least partially funnel-shaped in the direction of the crankcase interior
Implementation Method 2
the connecting channel having a base which slopes down toward the crankcase interior when the work apparatus is in the set-down position on the rest surface
Implementation Method 3
the temperature sensor is surrounded by gas in the crankcase from all sides
Implementation Method 4
a pressure sensor... arranged in the sensor housing... defining a connecting channel for causing the pressure sensor to communicate with the crankcase interior
Data Source
AI summary
A hand-guided work apparatus includes a combustion engine to drive a work tool. The combustion engine includes a crankcase (14) in which a crankshaft (16) is rotatably mounted about a rotational axis (44). A pressure sensor (27) and a temperature sensor (26) are arranged on the crankcase (14). The pressure sensor (27) and the temperature sensor (26) are arranged in a common sensor housing (31). In the typical put-down position (8) of the work apparatus, the pressure sensor (27) and the temperature sensor (26) are arranged below a plane (45) which is parallel to the horizontal storage surface (7) and contains the rotational axis (44) of the crankshaft (16). A connecting channel (25) is formed in the sensor housing (31). The connecting channel (25) connects the pressure sensor (27) to the crankcase interior (20) and the base (35) of the connecting channel (25) slopes down toward the crankcase interior (20) in the typical put-down position (8) of the work apparatus.