Battery Pack Tolerance Compensation via Thermoplastic Expanding Elements
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Solution Overview
Problem
Existing battery packs for hand-held power tools face challenges in tolerances, where large mechanical dimensions allow up to 1 mm of tolerance, leading to play between battery cells and housing, which is compensated by foam inserts that lose mechanical tension over time and hinder heat dissipation, or by elastic housings that are mechanically stressed and difficult to design.
Innovation Solution
A battery pack with a dimensionally stable housing and expanding elements made of thermoplastic materials like HDPE, which are elastic and thermally conductive, are used to compensate for tolerances without altering the housing's outer contour, allowing for efficient heat dissipation and secure cell positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If foam inserts are used to compensate for play between battery cells and housing, then the battery cells are securely positioned, but the mechanical tension decreases over time and heat dissipation is hindered
Solution Approach 1:
The patent changes the material parameter from foam (elastic, heat-insulating) to thermoplastic material (rigid, thermally conductive). The expanding element is made of thermoplastic material with thermal conductivity of 0.4 to 0.42 W/mK, which maintains mechanical tension over time while enabling efficient heat dissipation from battery cells.
2Reliability
If foam inserts are used to compensate for play between battery cells and housing, then the battery cells are securely positioned, but heat dissipation is hindered
Solution Approach 1:
The patent changes the thermal parameter by selecting thermoplastic material with thermal conductivity of 0.4 to 0.42 W/mK, which is comparable to battery cell conductivity (0.4 to 0.5 W/mK). This enables efficient heat dissipation while maintaining secure positioning, unlike foam material which is heat-insulating.
3Manufacturing precision
If an elastic housing is used to compensate for diameter tolerances of cells, then the tolerance compensation is achieved, but the housing is mechanically stressed and design complexity increases
Solution Approach 1:
The patent segments the tolerance compensation function from the housing structure. Instead of making the entire housing elastic, a separate expanding element made of thermoplastic material is inserted between battery cells and the housing. This expanding element absorbs dimensional variations while the housing remains dimensionally stable and structurally simple.
4Adaptability or versatility
If the housing is constructed to the maximum to accommodate tolerance variations, then all battery cells can be accommodated, but play between cells and housing occurs
Solution Approach 1:
The patent introduces an intermediary expanding element made of thermoplastic material between the battery cells and the housing. This intermediary component absorbs the dimensional tolerances (up to 1 mm) while maintaining firm contact, eliminating play between cells and housing without requiring maximum housing construction.
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
The solution ensures battery cells are securely seated without play, maintains mechanical stability, and facilitates efficient heat dissipation, addressing the issues of tolerance compensation and heat management in battery packs.
Implementation Method 1
The expansion element is intrinsically elastic. In particular, it is dimensioned larger than the space between the battery cells and/or the battery cells and the housing, so that when the spreading element is inserted into the space, the battery cells adjacent to the space are pressed apart.
Implementation Method 2
which has the advantage of being comparatively elastic and deformable and having a thermal conductivity of 0.4 to 0.42 W/mK, which is relatively good for plastics which is comparable to the thermal conductivity of the battery cells themselves of 0.4 to 0.5 W/mK.
Data Source
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AI summary
The invention describes a battery pack having a housing (10) and at least one battery cell (20) and also means for compensating tolerances of the battery cell (20), wherein the tolerance compensation means have at least one spreading element (30, 40) which is arranged in an intermediate space (22) between at least two battery cells (20) and/or between the one battery cell (20) and the housing (10).