Composite Gearwheel With Partial Steel Toothing for Torque Peaks
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Solution Overview
Problem
Existing composite gearwheels for electropneumatic hammer drills face challenges in achieving high stability while maintaining a low weight, particularly when exposed to varying torque levels due to the impact mechanism.
Innovation Solution
The composite gearwheel design features a toothed body made of steel along a limited circular arc, with the remaining arc formed by a lighter material, such as thermoplastic, and incorporates a balancing weight to compensate for imbalances, allowing for a lightweight yet stable construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the encircling toothing is reinforced with heavy material around the entire circumference, then the stability and load-bearing capacity are improved, but the overall weight of the gearwheel increases significantly
Solution Approach 1:
The encircling toothing is divided into two segments: a first circular arc with center angle less than 90 degrees formed by a toothed body made of steel (second material), and a remaining second circular arc formed by the basic body material (first material). This segmentation allows heavy reinforcement only where torque is highest, reducing overall weight while maintaining stability.
Solution Approach 2:
The gearwheel employs local quality by using different materials in different regions: the toothed body along the first circular arc uses steel for high strength where load is concentrated, while the remaining portion uses lighter basic body material. This resolves the contradiction by providing strength only where needed rather than uniformly throughout.
2Force
If heavy material is used for the entire encircling toothing, then the load-bearing capacity under maximum torque is improved, but the gearwheel becomes unnecessarily heavy for periods of lower torque
Solution Approach 1:
The invention applies partial action by providing heavy steel reinforcement (toothed body) only for the first circular arc where torque exceeds a predetermined threshold, rather than reinforcing the entire circumference. This allows the gearwheel to handle maximum torque loads effectively while minimizing weight during lower torque operation.
Solution Approach 2:
The torque in hammer drills varies periodically with crank angle, and the invention matches the reinforcement pattern to this periodic variation by concentrating the heavy toothed body in the angular range where torque is highest, allowing the gearwheel to adapt to the periodic load pattern without constant heavy reinforcement.
3Manufacturing precision
If the toothed body is made as a separate component for precise fitting, then the manufacturing precision and form-fitting accuracy are improved, but the device complexity increases
Solution Approach 1:
The toothed body is extracted as a separate component from the basic body, allowing it to be manufactured with high precision independently and then fitted into a corresponding slot in the basic body. This separation enables precise form-fitting while maintaining relatively simple overall device structure through modular construction.
Data Source
AI summary
Composite gearwheel for an electropneumatic hammer drill, wherein the composite gearwheel has a basic body, consisting of a first material, and an encircling toothing, and wherein the encircling toothing is formed, along a first circular arc, by a toothed body of the composite gearwheel, and is formed, along the remaining second circular arc, by the basic body itself, wherein the toothed body consists of a second material that is different than the first material.