Axial Motor Shaft Coupling for Compact Power Tools
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Solution Overview
Problem
Conventional drill hammers and chisel hammers have a relatively long structural length due to the radial offset between the motor shaft and the intermediate shaft, making them inconvenient to handle and difficult to start drilling accurately, especially with battery packs.
Innovation Solution
The motor shaft is coupled directly to the intermediate shaft along the same axis, eliminating the need for a gear stage and reducing the structural length by avoiding a radial offset, using an electronically commutated direct-current motor, such as an external rotor motor, which provides high torque and allows direct transmission of torque to the intermediate shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a radial offset between motor shaft and intermediate shaft is used with a gear stage, then torque transmission is achieved, but the structural length of the power tool increases
Solution Approach 1:
The motor shaft and intermediate shaft are merged into a single axial alignment, eliminating the radial offset and gear stage. This combining of functions allows direct torque transmission from the motor shaft to the intermediate shaft, reducing the structural length while maintaining power transmission capability.
Solution Approach 2:
The gear stage that was previously necessary for torque transmission in radial offset configurations is extracted/removed from the system. The motor shaft is directly coupled to the intermediate shaft axially, eliminating the intermediate gear mechanism and its associated space requirements.
2Power
If a radial offset between motor shaft and intermediate shaft is used, then torque transmission is enabled, but the power tool becomes more difficult to handle
Solution Approach 1:
By merging the motor shaft and intermediate shaft into axial alignment, the overall tool length is reduced, improving balance and ergonomics. This makes the power tool easier to handle and maneuver, while the direct coupling maintains efficient torque transmission.
3Power
If a radial offset between motor shaft and intermediate shaft is used, then torque transmission is achieved, but the power tool is difficult to start drilling accurately
Solution Approach 1:
The axial alignment and direct coupling of the motor shaft and intermediate shaft eliminate angular deviations and mechanical play that occur in radial offset configurations. This improves the precision of the drill bit alignment, making it easier to start drilling accurately.
4Power
If a gear stage is used between motor shaft and intermediate shaft, then torque transmission is achieved, but the device complexity increases
Solution Approach 1:
The gear stage is extracted from the system, reducing the number of components and simplifying the overall device structure. The direct axial coupling between motor shaft and intermediate shaft eliminates the need for gears, bearings, and associated lubrication and maintenance systems.
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 design results in a more compact and high-powered handheld power tool that is easier to handle and start, with the ability to transmit high torque directly to the intermediate shaft without the need for additional gearing, enhancing operational efficiency.
Implementation Method 1
an electronically commutated direct-current motor constructed as an internal or external rotor motor
Data Source
AI summary
A handheld power tool with a rotating and/or hammering drive mechanism for a tool (11) that can be inserted into a tool receptacle (10) has a unit which transmit the rotation of a motor shaft (5) to an intermediate shaft (7), by which the tool receptacle (10) is set into a rotary motion and/or a hammering motion. A compact construction of the handheld power tool is attained by providing that the motor shaft (5) is coupleable or is coupled to the intermediate shaft (7) in one axis.