Hammer Drill Motor Control for Rotation Speed Stability
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Solution Overview
Problem
Existing power tools, such as electric hammers and drills, experience rotation speed fluctuations due to varying loads during forward and backward strokes, leading to inefficient operation and reduced work efficiency.
Innovation Solution
A power tool with a controller that adjusts the voltage or duty ratio of the motor's driving pulse signal based on the detected position and rotation speed of the driving member, setting higher values during the stroke with greater load to maintain consistent rotation speed and prevent fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor is driven at high speed in the load applied state (hammer bit pressed in tool holder), then the motor can deliver sufficient power for hammering operation, but the rotation speed of the motor decreases due to load and becomes substantially same as in no load state, leading to inefficient operation
Solution Approach 1:
The patent applies dynamics by differentiating motor control between forward and backward strokes. The controller dynamically adjusts control factors (voltage or duty ratio) based on the stroke direction, recognizing that load conditions differ between strokes. This dynamic control optimizes motor performance for each specific operational phase, preventing rotation speed degradation during high-load forward strokes while maintaining efficiency during backward strokes.
Solution Approach 2:
The patent changes motor control parameters (voltage value or duty ratio of driving pulse signal) based on stroke direction. By setting control factors differently for forward and backward strokes, the system optimizes power delivery during hammering while preventing excessive rotation speed reduction. This parameter differentiation resolves the contradiction between delivering sufficient power and maintaining operational efficiency.
2Force
If the load applied on the motor is increased during the forward stroke to perform hammering operation, then the hammering force is sufficient, but the rotation speed fluctuation increases, leading to unstable motor operation
Solution Approach 1:
The patent applies local quality by implementing different control strategies for different strokes. The controller provides enhanced voltage or duty ratio specifically during the forward stroke when hammering force is needed, while using standard control during the backward stroke. This localized control enhancement ensures sufficient hammering force is delivered precisely when needed without causing rotation speed fluctuations that would compromise operational stability.
3Productivity
If the motor is controlled based on detection of power consumption or impact energy, then the overall operation can be optimized, but the control does not account for the different load conditions during forward and backward strokes, requiring more sophisticated control
Solution Approach 1:
The patent applies segmentation by dividing the motor control into distinct segments based on stroke direction. The controller separately manages forward stroke control (requiring higher power for hammering) and backward stroke control (with different load characteristics). This segmentation allows each stroke type to receive optimized control parameters, achieving sophisticated control without requiring complex overall system redesign.
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 controller effectively suppresses rotation speed fluctuations, ensuring stable motor operation and improved work efficiency by optimizing motor control during both forward and backward strokes.
Implementation Method 1
a duty ratio of a driving pulse signal utilized to drive the motor
Data Source
Figure 1
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AI summary
A hammer drill (100) comprises an electric motor (110), a piston (127) as a driving member and a controller (199) which controls and drives the electric motor (110). The piston (127) is reciprocated by rotation of the electric motor (110) and thereby a hammer bit (119) is driven in its longitudinal direction. The hammer bit (119) is moved forward in response to a forward movement stroke of the piston (127) and thereby a hammering operation is performed by the hammer bit (119). The controller (199) sets a duty ratio of a driving pulse signal which drives the electric motor (110) in the forward movement stroke of the piston (127) to be larger in order to prevent a reduction of a rotation speed of the electric motor (110) due to a load applied on the electric motor (110) during the forward movement stroke of the piston (127).