Dual-Load Detection for Motor Speed Control in Hammer Drills
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Solution Overview
Problem
Existing electric power tools, particularly hammer drills, face challenges in detecting loads during hammer mode operations, leading to inadequate motor speed adjustments, which affects efficiency in hammering and drilling tasks.
Innovation Solution
The electric power tool incorporates a dual-load detection system comprising a current detector and an acceleration sensor, along with a motor controller, to accurately determine load conditions and adjust rotational speed accordingly, even in hammer mode, ensuring efficient operation across different modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If current detection is used to detect load on the tip tool, then load detection is simple and低成本, but in hammer mode the load cannot be detected because current does not dramatically increase
Solution Approach 1:
The patent combines two different load detection methods: current detection (first load detector) and acceleration detection (second load detector). The controller integrates signals from both detectors to determine load conditions, allowing accurate load detection in both drilling mode and hammer mode where current detection alone fails.
2Loss of energy
If the motor is rotated at low speed under no-load conditions, then energy consumption is reduced, but in hammer mode the motor cannot be rotated at high speed because load detection fails
Solution Approach 1:
The system uses feedback from both the current detector and acceleration sensor to continuously monitor load conditions. When the controller detects no-load conditions through both detectors, it maintains low motor speed to save energy. When load is detected, it increases motor speed appropriately, including in hammer mode where acceleration detection provides the necessary feedback signal.
3Measurement precision
If dual-load detection system is implemented, then load detection accuracy is improved, but device complexity increases
Solution Approach 1:
The acceleration sensor serves multiple functions: it detects load conditions during hammer mode operation and also contributes to no-load detection when combined with current detection. This multi-functionality justifies the added component by providing versatility in detection capabilities across different operating modes.
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 enables rapid detection of loads and appropriate motor speed adjustments, enhancing the tool's efficiency in chipping and drilling tasks by preventing misinterpretation of load conditions and reducing operational delays.
Implementation Method 1
The second load detector detects, based on information indicating the behavior of the main body, a load imposed from the work piece to the tool bit
Data Source
AI summary
An electric power tool according to one aspect of the present disclosure includes a main body, a motor, a tool holder configured to hold a tool bit, a hammer, a motion converter, a rotation transmitter, a first load detector, a second load detector, and a motor controller. The first load detector detects, based on information indicating a drive state of the motor, a load imposed from a work piece to the tool bit. The second load detector detects, based on information indicating a behavior of the main body, a load imposed from the work piece to the tool bit. The motor controller sets an upper limit of rotational speed of the motor to a predetermined no-load rotational speed in response to no-load on the tool bit being detected by both the first load detector and the second load detector.