Impact Rotary Tool Double Hammer Torque Accuracy
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Solution Overview
Problem
In impact rotary tools, the circumferential clearance between the anvil and the tightened member leads to inaccurate torque detection and reduced power efficiency due to the hammer losing contact with the anvil before the tightening torque is applied, affecting torque management accuracy.
Innovation Solution
A double hammer configuration with a connection structure providing circumferential clearance allows the sub-hammer to follow and rotate with the main hammer, ensuring the sub-hammer applies a rotation force after the main hammer's impact has reduced the clearance, thereby maintaining contact and improving torque detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single hammer configuration is used, then the structure is simple, but the torque detection accuracy deteriorates due to clearance closure delay
Solution Approach 1:
The single hammer is segmented into two separate hammers: a first hammer that directly impacts the anvil to reduce clearance, and a second hammer that impacts the first hammer to apply rotation force. This segmentation allows the clearance closure delay problem to be solved by separating the clearance-reduction function from the rotation-force-application function, thereby improving torque detection accuracy while maintaining manageable structural complexity.
Solution Approach 2:
The first hammer performs a preliminary impact action on the anvil before the second hammer applies rotation force. This preliminary action reduces the circumferential clearance between the anvil and tightened member, ensuring that when the torque sensor detects strain, the clearance has already been closed, allowing accurate torque measurement.
2Measurement precision
If the hammer impacts the anvil immediately, then the clearance is reduced quickly, but the torque sensor cannot accurately detect the strain amount
Solution Approach 1:
The impact action is segmented into two sequential stages: first, the first hammer impacts the anvil to reduce clearance; second, the second hammer impacts the first hammer to apply rotation force. This timing sequence ensures that when the torque sensor detects strain, the clearance has been reduced but the rotation force has not yet been applied, allowing accurate strain detection without time loss.
Solution Approach 2:
The first hammer performs a preliminary impact to reduce clearance before the second hammer applies rotation force. This preliminary action creates the optimal timing condition where the torque sensor can detect strain accurately, as the clearance is reduced but the full rotation force is not yet applied to the tightened member.
3Productivity
If the hammer moves away from the anvil before tightening, then the torque transmission efficiency decreases, but maintaining contact requires complex control
Solution Approach 1:
The hammer system is segmented into two hammers with distinct functions: the first hammer is dedicated to reducing clearance through impact, while the second hammer is dedicated to applying rotation force. This functional segmentation ensures that the hammer maintains contact with the anvil throughout the process, improving torque transmission efficiency without requiring complex control mechanisms, as each hammer performs its specific function automatically through the mechanical linkage.
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 enhances torque management accuracy and power efficiency by ensuring the sub-hammer applies a rotation force after the initial impact, allowing the torque sensor to accurately detect the tightening torque and maintaining contact with the anvil.
Implementation Method 1
a spring member extending in a rotation axis direction of the spindle, and configured to apply a biasing force to the main hammer in the rotation axis direction
Implementation Method 2
a cam structure with steel balls disposed between a guide groove on the side of the spindle and an engagement groove on the side of the main hammer, and the main hammer repeats backward and forward movements at high speed by the cam structure
Implementation Method 3
the grooves of the main hammer engage with a needle-like roller fitted in the grooves of the sub-hammer. By the needle-like roller, the main hammer and the sub-hammer can rotate integrally, and the main hammer can move in the axis direction along the needle-like roller
Implementation Method 4
When a torque sensor for detecting a twisting strain of the anvil is used to estimate the tightening torque
Implementation Method 5
a rotary impact mechanism for converting the rotation of the spindle into a rotary impact and transmitting it to the anvil
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
An impact rotary tool 1 includes: a driver 10, a spindle 11, an anvil 22 disposed in front of the spindle 11 in a rotation axis direction, a main hammer 20 applying a rotation force to the anvil 22, and a sub-hammer 21 applying, to the main hammer 20 having applied the rotation force to the anvil 22, a rotation force in the same direction.