Differential Torque Transmission via Offset Through-Hole
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Solution Overview
Problem
Existing motor-driven screwdrivers face complications in machining due to complex part structures and high wear rates, particularly when alternating between forward and backward rotations.
Innovation Solution
A motor-driven screwdriver with a rotational driving force transmission device featuring a driving member, a driven member with a through-hole, and a power transmission member, where the through-hole's center axis does not intersect the rotation center axis, allowing for varying pressing forces between forward and backward rotations, enabling differential transmission of rotational driving forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a rotational driving force transmission device uses a complex part structure to achieve differential transmission forces, then the transmission of appropriate rotational driving forces is enabled, but the machining complexity increases
Solution Approach 1:
The patent applies asymmetry by configuring the through-hole in the driven member at an position that does not intersect with the rotation center axis. This asymmetric positioning creates different lever arms and mechanical advantages for forward and backward rotation, enabling differential transmission forces without requiring complex additional components. The asymmetric through-hole location directly generates the force differentiation effect.
Solution Approach 2:
The patent moves the through-hole center away from the rotation center axis, effectively utilizing the spatial dimension to create force differentiation. By positioning the through-hole at a specific offset location in the radial direction, the system exploits the geometric dimension to achieve different mechanical advantages for clockwise and counter-clockwise rotation, simplifying the overall structure while maintaining adaptability.
2Adaptability or versatility
If a rotational driving force transmission device uses complex engagement mechanisms, then differential transmission is achieved, but the wear rate increases particularly during alternating forward and backward rotations
Solution Approach 1:
The asymmetric through-hole positioning creates different engagement characteristics for forward and backward rotation. The power transmission member engages with the driven member at different effective radii depending on rotation direction, which distributes wear more evenly and reduces peak stress concentrations that would otherwise occur in symmetric engagement mechanisms during alternating rotation.
Solution Approach 2:
The patent changes the geometric parameter of the through-hole location to achieve differential transmission. By varying the radial position of the through-hole center relative to the rotation center axis, the system optimizes the mechanical advantage for each rotation direction, reducing excessive loading and minimizing wear on the power transmission member and driven member during alternating operations.
3Ease of manufacture
If the through-hole center axis intersects the rotation center axis, then symmetric engagement occurs, but differential transmission forces cannot be achieved
Solution Approach 1:
The patent deliberately introduces asymmetry by positioning the through-hole center axis to not intersect with the rotation center axis. This asymmetric configuration is essential for achieving differential transmission forces, as it creates different lever arms and mechanical advantages for forward and backward rotation. The offset positioning transforms a potentially symmetric simple structure into an asymmetric design that enables the required functional differentiation.
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 simplifies the part structure, reduces wear, and allows for appropriate rotational driving forces during screw tightening and loosening, preventing excessive load on screws or the screwdriver, ensuring safety and efficient operation.
Implementation Method 1
an urging member urging the power transmission member inward in the radial direction
Implementation Method 2
the projecting portion engages the power transmission member to transmit rotational driving force from the driving member to the driven member through the power transmission member
Data Source
AI summary
Provided is a motor-driven screwdriver configured such that the upper limit value of transmittable rotational driving force differs between forward and backward rotation. The motor-driven screwdriver has a bit holder and a rotational driving force transmission device for transmitting rotational driving force to the bit holder. The rotational driving force transmission device has a driving member, a driven member having through-holes, power transmission members held in the through-holes, respectively, and an urging member urging the power transmission members inward. Each through-hole is provided such that a through-hole center axis passing through a center between a forward rotation guide surface and backward rotation guide surface of the through-hole does not intersect a rotation center axis, whereby the force with which the power transmission member is pushed radially outward is made to differ between forward and backward rotation.