Sewing Machine Thread Tension Control via Torque Feedback
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Solution Overview
Problem
Existing sewing machines face challenges in accurately adjusting bobbin thread tension, leading to imbalances in needle thread and bobbin thread consumption, which affects seam quality and increases costs due to the need for additional components like magnets in tension control mechanisms.
Innovation Solution
A sewing machine that calculates and adjusts needle thread requirements based on stitch-specific data, using torque control and angle corrections to achieve a balanced consumption of needle and bobbin threads, even with existing configurations using a bobbin case with a tension spring, thereby optimizing thread usage and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a tension spring is used to adjust bobbin thread tension, then the tension can be adjusted, but the adjustment precision is insufficient and cannot achieve accurate balance between needle thread and bobbin thread consumption
Solution Approach 1:
The patent replaces the mechanical tension spring system with a motor-driven tension control system. The bobbin thread tension control motor rotates a rotation shaft to move a bobbin thread guide, thereby controlling bobbin thread tension through motor control rather than mechanical spring friction, achieving precise tension adjustment.
Solution Approach 2:
The patent changes the control parameter from friction-based mechanical tension (spring force) to motor torque control. By controlling the torque output of the bobbin thread control motor, the system achieves precise and adjustable bobbin thread tension, allowing accurate balance between needle and bobbin thread consumption.
2Manufacturing precision
If torque control is applied to the needle thread motor, then needle thread tension can be controlled, but the system complexity increases due to additional control mechanisms
Solution Approach 1:
The patent uses a unified motor control approach where the needle thread motor and bobbin thread control motor both operate under torque control principles. The control system integrates tension control functions into the existing motor control architecture, allowing precise tension management without proportionally increasing system complexity.
Solution Approach 2:
The patent implements feedback control by monitoring needle thread consumption and bobbin thread consumption and adjusting motor torque accordingly. The control section compares actual thread consumption with target values and modifies motor operation to achieve precise tension balance, reducing the need for complex mechanical adjustment mechanisms.
3Measurement precision
If additional components like magnets are added to tension control mechanisms, then tension control precision improves, but manufacturing costs increase
Solution Approach 1:
The patent replaces expensive magnetic tension control components with a motor-driven mechanical system. The bobbin thread control motor directly controls tension through rotation of the bobbin thread guide, eliminating the need for costly magnets while achieving comparable or superior control precision.
Solution Approach 2:
The patent uses standard motors and mechanical components instead of specialized expensive magnets. The motor-driven system employs readily available parts that are easier to manufacture and replace, reducing overall manufacturing cost while maintaining tension control functionality.
4Manufacturing precision
If the needle thread motor is controlled according to torque values, then needle thread tension is controlled, but the balance between needle thread and bobbin thread consumption cannot be achieved
Solution Approach 1:
The patent implements a feedback control system that monitors both needle thread consumption and bobbin thread consumption. The control section compares actual consumption with target values and adjusts the torque control parameters of both motors to maintain the desired balance, ensuring reliable thread consumption equilibrium.
Solution Approach 2:
The patent uses dynamic torque control where the motor torque values are continuously adjusted based on real-time thread consumption feedback. The control system adapts torque parameters during operation to maintain optimal tension balance, allowing dynamic response to changing sewing conditions.
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 approach allows for a stable balance between needle thread and bobbin thread consumption, enhancing seam quality and reducing operational costs by eliminating the need for costly additional components in tension control.
Implementation Method 1
A tension on the bobbin thread is adjusted by adjusting the degree of tightening of an adjustment screw fitted into the tension spring. In short, the tension on the bobbin thread is adjusted by frictional resistance of the tension spring.
Implementation Method 2
a bobbin thread control part having a bobbin thread motor that rotates a bobbin thread guide in a direction opposite to a rotating direction of the bobbin, and that rotates the bobbin thread guide by a torque
Implementation Method 3
the needle thread motor is controlled according to a torque value so as to impart tension on the needle thread against the direction of a thread take-up lever pulling the needle thread
Data Source
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AI summary
[Problem] To provide a low-cost sewing machine capable of achieving a desired balance between needle thread consumption and bobbin thread consumption. [Means for Resolution] A memory section 92 stores needle thread requirement data having precorrected needle thread requirement and postcorrected needle thread requirement. In a torque control zone, rotating force is imparted to a turning arm 1281 so as to impart a tension on the needle thread according to a torque value, while closing an upstream grip section main body 1241 and while opening a downstream grip section main body 1261. In a first position control zone, the needle thread is drawn according to the postcorrected needle thread requirement, while opening the upstream grip section main body 1241 and while closing the downstream grip section 1261. In a second position control zone, the turning arm 1281 is returned to an initial position, while closing the upstream grip section main body 1241 and while opening the downstream grip section main body 1261. Further, the precorrected needle thread requirement is compared with needle thread consumption in the torque control zone, to correct the postcorrected needle thread requirement.