Self-Piercing Rivet Tool Drive Unit Switching Control
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Solution Overview
Problem
Existing joining devices with multiple-step drive units, such as self-piercing rivet tools and clinching devices, face inefficiencies due to imprecise switching between movement and power steps, leading to delays in the joining process as a result of early or late switching, which affects the application of punch force and speed.
Innovation Solution
A joining device with a drive unit that operates in at least two steps, featuring a gear unit or dual-acting hydraulic cylinder, equipped with sensors and a control unit to detect mechanical load, punch path, and joining time, allowing precise switching between movement and power steps based on defined threshold values, ensuring optimal punch speed and force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If switching between movement step and power step is performed without precise control, then the joining process can proceed without complex control mechanisms, but the switching timing becomes imprecise causing delays in the joining process
Solution Approach 1:
The patent implements feedback control by detecting the mechanical load during the joining process and using this information to determine the optimal switching point between movement step and power step. The control unit continuously monitors the load and compares it against threshold values to trigger switching at the precise moment when it becomes advantageous to transition from high-speed movement to high-force application, thereby achieving precise switching control without excessive system complexity.
Solution Approach 2:
The patent replaces complex mechanical switching mechanisms with an electronically-controlled system that uses sensors to detect mechanical load and a control unit to manage the switching between drive steps. This substitution of mechanical switching with electronic control based on load feedback enables precise timing of the transition while simplifying the overall control architecture.
2Force
If switching from movement step to power step occurs early, then sufficient force can be applied for joining, but the punch path is traveled at low speed causing delays
Solution Approach 1:
The system uses real-time feedback from load sensors to determine the exact moment when switching from movement step to power step becomes advantageous. By continuously monitoring the mechanical load and comparing it against predetermined threshold values, the control unit ensures that the transition occurs at the optimal point - neither too early (which would waste time) nor too late (which would compromise force application). This feedback mechanism eliminates the need for conservative early switching while ensuring sufficient force is available when needed.
Solution Approach 2:
The patent implements dynamic switching between two operational modes: a movement step with high speed and low force, and a power step with low speed and high force. The system dynamically transitions between these modes based on real-time load conditions rather than using fixed timing, allowing the punch to travel the majority of the path at high speed and then apply maximum force only when the load indicates it is time for the joining action.
3Speed
If switching from movement step to power step occurs late, then high punch speed can be maintained, but the punch cannot apply required force causing joining delays
Solution Approach 1:
The feedback control system prevents late switching by continuously monitoring the mechanical load and triggering the transition to the power step as soon as the load reaches the threshold value that indicates it is time for force application. This ensures that the punch maintains high speed throughout the movement phase and then immediately transitions to high-force mode when the load feedback signals that the joining action should commence, eliminating delays caused by postponed switching.
4Power
If hydraulic hoses and remote hydraulic source are used, then the tool can be operated with centralized hydraulic power, but the equipment space and efficiency are reduced due to hose length and interruptions
Solution Approach 1:
The patent segments the hydraulic power system by providing each tool with its own integrated hydraulic pump and power unit rather than using a single centralized hydraulic source connected via long hoses. This segmentation allows each tool to operate independently with its own compact power unit, eliminating the efficiency losses and interruptions caused by long hydraulic hoses while maintaining the advantages of hydraulic power transmission.
Solution Approach 2:
The patent merges the hydraulic power source with the tool itself by integrating the hydraulic pump, control unit, and other components into a single self-contained operating module. This merging eliminates the need for separate remote hydraulic sources and connecting hoses, thereby improving efficiency and productivity while maintaining full hydraulic power capability for driving the punch and clamping device.
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 solution enables more efficient and controlled joining processes by accurately switching between drive steps, reducing delays and ensuring sufficient force application, thereby improving the quality and speed of the joining process.
Implementation Method 1
a hydraulic pump, which can provide, in a movement step, a high volumetric flow with low hydraulic pressure
Implementation Method 2
in a power step, a low volumetric flow with high hydraulic pressure can be provided
Implementation Method 3
a dual-acting hydraulic cylinder, which can move the punch and the clamping device in a joining direction
Data Source
AI summary
A joining device, in particular a self-piercing rivet tool, is disclosed that is operated with the assistance of different drive steps. These drive steps comprise at least one movement step with a fast punch speed, and a power step with a low punch speed and strong punch force. In combination with the joining device, a clamping device module is use that, based on the at least one spring in the clamping device module, generates discernible threshold values in the force/punch path diagram, with the assistance of which a switchover between different drive steps of the joining device is activated. Moreover, the present disclosure relates to a joining method for the above-described joining device.