Plastic HMI Interface Film Molding for Localized Haptic Feedback
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Solution Overview
Problem
Capacitive buttons in plastic human-machine interfaces lack tactile feedback, which is inadequate in noisy environments or when users cannot see the button being actuated, and conventional haptic actuators are bulky, making localized vibration difficult to achieve in multi-key systems, especially in materials that dampen vibrations.
Innovation Solution
A method for manufacturing a plastic part with a human-machine control interface that integrates a decorative film and a technical film with haptic actuators and capacitive sensors, using an injection mould with a support pad to create a free zone for the actuators, allowing for localized vibration and aesthetic integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If capacitive buttons are integrated in plastic facades to achieve a smooth surface, then aesthetic appearance and robustness are improved, but tactile feedback capability deteriorates
Solution Approach 1:
The patent combines capacitive buttons with haptic actuators into a single integrated unit. The haptic actuator is positioned behind the capacitive button, allowing the button to provide both capacitive sensing functionality and tactile feedback through vibration when actuated, thus merging two functions into one component.
Solution Approach 2:
The haptic actuator serves as an intermediary element between the capacitive button and the user's finger. When the capacitive button detects touch, it triggers the haptic actuator to generate vibration, which then provides tactile feedback to the user, mediating the interaction between the smooth capacitive interface and the user's sense of touch.
2Ease of operation
If conventional haptic actuators are used to provide tactile feedback, then vibration capability is improved, but device bulk and complexity increase
Solution Approach 1:
The patent employs thin-film haptic actuators that can be integrated directly into the plastic facade structure. These thin-film actuators provide the necessary vibration capability while occupying minimal space, avoiding the bulk associated with conventional haptic actuators.
Solution Approach 2:
The haptic actuator is designed to serve multiple functions: providing tactile feedback for capacitive buttons, enabling localized vibration in multi-key systems, and integrating seamlessly into the plastic facade manufacturing process through injection molding, thereby reducing overall system complexity.
3Ease of operation
If the entire facade is vibrated to provide haptic feedback, then tactile feedback is achieved, but localized vibration control deteriorates
Solution Approach 1:
The patent segments the haptic feedback capability by associating individual haptic actuators with specific capacitive buttons or button groups. Each haptic actuator can be independently controlled to provide localized vibration feedback at the specific location where user input is detected, rather than vibrating the entire facade.
Solution Approach 2:
The patent implements local quality by enabling different regions of the facade to have different haptic characteristics. Each button location can be equipped with its own haptic actuator, allowing customized vibration patterns and intensities at each control point while maintaining a completely smooth facade surface.
4Shape
If piezoelectric actuators are completely embedded in the plastic part, then integration and aesthetic appearance are improved, but vibration perception deteriorates
Solution Approach 1:
The patent addresses vibration perception by transitioning from a two-dimensional embedded actuator approach to a three-dimensional structure. A cavity or chamber is created behind the capacitive button during injection molding, allowing the haptic actuator to be positioned in this third dimension (depth) rather than being completely embedded in the flat facade surface. This enables the actuator to generate vibrations that can be effectively transmitted to the user's finger while maintaining a smooth external surface.
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
Enables localized haptic feedback through vibration while maintaining a smooth, aesthetic surface, effectively addressing the limitations of capacitive buttons and conventional haptic actuators by ensuring perceivable vibrations in a multi-key system without deforming the plastic part.
Implementation Method 1
The interface film (6) comprises a layer of haptic actuators (3) capable of generating a vibration
Implementation Method 2
a layer of capacitive sensors (4) arranged in the same pattern as the buttons of the visible interface
Data Source
AI summary
A method for manufacturing a plastic part forming a human-machine control interface includes formation of a decorative film, formation of a technical film including a layer of haptic actuators and a layer of capacitive sensors, assembly to form an interface film, positioning in an injection mould, including an upper portion and a lower portion including a moveable support pad capable of coming into contact with the interface film such that a thickness is left free between the interface film and the lower portion of the injection mould outside of the support pad, injection of a plastic material into the free thickness on either side of the support pad, and opening of the injection mould and ejection of the plastic part formed.