Resistive Button Spacer Geometry for Stable Tactile Press Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Control panels in motor vehicles face issues with mechanical clearances and temperature variations affecting the detection of tactile presses, leading to deformation and non-homogeneous pressure distribution, which degrades the external appearance and functionality.
Innovation Solution
A control panel design featuring a force sensor with a spacer made of elastically compressible material, where the spacer is mounted compressed between the sensor and the cover without tactile support on the detection zone, using intermediate pads with a transverse top surface and base surface to minimize reaction force and ensure homogeneous distribution of preload and tactile pressure forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spacer is mounted compressed axially between the force sensor and the cover to compensate for mechanical clearances, then direct transmission of tactile pressure force to the sensor is ensured, but the cover deforms outwardly at the level of the spacer degrading its external appearance and the pressure distribution on the spacer becomes non-homogeneous
Solution Approach 1:
The spacer is designed with non-uniform thickness, featuring a first region with greater thickness and a second region with lesser thickness. This local variation in geometry allows different parts of the spacer to perform different functions: the thicker first region provides adequate compression and force transmission, while the thinner second region minimizes outward deformation of the cover, thus resolving the contradiction between reliable force transmission and maintaining cover appearance.
2Difficulty of detecting and measuring
If the cover thickness in the detection zone is reduced to allow elastic deformation towards the sensor, then tactile press detection is enabled, but the cover becomes more susceptible to deformation under spacer compression
Solution Approach 1:
The spacer's non-uniform thickness creates a localized compression zone in the first region that transmits force effectively to the sensor while the thinner second region minimizes overall cover deformation. This allows the cover to be sufficiently thin for tactile detection without being overly susceptible to deformation under compression.
Solution Approach 2:
The spacer is pre-compressed during assembly to establish optimal contact between the cover, spacer, and sensor before any tactile input occurs. This preliminary compression ensures that the spacer is already in a state that facilitates direct force transmission while minimizing additional deformation during normal operation.
3Reliability
If a conventional parallelepiped block spacer is used to compensate for mechanical clearances, then direct force transmission is achieved, but excessively high bearing forces are applied to the sensor and cover leading to creep risks
Solution Approach 1:
The spacer features a first region with greater thickness and a second region with lesser thickness, creating a gradual transition zone. This non-uniform geometry distributes the bearing forces more evenly across the contact surfaces, reducing peak stresses and minimizing creep risks while maintaining direct force transmission capability.
Solution Approach 2:
The spacer's thickness parameter is varied along its axial direction, transitioning from a greater thickness in the first region to a lesser thickness in the second region. This parameter change optimizes the force distribution characteristics, reducing excessive bearing forces on the sensor and cover while ensuring adequate force transmission for reliable detection.
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 reduces stress on the cover, minimizes the risk of creep, and enhances the detection of control button activation, maintaining pre-stressing force consistency despite manufacturing and assembly tolerances and temperature variations.
Implementation Method 1
a spacer made of elastically compressible material which is interposed between the sensor and the cover
Implementation Method 2
a force sensor comprising a pressure sensitive zone is arranged between the cover and the support, behind the detection zone, so as to detect the actuation of the control button to produce an electrical control signal
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention relates to a control panel (10) comprising a cover (12) that is mounted on a supporting member (14) and that is equipped with a zone for detecting a tactile pressure, in which a pressure sensor (18) comprising a pressure-sensing region is arranged between the cover (12) and the supporting member (14) behind the detecting zone so as to produce an electrical control signal when a user applies a given tactile pressure to the detecting region, the tactile pressure being transmitted axially (X1) toward the sensing region via a spacer (34) made of an elastically compressible material that is placed intermediate in between the sensor (18) and the cover (12), characterized in that the spacer (34) comprises at least one intermediate pad (52) provided with a transverse top surface (44) that presses against the cover (12) and a transverse bottom surface (45) that presses against the sensing region of the sensor (18), the top surface (44) having a smaller area than the bottom surface (45).