Load detection sensor unit
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Solution Overview
Problem
Resin film-based load detection sensors used in vehicles are prone to erroneous detection due to decreased strength at high temperatures, leading to false readings even under normal loads, as they tend to bend easily and acquire a bending habit.
Innovation Solution
A load detection sensor unit with a metal plate and a sensor sheet bonded by an adhesive layer, where the metal plate is pressed by a harder pressing member, causing it to bend and contact electrodes, allowing for accurate load detection while minimizing the sensor's bending habit and resistance changes, even in varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a resin film is used as the load detection sensor, then the sensor can be flexibly manufactured and integrated, but the sensor strength decreases at high temperatures leading to erroneous detection
Solution Approach 1:
The patent uses a composite structure combining resin film and metal plate. The resin film provides flexibility and ease of manufacture, while the metal plate provides high strength and temperature resistance. The metal plate is bonded to the resin film, creating a composite sensor that maintains manufacturing advantages while overcoming the strength limitation at high temperatures.
2Measurement precision
If the resin film is pressed directly by the seat cushion, then the sensor responds to seating, but the resin film acquires bending habits leading to erroneous detection
Solution Approach 1:
The metal plate serves as an intermediary between the seat cushion and the resin film sensor. Instead of the resin film being pressed directly by the seat cushion, the metal plate receives the pressing force first and then transmits it to the resin film. This prevents the resin film from acquiring bending habits while maintaining accurate seating detection capability.
3Measurement precision
If the metal plate is pressed by the pressing portion, then the metal plate bends and contacts electrodes for load detection, but the adhesive layer must withstand temperature variations
Solution Approach 1:
The patent addresses temperature variations by selecting materials and designing the adhesive layer to maintain bonding strength across a wide temperature range. The adhesive layer is specifically chosen to withstand the thermal expansion and contraction of both the metal plate and resin film, ensuring that the bonding remains effective under varying temperature conditions while allowing the metal plate to bend for load 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
The solution effectively suppresses erroneous load detection due to temperature changes and bending habits, ensuring accurate seating or load detection in both high- and low-temperature environments.
Implementation Method 1
the metal plate and one surface of the sensor sheet made of the resin are bonded by an adhesive layer
Implementation Method 2
when the metal plate is pressed by the pressing portion, the metal plate is bent, the sensor sheet made of a resin is bent, the first electrode and the second electrode contact each other or a resistance value or an electrostatic capacitance value between the first electrode and the second electrode changes
Data Source
AI summary
A load detection sensor unit 1A includes: a load detection sensor 5 that has a sensor sheet 50 having a pair of resinous insulating sheets 56s and 57s, a first electrode 56e provided on a surface of one insulating sheet 56s, and a second electrode 57e forming a pair with the first electrode 56e, and a metal plate 60 provided in at least a portion overlapping with the first electrode 56e and the second electrode 57e on one surface of the sensor sheet 50; and a pressing member 4 that has a pressing portion 46 disposed on the side of the metal plate 60 opposite to the side of the sensor sheet 50 and pressing the metal plate 60. The pressing portion 46 is harder than the seat cushion SC and the sensor sheet 50 and the metal plate 60 are bonded by an adhesive layer 70.