Hand dryer
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Solution Overview
Problem
Capacitive sensors used in hand dryers cannot accurately detect the position of a hand, leading to misoperation due to water adhesion and inadequate control of airflow.
Innovation Solution
A hand dryer design featuring a recessed hand insertion portion with a high-pressure airflow nozzle and a capacitive sensor using multiple electrode pairs with different polarities to detect hand position and control airflow distribution based on hand detection patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive sensor with a pair of electrodes facing each other is used to detect a hand, then hand detection is achieved, but the position at which the hand is placed cannot be detected
Solution Approach 1:
The sensor is divided into multiple electrode pairs arranged in different regions (front, rear, left, right) of the hand insertion portion. Each electrode pair independently detects capacitance changes in its specific region, allowing the system to segment the detection area and identify which region contains a hand, thereby obtaining position information.
Solution Approach 2:
The detection system transitions from a single detection point to a two-dimensional detection matrix by arranging multiple electrode pairs in different spatial positions. This dimensional expansion enables the system to detect not only the presence of a hand but also its specific location within the insertion portion.
2Reliability
If water adheres to the sensor electrodes, then misoperation occurs, but using a single electrode pair cannot distinguish water adhesion from hand insertion
Solution Approach 1:
Multiple electrode pairs are distributed across different regions of the hand insertion portion. When water adheres to the sensor, it typically affects only specific electrode pairs rather than all of them simultaneously. By analyzing the pattern of affected electrodes and comparing signals across multiple pairs, the system can distinguish between water adhesion (affecting specific regions) and actual hand insertion (affecting the overall detection field).
Solution Approach 2:
The system continuously monitors capacitance changes across multiple electrode pairs and uses this feedback information to distinguish between false signals caused by water adhesion and genuine hand insertion events. The controller analyzes the spatial distribution and temporal patterns of capacitance changes to make accurate determination.
3Device complexity
If a single electrode pair is used, then the device complexity is low, but the control appropriateness for hand position is insufficient
Solution Approach 1:
The sensor is segmented into multiple electrode pairs positioned at different locations (front, rear, left, right sides) of the hand insertion portion. This segmentation allows the controller to identify which specific region contains a hand and adjust the airflow control accordingly, providing position-appropriate control without requiring overly complex sensor structures.
Solution Approach 2:
Different electrode pairs are positioned to detect specific regions of the hand insertion portion. The controller uses this localized detection information to provide differentiated control responses based on where the hand is positioned, ensuring appropriate operation for each location while maintaining a relatively simple overall device structure.
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
Prevents misoperation by accurately determining hand position and controlling airflow for efficient hand drying, ensuring effective water removal and user-friendly operation.
Implementation Method 1
The capacitive sensor detects a hand by measuring a change in capacitance between two electrodes with different polarities to each other
Implementation Method 2
an air blower provided in the body casing to generate the high-pressure airflow; and a nozzle provided on a wall of the hand insertion portion to transform the high-pressure airflow from the air blower into a high-speed airflow
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A hand dryer (1) includes: a hand insertion portion (3) formed in a recessed shape in a body casing; an air blower (6) provided in the body casing (2) and generating a high-pressure airflow; and nozzles (3a, 3b) each provided on a wall of the hand insertion portion (3), transforming the high-pressure airflow from the air blower (6) into a high-speed airflow, and blowing the high-speed airflow into the hand insertion portion, whereby the hand dryer removes water adhering to a hand inserted into the hand insertion portion (3) with the high-pressure airflow blown from the nozzles (3a, 3b). The hand dryer (1) includes: a hand sensor (13) including a plurality of electrode pairs and detecting a hand inserted into the hand insertion portion (3) from a change in capacitance between two electrodes included in the plurality of electrode pairs, each of the plurality of electrode pairs consisting of a first electrode and a second electrode having different polarities to each other; and a controller (14) that drives the air blower (6) on the basis of a combination of the two electrodes with which a hand has been detected by the hand sensor (13).