Dryer Drum Speed Control for Load-Dependent Laundry Drying
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Solution Overview
Problem
Conventional dryers face challenges in efficiently and gently drying laundry, as the warm process air often fails to effectively penetrate and dry the laundry due to inadequate contact, especially at varying loads, leading to prolonged drying times and increased energy consumption.
Innovation Solution
A method for load-dependent operation of a dryer using a moisture sensor, a speed-variable electric drive motor, and a control device to adjust the drum and process air fan speeds based on the dry weight and moisture content of the laundry, ensuring optimal air flow and penetration, even at maximum loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the drum is rotated at a low speed to allow laundry to fall, then the laundry fall is improved, but the drying time increases and productivity decreases
Solution Approach 1:
The patent applies dynamics by varying the drum rotation speed during different phases of the drying cycle. The control device rotates the drum at a first speed during an initial phase to enable laundry fall, then switches to a second, higher speed during a subsequent phase to improve productivity. This dynamic speed adjustment resolves the contradiction between maintaining stable laundry fall conditions and improving drying efficiency.
2Productivity
If the drum is rotated at a high speed to improve productivity, then the drying time decreases, but the laundry fall deteriorates and mechanical stress on laundry increases
Solution Approach 1:
The patent uses dynamic speed adjustment to resolve the contradiction between productivity and mechanical stress. By implementing a two-phase drying cycle with different rotation speeds, the system achieves high productivity during the second phase while protecting laundry from excessive mechanical stress during the initial phase when laundry fall is critical. The control device manages this transition to optimize both efficiency and garment care.
3Quantity of substance
If the load on the drum is high, then the laundry fall decreases, but the air contact with laundry becomes insufficient leading to prolonged drying times
Solution Approach 1:
The patent applies dynamics by adjusting drum speed based on load conditions. During an initial phase, the drum rotates at a lower speed to maintain adequate laundry fall even with high load. In a subsequent phase, the speed increases to improve air circulation and drying efficiency. This dynamic adaptation allows the system to handle high loads effectively while maintaining productivity.
Solution Approach 2:
The patent implements periodic action through a multi-phase drying cycle with distinct speed regimes. The control device alternates between a first rotation speed optimized for laundry fall and a second higher speed optimized for drying efficiency. This periodic variation in operational parameters enables the system to address both the reduced laundry fall from high loads and the need for effective air contact throughout the drying process.
4Productivity
If the warm process air temperature is increased to improve drying efficiency, then the drying time decreases, but the laundry may be damaged and the process becomes less gentle
Solution Approach 1:
The patent applies periodic action through a two-phase drying cycle with different temperature and speed characteristics. During the first phase, the drum rotates at a lower speed and the process air temperature is controlled to enable gentle drying with adequate laundry fall. In the second phase, the drum speed increases and temperature conditions are optimized for higher drying efficiency. This periodic variation resolves the contradiction between gentle treatment and drying efficiency.
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 approach significantly reduces drying time by ensuring intense air contact with the laundry and optimizing energy use, while minimizing mechanical stress on the laundry, resulting in a more efficient and gentle drying process.
Implementation Method 1
a process air fan (6) located in a process air duct (3)
Implementation Method 2
a heater (4) and a process air fan (6) located in a process air duct (3)
Implementation Method 3
the fall of the laundry carried along due to the drum movement by means of the catches and the effect of centrifugal force
Implementation Method 4
the fall of laundry depends on the load of laundry in the drum
Implementation Method 5
a moisture sensor (7)
Data Source
AI summary
The invention relates to a method for operating a dryer (1) comprising a drum (2) for pieces of laundry (5) to be dried, a moisture sensor (7), an electric, variable-speed drive motor (12) for the drum (2), a control unit (11) and a process air duct (3) in which a heating unit (4) and a process air blower (6) are located, said method comprising the steps: (a) determining a load Linit of the drum (2) at the start of loading; (b) operating the drive motor (12) at a speed v in a range v1 <= v <= v2; (c) producing hot process air by operating the heating unit (4) and the process air blower (6) and rotating the drum (2) at a speed ù, wherein ù1 < ù < ù2, and passing said air through the drum (2); (d) measuring a moisture W of the pieces of laundry (5) by means of the moisture sensor (7); (e) determining a load LWu of the drum (2) when a moisture W smaller or equal a predetermined threshold value Wu is reached; (f) determining the dry weight Wdry of the pieces of laundry (5) once it is established that the load L is within a range defined by a minimum load Lmin and a maximum load Lmax , such that Lmin <= L <= Lmax; and (g) increasing the speed v of the drive motor (12) and the speed ù of the drum (2) depending on the determined dry weight Wdry and the moisture W. The invention further relates to a dryer suitable for performing said method.