Generally, a dryer is provided to dry a wet object (like for example, wet textiles). The wet objects will be referred from now on as “textiles” or “clothes”, without being limited to just these only.
It is common practice to detect the level of moisture of the textiles in a rotating drum using moisture detectors provided on the drum and/or on a fluff duct and/or on an exit duct. A voltage signal of the moisture detector of the articles being washed is used based on the actual characteristics of the textile load being dried. That is, a measurement of electric resistance of the mentioned clothes is used: if the clothes contain water within their fibers, it is capable of conducting electricity, whereas if the clothes are dry and contain no water, it is not capable of conducting electricity and its electric resistance increases. The detectors are tested periodically to provide voltage values which are filtered, cleaned and input into a processor which contains a module to determine when the clothes are dry, almost dry or attain a desired level of moisture content and a module to determine when the drying cycle should cease.
The low effectiveness of the detector in determining with exactness the moisture content of the textiles being dried is common in these types of measurements, since sensitivity is lost when the clothes are almost dry or when the textile load is small. Thus the voltage signal of the moisture detector can be highly variable during the drying time and it can be that it does not accurately detect the exact moisture content of the textiles or clothes being dried. The articles can, from time to time, come into contact with the electrodes of the moisture detector and sometimes not be in contact with the electrodes, given the random rotation patterns of the textiles and given small loads.
As can be supposed, another factor which affects the detector's exactness in detecting the moisture level occurs when the textiles are not dried in a uniform manner. That is, some portions of the textiles may be more humid than other portions of the textiles, and the more humid portions cannot be detected with exactness by the detectors.
Thus, in order to avoid having parts of the clothes which are damp at the end of the cycle, the dryer extrapolates the drying time after the moisture level where the sensitivity of the measure is reduced, adding or lessening the drying time. The risk in drying cycles which save energy is that the clothes may not be sufficiently dried because the added time or the lessened time is not adequate, or rather, takes longer time and thus more energy than that which is necessary to dry during the drying cycles. Thus a processor is provided to calculate and compensate times in a precise manner and to predict the required drying time for the drying cycle. The problem therefore, is to provide for the dryer the flexibility to adjust the cycle time as a function of certain factors, such as the heat factor and the operation time of the dryer, the time necessary to achieve certain voltages, and weight determination: these factors themselves are a function of other factors. The benefit of the problem to be resolved is to have dry clothes at the conclusion of the drying cycle, in light of the predetermined or selected heat level selected by the user, in light of the user's cycle selection, the size of the load, the restrictions and the energy level, allowing a lesser level of energy consumption and the operator's satisfaction in attaining proper drying of the textiles in the dryer.
In the area, similar processes to determine certain drying aspects of a dryer are known. For example, Chinese patent number 1 715 544 makes known a control method for regulating the heater and the fan based on the drum's internal conditions, such as temperature and moisture to allow a microprocessor to regulate the heater and the fan, thus allowing for a drying time shortening.
Spanish patent number 2 212 436 makes known a process which watches the flow velocity of an air process current generated by a fan in an air channel and heated via a heating system in a household clothes dryer where the air process temperature is collected at a certain point situated in the current flow, after the heating system, characterized because the heating power of the heating system is changed, the provoked temperature variation is collected in this manner in the current flow of the air process in at least one point, and the difference in the moments where the temperature difference is collected of the current flow of the air process is a first point or a second point, respectively, or between the moments where the heating potential variation is collected or the temperature variation of the current flow of the air process at a second point, and is used as a measurement of the velocity of the current flow of the air process.
Japanese publication number 1131699 makes known that an energy source of the semi-conducting heater is an energy source of constant voltage, where the energizing is controlled to set the heater's energy consumption. When the dryer ends, the heater is turned off and shuts down the dryer's motor. Under the control, actual energy consumption is always maintained to be a desired energy consumption by the control phase through the surrounding temperature etc. is varied, the energy consumption is constant. Afterwards, when it is controlled in order to maximize the allowed energy consumption at a determined state, the heater always operates at maximum energy consumption without relating it to the surrounding temperature. As a result, the heater's ability is always set at the maximum in order to reduce the clothes' drying time.
Japanese publication number 2005245489 makes known a dryer provided with a rotating drum, an air entry section with a heater, an air exit section with a fan, an exit temperature detector placed in the exit section and a control which controls heat. The clothes are dried by adjusting the exiting air temperature to a pre-described temperature given the exiting air's temperature detected by the temperature detector in the control and controlling the heater. The clothes drying process controlling the dryer is composed by a multiple number of drying time length with a pre-described temperature which is sequentially low and a drying time of each drying time length being predetermined. It is desired that the set temperature for the last drying time length be approximately similar to the cooling temperature required during the cooling process.
U.S. Pat. No. 5,454,171 makes known a dryer which includes a drum which shuffles the clothes to be dried, a heater and a fan to provide hot air in the drum during the drying process, and a temperature detector which detects temperature in the drum. The drying process includes a drying step in which hot air is fed to the drum and a cooling step in which the heater is de-energized. The intermittent operation is started once the drying process is completed. The intermittent operation is completed once the temperature detected by the temperature detector has achieved a predetermined value to prevent the clothes from getting wrinkled.
U.S. Pat. No. 6,199,300 makes known a method and apparatus to control a dryer's heat entry where the initial heat for a load of clothes is set at maximum power until a temperature condition or predetermined time takes place. The dryer's heat entry is reduced to reduce energy consumption while effectively removing moisture of the load of clothes. When the moisture content of the load of clothes falls to a predetermined quantity, the maximum heat entry is applied once again to remove the remaining moisture of the load of clothes.
U.S. Pat. No. 6,700,102 makes known a control circuit which operates with a supply of energy of 120 volts which compensates for the surrounding temperature changes to compensate for premature advancement of the chronometer of the dryer's motor during a automatic drying cycle.
U.S. Pat. No. 6,822,201 makes known a dryer which has a control circuit of the heater to control the impulse of a dryer which uses one of a plurality of high voltages, which uses a circuit realized by a relay form of contact in C set between a micro-computer exit and a plurality of heater impulsions, so that the heater's impulse capacity be assured even when the current exit fails, and to avoid short circuit conditions even when the micro-computer has logical mal-functions.
US publication number 2007/0251119 makes known a dryer and a control method for the same dryer, through which the maintenance of energy savings and optimal temperature within the drum are equipped in a way to diversify the heater's temperature, varying the fan's rotational velocity used by the dryer. A drying drum is included to shuffle the objects to be dried, a fan is provided to provide air to pass through the drying drum, a heater to heat air supplied to the drying drum, an impulses motor which generates an impulse force to rotate the drum and the fan and a control unit which controls the motor's RPMs to be varied according to the results detected by the temperature detector.
U.S. Pat. No. 7,322,126 makes known a clothes dryer which has a control system for degrees of dryness which is responsive to the moisture level of the clothing articles rotating in a drum and an objective moisture value to control the drying cycle of the dryer. The cycle has a producing module with a parameter size of the load and a module of parameter of detection of air flow. These two modules generate one of two conditions of parameters used by the processor to modify or select a desired value of appropriate moisture. The producing module of desired size parameter generates a small load parameter and a large load parameter. The module of air flow detection produces one of first or second parameters of air flow to be used in the processor of drying degree. As a result, the processor selects one of four moisture values among these conditions.