Patent Publication Number: US-6987395-B2

Title: Dryness measurement device

Description:
TECHNICAL FIELD 
   The present invention relates to a drier, and more particularly to a device for measuring the dryness of laundry while the laundry is dried. 
   BACKGROUND ART 
     FIG. 1  is a side sectional view of a general drier, and  FIG. 2  is a plan view of the general drier. 
   Referring to  FIGS. 1 and 2 , the drier has an outer case  53  defining an outer shell thereof. A front plate  41  is connected to the leading end of the outer case  53  so as to form the front face of the drier. A drum  44  is rotatably installed inside the outer case  53  such that laundry is loaded into and dried in the drum  44 . The drum  44  is rotated by a drum-drive belt  54  which surrounds the outer surface of the drum  44 . 
   An exhaust hole  43  is formed to correspond to an inner surface of the front plate  41  and be opened toward the inside of the drum  44 . The exhaust hole  43  functions to exhaust air out of the drum  44 . A lint filter  36  is disposed at an entrance of the exhaust hole  43  so as to remove foreign particles contained in air. 
   At a portion of the exhaust hole  43 , an electrode sensor  38  is disposed for detecting the dryness of laundry within the drum  44  while the laundry is dried. The electrode sensor  38  detects the dryness of laundry based upon a difference of voltages applied to both end terminals of the electrode when the laundry is in contact with the electrode  38 . The electrode sensor  38  provides a microprocessor  100  with a detection signal in the form of a voltage signal. An exhaust passage  45  is placed inside the front plate  41  so as to be connected with the exhaust hole  43 . A blower assembly  30  is installed so as to communicate with the exhaust passage  45 . The exhaust passage  45  includes a second temperature sensor  32  for detecting the temperature of air which is exhausted out of the drum  44 . 
   The blower assembly  30  is connected to an exhaust duct  34  for discharging air which is exhausted via the exhaust passage  45  out of the drier. The blower assembly  30  includes a blower  31  which sucks and circulates air into/in the drum  44  to introduce heat of a heater  42 , and discharges moisture from laundry via the exhaust hole  43 . 
   A feed duct  46  to feed air into the drum  44  is disposed at a portion within the outer case  53  and corresponding to a lower portion of the drum  44 . The feed duct  46  feeds air into the drum  44  via a rear portion of the drum  44 . A heater  42  is disposed adjacent to a portion of the feed duct  46 . A temperature sensor  48  to detect the temperature of air sucked into the drum  44  is disposed in another portion of the feed duct  46 . 
     FIG. 3  is a block diagram of components used in controlling the general drier. 
   A mainboard  52  is disposed in a portion within the outer case  53  so as to electrically control the operation of the drier. The mainboard  52 , as shown in  FIG. 3 , includes a microcomputer  100  for generally controlling a drier, a drive unit  120  for driving components which should be electrically controlled within the drier, and a group of sensors  110  for detecting electric signals so as to judge the operational status of the drier. 
   The group of sensors  110  include: a key input unit  103  for providing the microcomputer  100  with a power supply signal, a drying operation signal and drying conditions which are selectively inputted by a user; an electrode sensor signal conversion unit  106  for converting a signal detected by the electrode sensor  38  into a signal readable by the microcomputer  100  and providing the converted signal to the microcomputer  100  so as to detect the current dryness of laundry; a first temperature sensor signal conversion unit  109  for converting a signal detected by the first temperature sensor  48  into a signal readable by the microcomputer and providing the converted signal to the microcomputer  100  so as to detect the temperature of hot air fed into the drum  44 ; a second temperature sensor signal conversion unit  112  for converting a signal detected by the second temperature sensor  32  into a signal readable by the microcomputer  100  and providing the converted signal into the microcomputer  100  so as to detect the temperature of hot air exhausted from the drum  44 ; and a door detection unit  115  for detecting the opening of a door while laundry is being dried, converting a result of the detection into a signal readable by the microcomputer  100  and providing the converted signal to the microcomputer  100 . 
   The drive unit  120  includes a drum motor drive unit  118  for driving a drum motor (not shown) which generates driving force for rotating the drum  44 , a blower motor drive unit  121  for generating driving force for rotating the blower  31  and a heater drive unit  124  for supplying heat source for drying laundry via the feed duct  46 . 
     FIG. 4  illustrates a construction of the second temperature sensor signal conversion unit shown in  FIG. 3 . 
   Referring to  FIG. 4 , when the electrode sensor  38  is in contact with laundry circulating within the drum  44 , the resistance value of the electrode sensor  38  is varied depending upon the dryness of laundry. The microcomputer  100  measures the dryness of laundry by receiving the resistance valve of the electrode sensor  38  varied with the dryness of laundry and a voltage divided by a resistor R 1 . 
   A dryness measuring device having the electrode sensor  38  and the resistor R 1  uninterruptedly outputs detection values regardless of a time point of when the microprocessor  100  detects the dryness, and the detection values are continuously inputted into the microcomputer  100 . The microcomputer  100  measures the dryness based upon the detection values which are inputted before and after the time point of a dryness measurement and which are currently being inputted. In other words, at the time point of measurement, the dryness is influenced by the detection values before and after the time point of the dryness measurement. 
   For example, where the electrode sensor  38  has a resistance value variable under the external influence, the resistance value is directly applied to a detection value, which may be used in dryness measurement together with other detection values which are being continuously detected. As a result, the microprocessor  100  fails to precisely measure the dryness owing to the resistance value which is under the external influence at the time point of the measurement. 
   DISCLOSURE OF THE INVENTION 
   Accordingly, the present invention is directed to a dryness measuring device that substantially obviate one or more of the problems due to limitations and disadvantages of the related art. 
   An object of the present invention is to provide a dryness measuring device in which any external influence is reduced. 
   Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings. 
   To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a dryness measuring device includes: a drum disposed rotatably and for receiving objects to be dried therein; detection means for detecting the dryness of the objects, the detection means including an electrode sensor which is disposed contactable by the objects, a capacitor for charging a voltage according to resistance variation occurring when the objects is in contact with the electrode sensor and a discharging circuit for discharging the charged voltage from the capacitor; and control means for operating the discharging circuit to discharge the charged voltage from the capacitor and measuring the current dryness based upon variation of a voltage which is newly charged into the capacitor. 
   It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
     In the drawings: 
       FIG. 1  is a side sectional view of a general drier; 
       FIG. 2  is a plan view of the general drier; 
       FIG. 3  is a block diagram of components used in controlling the general drier; 
       FIG. 4  illustrates a construction of a second temperature sensor signal conversion unit shown in  FIG. 3 ; and 
       FIG. 5  illustrates a construction of a dryness measuring device in a drier according to the invention. 
   

   BEST MODE FOR CARRYING OUT THE INVENTION 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     FIG. 5  illustrates a construction of a dryness measuring device in a drier according to the invention, in which such a construction of the drier necessary for explanation will be referred to  FIGS. 1 to 3 . 
   Referring to  FIG. 5 , in the dryness measuring device of the invention, an electrode sensor  38  and a capacitor C 1  are connected to a resistor R 1 , respectively, in series so that the voltage charged in the capacity C 1  is varied with the resistance value of the electrode sensor  38 . 
   A discharging circuit is disposed between the electrode sensor  38  and the capacitor C 1 . 
   The discharging circuit includes a resistor R 2  and a transistor Q 1  functioning as a switching device. When the transistor Q 1  is turned on under the control of the microcomputer  100 , the charged voltage of the capacitor C 1  is discharged. The transistor Q 1  has a turn-on period which is controlled by the microcomputer  100 . The voltage charged in the capacitor C 1  is provided to the microcomputer  100  via a resistor R 3 . 
   The drier of the invention constructed as above has a following dryness measuring process. 
   Hereinafter, there will be described an operational process of the drier of the invention constructed as above. 
   A user primarily loads laundry into the drum  44  so as to dry laundry. The user closes a door, and selects a dry mode from the key input unit  103 . A signal selected corresponding to the dry mode is inputted into the microcomputer  1 . 00 . The microcomputer  100  recognizes the dry mode of the drier in response to the selected signal, and outputs a drum drive signal to the drum motor drive unit  118 . As the drum motor (not shown) is actuated, the drum drive belt  54  is rotated and accordingly the drum  44  is rotated. 
   The microcomputer  100  outputs a blower motor drive signal to the blower motor drive unit  121 . The blower assembly  30  is operated in response to the blower motor drive signal, and the operation of the blower motor assembly  30  drives the blower  31 . As the blower  31  is driven, air in the drum  44  is exhausted to the exhaust duct  34  via the lint filter  36 . 
   When the blower  31  exhausts air out of the drum  44 , external air is sucked into the drum  44  via the feed duct  46 . Owing to heat generation of the heater  42  at an entrance of the feed duct  46 , air is heated up to a predetermined temperature while it is being introduced from the external environment into the drum  44 . That is, the heater  42  heats air, which is introduced under the suction force of the blower  31 , before it is fed into the drum  44 . 
   After introduced into the drum  44 , air absorbs moisture from laundry and then flows to the exhaust passage  45  via the exhaust hole. Moisture-containing air is exhausted to the outer environment under the suction force of the blower  31 , which is driven in response to the operation of the blower assembly  30 . After flowing to the exhaust passage  45 , air is exhausted to the outer environment via the exhaust duct  34 . The suction force of the blower  31  allows the air to be exhausted from the drum  44  through the exhaust hole  43 . The lint filter  36  purifies air passing through the exhaust hole  43  such that foreign particles (e.g. seam and fluff of laundry) contained in the air are not transferred into the blower assembly  30 . 
   The microcomputer  100  has a number of reference values set up according to types of objects to be dried and the dryness thereof. While air is circulating within the drum  44 , the resistance value of the electrode sensor  38  is varied whenever the objects are in contact with the electrode sensor  38 . Based upon the resistance value, a variable detection value is outputted. 
   The microcomputer  100  turns on the transistor Q 1  in the discharging circuit shown in  FIG. 5  at a given time point before measuring the dryness of laundry. This operation permits the voltage charged in the capacitor C 1  to be discharged. Upon completing discharge of the capacitor C 1 , the microcomputer  100  controls the transistor Q 1  into a turn-off mode again so as to prevent later discharge of the charged voltage in the capacitor C 1  according to the dryness to be detected. 
   At a time point when the above operation has minimized any external influence for measuring the current dryness, the microcomputer  100  detects a voltage, which is divided by the variable resistance value of the electrode sensor  38  and charged into the capacitor C 1 , via the resistor R 3 . The detected voltage value is determined as the current dryness by the microprocessor  100 . 
   As set forth above, the invention repeatedly discharges and charges the dryness measuring circuit for a predetermined period in order to measure the dryness, thereby minimizing the external influence in dryness measurement. 
   The electrode sensor signal conversion unit  106  converts a value detected by the electrode sensor  38  via discharging and charging for a predetermined period into a signal readable by the microprocessor  100 , and transfers the signal into the microprocessor  100 . The microprocessor  100  determines the current dried condition of laundry based upon variation of the voltage values detected by the electrode sensor  38 . 
   In addition, the microcomputer  100  detects the temperature of hot air fed into the drum  44  via the first temperature sensor  48  and a signal detected by the first temperature sensor signal conversion unit  109 , and detects the temperature of hot air exhausted from the drum  44  via the temperature sensor  32  and a signal detected by the second temperature sensor signal conversion unit  112 . That is, the microcomputer  100  comprehensively judges the value detected by the electrode sensor  38  as well as the temperature of hot air introduced/exhausted into/from the drum  44  so as to determine the dryness of laundry. When the comprehensively judged value reaches a predetermined value, the microcomputer  100  stops the heater  42 . 
   In addition to stopping the heater  42 , the microcomputer  100  interrupts the blower drive signal, which the microcomputer  100  has been providing to the blower motor drive unit  121  so far. The blower drive signal is interrupted to cut off power toward the blower  31 , thereby stopping the blower  31 . 
   As set forth above, in detection of the dryness, the drier of the invention detects variation of the voltage charged in the capacitor based upon variation of the resistance when laundry is in contact with the electrode sensor. The charged voltage is discharged from the capacitor for every predetermined period to minimize the external influence. 
   Accordingly, the present invention has a fundamental technical spirit in that the electrode sensor is utilized to detect the current dryness of laundry and the current dryness is measured based upon variation of the voltage which is charged in the capacitor according to variation of the resistance value of the electrode sensor. It is also to be understood that those skilled in the art can make various modifications and variations without departing from the spirit and scope of to the invention. 
   INDUSTRIAL APPLICABILITY 
   According to the present invention as set forth above, the dryness measured during the automatic dry mode in the drier has no external influence so as to further improve precision in detection. This allows the drier of the invention to prevent under-heat or over-heat via improvement in detection precision, thereby improving the dried condition of laundry as well as preventing damage of laundry. Furthermore, enhanced dryness can advantageously improve reliability and quality of an article. 
   While the present invention has been described and illustrated herein with reference to the preferred embodiments thereof, it will be apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of the appended claims and their equivalents.