Patent Publication Number: US-2005115102-A1

Title: Method and device for heater control in drying apparatus

Description:
This application claims the benefit of Korean Patent Application No. P2001-16564, filed on Mar. 29, 2001, which is hereby incorporated by reference for all purposes as if fully set forth herein.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a device for controlling a heating device, and more particularly, to a method and a device for controlling a heater of a drying machine (“dryer”).  
      2. Discussion of the Related Art  
      The development in semiconductor technology and related scientific fields has influenced many technologies affecting everyday life. Semiconductor technology is now available for use in multimedia applications including applications such as televisions and refrigerators associated with the internet, as well as sophisticated washing machines with associated drying machines.  
      With the advent of such changes, consumers have become more interested in energy efficiency of such appliances. More specifically, a consumer rates the reliability and quality of the product depending on its level of energy efficiency and the level of reliability of its components. Furthermore, government standards exist for energy efficiency levels. Thus, the products that do not meet specified energy efficiency standards cannot be sold in the market.  
      Therefore, manufacturers and distributors may only sell those products that conform to the energy efficiency standards recommended by the government. Also, consumers are more likely to have a positive attitude or feel more satisfied about their purchase because it is an environmentally conscious investment.  
      Specifically, the present invention relates to enhancing energy efficiency and product reliability in a device for controlling a drying machine heater.  
      A process of operating a dryer in the related art will be described with respect to  FIG. 1 . As shown in  FIG. 1 , an outer casing or enclosure  1  forms the outer shape of the drying machine. A front plate  3  is connected and fixed on the outer casing or enclosure  1 , so as to form the front surface of the drying machine.  
      A drum  5  is fixed inside the outer casing or enclosure  1 , so as to rotate during the course of a drying process. Wet laundry is introduced to the drum  5  prior to a drying cycle. A plurality of stirring blades or agitators  6  are located inside the drum  5 . The stirring blades or agitators  6  stir the laundry while the drum  5  rotates. A belt  7  is located about the circumference of the drum  5  to facilitate rotation of drum  5 . A separate motor operates the belt  7 , which drives the drum  5 .  
      Door  8  connects the inside and the outside of the drum  5  and penetrates the front plate  3 , which corresponds to the front portion of the drum  5 . Discharge hole  10  corresponds to the inside of the front plate  3  and opens towards the inside of the drum. The discharge hole  10  discharges the air existing inside the drum  5  to the outside. A filter  12  is associated with discharge hole  10  to remove impurities within the air.  
      A discharge flow tube  13  connected to the discharge hole  10  is located behind the front plate  3 . A blower assembly  15  is in fluid connection with the discharge flow tube  13 . A discharge duct  17  in conjunction with blower assembly  15  discharges the air, which flows through the discharge flow tube  13  to the outside of the drying machine.  
      Additionally, a supply duct  18  supplying air into the drum is located in a lower portion of the drum  5  inside the outer casing or enclosure  1 . The supply duct  18  supplies air for the drum  5  through the rear side of the drum  5 . A heater  19  is located adjacent to supply duct  18 .  
      Current heaters for drying machines may operate in various ways. In one method, a user opens the door  8  and puts wet laundry into the drum  5  of the drying machine. After the door  8  is closed, the user selects the desired settings or inputs operation signals. Then the temperature settings are selected and a motor rotates drum  5 . Subsequently, the blower assembly  15  is activated and forces or discharges the air inside the drum  5  through the discharge duct  17 .  
      While the air inside the drum  5  is discharged, the ambient air outside the drying machine is drawn into the drum  5  through the supply duct  18 . Heater  19  is located at the opening of the supply duct  18 , and heats the air flowing through supply duct  18  from outside the drying machine to a set temperature. The heated air is then drawn into the drum  5 .  
      The heated air inside the drum  5  absorbs the humidity associated with the wet laundry. Blower assembly  15  operates to circulate air through the discharge hole  10  into the discharge flow tube  13 . The humid air inside the discharge flow tube  13  then flows through the blower assembly  15  and the discharge duct  17  in order to be discharged to the outside.  
      The filter  12  filters the air flowing through the discharge hole, so as to prevent impurities, such as drawn thread, fuzz, or lint, from entering the blower assembly  15 .  
      Another method for controlling a drying machine heater includes a thermistor  24  fixed inside the drum  5 . Thermistor  24  is fixed inside the drum and detects the temperature within the drum. Controller  20  then uses the detected temperature to control a series of operations related to the drying process of the drying machine. The controller  20  is connected to a first terminal L 1  and a second terminal N, both supply of which supply voltage to the drying machine. A driving voltage of about 120V is supplied to the controller  20 , which is connected to the first terminal L 1  and the second terminal N.  
      In addition, other existing drying machines are equipped with a heater  19  that operates on a strict ON/OFF basis controlled by the controller  20 . In these drying machines, the heater  19  is connected between the first terminal L 1  and a third terminal L 2 , both of which supply voltage to the drying machine as illustrated in  FIG. 2 .  
      The connection to the first terminal L 1  and the third terminal L 2  provides a voltage of about 240V to the heater  19 . To prevent the heater from overheating, a thermostat  26  is connected in series with the heater  19  for automatic. turn-off when the temperature reaches a set level.  
      The process of controlling a heater of the related art drying machines will now be described in detail.  
       FIG. 3  is a graph that shows temperature settings or characteristics for different types of fabric. Heaters in currently existing drying machines control the heat according to fabric type as shown in  FIG. 3 . For example, the temperature should be a set temperature T 1  when drying cotton fabric. Also, when drying knitted fabric, the temperature inside the drum  5  should be set or controlled to another temperature T 3 , which is lower than the temperature setting for cotton fabric.  
      Therefore, the controller  20  selects or identifies the control temperature of the laundry put into the drum  5  prior to the drying process or cycle, or prior to controlling the drying process or cycle. The controller  20  sets the control temperature to an appropriate level either when the user selects the type of fabric or when the information corresponding to the fabric of the laundry is received from the washing machine.  
      Subsequently, when the heater  19  is turned ON and the drying operation begins accordingly, the controller  20  identifies the temperature inside the drum  5  by using the thermistor  24 . Heater  19  remains ON until the inside of the drum  5  reaches the pre-set temperature range, and then the heater is turned OFF. Therefore, the heater may be turned on or off multiple times during a cycle to maintain the inside of the drum  5  within the pre-set temperature range.  
      The above described systems related to drying machine temperature control have many disadvantages.  
      In methods where a heater  19  is connected to a first terminal L 1  and a third terminal L 2 , both of which supply voltage to the heater, the voltage is supplied such that a constant amount of power, about 240V, is always supplied to the heater  19 . These heaters  19  may only be controlled in two settings in accordance with the temperature detected from the thermistor  24  and the range of temperature pre-set from the thermistor  24 . Therefore, the frequent ON/OFF control of the heater results in a decrease in energy efficiency.  
      Additionally, when using this method of drying machine heat control, a frequent control of the ON/OFF operation is inevitable to maintain the temperature at a low level. This fatigues the heater switching device, therefore causing premature failure, thereby decreasing the reliability of the product.  
     SUMMARY OF THE INVENTION  
      Accordingly, the present invention is directed to a method and device for controlling the heater associated with a drying apparatus that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.  
      An advantage of the present invention is to provide a heater for a drying machine with an output that may be variably controlled by using different levels of input voltage.  
      Another advantage of the present invention is to provide a heater for a drying machine that may be variably controlled by using different levels of input voltage where the temperature setting for a drying operation is pre-set depending on the type of fabric that is to be dried.  
      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 hereof 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, the present invention relates to a device for controlling a heater for a drying machine including a plurality of switches, where each switch has a plurality of input terminals being supplied with different input voltages and an output terminal, and where each switch connects to any one of the input terminals with the output terminal according to a switching control signal; and also includes a heater connected to the output terminal of each switch varying the temperature of the heater according to the input voltage being supplied.  
      In another aspect of the present invention, a device for controlling a heater for a drying machine is provided and includes a plurality of switches, each switch having a plurality of input terminals being supplied with different input voltages and an output terminal, and each switch being adapted to connect any one of the input terminals to the output terminal according to a switching control signal, a plurality of heaters, each corresponding to each switch and varying its temperature according to an input voltage supplied thereto by each switch, where each heater includes a first end and a second end, where the first end is connected to an output terminal of a switch, and the second end is connected to the second switch of an adjacent heater; and a controller controlling connections of the switches, where the controller determines an output voltage of each heater depending on a desired temperature of a drying object corresponding to each laundry type, and where the controller controls the input voltage being supplied to each heater.  
      In another aspect of the present invention, a method is provided for controlling a heater for a drying machine by determining a range of temperatures for a heater according to each type of laundry and an output voltage according to the range of temperatures, selecting a type of laundry to be dried, identifying an output voltage of the heater corresponding to the selected type of laundry; and controlling an input voltage being supplied to the heater according to the identified output voltage.  
      In still another aspect of the invention, a device is provided for controlling a heater of a drying machine including first and second switches, each switch having first and second input terminals being supplied with different input voltages and an output terminal, and each switch connecting either one of the first and second input terminals to the output terminal according to a switching control signal, a first heater connected to the output terminal of the first switch and varying its temperature according to a first input voltage supplied thereto by the first switch, a second heater connected to the output terminal of the second switch, and varying its temperature according to the second input voltage supplied thereto by the second switch, where each heater includes a first end and a second end, so that the first end of each heater is connected to the output terminal of the switch, and the second end of each heater is commonly connected to one another; and a controller controlling the connection between the first and second switches, wherein the controller determines an output voltage of each of the first and second heaters depending on a desired temperature of a drying object corresponding to each laundry type and controls the input voltage being supplied to each of the first and second heaters.  
      To further achieve these and other advantages and in accordance with the purpose of the present invention, a method for controlling a heater of a drying machine according to the present invention includes deciding a range of temperatures for a heater according to each type of laundry and an output voltage according to the range of temperatures, selecting the type of laundry to be dried, identifying an output voltage of the heater corresponding to the selected type of laundry, and controlling an input voltage being supplied to the heater according to the identified output voltage.  
      As described above, the input voltage of the heater is variably controlled, so as to variably control the output voltage of the heater according to the range of temperatures. Therefore, as in the related art, frequent ON/OFF operations of the heater at a low temperature range may be prevented, thereby enhancing a reliability of components in the heater and switching device.  
      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.  
       FIG. 1  illustrates a structure of a general drying machine.  
       FIG. 2  illustrates a block diagram showing a device for controlling a heater of the related art drying machine.  
       FIG. 3  illustrates a graph showing temperature characteristics according to each type of fabric.  
       FIG. 4  illustrates a block diagram of a device for controlling a heater of a drying machine according to the present invention  
       FIG. 5  illustrates a control table of the heater according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS  
      Reference will now be made in detail to an embodiment of the present invention, example of which is illustrated in the accompanying drawings. In describing the identical structures of the present invention, the same terms and numeric references will be used and some supplemental descriptions will be omitted for simplicity.  
       FIG. 4  illustrates a block diagram of a device for controlling a heater of a drying machine according to the present invention. The structure of the heater will be made with reference to  FIG. 1 .  
      A device for controlling a heater according to the present invention includes two heaters  19   a  and  19   b  connected in parallel. The drying operation is controlled by the heaters  19   a  and  19   b  via the supply voltage.  
      One side of the first heater  19   a  is connected to a third terminal L 2 , which supplies an input voltage to the drying machine. Another side of the heater  19   a  is connected to a first relay  30  allowing a selective connection with either a first terminal L 1  and a second terminal N, both of which supply input voltages into the drying machine. Therefore, the heater  19   a  may be connected between the first terminal L 1  and the third terminal L 2  through the first relay  30 . In other embodiments, the first heater  19   a  may be connected between the second terminal N and the third terminal L 2  through the first relay  30 .  
      The second heater  19   b  may have a structure similar to that of the first heater  19   a . Specifically, one side of the second heater  19   b  is connected to a third terminal L 2 , which supplies an input voltage to the drying machine. Another side of the second heater  19   b  may be connected to a second relay  32  allowing a selective connection to either a first terminal L 1  and a second terminal N, both of which supply input voltages to the drying machine. Therefore, the second heater  19   b  may be connected between the first terminal L 1  and the third terminal L 2  through the second relay  32 . In another embodiment, the second heater  19   b  may be connected between the second terminal N and the third terminal L 2  through the second relay  32 .  
      In one embodiment of the present invention, a controller  20   a  preferably controls the operation of the first and second relays  30  and  32 . The controller  20   a  determines a temperature control setting according to the type of fabric being laundered. The controller  20   a  then controls the operation of the first and second relays  30  and  32 , thereby enabling the voltage output of the heater according to the desired temperature setting or temperature control range.  
      First and second relays  30  and  32  are controlled according to the controller temperature setting, as shown in  FIG. 5 . Specifically, when the temperature should be set to a higher temperature range, a high output control is executed in the first and second heaters  19   a  and  19   b . However, when the temperature setting should be set to a lower temperature setting, a low output control is carried out in the first and second heaters  19   a  and  19   b.    
      Therefore, the controller  20   a  pre-sets a value for an output control of the heater according to the temperature setting, as shown in  FIG. 5 . Corresponding control of the output voltage of the first and second heaters  19   a  and  19   b  is possible because the input voltage may be one of three levels: 0 V, 120V, and 240V.  
      The above-described device and method for controlling a heater for a drying machine according to the present invention will now be described in detail.  
      A user opens the door  8  to the drying machine and places a load of wet laundry into the drum  5  and shuts the door  8 . Next, the user inputs the drying operation signal, which is recognized by the controller  20   a . The controller  20   a  activates the motor, thereby allowing the drum  5  to rotate. Then, the blower assembly  15  is activated, discharging the air within the drum  5  through the discharge duct  17  to the outside.  
      Meanwhile, the controller  20   a  determines a temperature setting or temperature control range for the drying cycle based on the type of laundry fabric that was selected by the user or the laundry fabric information provided by the washing machine. When drying laundry that can be processed at a higher temperature range, the output voltage of the first and second heaters  19   a  and  19   b  may be set or controlled to a higher level. Conversely, when drying laundry that should be processed at a lower temperature range, the output voltage of the heaters  19   a  and  19   b  may be controlled to a lower level.  
      Thus, in order to carry out a drying operation or cycle within the desired temperature setting, the controller  20   a  controls the switching operation of the first and second relays  30  and  32 , thereby enabling the first and second heaters  19   a  and  19   b  to generate heat.  
      During a drying cycle, the air within the drum  5  is discharged to the outside, while cool air is drawn in from the outside through the supply duct  18  and to drum  5 . Because the first and second heaters  19   a  and  19   b  are located on the opening of each supply duct  18 , the air drawn into the drum is heated to a certain degree.  
      The heated air supplied to the drum  5  removes moisture from the laundry and is sent through the discharge hole  10  to the discharge flow  13  by the blower assembly  15 . The air is then externally discharged from the discharge flow.  13  and through the discharge duct  17 . Thus, the circulating movement of heated air allows the wet laundry inside the drum  5  to be dried.  
      The process of controlling the level of voltage supplied to the first and second heaters  19   a  and  19   b  will now be described in detail.  
      As shown in  FIG. 4 , a single-phase 3-wire type connection may include a total of three terminals for supplying input voltage (i.e., the first terminal L 1 , the second terminal N, and the third terminal L 2 ). Each of the three terminals is designed to generate different levels of voltage when connected to one another. When the first terminal L 1  is connected to the second terminal N, a voltage of about 120V is produced. Similarly, when the second terminal N is connected to the third terminal L 2 , a voltage of about 120V is generated. Finally, when the first terminal L 1  is connected to the third terminal L 2 , a voltage of 240V is produced.  
      Therefore, in the present invention, the output voltage of the heater may be variably controlled by using different levels of input voltage. In an embodiment in which the input voltage is constant, a structure for transforming current is also included to allow control of the input voltage of the heater.  
      Specifically, both the first relay  30  and the second relay  32  are designed to select either the first terminal L 1  and the second terminal N. In addition, the third terminal L 2  may be commonly connected to the side of both the first and second heaters  19   a  and  19   b . Therefore, heaters  19   a  and  19   b  may be supplied with either a voltage of 120V or a voltage of 240V, depending upon the configuration of the first relay  30  and the second relay  32 .  
      When the controller  20   a  connects the first relay  30  and the second relay  32  to the first terminal L 1 , both heaters  19   a  and  19   b  are connected between the first terminal. L 1  and the third terminal L 2 . Therefore, a voltage of 240V is supplied to operate the first and second heaters  19   a  and  19   b.    
      When the controller  20   a  connects the first relay  30  to the first terminal L 1  and the second relay  32  to the second terminal N, then the first heater  19   a  is supplied or operated with an input voltage of 240V, and the second heater  19   b  is supplied or operated with an input voltage of 120V. In an alternative embodiment, the controller  20   a  may connect the first relay  30  to the second terminal N and the second relay  32  to the first terminal L 1 , supplying or operating first heater  19   a  with an input voltage of 120V, and supplying or operating second heater.  19   b  with an input voltage of 240V.  
      In an embodiment in which controller  20   a  connects both the first relay  30  and the second relay  32  to the second terminal N, then both heaters  19   a  and  19   b  are connected between the second terminal N and the third terminal L 2 . Therefore, the two heaters  19   a  and  19   b  are supplied with an input voltage of 120V  
      In an embodiment in which controller  20   a  connects the first relay  30  to the first terminal L 1  and turns the second relay  32  OFF, then the first heater  19   a  is connected to the first terminal L 1  and the third terminal L 2 . Therefore, the first heater  19   a  is supplied or operated with a voltage of 240V. In this case, the second heater  19   b  is not supplied or operated with any voltage, i.e., it is off.  
      In an alternative embodiment, controller  20   a  may turn the first relay  30  off and may connect the second relay  32  to the first terminal L 1 , then the second heater  19   b  is supplied or operated with a voltage of 240V. In this embodiment, the first heater  19   a  is not supplied or operated with any voltage, i.e., it is off.  
      Additionally, when the controller  20   a  connects the first relay  30  to the second terminal N and turns the second relay  32  off then a driving voltage of 120V is supplied to or operates the first heater  19   a . At this point, the second heater  19   b  is not supplied with any voltage, i.e., it is turned off. In an alternative embodiment, when the controller  20   a  turns the first relay  30  OFF and connects the second relay  32  to the second terminal N, then a driving voltage of 120V is supplied to or operates second heater  19   b . In this case, the first heater  19   a  is not supplied or operated with any voltage, i.e., it is off..  
      Furthermore, when the controller  20   a  turns both the first and second relays  30  and  32  off, both heaters  19   a  and  19   b  are also turned off accordingly.  
      As described above in the present invention, the temperature setting or temperature control range for a drying operation or cycle is pre-set depending on the type of fabric that is to be dried. The output voltage of the heater is determined based on the pre-set temperature setting. Then, once the drying operation or cycle is initiated, an appropriate output voltage is selected in accordance with the pre-set temperature setting or temperature control range.  
      As described above, the device and method for heater temperature control in a drying machine according to the present invention may variably control the input voltage of a heater, thereby allowing an output voltage of the heater to be variably controlled in accordance with a temperature setting or temperature control range.  
      The present invention is advantageous in that frequent on/off operations of the heater at a low temperature range may be prevented. Thus, the reliability in the components of the heater and the switching device may be improved.  
      In addition, the output voltage of the heater according to a set temperature range may be variably controlled even without the frequent ON/OFF operations of the heater, enhancing the energy efficiency.  
      Finally, with the above-described advantages, reliability, product quality, and product life may also be enhanced.  
      It will be apparent to those skilled in the art that various modifications and variation can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.