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 L1 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 L1 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 L1 and a third terminal L2, both of which supply voltage to the drying machine as illustrated in FIG. 2.
The connection to the first terminal L1 and the third terminal L2 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 T1 when drying cotton fabric. Also, when drying knitted fabric, the temperature inside the drum 5 should be set or controlled to another temperature T3, 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 L1 and a third terminal L2, 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.