Abstract:
A printer and a method of driving a cooling fan of the printer include a storage unit temporarily stores printing option data and image data, and a control unit controls an operation of a printing unit in one of a warming-up mode, a standby mode, a printing mode and a sleep mode based on the printing option data and the image data as inputted into the control unit. The control unit outputs a control signal variably controlling an RPM (Rotation Per Minute) of the cooling fan based on the operation mode and a printing speed of the printing unit. A cooling fan driving unit drives the cooling fan at a different RPM based on the control signal input from the control unit. Accordingly, the printer and the method of driving the cooling fan of the printer are capable of shortening the warming-up time to increase an initial printing speed, preventing the printing unit from being overheated, extending a lifespan of the cooling fan, and reducing a power consumption.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of Korean Patent Application No. 2002-37130, filed Jun. 28, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a printer, and more particularly, to a printer capable of variably controlling a Revolution Per Minute (RPM) of a cooling-fan depending on an operation mode of a printing unit and a method of driving the cooling fan of the printer. 
   2. Description of the Related Art 
   As shown in  FIG. 1 , a conventional printer employing an electrophotographic developing method includes a pick-up roller  101 , a charging roller  103 , an organic photoconductive (OPC) drum  105 , a transfer roller  107 , a developing roller  109 , a supplying roller  111 , a fusing device  113 , and a light exposure device  115 , to print a predetermined image data on a sheet of printing paper  117 . That is, the charging roller  103  electrically charged with a high charging voltage rotates to electrically and uniformly charge a photosensitive material coated along an external circumference of the organic photoconductive drum  105 , and light emitted from the light exposure device  115  forms an electrostatic latent image on a surface of the electrically charged organic photoconductive drum  105 . An electric potential difference then occurs between the supplying roller  111  supplied with a supplying voltage, e.g., a higher voltage, and the developing roller  109  supplied with a developing voltage, e.g., a lower voltage, than that of the supplying roller  111 , thereby moving a negative charge from the supplying roller  111  to the developing roller  109 . Accordingly, toner supplied from the developing roller  109  is coated on the electrostatic latent image formed on the surface of the organic photoconductive drum  105  to thus form a visible image. The transfer roller  107  of a transfer voltage, e.g., another higher voltage, transfers the visible image formed with the toner coated on the surface of the organic photoconductive drum  105  to the printing paper  117 . A pre-transfer lamp (PTL)  123  emits light having a predetermined wavelength onto the organic photoconductive drum  105  to decrease an electric potential of the toner coated on the organic photoconductive drum  105 . As a result, a binding force of the toner with respect to the organic photoconductive drum  105  decreases to thus improve a transfer efficiency of the toner from the organic photoconductive drum  105  to the printing paper  117 . The visible image transferred to the printing paper  117  is settled down on the printing paper  117  due to a high temperature and a high pressure of a heating roller  119  and a compressing roller  121 , which are provided in the fusing device  113 , and printing work is then finished. 
   At this point, the supplying voltage, the developing voltage, the transfer voltage, and the charging voltage as described above are kept continuously supplied to the supplying roller  111 , the developing roller  109 , the transfer roller  107 , and the charging roller  103 , respectively, until the printing work is finished. Also, the heating roller  119  of the fusing device  113  maintains in a turned-on state and a predetermined temperature until the printing work is finished. A cooling fan  125  generates air current to cool heat that occurs in the printer due to the heating roller  119  and the printing work. 
     FIG. 2  is a view showing power supply signals to be supplied to the cooling fan  340  corresponding to operation modes of the printer of  FIG. 1  and RPMs of the cooling fan  340  corresponding to the power supply signals. 
   As shown in  FIG. 2 , the operation modes of the printer are a warming-up mode  201 , a standby mode  202 , a first printing mode  203 , a second printing mode  205 , and a sleep mode  207 . When the printer is applied with an initial power, in the warming-up mode  201 , the heating roller  119  is heated to a predetermined temperature, and the cooling fan  125  is supplied with a power, thereby switching the warming-up mode  201  to the standby mode  202 . The standby mode  202  maintains the predetermined temperature of the heating roller  119  at a predetermined degree such that the printing work is performed within a very short period of time (for example, from 0.5 seconds to 3 seconds) from an input of a printing command. In the first printing mode  203 , a series of printing operations are performed according to the input of the printing command, maintaining the temperature of the heating roller  119  at another predetermined degree higher than that of the standby mode  202 . In the second printing mode  205 , the printer performs printing on the printing paper  117  thicker than a general printing paper or printing on a special paper, such as an OHP film. In the second printing mode  205 , the printer performs the printing with the temperature of the heating roller  119  being lower than that of the first printing mode  203  and higher than that of the standby mode  202  and with a printing speed being slower than that of the first printing mode  203 . In the sleep mode  207 , the printer maintains a power saving condition by blocking a power from being applied to the heating roller  119  when the printer does not receive the printing command for a predetermined period of time on the standby mode  202 . At this time, the cooling fan  125  is continuously driven or a power to the cooling fan  125  is blocked after another predetermined period of time passes in the sleep mode  207 . 
   Since in the printer employing an electrophotographic developing method as described above, the temperature of the developing roller  119  becomes different (variable) according to each operation mode of the printer, an inner temperature of the printer also varies. However, the cooling fan  125  is always driven at the same RPM regardless of the inner temperature of the printer as shown in  FIG. 2 , to discharge the heat of the heating roller  125  outwardly even in the early time of the warming-up mode  201 . Accordingly, a warming-up time (from t 0  to t 1 ) to meet the condition of the standby mode  202  takes a longer time. Also, there occur problems of shortening a lifespan of the cooling fan  125  and an increased power consumption of the printer. Also, since the conventional printer drives the cooling fan  125  at the same RPM regardless of the printing speed on the printing mode, a higher printing speed of the printer causes an inside of the printer to be overheated. 
   SUMMARY OF THE INVENTION 
   The present invention has been developed in order to solve the above and/or other problems in the prior art. Accordingly, it is an aspect of the present invention to provide a printer and a method of driving a cooling fan of the printer capable of shortening a warming-up time, preventing a printing unit from being overheated, extending a lifespan of the cooling fan, and reducing a power consumption. 
   Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
   The foregoing and/or other aspects of the present invention is achieved by providing a printer including a printing unit printing an image on a sheet of paper according to input printing option data and input image data in a printing mode and a cooling fan preventing a temperature increase of the printing unit. The printing includes a control unit controlling the printing unit according to one of operation modes including the printing mode, a warming-up mode, a standby mode, and a sleep mode, and controlling the cooling fan to rotate at one of a plurality of RPMs according to the one of the operation modes of the printing unit. 
   The control unit controls the printing unit according to a printing speed corresponding to one of a material and a thickness of the paper in the printing mode and controls the cooling fan to rotate the one of the RPMs according to the printing speed of the printing unit. 
   The printer further includes a storage unit storing the image data and the printing option data corresponding to the printing speed of the printing unit and the rotation speed of the cooling fan. The stored printing option data represents a material and a thickness of the paper to be printed when the printing unit is controlled to operate in the printing mode. 
   The controlling unit includes a central processing device controlling the operation of the printing unit based on the stored printing option data and the image data read from the storage unit, and outputting the duty value of the driving pulse read from the storage unit corresponding to each operation mode and the printing speed of the printing unit, and a pulse width modulation signal generating unit outputting driving pulse signals obtained based on the duty value of the driving pulse output from the central processing device. 
   The printer further comprises a cooling fan driving unit driving the cooling fan in the one of the RPMs in response to the PWM signal. 
   The control unit controls the operation of the printing unit in the printing mode to print the image on the paper based on the printing option data and the image data, in the standby mode to be ready to start printing the image on the paper in the printing mode within a predetermined period of time after the printing command is input to the printing unit, in the sleep mode to switch the printing mode to a power saving state when there is no reception of the printing command in the standby mode for another predetermined period of time, and in the warming-up mode to be returned to the standby mode while being supplied with a power. 
   The controlling unit controlling the printing unit to operate in the printing mode variably controls the printing speed of the printing unit based on the stored printing option data and outputs the driving control signal to control the RPM of the cooling fan to be in proportion to the printing speed. 
   The controlling unit controlling the printing unit to operate in the standby mode and outputs the driving control signal to control the RPM of the cooling fan to maintain a predetermined speed slower than that of the printing mode. 
   The controlling unit controlling the printing unit to operate in the sleep mode and outputs the driving control signal to control the RPM of the cooling fan to gradually decrease from that of the standby mode. 
   The controlling unit controlling the printing unit to operate in the warming-up mode and outputs the driving control signal to control the RPM of the cooling fan to gradually increase to a predetermined speed. 
   The above and/or other aspects of the present invention are achieved by providing a method of driving a cooling fan of a printer generating a print command to control a printing unit to print an image on a sheet of paper and a cooling fan preventing a temperature increase of the printing unit. The method includes controlling the printing unit in one of a printing mode to print the image on the paper, a standby mode to be ready to start printing within a predetermined period of time after the printing commend is input to the printing unit, a sleep mode to switch from the printing mode to a power saving mode when there is no reception of the printing command in the standby mode for another predetermined period of time, and a warming-up mode to return to the standby mode while the printing unit is supplied with a power. The method includes variably controlling an RPM of the cooling fan based on the respective operation modes of the printing unit. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which: 
       FIG. 1  is a schematic view showing an inner structure of a conventional printer employing an electrophotographic developing method; 
       FIG. 2  is a view showing power supply signals being supplied to a cooling fan corresponding to an operation modes of the printer of  FIG. 1  and RPMs of the cooling fan corresponding to the power supply signals; 
       FIG. 3  is a block diagram schematically showing a printer according to an embodiment of the present invention; 
       FIG. 4  is a flow chart showing driving pulse signals being supplied to a cooling fan driving unit corresponding to operation modes of a printing unit of the printer of  FIG. 3  and RPMs of the cooling fan corresponding to the driving pulse signal; and 
       FIG. 5  is a flowchart showing an operation performed in the printer shown in  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described in order to explain the present invention by referring to the figures. Hereinafter, a preferred embodiment of the present invention will be described in greater detail with reference to the accompanying drawings. 
     FIG. 3  is a block diagram showing a printer according to an embodiment of the present invention. As shown in  FIG. 3 , the printer includes a printing unit  300 , a central processing device  312 , a pulse width modulation signal generating unit  314 , a storage unit  320 , a cooling fan driving unit  330 , and a cooling fan  340 . 
   The storage unit  320  stores a driving pulse duty value which is data for controlling an RPM (revolution per minute or rotation per minute) of the cooling fan  340  and corresponds to each operation mode of the printing unit  300 . Also, the storage unit  320  temporarily stores image data and printing option data relating to a material and a thickness of printing paper. 
   The central processing device  312  outputs the printing option data and the image data input from an external computer application program to the storage unit  320  and temporarily stores the printing option data and the image data in the storage unit  320 . Based on the printing option data and the image data, the central processing device  312  controls an image forming operation of the printing unit  300 . That is, when the printing option data is about a general paper, the central processing device  312  controls a printing speed of the printing unit  300  at a high degree (speed), and when the printing option data is about a special paper, such as an OHP film, the central processing device  312  controls the printing speed of the printing unit  300  at a low degree (speed). Also, the central processing device  312  reads the driving pulse duty value corresponding to the printing speed and the operation mode of the printing unit  300  from the storage unit  320  and outputs the driving pulse duty value to the pulse width modulation signal generating unit  314 . 
   The printing unit  300  is controlled to be on a warming-up mode, a standby mode, a printing mode, and a sleep mode based on a control signal input from the central processing device  312 . When the printing unit  300  is controlled to be in the printing mode; the printing unit  300  performs a printing operation with the printing speed, which is variable according to the material and the thickness of the printing paper based on a control signal of the central processing device  312 . 
   The pulse width modulation signal generating unit  314  outputs a driving pulse signal that is obtained based on the driving pulse duty values input from the central processing unit  312  to the cooling fan driving unit  330 . The driving pulse duty value is a ratio of an ‘on’ time to one cycle of a pulse. 
   The cooling fan driving unit  330  supplies and blocks a power to and from the cooling fan  340  according to a cycle of the driving pulse signal input from the pulse width modulation signal generating unit  314 , thereby varying the RPM of the cooling fan  340 . 
   The cooling fan  340  rotates with the RPM variable based on the driving pulse signal input from the cooling fan driving unit  330 . 
   Hereinafter, the descriptions will be made about the driving pulse signal (PWM signal) output from a control unit  310  with respect to each of the warming-up mode, the standby mode, the printing mode, and the sleep mode, and the RPM of the cooling fan  340  corresponding to the driving pulse signal when the control unit  310  controls the printing unit  300  in any one mode among the above-described operations modes. 
     FIG. 4  is a view showing the driving pulse signal supplied to the cooling fan diving unit  330  corresponding to each operation mode of the printing unit  300  of  FIG. 3  and the RPM of the cooling fan  340  corresponding to the diving pulse signal. 
   At a point t 0  when the printer is initially supplied with the power, and at a point when the printing command is input to the control unit  310  in the sleep mode  407 , the control unit  310  controls the printing unit  300  in the warming-up mode  401 . Operation modes of the printing unit  300  are represented by intervals between adjacent points t 1  through t 7 . As shown in  FIG. 4 , the control unit  310  generates the driving pulse signal with a duty value gradually increasing from 0% to 80% during the interval of the warming-up mode  401  based on the duty value read from the storage unit  320  and corresponding to the warming-up mode  401 . Corresponding to the driving pulse signal, the RPM of the cooling fan  340  gradually increases to a predetermined speed during the interval of the warming-up mode  401 . Accordingly, a heating part of the printing unit  300  is easily heated in the warming-up mode  401  and thus, the interval of the warming-up mode  401  is shortened. 
   In the standby mode  402 , the printer maintains the heating part of the printing unit  300  at a predetermined temperature, so that the printing unit  300  can start to perform printing within a predetermined short period of time (for example, from 0.5 seconds to 5 seconds) after the printing command is supplied to the printing unit  300 . When the control unit  310  controls the printing unit  300  in the standby mode  402 , the control unit  310  generates the driving pulse signal with the duty value of 80% during the interval of the standby mode  402  based on the duty value read from the storage unit  320  corresponding to the standby mode  402 , and the cooling fan  340  maintains a predetermined RPM corresponding to the driving pulse signal. 
   When the printing command is input to the control unit  310  in the standby mode  402 , the control unit  310  determines the printing speed based on the input printing option data and controls the printing unit  300  on a first printing mode  403 , i.e., a high-speed printing mode, and a second printing mode  405 , i.e., a low-speed printing mode. When the control unit  310  controls the printing unit  300  in the first printing mode  403 , the control unit  310  generates the driving pulse signal with the duty value of 100% during the interval of the first printing mode  403  based on the duty value read from the storage unit  320  corresponding to the high speed printing mode. Also, when the control unit  310  controls the printing unit  300  in the second printing mode  405 , the control unit  310  generates the driving pulse signal with the duty value of 90% during the interval of the second printing mode  405  based on the duty value read from the storage unit  320  corresponding to the low-speed printing mode. When the printing operation of the printing unit  300  is completed, the control unit  310  controls the printing unit  300  in the standby mode  402 . At this point, if the printing command is not input for a predetermined time, the control unit  310  controls the printing unit  300  in the sleep mode  407 . 
   When the control unit  310  controls the printing mode  300  in the sleep mode  407 , the control unit  310  generates the driving pulse signal with the duty value gradually decreasing from 80% to 0% during the interval of the sleep mode  407  based on the duty value read from the storage unit  320  corresponding to the sleep mode  407 . Corresponding to the driving pulse signal, the RPM of the cooling fan  340  decreases gradually to a predetermined speed for the interval of the sleep mode  407 . 
   The following table 1 shows driving pulse duty values corresponding to the respective operation modes of the printing unit  300  and stored in the storage unit  320 . 
   
     
       
             
             
             
           
         
             
                 
               TABLE 1 
             
             
                 
                 
             
             
                 
               Operation Modes 
               Driving Pulse Duty Values 
             
             
                 
                 
             
           
           
             
                 
               Warming-up mode 
               Gradually increasing to 80% 
             
             
                 
               Standby mode 
                80% 
             
             
                 
               High-speed printing mode 
               100% 
             
             
                 
               (first printing mode) 
             
             
                 
               Low-speed printing mode 
                90% 
             
             
                 
               (second printing mode) 
             
             
                 
               Sleep mode 
               Gradually decreasing from 80% 
             
             
                 
                 
             
           
        
       
     
   
   According to another aspect of the present invention, the control unit  310  determines the driving pulse duty values without reading the driving pulse duty values signals from the storage unit  320 . 
   Hereinafter, a method of driving the cooling fan  340  of the printer according to the present invention will be described with reference to  FIG. 5 . 
     FIG. 5  is a flowchart showing the operation of the printer according to the present invention. When the printer is supplied with the power in operation S 510 , the control unit  310  controls the printing unit  300  in one of the warming-up mode in operation S 520 , the standby mode in operation S 530 , the sleep mode in operation S 540 , and the printing mode in operation S 550 . The operation according to each operation mode is described as follows. 
   When the control unit  310  controls the printing unit  300  in the warming-up mode  401  in operation S 522 , the control unit  310  controls the RPM of the cooling fan  340  to gradually increase to the predetermined speed (for example to 800 rpm) in operation S 523  and switches the printing unit  300  to the standby mode  402 . If the printing unit  300  satisfies the condition of the standby mode  402  in operation S 524 , the control unit  310  controls the printing unit  300  in the standby mode  402  in operation S 520 . Also, if the printing unit  300  does not satisfy the condition of the standby mode  402 , the controls unit  310  determines whether the printing command is input to the control unit  310  in operation S 525 . If the printing command is not input, the control unit  310  returns to the operation S 522 , and if the printing command is input, the control unit  310  controls the printing unit  300  in the first or second printing mode  403  or  405  in operation S 550 . 
   When the control unit  310  controls the printing unit  300  in the standby mode  402  in operation S 532 , the control unit  310  controls the RPM of the cooling fan  340  to maintain the predetermined speed (for example, 800 rpm) in operation S 533 . The control unit  310  determines whether a sleep mode switching condition (that is, whether the printing command is not input for the predetermined period of time) is satisfied in operation S 534 . If the sleep mode switching condition is satisfied, the control unit  310  controls the printing unit  300  in the sleep mode  407  in operation S 540 . If the sleep mode switching condition is not satisfied, the control unit  310  determines whether the printing command is input to the control unit  310  in operation S 536 . If the printing command is not input, the control unit  310  returns to operation S 532 , and if the printing command is input, the control unit  310  controls the printing unit  300  in the first or second printing mode  403  or  405  in operation S 550 . 
   When the control unit  310  controls the printing unit  300  in the sleep mode  407  in operation S 542 , the control unit  310  controls the RPM of the cooling fan  340  to gradually decrease from the predetermined speed (for example from 800 rpm) in operation S 543 . When the power is blocked from being supplied to the printer in operation S 544 , all of the operations are completed. Also, the control unit  310  determines whether the printing command is input to the control unit  310  in operation S 546 . If the printing command is not input, the control unit returns to operation S 542 , and if the printing command is input, the control unit  310  controls the printing unit  300  in the first or second printing mode  403  or  405  in operation S 550 . 
   When the control unit  310  controls the printing unit  300  in the first or second printing mode  403  or  405  in operation S 550 , the control unit  310  determines the printing speed based on the input printing option data in operation S 552  to variably control the printing speed of the printing unit  300 . When the control unit  310  controls the printing unit  300  in the high-speed printing mode, i.e., in the first printing mode  403 , in operation S 553 , the control unit  310  controls the RPM of the cooling fan  340  at a highest speed (for example, 1000 rpm) (S 554 ). Also, when the control unit  310  controls the printing unit  300  in the low-speed printing mode, i.e., in the second printing mode  405 , in operation S 555 , the control unit  310  controls the RPM of the cooling fan  340  to maintain the predetermined speed (for example 900 rpm) that is higher than the speed of the standby mode  402  (for example, 800 rpm) and lower than the speed of the first printing mode  403  in operation S 556 . Also, the control unit  310  determines whether the printing is completed in operation S 558 . If the printing operation of the printing unit  300  is completed, the control unit  310  returns to the standby mode  402  in operation S 530 , and if the printing operation is not completed, the control unit  310  repeats operation S 552 . 
   Although the control unit  310  controls the pulse width modulation signal generating unit  314  to generate the driving pulse signal by reading the driving pulse duty value from the storage unit  320 , this should not be considered as limiting. That is, the control unit  310  can directly determine the driving pulse duty value corresponding to the each operation mode of the printing unit  300 , and also can directly generate the driving pulse signal. Also, the control unit  310  can make non-linear changes of the duty value by time, and a driving logic of the cooling fan  340  can be updated without a mechanical change. 
   According to the printer and the method of driving the cooling fan of the printer of the present invention, the warming-up time is shortened and thus, an initial printing speed is increased. Also, the printing unit can be prevented from being overheated, a lifespan of the cooling fan can be extended, and a power consumption can be reduced. 
   While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.