Automatic skew adjusting apparatus, image forming apparatus having the same and skew adjusting method thereof

Abstract

A skew adjusting apparatus is provided for an image forming apparatus having a plurality of skew adjusting parts arranged in a plurality of laser scanning units, respectively. The automatic skew adjusting apparatus comprises a driving source, an actuating part arranged on a driving shaft of the driving source so that the actuating part can be selectively connected with one of the skew adjusting parts depending on a position of the driving source. The actuating part actuates the connected skew adjusting part as the driving shaft rotates. A positioning part moves the driving source and a power transmission part transmits or cuts off the power of the driving source to the positioning part so as to move the driving source or stop the movement of the driving source.

1 . A skew adjusting apparatus for an image forming apparatus comprising first and second laser scanning units comprising first and second skew adjusting parts, respectively, the skew adjusting apparatus comprising: 
 a driving source comprising a driving shaft;    an actuating part arranged on the driving shaft;    wherein the actuating part can selectively connects with one of the first and second skew adjusting parts, actuating the one of the first and second skew adjusting parts as the driving shaft rotates.    
   
   
       2 . A skew adjusting apparatus as claimed in  claim 1 , further comprising: 
 a positioning part which moves the driving source; and    a power transmission part which transmits or cuts off the power of the driving source to the positioning part so as to move the driving source or stop the movement of the driving source.    
   
   
       3 . A skew adjusting apparatus as claimed in  claim 1 , wherein 
 at leat the one of the first and second parts comprises a skew adjusting shaft which adjusts a skew of a corresponding one of the first and second laser scanning units via rotatation; and    an adjusting gear arranged on the skew adjusting shaft.    
   
   
       4 . A skew adjusting apparatus as claimed in  claim 3 , wherein the actuating part comprises a plurality of worm gears arranged to vertically engage with the adjusting gear.  
   
   
       5 . A skew adjusting apparatus as claimed in  claim 2 , wherein the positioning part comprises: 
 a positioning shaft comprisng a first end including a positioning thread part;    a positioning block comprising a positioning thread hole, the positioning thread part being received in or extracted from the positioning thread hole depending on the rotational direction of the positioning shaft; and    a position detection part which detects an amount by which the driving source moves.    
   
   
       6 . A skew adjusting apparatus as claimed in  claim 5 , wherein the position detection part comprises a linear encoder.  
   
   
       7 . A skew adjusting apparatus as claimed in  claim 5 , wherein the positioning part further comprises: 
 a sliding guide which supports the driving source and guides the movement of the driving source; and    a driving shaft guide which supports the driving shaft of the driving source and guides the movement of the driving shaft.    
   
   
       8 . A skew adjusting apparatus as claimed in  claim 1 , wherein the power transmission part comprises a clutch which interconnects or cuts off power to the positioning shaft and the driving shaft.  
   
   
       9 . A skew adjusting apparauts as claimed in  claim 8 , wherein the clutch comprises: 
 a first clutch plate connected to an end of the driving shaft, the first clutch plate being axially movable by a predetermined distance;    a second clutch plate connected to a second end of the positioning shaft;    an armature arranged to move with respect to the first clutch plate;    a clutch coil which generates magnetic force when electric current is applied to the clutch coil to move the armature; and    a clutch spring which returns the first clutch plate to its original position when no electric current is applied to the clutch coil.    
   
   
       10 . A skew adjusting apparatus as claimed in  claim 1 , further comprising a skew detection part which detects a skew of a laser scanning unit.  
   
   
       11 . A skew adjusting apparatus as claimed in  claim 10 , wherein the skew detection part comprises two skew detection sensors located on a plane which extends vertically from a skew reference line to a running direction of one of a transfer belt, a photoconductive belt and a photoconductive drum, the skew detection sensors being spaced from each other by a predetermined distance.  
   
   
       12 . An image forming apparatus comprising: 
 a plurality of scanning units, each scanning unit comprising a skew adjusting part; and    a skew adjusting unit which actuates the skew adjusting parts, wherein the automatic skew adjusting unit comprises: 
 a driving source comprising a drive shaft;  
 an actuating part arranged on the driving shaft;  
 wherein the actuating part selectively connects with the skew adjusting part of a corresponding one of the plurality of scanning units actuating the skew adjusting part as the driving shaft rotates.  
   
   
   
       13 . An image forming apparatus as claimed in  claim 12  wherein 
 the plurality of scanning units form an electrostatic latent image on a plurality of photoconductors, respectively.    
   
   
       14 . An image forming apparatus as claimed in  claim 12  further comprising 
 a plurality of developing units which develop the electrostatic latent image on the photoconductor into visible images; 
 a transfer unit which transfers the images arranged on the respective photoconductors to a medium.  
   
   
   
       15 . An image forming apparatus as claimed in  claim 12  further comprising 
 a positioning part which moves the driving source; and    a power transmission part which transmits or cuts off the power of the driving source to the positioning part so as to move the driving source or stop the movement of the driving source.    
   
   
       16 . An image forming apparatus as claimed in  claim 12 , wherein each skew adjusting part comprises: 
 a skew adjusting shaft which adjusts a skew of the corresponding one of the laser scanning units via rotation; and    an adjusting gear arranged on the skew adjusting shaft.    
   
   
       17 . An image forming apparatus as claimed in  claim 16 , wherein the actuating part comprises a plurality of worm gears arranged to vertically engage with the adjusting gear.  
   
   
       18 . An image forming apparatus as claimed in  claim 13 , wherein the positioning part comprises: 
 a positioning shaft comprising a first end with a positioning thread part;    a positioning block comprising a positioning thread hole, the positioning thread part being received in or extracted from the positioning thread hole depending on the rotational direction of the positioning shaft; and    a position detection part which detects an amount by which the driving source moves.    
   
   
       19 . An image forming apparatus as claimed in  claim 18 , wherein the position detection part comprises a linear encoder.  
   
   
       20 . An image forming apparatus as claimed in  claim 13 , wherein the positioning part further comprises a sliding guide which supports the driving source and guides the movement of the driving source; and 
 a driving shaft guide which supports the driving shaft of the driving source and guides the movement of the driving shaft.    
   
   
       21 . An image forming apparatus as claimed in  claim 18 , wherein the power transmission part comprises a clutch which interconnects or cuts off the positioning shaft and the driving shaft.  
   
   
       22 . An image forming apparauts as claimed in  claim 21 , wherein the clutch comprises a first clutch plate connected to an end of the driving shaft, the first clutch plate being axially movable by a predetermined distance; 
 a second clutch plate connected to a second end of the positioning shaft;    an armature arranged to move with the first clutch plate;    a clutch coil which generates magnetic force when electric current is applied to the clutch coil to move the armature; and    a clutch spring which returns the first clutch plate to its original position when no electric current is applied to the clutch coil.    
   
   
       23 . An image forming apparatus as claimed in  claim 12 , further comprising: 
 a skew detection part which detects a skew of a laser scanning unit.    
   
   
       24 . An image forming apparatus as claimed in  claim 23 , wherein the skew detection part comprises two skew detection sensors located on a plane which vertically extends from a skew reference line vertical to a running direction of one of a transfer belt, a photoconductive belt and a photoconductive drum, the skew detection sensors being spaced from each other by a predetermined distance.  
   
   
       25 . A skew adjusting method of an image forming apparatus comprising: 
 a plurality of laser scanning units;    measuring a skew of at least one of the plurality of laser scanning units;    calculating a skew adjusting value of a skew adjusting part of the at least one laser scanning unit; and    selectively adjusting the skew adjusting part of the at least one laser scanning unit using a driving source according to the calculated skew adjusting value.    
   
   
       26 . A skew adjusting method as claimed in  claim 25 , wherein the measuring of the skew of the at least one laser scanning unit comprises calculating a skew value by comparing time points of outputting skew detection signals for detecting an image from at least two skew detection sensors.  
   
   
       27 . A skew adjusting method as claimed in  claim 25 , wherein the measuring of the skew of the at least one laser scanning unit comprises measuring, on the basis of a reference pattern for forming an image or an image of a certain color, a skew value of an image of a color different from the reference pattern of the certain color and formed on the medium by using a microscope.  
   
   
       28 . A skew adjusting method as claimed in  claim 25 , wherein the selectively adjusting of the skew adjusting part of the at least one laser scanning unit comprises selectively connecting an actuating part of the driving source with the skew adjusting part of the least one laser scanning unit; and 
 adjusting the skew adjusting part of the LSU to be adjusted by operating the actuating part of the driving source.    
   
   
       29 . A skew adjusting method as claimed in  claim 28 , wherein the selectively connecting of the actuating part with the skew adjusting part of the at least one laser scanning unit comprises reading out the position of the actuating part; 
 determining whether the read-out position of the actuating part conforms to the position of the skew adjusting part of the at least one laser scanning unit; and    moving the actuating part to a position where the actuating part is selectively connected with the skew adjusting part of the at least one laser scanning according to the read-out position of the actuating part.