Image forming apparatus and method for controlling the same

Abstract

There is disclosed an image forming apparatus and a method for controlling the apparatus, comprising a roller for conveying a sheet, and a sensor for detecting a time for conveying the sheet by the roller, the conveyance time of the sheet by the roller actually measured by the sensor is compared with an average conveyance time of the sheet corresponding to a sheet size, and a conveyance speed of the sheet by the roller is corrected so as to set the conveyance speed of the roller to be constant based on a comparison result.

What is claimed is:  
     
         1 . An image forming apparatus comprising: 
 a roller which conveys a sheet;    a sensor which detects a time for conveying the sheet by said roller; and    a controller which compares the conveyance time of the sheet by said roller actually measured by the sensor with an average conveyance time of the sheet corresponding to a sheet size, and correcting a conveyance speed of the sheet by said roller so as to set the conveyance speed of the roller to be constant based on a comparison result.    
     
     
         2 . The image forming apparatus according to  claim 1 , wherein said controller compares the conveyance time of a first sheet detected by the sensor with the conveyance time of the sheet after a predetermined number of sheets, and performs the correction control so as to set the conveyance speed of the sheet by said roller to be constant, when a difference of the time is large.  
     
     
         3 . The image forming apparatus according to  claim 1 , wherein said controller performs the correction control so as to set the conveyance speed of the sheet by the roller to be constant based on an output of said sensor, when a jam occurs in a conveyance process of the sheet by said roller.  
     
     
         4 . The image forming apparatus according to  claim 1 , wherein said controller performs the correction control so as to change the conveyance speed of the sheet by said roller in a range in which a change is prevented from being generated in a speed of image formation.  
     
     
         5 . The image forming apparatus according to  claim 1 , further comprising a display section for performing a predetermined warning display, 
 wherein the predetermined warning display is performed in said display section, when said correction controller judges a state of the roller to be outside a range capable of being handled by the correction control.    
     
     
         6 . The image forming apparatus according to  claim 1 , wherein said controller performs the correction control of the conveyance speed of the sheet by said roller also based on the size of the sheet conveyed by said roller.  
     
     
         7 . The image forming apparatus according to  claim 1 , wherein said controller performs the correction control of the conveyance speed of the sheet by said roller for every number of copy sheets based on a relation between the number of copy sheets and a friction amount of the roller.  
     
     
         8 . The image forming apparatus according to  claim 1 , further comprising a pulse motor for driving said roller, p 1  wherein said controller counts a pulse signal of the pulse motor, estimates a friction amount of the roller, and performs the correction control.  
     
     
         9 . A method for controlling an image forming apparatus, comprising: 
 a first step of conveying a sheet by a roller;    a second step of detecting a time for conveying the sheet by said roller by a sensor; and    a third step of comparing the conveyance time of the sheet by said roller actually measured by the sensor with an average conveyance time of the sheet corresponding to a sheet size, and correcting a conveyance speed of the sheet by said roller so as to set the conveyance speed of the roller to be constant based on a comparison result by a controller.    
     
     
         10 . The method for controlling the image forming apparatus according to  claim 9 , wherein said third step by the controller comprises steps of: comparing the conveyance time of a first sheet detected by the sensor with the conveyance time of the sheet after a predetermined number of sheets; and performing a correction control so as to set the conveyance speed of the sheet by said roller to be constant, when a difference of the time is large.  
     
     
         11 . The method for controlling the image forming apparatus according to  claim 9 , wherein said third step by the controller comprises a step of performing the correction control so as to set the conveyance speed of the sheet by the roller to be constant based on an output of said sensor, when a jam occurs in a conveyance process of the sheet by said roller.  
     
     
         12 . The method for controlling the image forming apparatus according to  claim 9 , wherein said third step by the controller comprises a step of performing the correction control so as to change the conveyance speed of the sheet by said roller in a range in which a change is prevented from being generated in a speed of image formation.  
     
     
         13 . The method for controlling the image forming apparatus according to  claim 9 , further comprising: a fourth step of performing a predetermined warning display by a display section, 
 wherein said fourth step comprises a step of performing the predetermined warning display in the display section, when said controller judges a state of the roller to be outside a range capable of being handled by the correction control in said third step.    
     
     
         14 . The method for controlling the image forming apparatus according to  claim 9 , wherein said third step by the controller comprises a step of performing the correction control of the conveyance speed of the sheet by said roller also based on the size of the sheet conveyed by said roller.  
     
     
         15 . The method for controlling the image forming apparatus according to  claim 9 , wherein said third step by the controller comprises a step of performing the correction control of the conveyance speed of the sheet by said roller for every number of copy sheets based on a relation between the number of copy sheets and a friction amount of the roller.  
     
     
         16 . The method for controlling the image forming apparatus according to  claim 9 , wherein said third step by the controller comprises steps of: counting a pulse signal of a pulse motor and estimating a friction amount of the roller; and performing the correction control.