Sheet transporting apparatus, image reading apparatus and image printing apparatus

Abstract

A sheet transporting apparatus, whereby the level of a transporting error for a sheet, such as a document or a printing medium, can be appropriately determined and coped with, and an image reading apparatus and an image printing apparatus equipped with this sheet transporting apparatus, are provided. In the image reading apparatus, in order to transport a sheet of a document, the driving amount per unit time of a transporting roller is compared with a plurality of different threshold values, and the results obtained by comparison are employed to determine whether a transporting error is a service error or an operator error.

What is claimed is: 
     
         1 . A sheet transporting apparatus, which includes a transporting mechanism to be driven by a motor to transport a sheet, and a detector for detecting a driving amount per unit time of the transporting mechanism driven by the motor, and which performs feedback control of the motor based on the driving amount per unit time of the transporting mechanism detected by the detector, comprising:
 a comparator for comparing, with a plurality of threshold values, the driving amount per unit time detected by the detector; and   a determination unit configured to determine a transporting error that has occurred during transporting of the sheet, based on the comparison results obtained by the comparator.   
     
     
         2 . The sheet transporting apparatus according to  claim 1 ,
 wherein the plurality of threshold values include a first threshold value and a second threshold value, a difference between the second threshold value and a target value of the driving amount per unit time being greater than a difference between the first threshold value and the target value; and   wherein the determination unit determines, based on a result of comparison of the driving amount per unit time and the first threshold value, whether the transporting error is an error that can be removed by an operator, and determines, based on a result of comparison of the driving amount per unit time and the second threshold value, whether the transporting error is an error that can not be removed by the operator.   
     
     
         3 . The sheet transporting apparatus according to  claim 2 ,
 wherein the error that can be removed includes jam of the sheet in the transporting mechanism; and   wherein the error that can not be removed includes at least either a failure of the transporting mechanism and a failure of the detector.   
     
     
         4 . The sheet transporting apparatus according to  claim 1 ,
 wherein the detector includes an encoder for outputting a detection signal each time the transporting mechanism is driven at a predetermined distance, and detects the driving amount per unit time based on the detection signal of the encoder.   
     
     
         5 . The sheet transporting apparatus according to  claim 1 ,
 wherein the detector includes an encoder for outputting a detection signal in accordance with a drive speed of the transporting mechanism, and detects the driving amount per unit time based on the detection signal of the encoder.   
     
     
         6 . The sheet transporting apparatus according to  claim 1 ,
 wherein the transporting mechanism includes a transporting roller to be driven by the motor.   
     
     
         7 . An image reading apparatus for reading an image on a sheet that is transported along a predetermined transporting path, comprising:
 a sheet transporting apparatus according to  claim 1  in order to transport the sheet.   
     
     
         8 . An image printing apparatus for printing an image on a sheet that is transported along a predetermined transporting path, comprising:
 a sheet transporting apparatus according to  claim 1  in order to transport the sheet.   
     
     
         9 . A sheet transporting method, which use a transporting mechanism to be driven by a motor for transporting a sheet and a detector for detecting a driving amount per unit time of the transporting mechanism driven by the motor, and which performs feedback control of the motor based on the driving amount per unit time of the transporting mechanism detected by the detector, comprising the steps of:
 comparing, with a plurality of threshold values, the driving amount per unit time detected by the detector; and   determining a transporting error that has occurred during transporting of the sheet, based on the comparison results obtained by the comparison step.