Conveying driving device, conveying driving device control method, and storage medium storing control program for conveying driving device, motor drive current setting table generating method and storage medium storing program for generating motor drive current setting table, image forming apparatus, image forming apparatus control method, and storage medium storing program for image forming apparatus

Abstract

A conveying driving device of the invention includes a first motor which transmits power to a drive shaft of a roller; a second motor which transmits power to the drive shaft along with the first motor at a torque smaller than that of the first motor; and a controller which sets each of drive current setting values of the first motor and the second motor so that a total value of a consumption current of the first motor and the second motor becomes minimal in a steady state in which the roller rotates at a constant setting speed.

1 . A conveying driving device comprising:
 a first motor which transmits power to a drive shaft of a roller;   a second motor which transmits power to said drive shaft along with said first motor at a torque smaller than that of said first motor; and   a hardware processor which sets each of drive current setting values of said first motor and said second motor so that a total value of a consumption current of said first motor and said second motor becomes minimal in a steady state in which said roller rotates at a constant setting speed.   
     
     
         2 . The conveying driving device according to  claim 1 ,
 wherein said hardware processor sets each of the drive current setting values of said first motor and said second motor in the steady state so that the total value of the consumption current of said first motor and said second motor becomes minimal in said steady state on the basis of a load condition on said roller.   
     
     
         3 . The conveying driving device according to  claim 2 ,
 wherein said load condition is at least one of a sheet type and a conveying speed of a recording medium conveyed by said roller.   
     
     
         4 . The conveying driving device according to  claim 1 ,
 wherein said first motor is a stepping motor and said second motor is a DC brushless motor.   
     
     
         5 . The conveying driving device according to  claim 1 ,
 wherein said hardware processor measures the total value of said consumption current which changes by decreasing the drive current setting value of said first motor in said steady state from a current value for generating a torque equal to or larger than a torque for transmitting required power to said drive shaft in said steady state and increasing the drive current setting value of said second motor and sets each of the drive current setting values of said first motor and said second motor when the total value of said measured consumption current becomes minimal as the drive current setting values of said first motor and said second motor in the steady state.   
     
     
         6 . The conveying driving device according to  claim 2 ,
 wherein said hardware processor calculates the drive current setting value of said first motor in which the total value of said consumption current in said steady state becomes minimal as a first setting value from a relational expression of the drive current setting value of said first motor in said steady state and the total value of said consumption current in said steady state corrected by a first load parameter depending on said load condition, calculates the drive current setting value of said second motor obtained by applying said calculated first setting value to a relational expression of the drive current setting value of said second motor in said steady state and said first setting value corrected by a second load parameter depending on said load condition as a second setting value, and sets each of the drive current setting values of said first motor and said second motor in said steady state on the basis of said first setting value and said second setting value.   
     
     
         7 . The conveying driving device according to  claim 2 ,
 wherein said hardware processor sets each of the drive current setting values of said first motor and said second motor in said steady state for each said load condition by referring to a table that the drive current setting values of said first motor and said second motor when the total value of said consumption current in said steady state becomes minimal are registered for each said load condition.   
     
     
         8 . The conveying driving device according to  claim 1 ,
 wherein said hardware processor linearly increases the drive current setting value of said second motor in accordance with an increase in rotation speed of said first motor at the time of increasing the rotation speed of said roller to said setting speed in said steady state.   
     
     
         9 . The conveying driving device according to  claim 2 ,
 wherein said load condition includes a nip pressure at a nip portion formed by said roller and the other roller.   
     
     
         10 . The conveying driving device according to  claim 2 ,
 wherein said load condition includes a temperature.   
     
     
         11 . The conveying driving device according to claim  2 ,
 wherein said load condition includes a load on said roller due to the pulling of the recording medium caused by a conveying speed difference at the upstream and downstream of said roller.   
     
     
         12 . The conveying driving device according to  claim 7 ,
 wherein said hardware processor performs a test mode when a sheet type of said recording medium conveyed by said roller is a special sheet not corresponding to any said load condition of said table that the drive current setting values of said first motor and said second motor are registered for each said load condition, and   wherein in said test mode, the hardware processor calculates a torque for transmitting required power to said drive shaft in said steady state on the basis of a thickness and a stiffness of said recording medium, measures a total value of a drive current of said first motor and said second motor in said steady state at the time of conveying said recording medium by said roller after setting the drive current setting value of said first motor to a value for generating a torque equal to or larger than at least the calculated torque, and determines the drive current setting values of said first motor and said second motor when the total value of the consumption current of said first motor and said second motor becomes minimal by repeatedly decreasing the drive current setting value of said first motor and increasing the drive current setting value of said second motor until the measurement value becomes equal to or larger than the previously measured total value of the drive current of said first motor and said second motor when the previously measured value is smaller than the total value of the drive current of said first motor and said second motor.   
     
     
         13 . A control method for a conveying driving device comprises a first motor which transmits power to a drive shaft of a roller and a second motor which transmits power to said drive shaft along with said first motor at a torque smaller than that of said first motor, the control method comprising:
 setting each of drive current setting values of said first motor and said second motor so that a total value of a consumption current of said first motor and said second motor becomes minimal in a steady state in which said roller is rotated at a constant setting speed.   
     
     
         14 . A non-transitory computer-readable storage medium storing a control program for a conveying driving device comprises a first motor which transmits power to a drive shaft of a roller and a second motor which transmits power to said drive shaft along with said first motor at a torque smaller than that of said first motor, the control program causing a computer to perform:
 setting each of drive current setting values of said first motor and said second motor so that a total value of a consumption current of said first motor and said second motor becomes minimal in a steady state in which said roller is rotated at a constant setting speed.   
     
     
         15 . A method of generating a table used to set drive current setting values of a first motor and a second motor in a steady state in which a roller rotates at a constant setting speed in a conveying driving device, the conveying driving device comprises said first motor which transmits power to a drive shaft of said roller and said second motor which transmits power to said drive shaft along with said first motor at a torque smaller than that of said first motor,
 the method of generating the table comprising:   measuring a total value of a consumption current of said first motor and said second motor which changes by decreasing the drive current setting value of said first motor in said steady state from a current value for generating a torque equal to or larger than a torque for transmitting required power to said drive shaft in said steady state and increasing the drive current setting value of said second motor;   determining the drive current setting values of said first motor and said second motor when the total value of said measured consumption current becomes minimal; and   generating said table by registering the determined drive current setting values of said first motor and said second motor.   
     
     
         16 . The method of generating the motor drive current setting table according to  claim 15 ,
 wherein in the step of measuring, the total value of said consumption current of said first motor and said second motor is measured for each load condition on said roller,   wherein in the step of determining, the drive current setting values of said first motor and said second motor when the total value of said measured consumption current becomes minimal are determined for each said load condition, and   wherein in the step of generating, the drive current setting values of said first motor and said second motor determined for each said load condition are registered to generate said table.   
     
     
         17 . A non-transitory computer-readable storage medium storing a program for generating a table used to set drive current setting values of a first motor and a second motor in a steady state in which a roller rotates at a constant setting speed in a conveying driving device, the conveying driving device comprises said first motor which transmits power to a drive shaft of said roller and said second motor which transmits power to said drive shaft along with said first motor at a torque smaller than that of said first motor, the program causing a computer to perform the method of  claim 15 . 
     
     
         18 . The non-transitory computer-readable storage medium storing the program for generating the motor drive current setting table according to  claim 17 ,
 wherein in the step of measuring, the total value of said consumption current of said first motor and said second motor is measured for each load condition of said roller,   wherein in the step of determining, the drive current setting values of said first motor and said second motor when the total value of said measured consumption current becomes minimal are determined for each said load condition, and   wherein in the step of generating, the drive current setting values of said first motor and said second motor determined for each said load condition are registered to generate said table.   
     
     
         19 . An image forming apparatus comprising:
 a first motor which transmits power to a drive shaft of a roller conveying a recording medium;   a second motor which transmits power to said drive shaft along with said first motor at a torque smaller than that of said first motor;   a hardware processor which sets each of drive current setting values of said first motor and said second motor so that a total value of a consumption current of said first motor and said second motor becomes minimal in a steady state in which said roller rotates at a constant setting speed; and   an image former which forms an image on said conveyed recording medium.   
     
     
         20 . The image forming apparatus according to  claim 19 , further comprising:
 a storage which stores a table that the drive current setting values of said first motor and said second motor when the total value of said consumption current becomes minimal in said steady state are determined for each load condition on said roller,   wherein said hardware processor sets each of the drive current setting values of said first motor and said second motor in said steady state for each said load condition by referring to said table.   
     
     
         21 . A control method for an image forming apparatus comprises a first motor which transmits power to a drive shaft of a roller conveying a recording medium, a second motor which transmits power to said drive shaft along with said first motor at a torque smaller than that of said first motor, and an image former which forms an image on said conveyed recording medium, the control method for the image forming apparatus comprising:
 specifying a load condition on said roller on the basis of a print job;   determining drive current setting values of said first motor and said second motor corresponding to said specified load condition by referring to a table that the drive current setting values of said first motor and said second motor when a total value of a consumption current of said first motor and said second motor in a steady state in which said roller rotates at a constant setting speed becomes minimal are determined for each said load condition; and   setting the drive current setting values of said first motor and said second motor in said steady state on the basis of the determined drive current setting values of said first motor and said second motor.   
     
     
         22 . A non-transitory computer-readable storage medium storing a control program for an image forming apparatus comprises a first motor which transmits power to a drive shaft of a roller conveying a recording medium, a second motor which transmits power to said drive shaft along with said first motor at a torque smaller than that of said first motor, and an image former which forms an image on said conveyed recording medium, the control program causing a computer to perform the method of  claim 21 .