Control unit and method for controlling motor for use in printer, and storage medium storing control program

Abstract

There is provided a control unit capable of suppressing the fluctuation in speed a motor for use in a printer. The control unit comprises: a speed detecting part for detecting the speed of a motor for use in a printer in a predetermined period t v ; an average speed calculating part for calculating an average speed using at least the current detected speed, which is detected by the speed detecting part, and a detected speed which has been detected n (≧2), which corresponds to substantially half period of the fluctuation in speed of the motor, before the timing in detecting the current detected speed; and a speed control part for controlling the speed of the motor on the basis of a speed deviation of the average speed, which is the output of the average speed calculating part, from a target speed of the motor.

What is claimed is:  
     
         1 . A control unit for controlling a motor for use in a printer, said control unit comprising: 
 a speed detecting part for detecting the speed of a motor for use in a printer in a predetermined period t v ;    an average speed calculating part for calculating an average speed using at least the current detected speed, which is detected by said speed detecting part, and a detected speed which has been detected n (≧2), which corresponds to substantially half period of the fluctuation in speed of said motor, before the timing in detecting said current detected speed; and    a speed control part for controlling the speed of said motor on the basis of a speed deviation of said average speed, which is the output of said average speed calculating part, from a target speed of said motor.    
     
     
         2 . A control unit for controlling a motor for use in a printer, as set forth in  claim 1 , wherein assuming that the period of the fluctuation in speed of said motor is T v , the number n used for calculating said average speed meets the following expression.  
         T   v /(2 t   v )−2≦ n<T   v /(2 t   v )+2  
     
     
         3 . A control unit for controlling a motor for use in a printer, as set forth in  claim 2 , wherein said average speed calculating part calculates an average speed of k+1 detected speeds from the current detected speed to a detected speed of k (n>k≧0) before, and k+1 detected speeds from a detected speed of n before to a detected speed of k+1 before.  
     
     
         4 . A control unit for controlling a motor for use in a printer, as set forth in  claim 3 , wherein said speed control part has a differentiating element which operates on the basis of said speed deviation of said average speed from said target speed.  
     
     
         5 . A control unit for controlling a motor for use in a printer, as set forth in  claim 4 , wherein said speed control part has a proportional element which operates on the basis of said speed deviation of said average speed from said target speed.  
     
     
         6 . A control unit for controlling a motor for use in a printer, as set forth in  claim 5 , wherein said speed detecting part comprises an encoder for generating an output pulse in accordance with the rotation of said motor, and a speed calculating part for calculating the speed of said motor in a period of said output pulse on the basis of said output pulse of said encoder.  
     
     
         7 . A control unit for controlling a motor for use in a printer, as set forth in  claim 6 , wherein said motor is a carriage motor for use in an ink jet printer, and said encoder generates said output pulse in accordance with the movement of a carriage driven by said carriage motor via a pulley, which is mounted of the rotating shaft of said carriage motor, and via a timing belt which is driven by said pulley.  
     
     
         8 . A control unit for controlling a motor for use in a printer, as set forth in  claim 7 , wherein assuming that the distance between adjacent slits of a code plate of said encoder is λ, that a pitch circle length of said pulley is L and that the number of phases of said motor is p, said n meets the following expression.  
         L /(4 p λ)≦ n<L /(4 p λ)+2  
     
     
         9 . A control unit for controlling a motor for use in a printer, as set forth in  claim 7 , wherein said speed control part further comprises: 
 a second speed calculating part for calculating the speed of said motor in a second predetermined period on the basis of said output pulse of said encoder;    a second average speed calculating part for calculating said average speed using at least the current calculated speed, which is calculated by said second speed calculating part, and a calculated speed which has been m (m≧2) before; and    a second differentiating element which operates on the basis of a speed deviation of the output of said second average speed calculating part from said target speed.    
     
     
         10 . A control unit for controlling a motor for use in a printer, as set forth in  claim 1 , wherein said motor is a DC motor.  
     
     
         11 . A method for controlling a motor for use in a printer, said method comprising the steps of: 
 detecting the speed of a motor for use in a printer in a predetermined period t v ;    calculating an average speed using at least the current detected speed and a detected speed which has been detected n (≧2), which corresponds to substantially half period of the fluctuation in speed of said motor, before the timing in detecting said current detected speed; and    controlling the speed of said motor on the basis of a speed deviation of said average speed from a target speed of said motor.    
     
     
         12 . A method for controlling a motor for use in a printer, as set forth in  claim 11 , wherein assuming that the period of the fluctuation in speed of said motor is T v , the number n used for calculating said average speed meets the following expression.  
         T   v /(2 t   v )−2≦ n<T   v /(2 t   v )+2  
     
     
         13 . A method for controlling a motor for use in a printer, as set forth in  claim 12 , wherein said step of calculating said average speed calculates an average speed of k+1 detected speeds from the current detected speed to a detected speed of k (n>k≧0) before, and k+1 detected speeds from a detected speed of n before to a detected speed of k+1 before.  
     
     
         14 . A method for controlling a motor for use in a printer, as set forth in  claim 13 , wherein said step of controlling the speed of said motor controls the speed of said motor on the basis of the sum of said speed deviation and the output of a differentiating element which operates on the basis of said speed deviation.  
     
     
         15 . A method for controlling a motor for use in a printer, as set forth in  claim 14 , wherein said step of detecting the speed of said motor includes a step of calculating the speed of said motor in a period of an output pulse of an encoder, which generates said output pulse in accordance with the rotation of said motor, on the basis of said output pulse of said encoder.  
     
     
         16 . A method for controlling a motor for use in a printer, as set forth in  claim 15 , wherein said motor is a carriage motor for use in an ink jet printer.  
     
     
         17 . A method for controlling a motor for use in a printer, as set forth in  claim 11 , wherein said motor is a DC motor.  
     
     
         18 . A computer-readable storage medium storing control program code for controlling a motor for use in a printer, comprising: 
 first program code means for detecting the speed of a motor for use in a printer in a predetermined period t v ;    second program code means for calculating an average speed using at least the current detected speed and a detected speed which has been detected n (≧2), which corresponds to substantially half period of the fluctuation in speed of said motor, before the timing in detecting said current detected speed; and    third program code means for controlling the speed of said motor on the basis of a speed deviation of said average speed from a target speed of said motor.