# US 6,911,800 B2 · Stepping motor controller, scanning apparatus, and image forming apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,911,800 B2 - Document ID: US6911800B2 - Status: Granted - Kind: B2 - Application number: 10/654,944 - Filed: 2003-09-05 - Published: 2004-06-17 - Granted: 2005-06-28 - Earliest claimed: 2002-09-06 - Assignees: Ricoh Company, Ltd. - Inventors: Masato Kobayashi; Atsuo Tokunaga; Nobuhito Komoda - Web page: https://patentgrep.com/patent/US6911800B2 ## CPC - G05B 19/40: Open loop systems, e.g. using stepping motor - G05B 2219/41043: Memory table with motor current and corresponding correction for lost motion - G05B 2219/41214: Lookup table for current as function of actual position - G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G) ## Abstract A stepping motor controller is disclosed that is capable of reducing power consumption of a stepping motor. The stepping motor controller includes a storage unit to store object values of a driving current of the stepping motor, an accumulation unit to accumulate an amount of operation of the stepping motor, and a driving current setting unit to read out an object value corresponding to the amount of operation from the storage unit and set the driving current to the object value. Alternatively, the stepping motor controller includes an accumulation unit that calculates a cumulative amount of operation of the stepping motor, and a driving current setting unit that, when the amount of operation is greater than a predetermined value, determines a critical out-of-step current of the stepping motor by changing in increments the value of the driving current of the stepping motor, and sets the critical out-of-step current with a predetermined margin added as an object driving current of the stepping motor. ## Claims ### Claim 1 A stepping motor controller for setting a driving current of a stepping motor, comprising: a storage unit configured to store a plurality of object values of the driving current; an accumulation unit configured to accumulate an amount of operation of the stepping motor; and a driving current setting unit configured to read out one of the object values corresponding to the amount of operation from the storage unit and to set the driving current to the one of the object values. ### Claim 2 (depends on 1) The stepping motor controller as claimed in claim 1, wherein the object values of the driving current stored in the storage unit are determined by using a relation between the amount of operation and a driving torque of the stepping motor for driving the amount of operation, and a relation between the driving current and the driving torque generated by the driving current; and the object values of the driving current are stored in the storage unit in conjunction with the amounts of operation of the stepping motor, respectively. ### Claim 3 A stepping motor controller for setting a driving current of a stepping motor, comprising: an accumulation unit configured to accumulate an amount of operation of the stepping motor; and a driving current setting unit configured to, when the amount of operation is greater than a predetermined value, determine a critical out-of-step current of the stepping motor by changing in increments the driving current of the stepping motor, and set the critical out-of-step current with a predetermined margin added thereto as an object driving current of the stepping motor. ### Claim 4 (depends on 3) The stepping motor controller as claimed in claim 3, further comprising a monitoring unit configured to monitor for an out-of-step state of the stepping motor provided with the driving current, and increase the driving current when the out-of-step state is detected. ### Claim 5 A scanning apparatus, comprising: a document scanning unit configured to scan a document; an image data reader configured to convert an image on the document into image data; a stepping motor configured to drive the document scanning unit to move; and a stepping motor controller for setting a driving current of the stepping motor, said stepping motor controller comprising: a storage unit configured to store a plurality of object values of the driving current; an accumulation unit configured to accumulate an amount of operation of the stepping motor; and a driving current setting unit configured to read out one of the object values corresponding to the amount of operation from the storage unit and to set the driving current to the one of the object values. ### Claim 6 A scanning apparatus, comprising: a document scanning unit configured to scan a document; an image data reader configured to convert an image on the document into image data; a stepping motor configured to drive the document scanning unit to move; and a stepping motor controller for setting a driving current of the stepping motor, said stepping motor controller comprising: an accumulation unit configured to accumulate an amount of operation of the stepping motor; and a driving current setting unit configured to, when the amount of operation is greater than a predetermined value, determine a critical out-of-step current of the stepping motor by changing in increments the driving current of the stepping motor, and set the critical out-of-step current with a predetermined margin added thereto as an object driving current of the stepping motor. ### Claim 7 An image forming apparatus, comprising: an image forming device that irradiates a laser beam to a photoconductor to form a static latent image thereon, develops the static latent image, and transfers the developed static latent image to paper; a stepping motor that drives a machinery portion of the image forming device to make mechanical motions; and a stepping motor controller for setting a driving current of the stepping motor, said stepping motor controller comprising: a storage unit configured to store a plurality of object values of the driving current; an accumulation unit configured to accumulate an amount of operation of the stepping motor; and a driving current setting unit configured to read out one of the object values corresponding to the amount of operation from the storage unit and to set the driving current to the one of the object values. ### Claim 8 An image forming apparatus, comprising: an image forming device that irradiates a laser beam to a photoconductor to form a static latent image thereon, develops the static latent image, and transfers the developed static latent image to paper; a stepping motor that drives a machinery portion of the image forming device to make mechanical motions; and a stepping motor controller for setting a driving current of the stepping motor, said stepping motor controller comprising: an accumulation unit configured to accumulate an amount of operation of the stepping motor; and a driving current setting unit configured to, when the amount of operation is greater than a predetermined value, determine a critical out-of-step current of the stepping motor by changing in increments the driving current of the stepping motor, and set the critical out-of-step current with a predetermined margin added thereto as an object driving current of the stepping motor. ### Claim 9 A stepping motor controller for setting a driving current of a stepping motor, comprising: storage means for storing a plurality of object values of the driving current; accumulation means for accumulating an amount of operation of the stepping motor; and driving current setting means for reading out one of the object values corresponding to the amount of operation from the storage means and setting the driving current to the one of the object values. ### Claim 10 (depends on 9) The stepping motor controller as claimed in claim 9, wherein the object values of the driving current stored in the storage means are determined by using a relation between the amount of operation and a driving torque of the stepping motor for driving the amount of operation, and a relation between the driving current and the driving torque generated by the driving current; and the object values of the driving current are stored in the storage means in conjunction with the amounts of operation of the stepping motor, respectively. ### Claim 11 A stepping motor controller for setting a driving current of a stepping motor, comprising: accumulation means for accumulating an amount of operation of the stepping motor; and driving current setting means for, when the amount of operation is greater than a predetermined value, determining a critical out-of-step current of the stepping motor by changing in increments the driving current of the stepping motor, and setting the critical out-of-step current with a predetermined margin added thereto as an object driving current of the stepping motor. ### Claim 12 (depends on 11) The stepping motor controller as claimed in claim 11, further comprising monitoring means for monitoring for an out-of-step state of the stepping motor provided with the driving current, and increasing the driving current when the out-of-step state is detected.