US20200290832A1 - Image forming apparatus - Google Patents

Image forming apparatus Download PDF

Info

Publication number
US20200290832A1
US20200290832A1 US16/810,293 US202016810293A US2020290832A1 US 20200290832 A1 US20200290832 A1 US 20200290832A1 US 202016810293 A US202016810293 A US 202016810293A US 2020290832 A1 US2020290832 A1 US 2020290832A1
Authority
US
United States
Prior art keywords
sheet
velocity
conveying
image forming
forming apparatus
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US16/810,293
Other languages
English (en)
Inventor
Misaki Shiozawa
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Canon Inc
Original Assignee
Canon Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Canon Inc filed Critical Canon Inc
Assigned to CANON KABUSHIKI KAISHA reassignment CANON KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SHIOZAWA, MISAKI
Publication of US20200290832A1 publication Critical patent/US20200290832A1/en
Abandoned legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H7/00—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles
    • B65H7/20—Controlling associated apparatus
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H5/00—Feeding articles separated from piles; Feeding articles to machines
    • B65H5/06—Feeding articles separated from piles; Feeding articles to machines by rollers or balls, e.g. between rollers
    • B65H5/062—Feeding articles separated from piles; Feeding articles to machines by rollers or balls, e.g. between rollers between rollers or balls
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/65—Apparatus which relate to the handling of copy material
    • G03G15/6529—Transporting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H29/00—Delivering or advancing articles from machines; Advancing articles to or into piles
    • B65H29/20—Delivering or advancing articles from machines; Advancing articles to or into piles by contact with rotating friction members, e.g. rollers, brushes, or cylinders
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H3/00—Separating articles from piles
    • B65H3/02—Separating articles from piles using friction forces between articles and separator
    • B65H3/06—Rollers or like rotary separators
    • B65H3/0684—Rollers or like rotary separators on moving support, e.g. pivoting, for bringing the roller or like rotary separator into contact with the pile
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H7/00—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles
    • B65H7/02—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles by feelers or detectors
    • B65H7/06—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles by feelers or detectors responsive to presence of faulty articles or incorrect separation or feed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H7/00—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles
    • B65H7/02—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles by feelers or detectors
    • B65H7/06—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles by feelers or detectors responsive to presence of faulty articles or incorrect separation or feed
    • B65H7/08—Controlling article feeding, separating, pile-advancing, or associated apparatus, to take account of incorrect feeding, absence of articles, or presence of faulty articles by feelers or detectors responsive to presence of faulty articles or incorrect separation or feed responsive to incorrect front register
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2511/00—Dimensions; Position; Numbers; Identification; Occurrences
    • B65H2511/50—Occurence
    • B65H2511/51—Presence
    • B65H2511/514—Particular portion of element
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2511/00—Dimensions; Position; Numbers; Identification; Occurrences
    • B65H2511/50—Occurence
    • B65H2511/52—Defective operating conditions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2513/00—Dynamic entities; Timing aspects
    • B65H2513/10—Speed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
    • B65H2515/00—Physical entities not provided for in groups B65H2511/00 or B65H2513/00
    • B65H2515/30—Forces; Stresses
    • B65H2515/32—Torque e.g. braking torque

Definitions

  • the present disclosure relates to an image forming apparatus that adjusts a conveying velocity of a sheet being conveyed.
  • an image forming apparatus configured to adjust, based on the detection result of a sensor provided in a conveying path, the conveying velocity of a sheet so that the sheet is conveyed according to an image forming sequence set in advance (so that the sheet is conveyed to an image forming position at an appropriate timing). Specifically, the image forming apparatus adjusts based on the detection result of a sensor, the conveying velocity of a sheet so that the sheet reaches a target position at a timing determined in advance.
  • the timing for detecting the load fluctuation is determined as the timing when the front end of the sheet reaches the nip position of the conveying rollers. Actually, at the timing when the load fluctuation is detected, however, the front end of the sheet is located upstream of the nip position of the conveying rollers due to the thickness of the sheet.
  • the conveying velocity is adjusted in the above manner in the state where the timing for detecting the load fluctuation is determined as the timing when the front end of the sheet reaches the nip position of the conveying rollers, the following issue may occur. Specifically, even if the conveying velocity is adjusted so that the front end of the sheet reaches a target position at a timing determined in advance, the position of the front end of the sheet at this timing may be located upstream of the target position. As a result, the sheet may reach an image forming position after the timing when the formation of an image on the sheet is started. As a result, the image may not be formed at an appropriate position on the sheet.
  • the present disclosure is directed to preventing the situation where an image is formed at an inappropriate position on a sheet.
  • an image forming apparatus includes a stacking unit on which a sheet is to be stacked, a pickup roller configured to feed the sheet stacked on the stacking unit, a first conveying roller configured to convey the sheet fed by the pickup roller, a transfer unit configured to transfer an image onto the sheet at an image forming position downstream of the first conveying roller in a conveying direction in which the sheet is conveyed, a motor configured to drive the first conveying roller, a determiner configured to determine a value of a parameter corresponding to a load torque applied to a rotor of the motor, and a velocity adjuster configured to, based on a length between a position of a front end of the sheet and a nip position of the first conveying roller at a first timing when the value of the parameter determined by the determiner changes from a value smaller than a predetermined value to a value greater than the predetermined value, and a length between the nip position of the first conveying roller and a predetermined position downstream of the
  • FIG. 1 is a cross-sectional view illustrating an image forming apparatus.
  • FIG. 2 is a block diagram illustrating a control configuration of the image forming apparatus.
  • FIG. 3 is a diagram illustrating a relationship between a two-phase motor including an A-phase and a B-phase, and a rotating coordinate system represented by a d-axis and a q-axis.
  • FIG. 4 is a block diagram illustrating a configuration of a motor control device.
  • FIG. 5 is a diagram illustrating a configuration for detecting a fed recording medium.
  • FIG. 6 is a diagram illustrating a deviation ⁇ in a case where thin paper is conveyed and a deviation ⁇ in a case where thick paper is conveyed, according to a first exemplary embodiment.
  • FIGS. 7A and 7B are diagrams illustrating a position of a front end of a recording medium at a timing when a sheet detector outputs a signal ‘ 1 ’ (a timing when the recording medium is detected), according to the first exemplary embodiment.
  • FIG. 8 is a diagram illustrating a relationship between a grammage of a recording medium to be conveyed, and a distance from the position of the front end of the recording medium at the timing when the sheet detector outputs the signal ‘ 1 ’ to conveying rollers.
  • FIG. 9 is a flowchart illustrating a control method for controlling a conveying velocity V by a central processing unit (CPU).
  • CPU central processing unit
  • FIG. 10 is a diagram illustrating a relationship between a grammage of a recording medium to be conveyed, and time Tc from when the recording medium is detected to when a front end of the recording medium reaches a nip position n.
  • FIGS. 11A and 11B are diagrams illustrating a position of a front end of a recording medium at a timing when a sheet detector outputs a signal ‘ 1 ’, according to a third exemplary embodiment.
  • FIG. 12 is a diagram illustrating a state of a deviation ⁇ according to the third exemplary embodiment.
  • FIG. 13 is a diagram illustrating a relationship between a grammage of the recording medium to be conveyed, and a distance Lc from the position of the front end of the recording medium at the timing when the sheet detector outputs the signal ‘ 1 ’ to conveying rollers.
  • FIG. 14 is a block diagram illustrating a configuration of a motor control device that performs velocity feedback control.
  • a motor control device is provided in an image forming apparatus.
  • the motor control device is provided not only in an image forming apparatus.
  • the motor control device is also used in a sheet conveying apparatus that conveys a sheet such as a recording medium or a document.
  • FIG. 1 is a cross-sectional view illustrating the configuration of a monochrome electrophotographic copying machine (hereinafter referred to as “image forming apparatus”) 100 that includes a sheet conveying apparatus used in the present exemplary embodiment.
  • the image forming apparatus 100 is not limited to a copying machine, and may be, for example, a facsimile apparatus, a printing machine, or a printer.
  • a recording method is not limited to an electrophotographic method, and may be, for example, an inkjet method.
  • the format of the image forming apparatus 100 may be either of monochrome and color formats.
  • the image forming apparatus 100 includes a document reading apparatus 200 and an image printing apparatus 301 .
  • a document feeding apparatus 201 that feeds a document to a reading position.
  • Documents P stacked in a document stacking portion 2 of the document feeding apparatus 201 are fed one by one by a pickup roller 3 .
  • each document P is conveyed by a sheet feeding roller 4 .
  • a separation roller 5 is provided that is in pressure contact with the sheet feeding roller 4 .
  • the separation roller 5 is configured to rotate if a load torque greater than or equal to a predetermined torque is applied to the separation roller 5 .
  • the separation roller 5 has the function of separating two documents fed in an overlapping state.
  • the pickup roller 3 and the sheet feeding roller 4 are linked together by a swinging arm 12 .
  • the swinging arm 12 is supported by a rotating shaft of the sheet feeding roller 4 so that the swinging arm 12 can pivot about the rotating shaft of the sheet feeding roller 4 .
  • the document P is conveyed by the sheet feeding roller 4 and discharged to a sheet discharge tray 10 by sheet discharge rollers 11 .
  • a document set sensor SS 1 is provided in the document stacking portion 2 that detects whether the documents P are stacked in the document stacking portion 2 .
  • a sheet sensor SS 2 is provided in a conveying path through which each document P passes that detects the front end of the document P (detects the presence or absence of the document P).
  • a document reading unit 16 is provided that reads an image on a first surface of the conveyed document P. Image information regarding the image read by the document reading unit 16 is output to the image printing apparatus 301 .
  • a document reading unit 17 is provided that reads an image on a second surface of the conveyed document P. Image information regarding the image read by the document reading unit 17 is output to the image printing apparatus 301 similarly to the method of the document reading unit 16 described above.
  • the document feeding apparatus 201 and the reading apparatus 202 function as the document reading apparatus 200 .
  • the document reading apparatus 200 has a first reading mode and a second reading mode as document reading modes.
  • the first reading mode is a mode for reading an image on a document conveyed by the above method.
  • the second reading mode is a mode where the document reading unit 16 moving at a constant velocity reads an image on a document placed on document glass 214 of the reading apparatus 202 . Normally, an image on a sheet-like document is read in the first reading mode, and an image on a bound document such as a book or a booklet is read in the second reading mode.
  • Sheet holding trays 302 and 304 are provided in the image printing apparatus 301 .
  • different types of recording media can be held.
  • A4-size plain paper is held in the sheet holding tray 302
  • A4-size thick paper is held in the sheet holding tray 304 .
  • the recording media include a sheet, a resin sheet, cloth, an overhead projector (OHP) sheet, and a label.
  • OHP overhead projector
  • a recording medium held in the sheet holding tray 302 is fed by a pickup roller 303 and sent out to pre-registration rollers 333 by feeding rollers 331 and conveying rollers 306 .
  • a recording medium held in the sheet holding tray 304 is fed by a pickup roller 305 and sent out to the pre-registration rollers 333 by feeding rollers 332 , conveying rollers 307 , and the conveying rollers 306 .
  • a sheet sensor 335 for detecting the front end of the recording medium is provided between the pre-registration rollers 333 and registration rollers 308 .
  • the front end of the recording medium conveyed by the pre-registration rollers 333 is detected by the sheet sensor 335 and then abuts the registration rollers 308 in a stopped state.
  • the pre-registration rollers 333 further rotate, thereby conveying the recording medium further in the conveying direction.
  • the recording medium bends.
  • an elastic force acts on the recording medium, and the front end of the recording medium abuts the registration rollers 308 along a nip portion thereof.
  • the skew of the recording medium is corrected.
  • the pre-registration rollers 333 are controlled to rotate for a predetermined time after the sheet sensor 335 detects the front end of the recording medium.
  • the predetermined time is set in advance to sufficient time to bend the recording medium by an amount required to correct the skew of the recording medium.
  • An image signal output from the document reading apparatus 200 is input to an optical scanning device 311 that includes a semiconductor laser and a polygon mirror.
  • the outer peripheral surface of a photosensitive drum 309 is charged by a charging device 310 .
  • laser light according to the image signal input from the document reading apparatus 200 to the optical scanning device 311 is emitted from the optical scanning device 311 to the outer peripheral surface of the photosensitive drum 309 via the polygon mirror and mirrors 312 and 313 .
  • an electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 309 .
  • the photosensitive drum 309 is charged by a charging method using, for example, a corona charger or a charging roller.
  • the electrostatic latent image is developed with toner in a developing device 314 , thereby forming a toner image on the outer peripheral surface of the photosensitive drum 309 .
  • the toner image formed on the photosensitive drum 309 is transferred onto the recording medium by a transfer charging device 315 as a transfer unit provided at a position (a transfer position) opposed to the photosensitive drum 309 .
  • the registration rollers 308 send the recording medium to the transfer position.
  • the recording medium onto which the toner image has been transferred as described above is sent to a fixing device 318 by a conveying belt 317 and is heated and pressurized by the fixing device 318 , thereby fixing the toner image to the recording medium. In this manner, an image is formed on a recording medium by the image forming apparatus 100 .
  • the recording medium having passed through the fixing device 318 is discharged to a sheet discharge tray (not illustrated) by sheet discharge rollers 319 and 324 .
  • a fixing process is performed on a first surface of the recording medium by the fixing device 318 , and then, the recording medium is conveyed to a reverse path 325 by the sheet discharge rollers 319 , conveying rollers 320 , and reverse rollers 321 .
  • the recording medium is conveyed to the registration rollers 308 again by conveying rollers 322 and 323 , and an image is formed on a second surface of the recording medium by the above method.
  • the recording medium is discharged to the sheet discharge tray (not illustrated) by the sheet discharge rollers 319 and 324 .
  • the recording medium having passed through the fixing device 318 is conveyed through the sheet discharge rollers 319 in a direction toward the conveying rollers 320 . Then, immediately before the rear end of the recording medium passes through a nip portion of the conveying rollers 320 , the rotation of the conveying rollers 320 is reversed, thereby discharging the recording medium to outside the image forming apparatus 100 via the sheet discharge rollers 324 in the state where the first surface of the recording medium faces down.
  • a stacking unit 327 is provided in which a recording medium is stacked.
  • the recording medium stacked in the stacking unit 327 is sent out in the conveying direction by a pickup roller 328 and then conveyed by sheet feeding rollers 329 .
  • the pickup roller 328 and one of the sheet feeding rollers 329 are linked together by a swinging arm 330 .
  • the swinging arm 330 is supported by the rotating shaft of the sheet feeding roller 329 so that the swinging arm 330 can pivot about the rotating shaft of the sheet feeding roller 329 .
  • FIG. 2 is a block diagram illustrating an example of the control configuration of the image forming apparatus 100 .
  • a system controller 151 includes a central processing unit (CPU) 151 a, a read-only memory (ROM) 151 b, and a random-access memory (RAM) 151 c.
  • the system controller 151 is connected to an image processing unit 112 , an operation unit 152 , an analog-to-digital (A/D) converter 153 , a high voltage control unit 155 , a motor control device 157 , sensors 159 , an alternating current (AC) driver 160 , a sheet sensor 334 , and the sheet sensor 335 .
  • the system controller 151 can transmit and receive data and a command to and from the units connected to the system controller 151 .
  • the CPU 151 a reads and executes various programs stored in the ROM 151 b , thereby executing various sequences related to an image forming sequence determined in advance.
  • the RAM 151 c is a storage device.
  • the RAM 151 c stores various types of data such as a setting value for the high voltage control unit 155 , an instruction value for the motor control device 157 , and information received from the operation unit 152 .
  • the system controller 151 transmits setting value data, required for image processing by the image processing unit 112 , of the various devices provided in the image forming apparatus 100 to the image processing unit 112 . Further, the system controller 151 receives signals from the sensors 159 , and based on the received signals, sets a setting value of the high voltage control unit 155 . According to the setting value set by the system controller 151 , the high voltage control unit 155 supplies a required voltage to a high voltage unit 156 (the charging device 310 , the developing device 314 , and the transfer charging device 315 ).
  • the sensors 159 include a sensor that detects a recording medium conveyed by the conveying rollers.
  • the motor control device 157 controls a motor 509 for driving the conveying rollers 307 .
  • the motor 509 is illustrated as a motor of the image forming apparatus 100 in FIG. 2
  • a plurality of motors is actually provided in the image forming apparatus 100 .
  • a configuration may be employed in which a single motor control device controls a plurality of motors.
  • a plurality of motor control devices is provided in the image forming apparatus 100 .
  • the A/D converter 153 receives a detected signal detected by a thermistor 154 that detects the temperature of a fixing heater 161 . Then, the A/D converter 153 converts the detected signal from an analog signal to a digital signal and transmits the digital signal to the system controller 151 .
  • the system controller 151 controls the AC driver 160 based on the digital signal received from the A/D converter 153 .
  • the AC driver 160 controls the fixing heater 161 so that the temperature of the fixing heater 161 becomes a temperature required to perform a fixing process.
  • the fixing heater 161 is a heater for use in the fixing process and is included in the fixing device 318 .
  • the system controller 151 controls the operation unit 152 to display, on a display unit provided in the operation unit 152 , an operation screen for a user to set the type of a recording medium to be used (hereinafter referred to as the “paper type”).
  • the system controller 151 receives information set by the user from the operation unit 152 , and based on the information set by the user, controls the operation sequence of the image forming apparatus 100 .
  • the system controller 151 transmits, to the operation unit 152 , information indicating the state of the image forming apparatus 100 .
  • the information indicating the state of the image forming apparatus 100 is, for example, information regarding the number of images to be formed, the progress state of an image forming operation, and a jam or multi-feed of a sheet in the document feeding apparatus 201 and the image printing apparatus 301 .
  • the operation unit 152 displays on the display unit the information received from the system controller 151 .
  • the system controller 151 controls the operation sequence of the image forming apparatus 100 .
  • a sheet detector 700 will be described below.
  • the motor control device controls a motor using vector control.
  • a sensor such as a rotary encoder for detecting the rotational phase of a rotor of the motor is not provided.
  • a sensor such as a rotary encoder may be provided.
  • FIG. 3 is a diagram illustrating the relationship between the stepper motor (hereinafter referred to as “motor”) 509 that has two phases including an A-phase (a first phase) and a B-phase (a second phase), and a rotating coordinate system represented by a d-axis and a q-axis.
  • motor stepper motor
  • FIG. 3 in a stationary coordinate system, an ⁇ -axis, which is an axis corresponding to windings in the A-phase, and a ⁇ -axis, which is an axis corresponding to windings in the B-phase, are defined.
  • the d-axis is defined along the direction of magnetic flux created by the magnetic poles of a permanent magnet used in a rotor 402
  • the q-axis is defined along a direction rotated 90 degrees counterclockwise from the d-axis (a direction orthogonal to the d-axis).
  • the angle between the ⁇ -axis and the d-axis is defined as ⁇
  • the rotational phase of the rotor 402 is represented by the angle ⁇ .
  • a rotating coordinate system based on the rotational phase ⁇ of the rotor 402 is used.
  • a q-axis component (a torque current component) and a d-axis component (an excitation current component), which are current components in the rotating coordinate system of a current vector corresponding to a driving current flowing through each winding, are used.
  • the q-axis component (the torque current component) generates a torque in the rotor 402
  • the d-axis component (the excitation current component) influences the strength of magnetic flux passing through the winding.
  • the vector control is a control method for controlling a motor by performing phase feedback control for controlling the value of a torque current component and the value of an excitation current component so that the deviation between an instruction phase indicating a target phase of a rotor and an actual rotational phase of the rotor becomes small.
  • FIG. 4 is a block diagram illustrating an example of the configuration of the motor control device 157 that controls the motor 509 .
  • the motor control device 157 includes at least one ASIC and executes functions described below.
  • the motor control device 157 includes, as a circuit for performing the vector control, a phase controller 502 , a current controller 503 , a coordinate inverse transformer 505 , a coordinate transformer 511 , and a pulse-width modulation (PWM) inverter 506 that supplies driving currents to the windings of the motor 509 .
  • the coordinate transformer 511 performs coordinate transformation on current vectors corresponding to driving currents flowing through the windings in the A-phase and the B-phase of the motor 509 , from the stationary coordinate system represented by the ⁇ -axis and the ⁇ -axis to the rotating coordinate system represented by the q-axis and the d-axis.
  • the driving currents flowing through the windings are represented by the current value of the q-axis component (a q-axis current) and the current value of the d-axis component (a d-axis current), which are current values in the rotating coordinate system.
  • the q-axis current corresponds to a torque current that generates a torque in the rotor 402 of the motor 509 .
  • the d-axis current corresponds to an excitation current that influences the strength of magnetic flux passing through each winding of the motor 509 .
  • the motor control device 157 can independently control the q-axis current and the d-axis current.
  • the motor control device 157 controls the q-axis current according to a load torque applied to the rotor 402 and thereby can efficiently generate a torque required for the rotation of the rotor 402 . That is, in the vector control, the magnitude of the current vector illustrated in FIG. 3 changes according to the load torque applied to the rotor 402 .
  • the motor control device 157 determines the rotational phase ⁇ of the rotor 402 of the motor 509 using a method described below, and based on the determination result, performs the vector control, Based on the operation sequence of the motor 509 , the CPU 151 a outputs, to an instruction generator 500 , driving pulses as an instruction to drive the motor 509 .
  • the operation sequence of the motor 509 (the driving pattern of the motor 509 ) is stored, for example, in the ROM 151 b .
  • the CPU 151 a Based on the operation sequence stored in the ROM 151 b, the CPU 151 a outputs driving pulses as a pulse train.
  • the number of pulses corresponds to an instruction phase, and the frequency of pulses corresponds to a target velocity.
  • the instruction generator 500 Based on the driving pulses output from the CPU 151 a, the instruction generator 500 generates an instruction phase ⁇ _ref representing a target phase of the rotor 402 and outputs the instruction phase ⁇ _ref.
  • the configuration of the instruction generator 500 will be described below.
  • a subtractor 101 calculates a deviation AO between the rotational phase ⁇ of the rotor 402 of the motor 509 and the instruction phase ⁇ _ref and outputs the deviation ⁇ .
  • the phase controller 502 acquires the deviation ⁇ in a period T (e.g., 200 ⁇ s). Based on proportional control (P-control), integral control (I-control), and differential control (D-control), the phase controller 502 generates a q-axis current instruction value iq_ref and a d-axis current instruction value id_ref as target values so that the deviation ⁇ output from the subtractor 101 becomes small. Then, the phase controller 502 outputs the q-axis current instruction value iq_ref and the d-axis current instruction value id_ref.
  • T e.g. 200 ⁇ s
  • P-control proportional control
  • I-control integral control
  • D-control differential control
  • the phase controller 502 Based on the P-control, the I-control, and the D-control, the phase controller 502 generates the q-axis current instruction value iq_ref and the d-axis current instruction value id_ref so that the deviation ⁇ output from the subtractor 101 becomes 0. Then, the phase controller 502 outputs the q-axis current instruction value iq_ref and the d-axis current instruction value id_ref.
  • the P-control is a control method for controlling the value of a target to be controlled, based on a value proportional to the deviation between an instruction value and an estimated value.
  • the I-control is a control method for controlling the value of the target to be controlled, based on a value proportional to the time integral of the deviation between the instruction value and the estimated value.
  • the D-control is a control method for controlling the value of the target to be controlled, based on a value proportional to a change over time in the deviation between the instruction value and the estimated value.
  • the phase controller 502 according to the present exemplary embodiment generates the q-axis current instruction value iq_ref and the d-axis current instruction value id_ref based on proportional-integral-derivative (PID) control.
  • PID proportional-integral-derivative
  • the phase controller 502 may generate the q-axis current instruction value iq_ref and the d-axis current instruction value id_ref based on proportional-integral (PI) control.
  • PI proportional-integral
  • the d-axis current instruction value id_ref which influences the strength of magnetic flux passing through each winding, is set to 0.
  • the configuration is not limited to this.
  • a driving current flowing through the windings in the A-phase of the motor 509 is detected by a current detector 507 and then converted from an analog value to a digital value by an A/D converter 510 .
  • a driving current flowing through the windings in the B-phase of the motor 509 is detected by a current detector 508 and then converted from an analog value to a digital value by the A/D converter 510 .
  • the cycle in which the current detectors 507 and 508 detect the currents is, for example, a cycle (e.g., 25 ⁇ s) less than or equal to the cycle T, in which the phase controller 502 acquires the deviation ⁇ .
  • the current values of the driving currents converted from the analog values to the digital values by the A/D converter 510 are represented as current values i ⁇ and i ⁇ in the stationary coordinate system by the following formulas (1) and (2), using a phase ⁇ e of the current vector illustrated in FIG. 3 .
  • the phase ⁇ e of the current vector is defined as the angle between the ⁇ -axis and the current vector.
  • I represents the magnitude of the current vector.
  • the current values i ⁇ and i ⁇ are input to the coordinate transformer 511 and an inductive voltage determiner 512 .
  • the coordinate transformer 511 transforms the current values i ⁇ and i ⁇ in the stationary coordinate system into a current value iq of the q-axis current and a current value id of the d-axis current in the rotating coordinate system by the following formulas (3) and (4).
  • the coordinate transformer 511 outputs the transformed current value iq to a subtractor 102 .
  • the coordinate transformer 511 outputs the transformed current value id to a subtractor 103 .
  • the subtractor 102 calculates the deviation between the q-axis current instruction value iq_ref and the current value iq and outputs the calculated deviation to the current controller 503 .
  • the subtractor 103 calculates the deviation between the d-axis current instruction value id_ref and the current value id and outputs the calculated deviation to the current controller 503 .
  • the current controller 503 Based on the PID control, the current controller 503 generates driving voltages Vq and Vd so that each of the deviations input to the current controller 503 becomes small. Specifically, the current controller 503 generates the driving voltages Vq and Vd so that each of the deviations input to the current controller 503 becomes 0. Then, the current controller 503 outputs the driving voltages Vq and Vd to the coordinate inverse transformer 505 . That is, the current controller 503 functions as a generation unit.
  • the current controller 503 according to the present exemplary embodiment generates the driving voltages Vq and Vd based on the PID control. The configuration, however, is not limited to this. For example, the current controller 503 may generate the driving voltages Vq and Vd based on the PI control.
  • the coordinate inverse transformer 505 inversely transforms the driving voltages Vq and Vd in the rotating coordinate system, which are output from the current controller 503 , into driving voltages V ⁇ and V ⁇ in the stationary coordinate system by the following formulas (5) and (6).
  • V ⁇ cos ⁇ * Vd ⁇ sin ⁇ * Vq (5)
  • V ⁇ sin ⁇ * Vd +cos ⁇ * Vq (6)
  • the coordinate inverse transformer 505 outputs the inversely transformed driving voltages V ⁇ and V ⁇ to the inductive voltage determiner 512 and the PWM inverter 506 .
  • the PWM inverter 506 includes a full-bridge circuit.
  • the full-bridge circuit is driven by PWM signals based on the driving voltages V ⁇ and V ⁇ input from the coordinate inverse transformer 505 .
  • the PWM inverter 506 generates driving currents i ⁇ and i ⁇ according to the driving voltages V ⁇ and V ⁇ and supplies the driving currents i ⁇ and i ⁇ to the windings in the respective phases of the motor 509 , thereby driving the motor 509 .
  • the PWM inverter 506 includes a full-bridge circuit.
  • the PWM inverter 506 may include a half-bridge circuit.
  • the rotational phase ⁇ of the rotor 402 is determined using the values of inductive voltages E ⁇ and E ⁇ induced in the windings in the A-phase and the B-phase of the motor 509 by the rotation of the rotor 402 .
  • the value of each inductive voltage is determined (calculated) by the inductive voltage determiner 512 .
  • the inductive voltages E ⁇ and E ⁇ are determined by the following formulas (7) and (8), based on the current values i ⁇ and i ⁇ input from the A/D converter 510 to the inductive voltage determiner 512 and the driving voltages V ⁇ and V ⁇ input from the coordinate inverse transformer 505 to the inductive voltage determiner 512 .
  • R represents winding resistance
  • L represents winding inductance.
  • the values of the winding resistance R and the winding inductance L are values specific to the motor 509 in use and are stored in advance in the ROM 151 b or a memory (not illustrated) provided in the motor control device 157 .
  • the inductive voltages E ⁇ and E ⁇ determined by the inductive voltage determiner 512 are output to the phase determiner 513 .
  • the phase determiner 513 determines the rotational phase ⁇ of the rotor 402 of the motor 509 by the following formula (9).
  • the phase determiner 513 determines the rotational phase ⁇ by performing calculation based on formula (9).
  • the configuration is not limited to this.
  • the phase determiner 513 may determine the rotational phase ⁇ by referencing a table stored in a memory 513 a and illustrating the relationships between the inductive voltages E ⁇ and E ⁇ , and the rotational phase ⁇ corresponding to the inductive voltages E ⁇ and E ⁇ .
  • the rotational phase ⁇ of the rotor 402 obtained as described above is input to the subtractor 101 , the coordinate inverse transformer 505 , and the coordinate transformer 511 .
  • the motor control device 157 repeatedly performs the above control.
  • the motor control device 157 performs the vector control using phase feedback control for controlling current values in the rotating coordinate system so that the deviation ⁇ between the instruction phase ⁇ _ref and the rotational phase ⁇ becomes small.
  • the vector control is performed, whereby it is possible to prevent a motor from entering a step-out state and prevent an increase in the motor sound and an increase in power consumption due to an excess torque.
  • the instruction generator 500 Based on the driving pulses output from the CPU 151 a, the instruction generator 500 generates the instruction phase ⁇ _ref using the following formula (10) and outputs the instruction phase ⁇ _ref.
  • ⁇ ini is the phase (initial phase) of the rotor 402 when the driving of the motor 509 is started.
  • ⁇ step is the amount of increase (the amount of change) in the instruction phase ⁇ _ref per driving pulse.
  • n is the number of pulses input to the instruction generator 500 .
  • FIG. 5 is a diagram illustrating a configuration for detecting a fed recording medium.
  • the conveying rollers 307 are driven by the motor 509 , and the motor 509 is controlled by the motor control device 157 .
  • the feeding rollers 332 and the pickup roller 305 are driven by motors (not illustrated).
  • the feeding rollers 332 are rollers adjacent to the conveying rollers 307 .
  • a conveying velocity V at which a recording medium is conveyed is set to a predetermined velocity V 0 in advance based on the operation sequence of the image forming apparatus 100 .
  • the sheet detector 700 detects whether the front end of the recording medium reaches a nip portion of the conveying rollers 307 .
  • it is detected (determined) whether the front end of the recording medium reaches the nip portion of the conveying rollers 307 not by a sensor such as a photosensor but based on a signal output from the motor control device 157 .
  • the sheet detector 700 outputs the detection result in a predetermined time cycle (e.g., the cycle in which the deviation ⁇ is input).
  • the front end of the recording medium conveyed downstream by the feeding rollers 332 is nipped by the conveying rollers 307 . If the front end of the recording medium is nipped by the conveying rollers 307 , the load torque applied to the rotor 402 of the motor 509 for driving the conveying rollers 307 increases. If the load torque increases, the absolute value of the deviation ⁇ increases.
  • the sheet detector 700 If the absolute value of the deviation ⁇ becomes greater than or equal to a threshold ⁇ th as a predetermined value, the sheet detector 700 outputs a signal ‘ 1 ’ indicating that the absolute value of the deviation ⁇ becomes greater than or equal to the threshold ⁇ th (the recording medium is detected). If the absolute value of the deviation ⁇ is less than the threshold ⁇ th, the sheet detector 700 outputs a signal ‘ 0 ’ indicating that the absolute value of the deviation ⁇ is less than the threshold ⁇ th.
  • the threshold ⁇ th will be described below.
  • the detection result of the sheet detector 700 is input to the CPU 151 a . If the sheet detector 700 outputs the signal ‘ 1 ’, the CPU 151 a adjusts the conveying velocity V of the recording medium. For example, the CPU 151 a changes the frequencies of driving pulses to be output to motor control devices provided in the image forming apparatus 100 , thereby adjusting the conveying velocity V.
  • X 1 represents the distance from the pickup roller 305 to the conveying rollers 307 .
  • X 2 represents the distance from the conveying rollers 307 to a detection position where the sheet sensor 334 detects the recording medium. That is, the distance from the pickup roller 305 to the detection position is represented by X 1 +X 2 .
  • T 0 corresponds to time required for the recording medium to be conveyed by the distance X 1 +X 2 at the conveying velocity V 0 .
  • the pickup roller 305 is repeatedly rotated and stopped at predetermined time intervals, thereby feeding recording media at predetermined intervals.
  • the CPU 151 a includes a timer 151 d and measures the time elapsed since the driving of the pickup roller 305 is started (since the CPU 151 a outputs an instruction to start driving the pickup roller 305 ).
  • the CPU 151 a sets as the conveying velocity V a velocity calculated based on the distance X 2 and time period obtained by subtracting from time period T 0 time period Ta, the time period Ta being a period from when the driving of the pickup roller 305 is started to when the sheet detector 700 outputs the signal ‘ 1 ’. Specifically, based on the following formula (11), the CPU 151 a sets the conveying velocity V in a section from the conveying rollers 307 to the detection position (i.e., the peripheral velocity of conveying rollers in the section from the conveying rollers 307 to the detection position).
  • the conveying velocity V in a section from the pickup roller 305 to the conveying rollers 307 after the conveying velocity V in the section from the conveying rollers 307 to the detection position is adjusted may be set to V 0 , or may be set to the conveying velocity V adjusted based on formula (11).
  • V X 2/( T 0 ⁇ Ta ) (11)
  • FIG. 6 is a diagram illustrating the deviation ⁇ output from the motor control device 157 in a case where thin paper is conveyed (a dashed line), and the deviation ⁇ output from the motor control device 157 in a case where thick paper is conveyed (a solid. line).
  • the deviation ⁇ having a positive value means that the rotational phase ⁇ is behind the instruction phase ⁇ _ref.
  • the deviation ⁇ having a negative value means that the rotational phase ⁇ is ahead of the instruction phase ⁇ _ref.
  • the relationships between the polarity of the deviation ⁇ , and the rotational phase ⁇ and the instruction phase ⁇ _ref are not limited to these.
  • a configuration may be employed in which, in a case where the rotational phase ⁇ is behind the instruction phase ⁇ _ref, the deviation ⁇ has a negative value, and in a case where the rotational phase ⁇ is ahead of the instruction phase ⁇ _ref, the deviation ⁇ has a positive value.
  • the absolute value of the deviation ⁇ becomes great due to the fact that the rotational phase ⁇ of the rotor 402 of the motor 509 is behind the instruction phase ⁇ _ref.
  • FIGS. 7A and 7B are diagrams illustrating the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’ (the timing when the recording medium is detected).
  • FIG. 7A is a diagram illustrating the position of the front end of the thin paper at the timing (a time ta) when the sheet detector 700 outputs the signal ‘ 1 ’ in a case where the thin paper is conveyed.
  • FIG. 7B is a diagram illustrating the position of the front end of the thick paper at the timing (a time tb) when the sheet detector 700 outputs the signal ‘ 1 ’ in a case where the thick paper is conveyed.
  • the front end of the recording medium conveyed downstream by the feeding rollers 332 is nipped by the conveying rollers 307 . If the front end of the recording medium is nipped by the conveying rollers 307 , the load torque applied to the rotor 402 of the motor 509 for driving the conveying rollers 307 increases. If the load torque increases, the absolute value of the deviation ⁇ increases, for example, as illustrated in FIG. 6 (the time ta or tb).
  • the conveying rollers 307 rotate at a peripheral velocity faster than the peripheral velocity of the feeding rollers 332 . If the recording medium is nipped by the conveying rollers 307 , the conveying rollers 307 pull the recording medium nipped by the feeding rollers 332 downstream. With such a configuration, it is possible to make the range of increase in the load torque when the recording medium is nipped by the conveying rollers 307 greater. Thus, the front end of the recording medium is detected with higher accuracy.
  • the threshold ⁇ th is set to, for example, a value smaller than the load torque applied to the conveying rollers 307 that increases due to a recording medium having the smallest rigidity and thickness among a plurality of types of recording media that can be conveyed in the image forming apparatus 100 , i.e., a value smaller than the maximum value (the peak value) of the absolute value of the deviation ⁇ .
  • the threshold ⁇ th is set to, for example, a value smaller than the load torque applied to the conveying rollers 307 that increases due to a recording medium having the greatest rigidity and thickness among the plurality of types of recording media that can be conveyed in the image forming apparatus 100 , i.e., a value smaller than the maximum value (the peak value) of the absolute value of the deviation ⁇ .
  • the threshold ⁇ th is set to, for example, a value greater than the absolute value of the deviation ⁇ assumed in the state where the recording medium is not nipped by the nip portion of the conveying rollers 307 and also the state where the conveying rollers 307 rotate at a constant velocity.
  • the front end of the recording medium is nipped at the timing when the front end of the recording medium is located upstream of a nip position n in the conveying direction due to the thickness of the recording medium.
  • a distance La from the position of the front end of the thin paper at the timing when the sheet detector 700 outputs the signal ‘ 1 ’ to the nip position n in a case where the thin paper is conveyed is shorter than a distance Lb from the position of the front end of the thick paper at the timing when the sheet detector 700 outputs the signal ‘ 1 ’ to the nip position n in a case where the thick paper is conveyed.
  • the position of the front end of the thick paper when the conveying rollers 307 start nipping the thick paper is located upstream of the position of the front end of the thin paper when the conveying rollers 307 start nipping the thin paper.
  • a distance Y from the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’ to the detection position is different from the distance X 2 .
  • the distance Y is longer than the distance X 2 .
  • the conveying velocity V is set based on formula (11)
  • the position of the front end of the recording medium at the timing when the recording medium is to reach the detection position is located upstream of the detection position due to the fact that the distance Y is longer than the distance X 2 . That is, the recording medium may reach the detection position after the timing when the recording medium is to reach the detection position.
  • the recording medium may reach the transfer position after the timing when the transfer of an image onto the recording medium is started, and the image may not be formed at an appropriate position on the recording medium.
  • the following configuration is applied, thereby preventing the situation where an image is formed at an inappropriate position on a recording medium.
  • FIG. 8 is a diagram illustrating the relationship between the grammage of the recording medium to be conveyed, and a distance Lc from the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’ to the conveying rollers 307 .
  • a grammage Ma in FIG. 8 corresponds to the grammage of the thin paper.
  • a grammage Mb in FIG. 8 corresponds to the grammage of the thick paper.
  • the relationship between the grammage and the distance Lc illustrated in FIG. 8 is obtained by experiment and stored in advance, for example, in the ROM 151 b.
  • a distance Lc_a is a value corresponding to La illustrated in FIG. 7A .
  • a distance Lc_b is a value corresponding to Lb illustrated in FIG. 7B .
  • Information regarding the paper type is, for example, input by the user through the operation unit 152 .
  • the information regarding the paper type includes the grammage and the rigidity of the recording medium.
  • the CPU 151 a determines the distance Lc. For example, if information indicating that the thin paper is to be conveyed is input by the user through the operation unit 152 , the CPU 151 a sets Lc_a corresponding to the thin paper as the distance Lc. If information indicating that the thick paper is to be conveyed is input by the user through the operation unit 152 , the CPU 151 a sets Lc_b corresponding to the thick paper as the distance Lc.
  • the CPU 151 a sets the conveying velocity V based on the following formula (12).
  • V ( X 2+ Lc )/( T 0 ⁇ Ta ) (12)
  • the CPU 151 a calculates the distance from the position of the front end of the recording medium at e timing when the sheet detector 700 outputs the signal ‘ 1 ’ to the registration rollers 308 . Then, the CPU 151 a sets the conveying velocity V by dividing the calculated distance by a value obtained by subtracting the time period Ta from the time period T 0 . That is, the CPU 151 a sets the conveying velocity V based on the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’.
  • FIG. 9 is a flowchart illustrating a control method for controlling the conveying velocity V by the CPU 151 a.
  • control of the conveying velocity V according to the present exemplary embodiment is described.
  • the processing of the flowchart is executed by the CPU 151 a.
  • the CPU 151 a resets and starts the timer 151 d each time the CPU 151 a outputs an instruction to start rotationally driving the pickup roller 305 .
  • step S 1001 if information regarding the paper type is input to the CPU 151 a through the operation unit 152 (YES in step S 1001 ), then in step S 1002 , the CPU 151 a sets the distance Lc based on the input information regarding the paper type.
  • step S 1003 the CPU 151 a starts a feeding operation for feeding a recording medium stored in a specified sheet holding tray. From this point forward, the pickup roller 305 is repeatedly driven and stopped at predetermined time intervals.
  • step S 1004 CPU 151 a determines whether the sheet detector 700 outputs the signal ‘ 1 ’. If the sheet detector 700 outputs the signal ‘ 1 ’ (YES in step S 1004 ), the processing proceeds to step S 1005 .
  • step S 1005 the CPU 151 a adjusts (sets) the conveying velocity V based on the distance Lc set in step S 1002 , the time period Ta from when the driving of the pickup roller is started to when the sheet detector 700 outputs the signal ‘ 1 ’, and the distance X 2 .
  • the CPU 151 a sets the conveying velocity V using formula (12).
  • step S 1006 the CPU 151 a determines whether a print job is to be ended. If a print job is to be ended (YES in step S 1006 ), then in step S 1007 , the CPU 151 a ends the feeding operation.
  • step S 1006 if the print job is not to be ended (NO in step S 1006 ), the processing returns to step S 1004 .
  • step S 1004 if the sheet detector 700 does not output the signal ‘ 1 ’ (NO in step S 1004 ), the processing proceeds to step S 1008 .
  • step S 1008 the CPU 151 a determines whether the state where the sheet detector 700 does not output the signal ‘ 1 ’ continues for a predetermined time. If the state where the sheet detector 700 does not output the signal ‘ 1 ’ does not continue for the predetermined time (NO in step S 1008 ), the processing returns to step S 1004 .
  • step S 1008 if the state where the sheet detector 700 does not output the signal ‘ 1 ’ continues for the predetermined time (YES in step S 1008 ), then in step S 1009 , the CPU 151 a stops the feeding operation.
  • the predetermined time is set to, for example, time longer than time required for the recording medium fed by the pickup roller 305 to be conveyed at the conveying velocity V 0 and reach the conveying rollers 307 .
  • step S 1010 the CPU 151 a notifies the user that an abnormality (e.g., a jam) occurs in the conveyance of the recording medium, by displaying the notification on the display unit provided in the operation unit 152 .
  • an abnormality e.g., a jam
  • the conveying velocity V is set by dividing the calculated distance by a value obtained by subtracting the time period Ta from the time period T 0 . That is, in the present exemplary embodiment, the conveying velocity V is set based on the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’.
  • the conveying velocity V is set based on the distance Lc corresponding to the paper type.
  • a second exemplary embodiment is described below. Components of the image forming apparatus 100 similar to those according to the first exemplary embodiment are not described here.
  • the CPU 151 a sets the conveying velocity V based on the distance from the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’ to the registration rollers 308 . In the present exemplary embodiment, the CPU 151 a sets the conveying velocity V based on the timing when the front end of the recording medium reaches a nip position of conveying rollers.
  • FIG. 10 is a diagram illustrating the relationship between the grammage of the recording medium to be conveyed, and time Tc from when the recording medium is detected to when the front end of the recording medium reaches the nip position n.
  • a grammage Ma in FIG. 10 corresponds to the grammage of the thin paper.
  • a grammage Mb in FIG. 10 corresponds to the grammage of the thick paper.
  • the relationship between the grammage and the time Tc illustrated in FIG. 10 is obtained by experiment and stored in advance, for example, in the ROM 151 b.
  • Time Tc_a and time Tc_b are values obtained by dividing by the conveying velocity V 0 the distance from the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’ to the nip position n of the conveying rollers 307 .
  • the time Tc_a and the time Tc_b are represented by the following formulas (13) and (14).
  • Information regarding the type of the recording medium (the paper type) specified by the user via the operation unit 152 is input to the CPU 151 a. Based on the acquired information regarding the paper type, and the relationship between the grammage and the time Tc stored in the ROM 151 b , the CPU 151 a determines the time Tc. For example, if information indicating that the thin paper is to be conveyed is input by the user via the operation unit 152 , the CPU 151 a sets the time Tc_a corresponding to the thin paper as the time Tc. If information indicating that the thick paper is to be conveyed is input by the user via the operation unit 152 , the CPU 151 a sets the time Tc_b corresponding to the thick paper as the time Tc.
  • the CPU 151 a sets the conveying velocity V based on the following formula (15). Specifically, the CPU 151 a sets the conveying velocity V in the section from the conveying rollers 307 to the detection position (i.e., the peripheral velocity of conveying rollers in the section from the conveying rollers 307 to the detection position). The conveying velocity V in the section from the pickup roller 305 to the conveying rollers 307 after the conveying velocity V in the section from the conveying rollers 307 to the detection position is adjusted may be set to V 0 , or may be set to the adjusted conveying velocity V.
  • V X 2/( T 0 ⁇ ( Ta+Tc )) (15)
  • the CPU 151 a calculates the time from when the driving of the pickup roller 305 is started to when the front end of the recording medium reaches the nip position n of the conveying rollers 307 . Then, the CPU 151 a sets the conveying velocity V by dividing the distance X 2 by a value obtained by subtracting the calculated time from the time T0. That is, the CPU 151 a sets the conveying velocity V based on the timing when the front end of the recording medium actually reaches a nip position of conveying rollers.
  • the conveying velocity V is set by dividing the distance X 2 by a value obtained by subtracting the calculated time from the time T 0 . That is, in the present exemplary embodiment, the conveying velocity V is set based on the timing when the front end of the recording medium reaches a nip position of conveying rollers.
  • the conveying velocity V is set based on the time Tc corresponding to the paper type.
  • a third exemplary embodiment is described below. Components of the image forming apparatus 100 similar to those according to the first exemplary embodiment are not described here.
  • FIGS. 11A and 11B are diagrams illustrating the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’, according to the present exemplary embodiment.
  • FIG. 11A is a diagram illustrating the position of the front end of the thin paper at the timing when the sheet detector 700 outputs the signal ‘ 1 ’ in a case where the thin paper is conveyed.
  • FIG. 11B is a diagram illustrating the position of the front end of the thick paper at the timing when the sheet detector 700 outputs the signal ‘ 1 ’ in a case where the thick paper is conveyed.
  • the conveying path from the feeding rollers 332 to the conveying rollers 307 is curved.
  • the front end of the recording medium conveyed downstream by the feeding rollers 332 collides with the conveying rollers 307 and then is guided to the nip position n of the conveying rollers 307 . Then, the front end of the recording medium is nipped by the conveying rollers 307 .
  • the amount of increase in the load torque applied to the rotor 402 of the motor 509 that occurs when the front end of the thin paper collides with the conveying rollers 307 is relatively small.
  • the amount of increase in the load torque applied to the rotor 402 of the motor 509 that occurs due to the fact that the front end of the thin paper is nipped by the conveying rollers 307 is greater than the amount of increase in the load torque that occurs when the front end of the thin paper collides with the conveying rollers 307 .
  • the amount of increase in the load torque that occurs when the front end of thick paper having greater rigidity and thickness than those of the thin paper collides with the conveying rollers 307 is greater than the amount of increase in the load torque that occurs when the front end of the thin paper collides with the conveying rollers 307 .
  • FIG. 12 is a diagram illustrating the state of the deviation ⁇ according to the present exemplary embodiment.
  • the absolute value of the deviation ⁇ increases at the timing (a time ta) when the front end of the thin paper collides with the conveying rollers 307 .
  • the absolute value of the deviation ⁇ increases at the timing (a time tc) when the front end of the thick paper collides with the conveying rollers 307 and the timing (a time tb) when the front end of the thick paper is nipped by the conveying rollers 307 .
  • a distance Lb′ has a value greater than that of the distance Lb in the first exemplary embodiment.
  • the distance Y from the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’ to the detection position is different from the distance X 2 .
  • the distance Y is longer than the distance X 2 .
  • the conveying velocity V is set based on formula (11)
  • the position of the front end of the recording medium at the timing when the recording medium is to reach the detection position is located upstream of the detection position due to the fact that the distance Y is longer than the distance X 2 .
  • the recording medium may reach the detection position after the timing when the recording medium is to reach the detection position.
  • the recording medium may reach the transfer position after the timing when the transfer of an image onto the recording medium is started, and the image may not be formed at an appropriate position on the recording medium.
  • the following configuration is applied, thereby preventing the situation where an image is formed at an inappropriate position on a recording medium.
  • FIG. 13 is a diagram illustrating the relationship between the grammage of the recording medium to be conveyed, and a distance Lc′ from the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’ to the conveying rollers 307 .
  • a grammage Mb′ corresponds to, for example, the smallest grammage among the grammages of the recording medium for which the sheet detector 700 outputs the signal ‘ 1 ’ due to the fact that the recording medium collides with the conveying rollers 307 .
  • the relationship between the grammage and the distance Lc′ illustrated in FIG. 13 is obtained by experiment and stored in advance, for example, in the ROM 151 b.
  • a distance L 1 is a value corresponding to La illustrated in FIG. 11A .
  • a distance L 2 is a value corresponding to Lb′ illustrated in FIG. 11B .
  • the CPU 151 a determines the distance Lc′ based on acquired information regarding the paper type, and the relationship between grammage and the distance Lc′ stored in the ROM 151 b.
  • a recording medium having a grammage greater than or equal to the grammage Mb′ is detected by the sheet detector 700 due to the fact that the recording medium collides with the conveying rollers 307 .
  • the timing when the recording medium fed by the pickup roller 305 collides with the conveying rollers 307 is approximately the same regardless of the paper type.
  • the distance from the position of the front end of the recording medium having a grammage greater than or equal to the grammage Mb′ at the timing when the recording medium is detected by the sheet detector 700 to the nip position n is approximately the same (Lb′) regardless of the paper type.
  • the CPU 151 a sets L 2 as the distance Lc′.
  • the CPU 151 a sets the distance Lc′ according to information regarding the input grammage.
  • the CPU 151 a sets the conveying velocity V based on formula (12).
  • the CPU 151 a calculates the distance from the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’ to the registration rollers 308 . Then, the CPU 151 a sets the conveying velocity V by dividing the calculated distance by a value obtained by subtracting the time Ta from the time T 0 . That is, the CPU 151 a sets the conveying velocity V based on the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’.
  • the conveying velocity V is set by dividing the calculated distance by a value obtained by subtracting the time Ta from the time T 0 . That is, in the present exemplary embodiment, the conveying velocity V is set based on the position of the front end of the recording medium at the timing when the sheet detector 700 outputs the signal ‘ 1 ’.
  • the conveying velocity V is set based on the distance Lc′ corresponding to the paper type.
  • the conveying velocity V may be adjusted by the method according to the second exemplary embodiment based on the position of the front end of the recording medium at the timing when the recording medium is detected due to the fact that the recording medium collides with the conveying rollers 307 . That is, a configuration may be used in which, based on the position of the front end of the recording medium at the timing when the recording medium is detected due to the fact that the recording medium collides with the conveying rollers 307 , the timing when the front end of the recording medium reaches the nip position n is calculated.
  • the conveying velocity V is adjusted based on the distance X 2 from the nip position n of the conveying rollers 307 to the detection position.
  • the configuration is not limited to this.
  • the conveying velocity V may be adjusted based on the distance from the nip position n of the conveying rollers 307 to a nip position of the registration rollers 308 . That is, the conveying velocity V may be adjusted based on the distance from the nip position n to a predetermined position downstream of the nip position n.
  • the predetermined position is a position upstream of the transfer position.
  • the number of pairs of rollers from the conveying rollers 307 to the detection position is two.
  • the configuration is not limited to this.
  • three or more pairs of conveying rollers may be provided between the conveying rollers 307 and the detection position.
  • the pickup roller 303 or 305 is repeatedly rotated and stopped at predetermined time intervals.
  • the configuration is not limited to this.
  • a configuration may be employed in which a swinging arm as a swinging member linking the pickup roller 305 and one of the feeding rollers 332 is supported by the rotating shaft of the feeding roller 332 so that the swinging arm can pivot about the rotating shaft of the feeding roller 332 .
  • the pickup roller 305 is moved up and down at predetermined time intervals using the swinging arm, thereby feeding recording media at predetermined intervals.
  • the CPU 151 a adjusts the conveying velocity V based on time Tb from when the CPU 151 a outputs an instruction to move down the pickup roller 305 to when the sheet detector 700 outputs the signal ‘ 1 ’.
  • the conveying velocity V is adjusted based on whether the front end of the recording medium reaches the nip position n of the conveying rollers 307 .
  • the configuration is not limited to this.
  • the conveying velocity V may be adjusted based on rollers other than the conveying rollers 307 .
  • the conveying velocity V may be adjusted based on whether the front end of the recording medium reaches a nip position of the conveying rollers 322 .
  • the time Tc or the distance Lc or Lc′ is set according to the grammage of the recording medium.
  • the configuration is not limited to this.
  • a configuration may be employed in which the time Tc or the distance Lc is set according to the rigidity or the thickness of the recording medium.
  • the time Tc and the distance Lc are set based on information regarding the paper type input by the user.
  • the configuration is not limited to this.
  • a configuration may be employed in which the time Tc and the distance Lc are set based on the detection result of a sensor for detecting the type of the recording medium, such as a thickness sensor.
  • the threshold for the deviation ⁇ is a predetermined value, regardless of the paper type.
  • the threshold may be set with respect to each paper type.
  • the sheet detector 700 if the absolute value of the deviation ⁇ is greater than the threshold, the sheet detector 700 outputs the signal ‘ 1 ’. If the absolute value of the deviation ⁇ is less than the threshold, the sheet detector 700 outputs the signal ‘ 0 ’.
  • the configuration is not limited to this. For example, a configuration may be employed in which, if the absolute value of the deviation ⁇ changes from a value smaller than the threshold to a value greater than or equal to the threshold, the sheet detector 700 outputs the signal ‘ 1 ’ to the CPU 151 a.
  • a configuration may be employed in which the CPU 151 a has the function of the sheet detector 700 according to the first, second, and third exemplary embodiments.
  • the recording medium is detected by comparing the absolute value of the deviation ⁇ with the threshold ⁇ th.
  • the configuration is not limited to this.
  • the recording medium may be detected by comparing the current value iq output from the coordinate transformer 511 with a threshold iqth.
  • An increase in the current value iq means that the load torque applied to the rotor 402 of the motor 509 increases.
  • a decrease in the current value iq means that the load torque applied to the rotor 402 of the motor 509 decreases.
  • the recording medium may be detected by comparing, with a threshold iq_refth, the q-axis current instruction value (target value) iq_ref determined based on the deviation ⁇ between the instruction phase ⁇ _ref and the rotational phase ⁇ determined by the phase determiner 513 .
  • An increase in the q-axis current instruction value iq_ref means that a torque required for the rotation of the rotor 402 of the motor 509 increases due to an increase in the load torque applied to the rotor 402 .
  • a decrease in the q-axis current instruction value iq_ref means that the torque required for the rotation of the rotor 402 of the motor 509 decreases due to a decrease in the load torque applied to the rotor 402 .
  • a configuration may be employed in which the recording medium is detected by comparing the amplitude (magnitude) of the current value i ⁇ or i ⁇ in the stationary coordinate system with a threshold.
  • An increase in the amplitude (magnitude) of the current value i ⁇ or i ⁇ in the stationary coordinate system means that the load torque applied to the rotor 402 of the motor 509 increases.
  • a decrease in the amplitude means that the load torque applied to the rotor 402 of the motor 509 decreases.
  • the first, second, and third exemplary embodiments are applied not only to motor control by vector control.
  • the first and second exemplary embodiments can be applied to any motor control device having a configuration for feeding back a rotational phase or a rotational velocity.
  • a stepper motor is used. as the motor for driving a load.
  • another motor such as a direct current (DC) motor or a brushless DC motor may be used.
  • the motor is not limited to a two-phase motor, and another motor such as a three-phase motor may be used.
  • the motor 509 is controlled by performing phase feedback control.
  • the configuration is not limited to this.
  • a configuration may be employed in which the motor 509 is controlled by feeding back a rotational velocity ⁇ of the rotor 402 .
  • a velocity determiner 514 is provided in the motor control device 157 , and the velocity determiner 514 determines the rotational velocity ⁇ based on a change over time in the rotational phase ⁇ output from the phase determiner 513 .
  • the rotational velocity ⁇ is determined using the following formula (16).
  • the CPU 151 a outputs an instruction velocity ⁇ _ref that indicates a target velocity of the rotor 402 .
  • a velocity controller 600 is provided in the motor control device 157 .
  • the velocity controller 600 generates the q-axis current instruction value iq_ref and the d-axis current instruction value id_ref so that the deviation between the rotational velocity ⁇ and the instruction velocity ⁇ _ref becomes small.
  • the velocity controller 600 outputs the q-axis current instruction value iq_ref and the d-axis current instruction value id_ref.
  • a configuration may be employed in which the motor 509 is controlled by performing such velocity feedback control.
  • a sheet is detected by the methods described in the first to third exemplary embodiments, for example, based on a deviation ⁇ between the rotational velocity ⁇ and the instruction velocity ⁇ _ref.
  • the instruction velocity ⁇ _ref is a target velocity of the rotor 402 of the motor 509 corresponding to a target velocity of the peripheral velocity of the conveying rollers 307 .
  • the deviations ⁇ and ⁇ , the current value iq, the current value iq_ref, and the amplitude of the current value i ⁇ or i ⁇ in the stationary coordinate system correspond to the values of parameters corresponding to the load torque applied to the rotor 402 of the motor 509 .
  • a permanent magnet is used as the rotor.
  • the configuration is not limited to this.
  • the configuration for detecting a sheet such as a recording medium is also applied to, for example, a motor for rotationally driving a conveying belt. That is, the configuration for detecting a sheet is applied to a motor for rotationally driving a rotating member, such as a roller or a conveying belt.
  • the photosensitive drum 309 , the charging device 310 , the developing device 314 , and the transfer charging device 315 are included in an image forming unit.
  • the registration rollers 308 are used as an abutment member that the front end of the recording medium abuts so that the skew of the recording medium is corrected.
  • the configuration is not limited to this.
  • a configuration may be employed in which a shutter as an abutment member is provided upstream of the registration rollers 308 and downstream of the pre-registration rollers 333 , or upstream of the transfer position and downstream of the registration rollers 308 in the conveying direction of the recording medium.
  • the front end of the recording medium is caused to abut the shutter, thereby correcting the skew of the recording medium by the above method.
  • the registration rollers 308 convey the recording medium to the transfer position in timing with a toner image, the shutter is retracted.
  • Embodiment(s) of the present disclosure can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s).
  • computer executable instructions e.g., one or more programs
  • a storage medium which may also be referred to more fully as a
  • the computer may include one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions.
  • the computer executable instructions may be provided to the computer, for example, from a network or the storage medium.
  • the storage medium include, for example, one or more of a hard disk, a random access memory (RAM), a read-only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BDTM), a flash memory device, a memory card, and the like.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Control Or Security For Electrophotography (AREA)
  • Delivering By Means Of Belts And Rollers (AREA)
  • Handling Of Sheets (AREA)
  • Paper Feeding For Electrophotography (AREA)
  • Electrophotography Configuration And Component (AREA)
  • Sheets, Magazines, And Separation Thereof (AREA)
US16/810,293 2019-03-13 2020-03-05 Image forming apparatus Abandoned US20200290832A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2019046342A JP7233987B2 (ja) 2019-03-13 2019-03-13 画像形成装置
JP2019-046342 2019-03-13

Publications (1)

Publication Number Publication Date
US20200290832A1 true US20200290832A1 (en) 2020-09-17

Family

ID=72424375

Family Applications (1)

Application Number Title Priority Date Filing Date
US16/810,293 Abandoned US20200290832A1 (en) 2019-03-13 2020-03-05 Image forming apparatus

Country Status (3)

Country Link
US (1) US20200290832A1 (enrdf_load_stackoverflow)
JP (1) JP7233987B2 (enrdf_load_stackoverflow)
CN (1) CN111694239B (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US12120274B2 (en) * 2022-08-15 2024-10-15 Konica Minolta, Inc. Image formation with increased productivity by determining surface state of medium conveying roller based on detected fluctuation range in roller driving load

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7638686B2 (ja) 2020-11-30 2025-03-04 キヤノン株式会社 シート搬送装置及び画像形成装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030230844A1 (en) * 2002-06-18 2003-12-18 Canon Kabushiki Kaisha Sheet material feeding device and recording apparatus
US20100187746A1 (en) * 2009-01-28 2010-07-29 Canon Kabushiki Kaisha Image forming apparatus
US20130094888A1 (en) * 2011-10-12 2013-04-18 Canon Kabushiki Kaisha Recording material conveyance apparatus and image forming apparatus

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH03119854U (enrdf_load_stackoverflow) * 1990-03-19 1991-12-10
JP2001139169A (ja) * 1999-11-18 2001-05-22 Ricoh Co Ltd 自動原稿給紙装置
US7065308B2 (en) * 2003-11-24 2006-06-20 Xerox Corporation Transfer roll engagement method for minimizing media induced motion quality disturbances
JP2006248644A (ja) 2005-03-09 2006-09-21 Ricoh Co Ltd 画像形成装置
JP4627049B2 (ja) 2006-06-05 2011-02-09 シャープ株式会社 画像形成装置
JP2013209220A (ja) 2012-03-01 2013-10-10 Ricoh Co Ltd 媒体搬送装置、画像形成装置及び媒体搬送システム
JP6606944B2 (ja) * 2015-09-18 2019-11-20 富士ゼロックス株式会社 搬送装置、定着装置、及び画像形成装置
EP3243775B1 (en) * 2016-05-09 2020-11-25 Canon Kabushiki Kaisha Sheet conveying apparatus that feeds sheet members, and document reading apparatus and image forming apparatus that include the sheet conveying apparatus
JP6897201B2 (ja) * 2017-03-22 2021-06-30 コニカミノルタ株式会社 給紙装置、原稿読取装置、画像形成装置および後処理装置
JP6991758B2 (ja) 2017-07-06 2022-01-13 キヤノン株式会社 シート搬送装置及び画像形成装置

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030230844A1 (en) * 2002-06-18 2003-12-18 Canon Kabushiki Kaisha Sheet material feeding device and recording apparatus
US20100187746A1 (en) * 2009-01-28 2010-07-29 Canon Kabushiki Kaisha Image forming apparatus
US20130094888A1 (en) * 2011-10-12 2013-04-18 Canon Kabushiki Kaisha Recording material conveyance apparatus and image forming apparatus

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US12120274B2 (en) * 2022-08-15 2024-10-15 Konica Minolta, Inc. Image formation with increased productivity by determining surface state of medium conveying roller based on detected fluctuation range in roller driving load

Also Published As

Publication number Publication date
JP7233987B2 (ja) 2023-03-07
JP2020148904A (ja) 2020-09-17
CN111694239B (zh) 2023-04-07
CN111694239A (zh) 2020-09-22

Similar Documents

Publication Publication Date Title
US9988227B2 (en) Sheet conveying apparatus and image forming apparatus
US10439531B2 (en) Sheet conveying apparatus and image forming apparatus
US11140289B2 (en) Motor control apparatus, sheet conveyance apparatus, and image forming apparatus
US10277152B2 (en) Motor control apparatus, sheet conveying apparatus, image forming apparatus
US10638006B2 (en) Sheet conveyance apparatus and image forming apparatus
US10787331B2 (en) Sheet conveying apparatus and image forming apparatus
US20200290832A1 (en) Image forming apparatus
US20180358913A1 (en) Motor control apparatus, sheet conveyance apparatus, document feeding apparatus, document reading apparatus, and image forming apparatus
US10474080B2 (en) Image forming apparatus
US20190312538A1 (en) Motor control apparatus, sheet conveyance apparatus, document feeding apparatus, document reading apparatus, and image forming apparatus
US20190218047A1 (en) Sheet conveyance apparatus, document feeding apparatus, document reading apparatus, and image forming apparatus
US11126128B2 (en) Image forming apparatus
US20200073281A1 (en) Sheet conveying apparatus, document reading apparatus, and image forming apparatus
US20200270083A1 (en) Sheet conveying apparatus
JP2019017181A (ja) シート搬送装置及び画像形成装置
US12351422B2 (en) Image forming apparatus
JP2019196272A (ja) シート搬送装置及び画像形成装置
US12362689B2 (en) Image forming apparatus
US10999453B2 (en) Motor control device, sheet conveying apparatus, and image forming apparatus
JP2019104552A (ja) シート搬送装置及び画像形成装置
JP2019101190A (ja) 画像形成装置
JP6580180B2 (ja) シート搬送装置及び画像形成装置
JP2020079130A (ja) 原稿給送装置、原稿読取装置及び画像形成装置
JP2020079131A (ja) シート搬送装置、原稿読取装置及び画像形成装置
JP2020092388A (ja) 原稿読取装置及び画像形成装置

Legal Events

Date Code Title Description
STPP Information on status: patent application and granting procedure in general

Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION

AS Assignment

Owner name: CANON KABUSHIKI KAISHA, JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SHIOZAWA, MISAKI;REEL/FRAME:053034/0051

Effective date: 20200221

STPP Information on status: patent application and granting procedure in general

Free format text: NON FINAL ACTION MAILED

STPP Information on status: patent application and granting procedure in general

Free format text: NON FINAL ACTION MAILED

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION