CN111694239A

CN111694239A - Image forming apparatus with a toner supply device

Info

Publication number: CN111694239A
Application number: CN202010127895.0A
Authority: CN
Inventors: 盐泽未沙树
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2019-03-13
Filing date: 2020-02-28
Publication date: 2020-09-22
Anticipated expiration: 2040-02-28
Also published as: JP7233987B2; US20200290832A1; CN111694239B; JP2020148904A

Abstract

The invention discloses an image forming apparatus. The image forming apparatus includes a stacking unit, a pickup roller, a conveying roller, a transfer unit, a motor, a determiner, and a speed adjuster. The conveying roller conveys the sheet fed by the pickup roller from the stacking unit in a conveying direction. The determiner determines a value of a parameter corresponding to a load torque applied to the motor. The speed adjuster adjusts a conveying speed at which the sheet is conveyed to a predetermined position based on a length between a leading end of the sheet and a nip position of the conveying roller at a first timing at which a value of the determined parameter changes from a value smaller than the predetermined value to a value larger than the predetermined value, and a length between the nip position and the predetermined position downstream of the conveying roller and upstream of the image forming position in the conveying direction.

Description

Image forming apparatus with a toner supply device

Technical Field

The present invention relates to an image forming apparatus that adjusts a conveying speed of a sheet being conveyed.

Background

Conventionally, there has been an image forming apparatus configured to detect whether or not a leading end of a sheet reaches (passes) a nip portion of a conveying roller based on a change (load fluctuation) in load torque applied to a rotor of a motor for driving the conveying roller for conveying the sheet (japanese patent application laid-open No. 2000-238934).

In addition, there has also been an image forming apparatus configured to adjust a conveying speed of a sheet based on a detection result of a sensor provided in a conveying path 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 the conveying speed of the sheet based on the detection result of the sensor so that the sheet reaches the target position at a predetermined timing.

In the configuration of the image forming apparatus discussed in japanese patent application laid-open No.2000-238934, the timing at which the load fluctuation is detected is determined as the timing at which the leading end of the sheet reaches the nip position of the conveying roller. However, in reality, due to the thickness of the sheet, the leading end of the sheet is located upstream of the nip position of the conveying roller at the timing at which the load fluctuation is detected.

If the conveying speed is adjusted in the above-described manner in a state where the timing at which the load fluctuation is detected is determined as the timing at which the leading end of the sheet reaches the nip position of the conveying roller, the following problem may occur. Specifically, even if the conveying speed is adjusted so that the leading end of the sheet reaches the target position at a predetermined timing, the position of the leading end of the sheet at this timing may be located upstream of the target position. Therefore, the sheet may reach the image forming position after the timing of starting forming an image on the sheet. Therefore, an image may not be formed at an appropriate position on the sheet.

Disclosure of Invention

The present invention is directed to preventing an image from being formed at an inappropriate position on a sheet.

According to one aspect of the present invention, an image forming apparatus includes: a stacking unit on which sheets are to be stacked; a pickup roller configured to feed sheets stacked on the stacking unit; a first conveying roller configured to convey a sheet fed by the pickup roller; a transfer unit configured to transfer an image onto a 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 speed adjuster configured to adjust a conveying speed at which the sheet being conveyed by the first conveying roller at the predetermined speed is conveyed to the predetermined position, based on a length between a position of a leading end of the sheet and a nip position of the first conveying roller at a first timing at which the value of the parameter determined by the determiner changes from a value smaller than the predetermined value to a value larger than the predetermined value, and a length between the nip position of the first conveying roller and the predetermined position downstream of the first conveying roller and upstream of the image forming position in the conveying direction.

Other features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

Drawings

Fig. 1 is a 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 a phase a and a phase B and a rotational coordinate system represented by a d axis and a q axis.

Fig. 4 is a block diagram illustrating a configuration of the motor control apparatus.

Fig. 5 is a diagram illustrating a configuration for detecting a fed recording medium.

Fig. 6 is a graph illustrating the deviation Δ θ in the case of conveying thin paper and the deviation Δ θ in the case of conveying thick paper according to the first exemplary embodiment.

Fig. 7A and 7B are diagrams illustrating a position of a leading end of a recording medium at a timing at which a sheet detector outputs a signal "1" (a timing at which the recording medium is detected) according to the first exemplary embodiment.

Fig. 8 is a diagram illustrating a relationship between the grammage of the recording medium to be conveyed and the distance from the position of the leading end of the recording medium at the timing at which the sheet detector outputs the signal "1" to the conveying roller.

Fig. 9 is a flowchart illustrating a control method for controlling the conveying speed V by a Central Processing Unit (CPU).

Fig. 10 is a diagram illustrating a relationship between the grammage of the recording medium to be conveyed and the time Tc from when the recording medium is detected to when the leading end of the recording medium reaches the nip position n.

Fig. 11A and 11B are diagrams illustrating a position of a leading end of a recording medium at a timing at which a sheet detector outputs a signal "1" according to the third exemplary embodiment.

Fig. 12 is a diagram illustrating a state of the deviation Δ θ according to the third exemplary embodiment.

Fig. 13 is a diagram illustrating a relationship between the grammage of the recording medium to be conveyed and the distance Lc from the position of the leading end of the recording medium at the timing at which the sheet detector outputs the signal "1" to the conveying roller.

Fig. 14 is a block diagram illustrating the configuration of a motor control apparatus that performs speed feedback control.

Detailed Description

Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. However, the shapes and relative arrangements of the components described in these exemplary embodiments should be appropriately changed depending on the configuration of the apparatus to which the present invention is applied and various conditions, and the scope of the present invention is not limited to the following exemplary embodiments. In the following description, a case where the motor control device is provided in the image forming apparatus is described. However, the motor control device is not provided only in the image forming apparatus. For example, the motor control apparatus is also used in a sheet conveying device that conveys a sheet such as a recording medium or a document.

[ image Forming apparatus ]

The first exemplary embodiment will be described below. Fig. 1 is a sectional view illustrating the configuration of a monochrome electrophotographic (electrophotographic) copying machine (hereinafter referred to as an "image forming apparatus") 100 including 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. The recording method is not limited to the electrophotographic method, and may be, for example, an inkjet method. The format (format) of the image forming apparatus 100 may be any one of a monochrome format and a color format.

Referring to fig. 1, the configuration and function of the image forming apparatus 100 are described below. As shown in fig. 1, the image forming apparatus 100 includes a document reading apparatus 200 and an image printing apparatus 301.

< document reading apparatus >

In the document reading device 200, a document feeding device 201 that feeds a document to a reading position is provided. The documents P stacked in the document stacking portion 2 of the document feeding device 201 are fed one by the pickup roller 3. Then, each document P is conveyed by the sheet-feed roller 4. At a position opposite to the sheet feeding roller 4, a separation roller 5 is provided 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 a function of separating two documents fed in an overlapped state.

The pickup roller 3 and the sheet feed roller 4 are linked together by a swing arm 12. The swing arm 12 is supported by a rotation shaft of the sheet feed roller 4 such that the swing arm 12 is pivotable about the rotation shaft of the sheet feed roller 4.

The document P is conveyed by the sheet-feed roller 4, and is discharged to the sheet-discharge tray 10 by the sheet-discharge roller 11. As shown in fig. 1, in the document stacking portion 2, there is provided a document setting sensor SS1 that detects whether or not a document P is stacked in the document stacking portion 2. In the conveying path through which each document P passes, a sheet sensor SS2 that detects the leading end of the document P (detects the presence or absence of the document P) is provided.

In the reading device 202, a document reading unit 16 is provided, and the document reading unit 16 reads an image on the first surface of the fed document P. Image information relating to the image read by the document reading unit 16 is output to the image printing apparatus 301.

In the document feeding device 201, a document reading unit 17 is provided, and the document reading unit 17 reads an image on the second surface of the conveyed document P. Image information relating to the image read by the document reading unit 17 is output to the image printing apparatus 301 in a method similar to that of the document reading unit 16 described above.

As described above, the document is read. That is, the document feeding device 201 and the reading device 202 function as the document reading device 200.

The document reading device 200 has a first reading mode and a second reading mode as the document reading mode. The first reading mode is a mode for reading an image on a document fed by the above-described method. The second reading mode is a mode in which the document reading unit 16 moving at a constant speed reads an image on a document placed on the document glass 214 of the reading device 202. Generally, an image on a sheet-like document is read in a first reading mode, and an image on a bound document (such as a book or a booklet) is read in a second reading mode.

Sheet holding trays

302 and 304 are provided in the image printing apparatus 301. In the

sheet holding trays

302 and 304, different types of recording media can be held. For example, a 4-sized plain paper is held in the sheet holding tray 302, and a 4-sized thick paper is held in the sheet holding tray 304. On each recording medium, an image is to be formed by the image forming apparatus 100. For example, the recording medium includes a sheet, a resin sheet, a cloth, an overhead projector (OHP) sheet, and a label.

The recording medium held in the sheet holding tray 302 is fed by a pickup roller 303, and is sent out to a pre-registration roller 333 by a feed roller 331 and a conveying roller 306. The recording medium held in the sheet holding tray 304 is fed by the pickup roller 305, and sent out to the pre-registration roller 333 by the feed roller 332, the conveying roller 307, and the conveying roller 306.

Between the pre-registration roller 333 and the registration roller 308, a sheet sensor 335 for detecting the leading end of the recording medium is provided. The leading end of the recording medium conveyed by the pre-registration roller 333 is detected by the sheet sensor 335, and then abuts against the registration roller 308 in the stopped state. Then, the pre-registration roller 333 is further rotated, thereby further conveying the recording medium in the conveying direction. Then, the recording medium is bent. Therefore, the elastic force acts on the recording medium, and the leading end of the recording medium abuts against the registration roller 308 along the nip portion of the registration roller 308. Thus, the skew of the recording medium is corrected. In the present exemplary embodiment, the pre-registration roller 333 is controlled to rotate for a predetermined time after the sheet sensor 335 detects the leading end of the recording medium. The predetermined time is set in advance to a time sufficient for the recording medium to be bent by an amount necessary for correcting the skew of the recording medium.

An image signal output from the document reading apparatus 200 is input to an optical scanning device 311 including a semiconductor laser and a polygon mirror. The peripheral surface of the photosensitive drum 309 is charged by a charging device 310. After charging the peripheral surface of the photosensitive drum 309, laser light corresponding to an image signal input from the document reading device 200 to the optical scanning device 311 is emitted from the optical scanning device 311 to the peripheral surface of the photosensitive drum 309 via one or more polygon mirrors 312 and 313. Thus, 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.

Next, the electrostatic latent image is developed with toner in the developing device 314, thereby forming a toner image on the peripheral surface of the photosensitive drum 309. The toner image formed on the photosensitive drum 309 is transferred onto a recording medium by a transfer charging device 315 as a transfer unit provided at a position (transfer position) opposing the photosensitive drum 309. The registration roller 308 sends the recording medium to the transfer position.

As described above, the recording medium to which the toner image has been transferred is sent to the fixing device 318 by the conveying belt 317, and is heated and pressurized by the fixing device 318, thereby fixing the toner image to the recording medium. In this way, an image is formed on a recording medium by the image forming apparatus 100.

In the case of forming an image in the one-sided printing mode, the recording medium having passed through the fixing device 318 is discharged to a sheet discharge tray (not shown) by

sheet discharge rollers

319 and 324. In the case of forming an image in the duplex printing mode, a fixing process is performed on a first surface of a recording medium by a fixing device 318, and then the recording medium is conveyed to a reverse path 325 by a sheet discharge roller 319, a conveying roller 320, and a reverse roller 321. Then, the recording medium is conveyed again to the registration roller 308 by the conveying

rollers

322 and 323, and an image is formed on the second surface of the recording medium by the above-described method. Then, the recording medium is discharged to a sheet discharge tray (not illustrated) by

sheet discharge rollers

319 and 324.

In a case where the recording medium having the image formed on the first surface thereof is discharged to the outside of the image forming apparatus 100 face down, the recording medium having passed through the fixing device 318 is conveyed through the sheet discharge roller 319 in a direction toward the conveying roller 320. Then, just before the trailing end of the recording medium passes through the nip portion of the conveying roller 320, the rotation of the conveying roller 320 is reversed, so that the recording medium is discharged to the outside of the image forming apparatus 100 via the sheet discharging roller 324 in a state where the first surface of the recording medium faces downward.

As shown in fig. 1, in the image printing apparatus 301, a stack unit 327 in which recording media are stacked is provided. The recording medium stacked in the stack unit 327 is sent out in the conveying direction by a pickup roller 328, and then conveyed by a sheet feed roller 329.

One of the sheet feed rollers 329 and the pickup roller 328 are linked together by a swing arm 330. The swing arm 330 is supported by a rotation shaft of the sheet feed roller 329 so that the swing arm 330 can pivot about the rotation shaft of the sheet feed roller 329.

On the recording medium conveyed to the conveying roller 306 by the sheet feed roller 329, an image is formed by the above-described method.

The configuration and function of the image forming apparatus 100 have been described above.

Fig. 2 is a block diagram illustrating an example of a control configuration of the image forming apparatus 100. As shown in fig. 2, the system controller 151 includes a Central Processing Unit (CPU)151a, a Read Only Memory (ROM)151b, and a Random Access Memory (RAM)151 c. The system controller 151 is connected to the image processing unit 112, the operation unit 152, an analog-to-digital (a/D) converter 153, a high-voltage control unit 155, a motor control device 157, a sensor 159, an Alternating Current (AC) driver 160, a sheet sensor 334, and a sheet sensor 335. The system controller 151 may transmit and receive data and commands to and from a unit connected to the system controller 151.

The CPU151a reads and executes various programs stored in the ROM151b, thereby executing various sequences related to a predetermined image forming sequence.

The RAM 151c is a storage device. The RAM 151c stores various types of data such as set values for the high-voltage control unit 155, instruction values for the motor control device 157, and information received from the operation unit 152.

The system controller 151 transmits setting value data of various devices set in the image forming apparatus 100, which are necessary for image processing by the image processing unit 112, to the image processing unit 112. In addition, the system controller 151 receives a signal from the sensor 159, and sets the set value of the high-voltage control unit 155 based on the received signal. The high-voltage control unit 155 supplies a required voltage to the high-voltage unit 156 (the charging device 310, the developing device 314, and the transfer charging device 315) according to a setting value set by the system controller 151. The sensor 159 includes a sensor that detects the recording medium conveyed by the conveying roller.

According to an instruction output from the CPU151a, the motor control device 157 controls a motor 509 for driving the conveying roller 307. Although fig. 2 illustrates only the motor 509 as the motor of the image forming apparatus 100, a plurality of motors are actually provided in the image forming apparatus 100. Alternatively, a configuration may be adopted in which a single motor control device controls a plurality of motors. In addition, although only a single motor control device is provided in fig. 2, actually, a plurality of motor control devices are provided in the image forming apparatus 100.

The a/D converter 153 receives a detection signal detected by the thermistor 154, and the thermistor 154 detects the temperature of the fixing heater 161. Then, the a/D converter 153 converts the detection 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 necessary to execute the fixing process. The fixing heater 161 is a heater used in a fixing process and is included in the fixing device 318.

The system controller 151 controls the operation unit 152 to display an operation screen for letting the user set the type of recording medium to be used (hereinafter referred to as "paper type") on a display unit provided in the operation unit 152. The system controller 151 receives information set by the user from the operation unit 152, and controls the operation sequence of the image forming apparatus 100 based on the information set by the user. The system controller 151 transmits information indicating the state of the image forming apparatus 100 to the operation unit 152. The information indicating the state of the image forming apparatus 100 is, for example, information related to the number of images to be formed in the document feeding apparatus 201 and the image printing apparatus 301, the progress state of the image forming operation, and a jam or multi-feeding of sheets. The operation unit 152 displays information received from the system controller 151 on the display unit.

As described above, the system controller 151 controls the operation sequence of the image forming apparatus 100. The sheet detector 700 will be described below.

[ Motor control apparatus ]

Next, a motor control apparatus according to the present exemplary embodiment is described. The motor control apparatus according to the present exemplary embodiment controls the motor using vector control.

< vector control >

First, with reference to fig. 3 and 4, a description is given of a method in which the motor control apparatus 157 according to the present exemplary embodiment performs vector control. In the motor in the following description, a sensor such as a rotary encoder for detecting a rotational phase of a rotor of the motor is not provided. Alternatively, a sensor such as a rotary encoder may be provided.

Fig. 3 is a diagram illustrating a relationship between a stepping motor (hereinafter referred to as "motor") 509 having two phases including an a phase (first phase) and a B phase (second phase) and a rotational coordinate system represented by a d axis and a q axis. In fig. 3, in the stationary coordinate system, an α axis corresponding to the winding in the a phase and a β axis corresponding to the winding in the B phase are defined. In fig. 3, a d-axis is defined along a direction of magnetic flux generated by magnetic poles of permanent magnets used in the rotor 402, and a q-axis is defined along a direction rotated 90 degrees counterclockwise from the d-axis (a direction orthogonal to the d-axis). An angle between the α -axis and the d-axis is defined as θ, and the rotational phase of the rotor 402 is represented by the angle θ. In the vector control, a rotating coordinate system based on the rotation phase θ of the rotor 402 is used. Specifically, in the vector control, a q-axis component (torque current component) and a d-axis component (excitation current component), which are current components of the current vector in the rotating coordinate system corresponding to the drive current flowing through each winding, are used. The q-axis component (torque current component) generates torque in the rotor 402, while the d-axis component (excitation current component) affects the strength of the magnetic flux through the windings.

The vector control is a control method of controlling the motor by performing phase feedback control for controlling the value of the torque current component and the value of the exciting current component so that a deviation between a command phase indicating a target phase of the rotor and an actual rotational phase of the rotor becomes small. There is also a method of controlling the motor by performing speed feedback control for controlling the value of the torque current component and the value of the field current component so that a deviation between a command speed indicating a target speed of the rotor and an actual rotational speed 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 performs the functions described below.

As a circuit for performing vector control, the motor control apparatus 157 includes a phase controller 502, a current controller 503, a coordinate inverter 505, a coordinate converter 511, and a Pulse Width Modulation (PWM) inverter 506 that supplies a drive current to a winding of a motor 509. The coordinate transformer 511 performs coordinate transformation from a stationary coordinate system represented by the α axis and the β axis to a rotating coordinate system represented by the q axis and the d axis on current vectors corresponding to the drive currents flowing through the windings in the a phase and the B phase of the motor 509. Therefore, the drive current flowing through the winding is represented by a current value of the q-axis component (q-axis current) and a current value of the d-axis component (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 affects the intensity of the magnetic flux through each winding of the motor 509. The motor control device 157 may independently control the q-axis current and the d-axis current. Therefore, the motor control apparatus 157 controls the q-axis current according to the load torque applied to the rotor 402, so that the torque required for the rotation of the rotor 402 can be efficiently generated. That is, in the vector control, the magnitude of the current vector shown in fig. 3 is changed according to the load torque applied to the rotor 402.

The motor control apparatus 157 determines the rotational phase θ of the rotor 402 of the motor 509 using the following method, and performs vector control based on the determination result. Based on the operation sequence of the motor 509, the CPU151a outputs a driving pulse to the instruction generator 500 as an instruction to drive the motor 509. The operation sequence of the motor 509 (driving mode of the motor 509) is stored in, for example, the ROM151 b. Based on the operation sequence stored in the ROM151b, the CPU151a outputs a drive pulse as a pulse train. The number of pulses corresponds to the commanded phase and the frequency of the pulses corresponds to the target speed.

Based on the driving pulse output from the CPU151a, the command generator 500 generates a command phase θ _ ref indicating a target phase of the rotor 402 and outputs the command phase θ _ ref. The configuration of the instruction generator 500 will be described below.

The subtractor 101 calculates a deviation Δ θ between the rotational phase θ of the rotor 402 of the motor 509 and the command phase θ _ ref, and outputs the deviation Δ θ.

The phase controller 502 acquires the deviation Δ θ in the period T (e.g., 200 μ s). Based on proportional control (P control), integral control (I control), and differential control (D control), phase controller 502 generates q-axis current reference value iq _ ref and D-axis current reference value id _ ref as target values so that deviation Δ θ output from subtractor 101 becomes smaller. Then, the phase controller 502 outputs a q-axis current reference value iq _ ref and a d-axis current reference value id _ ref. Specifically, based on the P control, the I control, and the D control, the phase controller 502 generates the q-axis current reference value iq _ ref and the D-axis current reference value id _ ref so that the deviation Δ θ output from the subtractor 101 becomes 0. Then, the phase controller 502 outputs a q-axis current reference value iq _ ref and a d-axis current reference value id _ ref. P control is a control method of controlling the value of a target to be controlled based on a value proportional to a deviation between a command value and an estimated value. I control is a control method of controlling the value of a target to be controlled based on a value proportional to the time integral of the deviation between a command value and an estimated value. D control is a control method of controlling the value of the target to be controlled based on a value proportional to the change over time of the deviation between the command value and the estimated value. The phase controller 502 according to the present exemplary embodiment generates a q-axis current reference value iq _ ref and a d-axis current reference value id _ ref based on proportional-integral-derivative (PID) control. However, the configuration is not limited thereto. For example, the phase controller 502 may generate a q-axis current reference value iq _ ref and a d-axis current reference value id _ ref based on proportional-integral (PI) control. In the case of using a permanent magnet in the rotor 402, normally, the d-axis current reference value id _ ref that affects the intensity of magnetic flux passing through each winding is set to 0. However, the configuration is not limited thereto.

The drive current flowing through the winding in the a phase of the motor 509 is detected by the current detector 507 and then converted from an analog value to a digital value by the a/D converter 510. The drive current flowing through the windings in the B phase of the motor 509 is detected by the current detector 508, and then converted from an analog value to a digital value by the a/D converter 510. The period in which

current detectors

507 and 508 detect the current is, for example, a period (for example, 25 μ s) that is less than or equal to the period T in which phase controller 502 acquires deviation Δ θ.

Using the phase θ e of the current vector shown in fig. 3, the current value of the drive current converted from an analog value to a digital value by the a/D converter 510 is expressed as current values i α and i β in the stationary coordinate system by the following equations (1) and (2). The phase θ e of the current vector is defined as the angle between the α -axis and the current vector. I denotes the magnitude of the current vector.

iα＝I*cosθe (1)

iβ＝I*sinθe (2)

The current values i α and i β are input to the coordinate transformer 511 and the induced voltage determiner 512.

The coordinate transformer 511 converts the current values i α and i β in the stationary coordinate system into the current value iq of the q-axis current and the current value id of the d-axis current in the rotating coordinate system by the following equations (3) and (4).

id＝cosθ*iα+sinθ*iβ (3)

iq＝-sinθ*iα+cosθ*iβ (4)

The coordinate transformer 511 outputs the transformed current value iq to the subtractor 102. The coordinate transformer 511 outputs the transformed current value id to the subtractor 103.

The subtractor 102 calculates a deviation between the q-axis current reference value iq _ ref and the current value iq, and outputs the calculated deviation to the current controller 503.

The subtractor 103 calculates a deviation between the d-axis current reference value id _ ref and the current value id, and outputs the calculated deviation to the current controller 503.

Based on the PID control, the current controller 503 generates the drive 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 drive 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 drive voltages Vq and Vd to the coordinate inverter 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 PID control. However, the configuration is not limited thereto. For example, the current controller 503 may generate the driving voltages Vq and Vd based on PI control.

The coordinate inverse transformer 505 inversely transforms the driving voltages Vq and Vd in the rotating coordinate system output from the current controller 503 into the driving voltages V α and V β in the stationary coordinate system by the following equations (5) and (6).

Vα＝cosθ*Vd-sinθ*Vq (5)

Vβ＝sinθ*Vd+cosθ*Vq (6)

The coordinate inverse transformer 505 outputs the inverse-transformed drive voltages V α and V β to the induction voltage determiner 512 and the PWM inverter 506.

The PWM inverter 506 includes a full bridge circuit. The full bridge circuit is driven by the PWM signal based on the drive voltages V α and V β input from the coordinate inverter 505. Thus, the PWM inverter 506 generates the driving currents i α and i β from the driving voltages V α and V β and supplies the driving currents i α and i β to windings in respective phases of the motor 509, thereby driving the motor 509. In the present exemplary embodiment, the PWM inverter 506 includes a full bridge circuit. Alternatively, the PWM inverter 506 may include a half-bridge circuit.

Next, a description is given of a configuration for determining the rotation phase θ. The rotational phase θ of the rotor 402 is determined using values of induced voltages E α and E β induced in windings in the a-phase and the B-phase of the motor 509 by the rotation of the rotor 402. The value of each induced voltage is determined (calculated) by the induced voltage determiner 512. Specifically, the induced voltages E α and E β are determined by the following equations (7) and (8) based on the current values i α and i β input from the a/D converter 510 to the induced voltage determiner 512 and the driving voltages V α and V β input from the coordinate inverse converter 505 to the induced voltage determiner 512.

Eα＝Vα-R*iα-L*diα/dt (7)

Eβ＝Vβ-R*iβ-L*diβ/dt (8)

In these formulas, R represents the winding resistance and L represents the 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 ROM151b or a memory (not shown) provided in the motor control device 157.

The induced voltages E α and E β determined by the induced voltage determiner 512 are output to the phase determiner 513.

Based on the ratio between the induced voltages E α and E β output from the induced voltage determiner 512, the phase determiner 513 determines the rotation phase θ of the rotor 402 of the motor 509 by the following formula (9).

θ＝tan^-1(-Eβ/Eα) (9)

In the present exemplary embodiment, the phase determiner 513 determines the rotational phase θ by performing calculation based on equation (9). However, the configuration is not limited thereto. For example, the phase determiner 513 may determine the rotation phase θ by referring to a table stored in the memory 513a and illustrating a relationship between the induced voltages E α and E β and the rotation phase θ corresponding to the induced voltages E α and E β.

The rotational phase θ 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 executes the above-described control.

As described above, the motor control apparatus 157 according to the present exemplary embodiment performs vector control using phase feedback control for controlling the current value in the rotational coordinate system so that the deviation Δ θ between the command phase θ _ ref and the rotational phase θ becomes small. By performing the vector control, it is possible to prevent the motor from entering a step-out state and to prevent an increase in motor sound and an increase in power consumption due to excessive torque.

< instruction Generator >

Based on the driving pulse output from the CPU151a, the instruction generator 500 generates an instruction phase θ _ ref using the following equation (10) and outputs the instruction phase θ _ ref.

θ_ref＝θini+θstep*n (10)

θ ini is the phase (initial phase) of the rotor 402 at the start of driving the motor 509. θ step is the amount of increase (amount of change) in the command phase θ _ ref for each drive pulse. n is the number of pulses input to the instruction generator 500.

[ control of sheet conveyance in image Forming apparatus ]

< sheet Detector >

Fig. 5 is a diagram illustrating a configuration for detecting a fed recording medium. As shown in fig. 5, the conveying roller 307 is driven by a motor 509, and the motor 509 is controlled by a motor control device 157. The feed roller 332 and the pickup roller 305 are driven by a motor (not shown). The feed roller 332 is a roller adjacent to the conveying roller 307. In the present exemplary embodiment, the conveying speed V at which the recording medium is conveyed is set in advance to the predetermined speed V0 based on the operation sequence of the image forming apparatus 100.

Next, a description is given of a configuration in which the sheet detector 700 detects whether the leading end of the recording medium reaches the nip portion of the conveying roller 307. In the present exemplary embodiment, whether or not the leading end of the recording medium reaches the nip portion of the conveying roller 307 is detected (determined) based on a signal output from the motor control device 157, not by a sensor such as a photosensor. In the following description, for example, the sheet detector 700 outputs the detection result at a predetermined time period (for example, a period of the input deviation Δ θ).

The leading end of the recording medium conveyed downstream by the conveying roller 332 is nipped by the conveying roller 307. If the leading end of the recording medium is nipped by the conveying roller 307, the load torque applied to the rotor 402 of the motor 509 for driving the conveying roller 307 increases. If the load torque increases, the absolute value of the deviation Δ θ increases.

If the absolute value of the deviation Δ θ becomes greater than or equal to the threshold value Δ θ th, which is a predetermined value, the sheet detector 700 outputs a signal "1" (recording medium detected) indicating that the absolute value of the deviation Δ θ becomes greater than or equal to the threshold value Δ θ th. If the absolute value of the deviation Δ θ is smaller than the threshold Δ θ th, the sheet detector 700 outputs a signal "0" indicating that the absolute value of the deviation Δ θ is smaller than the threshold Δ θ th. The threshold value Δ θ th will be described below.

< adjustment of conveying speed V >

The detection result of the sheet detector 700 is input to the CPU151 a. If the sheet detector 700 outputs a signal "1", the CPU151a adjusts the conveying speed V of the recording medium. For example, the CPU151a changes the frequency of drive pulses to be output to a motor control device provided in the image forming apparatus 100, thereby adjusting the conveying speed V.

In the following description, X1 denotes the distance from the pickup roller 305 to the conveying roller 307. X2 denotes a distance from the conveying roller 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 X1+ X2. T0 corresponds to the time required to convey the recording medium by the distance X1+ X2 at the conveying speed V0.

In the present exemplary embodiment, the pickup roller 305 is repeatedly rotated and stopped at predetermined time intervals to feed the recording medium at predetermined intervals. As shown in fig. 2, the CPU151a includes a timer 151d, and measures the time elapsed since the start of driving the pickup roller 305 (since the CPU151a outputs an instruction for starting driving the pickup roller 305).

The CPU151a sets, as the conveying speed V, a speed calculated based on the distance X2 and a time period obtained by subtracting a time period Ta, which is a period from when the driving of the pickup roller 305 is started to when the sheet detector 700 outputs the signal "1", from the time period T0. Specifically, the CPU151a sets the conveying speed V in a section from the conveying roller 307 to the detection position (i.e., the circumferential speed of the conveying roller in a section from the conveying roller 307 to the detection position) based on the following formula (11). The conveying speed V in the section from the pickup roller 305 to the conveying roller 307 after the conveying speed V in the section from the conveying roller 307 to the detection position is adjusted may be set to V0, or may be set to the conveying speed V adjusted based on equation (11).

V＝X2/(T0-Ta) (11)

Fig. 6 is a diagram illustrating a deviation Δ θ (broken line) output from the motor control device 157 in the case of conveying thin paper and a deviation Δ θ (solid line) output from the motor control device 157 in the case of conveying thick paper. In fig. 6, the timing of starting the feeding operation for feeding the recording medium is exemplified as t ═ 0.

In fig. 6, the deviation Δ θ having a positive value means that the rotational phase θ is after the command phase θ _ ref. A deviation Δ θ having a negative value means that the rotational phase θ precedes the command phase θ _ ref. However, the relationship between the polarity of the deviation Δ θ and the rotation phase θ and the command phase θ _ ref is not limited to these. For example, the following configuration may be adopted: the deviation Δ θ has a negative value in the case where the rotation phase θ is after the reference phase θ _ ref, and has a positive value in the case where the rotation phase θ is before the reference phase θ _ ref. As shown in fig. 6, if the load torque increases, the absolute value of the deviation Δ θ becomes large due to the fact that the rotation phase θ of the rotor 402 of the motor 509 is after the command phase θ _ ref.

Fig. 7A and 7B are diagrams illustrating the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" (the timing at which the recording medium is detected).

Fig. 7A is a diagram illustrating the position of the leading end of the thin paper at the timing (time ta) at which the sheet detector 700 outputs the signal "1" in the case of conveying the thin paper. Fig. 7B is a diagram illustrating the position of the leading end of the thick paper at the timing (time tb) at which the sheet detector 700 outputs the signal "1" in the case of conveying the thick paper.

The leading end of the recording medium conveyed downstream by the feed roller 332 is nipped by the conveying roller 307. If the leading end of the recording medium is nipped by the conveying roller 307, the load torque applied to the rotor 402 of the motor 509 for driving the conveying roller 307 increases. If the load torque increases, the absolute value of the deviation Δ θ increases, for example, as shown in fig. 6 (time ta or tb).

In the present exemplary embodiment, the conveying roller 307 rotates at a peripheral speed faster than that of the feed roller 332. If the recording medium is nipped by the conveying roller 307, the conveying roller 307 pulls the recording medium nipped by the conveying roller 307 downstream. With this configuration, the range of increase in the load torque when the recording medium is nipped by the conveying roller 307 can be made larger. Therefore, the leading end of the recording medium is detected with higher accuracy.

In the present exemplary embodiment, the threshold value Δ θ th is set to, for example, a value smaller than the load torque applied to the conveying roller 307 increased due to the recording medium having the smallest rigidity and thickness among the plurality of types of recording media that can be conveyed in the image forming apparatus 100, that is, a value smaller than the maximum value (peak value) of the absolute value of the deviation Δ θ. In addition, the threshold Δ θ th is set to, for example, a value smaller than the load torque applied to the conveying roller 307 which increases due to a recording medium having the largest rigidity and thickness among the plurality of types of recording media that can be conveyed in the image forming apparatus 100, that is, a value smaller than the maximum value (peak value) of the absolute value of the deviation Δ θ.

The threshold value Δ θ th is set to a value larger than, for example, the absolute value of the deviation Δ θ assumed in a state in which the recording medium is not nipped by the nip portion of the conveying roller 307 and a state in which the conveying roller 307 is rotated at a constant speed.

As shown in fig. 7A and 7B, due to the thickness of the recording medium, the leading end of the recording medium is nipped at a timing at which the leading end of the recording medium is located upstream of the nip position n in the conveying direction. As illustrated in fig. 7A and 7B, a distance La from a position of the leading end of thin paper at the timing at which the sheet detector 700 outputs the signal "1" to the nip position n in the case of conveying thin paper is shorter than a distance Lb from a position of the leading end of thick paper at the timing at which the sheet detector 700 outputs the signal "1" to the nip position n in the case of conveying thick paper. This means that, due to the fact that the thickness of the thick paper is greater than that of the thin paper, the position of the leading end of the thick paper when the conveying roller 307 starts nipping the thick paper is located upstream of the position of the leading end of the thin paper when the conveying roller 307 starts nipping the thin paper.

As described above, the distance Y of the leading end of the recording medium from the position at the timing of outputting the signal "1" from the sheet detector 700 to the detection position is different from the distance X2. In other words, distance Y is longer than distance X2. If the conveying speed V is set based on the formula (11), the position of the leading end of the recording medium at the timing at which 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 X2. That is, the recording medium may reach the detection position after the timing at which the recording medium is to reach the detection position. Therefore, the recording medium may reach the transfer position after the timing of starting the transfer of the image onto the recording medium, and the image may not be formed at an appropriate position on the recording medium.

In the present exemplary embodiment, the following configuration is applied, thereby preventing a situation in which an image is formed at an inappropriate position on a recording medium.

Fig. 8 is a diagram illustrating a relationship between the grammage of the recording medium to be conveyed and the distance Lc from the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" to the conveying roller 307. The grammage Ma in fig. 8 corresponds to the grammage of the tissue. The grammage Mb in fig. 8 corresponds to the grammage of thick paper. The relationship between the grammage and the distance Lc shown in fig. 8 is obtained through experiments, and is stored in advance in, for example, the ROM151 b.

The distance Lc _ a is a value corresponding to La shown in fig. 7A. The distance Lc _ B is a value corresponding to Lb shown in fig. 7B.

For example, information on the paper type is input by the user through the operation unit 152. The information on the paper type includes the grammage and stiffness of the recording medium. Based on the input information about the paper type and the relationship between the grammage and the distance Lc stored in the ROM151b, the CPU151a determines the distance Lc. For example, if the user inputs information indicating that thin paper is to be conveyed through the operation unit 152, the CPU151a sets Lc _ a corresponding to thin paper to the distance Lc. If the user inputs information indicating that thick paper is to be conveyed through the operation unit 152, the CPU151a sets Lc _ b corresponding to thick paper to the distance Lc.

Using the set distance Lc, the CPU151a sets the conveying speed V based on the following equation (12).

V＝(X2+Lc)/(T0-Ta) (12)

That is, the CPU151a calculates the distance from the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" to the registration roller 308. Then, the CPU151a sets the conveying speed V by dividing the calculated distance by a value obtained by subtracting the time period Ta from the time period T0. That is, the CPU151a sets the conveying speed V based on the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1".

Fig. 9 is a flowchart illustrating a control method of controlling the conveying speed V by the CPU151 a. Referring to fig. 9, control of the conveying speed V according to the present exemplary embodiment is described. The processing of the flowchart is executed by the CPU151 a. During the processing of the flowchart, each time the CPU151a outputs an instruction to start rotationally driving the pickup roller 305, the CPU151a resets and starts the timer 151 d.

In step S1001, if information on the paper type is input to the CPU151a through the operation unit 152 (yes in step S1001), then in step S1002, the CPU151a sets the distance Lc based on the input information on the paper type.

Then, in step S1003, the CPU151a starts a feeding operation to feed the recording medium stored in the designated sheet holding tray. From here, the pickup roller 305 is repeatedly driven and stopped at predetermined time intervals.

Next, in step S1004, the CPU151a determines whether the sheet detector 700 outputs the signal "1". If the sheet detector 700 outputs the signal "1" (yes in step S1004), the processing proceeds to step S1005.

In step S1005, the CPU151a adjusts (sets) the conveying speed V based on the distance Lc set in step S1002, the time period Ta from when the pickup roller starts to be driven to when the sheet detector 700 outputs the signal "1", and the distance X2. Specifically, the CPU151a sets the conveying speed V using the formula (12).

In step S1006, the CPU151a determines whether the print job is to be ended. If the print job is to be ended (yes in step S1006), in step S1007, the CPU151a ends the feeding operation.

On the other hand, in step S1006, if the print job is not to be ended (no in step S1006), the processing returns to step S1004.

In step S1004, if the sheet detector 700 does not output the signal '1' (no in step S1004), the processing proceeds to step S1008.

In step S1008, the CPU151a determines whether the state in which the sheet detector 700 does not output the signal "1" continues for a predetermined time. If the state in which the sheet detector 700 does not output the signal "1" does not continue for the predetermined time (no in step S1008), the processing returns to step S1004.

On the other hand, in step S1008, if the state in which the sheet detector 700 does not output the signal "1" continues for a predetermined time (yes in step S1008), then in step S1009, the CPU151a stops the feeding operation. The predetermined time is set to, for example, a time longer than the time required for the recording medium fed by the pickup roller 305 to be conveyed at the conveying speed V0 and reach the conveying roller 307.

Then, in step S1010, the CPU151a notifies the user of the occurrence of an abnormality (e.g., a paper jam) in the conveyance of the recording medium by displaying a notification on the display unit provided in the operation unit 152.

As described above, in the present exemplary embodiment, the distance from the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" to the registration roller 308 is calculated based on the distance X2 and the distance Lc occurring due to the thickness of the recording medium. The conveying speed V is set by dividing the calculated distance by a value obtained by subtracting the time period Ta from the time period T0. That is, in the present exemplary embodiment, the conveying speed V is set based on the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1". Therefore, the recording medium can be prevented from reaching the transfer position after the timing of starting the transfer of the image onto the recording medium. Therefore, it is possible to prevent a situation where an image is formed at an inappropriate position on the recording medium.

In addition, in the present exemplary embodiment, the conveying speed V is set based on the distance Lc corresponding to the paper type. Therefore, it is possible to prevent the recording medium from reaching the transfer position after the timing to start transferring the image onto the recording medium due to the fact that the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" differs depending on the paper type. That is, it is possible to prevent a situation where an image is not formed at an appropriate position on the recording medium.

The second exemplary embodiment is described below. The components of the image forming apparatus 100 similar to those according to the first exemplary embodiment are not described here.

In the first exemplary embodiment, the CPU151a sets the conveying speed V based on the distance from the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" to the registration roller 308. In the present exemplary embodiment, the CPU151a sets the conveying speed V based on the timing at which the leading end of the recording medium reaches the nip position of the conveying roller.

Fig. 10 is a diagram illustrating a relationship between the grammage of the recording medium to be conveyed and the time Tc from when the recording medium is detected to when the leading end of the recording medium reaches the nip position n. The grammage Ma in fig. 10 corresponds to the grammage of the tissue. The grammage Mb in fig. 10 corresponds to the grammage of thick paper. The relationship between the grammage and the time Tc shown in fig. 10 is obtained by experiment and stored in advance in, for example, the ROM151 b.

The time Tc _ a and the time Tc _ b are values obtained by removing, with the conveying speed V0, the distance from the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" to the nip position n of the conveying roller 307. Specifically, the time Tc _ a and the time Tc _ b are represented by the following equations (13) and (14).

Tc_a＝La/V0 (13)

Tc_b＝Lb/V0 (14)

Information on the type of recording medium (paper type) designated by the user via the operation unit 152 is input to the CPU151 a. Based on the acquired information about the paper type and the relationship between the grammage and the time Tc stored in the ROM151b, the CPU151a determines the time Tc. For example, if information indicating that thin paper is to be conveyed is input by the user via the operation unit 152, the CPU151a sets a time Tc _ a corresponding to the thin paper as the time Tc. If information indicating that thick paper is to be conveyed is input by the user via the operation unit 152, the CPU151a sets a time Tc _ b corresponding to thick paper to the time Tc.

Using the set time Tc, the CPU151a sets the conveying speed V based on the following formula (15). Specifically, the CPU151a sets the conveying speed V in a section from the conveying roller 307 to the detection position (i.e., the peripheral speed of the conveying roller in a section from the conveying roller 307 to the detection position). The conveying speed V in the section from the pickup roller 305 to the conveying roller 307 after the conveying speed V in the section from the conveying roller 307 to the detection position is adjusted may be set to V0, or may be set to the adjusted conveying speed V.

V＝X2/(T0-(Ta+Tc)) (15)

That is, based on the time Ta and the time Tc, the CPU151a calculates the time from when the pickup roller 305 starts to be driven to when the leading end of the recording medium reaches the nip position n of the conveying roller 307. Then, the CPU151a sets the conveying speed V by dividing the distance X2 by a value obtained by subtracting the calculated time from the time T0. That is, the CPU151a sets the conveying speed V based on the timing at which the leading end of the recording medium actually reaches the nip position of the conveying roller.

As described above, in the present exemplary embodiment, the time from when the pickup roller 305 starts to be driven to when the leading end of the recording medium reaches the nip position n of the conveying roller 307 is calculated based on the time Ta and the time Tc. The conveying speed V is set by dividing the distance X2 by a value obtained by subtracting the calculated time from the time T0. That is, in the present exemplary embodiment, the conveying speed V is set based on the timing at which the leading end of the recording medium reaches the nip position of the conveying roller. Therefore, the recording medium can be prevented from reaching the transfer position after the timing of starting the transfer of the image onto the recording medium. Therefore, it is possible to prevent a situation where an image is formed at an inappropriate position on the recording medium.

In addition, in the present exemplary embodiment, the conveying speed V is set based on the time Tc corresponding to the paper type. Therefore, it is possible to prevent the recording medium from reaching the transfer position after the timing to start transferring the image onto the recording medium due to the fact that the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" differs depending on the paper type. That is, it is possible to prevent a situation where an image is formed at an inappropriate position on the recording medium.

The third exemplary embodiment is described below. The components of the image forming apparatus 100 similar to those according to the first exemplary embodiment are not described here.

Fig. 11A and 11B are diagrams illustrating the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" according to the present exemplary embodiment. Fig. 11A is a diagram illustrating a position of the leading end of thin paper at a timing at which the sheet detector 700 outputs the signal "1" in a case where thin paper is conveyed. Fig. 11B is a diagram illustrating a position of the leading end of thick paper at a timing at which the sheet detector 700 outputs the signal "1" in a case where thick paper is conveyed.

In the present exemplary embodiment, the conveying path from the feed roller 332 to the conveying roller 307 is curved. Therefore, the leading end of the recording medium conveyed downstream by the feed roller 332 collides with the conveying roller 307, and is then guided to the nip position n of the conveying roller 307. Then, the leading end of the recording medium is nipped by the conveying roller 307.

In the case of conveying thin paper having a small rigidity (or thickness) as a recording medium, the amount of increase in the load torque applied to the rotor 402 of the motor 509, which occurs when the leading end of the thin paper collides with the conveying roller 307, is relatively small. On the other hand, the amount of increase in the load torque applied to the rotor 402 of the motor 509, which occurs due to the fact that the leading end of the thin paper is nipped by the conveying roller 307, is larger than the amount of increase in the load torque that occurs when the leading end of the thin paper collides with the conveying roller 307.

The amount of increase in the load torque occurring when the leading end of the thick paper having a rigidity and thickness larger than those of the thin paper collides with the conveying roller 307 is larger than the amount of increase in the load torque occurring when the leading end of the thin paper collides with the conveying roller 307.

Fig. 12 is a diagram illustrating a state of the deviation Δ θ according to the present exemplary embodiment. As indicated by the dotted line in fig. 12, at the timing (time ta) at which the leading end of the thin paper collides with the conveying roller 307, the absolute value of the deviation Δ θ increases. As indicated by the solid line in fig. 12, the absolute value of the deviation Δ θ increases at the timing (time tc) at which the leading end of the thick paper collides with the conveying roller 307 and the timing (time tb) at which the leading end of the thick paper is nipped by the conveying roller 307.

As shown in fig. 12, in the case of conveying thick paper, at a timing (time tc) before the timing (time tb) at which thick paper is nipped by the conveying rollers 307, the deviation Δ θ increases due to the fact that thick paper collides with the conveying rollers 307. That is, the value of the distance Lb' is larger than that in the first exemplary embodiment.

The distance Y from the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" to the detection position is different from the distance X2. Specifically, the distance Y is longer than the distance X2. If the conveying speed V is set based on the formula (11), the position of the leading end of the recording medium at the timing at which 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 X2. In other words, the recording medium may reach the detection position after the timing at which the recording medium is to reach the detection position. Therefore, the recording medium may reach the transfer position after the timing of starting the transfer of the image onto the recording medium, and the image may not be formed at an appropriate position on the recording medium.

In response, in the present exemplary embodiment, the following configuration is applied, thereby preventing a situation in which an image is formed at an inappropriate position on a recording medium.

Fig. 13 is a diagram illustrating a relationship between the grammage of the recording medium to be conveyed and the distance Lc' from the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" to the conveying roller 307. The 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 roller 307. The relationship between the grammage and the distance Lc' shown in fig. 13 is obtained through experiments, and is stored in advance in, for example, the ROM151 b.

The distance L1 is a value corresponding to La shown in fig. 11A. The distance L2 is a value corresponding to Lb' shown in fig. 11B.

The CPU151a determines the distance Lc 'based on the acquired information about the paper type and the relationship between the grammage and the distance Lc' stored in the ROM151 b.

For example, 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 roller 307. At this time, regardless of the paper type, the timing at which the recording medium fed by the pickup roller 305 collides with the conveying roller 307 is substantially the same. Therefore, regardless of the paper type, the distance from the position of the leading end of the recording medium having a grammage greater than or equal to the grammage Mb 'at the timing at which the sheet detector 700 detects the recording medium to the nip position n is substantially the same (Lb'). Therefore, in the present exemplary embodiment, if the grammage input by the user via the operation unit 152 is greater than or equal to Mb ', the CPU151a sets L2 to the distance Lc'.

On the other hand, if the grammage input by the user via the operation unit 152 is less than or equal to Mb ', the CPU151a sets the distance Lc' according to the information on the input grammage.

Using the set distance Lc', the CPU151a sets the conveying speed V based on the formula (12).

That is, the CPU151a calculates the distance from the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" to the registration roller 308. Then, the CPU151a sets the conveying speed V by dividing the calculated distance by a value obtained by subtracting the time Ta from the time T0. That is, the CPU151a sets the conveying speed V based on the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1".

As described above, in the present exemplary embodiment, the distance from the position of the leading end of the recording medium at the timing to the detection position is calculated based on the distance Lc' and the distance X2 at the timing at which the recording medium is detected by the sheet detector 700 due to the fact that the recording medium collides with the conveying roller 307. The conveying speed V is set by dividing the calculated distance by a value obtained by subtracting the time Ta from the time T0. That is, in the present exemplary embodiment, the conveying speed V is set based on the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1". Therefore, the recording medium can be prevented from reaching the transfer position after the timing of starting the transfer of the image onto the recording medium. Therefore, it is possible to prevent a situation where an image is formed at an inappropriate position on the recording medium.

In addition, in the present exemplary embodiment, the conveying speed V is set based on the distance Lc' corresponding to the paper type. Therefore, it is possible to prevent the recording medium from reaching the transfer position after the timing to start transferring the image onto the recording medium due to the fact that the position of the leading end of the recording medium at the timing at which the sheet detector 700 outputs the signal "1" differs depending on the paper type. That is, it is possible to prevent a situation where an image is formed at an inappropriate position on the recording medium.

Alternatively, the conveying speed V may be adjusted by the method according to the second exemplary embodiment based on the position of the leading end of the recording medium at the timing at which the recording medium is detected due to the fact that the recording medium collides with the conveying roller 307. That is, the following configuration may be used: the timing at which the leading end of the recording medium reaches the nip position n is calculated based on the position of the leading end of the recording medium at the timing at which the recording medium is detected due to the fact that the recording medium collides with the conveying roller 307.

In the first, second, and third exemplary embodiments, the conveying speed V is adjusted based on the distance X2 from the nip position n of the conveying roller 307 to the detection position. However, the configuration is not limited thereto. For example, the conveying speed V may be adjusted based on the distance from the nip position n of the conveying roller 307 to the nip position of the registration roller 308. That is, the conveying speed 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.

In the first, second, and third exemplary embodiments, the number of pairs of rollers from the conveying roller 307 to the detection position is two. However, the configuration is not limited thereto. For example, three or more pairs of conveying rollers may be provided between the conveying roller 307 and the detection position.

In the first, second, and third exemplary embodiments, the

pickup roller

303 or 305 is repeatedly rotated and stopped at predetermined time intervals. However, the configuration is not limited thereto. For example, a configuration may be adopted in which a swing arm as a swing member linking one of the feed rollers 332 with the pickup roller 305 is supported by a rotation shaft of the feed roller 332 so that the swing arm is pivotable about the rotation shaft of the feed roller 332. Then, in a state where the rotational driving of the pickup roller 305 is continued, the pickup roller 305 is moved up and down at predetermined time intervals using the swing arm, thereby feeding the recording medium at predetermined intervals. In this configuration, the CPU151a adjusts the conveying speed V based on the time Tb from when the CPU151a outputs an instruction to move the pickup roller 305 downward to when the sheet detector 700 outputs a signal "1".

In the first exemplary embodiment, the second exemplary embodiment, and the third exemplary embodiment, the description has been given of the method for adjusting the conveying speed V of the recording medium fed by the pickup roller 305. The conveying speed V of the recording medium fed by the

pickup roller

303 or 328 is also adjusted by a similar method.

In the first exemplary embodiment, the second exemplary embodiment, and the third exemplary embodiment, the conveying speed V is adjusted based on whether the leading end of the recording medium reaches the nip position n of the conveying roller 307. However, the configuration is not limited thereto. The conveying speed V may be adjusted based on rollers other than the conveying roller 307. For example, the conveying speed V may be adjusted based on whether the leading end of the recording medium reaches the nip position of the conveying roller 322.

In the first exemplary embodiment, the second exemplary embodiment, and the third exemplary embodiment, the time Tc or the distance Lc or Lc' is set in accordance with the grammage of the recording medium. However, the configuration is not limited thereto. For example, a configuration may be adopted in which the time Tc or the distance Lc is set in accordance with the rigidity or thickness of the recording medium.

In the first exemplary embodiment, the second exemplary embodiment, and the third exemplary embodiment, the time Tc and the distance Lc are set based on the information on the paper type input by the user. However, the configuration is not limited thereto. For example, a configuration may be adopted in which the time Tc and the distance Lc are set based on the detection result of a sensor (such as a thickness sensor) for detecting the type of recording medium.

In the first, second, and third exemplary embodiments, the threshold value of the deviation Δ θ is a predetermined value regardless of the paper type. Alternatively, the threshold value may be set with respect to each paper type.

In the first, second, and third exemplary embodiments, if the absolute value of the deviation Δ θ is greater than the threshold value, the sheet detector 700 outputs a signal "1". If the absolute value of the deviation Δ θ is smaller than the threshold value, the sheet detector 700 outputs a signal "0". However, the configuration is not limited thereto. For example, a configuration may be adopted in which if the absolute value of the deviation Δ θ changes from a value smaller than a threshold value to a value greater than or equal to the threshold value, the sheet detector 700 outputs a signal "1" to the CPU151 a.

A configuration may be adopted in which the CPU151a has the functions of the sheet detector 700 according to the first exemplary embodiment, the second exemplary embodiment, and the third exemplary embodiment.

In the first exemplary embodiment, the second exemplary embodiment, and the third exemplary embodiment, the recording medium is detected by comparing the absolute value of the deviation Δ θ with the threshold Δ θ th. However, the configuration is not limited thereto. For example, the recording medium may be detected by comparing the current value iq output from the coordinate converter 511 with a threshold value iqth. An increase in the current value iq means an increase in the load torque applied to the rotor 402 of the motor 509. The reduction in the current value iq means that the load torque applied to the rotor 402 of the motor 509 is reduced.

Alternatively, the recording medium may be detected by comparing a q-axis current reference value (target value) iq _ ref determined based on a deviation Δ θ between the reference phase θ _ ref and the rotation phase θ determined by the phase determiner 513 with a threshold iq _ refth. An increase in the q-axis current command value iq _ ref means that the torque required to rotate the rotor 402 of the motor 509 increases due to an increase in the load torque applied to the rotor 402. The decrease in the q-axis current command value iq _ ref means that the torque required to rotate the rotor 402 of the motor 509 decreases due to the decrease in the load torque applied to the rotor 402.

Alternatively, a configuration may be adopted in which the recording medium is detected by comparing the amplitude (magnitude) of the current value i α or i β in the stationary coordinate system with a threshold value. An increase in the amplitude (magnitude) of the current value i α or i β in the stationary coordinate system means an increase in the load torque applied to the rotor 402 of the motor 509. The reduction in amplitude means that the load torque applied to the rotor 402 of the motor 509 is reduced.

The first, second, and third exemplary embodiments are not only applied to motor control by vector control. For example, the first exemplary embodiment and the second exemplary embodiment may be applied to any motor control apparatus having a configuration for feeding back a rotational phase or a rotational speed.

In the first, second, and third exemplary embodiments, the stepping motor is used as a motor for driving a load. Alternatively, another motor such as a Direct Current (DC) motor or a brushless DC motor may be used. The motor is not limited to the two-phase motor, and another motor such as a three-phase motor may be used.

In the vector control according to the first, second, and third exemplary embodiments, the motor 509 is controlled by performing the phase feedback control. However, the configuration is not limited thereto. For example, a configuration may be adopted in which the motor 509 is controlled by feeding back the rotational speed ω of the rotor 402. Specifically, as shown in fig. 14, a speed determiner 514 is provided in the motor control apparatus 157, and the speed determiner 514 determines the rotation speed ω based on a change over time of the rotation phase θ output from the phase determiner 513. The rotational speed ω is determined using the following equation (16).

ω＝dθ/dt (16)

Then, the CPU151a outputs a command speed ω _ ref indicating a target speed of the rotor 402. In addition, a configuration is adopted in which the speed controller 600 is provided in the motor control apparatus 157. The speed controller 600 generates a q-axis current reference value iq _ ref and a d-axis current reference value id _ ref so that the deviation between the rotational speed ω and the reference speed ω _ ref becomes small. Then, the speed controller 600 outputs a q-axis current reference value iq _ ref and a d-axis current reference value id _ ref. A configuration may be adopted in which the motor 509 is controlled by performing such speed feedback control. In this configuration, for example, the sheet is detected by the methods described in the first to third exemplary embodiments based on the deviation Δ ω between the rotation speed ω and the command speed ω _ ref. The command speed ω _ ref is a target speed of the rotor 402 of the motor 509 corresponding to a target speed of the peripheral speed of the conveying roller 307.

The deviations Δ θ and Δ ω, the current value iq _ ref, and the amplitude of the current value i α or i β in the stationary coordinate system correspond to the values of the parameters corresponding to the load torque applied to the rotor 402 of the motor 509.

In the first and second exemplary embodiments, permanent magnets are used as the rotor. However, the configuration is not limited thereto.

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.

A photosensitive drum 309, a charging device 310, a developing device 314, and a transfer charging device 315 are included in the image forming unit.

In the first, second, and third exemplary embodiments, the registration rollers 308 function as abutment members against which the leading end of the recording medium abuts, thereby correcting skew (skew) of the recording medium. However, the configuration is not limited thereto. For example, a configuration may be adopted in which a flapper (shutter) is provided as an abutment member upstream of the registration roller 308 and downstream of the pre-registration roller 333 or upstream of the transfer position and downstream of the registration roller 308 in the conveying direction of the recording medium. The leading end of the recording medium is brought into abutment against the shutter, whereby skew of the recording medium is corrected by the above-described method. Then, when the registration roller 308 conveys the recording medium to the transfer position in synchronization with the toner image, the flapper is retracted.

According to the exemplary embodiments of the present invention, it is possible to prevent a situation in which an image is formed at an inappropriate position on a sheet.

The embodiments(s) disclosed herein may also be implemented by a computer of a system or apparatus that reads 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 embodiments and/or includes one or more circuits (e.g., an application-specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiments, and by a computer of a system or apparatus that executes the functions of one or more of the above-described embodiments by, for example, reading and executing the computer-executable instructions from the storage medium to perform the functions of one or more of the above-described embodiments and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiments The method of the row. The computer may include one or more processors (e.g., Central Processing Unit (CPU), Micro Processing Unit (MPU)) and may include a separate computer or network of separate processors to read out and execute computer-executable instructions. The computer-executable instructions may be provided to the computer, for example, from a network or from a storage medium. The storage medium may include, for example, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), a storage device for a distributed computing system, an optical disk such as a Compact Disk (CD), a Digital Versatile Disk (DVD), or a Blu-ray disk (BD)^TM) Flash memory devices, memory cards, etc.

OTHER EMBODIMENTS

The embodiments of the present invention can also be realized by a method in which software (programs) that perform the functions of the above-described embodiments are supplied to a system or an apparatus through a network or various storage media, and a computer or a Central Processing Unit (CPU), a Micro Processing Unit (MPU) of the system or the apparatus reads out and executes the methods of the programs.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An image forming apparatus includes:

a stacking unit on which sheets are to be stacked;

a pickup roller configured to feed sheets stacked on the stacking unit;

a first conveying roller configured to convey a sheet fed by the pickup roller;

a transfer unit configured to transfer an image onto a 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 speed adjuster configured to: the conveying speed at which the sheet being conveyed by the first conveying roller at the predetermined speed is conveyed to the predetermined position is adjusted based on a length between a position of a leading end of the sheet and a nip position of the first conveying roller at a first timing at which a value of the parameter determined by the determiner changes from a value smaller than the predetermined value to a value larger than the predetermined value, and a length between the nip position of the first conveying roller and the predetermined position downstream of the first conveying roller and upstream of the image forming position in the conveying direction.

2. The image forming apparatus according to claim 1, further comprising an acquisition unit configured to acquire information relating to a type of a sheet to be conveyed,

wherein the speed adjuster adjusts the conveying speed based on the information acquired by the acquisition unit.

3. The image forming apparatus according to claim 1,

wherein the speed adjuster adjusts the conveying speed using a first length that is a length between a position of a leading end of the sheet at the first timing and the nip position in a case where a grammage of the sheet to be conveyed is a first grammage, and

wherein the speed adjuster adjusts the conveying speed using a second length that is longer than the first length in a case where a grammage of the sheet to be conveyed is a second grammage that is longer than the first grammage.

4. The image forming apparatus according to claim 1, further comprising:

a second conveying roller disposed upstream of the image forming position and downstream of the first conveying roller in the conveying direction; and

an abutment member that is provided upstream of the image forming position and downstream of the second conveying roller in the conveying direction and against which a leading end of the sheet conveyed by the second conveying roller abuts,

wherein skew of the sheet is corrected by abutment of a leading end of the sheet with the abutment member, an

Wherein the predetermined position is a position between the first conveying roller and the second conveying roller.

5. The image forming apparatus according to claim 1, further comprising a controller configured to start and stop rotational driving of the pickup roller at predetermined time intervals,

wherein the speed adjuster adjusts the conveying speed based on (i) a time from a second timing at which the rotational driving of the pickup roller is started to a third timing at which the sheet is to reach the predetermined position, (ii) a time from the second timing to the first timing, and (iii) a length between a position of a leading end of the sheet and the nip position and a length between the nip position and the predetermined position at the first timing.

6. The image forming apparatus according to claim 1, further comprising:

a swing member configured to move the pickup roller, which is rotationally driven, up and down; and

a controller configured to control up and down movement of the swing member,

7. The image forming apparatus according to claim 1, further comprising a feed roller provided upstream of the first conveying roller in the conveying direction and configured to convey the sheet fed by the pickup roller downstream,

a conveying path, which is provided between the feed roller and the first conveying roller and in which the sheet is guided, is curved.

8. The image forming apparatus according to claim 7,

wherein the feed roller is adjacent to the first transport roller, an

Wherein the peripheral speed of the first conveying roller is faster than the peripheral speed of the feeding roller.

9. The image forming apparatus according to claim 1, wherein in a case where a state in which the value of the parameter determined by the determiner is smaller than a predetermined value continues for a predetermined time, the conveyance of the sheet is stopped.

10. The image forming apparatus according to claim 1, wherein the determiner is a first determiner, the image forming apparatus further comprising:

a second determiner configured to determine a rotational phase of a rotor of the motor; and

a controller configured to control the drive current flowing through the winding of the motor such that a deviation between the rotation phase determined by the second determiner and a command phase indicating a target phase of the rotor becomes small.

11. The image forming apparatus according to claim 10, wherein the controller controls the drive current based on a torque current component that is a current component expressed in the rotational coordinate system based on the rotational phase of the rotor determined by the second determiner and that is also a current component causing the rotor to generate the torque.

12. The image forming apparatus according to claim 1, wherein the determiner is a first determiner, the image forming apparatus further comprising:

a second determiner configured to determine a rotational speed of a rotor of the motor; and

a controller configured to control a drive current flowing through a winding of the motor such that a deviation between the rotation speed determined by the second determiner and a command speed indicating a target speed of the rotor becomes small.

13. The image forming apparatus according to claim 12, further comprising a third determiner configured to determine a rotational phase of a rotor of the motor,

wherein the controller controls the drive current based on a torque current component that is a current component expressed in the rotating coordinate system based on the rotation phase of the rotor determined by the third determiner and that is also a current component causing the rotor to generate the torque.

14. The image forming apparatus according to claim 1, further comprising a detector configured to detect a drive current flowing through a winding of the motor,

wherein the determiner determines the value of the parameter based on the drive current detected by the detector.

15. An image forming apparatus includes:

a stacking unit on which sheets are to be stacked;

a pickup roller configured to feed sheets stacked on the stacking unit;

a first conveying roller configured to convey a sheet fed by the pickup roller;

a motor configured to rotationally drive the first conveying roller;

a determination unit configured to determine a value of a parameter corresponding to a load torque applied to a rotor of the motor;

an acquisition unit configured to acquire information on a grammage of a sheet to be conveyed; and

a speed adjusting unit configured to adjust a conveying speed at which the sheet conveyed by the first conveying roller at the predetermined speed is conveyed to a predetermined position downstream of the first conveying roller in the conveying direction and upstream of the image forming position, according to a change in the value of the parameter determined by the determining unit from a value smaller than a predetermined value to a value larger than the predetermined value,

wherein, in a case where the acquisition unit acquires information indicating that the grammage of the sheet to be conveyed is a first grammage, the speed adjustment unit adjusts the conveying speed to a first speed, and

wherein the speed adjusting unit adjusts the conveying speed to a second speed that is faster than the first speed in a case where the acquiring unit acquires information indicating that the grammage of the sheet to be conveyed is a second grammage that is larger than the first grammage.

16. The image forming apparatus according to claim 15, further comprising:

17. The image forming apparatus according to claim 15, further comprising a control unit configured to start and stop rotational driving of the pickup roller at predetermined time intervals,

wherein the speed adjusting unit adjusts the conveying speed based on (i) a time from a third timing at which the rotational driving of the pickup roller is started to a second timing at which the sheet is to reach the predetermined position, (ii) a time from the third timing to the first timing, and (iii) a length between a position of a leading end of the sheet and the nip position and a length between the nip position and the predetermined position at the first timing.

18. The image forming apparatus according to claim 15, further comprising:

a control unit configured to control up and down movement of the swing member,

wherein the speed adjusting unit adjusts the conveying speed based on (i) a time from a third timing at which the rotational driving of the pickup roller is started to a second timing at which the sheet is to reach the predetermined position, (ii) a time from the third timing to the first timing, and (ii) a length between a position of a leading end of the sheet and the nip position and a length between the nip position and the predetermined position at the first timing.

19. The image forming apparatus according to claim 15, further comprising a feed roller provided upstream of the first conveying roller in the conveying direction and configured to convey the sheet fed by the pickup roller downstream,

20. The image forming apparatus as claimed in claim 19,

wherein the feed roller is adjacent to the first transport roller, an

21. An image forming apparatus according to claim 15, wherein in a case where a state in which the value of the parameter determined by the determining unit is smaller than a predetermined value continues for a predetermined time, the conveyance of the sheet is stopped.

22. The image forming apparatus according to claim 15, wherein the determination unit is a first determination unit, the image forming apparatus further comprising:

a second determination unit configured to determine a rotational phase of a rotor of the motor; and

a control unit configured to control the drive current flowing through the winding of the motor such that a deviation between the rotation phase determined by the second determination unit and a command phase indicating a target phase of the rotor becomes small.

23. The image forming apparatus according to claim 22, wherein the control unit controls the drive current based on a torque current component that is a current component expressed in the rotational coordinate system based on the rotational phase of the rotor determined by the second determining unit and that is also a current component causing the rotor to generate the torque.

24. The image forming apparatus according to claim 15, wherein the determination unit is a first determination unit, the image forming apparatus further comprising:

a second determination unit configured to determine a rotation speed of a rotor of the motor; and

a control unit configured to control the drive current flowing through the winding of the motor such that a deviation between the rotation speed determined by the second determination unit and a command speed indicating a target speed of the rotor becomes small.

25. The image forming apparatus according to claim 24, further comprising a third determining unit configured to determine a rotational phase of a rotor of the motor,

wherein the control unit controls the drive current based on a torque current component that is a current component expressed in the rotating coordinate system based on the rotation phase of the rotor determined by the third determination unit and that is also a current component causing the rotor to generate the torque.

26. The image forming apparatus according to claim 15, further comprising a detector configured to detect a drive current flowing through a winding of the motor,

wherein the determination unit determines the value of the parameter based on the drive current detected by the detector.