JP6776418B2 - Sheet transfer device and image forming device - Google Patents

Description

The present invention relates to a sheet transfer device and an image forming device for transporting sheets.

Conventionally, in an image forming apparatus for forming an image on a recording medium, when a toner image formed on the surface of a photosensitive drum is transferred to a predetermined position on the recording medium, the magnitude of the voltage supplied to the transfer charger is increased. A method of setting according to the type of recording medium is known. Further, there is known a method in which the temperature of the fixing heater of the fixing device is set according to the type of the recording medium when the toner transferred to a predetermined position on the recording medium is fixed on the recording medium.

In Patent Document 1, a sensor for discriminating the type (paper type) of the recording medium is provided in the transport path through which the recording medium is conveyed, and the magnitude of the voltage supplied to the transfer charger is based on the discrimination result of the sensor. A configuration in which the temperature of the fixing heater and the like are set is described.

Japanese Unexamined Patent Publication No. 2012-181223

However, in the method of discriminating the paper type in Patent Document 1, a space for providing a sensor is required, so that the image forming apparatus becomes large. In addition, the cost increases by providing the sensor.

In view of the above problems, an object of the present invention is to determine the type of sheet without using a dedicated sensor for determining the type of sheet.

In order to solve the above problems, the image forming apparatus according to the present invention is
An image forming unit that forms an image on a sheet,
The first roller that conveys the sheet and
A second roller adjacent to the first roller and provided on the downstream side of the first roller in the transport direction in which the sheet is transported,
The motor that drives the first roller and
A phase determining means for determining the rotational phase of the rotor of the motor,
A control means for controlling the drive current flowing in the winding of the motor so that the deviation between the command phase representing the target phase of the rotor and the rotation phase determined by the phase determining means becomes small.
A detection means for detecting the drive current flowing through the winding and
Conveyed by the first roller based on the value of the drive current detected by the detection means in a bent state of the sheet conveyed by the first roller and not conveyed by the second roller. A discriminating means for discriminating the type of the sheet to be formed, and
It is characterized by having.

According to the present invention, the type of sheet can be discriminated without using a dedicated sensor for discriminating the type of sheet.

It is sectional drawing explaining the image forming apparatus which concerns on 1st Embodiment. It is a block diagram which shows the control structure of the image forming apparatus. It is a figure which shows the relationship between the two-phase motor which consists of A phase and B phase, and d-axis and q-axis of a rotating coordinate system. It is a block diagram which shows the structure of the motor control device which concerns on 1st Embodiment. It is a figure explaining the structure which corrects the skew of the side on the tip side of a recording medium. It is a figure which shows the change of the current value iq in the process of performing the skew correction which concerns on 1st Embodiment. It is a block diagram which shows the structure of the paper type determinant 200 which concerns on 1st Embodiment. It is a table figure which shows the correspondence relationship between a paper type and a current value iq at time t2. It is a flowchart explaining the method of determining the paper type which concerns on 1st Embodiment. It is a flowchart explaining the method which the CPU which concerns on 1st Embodiment sets a set value based on the information of a paper type output from a paper type determinant. It is a figure which shows the change of the current value iq in the process of performing the skew correction which concerns on 2nd Embodiment. It is a block diagram which shows the example of the structure of the paper type determination device 200 which concerns on 2nd Embodiment. It is a table figure which shows the correspondence relationship between a paper type and a change amount Δiq. It is a flowchart explaining the method of determining the paper type which concerns on 2nd Embodiment. It is a figure which shows the transport path formed between the transport roller 330 and the transport roller 307. It is a figure which shows the change of the current value iq in the period when a recording medium is conveyed through a bent transport path. It is a block diagram which shows the example of the structure of the paper type determinant 200 which concerns on 3rd Embodiment. It is a table figure which shows the correspondence relationship between the paper type which concerns on 2nd Embodiment, and the sum total Σiq of a current value iq. It is a flowchart explaining the method of determining the paper type which concerns on 3rd Embodiment. It is a flowchart explaining the method of setting the set value by CPU 151a based on the information of the paper type output from the paper type determinant 200 which concerns on 3rd Embodiment. It is a block diagram of the motor control device which performs speed feedback control.

Preferred embodiments of the present invention will be described below with reference to the drawings. However, the shapes of the components and their relative arrangements described in this embodiment 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 defined. It is not intended to be limited to the following embodiments. It should be noted that the motor control device is not limited to the image forming device. In the following description, the case where the motor control device is provided in the image forming device will be described, but the case where the motor control device is provided is not limited to the image forming device. For example, it is also used in a sheet transfer device for transporting a sheet such as a recording medium or a document.

[First Embodiment]
[Image forming device]
FIG. 1 is a cross-sectional view showing the configuration of a monochrome electrophotographic copying machine (hereinafter, referred to as an image forming apparatus) 100 which is an image forming apparatus used in the present embodiment. The image forming apparatus is not limited to the copying machine, and may be, for example, a facsimile apparatus, a printing machine, a printer, or the like. Further, the recording method is not limited to the electrophotographic method, and may be, for example, an inkjet or the like. Further, the format of the image forming apparatus may be either monochrome or color.

The configuration and function of the image forming apparatus 100 will be described below with reference to FIG. As shown in FIG. 1, the image forming apparatus 100 includes a document feeding apparatus 201, a reading apparatus 202, and an image printing apparatus 301.

The documents loaded on the document loading section 203 of the document feeding device 201 are fed one by one by the paper feed roller 204, and are conveyed on the document glass base 214 of the reading device 202 along the transfer guide 206. Further, the original document is conveyed at a constant speed by the conveying belt 208, and is ejected by the paper ejection roller 205 to an output tray (not shown). The reflected light from the original image irradiated by the illumination 209 at the reading position of the reading device 202 is guided to the image reading unit 111 by the optical system including the reflecting mirrors 210, 211, and 212, and converted into an image signal by the image reading unit 111. Will be done. The image reading unit 111 includes a lens, a CCD which is a photoelectric conversion element, a driving circuit of the CCD, and the like. The image signal output from the image reading unit 111 is output to the image printing device 301 after various correction processes are performed by the image processing unit 112 configured by a hardware device such as an ASIC. As described above, the original is read. That is, the document feeding device 201 and the reading device 202 function as the document reading device.

Further, as the document scanning mode, there are a first scanning mode and a second scanning mode. The first scanning mode is a mode in which an image of a document conveyed at a constant speed is scanned by an illumination system 209 and an optical system fixed at a predetermined position. The second scanning mode is a mode in which the image of the document placed on the document glass 214 of the scanning device 202 is scanned by the illumination system 209 and the optical system moving at a constant speed. Normally, a sheet-shaped document is read in the first reading mode, and a bound document such as a book or booklet is read in the second reading mode.

Sheet storage trays 302 and 304 are provided inside the image printing device 301. Different types of recording media can be stored in the sheet storage trays 302 and 304. For example, the sheet storage tray 302 stores A4 size plain paper, and the sheet storage tray 304 stores A4 size thick paper. The recording medium is one in which an image is formed by an image forming apparatus, and for example, paper, a resin sheet, a cloth, an OHP sheet, a label, and the like are included in the recording medium.

The recording medium stored in the sheet storage tray 302 is fed by the paper feed roller 303, and is fed by the transfer rollers 329 and 306 and the pre-registration roller (hereinafter referred to as the pre-registration roller) 327 to the registration roller (hereinafter referred to as the registration roller). ) Sent to 308. Further, the recording medium stored in the sheet storage tray 304 is fed by the paper feed roller 305 and sent out to the register roller 308 by the transfer rollers 330, 307, 306 and the pre-registration roller 327. The pre-registration roller 327 in the present embodiment corresponds to the first roller in the present invention. Further, the registration roller 308 in the present embodiment corresponds to the contact member and the second roller in the present invention.

The image signal output from the reading device 202 is input to the optical scanning device 311 including the semiconductor laser and the polygon mirror. Further, the outer peripheral surface of the photosensitive drum 309 is charged by the charger 310. After the outer peripheral surface of the photosensitive drum 309 is charged, the laser beam corresponding to the image signal input from the reading device 202 to the optical scanning device 311 is photosensitiveed from the optical scanning device 311 via the polygon mirror and the mirrors 312 and 313. The outer peripheral surface of the drum 309 is irradiated. As a result, an electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 309.

Subsequently, the electrostatic latent image is developed by the toner in the developer 314, and the toner image is formed on the outer peripheral surface of the photosensitive drum 309.

A transfer charger 315 used for transferring the toner image to a recording medium is provided at a position (transfer position) facing the photosensitive drum 309. A voltage suitable for the paper type set by the user is applied to the transfer charger 315.

A sheet sensor 328 that detects the tip of the recording medium is provided between the register roller 308 and the pre-registration roller 327. The register roller 308 and the pre-registration roller 327 correct the skew of the side on the tip side of the recording medium based on the detection result of the seat sensor 328. The specific method of skew correction will be described later. After that, the registration roller 308 and the pre-registration roller 327 feed the recording medium to the transfer position at the transfer timing at which the image is transferred to the recording medium by the transfer charger 315. The seat sensor 328 in the present embodiment is, for example, an optical sensor, but is not limited thereto.

As described above, the recording medium on which the toner image is transferred is sent to the fixing device 318 by the transport belt 317, heated and pressurized by the fixing device 318, and the toner image is fixed on the recording medium. In this way, the image forming apparatus 100 forms an image on the recording medium. The temperature of the fixing device 318 is controlled so as to be a temperature suitable for the paper type.

When image formation is performed in the single-sided printing mode, the recording medium that has passed through the fixing device 318 is ejected to an output tray (not shown) by the output rollers 319 and 324. When image formation is performed in the double-sided printing mode, the recording medium is a paper ejection roller 319, a transport roller 320, and an inversion roller 321 after the fixing process is performed on the first surface of the recording medium by the fixing device 318. Is transported to the reverse path 325. After that, the recording medium is conveyed to the registration roller 308 again by the conveying rollers 322 and 323, and an image is formed on the second surface of the recording medium by the method described above. After that, the recording medium is ejected to an output tray (not shown) by the output rollers 319 and 324.

Further, when the recording medium on which the image is formed on the first surface is discharged face-down to the outside of the image forming apparatus 100, the recording medium that has passed through the fixing device 318 passes through the paper ejection roller 319 and is conveyed to the roller 320. It is transported in the direction toward. After that, just before the rear end of the recording medium passes through the nip portion of the transfer roller 320, the rotation of the transfer roller 320 is reversed, so that the recording medium is a paper ejection roller with the first surface of the recording medium facing downward. It is discharged to the outside of the image forming apparatus 100 via 324.

The above is a description of the configuration and function of the image forming apparatus 100. The motor control device of the present embodiment can be applied to a motor that drives a load. The load corresponds to, for example, various rollers such as a paper feed roller 204, 303, 305, a pre-registration roller 327, a registration roller 308, and a paper discharge roller 319, a photosensitive drum 309, a transport belt 208, 317, a lighting system 209, an optical system, and the like. ..

FIG. 2 is a block diagram showing an example of a control configuration of the image forming apparatus 100. As shown in FIG. 2, the system controller 151 includes a CPU 151a, a ROM 151b, and a RAM 151c. Further, the system controller 151 is connected to an image processing unit 112, an operation unit 152, an analog / digital (A / D) converter 153, a high pressure control unit 155, a motor control device 157, a paper type determining device 200, sensors 159, and the like. Has been done. The system controller 151 can send and receive data and commands to and from each connected unit.

The CPU 151a executes various sequences related to a predetermined image formation sequence by reading and executing various programs stored in the ROM 151b.

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

The system controller 151 receives signals from the operation unit 152, sensors 159, paper type determining device 200, etc., and based on the received signals, sets values of the high voltage control unit 155, command values for the motor control device 157, and the like. Set and store in RAM 151c. Further, the system controller 151 transmits the set value data of various devices provided inside the image forming apparatus 100, which is necessary for the image processing in the image processing unit 112, to the image processing unit 112. The method of determining the paper type by the paper type determining device 200 will be described later.

The high-voltage control unit 155 reads the set value set by the system controller 151 from the RAM 151c and supplies the necessary voltage to the high-voltage unit 156 (charger 310, developer 314, transfer charger 315, etc.).

The system controller 151 (CPU 151a) outputs a command to the motor control device 157 based on the detection result of the seat sensor 328. The motor control device 157 controls the motor 509 that drives the pre-registration roller 327 in response to a command received from the CPU 151a. Although only the motor 509 is described as the motor of the image forming apparatus in FIG. 2, in reality, the image forming apparatus is provided with a plurality of motors. Further, one motor control device may be configured to control a plurality of motors. Further, in FIG. 2, although only one motor control device is provided, two or more motor control devices may be provided in the image forming device.

The A / D converter 153 receives the detection signal detected by the thermistor 154 for detecting the temperature of the fixing heater 161, converts the detection signal from an analog signal to a digital signal, and transmits the detection signal to the system controller 151. The system controller 151 controls the AC driver 160 based on the digital signal received from the A / D converter 153. The AC driver 160 controls the fixing heater 161 so that the temperature of the fixing heater 161 becomes a temperature required for performing the fixing process on the sheet used. The fixing heater 161 is a heater used for the fixing process, and is included in the fixing device 318.

The system controller 151 controls the operation unit 152 so that the operation screen for the user to set the type of sheet to be used and the like is displayed on the display unit provided in the operation unit 152. The system controller 151 receives the 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. Further, the system controller 151 transmits information indicating the state of the image forming apparatus to the operation unit 152. The information indicating the state of the image forming apparatus is, for example, information regarding the number of images formed, the progress of the image forming operation, jams and double feeds of sheet materials in the document reading apparatus 201 and the image printing apparatus 301. The operation unit 152 displays the 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.

[Motor control device]
Next, the motor control device in this embodiment will be described. The motor control device in the present embodiment controls the motor by using vector control.

<Vector control>
First, a method in which the motor control device 157 in this embodiment performs vector control will be described with reference to FIGS. 3 and 4. Although the motor in the following description is not provided with a sensor such as a rotary encoder for detecting the rotation phase of the rotor of the motor, a sensor such as a rotary encoder may be provided.

FIG. 3 shows a stepping motor (hereinafter referred to as a motor) 509 composed of two phases, A phase (first phase) and B phase (second phase), and a rotating coordinate system represented by the d-axis and the q-axis. It is a figure which shows the relationship of. In FIG. 3, in the rest coordinate system, the α-axis, which is the axis corresponding to the A-phase winding, and the β-axis, which is the axis corresponding to the B-phase winding, are defined. Further, in FIG. 3, the d-axis is defined along the direction of the magnetic flux generated by the magnetic poles of the permanent magnet used in the rotor 402, and the direction is 90 degrees counterclockwise from the d-axis (perpendicular to the d-axis). The q-axis is defined along the direction of the magnet. The angle formed by the α-axis and the d-axis is defined as θ, and the rotation phase of the rotor 402 is represented by the angle θ. In vector control, a rotating coordinate system based on the rotation phase θ of the rotor 402 is used. Specifically, in vector control, the q-axis component (torque current component) and the winding, which are the current components in the rotation coordinate system of the current vector corresponding to the drive current flowing in the winding, and generate torque in the rotor. A d-axis component (exciting current component) that affects the strength of the magnetic flux penetrating the is used.

Vector control is a motor by performing phase feedback control that controls the value of the torque current component and the value of the exciting current component so that the deviation between the command phase representing the target phase of the rotor and the actual rotation phase becomes small. It is a control method to control. In addition, the motor is controlled by performing speed feedback control that controls the value of the torque current component and the value of the exciting current component so that the deviation between the command speed representing the target speed of the rotor and the actual rotation speed becomes small. There is also a method.

FIG. 4 is a block diagram showing an example of the configuration of the motor control device 157 that controls the motor 509. The motor control device 157 is composed of at least one ASIC, and executes each function described below.

As shown in FIG. 4, the motor control device 157 supplies a drive current to the phase controller 502, the current controller 503, the coordinate inverse converter 505, the coordinate converter 511, and the winding of the motor as a circuit for performing vector control. It has a PWM inverter 506 and the like. The coordinate converter 511 represents the current vector corresponding to the drive current flowing through the windings of the A phase and the B phase of the motor 509 from the stationary coordinate system represented by the α axis and the β axis by the q axis and the d axis. Convert coordinates to a rotating coordinate system. As a result, the drive current flowing through the winding is represented by the current value of the q-axis component (q-axis current) and the current value of the d-axis component (d-axis current), which are the current values in the rotating coordinate system. The q-axis current corresponds to the torque current that generates torque in the rotor 402 of the motor 509. Further, the d-axis current corresponds to an exciting current that affects the strength of the magnetic flux penetrating the winding of the motor 509, and does not contribute to the generation of torque of the rotor 402. The motor control device 157 can independently control the q-axis current and the d-axis current. As a result, the motor control device 157 can efficiently generate the torque required for the rotor 402 to rotate by controlling the q-axis current according to the load torque applied to the rotor 402. That is, in vector control, the magnitude of the current vector shown in FIG. 3 changes according to the load torque applied to the rotor 402.

The motor control device 157 determines the rotation phase θ of the rotor 402 of the motor 509 by a method described later, and performs vector control based on the determination result. The CPU 151a generates a command phase θ_ref representing the target phase of the rotor 402 of the motor 509, and outputs the command phase θ_ref to the motor control device 157.

The subtractor 101 calculates the deviation between the rotation phase θ of the rotor 402 of the motor 509 and the command phase θ_ref, and outputs the deviation to the phase controller 502 in a predetermined time period T (for example, 200 μs).

The phase controller 502 is based on the proportional control (P), the integral control (I), and the differential control (D) so that the deviation output from the subtractor 101 is reduced, so that the q-axis current command value iq_ref and the d-axis are reduced. Generates and outputs the current command value id_ref. Specifically, the phase controller 502 has a q-axis current command value iq_ref and a d-axis current command value id_ref so that the deviation output from the subtractor 101 based on P control, I control, and D control becomes zero. Is generated and output. The P control is a control method in which the value of the object to be controlled is controlled based on a value proportional to the deviation between the command value and the estimated value. Further, the I control is a control method in which the value of the object to be controlled is controlled based on a value proportional to the time integration of the deviation between the command value and the estimated value. Further, the D control is a control method in which the value of the object to be controlled is controlled based on a value proportional to the time change of the deviation between the command value and the estimated value. The phase controller 502 in the present embodiment generates the q-axis current command value iq_ref and the d-axis current command value id_ref based on the PID control, but is not limited thereto. For example, the phase controller 502 may generate the q-axis current command value iq_ref and the d-axis current command value id_ref based on PI control. When a permanent magnet is used for the rotor 402, the d-axis current command value id_ref, which normally affects the strength of the magnetic flux penetrating the winding, is set to 0, but the present invention is not limited to this.

The drive currents flowing through the A-phase and B-phase windings of the motor 509 are detected by the current detectors 507 and 508, and then converted from analog values to digital values by the A / D converter 510. The period in which the A / D converter 510 outputs the digital value is, for example, a period shorter than the period T in which the subtractor 101 outputs the deviation to the phase controller 502 (for example, 25 μs), but is limited to this. Do not mean.

The current value of the drive current converted from the analog value to the digital value by the A / D converter 510 is determined by the following equation using the phase θe of the current vector shown in FIG. 4 as the current values iα and iβ in the stationary coordinate system. expressed. The phase θe of the current vector is defined as the angle formed by the α axis and the current vector. Further, I indicates the magnitude of the current vector.
iα = I * cosθe (1)
iβ = I * sinθe (2)

These current values iα and iβ are input to the coordinate converter 511 and the induced voltage determinant 512.

The coordinate converter 511 converts the current values iα and iβ 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 equation.
id = cosθ * iα + sinθ * iβ (3)
iq = −sinθ * iα + cosθ * iβ (4)

The coordinate converter 511 outputs the converted current value iq to the subtractor 102. Further, the coordinate converter 511 outputs the converted current value id to the subtractor 103.

The subtractor 102 calculates the deviation between the q-axis current command value iq_ref and the current value iq, and outputs the deviation to the current controller 503.

Further, the subtractor 103 calculates the deviation between the d-axis current command value id_ref and the current value id, and outputs the deviation to the current controller 503.

Based on PID control, the current controller 503 generates drive voltages Vq and Vd so that the input deviations become smaller, respectively. Specifically, the current controller 503 generates drive voltages Vq and Vd so that the input deviations become 0, respectively, and outputs them to the coordinate inverse converter 505. That is, the current controller 503 functions as a generation means. The current controller 503 in the present embodiment generates drive voltages Vq and Vd based on PID control, but the present invention is not limited to this. For example, the current controller 503 may generate drive voltages Vq and Vd based on PI control.

The coordinate inverse converter 505 reversely converts the drive voltages Vq and Vd in the rotating coordinate system output from the current controller 503 into the drive voltages Vα and Vβ in the static coordinate system by the following equation.
Vα = cosθ * Vd-sinθ * Vq (5)
Vβ = sinθ * Vd + cosθ * Vq (6)

The coordinate inverse converter 505 outputs the inversely converted Vα and Vβ to the induced voltage determinant 512 and the PWM inverter 506.

The PWM inverter 506 has a full bridge circuit. The full bridge circuit is driven by a PWM signal based on the drive voltages Vα and Vβ input from the coordinate inverse converter 505. As a result, the PWM inverter 506 generates drive currents iα and iβ corresponding to the drive voltages Vα and Vβ, and supplies the drive currents iα and iβ to the windings of each phase of the motor 509 to drive the motor 509. .. That is, the PWM inverter 506 functions as a supply means for supplying a current to the windings of each phase of the motor 509. In the present embodiment, the PWM inverter has a full bridge circuit, but the PWM inverter may have a half bridge circuit or the like.

Next, a method of determining the rotation phase θ will be described. The values of the induced voltages Eα and Eβ induced in the A-phase and B-phase windings of the motor 509 by the rotation of the rotor 402 are used to determine the rotation phase θ of the rotor 402. The value of the induced voltage is determined (calculated) by the induced voltage determinant 512. Specifically, the induced voltages Eα and Eβ were input to the induced voltage determinant 512 from the coordinate inverse converter 505 and the current values iα and iβ input from the A / D converter 510 to the induced voltage determinant 512. It is determined by the following equation based on the drive voltages Vα and Vβ.
Eα = Vα-R * iα-L * diα / dt (7)
Eβ = Vβ-R * iβ-L * diβ / dt (8)

Here, R is the winding resistance and L is the winding inductance. The values of the winding resistance R and the winding inductance L are values specific to the motor 509 used, and are stored in advance in a memory (not shown) provided in the ROM 151b or the motor control device 157.

The induced voltages Eα and Eβ determined by the induced voltage determinant 512 are input to the phase determinant 513.

The phase determinant 513 determines the rotation phase θ of the rotor 402 of the motor 509 by the following equation based on the ratio of the induced voltage Eα and the induced voltage Eβ output from the induced voltage determinant 512.
θ = tan ^ -1 (-Eβ / Eα) (9)

In the present embodiment, the phase determinant 513 determines the rotation phase θ by performing an operation based on the equation (9), but this is not the case. For example, the phase determinant 513 rotates by referring to a table stored in ROM 151b or the like showing the relationship between the induced voltage Eα and the induced voltage Eβ and the rotation phase θ corresponding to the induced voltage Eα and the induced voltage Eβ. The phase θ may be determined.

The rotation phase θ of the rotor 402 obtained as described above is input to the subtractor 101, the coordinate inverse converter 505, and the coordinate converter 511.

The motor control device 157 repeats the above-mentioned control.

As described above, the motor control device 157 in the present embodiment performs vector control for controlling the current value in the rotating coordinate system so that the deviation between the command phase θ_ref and the rotation phase θ becomes small. By performing vector control, it is possible to suppress the motor from being out of step, the increase in motor noise due to excess torque, and the increase in power consumption.

[How to determine the paper type]
Next, a configuration in which the paper type is determined in the present embodiment will be described. In the present embodiment, by applying the following configuration to the image forming apparatus, the type of sheet is determined without using a sensor for determining the type of sheet.

FIG. 5 is a diagram illustrating a configuration for correcting the skew of the side on the tip end side of the recording medium.

The skew correction of the recording medium P is performed by the register roller 308 and the pre-registration roller 327. Specifically, the motor control device 157 controls the drive of the motor 509 to rotate the motor 509, and the rotation of the motor 509 causes the preregistration roller 327 to rotate. As the pre-registration roller 327 rotates, the recording medium P is conveyed in the conveying direction, and the tip of the recording medium P comes into contact with the nip portion of the register roller 308 in the stopped state. After that, the motor control device 157 further rotates the motor 509 to rotate the preregistration roller 327. As a result, the recording medium P is further conveyed in the conveying direction, and the recording medium P is bent.

In the above-mentioned process, the CPU 151a controls the motor control device 157 so as to rotate the T1 preregistration roller 327 for a predetermined time after the seat sensor 328 detects the tip of the recording medium P. That is, the CPU 151a controls the motor control device 157 so that the rotation of the preregistration roller 327 is stopped after a predetermined time T1 after the seat sensor 328 detects the tip of the recording medium P. The predetermined time T1 is necessary for the amount of deflection of the recording medium P after the predetermined time T1 after the sheet sensor 328 detects the tip of the recording medium so that the skew correction of the recording medium P is appropriately performed. The time is set so that the amount of deflection is reached.

The method of stopping the rotation of the pre-registration roller 327 is, for example, the following method. Specifically, the CPU 151a outputs the same command phase as the previously output command phase to the motor control device 157 as the command phase θ_ref. After that, the CPU 151a continues to output the same command phase to the motor control device 157. As a result, the motor control device 157 can fix the phase of the rotor 402. That is, the CPU 151a can stop the rotation of the pre-registration roller 327. Further, the CPU 151a may output an enable signal ‘L’ to the motor control device 157, and the motor control device 157 may stop the rotation of the pre-registration roller 327 by stopping the motor 509 that drives the pre-registration roller 327. The enable signal is a signal for permitting or prohibiting the operation of the motor control device 157. When the enable signal is'L (low level)', the CPU 151a prohibits the operation of the motor control device 157. That is, the control of the motor 509 by the motor control device 157 is terminated. When the enable signal is'H (high level)', the CPU 151a permits the operation of the motor control device 157, and the motor control device 157 controls the drive of the motor 509 based on the command output from the CPU 151a. Do.

As described above, the recording medium P is bent by the rotation of the T1 preregistration roller 327 for a predetermined time after the sheet sensor 328 detects the tip of the recording medium P. As a result, an elastic force acts on the recording medium P, and the tip of the recording medium P comes into contact with the nip portion of the registration roller. As a result, the skew of the recording medium P is corrected.

FIG. 6 is a diagram showing a change in the current value iq in the process of performing skew correction. In FIG. 6, as an example of the present embodiment, the current value iq when the skew correction of the thick paper is performed and the current value iq when the skew correction of the plain paper is performed are shown.

As shown in FIG. 6, when a predetermined time T1 elapses after the tip of the recording medium P is detected by the sheet sensor 328 at time t0, the motor control device 157 stops the rotation of the motor 509. The predetermined time T1 corresponds to the time from time t0 to time t3.

Elastic force acts on the recording medium during the period when the recording medium is bent. That is, not only a force in the transport direction but also a force in the direction opposite to the transport direction acts on the recording medium. As a result, a load torque due to a force in the direction opposite to the transport direction acts on the rotor 402 of the motor 509. The greater the amount of deflection of the recording medium, the greater the magnitude of the load torque. The following relationship holds between the load torque and the current value iq.
Tm = iq * kt (10)

Here, kt is a proportional coefficient indicating the relationship between the load torque value Tm and the current value iq, and is a value peculiar to the motor.

As shown in FIG. 6, the current value iq on the thick paper and the current value iq on the plain paper increase after the time t1. This indicates that the load torque applied to the rotor 402 is increasing. That is, at time t1, the side on the tip end side of the recording medium abuts on the nip portion of the register roller 308, indicating that the recording medium begins to bend.

Further, as shown in FIG. 6, the amount of increase in the current value iq per unit time on thick paper and the amount of increase in the current value iq per unit time on plain paper are different. Specifically, the amount of increase in the current value iq per unit time on thick paper is larger than the amount of increase in the current value iq per unit time on plain paper. This is because the elastic force generated in the thick paper when the thick paper is bent is larger than the elastic force generated in the plain paper when the plain paper is bent. As described above, the current value iq during the period in which the recording medium bends differs depending on the paper type. Therefore, the paper type can be determined by observing the current value iq during the period in which the recording medium bends.

As shown in FIGS. 4 and 5, in the present embodiment, the CPU 151a outputs an instruction (determination instruction signal) for determining the paper type to the paper type determining device 200. Specifically, the CPU 151a outputs a determination instruction signal to the paper type determining device 200 when the predetermined time T2 elapses from the time t0. The predetermined time T2 corresponds to the time from time t0 to time t2. Further, the time t2 is a predetermined time during the period from the time t1 to the time t3, and includes the time t3. That is, the predetermined time T2 is a time equal to or less than the predetermined time T1.

FIG. 7 is a block diagram showing an example of the configuration of the paper type determining device 200. Further, FIG. 8 is a table diagram showing the correspondence between the paper type and the current value iq at time t2 in the present embodiment. The current value iq shown in FIG. 8 is a value determined in advance by an experiment or the like. As shown in FIG. 7, the paper type determining device 200 is provided with a memory 200a for storing the current value iq output from the coordinate converter 511. Further, the paper type determining device 200 is provided with the table 200b shown in FIG. The memory 200a in the present embodiment updates the current value iq already stored in the memory 200a to the newly acquired current value iq.

When the determination instruction signal is input to the paper type determination device 200, the paper type determination device 200 acquires the current value iq first stored in the memory 200a from the memory 200a after the determination instruction signal is input, and obtains the current value iq from the memory 200a. The paper type is determined based on the value iq. Specifically, for example, as shown in FIG. 8, when the current value iq is a value in the range of 0.5 to 0.7 A, the paper type determining device 200 determines the type of recording medium being conveyed. Decide that it is plain paper. Further, when the current value iq is a value in the range of 1.0 to 1.2 A, the paper type determining device 200 determines that the type of the recording medium being conveyed is thick paper. That is, the paper type determining device 200 determines that the recording medium is plain paper (first sheet) when the current value iq is a value in the range of 0.5 to 0.7 A (first value). However, when the current value iq is a value in the range of 1.0 to 1.2 A (second value), it is determined that the recording medium is thick paper (second sheet) having a larger basis weight than plain paper. To do. In the present embodiment, when the determination instruction signal is input to the paper type determination device 200, the paper type determination device 200 sets the current value iq initially stored in the memory 200a after the determination instruction signal is input. The paper type was decided based on this, but this is not the case. For example, the paper type determining device 200 may acquire the current value iq already stored in the memory 200a when the determination instruction signal is input, and determine the paper type based on the current value iq. Further, for example, when the determination instruction signal is input from the CPU 151a to the paper type determining device 200 at the time t2-α and the time t2, the paper type determining device 200 receives the current value iq acquired from the memory 200a at the time t2-α. The paper type may be determined based on the average value with the current value iq acquired from the memory 200a at time t2.

The paper type determining device 200 outputs the determined paper type information to the CPU 151a.

FIG. 9 is a flowchart illustrating a method of determining a paper type. Hereinafter, a method for determining the paper type in the present embodiment will be described with reference to FIG. 9. The processing of this flowchart is executed by the CPU 151a.

First, when the enable signal ‘H’ is output from the CPU 151a to the motor control device 157, the motor control device 157 starts controlling the motor 509 based on the command output from the CPU 151a.

Then, when the sheet sensor 328 detects the tip of the recording medium P in S101, the CPU 151a advances the process to S102.

When a predetermined time T2 elapses after the sheet sensor 328 detects the tip of the recording medium P in S102, the CPU 151a outputs a determination instruction signal to the paper type determining device 200 in S103.

After that, in S104, the paper type determining device 200 determines the paper type based on the current value iq first stored in the memory 200a after the determination instruction signal is input, and outputs the paper type information to the CPU 151a.

As described above, in the present embodiment, the paper type is determined based on the current value iq during the period in which the recording medium bends. The load torque applied to the rotor of the motor differs depending on the paper type. Specifically, for example, the load torque applied to the rotor when the thick paper is conveyed is larger than the load torque applied to the rotor when the plain paper is conveyed. The current value iq is a value corresponding to the load torque. Therefore, the type of recording medium being conveyed is determined by observing the current value iq. In this way, in the present embodiment, the type of sheet can be discriminated without using the sensor for discriminating the type of sheet. As a result, it is possible to suppress an increase in size and cost of the image forming apparatus.
[Control of image forming apparatus based on paper type]
Next, the operation performed by the CPU 151a will be described based on the paper type information output from the paper type determining device 200.

Set values (hereinafter, referred to as set values) such as the voltage of the charger 310, the developer 314, the transfer charger 315, and the temperature of the fixing heater 161 are set by the system controller 151. Specifically, the set value set by the system controller 151 based on the paper type information or the like transmitted by the user to the system controller 151 using the operation unit 152 is stored in the RAM 151c. The charger 310, the developer 314, the transfer charger 315 and the fixing heater 161 are controlled based on the set values stored in the RAM 151c.

However, if the paper type information transmitted by the user to the system controller 151 is different from the type of the recording medium actually used, it may not be possible to properly form an image with the preset values. .. For example, the image quality may deteriorate due to insufficient transfer voltage, or the toner may peel off due to insufficient fixing temperature.

In the present embodiment, the system controller 151 (CPU 151a) sets the set value based on the information of the paper type determined by the paper type determining device 200.

FIG. 10 is a flowchart illustrating a method in which the CPU 151a sets a set value based on the paper type information output from the paper type determining device 200. Hereinafter, a method of setting the set value in the present embodiment will be described with reference to FIG. The processing of this flowchart is executed by the CPU 151a.

First, in S201, the CPU 151a stores the set value set based on the paper type information or the like set by the user in the RAM 151c.

After that, in S202, the CPU 151a outputs an enable signal ‘H’ to the motor control device that controls the motors that drive various rollers, and the motor control device starts controlling the motor based on the command output from the CPU 151a. As a result, the transfer of the recording medium is started.

Next, in S203, the paper type determining device 200 determines the paper type using the method described above, and outputs the paper type information to the CPU 151a.

Then, when a predetermined time T1 elapses after the sheet sensor 328 detects the tip of the recording medium P in S204, the CPU 151a controls the motor control device 157 so as to stop the rotation of the motor 509 in S205. As a result, the rotation of the pre-registration roller 327 is stopped.

After that, in S206, the CPU 151a determines whether or not the paper type set by the user and the paper type determined by the paper type determining device 200 match. If the paper type set by the user and the paper type determined by the paper type determining device 200 do not match, in S207, the CPU 151a performs the RAM 151c based on the information of the paper type determined by the paper type determining device 200. Update (change) the setting value stored in. Specifically, for example, when the paper type set by the user is plain paper and the paper type determined by the paper type determining device 200 is thick paper, the CPU 151a sets the voltage of the transfer charger 315 in S201. Make it higher than the set voltage. More specifically, for example, the CPU 151a changes the voltage of 500 V corresponding to plain paper to the voltage of 1300 V corresponding to thick paper. This is because the thicker the paper, the higher the voltage required to transfer the image to the paper. In this way, the CPU 151a updates the set value stored in the RAM 151c based on the information of the paper type determined by the paper type determining device 200. The RAM 151c stores data indicating the correspondence between the paper type and the set value, and the CPU 151a changes the set value based on the data.

Next, in S208, the CPU 151a controls the motor control device 157 so as to resume the control of the motor 509. As a result, the transport of the recording medium is restarted. After that, in S209, the image forming apparatus 100 forms an image on the recording medium based on the set value stored in the RAM 151c, and the CPU 151a advances the process to S212.

Further, in S206, when the paper type set by the user and the paper type determined by the paper type determining device 200 match, in S210, the CPU 151a restarts the control of the motor 509 so that the motor control device 157 resumes control. To control. As a result, the transport of the recording medium is restarted. After that, in S211 the image forming apparatus 100 forms an image on the recording medium, and the CPU 151a advances the process to S212.

After that, the CPU 151a repeats the above-described processing until the image forming job is completed.

As described above, in the present embodiment, when the paper type set by the user and the paper type determined by the paper type determining device 200 do not match, the CPU 151a determines the paper type by the paper type determining device 200. The set value stored in the RAM 151c is updated based on the information of. Further, when the paper type set by the user and the paper type determined by the paper type determining device 200 match, the CPU 151a does not change the set value. That is, the image forming apparatus 100 forms an image in a state where the set value is set to a value suitable for the paper type. As a result, it is possible to prevent the image quality from being deteriorated due to the insufficient transfer voltage and the toner from being peeled off due to the insufficient fixing temperature. The set value also includes the transport speed for transporting the sheet. For example, the transport speed in the case of thick paper is slower than the transport speed in the case of plain paper.

In the present embodiment, the time t2 is a predetermined time in the period from the time t0 to the time t3, but in order to accurately determine the paper type, it is better to set the time as close to the time t3 as possible to the time t2. This is because, as shown in FIG. 6, the closer the time is to time t3, the larger the difference between the current value iq on thick paper and the current value iq on plain paper.

[Second Embodiment]
Since the configurations of the image forming apparatus and the motor control apparatus are the same as those of the first embodiment, the description thereof will be omitted. Further, the operation performed by the CPU 151a based on the paper type information output from the paper type determining device 200 is the same as that in the first embodiment, and thus the description thereof will be omitted.

In the present embodiment, the paper type determining device 200 determines the paper type based on the amount of change (inclination) of the current value iq per unit time during the period in which the pre-registration roller 327 bends the recording medium.

Hereinafter, a method for determining the paper type in the present embodiment will be described. FIG. 11 is a diagram showing a change in the current value iq in the process of performing skew correction in the present embodiment. In FIG. 11, the current value iq (black circle) when the skew correction of the thick paper is performed and the current value iq (white circle) when the skew correction of the plain paper is performed are shown. The dotted line shown in FIG. 11 is a line that linearly approximates the current value iq when the skew correction of thick paper is performed, and the alternate long and short dash line shown in FIG. 11 is a line when the skew correction of plain paper is performed. It is a line which linearly approximates the current value iq in. Since the predetermined times T1 and T2 and the times t0 to t3 are the same as those in the first embodiment, the description thereof will be omitted.

As shown in FIG. 11, the amount of change in the current value iq per unit time on thick paper is different from the amount of change in the current value iq per unit time on plain paper. Specifically, the amount of increase in the current value iq per unit time on thick paper is larger than the amount of increase in the current value iq per unit time on plain paper. This is because the elastic force generated in the thick paper during the bending period of the thick paper is larger than the elastic force generated in the plain paper during the bending period of the plain paper. As described above, the amount of increase in the current value iq per unit time during the period in which the recording medium bends differs depending on the paper type. Therefore, the paper type can be discriminated by observing the amount of change in the current value iq per unit time during the period in which the recording medium bends.

Similar to the first embodiment, in this embodiment as well, the CPU 151a outputs an instruction (determination instruction signal) for determining the paper type to the paper type determining device 200. Specifically, the CPU 151a outputs a determination instruction signal to the paper type determining device 200 when the predetermined time T2 elapses from the time t0.

FIG. 12 is a block diagram showing an example of the configuration of the paper type determining device 200 in the present embodiment. Further, FIG. 13 is a table diagram showing the correspondence between the paper type and the amount of change Δiq of the current value iq per unit time in the present embodiment. As shown in FIG. 12, the paper type determining device 200 in the present embodiment acquires the current value iq output from the coordinate converter 511 at different timings, and the time at which the current value iq and the current value iq are acquired. A memory 200a for storing a plurality of memory 200a corresponding to t is provided. Further, the paper type determining device 200 is provided with a changing amount determining device 200c that determines the changing amount Δiq per unit time by linearly approximating the current value iq stored in the memory 200a. Further, the change amount determining device 200c is provided with the table 200b shown in FIG.

When the determination instruction signal is input, the change amount determinant 200c linearly approximates all the current values iq stored in the memory 200a during the period from time t1 to time t2 to obtain the change amount Δiq per unit time. decide. Further, the change amount determinant 200c determines the paper type based on the change amount Δiq per unit time. Specifically, for example, as shown in FIG. 13, when the change amount Δiq is a value within the range of 2 to 4 A / s, the change amount determinant 200c uses plain paper as the type of recording medium being conveyed. To determine that. When the change amount Δiq is a value within the range of 10 to 12 A / s, the change amount determinant 200c determines that the type of recording medium being conveyed is thick paper. That is, when the change amount Δiq is a value within the range of 2 to 4 A / s (first value), the paper type determinant 200 determines that the recording medium is plain paper (first sheet) and changes. When the amount Δiq is a value in the range of 10 to 12 A / s (second value), it is determined that the recording medium is thick paper (second sheet) having a higher rigidity than plain paper. The paper type determining device 200 outputs the determined paper type information to the CPU 151a. The time t1 is the time when the predetermined time T3 has elapsed from the time t0, and the predetermined time T3 is determined by a preset control sequence of the motor. Further, in the present embodiment, when the memory 200a outputs the information of the paper type determined by the paper type determining device 200 to the CPU 151a, the stored current value iq is deleted. The correspondence between the paper type and the amount of change Δiq is a value determined in advance by an experiment or the like.

FIG. 14 is a flowchart illustrating a method of determining a paper type. Hereinafter, a method for determining the paper type in the present embodiment will be described with reference to FIG. The processing of this flowchart is executed by the CPU 151a.

First, when the enable signal ‘H’ is output from the CPU 151a to the motor control device 157, the motor control device 157 starts the drive control of the motor 509 based on the command output from the CPU 151a.

Then, when the sheet sensor 328 detects the tip of the recording medium P in S301, the CPU 151a advances the process to S302.

When a predetermined time T2 elapses after the sheet sensor 328 detects the tip of the recording medium P in S302, the CPU 151a outputs a determination instruction signal to the paper type determining device 200 in S303.

After that, in S304, the change amount determinant 200c determines the change amount Δiq per unit time of the current value iq in the period from the time t1 to the time t2 stored in the memory 200a.

Then, in S305, the paper type determining device 200 determines the paper type based on the change amount Δiq, and outputs the paper type information to the CPU 151a.

As described above, in the present embodiment, the paper type is determined based on the amount of change (inclination) of the current value iq per unit time during the period in which the recording medium bends. As a result, the type of sheet can be discriminated without using a sensor for discriminating the type of sheet. As a result, it is possible to suppress an increase in size and cost of the image forming apparatus.

In the present embodiment, the time t2 is a predetermined time in the period from the time t0 to the time t3, but in order to accurately determine the paper type, the time t2 should be as close to the time t3 as possible. good. This is because the closer the time t2 is to the time t3, the more data the q-axis current value is, and the more accurate the change amount Δiq is determined.

Further, in the present embodiment, the amount of change Δiq is determined by linearly approximating all the q-axis current values stored in the memory 200a during the period from time t1 to time t2, but this is not the case. For example, the amount of change Δiq may be determined by linearly approximating two or more q-axis current values in the period from time t1 to time t2. That is, it is not necessary to use all the q-axis current values to determine the paper type.

[Third Embodiment]
Since the configurations of the image forming apparatus and the motor control apparatus are the same as those of the first embodiment, the description thereof will be omitted.

In the first embodiment and the second embodiment, the paper type is determined based on the current value iq during the period in which the recording medium bends between the pre-registration roller 327 and the registration roller 308. In the present embodiment, the recording medium is conveyed along the bent transport path, and the paper type is determined based on the current value iq during the period in which the recording medium bends in the bent transport path.

FIG. 15 is a diagram showing a transport path formed between the transport roller 330 and the transport roller 307. As shown in FIG. 15, the transport path formed between the transport roller 330 and the transport roller 307 is formed by the transport guide a and the transport guide b. The shape of the transport path formed by the transport guide a and the transport guide b is an example of a bent transport path, and the shape of the transport path (angle at which the transport path bends, the distance between the guide a and the guide b, etc.). Is not limited to this.

As shown in FIG. 15, the transfer roller 330 is driven by the motor M1, and the motor M1 is controlled by the motor control device 158. The motor control device 158 is connected to the CPU 151a (system controller 151) and controls the motor M1 based on a command from the CPU 151a. Since the configuration of the motor control device 158 is the same as the configuration of the motor control device 157, the description thereof will be omitted.

Further, as shown in FIG. 15, a sheet sensor 331 for detecting the presence or absence of a recording medium is provided between the feeding roller 305 and the conveying roller 330. The sheet sensor 331 is connected to the CPU 151a (system controller 151), and the CPU 151a outputs a determination instruction signal to the paper type determining device 200 based on the detection of the tip of the recording medium by the sheet sensor 331.

The recording medium conveyed by the transfer roller 330 is conveyed while being in contact with the bent transfer path. When the recording medium is conveyed while being in contact with the bent transfer path, a frictional force acts on the recording medium in the direction opposite to the transfer direction due to the friction between the recording medium and the transfer path. The frictional force generated by the friction between the recording medium and the transport path increases as the friction coefficient on the surface of the transportable recording medium increases. That is, the load torque applied to the transport roller 330 increases as the friction coefficient on the surface of the transport recording medium increases.

Further, when the recording medium is conveyed while being in contact with the bent transfer path, the recording medium is conveyed in a bent state. The larger the angle δ formed by the straight line connecting the nip portion of the transport roller 330 and the tip of the recording medium shown in FIG. 15 and the horizontal direction, the larger the amount of deflection of the recording medium. As described in the first to third embodiments, when the amount of bending of the recording medium increases, the elastic force acting on the recording medium also increases. That is, as the amount of bending of the recording medium increases, the load torque applied to the transport roller 330 also increases. The amount of increase (change amount) in load torque increases as the rigidity (basis weight) of the recording medium increases. That is, the amount of change in the load torque when the amount of bending of the thick paper increases is larger than the amount of change in the load torque when the amount of bending of the thin paper increases.

Hereinafter, a method for determining the paper type in the present embodiment will be described. FIG. 16 is a diagram showing changes in the current value iq during the period in which the recording medium is conveyed through the bent transfer path. In FIG. 16, the current value iq (black circle) when the thick paper is conveyed and the current value iq (white circle) when the plain paper is conveyed are shown. Further, the dotted line shown in FIG. 16 is a line that linearly approximates the current value iq when the thick paper is conveyed, and the one-point chain line shown in FIG. 16 is a linear approximation of the current value iq when the plain paper is conveyed. It is a line.

In the present embodiment, the CPU 151a outputs a determination instruction signal to the paper type determining device 200 at a time t6 when a predetermined time T5 has elapsed from a time t4 which is a time when the sheet sensor 331 detects the recording medium. The predetermined time T5 is a time after the time t6 is later than the time t5 when the predetermined time T4 has elapsed from the time t4, and is a time before the timing when the tip of the recording medium reaches the nip portion of the transport roller 307. Is set to be. The predetermined time T4 is set based on a preset control sequence of the motor.

FIG. 17 is a block diagram showing an example of the configuration of the paper type determining device 200 in the present embodiment. As shown in FIG. 17, the paper type determining device 200 in the present embodiment acquires the current value iq output from the coordinate converter 511 at different timings, and the time at which the current value iq and the current value iq are acquired. A memory 200a for storing a plurality of memories in correspondence with t is provided. Further, the paper type determining device 200 is provided with a total sum determining device 200d that linearly approximates the current value iq stored in the memory 200a and determines the total sum Σiq of the current value iq based on the linearly approximated equation. There is. The sum (integral value) of the current values iq corresponds to the area surrounded by the linearly approximated line and the horizontal axis (axis indicating the time t) in the period from the time t5 to the time t6 in FIG.

When the determination instruction signal is input, the summation determinant 200d linearly approximates all the current values iq stored in the memory 200a during the period from time t5 to time t6, and linearly approximates the time t5 based on the linearly approximated equation. The total Σiq of the current value iq in the period from to time t6 is determined.

FIG. 18 is a table diagram showing the correspondence between the paper type and the total sum Σiq of the current value iq in the present embodiment. As shown in FIG. 17, the summing device 200d has the table 200e shown in FIG.

As shown in FIG. 18, when the total sum Σiq is a value in the range of 8 to 12A, the total sum determination device 200d (paper type determination device 200) is the type of the recording medium being conveyed. Is determined to be plain paper. When the total Σiq is a value in the range of 15 to 20 A, the paper type determining device 200 determines that the type of the recording medium being conveyed is thick paper. That is, when the total Σiq is a value in the range of 8 to 12A (first value), the paper type determining device 200 determines that the recording medium is plain paper (first sheet), and the total Σiq is 15. When the value is in the range of ~ 20A (second value), it is determined that the recording medium is thick paper (second sheet) having a higher rigidity than plain paper. The paper type determining device 200 outputs the determined paper type information to the CPU 151a. In the present embodiment, when the memory 200a outputs the information of the paper type determined by the paper type determining device 200 to the CPU 151a, the stored current value iq is deleted. The correspondence between the paper type and the total sum Σiq is a value determined in advance by an experiment or the like.

FIG. 19 is a flowchart illustrating a method of determining a paper type. Hereinafter, a method for determining the paper type in the present embodiment will be described with reference to FIG. The processing of this flowchart is executed by the CPU 151a.

First, when the enable signal ‘H’ is output from the CPU 151a to the motor control device 157, the motor control device 157 starts controlling the motor 509 based on the command output from the CPU 151a.

Then, when the sheet sensor 331 detects the tip of the recording medium P in S401, the CPU 151a advances the process to S402.

When a predetermined time T5 elapses after the sheet sensor 331 detects the tip of the recording medium P in S402, the CPU 151a outputs a determination instruction signal to the paper type determining device 200 in S403.

After that, in S404, the total sum determinant 200d linearly approximates the current value iq in the period from time t5 to time t6 stored in the memory 200a, and from time t5 to time t6 based on the linearly approximated equation. The total sum Σiq of the current value iq in the period of is determined.

Then, in S405, the paper type determining device 200 determines the paper type based on the total sum Σiq, and outputs the paper type information to the CPU 151a.

[Control of image forming apparatus based on paper type]
Next, the operation performed by the CPU 151a will be described based on the paper type information output from the paper type determining device 200.

FIG. 20 is a flowchart illustrating a method in which the CPU 151a sets a set value based on the paper type information output from the paper type determining device 200. Hereinafter, a method of setting the set value in the present embodiment will be described with reference to FIG. 20. The processing of this flowchart is executed by the CPU 151a.

Since the processes from S501 to S503 are the same as the processes from S201 to S203 in FIG. 10, the description thereof will be omitted. Further, since the processing of S504 and S505 is the same as the processing of S206 and S207 in FIG. 10, the description thereof will be omitted.

In S506, the image forming apparatus 100 forms an image on the recording medium based on the set value stored in the RAM 151c, and the CPU 151a advances the process to S507.

Further, in S504, when the paper type set by the user and the paper type determined by the paper type determining device 200 match, in S508, the image forming apparatus 100 is based on the set value stored in the RAM 151c. An image is formed on the recording medium, and the CPU 151a advances the process to S507.

After that, the CPU 151a repeats the above-described processing until the image forming job is completed.

As described above, in the present embodiment, the recording medium is conveyed through the bent transport path, and the paper type is determined based on the current value iq during the period in which the recording medium is bent in the bent transport path. Specifically, the paper type is determined based on the sum of the current values iq during the period in which the recording medium passes through the bent transport path. As a result, the type of sheet can be discriminated without using a sensor for discriminating the type of sheet. As a result, it is possible to suppress an increase in size and cost of the image forming apparatus.

Further, the paper type determined by the paper type determining device 200 and the paper type set by the user are compared without stopping the transport of the recording medium. Then, when the paper type set by the user and the paper type determined by the paper type determining device 200 do not match, the CPU 151a enters the RAM 151c based on the information of the paper type determined by the paper type determining device 200. Update the stored setting value. Further, when the paper type set by the user and the paper type determined by the paper type determining device 200 match, the CPU 151a does not change the set value. In this way, the image forming apparatus 100 can perform image forming in a state where the set value is set to a value suitable for the paper type without stopping the transport of the recording medium. As a result, it is possible to prevent the image formation from being delayed due to the suspension of the transport of the recording medium. Further, it is possible to prevent the image quality from being deteriorated due to the insufficient transfer voltage and the toner from being peeled off due to the insufficient fixing temperature. The set value also includes the transport speed for transporting the sheet. For example, the transport speed in the case of thick paper is slower than the transport speed in the case of plain paper.

As described above, in the first to third embodiments, the current value in the state where the sheet conveyed by the upstream transfer roller and not conveyed by the downstream transfer roller is bent in the adjacent transfer rollers. The type of sheet is determined based on iq.

As in the present embodiment, the CPU 151a stops the transfer of the recording medium by determining the paper type when the recording medium first passes through the bent transfer path after the recording medium is fed. You can change the set value without any.

Further, in the present embodiment, when the paper type is determined when the recording medium passes through the bent transport path, the tip of the recording medium passes through the nip portion of the transport roller 330 and then reaches the nip portion of the transport roller 307. The paper type is determined based on the current value iq in the period until the paper is reached. This is because when the recording medium is conveyed by the transfer roller 307, the elastic force generated in the recording medium becomes small, and the load torque applied to the rotor of the motor M1 may become small.

In the present embodiment, the total sum determinant 200d determines the total Σiq of the current value iq in the period from time t5 to time t6, but this is not the case. For example, the total sum determination device 200d may be configured to determine the total Σiq of the current value iq in a predetermined period of the period from time t5 to time t6.

Further, the configuration described in the present embodiment, that is, the configuration in which the paper type is determined based on the total sum Σiq, may be applied during the period in which the skew correction is performed.

Further, the configuration in which the paper type is determined based on the current value iq at a predetermined timing described in the first embodiment may be applied to the method of determining the type of the recording medium passing through the bent transport path. Further, the configuration in which the paper type is determined based on the amount of change in the current value iq described in the second embodiment may be applied to the method for determining the type of recording medium passing through the bent transport path.

The paper type information in the first to third embodiments includes information such as the basis weight of the sheet.

Further, in the first to third embodiments, the paper type determining device 200 determines the paper type, but the CPU 151 may determine the paper type described above. That is, the CPU 151a may have the function of the paper type determining device 200.

In the first embodiment and the second embodiment, the skew correction of the recording medium is performed by the tip of the recording medium coming into contact with the nip portion of the registration roller 308, but the present invention is not limited to this. Absent. For example, recording is performed on the upstream side of the registration roller 308 and downstream of the sheet sensor 328, or on the upstream side of the transfer position and downstream of the registration roller 308 with respect to the transport direction of the recording medium. A shutter is provided as a contact member with which the tip of the medium comes into contact. Then, the tip of the recording medium comes into contact with the shutter, and the skew correction of the recording medium is performed by the method described above. After that, the shutter may be retracted when the pre-registration roller 308 transfers the recording medium to the transfer position in time with the toner image.

Further, in the first embodiment and the second embodiment, the paper type is determined based on the current value iq, but the load torque Tm applied to the rotor may be used. That is, the load torque Tm may be determined from the q-axis current value based on the equation (10), and the paper type may be determined based on the load torque Tm. Further, when the load torque Tm is determined, for example, the load torque value Tm may be determined from the deviation between the rotation phase θ of the rotor and the command phase θ_ref instead of the current value iq. Further, a table showing the relationship between the load torque value Tm and the current value iq may be stored in advance in the ROM 151b or the like, and the load torque value Tm corresponding to the current value iq may be read out from the ROM 151b based on the table.

In the first to third embodiments, the stepping motor is used as the motor for driving the pre-registration roller 327, but other motors such as a DC motor may be used. Further, the motor is not limited to a two-phase motor, and the present embodiment can be applied to other motors such as a three-phase motor.

Further, in the first to third embodiments, a permanent magnet is used as the rotor, but the present invention is not limited to this.

Further, in the first to third embodiments, if the paper type set by the user and the paper type determined by the paper type determining device 200 do not match, the CPU 151a is determined by the paper type determining device 200. The set value was set based on the paper type, but this is not the case. For example, when the paper type set by the user and the paper type determined by the paper type determining device 200 do not match, the CPU 151a uses the display unit provided on the operation unit 152 to change the set paper type. It may be configured to notify the user. As a result, the user changes the paper type setting, and the CPU 151a sets the set value based on the paper type changed by the user. As a result, the image forming apparatus 100 can perform image forming in a state where the set value is set to a value suitable for the paper type. That is, it is possible to prevent the image quality from being deteriorated due to the insufficient transfer voltage and the toner from being peeled off due to the insufficient fixing temperature. Further, for example, when the current value iq, the amount of change Δiq, and the total sum Σiq do not correspond to the information stored in the table, the CPU 151a is provided on the operation unit 152 via a display unit so as to confirm the set paper type. It may be configured to notify the user. The case where the current value iq does not correspond to the information stored in the table is, for example, the case where the current value iq is 1.5 A (see FIG. 8). Further, the case where the amount of change Δiq does not correspond to the information stored in the table is, for example, the case where the current value Δiq is 15 A (see FIG. 13). Further, the case where the sum Σiq does not correspond to the information stored in the table is, for example, the case where the sum Σiq is 25A (see FIG. 18).

Further, in the vector control in the first to third embodiments, the motor is controlled by performing phase feedback control, but the present invention is not limited to this. For example, the motor may be controlled by feeding back the rotation speed ω of the rotor 402. Specifically, as shown in FIG. 21, a speed determinant 514 is provided inside the motor control device, and the speed determinant 514 determines the rotation speed ω based on the time change of the rotation phase θ output from the phase determinant 513. decide. The following equation (11) shall be used to determine the speed.
ω = dθ / dt (11)

Then, the CPU 151a outputs a command speed ω_ref indicating the target speed of the rotor. Further, a speed controller 500 is provided inside the motor control device, and the speed controller 500 generates the q-axis current command value iq_ref and the d-axis current command value id_ref so that the deviation between the rotation speed ω and the command speed ω_ref becomes small. And output. The motor may be controlled by performing such speed feedback control.

100 Image forming device 151a CPU
157 Motor controller 200 Paper type determinant 308 Registration roller 327 Pre-registration roller 307,330 Conveyor roller 402 Rotor 502 Phase controller 507,508 Current detector 509 Stepping motor 513 Phase determiner

Claims (12)

The first roller that conveys the sheet and
A second roller adjacent to the first roller and provided on the downstream side of the first roller in the transport direction in which the sheet is transported,
An image forming unit provided on the downstream side of the second roller in the conveying direction and forming an image on the sheet, and an image forming unit.
The motor that drives the first roller and
A phase determining means for determining the rotational phase of the rotor of the motor,
A control means for controlling the drive current flowing through the winding of the motor so that the deviation between the command phase representing the target phase of the rotor and the rotation phase determined by the phase determining means becomes small.
A discriminating means for determining the type of the sheet conveyed by the first roller based on the deviation in a state in which the sheet conveyed by the first roller and not conveyed by the second roller is bent. When,
An image forming apparatus characterized by having. The image forming unit is
An image carrier that supports a toner image and
A developing unit that develops the toner image on the image carrier, and a transfer unit that transfers the toner image developed on the image carrier by the developing unit onto the sheet.
Have,
The second roller is a roller that conveys the sheet at the transfer timing at which the transfer unit transfers an image to the sheet.
The control means controls the motor so that the first roller bends the sheet by transporting the sheet in the transport direction in a state where the tip of the sheet is in contact with the second roller. And
The first aspect of claim 1 is characterized in that the discriminating means discriminates the type of the sheet conveyed by the first roller based on the deviation in the period in which the first roller bends the sheet. Image forming device. The control means is such that the first roller bends the sheet by transporting the sheet in the transport direction in a state where the tip of the sheet is in contact with the second roller in a stopped state. The image forming apparatus according to claim 2, wherein the motor is controlled. The transport path through which the sheet transported by the first roller passes is curved between the first roller and the second roller.
In the discriminating means, the sheet is not conveyed by the second roller, and the sheet is conveyed by the first roller along a curved portion where the transfer path is curved, so that the sheet is bent. The image forming apparatus according to claim 1, wherein the type of the sheet conveyed by the first roller is determined based on the deviation in the state. The image forming apparatus
The loading section on which the sheet is loaded and
A pickup roller that feeds the sheet loaded on the loading unit, and
Have,
The image forming apparatus according to claim 4, wherein the first roller is a roller adjacent to the pickup roller and provided on the downstream side of the pickup roller in the transport direction. A transport roller that transports the sheet and
An abutting member provided on the downstream side of the transport roller in the transport direction in which the sheet is transported, and the tip of the recording medium transported by the transport roller abuts.
An image forming unit provided on the downstream side of the contact member in the transport direction and forming an image on the sheet, and an image forming unit.
The motor that drives the transfer roller and
A phase determining means for determining the rotational phase of the rotor of the motor,
A control means for controlling the drive current flowing through the winding of the motor so that the deviation between the command phase representing the target phase of the rotor and the rotation phase determined by the phase determining means becomes small.
The sheet transported by the transport roller based on the deviation in the period in which the sheet is flexed by the transport roller transporting the sheet with its tip in contact with the contact member in the transport direction. An output means that outputs a signal indicating the type, and
A setting means for setting information on the sheet to be transported, and
When the information on the sheet set by the setting means and the information on the sheet indicated by the signal output from the output means are different, the sheet corresponding to the set information on the sheet and the sheet being conveyed are conveyed. Notification means to notify the user that is different from
An image forming apparatus characterized by having. The first roller that conveys the sheet and
A second roller adjacent to the first roller and provided on the downstream side of the first roller in the transport direction in which the sheet is transported,
A transport path through which a sheet transported by the first roller passes, and a transport path curved between the first roller and the second roller.
An image forming unit provided on the downstream side of the second roller in the conveying direction and forming an image on the sheet, and an image forming unit.
The motor that drives the first roller and
A phase determining means for determining the rotational phase of the rotor of the motor,
A control means for controlling the drive current flowing through the winding of the motor so that the deviation between the command phase representing the target phase of the rotor and the rotation phase determined by the phase determining means becomes small.
The deviation in a state in which the sheet is bent by the sheet being conveyed by the first roller along a curved portion where the sheet is not conveyed by the second roller and the transfer path is curved. An output means that outputs a signal indicating information on the sheet conveyed by the first roller based on the above.
An image forming apparatus characterized by having. The image forming apparatus
The loading section on which the sheet is loaded and
A pickup roller that feeds the sheet loaded on the loading unit, and
Have,
The image forming apparatus according to claim 7, wherein the first roller is a roller adjacent to the pickup roller and provided on the downstream side of the pickup roller in the transport direction. 7. The image forming apparatus according to claim 7 or 8, wherein the image forming apparatus includes a setting means for changing a set value of the image forming unit to a set value corresponding to the sheet indicated by a signal output from the output means. Image forming device. The image forming apparatus
A setting means for setting information on the sheet to be transported, and
When the information on the sheet set by the setting means and the information on the sheet indicated by the signal output from the output means are different, the sheet corresponding to the set information on the sheet and the sheet being conveyed are conveyed. Notification means to notify the user that is different from
The image forming apparatus according to claim 7 or 8, wherein the image forming apparatus has. The control means is based on a torque current component which is a current component represented in a rotating coordinate system based on a rotation phase determined by the phase determining means and which is a current component for generating torque in the rotor. The image forming apparatus according to any one of claims 1 to 10, wherein the drive current flowing through the winding is controlled. The first roller that conveys the sheet and
A second roller adjacent to the first roller and provided on the downstream side of the first roller in the transport direction in which the sheet is transported,
The motor that drives the first roller and
A phase determining means for determining the rotational phase of the rotor of the motor,
A control means for controlling the drive current flowing through the winding of the motor so that the deviation between the command phase representing the target phase of the rotor and the rotation phase determined by the phase determining means becomes small.
Outputs information indicating the type of the sheet conveyed by the first roller based on the deviation in a state in which the sheet conveyed by the first roller and not conveyed by the second roller is bent. Output means to be
A sheet transfer device characterized by having.

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