Image formation device

Abstract

To reduce damage to a sheet.SOLUTION: An image formation device comprises: a fixing rotary body (151) which fixes an image on a sheet; a first motor which drives the fixing rotary body (151); a fixing downstream rotary body (184) which is arranged downstream from the fixing rotary body (151) in a sheet conveying direction, and conveys the sheet; a second motor which drives the fixing downstream rotary body (184); first guide parts (302, 303) which forms a first conveyance path (301) curved between the fixing rotary body (151) and fixing downstream rotary body (184) in the sheet conveying direction; and a control part which controls the first motor and second motor. The control part controls the second motor so that the sheet conveyed from the fixing downstream rotary body (184) less warps in the first conveyance path (301) when guided in a first direction (V1) of a vertical direction than when guided in a second direction (V2).SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus including a pair of fixing rollers for fixing an image on a sheet, and a pair of downstream fixing rollers disposed downstream of the pair of fixing rollers. [Background technology]

[0002] Some image forming devices discharge (convey) sheets from a pair of discharge rollers to a space (discharge stacking section) provided above the device body (see Patent Document 1). This image forming device is configured so that an intermediate conveying unit can be placed in the space, and when the intermediate conveying unit is installed, the device is configured to convey sheets from the pair of discharge rollers to the intermediate conveying unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-205520 Summary of the Invention [Problem to be solved by the invention]

[0004] In an image forming apparatus such as that described in Patent Document 1, a sheet on which an image has been fixed by a fixing device is guided and transported along a curved transport path to a pair of discharge rollers. Furthermore, in an image forming apparatus such as that described in Patent Document 1, the direction of the sheet transported from the pair of discharge rollers differs between when the sheet is transported to the discharge stacking section and when the sheet is transported to the intermediate transport unit. With this configuration, when the sheet is transported to the discharge stacking section, the sheet is transported downward, which may cause the sheet to bend along the curved transport path and slide against the upper guide. On the other hand, when the sheet is transported to the intermediate transport unit, the sheet is transported horizontally or upward, which may reduce the force that causes the sheet to bend along the curved transport path and cause the sheet to slide against the lower guide. In other words, the sheet's posture along the curved transport path differs depending on whether the intermediate transport unit is installed or not, which may result in damage such as scratches on the sheet.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image forming apparatus that can reduce damage to sheets. [Means for solving the problem]

[0006] One aspect of the present invention is an image forming device comprising: a fixing rotor that fixes an image on a sheet; a first motor that drives the fixing rotor; a fixing downstream rotor that is arranged downstream of the fixing rotor in the sheet transport direction and transports the sheet; a second motor that drives the fixing downstream rotor; a first guide unit that forms a curved first transport path between the fixing rotor and the fixing downstream rotor in the sheet transport direction; and a control unit that controls the first motor and the second motor, wherein the control unit controls the second motor so that the deflection of the sheet in the first transport path is smaller when the direction in which the sheet transported from the fixing downstream rotor is guided is a first direction in the vertical direction than when it is a second direction different from the first direction.

[0007] One aspect of the present invention is a mounting unit that can selectively mount a fixing rotator that fixes an image on a sheet, a first motor that drives the fixing rotator, a fixing downstream rotator that is disposed downstream of the fixing rotator in a sheet transport direction and transports the sheet, a second motor that drives the fixing downstream rotator, a first guide unit that forms a curved first transport path between the fixing rotator and the fixing downstream rotator in the sheet transport direction, a second guide unit that has a second transport path downstream of the fixing downstream rotator in the sheet transport direction through which the sheet transported by the fixing downstream rotator is guided, and a third guide unit that has a fourth transport path through which the sheet transported by the fixing downstream rotator is guided, and the first motor and a control unit that controls the second motor and the second motor, wherein when the second guide unit is attached to the attachment unit, the sheet transported from the fixing downstream rotating body is guided in a second direction in the up-down direction, and when the third guide unit is attached to the attachment unit, the sheet transported from the fixing downstream rotating body is guided in a third direction different from the second direction in the up-down direction, and the control unit controls the second motor so that the deflection of the sheet in the first transport path is greater when the direction in which the sheet transported from the fixing downstream rotating body is guided is the second direction in the up-down direction than when it is guided in the third direction. [Effects of the Invention]

[0008] According to the present invention, damage to the sheet can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing a control system of the image forming apparatus. [Figure 3] FIG. 2 is a schematic diagram illustrating the configuration of a secondary transfer unit, a fixing unit, and a paper discharge unit. [Figure 4] FIG. 2 is a block diagram showing a drive control system for a fixing unit and a paper discharge unit. [Figure 5] FIG. 2 is an explanatory diagram showing vector control of a motor. [Figure 6] FIG. 2 is a block diagram showing the control functions of a motor control unit. [Figure 7] FIG. 2 is a block diagram showing the control function of a speed command determiner. [Figure 8] 10 is a time chart showing a speed command value and a current value of a motor M2 when a sheet is conveyed. [Figure 9] 10 is a flowchart showing general drive control of a motor M2. [Figure 10] 10 is a flowchart showing general drive control of the motors M2 and M3. [Figure 11] (a) is a schematic diagram showing the configuration when no conveying device is installed, (b) is a schematic diagram showing the configuration when a first conveying device is installed, and (c) is a schematic diagram showing the configuration when a second conveying device is installed. [Figure 12] 6 is a flowchart showing control of a motor M2 according to the present embodiment. [Figure 13] 6 is a flowchart showing a control for setting a target current value according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings.

[0011] [Schematic configuration of image forming device] First, the general configuration of the image forming apparatus will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the general configuration of the image forming apparatus according to this embodiment.

[0012] As shown in FIG. 1, image forming apparatus 100 includes apparatus main body 101, which includes a feed section 101A for feeding sheets, an image forming section 101B for forming an image on a sheet, and a conveying section 101C for conveying the sheet with the image formed thereon. A space SP is formed above apparatus main body 101 to discharge sheets S that are conveyed to conveying section 101C and then discharged. FIG. 1 shows a state in which discharge trays 160 and 161 are disposed in this space SP so that they can be attached. However, the space SP is configured so that a first conveying device 700 serving as a second guide section for conveying sheets S, such as a relay device (described in detail below), or a second conveying device 800 serving as a third guide section (see FIG. 11) can be selectively attached to the space SP. An image reading device or the like may be disposed above this space SP.

[0013] The feeding section 101A is provided with a sheet tray T as a sheet supporting section that is arranged in a cassette and that supports a stack of multiple sheets S. The feeding section 101A also has a pickup roller 102 that picks up the uppermost sheet S of the sheet stack supported by the sheet tray T and starts feeding it. The feeding section 101A also has a separation roller pair 103 that separates the sheets S that have started to be fed by the pickup roller 102 into individual sheets.

[0014] The feeding unit 101A is also provided with a pair of pull-out rollers 104 that conveys the sheets S separated one by one by the separation roller pair 103 inside a conveying path 105 formed by a guide. The feeding unit 101A is also provided with a pair of registration rollers 106 that corrects skew by abutting the leading edge of the sheet S that has been guided and conveyed along the conveying path 105 to form a flexure, and conveys the sheet to the secondary transfer unit 110 while adjusting the timing.

[0015] On the other hand, image forming unit 101B has four sets of stations corresponding to the colors of yellow (Y), magenta (M), cyan (C), and black (Bk). Image forming unit 101B also has an intermediate transfer belt 130 onto which a full-color toner image is primarily transferred and formed by these stations. Image forming unit 101B also has a secondary transfer unit 110 that secondarily transfers the toner image formed on intermediate transfer belt 130 onto a sheet.

[0016] Here, the yellow (Y) station 120Y will be described as an example. The station 120Y is composed of a photoconductor 121Y, an exposure device 122Y, a charger 125Y, a developer 126Y, a primary transfer roller 123Y, and a photoconductor cleaner 124Y. The photoconductor 121Y rotates in the direction of arrow A in the figure, and the surface is uniformly charged by the charger 125Y. The exposure device 122Y irradiates the photoconductor 121Y with laser light based on an image signal representing the image to be formed, exposing the photoconductor 121Y whose surface is uniformly charged. As a result, an electrostatic latent image corresponding to the yellow image is formed on the surface of the photoconductor 121Y. The developer 126Y develops the electrostatic latent image formed on the photoconductor 121Y with yellow toner. As a result, a yellow toner image is formed on the photoconductor 121Y. The primary transfer roller 123Y primarily transfers the toner image onto the intermediate transfer belt 130 by applying a predetermined pressure and an electrostatic bias. The photosensitive member cleaner 124Y collects toner remaining on the photosensitive member 121Y after transfer. Similarly, magenta, cyan, and black toner images are formed on the photosensitive member at each station, and then transferred to the intermediate transfer belt 130 by the primary transfer unit. While only the yellow (Y) image forming unit is designated by a reference number in FIG. 1, the stations for each color other than yellow have the same configuration, and therefore their description will be omitted. Furthermore, the number of colors is not limited to four. Furthermore, the order of the stations corresponding to each color is not limited to this.

[0017] The intermediate transfer belt 130 is stretched by rollers such as a drive roller 131 and tension rollers 132a and 132b, and is driven to be transported in the direction of arrow B in the figure. The image formation process for each color by the four sets of stations is performed at a timing when a toner image formed by an image forming unit on the upstream side in the rotation direction of the intermediate transfer belt 130 is superimposed on a toner image formed by an image forming unit on the downstream side in the rotation direction. As a result, a full-color toner image is formed on the intermediate transfer belt 130. The toner image is transported to the secondary transfer unit 110 by the rotation of the intermediate transfer belt 130.

[0018] The secondary transfer unit 110 has a pair of secondary transfer rollers 111 as a transfer rotating body. The pair of secondary transfer rollers 111 secondarily transfers a toner image onto the surface of the sheet S by a predetermined pressure force and an electrostatically applied bias. The pair of secondary transfer rollers 111 are controlled to rotate at a set constant rotation speed (circumferential speed) in accordance with the speed at which an image is formed on the sheet, which is set according to the type and size of the sheet.

[0019] The conveying section 101C is provided with a fixing device 150 that fixes an image on the sheet S, a paper discharge unit 180 that discharges the sheet S with the fixed image, and a reversing conveying mechanism 162 that determines the front and back of the sheet S with the image fixed on one side. That is, the sheet S onto which a toner image has been transferred in the secondary transfer section 110 of the image forming section 101B is conveyed to the fixing device 150 that fixes the image on the sheet S. Note that a flexure detection sensor 115 is provided between the secondary transfer section 110 and the fixing device 150 as a flexure detection unit that detects flexure of the sheet S. The fixing device 150 applies pressure, heat, etc. to the sheet S onto which the toner image has been transferred, thereby melting and fixing the toner image to the sheet S.

[0020] The sheet S on which the image has been fixed by the fixing device 150 is conveyed to a path selected by a flapper 182 of a paper discharge unit 180 provided in the conveying section 101C. For example, when the sheet S is discharged directly to the outside of the apparatus main body 101, the sheet S is conveyed to and discharged onto a paper discharge tray 160 or a paper discharge tray 161. When double-sided image formation is performed, the sheet S on which the image has been formed on one side is conveyed again to the registration roller pair 106 via a reversing conveying mechanism 162 and a double-sided conveying path 163. Then, an image is formed on the other side of the sheet S in the same manner as above.

[0021] [Configuration of the control system of the image forming device] Next, the configuration of the control system of the image forming apparatus 100 will be described with reference to Fig. 2. Fig. 2 is a block diagram showing the control system of the image forming apparatus.

[0022] The system controller 190 of the image forming apparatus 100 includes a CPU 190a, a ROM 190b, and a RAM 190c as control units. The system controller 190 is connected to an analog-to-digital (A / D) converter 200, a high-voltage control unit 201, motor control units 192, 193, and 194, sensors 202, and an AC driver 203. The system controller 190 can send and receive data and commands to and from each of the connected units.

[0023] The CPU 190a executes various programs stored in the ROM 190b to execute various sequences related to predetermined image formation sequences. The RAM 190c is a storage device. The RAM 190c stores various data, such as setting values ​​for the high-voltage control unit 201 and command values ​​for the motor control units 192, 193, and 194.

[0024] System controller 190 receives signals from sensors 202 and sets a setting value for high voltage control unit 201 based on the received signals. High voltage control unit 201 supplies the necessary voltage to high voltage unit 156 (charger, developer, secondary transfer unit, etc.) in accordance with the setting value set by system controller 190.

[0025] Motor control units 192, 193, and 194 control motors M1, M2, and M3 that drive loads in response to commands output from CPU 190a. While only motors M1, M2, and M3 are shown in FIG. 2 as motors for image forming apparatus 100, this is not limiting. A single motor control unit may control multiple motors. While only three motor control units are shown in FIG. 2, this is not limiting.

[0026] The A / D converter 200 receives a detection signal detected by the thermistor 154 for detecting the temperature of the fixing heater 204, converts the detection signal from an analog signal to a digital signal, and transmits the digital signal to the system controller 190. The system controller 190 controls the AC driver 203 based on the digital signal received from the A / D converter 200. The AC driver 203 controls the fixing heater 204 so that the temperature of the fixing heater 204 reaches a temperature required for performing the fixing process. The fixing heater 204 is a heater used for the fixing process, and is included in the fixing unit 150.

[0027] [Details of the fuser, paper delivery unit, and reverse delivery mechanism] Next, the details of the fixing unit, paper discharge unit, and reverse discharge mechanism will be described with reference to Figures 3 and 4. Figure 3 is a schematic diagram showing the configuration of the secondary transfer unit, fixing unit, and paper discharge unit. Figure 4 is a block diagram showing the drive control system for the fixing unit and paper discharge unit.

[0028] As shown in FIG. 3, the fixing unit 150 is configured to have a fixing roller pair 151 as a fixing rotor, an inner paper discharge roller pair 152, and a fixing paper discharge roller pair 153. When the sheet S conveyed by the secondary transfer roller pair 111 is nipped by the fixing roller pair 151, the fixing roller pair 151 rotates at a rotation speed that is a conveying speed slower than the conveying speed of the sheet S of the secondary transfer roller pair 111. As a result, the sheet S is bent (forms a loop) between the fixing roller pair 151 and the secondary transfer roller pair 111. Therefore, the fixing roller pair 151 pulls the sheet S, onto which a toner image has been transferred by the secondary transfer roller pair 111, downstream, preventing slippage at the secondary transfer roller pair 111.

[0029] In this embodiment, controlling the rotation speed of the fixing roller pair 151 so as to form a flexure (loop) of the sheet S between the fixing roller pair 151 and the secondary transfer roller pair 111 is referred to as fixing loop control. Details of this fixing loop control will be described below.

[0030] The amount of slack (loop amount) of the sheet S is detected by a slack detection sensor 115 disposed between the fixing roller pair 151 and the secondary transfer roller pair 111 in the sheet conveying direction. In this embodiment, for example, when the loop amount (i.e., the detection result) detected by the slack detection sensor 115 reaches a predetermined amount, the fixing roller pair 151 is driven and controlled so that the conveying speed becomes the same as the conveying speed of the secondary transfer roller pair 111. The conveying speed of the fixing roller pair 151 fluctuates due to the roller diameter expanding due to heat during the fixing process and contracting due to heat absorbed by the sheet S. As a result, the amount of slack of the sheet S fluctuates.

[0031] If the amount of sagging of the sheet S is too large, the sagging sheet S may come into contact with the fixing roller pair 151. In this embodiment, for example, when the amount of sagging exceeds the maximum value of a predetermined range, the fixing roller pair 151 is driven and controlled so that its conveying speed is faster than the conveying speed of the secondary transfer roller pair 111. As a result, the amount of sagging of the sheet S decreases. On the other hand, when the amount of sagging becomes smaller than the minimum value of the predetermined range, the fixing roller pair 151 is driven and controlled so that its conveying speed is slower than the conveying speed of the secondary transfer roller pair 111. As a result, the amount of sagging increases. In other words, the rotation speed (conveying speed) of the fixing roller pair 151 is controlled (adjusted) so that the amount of sagging of the sheet S is maintained within a predetermined range. Note that a technology for controlling the conveying speed of the fixing roller pair 151 relative to the conveying speed of the secondary transfer roller pair 111 (i.e., fixing loop control) in this manner is described in Japanese Patent Application Laid-Open No. 2015-69068.

[0032] 4, the fixing roller pair 151, the inner paper discharge roller pair 152, and the fixing paper discharge roller pair 153 are driven by a motor M1. The motor M1 is driven and controlled by a motor control unit 192. The fixing paper discharge roller pair 153 has a one-way clutch between a rotation shaft (not shown) and the motor M1. This allows the sheet S sandwiched between the fixing paper discharge roller pair 153 to be pulled out by a paper discharge unit 180 located downstream in the sheet conveyance direction.

[0033] As shown in FIG. 3, the paper discharge unit 180 has a pair of pre-discharge rollers 181 serving as a first rotating body or a first roller pair, and a pair of discharge rollers 184 serving as a fixing downstream rotating body, a second rotating body, a discharge rotating body, or a second roller pair. The pair of pre-discharge rollers 181 and the pair of discharge rollers 184 are disposed adjacent to each other in the sheet conveyance direction. The paper discharge unit 180 also has a paper discharge sensor 183, a pair of vertical discharge path rollers 185, and a flapper 182 that switches the conveyance path. As shown in FIG. 4, the pair of pre-discharge rollers 181, the pair of discharge rollers 184, and the pair of vertical discharge path rollers 185 are driven by a motor M2. The motor M2 is driven and controlled by a motor control unit 193.

[0034] The sheet S on which printing has been completed passes from the fixing unit 150 through the paper discharge unit 180 and is discharged onto the paper discharge trays 160, 161 (see FIG. 1). When double-sided printing is being performed and the sheet S needs to be reversed, the flapper 182 is switched and the sheet S is handed over from the paper discharge unit 180 to a reverse conveyance mechanism 162 including a pair of reversing rollers 164 driven by a motor M3. In the reverse conveyance mechanism 162, the sheet S is conveyed by the pair of reversing rollers 164 until the trailing edge passes the flapper 182, and at the timing when the trailing edge passes, the flapper 182 is switched and the rotation direction of the pair of reversing rollers 164 is reversed. As a result, the sheet S is conveyed upside down to the double-sided conveyance path 163 (see FIG. 1).

[0035] [Motor control unit] Next, the functional configuration of the motor control unit 193, which controls the rotation speed and torque of the motor M2 that drives the pre-discharge roller pair 181, the discharge roller pair 184, and the discharge vertical path roller pair 185, and its general control (processing) will be described with reference to Figs. 5 to 10. Fig. 5 is an explanatory diagram showing vector control of the motor. Fig. 6 is a block diagram showing the control function of the motor control unit. Fig. 7 is a block diagram showing the control function of the speed command determiner. Fig. 8 is a time chart showing the speed command value and current value of the motor M2 when conveying a sheet. Fig. 9 is a flowchart showing general drive control of the motor M2. Fig. 10 is a flowchart showing general drive control of the motors M2 and M3.

[0036] In the following description, the motor control unit will be described using motor control unit 193, which controls motor M2, as an example. However, a similar configuration can be used for motor control unit 192, which controls motor M1, and motor control unit 194, which controls motor M3. Japanese Patent Application Laid-Open No. 2019-151486 describes a motor control unit technology that performs speed control based on the difference between the torque when the paper discharge unit is not conveying a sheet and the torque when the fuser and paper discharge unit are conveying a sheet. Japanese Patent Application Laid-Open No. 2011-81347 describes a technology that acquires torque information acting on a secondary transfer roller and controls the rotation speed of the fuser roller.

[0037] (Vector control) First, vector control by the motor control unit will be described with reference to Fig. 5. Motor control unit 193 controls motor M2 using vector control. Note that the motor in the following description is not provided with a sensor such as a rotary encoder for detecting the rotational phase of the rotor of the motor, but a sensor such as a rotary encoder may be provided.

[0038] FIG. 5 is a diagram showing the relationship between a stepping motor (hereinafter referred to as "motor") M2 consisting of two phases, A phase (first phase) and B phase (second phase), and a rotating coordinate system represented by a d-axis and a q-axis. In FIG. 5, an α-axis corresponding to the A-phase winding and a β-axis corresponding to the B-phase winding are defined in the stationary coordinate system. Also in FIG. 5, 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 q-axis is defined along the direction 90 degrees counterclockwise from the d-axis (direction perpendicular to the d-axis). The 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 vector control, a rotating coordinate system based on the rotational phase θ of the rotor 402 is used. Specifically, vector control uses a q-axis component (torque current component) that generates torque in rotor 402 and a d-axis component (excitation current component) that affects the strength of the magnetic flux that penetrates windings 401a-401d. The torque current component is a current component in a rotating coordinate system of a current vector that corresponds to the drive current that flows through windings 401a-401d. In other words, vector control is a method of controlling a motor by performing speed feedback control that controls the value of the torque current component and the value of the excitation current component so as to reduce the deviation between a command speed that represents a target speed of rotor 402 and the actual rotation speed.

[0039] (Functional configuration of the motor control unit) Next, the functional configuration of the motor control unit 193 that controls the motor M2 will be described with reference to Fig. 6. The motor control unit 193 is configured with at least one ASIC (Application Specific Integrated Circuit) and executes the functions described below.

[0040] Motor control unit 193 has, as circuits for performing vector control, speed controller 502, current controller 503, coordinate inverse converter 505, coordinate converter 511, PWM inverter 506 that supplies drive current to windings 401a to 401d of the motor, and the like.

[0041] The coordinate converter 511 converts the current vectors corresponding to the drive currents flowing through the A-phase and B-phase windings 401a-401d of the motor M2 from a stationary coordinate system represented by the α-axis and β-axis to a rotating coordinate system represented by the q-axis and d-axis. As a result, the drive currents flowing through the windings 401a-401d are 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 current values ​​in the rotating coordinate system. The q-axis current corresponds to a torque current that generates torque in the rotor 402 of the motor M2. The d-axis current corresponds to an excitation current that affects the strength of the magnetic flux passing through the windings 401a-401d of the motor M2, but does not contribute to the generation of torque in the rotor 402. The motor control unit 193 can control the q-axis current and the d-axis current independently. As a result, motor control unit 193 can efficiently generate the torque required to rotate rotor 402 by controlling the q-axis current in accordance with the load torque applied to rotor 402. That is, in vector control, the magnitude of the current vector shown in FIG.

[0042] The motor control unit 193 determines the rotation speed ω of the rotor 402 of the motor M2 by a method described below, and performs vector control based on the determination result. The CPU 190a outputs a command to drive the motor M2 to the speed command determiner 191. The command output from the CPU 190a includes a command speed ω_ref1 that indicates a target speed of the rotor 402 of the motor M2. The speed command determiner 191 generates and outputs a command speed ω_ref2 that indicates the target speed of the rotor 402 of the motor M2 based on the command speed ω_ref1.

[0043] A subtractor 601 calculates and outputs the deviation between the rotation speed ω of the rotor 402 of the motor M2 output from the speed determiner 514 and the command speed ω_ref.

[0044] The speed controller 502 acquires the deviation output from the subtractor 601 at a period T (for example, 200 microseconds). The speed controller 502 generates and outputs a q-axis current command value iq_ref and a d-axis current command value id_ref based on proportional control (P), integral control (I), and differential control (D) so that the deviation acquired from the subtractor 601 becomes small. Specifically, the speed controller 502 generates and outputs a q-axis current command value iq_ref and a d-axis current command value id_ref based on P control, I control, and D control so that the deviation acquired from the subtractor 601 becomes "0". Note that P control is a control method in which the value of a controlled object is controlled based on a value proportional to the deviation between a command value and an estimated value. I control is a control method in which the value of a controlled object is 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 in which the value of a controlled object is controlled based on a value proportional to the time change in the deviation between a command value and an estimated value. The speed controller 502 shown in FIG. 6 generates the q-axis current command value iq_ref and the d-axis current command value id_ref based on PID control, but the present invention is not limited to this. For example, the speed 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 affects the strength of the magnetic flux penetrating the windings 401a to 401d, is usually set to 0, but the present invention is not limited to this.

[0045] The drive currents flowing through the A-phase and B-phase windings 401a-401d of the motor M2 are detected by current detectors 507 and 508, and then converted from analog values ​​to digital values ​​by an A / D converter 510. The cycle at which the current detectors 507 and 508 detect the currents is, for example, equal to or shorter than the cycle T at which the speed controller 502 acquires the deviation (for example, 25 microseconds).

[0046] 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 the current values ​​iα and iβ in the stationary coordinate system by the following equation using the phase θe of the current vector shown in Figure 5. The phase θe of the current vector is defined as the angle between the α axis and the current vector. Furthermore, 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 a coordinate converter 511 and an induced voltage determiner 512 .

[0047] The coordinate converter 511 converts the current values ​​iα and iβ in the stationary coordinate system into a current value iq of the q-axis current and a current value id of the d-axis current in the rotating coordinate system using the following equations. 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 602 and the speed command determiner 191. The coordinate converter 511 also outputs the converted current value id to the subtractor 603. The speed command determiner 191 will be described later.

[0048] The subtractor 602 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. The subtractor 603 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.

[0049] The current controller 503 generates drive voltages Vq and Vd based on PID control so that the input deviations are each reduced. Specifically, the current controller 503 generates drive voltages Vq and Vd so that the input deviations are each reduced to "0" and outputs the drive voltages Vq and Vd to the coordinate inverse converter 505. That is, the current controller 503 functions as a means for generating drive voltages Vq and Vd. Note that the current controller 503 shown in FIG. 6 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.

[0050] The coordinate inverse converter 505 inversely converts the drive voltages Vq and Vd in the rotating coordinate system output from the current controller 503 into drive voltages Vα and Vβ in the stationary coordinate system using the following equations. Vα=cosθ*Vd-sinθ*Vq (5) Vβ=sinθ*Vd+cosθ*Vq (6) The coordinate inverse converter 505 outputs the inversely converted drive voltages Vα and Vβ to the induced voltage determiner 512 and the PWM inverter 506 .

[0051] The PWM inverter 506 has a full-bridge circuit. The full-bridge circuit is driven by a PWM (Pulse Width Modulation) 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 according to the drive voltages Vα and Vβ, and supplies the drive currents iα and iβ to the windings 401a to 401d of each phase of the motor M2, thereby driving the motor M2. In other words, the PWM inverter 506 functions as a supply means for supplying current to the windings 401a to 401d of each phase of the motor M2. Note that although the PWM inverter 506 shown in FIG. 6 has a full-bridge circuit, the PWM inverter 506 may also be a half-bridge circuit, etc.

[0052] Next, a method for determining the rotational phase θ will be described. The rotational phase θ of the rotor 402 is determined using the values ​​of induced voltages Eα and Eβ induced in the A-phase and B-phase windings 401a to 401d of the motor M2 by the rotation of the rotor 402. The values ​​of the induced voltages Eα and Eβ are determined (calculated) by an induced voltage determiner 512. Specifically, the induced voltages Eα and Eβ are determined by the following equations from the current values ​​iα and iβ input to the induced voltage determiner 512 from the A / D converter 510 and the drive voltages Vα and Vβ input to the induced voltage determiner 512 from the coordinate inverse converter 505. 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 winding resistance R and winding inductance L are specific to the motor 509 being used, and are stored in advance in ROM 190b or a memory (not shown) provided in the motor control unit 193. The induced voltages Eα and Eβ determined by the induced voltage determiner 512 are output to the phase determiner 513.

[0053] Based on the ratio between the induced voltages Eα and Eβ output from the induced voltage determiner 512, the phase determiner 513 determines the rotational phase θ of the rotor 402 of the motor M2 using the following equation. θ=tan^-1(-Eβ / Eα) (9) 6 determines the rotation phase θ by performing a calculation based on equation (9), but this is not limiting. For example, the phase determiner 513 may determine the rotation phase θ by referring to a table stored in the ROM 190b or the like that indicates the relationship between the induced voltages Eα and Eβ and the rotation phase θ corresponding to the induced voltages Eα and Eβ. The rotation phase θ of the rotor 402 obtained as described above is input to the coordinate inverse converter 505 , the coordinate converter 511 and the speed determiner 514 .

[0054] Based on the amount of change in the input rotation phase θ over a predetermined period, speed determiner 514 determines rotation speed ω of rotor 402. Specifically, speed determiner 514 determines rotation speed ω of rotor 402 based on the following equation (10): ω=dθ / dt (10) The rotation speed ω of the rotor 402 obtained as described above is input to a subtractor 601 .

[0055] As described above, the motor control unit 193 repeatedly performs the above functions (controls) to perform vector control, which controls the current value in the rotating coordinate system so as to reduce the deviation between the command speed ω_ref2 and the rotation speed ω. By performing vector control, it is possible to prevent the motor from going out of step, and to prevent an increase in motor noise and power consumption due to excess torque.

[0056] (Details of the speed command determiner 191) Next, the function (control) of the speed command determiner 191 will be described with reference to FIGS. 6 and 7. As shown in FIG. 6, the CPU 190a outputs a command speed ω_ref1 to a motor control unit 192 that controls the motor M1 that controls the rotation of the fixing roller pair 151. The motor control unit 192 performs, for example, the above-mentioned vector control based on the command speed ω_ref1. Note that the motor control unit 192 may also perform, for example, constant current control based on the command speed ω_ref1. This command speed ω_ref1 is also output to the speed command determiner 191.

[0057] 7, the speed command determiner 191 is configured to include a first calculation unit 191a and a second calculation unit 191b. A command speed ω_ref1 of the motor M1 is input as a first speed command value output from the motor control unit 192 to the first calculation unit 191a. As described above, the rotation speed of the fixing roller pair 151 is controlled based on the loop amount of the sheet S detected by the slack detection sensor 115. That is, the command speed ω_ref1 changes depending on the loop amount of the sheet S.

[0058] The first calculation unit 191a has a memory 1910a that stores the input command speed ω_ref1, and updates the memory 1910a every time the command speed ω_ref1 is input. The first calculation unit 191a generates a first adjustment value for adjusting a command speed ω_ref0 that is a reference speed command value, based on, for example, a value δω_ref obtained by subtracting the command speed ω_ref1 stored in the memory 1910a from the acquired command speed ω_ref1.

[0059] For example, when the value δω_ref is negative (i.e., the acquired command speed ω_ref1 is smaller than the command speed ω_ref1 stored in the memory 1910a), the first calculation unit 191a generates the first adjustment value as follows: Specifically, the first calculation unit 191a generates the first adjustment value so that the conveying speed of the pre-discharge roller pair 181 decreases by an amount corresponding to the decrease in the conveying speed of the fixing roller pair 151 that occurs when the command speed ω_ref1 decreases by the value δω_ref.

[0060] Furthermore, for example, when the value δω_ref is positive (i.e., the acquired command speed ω_ref1 is greater than the command speed ω_ref1 stored in the memory 1910a), the first calculation unit 191a generates the first adjustment value as follows: Specifically, the first calculation unit 191a generates the first adjustment value so that the conveying speed of the pre-discharge roller pair 181 increases by an amount corresponding to the increase in the conveying speed of the fixing roller pair 151 that occurs when the command speed ω_ref1 increases by the value δω_ref.

[0061] The second calculation unit 191b receives the current value iq of the q-axis current output from the coordinate converter 511. An increase in the current value iq means that the force with which the pre-discharge roller pair 181 pulls the sheet S downstream in the transport direction relative to the fixing device 150 has increased. A decrease in the current value iq means that the force with which the pre-discharge roller pair 181 pulls the sheet S downstream in the transport direction relative to the fixing device 150 has decreased. Note that here, the tension and deflection (slack) of the sheet S between the pre-discharge roller pair 181 and the fixing device 150 is detected using the current value iq, but is not limited to the current value iq and motor control information such as rotor position fluctuation may also be used.

[0062] The second calculation unit 191b has a memory 1910b that stores a reference value iq0 of the current value iq. The reference value iq0 is, for example, the average value of the current value iq within a predetermined period when the motor M2 is controlled at a command speed ω_ref0 and plain paper is transported by the pre-discharge roller pair 181 and the fuser roller pair 151, which rotates at a transport speed corresponding to a preset sheet transport speed. This reference value iq0 is stored in advance in the memory 1910b. Note that, although the memory 1910b described here stores only one reference value (i.e., the reference value does not depend on the paper type / transport speed), a reference value corresponding to the paper type / transport speed may also be stored in the memory 1910b.

[0063] The second calculation unit 191b generates a second adjustment value for adjusting the command speed ω_ref0 so that the acquired current value iq becomes the reference value iq0 stored in the memory 1910b. For example, if the acquired current value iq is smaller than the reference value iq0 stored in the memory 1910b, the second calculation unit 191b generates the second adjustment value as follows. Specifically, the second calculation unit 191b generates the second adjustment value so that the conveying speed of the pre-discharge roller pair 181 increases by an amount corresponding to the difference between the current value iq and the reference value iq0.

[0064] Furthermore, for example, if the acquired current value iq is greater than the reference value iq0 stored in the memory 1910b, the second calculation unit 191b generates the second adjustment value as follows: Specifically, the second calculation unit 191b generates the second adjustment value so that the conveying speed of the pre-discharge roller pair 181 is reduced by an amount corresponding to the difference between the current value iq and the reference value iq0.

[0065] The speed command determiner 191 outputs a command speed ω_ref2 as a second speed command value obtained by adding the first adjustment value calculated by the first calculation unit 191a and the second adjustment value calculated by the second calculation unit 191b to the command speed ω_ref0. Note that the command speed ω_ref0 is a speed command value that indicates the conveying speed of the sheet S by the paper discharge unit 180 when, for example, the fixing roller pair 151 is not thermally expanded.

[0066] Note that the fixing loop control ends when the trailing edge of the sheet S passes through the secondary transfer unit 110. Therefore, the speed command determiner 191 does not perform the process of adding the first adjustment value to the speed command value when the trailing edge of the sheet S passes through the secondary transfer unit 110. Note that the timing when the trailing edge of the sheet S passes through the secondary transfer unit 110 is determined based on, for example, the timing when the sheet detection sensor 107 (see FIG. 3) detects the leading edge of the sheet S, the length of the sheet S being conveyed, and the conveying speed of the sheet S.

[0067] [Motor M2 operating period and current value] Next, the operation period and current value of the motor M2 that drives the pre-discharge roller pair 181, the discharge roller pair 184, and the discharge vertical path roller pair 185 when transporting one sheet S will be described with reference to Fig. 8. In Fig. 8, the upper part shows the change in the speed command value of the motor M2, and the lower part shows the change in the current value (torque) of the motor M2.

[0068] 8, period D1 is the period before the above-described fixing loop control is performed. Period D2 is the period during which the fixing loop control is performed. Period D3 is the period from when the trailing edge of sheet S passes through the pair of secondary transfer rollers 111 and the fixing loop control ends until the trailing edge of sheet S passes through the pair of fixing discharge rollers 153. Period D4 is the period after the trailing edge of sheet S passes through the pair of fixing discharge rollers 153.

[0069] 8, current I1 is the average current value of motor M2. Current I2 is the current value of motor M2 in a state where sheet S is being transported by fixing device 150 before the leading edge of sheet S enters pre-discharge roller pair 181. However, current I2 is not limited to the current value before the leading edge of sheet S enters pre-discharge roller pair 181, and may be the current value of motor M2 immediately after the leading edge of sheet S enters pre-discharge roller pair 181.

[0070] [Drive control of motor M2] Next, general drive control of the motor M2 will be described with reference to Fig. 9. The process of the flowchart relating to drive control shown in Fig. 9 is executed by the CPU 190a. As described above, the conveyance speed of the sheet S in the paper discharge unit 180 located downstream of the fixing device 150 in the conveyance direction of the sheet S is controlled by controlling the rotation speed of the motor M2. This allows stable conveyance of the sheet S.

[0071] The speed command determiner 191 starts driving the motor M2, and acquires the current value of the motor M2 multiple times from time t1, a predetermined time after the start of driving, to a predetermined time t2 (see FIG. 8) (S101). The speed command determiner 191 calculates an average current value, which is the average value of the multiple current values ​​acquired from time t1 to time t2 (S102). In this way, the speed command determiner 191 acquires the average value of the current value supplied to the motor M2 over a predetermined period of time before the sheet S enters the pair of pre-discharge rollers 181.

[0072] The trigger for determining time t1 and time t2 is, for example, the time calculated from the start of driving of a registration motor (not shown) that drives the pair of registration rollers 106. It is desirable to set time t1 to avoid a period in which the current value of motor M2 is unstable at the start of its ramp-up. Therefore, time t1 is set to a timing after motor M2 starts to drive. Furthermore, the number of times to obtain multiple current values ​​used to calculate the average current value is determined taking into account the frequency of noise.

[0073] The speed command determiner 191 acquires a current value iq of the motor M2 at time t3 when the leading edge of the sheet S in the conveyance direction enters the pair of pre-discharge rollers 181, and calculates the difference between this current value and the calculated average current value (reference value iq0) as a "second difference (second adjustment value)." The speed command determiner 191 also calculates the difference between the speed command value of the motor M1 (command speed ω_ref1) and the average speed of the motor M1 (command speed ω_ref1 stored in the memory 1910a) at time t3 as a "first difference (first adjustment value)" (S103). These calculation processes are executed by the first and second calculation units 191a and 191b (see FIG. 7), as described above. When acquiring the current value of the motor M2 after the sheet S enters the pair of pre-discharge rollers 181, the acquisition interval and the number of acquisitions are determined taking into account the frequency of noise.

[0074] The speed command determiner 191 adds the second speed control value, which is generated by multiplying the second difference by a predetermined gain, and the first speed control value, which is the first difference, to the input speed command value (command speed ω_ref0) of the motor M2. This calculates the speed command value (command speed ω_ref2) of the motor M2 (S104). The addition of the first speed control value is continued until time t4, when the fixing loop control ends. That is, at time t4 (see FIG. 8), the speed command determiner 191 ends the addition process of the first speed control value (S105). After time t5 (see FIG. 8), when the rear end of the sheet S leaves the pair of fixing rollers 151 of the fixing unit 150, the speed command determiner 191 ends the addition process of the second speed control value (S106). After time t5, when the sheet S leaves the fixing unit 150, the addition process of the input speed command value of the motor M2 ends. As described above, speed control using the current value of the motor M2 is performed only when necessary, thereby reducing the processing load on the speed command determiner 191 (CPU 190a).

[0075] (Summary of motor M2 drive control) The temperature of the fixing roller pair 151 changes due to temperature control of the fixing unit 150, which changes the diameter, and therefore the conveying speed fluctuates. The pre-discharge roller pair 181 and the discharge roller pair 184 are heated by the fixed sheet S and expand in diameter, which also causes the conveying speed (actual speed) to fluctuate. As a result, it is difficult to predict the actual speed difference between the fixing roller pair 151 and the pre-discharge roller pair 181 and the discharge roller pair 184.

[0076] Therefore, by performing speed control using the current value (torque) of the motor M2, the rotation speed (i.e., conveying speed) of the pre-discharge roller pair 181 and the discharge roller pair 184 is adjusted to an appropriate value relative to the rotation speed (i.e., conveying speed) of the fixing roller pair 151. As a result, when the fixing loop control is not being executed, the sheet S is conveyed with an appropriate torque while maintaining an appropriate slack between the fixing roller pair 151 and the pre-discharge roller pair 181 and the discharge roller pair 184.

[0077] However, during the execution of the fixing loop control, the speed of the motor M1 is adjusted according to the amount of slack of the sheet S between the secondary transfer roller pair 111 and the fixing roller pair 151, which is detected by the slack detection sensor 115. This speed adjustment (speed change) causes tension and slack in the sheet S between the fixing roller pair 151 and the pre-discharge roller pair 181 and the discharge roller pair 184. It is difficult to respond to such speed changes due to the fixing loop control only by speed control using the current value (torque) of the motor M2.

[0078] Therefore, by feeding back the speed command value of the motor M1 to the speed command determiner 191 while the fixing loop control is being executed, it is possible to respond to the speed change due to the fixing loop control.

[0079] It is preferable that upper and lower limit values ​​be set for the command speed ω_ref2 output from the speed command decider 191. For example, when the command speed ω_ref2 increases due to noise, disturbance, or the like and exceeds the upper limit ωmax, the speed command decider 191 outputs ωmax as the command speed. On the other hand, when the command speed ω_ref2 decreases due to noise, disturbance, or the like and becomes smaller than the lower limit ωmin, the speed command decider 191 outputs ωmin as the command speed. By setting upper and lower limit values ​​in this way, it is possible to suppress large speed changes and prevent the speed from increasing or decreasing too much.

[0080] Furthermore, in the above description, the "second difference" is described as the difference between the average current value of motor M2 during the period from time t1 to time t2 and the current value of motor M2 from time t3 onward, but this is not limited to this. For example, the "second difference" may be the difference between the average current value as a reference current value, a value greater than this reference current value as a target current value, and the current value of motor M2 from time t3 onward. In this case, the target current value may be, for example, a value greater than 1.2 times the reference current value, or may be a value obtained by offsetting the reference current value by +10 Nm.

[0081] [Regarding slack in the sheet between the fixing roller pair 151 and the pre-discharge roller pair 181 and the discharge roller pair 184] The conveyance path from the pair of fixing rollers 151 to the pair of pre-discharge rollers 181 is passed by the sheet S, which has a large curl immediately after the fixing process, and therefore needs to be narrowed to suppress the curl, meaning that the space to allow slack in the sheet S is narrow. Therefore, it is not desirable to allow slack in the sheet S on the conveyance path from the pair of fixing rollers 151 to the pair of pre-discharge rollers 181.

[0082] The fixing roller pair 151 is pressurized for the fixing process, and the contact pressure between the rollers is set to be large. Therefore, the pressure with which the fixing roller pair 151 contacts the sheet S is relatively larger than the pressure with which the pre-discharge roller pair 181 and the discharge roller pair 184 contact the sheet S.

[0083] Therefore, by making the target current value of the motor M2 larger than the reference current value as described above, the torque of the motor M2 is controlled to be relatively large. As a result, when the sheet S is being transported by the fixing roller pair 151, the pre-discharge roller pair 181, and the discharge roller pair 184, the sheet S is transported in a state where it always slips slightly relative to the pre-discharge roller pair 181 and the discharge roller pair 184.

[0084] The speed command value ω_ref0 (see FIG. 7) before adjustment of the pre-discharge roller pair 181 and the discharge roller pair 184 may be a value greater than the speed command value of the fixing roller pair 151. In this case, the pre-discharge roller pair 181 and the discharge roller pair 184 are set to speeds that constantly pull the sheet S relative to the fixing roller pair 151. By setting them in this way, it is possible to prevent the sheet S from becoming loose due to a delay in control immediately after the sheet S enters the pre-discharge roller pair 181 or immediately after speed control using the current value of the motor M2 is performed.

[0085] [Drive control of motor M2 when transporting sheets from the discharge unit to the reverse discharge mechanism] Here, the drive control of the motor M2 when the sheet is transported from the sheet discharge unit to the reverse discharge mechanism will be described with reference to Fig. 10. Fig. 10 is a flowchart showing the drive control of the motors M2 and M3.

[0086] As described above, the sheet S is conveyed between the fixing roller pair 151 and the pre-discharge roller pair 181 by controlling the speed using the current value (torque) of the motor M2. Then, the sheet S is conveyed between the delivery vertical path roller pair 185 and the reversing roller pair 164 (see FIG. 3). In this case, the tension and slack between the delivery vertical path roller pair 185 and the reversing roller pair 164 are dominated by torque fluctuations due to the tension and slack between the delivery vertical path roller pair 181 and the fixing roller pair 151. Therefore, it is difficult to determine the tension and slack between the delivery vertical path roller pair 185 and the reversing roller pair 164 from torque information acting on the motor M2. Therefore, the rotational speed control of the motor M2 is reflected (synchronized) in the rotational speed control of the motor M3.

[0087] That is, as shown in Fig. 10, the processes of steps S101 to S106 described above are executed to control the rotation speed of motor M2. Then, in step S107, the speed control value of motor M2 obtained by the addition process of the first speed control value and the addition process of the second speed control value is reflected as the speed control value of motor M3. As a result, motor control unit 194 drives and controls motor M3 using the speed control value of motor M3 (i.e., the speed control value of motor M2). This makes it possible to prevent tension or slack from occurring between the paper discharge vertical path roller pair 185 and the reversing roller pair 164.

[0088] [When no conveying device is installed, when the first conveying device 700 is installed, and when the second conveying device 800 is installed] Next, referring to FIGS. 11 to 13, the following cases will be described: when no conveying device is installed in the space SP, which is the sheet discharge space of the image forming apparatus 100, and when the discharge trays 160, 161 are installed as discharge stacking sections; when the first conveying device 700 is installed as the conveying device; and when the second conveying device 800 is installed as the conveying device. FIG. 11(a) is a schematic diagram showing the configuration when no conveying device is installed. FIG. 11(b) is a schematic diagram showing the configuration when the first conveying device 700 is installed. FIG. 11(c) is a schematic diagram showing the configuration when the second conveying device 800 is installed. FIG. 12 is a flowchart showing the control of the motor M2 according to this embodiment. FIG. 13 is a flowchart showing the control of setting a target current value according to this embodiment.

[0089] 11(a), 11(b), and 11(c), the paper discharge unit 180 is disposed above the secondary transfer unit 110 and the fixing device 150. That is, the sheet S is conveyed to the paper discharge unit 180 from bottom to top inside a conveyance path oriented in the Z direction, which is the up-down direction. Therefore, in the paper discharge unit 180, the pre-paper discharge roller pair 181 is disposed so that a first nip line LN1, which is a tangent to the nip portion formed by the pair of rollers, faces in the Z direction or approximately in the Z direction. On the other hand, the paper discharge roller pair 184 is disposed so that the direction of a second nip line LN2, which is a tangent to the nip portion formed by the pair of rollers, approaches the X direction, which is the horizontal direction, relative to the direction of the first nip line LN1. Between the pre-discharge roller pair 181 and the discharge roller pair 184 in the conveyance direction of the sheet S, an upper guide 302 and a lower guide 303 serving as a first guide unit form a conveyance path 301, which serves as a first conveyance path that is curved when viewed in the width direction (front-rear direction) of the sheet. That is, the conveyance path 301 is formed so that its upstream end in the conveyance direction faces the first nip line LN1 and its downstream end in the conveyance direction faces the second nip line LN2. In other words, the conveyance path 301 is formed so that it curves from the up-down direction and gradually faces the horizontal direction as it progresses in the conveyance direction, and the sheet S discharged from the apparatus main body 101 is discharged facing diagonally upward. The width direction (front-rear direction) of the sheet is a direction perpendicular to the up-down direction (Z direction) and the horizontal direction (X direction).

[0090] 11(a), when a first conveying device 700 or a second conveying device 800 (described later) is not installed in the space SP serving as an installation section, the paper discharge trays 160 and 161 are installed and disposed in the space SP (see FIG. 1). Note that, in the present embodiment, the paper discharge trays 160 and 161 are described as being installed in the space SP, but it is also possible that nothing is installed in the space SP and the top surface of the device main body 101 (the bottom surface of the space SP) is formed as the paper discharge tray.

[0091] When the discharge tray 160 is disposed in the space SP in this manner, the sheet S conveyed and discharged by the discharge unit 180 is conveyed in the first direction V1 from the discharge roller pair 184 through a virtual conveyance path 901, which serves as a third conveyance path facing downward from the second nip line LN2. Therefore, due to the rigidity of the sheet S, an upward force is generated inside the conveyance path 301, that is, a force that increases the bending of the sheet S to form an upward convex shape is generated. In this case, the sheet S slides against the upper guide 302 above, which may cause damage such as scratches or streaks to the sheet S, so measures are required to reduce the bending of the sheet S in the conveyance path 301.

[0092] 11(a), one possible solution to the situation where the discharge tray 160 is installed without installing a processing device in the space SP is to increase the target current value of the motor M2 above the reference current value. That is, when the sheet S is transported by the pair of fuser rollers 151, the pair of pre-discharge rollers 181, and the pair of discharge rollers 184, the pressure applied by the pair of fuser rollers 151 is large as described above, causing slippage in the pair of pre-discharge rollers 181 and the pair of discharge rollers 184. In this state, if the current value of the motor M2 is increased above the reference current value, the conveying forces (torque) of the pair of pre-discharge rollers 181 and the pair of discharge rollers 184 become relatively large. In this case, because the pair of pre-discharge rollers 181 is closer to the pair of fuser rollers 151 than the pair of discharge rollers 184 in the conveying direction, the conveying force of the pair of pre-discharge rollers 181 is pulled more by the pair of fuser rollers 151 than by the pair of discharge rollers 184. This allows the conveying force of the sheet S by the pair of discharge rollers 184 to be greater than the conveying force of the sheet S by the pair of pre-discharge rollers 181. This allows the pair of discharge rollers 184 to pull the sheet S more tightly than the pair of pre-discharge rollers 181, reducing the sagging of the sheet S in the conveying path 301 and reducing damage to the sheet S such as scratches and streaks.

[0093] 11(b), a case where a first conveying device 700 is installed in the space SP will be described. The first conveying device 700 is a device that relays and conveys the sheet S from the pair of paper discharge rollers 184 to a first processing device (not shown) that processes the sheet S when the first processing device is disposed downstream of the first conveying device 700 in the conveying direction of the sheet S. That is, the first processing device may be one of processing devices that performs binding, folding, cutting, punching, inspection, etc.

[0094] The first conveying device 700 has a pair of conveying rollers 710, 711 driven by a motor (not shown), and conveys the sheet S conveyed from the pair of discharge rollers 184 to a first processing device (not shown) by the pair of conveying rollers 710, 711. The first conveying device 700 is located at the most upstream side in the conveying direction, and has a conveying path 701 as a second conveying path along which the sheet conveyed by the pair of discharge rollers 184 is guided. The conveying path 701 is formed by an upper guide 702 and a lower guide 703. A second direction V2, which is a direction in which the sheet S is guided in the conveying path 701, is a direction upward relative to a second nip line LN2 of the pair of discharge rollers 184.

[0095] When the first conveying device 700 is installed in the space SP in this manner, the sheet S conveyed and discharged by the discharge unit 180 is conveyed from the discharge roller pair 184 in the second direction V2, which is directed upward from the second nip line LN2. Therefore, due to the sheet S's rigidity, a downward force is generated inside the conveying path 301, that is, a force that reduces the bending that causes the sheet S to be convex upward is generated. In this case, the sheet S slides against the lower guide 303 below, which may cause damage such as scratches or streaks to the sheet S, so measures are required to increase the bending of the sheet S in the conveying path 301.

[0096] 11(b), one possible solution to the problem of installing the first conveying device 700 in the space SP is to reduce the target current value of the motor M2 below the reference current value. That is, when the sheet S is conveyed by the pair of fixing rollers 151, the pair of pre-discharge rollers 181, and the pair of discharge rollers 184, the pressure applied by the pair of fixing rollers 151 is large, as described above, causing slippage in the pair of pre-discharge rollers 181 and the pair of discharge rollers 184. In this state, if the current value of the motor M2 is reduced below the reference current value, the conveying forces (torque) of the pair of pre-discharge rollers 181 and the pair of discharge rollers 184 become relatively small. In this case, since the pair of pre-discharge rollers 181 is closer to the pair of fixing rollers 151 than the pair of discharge rollers 184 in the conveying direction, the conveying force of the pair of pre-discharge rollers 181 is pulled more by the pair of fixing rollers 151 than by the pair of discharge rollers 184. This allows the conveying force of the sheet S by the pair of discharge rollers 184 to be smaller than the conveying force of the sheet S by the pair of pre-discharge rollers 181. This allows the pair of discharge rollers 184 to be in a state where they do not pull the sheet S as much as the pair of pre-discharge rollers 181, reduces the sagging of the sheet S in the conveying path 301, and reduces damage to the sheet S such as scratches and streaks.

[0097] Next, a case where a second conveying device 800 is installed in the space SP as shown in Fig. 11(c) will be described. The second conveying device 800 is a device that relays and conveys the sheet S from the pair of paper discharge rollers 184 to a second processing device (not shown) that processes the sheet S when the second processing device is disposed downstream of the second conveying device 800 in the conveying direction of the sheet S. That is, the second processing device may be one of the processing devices that performs binding, folding, cutting, punching, inspection, etc.

[0098] The second conveying device 700 has a pair of conveying rollers 810, 811 driven by a motor (not shown), and conveys the sheet S conveyed from the pair of discharge rollers 184 to a second processing apparatus (not shown) by the pair of conveying rollers 810, 811. The second conveying device 800 is located at the most upstream side in the conveying direction and has a conveying path 801 as a fourth conveying path along which the sheet conveyed by the pair of discharge rollers 184 is guided. The conveying path 801 is formed by an upper guide 802 and a lower guide 803. A third direction V3, which is a direction along which the sheet S is guided in the conveying path 801, is oriented in the same direction (parallel to) the second nip line LN2 of the pair of discharge rollers 184.

[0099] When the second conveying device 800 is installed in the space SP in this manner, the sheet S conveyed and discharged by the discharge unit 180 is conveyed from the discharge roller pair 184 in the third direction V3, which faces the same direction as the second nip line LN2. Therefore, due to the sheet S's rigidity, little force is generated in the vertical direction inside the conveying path 301, meaning that little force is generated to change the sag. In this case, there is little risk of damage such as scratches or streaks being generated on the sheet S, so no particular measures are required to change the sag of the sheet S in the conveying path 301.

[0100] 11(c), one possible solution to the situation when the second conveying device 800 is installed in the space SP is to set the target current value of the motor M2 to a reference current value. That is, when the sheet S is conveyed by the pair of fixing rollers 151, the pair of pre-discharge rollers 181, and the pair of discharge rollers 184, the pressure applied by the pair of fixing rollers 151 is large, as described above, causing slippage in the pair of pre-discharge rollers 181 and the pair of discharge rollers 184. In this state, if the current value of the motor M2 is set to a reference current value, the conveying forces (torque) of the pair of pre-discharge rollers 181 and the pair of discharge rollers 184 will be relatively equal to the reference. This allows the conveying force of the pair of discharge rollers 184 on the sheet S to be approximately the same as the conveying force of the pair of pre-discharge rollers 181 on the sheet S, maintaining the magnitude of sagging of the sheet S in the conveying path 301 and reducing damage to the sheet S, such as scratches and streaks.

[0101] (Control of the motor M2 according to this embodiment) Next, the control of the motor M2 according to this embodiment will be described with reference to Fig. 12 and Fig. 13. Fig. 12 is a flowchart showing the control of the motor M2 according to this embodiment. Fig. 13 is a flowchart showing the control for setting a target current value according to this embodiment.

[0102] In the control of the motor M2 according to this embodiment, as compared with the general control of the motor M2 (see FIG. 9), a control (S300) for setting a target current value to be applied to the motor M2 is added, as shown in FIG. 12. That is, before setting the target current value, an average current value is calculated, and control related to the speed control value of the motor M2 is performed based on the calculated average current value, while the current value to be applied to the motor M2 is set to the target current value.

[0103] 13, in the control for setting the target current value (S300), first, the CPU 190a acquires information (path information) about the transport path downstream of the paper discharge unit 180 in the transport direction (S301). That is, the transport path information is information about whether the first transport device 700 or the second transport device 800 is installed in the space SP. This information may be acquired, for example, as an electrical signal from a wiring connected when the first transport device 700 or the second transport device 800 is installed in the image forming apparatus 100, or may be information set as device information via the operation panel.

[0104] Next, the CPU 190a determines whether any transport device is installed in the space SP (S302). If any transport device is installed (Yes in S302), angle information of the transport path of that transport device is acquired (S303). That is, in this embodiment, for example, if the first transport device 700 is installed, an angle above the second nip line LN2 (see FIG. 11(b)) is acquired. Also, for example, if the second transport device 800 is installed, an angle the same as the second nip line LN2 (see FIG. 11(c)) is acquired. Note that this embodiment does not describe a processing device in which the transport path is angled below the second nip line LN2, but such a processing device may also be installed.

[0105] Next, when the angle information of the conveying path is an angle above the second nip line LN2 (see FIG. 11(b)), the CPU 190a selects, for example, target current value table A stored in ROM 190b (S304). When the angle information of the conveying path is the same angle as the second nip line LN2 (see FIG. 11(c)), the CPU 190a selects, for example, target current value table B stored in ROM 190b (S305). When the conveying device is not installed (No in S302) (see FIG. 11(a)), or when the angle information of the conveying path is an angle below the second nip line LN2, the CPU 190a selects, for example, target current value table C stored in ROM 190b (S306). Note that the current values ​​stored in target current value table A are relatively larger than the current values ​​stored in target current value table C. The current values ​​stored in the target current value table B are between the current values ​​stored in the target current value table A and the current values ​​stored in the target current value table C.

[0106] Next, the CPU 190a acquires information on the paper type of the sheet S, for example, included in the print job (S307). That is, the target current value tables A to C store different target current values ​​according to the paper type information. In particular, the higher the rigidity (stiffness) of the sheet S, the more susceptible it is to the vertical angle of the sheet S conveyed downstream from the pair of paper discharge rollers 184. Therefore, it is preferable that the higher the rigidity (stiffness) of the sheet S, the greater the change range of the target current value is set.

[0107] Then, the CPU 190a selects a target current value corresponding to the paper type information, which is information on the type of sheet, from one of the selected target current value tables A to C, and sets it as the target current value (S308). As a result, the target current value is applied to the motor M2, and a torque corresponding to the target current value is output, and the magnitude of the sag (amount of sag) in the conveying path 301 is controlled to a desired magnitude.

[0108] That is, when target current value table A is selected, the current value of motor M2 is relatively large and the torque of motor M2 is large, so that the deflection of conveying path 301 is likely to be large and sheet S is likely to separate from lower guide 303. In other words, sheet S is less likely to be pressed against lower guide 303. In this embodiment, the torque of motor M2 when target current value table A is selected is a relatively large first torque.

[0109] Conversely, when target current value table C is selected, the current value of motor M2 is relatively small and the torque of motor M2 is small, so that the deflection of conveying path 301 is likely to be small and sheet S is likely to separate from upper guide 302. In other words, sheet S is less likely to be pressed against upper guide 302. In this embodiment, the torque of motor M2 when target current value table C is selected is a second torque that is smaller than the first torque.

[0110] When target current value table B is selected, the current value of motor M2 approaches a reference value, and the torque of motor M2 approaches the reference value, so that the deflection of conveying path 301 tends to be normal, and sheet S tends to separate from upper guide 302 and lower guide 303. In other words, sheet S becomes less likely to be pressed against upper guide 302 and lower guide 303. In this embodiment, the torque of motor M2 when target current value table B is selected is a third torque that is smaller than the first torque and larger than the second torque.

[0111] [Summary of this embodiment] As described above, in the image forming apparatus 100 according to this embodiment, the CPU 190a controls the motor M2 so that the deflection of the sheet in the conveying path 301 is smaller when the direction in which the sheet S conveyed from the pre-discharge roller pair 181 is guided is the first direction V1 in the up-down direction than when the direction is the second direction V2 different from the first direction V1. This makes it possible to reduce damage to the sheet S in the conveying path 301.

[0112] In this embodiment, the motor M2 drives the pair of pre-discharge rollers 181 and the pair of discharge rollers 184, but even in this configuration, when the direction in which the sheet S conveyed from the pair of pre-discharge rollers 181 is guided is the first direction V1 in the up-down direction, the motor M2 is controlled so that the deflection of the sheet in the conveying path 301 is smaller than when the direction is the second direction V2 different from the first direction V1. This makes it possible to reduce damage to the sheet S in the conveying path 301.

[0113] In particular, when the direction in which the sheet conveyed from the pre-discharge roller pair 181 is guided is the first direction V1, the current value of the motor M2 is set so that the torque acting on the sheet from the pre-discharge roller pair 181 and the discharge roller pair 184 becomes a first torque, and when the direction in which the sheet conveyed from the pre-discharge roller pair 181 is guided is the second direction V2, the current value of the motor M2 is set so that the torque acting on the sheet from the pre-discharge roller pair 181 and the discharge roller pair 184 becomes a second torque that is smaller than the first torque. This makes it possible to adjust the degree of sagging of the sheet in the conveying path 301 even in a configuration in which the motor M2 drives the pre-discharge roller pair 181 and the discharge roller pair 184.

[0114] [Possibilities for other embodiments] In this embodiment, the pre-discharge roller pair 181 and the discharge roller pair 184 are driven by the same motor M2. However, the present invention is not limited to this. The pre-discharge roller pair 181 may be driven independently by a motor separate from the motor M2. In this case, the degree of slack of the sheet in the conveyance path 301 can be adjusted by adjusting the difference in conveyance speed (difference in rotational speed) between the pre-discharge roller pair 181 and the discharge roller pair 184, rather than by controlling the current value (torque). Therefore, even in this configuration, it is possible to control the second motor M2 that drives the discharge roller pair 184 so that the slack of the sheet in the conveyance path 301 is smaller when the direction in which the sheet conveyed from the discharge roller pair 184 is guided is a first direction V1 in the up-down direction than when the sheet is guided in a second direction V2 different from the first direction V1. In other words, the degree of slack of the sheet in the conveyance path 301 can be changed by changing the conveyance speed of the discharge roller pair 184 depending on the direction in which the sheet is conveyed from the discharge roller pair 184. Furthermore, in such a configuration, a separate motor that drives the pre-discharge roller pair 181 may be controlled to adjust the conveyance speed difference (rotational speed difference) between the pre-discharge roller pair 181 and the discharge roller pair 184.

[0115] In addition, in the present embodiment, the pre-discharge roller pair 181 is provided between the discharge roller pair 184 and the fuser roller pair 151 in the conveyance direction. However, this is not limiting, and the pre-discharge roller pair 181 may not be provided. In this case, a curved conveyance path 301 is provided between the discharge roller pair 184 and the fuser roller pair 151, and a conveyance speed difference (rotational speed difference) between the discharge roller pair 184 and the fuser roller pair 151 may be adjusted. Even with this configuration, when the direction in which the sheet conveyed from the discharge roller pair 184 is guided is a first direction V1 in the up-down direction, it is possible to control the second motor M2 that drives the discharge roller pair 184 so that the slack of the sheet in the conveyance path 301 is smaller than when the sheet is guided in a second direction V2 different from the first direction V1. In other words, the degree of slack of the sheet in the conveyance path 301 can be changed by changing the conveyance speed of the discharge roller pair 184 depending on the direction of the sheet conveyed from the discharge roller pair 184.

[0116] In addition, in this embodiment, roller pairs such as the fixing roller pair 151, the pre-discharge roller pair 181, and the discharge roller pair 184 are described as being composed of a pair of rollers, but this is not limited to this, and they may be composed of a rotating body such as a conveyor belt.

[0117] In the present embodiment, the first conveying device 700 and the second conveying device 800 are configured as relay devices that relay and convey sheets to a processing device such as a finisher that is arranged downstream in the sheet conveying direction of the image forming apparatus 100. However, the present invention is not limited to this, and the conveying device itself may be provided with a sheet processing function such as binding or punching a sheet.

[0118] In the present embodiment, the rotation speed of the pair of fixing rollers 151 is changed according to the amount of deflection between the pair of secondary transfer rollers 111 and the pair of fixing rollers 151 by performing fixing loop control, and therefore the rotation speed of the pair of paper discharge rollers 184 is changed accordingly. However, the rotation speed of the pair of paper discharge rollers 184 (motor M2) may be controlled to a constant speed that is faster than the rotation speed of the pair of fixing rollers 151.

[0119] In addition, in this embodiment, stepping motors are used as the motors M1 to M3, but other types of motors such as DC motors may also be used. Furthermore, the motors are not limited to two-phase motors, but may be, for example, three-phase motors. Furthermore, the motors are not limited to those with magnets in the rotor, but may be, for example, reluctance motors.

[0120] Furthermore, in this embodiment, the first conveying device 700 and the second conveying device 800 are described as being mounted in the space SP, that is, the space SP is described as being the mounting part, but it is also possible to physically form the space SP and consider the outer wall of the image forming device 100 as being the mounting part. [Explanation of symbols]

[0121] 100...Image forming apparatus / 111...Transfer roller pair (transfer rotor) / 115...Deflection detection sensor (deflection detection unit) / 151...Fusing roller pair (fusing rotor) / 160...Paper discharge tray (discharge stacking unit) / 181...Paper discharge front roller pair (first rotor, first roller pair) / 184...Paper discharge roller pair (fixing downstream rotor, second rotor, discharge rotor, second roller pair) / 190a...CPU (control unit) / 301...Conveying path (first conveying path) / 302...Upper guide (first guide unit) / 303...Lower guide (first guide unit) / 700...First conveying device (conveying device, (Second guide unit) / 701...Transport path (second transport path) / 800...Second transport device (transport device, third guide unit) / 801...Transport path (fourth transport path) / 901...Transport path (third transport path) / M1...Motor (first motor) / M2...Motor (second motor) / LN1...First nip line / LN2...Second nip line / S...Sheet / SP...Space (mounting unit) / V1...First direction / V2...Second direction / V3...Third direction / iq...Current value of q-axis current / ω_ref0...Reference speed command value / ω_ref1...First speed command value / ω_ref2...Second speed command value

Claims

1. a fixing rotor for fixing the image onto the sheet; a first motor that drives the fixing rotor; a downstream fixing rotor disposed downstream of the fixing rotor in a sheet conveying direction and configured to convey a sheet; a second motor that drives the fixing downstream rotating body; a first guide portion that forms a curved first conveying path between the fixing rotary member and the fixing downstream rotary member in the sheet conveying direction; a control unit that controls the first motor and the second motor, the control unit controls the second motor so that the deflection of the sheet in the first conveying path is smaller when the direction in which the sheet conveyed from the fixing downstream rotating body is guided is a first direction in the up-down direction than when the deflection is a second direction different from the first direction. An image forming apparatus characterized by:

2. a first rotating body disposed downstream of the fixing rotating body in the sheet conveying direction and configured to convey the sheet; the fixing downstream rotor is a second rotor disposed adjacent to the first rotor in the sheet conveying direction, the first conveying path is formed between the first rotating body and the second rotating body in the sheet conveying direction, the second motor drives the first rotating body and the second rotating body; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. The control unit a current value of the second motor is set so that a torque acting on the sheet from the first rotating body and the second rotating body becomes a first torque when a direction in which the sheet conveyed from the second rotating body is guided is the first direction; a current value of the second motor is set so that, when a direction in which the sheet conveyed from the second rotating body is guided is the second direction, a torque acting on the sheet from the first rotating body and the second rotating body becomes a second torque smaller than the first torque.

3. The image forming apparatus according to claim 2, wherein the image forming apparatus is a recording medium.

4. a mounting portion capable of mounting a second guide portion having a second conveyance path through which the sheet conveyed by the second rotating body is guided, downstream of the second rotating body in the sheet conveyance direction; When the second guide portion is not attached to the attachment portion, a third conveying path is formed along which the sheet conveyed by the second rotating body is guided, When the second guide unit is not attached to the attachment unit, the sheet conveyed by the second rotating body toward the third conveying path is guided in the first direction, When the second guide portion is attached to the attachment portion, the sheet conveyed by the second rotating body toward the second conveyance path is guided in the second direction, The control unit When the second guide portion is not attached to the attachment portion, a current value of the second motor is set so that a torque acting on the seat from the first rotating body and the second rotating body becomes the first torque; a current value of the second motor is set so that, when the second guide portion is attached to the attachment portion, a torque acting on the seat from the first rotating body and the second rotating body becomes the second torque; 4. The image forming apparatus according to claim 3, wherein the image forming apparatus is a recording medium.

5. the second rotor is a discharge rotor, the third conveying path is a conveying path through which the sheet is discharged to a discharge stacking section that stacks the sheet discharged by the discharge rotating body, the second guide portion is a conveying device that conveys the sheet discharged by the discharge rotor, the second conveying path is a conveying path along which the sheet is guided in the conveying device; 5. The image forming apparatus according to claim 4.

6. the control unit changes the first torque and the second torque depending on the type of seat.

4. The image forming apparatus according to claim 3, wherein the image forming apparatus is a recording medium.

7. the mounting portion is capable of selectively mounting the second guide portion and a third guide portion having a fourth conveyance path along which the sheet conveyed by the second rotating body is guided, When the third guide unit is attached to the attachment unit, the sheet conveyed by the second rotating body toward the second conveyance path is guided in a third direction between the first direction and the second direction in the up-down direction, the control unit sets a current value of the second motor so that, when the third guide unit is attached to the attachment unit, a torque acting on the seat from the first rotating body and the second rotating body becomes a third torque that is smaller than the first torque and larger than the second torque.

5. The image forming apparatus according to claim 4.

8. the second rotor is a discharge rotor, the second guide portion is a first conveying device that conveys the sheet discharged by the discharge rotating body, the second conveying path is a conveying path along which the sheet is guided in the first conveying device, the third guide portion is a second conveying device that conveys the sheet discharged by the discharge rotating body, the fourth conveying path is a conveying path along which the sheet is guided in the second conveying device; 8. The image forming apparatus according to claim 7,

9. the control unit changes the first torque, the second torque, and the third torque depending on the type of seat.

8. The image forming apparatus according to claim 7,

10. the first rotating body is a first roller pair, the second rotating body is a second roller pair, the second roller pair is disposed such that a direction of a second nip line of the second roller pair approaches a horizontal direction relative to a direction of a first nip line of the first roller pair, the first direction is a direction downward from the second nip line, the second direction is a direction directed upward from the second nip line; 3. The image forming apparatus according to claim 2, wherein the image forming apparatus is a recording medium.

11. a transfer rotor disposed upstream of the fixing rotor in the sheet conveying direction and configured to transfer an image onto the sheet; a slack detection unit disposed between the transfer rotor and the fixing rotor in the sheet conveying direction, the slack detection unit detecting a slack amount of the sheet; The control unit setting a first speed command value for a rotation speed of the first motor in accordance with a detection result of the deflection detection unit; adjusting a speed command value serving as a reference for the rotation speed of the second motor in accordance with the first speed command value and a current value of a q-axis current applied to the second motor, and setting a second speed command value for the rotation speed of the second motor; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

12. a fixing rotor for fixing the image onto the sheet; a first motor that drives the fixing rotor; a downstream fixing rotor disposed downstream of the fixing rotor in a sheet conveying direction and configured to convey a sheet; a second motor that drives the fixing downstream rotating body; a first guide portion that forms a curved first conveying path between the fixing rotary member and the fixing downstream rotary member in the sheet conveying direction; a mounting unit capable of selectively mounting a second guide unit having a second conveyance path through which the sheet conveyed by the fixing downstream rotor is guided, and a third guide unit having a fourth conveyance path through which the sheet conveyed by the fixing downstream rotor is guided, downstream of the fixing downstream rotor in the sheet conveyance direction; a control unit that controls the first motor and the second motor, When the second guide portion is attached to the attachment portion, the sheet conveyed from the fixing downstream rotating body is guided in a second direction in the up-down direction, When the third guide portion is attached to the attachment portion, a direction in which the sheet conveyed from the fixing downstream rotating body is guided is a third direction different from the second direction in the up-down direction, the control unit controls the second motor so that the deflection of the sheet in the first conveying path is greater when the direction in which the sheet conveyed from the fixing downstream rotating body is guided is the second direction in the up-down direction than when the direction in which the sheet is guided is the third direction. An image forming apparatus characterized by:

Images