JP6771953B2 - Image forming device - Google Patents

Description

The present invention relates to an electrophotographic image forming apparatus.

In an image forming apparatus, there is known a method of fixing an unfixed toner image formed on a sheet on a recording material by applying heat and pressure to the sheet. In Patent Document 1, the sheet is sandwiched and conveyed by the nip portion formed by the fixing film heated by the heater and the pressure roller, and the unfixed toner image is fixed on the sheet by the heat from the heater through the fixing film. The configuration to be made is disclosed.

JP-A-2007-101861

However, when the sheet is passed through the nip portion, a peeling discharge may occur between the fixing member (for example, the fixing film) and the rear end of the sheet. When a peeling discharge occurs between the fixing member and the rear end of the sheet, potential unevenness occurs between a portion where the peeling discharge occurs and a portion where the peeling discharge does not occur on the surface of the fixing member. When a plurality of sheets are continuously fixed in the image forming apparatus described in Patent Document 1, a peeling discharge occurs between the rear end of the preceding sheet and the fixing film, and the portion of the fixing film where the peeling discharge occurs. May come into contact with the image area of the next sheet. When the portion where the peeling discharge of the fixing member occurs comes into contact with the unfixed toner image of the subsequent sheet, the toner image on the sheet is distorted and becomes apparent as a streak-like image defect (hereinafter referred to as an image streak). There is a fear.

As will be described later, the present inventors have found a method of suppressing the appearance of image streaks due to peeling discharge by slightly widening the transfer interval between sheets. However, this method has a problem that the productivity can be reduced while the image quality can be improved.

On the other hand, the image streaks associated with the peeling discharge become more prominent in the halftone image, and not necessarily in the deliverables of all users. For users who place importance on image quality, it is not preferable that image streaks due to peeling discharge appear in the deliverables. However, for a user who mainly prints an image of a document, for example, the image streaks associated with the peeling discharge are often invisible, or even if they can be visually recognized, they are not noticeable. Such users are required not to reduce productivity, rather than taking measures against image streaks even after reducing productivity.

Therefore, an object of the present invention is to provide an image forming apparatus that can meet the needs of both a user who emphasizes productivity and a user who emphasizes image quality.

In order to achieve the above object, the present invention has an image forming portion that forms an unfixed toner image on the sheet, and a sheet having an unfixed toner image in which a surface layer containing a fluorine resin is formed by the image forming portion. A first rotating body that comes into contact with a surface, a second rotating body that has an elastic layer and cooperates with the first rotating body to form a nip portion, and a second rotating body for driving the second rotating body. The first rotating body has a drive motor, and the first rotating body rotates in accordance with the rotation of the second rotating body, and the image forming unit conveys a sheet continuously conveyed from the image forming unit. In the execution of the image forming process of continuously forming a toner image on a plurality of sheets made of the same type and size of the fixing portion for fixing the unfixed toner image formed by the above on the sheet. The period from when the rear end of the preceding sheet of the sheet passes through the nip portion to when the tip of the next sheet reaches the nip portion is the first period, and the rear end of the preceding sheet. The first sheet is conveyed so that the surface layer portion of the first rotating body in contact with the first rotating body comes into contact with the image area on the next sheet without contacting the margin area on the tip side on the next sheet. In the mode and the execution of the image forming process, the portion of the first rotating body whose period is longer than that of the first period and which is in contact with the rear end of the preceding sheet is the tip side on the next sheet. It is characterized by having a second mode for transporting the sheet and an execution unit for executing the second mode so as to be in contact with the central portion of the margin region in the transport direction of the sheet.

According to the present invention, it is possible to provide an image forming apparatus that can meet the needs of both a user who emphasizes productivity and a user who emphasizes image quality.

It is a figure which shows an example of an image forming apparatus. It is sectional drawing which shows an example of the fixing device. (A) is a diagram showing the configuration in the longitudinal direction of the induction heating device, and (b) is a diagram showing the configuration in the longitudinal direction of the inner core. It is a figure which shows the structure in the longitudinal direction of a fixing device. It is a figure which shows an example of the pressurizing mechanism of a fixing device. It is a figure explaining the structure of the fixing belt. It is a figure which shows the transition (xth sheet) of the surface potential of a fixing belt and the surface potential of a paper. It is a figure which shows the transition (during continuous paper-passing) of the surface potential of a fixing belt and the surface potential of a paper. It is a figure which shows the space between papers for each mode. It is a flowchart about setting of a mode. It is a figure which shows an example of the mode selection screen. It is a flowchart about control according to a mode. It is a block diagram which shows an example of the structure of a control system.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the components described in this embodiment are merely examples, and the present invention is not limited to those described in the embodiments.

[Example 1]
<Image forming device>
FIG. 1 is a diagram showing an example of an image forming apparatus. The image forming apparatus 1 applies heat and pressure to the image forming portions 200Y, 200M, 200C, 200K for forming an image on the recording material and the unfixed image formed on the recording material by an electrophotographic method to perform fixing processing. The fixing device 27 is provided. In this embodiment, as the image forming apparatus 1, an apparatus having a full-color intermediate transfer type image forming apparatus will be described as an example, but the present invention is not limited thereto. For example, it may be a direct transfer type device that directly transfers from the photoconductor drum 20 to the recording material without using the intermediate transfer belt 25 described later, or a device that forms a monochrome toner image (for example, a monochrome machine). It may be. Further, the image forming apparatus 1 may be a copying machine, a printer, a facsimile apparatus, or a multifunction device having a plurality of these functions.

A reading device 160 is provided on the upper part of the image forming device 1. The reading device 160 includes a document stand (mounting section) on which a document is placed by an operator, a document cover (cover section) for shielding the mounted document, and a CCD that reads image information of the document. A document reading unit is provided. In the image forming apparatus 1, the image forming is performed based on the image information read by the document reading unit in the reading device 160 as the operator inputs the copy start instruction in the operation unit 180. .. Further, information corresponding to the size, type, and number of sheets of the paper P on which the toner image should be formed is input by the operator from the operation unit 180. The size and type of the paper P on which the toner image should be formed are not limited to those for which instructions are input from the operation unit 180. For example, if there is no instruction from the operation unit 180, the size of the paper P on which the toner image should be formed may be adjusted to match the size of the document read by the reading device 160.

The image forming apparatus 1 of this embodiment can also be used as a printer. Specifically, the configuration is such that it can be connected to an external personal computer (not shown) via a LAN cable (communication line) (not shown), and based on the image information input from the connected external personal computer. Perform image formation. At that time, information corresponding to the size, type, and number of sheets P on which the toner image is to be formed is also input to the CPU (Central Processing Unit) 10 from the connected external personal computer. In the image forming apparatus 1, image forming is performed when image information is input from an external personal computer connected to the image forming apparatus 1. In this case, the image forming apparatus 1 receives an instruction to start printing together with image information from an external personal computer. Even if the image information is input from the connected external personal computer, the image information may not be executed immediately, and the image formation may be started after the print start instruction is input by the operation unit 180.

The operation unit 180 functions as an input means for inputting various information by the operator and a display means for displaying the information. In this embodiment, as shown in FIG. 11, the operation unit 180 has an operation button unit 180A for inputting an instruction by the operator and a display unit (information display unit) 180B for displaying various messages and the like. The display unit 180B is a touch panel type liquid crystal screen, and various messages are displayed and various operation buttons (keys) are also displayed. Various settings of the printing operation performed by the image forming apparatus 1 are also input by the displayed operation buttons. Instructions such as copy start and print start by the operator are also input from the operation unit 180.

Inside the main body 1A of the image forming apparatus 1, four image forming portions 200Y, 200M, 200C, and 200K corresponding to each color of Y (yellow), M (magenta), C (cyan), and K (black) are connected in series. Is located in. That is, a tandem method is adopted in which the process of creating a visible image is processed in parallel with each color of Y (yellow), M (magenta), C (cyan), and K (black).

Hereinafter, in order to prevent the description from becoming complicated, the four image forming portions of each color of Y, M, C, and K will be described by being represented by reference numeral 200, and the same applies to the following related process means. Further, the arrangement order of the image forming unit 200 of each color of Y, M, C, and K is not limited to that.

Each image forming unit 200 is provided with the following electrophotographic process means. That is, the photoconductor drum 20 as an image carrier that supports an electrostatic latent image on the surface corresponding to each color of Y, M, C, and K, the primary charging device 21, the exposure device 22, and the developing device 23. , A primary transfer device 24 and a cleaning device (not shown) are provided.

The photoconductor drum 20 is rotationally driven counterclockwise in FIG. The primary charging device 21 applies a voltage to uniformly charge the surface of the corresponding photoconductor drum 20, and the surface of the charged photoconductor drum 20 is exposed by the exposure device 22 corresponding to the image data. By doing so, an electrostatic latent image is formed on the photoconductor drum 20. Then, the electrostatic latent image on the photoconductor drum 20 is developed by the developing device 23 using toner (developer) and visualized as a toner image. In this embodiment, the toner is negatively charged by the developing device 23 and developed on the photoconductor drum 20.

The toner image on the photoconductor drum 20 developed by the developing device 23 is sequentially superposed on the intermediate transfer belt (intermediate transfer body) 25, which is an endless belt, by the primary transfer device 24 for primary transfer. After the primary transfer, the toner remaining on the photoconductor drum 20 is removed by a cleaning device (not shown).

The full-color toner image formed on the intermediate transfer belt 20 by superimposing the toner images of all colors Y, M, C, and K was subsequently fed to the secondary transfer device 26 by the secondary transfer device 26. The secondary transfer is collectively performed on the paper P as a recording medium (sheet). The opposing roller 34 inside the intermediate transfer belt 20 and the secondary transfer device 26 form a transfer nip portion via the intermediate transfer belt 20. The toner image formed on the intermediate transfer belt 20 is transferred to the paper P by the secondary transfer device 26 at the transfer nip portion.

Here, the paper P as a recording medium includes an image formed by the image forming apparatus 1, and includes, for example, an envelope and the like in addition to plain paper, coated paper, thick paper, and thin paper.

The cassette 31 is an accommodating portion for accommodating the paper P used for image formation. The paper feed roller 32 separates and feeds the paper P of the cassette 31 one by one. The paper P fed from the cassette 31 by the paper feed roller 32 is conveyed to the resist roller 33 and temporarily stopped by the resist roller 33. The resist roller 33 reaches the transfer nip portion so that the toner image formed on the intermediate transfer belt 20 at the transfer nip portion is transferred to a predetermined position on the paper P. The paper P is sent out to the transfer nip portion in accordance with the timing.

The paper P on which the toner image is transferred at the transfer nip portion is conveyed to the fixing device (fixing portion) 27.

The fixing device 27 heats and pressurizes the paper P carrying the unfixed toner image while being sandwiched and conveyed by the fixing nip portion N. As a result, the fixing device 27 fixes the toner image on the paper P to the paper P. Details of the fixing device 27 will be described later. The paper P fixed by the fixing device 27 is discharged to the paper ejection tray 28 by the paper ejection roller 35.

When an image is also formed on the back surface side, the paper P on which the toner image on the first surface (front surface side) is fixed by the fixing device 27 is inverted by the inversion path 29 and then transferred to the transport path 30. Be transported. Then, the paper P on which the toner image on the first surface (front surface side) is fixed by the fixing device 27 is conveyed to the transfer nip portion again, and the toner image is transferred to the back surface side. After that, the paper P on which the toner image is transferred to the back surface side is fixed by the fixing device 27 and then discharged to the paper ejection tray 28 by the paper ejection roller 35.

<Fixing device>
Next, the configuration of the fixing device 27 will be described with reference to FIGS. 2 to 6. FIG. 2 is a cross-sectional view showing an example of the fixing device. FIG. 3A is a diagram showing a configuration in the longitudinal direction of the induction heating device, and FIG. 3B is a diagram showing a configuration in the longitudinal direction of the inner core. FIG. 4 is a diagram showing a configuration in the longitudinal direction of the fixing device. FIG. 5 is a diagram showing an example of a pressurizing mechanism of the fixing device.

The fixing belt 100 as a fixing rotating body (rotating body) and the pressure roller 600 as a pressure rotating body (rotating body) cooperate with each other to form a fixing nip portion N as a pair of rotating bodies. The induction heating device 300, which will be described later, heats the fixing belt 100. The fixing belt 100 is an endless belt having a metal layer, and is induced and heated by an induction heating device 300 described later. The pressure roller 600 is arranged so as to be in contact with the outer circumference of the fixing belt 100. The pad member 101 provided inside the fixing belt 100 exerts a pressing force between the fixing belt 100 and the pressure roller 600, so that the fixing belt 100 and the pressure roller 600 form a fixing nip portion N. The fixing device 27 applies heat and pressure to the paper P that carries the toner image by sandwiching and transporting the paper P at the fixing nip portion N, and fixes the paper P. The fixing belt 100 comes into contact with the surface (sheet surface) of the paper P that carries the unfixed toner image.

The pad member 101 is a member that forms a fixing nip portion N by applying a pressing force between the fixing belt 100 and the pressure roller 600, and is held by a metal stay 102. The pad member 101 is a heat-resistant resin, and holds the fixing pad 103 on the pressure roller 600 side thereof. The fixing pad 103 is made of a metal such as stainless steel or a material having high hardness such as ceramics, has a thickness of about 1 mm, and has a shape extending in the longitudinal direction of the fixing belt 100.

The separation guide 106 is a guide member provided on the downstream side of the fixing nip portion N in the transport direction of the paper P so that the paper P passing through the fixing nip portion N does not wind around the fixing belt 100. The separation guide 106 is arranged at a certain interval (gap) from the fixing belt 100 so that the fixing belt 100 is not damaged by contact with the fixing belt 100. The separation guide 106 is engaged with a part of the flange 105 by an urging means such as a spring.

(Induction heating device)
The induction heating device 300 is a heating source (induction heating means) for inductively heating the fixing belt 100. The induction heating device 300 includes an exciting coil 301, an outer magnetic core 302, a coil holding member 303, and a power supply device (not shown). The exciting coil 301 is formed by using, for example, a litz wire as an electric wire, making it horizontally long and having a ship bottom shape, and winding it so as to face a part of the peripheral surface and the side surface of the fixing belt 100. The power supply device (excitation circuit) applies a high-frequency current of 20 to 60 kHz to the exciting coil 301 while the fixing belt 100 is rotating. The metal layer (conductive layer) of the fixing belt 100 is induced to generate heat by the magnetic flux generated by the exciting coil 301 due to the high frequency current. The outer magnetic core 302 covers the exciting coil 301 so that the magnetic flux generated by the exciting coil 301 does not substantially leak to other than the metal layer (conductive layer) of the fixing belt 100. The outer magnetic core 302 is made of a material having a high magnetic permeability such as ferrite that shields the magnetic flux so that the magnetic flux generated by applying a high frequency current to the exciting coil 301 can be used for heating the fixing belt 100 more efficiently. It is made of.

The coil holding member 303 is an electrically insulating resin having a thickness of about 2 mm that supports the exciting coil 301 and the outer magnetic core 302. The induction heating device 300 is arranged on the upper surface side of the outer peripheral surface of the fixing belt 100 with a predetermined gap (gap) in the fixing belt 100.

Further, inside the fixing belt 100, an internal core 104 is provided on the coil side of the stay 102 in order to perform induction heating more effectively. The inner core 104 is made of a material having a high magnetic permeability such as ferrite that shields the magnetic flux so that the magnetic flux generated by applying a high frequency current to the exciting coil 301 can be used for heating the fixing belt 100 more efficiently. ing.

Further, the fixing device 27 includes a temperature sensor TH1 that detects the temperature of the fixing belt 100. The temperature sensor TH1 is a temperature detection element such as a thermistor. The temperature sensor TH1 is provided so as to come into contact with the inner surface of the fixing belt 100 at the central portion in the longitudinal direction of the fixing belt 100. The temperature sensor TH1 is connected to the CPU 10. Based on the detection temperature input from the temperature sensor TH1, the CPU 10 controls the power input to the exciting coil 301 by the power supply device so that the fixing belt 100 is maintained at the target temperature (for example, 180 ° C.). There is. In this embodiment, the CPU 10 changes the frequency of the high-frequency current input by the power supply device based on the detection value of the temperature sensor TH1 so that the temperature becomes constant at 180 ° C., which is the target temperature of the fixing belt 100.

In this embodiment, the induction heating device 300 by the electromagnetic induction method is provided as the heating means of the fixing belt 100, but the heating means of the fixing belt 100 is not limited to this. For example, a heating source such as a halogen heater, a ceramic heater, or an infrared lamp may be provided inside the fixing belt 100. Further, the heating source of the fixing belt 100 may be provided outside the fixing belt 100. Further, a heating source for heating the pressure roller 600 may be further provided.

(Fixing belt)
FIG. 6 is a diagram for explaining the configuration of the fixing belt of the fixing device, and shows a cross section of the fixing belt 100. The fixing belt 100, which is an endless belt, has a slippery layer 100d, a base layer 100a, an elastic layer 100b, and a release layer 100c in this order from the inside to the outside.

The base layer 100a is a metal layer having an inner diameter of about 20 to 40 mm. As the base layer 100a of the fixing belt 100, an iron alloy, a nickel alloy, copper, silver, or the like can be appropriately selected. The fixing belt 100 of this embodiment has an outer diameter of 30 mm, and the inner diameter of the base layer 100a is about 29.6 mm.

The elastic layer 100b provided on the outer periphery of the base layer 100a is a heat-resistant rubber layer. The thickness of the rubber layer is preferably set within the range of 100 to 800 μm. In this embodiment, the thickness of the rubber layer is set to 200 μm in consideration of reducing the heat capacity of the fixing belt 100 to shorten the warm-up time and obtaining a fixing image suitable for fixing a color image. There is.

A release layer 100c is provided as a surface layer on the outer periphery of the elastic layer 100b, and the surface resistance of the fixing belt 100 is 1.0E + 6 (Ω) or more. The release layer 100c is a fluororesin (for example, PFA (perfluoroalkoxy alkane resin) or PTFE (polytetrafluoroethylene) layer. The release layer 100c is the surface layer of the fixing belt 100 and has a releasability to toner. Further, in this embodiment, the thickness of the release layer 100c is 40 μm. The release layer 100c contains carbon black in addition to the fluororesin within a range satisfying the above-mentioned surface resistance. It may be configured.

Further, on the inner surface side of the base layer 100a, a slippery layer 100d having high slidability may be provided in an amount of 10 to 50 μm in order to reduce the sliding friction with the temperature sensor TH1. In this embodiment, a 30 μm polyimide layer is provided as the slippery layer 100d, and heat-resistant grease as a lubricant is further applied to the surface thereof. As a result, the lubricity of the inner surface of the fixing belt 100 is maintained.

(Pressurized roller)
Further, the pressure roller (pressurized rotating body) 600 forming the fixing nip portion N with the fixing belt 100 includes a metal core metal 600a having an outer diameter of 30 mm, an elastic layer 600b which is a rubber layer, and a mold release. A layer 600c is provided. The release layer 600c is a surface layer of the pressure roller 600 and is a fluororesin layer (for example, PFA or PTFE).

(Pressurization mechanism)
The fixing device 27 includes a pressurizing mechanism 500 that presses the pad member 101 toward the pressurizing roller 600 side in order to form the fixing nip portion N. Both ends of the stay 102 holding the pad member 101 are fixed to the flange 105. The pressurizing mechanism 500 applies a pressing force to the flange 105 by the pressurizing spring 508.

FIG. 5 is a diagram showing an example of the pressurizing mechanism of the fixing device, and shows one end side of the fixing device 27 in the longitudinal direction. The pressurizing mechanism 500 includes a pressurizing cam 501, a pressurizing plate rotating shaft 502, a pressurizing cam rotating shaft 504, a pressurizing plate 505, a pressurizing adjusting screw 506, a pressurizing support plate 507, and a pressurizing spring 508.

The pressure support plate 507 is supported by the pressure plate rotation shaft 502 penetrating the front side plate 400 and the rear side plate 401, and is supported by the tip 507a portion provided at the tip of the pressure support plate 507. It is fixed to each of the side plate 400 and the rear side plate 401 by means such as screws.

The pressure plate 505 is pivotally supported by the pressure plate rotation shaft 502, and is rotatably provided about the pressure plate rotation shaft 502 with respect to the pressure support plate 507.

The pressure spring 508 is a spring that applies a load to the pressure plate 505. A pressure adjusting screw 506 is fastened to the pressure support plate 507. The seating surface of the pressure adjusting screw 506 shortens the spring length of the pressure spring 508 and applies a load to the pressure plate 505. Since the pressure plate 505 is rotatably supported by the pressure support plate 507 as described above, a moment is generated around the pressure plate rotation shaft 502 by the compressive force of the pressure spring 508.

Since the pressure plate 505 is arranged so as to abut against the flange 105, the flange 105 is pushed in the direction of the pressure roller 600 by the moment generated in the pressure plate 505, and the fixing nip between the pressure roller 600 and the fixing belt 100. Part N will be formed.

The pressing force applied by the pressure plate 505 to the flange 105 can be released by the pressure cam 501 pushing up the pressure plate 505. When releasing the pressing force, the pressure cam 501 having a predetermined eccentricity rotates around the pressure cam rotation shaft 504, pushes up the pressure plate 505, and releases the contact between the pressure plate 505 and the flange 105. The pressure plate 505 is rotated until the pressure is increased. As a result, the pressing force is released. Further, the pressing force (for example, 550N) is applied by rotating the pressurizing cam 501 from the state where the pressing force is released and bringing the pressurizing plate 505 into contact with the flange 105.

The pressurizing cam rotation shaft 504 is connected to the motor M1 of the pressurizing mechanism as a drive source, and the motor M1 of the pressurizing mechanism rotates the pressurizing cam rotating shaft 504 to rotate the pressurizing cam 501. Rotate. The motor M1 of the pressurizing mechanism is electrically connected to the CPU 10, and the CPU 10 operates the motor M1 of the pressurizing mechanism to determine the position of the pressurizing cam 501. The pressurizing mechanism 500 can take a pressurizing state in which the pressurizing plate 505 applies a pressing force to the flange 105 and a releasing state in which the pressing force is released.

Although the fixing device 27 has been described with reference to one end side in the longitudinal direction in FIG. 5, a similar pressurizing mechanism 500 is provided on the other end side in the longitudinal direction as shown in FIG. The pressure cam rotation shaft 504 and the pressure cam 501 on the other end side are also connected. The motor M1 of the pressurizing mechanism rotates the pressurizing cams 501 at both ends at the same time by rotating the pressurizing cam rotating shaft 504. As a result, the pressurizing mechanisms 500 at both ends can be simultaneously pressurized, and the pressurizing mechanisms 500 at both ends can be released at the same time.

Further, the fixing device 27 includes a drive motor M2 that rotationally drives the pressurizing roller 600. The drive motor M2 is connected to the core metal 600a of the pressurizing roller 600, and when the drive motor M2 of the pressurizing roller is driven, the pressurizing roller 600 is rotationally driven. The CPU 10 is connected to the drive motor M2 and controls the rotation / stop of the drive motor M2 of the pressurizing roller. The fixing belt 100 is driven to rotate by the pressure roller 600.

Here, the operation of the fixing device 27 in the case of executing the image forming process corresponding to the input print command is summarized. Here, the print command is an execution command for the image forming process to the image forming unit 200. The print command is, for example, a print start instruction input from the operation unit 180 or an external personal computer by the operator, or a copy start instruction input from the operation unit 180 by the operator.

First, the CPU 10 drives the motor M1 of the pressurizing mechanism to pressurize the pressurizing roller 600 against the fixing belt 100 to form the fixing nip portion N.

In the state where the fixing nip portion N is formed, the CPU 10 rotates the pressure roller 600 by the drive motor M2 of the pressure roller, and causes the fixing belt 100 to rotate in a driven manner. The CPU 10 maintains the fixing belt 100 at a predetermined temperature by the induction heating device 300.

In this state, the fixing device 27 fixes the toner image on the paper P by sandwiching and transporting the paper P carrying the unfixed toner image conveyed from the transfer nip portion side by the fixing nip portion N. .. When the fixing process is continuously performed on a plurality of sheets of paper P, the fixing belt 100 continues to rotate drivenly until the last paper P has passed through the fixing nip portion N.

When the final sheet P for the image forming process to be executed has passed through the fixing nip portion N, the CPU 10 stops the rotation of the pressurizing roller 600 and releases the pressurizing force by the pressurizing mechanism 500.

<Generation of peeling discharge trace>
When the paper P is passed through the fixing nip portion N, a peeling discharge may occur between the fixing belt 100 and the rear end of the paper P. When the peeling discharge occurs, the potential becomes high (on the positive side) at the portion where the peeling discharge of the fixing belt 100 occurs as a peeling discharge mark. When the portion of the fixing belt 100 in which the peeling discharge has occurred comes into contact with the unfixed toner image of the next paper P, the toner image on the paper P may be disturbed and become apparent as image streaks. Image defects due to peeling discharge traces refer to the manifestation of these image streaks. The details will be described below.

The phenomenon of peeling discharge traces will be described with reference to FIGS. 8 to 10.

FIG. 7 is a diagram showing changes in the surface potential of the fixing belt and the surface potential of the paper (xth sheet). FIG. 7 shows the surface potential of the xth sheet of paper P when a plurality of sheets of paper P are continuously passed through the fixing nip portion N in the image forming apparatus 1 of the present embodiment, and the fixing belt at that time. It shows the surface potential and transition of 100. The horizontal axis shows time and the vertical axis shows electric potential. The area between the dotted lines in FIG. 7 is the area during the passing of the xth sheet, and the area outside the dotted line indicates the space between the sheets.

FIG. 8 is a diagram showing changes in the surface potential of the fixing belt and the surface potential of the paper (during continuous paper passing). FIG. 8 shows the surface potential of the paper and the surface potential of the fixing belt 100 when a plurality of sheets of paper P are continuously passed through the fixing nip portion N in the image forming apparatus 1 of the present embodiment. The horizontal axis shows time and the vertical axis shows electric potential.

Here, the surface potential of the paper P is the surface potential of the paper P measured at the measurement point U (FIG. 2) on the downstream side of the fixing nip portion N.

Further, FIGS. 7 and 8 show a state when CS-680 manufactured by Canon is used as the paper P. The paper P that can be used in the image forming apparatus 1 is not limited to the CS-680 manufactured by Canon.

When the paper P passes through the fixing nip portion N, the surface of the fixing belt 100 is charged by triboelectric charging and / or peeling charging between the fluororesin layer (PFA in this embodiment) and the paper P, which is the surface of the fixing belt 100. To do. Due to this triboelectric and / or peeling electrification, the surface of the fixing belt 100 is negatively charged. As shown in FIG. 8, the surface potential of the fixing belt 100 gradually decreases as a plurality of sheets of paper P are continuously passed through the fixing nip portion N.

On the other hand, during continuous paper passing, the surface potential of the paper P changes on the zero side (plus side) as compared with the fixing belt 100 on any paper P. Further, when viewed one by one, the result was obtained that the surface potential of the paper P increased toward the rear end of the paper P as shown in FIGS. 7 and 8.

When the surface potential of the fixing belt 100 becomes negative due to the continuous passing of the paper P to the fixing nip portion N, the potential difference between the paper P and the fixing belt 100 becomes large, and discharge is likely to occur. Then, at the time of passing the xth sheet in a state where the potential of the fixing belt 100 is low, a discharge (peeling discharge) occurs between the fixing belt 100 and the rear end of the paper P. At the rear end of the paper P, the potential difference between the fixing belt 100 and the paper P is particularly large among the sheets of paper P.

When an electric discharge occurs between the fixing belt 100 and the rear end of the paper P, the surface potential of the fixing belt 100 becomes in contact with the portion where the electric discharge occurs (that is, the rear end of the paper P) as shown in FIGS. It has a particularly high potential value at the site where it was discharged. This is the peeling discharge mark on the fixing belt 100.

In addition, there is almost no change in the surface potential of the fixing belt 100 in the region between the papers during continuous paper passing. Therefore, the potential of the peeling discharge trace remains at the portion where the peeling discharge occurs on the fixing belt 100. At the portion on the surface of the fixing belt 100 where the peeling discharge occurs, the potential is partially high in the circumferential direction of the fixing belt 100. An unfixed toner image with weak toner adhesion to the paper P is supported on the paper P ((x + 1) th sheet) of the subsequent paper. Therefore, when the paper P ((x + 1) th sheet) of the succeeding paper is conveyed by the fixing nip portion N, the portion where the peeling discharge occurs on the surface of the fixing belt 100 comes into contact with the image region of the succeeding paper. , The potential of the peeling discharge trace disturbs the unfixed toner image on the paper P. As a result, the peeling discharge mark may become apparent as an image streak on the paper P ((x + 1) sheet) as a product, resulting in an image defect.

<Realization of image streaks due to peeling discharge traces>
According to the study, the present inventors have made contact with the margin area of the paper P before the part where the peeling discharge mark is generated comes into contact with the image area of the succeeding paper. It has been found that the appearance of image streaks in the image region can be suppressed.

FIG. 9 is a diagram showing the space between papers for each mode. In the following, an example will be shown in which a plurality of sheets are continuously formed on the same type of paper P (that is, paper of the same size, the same basis weight, and the same material). For example, when printing A4, plain paper, and 10 sheets.

The normal mode is a mode in which productivity is prioritized. In the normal mode, the inter-paper time is P1 (ms), and the portion corresponding to the rear end of the preceding paper (xth sheet) on the circumference of the fixing belt 100 is within the image area of the succeeding paper ((x + 1)th sheet). Come to Here, the inter-paper time is the subsequent paper ((x + 1) sheets) that is conveyed to the fixing nip portion N next to the leading paper after the rear end of the preceding paper (xth sheet) passes through the fixing nip portion N. It is the time (period) until the tip of the eye) passes through the fixing nip portion N. FIG. 9 shows a case where the distance between the papers in the normal mode is less than one circumference of the fixing belt 100.

The countermeasure mode for image defects due to peeling discharge traces (hereinafter referred to as the countermeasure mode) is less productive than the normal mode, and the paper-to-paper time is P2 (ms). That is, P2> P1. In the countermeasure mode, the portion of the peripheral surface of the fixing belt 100 that comes into contact with the rear end portion of the preceding paper (xth sheet) comes into contact with the margin area on the front end side of the following paper ((x + 1)th sheet). The inter-paper time P2 in the countermeasure mode is set to a time obtained from the peripheral length of the fixing belt 100 so that the portion of the fixing belt 100 in contact with the rear end portion of the preceding paper hits the margin area of the following paper. .. In FIG. 9, the portion where the space between the papers in the countermeasure mode comes into contact with the rear end portion of the preceding paper (xth sheet) on the peripheral surface of the fixing belt 100 is approximately one round of the succeeding paper ((x + 1)th sheet). The case where the space between the papers is in contact with the margin area on the tip side is shown.

Here, the margin area is an area in which the toner image is not formed by the image forming apparatus 1 regardless of the content of the image information formed on the paper P. The margin area is preset in the image forming apparatus 1. The margin area on the tip side is a margin area located on the tip side of the image area in the transport direction of the paper P. In FIG. 9, the margin area (tip margin) on the tip side of the subsequent paper ((x + 1) th sheet) is indicated by a shaded area. The image region is an region in which a toner image can be formed by the image forming apparatus 1.

The present inventors have made a study by forming a halftone image in an image region in which image streaks are likely to appear. As the paper P, CS-680 manufactured by Canon was used. In the normal mode, when a peeling discharge occurs between the rear end of the xth sheet P and the fixing belt 100, it is used as an image streak due to the peeling discharge mark in the image area of the (x + 1) th sheet P. The manifestation was confirmed. On the other hand, in the countermeasure mode, when a peeling discharge occurs between the rear end of the xth sheet P and the fixing belt 100, an image streak due to the peeling discharge mark is generated in the image area of the (x + 1) th sheet P. Was not visible.

Therefore, the space between the papers should be wider than in the normal mode, and the part where the peeling discharge mark is generated should be brought into contact with the margin area on the tip side of the succeeding paper before the part where the peeling discharge mark is generated comes into contact with the image area of the succeeding paper. Therefore, it is possible to suppress the appearance of image streaks in the image area of the subsequent paper.

When a peeling discharge occurs between the rear end of the xth sheet P and the fixing belt 100, the peeling discharge trace is eliminated by the idle rotation of the fixing belt 100, and then the (x + 1) third sheet P When contacting the image area, it takes about 120 seconds for idle rotation. On the other hand, when the portion where the peeling discharge mark is generated is brought into contact with the margin area on the tip end side of the subsequent paper as in the countermeasure mode, the peeling discharge mark takes about one circumference of the fixing belt 100. Can be eliminated. In the configuration of this embodiment, the time required for one round of the fixing belt 100 is about 304 (ms). Therefore, by bringing the part where the peeling discharge mark is generated into contact with the margin area on the tip side of the succeeding paper as in the countermeasure mode, the image streaks in the image area of the succeeding paper can be suppressed while suppressing a significant decrease in productivity. It is possible to suppress the manifestation.

Therefore, the image forming apparatus 1 widens the space between the papers with respect to the normal mode, and between the papers in contact with the margin area on the tip side of the succeeding paper before the portion where the peeling discharge mark is generated comes into contact with the image area of the succeeding paper. By executing the countermeasure mode for transporting the paper P, the appearance of image streaks is suppressed. As a result, it is possible to meet the needs of users who place importance on image quality rather than productivity.

By the way, the image streaks associated with the peeling discharge become more prominent in the halftone image, and not necessarily in the deliverables of all users. For example, for a user who mainly prints an image of a document, the image streaks associated with the peeling discharge are often invisible, or even if they can be visually recognized, they are not noticeable. Such users are required not to reduce productivity, rather than taking measures against image streaks even after reducing productivity. Therefore, the image forming apparatus 1 meets the needs of the user who emphasizes productivity rather than image quality by executing the normal mode in which productivity is emphasized.

Note that FIG. 9 shows an example in which the paper spacing in the normal mode is less than one circumference of the fixing belt 100 in terms of distance, but the paper spacing in the normal mode may be appropriately set depending on the configuration of the apparatus. .. That is, the distance between the papers in the normal mode may be one circumference or more of the peripheral length of the fixing belt 100. In this case, the inter-paper time P1 in the normal mode is longer than the time required for the fixing belt 100 to make one rotation. Even in this case, the space between the papers in the countermeasure mode is longer than that in the normal mode, and the part where the peeling discharge mark is generated is the subsequent paper before the part where the peeling discharge mark is generated comes into contact with the image area of the succeeding paper. Set between the papers to be in contact with the margin area on the tip side of.

Further, in FIG. 9, the space between the papers in the countermeasure mode is longer than the space between the papers in the normal mode, and the part where the peeling discharge mark is generated is before the portion where the peeling discharge mark is generated comes into contact with the image area of the subsequent paper. The shortest space between papers that comes into contact with the margin area on the tip side of the succeeding paper is used, but the limitation is not limited to this. The space between the papers in the countermeasure mode is longer than that in the normal mode, and before the part where the peeling discharge mark occurs comes into contact with the image area of the succeeding paper, the part where the peeling discharge mark occurs is the margin on the tip side of the succeeding paper. It may be set between the papers in contact with the area. For example, in FIG. 9, the portion of the paper in the countermeasure mode that comes into contact with the rear end portion of the preceding paper (xth sheet) on the peripheral surface of the fixing belt 100 is the subsequent paper ((x + 1)th sheet) after two laps. It may be between papers in contact with the margin area on the tip side of the paper. However, it is more preferable to set the space between shorter papers in order to suppress the decrease in productivity with respect to the normal mode as much as possible.

<Countermeasure mode setting>
In the image forming apparatus 1, the operator displays one mode on the operation unit 180 from any one of a plurality of modes including a normal mode for emphasizing productivity and a countermeasure mode for emphasizing image quality according to the needs of the user. It can be set on the unit 180B.

The control flow in which the mode is set will be described with reference to the flowchart shown in FIG. 10 and the block diagram shown in FIG. The control shown in the flowchart is performed by the CPU 10 functioning as an execution unit executing a control program stored in the built-in storage means. FIG. 10 is a flowchart relating to mode setting, and FIG. 13 is a block diagram showing an example of a control system configuration. The CPU 10 is electrically connected to the operation unit 180.

The storage means is not limited to the configuration built in the CPU 10, and a memory that is separate from the CPU 10 and is electrically connected to the CPU 10 is provided in the image forming apparatus 1, and the memory stores programs and data. It may be configured to function as a means.

When the operator inputs an instruction to display the mode selection screen on the operation unit 180 (S101), the CPU 10 causes the display unit 180B of the operation unit 180 to display the mode selection screen (S102). Specifically, as shown in FIG. 11, the CPU 10 causes the display unit 180B to display the "normal mode" softkey 180C and the "countermeasure mode" softkey 180D. FIG. 11 is a diagram showing an example of a mode selection screen.

When the "normal mode" softkey 180C is pressed on the mode selection screen (that is, when the selected mode is the "normal mode"), the CPU 10 sets the productivity-oriented normal mode (that is, when the selected mode is the "normal mode"). S103, S104). When the "countermeasure mode" softkey 180D is pressed on the mode selection screen (that is, when the selected mode is the "countermeasure mode"), the CPU 10 sets the countermeasure mode to emphasize image quality (S103). , S105). Image formation processing according to the mode is executed. The CPU 10 holds the information corresponding to the set mode in the storage means built in the CPU 10.

By doing so, the user can select the mode to be executed by the image forming apparatus 1 according to his / her own needs.

In the present embodiment, the image forming apparatus 1 can select or change the mode when the operator inputs an instruction to display the mode selection screen on the operation unit 180. After the mode is set, the mode executed by the CPU 10 is not changed unless the mode selected by the operator on the mode selection screen is changed. As a result, once the mode is set, the operator does not have to repeat the mode setting unless necessary.

The normal mode may be set as the initial setting. In this case, if the operator does not input an instruction to display the mode selection screen, the CPU 10 executes the normal mode. In addition, the operator can change from the initial setting on the mode selection screen.

In this embodiment, the case where there are two mode options, a normal mode for which productivity is emphasized and a countermeasure mode for which image quality is emphasized, is shown as an example, but other modes can be set by the image forming apparatus 1. The mode may be provided. Further, in the present embodiment, the mode is selected by pressing the soft key, but the mode may be selected by using the operation button unit 180A.

<Execution of image formation processing according to the mode>
Next, the execution of the image forming process according to the mode will be described with reference to the flowchart shown in FIG. 12 and the block diagram shown in FIG. FIG. 12 is a flowchart relating to control according to the mode. The control shown in the flowchart is performed by the CPU 10 functioning as an execution unit executing a control program stored in the built-in storage means. Further, as shown in FIG. 13, the CPU 10 is electrically connected to the image forming unit 200, and controls the image forming operation by the image forming unit 200. Further, the CPU 10 is connected to the registration roller motor M3, the paper feed roller motor M4, the intermediate transfer belt motor M5, and the fixing device 27, and controls the image forming operation, the fixing operation, and the paper P transfer. ..

When the CPU 10 receives the energization command of the image forming apparatus 1 (for example, the power switch is turned on), the CPU 10 shifts to the start-up control and then waits for the input of the print command. Here, the print command is an execution command for the image forming process to the image forming unit 200. The print command is, for example, a print start instruction input from the operation unit 180 or an external personal computer by the operator, or a copy start instruction input from the operation unit 180 by the operator.

When a print command is input while the CPU 10 is waiting for input of a print command, the CPU 10 includes sheet information including information corresponding to the size and basis weight of the paper P on which the toner image should be formed in the print command, and the type of sheet material. (S201, S202). This information is input from the operation unit 180 or an external personal computer as an instruction by the operator. In this embodiment, when the image forming process to be executed for the input print command forms a plurality of consecutive images on the same type of paper P (that is, paper of the same size, the same basis weight, and the same material). Is shown as an example. For example, when printing A4, plain paper, and 10 sheets.

Next, the CPU 10 refers to the storage means and determines the mode set in the image forming apparatus 1 (S203). The mode settings are as described above.

The CPU 10 executes the set mode. That is, the CPU 10 selectively executes a set mode from a plurality of modes including a normal mode that emphasizes productivity and a countermeasure mode that emphasizes image quality.

When the set mode is the "normal mode", the CPU 10 conveys the paper P to the fixing nip portion N so that the paper-to-paper time becomes the time P1 in which productivity is prioritized (S204).
The inter-paper time P1 is determined based on the sheet information acquired in S202. For example, the storage means holds a table in which the sheet information and the paper-to-paper time P1 are associated with each other in advance, and the CPU 10 determines the paper-to-paper time P1 by referring to the table based on the information acquired in S202. .. As described above, the inter-paper time is the subsequent paper (xth sheet) that is conveyed to the fixing nip portion N next to the preceding paper after the rear end of the preceding paper (xth sheet) passes through the fixing nip portion N ( This is the time until the tip of the (x + 1) th sheet) passes through the fixing nip portion N.

On the other hand, when the set mode is the countermeasure mode, the CPU 10 conveys the paper P to the fixing nip portion N so that the paper-to-paper time becomes the time P2 in which the above-mentioned image quality is prioritized (S205). Here, as described above, the inter-paper time P2 for the countermeasure mode is set so that the portion of the fixing belt 100 that comes into contact with the rear end portion on the peripheral surface of the fixing belt hits the margin area on the front end side of the following paper. It is the time between papers. The inter-paper time P2 is determined based on the sheet information acquired in S202. For example, the storage means holds a table in which the sheet information and the paper-to-paper time P2 are associated with each other in advance, and the CPU 10 determines the paper-to-paper time P2 by referring to the table based on the information acquired in S202. ..

Here, the transport of the paper P will be described more specifically. In this embodiment, the CPU 10 controls the motor M3 of the resist roller 33, and adjusts the inter-paper time by changing the time for stopping the next paper P of the preceding paper on the resist roller 33 in the normal mode and the countermeasure mode. When forming an image under the same conditions, the rotation speed of the pressurizing roller 600 is the same in the normal mode and the countermeasure mode.

Specifically, the CPU 10 is a paper feed roller of a paper feed cassette (here, cassette 31) in which the paper P for forming the toner image is stored in response to the print command input in S201. Drive the motor M4. As a result, the CPU 10 feeds the first sheet P of the print command input in S201 to the paper feed roller 32 from the cassette 31. The first sheet of paper P that has been fed is conveyed to the registration roller 33.

Further, the CPU 10 starts the operation of the image forming unit 200, the motor M4 of the intermediate transfer belt, and the fixing device 27. The CPU 10 causes the image forming unit 200 to form an image to be transferred on the first sheet P. The CPU 10 causes the registration roller 33 to send the paper P to the transfer nip portion at the timing when the toner image corresponding to the first sheet P on the intermediate transfer belt 25 reaches the transfer nip portion.

When the resist roller 33 finishes feeding out the first sheet P, the CPU 10 stops the second sheet P at the resist roller 33. The image forming unit 200 forms an image to be transferred to the second sheet P with a predetermined space following the image to be transferred to the first sheet P. The CPU 10 tells the image forming unit 200 that the interval between the toner image to be transferred to the first sheet and the toner image to be transferred to the second sheet is an interval corresponding to the paper-to-paper time according to the mode. Toner images are formed on the intermediate transfer belt 25. The inter-paper time according to the mode is the inter-paper time P1 in the normal mode and the inter-paper time P2 in the countermeasure mode.

The CPU 10 controls the motor M3 of the resist roller, and the toner image on the intermediate transfer belt 25 corresponding to the second sheet P formed at intervals of images based on the inter-paper time according to the mode is transferred. The paper P is fed out at the timing of reaching the nip portion. That is, in the normal mode, the CPU 10 causes the registration roller 33 to stop the second sheet P until the time between the sheets P and the first sheet P becomes P1, and in the countermeasure mode, the CPU 10 stops the second sheet P. The registration roller 33 stops the second sheet P until the time between the sheets and the sheet P becomes P2. As for the inter-paper time, as described above, after the rear end of the preceding paper passes through the fixing nip portion N, the tip of the succeeding paper conveyed to the fixing nip portion N next to the preceding paper is the fixing nip portion N. Refers to the time it takes to pass.

That is, the paper-to-paper time between the preceding paper and the succeeding paper in the fixing nip N is adjusted by the time stopped by the resist roller 33.

When the time to be stopped by the resist roller 33 elapses, the CPU 10 drives the motor M3 of the resist roller to rotate the resist roller 33 and start the transfer of the second sheet P. In the normal mode, the second sheet P that has passed through the transfer nip section passes through the fixing nip section N at the time P1 between the sheets and the first sheet P, and in the countermeasure mode, the first sheet sheet. It passes through the fixing nip portion N at the paper-to-paper time P2 with P.

Similarly, the CPU 10 controls the transfer of the third sheet P so that the inter-paper time with the second sheet P becomes the inter-paper time according to the mode in the transfer of the third sheet P. Hereinafter, the same applies until the last paper P corresponding to the input print command is conveyed.

In this way, the resist roller 33 is determined based on the sheet information by feeding out the paper P at the timing when the toner image on the intermediate transfer belt 20 corresponding to the subsequent paper P reaches the transfer nip portion. Achieves the transfer of paper P between papers.

Here, as an example, the set value of the inter-paper time when the A4 size paper P is passed is shown for each mode. In this embodiment, the fixing belt 100 has an outer diameter of 30 mm, a peripheral length of about 94 mm, and a margin size of 3.5 mm. Note that these values are examples and are not limited to these values. Further, the length of the A4 size paper P in the transport direction is about 210 mm.

The distance between the papers in the normal mode in which productivity is emphasized in this embodiment is about 30 mm. The inter-paper time P1 is calculated by dividing this by the rotation speed of the fixing belt 100 determined by the paper type. The paper spacing in the normal mode is a value determined from the productivity of the image forming apparatus 1, and is preset for each paper type and paper size. In this embodiment, since the peripheral length of the fixing belt 100 is about 210 mm, as shown in FIG. 9, the distance between the papers in the normal mode is less than one circumference of the fixing belt 100 in terms of distance.

Next, the setting of the inter-paper time in the countermeasure mode will be described. Since the portion of the fixing belt 100 in contact with the rear end of the leading paper is brought into contact with the margin area on the front end side of the trailing paper, here, the portion in contact with the rear edge of the leading paper is the margin on the front end side of the paper P. Set the target paper spacing based on the position of the area that contacts the central part in the transport direction. That is, the target paper spacing is the interval obtained by adding the value obtained by dividing the length of the margin portion by 2 to the length of one circumference of the fixing belt. Assuming that the fixing belt 100 has a diameter of 30 mm, a peripheral length of about 94 mm, and a margin size of 3.5 mm, the target paper spacing is about 92.5 mm. The inter-paper time P2 is calculated by dividing this by the rotation speed of the fixing belt 100 determined by the paper type.

The storage means of the image forming apparatus 1 holds in advance the value of the inter-paper time for each mode calculated in this way, and the CPU 10 sets the inter-paper time according to the set mode on the paper P. Control transport. When the set mode is the countermeasure mode, the CPU 10 may calculate the paper-to-paper time in the countermeasure mode as described above according to the acquired sheet information.

As a result, in the countermeasure mode, the space between the papers is adjusted so that the portion of the leading paper in contact with the rear end of the paper P falls within the margin area of the trailing paper. That is, when the countermeasure mode is executed, in the image forming apparatus 1, even if the peeling discharge mark is generated on the fixing belt 100 by the rear end portion of the xth sheet P, the portion where the peeling discharge mark is generated is (x + 1). ) Before contacting the image area of the third sheet, it contacts the margin area on the tip side of the (x + 1) th sheet. As a result, the peeling discharge trace on the fixing belt 100 can be alleviated, and it is possible to suppress the latent image streaks in the (x + 1) th image region.

In this embodiment, as a specific example of continuously forming a plurality of images on the same type of paper P (that is, paper of the same size, the same basis weight, and the same material), a case where A4 size paper P is used is taken as an example. As described above, the size of the paper P is not limited to this. Even when a paper P having the maximum width size (size in the direction orthogonal to the transport direction) that can be conveyed by the image forming apparatus 1 is used as the same type of paper P that continuously forms images on a plurality of sheets, this embodiment The image forming apparatus 1 of the above conveys the paper P in the paper-to-paper time according to the mode. That is, in the normal mode, the CPU 10 controls the transfer of the paper P so that the paper-to-paper time gives priority to productivity. In the countermeasure mode, the CPU 10 uses a paper in which the portion of the fixing belt 100 that comes into contact with the rear end of the leading paper (xth sheet) comes into contact with the margin area on the front end side of the succeeding paper ((x + 1)th sheet). The transport of the paper P is controlled so that the time is between. However, the values of the inter-paper time P1 and P2 may be different from the case where the A size paper P is used.

In this embodiment, the paper-to-paper time according to the mode is adjusted by the CPU 10 controlling the drive / stop timing of the resist roller 33, but the paper-to-paper time adjustment method is limited to this. Absent. For example, the CPU 10 may be configured to control the timing at which the paper feed roller 32 feeds out the paper P according to the paper-to-paper time according to the mode.

In this embodiment, in the image formation corresponding to the input print command, a constant paper-to-paper time (P1 in the normal mode, countermeasure mode) from the first sheet to the last paper P corresponding to the input print command. Then, the paper P is conveyed by P2). However, when the image formation process is interrupted due to, for example, the occurrence of jam or abnormal temperature rise of the member, the inter-paper time before and after the interruption is an exception, which is the inter-paper time according to the set mode. It does not have to be. For example, when a jam occurs in the countermeasure mode, the time between the xth sheet immediately before the jam occurs and the (x + 1) th sheet P immediately after the jam occurs is for the countermeasure mode. Even if the inter-paper time is not satisfied, the configuration is within the range of this embodiment.

As described above, the image forming apparatus 1 allows the operator to select one mode from any of a plurality of modes including a normal mode that emphasizes productivity and a countermeasure mode that emphasizes image quality, depending on the needs of the user. It can be set on the display unit 180B of the operation unit 180. As a result, the user can select the mode to be executed by the image forming apparatus 1 according to his / her needs.

As described above, when the normal mode is set, the image forming apparatus 1 executes the normal mode and puts the paper P on the fixing nip portion N so that the paper-to-paper time P1 gives priority to productivity. Transport. As a result, it is possible to meet the needs of users who place importance on productivity rather than image quality.

Further, as described above, the image forming apparatus 1 executes the countermeasure mode when the countermeasure mode is set. That is, in the image forming apparatus 1, when the countermeasure mode is set, the portion of the fixing belt 100 that comes into contact with the rear end portion of the preceding paper (xth sheet) is the succeeding paper ((x + 1) sheet). ), The paper P is conveyed to the fixing nip portion N so that the inter-paper time P2 for contacting the margin region on the tip side of) is set. As a result, it is possible to suppress the appearance of image streaks, and it is possible to meet the needs of users who place importance on image quality rather than productivity.

Therefore, it is possible to provide an image forming apparatus that can meet the needs of both a user who emphasizes productivity and a user who emphasizes image quality.

1 Image forming device 10 CPU
27 Fixing device 100 Fixing belt 180 Operation part 180B Display part 200 Image forming part 600 Pressurizing roller N Fixing nip part P paper

Claims (7)

An image forming part that forms an unfixed toner image on the sheet,
In cooperation with the first rotating body having an elastic layer and having a surface layer containing a fluorine resin in contact with a sheet surface having an unfixed toner image formed by the image forming portion, and the first rotating body having an elastic layer. It has a second rotating body forming a nip portion and a drive motor for driving the second rotating body, and the first rotating body is driven by the rotation of the second rotating body. A fixing portion that fixes an unfixed toner image formed by the image forming portion on the sheet while rotating and conveying a sheet that is continuously conveyed from the image forming portion .
In executing an image forming process for continuously forming a toner image on a plurality of sheets made of the same type and the same size, after the rear end of the preceding sheet among the plurality of sheets passes through the nip portion. The period until the tip of the next sheet reaches the nip portion is the first period, and the surface layer portion of the first rotating body in contact with the rear end of the preceding sheet is on the next sheet. In the first mode of transporting the sheet and the execution of the image forming process so that the sheet is in contact with the image area on the next sheet without touching the margin area on the tip side of the sheet, the period is the first period. A second portion of the first rotating body that is longer and is in contact with the rear end of the preceding sheet so as to contact the central portion of the front end side margin region on the next sheet in the sheet transport direction. An image forming apparatus comprising: a second mode of transporting a sheet and an execution unit for executing the sheet so as to be a period. It has an operation unit that receives an instruction of a mode to be executed by the execution unit from an operator.
When the first mode is instructed by the operation unit as the mode to be executed by the execution unit, the execution unit executes the first mode, and the execution unit executes the first mode. The image forming apparatus according to claim 1, wherein when the second mode is instructed as the mode to be executed, the second mode is executed. The operation unit has a display unit and has a display unit.
The display unit is characterized in that a screen for inputting an instruction of a mode to be executed by the execution unit among a plurality of modes including the first mode and the second mode is displayed by an operator's instruction. The image forming apparatus according to claim 2. When either the first mode or the second mode is instructed on the screen as the mode to be executed by the execution unit, the execution unit should be executed on the screen by the operator. The image forming apparatus according to claim 3, wherein the image forming process is executed in the same mode as long as the mode is not changed. The image forming apparatus according to any one of claims 3 or 4, wherein the display unit displays a plurality of mode options including the first mode and the second mode on the screen. .. The image forming apparatus according to any one of claims 1 to 5, wherein the first period is longer than the time required for the first rotating body to make one rotation. The image forming apparatus according to any one of claims 1 to 6, wherein the surface layer of the first rotating body is a layer made of a fluororesin.

Images