JP7130414B2 - image forming device - Google Patents

Description

The present invention relates to an image forming apparatus. An image forming apparatus forms a toner image (developer image) on a sheet-shaped recording medium (media, recording material, sheet) using an image forming process such as an electrophotographic process, an electrostatic recording process, or a magnetic recording process. It is something to do. For example, copiers, printers (laser beam printers, LED printers, etc.), facsimiles, multifunction machines thereof, word processors, and the like are included.

2. Description of the Related Art As an image forming apparatus such as a printer or a copier, it is well known that a toner image formed on a photoreceptor, which is an image carrier, is transferred onto a sheet of paper by an electrophotographic recording method, and then the toner image is fixed by a fixing device. ing. As a fixing device, a nip portion (fixing nip portion) formed by pressure contact between a fixing roller and a pressure roller, which are a pair of rotating bodies, heats the toner image by nipping and conveying paper carrying an unfixed toner image. A method of carrying out a fixing process is well known. In such an image forming apparatus, there is a case where a sheet conveying failure (jam) occurs, and a configuration for detecting it is widely put into practical use.

Here, in the following description, upstream and downstream are upstream and downstream with respect to the paper transport direction. In Patent Document 1, a paper sensor for detecting the presence of paper is provided on the downstream side of the fixing nip portion. A method for interrupting the imaging process is disclosed.

When the image forming process is interrupted due to the occurrence of a jam, the fixing device also stops driving, but the motor that drives the fixing device rotates due to inertia even if a stop command is received, and the trailing edge of the paper is pulled into the fixing device. Sometimes. In the configuration of Patent Document 1, when a jam occurs inside the fixing device, the motor driving the fixing device is braked to stop the motor abruptly, thereby reducing the pull-in of the trailing edge of the paper.

Further, when a jam occurs inside the fixing device, the operator removes the paper (jammed paper) remaining in the fixing device. A configuration is known in which removal of jammed paper is detected by a sensor that detects the presence or absence of paper as retention detection means (Patent Documents 2 and 3).

Japanese Patent Application Laid-Open No. 2002-200001 discloses a configuration in which a residual paper presence/absence sensor is provided upstream of a fixing nip portion. Further, Japanese Patent Laid-Open No. 2002-200013 discloses a method of detecting the removal of jammed paper by detecting the operation of a lever member with a photosensor, and a method of detecting the presence or absence of jammed paper by irradiating the back surface of the paper with infrared rays. is disclosed.

Further, Japanese Patent Application Laid-Open No. 2002-200001 discloses a configuration in which a sensor lever is provided in a guide section for introducing paper into the fixing device in order to detect the trailing edge of the paper drawn into the fixing device.

Japanese Patent Application Laid-Open No. 2005-181508 JP-A-6-175524 JP 2007-248790 A

2. Description of the Related Art In recent years, image forming apparatuses such as printers and copiers have been required to respond to higher speeds, and there is a tendency to increase the sheet conveying speed in fixing devices. In addition, there is a tendency to increase the size of the drive source and drive transmission device for driving the fixing device. As the paper transport speed in the fixing device increases and the inertia increases due to the increase in size of the driving motor, which is the driving source, the amount of rotation of the motor that drives the fixing device due to inertia after receiving a stop command increases. That is, the movement distance of the paper from the stop command until the paper conveyance is sufficiently stopped increases, and the length of the paper trailing edge pulled into the fixing device from the stop command to the time when the paper conveyance is sufficiently stopped increases. .

Here, if the jam that occurred inside the fixing device is a winding jam in which the paper wraps around the fixing rotator (for example, the fixing roller), the leading edge of the paper reaches the retention detection means on the downstream side of the fixing nip portion. do not do. Therefore, in order to detect that the jammed paper has been removed, it is necessary to detect the paper by the retention detection means on the upstream side of the fixing nip portion.

However, due to the above-described increase in the retraction length of the paper (sheet), there is a possibility that the retention detection means on the upstream side of the fixing nip portion cannot detect the trailing edge of the paper (sheet) that is retained in the fixing nip portion. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus capable of more reliably detecting sheets staying in a fixing nip portion due to occurrence of a jam.

A representative configuration of an image forming apparatus according to the present invention for achieving the above object includes an image forming unit that forms an unfixed toner image on a conveyed sheet;
first and second rotating bodies forming a nip portion for fixing an unfixed toner image on the sheet while conveying the sheet conveyed from the image forming section;
a jam detector that detects the occurrence of a jam;
a detector that detects the sheet remaining in the nip portion at a detection position on the upstream side of the nip portion with respect to the conveying direction of the sheet;
a controller that stops rotation of the first rotating body in response to the jam detecting unit detecting the occurrence of a jam;
A first sheet having a first length in the conveying direction, a first width size in a width direction perpendicular to the conveying direction, and a first basis weight is formed in the nip. section, the first rotating body conveys the first sheet while rotating at a first speed;
a second sheet having a length in the conveying direction that is a second length shorter than the first length, a length in the width direction that is the first width size, and a basis weight that is the first basis weight; is conveyed to the nip portion, the first rotor conveys the second sheet while rotating at a second speed slower than the first speed .

According to the present invention, it is possible to provide a device that can more reliably detect a sheet staying in the fixing nip portion when a jam occurs in the fixing device.

4A and 4B are diagrams of an example of sheet length and sensor arrangement in the fixing device of the first embodiment; Schematic diagram of the configuration of the image forming apparatus of the first embodiment Schematic cross-sectional view of main parts of the fixing device of Example 1 FIG. 10 is a diagram of an example of a state in which a sheet remains inside the fixing device; Block diagram of an example of a control system of an image forming apparatus Flowchart for explaining jam detection operation Flowchart diagram for explaining the jam processing operation A diagram of an example of an operation unit Example of paper setting screen Example of paper size setting screen Example of paper type selection screen FIG. 4 is a flow chart of print operation in the first embodiment; Example of notification screen (Part 1) Example of notification screen (Part 2) Another flow chart of the print operation in the first embodiment. diagram chart diagram diagram chart diagram FIG. 10 is a flow chart of print operation in the second embodiment; Another flow chart of the print operation in the second embodiment FIG. 10 is a flow chart of print operation in the third embodiment; FIG. 10 is a flow chart of print operation in the fourth embodiment;

<<Example 1>>
(Image forming section)
FIG. 2 is a schematic diagram of the configuration of the image forming apparatus 1 in this embodiment. This image forming apparatus 1 is a tandem system-intermediate transfer system four-color full-color laser beam printer (hereinafter referred to as a printer) employing an electrophotographic system. The printer 1 executes a printing operation (image forming operation: printing operation) corresponding to a print job (image forming job, print job) input from the host device 201 to the control unit 24 to produce a full-color or mono-color image formed product (result to print out (print out).

Sheet-shaped recording media (media, recording materials, sheets) on which a toner image can be formed by an image forming apparatus include, for example, plain paper, thick paper, envelopes, postcards, stickers, resin sheets, overhead projector sheets (OHT sheets ) etc. are included. In the following description, paper is used as an example of a recording medium on which a toner image is formed by an image forming apparatus. Although terms related to paper, such as paper feeding, paper feeding, and paper ejection, are used in the description, the material is not limited to paper.

A host device 201 is a personal computer, an image reader, a facsimile, a network, or the like. A print job is an image formation instruction to which print condition information such as image data, specified paper (sheet) type, basis weight, size, number of sheets, number of copies, layout, and post-processing is added.

Reference numeral 23 denotes an operation unit (user interface) for inputting various kinds of information to the control unit 24, and has a display unit (notification unit) 32 (FIG. 8) and an operation input unit 33, as will be described later. As will be described later, the control unit 24 controls all the devices of the printer 1 and the sequence control of the printing operation (FIG. 5).

The image forming unit 2 that forms a toner image on the conveyed paper P uses yellow (Y), magenta (M), and cyan (C), which are the three subtractive primary colors, and black (Bk). It has four image forming units U (Y, M, C, and Bk) that respectively form color toner images. It also has an endless intermediate transfer belt (hereinafter referred to as belt) 8 .

Each image forming unit U has electrophotographic process equipment such as a photosensitive drum 3, a charging roller 4, a laser scanner 5, a developing device 6, a primary transfer roller 7, and the like. To avoid complication of the drawing, reference numerals for these devices in the image forming units UM, UC, and UBk other than the image forming unit UY are omitted.

In the full-color mode, each image forming unit U forms Y, M, C, and Bk toner images on the photosensitive drum 3, respectively. Note that the electrophotographic principle and process for forming a toner image are well known, so the description thereof will be omitted. The toner images of the four colors are sequentially superimposed in a predetermined manner and primarily transferred onto the belt 8 from the photosensitive drum 3 of each image forming unit U. As shown in FIG. As a result, a superimposed color toner image of Y+M+C+Bk is formed on the belt 8 .

The toner image formed on the belt 8 is secondarily transferred onto the sheet P at the secondary transfer portion 16 which is a pressure contact nip portion between the belt 8 and the secondary transfer roller 15 . The paper P is separated and fed one by one from one of the first paper feed cassette 9, the second paper feed cassette 10, the large-capacity paper feeder 11, and the manual feed tray 12, which are paper feed units (sheet storage units). Then, it is conveyed to a pair of registration rollers (hereinafter referred to as registration rollers) 14 through a conveying path 13 .

The registration rollers 14 once receive the leading edge of the paper P, and straighten the paper P if it is skewed. The registration roller 14 is driven at a predetermined control timing in synchronization with the toner image on the belt 8 . By driving the registration roller 14, the paper P is conveyed to the secondary transfer portion 16, and the toner images on the belt 9 are secondarily transferred onto the paper P in sequence. After passing through the secondary transfer section 16, the sheet P is introduced into the fixing device (fixing section) 100 through the conveying path 17, where the toner image is thermally and pressure fixed.

In the single-sided print mode, the paper P exiting the fixing device 100 passes over the flapper 18 and is conveyed to the discharge tray 20 as a single-sided printed product by the pair of discharge rollers 19 and discharged.

In the double-sided printing mode, the single-sided printed paper P exiting the fixing device 100 is guided to the reversing conveying path 21 by the flapper 18 , and is conveyed back to the double-sided conveying path 22 . Then, it passes through the conveying path 13 again from the double-sided conveying path 22 and is conveyed to the secondary transfer portion 16 by the registration rollers 14 to receive the secondary transfer of the toner image on the second side. After that, as in the case of the single-sided print mode, the double-sided printed product is conveyed and discharged to the discharge tray 20 through the conveying path 17, the fixing device 100, the upper side of the flapper 18, and the discharge roller pair 19. .

In the case of the monochromatic mode, of the four image forming units, only the image forming unit required for forming a designated monocolor image performs image forming operation, and the other image forming units operate on the photosensitive drum 3. is idly rotated.

(fixing device)
FIG. 3 is a schematic cross-sectional view of a main part of the fixing device (fixing section) 100 in this embodiment. Here, in the following description, upstream and downstream are upstream and downstream with respect to the paper conveying direction (sheet conveying direction) Z. As shown in FIG.

The fixing device 100 has a fixing roller (first rotating member: heating member) 40 and a pressure roller (second rotating member: pressing member) 41 which are a pair of rotating members. The fixing roller 40 and the pressure roller 41 form a nip portion (heating nip portion, fixing nip portion) where the paper P from the image forming portion 2 is nipped and conveyed by rotating operation, and the toner image t on the paper (sheet) is heated and fixed. part) N cooperatively.

The fixing roller 40 is configured to have a diameter of 60 mm by arranging an elastic layer with a thickness of 3 mm on the outer peripheral surface of an aluminum cylindrical core metal. The elastic layer is an HTV (high temperature vulcanization) silicone rubber layer. A fluorine resin layer is arranged on the outermost layer.

The pressure roller 41 is configured to have a diameter of 45 mm by arranging an elastic layer with a thickness of 1 mm on the outer peripheral surface of an aluminum cylindrical core metal. The lower layer of the elastic layer is the HTV silicone rubber layer, and the fluorine resin layer is arranged on the outer peripheral surface of the HTV silicone rubber layer.

The fixing roller 40 and the pressure roller 41 are vertically arranged substantially in parallel, and both ends are rotatable via bearing members (ball bearings) between side plates on one end side and the other end side of a fixing device frame (not shown). supported by The pressure roller 41 is disposed so as to be able to come into contact with and separate from the fixing roller 40, and is pressed against the fixing roller 40 with a predetermined pressure by a pressure contact mechanism (not shown). A nip portion N having a predetermined width in the conveying direction Z of the paper P is formed between them. In this embodiment, the pressure roller 41 is pressed against the fixing roller 40 with a total pressure of approximately 784 N (approximately 80 kg).

Further, when the printer 1 is on standby, the pressing roller 41 is moved in a direction away from the fixing roller 40 against the pressing force of the pressing mechanism by a pressing release mechanism (not shown), so that the nip portion N is not formed. Retained in released state.

A halogen heater 40a serving as a heat source is non-rotatably arranged in the central portion inside the fixing roller 40 . When the heater 40a is turned on, the fixing roller 40 is heated from the inside. The surface temperature of the fixing roller 40 is detected by a thermistor TH as a temperature sensor, and the detected temperature information is fed back to the controller 24 . The control unit 24 controls the power supplied to the heater 40a based on the detected temperature information to be input so that the surface temperature of the fixing roller 40 is within a predetermined range.

The fixing roller 40 and the pressure roller 41 are connected to each other by a gear mechanism (not shown) through a gear fixed to one shaft end of each, and the gear mechanism is connected to a fixing motor 45 (see FIG. The driving force of (b)) is transmitted. This drive transmission causes the fixing roller 40 and the pressure roller 41 to rotate at a predetermined speed in the directions of arrows R40 and R41, respectively.

A first paper guide (sheet guide: hereinafter referred to as an entrance guide) 46 is arranged upstream of the nip portion N so as to guide the leading edge of the paper to the nip portion N. As shown in FIG. A second sheet guide (hereinafter referred to as an exit guide) 50 is arranged downstream of the nip portion N. As shown in FIG. The exit guide 50 is arranged so as to guide the sheet P separated from the fixing roller 40 after exiting the nip portion N in a direction in which the sheet P is discharged from the fixing device 100 .

During the printing operation of the printer 1 , in the fixing device 100 , the pressure roller 41 is pressed against the fixing roller 40 to form a nip portion N. As shown in FIG. Further, the fixing roller 40 and the pressure roller 41 are rotationally driven at a predetermined speed in the directions of arrows R40 and R41, respectively. Further, the fixing roller 40 is heated and controlled so that the surface temperature is within a predetermined range.

In this fixing device state, the sheet P bearing the toner image t is introduced from the image forming section 2 side into the nip portion N while being guided by the entrance guide 46 . The image surface of the paper P contacts the fixing roller 40, and the paper P is nipped and conveyed by the nip portion N, and the toner image t is heated and fixed. After exiting the nip portion N, the paper P is separated from the surface of the fixing roller 40 and guided by the exit guide 50 to exit the fixing device 100 .

(Paper detection means)
The printer 1 has a plurality of sheet sensors (sheet detectors, detectors) for detecting the presence of paper in the transport path of the paper P (on the transport path). An entrance sensor S1, which will be described later, is one of the plurality of sensors. An exit sensor S2, which will be described later, is one of the plurality of sensors.

The entrance guide 46 is provided with a sensor support base 47. The sensor support base 47 has a first paper detection section (first detector ( sheet detection section ) , detector, sheet sensor: hereinafter referred to as an entrance A sensor S1 is provided. The detection position where the paper P is detected by the entrance sensor S1 is upstream of the nip portion N in the transport direction Z. As shown in FIG.

When a plurality of sheet sensors are provided on the upstream side of the nip portion N in the printer 1, the entrance sensor S1 is the closest distance to the entrance of the nip portion N among the sensors provided on the upstream side of the nip portion N. is set to the closest detection position (first detection position). As the entrance sensor S1, there is a method of directly detecting the paper with a reflective photosensor.

The entrance sensor S1 in this embodiment is composed of a sensor lever 49 mounted rotatably around a rotation shaft 48 and a photointerrupter (sensor section) 42 . The sensor lever 49 has a contact portion 49b projecting upward from the upper surface of the inlet guide 46 while being urged to rotate in a standing direction by a spring (biasing portion) 43, and a shutter portion 49a for shielding the photointerrupter 42 from light. and The inlet guide 46 is formed with an opening (not shown) for allowing the contact portion 49b of the sensor lever 49 to protrude upward from the upper surface of the inlet guide 46. As shown in FIG.

In the free state, the sensor lever 49 is in a standing and rotating posture in which the abutment portion 49b projects upward from the upper surface of the inlet guide 46 as shown in FIG. When the sensor lever 49 is in this standing and rotating posture, the shutter portion 49a is moved to a position where the photointerrupter 42 is transmitted (opened). The controller 24 determines from the light transmission signal of the photointerrupter 42 that the sheet P does not exist at the position (detection position) of the entrance sensor S1.

In addition, the sensor lever 49 is easily pushed down in the paper conveying direction against the spring force of the spring 43 about the rotary shaft 48 by the contact of the paper P with the contact portion 49b. 4). When the sensor lever 49 is in this fallen and rotated posture, the shutter portion 49a moves to a position where the photointerrupter 42 is shielded. The controller 24 determines from the light shielding signal of the photointerrupter 42 that the paper P exists at the position of the entrance sensor S1.

When the paper P passes the position of the inlet sensor S1 and the trailing edge of the paper separates from the contact portion 49b of the sensor lever 49, the sensor lever 49 returns to the upright rotating posture. Along with this, the shutter portion 49a moves from the position where the photointerrupter 42 is blocked to the position where the light is transmitted, and the output signal of the photointerrupter 42 changes from the light blocking signal to the light transmitting signal.

That is, the control unit 24 detects the presence or absence of the paper P upstream of the nip portion N inside the fixing device 100 based on the light transmission signal and the light shielding signal of the photointerrupter 42 of the entrance sensor S1. In this embodiment, the output signal of the photointerrupter 42 is a light shielding signal, so that the presence of the sheet P at the position of the entrance sensor S1 is detected. Not limited to this, the entrance sensor S1 may be configured to detect the existence of the sheet P at the entrance sensor S1 position by detecting that the output signal of the photointerrupter 42 is a translucent signal.

The outlet guide 50 also includes a second sheet detection section (second detector ( sheet detection section ) , sheet sensor) for detecting the presence or absence of the sheet P downstream of the nip portion N inside the fixing device 100. , outlet sensor) S2. The detection position where the paper P is detected by the exit sensor S2 is downstream of the nip portion N in the transport direction Z. As shown in FIG. When a plurality of sheet sensors are provided on the downstream side of the nip portion N in the printer 1, the exit sensor S2 is the closest distance from the nip portion N to the exit of the nip portion N among the sensors provided on the downstream side of the nip portion N. to the closest detection position (second detection position).

As the outlet sensor S2, a configuration in which a photointerrupter or the like detects the operation of a lever member that operates upon contact with the paper, or a method in which a reflective photosensor directly detects the paper can be adopted. A photosensor that can perform detection without contacting the paper is more desirable because it does not affect the transportation of the paper or the image.

In this embodiment, a reflective photosensor is used as the exit sensor S2, and the presence or absence of the paper P is detected by irradiating the paper with a laser and detecting the reflected light. That is, it is determined from the reflected light detection signal of the photosensor that the paper exists at the position of the exit sensor S2, and from the reflected light non-detection signal it is determined that the paper does not exist at the position of the exit sensor S2.

In this embodiment, jam detection of the paper P inside the fixing device 100 is performed by a jam detection logic to be described later. FIG. 4 shows a state in which the fixing operation/control of the fixing device 100 is urgently stopped due to a jam of the paper P wrapped around the fixing roller 40 .

In this winding jam, the leading edge of the paper coming out of the nip portion N sticks to the fixing roller 40 and cannot be separated, so the exit sensor S2 does not detect the paper. The sensor lever 49 of the entrance sensor S1 is tilted by the sheet P whose conveyance has stopped due to the emergency stop of the fixing device 100, and remains in a rotating attitude. Continue to detect presence.

(control part)
FIG. 5 is a block diagram of the control system of the printer 1 and the fixing device 100. As shown in FIG. FIG. 5(a) is a block diagram of the printer controller. The control unit 24 (printer control unit 309) includes an arithmetic processing unit including a CPU, memory, etc., an input/output unit (I/O port), a communication interface, and other circuits for exchanging data with the outside. .

The control unit 24 exchanges various types of electrical information with the host device 201 and the operation unit 23, and controls the print operation of the image forming unit 2 comprehensively according to a predetermined control program and reference table. Further, the control unit 24 stores the input information, determines the printing conditions based on the stored information, and performs the printing operation under the predetermined conditions when executing the print job.

Further, when the operator inputs the information of the paper to be used from the operation part 23 or the like, the control part 24 sets the operating conditions of the fixing device 100 according to the type and basis weight of the paper to be printed. After waiting for the fixing device 100 to start up, the image forming section 2 is instructed to start writing. Thus, sheet transport control is performed.

(b) of FIG. 5 is a control block diagram showing a control target of a control unit related to control of the fixing device 100 among the control units shown in the control block diagram of (a). The sensor detection section 205 has an entrance sensor detection section 304 and an exit sensor detection section 305 . The entrance sensor detection unit 304 notifies the printer control unit 309 (control unit 24) of detection information detected by the entrance sensor S1, and the exit sensor detection unit 305 notifies the printer control unit 309 of detection information detected by the exit sensor S2. .

A fixing control unit (controller of the fixing unit) 206 has a fixing conveyance control unit (rotation control unit) 302 and a temperature adjustment control unit 303 . The fixing conveyance control section 302 rotates and stops the fixing motor 45 based on the rotation and stop instructions of the fixing roller 40 given from the control section 24 and the conveyance control section 300 . The temperature adjustment control unit 303 controls the temperature of the fixing roller 40 as instructed by the control unit 24, so that power is supplied to and stopped from the halogen heater 40a.

A control section (jam detection section) 24 detects the occurrence of a jam based on the output of the sensor detection section 24 . The control unit 24 has a system timer 301 for measuring the time after the printer 1 is powered on. The control unit 24 refers to the detection information notified from the entrance sensor detection unit 304 and the exit sensor detection unit 305 of the sensor detection unit 205 and the timer value of the system timer 301 to determine whether a jam has occurred in the fixing device 100 . When determining that a jam has occurred, the control section 24 notifies the conveyance control section 300 of the occurrence of a jam in the fixing device 100 .

The conveying control unit 300 instructs the fixing conveying control unit 302 to stop the fixing motor 45, and brakes the fixing motor 45 to make it stop suddenly. That is, when the fixing motor 45 is normally stopped, it is stopped by inertia due to power cutoff, and only when it is determined that the paper has jammed in the fixing device 100, the fixing motor 45 is stopped by the motor control IC (brake means: not shown). Perform control such that the brakes are applied to bring the vehicle to a sudden stop.

Due to the sudden stop by the brake, the amount of rotation due to inertia can be shortened to about one tenth of that in the case of stopping by power cutoff at normal times. However, in reality, inertia is slightly generated even when the brake is suddenly stopped (for example, about 50 mm in paper transport distance). Further, the transport control unit 300 instructs the fixing transport control unit 302 to rotate the fixing motor 45, and controls the rotational speed of the fixing motor 45 so that the fixing roller 40 rotates at a predetermined rotational speed. Further, the transport control section 300 also controls transport in the transport sections other than the fixing device.

(Jam detection logic in fixing device)
Next, the printing operation of the printer 1 of the present embodiment and the control operation in the case where a conveyance failure (jam) of the paper P occurs in the fixing device 100 will be described with reference to the flowchart shown in FIG.

Whether or not the paper P is jammed in the fixing device 100 is detected by an exit sensor S2 provided downstream of the nip portion N. FIG. The timer value of the system timer 301 is referred to after the registration rollers (registration roller pair) 14 start conveying the paper P in accordance with the image forming timing. If the exit sensor S2 cannot detect the sheet P even after a predetermined time has passed (the entrance sensor S1 detects the sheet), the control unit 24 determines that the sheet P has jammed inside the fixing device 100. FIG.

After the fixing motor 45 is started (step S101), the process waits for the registration rollers 14 to start conveying the paper P fed from any one of the paper feeding units 9 to 12 in accordance with the image forming timing (step S102). When the paper P starts to be conveyed by the registration rollers 14, the process waits for the paper P to reach the exit sensor S2 (S103). Then, when a predetermined time has passed since the start of driving of the registration roller 14 (at S106), it is determined that there is a possibility that the paper P has jammed inside the fixing device 100. FIG.

The predetermined time is the time required for the paper P, which has been started to be transported by the registration rollers 14, to be smoothly transported and reach the exit sensor S2. In other words, if the paper P cannot be detected by the exit sensor S2 (the paper is detected by the entrance sensor S1) even after the predetermined time has passed, it is determined that the paper P may have jammed inside the fixing device 100 . Then, the control unit 24 urgently stops the printing operation/control of the printer 1 including the fixing operation/control of the fixing device 100 .

In this embodiment, the starting point of the predetermined time is the start of driving of the registration rollers 14, but the starting point is not limited to this. For example, the starting point may be the timing at which a sheet sensor on the upstream side of the nip portion N with respect to the paper transport direction Z detects the presence of the paper.

As for the fixing motor 45, the motor control IC as a braking means applies a brake to the fixing motor 45 and controls the fixing motor 45 to abruptly stop (S107). As for the image forming section 2, the photosensitive drum motor (not shown) is stopped.

In addition, as will be described later, a message prompting the operator to clear the jam is displayed on the display section (notification section) of the operation section 23 .

If the paper P is normally conveyed and detected by the outlet sensor S2 within a predetermined time, the paper P is ejected from the fixing device 100 (S104). If there is more succeeding paper, the process returns to step S102. If there is no succeeding paper, the fixing motor 45 is stopped to end the printing operation (step S108). That is, when the fixing motor 45 is stopped at the end of the normal printing operation, it is stopped by inertia due to power interruption.

As described above, a brake function is added to the fixing motor 45, and the fixing motor 45 is suddenly stopped by the brake only when it is determined that the paper P has jammed in the fixing device. As a result, it is possible to minimize the amount of the jammed paper P that is further caught in the fixing device due to the inertia of the fixing motor 45, thereby facilitating post-processing when the paper P is jammed.

(Sensor placement, paper length, and jam stop)
Next, referring to FIG. 1, when the fixing device 100 is emergencyly stopped due to the detection of a jam that has occurred inside the fixing device 100, the distance until the paper P stops, the length of the paper P, the entrance sensor S1, and the exit A relationship with each detection position of the sensor S2 will be described. As described above, when an emergency stop of the fixing device 100 is caused by a jam that has occurred inside the fixing device 100, jam processing (removal of the jammed paper P) is performed by the operator. The printer 1 detects whether or not there is paper P remaining in the fixing device 100 in order to confirm that jam processing has been completed.

Let L be the length of the sheet P in the transport direction Z. As shown in FIG. From the first paper detection position (first sheet detection position) A1 by the entrance sensor S1 on the conveying path of the paper passing through the nip portion N to the second paper detection position (second sheet detection position) of the exit sensor S2 Let Ls be the distance between the detection units up to A2 (the length along the paper transport path). At this time, the first paper detection position A1 is at least the length of the paper P having the shortest length in the transport direction Z among the sizes of the paper P allowed to pass through the printer 1, where the distance Ls between the detection units is the length of the paper P. A position where the height is smaller than Lmin.

It is preferable that the first paper detection position A1 is as close to the nip portion N as possible in order to more preferably detect that the paper P remains in the nip portion N when a winding jam occurs. In the present embodiment, the first paper detection position A1 is set to the sensor lever 49 by the jam-stopped paper P when the paper P of the minimum length Lmin causes a winding jam when the conveying speed control described later is executed. The contact portion 49b of is set to a position where the contact portion 49b can be pushed down.

The sheet conveying speed at the nip portion N due to the rotating operation of the fixing roller 40 and the pressure roller 41 during the printing operation is assumed to be Vw (first conveying speed). At this conveying speed Vw, the sheet conveying distance until the fixing motor 45 is braked and suddenly stopped is assumed to be Lm. Let Tm be the waiting time (delay margin time) from the nominal time of paper detection by the exit sensor S2 based on the system timer 301 until the control unit 24 performs jam determination. Also, let Td be the delay time required from jam determination to start of abrupt stop by braking of the fixing motor 45 .

Let ΔL be the maximum distance that the trailing edge of the paper P advances from the jam determination by the controller 24 until the paper P stops (movement amount at stop: hereinafter referred to as movement amount after jam). .DELTA.L is the deceleration of the rotating operation of the pair of rotating bodies from jam determination when the fixing roller 40 and pressure roller 41, which are a pair of rotating bodies that are nipping and conveying the paper P at the nip portion N, stop driving due to jam determination. This is the movement amount of the paper conveyed in the nip portion N from the start to the stop.

The post-jam movement amount ΔL becomes maximum when the controller 24 determines that the paper P is jammed just before the second paper detection position A2. This is because the paper P may wind around the fixing roller 40 . At this time, the post-jam movement amount ΔL is
ΔL=Lm+Vw×(Tm+Td)
becomes.

Here, the waiting time (delay margin time) Tm will be described more specifically. If the leading edge of the paper does not reach the second paper detection position A2 detected by the outlet sensor S2 within 10.0 to 10.5 seconds after the reference time T1 (for example, the time at which the registration roller starts conveying the paper), If it is judged as a delay jam, it will be as follows. That is, the waiting time Tm in this case is the time from "time A=T1+10.0" to "time B=T1+10.5". If the exit sensor S2 does not detect the paper P even at time B, the controller 24 judges that a delay has occurred due to a paper conveyance failure, and that a jam has occurred.

Here, the range of 10.0 seconds to 10.5 seconds after is assumed to be an error in the transport speed that may occur when the same sheet P is transported. The time A is the shortest time at which the paper P reaches the nip portion N when conveyed without jamming.

When the length obtained by subtracting the post-jam movement amount ΔL from the length L of the sheet P in the transport direction Z is equal to or greater than the nip portion front-rear detection distance Ls (L−ΔL≧Ls), a jam has occurred. Even if the paper P winds around the fixing roller 40, the trailing edge of the paper P can be detected by the sensor S1.

That is, if the length of the paper P in the conveying direction, the arrangement of the sensors, and the rotational speed of the fixing roller 40 satisfy such a relationship, the following is obtained. When the rotation of the fixing roller 40 is stopped in response to detection of a jam while passing through the nip portion N, even if the paper P winds around the fixing roller 40, the paper P cannot be detected by the exit sensor S1. Even without it, the paper P can be detected by the entrance sensor S1.

In the fixing device 100 having such a positional relationship, it is possible to detect the presence of paper P stopped due to a jam occurring inside the fixing device by either the entrance sensor S1 or the exit sensor S2. Then, it is possible to preferably detect that the paper P remains inside the fixing device 100 .

A jam clearing operation when it is detected that the paper P remains inside the fixing device 100 will be described with reference to the flow chart shown in FIG. When the paper P is removed from the jammed state of FIG. 4, the entrance sensor S1 does not detect the paper P, so the controller 24 determines that the jammed paper P has been removed.

On the other hand, if the operator overlooks the stopped sheet P due to a jam occurring in the fixing device 100 and does not remove the sheet P from the jammed state shown in FIG. As a result, the shutter portion 49a continues to shield the photointerrupter 42, so that the entrance sensor S1 continues to detect the sheet P. As shown in FIG.

That is, the entrance sensor S1 functions as a detector that detects the paper P remaining in the nip portion N at a detection position upstream of the nip portion N in the paper transport direction. When the presence of jammed paper P is detected by the entrance sensor S1 (Y in S7-2), the control unit 24 displays the detection signal from the entrance sensor S1 to display the display unit 32 (FIG. 8) of the operation unit 23 while remaining inside the fixing device. A processing instruction for the jammed paper is displayed (S7-3). After this, when the operator completes the remaining paper processing according to the remaining paper processing display, the print signal is received again, and the printer 1 becomes ready for the printing operation.

On the other hand, even if the remaining paper is processed in this way and the entrance sensor S1 is in the paper non-detection state (N in S7-2), if the jam state in the printer 1 is not cleared (N in S7-4 ), the control unit 24 detects the location of the jam other than the fixing device 100 . Then, the jam processing of the detected jam occurrence location is displayed on the display section 32 of the operation section 23 (S7-6). After this, when the operator completes the jam processing according to the jam processing display, the print signal is received again, and the printer 1 becomes ready for printing (S7-5).

In the fixing device 100 as described above, even if the operator neglects to remove the jammed paper P, the paper remaining inside the fixing device is detected by the inlet sensor S1. Then, the error display continues without returning to the normal print mode.

(operation part)
FIG. 8 is a schematic diagram of the operation unit 23. As shown in FIG. The operation unit 23 has a display unit (notification unit) 32 and an operation input unit 33 . The operation input unit 33 is provided with a power switch 31, a numeric keypad 29 for inputting numerical values, a start key 30 for starting printing, a clear key 28, and the like.

The display unit 32 is a touch panel type liquid crystal screen. Various types of information (message display) can be displayed (notified) on the display unit 32 by the control unit 24, such as printer status, error information, jam information, and other information. The display unit 32 also displays various operation buttons (keys). The operator can also instruct printing conditions (various settings) by using the displayed buttons.

Using the display unit 32 and the operation input unit 33, the operator not only issues a print start command, but also sets the image quality of the image and inputs information (paper feed paper registration) can be performed. That is, the operation unit 23 functions as an input unit, and can select or input the length of the sheet to be used in the transport direction. Thereby, the control section (acquisition section) 24 can acquire information on the length of the paper sheets set in the paper feeding sections 9 to 12 in the conveying direction. The control unit 24 determines print conditions based on information input from the display unit 32 and the operation input unit 33, and performs print operations under predetermined conditions at the time of printing.

9A to 9C show examples of paper size input screens on the display unit 32 when paper is registered in the paper feed unit. FIG. 9A is the paper setting screen. Paper sizes are displayed on central buttons 321 to 324 corresponding to the first and second paper feed cassettes 9 and 10, paper feed device 11, and tray 12, respectively. If the paper to be used is a standard size (size defined by ISO, JIS, ANSI A-E, etc., A4, B5, Letter (LTR) size, etc.), the paper size detected by automatic size detection, which will be described later, is displayed. there is

If there is an irregular size other than the standard size or an error in the detection result, the screen shifts to a paper size input screen by selecting a "user setting size" button 326 after selecting a button corresponding to each paper feeding position.

FIG. 9B is a screen for inputting standard and irregular paper sizes. The length corresponding to the paper size can be set in windows 328 and 329 at the lower left of the screen using the numeric keypad 330 on the screen or the numeric keypad 29 of the operation input unit 33 .

FIG. 9C is a screen for selecting paper types such as plain paper, thick paper, thin paper, coated paper, and OHP. It is possible to move to the screen of FIG. 9C by selecting the setting button 325 after selecting the buttons 321 to 324 corresponding to the paper feed position of FIG. 9A. Since the paper type and paper thickness settings are not automatically detected, the operator must manually set them.

(Paper size detection in cassette)
Regarding the paper size detection method in the paper feed cassettes 9 and 10 and the large-capacity paper feeder 11 (storage unit for storing paper to be supplied to the image forming unit 2) shown in FIG. The configuration of the cassette 9 will be described.

At the bottom of the paper feed cassette 9, a bottom plate (not shown) is arranged to raise the paper stack P to an arbitrary position. The stacked sheet bundle 151 is regulated by a pair of side fences (moving members) 54 that are slidable (movable) in the width direction perpendicular to the feeding direction, and end fences (movable members) that are slidable (movable) in the feeding direction. member) 52. The side fences 54 and the end fences 52 are slid by the operator when the paper P is stacked on the paper feed cassette 9 .

The side fence 54 constitutes a side detection unit that detects the size of the sheet P in the horizontal direction. That is, the side fence 54 is an acquisition unit that acquires information corresponding to the size in the width direction orthogonal to the conveying direction of the sheets accommodated in the accommodation unit. The end fence 52 constitutes an end detector that detects the length of the sheet in the longitudinal direction. That is, the end fence 52 is an acquisition unit that acquires information corresponding to the size in the transport direction. The positions of the fences 52 and 54 are detected by a sensor (position detection section: not shown), and the detection information is input to the control section 24 .

Based on the input information, the control unit 24 can automatically detect the width direction and the length direction of the paper P set in the first paper feed cassette 9 . The same applies to the second paper feed cassette 10 and large capacity paper feeder 11 .

As for the manual feed tray 12, when the paper P is set on the tray 12, the irregular size input screen shown in FIG. 9B is automatically displayed on the display unit 32 of the operation unit 23. This saves the operator the trouble of manually inputting or manually selecting the paper size when the paper size (especially irregular paper size) cannot be detected by the paper size detection unit of the machine. .

(Handling of paper with a length that cannot be detected as remaining paper inside the fixing device at the paper transport speed Vw)
Next, under the setting of the paper transport speed Vw, the length obtained by subtracting the post-jam movement amount ΔL from the length L of the transport direction V of the paper P to be used is shorter than the nip front-rear detection distance Ls. The operation of the printer 1 when (L−ΔL<Ls) will be described. In the fixing device 100 of this embodiment, the rotational speed of the fixing roller 40 is determined based on the length of the sheet in the conveying direction. Therefore, when sheets having the same size and basis weight in the width direction orthogonal to the transport direction are compared, the rotational speed of the fixing roller 40 changes according to the length of the sheet in the transport direction.

Specifically, it is as follows. Assume that the first sheet has a length in the width direction of the first width size, a basis weight of the first basis weight, and a length L=L1 in the transport direction. When the sheet to be conveyed to the nip portion N is the first sheet, the control section 24 rotates the fixing roller 40 at the first speed to convey the first sheet. Here, the first speed refers to the time when the rotation of the first sheet of paper stops in response to the occurrence of a jam being detected by the jam detector while the sheet of paper is passing through the nip portion N. is the speed at which the presence of the first paper can be detected.

The second paper has the same length in the width direction as the first paper, the same width size as the first paper, the first basis weight as the first paper, and the first basis weight in the transport direction. It is assumed that L=L2, which is shorter than the length L1 of the sheet in the transport direction. Here, if the second sheet is conveyed to the nip portion N at the same conveying speed (first speed) as the first sheet is conveyed, the conveying direction length L2 of the second sheet is the second length at the nip portion N. The trailing edge of the second sheet cannot be detected by the inlet sensor S1 when the first sheet stops.

The controller 24 rotates the fixing roller 40 at a second speed slower than the first speed. That is, when the rotation of the fixing roller 40 stops in response to the occurrence of a jam being detected by the jam detector while a predetermined sheet of paper is passing through the nip portion N, the entrance sensor S1 detects the presence of the predetermined sheet of paper. is detectable, the fixing roller 40 is rotated.

For example, it is assumed that the range of the transport direction length of the paper that can be used in the image forming apparatus 1 is Lmin or more and Lmax or less, Lmin≦182 mm≦Lmax, and detection by the entrance sensor S1 is difficult when L≦182 mm. If so: If the length L of the paper P in the transport direction is Lmin≦L≦182 mm, the second speed is used, and if 182 mm<L≦Lmax, the first speed is used.

It should be noted that the rotation speed of the fixing roller 40 is such that the paper P is nipped in the nip portion N, and the speed of rotation of the paper P from the transport nip (for example, the transport roller pair, the transfer nip portion, etc.) on the upstream side of the nip portion N is It refers to the rotation speed when the end is missing.

Below, FIG. 10 is used as an example of specific control, and a detailed description will be given. FIG. 10 is a flow chart of paper setting work and printing operation. In summary, the control unit (determining unit) 24 determines whether “L≧Ls+ΔL” or “L <Ls+ΔL” is determined. Then, the printing operation of the printer 1 is controlled based on the determination result.

The control unit (acquisition unit) 24 makes the following determinations regarding the paper to be used. That is, when the paper size is input from the operation unit 23 or the paper size is detected by the above-described automatic detection in the paper feed cassettes 9 and 10 or the large-capacity paper feeder 11 (S10-1), the paper is is determined (S10-2).

L≧Ls+ΔL means that when a jam occurs in the fixing device 100 and the printing operation/control of the printer 1 including the fixing operation/control of the fixing device is urgently stopped, the trailing edge of the sheet P stopped by the fixing device is This is the case where the paper length is detectable by the entrance sensor S1. In this case, the paper setting is accepted by the control section 24, and the control section 24 shifts to the printing operation (S10-3).

The printing operation here is performed under the setting that the sheet conveying speed of the entire printer 1 including the rotating operation of the fixing roller 40 and the pressure roller 41 of the fixing device is set to a predetermined first conveying speed Vw. (normal print operation). That is, the control section 24 controls the number of rotations of the fixing roller 45 so that the sheet conveying speed becomes Vw. At this time, the moving speed of the surface of the fixing roller 45 becomes the first speed at which the paper conveying speed becomes Vw.

On the other hand, L<Ls+ΔL is the case where the trailing edge of the sheet P stopped at the fixing device 100 due to jamming is too long to be detected by the entrance sensor S1. In this case, the control unit 24 sets the sheet conveying speed (fixing rotation speed) in the fixing device 100 to a deceleration speed (second conveying speed) which is a predetermined lower speed than the first conveying speed Vw. ) to Vw' (S10-4). That is, the control section 24 controls the number of rotations of the fixing roller 45 so that the sheet conveying speed becomes Vw'. At this time, the moving speed of the surface of the fixing roller 45 becomes the second speed at which the paper conveying speed becomes Vw'.

In this embodiment, the setting of the paper transport speed from the paper feed units 9 to 12 to the fixing device 100 to the nip portion N of the fixing device 100 remains at the first transport speed Vw.

When the sheet conveying speed in the fixing device 100 is reduced from the speed Vw to the speed Vw', the rotational inertia of the fixing motor 45 is reduced. Therefore, when the fixing motor 45 is abruptly stopped by the brake, the amount of rotation until the rotation stops is reduced (Lm→Lm′), and the paper conveyed at the nip portion N between the delay margin time Tm and the delay time Td is reduced. The post-jam movement amount of P is also reduced (ΔL→ΔL′) (S10-5).

Then, under the condition that the setting of the sheet conveying speed in the fixing device 100 is changed from the speed Vw to the deceleration speed Vw', in S10-6, if L≧Ls+ΔL', the fixing device 100 stops due to a jam. The trailing edge of the paper P can be detected by the entrance sensor S1. However, in order to reduce the sheet conveying speed in the fixing device 100 from the speed Vw to the speed Vw', the control section 24 displays (notifies) a warning message on the display section (notification section) 32 as shown in FIG. 11 (S10- 7) Do. Then, when the operator selects the execution of the relief operation on the display, the process proceeds to the printing operation (S10-3).

The printing operation here is a relief operation. The paper transport speed is set at the speed Vw.

In S10-6, when L<Ls+ΔL', the control section 24 displays a warning message 340 on the display section 32 as shown in FIG. is grayed out and cannot be selected. This prompts the operator to change the paper (S10-9). Judgment for the changed paper size is performed in the same way in (S10-2).

According to the printer 1 of this embodiment, by changing the printing operation based on the operator's input or the length of the sheet in the conveying direction automatically detected by the printer, when a jam occurs in the fixing device 100, It is possible to suitably prevent paper from remaining inside the fixing device.

1) In the first embodiment, two values, Vw and Vw', were used as examples for setting the sheet conveying speed. may be

Regarding the paper to be used, the paper size input from the operation unit 23 or the paper size L detected by the above-mentioned automatic detection in the paper feed cassettes 9 and 10 or the large capacity paper feeder 11 is L≧Ls+ΔL. If you meet In this case, the printing operation is performed under the setting that the paper transport speed is set to the first transport speed Vw.

On the other hand, if L≧Ls+ΔL is not satisfied (that is, L<Ls+ΔL), the trailing edge of the paper P stopped at the fixing device 100 due to jamming at this paper transport speed Vw cannot be detected by the entrance sensor S1. is the case. Here, under the condition that the sheet conveying speed (fixing rotation speed) is changed from the first conveying speed Vw to a deceleration speed (second conveying speed) Vw′ which is a predetermined lower speed than the first conveying speed Vw. Then, when L≧Ls+ΔL′ is satisfied, the printing operation is performed at the speed Vw′.

If L≧Ls+ΔL′ is not satisfied under the condition changed to Vw′ (that is, L<Ls+ΔL′), a deceleration speed (second 3 conveying speed) Vw'', it is determined whether detection by the entrance sensor S1 is possible.

Assuming that the amount of movement of the paper P after jamming at the third conveying speed Vw'' is .DELTA.L'', if L.gtoreq.Ls+.DELTA.L'', the printing operation is executed at the third conveying speed Vw''. If L≧Ls+ΔL″ (that is, L<Ls+ΔL″), the user is prompted to change the paper as in S10-8 and S10-9 of FIG.

That is, when the length in the transport direction satisfies L≧Ls+ΔL, the sheet transport speed is set to the first transport speed Vw. When the length in the transport direction is L<Ls+ΔL and L≧Ls+ΔL′, the sheet transport speed is set to the second transport speed Vw′. When the length in the transport direction is L<Ls+ΔL′ and L≧Ls+ΔL″, the paper transport speed is set to the third transport speed Vw″.

2) In the present embodiment 1, regarding the determination in S10-2 of FIG. However, it is not limited to this.

For example, the memory in the control unit 24 stores in advance a paper transport speed setting (Vw or Vw') that satisfies L≧Ls+ΔL (or L≧Ls+ΔL') for each inputtable or detectable paper size. The control section 24 may be configured to control the sheet conveying speed based on the information in this memory. The relationship between the length of the paper in the transport direction and the paper transport speed is as described above. The same applies when the paper transport speed is set in three or more stages (Vw, Vw', Vw'').

3) In the first embodiment, the entrance sensor S1 and the exit sensor S2 are explained using a method using a photointerrupter and a paper detection arm, or a configuration using a detection means based on laser reflection, but the present invention is not limited to this. As long as the method detects the presence or absence of paper before and after the nip portion N, the methods and arrangement positions are not limited to those described above.

4) In addition, in the first embodiment, a pair of rotating members for fixing the toner image t on the paper P is formed in a nip by a roller-shaped member. Any configuration that performs fixing may be used. For example, a configuration using a belt-like member instead of a roller member or a configuration using an IH or a laser as a heat source can be suitably applied.

5) In the flowchart described in FIG. 10, in step S10-2, when L<Ls+ΔL, the sheet conveying speed (fixing rotation speed) in the fixing device 100 is automatically changed from the setting of speed Vw to speed Vw′. is decreasing. However, it is not limited to this control configuration. For example, as shown in FIG. 13, a flow chart of paper setting work and print operation may be used.

That is, in the flowchart of FIG. 13, if L<Ls+ΔL in step S13-2, a screen prompting selection of whether or not to perform the relief operation is displayed on the display unit 32, and the operator's instruction is requested ( S13-4). At this time, in the method of reducing the sheet conveying speed (fixing rotation speed) in the fixing device 100 from the speed Vw to the speed Vw', which is a relief operation, the productivity may be lowered due to the decrease in the conveying speed of the sheet P. There is

Therefore, as shown in Fig. 11, by displaying a warning message "The paper length is inappropriate, productivity may be reduced." . Then, the control unit 24 determines whether or not to perform the relief operation according to the operator's instruction (S13-5).

Further, in S13-4, by changing the orientation of the paper P stacked in the paper feed cassettes 9 and 10, the large-capacity paper feeder 11, or the manual feed tray 12, L≧L is satisfied without reducing the paper transport speed. If the relationship Ls+ΔL can be satisfied, the following display may be performed. In other words, a display may be displayed to prompt the user to switch the paper P set in the direction in which the length in the transport direction Z is the short side to the direction in which the length in the transport direction Z is the long side.

That is, the acquired paper size information has a first length in which the length in the transport direction is equal to or less than the short side of the predetermined paper, and a first length in which the length in the width direction is equal to or greater than the long side of the predetermined paper. When it indicates that the length is 2, it is notified that the orientation of the sheets accommodated in the accommodation section should be changed.

This configuration can also be applied when it is determined No in S13-8 (or S10-6 in FIG. 10).

Since other operations conform to the flowchart described in FIG. 10, further description of FIG. 13 is omitted.

6) Means for Changing Paper Conveyance Speed There are several methods for changing the paper conveyance speed (fixing rotation speed) Vw in the fixing device 100 .

The first method is to change only the sheet conveying speed Vw in the fixing device 100 without changing the sheet conveying speeds other than the fixing device 100 . That is, the change in the sheet conveying speed (fixing rotation speed) Vw in the fixing device 100 is changed by the gap time ΔT to the extent that it can be absorbed. That is, the sheet conveying speed Vw in the fixing device 100 is changed within the range of L/(Vw−Vw′)>ΔT.

When L/(Vw−Vw′)≦ΔT, the trailing edge of the preceding sheet overlaps the leading edge of the succeeding sheet and is ejected from the nip portion N of the fixing device 100, so the sheet P passes through the exit sensor S2. This is because it becomes impossible to detect

As a second method, in order to satisfy L/(Vw−Vw′)>ΔT, there is a method of widening the interval at which the paper P is fed from the paper feed units 9 to 12 (a method of simply widening the paper interval). be. This method is simpler than the first method as a method that can reduce the sheet conveying speed Vw in the fixing device 100 to a lower speed. However, the productivity (ppm: the number of sheets that can be printed per minute), which is the number of sheets of paper P discharged from the printer 1 per hour, decreases.

Therefore, as a third method, there is a method of once increasing the speed of conveying the paper before or after the fixing device 100 (method of increasing the distance between the papers by increasing the speed). In this method, for example, the gap time ΔT can be increased by increasing the transport speed of the sheet after the trailing edge of the sheet has passed through the nip portion N of the fixing device 100 . As a result, the sheet conveying speed Vw in the fixing device 100 can be reduced to a lower speed than the first method while suppressing a decrease in productivity.

FIG. 14(a) is a transportation diagram chart of preceding paper and subsequent paper in a normal printing operation under the setting that Vw is the paper transportation speed in the entire printer 1 including the fixing rotation speed of the fixing device 100. FIG. be. In (b), when L/(Vw−Vw′)≦ΔT, the trailing edge of the preceding sheet overlaps the leading edge of the following sheet to be conveyed next by reducing the sheet conveying speed Vw in the fixing device 100 . 1 is a diagram chart showing a situation where

FIG. 15A is a diagram showing the positional relationship between the trailing edge of the preceding sheet and the succeeding sheet to be conveyed next when the sheet feeding interval is widened and the sheet conveying speed is increased behind the fixing device 100. Show chart. 14(b) shows the position of the leading edge of the preceding sheet at that time as a diagram chart for comparison with the example of FIG. 14(a).

In both FIGS. 14 and 15, the horizontal axis indicates the timer time, and the vertical axis indicates the transport path position of the paper P in the printer 1. The lower end of the continuous line graph indicates the paper feed position, and the upper end indicates the paper discharge position. . The slope of the line graph indicates the paper transport speed. A sheet that has stopped once is conveyed by a pair of registration rollers and decelerated by the fixing device 100 so that the relationship L≧Ls+ΔL′ is satisfied. The distance between the leading edge and the trailing edge of the preceding sheet and the succeeding sheet is approximately the length in the sheet conveying direction.

In (b) of FIG. 14 , the preceding sheet decelerates as the sheet conveying speed Vw decreases in the fixing device 100, and as a result, the trailing edge of the preceding sheet and the leading edge of the succeeding sheet conveyed at the velocity Vw overlap. (Arrow in the figure).

On the other hand, in the method of (a) of FIG. 15, by securing a sufficient gap time ΔT before the conveying speed of the preceding sheet in the fixing device 100 decreases, the sheet conveying speed Vw in the fixing device 100 similarly decreases. However, it is possible to prevent the trailing edge of the preceding sheet from overlapping the leading edge of the succeeding sheet. Further, according to FIG. 15(b), by increasing the paper transport speed after passing through the fixing device, the paper interval time ΔT is increased and the paper transport speed Vw in the fixing device 100 is reduced. It is possible to equalize the arrival timing of the leading edge of the preceding sheet to the discharge position.

Further, in the first embodiment, a method of reducing only the paper conveying speed (fixing rotation speed) of the fixing device 100 without reducing the paper conveying speed of other than the fixing device 100 in performing the relief operation has been described. However, as a fourth method, it is possible to obtain the same effect by reducing the paper transport speed of the entire printer 1 (that is, by also reducing the fixing rotation speed) to reduce productivity. This fourth method makes it easier to control the transport speed.

7) The first rotational speed and the second rotational speed are the following speeds. Let Ls be the distance from the first paper detection position A1 by the entrance sensor S1 to the second paper detection position A2 by the exit sensor S2.

A case where the fixing roller 40 rotating at the first rotational speed conveys the first sheet having the length L1 in the conveying direction at the nip portion N is as follows. From a predetermined timing at which the paper should reach the second paper detection position A2, the jam detector stops the rotation of the fixing roller 40 based on the output of the exit sensor S2. At this time, let ΔL1 be the distance that the paper is conveyed by the fixing roller 40 until the rotation of the fixing roller 40 stops in response to the detection of the occurrence of the jam by the jam detector.

A case where the fixing roller 40 rotating at the second rotational speed conveys the second sheet having the length L2 in the conveying direction at the nip portion N is as follows. From a predetermined timing at which the paper should reach the second paper detection position A2, the jam detector stops the rotation of the fixing roller 40 based on the output of the exit sensor S2. At this time, let ΔL2 be the distance that the paper is conveyed by the fixing roller 40 until the rotation of the fixing roller 40 stops in response to the detection of the occurrence of the jam by the jam detector.

The first rotational speed is a speed that satisfies the relationship of L2<Ls+ΔL1≦L1. The second rotation speed is a speed that satisfies the relationship of Ls+ΔL2≦L2.

In addition, the length in the conveying direction is a third length L3 shorter than the conveying direction length L2 of the second sheet, and the width size and basis weight of the third sheet are the same as those of the first and second sheets. The case where the paper is conveyed to the nip portion N is as follows. The controller 24 may rotate the fixing roller 40 at a third speed slower than the second speed. That is, when the rotation of the fixing roller 40 stops in response to the occurrence of a jam being detected by the jam detector while the third sheet of paper is passing through the nip portion N, the entrance sensor S1 detects the third sheet of paper. The fixing roller 40 is rotated at a third speed at which the presence of is detectable.

8) In the configuration of this embodiment, the following cases exist.

When a predetermined sheet having a long side length L1 and a short side length L2 is conveyed to the nip portion N, the length in the conveying direction is the long side of the predetermined sheet. A case where a predetermined sheet is conveyed to the nip portion N is as follows. The control unit 24 detects the presence of the predetermined paper by the entrance sensor S1 when the jam detection unit detects the occurrence of a jam while the predetermined paper is passing through the nip portion N, and the rotation stops. The fixing roller 40 is rotated at a first speed capable of detecting .

Further, the case where the predetermined paper is conveyed to the nip portion N in the second orientation in which the length in the conveying direction is the short side of the predetermined paper is as follows. The controller 24 rotates the fixing roller 40 at a second speed slower than the first speed. That is, when the rotation of the fixing roller 40 stops in response to the occurrence of a jam being detected by the jam detector while a predetermined sheet of paper is passing through the nip portion N, the entrance sensor S1 detects the presence of the predetermined sheet of paper. is detectable, the fixing roller 40 is rotated.

<<Example 2>>
FIG. 16 is a flow chart of paper setting and printing operation in the second embodiment. Although basically the same as the flow chart of FIG. 10 in the first embodiment, in the second embodiment, paper selection based on the transport direction length L of the paper P detected by the paper feeding unit of the printer 1 will be described. The paper feed cassettes 9 and 10 or the large-capacity paper feeder 11, which are the paper feed units described in the first embodiment, are set with respect to the paper, as described above, by the end fence 52 (FIG. 2) that is slidable in the paper feed direction. It has an end detection unit that detects the length in the paper transport direction.

In the second embodiment, the sheet length L detected by the end detection section is notified to the control section 24 (S16-1, S16-2, S16-3). The operational flow of S16-4 to S16-10 based on the determination of YES or NO in S16-3 is the same as the operational flow of S10-3 to S10-9 in the flowchart of FIG.

FIG. 17 is another flow chart in the second embodiment. Basically, this is the same as the flow chart of FIG. 13 in the first embodiment, but paper selection is based on the transport direction length L of the paper P detected by the paper feeder of the printer 1, as in FIG. That is, the sheet length L detected by the end detection section is notified to the control section 24 (S17-1, S17-2, S17-3). The operational flow of S17-4 to S17-11 based on the determination of YES or NO in S17-3 is the same as the operational flow of S13-4 to S13-10 in the flowchart of FIG.

<<Example 3>>
FIG. 18 is a flow chart of paper setting and printing operation in the third embodiment. In the third embodiment, print operation control based on the paper length L in the transport direction detected for the paper being transported in the printer 1 will be described. The rest of the configuration is the same as that of the first and second embodiments, so the description is omitted.

In the printer 1 of the third embodiment, the paper feeding rollers or registration rollers 14 in the paper feeding units, that is, the paper feeding cassettes 9 and 10, the large-capacity paper feeding device 11, and the manual feed tray 12, have the length of the paper being conveyed. A paper length detector is provided to automatically detect the This detection unit automatically detects the length of the paper being conveyed from, for example, the roller rotation time required for one paper P to pass through and the outer circumference length of the roller. Paper length information automatically detected by the paper length detection unit is transmitted to the control unit 24 .

In the third embodiment, the print operation is controlled based on the transport direction length L of the paper being transported, which is detected by the paper length detection unit. That is, as shown in FIG. 18, the conveying direction length L of the sheet being conveyed detected by the sheet length detecting section is notified to the control section 24 (S18-1, S18-2, S18-3). The operational flow of S18-4 to S18-8 based on the determination of YES or NO in S18-3 is the same as the operational flow of S10-3 to S10-7 in the flowchart of FIG.

On the other hand, if L<Ls+ΔL' in S18-7, a warning message is displayed before the paper P arrives at the fixing device 100 in view of the situation in which paper retention cannot be detected inside the fixing device (S18-7). 9). Then, the control section 24 makes a jam determination to intentionally jam the paper P before the paper P reaches the fixing device 100 (S18-10), and stops the conveyance of the paper P (S18-11).

At this time, any method that can prevent the paper P from remaining inside the fixing device 1, such as a method of reducing the conveying speed Vw without displaying a warning message (S18-8) or the like, may be used.

<<Example 4>>
FIG. 19 is a flow chart of paper setting and printing operation in the fourth embodiment. In the fourth embodiment, paper setting and printing operation based on the physical property information of the paper and the paper length L in the transport direction will be described. The rest of the configuration is the same as in Examples 1 to 3, so the description is omitted.

When the paper size is detected by inputting the paper size from the operation unit 23 or by automatic detection by the paper feed cassettes 9 and 10 or the large-capacity paper feeder 11 (S19-1), the length of the paper in the transport direction is determined. The length L is determined (S19-2).

At S19-2, if L≧Ls+ΔL, even if a jam occurs in the fixing device 100 as described above, the entrance sensor S1 can detect the trailing edge of the jam-stopped sheet. In this case, as in S10-3 of FIG. 10, the print operation is started (S19-3). The printing operation here is a normal printing operation under the setting that the sheet conveying speed in the entire printer 1 is set to Vw.

By the way, among the jams that occur inside the fixing device, jams in which the leading edge of the paper P does not reach the exit sensor S2 are jams in which the paper P winds around the fixing roller 40 (FIG. 4). A winding jam occurs when the toner image t formed on the paper P melts at the nip portion N, thereby increasing the adhesiveness, and the adhesive force of the paper P exceeds the rigidity (stiffness) of the paper.

If Wp≧W, where Wp is the grammage of the paper selected when setting the paper, and W is the grammage of the paper that can ensure the rigidity that does not cause jamming due to winding of the fixing paper, then Wp≧W (YES in S19-4). The print operation is started (S19-3). The printing operation here is a normal printing operation under the setting that the sheet conveying speed in the entire printer 1 is set to Vw.

It is assumed that the paper basis weight W that can ensure the rigidity that does not cause a fixer winding jam is within the range of basis weights that can be set in the paper settings. That is, if the range of basis weights that can be set in paper settings (images can be formed by the image forming apparatus 1) is Wmin or more and Wmax or less, including the case where L≧Ls+ΔL, then Wmin≦W≦Wmax. Yes, and Wmin≦Wp≦Wmax.

On the other hand, if Wp≧W does not hold, that is, if the basis weight Wp of the paper to be used is less than the predetermined amount (NO in S19-3), the operation flow proceeds from S19-5 onwards. The operation flow of S19-5 to S19-10 is the same as the operation flow of S10-4 to S10-9 in the flowchart of FIG. Any method that can prevent the paper P from remaining inside the fixing device, such as a method of reducing the conveying speed Vw without displaying a warning message or the like, may be used.

That is, in this embodiment, when the sheet has a basis weight that does not cause a winding jam (Wp≧W), the sheet conveying speed is not reduced from Vw even if the length L in the conveying direction is L<Ls+ΔL. to execute the print operation.

If the paper size is L<Ls+ΔL, there is a possibility that the entrance sensor S1 cannot detect the paper P staying in the fixing device 100 . However, since the relationships of L>ΔL and L>Ls are satisfied, if the winding jam does not occur, the exit sensor S2 can detect the retention of the paper. As a result, it is possible to more reliably detect the sheet staying in the fixing nip portion with respect to the sheet P that satisfies L<Ls+ΔL and Wp≧W. Further, when applied to a device that lowers productivity as the paper transport speed Vw is reduced, it is possible to suppress a decline in productivity for paper P that satisfies L<Ls+ΔL and Wp≧W. .

<<Example 5>>
In Embodiments 1 to 4 described above, when the input or detected length L of the paper in the paper transport direction is L<Ls+ΔL, the paper transport speed is set to Vw so that L≧Ls+ΔL′. '. In the fifth embodiment, when L<Ls+ΔL (for example, when No in S10-2 of FIG. 10), the sheet conveying speed is not reduced. The rest of the configuration is the same as that of the above-described embodiment, so description thereof will be omitted.

In the fifth embodiment, in the paper setting, if the length L of the paper in the conveying direction that is input or detected is L<Ls+ΔL, the paper conveying speed is not changed, and paper with a basis weight that does not cause a winding jam ( Wp≧W) is allowed for use in the printing operation. That is, if L<Ls+.DELTA.L and Wp.gtoreq.W, it is allowed to be used for printing operations. Here, Wp is the paper basis weight selected by the operator at the time of paper setting, as in the fourth embodiment, and W is the paper basis weight that can ensure the rigidity that does not cause a fixer winding jam.

In the paper setting, if the length L of the paper in the transport direction that is input or detected is L<Ls+ΔL, and if the paper has a basis weight (Wp<W) that can cause a winding jam, the print operation is not started. Prohibit use.

The use of paper satisfying L≧Ls+ΔL is permitted. That is, when L≧Ls+ΔL, both the paper satisfying Wp<W and the paper satisfying Wp≧W are allowed to be used in the printing operation.

With the configuration of the fifth embodiment as well, it is possible to more reliably detect the sheet of paper P that satisfies L<Ls+ΔL and Wp≧W and that is staying in the fixing nip portion.

As a specific example of control, the control unit (registration control unit) 24 controls the operation unit 23 to display the information input screen of the paper P to be set in the paper feed units 9 to 12 (FIGS. 9A to 9C). , L<Ls+ΔL, and Wp<W.

It is assumed that the basis weight W of the rigidity that does not cause a fixer winding jam is within the range of basis weights that can be set in paper settings. That is, if the range of basis weights that can be set in paper settings (images can be formed by the image forming apparatus 1) is Wmin or more and Wmax or less, including the case where L≧Ls+ΔL, then Wmin≦W≦Wmax. Yes, and Wmin≦Wp≦Wmax. In the example of FIG. 9C, as an example, Wmin=52 gsm and Wmax=300 gsm. Similarly, L input in paper setting is within a settable range in paper setting (Lmin or more and Lmax or less).

Specifically, when a paper size that satisfies L<Ls+ΔL is input on the paper size setting screen shown in FIG. 9B, Wp< Gray out the option that is W. It should be noted that it is also possible not to display options where Wp<W.

Further, for example, in the case of a configuration in which the basis weight is selected before the paper size, if the basis weight satisfying Wp<W is selected on the screen shown in FIG. 9C, the paper size shown in FIG. 9B is entered. On the screen, input of a paper size that satisfies L<Ls+ΔL is prohibited. Then, input of a paper size that satisfies L≧Ls+ΔL is allowed. For example, if Lmin ≤ 182mm ≤ Lmax and L ≤ 182mm and detection by the entrance sensor S1 is difficult, input of a size that satisfies Lmin ≤ L ≤ 182mm is prohibited, and 182mm < L ≤ Lmax. It allows for input of a certain size, and so on.

In this example, input is prohibited, but in response to the operator inputting paper information that satisfies L<Ls+ΔL and Wp<W, an error screen is displayed to indicate that L<Ls+ΔL and A configuration may be adopted in which the registration of a sheet satisfying Wp<W is prohibited.

Also, in FIGS. 9B and 9C, an example of inputting a non-standard paper size has been described, but this may be applied to a configuration in which a standard paper size is selected.

The paper setting control described in the fifth embodiment is organized and the paper setting control is supplemented as follows.

1) The control unit (registration control unit) 24 allows registration of a first sheet having a predetermined length in the transport direction and a first basis weight in association with the storage unit. It is prohibited to register a second sheet having a predetermined length in the transport direction and a second grammage smaller than the first grammage in association with the storage section.

2) A first reception unit ( FIG. 9B : window 329) that receives information corresponding to the length of the sheets accommodated in the storage unit in the conveying direction, and information corresponding to the basis weight of the sheets stored in the storage unit. and a second receiving unit (FIG. 9C) for receiving.

When the first reception unit receives the information indicating that the length of the sheet accommodated in the storage unit in the conveying direction is the predetermined length, the control unit (registration control unit) 24 controls the second reception unit. department to accept information corresponding to the first basis weight. The second receiving unit is prohibited from receiving information corresponding to the second basis weight.

3) The control unit (registration control unit) 24 can display on the display unit 32 a first screen (FIG. 9B) for inputting information corresponding to the length of the sheets accommodated in the accommodation unit in the conveying direction. . When the information corresponding to the predetermined length is input on the first screen, the second screen (Fig. 9C ) allows entry of information corresponding to the first basis weight. Prohibit entry of corresponding information for the second basis weight.

4) The control unit (registration control unit) 24 causes the display unit 32 to display a first screen (FIG. 9B) for inputting information corresponding to the length of the sheets accommodated in the accommodation unit in the conveying direction. When the information corresponding to the predetermined length is input on the first screen, on the second screen (FIG. 9C) for selecting the basis weight of the paper stored in the storage unit displayed on the display unit, the first The option corresponding to the second basis weight is displayed, and the option corresponding to the second basis weight is not displayed.

5) A first reception unit (FIG. 9C) that receives information corresponding to the basis weight of the sheets stored in the storage unit, and a second reception unit that receives information corresponding to the length in the transport direction of the sheets stored in the storage unit. reception unit (FIG. 9B).

The control unit (registration control unit) 24 allows the second reception unit to receive information corresponding to the predetermined length when the first reception unit receives information corresponding to the first basis weight. . When the first reception unit receives information corresponding to the second basis weight, the second reception unit is prohibited from receiving information corresponding to the predetermined length.

6) The control unit (registration control unit) 24 causes the display unit 32 to display the first screen (FIG. 9C) for inputting information corresponding to the basis weight of the sheets accommodated in the accommodation unit. When the information corresponding to the first grammage is input on the first screen, the control unit 24 inputs information corresponding to the length of the sheet accommodated in the accommodation unit in the conveying direction displayed on the display unit. A second screen that appears allows the entry of a predetermined length. When information corresponding to the second grammage is input on the first screen, input of a predetermined length is prohibited on the second screen.

7) The control unit (registration control unit) 24 causes the display unit 32 to display the first screen (FIG. 9C) for inputting information corresponding to the basis weight of the sheets accommodated in the accommodation unit. When the information corresponding to the first grammage is input on the first screen, the control unit 24 selects the information corresponding to the length in the conveying direction of the sheets accommodated in the accommodation unit to be displayed on the display unit. In the second screen (FIG. 9B) displayed, options of a predetermined length are displayed. Then, when the information corresponding to the second basis weight is input on the first screen, the options for the predetermined length are not displayed on the second screen.

《Other Matters》
(1) As the fixing device 100, a device that heats and fixes an unfixed toner image t formed on a sheet has been described as an example, but the present invention is not limited to this. For example, it may be a device (also referred to as a fixing device) that increases the gloss of the image by heating and re-fixing the toner image temporarily adhered to the paper.

(2) The image forming apparatus is not limited to the electrophotographic full-color image forming apparatus of the embodiment, and may be an image forming apparatus that forms a monochrome image. Further, the image forming apparatus is not limited to the electrophotographic method, and may be an image forming apparatus that forms a toner image by a direct method or a transfer method using other methods such as an electrostatic recording method and a magnetic recording method.

1 Image forming apparatus 2 Image forming unit P Sheet t Toner image 40 41 Rotating body pair N Nip portion Z Sheet conveying direction S1 S2 . First and second detectors A1 and A2 . Sheet detection position 24 .

Claims (16)

an image forming unit that forms an unfixed toner image on the conveyed sheet;
first and second rotating bodies forming a nip portion for fixing an unfixed toner image on the sheet while conveying the sheet conveyed from the image forming section;
a jam detector that detects the occurrence of a jam;
a detector that detects the sheet remaining in the nip portion at a detection position on the upstream side of the nip portion with respect to the conveying direction of the sheet;
a controller that stops rotation of the first rotating body in response to the jam detecting unit detecting the occurrence of a jam;
A first sheet having a first length in the conveying direction, a first width size in a width direction perpendicular to the conveying direction, and a first basis weight is formed in the nip. section, the first rotating body conveys the first sheet while rotating at a first speed;
a second sheet having a length in the conveying direction that is a second length shorter than the first length, a length in the width direction that is the first width size, and a basis weight that is the first basis weight; is conveyed to the nip portion, the first rotating body conveys the second sheet while rotating at a second speed slower than the first speed. 2. An image forming apparatus according to claim 1, wherein said detector includes a lever, a biasing portion that biases said lever toward said detection position, and a sensor that detects the position of said lever. Device. a storage unit that stores sheets to be supplied to the image forming unit;
an acquisition unit that acquires information on the length of the sheet accommodated in the accommodation unit in the conveying direction;
3. The image forming apparatus according to claim 1, wherein the controller controls the rotation speed of the first rotor based on the information acquired by the acquisition unit. an operation unit capable of inputting the information about the length of the sheet accommodated in the accommodation unit in the conveying direction by an operator's operation;
4. The image forming apparatus according to claim 3, wherein the acquisition unit acquires the information about the length in the conveying direction input from the operation unit. At the first speed, rotation of the first rotating body is stopped in response to detection of a jam by the jam detector while the first sheet is passing through the nip portion. at a speed at which the detector can detect the first sheet remaining in the nip portion,
At the second speed, rotation of the first rotating body is stopped in response to detection of a jam by the jam detector while the second sheet is passing through the nip portion. 5. The image forming apparatus according to claim 1, wherein the speed is such that the detector can sometimes detect the second sheet remaining in the nip portion. With respect to the conveying direction, when the detector is the first detector and the detection position by the first detector is the first detection position, the sheet is detected at the second detection position next to the first detection position. further comprising a second detector for detecting
L1 for the first length, L2 for the second length,
Ls the distance from the first detection position to the second detection position,
When the first rotating body rotating at the first speed conveys the first sheet, from a predetermined timing at which the first sheet should reach the second detection position, the second Until the rotation of the first rotating body is completely stopped in response to the jam detection section detecting the occurrence of a jam based on the output of the detector, the first sheet is moved to the first rotating body. Let ΔL be the distance conveyed by
When the first rotating body rotating at the second speed conveys the second sheet at the nip portion, from a predetermined timing at which the second sheet should reach the second detection position. , until the rotation of the first rotating body is finished in response to the jam detecting section detecting the occurrence of a jam based on the output of the second detector, the second sheet is ΔL2 is the distance conveyed by the first rotating body,
, the first speed is a speed that satisfies the relationship of L2<Ls+ΔL1≦L1, and the second speed is a speed that satisfies the relationship of Ls+ΔL2≦L2. 6. The image forming apparatus according to any one of 5. When the sheet to be conveyed to the nip portion is a third sheet having the same size as the second sheet and having a basis weight larger than that of the second sheet, the controller sets the first speed. 7. The image forming apparatus according to any one of claims 1 to 6 , wherein the third sheet is conveyed by the first rotating body rotating at a . The controller determines that the sheet to be conveyed to the nip portion has a third length shorter than the second length in the conveying direction and a first width size in the width direction. 7. The third sheet according to any one of claims 1 to 6 , wherein in the case of a certain third sheet, the third sheet is conveyed by the first rotating member rotating at a third speed slower than the second speed. 1. The image forming apparatus according to item 1 or 1. a reporting unit that reports information to an operator;
a storage unit that stores sheets to be supplied to the image forming unit;
an acquisition unit that acquires information about the length of the sheet accommodated in the storage unit in the conveying direction and information about the width size of the sheet in the width direction perpendicular to the conveying direction;
The information acquired by the acquisition unit indicates that the length in the conveying direction is the second length, and the width size in the width direction is a second width size equal to or greater than the first length. 9. The image forming apparatus according to any one of claims 1, 2, and 5 to 8 , wherein the notification unit urges the operator to change the orientation of the sheets accommodated in the accommodation unit when indicating the direction of the sheets. . a storage unit that stores a sheet on which a toner image is to be formed;
an image forming unit that forms an unfixed toner image on the sheet conveyed from the storage unit;
first and second rotating bodies forming a nip portion for fixing an unfixed toner image on the sheet while conveying the sheet conveyed from the image forming section;
a jam detector that detects the occurrence of a jam;
a detector that detects the sheet remaining in the nip portion at a detection position on the upstream side of the nip portion with respect to the conveying direction of the sheet;
The rotation speed of the first rotating body is controlled according to the length of the sheet to be conveyed to the nip portion in the conveying direction, and the jam detecting portion detects the occurrence of a jam. a rotation control unit that stops the rotation of one rotating body;
a registration control unit that registers information on the sheets to be stored in the storage unit in association with the storage unit;
The registration control unit allows a first sheet having a first length in the transport direction and a first basis weight to be registered in association with the storage unit, and allowing a second sheet having a length equal to the first length and a second basis weight smaller than the first basis weight to be registered in association with the storage unit, and allowing a third sheet having a direction length of a second length shorter than the first length and having the first basis weight to be associated and registered with the storage unit, and An image forming apparatus, wherein registration of a fourth sheet having a direction length equal to the second length and a basis weight equal to the second length is prohibited in association with the storage portion. 11. An image forming apparatus according to claim 10 , wherein said detector includes a lever, a biasing portion that biases said lever toward said detection position, and a sensor that detects the position of said lever. Device. The registration control unit has a first screen for inputting the length of the sheet accommodated in the accommodation unit in the conveying direction, and a second screen for inputting the basis weight of the sheet accommodated in the accommodation unit. and can be displayed on the display unit, and when the second length is input on the first screen, the first basis weight is displayed on the second screen displayed on the display unit 12. The image forming apparatus according to claim 10 , wherein the input of the second basis weight is permitted and the input of the second basis weight is prohibited. 13. The image forming apparatus according to claim 12 , wherein the image forming apparatus has the display section. The registration control unit has a first screen for inputting the basis weight of the sheets accommodated in the accommodation unit, and a second screen for inputting the length of the sheets accommodated in the accommodation unit in the conveying direction. and can be displayed on the display unit, and when the information corresponding to the first basis weight is input on the first screen, the second screen displayed on the display unit displays the second When the input of information corresponding to the length of is allowed and the information corresponding to the second basis weight is input on the first screen, the second screen displayed on the display unit displays the second 12. The image forming apparatus according to claim 10 , wherein input of information corresponding to a length of 2 is prohibited. 15. The image forming apparatus according to claim 14 , wherein the image forming apparatus has the display section. With respect to the conveying direction, when the detector is the first detector and the detection position by the first detector is the first detection position, the sheet is detected at the second detection position next to the first detection position. further comprising a second detector for detecting
the second length is L;
Ls the distance from the first detection position to the second detection position,
When the second sheet is conveyed in the nip portion, the jam is detected based on the output of the second detector from a predetermined timing when the second sheet should reach the second detection position. ΔL is the distance that the second sheet is conveyed by the first rotating body until the rotation of the first rotating body stops in response to detection of the occurrence of a jam by the unit;
16. The image forming apparatus according to claim 10 , wherein the second length L satisfies L<Ls+.DELTA.L.

Images