JP2000250352A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image shock when a large-sized sheet is in use and to prevent the occurrence of irregularities in an image, and also, to prevent defective carriage when a small-sized sheet is in use by controlling the moving position of an entrance guide based on the corresponding relation between the size of a transfer material sheet, the positions of the leading and trailing ends of the sheet and the moving posi tion of the entrance guide as a guiding member. SOLUTION: The moving position of the entrance guide is controlled by a control part based on the corresponding relation between the size of the sheet, the positions of the leading and trailing ends of the sheet and the moving position of the entrance guide. The storage of the corresponding relation, the selection of the stored corresponding relation and the control based on the storage and the selection are executed by the control part. In the case the large-sized sheet is in use (S1), the entrance guide is laid in the upper position when the leading end of the sheet passes through the entrance guide (S2), and a little distance before the trailing end passes through the entrance guide (for example, 15 mm from the trailing end), the entrance guide is laid in the lower position (S3 and S4). And copying is finished (S5). In the case the small-sized sheet is in use, the entrance guide is laid in the lower position (S6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device and an image forming apparatus for fixing a sheet on which an image is recorded and formed, for example, an image forming apparatus such as a copying machine, a printer and a facsimile.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, a facsimile, etc., a sheet fed from a paper feed cassette is first sent to a transfer unit as an image forming unit, where it is formed on a photosensitive drum. The transferred toner image is transferred. The sheet after the transfer is subsequently sent to a fixing device, where the toner image is fixed.

In a conventional fixing device, a fixing entrance guide for guiding a sheet to a roller pair of a fixing roller and a pressure roller has a fixed type and a sheet size for ensuring high image quality and transportability. In some cases, the position of the entrance guide is movable.

The reason why the position of the entrance guide is movable depending on the size of the sheet will be described below. To move the entrance guide, when transporting a sheet whose size is longer than the transfer unit to the fixing unit (hereinafter, referred to as “large size”), set the entrance guide to the upper position, and conversely, Moves downward when a sheet of a size shorter than the fixing unit (hereinafter, referred to as “small size”) is conveyed from the transfer unit.

[0005] This is because when the sheet is large, when the sheet enters the nip of the fixing roller pair, the length of the sheet is long, so that the rear end of the sheet is located at the transfer portion.

For this reason, when the leading edge of the sheet enters the fixing nip, the shock propagates to the trailing edge of the sheet and causes image blurring (hereinafter referred to as image shock).

Therefore, by positioning the entrance guide on the upper side (positioning the tip of the entrance guide above the fixing nip), the sheet is deformed in an S-shape in the conveying direction, thereby weakening the stiffness of the sheet. The transmission of shock at the time of injection is reduced, and image blur is prevented.

When the sheet is small in size, when the leading edge of the sheet enters the fixing section, the rear end of the sheet passes through the resist section and the transfer section. No force can be obtained, and the contact area of the sheet on the conveyance belt decreases, thereby reducing the conveyance force. For this reason, if the guide is high, there is a possibility that a sheet cannot enter the nip between the fixing roller and the pressure roller, and a defect that cannot be conveyed occurs (hereinafter, referred to as a conveyance defect). In order to prevent this, the entrance guide is lowered.

As described above, the position of the entrance guide can be moved depending on the size of the sheet in order to ensure both high image quality and transportability (to prevent image shock and transport failure).

[0010] In addition, by making the moving position of the entrance guide adjustable and performing the adjustment, at a higher level,
It is possible to ensure both high image quality and transportability.

Conventionally, the entrance guide is determined to be placed at the upper position or the lower position depending on the size of the sheet.

[0012]

However, when the moving position is the upper position, since the leading end of the entrance guide is close to the fixing roller, an image on the sheet may be disturbed due to the curl state of the leading and trailing ends of the sheet. Was. If the curl is a lower curl, the sheet surface comes into contact with the fixing roller surface, toner scatters due to pressure fluctuation between the fixing roller and the sheet, or the adsorbed toner is disturbed due to electrostatic causes, and the image is disturbed. (Hereinafter, this will be referred to as image disorder).

In recent years, due to the diversification of types of sheets, the number of sheets, such as recycled paper and cardboard, which are likely to be curled has increased. For this reason, the curl at the leading edge and the trailing edge of the sheet becomes large, and the case where the image on the sheet is disturbed is increasing.

It is an object of the present invention to provide a fixing device and an image forming apparatus which can prevent image shock and poor conveyance by moving a position of an entrance guide and further prevent image disturbance. It is intended to provide.

Another object of the invention of the present application is to provide a fixing device and an image forming apparatus capable of improving usability by making it possible to select which one of image shock prevention and image disorder is given priority. .

[0016]

According to a first aspect of the present invention, there is provided a fixing device for guiding a transfer material carrying unfixed toner to a fixing nip and a guide for guiding the transfer material. At least the tip of the means is located at a first position higher than the fixing nip and a second position lower than the first position.
And a driving means for driving the moving means, a guiding means position detecting means for detecting a moving position of the guiding means moved by the moving means, Size detection means for detecting the size, transfer material end position detection means for detecting the positions of the leading and trailing ends of the conveyed transfer material, and the transfer position of the guide means in accordance with the size of the transfer material; Storage means for storing a plurality of modes set for each material passing position; selection means for selecting a plurality of modes stored in the storage means; and control for controlling the driving means in accordance with the mode selected by the selection means Means.

According to a second configuration of the fixing device for realizing the object of the invention according to the present application, in the above-described first configuration, the control unit sets the position of the guide unit to the first position and the second position. It is to be selectively located at the position.

A third configuration of the fixing device for realizing the object of the present invention according to the present invention is such that in the first or second configuration, the positioning means for determining the position of the guide means can be adjusted independently. It is.

According to a fourth configuration of the fixing device for realizing the object of the invention according to the present application, in any one of the above-mentioned configurations, the storage unit passes the guide unit when the size of the transfer material is large. And a first mode for setting the position of the guide means at the first position regardless of the position of the transfer material to be transferred.

According to a fifth configuration of the fixing device for realizing the object of the invention according to the present application, in the above-described first, second or third configuration, the storage unit may be configured such that the transfer material has a large size. And a second mode for setting the position of the guide means to the second position only when the rear end of the transfer material passes through the guide means at the time of the second side of both sides.

According to a sixth aspect of the present invention, there is provided a fixing device according to the first, second, or third aspect, wherein the storage means is provided when the size of the transfer material is large. A second mode for setting the position of the guide means to the second position only when the rear end of the transfer material passes through the guide means.

According to a seventh aspect of the present invention, there is provided a fixing device according to the first, second, or third aspect, wherein the storage means is provided when the size of the transfer material is large. And a fourth mode in which the position of the guide means is set to the second position only when the leading end and the rear end of the transfer material pass through the guide means at the time of the second side of both sides.

According to an eighth aspect of the present invention, there is provided a fixing device according to the first, second, or third configuration, wherein the storage means is provided when the size of the transfer material is large. A fifth mode for setting the position of the guide means to the first position only when the central portion of the transfer material passes through the guide means.

An image forming apparatus for realizing the object of the present invention according to the present invention has any one of the above fixing devices as a means for fixing a toner image on a transfer material on which an image is recorded and formed. .

In the above structure, the moving position of the entrance guide is controlled in accordance with the correspondence between the size of the transfer material such as a sheet, the positions of the leading and trailing ends of the sheet, and the moving position of the entrance guide as the guide means. Depending on the size of the sheet, when the leading edge of the sheet passes through the entrance guide,
After the leading end of the sheet has passed through the entrance guide and shortly before the trailing end of the sheet has passed through the entrance guide, the position of the entrance guide is set to the first position, the upper position, and the lower position, the second position, to the user / Control can be performed as set by the service person in advance.

By setting the entrance guide to the upper position when the leading edge of the sheet passes through the entrance guide when the sheet is large, image shock when the leading edge of the sheet enters the fixing nip is prevented.

When the sheet is large in size, the leading edge of the sheet passes through the entrance guide, and the entrance guide is located at the lower position, so that the leading end of the entrance guide is separated from the fixing roller forming the fixing nip, and the sheet is curled by the sheet. Prevent the image from being distorted.

When the sheet is large, shortly before the trailing edge of the sheet passes through the entrance guide, the entrance guide is set to the lower position, the tip of the entrance guide is separated from the fixing roller, and the image on the sheet due to the curl state of the sheet is removed. Prevent turbulence.

When the sheet is small in size, lowering the entrance guide prevents poor conveyance.

In this way, by controlling the moving position of the entrance guide in accordance with the correspondence between the sheet size, the positions of the leading and trailing ends of the sheet, and the moving position of the entrance guide, image disturbance does not occur. A fixing device having both high image quality and transportability can be provided.

Further, it is possible to provide a high-performance fixing device in which the position of movement of the entrance guide can be adjusted to achieve both high image quality and high transportability.

In order to prevent image disturbance from giving priority to image shock, when the sheet is large in size, the leading edge of the sheet is set to the lower position when the leading edge of the sheet passes through the entrance guide, so that the leading edge of the sheet is fixed. Although it is not possible to prevent an image shock when entering the nip, it is possible to prevent the image on the sheet from being disturbed due to the curl state of the sheet by separating the tip of the entrance guide from the fixing roller. It is possible to provide an easy-to-use fixing device and an image forming apparatus which are suitable for use conditions and which can be selected to give priority to prevention of image shock or prevention of image disorder.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A first embodiment of the present invention will be described below with reference to the drawings.

First, the overall configuration of the image forming apparatus main body (multifunctional digital copying machine) will be described with reference to FIG.

In FIG. 10, the image forming apparatus main body A is
A scanner unit B serving as an image reading means for reading image information of an image surface of a book document is provided at an upper portion thereof, and a sheet deck D is further assembled at a lower portion thereof.

The scanner section B includes a first mirror 201 composed of a scanning system light source and a mirror, and a platen glass 20.
2. It includes a document pressure plate 203, a second mirror 204, a lens 205, a light receiving element (photoelectric conversion element) 206, an image processing unit, and the like, which can be opened and closed with respect to the apparatus main body A. The reading unit 200 includes a first mirror 201, a second mirror 204, a lens 205, and a light receiving element (photoelectric conversion element) 206.

Then, a book original or a sheet original such as a book, thick paper, curled paper or the like is placed on the platen glass 202 with the original surface facing down, and the back side is pressed by the original pressing plate 203 and set in a stationary state. When the reading start key is pressed, the scanning system light source 201 scans the lower part of the platen glass 202 in the direction of arrow a in FIG. The image information of the document scanned by the first mirror 201 is projected onto the light receiving element 206 by the second mirror 204 and the lens 205, the image information is read, processed by the image processing unit, converted into an electric signal, and The data is transmitted to the scanner 111.

Here, the image forming apparatus main body A functions as a copying machine when the processing signal of the image processing unit is input to the laser scanner 111, and functions as a printer when the output signal of the personal computer is input. If a transmission signal from a facsimile device of another device is input or a processing signal of the image processing unit is transmitted to a facsimile device of another device, the device functions as a facsimile device.

On the other hand, a sheet cassette 1 is mounted below the image forming section C, and the sheet cassette 1 is composed of a lower cassette 1a and an upper cassette 1b as one feeding unit. In this embodiment, three feeding units U1, U2, and U3 are mounted, and six cassettes are mounted. One upper feeding unit U1 is detachably attached to the apparatus main body A, and two lower feeding units U2 and U3 are detachably attached to the sheet deck D.

The sheets accommodated in the cassettes 1a and 1b are fed out by a big-up roller 3, separated and fed one by one by the cooperation of a feed roller 4 and a retard roller 5, and then conveyed. Rollers 104, 10
5 and is guided to the registration roller 106,
The sheet is fed to the image forming section C by the roller 106 in synchronization with the image forming operation.

The image forming section C includes the electrophotographic photosensitive drum 1
12, an image writing optical system 113, a developing device 114, a transfer charger 115, and the like. And
A laser beam corresponding to image information emitted from the laser scanner 111 is scanned on the surface of the photosensitive drum 112 uniformly charged by the charger by the image writing optical system 113 to form a latent image, and the latent image is formed on the latent image. A toner image is formed by the developing device 114, and the toner image is transferred to the first surface of the sheet S by the transfer charger 115 on the sheet S conveyed in synchronization with the rotation of the photosensitive drum 112 by the registration roller 106.

Reference numeral 117 denotes a conveyance belt for conveying the sheet S on which toner is formed, 118 denotes a fixing device, and 119 denotes a discharge roller pair. The sheet S on which the toner image is formed is conveyed to the fixing device 118 by the conveyance belt 117, and is heated and pressed to fix the toner image on the surface of the sheet S.

The sheet S having been fixed is guided in the discharge direction by the conveyance path, and is discharged and stacked on a discharge tray 9 disposed outside the apparatus by a discharge roller pair 119. In this case, the sheet S is discharged face-up on the discharge tray 9 with the recording surface facing up.

A means 701 (not shown) for detecting a sheet size is attached to the cassette. A position detecting unit 702 for detecting the positions of the leading edge and the trailing edge of the sheet is disposed near the registration roller 106.

Next, details of the fixing device of the present embodiment will be described with reference to FIGS.

Reference numeral 21 denotes a fixing roller heated by a heater installed therein, 22 denotes a pressure roller that presses the fixing roller, 40 denotes an entrance guide unit that guides a sheet to the fixing roller pair, and 24 denotes a fixing roller. Is a separation claw unit that separates the sheet from the fixing roller and conveys it to the paper discharge unit 30 is a web unit that cleans the fixing roller 21, 25 is a thermistor that detects a temperature adjustment temperature, and 26 is a temperature adjustment error The safety device sub thermistor 27 is a thermo switch of the safety device.

Reference numeral 41 denotes an entrance guide, reference numeral 42 denotes an upper and lower plate for moving the entrance guide 41 up and down (rotating integrally with the entrance guide 41 and moving the tip of the entrance guide 41 up and down), and reference numeral 43 denotes an entrance guide. An adjustment plate for adjusting the height of 41.

44 is a guide auxiliary plate for detachably fixing the entrance guide 41 to the upper and lower plates 42, 45 is a fixing plate, 46 is a lower position adjusting plate for adjusting the lower position (downward rotation position) of the entrance guide 41. , 49 are vertical drive devices for moving the entrance guide 41 up and down.

The entrance guide 41 can be moved up and down, and the positions of the upper (rotating) position and the lower (rotating) position of the tip of the entrance guide 41 are adjusted by the positioning means of the adjusting plate 43 and the lower position adjusting plate 46. Decide. Further, by adjusting the positions of the adjustment plate 43 and the lower position adjustment plate 46, the positions of the upper position and the lower position can be adjusted. The upper and lower positions of the tip of the entrance guide 41 are adjusted and incorporated in the main body.

The entrance guide 41 is usually at the upper position,
It is moved to the lower position by the vertical drive 49 (FIG. 3).

The entrance guide 41 is formed by engaging a guide auxiliary plate 44 slidably attached to the entrance guide 41 with a fixed plate 45 fixed to the upper and lower plates 42.
It is fixed to. The fixed plate 45 is a leaf spring, and is fixed to a step of the guide auxiliary plate 44 by using spring properties.
The guide auxiliary plate 44 can be slid in the direction of the arrow shown in FIG.

The vertical drive unit 49 includes a solenoid 47, a vertical arm 48, and a fulcrum 48a. Solenoid 4
When the actuator 7 is driven, the upper and lower arms 48 move up and down around the fulcrum 48a, and push the operating portion 42a of the upper and lower plates 42. The upper and lower plates are rotatable around 51, and the distal ends of the upper and lower arms 48 push the operating portions 42a of the upper and lower plates 42, so that
The entrance guide 41 is moved up and down from the state of FIG. 1 to the state of FIG.

The driving force from the vertical driving device 48 is transmitted to the operating portion 42a of the upper and lower plates 42, and the entrance guide 41 is independently attached and detached from the upper and lower plates 42, so that the vertical driving device 48
It is possible to attach and detach the entrance guide 41 independently without removing the entrance guide 41 by a unit while providing a drive mechanism (FIG. 4).

At this time, the entrance guide 41 can be detached independently without removing the unit and without pulling out the unit.

A control section 300 (not shown) is arranged on the back of the apparatus.

Referring to FIG. 5, a block diagram of the control section 300 of the image forming apparatus embodying the present invention will be described.

The control unit 300 includes a reading unit 304, a recording unit 3
05, operation unit 302, communication control unit 306, LCD (display unit) 303, speaker 307, CPU (central processing unit) 301, MPU 311, RAM 313, ROM 31
2. An image processing unit 314.

A CP 301 controls the entire image forming apparatus.
U, a ROM 312 for storing an MPU 311, a control program for the MPU 311, and a RA used as a work area for various data processing and a temporary storage for image information.
M313, an image processing unit 314 that performs image scaling, resolution conversion, and the like.

The CPU 301 is provided with a calendar, a clock function, and the like having a known configuration. An area in the RAM 313 for storing important system setting information such as one-touch key destination information, software, switch information, etc. Protected from accidental obstacles. The control system of the image forming apparatus is the CPU 30 described above.
1 and the following elements 302 to 310 are connected via an interface.

The reading unit 304 includes a driving unit 3 such as a reading motor.
21 (not shown), a reading sensor 322 for reading an image
(Not shown), an image processing unit 323 (not shown) that performs shading and binarization of the read image, and various sensors 324 (not shown) that perform document detection and the like.

The recording unit 305 is a driving unit 32 such as a recording motor.
5 (not shown), a recording unit 326 (not shown) for controlling a laser scanner or an electrophotographic process, an image processing unit 327 (not shown) for performing smoothing of an image to be recorded, various types of detecting recording paper and the like. It comprises a sensor 328 (not shown).

The communication control unit 306 has a connection unit 329 (not shown) composed of a MODEM, an NCU, etc., for performing outgoing calls, incoming calls, encoding of image data, etc., and a connection unit 329 (not shown).
Is connected to a communication network 337 (not shown) and a handset 338 (not shown).

The CPU external interface 309 is
An interface for directly transmitting and receiving data from the U301. For example, by connecting to an external computer via a line such as RS232C, SCSI, or LAN, the device is used as a scanner printer of the external computer. The HDD 310 is used as a large-capacity nonvolatile memory for storing image information and the like.

The size detecting means 701, the means 702 (not shown) for detecting the positions of the leading edge and the trailing edge of the sheet, and the vertical drive 49 are connected to the recording section 305.

The control section 300 controls the moving position of the entrance guide 41 in accordance with the correspondence between the sheet size, the positions of the leading and trailing ends of the sheet, and the moving position of the entrance guide, as described below. The storage of the correspondence (storage means), the selection of the stored correspondence (selection means), and the control along the selection (control means) are performed by the control unit 300.

FIG. 6 is a flowchart showing the operation of the control unit 300. When the leading end of the sheet passes through the entrance guide 41 when the sheet is large (S1), the entrance guide 41 is set to the upper position (S2). A little before the rear end passes through the entrance guide 41 (15 m from the rear end in this embodiment).
m) Set the entrance guide 41 to the lower position (S3, S
4). Then, the copying is ended (S5). When the sheet is of a small size, the entrance guide 41 is set to the lower position (S6).

FIG. 8 is a table summarizing the above operation.

As described above, when the sheet is large in size, the image shock when the leading end of the sheet enters the fixing nip is prevented, and at the rear end of the sheet, the entrance guide 41 is set to the lower position. The fixing roller 21 is released to prevent image disturbance on the sheet due to the curl state of the sheet. In addition, when the sheet is of a small size, lowering the entrance guide 41 prevents poor conveyance.

[Second Embodiment] The control of the second embodiment will be described.

FIGS. 7 and 9 show a second embodiment of the present invention.

In this embodiment, the modes 1, 2, 3, 4,
5 modes, and storing of these control modes,
Selection, control, and the like are performed by the control unit 300.

FIG. 7 is a flowchart showing the operation of the present embodiment. The compensation for the sheet size is determined (S11). If the sheet size is small, the entrance guide 41 is lowered (S11a).
This operation ends.

If the size is large, the mode setting is checked (S12).

In the case of mode 1, the entrance guide 41 is left as it is (up position) (S13).

In the case of mode 2, when the leading end of the sheet passes through the entrance guide 41, the entrance guide 41 is set to the upper position, and the rear end of the sheet passes shortly before the entrance guide 41 passes (only in the present embodiment). The entrance guide 41 is set at the lower position (15 mm from the rear end). When the sheet is small, the entrance guide 41 is set to the lower position (S
13, S14, S15, S16, S17, S18, S1
8a, S18b, S19). If it is not the second side of both sides,
The entrance guide 41 is set to the upper position (S15, S16).

In the mode 3, when the leading edge of the sheet passes through the entrance guide 41, the entrance guide 41 is set to the upper position (S13, S20), and the trailing edge of the sheet is slightly before passing through the entrance guide 41 (in the present embodiment, the rear end). The entrance guide 41 is set to the lower position (15 mm from the end). When the sheet is small, the entrance guide 41 is set to the lower position (S21,
S22, S23).

In the mode 4, when the leading edge of the sheet passes through the entrance guide 41 on only the second side of both sides, the entrance guide 41 is set to the lower position (S12, S24, S26, S2).
9) After the leading edge of the sheet has passed through the entrance guide 41 and is short (in this embodiment, 15 mm from the leading end), the entrance guide 41 is set to the raised position (S30, S31).

Then, just before the rear end of the sheet passes through the entrance guide 41 (15 mm from the rear end in this embodiment), the entrance guide 41 is set to the lower position (S32, S33, S33).
34).

In the case other than the second side of the both sides, the entrance guide 4
1 is set to the upper position (S28).

In mode 5, when the sheet is large in size, when the leading edge of the sheet passes through the entrance guide 41, the entrance guide 41 is set to the lower position (S12, S29), and the leading edge of the sheet passes through the entrance guide 41. After a short time (15 mm from the tip in this embodiment), the entrance guide 41 is set to the raised position (S30, S31).

Then, just before the rear end of the sheet passes through the entrance guide 41 (in this embodiment, 15 mm from the rear end), the entrance guide 41 is set to the lower position (S32, S33, S33).
34).

The above five modes can be switched by the operation unit 302.

In the initial setting, only a service person can perform the switching. However, it is possible for the user to be able to switch according to the setting of the service person.

In the mode 1, since the entrance guide 41 does not move, there is no driving sound for the movement. Also, no energy for driving is required. However, when the size of the sheet is large, the entrance guide 41 is in the upper position, and the fixing roller 21 and the entrance guide 41 are close to each other, so that image disturbance may occur. No image shock and poor transport occur.

In the case of mode 2, only the second side of both sides
When the sheet is large, the rear end of the sheet is slightly before passing through the entrance guide 41 (in this embodiment, 15 m from the rear end).
m) Since the entrance guide 41 is at the lower position, the fixing roller 21 and the entrance guide 41 are separated from each other, so that image distortion at the rear end can be prevented.

Normally, the first side of the sheet has little curl,
Since image disturbance is unlikely to occur, image disturbance is prevented only at the rear end of the second surface. Since the movement of the entrance guide 41 is performed only at the rear end of the second surface when the sheet is large, the driving sound for movement is generated only at the rear end of the second surface when the sheet is large. Further, energy for driving is required only at the rear end of the second surface. No image shock and poor transport occur.

In mode 3, when the sheet is large, always slightly before the trailing end of the sheet passes through the entrance guide 41 (15 mm from the trailing end in this embodiment), the entrance guide 41 is set to the lower position. Therefore, the fixing roller 21 and the entrance guide 41 are separated from each other, so that the rear end of the image can be prevented from being disordered. Although image disturbance at the rear end can be prevented, since the entrance guide 41 always moves when the sheet is large, a driving sound for the movement is generated and energy for driving is required.

In the case of mode 4, only the second side of both sides
When the sheet is of a large size, the entrance guide 41 is set to the lower position just before the front end and the rear end of the sheet pass through the entrance guide 41 (15 mm from the rear end in this embodiment), so that the fixing roller 21 and the entrance guide Because 41 leaves
It is possible to prevent image distortion at the front and rear ends of the second surface.

Normally, the sheet has little curl on the first side,
Since image disturbance is unlikely to occur, the image disturbance is prevented only on the second side. Since the movement of the entrance guide 41 is performed only at the front end and the rear end of the second surface when the sheet is large, the driving sound for movement is generated only on the second surface when the sheet is large.

Also, energy for driving is required only for the second surface. However, since the entrance guide 41 is at the lower position at the end of the second surface, there is a possibility that an image shock may occur on the second surface. No transport failure occurs.

In the mode 5, when the sheet is large, the front end and the rear end of the sheet always pass a little before the entrance guide 41 passes (in this embodiment, 15 m from the rear end).
m) Since the entrance guide 41 is at the lower position, the fixing roller 21 and the entrance guide 41 are separated from each other, so that image disturbance can be prevented. Although image disturbance can be prevented, since the entrance guide 41 always moves when the sheet is large, a driving sound for the movement is generated and energy for driving is required. In addition, since the entrance guide 41 is at the lower position at the tip, an image shock may occur.

By switching the above five modes, it is possible to use the apparatus in accordance with the usage of the user, and the usability is improved.

The modes in the above-described second embodiment are merely examples, and do not limit the control of the movement of the entrance guide 41.

[0094]

As described above, according to the present invention,
By controlling the moving position of the entrance guide according to the correspondence between the size of the transfer material such as the sheet, the positions of the leading and trailing ends of the sheet, and the moving position of the entrance guide as a guide member, when the sheet is large, To prevent image shock and prevent image distortion. In addition, when the sheet is of a small size, conveyance failure is prevented.

In this way, by controlling the moving position of the entrance guide in accordance with the correspondence between the size of the sheet, the positions of the leading and trailing ends of the sheet, and the moving position of the entrance guide, image disturbance does not occur. A fixing device having both high image quality and transportability can be provided.

Further, it is possible to provide a high-performance fixing device in which the position of movement of the entrance guide can be adjusted to achieve both high image quality and high transportability.

Further, it is possible to select which of the image shock prevention and the image disorder prevention is prioritized, and to provide an easy-to-use fixing device suitable for use conditions.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a fixing device according to a first embodiment.

FIG. 2 is an explanatory diagram of the fixing device according to the first embodiment.

FIG. 3 is an explanatory diagram illustrating movement of an entrance guide of the fixing device according to the first embodiment.

FIG. 4 is an explanatory diagram of attachment and detachment of an entrance guide of the fixing device according to the first embodiment.

FIG. 5 is a block diagram of the first embodiment.

FIG. 6 is a flowchart according to the first embodiment.

FIG. 7 is a flowchart showing the operation of the first embodiment.

FIG. 8 is a table in which the operation of FIG. 6 is divided into cases;

FIG. 9 is a diagram illustrating the operation of FIG. 7 in different cases;

FIG. 10 is a sectional view of a multi-function digital copying machine including the fixing device of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Fixing roller 22 Pressure roller 24 Separating claw unit 30 Web unit 40 Entrance guide unit 41 Entrance guide 42 Upper and lower plates 43 Adjusting plate 44 Guide auxiliary plate 45 Fixing plate 46 Lower position adjusting plate 49 Entrance vertical drive 118 Fixing device 300 Control means

Claims (9)

[Claims] A guide for guiding a transfer material carrying unfixed toner to a fixing nip; a first position having at least a leading end of the guide means higher than the fixing nip; and a first position higher than the first position. Moving means for moving between the second position and the lower position, a driving means for driving the moving means, a guide means position detecting means for detecting a moving position of the guide means moved by the moving means, Size detecting means for detecting the size of the transfer material, transfer material end position detecting means for detecting the positions of the leading and trailing ends of the conveyed transfer material, and movement of the guide means in accordance with the size of the transfer material Storage means for storing a plurality of modes in which the positions are set for each passing position of the transfer material; selecting means for selecting a plurality of modes stored in the storing means; and a mode selected by the selecting means. Therefore, the fixing device includes a control unit for controlling the driving unit. 2. The fixing device according to claim 1, wherein the control unit selectively positions the guide unit at the first position and the second position. 3. The fixing device according to claim 1, wherein a positioning unit that determines a position of the guide unit is independently adjustable. 4. The storage device according to claim 1, wherein the storage unit sets the position of the guide unit to the first position regardless of the position of the transfer material passing through the guide unit when the size of the transfer material is large. The fixing device according to claim 1, wherein the fixing device has a mode. 5. When the size of the transfer material is large, the storage means changes the position of the guide means only when the rear end of the transfer material passes through the guide means on the second side of both surfaces. 4. The fixing device according to claim 1, further comprising a second mode that is set to the second position. 5. 6. The storage unit sets the position of the guide unit to the second position only when a rear end of the transfer material passes through the guide unit when the size of the transfer material is large. The fixing device according to claim 1, wherein the fixing device has a second mode. 7. The storage means, when the size of the transfer material is large, when the front and rear ends of the transfer material pass through the guide means at the time of the second side of both surfaces. 4. The fixing device according to claim 1, further comprising a fourth mode for setting a position to the second position. 8. When the size of the transfer material is large, the storage unit sets the position of the guide unit to the first position only when the center of the transfer material passes through the guide unit. The fixing device according to claim 1, wherein the fixing device has a fifth mode. 9. An image forming apparatus comprising the fixing device according to claim 1 as means for fixing a toner image on a transfer material on which an image is recorded and formed.