JPH1020718A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the failure of the components of a fixing device by tempo rarily interrupting an image forming device, when the recording material is judged to be the paper of irregular size of more than a proper length. SOLUTION: A size of the first recording material P is detected by a rear end detecting sensor 23 after the start of the printing operation, and the printing is performed onto the second and following sheets by, for example, throughput 12ppm continuous printing, when the length of the recording material is judged to be a regular size. The printing is performed onto the second and following sheets by, for example, throughput 8ppm, when the size of the recording material is judged to be small. Further the counting of the printed sheets is started simultaneously with the starting of the printing to the second and following sheets by the throughput 12ppm, when the result of the detection of the length of the recording material is neither the regular size nor the small size. When the number of sheets in the continuous printing reaches, for example, 35, the paper supply is stopped, a heater is switched off, the stop time is counted by a timer, the printing is automatically restarted when the stop time reaches, for example, 90 seconds, and the number of sheets of the continuous printing is counted again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic and electrostatic recording type image forming apparatus, for example, a contact heating type fixing apparatus mounted on a copying machine, a laser beam printer or the like, and an image forming apparatus provided with the same. Related to the device.

[0002]

2. Description of the Related Art Conventionally, as a fixing means in an image forming apparatus such as an electrophotographic copying machine and a printer, generally, a heat roller type excellent in thermal efficiency and safety, and an energy saving type film heating type fixing device are used. Has been adopted.

A fixing device of a heat roller type has a heating roller (fixing roller) in which a heat-resistant release layer is coated on the surface of an aluminum or iron core, and a heat-resistant elastic layer formed around a core of stainless steel or the like. A pressure roller has a basic configuration, and the pair of rollers is pressed and rotated to form a fixing nip portion (pressing nip portion) between the two rollers. A recording material (recording material sheet, electrostatic recording paper, electrofax paper, printing paper, etc.) as an object to be heated carrying an unfixed image (unfixed toner image) is introduced into the fixing nip, and the fixing nip is formed. The recording material is nipped and conveyed, so that the unfixed image is heat-pressure fixed as a permanently fixed image on the surface of the recording material by the heat from the heating roller and the pressing force of the fixing nip portion. A halogen heater is disposed as a heating element inside the core of the heating roller, and a paper passing portion on the surface of the heating roller (hereinafter, an area where the recording material passes through the fixing nip portion is referred to as a “paper passing area”, and A portion corresponding to a paper passing area of a heating roller, a pressure roller, a heating element or the like to be described later is referred to as a "non-paper passing area", and a portion corresponding to a non-paper passing area is referred to as a "non-paper passing area". ) Is provided with a temperature detecting element. Based on the detection result of the temperature of the heating roller surface by the temperature detecting element, the halogen heater is turned ON / OFF to adjust the fixing temperature of the heating roller surface or print. Maintains a constant temperature during standby temperature control during standby.

Further, a fixing device of a film heating system is disclosed in, for example, JP-A-63-313182 and JP-A-2-15.
7878, JP-A-4-44075-44083, JP-A-4-204980-204984, and the like. In this apparatus, a heating element having a current-carrying heating element is disposed inside a heat-resistant fixing film formed in an endless shape, and a pressure roller (pressing member) made of an elastic body is disposed outside the fixing film. The fixing film is brought into close contact with the heating element, and the pressure roller is rotated to rotate the fixing film. The recording material carrying the unfixed image is introduced into the fixing nip formed between the pressure roller and the fixing film in this manner, and the recording material is nipped and conveyed at the fixing nip. Thus, the unfixed image is fixed as a permanent image on the recording material by the heat from the heating body applied through the fixing film and the pressing force of the fixing nip. This film heating type fixing device uses a linear heating element with a low heat capacity as a heating element and a thin film with a low heat capacity as a fixing film, so that power saving and shortening of the wait time (quick start sex)
Is possible. The temperature of the heating element is detected by a temperature detecting element arranged at a position corresponding to the sheet passing area on the back of the heating element substrate, and the detection information is fed back to the energization control circuit, and the current is supplied from the AC power supply to the energizing heating element. Is controlled so that the temperature of the heating element detected by the temperature detecting element at the time of fixing execution becomes a predetermined temperature (fixing temperature).

In any of the above two types of fixing devices, the temperature detecting element always keeps the paper passing area even when the paper passing width of the recording material changes, in order to keep the paper passing portion of the heating body at a constant temperature. Are arranged at positions corresponding to the area of

[0006]

However, in the above-described fixing apparatus of the heat roller type or the film heating type,
When a recording material (small size paper) having a smaller paper passing width than the maximum paper passing width that can be introduced into the apparatus is continuously passed and heat fixing is performed, a heating roller, a pressure roller, a heating roller In the paper passing portion of the body, fixing film, etc., the heat consumed for heating the recording material is compensated by the temperature control system and maintained at a predetermined temperature, whereas in the non-paper passing portion, the heat is consumed by the heating of the recording material. Because heat is not consumed, heat is accumulated,
A so-called non-sheet-passing portion temperature rise occurs in which the temperature of the non-sheet-passing portion rises higher than the temperature of the sheet-passing portion maintained and maintained at a predetermined temperature.
When the temperature rise in the non-sheet passing portion is extremely high, there is a problem that the fixing roller bearing, the pressure roller, the fixing film, the film guide stay, and other components around the heating portion are easily damaged by heat.

Further, since the pressure roller made of an elastic material such as heat-resistant rubber has a large coefficient of thermal expansion, the temperature of the non-paper-passing portion is increased by increasing the temperature of the non-paper-passing portion. An outer diameter difference easily occurs with the outer diameter of the roller. In particular, in the case of a film heating type fixing device in which the pressure roller is a driving roller for conveying a recording material or a fixing film, the conveying speed of the recording material or the fixing film is determined by the peripheral speed of the driving roller. Therefore, when a difference in the outer diameter in the longitudinal direction occurs due to the temperature rise of the non-paper passing portion between the paper passing portion and the non-paper passing portion of the pressure roller as the driving roller, the fixing film of the paper passing portion / non-paper passing portion is formed. A speed difference occurs in the transport speed, which may cause the fixing film to shift, buckle, or the like. In this case, there is a problem that the fixing film is damaged.

In order to solve the above-mentioned problems such as the heat damage and the damage of the fixing film, the conventional image forming apparatus is provided with another temperature detecting element in the non-sheet passing portion to detect the temperature of the non-sheet passing portion. In some cases, the temperature of the non-sheet passing portion is prevented from rising by changing the throughput. However, this requires the provision of two or more temperature detecting elements, and has the disadvantage of increasing the cost. In addition, there is a method in which the recording material size is detected and the throughput is automatically reduced in the case of small-size paper to mitigate the temperature rise in the non-paper passing portion. Even when the temperature is small (the temperature rise in the non-sheet passing portion is small), the throughput is reduced, and even when the temperature rise in the non-sheet passing portion is small, it takes a long time until printing is completed. When the length of the recording material is detected by a trailing edge detection sensor or the like to determine the width of the recording material, the width of the recording material can be detected with respect to the fixed size paper, but the recording material having an irregular size is passed. In some cases, the temperature of the non-sheet-passing area cannot be prevented automatically because the width of the recording material cannot be detected.When passing irregular-size paper, the user sets the recording material size to be passed beforehand. There is also a disadvantage that the setting work such as the above becomes necessary and complicated.

Accordingly, the present invention provides a method for reducing heat damage to peripheral components due to an increase in the temperature of a non-sheet passing portion without increasing costs, extending printing time, or performing a complicated recording material size setting operation by a user. An object of the present invention is to provide a fixing device for preventing damage to a fixing film and an image forming apparatus provided with the fixing device.

[0010]

According to the first aspect of the present invention, a heating member and a pressing member are pressed against each other to form a fixing nip portion, and a recording material carrying a toner image is formed on the fixing nip portion. In an image forming apparatus provided with a fixing device for fixing the toner image on the surface of the recording material by heating and pressurizing the toner image by being inserted, a length detecting unit configured to detect a length of the recording material in a conveying direction; Counting means for detecting the number of continuous image formations, and image formation interrupting means for interrupting image formation, wherein the length detection means detects an irregular size and the counting means Is configured to temporarily stop image formation when detecting a predetermined number of continuous image formations.

According to a second aspect of the present invention, the heating member and the pressing member are pressed against each other to form a fixing nip portion, and a recording material carrying a toner image is inserted through the fixing nip portion. In an image forming apparatus including a fixing device that heats and presses a toner image and fixes the toner image on the surface of the recording material, a length detecting unit that detects a length of the recording material in a conveying direction, and a number of continuous images formed on the recording material. Counting means for detecting, and supply interval changing means for changing a supply interval of the recording material, wherein the supply interval changing means is configured such that the length detecting means detects an irregular size, and the counting means determines a predetermined size. The supply interval of the recording material is changed when the number of consecutive images to be formed is detected.

According to a third aspect of the present invention, the heating member and the pressing member are pressed against each other to form a fixing nip portion, and a recording material carrying a toner image is inserted through the fixing nip portion. In an image forming apparatus including a fixing device that heats and presses a toner image and fixes the toner image on the surface of the recording material, a length detecting unit that detects a length of the recording material in a conveying direction, and a number of continuous images formed on the recording material. Counting means for detecting, image forming suspending means for suspending image formation, supply interval changing means for changing the supply interval of the recording material, and when a continuous image formation of a plurality of sheets is instructed, the length detecting means A first mode in which, when a small-size recording material or an irregular-size recording material is detected, the counting unit temporarily suspends image formation by the image forming suspension unit after detecting a predetermined number of continuous image formations; A second mode for changing the feed interval of the recording material by the serial supply interval changing means, these first
And a control means for determining any one of the recording material supply modes having a third mode in which the second mode and the second mode are appropriately combined.

According to a fourth aspect of the present invention, the recording material supply mode is corrected according to the length of the recording material detected by the length detecting means.

According to a fifth aspect of the present invention, there is provided an image carrier having a toner image formed on a surface thereof, and a voltage applied to a transfer member arranged in contact with the image carrier being controlled at a constant voltage. A transfer unit for transferring the toner image on the recording material, a heating member and a pressing member are pressed against each other to form a fixing nip portion, and the recording material carrying the toner image is inserted through the fixing nip portion. An image forming apparatus including a fixing device that heats and presses the toner image to fix the toner image on the recording material surface,
Sheet passing width detecting means for detecting the sheet passing width of the recording material by a current based on constant voltage control at the time of transferring the toner image, counting means for detecting the number of continuous image formation of the recording material,
Image forming suspending means for suspending image formation, the image forming suspending means, when the length detecting means detects the irregular size, and when the counting means detects a predetermined number of continuous image formation , Image formation is temporarily stopped.

According to a sixth aspect of the present invention, there is provided an image carrier having a toner image formed on a surface thereof, and a voltage applied to a transfer member arranged in contact with the image carrier being controlled at a constant voltage. A transfer unit for transferring the toner image on the recording material, a heating member and a pressing member are pressed against each other to form a fixing nip portion, and the recording material carrying the toner image is inserted through the fixing nip portion. An image forming apparatus including a fixing device that heats and presses the toner image to fix the toner image on the recording material surface,
Sheet passing width detecting means for detecting the sheet passing width of the recording material by a current based on constant voltage control at the time of transferring the toner image, counting means for detecting the number of continuous image formation of the recording material,
Image forming suspending means for suspending image formation, and supply interval changing means for changing the supply interval of the recording material, wherein the supply interval changing means detects the irregular size by the paper passing width detecting means. And when the counting means detects a predetermined number of continuous image formations, the supply interval of the recording material is changed.

According to the present invention, the image carrier having a toner image formed on a surface thereof and a voltage applied to a transfer member arranged in contact with the image carrier are controlled at a constant voltage to control the image carrier. A transfer unit for transferring the toner image on the body to the recording material, a heating member and a pressing member are pressed against each other to form a fixing nip portion, and the recording material carrying the toner image is inserted through the fixing nip portion. In the image forming apparatus provided with a fixing device that heats and pressurizes the toner image to fix the toner image on the surface of the recording material, the detection of the paper passing width of the recording material by a current based on constant voltage control during the transfer of the toner image is performed. Paper width detecting means, counting means for detecting the number of continuous images formed on the recording material, image forming suspending means for interrupting image formation, supply interval changing means for changing the supply interval of the recording material, and Image formation When instructed, when the sheet passing width detecting means detects a recording material of a small size or a recording material of an irregular size, the counting means detects the predetermined number of continuous images to be formed, and the image forming interrupting means detects the image formation. A first mode in which the supply interval of the recording material is changed by the supply interval changing means,
It is characterized by comprising a control means for determining any one of the recording material supply modes having a third mode in which the first mode and the second mode are appropriately combined.

According to an eighth aspect of the present invention, the recording material supply mode is corrected according to the recording material passing width detected by the paper passing width detecting means. Image forming device.

[Operation] Based on the above configuration, it is possible to suppress the temperature rise of the non-sheet passing portion during continuous image formation.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus to which a fixing device according to the present invention is applied.

In FIG. 1, reference numeral 1 denotes a drum-type electrophotographic photosensitive member (hereinafter, referred to as a "photosensitive drum") as an image carrier, which is formed on a surface of a substrate on which a conductive member such as aluminum or nickel is formed in a cylindrical shape. It is provided with a photosensitive layer. As the photosensitive layer, OPC (organic semiconductor), a-Si (amorphous silicon), or the like can be used. The photosensitive drum 1 is rotatably supported by an image forming apparatus main body (not shown), and is driven to rotate clockwise in the figure at a predetermined peripheral speed (process speed) by a driving means (not shown).

Around the photosensitive drum 1, a charging roller (charging means) 2 for uniformly charging the surface of the photosensitive drum 1 to a predetermined polarity substantially in the direction of rotation thereof, and exposing the charged surface of the photosensitive drum 1 to light. An exposure device (exposure means) 3 for forming an electrostatic latent image according to image information, a developing device (developing means) 4 for attaching toner to the electrostatic latent image and developing it as a toner image,
A transfer roller (transfer means) for transferring the toner image on the photosensitive drum 1 onto a recording material P such as paper, and a cleaner (cleaning means) 7 for removing transfer residual toner remaining on the surface of the photosensitive drum 1 after transfer are provided. ing. A fixing device 6 that heats and presses the unfixed toner transferred onto the recording material P and fixes the unfixed toner transferred onto the recording material P is provided downstream of the transfer roller 5 in the transport direction of the recording material P.

On the upstream side of the transfer roller 5 in the conveying direction of the recording material P, a manual tray 21 and a manual tray 2 on which a recording material P other than a fixed type to be manually inserted are set.
1, a paper feed roller 22 for feeding the recording material P on the recording medium P, and a registration roller 24 for synchronizing the conveyed recording material P with the toner image on the photosensitive drum 1 are provided. Further, below the transfer roller 5, there are provided a paper feed cassette 26 for storing a fixed recording material P, and a paper feed roller 27 for feeding the recording material P from this to the registration roller 24. In the figure, reference numeral 23 denotes a trailing end detection sensor for detecting the trailing end of the manually inserted recording material P, and reference numeral 25 denotes a registration sensor. Each of them functions as a length detecting means of the recording material P as described later.

Next, the operation of the above-described image forming apparatus will be briefly described.

The surface of the photosensitive drum 1 driven to rotate clockwise in FIG. 1 is uniformly charged to a predetermined potential by the charging roller 2. An electrostatic latent image is formed on the surface of the charged photosensitive drum 1 by receiving scanning exposure (image exposure) of a laser beam from an exposure device 3 that is turned on / off in accordance with image information. The electrostatic latent image is developed with a toner by a developing device 4 as a toner image (visible image). As a developing method, a jumping developing method, a two-component developing method, an FEED developing method, or the like is used. In many cases, reversal developing is used in combination with the above-described image exposure.

The recording material P is taken out from the manual feed tray 21 or the paper feed cassette 26 by the paper feed roller 22 or the paper feed roller 27. When the paper is fed from the manual feed tray 21, the trailing edge detection sensor 23 detects the size of the recording material. That is, the conveyance length of the recording material P is detected. Regardless of whether paper is fed from the manual feed tray 21 or the paper feed cassette 26, the recording material P
Is supplied to a transfer nip formed by the photosensitive drum 1 and the transfer roller 5 in synchronization with the toner image formed on the surface of the photosensitive drum 1 by the registration roller 24. In the transfer nip portion, the toner image on the photosensitive drum 1 is transferred onto the surface of the recording material P by the action of a transfer bias from a power supply (not shown). Recording material P carrying unfixed toner image on its surface
Is transported to the fixing device 6, and after the unfixed toner image on the surface is heated and pressed at the fixing nip portion of the fixing device 6,
It is discharged outside the device body. On the other hand, the transfer residual toner remaining on the surface of the photosensitive drum 1 after the transfer of the toner image is removed by the cleaner 7 and is used for the next image formation.

Next, the fixing operation in the fixing device 6 will be described in detail.

FIG. 2 is a schematic sectional view of a film heating type fixing device as an example of the fixing device according to the present invention.
The configuration and operation will be described below with reference to FIG.

In the figure, 10 is endless (endless)
Is a belt-shaped heat-resistant film (fixing film) formed in a semicircular arc-shaped film guide member (stay).
13 is fitted outside with a margin in the circumferential length.

The fixing film 10 has a total thickness of 100 μm or less, preferably 40 μm or less and 20 μm or more in order to reduce the heat capacity and improve the quick start property. Durable P
It is a single-layer film of TFE, PFA, PPS, or the like, or a composite layer film in which a film of polyimide, polyamideimide, PEEK, PES, or the like is coated with PTFE, PFA, FEP, or the like as a release layer.

Reference numeral 12 denotes a ceramic heater as a heating member, which is formed by sequentially forming a heating element on which a heating paste is printed on a ceramic substrate, and a glass coating layer for protecting the heating element and ensuring insulation. Heat is generated by applying an AC current whose power is controlled to the heating element on the heater 12. A chip thermistor (temperature detecting element) 14 is provided on the substrate surface side (upper surface in the figure) of the ceramic substrate.
The chip thermistor 14 detects a temperature change within a time when the power supply to the heater is turned OFF or ON for a certain period of time when paper is not passed, and determines a target temperature of the heater based on the detection result. By controlling the heater driving means (not shown), the electric power to the heater 12 is controlled, whereby
The heater temperature is maintained at a target temperature (print temperature).

In the fixing device 6 of the present embodiment, as shown in the front view of FIG. 3, a thermistor 14 is arranged near the longitudinal end of the ceramic heater 12, and the size of recording material (paper passing width) is different. However, this is a one-side reference configuration in which the end of the recording material always passes through the point a on the fixing film 10 (paper passing reference). That is, the recording material introduced into the fixing device 6 has a maximum width (indicated as a maximum paper passing area in FIG. 4) to a minimum width (in the figure, a minimum recording material width passing area). ), Everything passes through the point a.

Reference numeral 11 denotes a pressure roller as a pressure member, which is a rotating body provided with an elastic layer formed by molding a heat-resistant rubber such as silicone rubber on a cored bar, or a sponge elastic layer formed by foaming silicone rubber. , PFA, P on the elastic layer
A heat-resistant release layer made of a fluororesin such as TFE or FEP may be formed. The pressure roller 11 is urged from below by a spring (not shown) toward the upper ceramic heater 12, thereby bringing the fixing film 10 into close contact with the ceramic heater 12. The pressure roller 11 is rotationally driven by a driving unit (not shown). Due to the rotation of the pressure roller 11, the fixing film 10 and the recording material P are respectively driven and rotated in the direction of the arrow (clockwise in the figure), and are conveyed in the direction of the arrow (the left in the figure). It has a configuration.

The recording material P introduced into the fixing device 6 has a fixing nip portion in which an unfixed toner image T on the surface is formed between a heating portion (the fixing film 10 and the ceramic heater 12) and the pressure roller 11. (Abutting nip) is heated and pressurized in N, is fixed on the surface of the recording material P, and is then discharged out of the image forming apparatus main body.

In FIG. 4, a polyimide-based seamless film having a film thickness of 40 μm and an outer diameter of 25 mm is used as the fixing film 10, and a silicone rubber roller having an outer diameter of 25 mm and an elastic layer thickness t = 3 mm is used as a pressing roller. mm / sec], throughput 12 ppm,
A recording material of small size (narrow size) (105 ×) immediately after the apparatus is started at an initial temperature control temperature of 200 ° C. to a final temperature control of 160 ° C.
241 mm), the surface temperature of the pressure roller 11 (FIG. 4A) when the paper is continuously fed, and the film guide stay 13
(FIG. 4B).

A curve T ₁ shown in FIG. 4A is the temperature of the paper passing portion on the surface of the pressure roller 11, and the temperature is increased by the heat given from the ceramic heater 12 via the fixing film 10 at the same time as the start of the paper passing. The temperature at which the heat taken up by the recording material P and the amount of heat supplied from the ceramic heater 12 are in an equilibrium state, specifically, about 110
It is kept at a constant temperature in ° C. On the other hand, a curve T ₂ shown in FIG. 4A is the temperature of the non-sheet passing portion on the surface of the heating roller 11. The temperature of the non-sheet passing portion is excessively accumulated in the pressure roller 11 because the heat supplied from the ceramic heater 12 is not deprived by the recording material P, and the temperature of the non-sheet passing portion is higher than that of the sheet passing portion. The temperature reaches about 200 ° C. after about 100 sheets of paper.
The pressure roller temperature difference between the paper passing portion and the non-paper passing portion after 100 sheets of small size continuous paper is about 90 ° C. Due to the difference in outer diameter, there is a possibility that a speed difference occurs in the conveyance speed of the fixing film 10 being conveyed by the pressure roller 11 and the film may buckle or break.

A curve T ₃ shown in FIG. 4B is the temperature of the surface of the film guide stay 13 that guides the fixing film 10, facing the heater, and the curve T ₄ is the same.
This is the temperature of the non-sheet passing portion of the film guide stay 13 facing the heater. The temperature of the paper passing portion of the film guide stay 13 gradually rises by the heat transmitted from the back of the heating body 12 at the same time as the continuous paper passing starts, reaches about 190 ° C., saturates, and is thereafter maintained at a constant temperature. On the other hand, the non-sheet passing portion temperature is over supplied heat is accumulated from the heating member 12 the temperature rises according overlapping continuous paper feed, the temperature is 100-sheet continuous paper feed of the film guide stay 13 shown by a curve T ₄ About 280 ℃
Reach

In general, a heat-resistant plastic such as PPS (polyphenylene sulfide) is used as a constituent material of the film guide stay 13, and its thermal deformation temperature is about 260 ° C. (at a load of 18.5 kg / cm ² ). Therefore, if the temperature of the non-sheet passing portion rises excessively, the film guide stay 13 may be deformed or melted.

FIG. 5A shows a state in which the fixing device according to the present embodiment is used, the process speed is 63 mm / sec, the initial temperature control temperature is 200.degree. C. to the final temperature control 160.degree. Small-size recording material (envelope: 105 × 241m)
m), when the paper is continuously passed at a throughput of 8 ppm and 12 ppm, the non-paper passing portion surface temperature T ₅ of the pressure roller 11,
Indicates T _6, also shows a non-sheet passing portion temperature T _7, T ₈ of the film guide stay 13 when the same in FIG. (B), further, a continuous throughput of 12ppm in the same conditions in Figure 6 stop printing after 35 sheets printed, indicating the temperature T ₉ of the non-sheet passing portion of the film guide stay 13 in the case where the ceramic heater 12 was left turn OFF.

As shown in FIGS. 5 (a) and 5 (b), both the surface temperature of the pressure roller 11 and the temperature of the film guide stay 13 increase the non-sheet passing portion temperature at a rate of 12 ppm when the throughput is faster. As the throughput decreases to 8 ppm, the temperature reached by raising the temperature of the non-sheet passing portion also decreases. This is because the heat accumulated in the non-sheet passing portion due to the passing of the small size paper moves to the sheet passing portion between the recording materials, and the pressure roller 11
The effect of trying to make the surface temperature uniform is that the interval between recording materials (non-sheet passing time) is shorter than the sheet passing time by 12 ppm.
In this case, the heat is hardly obtained and heat is accumulated in the non-sheet passing portion. On the other hand, as the throughput is reduced and the distance between the recording materials is increased relative to the sheet passing time, the temperature of the sheet passing portion / non-sheet passing portion becomes higher. This is because uniformization is promoted. By reducing the throughput in this way, the temperature rise in the non-sheet passing portion can be suppressed to a temperature equal to or lower than the temperature at which the components of the fixing device 6 are damaged.
Further, as shown in FIG. 6, when the paper supply is temporarily stopped in a state where the temperature of the non-sheet passing portion has reached 240 ° C. and the supply of heat from the ceramic heater 12 is stopped, the non-sheet passing is stopped for about 90 seconds. It can be seen that the paper temperature drops to 50 ° C. From this, it can be seen that by temporarily stopping paper feeding at every fixed number of prints and turning off the ceramic heater 12, the temperature rise in the non-paper passing portion can be eased.

In a conventional image forming apparatus, the size of a recording material is detected by a trailing end detection sensor or the like, and if the length of the recording material in the transport direction (hereinafter, simply referred to as "recording material length") is less than a certain length, The fixing device 6 is determined to be a small size paper such as an envelope, and automatically lowers the throughput to raise the temperature of the non-paper passing portion.
The damage of the component members was prevented.

However, when judging the recording material size from the result of detection of the recording material length by the trailing edge detection sensor, for example, irregular-sized paper having a long recording material length but a narrow paper passing width is continuously fed. In such a case, the temperature rise in the non-sheet passing portion cannot be automatically prevented, and the components of the fixing device 6 may be damaged.

Therefore, in the present embodiment, the conventional method,
That is, when the recording material length is detected by the trailing edge detection sensor and the recording material length is equal to or less than a predetermined value, the size is determined to be small, and the throughput is reduced to prevent the non-sheet passing portion from rising in temperature.
When the recording material size is determined to be irregular paper of a certain length or more based on the detection result of the recording material length, a mode is provided in which printing is automatically stopped for 90 seconds for every 35 sheets passed, and the irregular size paper is used. Of the non-sheet passing portion is prevented from rising. As described above, the reason why the printing is temporarily interrupted only when a predetermined number of sheets are continuously passed when the irregular-size paper is passed is that the irregular-size paper is a paper that is used less frequently. It is considered that it is rare that a large amount of continuous printing is performed using a small size dedicated feeder like regular small size paper, so if an irregular size with a wide paper width is passed, This is to prevent the time until the end of printing from becoming long as much as possible.

FIG. 26 shows the recording material size of the main fixed size paper which is usually used. Since all the image forming apparatuses used in the present invention have the configuration of the vertical feeding, the size in the vertical feeding, that is, the length in the transport direction is shown.

The size of the recording material is determined by the time T from when the leading edge of the recording material enters the trailing edge detection sensor to when the trailing edge of the recording material comes off.
[Sec] is measured, and this value and the process speed V _P = 6
From 3 [mm / sec], the recording material length L [mm] is calculated by the following equation:
L = 63 × T. In the present embodiment, the size detection of the recording material is performed by the trailing edge detection sensor, but this detection can be similarly performed by the registration sensor. FIG.
Further, among the envelopes / postcards, which are typical small-size papers, the longest recording material length is L = 241 [mm]. Therefore, in the present embodiment, a measurement error is also expected L ≦ 243 [m].
m], it was determined that the paper was small size paper. Also, L = 279
± 2 [mm] (standard LETTER size), L = 356
± 2 [mm] (standard LEGAL size), L = 297 ±
In this embodiment, three sizes of 2 [mm] (standard A4 size) are defined as standard large-size paper, and in the case of other recording material lengths L, it is determined to be an irregular size. In the present embodiment, the throughput is switched from 12 ppm to 8 ppm in the case of small-size paper. However, the throughput can be changed without changing the rotation speed of the photosensitive drum 1 or the fixing device 6 and recording using the rear end detection sensor. This was performed by controlling the distance between the materials.

FIG. 7 shows how to determine the paper feed interval. The length of the recording material is L ₁ [mm], the interval between the required recording materials is L ₂ [mm],
If the process speed V _P = 63 [mm / sec],
Between recording materials having a throughput of 12 ppm, L ₂ = (63 ×
60-12 × L ₁₎ / 11, between the recording material throughput 8ppm becomes _{L 2 = (63 × 60-8 ×} L 1) / 7.

FIG. 8 is a block diagram of the fixing sequence control of the image forming apparatus according to the first embodiment. The fixing sequence will be described with reference to FIG.

When the recording material P is supplied from the paper feed cassette 26, the recording material size information (paper size information) from the cassette size detecting means 31 of the printer engine unit 30 is sent to the CPU 51 of the engine controller unit 50. Can be On the other hand, when the recording material P is supplied from the manual feed tray 21, the size of the recording material is detected from the passage time when the recording material P passes through the trailing edge detection sensor 23 or the registration sensor 25, and the result is sent to the CPU 51. send. When it is determined from the result of the above-described recording material size detection that the paper is a fixed-size small-size paper, the CPU 51 determines the throughput to be 8 ppm, and the paper feeding controller 52 controls the paper feeding driving unit 32.
, The recording material interval at the time of paper feeding is controlled, and printing is performed at a desired throughput until the printing is completed. On the other hand, if it is determined from the result of the recording material size detection that the paper is a regular large-size paper, the CPU 51 determines the throughput to be 12 ppm, and controls the recording material interval by the paper feed controller 52 until printing is completed at a desired throughput. When the CPU 51 determines that the paper is of an irregular size based on the result of the recording material size detection, the CPU 51 determines the throughput to be 12 ppm, and controls the recording material interval by the paper supply controller 33 to start printing at a desired throughput. The number of sheets is counted and the continuous sheet number information is sent to the CPU 51. The CPU 51
When the paper feeding mode is specified and the continuous paper feeding reaches 35 sheets, the paper feeding is stopped by the paper feeding driving means 32 for 90 seconds,
In the meantime, the power supply to the heater is turned off by the heater controller 53 via the heater driving means 33. The 90 seconds are counted by the timer counter 55, printing is restarted 90 seconds after the stop of sheet feeding, and the number of continuous sheets fed is counted again.

FIG. 9 shows a flowchart of a fixing sequence according to the present embodiment. After the start of printing, the size of the first recording material is detected by the trailing edge detection sensor 23 or the like, and the recording material size is determined (S1). When the recording material length L is L = 279
± 2 [mm] or L = 356 ± 2 [mm] or L = 29
In the case of 7 ± 2 [mm], it is determined to be a fixed size and large size, and printing of the second and subsequent sheets is performed until the end of printing with continuous printing at a throughput of 12 ppm (S2). When the recording material size is L ≦ 243 [m
m], the size is determined to be small, and the throughput is 8 ppm.
Is performed until printing of the second and subsequent sheets is completed (S3). If the detection result of the recording material length does not apply to any of the above-mentioned standard large size or small size, the throughput is 12p
pm to start printing on the second and subsequent sheets (S4).
The counting of the number of printed sheets is started (S5). When the number of continuous prints reaches 35, the paper supply is stopped (S6), the heater is turned off, and the stop time is counted by a timer (S7). When the stop time reaches 90 seconds, printing is automatically restarted (S8), and the number of continuous printing sheets is counted again.

FIG. 10 shows the transition (shown by (b)) of the surface temperature of the non-sheet passing portion of the pressure roller 11 when continuous printing of irregular-sized small-size paper (140 × 270 mm) is performed in this embodiment. And the transition of the non-sheet passing portion temperature of the film guide stay 13 (illustrated by (a)). As shown in the figure, the maximum temperature of the surface of the non-sheet passing portion of the pressure roller 11 was 160 ° C., and no buckling or breakage of the fixing film due to the difference in the outer diameter in the longitudinal direction of the pressure roller occurred. The maximum temperature of the non-sheet passing portion of the film guide stay 13 is 23.
The temperature was 5 ° C., and no thermal deformation of the film guide stay 13 occurred. As described above, as a result of recording material size detection,
By providing a mode that automatically stops printing at a fixed number of prints when it is determined that the recording material is irregular, the user can perform irregular printing without having to perform any troublesome work such as specifying the irregular size. Even when printing is performed on a recording material with a narrow paper width, it is possible to prevent deformation and damage of the constituent members of the fixing device 6 due to excessive heating of the non-paper passing portion. In addition, when the number of printed sheets is relatively small even for irregular-size paper, printing can be performed at the same throughput as that for regular large-size paper, and there is little increase in the time until printing is completed. <Embodiment 2> In the present embodiment, based on the recording material size detection result and the continuous paper number information obtained from the host computer, if the recording material has a fixed small size or an irregular size, it depends on the continuous printing number. An example in which the throughput is determined by the following will be described.

In this embodiment, an experiment was conducted using a film heating type fixing device having the same configuration as that of the first embodiment.

FIG. 11 is a block diagram of the fixing sequence control of the image forming apparatus according to the second embodiment.

When the recording material P is supplied from the sheet feeding cassette 26, the recording material size information of the recording material P is transmitted from the cassette size detecting means 31 to the CP of the engine controller 50.
It is input to U51. On the other hand, the recording material P is
1 is supplied from the rear end detection sensor 23.
Alternatively, the size of the recording material is detected based on the time of passage through the registration sensor 25, and the result is input to the CPU 51 as recording material size information. On the other hand, if the information on the number of prints sent from the host computer 56 is C
It is input to PU51. If it is determined from the result of the above-described recording material size detection that the size is the standard small size or the irregular size, the throughput is determined from the information on the number of printed sheets sent from the host computer 56 in advance, and
The printing is performed at a desired throughput by controlling the paper feeding interval of the recording material according to (2).

FIG. 12 shows a flowchart of a fixing sequence according to the present embodiment.

After the start of printing, the size of the first recording material is detected by a trailing edge detection sensor or the like, and the size of the recording material is determined (S11). If it is determined that the size is the large size of the standard size, the printing of the second and subsequent sheets is performed until the end of printing in continuous printing at a throughput of 12 ppm (S12). When it is determined that the recording material size is the standard small size or the irregular size, the number of prints is determined (S13), and the throughput is determined according to the number of prints. Throughput 1 when the number of prints N is N ≦ 35
2 ppm (S12), the throughput is set to 10 ppm (S14) when 35 <N ≦ 50, and the throughput is set to 8 ppm (S15) when N> 50. Applying this embodiment to FIG. 27,
Continuous printing of irregularly shaped recording materials with narrow paper width (irregular narrow paper)
This shows the time until the end of printing when 0 sheets are continuously printed and 50 sheets are printed. The numbers in parentheses in the figure indicate the uniform throughput of 8p.
pm is the time required to complete printing. In the case of applying the present embodiment, the time until printing is completed for 75 seconds is shortened in the case of continuous 50 sheets and in the case of continuous 30 sheets. Further, in this case, the maximum temperature of the non-sheet passing portion is 160 ° C. or less for the pressure roller 11 and 240 ° C. or less for the film guide stay 13, and the temperature of the non-sheet passing portion is increased. No damage occurred.

As described above, when the recording material size is detected, if the fixed size or the irregular size is detected, the throughput is determined according to the number of prints and printing is performed.
Only when the number of printed sheets is excessive and the excessive temperature rises in the non-sheet passing portion, the temperature rise in the non-sheet passing portion of irregularly shaped narrow paper is suppressed. By setting the speed quickly, it is possible to shorten the time until the end of printing and to reduce the delay of the printing time while preventing damage to the components of the fixing device 6 due to the temperature rise in the non-sheet passing portion. <Third Embodiment> In the third embodiment, based on the detection result of the recording material size and the information on the number of continuous sheets passed from the host computer, in the case of the standard small size or the irregular size,
Depending on the number of continuous prints, select a paper-passing mode in which the time until printing ends is short at 12 ppm for every 35 sheets or 90 seconds for every 65 sheets at 10 ppm depending on the continuous printing number, and the configuration of the fixing device by raising the temperature of the non-paper-passing portion. An example will be described in which the time until printing is completed is minimized while preventing damage to members.

Also in this embodiment, an experiment was conducted using a film heating type fixing device having the same configuration as that of the first embodiment.

FIG. 13 shows the relationship between the number of continuous prints and the time required until the end of printing. The time required for printing includes the number of printed sheets and the throughput (a mode for changing the throughput is referred to as a “second mode”), and a printing stop time (a mode for providing the printing stop time is referred to as a “first mode”. The mode appropriately combined with the second mode and the first mode is referred to as “third mode”. As shown in FIG. 13, when the number of prints N is 1 ≦ N ≦ 35, the required time is shorter at 12 ppm than at 10 ppm. 10 ppm requires less time. In the present embodiment, the throughput is selected based on the number of prints N shown in FIG. In the image forming apparatus described in the present embodiment, since the maximum number of envelope feeders that can be stacked is 80, printing is performed once every 80 sheets.
After stopping for more than a second, the count of the number of sheets is reset once, and for subsequent printing, the number of sheets is counted again from the first sheet.

FIG. 14 is a block diagram of the fixing sequence control of the image forming apparatus to which the present embodiment is applied. The first embodiment (FIG. 8) and the second embodiment (FIG. 11)
The same reference numerals are given to the same components as those described above, and the description thereof will be omitted.

When the recording material P is supplied from the paper feed cassette 26, the recording material size information of the recording material P is transmitted from the cassette size detecting means 31 to the CP of the engine controller 50.
It is input to U51. On the other hand, the recording material P is
1 is supplied from the rear end detection sensor 23.
Alternatively, the size of the recording material is detected based on the time of passage through the registration sensor 25, and the result is input to the CPU 51 as recording material size information. On the other hand, if the information on the number of prints sent from the host computer 56 is C
It is input to PU51. If it is determined from the result of the above-described recording material size detection that the size is the standard small size or the irregular size, the paper feed mode is selected from the print number information transmitted from the host computer 56 in advance, and the paper feed drive unit 3 is selected.
2, the printing is performed in a predetermined feeding mode by controlling the feeding interval of the recording material.

FIG. 15 shows a flowchart of a fixing sequence according to the present embodiment.

The size of the first recording material after the start of printing is detected by the trailing edge detection sensor 23 and the like, and the size of the recording material is determined (S21). If it is determined that the size is the large size of the standard size, the printing of the second and subsequent sheets is performed until the end of printing in continuous printing at a throughput of 12 ppm (S22). When the recording material size is determined to be the fixed small size or the irregular size, the throughput is determined according to the number of prints (S23). When the number of prints N is 1 ≦ N ≦ 35 or 66 ≦ N ≦ 70, printing of the second and subsequent sheets is started at a throughput of 12 ppm (S2
4) Count the number of prints (S25), stop printing for every 35 sheets for 90 seconds (S26), start timer counting (S27), and restart printing after 90 seconds. In this way, printing is completed or up to 80 sheets. Number of prints is 3
When 6 ≦ N ≦ 65 or 71 ≦ N ≦ 80, printing of the second and subsequent sheets is started at a throughput of 10 ppm (S27),
The number of printed sheets is counted (S28), printing is stopped for every 65 sheets for 90 seconds (S31), timer counting is started (S27), and printing is resumed after 90 seconds. In this way, printing is completed or printing is performed up to 80 sheets. Although not shown when the total number of printed sheets is 80 or more, after 80 sheets are printed, feeding is stopped, and printing is stopped for 120 seconds.

FIG. 29 shows the required printing time before and after the throughput switching number in this embodiment.

The rightmost column in FIG. 29 shows the required printing time which is shorter when printing is performed at the throughput designated in this embodiment than when printing is performed at the other throughput. By switching the paper feed mode according to the number of prints in this manner, in the present embodiment, the required printing time can be reduced by up to 70 seconds.

As described above, when the recording material size is detected, if the fixed size or irregular size is selected, the paper feed mode is automatically selected according to the number of prints and printing is performed. Only when excessive excessive temperature rise in the non-sheet passing portion occurs, the temperature rise in the non-sheet passing portion of the irregularly shaped narrow width paper is suppressed to fix the fixing device 6.
Can be prevented, and the required printing time can be minimized. <Embodiment 4> In this embodiment, a transfer current flowing to a photosensitive drum via a recording material during constant voltage transfer is monitored.
The paper feed width of the recording material is determined from the detection result of the current value,
A specific example of preventing a non-sheet passing portion of a non-standard-size narrow-size sheet (a non-standard-size sheet) from rising in temperature will be described.

The image forming apparatus of this embodiment shown in FIG. 16 employs a roller transfer system. In this transfer method, a transfer voltage is applied to the recording material P by a transfer roller 5 of a medium-resistance elastic body which is formed by dispersing carbon in EPDM or the like on a metal core, and is formed by foaming. Is applied to the transfer roller 5, and from the voltage generated at that time,
Determines the transfer voltage V _T by the control equation is set in advance, applies a constant voltage control V _T at the time of transfer, control is performed by the so-called PTVC scheme. In the present embodiment, as shown in FIG. 16, a transfer high-voltage power supply 61 and a transfer current detection circuit (transfer current detection means) 62 are provided to the transfer roller 5.
Constitutes a transfer voltage application circuit, and
The D / A converter 63 and the engine controller 50 are connected. Then, the transfer current detection circuit 62 described above transfers the transfer current value I when the transfer voltage V _T (constant voltage control) is applied.
_tr was measured.

FIG. 17 shows the relationship between the transfer voltage and the transfer current in the image forming apparatus according to the fourth embodiment. FIG.
The middle curve (a) shows the transfer current value when there is no recording material, the curve (b) shows the transfer current value when transferring a recording material having a half width of the maximum paper width, and the curve (c) shows the maximum. This is a transfer current value at the time of transfer of the recording material of the sheet passing width. The transfer current value I _tr is I _max when there is no paper, and I _{max is} the value when the maximum paper width recording material is transferred.
_{If it is min} , it changes almost in inverse proportion to ΔI = I _max −I _min . From this relationship, the transfer voltage V _T and the transfer current I _tr
From this, the recording material width can be predicted. In this embodiment, when _Itr ≧ _Imin + 2/3 △ I, it is determined that the recording material is narrow (small size paper). As for the standard paper, the size detection by detecting the length of the recording material,
Small size / large size was determined by cassette size detection.

In this embodiment, specific control will be described using a film heating type fixing device having the same configuration as that of the above-described embodiment.

FIG. 18 is a block diagram of a fixing sequence control of the image forming apparatus to which the present embodiment is applied. The same components as those described above are denoted by the same reference numerals, and the description of the fixing device is omitted.

When the recording material is fed from the paper feed unit, the size of the recording material is detected from the passage time of the recording material passing through the trailing edge detection sensor 23 or the registration sensor 25, and the result is sent to the CPU 51 of the engine controller 50. send. In the case of paper feeding from the paper feeding cassette 26, the cassette size detecting means 31
The size of the recording material is detected by the
Send to Next, at the time of transfer, the transfer current is detected by the transfer current detecting means 62 and the result is transmitted to the engine controller 5.
0 to the CPU 51. The CPU 51 determines the recording material size based on the detection result of the recording material length, the detection result of the transfer current and the transfer voltage _VT data to determine the throughput, and feeds the paper by the paper feed driving unit 32 via the paper feed controller 52. Printing is performed at a desired throughput by controlling the interval.

FIG. 19 shows a flowchart of a fixing sequence according to the present embodiment.

After the start of printing, the size of the first recording material is detected by the trailing edge detection sensor 23 or the like (S51), and the length of the recording material is detected. When it is determined from the detection result that the size is the large size of the standard size, the second and subsequent sheets are continuously printed until the end of printing in continuous printing at a throughput of 12 ppm (S52). If it is determined from the detection result that the recording material size is the standard small size, the second and subsequent sheets are printed until the end of printing in continuous printing at a throughput of 8 ppm (S53). From the detection result, the recording material size when it is determined that the irregular size, detects a transfer current value when the transfer (S54), determines recording material sheet passing width than the transfer voltage V _T. The transfer current value is I _tr ≧ I _min +
(2/3) In the case of ΔI, it is determined that the size is small, printing is performed at a throughput of 8 ppm (S53), and the transfer current value is I
_{If tr} <I _min + (2/3) △ I, it is determined that the size is large, and printing is performed at a throughput of 12 ppm until the printing is completed (S55).

As described above, by monitoring the transfer current and detecting the sheet passing width of the recording material, it is possible to determine the small size or the large size even with an irregular size, and a sensor such as a sheet passing width detecting sensor is used. It is possible to execute the print mode for preventing the non-sheet-passing portion temperature from increasing only in the case of the small size without adding. In the present embodiment, the throughput is switched based on the result of the sheet passing width detection. However, the method of alleviating the temperature rise in the non-sheet passing section is not limited to this, and may be performed in combination with, for example, temporarily stopping printing. The print mode may be corrected based on the print number information from the computer. <Embodiment 5> In the present embodiment, the rear end detection sensor 2
The paper feed mode is determined based on the result of detecting the recording material length by step 3 and the result of monitoring the transfer current and detecting the sheet passing width of the recording material. A specific example will be described in which the sheet feeding mode is corrected according to the length of the recording material to prevent the temperature rise in the non-sheet passing portion.

FIG. 20 is a schematic sectional view of a heat roller type fixing device 6A as another example of the fixing device used in the image forming apparatus to which the present invention is applied. Hereinafter, the configuration and operation will be described.

In FIG. 20, reference numeral 70 denotes a heating roller having a halogen heater therein, and reference numeral 71 denotes a pressure roller having an elastic layer, and both rollers are arranged so as to be parallel to each other above and below. The pressure roller 71 is disposed in pressure contact with the heating roller 70 by a spring (not shown). N is a fixing nip portion formed by pressing the rollers 20 and 21 against each other. The heating roller 70 is rotationally driven in a direction indicated by an arrow (clockwise) by a driving unit (not shown), and the pressure roller 71 is rotated by following the rotation. The recording material P carrying the unfixed toner image is nipped and conveyed at the fixing nip N, and the toner is heated and melted by applying heat and pressure, and is fixed on the recording material to obtain a permanently fixed image.

The heating roller 70 is provided with a heat-resistant release layer 70b made of a fluororesin such as PFA or PTFE on a core metal 70a obtained by processing aluminum or stainless steel into a hollow cylindrical shape to improve the releasability from the toner. It is a coated roller. The heating roller 70 is a bearing (FIG. 22) made of heat-resistant resin.
24).

The pressure roller 71 is a roller in which a heat-resistant elastic layer 71b such as silicone rubber is formed on a cored bar 71a. A temperature detecting element 72 is provided on the surface of the heating roller 70, and the temperature of the surface of the heating roller 70 is detected by the temperature detecting element 72. Based on the detection result, a halogen heater 73 is provided by heater driving means (not shown). ON /
By performing the OFF control, the surface temperature of the heating roller 70 is maintained at a predetermined set temperature (print temperature) or a standby temperature at the time of non-fixing (standby temperature).

In this embodiment, the core metal thickness is 3.0 mm /
A heating roller 70 having an outer diameter of 25 mm and provided with a PFA coating layer on the surface, and a pressure roller 71 having an outer diameter of 25 mm and a roller hardness of 45 degrees (Asker C) formed by molding silicone rubber on a core metal having an outer diameter of 8 mm were used. . Further, in the fixing device 6A shown in the present embodiment, the temperature detection 72 is arranged in the paper passing area on the recording material as shown in FIG. , Through which the recording material passes.

FIG. 22 shows a process speed of 94 [mm / sec] and 200 using the fixing device of the present embodiment.
Immediately after the apparatus was started at a constant temperature of 150 ° C., a small-sized recording material (105 × 240 mm) was used at a throughput of 16 ppm and 8 ppm.
The transition of the surface temperature of the heating roller when the paper is continuously passed at ppm is shown.

As shown in FIG. 22, since the surface of the heating roller 70 is always kept at a constant temperature by the temperature detecting element 72 in the paper passing portion, the temperature is 200 ° C. regardless of the throughput.
On the other hand, while the temperature is constant, the temperature of the non-sheet passing portion gradually increases because the heat is not taken away by the recording material. The temperature rise in the non-sheet passing portion is greater when the throughput is faster, and the temperature rise in the non-sheet passing portion becomes smaller as the throughput becomes slower at 8 ppm. This is because the heat accumulated in the non-sheet passing portion due to the passing of the small size paper moves to the sheet passing portion between the recording materials and the heat roller 7
This is because the effect of making the temperature above zero uniform is promoted as the interval between the recording materials becomes longer relative to the sheet passing time by reducing the throughput.

When fixing is performed at a throughput of 16 ppm, the temperature of the non-sheet passing portion (curve (a) in FIG. 22) rises rapidly, and after 8 minutes from the start of sheet passing (corresponding to about 128 sheets of continuous sheet passing). The temperature reaches about 240 ° C., and there is a possibility that nearby components may be damaged. For example, heating roller 7
As the 0 bearing 74, a PPS (polyphenylene sulfide) resin-based material is often used, and since the heat resistant temperature in that case is around 230 ° C., if small size paper such as an envelope is continuously passed at 16 ppm. The temperature may exceed the heat-resistant temperature of the bearing 74 of the heating roller 70, and the bearing 74 may be damaged. In the case of the throughput of 8 ppm, the temperature of the non-sheet passing portion (curve (b) in FIG. 22) increases more slowly than that of the case of 16 ppm, and reaches 14 minutes after the start of sheet passing (corresponding to about 112 continuous sheets). The temperature is about 21
Since the temperature is as low as 5 ° C., there is no possibility of damaging the bearing 74 of the heating roller 70.

FIG. 23 shows the relationship between the length of the recording material, the ratio between the sheets, and the non-sheet passing portion temperature increase ΔT. The non-sheet-passing portion temperature increase ΔT is a fixing time for generating a temperature difference between the sheet-passing portion and the non-sheet-passing portion = the length of the recording material to be passed and the temperature difference between the sheet-passing portion and the non-sheet-passing portion. The non-fixing time is determined by the relationship between the lengths of the recording materials, and when the length of the recording materials is longer than the length of the recording materials, as in the case where the length between the recording materials is increased (the throughput is reduced). Also, the temperature increase ΔT of the non-sheet passing portion becomes small. Therefore, in the present embodiment, the paper feeding mode determined by the recording material paper passing width is corrected based on the detection result of the recording material length by the trailing edge detection sensor 23 and the like to more effectively reduce the temperature rise in the non-paper passing portion. I try to make it.

The temperature control of the fixing device 6A of the heat roller type shown in the present embodiment is performed for 15 minutes immediately after the apparatus is started when the apparatus is started from a cold state (one state in the morning). A temperature control at 200 ° C. (one temperature control in the morning) is performed to secure the fixing property, and then a temperature control at 175 ° C. (normal temperature control) is performed to stabilize the fixing property by heating the pressure roller 70. In this embodiment, when the surface temperature of the fixing roller at the time of starting the apparatus is 50 ° C. or less, the temperature is adjusted once in the morning for 15 minutes from the start-up, and when the surface temperature of the fixing roller at the time of starting the apparatus is 50 ° C. or more, the apparatus is Immediately after startup, normal temperature control at 175 ° C is performed. In normal temperature control, the fixing temperature control is as low as 175 ° C, and the throughput in the non-paper passing portion does not exceed 220 ° C even if continuous paper passing is performed with the throughput maintained at 16 ppm. Was uniformly set to 16 ppm.

FIG. 24 is a block diagram of the fixing sequence control of the image forming apparatus to which the present embodiment is applied. In addition,
The same components as those described above are denoted by the same reference numerals, and description thereof is omitted.

When the operation for starting the printing operation is sent,
First, at that time, it is determined whether the temperature control is the first temperature control in the morning or the normal temperature control. When the recording material is fed from the paper feeding unit, the size of the recording material is detected from the passage time when the recording material passes through the trailing edge detection sensor 23 or the registration sensor 25, and the result is sent to the CPU 51 of the engine controller 50. Paper cassette 26
In the case of paper feeding from the printer, the recording material size is detected by detecting the cassette size, and the result is sent to the CPU 51 similarly. next,
At the time of transfer, the transfer current is detected by the transfer current detecting means 62, and the result is transferred to the CPU 51 of the engine controller 50.
Send to

The CPU 51 determines the recording material size based on the detection result of the recording material length, the detection result of the transfer current and the transfer voltage _VT data, determines the throughput based on the recording material passing width and the recording material length. Printing is performed at a desired throughput by controlling the paper feeding interval by the paper feeding driving means 32 via the reference numeral 52.

FIG. 25 shows a flowchart of a fixing sequence according to the present embodiment.

After receiving the print signal (S61), the fixing temperature control mode (S62) is determined. In the case of normal temperature control, sheet feeding is started (S63, S64, S65), and continuous printing is performed at 16 ppm until the printing is completed (S66). If the temperature control mode is the first temperature control in the morning, after the start of sheet feeding (S67), the size of the first recording material is detected by the trailing edge detection sensor 23 and the like, and the length of the recording material is detected (S68).

Next, the transfer current value at the time of transfer is detected (S6).
9), determines a recording material sheet passing width than the transfer voltage V _T. If the transfer current value is I _tr <I _min + (2/3) △ I, it is determined that the size is large, and the printing of the second and subsequent sheets is performed at 16 ppm until the printing is completed (S66). When the transfer current value is I _tr ≧ I _min + (2 /
3) In the case of ΔI, it is determined that the size is small.

If it is determined from the detection result of the recording material length that the size is the fixed size and the large size (S70), the printing of the second and subsequent sheets is performed until the printing is completed by continuous printing at a throughput of 16 ppm (S6).
6). In addition, according to the transfer current value measured at this time, I
_{The min} is corrected to further improve the detection accuracy of the recording material passing width.

If the size of the recording material is determined to be small or irregular based on the detection of the length of the recording material, and if the size is determined to be smaller than the result of detecting the transfer current value, the length L of the recording material is determined from the result of detection of the length of the recording material. ₁ <50 for 16 ppm (S66), 5
12 ppm (S71) for 0 ≦ L ₁ <100, L ₁ ≧ 1
At 00, printing starts at a throughput of 8 ppm (S72). When printing at 12 ppm or 8 ppm,
Check the time T _ON since the power supply of the main body was turned on (S73, S
74) When T _ON ≧ 15 minutes, change the throughput to 16 ppm. When T _ON <15 minutes, continuous printing of 12 ppm and 8 ppm is returned.

As described above, the correction of the feeding mode of small-size paper according to the length of the recording material makes it possible to more accurately predict the temperature rise in the non-sheet-passing portion, and to set the printing mode more finely. be able to. In the present embodiment, the throughput is switched as a method of changing the paper feeding mode. However, the method of alleviating the temperature rise in the non-sheet passing portion is not limited to this, and may be performed in combination with, for example, temporarily stopping printing. The print mode may be corrected based on the print number information from the host computer.

In the foregoing and the first to fifth embodiments, one of the film heating system and the heat roller system has been described as the fixing device according to the present invention. It is needless to say that the same effect can be obtained by applying the same method to the system.

[0093]

As described above, according to the present invention,
In an image forming apparatus in which an unfixed toner image on an image carrier is fixed by a fixing device of a heating type, (1) from a detection result of a recording material size, for example, an irregular size paper having a recording material length equal to or more than a certain length; If it is determined that the image forming apparatus is temporarily (automatically) temporarily stopped, the temperature rise in the non-sheet passing portion is suppressed, and damage to the components of the fixing device due to the temperature rise in the non-sheet passing portion is prevented. be able to. (2) Non-sheet-passing temperature rise is predicted based on the detection result of the recording material size and the number of continuous image formations. If the number of continuous image formations is equal to or more than a predetermined number, the throughput is automatically reduced. By doing so, it is possible to suppress the temperature rise in the non-sheet passing portion, and effectively prevent damage to the constituent members of the fixing device due to the temperature rise in the non-sheet passing portion. (3) When it is determined from the detection result of the recording material length and the detection result of the recording material passage width obtained by monitoring the transfer current or the like that the paper is a small size paper of a standard size or an irregular size small size paper, A mode that automatically lowers the throughput, automatically suspends image formation, etc. is used to suppress the temperature rise in the non-sheet passing area, and to effectively damage the components of the fixing device due to the temperature rise in the non-sheet passing area. Can be prevented. (4) The temperature rise of the non-sheet-passing portion is predicted from the detection result of the recording material length, the detection result of the recording material passing width obtained by monitoring the transfer current, and the number of continuous images, and the number of continuous images formed. If the number is more than a certain number, automatically lower the throughput,
By providing a mode in which image formation is automatically temporarily stopped, for example, the temperature rise in the non-sheet passing portion can be suppressed, and damage to the components of the fixing device due to the temperature rise in the non-sheet passing portion can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to the present invention.

FIG. 2 is a longitudinal sectional view illustrating a schematic configuration of a film heating type fixing device.

FIG. 3 is a longitudinal sectional view showing a positional relationship in a longitudinal direction of a fixing device of a film heating type.

FIG. 4A is a diagram illustrating a relationship between the number of sheets passed and the surface temperature of a pressure roller. FIG. 3B is a diagram illustrating a relationship between the number of passed sheets and a film guide stay temperature.

FIG. 5A is a diagram illustrating a relationship between the number of sheets passed and the temperature of a non-sheet passing portion on the surface of a pressure roller. FIG. 3B is a diagram illustrating a relationship between the number of passed sheets and a film guide stay temperature.

FIG. 6 is a diagram showing a relationship between a standing time after heating and a film guide stay temperature.

FIG. 7 is a diagram for explaining how to obtain a sheet interval (recording material interval).

FIG. 8 is a control block diagram of the image forming apparatus according to the first embodiment.

FIG. 9 is a flowchart illustrating print sequence control of the image forming apparatus according to the first embodiment.

FIG. 10 is a diagram showing the relationship between the number of sheets passed and the temperature of the surface of the pressure roller and the non-sheet passing portion of the film guide stay in the first embodiment.

FIG. 11 is a control block diagram of the image forming apparatus according to the second embodiment.

FIG. 12 is a flowchart illustrating print sequence control of the image forming apparatus according to the second embodiment.

FIG. 13 is a diagram illustrating a relationship between the number of prints and a required printing time according to the third embodiment.

FIG. 14 is a control block diagram of the image forming apparatus according to the third embodiment.

FIG. 15 is a flowchart illustrating print sequence control of the image forming apparatus according to the third embodiment.

FIG. 16 is a block diagram illustrating a configuration of a fixing device according to a fourth embodiment.

FIG. 17 is a diagram illustrating a relationship between a transfer voltage and a transfer current according to the fourth embodiment.

FIG. 18 is a control block diagram of the image forming apparatus according to the fourth embodiment.

FIG. 19 is a flowchart illustrating print sequence control of the image forming apparatus according to the fourth embodiment.

FIG. 20 is a longitudinal sectional view illustrating a configuration of a fixing device according to a fifth embodiment.

FIG. 21 is a front view showing the positional relationship in the longitudinal direction of the fixing device according to the fifth embodiment.

FIG. 22 is a diagram illustrating a relationship between a time from the start of sheet passing and a roller surface temperature according to the fifth embodiment.

FIG. 23 is a diagram illustrating a relationship between a recording material length and a non-sheet passing portion temperature increase according to the fifth embodiment.

FIG. 24 is a control block diagram of the image forming apparatus according to the fifth embodiment.

FIG. 25 is a flowchart illustrating print sequence control of the image forming apparatus according to the fifth embodiment.

FIG. 26 is a diagram illustrating a recording material size of main fixed size paper.

FIG. 27 is a diagram showing a required printing time in the second embodiment.

FIG. 28 is a diagram showing the relationship between the number of prints and throughput in the third embodiment.

FIG. 29 is a diagram illustrating a required printing time when a sheet feeding mode is changed in the third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive drum) 2 Charging means (charging roller) 3 Exposure means 4 Developing means (developing device) 5 Transfer means (transfer member, transfer roller) 6, 6A Fixing device 7 Cleaner 10 Fixing film 11 Pressing member ( Pressure roller) 12 heating member (ceramic heater) 13 film guide stay 14, 72 temperature detecting element 23 length detecting means (rear end detecting sensor) 25 length detecting means (rear end detecting sensor) 26 length detecting means (supply) Paper cassette) 51 counting means, image formation interrupting means, supply interval changing means (CPU) 62 paper passing width detecting means 70 heating member (heating roller) 71 pressing member (pressure roller) N fixing nip portion P recording material

Claims (8)

[Claims] 1. A heating member and a pressing member are pressed against each other to form a fixing nip portion, and a recording material bearing a toner image is inserted into the fixing nip portion to heat and press the toner image. An image forming apparatus provided with a fixing device for fixing the recording material to a surface of the recording material; a length detecting unit configured to detect a length of the recording material in a conveying direction; a counting unit configured to detect a continuous image forming number of the recording material; Image forming interrupting means for interrupting the formation, the image forming interrupting means, when the length detecting means detects the irregular size, and when the counting means detects a predetermined number of continuous image formation, An image forming apparatus for temporarily stopping image formation. 2. A heating member and a pressing member are pressed against each other to form a fixing nip portion, and a recording material bearing a toner image is inserted into the fixing nip portion to heat and press the toner image. An image forming apparatus including a fixing device for fixing the recording material to a surface of the recording material; a length detecting unit configured to detect a length of the recording material in a conveying direction; a counting unit configured to detect a continuous image forming number of the recording material; Supply interval changing means for changing the supply interval of the recording material,
Wherein the supply interval changing unit changes the supply interval of the recording material when the length detecting unit detects an irregular size and the counting unit detects a predetermined number of continuous image formations. An image forming apparatus comprising: 3. A heating member and a pressing member are pressed against each other to form a fixing nip portion, and a recording material carrying a toner image is inserted into the fixing nip portion to heat and press the toner image. An image forming apparatus provided with a fixing device for fixing the recording material to a surface of the recording material; a length detecting unit configured to detect a length of the recording material in a conveying direction; a counting unit configured to detect a continuous image forming number of the recording material; Image forming suspending means for interrupting the formation, supply interval changing means for changing the supply interval of the recording material, and when the continuous image formation of a plurality of sheets is instructed, the length detecting means is used for a small-size recording material or A first mode in which the counting means detects a predetermined number of continuous images to be formed, and temporarily stops image formation by the image formation interrupting means when detecting a recording material of a fixed size; Therefore a second mode for changing the feed interval of the recording material,
Control means for determining any one of a recording material supply mode having a third mode in which the first mode and the second mode are appropriately combined. apparatus. 4. The image forming apparatus according to claim 3, wherein the recording material supply mode is corrected according to a length of the recording material detected by the length detecting unit. 5. An image carrier on which a toner image is formed on a surface thereof, and a voltage applied to a transfer member arranged in contact with the image carrier is controlled at a constant voltage to record the toner image on the image carrier on a recording material. A fixing member is formed by pressing a transfer member for transferring the toner image to a heating member and a pressing member, and a recording material carrying a toner image is inserted into the fixing nip portion to heat the toner image. An image forming apparatus provided with a fixing device that presses and fixes the recording material on the surface of the recording material, wherein a paper passing width detecting unit that detects a paper passing width of the recording material by a current based on constant voltage control during the transfer of the toner image; Counting means for detecting the number of continuous image formations, and image formation interruption means for interrupting image formation, wherein the length detection means detects an irregular size, and the counting means Place Of when detecting a continuous image formation sheet number, thereby temporarily interrupted image formation, the image forming apparatus, characterized in that. 6. A recording material in which a toner image is formed on a surface of the image carrier, and a voltage applied to a transfer member disposed in contact with the image carrier is controlled by a constant voltage to record the toner image on the image carrier. A fixing member is formed by pressing a transfer member for transferring the toner image to a heating member and a pressing member, and a recording material carrying a toner image is inserted into the fixing nip portion to heat and heat the toner image. An image forming apparatus provided with a fixing device that presses and fixes the recording material on the surface of the recording material, wherein a paper passing width detecting unit that detects a paper passing width of the recording material by a current based on constant voltage control during transfer of the toner image; Counting means for detecting the number of continuous images formed, and image formation suspending means for suspending image formation, a supply interval changing means for changing a supply interval of the recording material,
Wherein the supply interval changing unit changes the supply interval of the recording material when the sheet passing width detecting unit detects an irregular size and the counting unit detects a predetermined number of continuous image formations. An image forming apparatus comprising: 7. An image bearing member on which a toner image is formed on a surface thereof, and a voltage applied to a transfer member arranged in contact with the image bearing member is controlled at a constant voltage to record the toner image on the image bearing member on a recording material. A fixing member is formed by pressing a transfer member for transferring the toner image to a heating member and a pressing member, and a recording material carrying a toner image is inserted into the fixing nip portion to heat and heat the toner image. An image forming apparatus provided with a fixing device that presses and fixes the recording material on the surface of the recording material, wherein a paper passing width detecting unit that detects a paper passing width of the recording material by a current based on constant voltage control during transfer of the toner image; Counting means for detecting the number of continuous image formation sheets, image formation interruption means for interrupting image formation, supply interval change means for changing the supply interval of the recording material, and when a plurality of continuous image formation is instructed, Said When the width detecting means detects a small-sized recording material or an irregular-sized recording material, the counting means temporarily stops image formation by the image forming suspending means after detecting a predetermined number of continuous image formations. Recording mode, a second mode in which the supply interval of the recording material is changed by the supply interval changing unit, and a third mode in which the first mode and the second mode are appropriately combined. And a control unit for determining any one of the modes. 8. The image forming apparatus according to claim 7, wherein the recording material supply mode is corrected according to a recording material passing width detected by the paper passing width detecting unit.