JP2012194588A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that supports the use of a wide-width (so-called elongated size) recording material, and ensures productivity with the use of small-sized recording material.SOLUTION: An image forming apparatus has a heat generator having width Wh of approximately 312 mm, which is shorter than SRA3 size (320 mm in width) as the maximum feeding width Wp, and fixes images on an A3 elongated size recording material at the fixing speed of 1/2 speed (approximately 70 mm/s), which is slower than the fixing speed for an A3 size recording material (approximately 140 mm/s).

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer having a function of forming an image on a recording material (recording medium) such as a sheet.

  In recent years, there has been an increasing demand for producing a small number of printed materials such as pamphlets that have been created by conventional printing using an image forming apparatus such as a copying machine or a printer using electrophotographic technology.

  In many image forming apparatuses such as printers and copiers, it is usually difficult to print to the corner of the recording material. If it is an A3-compatible machine, there is a range in which about several millimeters cannot be printed around the recording material of A3 size paper (width 297 mm × length 420 mm).

  On the other hand, in the case of printed matter, ruled lines called “register marks” are attached outside the final finished dimensions. The register marks serve as marks for “alignment” when performing color printing and for cutting the recording material into a predetermined size after printing. Therefore, in the printing-related world, the A4 design is often printed on the B4 recording material, and the B4 design is printed on the A3 recording material with registration marks. However, the A3 design cannot be printed on the A3 size recording material with registration marks. Moreover, A4 size brochures are often printed in A3 size and folded in half. In other words, there is much demand for A3 size design.

  For this reason, a recording material of A3 size, which is one size larger than the A3 size (for example, SRA3 size paper: 320 mm in width × 450 mm in length) is obtained by adding a registration mark space to an A3 size recording material. The image forming apparatus is required to cope with it.

On the other hand, cost reduction, power saving, and wait time reduction (quick start property: operating on demand) of image forming apparatuses are progressing. Such devices are being put to practical use. This is a film heating method using a so-called ceramic heater in which a resistance heating element is formed on a ceramic substrate such as alumina (Al ₂ O ₃ ) or aluminum nitride (AlN) as a heating source, and using a fixing film having a small heat capacity. It is a fixing device, a so-called film fixing device.

As an example of an image forming apparatus using such a conventional film fixing device, there is one corresponding to A3 Nobi paper.
In such an image forming apparatus, a recording material having a maximum sheet passing width of 312 mm is supported as A3 Nobi paper. The heating element width of the heat source of the fixing device is about 324 mm which is wider than the maximum sheet passing width. Further, the fixing speed at the time of A3 Nobi is the same as that at the A3 size, and the fixable width is about 305 mm.

JP 2002-341682 A

  Conventionally, in order to ensure the fixability of the edge portion of a toner image formed on the maximum size recording material, the width of the resistance heating element is generally set slightly larger than the maximum sheet passing width as in Patent Document 1. is there.

  However, in the conventional fixing device as described above, if the heating element width of the heating element is increased so as to correspond to the so-called A3 Nobi paper having a wide recording material, production of a small size recording material is possible. There was a concern that the performance would decline.

  On the other hand, if priority is given to the productivity of recording materials of a small size and the heating element width of the heating element is shortened, the fixable width becomes narrow and it is not possible to cope with the fixing of the register mark portion of the A3 Nobi paper. There was concern.

  The present invention has been made in view of the above-described circumstances, and is an image forming apparatus capable of satisfying both a wide response to a so-called nobi-size recording material and a productivity of a small-size recording material. The purpose is to provide.

In order to achieve the above object, the present invention provides:
A heating source having a heating element;
A nip for nipping and conveying the recording material;
In an image forming apparatus for fixing an image on a recording material at the nip portion,
The width of the heating element in the longitudinal direction of the nip portion is shorter than the first width in the longitudinal direction of the recording material of the maximum size among the recording material sizes capable of forming an image, and an image is formed with the recording material of the maximum size. Provided with a length capable of fixing an image with respect to the second width in the longitudinal direction that needs to be formed,
The recording material having a longitudinal width smaller than the second width when the recording material having the longitudinal width equal to or larger than the second width is conveyed at the nip portion is the nip portion. Drive means for driving the nip portion so as to be lower than the recording material conveyance speed in the case of being conveyed by the recording medium.

  According to the present invention, it is possible to provide an image forming apparatus capable of satisfying both a response to a wide so-called nobi size recording material and a productivity of a small size recording material.

(A) is a figure which shows schematic structure of the heater used for the fixing apparatus of Example 1, (b)-(d) is a figure which shows the temperature distribution of the longitudinal direction of a heat generating body. 1 is a schematic sectional view of an image forming apparatus according to the present invention. 1 is a schematic cross-sectional view of a fixing device according to a first exemplary embodiment. In the fixing device, it is a diagram for explaining the heating element width and the surface temperature distribution in the longitudinal direction of the fixing film. FIG. 5 is a diagram illustrating a relationship between a heating element width and a fixable width in the fixing device according to the first exemplary embodiment. In the image forming apparatus according to the first exemplary embodiment, the heating element width of the heating source of the fixing device and the productivity of a recording material of a small size (B4 size as an example) are shown. It is a figure shown about the various setting matter of Example 1 and a prior art example. FIG. 10 is a diagram illustrating various setting items in the second embodiment.

The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

  The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer (referred to as LBP), a printer, a facsimile, a microfilm reader printer, and a recording machine.

More specifically, the present invention relates to the following image forming apparatus.
First, using image forming process means such as electrophotography, electrostatic recording, magnetic recording, and the like, a toner made of heat-meltable resin or the like, and the desired image information on the surface of the recording material by a direct transfer method or an indirect transfer method. An unfixed toner image corresponding to the above is formed and supported. The present invention also relates to an image forming apparatus using a fixing device as an image heating device of a system in which the unfixed toner image is heated and fixed as a permanently fixed image on a recording material surface carrying the image. In particular, the present invention relates to an image forming apparatus that achieves both the fixing of a wide, so-called nobi-size paper, and the productivity of a small-size recording material. Examples of the recording material include paper, printing paper, recording material sheet, electrofax sheet, electrostatic recording sheet, OHT sheet, glossy paper, and glossy film.

  FIG. 2 is a schematic cross-sectional view of an example of an image forming apparatus according to Embodiment 1 of the present invention. The image forming apparatus shown in the present embodiment is a laser printer using an electrophotographic image forming process.

  The image forming apparatus according to the present exemplary embodiment includes four image forming units (image forming units). The image forming unit 1a for forming a yellow image, the image forming unit 1b for forming a magenta image, the image forming unit 1c for forming a cyan image, and the image forming for forming a black image. Part 1d. These four image forming units 1a, 1b, 1c, and 1d are arranged in a line at a constant interval.

  In each of the image forming units 1a, 1b, 1c, and 1d, drum-type electrophotographic photosensitive members (hereinafter referred to as photosensitive drums) 2a, 2b, 2c, and 2d are installed as image carriers. Around the photosensitive drums 2a, 2b, 2c, and 2d, chargers 3a, 3b, 3c, and 3d, developing devices 4a, 4b, 4c, and 4d, and drum cleaning devices 5a, 5b, 5c, and 5d are installed, respectively. Yes. Exposure devices 6a, 6b, 6c, and 6d are installed above the charger 3 and the developing device 4, respectively. Each developing device 4a, 4b, 4c, 4d contains yellow toner, magenta toner, cyan toner, and black toner, respectively.

  Each of the photosensitive drums 2a, 2b, 2c, and 2d is a negatively charged OPC photosensitive member having a photoconductive layer on an aluminum drum base, and is driven by a driving device (not shown) in the direction of the arrow (reverse direction) shown in FIG. It is rotated at a predetermined process speed (clockwise). The chargers 3a, 3b, 3c and 3d as charging means uniformly charge the surfaces of the photosensitive drums 2a, 2b, 2c and 2d to a predetermined negative potential by a charging bias applied from a charging bias power source (not shown). To do.

  The developing devices 4a, 4b, 4c, and 4d develop the toner images by making each color toner adhere to the electrostatic latent images formed on the photosensitive drums 2a, 2b, 2c, and 2d, respectively. . As a developing method using the developing devices 4a, 4b, 4c, and 4d, for example, toner particles mixed with a magnetic carrier are used as a developer, conveyed by magnetic force, and developed in contact with each photosensitive drum. A two-component contact development method can be used.

  The transfer rollers 7a, 7b, 7c, and 7d as transfer means are constituted by elastic members, and each photosensitive member passes through an endless belt-like recording material conveyance belt (hereinafter referred to as a transfer belt) 8 at each transfer nip. The drums 2a, 2b, 2c and 2d are in contact with each other. Here, the transfer roller 7 is used as the transfer means, but a transfer blade that is applied with a high pressure when the toner image is transferred onto the recording material and contacts the transfer belt 8 may be used.

  The drum cleaning devices 5a, 5b, 5c, and 5d remove and collect the transfer residual toner remaining on the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d, respectively.

  The exposure devices 6a, 6b, 6c and 6d output a laser beam modulated in accordance with a time-series electric digital pixel signal of image information from a laser output unit (not shown) and rotate at a high speed polygon mirror (not shown). The surface of each of the photosensitive drums 2a, 2b, 2c, and 2d is exposed through the above. As a result, the exposure devices 6a, 6b, 6c, and 6d have electrostatic colors of respective colors corresponding to image information on the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d charged by the chargers 3a, 3b, 3c, and 3d. A latent image is formed.

  The transfer belt 8 is stretched between the drive roller 9 and the tension roller 10 and is rotated (moved) in the direction of the arrow (counterclockwise) shown in FIG. The transfer belt 8 is made of a dielectric resin such as a polycarbonate, a polyethylene terephthalate resin film, a polyvinylidene fluoride resin film, or the like.

  A fixing device 13 having a fixing film 11 as a flexible sleeve that encloses a heating source and a pressure roller 12 as a driving member is installed on the downstream side of the transfer belt 8 in the recording material conveyance direction. Yes.

  Next, an image forming operation by the image forming apparatus of this embodiment will be described.

  When the image formation start signal is issued, the photosensitive drums 2a, 2b, 2c, and 2d of the image forming units 1a, 1b, 1c, and 1d that are rotationally driven at a predetermined process speed are respectively charged by the chargers 3a, 3b, and 3c. , 3d is uniformly negatively charged. The exposure devices 6a, 6b, 6c, and 6d convert the image signal of the output image into an optical signal by a laser output unit (not shown), respectively, and the laser beam that is the converted optical signal is charged to each photosensitive element. Each of the drums 2a, 2b, 2c, and 2d is scanned and exposed to form an electrostatic latent image.

  First, yellow toner is adhered to the electrostatic latent image formed on the photosensitive drum 2a by the developing device 4a to which a developing bias having the same polarity as the charging polarity (negative polarity) of the photosensitive drum 2a is applied. Visualize as an image.

  Then, the recording material P fed from the feeding cassette 14 through the recording material transport guide 15 is synchronized with the timing when the leading edge of the toner image on the photosensitive drum 2a is moved to the transfer portion between the photosensitive drum 2a and the transfer roller 7a. Then, it is conveyed to the transfer section by the registration roller 16. Then, the yellow toner image is transferred onto the recording material by the transfer roller 7a to which the transfer bias (polarity opposite to the toner (positive polarity)) is applied to the recording material P conveyed to the transfer portion.

  The recording material P to which the yellow toner image is transferred is moved to the image forming unit 1b by the recording material conveyance belt 8. Also in the transfer portion constituted by the image forming portion 1b and the transfer roller 7b, the magenta toner image formed on the photosensitive drum 2b in the same manner as the transfer portion between the photosensitive drum 2a and the transfer roller 7a is recorded on the recording material P. It is superimposed and transferred onto the upper yellow toner image.

  Similarly, cyan and black toner images formed on the photosensitive drums 2c and 2d of the image forming units 1c and 1d on the yellow and magenta toner images superimposed and transferred onto the recording material P are similarly transferred to the transfer units. Then, a full-color toner image is formed on the recording material P by sequentially superimposing them.

The recording material P on which the full-color toner image is formed is conveyed to the fixing device 13. Fixing device 1
3, the recording material is nipped and conveyed by a nip portion (fixing nip portion) formed by the fixing film 11 and the pressure roller 12, whereby a full-color toner image is heated and pressed to be applied to the surface of the recording material P. Heat-fixed. Thereafter, the recording material P on which the full-color toner image is fixed is discharged onto the discharge tray 18 by the discharge roller 17, and a series of image forming operations is completed.

  When the above image is transferred from the photosensitive drum to the recording material, the transfer residual toner remaining on the photosensitive drums 2a, 2b, 2c, and 2d is removed by the drum cleaning devices 5a, 5b, 5c, and 5d, respectively. And recovered.

  When outputting a monochrome image, the above-described image forming process is performed only in the image forming unit 1d that forms a black image.

  Next, the fixing device in this embodiment will be described with reference to FIG.

  FIG. 3 is a schematic cross-sectional view of the fixing device in FIG.

  The fixing device in this embodiment includes a heater 19, a heater holder 20, a main thermistor 21, a sub thermistor 22, a fixing film 11, a pressure roller 12, and an entrance guide 23. Here, the heater 19 and the heater holder 20 constitute a heating source.

  The heater holder 20 is formed of a liquid crystal polymer resin having high heat resistance, plays a role of holding the heater 19 and guiding the fixing film 11.

  In this example, model number E4205L B manufactured by Sumitomo Chemical Co., Ltd. was used as the liquid crystal polymer used for the material of the heater holder. The maximum usable temperature (load deflection temperature) of this liquid crystal polymer is about 305 ° C.

  The main thermistor 21 detects the temperature of the inner surface of the fixing film 11 and is arranged for controlling the temperature of the fixing device 13.

  The main thermistor 21 has a thermistor element attached to the tip of a stainless steel (SUS) arm, and even if the movement of the inner surface of the fixing film 11 becomes unstable due to the swinging of the arm, the thermistor element remains on the inner surface of the fixing film 11. It is always kept in contact.

  The main thermistor 21 is connected to a CPU (not shown) as control means, and the CPU determines the temperature control content of the heater 19 based on the output of the main thermistor 21 and controls the energization of the heater 19.

  The sub-thermistor 22 is disposed on the back surface of the heater 19 and plays a role of performing limiter control when the heater 19 is excessively heated for some reason. In this embodiment, the sub-thermistor 22 is disposed at the longitudinal end of the heater 19 and detects the temperature rise at the end of the fixing device 13 when a small-size recording material is passed. Here, the longitudinal direction is a direction orthogonal to the recording material conveyance direction, the axial direction of the pressure roller 12, and the longitudinal direction of the fixing nip portion formed by the fixing film 11 and the pressure roller 12. . When the CPU determines from the detection result of the sub-thermistor 22 that the temperature of the end of the fixing device 13 is rising, the CPU controls the temperature of the fixing device to be lowered to prevent the fixing device from being overheated.

The fixing film 11 is formed by forming a silicone rubber layer as an elastic layer on a stainless steel film formed as an endless belt (endless) having a thickness of about 30 μm as a metal base layer, and as a release layer. A PFA resin tube having a thickness of about 30 μm is coated. Here, PFA is a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer.

It is desirable from the viewpoint of temperature rise to use a material having a high thermal conductivity as much as possible for the silicone rubber layer and to reduce the heat capacity of the fixing film 11. In this example, the thermal conductivity is about 1.0 × 10 ⁻³ cal / sec · cm · K (4.2 × 10 ⁻³ W / cm · K), and the silicone rubber has a thermal conductivity of A material belonging to a high class was used.

  On the other hand, it is desirable to make the silicone rubber layer of the fixing film 11 as thick as possible from the viewpoint of image quality, such as OHT permeability and “s” (small gloss unevenness) on the image. According to the study by the present inventors, it has been found that a rubber thickness of 200 μm or more is necessary to obtain a satisfactory level of image quality.

  The silicone rubber layer in this example had a thickness of about 250 to 300 μm. In addition, the inner diameter of the fixing film 11 in this example was 24 mm.

  The size in the longitudinal direction is about 330 mm to 340 mm in order to correspond to the SRA3 size as A3 Nobi paper.

When the heat capacity of the fixing film 11 thus formed was measured, it was about 3 × 10 ⁻² cal / cm ² · K (12.6 × 10 ⁻² J / cm ² · K) (heat capacity per 1 cm ^{2 of the} fixing film). Met. Generally, when the heat capacity of the fixing film 11 is 1.0 cal / cm ² · K (4.2 J / cm ² · K) or more, the temperature rise becomes dull and the on-demand property is impaired. On the other hand, if an attempt is made to make it less than 1.0 × 10 ⁻² cal / cm ² · K (4.2 × 10 ⁻² J / cm ² · K), the rubber layer of the fixing film 11 must be extremely thinned. Thus, the thickness of the rubber layer necessary for maintaining the image quality such as the OHT permeability and the level of “su” cannot be secured.

Therefore, the on-demand property, the heat capacity of the fixing film 11 that satisfies both of the image ^{quality, 1.0 × 10 -2 cal / cm} 2 · K or more 1.0cal / cm ² · K be included in the following ranges I understand.

  Furthermore, by providing a fluororesin layer on the surface of the fixing film 11, the surface releasability is improved, and the offset phenomenon that occurs when the toner once adheres to the surface of the fixing film 11 and moves to the recording material P again is prevented. can do.

  Further, by using a PFA tube as the release layer 20c on the surface of the fixing film 11, a uniform release layer can be more easily formed.

  The pressure roller 12 is formed by forming a conductive silicone rubber layer having a thickness of about 2 mm on a cored bar and coating a conductive PFA resin tube having a thickness of about 50 μm thereon. As the longitudinal size, the length in the longitudinal direction is about 330 mm so as to correspond to the recording material of SRA3 size.

  The entrance guide 23 serves to guide the recording material so that the recording material P that has passed through the secondary transfer nip is accurately guided to the fixing nip portion.

  The pressure roller 12 and the entrance guide 23 are each assembled to the frame 24.

Below that, a fixing film unit 25 containing the heater 19, the main thermistor 21, and the sub-thermistor 22 mounted on the heater holder 20 is placed. Fixing film unit 2
5 is pressurized with a force of about 30 kgf (294 N) (about 15 kgf on one side) by a pressurizing mechanism (not shown) through a T stay 26 arranged along the heater holder 20.

  In the fixing device of this embodiment, the pressure roller 12 rotates and the fixing film 11 is driven, whereby the fixing film 11 is driven to rotate. At that time, the inner surface of the fixing film 11 and the heater holder 20 are configured to slide. Grease is applied to the inner surface of the fixing film 11 to ensure slidability between the heater holder 20 and the inner surface of the fixing film 11.

  In normal use, as the fixing device starts rotating, the driven rotation of the fixing film 11 starts. As the temperature of the heater 19 rises, the inner surface temperature of the fixing film 11 also rises, and accordingly, the surface temperature of the fixing film 11 also rises. Go.

  A so-called ceramic heater is used as the heater 19.

  Fig.1 (a) is a figure which shows schematic structure of the heater 19 of a present Example, FIG.1 (b)-(d) is a figure which shows the temperature distribution of the longitudinal direction of a heat generating body.

As the heater 19 of the present embodiment, the following is used as an example of a ceramic heater. This is obtained by printing a heating element 19b on a ceramic substrate 19a (on a ceramic substrate) by applying a heat-generating paste of AgPd (silver palladium alloy) whose resistance is adjusted as a resistance heating element that generates heat when energized by screen printing. It is. As the ceramic substrate 19a, alumina (Al ₂ O ₃ ) having a length (width) of about 380 mm in the longitudinal direction, a length of about 8 mm in the recording material conveyance direction, and a thickness of about 1 mm was used. Furthermore, in order to protect this heat generating body 19b, it coats with the glass protective film 19c (not shown).

  The heater 19 of this embodiment has three heating elements 19b, and the heat generation distribution in the longitudinal direction is different between the heating element in the center and the heating elements on both sides.

  As the drive control of the heater 19, the ratio of energization to the central heating element (hereinafter referred to as sub-heating element) and the energization to the heating elements on both sides (hereinafter referred to as main heating element) is passed through the paper recording material. It changes according to the size. Thus, the heat generation distribution in the longitudinal direction is optimized in accordance with the recording material size.

  An example of the longitudinal heat generation distribution of the main heating element is shown in FIG. 1B, an example of the longitudinal heating distribution of the sub heating element is shown in FIG. 1C, and both the main heating element and the sub heating element are 100%. An example of the heat generation distribution in the longitudinal direction when the lamp is lit is shown in FIG.

  Here, the width in the longitudinal direction of the heating element 19b of the heating source is defined as the heating element width Wh. In the image forming apparatus of this embodiment, the width in the longitudinal direction of the recording material of the maximum size among the recording material sizes capable of image formation. Let (first width) be the maximum sheet passing width Wp. In this case, in this embodiment, unlike the conventional example, the heating element width Wh is about 312 mm shorter than the SRA3 size (A3 nobi size, width 320 mm) as the maximum sheet passing width Wp. The heating element width Wh is a width in the longitudinal direction (second width, SRA3 as described below) that requires image formation on a recording material (in this embodiment, an SRA3 size recording material) having the maximum sheet passing width Wp. In the case of a recording material of a size, the length is such that the image can be fixed to about 306 mm.

  FIG. 5 is a graph showing the fixable width in the longitudinal direction when the heating element width is changed in the study by the present inventors. FIG. 7 is a table showing various setting items between the present embodiment and the conventional example.

As the recording material, an SRA3 size recording material having a basis weight of 105 g / m ² was used.

  Regarding the fixable width, the recording material after fixing was bent, the recording material was spread, the width where the fixed toner image was peeled was measured, and the range within a certain allowable level was determined as the fixable width.

  First, the case where the fixing speed was fixed at about 140 mm / s, which is substantially the same as the fixing speed in the conventional example, was examined. Here, the fixing speed is the recording material conveyance speed when the recording material is conveyed at the fixing nip portion. The fixing speed can be changed by a driving unit that drives the nip portion.

  When the width of the heating element was about 324 mm as in the conventional example, the fixable width was about 306 mm.

  FIG. 4 is a diagram for explaining the heating element width and the surface temperature distribution in the longitudinal direction of the fixing film in the fixing device. FIG. 6 is a graph showing the heating element width of the heating source of the fixing device and the productivity of a small size (for example, B4 size) recording material in the image forming apparatus of this embodiment.

  Since the fixing film surface temperature has heat escape from both ends of the fixing film, as shown in FIG. 4, the fixing film surface temperature is lowered at both ends, and the position in the longitudinal direction starting to fall is less than the heating element width of the heating source. Will also be inside. For this reason, the fixable width is usually shorter than the heating element width.

In this case, when a B4 size recording material (for example, basis weight of about 80 g / m ² ) is continuously fed as a small size recording material, the number of sheets whose productivity (throughput) decreases due to the temperature rise of the non-sheet passing portion As shown in FIG. 6, the productivity may be reduced by about ten or more sheets.

  When the heating element width was shortened to about 312 mm so as to reduce the non-sheet-passing temperature rise, the fixable width was also shortened to about 295 mm, and it became impossible to cope with the A3 nobi size registration mark portion fixing.

  Next, in this embodiment, the fixing speed of the A3 size recording material is fixed at about 1/2 speed (about 70 mm / s), which is lower than the fixing speed of the A3 size recording material (about 140 mm / s). The case where it was made to investigate was done.

  In this case, the heating element width for obtaining the same fixable width as that at the substantially constant speed (140 mm / s) may be short.

  As can be seen from FIG. 5, in order to secure the fixable width of about 306 mm, the heating element width is required to be about 324 mm at approximately constant speed (140 mm / s), whereas half speed (about 70 mm / s). ), The width of the heating element may be about 312 mm. In the case of such a heating element width of 312 mm, the productivity of a B4 size recording material as a small size recording material was confirmed. As a result, the productivity did not decrease to about 100 sheets having no practical problem.

Thus, in the present embodiment, the heating element width Wh is set to about 312 mm, which is shorter than the SRA3 size (A3 nobi size, width 320 mm) as the maximum sheet passing width Wp. The heating element width Wh is such that the image can be fixed with respect to the longitudinal width (second width, approximately 306 mm) in which image formation is required with a recording material having the maximum sheet passing width Wp. . The heating element width Wh is, as shown in FIG. 5, the width of the heating element, the fixing speed, the fixable width determined from the width of the heating element and the fixing speed (width of the fixed image in the longitudinal direction), Based on the relationship, the second width is derived. Further, a recording material (A3 size) having a fixing speed of a recording material (A3 Novi size recording material) having a width in the longitudinal direction equal to or greater than the second width (A3 size) is smaller than the second width. , B4 size recording material) is provided at a lower speed than the fixing speed.

  As a result, in this embodiment, it is possible to realize an image forming apparatus that achieves both compatibility with a so-called nobi-sized recording material having a wide longitudinal direction and productivity of a small-sized recording material that has no practical problem. Yes.

  Here, in this example, a type in which an elastic layer and a release layer were provided on a metal base layer was used as the fixing film 11, but an extremely thin release layer was provided on the base layer without providing an elastic layer. A type of fixing film may be used.

  In the image forming apparatus of the present embodiment, the color image forming apparatus has been described. However, the present invention is not limited to this, and the present invention can be applied to a monochrome image forming apparatus.

  The second embodiment of the present invention will be described below. In the present embodiment, only components that are different from those in the first embodiment will be described, and the description of the same components as those in the first embodiment will be omitted.

  In this embodiment, a monochrome image forming apparatus instead of a color is used as the image forming apparatus. As the fixing film 11, a resin such as polyimide is used for the base layer instead of the metal base layer. Further, in this example, the examination was performed using a fixing film of a type in which an elastic layer was not formed on the base layer but a release layer was formed on the base layer.

  In this example, since the resin type is used as the base layer of the fixing film, the heat escape from both ends is small as compared with the fixing film using the metal base layer of Example 1. For this reason, it is not necessary to make the heating element width so large with respect to the fixable width.

  Various setting items in this embodiment are shown in FIG.

  In this example, the heating element width was about 306 mm. In this case, as in the first embodiment, the fixing width when the fixing operation is performed at about 70 mm / s, which is about 1/2 speed, compared to the fixing speed (about 140 mm / s) when the A3 size recording material is passed. Was about 305 mm. Further, when the small size productivity in this case was confirmed in the same manner as in Example 1 for the B4 size recording material, the productivity decreased with about 120 sheets.

  Even in the case where a fixing film using a resin layer such as polyimide instead of the metal base layer in Example 1 is used as the fixing film as in this example, it is practically compatible with A3 Novi size recording materials. It is possible to achieve both the productivity of a small-size recording material without any problem.

  DESCRIPTION OF SYMBOLS 11 Fixing film, 12 Pressure roller, 13 Fixing apparatus, 19 Heater, 19a Ceramic substrate, 19b Heat generating body, 20 Heater holder

In order to achieve the above object, the present invention provides:
An endless belt, a heater that is in contact with the inner surface of the endless belt and has a heating element on a substrate, and a pressure roller that forms a nip portion together with the heater via the endless belt, and the nip portion In the image forming apparatus having a fixing unit that heat- fixes the toner image formed on the recording material to the recording material .
The length of the heating element in a direction perpendicular to the recording material moving direction, is shorter remote by the recording material of the imageable maximum width in the device, formed on the recording material of the maximum width toner
When fixing an image at the fixing unit, the recording material conveyance speed at the fixing unit is set to be lower than when fixing a toner image formed on a recording material having a width smaller than the length of the heating element. characterized in that it.

Claims (6)

A heating source having a heating element;
A nip for nipping and conveying the recording material;
In an image forming apparatus for fixing an image on a recording material at the nip portion,
The width of the heating element in the longitudinal direction of the nip portion is shorter than the first width in the longitudinal direction of the recording material of the maximum size among the recording material sizes capable of forming an image, and an image is formed with the recording material of the maximum size. Provided with a length capable of fixing an image with respect to the second width in the longitudinal direction that needs to be formed,
The recording material having a longitudinal width smaller than the second width when the recording material having the longitudinal width equal to or larger than the second width is conveyed at the nip portion is the nip portion. An image forming apparatus comprising: a driving unit that drives the nip portion so that the recording material is transported at a speed lower than that of the recording material.   The width of the heating element is determined by the width of the heating element, the recording material conveyance speed of the recording material conveyed at the nip, the width of the heating element, and the width of the fixing image in the longitudinal direction. The image forming apparatus according to claim 1, wherein the image forming apparatus is derived on the basis of the second width from the relationship between the first and second widths. The nip portion is formed by a flexible sleeve that slides on the heating source, and a drive member that drives the flexible sleeve,
3. The flexible sleeve is provided with an endless shape in which a release layer or a release layer via an elastic layer is formed on a base layer made of metal. The image forming apparatus described in 1. The nip portion is formed by a flexible sleeve that slides on the heating source, and a drive member that drives the flexible sleeve,
The flexible sleeve is an endless flexible sleeve in which a release layer or a release layer via an elastic layer is formed on a base layer made of a resin. The image forming apparatus according to 1 or 2. The heating element is a resistance heating element that generates heat when energized,
The image forming apparatus according to claim 1, wherein the heat source is a ceramic heater in which the resistance heating element is formed on a ceramic substrate.   The image forming apparatus according to claim 3, wherein the metal used for the base layer is made of stainless steel.

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