JP2011033713A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve throughput in feeding small-size paper, and thereby extending the livfetime of an image forming part and a fixing device. <P>SOLUTION: When the width of a recording material P is smaller than a predetermined width (S102: Y), and the number of recording materials P for print JOB is less than the number of sheets for changing image forming speed (S104: Y), the image forming speed is changed to a first image forming speed (S105). When the number of recording materials P for print JOB is equal to or more than the number of sheets for changing the image forming speed (S104: N), the image forming speed is changed to a second image forming speed lower than the first image forming speed (S106). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using a fixing device, and relates to an improvement in throughput of small-size paper.

  Conventionally, the following techniques have been proposed in order to keep the temperature rise of the non-sheet passing portion generated in a film fixing device used in an electrophotographic image forming apparatus below a desired value. For example, in Patent Document 1, the throughput (feeding interval) (productivity) is changed in accordance with the recording material width, and when the recording material width is narrow, the throughput is lowered (increasing the feeding interval) to raise the non-sheet passing portion. Control so that the temperature does not become excessive.

  For example, Patent Document 2 proposes an image forming apparatus that changes an image forming speed according to a recording material width, instead of changing a throughput by changing a feeding interval (between sheets) according to the recording material width. ing. In Patent Document 2, the image forming speed (mm / sec) is 200 mm / sec and 100 mm / sec, and the resolution is set to 600 dpi. All the surfaces of the 6-sided polygon mirror of the laser scanner are used at high speed, and half of the 6-sided polygon mirror is used at low speed to print an image on every other side. As a result, it is possible to form an image at the same 600 dpi resolution at low speed as at high speed, and the image clock is also the same.

  For A4, letter, and legal size recording materials, the sheet interval (distance between the trailing edge of the Nth page and the leading edge of the (N + 1) th page when continuously fed) is 65 mm, and the throughput is 33 sheets in A4 size. / Minute, letter size is 34.8 sheets / minute, legal size is 28.5 sheets / minute. Here, the numerical value of 65 mm between papers means the minimum amount of paper that can be guaranteed by the variation in paper feed timing and the response timing of sensors in the conveyance path among the minimum papers that the image forming apparatus can take. Also, B5, A5, and EXE size recording materials of small size paper are set as one group, the image forming speed is 100 mm / sec, which is half of the A4 size, and the EXE paper size is the maximum length of the recording material group. The throughput is controlled so as to be 65 mm. As a result, the throughput of B5, A5, and EXE sizes is 18 sheets / minute. As a result, according to Patent Document 2, even if a narrow recording material is conveyed at a half-speed image forming speed with respect to the letter size that can obtain the maximum throughput, a throughput of 1/2 or more can be obtained. In this way, the image forming speed is switched according to the recording material width, and in the case of small size paper, the image forming speed is slowed down to reduce the throughput, and the non-sheet-passing portion temperature rise response is performed.

JP 7-199694 A JP 2003-50519 A

  However, in Patent Document 1, there is a difference between the throughput of the recording material having the maximum size width and the narrow width, and the increase in the speed of the image forming apparatus increases the throughput in proportion to the image forming speed only for the recording material having the maximum size width. A narrow recording material does not improve the throughput. When the throughput is reduced, the gap between the sheets is widened. Therefore, the rotation time of the cartridge of the image forming unit is increased for a predetermined number of prints, and the life is shortened. Further, in order to cope with the temperature rise of the non-sheet passing portion, it is necessary to reduce the throughput by widening the gap between the sheets with a small number of sheets, and the total productivity (average throughput) when printing a large number of sheets is lowered.

  In Patent Document 2, the image forming speed is fixed depending on the recording material width, and small-size paper has a low image forming speed and a low throughput. Sometimes throughput decreases. In particular, in a multi-function peripheral (MFP) that supports A3 size, small-size paper printing occurs at the time of reduced copy or rotational sorting, and the frequency of small-size paper printing is high. For example, when A3 size paper is reduced and copied to A4 size paper, printing is performed with A4 portrait feed, so that small size paper is printed. Further, the rotation sort is a sort output by alternately rotating the direction of the document vertically / horizontally for each number of copies, and a vertical feed occurs alternately and a small size print occurs. For example, when A4 size paper is rotated and sorted, small size paper prints such as A4 portrait paper such as A4 landscape paper ⇒ A4 portrait paper ⇒ A4 landscape paper ⇒ A4 portrait paper ... appear. For this reason, it is desirable that the throughput when printing small-size paper is high. However, in Patent Document 2, small-size paper has a low image formation speed and is fixed at a low throughput, and cannot increase the throughput in the case of reduced copy or rotational sort.

  The present invention has been made in such a situation, and it is an object of the present invention to improve the throughput when a small-size sheet is passed and to prolong the life of an image forming unit and a fixing device.

  In order to solve the above problems, the present invention comprises the following arrangement.

  (1) An image forming apparatus for fixing an image on a recording material formed by an image forming unit by a fixing device, comprising control means for changing an image forming speed in accordance with the width of the recording material, When the width of the recording material is smaller than the predetermined width and the number of print jobs on the recording material is less than the predetermined number, the first image forming speed is changed, and the number of print jobs on the recording material is equal to or greater than the predetermined number. If it is, the image forming apparatus is changed to a second image forming speed slower than the first image forming speed.

  According to the present invention, it is possible to improve the productivity at the time of passing small-size paper and to prolong the lifetime of the image forming unit and the fixing device.

1 is a schematic cross-sectional view of a color image forming apparatus and a fixing device according to a first exemplary embodiment. The figure explaining the fixing heater of Example 1, the graph which shows heat_generation | fever distribution Graph and table showing average throughput of Example 1 and Comparative Example The flowchart which shows the process of Example 1. The flowchart which shows the process of a prior art example

  Exemplary embodiments of the present invention will be 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.

[Image forming apparatus]
FIG. 1A is a schematic configuration diagram illustrating a color image forming apparatus according to the first embodiment. The image forming apparatus according to the present embodiment is an electrophotographic tandem type full color capable of passing a recording material up to A3 size. It is a printer. The image forming apparatus includes four image forming units 1Y, 1M, 1C, and 1Bk (image forming units) that respectively form yellow (Y), magenta (M), cyan (C), and black (Bk) images. Units), which are arranged in a row at regular intervals. In the figure, symbol a corresponds to Y, b corresponds to M, c corresponds to C, and d corresponds to Bk. In the following description, these symbols are omitted unless necessary.

  When an image forming operation start signal is issued, the photosensitive drum 2 of the image forming unit 1 is rotationally driven in a direction indicated by an arrow at a predetermined process speed (circumferential speed), and is uniformly charged to, for example, negative polarity by the charging roller 3. The exposure device 7 converts an input color-separated image signal into an optical signal by a laser output unit (not shown), and scans and exposes the laser beam, which is the converted optical signal, onto the charged photosensitive drum 2. To form an electrostatic latent image. The developing device 4a to which a developing bias having the same polarity as the charging polarity (negative polarity) is applied electrostatically adsorbs yellow toner on the photosensitive drum 2a on which the electrostatic latent image is formed in accordance with the charging potential. The latent image is visualized to be a developed image. A transfer roller 5a to which a primary transfer bias (opposite polarity (positive polarity) to toner) is applied has a yellow toner image on the intermediate transfer belt 40 rotated in the direction of the arrow by the drive roller 141 at the primary transfer nip portion N. After the transfer, the intermediate transfer belt 40 rotates to the image forming unit 1M side. Similarly, magenta, cyan, and black toner images formed by the photosensitive drums 2b, 2c, and 2d are sequentially superimposed on the yellow toner image on the intermediate transfer belt 40 at each primary transfer portion N, and a full-color toner image is formed. Form.

  The registration roller 146 conveys the recording material P to the secondary transfer nip M in accordance with the timing at which the front end of the full color toner image on the intermediate transfer belt 40 is moved to the secondary transfer nip M. A secondary transfer roller 144 to which a secondary transfer bias (opposite polarity (positive polarity) with respect to toner) is applied performs a secondary transfer of a full color toner image onto a recording material. The fixing device 12 heats and presses the conveyed recording material P at a fixing nip portion between the fixing sleeve 20 and the pressure roller 22 (pressure member) to melt and fix the toner image on the recording material P. Thereafter, the recording material P is discharged to the outside, and a series of image forming operations is completed. The primary transfer residual toner remaining on the photosensitive drum 2 during the primary transfer is removed by the drum cleaning device 6, and the secondary transfer residual toner remaining on the intermediate transfer belt 40 after the secondary transfer is removed by the belt cleaning device 145. Collected.

  The image forming apparatus includes an environmental sensor 37 for adjusting the density of the toner image formed on the recording material P and achieving optimum transfer and fixing conditions, and includes biases for charging, developing, primary transfer, and secondary transfer. The fixing conditions can be changed according to the atmospheric environment (temperature, humidity) in the image forming apparatus. Further, in order to achieve optimum transfer and fixing conditions for the recording material P, a media sensor 38 is provided, and by determining the type of the recording material P, the transfer bias and the fixing conditions can be changed.

[Fixing device 12]
FIG. 1B is a schematic configuration diagram of the fixing device 12 of this embodiment, which is a heating device of a fixing sleeve heating method and a pressing rotary member driving method (tensionless type). The fixing sleeve 20 is a cylindrical (endless belt-like) member in which an elastic layer is provided on a belt-like member, the pressure roller 22 is a backup member, and the heater holder 17 has a substantially semicircular arc-shaped saddle-shaped heat resistance. It is a member having rigidity. The fixing heater 16 is a heating body (heat source), for example, a ceramic heater, and is disposed on the lower surface of the heater holder 17 along the longitudinal direction of the heater holder 17 (direction perpendicular to the recording material conveyance direction). The fixing sleeve 20 is loosely fitted to the heater holder 17. The heater holder 17 is formed of a liquid crystal polymer resin having high heat resistance, holds the fixing heater 16, and guides the fixing sleeve 20. In this example, Sumika Super LCP model number E4205L (trade name) manufactured by Sumitomo Chemical Co., Ltd. was used as the liquid crystal polymer. The maximum usable temperature (load deflection temperature) of E4205L is about 305 ° C.

  The pressure roller 22 is formed by forming a silicone rubber layer having a thickness of about 3 mm on a hollow core metal such as aluminum or iron (STKM material, carbon steel pipe for machine structure, JIS G 3445 standard), and having a thickness of about 50 μm thereon. Cover the PFA resin tube. The pressure roller 22 is arranged such that both end portions of the core metal are rotatably supported by bearings between a side plate (not shown) and a front side plate of the apparatus frame 24. On the upper side of the pressure roller 22, a fixing sleeve unit including the fixing heater 16, the heater holder 17, the fixing sleeve 20 and the like is disposed in parallel with the pressure roller 22 with the fixing heater 16 side facing downward. Both ends of the heater holder 17 are urged in the axial direction of the pressure roller 22 by a force of one side 147N (15 kgf) and a total pressure 294N (30 kgf) by a pressure mechanism (not shown). As a result, the downward surface of the fixing heater 16 is brought into pressure contact with the elastic layer of the pressure roller 22 via the fixing sleeve 20 against the elasticity of the elastic layer with a predetermined pressing force, and has a predetermined width necessary for heat fixing. The fixing nip portion 27 is formed. The pressure mechanism has an automatic pressure variable mechanism, and the pressure can be changed according to the type of the recording material P.

  Reference numerals 23 and 26 denote an entrance guide and a fixing paper discharge roller assembled to the apparatus frame 24. The entrance guide 23 allows the recording material P that has passed through the secondary transfer nip portion M to be accurately guided to the fixing nip portion 27. The recording material P is guided. The entrance guide 23 of this embodiment is formed of a modified PET (polyethylene terephthalate) resin, which is Hyperlight (trade name) manufactured by Kaneka Corporation.

  The pressure roller 22 is rotationally driven in a counterclockwise direction indicated by an arrow by a driving means (not shown), and a rotational force acts on the fixing sleeve 20 by a pressure frictional force at the fixing nip portion 27. While the inner surface side of the fixing sleeve 20 is in close contact with the downward surface of the fixing heater 16 and slides, the outer periphery of the heater holder 17 is driven to rotate in the clockwise direction indicated by the arrow. Grease is applied to the inner surface of the fixing sleeve 20 to ensure slidability between the heater holder 17 and the inner surface of the fixing sleeve 20. The pressure roller 22 is driven to rotate, and the fixing sleeve 20 is driven to rotate. The fixing heater 16 is energized to increase the temperature to a predetermined temperature, and the temperature is controlled by the control unit 21. In this state, the recording material P carrying the unfixed toner image t is introduced into the fixing nip 27 along the entrance guide 23. At the fixing nip portion 27, the toner image carrying surface side of the recording material P is in close contact with the outer surface of the fixing sleeve 20 and is nipped and conveyed together. The heat of the fixing heater 16 is applied to the recording material P through the fixing sleeve 20, and the unfixed toner image on the recording material P is heated and pressurized to be melted and fixed. The recording material P that has passed through the fixing nip 27 is separated from the fixing sleeve 20 by the curvature, and is discharged by the fixing discharge roller 26.

[Fixing heater 16]
FIG. 2A shows a cross-sectional view of the fixing heater 16. The alumina substrate 41 is a horizontally long ceramic substrate whose longitudinal direction is a direction orthogonal to the conveying direction of the recording material P. The resistance heating element layers 42 and 43 (43a, 43b) (electric heating resistance layer) (hereinafter referred to as heating element) are coated on the surface side of the alumina substrate 41 in the form of a line or strip by screen printing along the longitudinal direction. A plurality of heating elements having a width of about 10 μm and a width of about 1 mm. The heating elements 42 and 43 print on the alumina substrate 41 a conductive paste containing a silver palladium (Ag / Pd) alloy that generates heat when an electric current is applied. The electrode portion 44 (see FIG. 2B) forms a pattern on the surface side of the alumina substrate 41 as a power supply pattern for the heating elements 42 and 43 by screen printing of silver paste or the like. The glass coat 45 is a thin one having a thickness of about 60 μm, and ensures protection and insulation of the heating elements 42 and 43. The sliding layer 46 is made of polyimide provided on the contact surface between the alumina substrate 41 and the fixing sleeve 20.

  FIG. 2B-1 is a diagram showing the surface side of the fixing heater 16, and FIG. 2B-2 is a graph of heat generation distribution of the fixing heater 16. As shown in FIG. The heating element 42 has a resistance ratio per unit length of the end with respect to the central portion in the heater longitudinal direction larger than that of the heating element 43. The heating element 43 (43a, 43b) is continuously thicker from the longitudinal center to the end, and the amount of heat generation gradually decreases from the longitudinal central region toward the end. On the other hand, the heating element 42 is continuously thinned from the longitudinal center to the end, and the amount of heat generation gradually increases from the longitudinal central region toward the end. In this way, by continuously changing the heat generation amount in the longitudinal direction, it is possible to effectively suppress non-sheet passing portion temperature rise (edge temperature rise) of a fixing device having a large number of compatible paper types that can handle A3 size paper. it can. A power supply connector is attached to the electrode portion 44 of the fixing heater 16, and power is supplied from the heater drive circuit portion to the electrode portion 44 through the power supply connector, whereby the heating elements 42 and 43 generate heat and the fixing heater 16 is heated. The temperature rises quickly. In normal use, the rotation of the fixing sleeve 20 starts with the rotation of the pressure roller 22, and the temperature of the inner surface of the fixing sleeve 20 increases with the temperature of the fixing heater 16. The control unit 21 controls energization to the fixing heater 16 by PID control, and controls the input power so that the detected temperature of the sleeve thermistor 18 (see FIG. 1B) indicating the inner surface temperature of the fixing sleeve 20 becomes a target value. To do.

  FIG. 2C shows the positional relationship between the fixing heater 16 and the thermistor. In this embodiment, in order to detect the temperature rise of the non-sheet passing portion when a recording material having a width smaller than the maximum sheet passing width is passed, in addition to the sleeve thermistor 18 and the main thermistor 19, the end thermistors 28 at both ends. Is provided. Here, the width of the recording material refers to the length of the recording material in a direction perpendicular to the recording material conveyance direction. In the sleeve thermistor 18 for detecting the inner surface temperature of the fixing sleeve 20, a thermistor element is attached to the tip of a stainless steel arm 25 fixedly supported by the heater holder 17 (see FIG. 1B). Due to the elastic swing of the arm 25, the thermistor element is always kept in contact with the inner surface of the fixing sleeve 20 even when the movement of the inner surface of the fixing sleeve 20 becomes unstable. The main thermistor 19 contacts the vicinity of the longitudinal center of the back surface of the fixing heater 16 and detects the temperature of the back surface of the fixing heater 16. The end thermistor 28 is disposed in a non-sheet passing portion of LTR lateral feed size having a width of 279 mm, and can detect the temperature of the non-sheet passing portion when an LTR size recording material is passed. In this embodiment, the control unit 21 controls energization to the fixing heater 16 so that the detected temperature of the main thermistor 19 maintains the set temperature. However, when the detected temperature of the sleeve thermistor 18 deviates from the target value, Correct the set temperature to be compared with the detected temperature.

[Fixing sleeve 20]
In this embodiment, the fixing sleeve 20 uses SUS as a material and forms a silicone rubber layer (elastic layer) having a thickness of about 300 μm on an endless belt (belt base material) formed in a cylindrical shape having a thickness of 30 μm. A PFA resin tube (outermost surface layer) having a thickness of 20 μm is coated on the silicone rubber layer. When the heat capacity of the fixing sleeve 20 was measured, it was 2.9 × 10 ⁻² cal / cm ² · ° C. (heat capacity per 1 cm ^{2 of the} fixing sleeve). Polyimide or the like can be used for the base layer of the fixing sleeve 20, but SUS is used because SUS has a thermal conductivity about 10 times larger than polyimide and can obtain higher on-demand characteristics. In order to obtain higher on-demand properties, the elastic layer of the fixing sleeve 20 is made of a rubber layer having a high thermal conductivity and a material having a specific heat of about 2.9 × 10 ⁻¹ cal / g · ° C. By providing a fluororesin layer on the surface of the fixing sleeve 20, the surface releasability can be improved, and an offset phenomenon that occurs when the toner once adheres to the surface of the fixing sleeve 20 and moves to the recording material P again can be prevented. By using a PFA tube as the fluororesin layer on the surface of the fixing sleeve 20, a uniform fluororesin layer can be formed more easily.

In general, as the heat capacity of the fixing sleeve 20 increases, the temperature rise becomes dull and the on-demand property is impaired. For example, when temperature control is not performed by a device that does not generate heat during standby and a print instruction is input and a rise is assumed within one minute, the heat capacity of the fixing sleeve 20 is about 1.0 cal / cm ² · ° C. or less. There must be. In this embodiment, when the power is turned off and then turned on after a while, the fixing heater 16 is turned on and the fixing sleeve 20 rises to 190 ° C. within 20 seconds. To do. When a material having a specific heat of about 2.9 × 10 ⁻¹ cal / g · ° C. is used for the silicon silicone rubber layer, the thickness of the silicone silicone rubber must be 500 μm or less, and the heat capacity of the fixing sleeve 20 is about 4.5. It is necessary to be × 10 ⁻² cal / cm ² · ° C. or lower. On the other hand, if the temperature is set to 1.0 × 10 ⁻² cal / cm ² · ° C. or less, the rubber layer of the fixing sleeve 20 becomes extremely thin, and the elastic layer is used in terms of image quality such as OHT permeability and gloss unevenness. It becomes equivalent to the on-demand fixing device that does not have.

In this example, the thickness of the silicone silicone rubber necessary for obtaining a high-quality image such as OHT permeability and gloss setting is 200 μm or more, and the heat capacity at this time is 2.1 × 10 ⁻² cal / cm ² · ° C. That heat capacity of the fixing sleeve 20 is ^{1.0 × 10 -2 cal / cm 2} · ℃ more 1.0cal / cm ² · ℃ below the general subject. Among these, a fixing sleeve of 2.1 × 10 ⁻² cal / cm ² · ° C. or higher and 4.5 × 10 ⁻² cal / cm ² · ° C. or lower can achieve both on-demand and high image quality. Was used.

[Controlling Throughput of this Example]
The image forming apparatus of this embodiment has two types of image forming speeds. The first image forming speed is about 150 mm / sec, and the second image forming speed is slower than the first image forming speed and about 2/3 speed, which is about 100 mm / sec.

  FIG. 3A shows the number of continuously printed sheets when a small size paper (small size paper) is passed at a first image forming speed and a second image forming speed in a low temperature environment (about 15 ° C.). ] And the throughput (ppm: the number of prints per minute). Xerox Business Multipurpose white paper 4200, paper size: letter length (width 216 mm × length 279.4 mm, basis weight: about 90 g / m 2) was used as a small size paper.

  The fixing temperature at the first image forming speed (the temperature detected by the sleeve thermistor 18) is about 175 ° C. in this embodiment from the viewpoint of fixing properties. When paper is passed at the first image forming speed, the paper starts at about 20 ppm in the initial stage, and the temperature detected by the end thermistor 28 is increased by about 15 sheets due to the temperature rise of the non-sheet-passing portion, so that the throughput reduction threshold temperature (for example, about 270). ° C). For this reason, the throughput is reduced from 20 ppm to 10 ppm (the paper interval is increased). Thereafter, the detection temperature of the end thermistor 28 reaches the throughput down threshold again with about 150 sheets, and the throughput is reduced from 10 ppm to 8 ppm. Thereafter, the detected temperature of the end thermistor 28 reaches the throughput down threshold again with about 193 sheets, and the throughput is reduced from 8 ppm to 6 ppm.

  The fixing temperature at the second image forming speed is about 155 ° C., which is lower than the fixing temperature setting at the first image forming speed, because the image forming speed is slower than the first image forming speed. For this reason, since the fixing speed is slow and the fixing temperature itself is low, the temperature rise at the non-sheet passing portion is low, and when the paper is passed at the second image forming speed, the paper feeding starts at about 13.4 ppm initially. Thereafter, the end thermistor 28 did not reach the throughput down threshold temperature.

  For comparison, FIG. 5 shows a flowchart of throughput control of a conventional example (for example, Patent Document 2). In the conventional example, if there is a print instruction in step 1001 (hereinafter referred to as S1001 or the like), printing is performed at the first image forming speed in S1004 if the small-size sheet is not passed in S1002. If it is during the small-size sheet passing in S1002, printing is performed at a second image forming speed slower than the first image forming speed in S1003. In the conventional example, the image forming speed is fixed according to the sheet passing size. FIG. 3B shows the average throughput when passing a small size in this case as Comparative Example 1 with respect to the present embodiment. In Comparative Example 1, which is fixed to the conventional second image forming speed, the initial average throughput is about 13.4 ppm, and the average throughput remains about 13.4 ppm even when the number of printed sheets increases.

  As another conventional example (for example, Patent Document 1), the case where the image forming speed at the time of small-size paper passing is fixed to the first image forming speed and the gap between the papers is widened to cope with the temperature rise of the non-paper passing portion is implemented. It shows in FIG.3 (b) as the comparative example 2 with respect to an example. In Comparative Example 2, printing is performed with a fast throughput of 20 ppm in the initial stage, but the throughput decreases with about 14 sheets due to the temperature rise of the non-sheet passing portion (the gap between the sheets is widened). For this reason, the average throughput decreases as the number of printed sheets increases.

  FIG. 4 shows a flowchart of throughput control according to this embodiment. If there is a print instruction in S101, and an engine controller (not shown) determines in S102 that it is not a small-size sheet, printing is performed at the first image forming speed in S107 as in the conventional example. If the engine controller determines in S102 that the paper is smaller than the predetermined width, for example, B5, A5, EXE size or A4 vertical paper, the process proceeds to S103. In S103, the engine controller checks the number of print jobs, for example, the number of image formations, and compares the predetermined number of image formation speed switching sheets with the number of print jobs in S104. If the engine controller determines in S104 that the number of print JOB sheets is less than the number of image forming speed switching sheets, that is, less than the predetermined number, in S105, the engine controller controls to execute printing at the first image forming speed. If the engine controller determines in S104 that the number of print JOB sheets is greater than the number of image forming speed switching sheets, that is, a predetermined number or more, in S106, the engine controller executes printing at a second image forming speed that is slower than the first image forming speed. To control. Note that the image forming speed switching sheet number is set to 30 sheets, for example.

  3B and 3C show the number of print jobs and the average throughput in this embodiment and Comparative Examples 1 and 2, respectively. In this embodiment, when the number of print jobs is less than the number of image forming speed switching sheets (14 sheets), the average throughput (average ppm) can be made larger than that of the first comparative example. In this embodiment, when the number of print jobs is larger than the number of image forming speed switching sheets (100 sheets, 200 sheets), the average throughput (average ppm) can be made larger than that of Comparative Example 2.

  As described above, according to the present embodiment, since the image forming speed for printing is switched according to the number of print jobs, productivity (performance) at the time of passing small-size paper can be improved, and the image forming unit And the life of the fixing device and the like can be extended.

  In this embodiment, the film fixing device has been described. However, the present invention is not limited to the film fixing device, and the same effect can be obtained by using another fixing device such as a roller fixing device. .

1 Image forming unit 12 Fixing device P Recording material

Claims (2)

An image forming apparatus for fixing an image on a recording material formed by an image forming unit by a fixing device,
Comprising a control means for changing the image forming speed in accordance with the width of the recording material;
When the width of the recording material is smaller than the predetermined width and the number of print JOBs on the recording material is less than the predetermined number, the control unit changes to the first image forming speed, and the number of print JOBs on the recording material is An image forming apparatus that changes to a second image forming speed slower than the first image forming speed when the predetermined number of sheets is exceeded.   The image forming apparatus according to claim 1, wherein the fixing device is a film fixing device.

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