JP4003079B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a fax machine that forms a color image using electrophotographic technology.

  In the electrophotographic system, an electrostatic latent image corresponding to image data is formed on a photoconductor, and toner particles, which are charged particles, are attached to the photoconductor in accordance with the potential pattern of the electrostatic latent image. Is visualized as a toner image, and the toner image is transferred to a recording medium such as paper to form an image on the paper. When a color image is formed by this process, an image must be formed by superposing a plurality of color toners, for example, color toners such as yellow, magenta, and cyan.

  An image forming apparatus that forms a color image has various features in the method of superimposing the toners of the respective colors. Two types of color image forming methods have been proposed. One is a repetitive development method in which each color toner is repeatedly developed on one photoconductor to form a color image, and the other is a color image formed by simultaneously developing each color toner on a plurality of photoconductors. It is a simultaneous development method. Hereinafter, each color image forming method will be described in detail.

  The repetitive development method is a method of forming a color image using one photoconductor. There are three examples of this method: a color superimposing method on the photosensitive member, a transfer drum method, and an intermediate transfer member method.

  Among them, the intermediate transfer body system, which is a system capable of recording high-quality images, has a plurality of developing units and intermediate transfer bodies for developing different color toners around the photosensitive body as described in Patent Document 1. The toner image formed on the photosensitive member is transferred onto the intermediate transfer member, and this is repeated for each color to superimpose a plurality of color toners on the intermediate transfer member. The color image is output by transferring to

  The simultaneous development method includes a plurality of photoconductors as described in Patent Document 2 and Patent Document 3, each of which forms a toner image at the same time, and transfers the toner image corresponding to the conveyance of the paper. There is a method represented by a color image forming method called a tandem method for forming a color image.

JP-A-8-137179 Japanese Patent Laid-Open No. 10-186894 Japanese Patent Laid-Open No. 10-260593

  With the colorization and digitization of the office environment, there is an increasing demand for printing color images on recording media such as paper. A color image forming apparatus that meets these requirements has a compact footprint that can be installed in an office, high image quality that can output photographs, etc., and printing on various recording media such as OHP and cardboard in addition to plain paper. Four types of performance are required: compatibility with various types of paper, and high-speed printing of a large amount of office documents in a short time.

  Above all, the two requirements of compact image quality, which is a prerequisite for office use, and the high-speed printing that comes from the speedup of color image processing and transmission technology supported by advances in personal computers and networks are the future color images. It has become an important performance indispensable for forming apparatuses.

  As a configuration for facilitating this increase in speed, there is the tandem method described above. In the tandem method, since the toner images of the respective colors are formed almost simultaneously, a color image can be formed at a speed equivalent to that of a monochrome printer. However, since an image is formed independently on each photoconductor, it is very difficult to superimpose toner images of respective colors. The alignment of the toner images of each color is affected by the placement accuracy such as the pitch and parallelism of each photoconductor and exposure device. If these are not placed accurately, the hue change due to the misalignment of the toner images of each color In addition, there is a problem that the image quality is greatly deteriorated such that the image looks double. Furthermore, when the user removes or removes the photoconductor, which is a consumable item, the placement accuracy is greatly reduced. For this reason, in the tandem system, the alignment of each color toner image is an important issue from the viewpoint of high image quality recording.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that is small, high-speed, and capable of high-quality recording.

  Another object of the present invention is to provide an image forming apparatus with excellent maintainability.

The present invention includes a housing of the image forming apparatus, a plurality of photosensitive elements arranged in the longitudinal direction one column, a plurality of developing machines and multiple exposure devices arranged on one side of the plurality of photosensitive members, said plurality An intermediate transfer member disposed on the other side of the photosensitive member, and a paper cassette disposed below the plurality of photosensitive members. The plurality of photoconductors in the integrated unit are driven by a gear. Further, a photosensitive member driving gear is provided on each photosensitive member of the plurality of photosensitive members, and the plurality of photosensitive members in the integrated unit are driven by the one gear.

Further, the image forming apparatus includes a transfer unit and a fixing device arranged on one side of the intermediate transfer member. The plurality of exposure units may be fixedly disposed on the casing. In addition, a belt-type fixing device in which a belt is stretched in substantially the same direction as the arrangement direction of the plurality of photosensitive members is disposed on one side of the intermediate transfer member. The heights of the plurality of developing machines and the plurality of exposure units may be shorter than the length in the horizontal direction. Each of the plurality of developing machines includes a developing unit and a toner hopper, and the toner hopper can be replaced while leaving the developing unit in the housing. In addition, a sheet heating member for heating the recording medium is provided between the transfer unit and the fixing device.

  Since printing is performed using a plurality of photoconductors as described above, high-speed printing is possible as compared with the case where only one photoconductor is used. In addition, by making a plurality of photoconductors as an integrated unit, there is no fear of displacement of each photoconductor due to attachment and detachment at the time of replacement of the photoconductor, and there is no image shift at the time of printing, and high-quality recording is possible. Maintenance becomes easy.

  Furthermore, by arranging the exposure device fixed on the housing side of the image forming apparatus, it is possible to provide an image forming apparatus that is free from design exposure deviation, can be stably exposed, and can record high-quality images. .

  As described above, the present invention can provide an image forming apparatus that is compact, capable of high-speed recording with high speed. Further, it is possible to provide an image forming apparatus excellent in maintainability such as replacement of consumables.

  This will be described below with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to a first embodiment of the present invention, which can provide an image forming apparatus capable of small size and high-speed printing and simultaneously recording high-quality images. .

  In the central portion of the housing 200, four photoconductors 1a, 1b, 1c, and 1d corresponding to toners of four colors yellow, magenta, cyan, and black that are necessary for color image formation are arranged vertically and each is arranged. Each shaft is connected by a support so as to be rotatable, and is provided as an integral photoconductor unit 22 configuration. Further, the intermediate transfer belt 2 is moved in the arrangement direction of the plurality of photoconductors by the four belt stretching rollers 10a, 10b, 10c, and 10d so as to be in contact with the plurality of photoconductors 1a, 1b, 1c, and 1d arranged side by side. It is stretched almost horizontally and vertically. At that time, auxiliary transfer rollers 9a, 9b, 9c, 9d for transferring the toner image from the photosensitive member onto the belt are provided at positions facing the photosensitive members 1a, 1b, 1c, 1d via the intermediate transfer belt 2. It was. In each photoconductor 1a, 1b, 1c, 1d arranged side by side, the surface of each photoconductor 1a, 1b, 1c, 1d is exposed to the side opposite to the side on which the intermediate transfer belt 2 is arranged to electrostatically Exposure units 4a, 4b, 4c, and 4d that form latent images and developing units 5a, 5b, 5c, and 5d that visualize the electrostatic latent images with toner are alternately stacked in the vertical direction. There may be a slight gap between each exposure device 4a, 4b, 4c, 4d and each developing device 5a, 5b, 5c, 5d, or some other member may be interposed. However, in order to reduce the size of the apparatus, the interval between them is set as small as possible.

  Further, the respective photoreceptors 1a, 1b, 1c, and 1d are rotated counterclockwise in FIG. At a position in contact with the so-called intermediate transfer belt 2, the belt rotates from the top to the bottom. If the photosensitive member rotates in this way, the arrangement of other printing processes and the rotation direction of the intermediate transfer belt 2 are determined. In this case, the intermediate transfer belt 2 rotates from the upper side to the lower side in the same manner as the photoconductor at a position where the intermediate transfer belt 2 is in contact with the photoconductor.

  Further, on the outer periphery of the intermediate transfer belt 2, an image sensor 11 for detecting the displacement of each color image, a toner charger 12 for adjusting the chargeability of the toner, and a transfer for transferring the toner image on the intermediate transfer belt 2 to a sheet of recording medium. A device 13, a sheet neutralizer 14 for separating the sheet from the intermediate transfer belt 2, and an intermediate transfer belt cleaner 15 for cleaning the toner on the intermediate transfer belt 2 are provided. A belt waste toner collecting section 52 for collecting the waste toner cleaned by the intermediate transfer belt cleaner 15 is provided. Further, a paper cassette 16, a paper feed mechanism 17, a separation pad 87, a registration roller 18, and a fixing device 19 are disposed on the paper transport path.

  Next, FIG. 3 shows an enlarged view of the configuration of the peripheral portion of the photoreceptor. Hereinafter, the periphery of the photoreceptor 1a will be described, but the same applies to the other photoreceptors 1b, 1c, and 1d.

  Around each photoconductor 1a, a charger 3a for charging the photoconductor 1a, an exposure device 4a, a developing device 5a, an intermediate transfer belt 2, an erase lamp 8a for discharging the surface of the photoconductor 1a, and residual toner are cleaned. In the intermediate transfer belt 2, the toner image formed on the photosensitive member 1 a by the developing device 5 a in the intermediate transfer belt 2 is collected in the photosensitive member cleaner 6 a, the waste toner collecting unit 7 a that collects the waste toner cleaned by the photosensitive member cleaner 6 a. A transfer assisting roller 9a for assisting the transfer on the upper side is provided.

  In this embodiment, the photoreceptor cleaner 6a is used to remove the toner remaining on the photoreceptor 1a after the toner is transferred to the intermediate transfer belt 2 and the toner attached by reverse transfer of the toner image on the intermediate transfer belt 2. , 6b, 6c, 6d.

  If toner remains on the photosensitive member 1a, uneven exposure amount and color mixture of toner in the developing device 5a occur. Therefore, it is necessary to remove these toners with certainty. Therefore, the photosensitive member may be cleaned using a cleaning blade for the photosensitive member cleaners 6a, 6b, 6c, and 6d. Since the cleaning blade scrapes the toner by bringing an elastic blade made of rubber or the like into direct contact with the photosensitive member, cleaning can be performed reliably. Furthermore, since the configuration is simple with only the blade, the cleaner configuration can be reduced in size and the cost can be reduced.

  The toner scraped off by the photoreceptor cleaners 6a, 6b, 6c, and 6d is discharged to the waste toner collecting portions 7a, 7b, 7c, and 7d disposed below the photoreceptors 1a, 1b, 1c, and 1d using gravity. ing. The waste toner collection units 7a, 7b, 7c, and 7d use spiral rollers and rotate them to convey toner. The toner collected by the waste toner collecting portions 7a, 7b, 7c, and 7d is finally transported to a waste toner case or the like through a waste toner discharge path 102 (see FIG. 2) disposed in the apparatus, and batched. I try to throw away.

  In order to stabilize the potential on the surface of the photoreceptors 1a, 1b, 1c, and 1d, it is effective to attenuate the potential on the surface of the photoreceptor in advance before charging. Further, when the potential on the surface of the photosensitive member is lowered, the electrostatic connection between the photosensitive member and the toner is weakened, and the toner remaining on the photosensitive member can be reliably cleaned. Further, erase lamps 8a, 8b, 8c, and 8d are provided for neutralizing the photosensitive members 1a, 1b, 1c, and 1d, respectively. The erase lamps 8a, 8b, 8c, and 8d are LED arrays, and neutralize the surface of the photoreceptor by light irradiation.

  Next, the positional relationship between the photoreceptors 1a and 1b and the position of the image will be described with reference to FIG. 4A shows the case where the photoconductors 1a and 1b are in the normal positions, FIG. 4B shows the case where the photoconductor 1b is displaced, and FIG. 4C shows the photoconductor 1a. , 1b, the images 20 and 21 are overlapped.

  The image forming apparatus of the present invention is required to output a high-resolution and high-quality image such as a photograph. In order to realize high-quality recording, it is necessary to accurately print minute dots and improve the uniformity of solid images. However, misregistration of toner images of each color may cause blurring or hue of the image. In order to cause a shift and greatly reduce the image quality, it is necessary to accurately align the images of the respective colors.

  For the alignment of the toner images of each color, the arrangement position of each photoconductor and the arrangement position of the exposure device are important.

  First, exposure is started by the exposure device 4a on the first photosensitive member 1a located at the most upstream portion in the rotation direction of the intermediate transfer belt 2. In the image exposure on the second photoconductor 1b immediately below the photoconductor 1a, the image 20 formed on the photoconductor 1a and the image 21 formed on the photoconductor 1b are superimposed on the intermediate transfer belt 2, so that the photoconductor From the start time of image exposure in the exposure device 4b to 1a, the time during which the electrostatic latent image moves from the exposure position to the contact portion with the intermediate transfer belt 2 and the surface of the intermediate transfer belt 2 between the photoconductors 1a and 1b. Delay the time to pass. Therefore, in the image alignment of each color, the distance from the exposure position on each photoconductor to the contact position to the intermediate transfer belt 2, the interval between the photoconductors 1a and 1b, and the surface speed of the photoconductor and the intermediate transfer belt. is important. At this time, as shown in FIG. 4B, if the photosensitive member 1b is arranged so as to be displaced from a predetermined position, the leading ends of the images 20 and 21 are displaced corresponding to the displacement. For this reason, high accuracy is required for the arrangement position accuracy of each photoconductor and exposure device.

  However, the photoconductor needs to be replaced because it causes surface wear and deterioration of photosensitivity with printing. Furthermore, in an image forming apparatus used in a business environment, it is required that a user replaces consumables by himself / herself. Such an easily replaceable configuration, on the other hand, causes a reduction in the placement accuracy of the photoconductor, and it is difficult to place it with high accuracy.

  If each photoconductor is configured as a separate unit and is replaced separately, the placement accuracy of each photoconductor, which is important for the alignment of each color image, is that each photoconductor is a separate unit and that they are separate units. It becomes low by being exchanged.

  Therefore, in the embodiment of FIG. 1, a plurality of photoconductors 1a, 1b, 1c, and 1d on which toner images of respective colors are formed are fixedly arranged in a unit called a photoconductor unit 22, and the entire photoconductor unit 22 is replaced. The configuration.

  In this embodiment, the photoreceptors 1a, 1b, 1c, and 1d, the chargers 3a, 3b, 3c, and 3d, the photoreceptor cleaners 6a, 6b, 6c, and 6d, and the waste toner collection units 7a, 7b, 7c, and The photoconductor unit 22 is provided with 7d as an integrated unit. Note that the erase lamps 8a, 8b, 8c, and 8d may be disposed in the photoreceptor unit 22 or provided outside.

  Further, when the photosensitive unit 22 itself is displaced from the specified position as shown in FIG. 4C, the photosensitive member is displaced as shown in FIGS. 4A to 4C. However, since the photoconductors are unitized, the shift amounts of the photoconductors 1a and 1b are equal. For this reason, the images 20 and 21 formed by the photoconductors 1a and 1b are transferred from the specified position and transferred onto the intermediate transfer belt 2. However, both the images 20 and 21 have the same amount of shift, and finally. Images overlap exactly. At this time, the deviation of the leading end position of the image in which the respective colors are superimposed is sufficiently smaller than the alignment accuracy of the leading end of the image and the leading end of the sheet at the time of feeding and transferring the recording medium. As described above, each of the photoconductors 1a, 1b, 1c, and 1d is fixedly disposed in the unit called the photoconductor unit 22, and the photoconductor unit 22 can be replaced, so that each color image can be accurately aligned. Thus, an image forming apparatus capable of high-quality recording can be realized.

  In addition, regarding the alignment of the toner of each color image, the arrangement accuracy of the exposure devices 4a, 4b, 4c, and 4d that expose the photosensitive members 1a, 1b, 1c, and 1d is also important. For example, if the exposure device that exposes each photoconductor is attached to a member that can be opened and closed, such as the upper cover of the main body, the position of each exposure device is likely to be shifted when these members are opened and closed. Misalignment is likely to occur.

  Therefore, in the image forming apparatus according to the present embodiment, by arranging each exposure unit 4a, 4b, 4c, 4d fixedly on the main body housing 200, the arrangement position of each exposure unit 4a, 4b, 4c, 4d is accurate and fluctuates. Can be eliminated.

  However, when the resolution is increased in correspondence with higher-definition image recording, the alignment of each color image must be performed with extremely high accuracy, and this configuration may be insufficient.

  As a case like this, in this embodiment, when the consumables are replaced in order to accurately align each color image, or when the displacement of each color image is large due to some trouble, a sample pattern is printed, Based on this, a mechanism that allows the user or operator to adjust the image writing position is provided to always enable high-quality recording.

  Furthermore, as a method for accurately aligning each color image, a mechanism can be applied in which the above is further developed to detect the position of each color image and control the timing and position of writing according to the amount of image shift. This image displacement control unit detects the position of each image (for example, four color images of yellow, magenta, cyan, and black), and the image to be actually printed based on the detection result of the image sensor 11. The shift calculation unit is configured to determine how much shift occurs, and the image correction unit performs image correction on each image based on the result of the shift calculation unit. The position of the image is accurately measured by previously printing a pattern on which the image shift of each color can be easily measured, for example, an image position detection pattern on the intermediate transfer belt 2 and measuring the time when the image is detected. It is possible. This image position detection pattern is printed in a non-image area such as between sheets at a predetermined timing such as during printing when the apparatus is started up.

  Here, an embodiment of the image sensor 11 will be described. The image sensor 11 is disposed on the intermediate transfer belt 2 and detects the position of each color image on the intermediate transfer belt 2. In the image sensor 11, a light emitting unit and a light receiving unit are provided. Light emitted from the light emitting unit is applied to the surface of the intermediate transfer belt 2, and the reflected light is received by the light receiving unit. Since the intensity of the reflected light differs depending on whether or not there is toner on the intermediate transfer belt 2, this difference is detected to detect the presence or absence of toner. At this time, in order to increase the position detection accuracy of the toner image, it is necessary to make the spot diameter of the light emitted from the light emitting portion smaller than the allowable value of the image position deviation. In this embodiment, since the positional deviation of the images of the respective colors is set to 100 μm or less, the spot diameter of the light emitted from the light emitting unit is set to 100 μm or less. A laser diode, LED, or the like can be used for the light emitting unit. As an image sensor, an electrometer that measures the potential of the toner, which is charged particles, can be used in addition to the above-described light.

  In addition, each color toner image has a parallel vertical / horizontal shift, an image angular shift, and vertical / horizontal expansion / contraction of the image. In this embodiment, as shown in FIG. 20, a total of two image sensors 11 for detecting image positional deviation are arranged on the right side and the left side of the intermediate transfer belt 2, and measurement is performed by a plurality of image sensors 11. The detailed position is measured. This is because if the images detected by the image sensor 11 deviate from the expected positions, the exposure writing timing and the positions of the processes are deviated. Based on this result, the shift calculation unit determines how much and how much each image is shifted. The shift calculation unit determines the position of each image, the angle shift, and the expansion / contraction of the image not only from the leading edge position of each image pattern but also from the position measurement results such as the rear edge position and its left and right. For example, by measuring each line of a character pattern such as a wedge shape, it is possible to know the position of the tip, the angular deviation, and the like.

  Based on this result, the image correction unit adjusts the x and y coordinates of the writing start position of the image to be actually printed, the angle of the image, and the length of the image. When each color image is rotated or stretched by the image correction unit, a method of storing the entire image to be printed on the memory and performing image processing can be applied.

  Since the image sensor 11 is disposed at a position facing the surface of the intermediate transfer belt 2 to which the toner adheres, the image sensor 11 may be contaminated with scattered toner from the intermediate transfer belt 2, which is a factor that reduces detection accuracy. Become. In order to prevent this, it is possible to provide a mechanism for cleaning the image sensor 11. Further, when the image position is not measured, a configuration in which a cover that covers the light emitting / receiving portion of the image sensor 11 is also effective for preventing the sensor from being stained.

  Further, since the level of the light detected by the light receiving portion of the sensor changes in accordance with the amount of toner attached, the amount of toner attached on the intermediate transfer belt 2 can be detected. Therefore, when improving the image quality by providing a control mechanism that controls the exposure intensity, exposure time, development bias, etc., corresponding to the toner adhesion amount as described above, another implementation as a sensor for measuring the toner adhesion amount. The image sensor 11 of an example can also be used.

  Next, FIG. 2 shows details of one embodiment of the above-described photoreceptor unit 22. 2 (a) and 2 (b) are side views of the photosensitive unit, FIG. 2 (c) is a plan view of the photosensitive unit, and the side opposite to FIGS. 2 (d) and 2 (a). A side view is shown.

  2B, the photosensitive unit 22 shown in FIG. 2B includes a plurality of photosensitive members 1a, 1b, 1c, and 1d, and photosensitive member cleaners 6a that clean the respective photosensitive members 1a, 1b, 1c, and 1d. 6b, 6c, 6d, waste toner collecting portions 7a, 7b, 7c, 7d for collecting the waste toner cleaned by the respective photoreceptor cleaners 6a, 6b, 6c, 6d, and the respective photoreceptors 1a, 1b, 1c, Chargers 3a, 3b, 3c, and 3d that uniformly charge 1d are provided.

  As shown in FIG. 2C, at least each of the photoconductors 1a, 1b, 1c, and 1d is arranged so as to be supported by two supporters 110a and 110b. A holding body for holding the supports 110a and 110b is provided. So-called photoreceptors 1a, 1b, 1c, and 1d are configured as an integral unit. Further, by adjusting the accuracy at the time of manufacture, it is possible to arrange the intervals and parallelism of the photosensitive members 1a, 1b, 1c, and 1d with high accuracy and to maintain the accuracy. Furthermore, even when the user replaces the photoconductors, the photoconductor units 22 are replaced as the photoconductor units 22 in which the photoconductors 1a, 1b, 1c, and 1d are integrated, so that the interval and parallelism between the photoconductors can be stabilized. . Further, in this configuration, since each of the photoconductors 1a, 1b, 1c, and 1d is replaced and detached as the photoconductor unit 22, the arrangement position of the photoconductor unit 22 may be displaced from the specified position. Each of the photoconductors 1a, 1b, 1c, and 1d in 22 keeps a predetermined interval and is parallel to each other, so that the positions of the photoconductors are not shifted, and image alignment is easy. The so-called upper, lower, left, and right distances between the photoconductors do not shift, and the photoconductors can be easily replaced, improving the maintainability.

  In addition, peripheral devices such as the chargers 3a, 3b, 3c, and 3d related to the plurality of photoconductors 1a, 1b, 1c, and 1d are integrated with the plurality of photoconductors so as not to deteriorate the maintainability. In addition, more stable high image quality and high-definition image recording becomes possible.

  Next, a method for driving the plurality of photoconductors 1a, 1b, 1c, and 1d will be described (see FIGS. 2C and 2D). For driving the photoconductors, a method of setting the photoconductors 1a, 1b, 1c, and 1d to the same rotational speed or a method of setting different rotational speeds can be applied. When the variation in diameter of each photoconductor 1a, 1b, 1c, 1d can be reduced, a method of driving each photoconductor at the same rotational speed is used.

  Each photoconductor 1a, 1b, 1c, and 1d is provided with a photoconductor drive gear 100 that rotationally drives each shaft in order to connect to the supports 110a and 110b, and from the main body side (outside the photoconductor unit, the housing 200 side). These photoreceptors 1a, 1b, 1c, and 1d are driven by one gear. At the same time, a waste toner collecting portion drive gear 101 for driving the waste toner collecting portions 7a, 7b, 7c and 7d is provided. Further, a waste toner discharge path 102 for discharging the waste toner is provided on the side opposite to the side where the photoconductor driving gear 100 is disposed, that is, the so-called support 110a side.

  It is also possible to dispose a coupling of gears for driving the photosensitive members 1a, 1b, 1c, and 1d on the main body side, and drive the photosensitive members 1a, 1b, 1c, and 1d with four gears from the main body side. . In this case, the photoconductor drive gear 100 for driving the photoconductors 1a, 1b, 1c, and 1d assumes that the photoconductor unit 22 is attached and detached upward, and the main body gear and the photoconductor drive gear 100 are connected to the photoconductor. In order to avoid interference when the unit 22 is attached or detached, the units 22 are arranged slightly different from each other.

  Further, the photoconductors 1a, 1b, 1c, and 1d can be connected by a belt without using the gear as described above.

  When there is a large variation in diameter among the plurality of photoconductors 1a, 1b, 1c, and 1d, driving the photoconductors 1a, 1b, 1c, and 1d at the same rotational speed causes a difference in peripheral speed between the photoconductors, and the position of the image. Misalignment and slippage occur. These peripheral speed differences can be reduced by a method in which each of the photosensitive members 1a, 1b, 1c, and 1d is driven independently. Each photoconductor 1a, 1b, 1c, 1d is provided with a driving motor, and the difference in peripheral speed between the photoconductors 1a, 1b, 1c, 1d caused by variations in the diameter of the photoconductors 1a, 1b, 1c, 1d is determined. By correcting, it becomes possible to improve the alignment accuracy of the image, which is effective for improving the image quality. At this time, in order to prevent the intermediate transfer belt 2 from being bent between the photosensitive members 1a, 1b, 1c, and 1d, the photosensitive member 1d downstream in the moving direction of the intermediate transfer belt 2 is moved from the upstream photosensitive member 1a. You may drive quickly.

  When the friction loads of the developing machines 5a, 5b, 5c, and 5d and the photoreceptor cleaners 6a, 6b, 6c, and 6d can be reduced, it is not necessary to apply a driving force to the photoreceptors 1a, 1b, 1c, and 1d. The belt 2 can be driven and driven. In this case, since the peripheral speeds of the photoreceptors 1a, 1b, 1c, and 1d can be matched with the speed of the intermediate transfer belt 2, the alignment of the toners of the respective colors can be easily performed. At this time, in order to reliably transmit the driving force of the intermediate transfer belt 2 to the photoreceptors 1a, 1b, 1c, and 1d, a member that increases the friction coefficient on the surface of the intermediate transfer belt 2, such as the intermediate transfer belt 2 or the photoreceptor 1 is used. It is also possible to provide a high friction material such as rubber in the non-printing area.

  As described above, the intermediate transfer belt 2 does not cause deflection on the belt surface in contact with the photoconductors 1a, 1b, 1c, and 1d. The belt tension roller 10b arranged below is driven. The belt stretching roller 10b is provided with a friction layer such as rubber on the roller surface so that the belt and the roller do not slip. Further, by slightly changing the peripheral speed of the photoreceptors 1a, 1b, 1c, and 1d and the speed of the intermediate transfer belt 2 to increase the speed of the intermediate transfer belt 2, it is possible to suppress the occurrence of the belt deflection described above. it can. As a driving method of the intermediate transfer belt 2, the following configuration can be used depending on a method of applying tension to the belt. The deflection of the photosensitive element array surface of the intermediate transfer belt 2 is caused by the rotation of the intermediate transfer belt 2, a member serving as a rotational load, in this embodiment, the transfer device 13 (see FIG. 1) and the intermediate transfer belt cleaner 15 in contact. This can also be reduced by applying tension to the belt on the surface of the photoreceptor. For this reason, the belt is driven by the belt stretching rollers 10a, 10c, and 10d by applying the tension of the intermediate transfer belt 2 using the belt stretching rollers 10a and 10b or another member provided on the photosensitive member side. It may be driven. For example, even when tension is applied to the belt by the belt stretching roller 10b and the belt stretching roller 10a is driven, the belt surface on which each photoconductor is disposed is always stretched, so that no deflection occurs.

  Furthermore, if the contact load of the intermediate transfer belt cleaner 15 can be reduced, the intermediate transfer belt 2 can be driven by the photoreceptor. In this case as well, when the photosensitive members 1a, 1b, 1c, and 1d described above are driven by the intermediate transfer belt 2, the surface speeds of the two coincide with each other, so that the alignment of each color image is easy.

  When the rotational speed of the photoreceptors 1a, 1b, 1c, 1d and the intermediate transfer belt 2 is varied, a motor capable of controlling the rotational speed, such as a pulse motor or a servo motor, is used for driving them.

  Next, driving methods of other main processes will be described.

  In this embodiment, the charging rollers shown in FIGS. 1 and 2 are used as the chargers 3a, 3b, 3c, and 3d. However, the driving of the charging roller is performed in order to simplify the configuration around the photosensitive member. The body 1a, 1b, 1c, 1d is configured to be driven. However, if the charging roller has a large diameter for the purpose of extending the life, or if a surface layer with high lubricity is formed on the surface of the charging roller to suppress toner adhesion, sufficient frictional force with the photoreceptor In the case where it is not possible to obtain the above, it may be configured to be driven by applying power from a driving mechanism other than the photosensitive member.

  Further, as shown in FIG. 5, each of the developing units 5a, 5b, 5c, and 5d is configured as a detachable unit, so that power is separately transmitted to the individual developing units 5a, 5b, 5c, and 5d. . In this embodiment, the power of the developing device drive motor is branched into four on the main body side, and each developing device is driven. It is also possible to drive each developing device with each photoconductor.

  Further, as shown in FIG. 11, in the image forming apparatus using the non-magnetic one-component developing method, the toner adhesion amount can be controlled by changing the rotation speed of the developing roller 37, so the adhesion amount of each color is adjusted. For the purpose, the developing devices 5a, 5b, 5c, and 5d can be driven by different motors so that the rotational speeds of the developing devices 5a, 5b, 5c, and 5d of the respective colors are different.

  In the embodiment of FIG. 1, a transfer roller is used for the transfer device 13. This transfer roller is driven by the intermediate transfer belt 2 in order to simplify the mechanism. When the transfer roller applies a large rotational load to the intermediate transfer belt 2, it can be driven.

  Next, an example of a printing sequence of the image forming apparatus of this embodiment will be described with reference to FIGS.

  When a print command is first sent to a controller (not shown), driving of the intermediate transfer belt 2, driving of the photosensitive members 1a, 1b, 1c, and 1d and charging are started. Subsequently, the photosensitive member 1a in contact with the intermediate transfer belt 2 is image-exposed by the exposure device 4a to form an electrostatic latent image on the photosensitive member 1a, and the electrostatic latent image is developed by the developing device 5a to form a toner image. Is formed on the photosensitive member 1a, and a toner image is transferred onto the intermediate transfer belt 2. Image exposure is also performed on the photoreceptor 1b located almost immediately at the same time, and a toner image is formed by the developing device 5b. The exposure start of the photoreceptor 1b is adjusted so that the toner image formed on the photoreceptor 1b accurately overlaps the image previously formed on the photoreceptor 1a on the intermediate transfer belt 2. In this process, an image in which two color toner images are superimposed on the intermediate transfer belt 2 is formed. Similarly, exposure, development, and transfer are performed on the photoconductors 1c and 1d of the third color and the fourth color, and a full color image in which the toner images of the respective colors are superimposed on the intermediate transfer belt 2 is formed. The full-color image on the intermediate transfer belt 2 is fed from the paper cassette 16 by the transfer device 13, transferred to a recording medium such as paper that has been conveyed, fixed by the fixing device 19, and discharged from above the housing 200. . In this embodiment, a full-color image is recorded using four color toners in order to record a high-quality full-color image. However, a full-color image can be recorded using three-color toners of yellow, magenta, and cyan. Yes, there may be three printing processes such as a photoconductor and a developing machine.

  A color image forming apparatus using an electrophotographic system forms a color image by superimposing toners of different colors. In the image forming apparatus of this embodiment, it corresponds to toners used, yellow, magenta, cyan, and black. A simultaneous printing method using four photoconductors and forming an image almost simultaneously is adopted.

  Further, an arrangement relationship including the photosensitive member and the intermediate transfer member of the image forming apparatus of the present embodiment shown in FIG. 1 will be described below. In particular, a belt-like intermediate transfer member is shown below.

  In the image forming apparatus of this embodiment, after the toner images of the respective colors formed on the photoreceptors 1a, 1b, 1c, and 1d are superimposed on the belt-shaped intermediate transfer member, the sheet as a final recording medium is collectively collected. Therefore, it is not necessary to arrange the photoconductor unit 22 and the fixing device 19 on the same straight line. In the image forming apparatus of FIG. 1, the intermediate transfer belt 2 is disposed between the photoreceptor unit 22 and the fixing device 19. As a result, it is possible to improve the configuration of the apparatus that is elongated in the photoconductor arrangement direction, and to save space.

  Further, by stretching the intermediate transfer belt 2 so as to reduce the cross-sectional area of the entire belt, the entire apparatus can be reduced in size. Further, exposure devices 4a, 4b, 4c, and 4d for exposing and developing each photosensitive member 1 and developing devices 5a, 5b, 5c, and 5d are stacked in the vertical direction. For this reason, when these members become large, the size, especially the height of the device increases. In this embodiment, the overall length of the exposure apparatus 4a, 4b, 4c, 4d and the developing units 5a, 5b, 5c, 5d is reduced by making the length in the height direction smaller than the length in the horizontal direction.

  Further, in this embodiment, the photoconductors 1a, 1b, 1c, and 1d are arranged substantially in a straight line in the vertical direction, and the intermediate transfer belt 2 is stretched substantially horizontally in the arrangement direction of the photoconductors 1a, 1b, 1c, and 1d. ing. By making the surface of the intermediate transfer belt 2 on the photoconductor side flat, it is possible to stabilize the running of the belt which is important when the toner images formed by the photoconductors 1a, 1b, 1c, and 1d are overlaid. The process parts around the photoconductors 1a, 1b, 1c, and 1d are made the same shape and used in common, so that the parts cost can be reduced and the printing conditions can be easily adjusted.

  As described above, in this embodiment, the photoconductor units 22 including the photoconductors 1a, 1b, 1c, and 1d are arranged vertically, and the photoconductor units 22, the intermediate transfer belt 2, and the fixing device 19 are arranged in the horizontal direction (gravity). In a direction perpendicular to the direction). With the above arrangement, the transfer unit 13 and the fixing unit 19 can be arranged at a position close to the outer surface of the apparatus, and the sheet conveyance path can be arranged along the outer surface of the main body. For this reason, even when a paper jam occurs and the paper remains in the main body, it is possible to easily remove the paper by opening the back surface (transfer device arrangement side) of the housing 200. For example, when a recording medium is transported between each photoconductor and a transfer belt, it is necessary to remove the recording medium remaining inside the apparatus after a paper jam occurs after removing each photoconductor or transfer belt. A very complicated procedure is required.

  Next, referring to FIG. 5, an example of a method for replacing each process including the photosensitive unit 22 and the developing units 5a, 5b, 5c, and 5d of the image forming apparatus of the present embodiment and an open structure of each part of the housing will be described. explain.

  As described above, since the surface of the photoconductor is worn or deteriorated with printing, the photoconductor needs to be replaced. Furthermore, the developing machine needs to be replaced as the toner is consumed. In order to realize excellent maintainability, it is important that these consumables such as the photoconductor and the developing machine can be easily replaced.

  In this embodiment, the photoconductor unit 22 in which the photoconductors 1a, 1b, 1c, and 1d are integrated is configured to be detachable in the arrangement direction of the photoconductors 1a, 1b, 1c, and 1d, that is, the vertical direction. In the embodiment of FIG. 1, the photoconductor unit 22 that is long in the vertical direction is disposed between the exposure units 4a, 4b, 4c, and 4d that are fixed to the main body casing and the intermediate transfer belt 2. Therefore, the replacement is easy.

Further, in the image forming apparatus according to the present embodiment, the developing units 5a, 5b, 5c, and 5d of the respective colors are arranged in the vertical direction with respect to the arrangement direction of the photosensitive unit 22 (vertical direction or an oblique direction slightly inclined from the vertical direction). In addition, it is arranged along the photoconductor unit 22 and is detachably attached by sliding in the horizontal direction, that is, the direction perpendicular to the arrangement direction of the photoconductor unit 22. In this embodiment, developing units 5 a, 5 b, 5 c, 5 d are arranged between the exposure units 4 a, 4 b, 4 c, 4 d fixed to the main body casing 200, and alternately along the photoconductor units 22. It is arranged. By adopting such a configuration, the replacement becomes easy and the burden on the exchanger who replaces the consumables is reduced.
Further, the chargers 3a, 3b, 3c, and 3d and the photoreceptor cleaners 6a, 6b, 6c, and 6d are soiled due to toner adhering to the printing and can be replaced. In the image forming apparatus of this embodiment, as shown in FIG. 2, the image forming apparatus is arranged in the photoconductor unit 22 and is exchanged at the same time as the photoconductor unit 22. At this time, the chargers 3 a, 3 b, 3 c, 3 d and the photoreceptor cleaners 6 a, 6 b, 6 c, 6 d themselves may be configured as units so as to be easily detached from the photoreceptor unit 22.

  Since the photoconductors 1 a, 1 b, 1 c, and 1 d are fixedly arranged in the photoconductor unit 22, all the photoconductors are replaced when the photoconductor unit 22 is replaced. However, printing is performed using only the photosensitive member of toner necessary for printing by using the mechanism for separating and contacting the respective photosensitive members 1a, 1b, 1c, 1d and the intermediate transfer belt 2 as described above. In such a case, the degree of wear or deterioration differs for each photoconductor. At this time, in the configuration in which the respective photosensitive members are replaced at the same time, the replacement of the photosensitive unit 22 is determined by the most used photosensitive member, so that the other photosensitive members with less printing are wasted. At this time, each photoconductor may be detachable from the photoconductor unit 22, and each photoconductor may be replaced in accordance with the number of printed sheets.

  Further, the exposure devices 4a, 4b, 4c, and 4d are directly fixed to the housing 200 in order to accurately align the color toner images. As another configuration applicable to the image forming apparatus of the present embodiment, an exposure unit in which each exposure unit is fixed using an exposure unit fixing member or the like and four exposure units 4a, 4b, 4c, and 4d are fixedly arranged. There is also a method of fixing to the main body housing 200. Although the exposure devices 4a, 4b, 4c, and 4d are not particularly replaced as consumables, the apparatus can be easily adjusted by adopting a structure that can be detached from the main body.

  The erase lamps 8a, 8b, 8c, and 8d can be fixedly disposed in the main body casing or disposed in the photosensitive unit 22.

  In this embodiment, since the life of the intermediate transfer belt 2 is the same as that of the main body, the belt stretching rollers 10a, 10b, 10c, and 10d are fixedly disposed on the housing 200. However, the user may be damaged or broken due to an erroneous operation or the like, and may need to be replaced. For this reason, the intermediate transfer belt 2 can be replaced as a unit.

  The intermediate transfer belt cleaner 15 is fixedly disposed in the main body casing because it is not exchanged in the image forming apparatus of this embodiment. Of course, the intermediate transfer belt cleaner 15 can be replaced with a unit configuration, and the intermediate transfer belt cleaner 15 can be arranged in the intermediate transfer belt unit described above so that the intermediate transfer belt 2 can be replaced at the same time. it can.

  The transfer device 13 is soiled by the adhesion of toner, paper powder, or the like. If the stain greatly affects the transfer performance, the transfer device 13 can be replaced.

  Since the fixing device 19 is hot and various types of recording media are passed, it is difficult to maintain high fixing performance. For this reason, in the image forming apparatus of this embodiment, the fixing device 19 is configured as a replaceable unit. Of course, when the oil application mechanism 83 (see FIG. 16) for applying oil such as silicon is used to improve the fixing performance, or when the cleaning mechanism 84 for cleaning the surface of the fixing roller is provided, each of them is also changed. It is also possible to arrange and replace the fuser 19 as a separate unit.

  Furthermore, the toner images formed on the plurality of photoconductors 1a, 1b, 1c, and 1d need to be aligned with high accuracy. In the image forming apparatus shown in FIG. A sandwiching configuration is applied. By adopting such a configuration, the arrangement positions of the photosensitive drum unit 22, the exposure devices 4a, 4b, 4c, and 4d, the belt stretching roller that stretches the intermediate transfer belt 2, and the like can be accurately positioned by the side plate. it can.

  Therefore, when each process is exchanged, the process is configured to be detached in the vertical direction or the horizontal direction in FIG.

  A top cover that can be opened and closed is provided on the upper surface of the housing 200, and the photoconductor unit 22 and the fixing device 19 are exchanged by releasing the cover and pulling it upward in the vertical direction. Further, an openable / closable cover for replacing the developing devices 5a, 5b, 5c and 5d is provided on the right side of the main body of FIG. Since the developing units 5a, 5b, 5c, and 5d must bring the developing roll into contact with the photoconductor, it is necessary to apply a load to the photoconductors 1a, 1b, 1c, and 1d. In the image forming apparatus of this embodiment, a developing device pressing member is attached to a cover that is opened when the developing devices 5a, 5b, 5c, and 5d are replaced, and the developing device is pushed in with an appropriate load when the door is closed.

  A door for removing the recording medium remaining in the main body is provided on the left side of FIG. In this embodiment, since the paper transport path is arranged substantially vertically without being extremely bent along the outer surface of the main body, the paper of the recording medium is not bent, so that it can be applied to various kinds of paper such as cardboard. In addition, the recording medium can be easily removed.

  The paper cassette 16 for replenishing paper can be inserted and removed from the right side of the main body.

  5 shows a configuration in which each process is sandwiched between side plates. For example, the side plate in the present configuration, that is, a side plate is provided with respect to the sheet discharge direction of the recording medium, and each process unit is formed therefrom. It is also possible to apply a configuration for exchanging. In this case, the photosensitive unit 22 and the developing machines 5a, 5b, 5c, 5d and the like are attached and detached in the axial direction of the rotation shaft.

Next, the detailed configuration of each process will be described.
As described above, the image forming apparatus of FIG. 1 has a process speed that is a moving speed of the photosensitive member, the intermediate transfer belt, and the recording medium in order to make the printing speed at the time of color printing equal to that of the current monochrome printer. 100 mm / s (100 mm / second). When the process speed is 100 mm / s, when A4 size paper is passed vertically and horizontally, printing speeds of about 16 PPM and about 24 PPM can be obtained even if the gap between the papers is taken into account. It is possible to ensure a printing speed equivalent to

  The photoconductors 1a, 1b, 1c, and 1d used in the image forming apparatus of FIG. 1 are drum-shaped photoconductors having the same diameter, and have an organic photosensitive layer provided on the surface of an aluminum cylindrical tube. Of course, an inorganic photoreceptor such as an amorphous silicon photoreceptor can also be used as the photoreceptor. By making the photoconductors 1a, 1b, 1c, and 1d into drum-shaped rigid bodies, it is possible to stabilize the surface speed of the photoconductor, which is important for the alignment of the toner images formed on the color photoconductors. Furthermore, the cost of parts can be reduced by using a drum having the same diameter.

  Next, the diameters of the photoreceptors 1a, 1b, 1c, and 1d will be described. The overall diameter of the apparatus can be reduced when the diameter of the photoreceptor is as small as possible. However, the potential on the surface of the photoreceptor requires a certain long response time from when it is irradiated with light until it decays. Although the response time varies depending on the sensitivity of the photoconductor, the response time of an organic photoconductor that is currently provided at a low price is about 0.1 to 0.2 seconds. For this reason, since the process speed is 100 mm / s in the image forming apparatus in FIG. 1, the distance between the exposure point where the light of the exposure device on the photosensitive member hits and the development point where the developing device develops the photosensitive member is exposure. The dots and development points are required to be about 10 mm to 20 mm. As a result of examining the diameter of the photoconductor in consideration of the response speed and the arrangement of processes such as the charger around the photoconductor and the photoconductor cleaner, it was found that 40 mm or more is necessary at present. If the photoreceptor is 40 mm or less, the distance between the exposure point and the development point cannot be secured, and the response of the photoreceptor cannot catch up. From this result, in this embodiment, the diameter of the photoreceptor is set to 40 mm. Of course, when the sensitivity of the photosensitive member is improved, it is possible to use a photosensitive member having a smaller diameter, for example, a diameter of about 30 mm. If it is important to perform higher speed printing, it is also necessary to increase the diameter of the photoreceptor.

  Further, it is possible to use a belt-shaped photoconductor. If the photosensitive member is belt-shaped, there are problems that the belt must be offset, and the configuration is more complicated than the drum-shaped photosensitive member. In addition, since the arrangement latitude of each process around the photoconductor is increased, the size around the photoconductor can be further reduced.

  Further, the chargers 3a, 3b, 3c, and 3d used in this embodiment charge the photosensitive member 1 using a charging roller to which a bias voltage is applied. In the charging roller, a charging roller elastic layer is formed on a charging roller metal shaft, and a charging roller surface layer is formed thereon. In order to uniformly charge the photosensitive member using the charging roller, it is necessary to ensure contact between the charging roller and the photosensitive member. For this reason, the charging roller has a structure in which the surface of the charging roller metal shaft is covered with a charging roller elastic layer formed of a rubber material such as solid rubber or sponge rubber, and is appropriately connected to the photoreceptor so that a stable nip can be formed. The contact is made with a heavy load. Further, by making the rubber material of the charging roller elastic layer conductive or semiconductive, the bias voltage applied to the charging roller metal shaft is effectively applied to the photoconductor, and charging is performed reliably. On the surface of the charging roller, the plasticizer contained in the rubber material of the charging roller elastic layer prevents the toner and the photoreceptor from being deteriorated, and the charging roller 23 has a long life and improved toner releasability. A charging roller surface layer such as a fluororesin is provided on the surface for the purpose.

  The charging rollers of the chargers 3a, 3b, 3c, and 3d of the image forming apparatus in FIG. 1 are provided with a charging roller elastic layer of urethane sponge rubber having a thickness of 2 mm on a charging roller metal shaft having a diameter of 5 mm, and a fluororesin on the surface thereof. A charging roller surface layer, which is a tube, is provided. For this reason, the diameter of the charging roller is about 9 mm, which is very small. However, since sponge rubber is used for the charging roller elastic layer 25, the contact property with the photosensitive member is good. By using such a small-diameter charging roller, it is possible to give a margin to the arrangement of processes around the photosensitive member. Further, since the resistance value of the charging roller elastic layer and the surface layer is as low as about 10 kΩcm, the photosensitive member can be charged with a low voltage. Furthermore, in the image forming apparatus of this embodiment, a corona charger can be used as another configuration of the charger 3.

  In the corona charger, a corona wire is arranged in a shield case provided with an opening, a high voltage is applied to the wire to generate a corona discharge, and a discharge charge is applied to the photoconductor from the opening, whereby the photoconductor 1 is applied. It is a charging device that charges. For the purpose of stabilizing the charging potential of the photosensitive member, it is also possible to use one provided with a grid with a specified voltage applied to the opening. In the corona charger, if the distance between the wire and the shield case is narrow, spark discharge occurs and the discharge becomes unstable, so the gap between the wire and the shield case cannot be narrowed. Accordingly, the overall size of the charger tends to be larger than that of the charging roller described above. However, since the corona charger can be charged without being in direct contact with the photosensitive member, it is possible to extend the life of the charger, and when longer life is more important, the corona charger Can also be used.

  FIG. 6 shows an embodiment of the exposure device 4a of the image forming apparatus of this embodiment. The same applies to the other exposure devices 4b, 4c, and 4d.

  In offices, with recent advances in computers, not only text documents but also photographic images have been handled. In order to cope with this, the image forming apparatus of FIG. 1 has a printing density (resolution) of 600 dpi (dots / inch). In order to enable high-quality photographic image recording in an electrophotographic image forming apparatus, at least 300 dpi or more is required, and the image forming apparatus of this embodiment having a printing density of 600 dpi is sufficiently compatible.

  In this embodiment, a laser exposure apparatus including a semiconductor laser 27, a polygon mirror 28, a polygon motor 29, and an fθ lens 30 is used.

  The laser exposure device of FIG. 6 reflects and scans the laser beam of the semiconductor laser 27 with the polygon mirror 28, and the focal length difference due to the optical path difference to the non-exposure target photoconductor with the Fθ lens 30 and the unit of the polygon mirror 28. The fluctuation of the moving distance on the scanning surface per rotation angle is corrected. In order to ensure the laser scanning width of the recorded image width, a long optical path length is required between the polygon mirror 28 and the photosensitive member. When the scanning angle of the polygon mirror 28 is reduced, the correction amount by the Fθ lens 30 is small, so that a stable exposure amount in the scanning direction can be obtained, and the number of surfaces of the polygon mirror 28 can be increased, so that high-speed printing is possible. Become. However, if the scanning angle is small, the distance from the polygon mirror 28 to the photosensitive member is required to be long, and the overall size of the laser exposure unit is increased. In this embodiment, in order to ensure the same printing speed as that of a monochrome printer, a 6-sided polygon mirror generally used in a monochrome printer is used.

  The polygon motor 29 for rotating the polygon mirror 28 is preferably arranged so as to rotate the polygon mirror 28 horizontally with respect to the direction of gravity in order to rotate it stably. At this time, the height of the exposure unit cannot be made smaller than the height of the polygon motor 29 that rotates the polygon mirror 28 plus the space of the fθ lens 30 above the laser scanning surface. In the image forming apparatus of FIG. 1, since the process speed is 100 mm / s, in order to obtain a printing density of 600 dpi, the six-sided polygon mirror 28 must be rotated about 24000 per second. At present, the height required for the polygon motor 29 rotating at this rotational speed is about 20 mm, and the height of the fθ lens 30 is also required to be about 10 mm in order to ensure manufacturing stability. Therefore, the height of the current laser exposure apparatus is about 30 mm. In the laser exposure device of this embodiment, the polygon mirror 28 is rotated horizontally and the height of the entire laser exposure device is minimized, so that the laser beam reflected by the polygon mirror 28 is applied to the fθ lens 30 as shown in FIG. After passing, the light is reflected by the folding mirror 31, and the photosensitive member 1a disposed obliquely above the laser exposure device is exposed.

  Further, in the configuration of FIG. 6, since the upper and lower portions of the exposure device are flat, it is easy to replace the developing devices disposed between the exposure devices.

  The exposure apparatus shown in FIG. 6 has a structure in which the height of the exposure apparatus becomes as small as possible, and as a result, the height of the exposure apparatus can be reduced to about 30 mm.

  As described above, when the number of faces of the polygon mirror 28 is increased in order to increase the printing speed or when the printing width is widened to cope with a larger paper size, the optical path length is increased. There is a need. At this time, it is necessary to arrange the folding mirror 31 inside the laser exposure device so that the optical path length can be long. FIG. 7 shows an example of a laser exposure device in which the lower part of the exposure device has a convex shape and a part of the folding mirror 31 is arranged in order to increase the optical path length. Since the lower part of the exposure units 4a, 4b, 4c, and 4d has a convex structure, the optical path length can be secured longer than that of the laser exposure unit of FIG. 6, but the height of the exposure unit is higher than the configuration of FIG. In the image forming apparatus shown in FIG. 1, when the laser exposure device as shown in FIG. 7 is used, the convex portions are arranged on the photoconductors 1a, 1b, 1c, 1d side of the exposure devices 4a, 4b, 4c, 4d. In other words, the folding mirror 31 is disposed on the photosensitive members 1a, 1b, 1c, and 1d side of the exposure devices 4a, 4b, 4c, and 4d, and the developing devices 5a and 4d are disposed above and below the exposure devices 4a, 4b, 4c, and 4d, respectively. By providing irregularities by matching the shapes of 5b, 5c, and 5d with the convex shapes of the exposure devices 4a, 4b, 4c, and 4d, it is possible to effectively use the space in the apparatus. As a result, the overall size of the apparatus is slightly increased, but the toner in the developing devices 5a, 5b, 5c, and 5d is changed by changing the outer shape of the developing devices 5a, 5b, 5c, and 5d, that is, by increasing the size of the developing device. The storage capacity can be increased, and the convex portions of the exposure devices 4a, 4b, 4c, 4d are provided on the photoconductors 1a, 1b, 1c, 1d side, so that the developing devices 5a, 5b, 5c, 5d can be replaced. Is as easy as in FIG.

  In order to reduce the overall size of the apparatus, it is effective to reduce the height of the exposure unit. The heights of the exposure units 4a, 4b, 4c, and 4d are determined by the height of the polygon motor 29 and the height of the space for securing the size of the fθ lens 30. Among these, the polygon motor 29 needs to be provided with a mechanism such as a bearing in the axial direction in order to stably rotate, and it is difficult to reduce the thickness. In the embodiment of FIG. 8, the polygon mirror 28 and the polygon motor 29 are arranged on the inner side of the main body, that is, the polygon mirror 28 and the polygon motor 29 are stacked with the developing device 5a (b, c, d) indicated by dotted lines. The structure provided in the exterior of the part is shown. In this configuration, since only the fθ lens 30 and the mirror 31 that reflects the laser light are arranged in the exposure device 4a (b, c, d) in the portion laminated with the developing device 5, the height is reduced. Can do. In order to construct such an optical system, it is necessary to devise the structure of the fθ lens 30, but it is effective for downsizing the apparatus. Further, instead of the fθ lens 30 and the folding mirror 31, it is also possible to use an fθ mirror having fθ characteristics.

  When forming a final image by forming an image using a plurality of different laser exposure apparatuses, it is necessary to minimize distortion and deformation of the polygon mirror, the fθ lens, and the folding mirror. However, such an optical component increases significantly when the accuracy is increased. Therefore, in reality, there is a shape error such as distortion or deformation of each component, and each image exposed to each exposure device is different. Distortion will occur. For this reason, in the image forming apparatus according to the present embodiment, four exposure units are configured in advance by combining parts having the same distortion and deformation, and incorporated in the main body. By combining such components, the image distortion of each exposure unit becomes the same, and the image shift can be suppressed. When such a combination of components is performed, a mechanism for adjusting the position of the optical component such as a mechanism for adjusting the position of the fθ lens may be provided. Furthermore, the following can be used as another embodiment of the exposure device.

  FIG. 9 shows an embodiment in which the LED array 32 is applied to the exposure devices 4a, 4b, 4c, and 4d of the image forming apparatus of this embodiment. Since the exposure device of the LED array arranges the same number of LEDs as the print dots of the image width and exposes the photosensitive member, a long optical path as in the laser exposure device described above is not necessary, and the exposure device can be made compact. Furthermore, since the LED corresponding to each dot is caused to emit light independently, speeding up is easy. The LED array exposure device is composed of a required number of LED arrays 32 arranged on a straight line, a driver circuit 33 for driving them, and a lens 34 for imaging light emitted from the LED array 32 on a photoconductor. . The number of LEDs necessary for exposure at a printing density of 600 dpi is 600 per inch, that is, 230 to 240 per 1 cm. When A4 is fed vertically, the required printing width is 21 cm or more. About 5400 to 6000 because it is necessary, and when passing A4 sideways, the print width is 30 cm or more, so it is 7000 to 9000. The LED array 32 and the driver circuit 33 are created using a semiconductor process.

  Since it is necessary to drive a large number of LEDs independently in the LED array exposure device, it is not practical to provide a driver circuit outside the exposure device because wiring becomes complicated. For this reason, in the image forming apparatus of the present embodiment, the driver circuit 33 is also formed on the same chip on which the LED array 32 is formed, so that an interface with the outside is easy. On this chip, in order to make the light emission luminance of each LED uniform, it is possible to provide a circuit for correcting variations in the light emission luminance of each LED and a circuit that enables gradation output. These LED array 32, driver circuit 33, and the like are made into chips in units of several hundred to several thousand from the viewpoint of mass productivity and yield improvement, and by combining several to several tens of chips, a printing width is secured. Yes. At this time, if the alignment between the LED chips is not accurate, image shading occurs between the chips, and if the alignment differs for each LED array exposure device that exposes each photoconductor, the toner images of each color are accurately aligned. I can't. For this reason, the alignment between chips must be 1 dot or less (42 μm or less at 600 dpi).

  In this embodiment, the lens 34 is arranged to form an image of the light emitted from the LED on the photosensitive member 1 and uses a rod lens array.

  FIG. 10 is a diagram in which the LED array exposure device is arranged on the photoreceptor 1a as the exposure device 4a. The same applies to other exposure units and photoconductors.

  In the image forming apparatus of the present embodiment, the processes around the photosensitive member 1a are concentrated on the lower part from the center of the photosensitive member 1a. Therefore, if the main body of the exposure device 4a is arranged away from the photosensitive member, the surroundings of the photosensitive member 1a are arranged. The placement margin of each process can be increased. In order to enable this, the lens length of the LED array exposure device is increased, for example, about 10 to 30 mm in the image forming apparatus of FIG. 1, or the focal length of the lens is increased, for example, the image of FIG. It is effective to use 10 to 50 mm in the forming apparatus.

  As another embodiment of the exposure device, there is a case in which a long-focus lens is used and a folding mirror 31 is provided to expose the photosensitive member. In this configuration, since the LED array exposure device is arranged at a position away from the photoconductor 1a, a margin can be given to the process arrangement around the photoconductor.

  FIG. 11 is a sectional view of the developing machines 5a, 5b, 5c, and 5d applied to this embodiment.

  The developing device 5a (5b, 5c, 5d) includes a developing unit 35 that develops a latent image on the surface of the photoreceptor 1a (1b, 1c, 1d) and a toner storage unit 36 that stores toner. Since the performance of the developing unit 35 decreases with printing, and the toner storage unit 36 consumes toner, the developing unit 35 needs to be replaced according to the number of printed sheets. In this embodiment, the development unit 35 and the toner storage unit 36 are simultaneously replaced as an integrated configuration, thereby reducing the frequency of replacement of consumables and reducing the production cost.

  Further, in the developing machine 5a of the present embodiment, the developing unit 35 and the toner storage unit 36 are arranged horizontally, whereby the height of the developing machine 5a is reduced and the entire apparatus is downsized.

  The developing unit 35 of the developing machine 5a of this embodiment uses a non-magnetic one-component contact developing method. In the non-magnetic one-component developing method, the toner adhering to the developing roller 37 is rubbed using a blade-shaped member to form a thin toner layer and to charge the toner to a specified charge amount. Furthermore, this toner thin layer is directly contacted and adhered to the photoreceptor 1a to develop the electrostatic latent image on the photoreceptor 1a, and does not use a carrier.

  As described above, since the toner thin layer formed on the surface of the developing roller 37 is directly brought into contact with the photosensitive member 1a and developed, the electrostatic latent image is sharply developed and high-quality recording is possible. Since the layer thickness is optimized using simple members such as the developing roller 37 and a blade, the price of the developing unit 35 can be reduced and the price can be reduced.

  The developing unit 35 includes a developing roller 37, a toner regulating blade 38, a reset roller 39, a toner adhering blade 40, a scraping paddle 41, and a toner feed paddle 42.

  The developing roller 37 uses a roller whose metal shaft is covered with an elastic body such as rubber in order to reliably contact the rigid and drum-shaped photoconductor 1a, and in order to stably convey the toner, the developing roller 37 The surface is roughened with an appropriate roughness. In order to develop the toner on the surface of the developing roller 37 onto the photoreceptor 1a, a bias voltage is applied to the developing roller 37. The developing roller 37 rotates its surface in the same direction as the movement direction of the surface of the photosensitive member in order to sufficiently supply toner to the surface of the photosensitive member 1a. In this embodiment, the developing roller 37 is positioned at a position facing the photosensitive member. Rotates from the lower side to the upper side, and the peripheral speed of the developing roller 37 is rotated at a speed higher than the surface speed of the photosensitive member. A toner regulating blade 38 that charges the toner and forms a thin toner layer having a predetermined thickness on the surface of the developing roller 37 is disposed below the developing roller 37. For the toner charging and the layer pressure regulation, the contact pressure of the toner regulating blade 38 is important, but the image forming apparatus of this embodiment uses a thin metal plate in order to make this stable and uniform. Further, the toner regulating blade 38 counters the toner regulating blade 38 with respect to the rotation direction of the developing roller 37 so that the toner does not stay at the contact portion between the toner regulating blade 38 and the developing roller 37 as the developing roller 37 rotates. In contact. At this time, in order not to scrape off the toner adhering to the surface of the developing roller too much, the flat portion of the toner regulating blade 38 is brought into contact without directly contacting the tip of the toner regulating blade 38 with the developing roller 37. The reset roller 39 once removes the toner remaining on the surface of the developing roller 37 without being developed and attaches new toner to the surface of the developing roller 37. The reset roller 39 is rotated in the same direction as the developing roller 37 and scraped. Take and supply at the same time. In this embodiment, in order to ensure contact with the developing roller 37 and scraping and adhesion of the toner, a roller whose surface is covered with a sponge is used. The toner adhering blade 40 is provided so that the toner adhering to the developing roller 37 by the reset roller 39 does not fall from the surface of the developing roller 37 due to gravity. The scraping paddle 41 is provided to prevent the toner scraped off by the toner regulating blade 38 from staying in the vicinity of the blade and aggregating and adhering. The scraping paddle 41 rotates counterclockwise and is scraped by the toner regulating blade 38. The dropped toner is discharged toward the toner storage unit 36.

  The toner feed paddle 42 is provided to supply the toner in the toner storage chamber 36 to the reset roller 39. Since the reset roller 39 is disposed above the developing unit, in order to supply toner to this portion, it is necessary to convey the toner to the reset roller 39 against gravity. The toner feed paddle 42 scrapes the toner in the toner storage chamber to the reset roller 39 and supplies the toner to the reset roller 39. When the toner is fed up to the reset roller 39 by the toner feed paddle 42, the toner scraping operation is surely performed by synchronizing the rotation of the two so that the toner scraping paddle 41 contacts the toner feed paddle 42.

  As shown in FIG. 11, the toner storage unit 36 includes a toner storage chamber 43 and a toner supply paddle 44.

  The toner storage chamber 43 is a portion that stores toner determined by the number of printed sheets. One or more toner supply paddles 44 are disposed in the toner storage chamber 43 and rotate to supply toner to the developing unit 35.

  In the developing machines 5a, 5b, 5c, and 5d shown in FIG. 11 applied to the image forming apparatus shown in FIG. 1, since the developing unit and the toner storage unit 36 are arranged horizontally as described above, the developing machines 5a, 5b, 5c, and 5d The height h is about 40 mm.

  In the developing machine 5a of FIG. 11, the developing unit 35 and the toner storage unit 36 are integrated. However, when the life of the developing unit 35 can be extended, these members are separate members, and the developing unit 35 and the toner storage unit 36 are connected to the toner hopper. It is also possible to configure as 45. At this time, the developing unit remains in the main body and only the toner hopper 45 is replaced. However, in the image forming apparatus of FIG. 1, the toner hopper 45 can be disposed closer to the outer surface of the main body than the developing unit 5a. Exchange is easy.

  FIG. 12 shows an example of a developing machine in which the developing unit 35 and the toner hopper 45 can be separated. The developing machine 5a shown in FIG. 12 uses a developing system called a two-component developing system, and is composed of a developing unit 35 and a toner hopper 45. Is arranged. In the two-component development system, the toner is mixed with a carrier that is magnetic powder to charge the toner, and the developer having the toner attached to the carrier is transported to the surface of the photoreceptor using magnetic force and developed. is there.

  12 includes a magnet roller 46, a developer regulating blade 47, a developer feed paddle 48, a stirring paddle 49, and a toner density sensor 50 in the developing roll.

  The magnet roller 46 is provided with a roller that applies a magnetic force inside the sleeve. The magnet roller 46 rotates the sleeve to convey the developer, and forms a magnetic brush with the developer in the vicinity of the photosensitive member. Develop the electrostatic latent image. The developer feed paddle 47 is provided to supply the developer to the magnet roller 46. The developer regulating blade 48 is provided in order to make the amount of developer adhering to the surface of the magnet roller 46 appropriate, and regulates excess developer using a blade-shaped member. The stirring paddle is provided to stir the toner and the carrier in the 49 developer so as to charge the toner and to mix well, thereby stabilizing the image quality. The toner density sensor 50 is provided to measure the amount of toner contained during development, and detects the toner density by measuring the bulk density of the developer using a magnetic sensor.

  The toner hopper 45 includes a toner storage chamber 43, a toner supply paddle 44, and a toner supply roller 51. As in the example of FIG. 11, the toner storage chamber 43 is a portion that stores an amount of toner determined by the number of printed sheets. The toner supply paddle 44 is provided to send toner to the toner supply roller. The toner supply roller 51 is provided to supply toner to the developing unit 35.

  In the developing machine of FIG. 12, the developer stirred by the stirring paddle 49 is sent to the surface of the magnet roller 46 by the developer feed paddle 48, and the magnet roller 46 transports the developer, and includes the toner and the carrier formed on the surface. Develop with a magnetic brush. The developer is again refluxed to the stirring paddle 49 and stirred.

  Further, when the toner concentration sensor 50 detects a decrease in the toner concentration in the developer, the toner is sent from the toner hopper 45 to the developing unit 35, mixed with the carrier by the stirring paddle 49, and charged.

  Compared to the non-magnetic one-component development method, the two-component development method requires a mechanism for stirring the toner and the carrier and a sensor for measuring the toner concentration, so that the developing device is enlarged and complicated. However, since the development of the toner on the photoconductor is performed by a magnetic brush that is magnetically formed on the surface of the magnet roller, the contact load between the photoconductor and the developing device is small, and the rotational torque of the photoconductor and the developing device can be reduced. For this reason, it is easy to stabilize the rotation of the photosensitive member, which is important for the alignment of the toner images of each color, and from the viewpoint of the alignment of the images, the developing device shown in FIG. 12 can be used.

  As described above, the image forming apparatus shown in FIG. 1 is configured such that, for example, the height of the exposure units 4a, 4b, 4c, and 4d is about 30 mm, and the height of the developing units 5a, 5b, 5c, and 5d is about 40 mm. The interval between the photosensitive members is 70 to 75 mm. Since the height of these processes overlaid for four colors is about 280 to 300 mm, the height of the main body obtained by adding the height of the paper cassette or the upper panel of the main body to this is about 500 mm at most. . This is a height that can be accepted without problems in the office.

  Next, the configuration of the intermediate transfer belt 2 used in the image forming apparatus of this embodiment will be described with reference to FIG.

  In the intermediate transfer belt 2 of this embodiment, the intermediate transfer belt 2 is stretched by belt stretching rollers 10a, 10b, 10c, and 10d, which are four rollers, and the photoreceptor 1a is placed in the space inside the intermediate transfer belt 2. , 1b, 1c, 1d and transfer auxiliary rollers 9a, 9b, 9c, 9d for contacting the intermediate transfer belt 2 are disposed.

  The belt stretching rollers 10a and 10b stretch the intermediate transfer belt 2 vertically in order to secure a surface on which the photoreceptors 1a, 1b, 1c, and 1d of the respective colors are arranged.

  The belt stretching roller 10c is disposed on the surface of the intermediate transfer belt 2 opposite to the photoreceptor arrangement surface. A transfer device 13 is disposed outside the belt stretching roller 10c to transfer the toner image formed on the surface of the intermediate transfer belt 2 to a recording medium. The belt stretching roller 10d is disposed above the belt stretching roller 10d. Unlike the other belt stretching rollers 10a, 10b, and 10c, the belt stretching roller 10d is provided outside the intermediate transfer belt 2 so that the intermediate transfer belt 2 is disposed from the outside to the inside. It is arranged so as to push into. By disposing the belt stretching roller 10d in this manner, a space for disposing the fixing device 19 and the intermediate transfer belt cleaner 15 disposed above the transfer device 13 is secured, and the cross-sectional area of the intermediate transfer belt 2 is reduced. The mounting density can be increased.

  Further, the belt stretching rollers 10c and 10d are installed at positions where the transfer device 13 and the fixing device 19 can be arranged so that the paper conveyance path important for paper conveyance becomes a smooth curve, so that various types of paper can be used. We are trying to deal with various types of paper and reduce jamming.

  Since the intermediate transfer belt 2 is stretched in this way, the circumference of the belt is about 200 to 350 mm. The diameter of the belt stretching roller is about 40 mm because if the diameter is small, the belt is wrinkled by the curvature of the belt stretching roller. Furthermore, by making the photosensitive member and the belt tension roller have the same diameter, it is possible to make the speed fluctuation due to the eccentricity of the photosensitive member and the belt tension roller the same period, and the alignment of each color image is easy. can do.

  In this embodiment, the toner images formed by the photoreceptors 1a, 1b, 1c, and 1d are transferred onto the intermediate transfer belt 2 and overlapped. It is necessary to reduce the speed fluctuation and deviation. In particular, the deviation of the belt may be accompanied by the destruction of the belt, and it is important from the viewpoint of ensuring the reliability of the apparatus that the belt is not moved by the belt stretching rollers 10a, 10b, 10c, 10d. It is necessary to keep it stretched at all times.

  In the image forming apparatus of the present embodiment, the belt tension roller 10b disposed downstream of the photosensitive member 1d is used as a drive shaft, and the belt surface in contact with the photosensitive members 1a, 1b, 1c, 1d is driven so as to be always pulled. ing. As a result, the slack of the belt surface in contact with the photoreceptors 1a, 1b, 1c, and 1d is less likely to occur, and the color toner images can be easily aligned. Further, in order to perform the transfer well, the belt stretching roller 10d on which the process parts such as the photosensitive members 1a, 1b, 1c, and 1d and the transfer device 13 are not directly arranged is elastically supported. The belt is tensioned.

  It is important for the reliability and high image quality of the apparatus to suppress the belt of the intermediate transfer belt 2. The deviation of the belt is generated when the belt receives a force in a direction perpendicular to the rotation direction due to a variation in parallelism of the members in contact with the intermediate transfer belt 2. Since it is difficult to arrange these members in parallel with the current machining technique, a belt shift occurs. In the image forming apparatus of this embodiment, in order to prevent an excessive shift of the belt, a rib is provided at the belt end, and a belt having a tapered shape is prevented at the end of the belt stretching roller 10a disposed inside the intermediate transfer belt 2. Provide a cap. When the belt starts to receive a force in a direction perpendicular to the rotational direction, the belt rib comes into contact with the taper portion of the prevention cap from the belt tension belt end belt and stops the shift. The rib is made of a material satisfying a thickness and strength capable of sufficiently stopping the belt, such as a resin or a rubber material.

  Similarly, as another configuration for suppressing the belt deviation, a reverse belt-shaped belt deviation prevention member is provided outside the belt stretching roller 10a. In this configuration, when a deviation occurs in the intermediate transfer belt 2, the belt end portion rides on the belt deviation prevention member and regulates the belt deviation.

  Furthermore, a mechanism for positively correcting the belt deviation can be provided in order to reliably suppress an excessive deviation of the belt. FIG. 13 is a side view (a) and a front view (b) of a belt deviation correction mechanism that generates a force to move the belt in the opposite direction by weakening the tension of the belt on which the belt approaches. It is the figure shown about. In this configuration, the end of the belt tension roller 10a is configured by a taper-shaped rotatable taper piece 56, and the rotational force received by the taper piece 56 is transmitted to the belt tension roller 10d and linked so as to weaken the tension. Yes. When the belt approaches and the rib 53 of the belt comes into contact with the taper piece 56, the taper piece 56 receives rotational force due to friction with the rib 53. When the taper piece 56 receives the rotational force, the belt tension roller support member 57 is pulled by the rotational force transmission shaft 58 as shown in the figure, and the tension of the belt tension spring 59 on the side where the belt is offset is reduced. For this reason, an axial imbalance occurs in the tension of the belt, and the belt can receive a force that moves in the opposite direction to return the belt to an offset.

  If a material that greatly expands and contracts, such as a rubber material, is selected as the main structure for the intermediate transfer belt 2, it is impossible to accurately position each color image. For this reason, the belt material to be used needs to have a structure that has elasticity necessary for the belt and has a small elongation. For this reason, although a resin or metal belt member is used, it is also possible to constitute a belt by combining these materials. For example, a configuration in which resin and metal are stacked, a configuration in which rubber and metal, and resin are stacked can be used. In this embodiment, a polycarbonate resin resin belt having a thickness of 0.1 to 0.2 mm is used.

  The cross-sectional structure of the intermediate transfer belt 2 includes a single-layer structure of only a belt base material, a belt base material and a belt surface layer, a belt base material and a belt back surface layer, a belt base material and a belt surface layer, and a multi-layer structure of a belt base material Etc. can be applied. The intermediate transfer belt of this embodiment has a single-layer structure using the above-described resin material as a belt base material. However, a belt surface layer formed of a thin layer of fluororesin or the like to prevent the belt from deteriorating from ozone, heat, etc., in order to make the adhesion of the toner adhering to the surface appropriate, to prevent surface abrasion May also be provided. In order to further increase the strength of the belt, a belt back surface layer formed of a thin metal belt material can be used. Further, toner transfer is greatly influenced by the surface property of the intermediate transfer belt 2. When the toner releasability on the surface of the intermediate transfer belt 2 is poor, the toner adheres to the intermediate transfer belt 2 mechanically and chemically, and image defects such as a decrease in transfer efficiency and voids in fine character lines occur. The surface of the intermediate transfer belt 2 needs to be hard to adhere toner. For this reason, a coating layer such as a fluororesin may be provided on the belt surface, or a fine powder such as silica or a low molecular material such as wax may be adhered to the surface of the intermediate transfer belt 2 as a release material.

  As a general manufacturing method of a belt member, there is a method of joining film materials into a belt shape. The belt material produced by such a manufacturing method necessarily has a seam. At the joint of the intermediate transfer belt 2, a contact load is generated due to the step of the joint at a portion in contact with the intermediate transfer belt 2 such as the photoconductor 1, the transfer device 13, and the intermediate transfer belt cleaner 15, which causes fluctuations in belt speed. Also, it is necessary to prevent the seam from entering the print area. For this reason, in the image forming apparatus of this embodiment, a seamless belt material is used as the intermediate transfer belt. In such a belt having a seam, the step of the seam is reduced by crushing or polishing with heat or pressure, and a mechanism for detecting the position of the seam is provided to transfer an image formed on the photoreceptor 1 to the seam. It can be used by not doing so.

  Next, the electrical characteristics of the intermediate transfer belt 2 will be described.

The transfer from the photoreceptors 1a, 1b, 1c, and 1d to the intermediate transfer belt 2 and the transfer from the intermediate transfer belt 2 to the recording medium are particles charged with toner, and thus electrostatic force is used. The toner is transferred by applying an electric charge having the same polarity as that of the toner or a reverse polarity to the photoreceptors 1a, 1b, 1c and 1d, the intermediate transfer belt 2 and the transfer unit 13, and an electric field generated by the charges. For this reason, the intermediate transfer belt 2 needs to have electrical characteristics capable of effectively and stably generating such a transfer electric field.
The electrical characteristics of the intermediate transfer belt 2 of this embodiment are semiconductive. At the time of transfer, an electric charge is given to the intermediate transfer belt 2, but if the intermediate transfer belt 2 has a high resistance, the electric charge given at each transfer portion remains on the intermediate transfer belt 2 and makes the transfer unstable. Or image defects such as uneven discharge.

At the contact portion between the photoconductors 1a, 1b, 1c, and 1d and the intermediate transfer belt 2, the transfer of toner from the photoconductor 1 to the intermediate transfer belt 2 is performed by transfer auxiliary rollers 9a, 9b, 9c, and 9d on the back surface of the intermediate transfer belt 2. This is done by applying a bias voltage. At this time, charges are applied from the auxiliary transfer rollers 9a, 9b, 9c, and 9d to the back surface of the intermediate transfer belt 2, and the intermediate transfer belt 2 moves as the process proceeds, so that the applied charges are also on the belt. Go on board. When the intermediate transfer belt 2 starts to move away from the photoconductors 1a, 1b, 1c, and 1d, the capacity of the gap between the photoconductors 1a, 1b, 1c, and 1d and the intermediate transfer belt 2 rapidly decreases, and the potential of the intermediate transfer belt is reduced. As a result, the discharge is generated and the toner on the intermediate transfer belt 2 is unevenly charged. In order to suppress this, it is necessary to leak the charge on the intermediate transfer belt 2 as the potential increases, that is, to lower the resistance value of the intermediate transfer belt. The capacity of the gap is 100 p to 0.1 pF / cm ^{2. In} order to attenuate the potential applied to this capacity faster than the process speed, the product of the resistance value in the surface direction of the intermediate transfer belt 2 and this capacity is used. It is necessary to set a certain time constant smaller than the process speed. In the image forming apparatus of FIG. 1 having a process speed of 100 mm / s, the intermediate transfer belt 2 moves 1 cm in 0.1 second, so that the resistance value must be 1 G to 10 TΩ or less so that the time constant is less than this. Must not. In the present embodiment, the resistance of the belt material is adjusted so that the resistance value per 1 cm width and 1 cm length which is sufficiently smaller than this is 0.1 GΩ.

  Incidentally, in order to stabilize the potential of the intermediate transfer belt 2, a configuration in which a low resistance member is provided on the back surface of the intermediate transfer belt 2 is also applicable. This configuration can be realized by making the intermediate transfer belt 2 into two layers of a resistance layer and a conductive layer, or by reducing the surface resistance of the back surface of the intermediate transfer belt 2. 2 It becomes possible to make the back surface the same potential. In the case of this configuration, if the resistance layer has a high resistance, the charge imparted by the transfer portion remains on the surface of the intermediate transfer belt 2 and accumulates, so that the semiconductive resistance layer is the same as described above. It is necessary to provide. In order to prevent the charge from remaining on the surface of the intermediate transfer belt 2, it is necessary to select a resistance so that the charge is attenuated while the intermediate transfer belt 2 is moving through each transfer portion. In the image forming apparatus of this embodiment, the surface speed of the intermediate transfer belt 2 is 100 mm / s, and the distance between each transfer unit and the toner charger 11 is several centimeters. A time constant, which is a product of a value and a capacity, takes a time required for moving each part, and a material having a length of several hundred ms or less may be used. In this configuration, the configuration of the intermediate transfer belt 2 is complicated, but since the potential of each part is stabilized, there is an advantage that transfer control of each part becomes easy.

  Further, even if the intermediate transfer belt 2 itself has a low resistance, the entire intermediate transfer belt 2 can have the same potential over the entire circumference. In this case, since the current flowing in each transfer portion increases, it is necessary to increase the capacity of the power supply, but the transfer can be stabilized.

  The resistance of the material used for the intermediate transfer belt 2 can be a high resistance by providing a charge control member for controlling the charging of the surface of the intermediate transfer belt 2. As such a charge control member, a scorotron charger or a corotron charger to which AC or DC is added is used, and a predetermined charge is applied to the surface of the intermediate transfer belt 2 to control the charging of the belt.

  In order to transfer the toner on the photoreceptors 1a, 1b, 1c, and 1d to the intermediate transfer belt 2, a charge having a polarity opposite to that of the toner is applied to the intermediate transfer belt 2 side, or the photoreceptors 1a, 1b, 1c, and 1d are provided. It is necessary to apply a charge having the same polarity as that of the toner to the side. Furthermore, in order to reliably perform the transfer, it is important that the photoreceptors 1a, 1b, 1c, 1d and the intermediate transfer belt 2 are in close contact with each other. In the image forming apparatus of the present embodiment, roller-shaped transfer auxiliary rollers 9a, 9b, 9c, 9d are arranged on the back surface of the intermediate transfer belt 2, a bias voltage is applied to the roller, and the intermediate transfer belt 2 is attached to the photoreceptors 1a, 1b. , 1c, 1d to be in close contact with each other. The transfer auxiliary rollers 9a, 9b, 9c, and 9d are elastic rollers in which a metal shaft is covered with a sponge, and a force is applied so as to press the intermediate transfer belt 2 against the photoreceptors 1a, 1b, 1c, and 1d with an appropriate pressure. ing.

  As the configuration of the transfer unit that transfers the toner on the photoreceptors 1a, 1b, 1c, and 1d to the intermediate transfer belt 2, configurations other than those described above are also applicable.

  When the corona charger is disposed on the back surface of the intermediate transfer belt 2, charges necessary for transfer are supplied to the back surface of the intermediate transfer belt 2 by the corona charger, and the intermediate transfer belt 2 is further attached using a blade-shaped belt pressing member. The photoreceptors 1a, 1b, 1c, and 1d are in close contact with each other. When the auxiliary transfer rollers 9a, 9b, 9c, 9d are arranged to be pushed into the photoconductor side between the transfer positions of the photoconductors 1a, 1b, 1c, 1d, the charge required for transfer is transferred to the transfer auxiliary roller 9a. , 9b, 9c, 9d are applied to the back surface of the belt.

  In this embodiment, since the photoreceptors 1a, 1b, 1c, and 1d are always in contact with the intermediate transfer belt 2, the photoreceptor that prints an unnecessary color when printing a monochrome image is also the intermediate transfer belt 2. In contact. When only one part of the photoconductor is required for printing, it is possible to extend the life of the photoconductor by separating the unused photoconductor from the intermediate transfer belt so that printing is not performed. For this reason, a mechanism for separating the intermediate transfer belt from the photosensitive member may be provided.

  Next, FIGS. 14A and 14B illustrate another embodiment of the intermediate transfer belt cleaner of the present invention.

  The intermediate transfer belt cleaner 15 is provided for cleaning the transfer residual toner on the intermediate transfer belt 2, and mechanically scrapes off the toner using an elastic blade, similarly to the photoreceptor cleaner 6. A cleaning blade method is used. In the image forming apparatus of this embodiment, as shown in FIG. 1, a cleaning blade is disposed on the belt stretching roller 10 a located at the uppermost part of the intermediate transfer belt 2 to clean the toner on the intermediate transfer belt 2. Further, a similar cleaning blade is provided on the belt stretching roller 10d that is located immediately below the cleaning blade provided on the belt stretching roller 10a and is disposed on the surface of the intermediate transfer belt 2. Since the belt stretching roller 10d disposed on the surface of the intermediate transfer belt 2 may be in direct contact with the toner, it is desirable to provide such a cleaning member. A belt waste toner collecting portion 52 that collects waste toner is disposed below the side of the belt stretching roller 10d. The toner scraped off by the cleaning blade disposed on the belt stretching roller 10a falls on the belt stretching roller 10d and is collected by the cleaning blade that cleans the belt stretching roller 10d.

  Further, FIG. 14A shows another embodiment. In this configuration, the belt stretching roller 10a is provided with a cleaning blade, and the belt waste toner collecting portion 52 is disposed in a space formed by the belt stretching roller 10d that pushes the intermediate transfer belt 2 from the outside. In this configuration, the toner scraped off by the cleaning blade is transferred to the belt waste toner collecting unit 52 by gravity. In the image forming apparatus of this embodiment, a part of the belt stretching roller is provided on the surface of the intermediate transfer belt 2 and is arranged so as to be pushed into the belt. Thus, the intermediate transfer belt cleaner is arranged in this way. It is easy to secure space.

  As another method, a brush roller method in which toner is mechanically and electrically cleaned using a brush roll to which a potential is applied can be used. The brush roller method is more complicated than the cleaning blade method and requires a power source. However, since the cleaning direction is not selected, it is effective when cleaning is performed from above the intermediate transfer belt 2. In addition, since the contact load with the intermediate transfer belt is small, there is an advantage that the belt can be driven with low torque. In the configuration of FIG. 14B, the brush cleaner 65 is brought into contact with both the intermediate transfer belt 2 and the belt stretching roller 10d, and the belt stretching roller 10d in contact with the intermediate transfer belt 2 and the photosensitive member surface is simultaneously cleaned. Show. The toner cleaned by the brush cleaner 65 moves to the collection roller 66 and is scraped off by the collection blade 67. The toner scraped off falls to the belt waste toner collecting unit 52 and is collected. In addition, the brush roller 65 is disposed in contact with both the intermediate transfer belt 2 and the belt stretching roller 10d as in FIG. 14B, and a cleaning blade is provided on the belt stretching roller 10d so that the cleaned toner is belt-stretched. The method of transferring to the collection roller 10d and collecting it can also be applied to the image forming apparatus of this embodiment.

  The toner on the intermediate transfer belt 2 may cause uneven charging due to contact with the surfaces of the photoreceptors 1a, 1b, 1c, and 1d. The uneven charging causes difference in transfer efficiency and causes image unevenness. In the image forming apparatus of this embodiment, a toner charger 11 is provided in order to make the toner on the intermediate transfer belt 2 charged uniformly. The toner charger 11 is a scorotron charger that is provided with a shield case so as to surround a wire and is provided with a grid between the wire and the intermediate transfer belt 2. The toner charger 11 is charged on the surface of the intermediate transfer belt 2 by the potential of the grid. Control.

  At this time, in order to make the toner charger 12 work effectively, a conductive member set to a specified potential may be disposed on the back surface of the intermediate transfer belt 2 facing the toner charger 12.

  In this embodiment, a transfer device 13 is provided to transfer the toner image on the intermediate transfer belt 2 to a recording medium.

  Since the toner image on the intermediate transfer belt 2 is a color, the thickness of the toner in each part of one image is different. In order to transfer these images completely and reliably to the paper, it is necessary to bring the toner and the paper into close contact with each other. For this reason, in this embodiment, the roller-shaped transfer device 13 is used to bring the recording medium into close contact with the toner, and a bias voltage is applied to transfer the toner. The transfer unit 13 uses a roller in which the surface of the metal shaft is covered with an elastic layer formed of a solid or sponge rubber material in order to ensure that the recording medium is in close contact with the toner. The voltage required to transfer the toner from the intermediate transfer belt 2 to the recording medium is applied to the metal shaft, and the elastic layer is semiconductive or conductive in order to effectively work the electrostatic force for transferring the toner. Something is used. The transfer device 13 is configured to press the recording medium against the intermediate transfer belt 2 with an appropriate load in order to press the recording medium against the intermediate transfer belt 2 with certainty.

  When the intermediate transfer belt 2 and the transfer device 13 are in contact with each other as in this embodiment, fog toner or the like on the intermediate transfer belt 2 may adhere to the transfer device 13 when paper is not passed. Since the toner adhering to the transfer unit 13 adheres to the back surface of the recording medium and becomes dirty, a mechanism for retracting the transfer unit 13 from the intermediate transfer belt 2 can be provided for the purpose of preventing this. The transfer device 13 is kept away from the intermediate transfer belt 2 except when it is necessary to bring the transfer device 13 into contact with the intermediate transfer belt 2 such as when paper is passed, so that contamination of the transfer device 13 can be minimized. it can. Such contamination of the transfer device 13 by the toner may be caused by a mechanism for cleaning the transfer device 13 or by applying an appropriate bias voltage having the same polarity as the toner to the transfer device 13 so that the toner adhered on the transfer device 13 is transferred to the intermediate transfer member. It is also possible to remove it positively by providing a reverse transfer mechanism.

  Further, as another configuration used in the transfer device of the image forming apparatus of this embodiment, a corona transfer device can be used as long as the paper and the toner can be brought into close contact with each other using a blade-shaped paper pressing member.

  Further, in the color image forming apparatus of the present embodiment, a sheet static eliminator 14 (see FIG. 1) is disposed downstream of the transfer unit 13 in the sheet conveyance direction.

Since the recording medium after toner transfer partially retains the charge injected during the transfer, it is adsorbed to the intermediate transfer belt 2 by electrostatic force. In this embodiment, since the small-diameter belt stretching roller 10c is disposed at a position facing the transfer device 13, the recording medium can be peeled off by the curvature of the belt stretching roller 10c and the sheet rigidity. However, there are cases in which thin paper with low rigidity, high-resistance OHP sheet or the like in which transfer charge tends to remain cannot be peeled stably. In the image forming apparatus according to the present embodiment, a sheet static eliminator 14 that neutralizes the remaining transfer charge is disposed in order to facilitate peeling of the recording medium.
The sheet static eliminator 14 of the present embodiment arranges needle-like microelectrodes to which a predetermined potential is applied, along the transfer unit 13, and generates a discharge between the potential on the back surface of the recording medium and the microelectrodes, thereby forming the back surface of the recording medium. It is a static eliminator that removes the electric charge.

  Further, when it is necessary to more reliably remove the sheet due to an increase in printing speed or the like, an AC neutralization system using AC corona discharge can be used as another method of the sheet neutralizer 14.

  In addition, when it is necessary to stably transport the paper after the transfer, a belt transfer device having both functions of toner transfer and paper peeling / conveying is used in place of the transfer device 13 and the paper discharger 14. It can be used for the image forming apparatus.

  Furthermore, a method of roughening the surface of the intermediate transfer belt 2 can also be applied in order to improve the peeling of the recording medium. When the surface of the intermediate transfer belt 2 is roughened, a gap is formed between the recording medium and the paper and the adsorbing force is weakened, so that the paper can be peeled off very easily. On the other hand, roughening the intermediate transfer belt 2 tends to cause image defects such as white spots in the image. However, this method is effective when the charging of the toner can be improved to prevent the image quality from being deteriorated. is there.

  Next, an embodiment of the fixing device 19 of the image forming apparatus of the present invention will be described.

  In the image forming apparatus of the present invention, the fixing device is required to ensure the color image colorability and to sufficiently cope with a high printing speed.

  For this reason, the fixing device needs to be able to supply the amount of heat necessary for dissolving the toner with good response. Further, in a small image forming apparatus as in the present invention, it is desirable to fix at a temperature as low as possible because the heat generated by the fixing device tends to affect other processes.

  In this embodiment, toner is fixed using a fixing belt. By fixing the fixing belt long along the paper conveyance path or by arranging the fixing belts in substantially the same direction in the arrangement direction of the plurality of photoconductors 1a, 1b, 1c, and 1d, a section for fixing the toner and a heating time are ensured long. be able to. Accordingly, the recording medium on which the toner is adhered can be sufficiently heated, so that the toner can be reliably fixed. Further, since heat conduction is performed using a thin member such as a fixing belt, the response is quick, and it is not necessary to input extra heat, so that the toner can be fixed at a relatively low temperature.

  Further, as shown in FIG. 1, the photosensitive members 1 a, the intermediate transfer belt 2, and the fixing device 19 are arranged horizontally, and the intermediate transfer belt 2 is stretched vertically in the length of the arrangement of the photosensitive members 1. Therefore, a fixing device that is long in the sheet conveyance path direction can be arranged without increasing the size of the apparatus. For this reason, there is no problem in using the fixing device constituted by the belt-shaped member as described above.

The detailed configuration of the fixing device 19 is shown in FIG.
The fixing device 19 according to the present embodiment includes a belt-shaped fixing belt 74, fixing belt stretching rollers 75a and 75b, a heater 76, and a contact roller 77 that closely contacts the fixing belt, and a peeling that peels the paper. It comprises a roller 78 and a tension roller 79 that applies tension to the fixing belt.

  As the fixing belt 74, heat-resistant resin, heat-resistant rubber, metal belt, or a combination thereof can be used. In this embodiment, a metal nickel belt having a high thermal conductivity is coated with a silicon rubber having a thickness of 20 to 40 [mu] m, which has good toner releasability. The fixing belt 74 is stretched by three rollers. The fixing belt stretching rollers 75a and 75b are metal rollers, and a contact roller 77 and a peeling roller 78 are arranged at opposing positions, respectively. The tension roller 79 applies tension to the fixing belt and is fixed by a spring. A heater 76 such as a nichrome wire heater is disposed inside the fixing belt stretching roller 75a. The contact roller 77 is a metal roller having an elastic layer on the surface, and is disposed so as to be pressed against the fixing belt stretching roller 75a, thereby bringing the recording medium into close contact with the fixing belt 74 and making it easy to transfer the heat of the fixing belt 74 to the toner. I am doing so. The peeling roller 78 disposed at a position opposite to the belt stretching roller 75 b is provided to peel off the recording medium and apply shearing force to the melted toner to prevent the toner from sticking to the fixing belt 74. . As with the contact roller 77, the peeling roller 78 is a metal roller having an elastic layer on the surface.

  In order to prevent the heat generated in the fixing device 19 from affecting the inside of the main body, the fixing device 19 of this embodiment is provided with a heat insulating member 80 on the inner side of the main body.

  In the fixing device of FIG. 15, the distance between the contact roller 77 and the peeling roller 78 can be set to 40 to 100 mm in consideration of the arrangement configuration of other process parts. For this reason, at a process speed of 100 mm / s, it is possible to secure 0.4 to 1 second for heating the toner on the recording medium. A roller fixing device that performs fixing using two rollers can secure a nip width of only about several millimeters, so considering that the heating time is 0.02 to 0.06 seconds, the toner is sufficiently heated. Is possible.

  When fixing can be easily performed using a low-melting toner or the like, or when fixing performance can be secured by using a method of reducing the fixing speed corresponding to the type of recording medium, two pieces heated to a specified temperature are used. It is also possible to use a roller fixing type fixing device in which the recording medium is passed between the rollers to fix the toner.

  FIG. 16 shows a configuration of a roller fixing device which is another embodiment of the fixing device of the present invention.

  In this configuration, the toner on the recording medium is fixed with heat and pressure by a pair of heat roller 81 and backup roller 82 having a heat source therein. The heat roller 81 and the backup roller 82 are rollers whose surfaces are covered with an elastic body such as silicon rubber or fluorine rubber. A surface layer such as a fluororesin may be provided on the roller surface for the purpose of improving releasability from the toner. Further, by providing an oil application mechanism 83 for applying silicon oil or the like on the surface of the heat roller 81, the releasability between the toner and the surface of the heat roller 81 is improved.

  In addition, a small amount of toner or paper dust may adhere to the fixing member during fixing. These toners and paper dust accumulate on the roller surface and may cause a decrease in the life of the roller. For this reason, a cleaning roller 84 for cleaning the surface of these roll members is provided in the heat roller 81 and the backup roller 82 for the purpose of removing this minute amount of toner and paper dust.

  Of course, the oil application mechanism and the cleaning mechanism as described above can also be applied to the embodiment of FIG.

  In addition, as shown in FIG. 17, a paper heating member 85 that heats the paper may be provided upstream of the fixing device 19 in the paper transport direction. As the sheet heating member 85, an infrared heater or a plate heater is used, and heats the recording medium in a non-contact manner. By providing such a sheet heating member 85, it is possible to heat the sheet in advance so that fixing can be performed easily.

  Next, an embodiment of the paper cassette and its peripheral part according to the present invention will be described with reference to FIG. The paper cassette 16 of this embodiment is for storing paper, and is arranged at the lowermost part of the main body, and can store hundreds of paper. In order to make the paper feeding mechanism 17 work reliably, a mechanism for pressing the recording medium against the paper feeding mechanism from below is necessary. In this embodiment, the paper cassette 16 has a built-in spring, and the paper cassette 16 is in the main body. A mechanism is used to push the recording medium upward when it is mounted. When a large number of recording media are set in the paper cassette 16, it is possible to provide a mechanism for moving the recording media up and down by a power source from the main body.

  As shown in FIG. 21, when the sheet cassette 16 is added, the extension cassettes 103 are stacked below the main body so as to be added without changing the grounding area. Further, the expansion cassette 103 can store papers of various sizes and various kinds of papers, which can be handled by the embodiments described above.

Specifically, paper feeding as a recording medium will be described.
The paper feed mechanism 17 that feeds the recording medium from the paper cassette 16 includes at least a pick roller 86 and a separation pad 87. The pick roller 86 is a roller provided with a member such as rubber having a high friction coefficient with the recording medium on the surface thereof. The pick roller 86 is disposed in contact with the recording medium, and pulls out the recording medium from the cassette by rotation. The separation pad 87 is a friction material such as rubber or cork, and is disposed in contact with the surface of the pick roller 86, and separates the recording medium pulled out by the pick roller 86 into only one sheet.

  Further, since it is necessary to bring the pick roller 86 into contact with both the front end of the recording medium and the separation pad 87, the diameter of the pick roller 86 cannot be reduced. Therefore, it is necessary to secure a space for arranging the pick roller 86 between the paper cassette 16 and the main body printing process. When it is necessary to reduce this space due to the apparatus configuration, the following paper feeding mechanism can be applied.

Next, an embodiment of the paper feed mechanism of the present invention will be described below.
First, a part for picking up the recording medium and a part for separating the recording medium are divided and provided with a pick roller 86, a feed roller, and a retard roller, respectively. More specifically, the recording medium in the cassette is pulled out from the paper cassette 16 by the pick roller 86. At this time, there may be two or more recording media to be picked. At this time, in order to separate two or more recording media, a feed roller and a retard roller arranged above and below the recording medium are provided, and the feed roller arranged above rotates in the same direction as the pick roller 86, The retard roller disposed below is rotated in the reverse direction by a torque limiter. When two or more recording media are sent, the lower retard roller rotates reversely and works to push the excess recording media back toward the paper cassette 16 side. When one or all of the recording media are pushed into the cassette side, the torque limiter works by the frictional force of the recording media and the feed roller disposed above, and the paper is conveyed to the registration roller 18 side. In this system, the pick roller 86, the feed roller, and the retard roller can be arranged on a straight line, and a small-diameter roller can be used, so that the arrangement space of the paper feed mechanism 17 can be reduced.

  Another embodiment of the paper feed mechanism 17 will be described.

  The separation pad 87 is disposed horizontally with the paper cassette 16, and the member for pulling out the recording medium from the paper cassette 16 is a belt-shaped pick belt. As the pick belt, a rubber material having a high friction coefficient, or a hard rubber belt whose surface is covered with a rubber having a high friction coefficient is used in order to provide strength. Although the paper feeding method is as described above, since a small-diameter object can be used for the pick belt stretching roller for stretching the pick belt, the arrangement space of the paper feeding mechanism 17 can be reduced.

  Further, the registration roller 18 of the present embodiment is provided to align the front end of the paper and to feed the paper to the transfer unit in synchronization with the toner image on the intermediate transfer belt 2, and to improve the rotational speed accuracy. A metal roller for increasing and an elastic roller covering the metal shaft with rubber or the like for obtaining a sufficient conveying force of the recording medium are used in combination. The registration roller 18 is also provided with a paper sensor. When the paper reaches the registration roller 18 portion, the pick roller 86 is stopped, and the registration roller 18 is driven at a timing that matches the leading edge of the image on the intermediate transfer belt 2 to obtain an image. Align the paper.

  Next, application of a bias voltage to each process component of the image forming apparatus of the present invention will be described with reference to FIG.

  In order to develop and transfer the toner, it is necessary to apply a bias to the developing machines 5a, 5b, 5c and 5d and the transfer unit 13. The direction of bias during development and transfer is determined by the polarity of the toner, the development method, and the setting of the zero potential portion.

  FIG. 18 shows an embodiment of bias voltage application showing what potential is applied to each part.

  In this embodiment, an organic photosensitive member and a negatively charged toner are used as the photosensitive material of the photosensitive member, and a reversal developing method capable of developing at higher resolution is adopted.

  Accordingly, the chargers 3a, 3b, 3c, and 3d charge the photoreceptors 1a, 1b, 1c, and 1d to a negative potential, so that a negative bias is applied to the developing units 5a, 5b, 5c, and 5d. . At this time, as the bias applied to the chargers 3a, 3b, 3c, and 3d, since the charger is a charging roller, an AC voltage may be superimposed to stabilize the photoreceptor potential. Transfer of toner from the photoconductors 1a, 1b, 1c, and 1d to the intermediate transfer belt 2 is performed by setting the photoconductor side to be negative or the intermediate transfer belt 2 side to be positive. In this embodiment, the photoconductor 1a is transferred. , 1b, 1c, 1d, members having different bias voltages such as the chargers 3a, 3b, 3c, 3d and developing machines 5a, 5b, 5c, 5d are disposed. 1d is set to a reference potential, that is, zero potential, and a positive potential is applied to the intermediate transfer belt 2 side, that is, a positive voltage is applied to the auxiliary transfer rollers 9a, 9b, 9c, and 9d. When the toner is transferred from the intermediate transfer belt 2 to the sheet, a positive potential higher than the potential applied to the intermediate transfer belt 2 is applied to the transfer device 13.

  A negative bias having the same polarity as the toner is applied to the belt stretching roller 10d pushed into the intermediate transfer belt 2 in order to make it difficult for the toner on the intermediate transfer belt 2 to adhere. Further, since the toner remaining without being transferred by the transfer device 13 may be reversed in polarity, a plus bias may be applied to the belt stretching roller 10d.

  In addition to the bias configuration described above, the belt tensioning rollers 10a, 10b, 10c, and 10d for stretching the intermediate transfer belt 2 and the auxiliary transfer rollers 9a, 9b, 9c, and 9d are set to zero potential, and the respective photoreceptors 1a. , 1b, 1c, 1d may be applied with a negative bias to transfer the toner to the intermediate transfer belt 2.

  The bias voltage applied to each of these processes is configured to be adjustable by the user in order to stabilize the image quality and improve the image quality. For example, the exposure level of the exposure devices 4a, 4b, 4c, and 4d and the bias voltage for development can be adjusted by an operation panel or switch corresponding to the characteristics of the photoreceptors 1a, 1b, 1c, and 1d. With a simple operation, the image quality can be adjusted.

  Further, developing the above and controlling the bias of each unit is also effective for stabilizing the image quality. For example, when the toner image on the intermediate transfer belt 2 is transferred to a recording medium, the type of the recording medium, for example, the high resistance OHP and the bias voltage required for the moisture-absorbing paper may differ. By providing a transfer voltage control mechanism as shown in FIG. 19, it is possible to realize transfer stabilization against changes in the type of recording medium and environmental conditions.

  The transfer voltage control mechanism of FIG. 19 includes a transfer device current detection unit 93 that detects a current flowing through the transfer device 13, and a transfer voltage control unit 94 that determines the bias voltage of the transfer device 13 based on the result of the transfer device current detection unit 93. , And a high voltage power supply 95 capable of applying a bias voltage to the transfer unit and changing an output value. By detecting the current flowing through the transfer device 13 and changing the transfer bias voltage in accordance with the current value, stable transfer can be realized constantly against changes in the type of recording medium and environmental conditions. Furthermore, the amount of toner attached is detected, and based on this, the exposure amount and the bias voltage for development / transfer are changed, and the temperature / humidity sensor is used to detect the environmental conditions of the device. It is also possible to use a method for controlling the bias of each process.

  Next, a configuration provided with a double-sided printing mechanism, which is another embodiment of the image forming apparatus of the present invention, will be described with reference to FIGS.

  When performing double-sided printing, it is necessary to provide a paper passing path for folding the paper, and the following configuration can be applied to the image forming apparatus of this embodiment.

FIG. 22 shows an example in which a configuration in which the paper on which the front surface is printed is turned back at the paper discharge unit. In the double-sided mechanism, a conveying roller 104 that can rotate forward and backward and a guide member 105 that guides the paper to a double-sided paper passing path 106 are provided in the paper discharge unit, and a double-sided paper passing path 106 is disposed on the left outer surface of the main body. The sheet guide rollers 107 that convey the sheet through the double-sided sheet passing path 106 are arranged at an interval smaller than the longest sheet length to be printed. The exit of the double-sided paper path 106 is provided below the main body registration roller 18, and the paper conveyed through the double-sided paper path 106 is configured to be conveyed again to the transfer position by the registration roller 18. In this configuration, the paper printed on the front side is temporarily fed onto the paper discharge tray on the upper surface of the main body by the front end being bitten by the transport roller, and at the timing when the rear end of the paper passes the guide member 105. , And the position of the guide member 105 is switched at the same time so that the rear end of the sheet is fed into the double-sided sheet passing path 106. Thereafter, the sheet is conveyed through the double-sided sheet passing path 106 and reaches the position before the registration roller 18. An image to be printed on the back side of the paper is formed on the intermediate transfer belt 2, and the paper is sent to the transfer portion by the registration roller 18 at the transfer timing to form an image on the back side. This method is characterized in that the double-sided sheet passing path 106 can be configured to be relatively small. Further, since the double-sided paper passing mechanism itself does not require complicated connection with the main body, there is an advantage that the user can set it.
FIG. 23 shows a method in which the paper on which the surface is printed is folded back on the left side of the apparatus, outside the transfer device 13 and the fixing device 19. In this double-sided mechanism, a guide member 105 that guides the paper to the double-sided paper passing path 106 is provided in the paper discharge unit, and an S-shaped double-sided paper passing path 106 that can fold the paper on the left outer surface of the main body is disposed. . The exit of the double-sided paper path 106 is provided below the main body registration roller 18 so that the paper conveyed through the double-sided paper path 106 is conveyed again to the transfer position by the registration roller 18. In this configuration, the paper printed on the front side is sent to the double-sided paper path 106 by the guide member 105. Thereafter, the sheet is conveyed through the double-sided sheet passing path 106 and is conveyed to the position A, and the sheet guide roller 107 is rotated in the reverse direction, whereby the sheet is conveyed to the front of the registration roller 18. An image to be printed on the back side of the sheet is formed on the intermediate transfer belt 2, and the sheet is sent to the transfer unit by the registration roller 18 at the transfer timing to form an image on the back side. The paper guide before the registration is provided to prevent the paper that has been fed to the position A and reversely conveyed from being reversely fed through the double-sided paper path 106. This method has an advantage that the user can set the double-sided sheet passing mechanism itself because it does not require complicated connection with the main body. In addition, double-sided printing is possible without the paper once coming out of the main body, and high-quality images can be recorded without the paper being soiled from paper feeding to paper ejection.

  FIG. 24 shows a method in which the paper on which the front surface is printed is folded under the apparatus. This double-sided mechanism is provided with a guide member 105 that guides the paper to the double-sided paper path 106 in the paper discharge unit, a double-sided paper path 106 on the left outer surface of the main body, and a double-sided paper storage tray 108 below the main body. Yes. The exit of the double-sided paper path 106 is provided in the double-sided paper storage tray 108 below the main body, and the paper transported through the double-sided paper path 106 is sent to the double-sided paper storage tray 108 where it is transported in the reverse direction. Then, it is conveyed to 18 parts of the registration roller. In this configuration, the sheet printed on the front side is guided to the double-sided sheet passing path 106 by the guide member 105 and stored in the double-sided sheet storage tray 108 through the double-sided sheet passing path 106. Thereafter, the paper guide roller 107 is rotated in the reverse direction, and the paper is conveyed to the front of the registration roller 18. An image to be printed on the back side of the sheet is formed on the intermediate transfer belt 2, and the sheet is conveyed to the transfer unit by the registration roller 18 at the transfer timing to form an image on the back side. The paper guide at the entrance of the double-sided tray is provided to prevent paper conveyed from the double-sided tray from being sent to the double-sided paper path 106. This method is characterized in that since the double-sided paper storage tray 108 is arranged horizontally, a large amount of paper for double-sided printing can be stored, and thus it is suitable for printing a large number of copies. In addition, since the double-sided paper passing path 106 is simple, jamming does not easily occur and maintenance is easy.

Since the double-sided printing path is required to be long, the sheet may be shifted or tilted from the normal position while the sheet is conveyed. In order to correct these, a restricting member that restricts the end of the sheet or a mechanism that positively operates the restricting member to correct the position of the sheet may be provided.

  As described above, in order to provide small size, high speed, high image quality, and high maintainability, the image forming apparatus of the present embodiment is provided with the intermediate transfer belt 2 that is elongated vertically in the central portion of the main body and is elongated. The same number of photoreceptors 1 as the number of necessary color toners are arranged vertically on one surface, and the transfer device 13 and the fixing device 19 are arranged on the opposite surface. In addition, the paper cassette 16 is disposed below the main body, and the transfer device 13 and the fixing device 19 are disposed in this order from the bottom so that the recording medium is conveyed upward and the transfer and fixing are performed. Further, a plurality of photoconductors 1a, 1b, 1c, and 1d are fixedly disposed in the photoconductor unit 22, and the exposure units 4a, 4b, 4c, and 4d are fixed to the main body housing 200. The photoconductor unit 22 is photosensitive. The developing units 5a, 5b, 5c, and 5d are detached in the direction perpendicular to the arrangement direction of the photoreceptors 1a, 1b, 1c, and 1d.

  As a result, the image forming apparatus according to the present embodiment achieves both high-quality color image recording and high-speed printing, is small in size and low in price, and has excellent user maintenance.

  Hereinafter, another embodiment of the image forming apparatus of the present invention will be described.

  First, FIG. 25 illustrates an embodiment of an image forming apparatus including an exposure device in the photosensitive unit 22 shown in FIG.

  The image forming apparatus of FIG. 25 is arranged in such a manner that the photoreceptors 1a, 1b, 1c, and 1d of the respective colors are arranged vertically and the intermediate transfer belt 2 is arranged on one side of the photoreceptor arrangement surface. 1, the image forming apparatus of FIG. 1 is arranged by stacking the developing devices 5 a, 5 b, 5 c, 5 d for each color and the exposure devices 4 a, 4 b, 4 c, 4 d on the opposite surface of the intermediate transfer belt on the photoconductor arrangement surface. In contrast, the image forming apparatus shown in FIG. 25 is characterized in that the exposure devices 4a, 4b, 4c, and 4d for the respective colors are arranged in the photosensitive unit 22 in which the photosensitive members 1a, 1b, 1c, and 1d are arranged. is there. At this time, in order to make the photosensitive unit 22 as small as possible, it is desirable to use a small exposure device. In the embodiment of FIG. 24, the LED exposure device described above is used. In this embodiment, the exposure units 4a, 4b, 4c, and 4d corresponding to the respective colors and the photosensitive members 1a, 1b, 1c, and 1d are configured as an integral unit. In addition, the positional relationship between the photoconductor and the exposure device can be accurately arranged and stably held. For this reason, alignment of each color image can be performed more accurately. Further, since it is possible to increase the volume of each developing unit 5a, 5b, 5c, 5d by the space where the exposure units 4a, 4b, 4c, 4d are arranged in the embodiment of FIG. Long life can be achieved.

  The outer peripheral length of the photosensitive member cannot be at least smaller than the size (length, etc.) of the recording medium, and the length between the photosensitive members is limited by design. Although it cannot be configured to be reduced in the vertical direction by the space that has been arranged, it is also possible to make the apparatus compact by shortening it as much as possible.

  Further, another embodiment of the image forming apparatus of the present invention will be described below.

  In the embodiment shown in FIG. 1, a charger 3, an exposure device 4, a developing device 5, an intermediate transfer belt 2, a photoconductor cleaner 6, and an erase lamp 8 are arranged around the photoconductor 1. From the arrangement order and the rotation direction of the photoconductor, it is necessary to arrange the photoconductor below the line connecting the development point and the transfer point of the photoconductor. In order to increase the printing speed and the resolution, it is necessary to increase the size and complexity of these processes. In the embodiment of FIG. 26, in order to widen the space below the photoconductor, the photoconductor unit 22 in which the photoconductors 1a, 1b, 1c, and 1d are fixedly arranged is slanted toward the developing devices 5a, 5b, 5c, and 5d. The arrangement arrangement is applied. Further, the photoconductor unit 22 can be exchanged by pulling it obliquely upward, which is the arrangement direction of the photoconductor. By moving the contact point between the photosensitive member and the intermediate transfer belt upward in this way, it is possible to give a margin to the structure of the process arranged below the photosensitive member and increase the arrangement margin.

  Next, a configuration in which the intermediate transfer belt 2 as an embodiment of the image forming apparatus of the present invention is stretched in the lateral direction will be described.

  In the embodiment of FIG. 27, the photoconductors are arranged side by side in the embodiment of FIG. 1, but the photoconductors of the respective colors are arranged horizontally. The size of the apparatus is reduced by arranging the fixing device on one side and the fixing device on the other side.

  In addition, an intermediate transfer belt 2 that is long and stretched laterally with respect to the direction of gravity is disposed in the central portion of the main body. On the upper surface of the intermediate transfer belt 2, the same number of photoreceptors 1a, 1b, 1c, and 1d as the four color toners to be used are arranged in the lateral direction, that is, in the stretching direction of the intermediate transfer belt. Around each photoconductor, printing units 109a, 109b, 109c, and 109d and exposure devices 4a, 4b, 4c, and 4d for charging, developing, cleaning, and the like are arranged. Further, a transfer device 13 and an intermediate transfer belt cleaner 15 are disposed around the intermediate transfer belt 2, and a paper transport path for passing paper is provided below the intermediate transfer belt 2, and transported on the paper transport path. A paper cassette 16, a pick roller 86, a registration roller 18, a transfer device 13, a fixing device 19, and a paper discharge route are arranged along the route.

  In this embodiment of FIG. 27, the photosensitive member is disposed on one side of the intermediate transfer member and the fixing device is disposed on the opposite side, so that the intermediate transfer member and the fixing device are arranged in parallel. Further, in order to enable stable conveyance of the recording medium, the paper cassette 16 is disposed below the main body, the transfer device 13 and the fixing device 19 are disposed in this order from the bottom, and the recording medium is conveyed and transferred. It is characterized by fixing.

  Further, in one embodiment of FIG. 28, an intermediate transfer belt 2 stretched horizontally in the direction of gravity is disposed at the central portion of the main body. Above the intermediate transfer belt 2, the same number of photoreceptors 1 a, 1 b, 1 c, 1 d as the four-color toner used and a fixing device 19 are arranged side by side. Printing units 109a, 109b, 109c, and 109d and exposure units 4a, 4b, 4c, and 4d for charging, developing, cleaning, and the like are disposed around the photosensitive members and the respective photosensitive members. The fixing device 19 is disposed above the belt stretching roller 10e located at the most upstream portion of the photoreceptor arrangement surface of the intermediate transfer belt 2. Further, a transfer device 13 and an intermediate transfer belt cleaner 15 are provided around the intermediate transfer belt 2, and the transfer device 13 includes a belt stretching roller 10 e positioned at the most upstream portion of the photosensitive member arrangement surface of the intermediate transfer belt 2. The intermediate transfer belt cleaner 15 is disposed on the upper surface of the intermediate transfer belt 2. In the image forming apparatus according to the present exemplary embodiment, a sheet conveyance path that can convey a sheet without bending the intermediate transfer belt 2 from the lower side to the upper left side is provided. On the paper transport path, a paper cassette 16, a pick roller 86, a registration roller 18, a transfer device 13, a fixing device 19, and a paper discharge path are arranged along the transport path.

  In this way, the paper path that is the paper transport path has a large arc shape and is located close to the outer surface of the apparatus. Therefore, various recording media such as thick paper, envelopes, and postcards can be stably fed from the paper cassette 16 without jamming, and the removal of paper after jamming can be facilitated.

1 is a diagram showing an embodiment of an image forming apparatus of the present invention. FIG. 2 is a diagram illustrating a detailed configuration of a photoconductor unit of the image forming apparatus of the present invention. FIG. 3 is a detailed view of a peripheral portion of the photoconductor of the image forming apparatus of the present invention. FIG. 6 is a diagram illustrating a positional deviation of a plurality of photoconductors in the image forming apparatus of the present invention. It is a diagram showing a method for attaching and detaching each process of the image forming apparatus of the present invention. It is the figure which showed one Example of the exposure device of the image forming apparatus of this invention. It is the figure which showed the other Example of the exposure device of the image forming apparatus of this invention. It is the figure which showed the other Example of the exposure device of the image forming apparatus of this invention. It is the figure which showed one Example which used the LED light source for the exposure device of the image forming apparatus of this invention. It is the figure which showed schematic structure using the exposure device of the LED light source for the image forming apparatus of this invention. 1 is a diagram illustrating an example of a developing machine of an image forming apparatus according to the present invention. It is a figure which shows the other Example of the image development apparatus of the image forming apparatus of this invention. It is a figure which shows one Example of the belt deviation correction mechanism of the image forming apparatus of this invention. FIG. 3 is a diagram illustrating an embodiment of an intermediate transfer belt cleaner of the image forming apparatus according to the present invention. 1 is a diagram illustrating an example of a fixing device of an image forming apparatus according to the present invention. FIG. 6 is a view showing another embodiment of the fixing device of the image forming apparatus of the present invention. It is a figure which shows one Example of the paper heating member of the image forming apparatus of this invention. It is a figure explaining the bias voltage application applied to each process of the image forming apparatus of this invention. It is a figure which shows one Example of the transfer voltage control mechanism of the image forming apparatus of this invention. It is a figure explaining the image sensor and image shift of the image forming apparatus of the present invention. FIG. 3 is a diagram illustrating an embodiment in which a sheet cassette of the image forming apparatus of the present invention is added. It is a figure which shows one Example of the double-sided printing mechanism of the image forming apparatus of this invention. It is a figure which shows the other Example of the double-sided printing mechanism of the image forming apparatus of this invention. It is a figure which shows the other Example of the double-sided printing mechanism of the image forming apparatus of this invention. It is the figure which showed the other Example of the image forming apparatus of this invention. It is the figure which showed the other Example of the image forming apparatus of this invention. FIG. 3 is a diagram illustrating an embodiment having a horizontally long intermediate transfer belt in the image forming apparatus of the present invention. FIG. 6 is a view showing another embodiment having a horizontally long intermediate transfer belt in the image forming apparatus of the present invention.

Explanation of symbols

1a, 1b, 1c, 1d ... photoconductor, 2 ... intermediate transfer belt, 3a, 3b, 3c, 3d ... charger, 4a, 4b, 4c, 4d ... exposure unit, 5a, 5b, 5c, 5d ... developer, 6a, 6b, 6c, 6d... Photoreceptor cleaner, 7a, 7b, 7c, 7d. 10b, 10c, 10d ... belt tension roller, 11 ... image sensor, 12 ... toner charger, 13 ... transfer device, 14 ... paper discharger, 15 ... intermediate transfer belt cleaner, 16 ... paper cassette, 17 ... paper feed mechanism , 18, registration rollers, 19, a fixing device, 20, the position of the image formed by the photoreceptor 1 a, 21, the position of the image formed by the photoreceptor 1 b, 22, the photoreceptor unit, 27, a semiconductor laser, 28, polygon 29 ... Polygon motor, 30 ... fθ lens, 31 ... Folding mirror, 32 ... LED array, 33 ... Driver circuit, 34 ... Lens, 35 ... Developing unit, 36 ... Toner storage unit, 37 ... Developing roller, 38 ... Toner Restricting blade, 39 ... Reset roller, 40 ... Toner adhering blade, 41 ... Scraping paddle, 42 ... Toner feed paddle, 43 ... Toner storage chamber, 44 ... Toner supply paddle, 45 ... Toner hopper, 46 ... Magnet roller, 47 ... Developer Restricting blade, 48 ... developer feed paddle, 49 ... stirring paddle, 50 ... toner density sensor, 51 ... toner supply roller, 52 ... belt waste toner collecting part, 53 ... rib, 56 ... taper piece, 57 ... belt stretching roller 1d Holding member, 58 ... rotational force transmission shaft, 59 ... belt tension spring, 60 ... belt base material, 65 ... Brush cleaner, 66 ... Recovery roller, 67 ... Recovery blade, 74 ... Fixing belt, 75 ... Fixing belt stretching roller, 76 ... Heater, 77 ... Paper contact roller, 78 ... Paper peeling roller, 79 ... Tension roller, 80 DESCRIPTION OF SYMBOLS ... Heat insulation member 81 ... Heat roller 82 ... Backup roller 83 ... Oil application mechanism 84 ... Cleaning mechanism 85 ... Paper heating member 86 ... Pick roller 87 ... Separation pad 93 ... Transfer device current detection part 94 DESCRIPTION OF SYMBOLS ... Transfer voltage control part, 95 ... High voltage power supply, 100 ... Photoconductor drive gear, 101 ... Waste toner collection part drive gear, 102 ... Waste toner discharge path, 103 ... Additional cassette, 104 ... Conveyance roller, 105 ... Guide member, 106 ... Double-sided paper path 107: Paper guide roller 108 ... Double-sided paper storage tray 109 109 Printing unit 200 .

Claims (6)

A housing of the image forming apparatus, a plurality of photosensitive drums arranged in a line in the vertical direction, a plurality of developing units and a plurality of exposure units disposed on one side of the plurality of photosensitive drums, and the plurality of photosensitive drums an intermediate transfer member arranged on the other side of the body drum, the fixing device and the intermediate transfer member wherein the plurality of photosensitive drums arranged side opposite to the arranged transfer part of the plurality of photosensitive drums A plurality of photosensitive drums that can be pulled out from above , a photosensitive member drive gear provided on each photosensitive drum of the plurality of photosensitive drums, and the housing. An image forming apparatus that drives the plurality of photosensitive drums in the integrated unit with one gear from the body side.   2. The image forming apparatus according to claim 1, wherein the plurality of exposure units are fixedly disposed on the casing. 3. The image forming apparatus according to claim 2, wherein a belt type fixing device having a belt stretched in substantially the same direction as the arrangement direction of the plurality of photosensitive drums is disposed on one side of the intermediate transfer member.   4. The image forming apparatus according to claim 3, wherein the heights of the plurality of developing machines and the plurality of exposure units are smaller than the length in the horizontal direction.   5. The image forming apparatus according to claim 4, wherein each of the plurality of developing machines includes a developing unit and a toner hopper, and the toner hopper can be replaced while leaving the developing unit in the housing. 6. The image forming apparatus according to claim 5, further comprising a sheet heating member that heats a recording medium between the transfer unit and the fixing device.
more than

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