JP4712499B2 - Image forming apparatus - Google Patents

Description

The present invention is a copying machine for forming a multi-color image composed of a plurality of colors of toner, the printer, relates to an image forming equipment such as a facsimile, details, which form a plurality of colors image on the latent image bearing member Is finally transferred onto a recording material to form a multi-color image.

As this type of image forming apparatus, conventionally, the following two methods are mainly known.
In the first method, each color image is sequentially formed on a single latent image carrier, and these are primary-transferred so as to overlap each other on the intermediate transfer member, whereby a multi-color image formed on the intermediate transfer member. Is secondarily transferred onto the recording material. This method has an advantage that the number of parts is small and the cost is lower than the second method described later. However, since it is necessary to rotate the latent image carrier by one image for each color, it is necessary to rotate the latent image carrier by the number of colors constituting the multicolor image when forming a multicolor image. . Therefore, there is a drawback that the image forming speed is slower than that of the second method described later.
On the other hand, in the second method, a latent image carrier for each color is provided, each color image is formed in parallel on each latent image carrier, and these are primary-transferred so as to overlap each other on the intermediate transfer member. In this manner, the multi-color image formed on the intermediate transfer member is secondarily transferred onto the recording material. This method has a higher image forming speed when forming a multi-color image than the first method. However, since it is necessary to provide a member (latent image carrier, charging device, etc.) for forming each color image on the intermediate transfer member for each color, there are disadvantages that the number of parts is large and the cost is increased.

  However, an image forming apparatus having both advantages of these methods is desired, but at present, such an image forming apparatus has not been provided. Therefore, there is a demand for a new image forming system that can realize an increase in image forming speed when forming a multi-color image at low cost.

The present invention has been made in view of the above background, and an object of the present invention is to provide a new image formation that can realize low-cost and high-speed image formation when forming a multi-color image. it is to provide an image forming equipment which employs the system.

In order to achieve the above-mentioned object, the invention of claim 1 is characterized in that the latent image carrier that moves on the surface and each division obtained by dividing the latent image carrier in the direction orthogonal to the surface movement direction of the latent image carrier is the minimum of each color. A plurality of minimum division groups each including one minimum division of each color are arranged in the orthogonal direction, and each color latent image formable region is set on the surface of the same latent image carrier, a latent image forming means that form a latent image corresponding to each color for each Irosen image formable region, a plurality of toner carriers corresponding to the respective colors are opposed to the surface of the of identity one latent image bearing member In this way, a concave portion is formed in the surface portion of each toner carrier that is arranged along the surface moving direction of the latent image carrier and faces the latent image formable region of the corresponding color, and the toner of the corresponding color is supplied to the toner supply means. Respectively, to the entire surface of each toner carrier, By removing the toner carried on the surface portion other than the recess from the surface of each of the toner carrying member by the removal means in contact with the surface of the toner carrying member, each Irosen image formation on the latent image bearing member of identity one Development means for developing each color latent image formed in the possible area with the corresponding color toner carried on each toner carrier, and formed on the surface of the same latent image carrier. In an image forming apparatus that finally transfers a multi-color image onto a recording material, each color latent image is formed by displacing each toner carrier along a direction orthogonal to the surface movement direction of the latent image carrier. Each of the possible areas has an adjusting means for adjusting so that the concave portions of the toner carrier of the corresponding color face each other.
The “minimum division of each color” means one area divided by areas where latent images of other colors can be formed.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the adjusting means controls the voltage applied to the thickness variable member whose thickness changes in accordance with the applied voltage, thereby controlling the surface of the latent image carrier. Each of the toner carriers is displaced along a direction orthogonal to the moving direction .
Also, the invention of claim 3, the image forming apparatus according to claim 1 or 2, the developing means performs charge processing for increasing the charge amount of the toner carried on the surface of each toner carrier It has a toner charging means .

In the present invention, each color latent image is formed in a corresponding color latent image formable region among the color latent image formable regions that do not overlap each other on the surface of the same latent image carrier. Then, the corresponding color toner is opposed to each of the color latent image formable area portions, and the corresponding color toner is attached to each latent image of each color and developed. According to such images forming system, it is not necessary to provide a latent image carrier for each color, it is possible to achieve the above first method and equal or lower cost. Furthermore, since a multi-color image can be formed on the surface of the latent image carrier at once, there is no need to rotate the latent image carrier by one image for each color, and image formation equivalent to or higher than that of the second method is formed. Speed can be realized.

  As described above, according to the present invention, an image forming apparatus employing a new image forming system that can realize low-cost and high-speed image formation when forming a multi-color image, and a developing device used therefor, There is an excellent effect that a latent image forming apparatus can be provided.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic laser printer (hereinafter referred to as “printer”) as an image forming apparatus will be described.
FIG. 1 is an explanatory diagram showing a schematic configuration of the entire printer according to the present embodiment.
This printer includes a charging device 2 as charging means for uniformly charging the surface of the photosensitive member 1 around a drum-shaped photosensitive member 1 as a latent image carrier, and writing light L modulated based on image information. Exposure apparatus 3 as a latent image forming means for irradiating the photosensitive member 1 with the toner, and a multicolor image (hereinafter referred to as “color toner image”) by attaching charged toner to the latent image formed on the photosensitive member 1. A developing device 4 as a developing means for forming the toner, a transfer device 5 for transferring a color toner image formed on the photosensitive member 1 onto a transfer paper P as a recording material, and a toner remaining on the photosensitive member 1 after the transfer is removed. A cleaning device 6 and the like are sequentially arranged. In addition, a paper feeding / conveying device (not shown) that feeds and conveys the transfer paper P from a paper feeding tray (not shown), a fixing device 7 for fixing the color toner image transferred by the transfer device 5 to the transfer paper P, and the like are also provided. It has been.

  The printer of this embodiment can form a full-color image using toners of four colors of yellow (Y), magenta (M), cyan (C), and black (K). The developing device 4 according to this embodiment includes four developing devices 40Y, 40M, 40C, and 40K for each color. Each of the developing devices 40Y, 40M, 40C, and 40K develops a corresponding color latent image formed on the same photoreceptor 1 with a corresponding color toner. A detailed description of the developing device 4 will be described later.

  The charging device 2 of the present embodiment is a non-contact type charging device that uniformly charges the surface of the photoreceptor 1 with a predetermined polarity (negative polarity in the present embodiment) in a non-contact state, specifically, A scorotron charger or the like is used. The configuration of the charging device 2 is not limited to this, and any known charging device can be used. For example, a contact-type charging device can be used in which a charging roller, a charging brush, or the like is brought into contact with the surface of the photoreceptor 1 to uniformly charge the surface. Further, for example, a charging device using an electron-emitting device such as a carbon nanotube can be used.

  The exposure apparatus 3 of the present embodiment irradiates the photosensitive member 1 with the writing light L using a laser diode (LD) as a light source. The configuration of the exposure apparatus 3 is not limited to this, and any known exposure apparatus can be used. For example, an exposure apparatus using an LED array as a light source can be used. However, in the case where an exposure apparatus using an LED array needs to be arranged close to the surface of the photoreceptor 1, it is necessary to secure a space for arranging the exposure apparatus near the surface of the photoreceptor 1. On the other hand, since the exposure apparatus 3 of the present embodiment can perform exposure from a position away from the surface of the photoreceptor 1, it is not necessary to arrange an exposure apparatus near the surface of the photoreceptor 1. Therefore, it is only necessary to secure a gap in the vicinity of the surface of the photoconductor 1 so that the writing light L can pass therethrough, and space saving in the vicinity of the surface of the photoconductor 1 can be achieved.

The transfer device 5 of the present embodiment uses a transfer roller, but is not limited to this, and any known cleaning device can be used.
The cleaning device 6 of the present embodiment uses a cleaning blade, but is not limited to this, and any known cleaning device can be used.
The fixing device 7 of the present embodiment forms a fixing nip between the heating roller and the pressure roller, and passes the transfer paper P through the fixing nip, thereby applying heat and pressure to the color toner image on the transfer paper P. Is added to the transfer paper P. The configuration of the fixing device 7 is not limited to this, and any known fixing device can be used.

  Some of the plurality of devices constituting the printer may be configured as an integral structure (unit) so as to be detachable from the printer main body. In this embodiment, the photosensitive member 1, the charging device 2, the developing device 4, and the cleaning device 6 are integrally supported and configured as a process cartridge that can be attached to and detached from the printer main body. The process cartridge is not limited to such a configuration, and any process cartridge may be used as long as it integrally supports at least the photosensitive member 1 and at least one developing device 40Y, 40M, 40C, 40K constituting the developing device 4.

Next, the operation of this printer will be described.
When this printer receives a print command, it rotates the photosensitive member 1 in the direction of arrow A in the figure. Then, the surface of the photoreceptor 1 is uniformly charged by the charging device 2. The writing light L modulated based on the image information is scanned and irradiated from the exposure device 3 in the axial direction of the photosensitive member 1 on the surface of the photosensitive member 1 after being charged. Thereby, a latent image is formed on the photoreceptor 1.

FIG. 2 is an explanatory diagram of a latent image forming area of each color determined in advance on the surface of the photoreceptor 1.
In the present embodiment, a large number of latent image formable areas for each color are set on the surface of the same photoreceptor 1 so as not to overlap each other. Specifically, each segment obtained by segmenting in the direction orthogonal to the photoreceptor surface movement direction (photoreceptor axis direction) is set as the minimum segment for each color, and the minimum including one minimum segment for each color. A large number of division groups are arranged in the direction of the photosensitive member axis, and each color latent image formable region is set. The latent image formable area of each color is configured by all the minimum segments of the corresponding color. Further, it is necessary that the latent image formable areas of the respective colors have portions that do not overlap each other. In this embodiment, the latent image formable areas of the respective colors are set so as not to completely overlap each other. The width of the minimum division of each color is desirably 10 [μm] or less in order to obtain a high-definition color image. In the following description, the case where the width of the minimum division of each color is set to 10 [μm] will be described as an example. In this case, the width of the minimum section group including one minimum section for each of the four colors is 40 [μm]. The width of this minimum section group is the minimum unit of color reproduction, and corresponds to the length of one pixel on the image.

FIG. 3 is a graph showing an outline of the potential distribution of one latent image formed on the surface of the photoreceptor 1.
The exposure apparatus 3 irradiates writing light L on the corresponding color latent image formable region, that is, each minimum section of the corresponding color, thereby forming a latent image corresponding to each color in each color latent image formable region. To do. In the present embodiment, latent images of all colors are formed by a single writing process, but the writing process may be performed multiple times (for example, for each color). Here, the width of each color latent image formed on the surface of the photoreceptor 1 is set to fall within each minimum section of the corresponding color. For this purpose, it is necessary to set the writing light L sufficiently narrow so that the width of the writing light L on the surface of the photoreceptor 1 is 10 [μm] or less. However, the potential of the latent image portion on the surface of the photoreceptor 1 is relatively broadly distributed around the optical axis as shown in FIG. In the present embodiment, the width of a region where toner can adhere during development, which will be described later, is defined as the width of the latent image, and the maximum charge removal amount by the writing light L with respect to the charging potential V _G on the surface of the photoreceptor by the charging device 2 is e. The width between the points where the surface potential of the photoconductor 1 is 1 / e ² is defined as the width of the latent image. Therefore, in the present embodiment, the width of the writing light L is set so that the width is 10 [μm]. The relationship between the width of the writing light L on the surface of the photoconductor 1 and the width of the latent image varies depending on the configuration and characteristics of the photoconductor 1. Therefore, the width of the writing light L is set so that the latent image width becomes 10 [μm] in consideration of the configuration and characteristics of the photosensitive member 1.

  Each color latent image formed on the photoreceptor 1 is developed by the corresponding color developing devices 40Y, 40M, 40C, and 40K. Specifically, each of the developing devices 40Y, 40M, 40C, and 40K causes the toner to oppose the corresponding color latent image formable region, and attaches the toner to the latent image formed in the latent image formable region. Develop. Examples of the configuration of the developing unit that enables such development include the following.

FIG. 4 is an explanatory diagram showing a schematic configuration of the developing device in the present embodiment.
FIG. 5 is an explanatory diagram of the developing roller provided in the developing device.
The developing units 40Y, 40M, 40C, and 40K according to the present embodiment have substantially the same configuration except that the toner to be used is different. Therefore, in the following description, the black developing unit 40K will be described as an example.

  The developing device 40K of the present embodiment mainly includes a developing roller 41K as a toner carrier, a developing casing 42K, a regulating blade 43K as a removing unit, and a corona charger 44K as a toner charging unit. A negatively charged black toner is accommodated in the developing casing 42K, and a developing roller 41K is disposed so as to be in contact with the black toner. The developing roller 41K is rotationally driven in the direction of arrow B in the drawing, and conveys the black toner carried on the surface to the developing region facing the surface of the photoreceptor 1.

  On the surface of the developing roller 41K in this embodiment, as shown in FIG. 5, a number of grooves 45K that are concave portions extending in the photosensitive member surface moving direction, that is, the developing roller surface moving direction, are arranged along the developing roller axial direction. . These grooves 45K correspond to the respective minimum sections corresponding to black on the surface of the photoreceptor 1, and the width of the grooves 45K is set to the same width as that of the black minimum section, that is, 10 [μm]. ing.

FIG. 6 is an explanatory diagram showing an example of the relative arrangement of the developing rollers 41Y, 41M, 41C, and 41K for the respective colors.
In the present embodiment, as shown in FIG. 2, the minimum sections constituting the latent image formable areas of the respective colors are yellow (Y), magenta (M), and cyan (C) along the photosensitive body axis direction. , Black (K). The black developing roller 41K is positioned such that each groove 45K formed on the surface thereof faces each black minimum section on the surface of the photoreceptor 1. Similarly, with respect to the yellow developing roller 41Y, the magenta developing roller 41M, and the cyan developing roller 41C, the grooves 45Y, 45M, and 45C formed on the surfaces thereof correspond to the minimum sections of the corresponding colors on the surface of the photoreceptor 1. Are positioned so as to face each other. As a result, as shown in FIG. 6, the developing rollers 41Y, 41M, 41C, and 41K have a relative arrangement in which the positions of the grooves 45Y, 45M, 45C, and 45K are sequentially shifted. In order to realize such an arrangement, the width between the grooves formed on the developing rollers 41Y, 41M, 41C, and 41K is set to a width corresponding to the sum of the groove widths of the other three colors. In this embodiment, it is set to 30 [μm].

  In the developing devices 40Y, 40M, 40C, and 40K having the above-described configurations, the color toners in the developing casings 42Y, 42M, 42C, and 42K are carried on the surfaces of the corresponding developing rollers 41Y, 41M, 41C, and 41K, respectively. The The toner used in this embodiment has an average particle size sufficiently smaller than the width of the grooves 45Y, 45M, 45C, and 45K. Specifically, the toner is a spherical toner having an average particle size of 3 [μm]. . Therefore, the toner also enters the grooves 45Y, 45M, 45C, and 45K on the surfaces of the developing rollers 41Y, 41M, 41C, and 41K. Here, the regulating blades 43Y, 43M, 43C, and 43K are in contact with the surfaces of the developing rollers 41Y, 41M, 41C, and 41K on the downstream side in the developing roller surface movement direction in the developing casings 42Y, 42M, 42C, and 42K. Therefore, the toner carried on the surface of the developing rollers 41Y, 41M, 41C, and 41K is scraped off by the regulating blades 43Y, 43M, 43C, and 43K. As a result, only the toner in the grooves 45Y, 45M, 45C, and 45K is carried on the developing rollers 41Y, 41M, 41C, and 41K. The restriction blades 43Y, 43M, 43C, and 43K of the present embodiment are made of stainless steel having a tip thickness of about 2 [μm].

  The toner carried in the grooves 45Y, 45M, 45C, and 45K in this way is then charged negatively by the corona chargers 44Y, 44M, 44C, and 44K, and the amount of charge increases. When these toners are conveyed to the development area, the color toners in the grooves 45Y, 45M, 45C, and 45K face the corresponding latent image formable areas. In the present embodiment, since the surface of the photoreceptor 1 and the surfaces of the developing rollers 41Y, 41M, 41C, and 41K (portions other than the grooves) are in contact with each other, each color toner has a corresponding color latent in the developing area. Each of the imageable areas will be in contact with or in close proximity. A predetermined developing bias (negative bias in the present embodiment) is applied to each developing roller 41Y, 41M, 41C, 41K from a developing power source (not shown). Due to this developing bias, a developing electric field is formed in the developing area to move the negatively charged toner on the developing rollers 41Y, 41M, 41C, and 41K to a latent image located at an opposite location on the surface of the photoreceptor 1. The As a result, each color toner in the grooves 45Y, 45M, 45C, and 45K adheres to the corresponding color latent image formed in the corresponding color latent image formable region on the surface of the photoreceptor 1.

As a material for the developing rollers 41Y, 41M, 41C, and 41K, a resin such as carbon dispersed in a conductive material or a metal such as aluminum can be used. In this case, in order not to disturb the latent image formed on the surface of the photoreceptor 1, it is preferable to form an insulating film of about several microns at least on the outermost layer of the developing roller. In this embodiment, a fluororesin roller to which carbon is dispersed and imparted with conductivity is formed to have grooves 45Y, 45M, 45C, and 45K on its surface as shown in FIG. Developing rollers 41Y, 41M, 41C and 41K coated with a system insulating film are used. The internal dimensions of the grooves 45Y, 45M, 45C, and 45K are appropriately determined according to the maximum amount of toner that adheres to the latent image. In the present embodiment, the groove cross-sectional shape is rectangular, and the depth is 12 [μm]. Therefore, the maximum thickness of the toner layer attached to the latent image formed on the surface of the photoreceptor 1 is approximately 12 [μm].
Each color toner to be used is a spherical toner having an average particle diameter of 3 [μm] as described above. Such a spherical toner can be formed by a polymerization method or the like.
The photosensitive member 1 has a photosensitive layer of 10 [μm] and a protective surface layer of 4 [μm], and is uniformly charged to −400 [V] by the charging device 2. The maximum exposure portion potential by the writing light L of the exposure apparatus 3 is −40 [V]. The developing bias applied to each developing roller 41Y, 41M, 41C, 41K is set to −350 [V].

FIG. 7 is an explanatory diagram showing the state of toner adhering to the surface of the photoreceptor 1 when a solid image is formed.
When a solid image is formed, a latent image is formed on the entire surface of each color latent image formable region on the surface of the photoreceptor 1. Therefore, the toner of each color adheres to the entire area where the corresponding color latent image can be formed. As a result, as shown in FIG. 7, on the surface of the photoreceptor 1, yellow (Y), magenta (M), cyan (C), and black (K) bands extending in the direction of movement of the photoreceptor surface are in that order. Thus, it is repeatedly arranged along the photosensitive body axis direction. In this case, the image formed on the transfer paper P is a black solid image.

In this embodiment, the latent image formable areas do not overlap each other, and the toners of the respective colors adhere to the surface of the photoreceptor without overlapping each other. Therefore, primary colors of yellow (Y), magenta (M), cyan (C), and black (K) can also be reproduced on the image. Also, secondary colors such as red, green, and blue can be reproduced by combining yellow (Y), magenta (M), cyan (C), and black (K) colors. Therefore, in this embodiment, it is possible to reproduce a large number of colors on the image. However, in order to reproduce many colors, it is necessary to control the amount of toner attached to each color latent image. As the control method, known methods can be widely used.
For example, the amount of toner attached to each color latent image can be controlled by changing the depth (potential contrast) of the electrostatic latent image with high resolution by PWM (pulse width modulation) in laser writing scanning. Note that PWM modulation is to control the time for turning on the laser while fixing the laser light quantity. In principle, the dot size changes, but it is possible to control the latent image depth with high resolution without changing the dot size. There is a PM (power modulation) method as another method, but there is compatibility with a photoconductor, and generally the control resolution is low.

  Thus, the color toner images are formed on the surface of the photosensitive member 1 by the toners of the respective colors adhering to the surface of the photosensitive member 1. The color toner image is conveyed to a transfer area facing the transfer device 5 by the surface movement of the photoreceptor 1. On the other hand, the transfer paper P is fed and transported to the transfer area by a paper feeding / conveying device (not shown), and is fed by a registration roller at a predetermined timing. The transfer device 5 applies a charge (positive charge) having a polarity opposite to that of the color toner image on the photoconductor 1 to the transfer paper P, whereby the color toner image formed on the photoconductor 1 is transferred to the transfer paper. Transferred to P. Next, the transfer paper P is separated from the surface of the photoreceptor 1 and sent to the fixing device 7. In the fixing device 7, the transfer paper P is sandwiched between the fixing nips, the toner is melted or softened by heat, and the color toner image on the transfer paper P is fixed to the transfer paper P by further applying pressure. The transfer paper P that has been subjected to the fixing process in this manner is discharged outside the apparatus. The surface of the photoconductor 1 after the color toner image is transferred by the transfer device 5 is cleaned by the cleaning device 6, and the toner remaining on the photoconductor 1 is removed.

FIGS. 8A to 8C are explanatory views showing the state of the toner layer attached to one latent image.
The toner in the grooves 45Y, 45M, 45C, and 45K on the developing rollers 41Y, 41M, 41C, and 41K is a minimum that constitutes a latent image that exists at the opposite position in the developing area, that is, a latent image formable area of the corresponding color. It adheres to the latent image formed in the section. Then, as the grooves 45Y, 45M, 45C, and 45K pass through the development area, as shown in FIG. 8A, the toner layer in the same state as that in the grooves adheres on the photosensitive member 1.
Thereafter, the toner layer is transferred to the transfer paper P in the transfer region. At the time of the transfer, the shape of the toner layer is slightly broken and widened as shown in FIG. As a result, the toner layer extends to the minimum section of other colors located next to it. At this time, when the other color toner is also attached to the minimum section of the other color located next to the toner, a part of the toner layer is a part of the toner layer composed of the other color toner. It will be mixed.
When the transfer paper P carrying the toner layer in such a state is subjected to a fixing process by the fixing device 7, it further spreads as shown in FIG. Thereby, the width of the toner layer is further expanded. This toner layer is melted or softened and fixed on the transfer paper P.

  As described above, in the present embodiment, each color toner adheres only to the latent image formable area of the corresponding color on the surface of the photoreceptor 1 and does not adhere to the latent image formable area of the other colors. And through the fixing process, it also spreads to locations corresponding to areas where latent images of other colors can be formed. For example, when forming a solid image of the primary color, if such a spread is small, the image portion corresponding to the latent image formable region of the other color is white, and the hue of the primary color looks light as a whole, Color reproducibility deteriorates. On the other hand, if the area is sufficiently wide as in the present embodiment, the primary color toner adheres to the image portion corresponding to the latent image formable area of the other color, and the entire image is limited to the primary color itself. The color reproducibility is improved because it is visible in near colors. Similarly, when a full color image is formed, for example, if such a spread is small, the mixing of toners among the color toners is reduced. As a result, it becomes easy to produce a rough feeling in the image. On the other hand, if the ink is sufficiently wide as in the present embodiment, different color toners attached to the adjacent latent image formable regions can be mixed with each other by the transfer process and the fixing process. As a result, an image with less roughness can be formed.

Thus, it can be said that it is preferable in terms of image quality improvement that toners of different colors are appropriately mixed. From this point of view, strictness is not required until the latent color image forming regions on the surface of the photoreceptor 1 are set so that they do not completely overlap each other. However, it should be noted that if there is an overlapping portion in a part of each color latent image formable region, in this embodiment, the color toner to be developed first adheres to the latent image in the overlapping portion. There is a need.
In addition, when forming a full-color image, in order to avoid an excessive amount of toner attached to the transfer paper P, the amount of toner attached to the latent image is controlled by changing the latent image potential. It is preferable to use a small amount.

As described above, according to the printer of this embodiment, latent images for four colors can be formed on the photosensitive member 1 at a time, and a full-color image can be formed on the transfer paper P by one transfer process.
As a full-color printer in recent years, a first method which is a one-drum type image forming apparatus adopting a so-called intermediate transfer method and a second method which is a tandem type image forming apparatus adopting a so-called intermediate transfer method are mainstream. It is. As described above, the first method has an advantage that the number of parts is smaller and the cost is lower than that of the second method, but has a disadvantage that the image forming speed is slow. Conversely, the second method has the advantage that the image forming speed is faster than the first method, but has the disadvantage that the cost increases. In contrast to these methods, the printer according to the present embodiment uses only one photoconductor as in the first method, so that it is possible to realize a cost reduction equal to or higher than that of the first method. Since the multi-color image can be formed on the transfer paper P by only rotating the photoconductor 1 for one image, an image forming speed equal to or higher than that of the second method can be realized.
Moreover, the printer of this embodiment can form a full-color image on the transfer paper P with only one transfer process. In general, the more the transfer process is, the more the toner image is disturbed and the image quality is deteriorated. Therefore, the printer can minimize the image quality deterioration due to the transfer process, and the image quality can be improved in this respect.

Further, the printer of this embodiment has an advantage that it is not necessary to align the color toner images in the sub-scanning direction, that is, the photosensitive member surface moving direction. More specifically, in the first method and the second method, since each color toner image formed on the photosensitive member is superimposed on the intermediate transfer member to form a full color image, each color toner image is accurately obtained. It is necessary to align, and this alignment is extremely difficult. On the other hand, in the printer of this embodiment, the grooves 45Y, 45M, 45C, and 45K on the developing rollers 41Y, 41M, 41C, and 41K are provided in the respective color latent image formable areas set on the surface of the photoreceptor 1. Correspondingly, if each developing roller is positioned in the main scanning direction, that is, the developing roller axial direction, positioning between the developing rollers in the sub-scanning direction is unnecessary.
On the other hand, in the printer of this embodiment, it is necessary to align the developing rollers 41Y, 41M, 41C, and 41K with high accuracy in the main scanning direction (developing roller axial direction). Therefore, in this embodiment, after assembling, the axes of the developing rollers 41Y, 41M, 41C, and 41K and the axis of the photosensitive member 1 are accurately positioned, and then these axes are aligned with a single frame made of aluminum die cast. In this way, the error in the main scanning direction (developing roller axial direction) is 0.5 [μm] or less.

Further, as a positioning method of the developing rollers 41Y, 41M, 41C, and 41K in the main scanning direction (developing roller axial direction), the following configuration can be adopted.
FIG. 9 is an explanatory diagram showing an example of a mechanism for adjusting the developing roller axial position of each developing roller 41Y, 41M, 41C, 41K.
On the side plate 8A of the printer main body located on the left side in the drawing of each developing roller 41Y, 41M, 41C, 41K, four thicknesses composed of piezo elements whose thickness (length in the left-right direction in the drawing) varies according to the applied voltage. Variable members 46Y, 46M, 46C, and 46K are attached. Power sources 47Y, 47M, 47C, and 47K are connected to the thickness variable members 46Y, 46M, 46C, and 46K, respectively, so that individual voltages can be applied to the respective thickness variable members. The variable thickness members 46Y, 46M, 46C, and 46K rotatably support one end portions of the shafts of the developing rollers 41Y, 41M, 41C, and 41K through ball bearings 48Y, 48M, 48C, and 48K, respectively. Drive gears 49Y, 49M, 49C, and 49K connected to a drive motor (not shown) are attached to the other ends of the shafts of the developing rollers 41Y, 41M, 41C, and 41K. It is supported by 8C. Springs 50Y, 50M, 50C, and 50K as biasing means are interposed between the drive gears 49Y, 49M, 49C, and 49K and the side plate 8C, and the drive gears 49Y, 49M, 49C, and 49K are moved from the side plate 8C to the side plate 8B. It is energized in the direction toward. That is, the developing rollers 41Y, 41M, 41C, and 41K are biased toward the thickness variable members 46Y, 46M, 46C, and 46K (leftward in the drawing) by the springs 50Y, 50M, 50C, and 50K.

  When the applied voltage to the thickness variable members 46Y, 46M, 46C, and 46K made of piezoelectric elements is changed, the thickness of the thickness variable member (length in the left-right direction in the figure) changes according to the change. As a result, the axial positions of the developing rollers 41Y, 41M, 41C, and 41K change. Therefore, according to this configuration, the axial directions of the developing rollers 41Y, 41M, 41C, and 41K are controlled by controlling the power supplies 47Y, 47M, 47C, and 47K that apply voltages to the developing rollers 41Y, 41M, 41C, and 41K. The position can be adjusted individually. As a specific adjustment method, for example, a linear image having a fixed interval extending in the sub-scanning direction composed of each primary color is formed on the transfer paper P as a test image. Then, by looking at the interval of the straight line images between the colors, the user or the like determines a portion that is not equally spaced, and inputs the portion using the operation panel or the like. In response to this input, a control unit (not shown) controls the power supplies 47Y, 47M, 47C, and 47K, and adjusts the axial positions of the developing rollers 41Y, 41M, 41C, and 41K so as to correct the misalignment of the places related to the input. . In particular, the control unit stores the voltage values of the power supplies 47Y, 47M, 47C, and 47K when the intervals between the linear images of the respective colors become uniform by performing such adjustment. Thus, when the power is turned on next time, the stored voltage value is read and the power supplies 47Y, 47M, 47C, and 47K are controlled, so that it is not necessary to make another adjustment.

[ Reference example ]
Next, a reference example of the above embodiment will be described.
FIG. 10 is an explanatory diagram of a latent image formable area for each color determined in advance on the surface of the photoreceptor 1 in this reference example .
Also in this reference example , in the same manner as in the above-described embodiment, a large number of latent image formable areas for each color are set on the surface of the same photoreceptor 1 so as not to overlap each other. However, in this reference example , each segment obtained by segmenting in the photosensitive member surface moving direction is set as the minimum segment of each color, and many minimum segment groups each including one minimum segment of each color are included in the photosensitive member surface moving direction. Arrange each other and set each color latent image formable area. The latent image formable area of each color is configured by all the minimum segments of the corresponding color. Further, the latent image formable areas of the respective colors are set so that they do not completely overlap each other. Settings such as the width of the minimum division of each color are the same as in the above-described embodiment.

In this reference example , grooves extending in the axial direction are formed on the surfaces of the developing rollers 41Y, 41M, 41C, and 41K so that the toners of the corresponding colors are opposed to the areas where the color latent images can be formed as described above. Form. Similar to the above embodiment, the groove corresponds to each minimum section of the corresponding color on the surface of the photoreceptor 1, and the width of the groove is set to the same width as that of the minimum section, that is, 10 [μm]. The width between the grooves is set to 30 [μm].

FIG. 11 is an explanatory diagram showing the state of toner adhering to the surface of the photoreceptor 1 when a solid image is formed.
When a solid image is formed, a latent image is formed on the entire surface of each color latent image formable region on the surface of the photoreceptor 1. Therefore, the toner of each color adheres to the entire area where the corresponding color latent image can be formed. As a result, in this reference example , as shown in FIG. 11, yellow (Y) and magenta (M) extending on the surface of the photosensitive member 1 in a direction orthogonal to the photosensitive member surface moving direction (photosensitive member axial direction). ), Cyan (C), and black (K) bands are repeatedly arranged in this order along the photosensitive body axis direction. In this case, the image formed on the transfer paper P is a black solid image.

Also in this reference example , as in the above-described embodiment, a latent image for four colors can be formed on the photosensitive member 1 at a time, and a full-color image can be formed on the transfer paper P by one transfer process. it can. Since only one photoconductor is used in the same manner as the first type printer described above, the cost can be reduced to be equal to or higher than that of the first type, and at the same time, the photoconductor 1 can be used for one image. Since an image can be formed on the transfer paper P simply by rotating it, an image forming speed equivalent to or higher than that of the above-described second type printer can be realized. In addition, the printer of this reference example can form a full-color image on the transfer paper P by only one transfer process as in the above embodiment. In general, the more the transfer process is, the more the toner image is disturbed and the image quality is deteriorated. Therefore, the printer can minimize the image quality deterioration due to the transfer process, and the image quality can be improved in this respect.
However, it should be noted that the printer of this reference example needs to be aligned in the sub-scanning direction, that is, the photosensitive member surface movement direction, unlike the above-described embodiment.

In this reference example , each segment obtained by segmenting in the photosensitive member surface movement direction is set as the minimum segment of each color, and a plurality of minimum segment groups each including one minimum segment of each color are included in the photosensitive member surface movement direction. Although arranged, the present invention is not limited to this and the above-described embodiments. Thus, for example, each segment obtained by dividing the latent image formable region into a direction inclined obliquely with respect to the photosensitive body surface moving direction is set as the minimum segment of each color, and one minimum segment of each color is included. It is possible to use a latent image formable area in which a plurality of minimum division groups are arranged in the direction of movement of the photoreceptor surface. Further, for example, a square image having a quadruple size may be combined by combining the square-shaped minimum sections of each color one by one, and a latent image formable area may be set with the square area as the minimum section group. .

As described above, the printers of the above-described embodiment and the above-described reference example are the photoreceptor 1 as the latent image carrier that moves on the surface, and the latent image forming unit that forms the latent image corresponding to each color on the surface of the same photoreceptor 1. An exposure device 3 and a developing device 4 as developing means for developing each latent image formed on the photosensitive member 1 with a corresponding color toner are formed on the surface of the same photosensitive member 1. This is an image forming apparatus that finally transfers a multi-color image onto a transfer paper P as a recording material. Then, the exposure apparatus 3 sets a large number of latent image formable areas for each color that do not overlap each other, and forms a latent image of a corresponding color for each color latent image formable area. The apparatus 4 causes each color latent image formable area to face a corresponding color toner, and attaches a corresponding color toner to each color latent image formed area in each color latent image formable area. Is to do. With such a configuration, it is not necessary to provide the photoconductor 1 for each color, so that the cost can be reduced to be equal to or higher than that of the first method, and at the same time, a color toner image can be formed on the photoconductor surface at a time. Since it can be formed, it is not necessary to rotate the photoreceptor 1 by one image for each color, and an image forming speed equal to or higher than that of the second method can be realized.
In the embodiment and the reference example , the exposure apparatus 3 can form each color latent image by arranging a plurality of minimum division groups each including one minimum division of each color constituting each color latent image formable region. Set the area. Thereby, the minimum division group can be used as a unit of color, and a higher-definition multi-color image can be formed.
Further, in the above reference example , the exposure apparatus 3 sets each section obtained by dividing in the direction of movement of the photoreceptor surface as the minimum section of each color, and sets the minimum section group including one minimum section of each color as the photoreceptor. A large number of color latent image formable areas are set by arranging them in the surface moving direction. This eliminates the need for alignment in the photosensitive member axial direction, ie, the main scanning direction, which is a direction orthogonal to the photosensitive member surface movement direction.
In the above-described embodiment, the exposure apparatus 3 sets each section obtained by dividing in the direction of the photoreceptor axis as the minimum section of each color, and sets the minimum section group including one minimum section of each color as the photoreceptor axis. A plurality of color latent image formable areas are set by arranging a large number in the direction. This eliminates the need for alignment in the photosensitive member surface movement direction, that is, the sub-scanning direction.
Further, in the embodiment and the reference example described above, the developing device 4 includes the developing rollers 41Y, 41M, 41C, and 41K as toner carrying members disposed opposite to the surface of the same photosensitive member 1, and these developing rollers. And a toner carrying control means for carrying the toner of the corresponding color at each surface portion facing the latent image formable area of the corresponding color. As a result, the toner of the corresponding color can be made to face each of the regions where the color latent images can be formed with a relatively simple configuration.
In the embodiment and the reference example , the developing device 4 includes a plurality of developing rollers 41Y, 41M, 41C, and 41K corresponding to the respective colors, and the toner carrying control unit is provided on the surface of each developing roller. The toner of the corresponding color is carried on the surface portion facing the latent image formable region of the corresponding color. By providing the developing roller corresponding to each color, the configuration can be simplified as compared with the case where each color toner is carried on a single developing roller.
In particular, the toner carrying control means is provided with grooves 45Y, 45M, 45C, 45K, which are concave portions formed in the surface portions of the developing rollers 41Y, 41M, 41C, 41K, and corresponding color toners. The developing casings 42Y, 42M, 42C, and 42K serving as toner supply means that respectively supply the entire surface, and the toner carried on the surface portions other than the grooves in contact with the surfaces of the developing rollers are removed from the surfaces of the developing rollers. If the restriction blades 43Y, 43M, 43C, and 43K are used as the removing means, the toner of the corresponding color can be opposed to each of the latent color image forming areas with a very simple configuration.
In the embodiment and the reference example , the developing device 4 is a corona as a toner charging unit that performs a charging process for increasing the charge amount of the toner carried on the surfaces of the developing rollers 41Y, 41M, 41C, and 41K. Chargers 44Y, 44M, 44C and 44K are provided. As a result, sufficiently charged toner can be fed into the development area, and good development can be performed.

In this embodiment, the case where the color toner image formed on the surface of the photosensitive member 1 is directly transferred to the transfer paper P has been described. However, after the color toner image is once transferred onto the intermediate transfer member, the intermediate transfer is performed. You may make it transfer on the transfer paper P from the body. By providing such an intermediate transfer member, the transfer area of the photosensitive member 1 and the transfer path of the transfer paper can be designed separately, and the degree of freedom in apparatus layout increases.
Further, in the present embodiment, a case has been described in which latent images of all colors are written at once by the exposure apparatus 3, but the latent image writing of each color may be performed separately for each color.
In the present embodiment, the case where the present invention is applied to a printer has been described. However, the present invention can be similarly applied to other image forming apparatuses such as a copying machine and a facsimile.

FIG. 3 is an explanatory diagram illustrating a schematic configuration of the entire printer according to the embodiment. FIG. 3 is an explanatory diagram of a latent image forming area for each color determined in advance on the surface of a photoconductor provided in the printer. 3 is a graph showing an outline of a potential distribution of one latent image formed on the surface of the photoconductor. FIG. 3 is an explanatory diagram illustrating a schematic configuration of a developing device provided in the printer. Explanatory drawing of the developing roller provided in the developing device. FIG. 3 is an explanatory diagram illustrating an example of a relative arrangement of developing rollers for each color. FIG. 4 is an explanatory diagram illustrating a state of toner that adheres to the surface of a photoreceptor when a solid image is formed. (A) thru | or (c) is explanatory drawing which shows the mode of the toner layer adhering to one latent image. FIG. 3 is an explanatory diagram illustrating an example of a mechanism for adjusting the position of each developing roller in the axial direction of the developing roller. FIG. 6 is an explanatory diagram of areas where latent images can be formed for each color determined in advance on the surface of a photoconductor in a reference example . FIG. 4 is an explanatory diagram illustrating a state of toner adhering to the surface of a photoreceptor when a solid image is formed in a reference example .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 3 Exposure device 4 Developing device 5 Transfer device 6 Cleaning device 7 Fixing device 8A, 8B, 8C Side plate 40Y, 40M, 40C, 40K Developer 41Y, 41M, 41C, 41K Developing roller 42Y, 42M, 42C , 42K Development casing 43Y, 43M, 43C, 43K Regulating blade 44Y, 44M, 44C, 44K Corona charger 45Y, 45M, 45C, 45K Groove 46Y, 46M, 46C, 46K Thickness variable member 47Y, 47M, 47C, 47K Power supply 48Y, 48M, 48C, 48K Ball bearing 49Y, 49M, 49C, 49K Drive gear 50Y, 50M, 50C, 50K Spring

Claims (3)

A latent image carrier that moves on the surface;
Each segment obtained by segmenting the latent image carrier surface in the direction orthogonal to the moving direction of the latent image is defined as a minimum segment of each color, and a minimum segment group including one minimum segment of each color is defined in the orthogonal direction. the number and sequence, set each Irosen image formable region in the surface of the same latent image bearing member, a latent image forming that form a latent image corresponding to each color for respective Irosen image formable region Means,
A plurality of toner carriers corresponding to the respective colors are arranged along the surface movement direction of the latent image carrier so as to face the surface of the same latent image carrier, and face the corresponding latent image formable region. A concave portion is formed on the surface portion of each toner carrier, and the corresponding color toner is supplied to the entire surface of each toner carrier by the toner supply means, and the removing means is in contact with the surface of each toner carrier. By removing the toner carried on the surface portion other than the concave portion from the surface of the respective toner carrier by the above , a latent image of each color formed in each color latent image formable region on the same latent image carrier And developing means for developing the toner with the corresponding color toner carried on each toner carrier ,
In an image forming apparatus for finally transferring a multi-color image formed on the surface of the same latent image carrier onto a recording material,
By displacing each toner carrier along a direction orthogonal to the moving direction of the latent image carrier surface, the concave portion of the corresponding color toner carrier is opposed to each of the color latent image formable regions. An image forming apparatus having an adjusting means for adjusting the image.   The image forming apparatus according to claim 1.
  The adjusting means controls the voltage applied to the thickness variable member whose thickness changes in accordance with the applied voltage, thereby displacing each toner carrier along a direction orthogonal to the surface movement direction of the latent image carrier. An image forming apparatus. The image forming apparatus according to claim 1 or 2 ,
The image forming apparatus according to claim 1, wherein the developing unit includes a toner charging unit that performs a charging process for increasing a charge amount of the toner carried on the surface of each toner carrier .

Images