JP4961974B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which the cleaning performance of an image forming unit can be improved, the image forming unit capable of being made compact and having an image carrier larger than those of the other image forming units. <P>SOLUTION: Each of the image forming units includes: the image carrier; a means for transferring a toner image formed on the surface of the image carrier to a transfer body; a cleaning member disposed in contact with the image carrier and used for cleaning off residual toner after the transfer; and an optical destatisizing means for removing charges on the surface of the image carrier after the transfer. The image carrier of some of the image forming units is larger than the image carriers of the other image forming units. Some of the image forming units have the optical destatisizing means at positions from their transfer positions to the disposed positions of the cleaning members on the rotating path of the surfaces of the image carriers. Each of the other image forming units has an optical destatisizing means at a position from the disposed position of the cleaning member to its transfer position on the rotating path of the surface of the image carrier. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a color image forming apparatus, and more particularly to an image forming apparatus in which some image carriers have a larger configuration than other image image carriers.

  The tandem color image forming apparatus includes color (yellow, magenta, cyan) image forming units and monochrome (black) image forming units, and each image forming unit includes a photosensitive drum. A charging device, an exposure device, a developing device, and the like. In recent years, with the miniaturization of image forming apparatuses, miniaturization of image forming units is required. However, when all photosensitive drums have the same size, monochrome is used more frequently than color. Therefore, the monochrome photosensitive drum is more likely to deteriorate faster than the color photosensitive drum. Therefore, from the viewpoint of suppressing the deterioration, a technique for making the diameter of the monochrome photosensitive drum 911K larger than the diameters of the other photosensitive drums 911Y to 911C as shown in the schematic diagram of FIG. (For example, patent document 1).

In the image forming apparatus having the above-described configuration, the photosensitive drums 911Y to 911K are rotationally driven to form corresponding color toner images on the surfaces of the photosensitive drums 911Y to 911K, and these toner images are formed on the intermediate transfer belt 91a. A step of performing multiple transfer and outputting to a recording medium is performed. In this step, the toner may remain on the photosensitive drums 911Y to 911 after transfer. Therefore, cleaning members 916Y to 916K for cleaning residual toner are arranged in the respective image forming units 910Y to 910K to remove the residual toner. However, since the cleaning members 916Y to 916K are arranged so that the front ends thereof are in contact with the photosensitive drums 911Y to 911K, the cleaning members 916Y to 916K and the photosensitive drums 911Y to 911K are rotated by the rotation of the photosensitive drums 911Y to 911K. Deteriorate due to wear or the like. Therefore, the above-described deterioration is suppressed by applying a lubricant to the surface of each photosensitive drum (for example, Patent Document 2).
JP 2000-242057 A JP 2005-70274 A

However, the monochrome image forming unit 910K using the photoconductor drum 911K having a large diameter as in Patent Document 1 has a streak shape or a certain period when outputting an image, compared to the color image forming units 910Y to 910C. It was confirmed that noise such as sunspots was conspicuous. As a result of examination of this phenomenon by the present inventors, it has been found that there are the following factors.
That is, the monochrome image forming unit 910K has a higher residual toner generation rate first, and second, the cleaning member 916K changes the frictional force generated by the rotation of the photosensitive drum 911K, thereby causing the surface of the photosensitive drum. This is considered to be caused by the phenomenon that the phenomenon of so-called stick-slip phenomenon is easily generated.

More specifically, since the monochrome photosensitive drum 911K has a large diameter and a small curvature, the nip width corresponding to the transfer position S1 shown in the schematic diagram of FIG. For this reason, the ratio of toner that is electrically affected during transfer increases, and residual toner is more likely to be generated than the color image forming units 910Y to 910C.
Even when a lubricant is used as in Patent Document 2, a certain amount of time is required from the start of use (start of rotation of the photosensitive drum) until the effect of suppressing the frictional force is exhibited. Thus, it was found that the monochrome image forming unit 910K requires more time than the color image forming units 910Y to 910C. This is presumably because the monochrome photosensitive drum 911K has a large diameter, and monochrome requires more time to rotate until the lubricant becomes familiar. Therefore, the monochrome image forming unit 910K has a higher frictional force until a predetermined time, and the stick-slip phenomenon is likely to occur.

  Therefore, as shown in FIG. 13B, when the negative charge N1 remaining on the surface of the monochrome photosensitive drum 911K passes the cleaning position by the cleaning member 916K, the residual toner P1 cleaned by the negative charge N1 is removed. Adsorption and slipping through the cleaning member 916K due to the stick-slip phenomenon are likely to occur. In the color image forming units 910Y to 910C having the small-diameter photosensitive drums 911Y to 911C, the image quality is hardly lowered due to the above factors.

Although the description of the problem is limited to the photosensitive drum, the above-described content also exists in the belt-shaped photosensitive body, and these are problems common to so-called image carriers.
The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of realizing downsizing and improving the cleaning performance in an image forming unit having an image carrier having a larger configuration than the others. And

Therefore, the present invention adopts the following configuration in order to solve the above problems.
An image forming apparatus for forming a color image by multiply transferring toner images of respective colors formed by a plurality of image forming units onto a transfer target, wherein each of the plurality of image forming units includes an image carrier and A charging means for charging the surface of the image carrier, a transfer means for transferring a toner image formed on the surface of the image carrier to be driven in rotation, to the transfer target, and a residual after transfer. A cleaning member that cleans the toner, and an optical charge eliminating unit that removes the charge on the surface of the image carrier after the transfer, and some of the image forming units have a diameter larger than that of the image carrier in the other image forming units. In some of the image forming units, a light neutralizing unit is disposed between the transfer position on the rotation driving path on the surface of the image carrier and the position where the cleaning member is disposed. In the image forming unit, the image carrier And a light discharging device is disposed from the installation position of the cleaning member until the charging means on the orbiting drive path surface.

In the image forming apparatus, the cleaning member of the part of the image forming units is supported by a rotatable support member that is elastically biased, and the cleaning member of the other image forming unit is supported by a fixed support member. The configuration is as follows.
In addition, in some of the image forming units, a light discharging unit that is different from the light discharging unit is further disposed between the position where the cleaning member is disposed on the rotation driving path on the surface of the image carrier and the charging unit. It can also be set as the structure currently made.

Each of the cleaning members is supported by a support member at the base end, and is not supported by the support member among the cleaning members of the partial image forming units in the direction from the base end to the tip. The length of the portion may be shorter than the length of the other image forming unit.
Further, the cleaning member in the part of the image forming units may be configured such that a base end portion is supported by a metal support member, and the support member is grounded.

In addition, a voltage applying unit that applies a voltage to the support member is provided between connection paths until the support member is grounded, and each of the image forming units includes a charging unit that charges the surface of the image carrier. In addition, a voltage having a polarity opposite to the charged polarity of the surface of the image carrier in the partial image forming unit may be applied to the support member by the voltage applying unit.
Further, the part of the image forming units may be a monochrome image forming unit, and the other image forming unit may be a color image forming unit.

  According to the present invention, if the image forming unit having a frequently used color is the above-mentioned part of the image forming units, the light discharging means is disposed between the transfer position and the cleaning member disposition position. The charge on the image carrier can be removed before reaching the cleaning member. Such removal can reduce the adhering of the cleaned residual toner to the image carrier and suppress the generation of the noise that causes the image quality to be lowered.

On the other hand, in the other image forming unit, there is little noise generation that can be visually recognized because the image carrier is small, and by disposing a static eliminator between the cleaning member disposition position and the transfer position, It is possible to stabilize the potential of the image carrier and to meet the expectation of downsizing the image forming unit.
Therefore, while reducing the size of the entire image forming apparatus, it is possible to extend the life of some of the image forming units that are frequently used to the same level as other image forming units and to improve the cleaning performance. .

Further, in some image forming units, when the cleaning member is supported by a rotatable support member that is elastically biased, the cleaning member is caused by friction with the surface of the image carrier as time passes. Even when worn, the state of being elastically contacted with the surface of the image carrier can be maintained. Therefore, if the image forming unit with a frequently used color is the above-mentioned part of the image forming unit, the cleaning member is expected to be worn more severely than the other image forming units, but the service life can be ensured for a long period of time. As a result, it is possible to match the service life of other image forming units. In addition, in some of the image forming units, in addition to the above-described position, the cleaning member is disposed between the position where the cleaning member is disposed and the transfer position. However, if a configuration in which another static eliminator is provided, the cleaning performance is further improved. Such a configuration can be realized because the part of the image forming units has a large image carrier, and the restriction on the surrounding arrangement area is smaller than that of the other image forming units.

  Each of the image forming units includes a cleaning member having a base end portion supported by a support member, and among the cleaning members according to some of the image forming units, in a direction from the base end portion toward the tip end portion. The length of the portion not supported by the support member is set to be shorter than the length related to the other image forming unit. By setting in this way, since the distance to the support part serving as a fulcrum is short with respect to the tip part (operation point) of the cleaning member, vibration of the cleaning member based on the stick-slip phenomenon can be reduced.

  In addition, since the support member is made of metal and grounded, electric charges accumulated with time due to friction with the image carrier can be discharged. This suppresses discharge that may occur between the image carrier, the cleaning member, and the support member. As a result, it is possible to suppress the phenomenon that the residual toner adhering to the cleaning member adheres to the image carrier electrically and mechanically due to the influence of the discharge, and further improves the cleaning performance in the image forming unit. Further, in the grounded connection circuit, by providing a voltage application means for applying a voltage having a polarity opposite to the charge that can be accumulated as described above, the residual toner similarly adheres to the image carrier. The phenomenon can be suppressed.

  Furthermore, by using some of the image forming units for monochrome and the other image forming units for color, the service life of the frequently used monochrome image forming units can be reduced to the service life of the color image forming units. And the cleaning performance of the monochrome image forming unit can be improved.

Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings, taking a tandem color printer (hereinafter simply referred to as “printer”) as an example.
[First embodiment]
<Overall configuration>
FIG. 1 is a schematic diagram of the overall configuration of the printer 100. The printer 100 includes an image process unit 1, a feeding unit 2, a fixing unit 4, and a control unit 6. In the printer 100, the control unit 6 is connected to a network, in this embodiment, a LAN, and executes image formation based on a print instruction from an external terminal device (not shown).

  The image processing unit 1 is stretched between image forming units 10Y to 10K corresponding to yellow (Y), magenta (M), cyan (C), and black (K) colors, a driving roller 1c, and a backup roller 1d. , An endless intermediate transfer belt 1a rotated in the direction of arrow A is provided. The residual toner on the intermediate transfer belt 1a is electrically and mechanically removed by the transfer belt cleaning device 1b disposed in a part of the rotation path of the intermediate transfer belt 1a.

The four types of image forming units 10Y to 10K include three types of color image forming units (hereinafter referred to as “color image forming units”) 10Y to C, and the remaining one type of image forming unit for monochrome ( (Hereinafter referred to as “monochrome image forming unit”). The configuration of these image forming units 10Y to 10K will be described later.
The feeding unit 2 includes a sheet feeding cassette 21 that accommodates a sheet S that is a recording medium, a pickup roller 22 that feeds out the sheet S from the cassette 21, a conveyance roller pair 31 that conveys the fed sheet S, and a sheet. A timing roller pair 32 for taking the timing of sending S to the secondary transfer position 3a, a secondary transfer roller 33 disposed opposite to the backup roller 1d with the intermediate transfer belt 1a interposed therebetween, and the like are provided.

The fixing unit 4 has a configuration in which a fixing roller 41 having an internal heater and a pressure roller are arranged to face each other.
In such a configuration, when a print instruction is received, a toner image of each color is formed by the image forming units 10Y to 10K, and each formed toner image is transferred (primary transfer) to the intermediate transfer belt 1a. Each color toner image transferred to the intermediate transfer belt 1a moves to the secondary transfer position 3a as the intermediate transfer belt 1a rotates. Along with the movement of each color toner image, the sheet S is conveyed to the secondary transfer position 3a via the timing roller pair 33, and each color toner image on the intermediate transfer belt 1a is transferred to the secondary transfer position 3a. The images are collectively transferred onto the sheet S. The sheet S that has passed the secondary transfer position 3 a is conveyed to the fixing unit 4, where the toner image is fixed on the sheet S by heating and pressurization in the fixing unit 4, and is discharged outside the apparatus via the discharge roller pair 5. .
<Configuration of image forming unit>
Each of the color image forming units 10Y to 10C has the same configuration except only the toner. The basic structure of the monochrome image forming unit 10K is the same as that of the color image forming units 10Y to 10C. However, there is a difference in the structure of the cleaning device and the arrangement position of the light neutralizing device, compared with the large drum diameter of the photosensitive member. There is. The configuration of each of the image forming units 10Y to 10K will be described with reference to the schematic diagram of FIG.
<Color image forming units 10Y, 10M, 10C>
The color image forming units 10Y to 10C have charging devices 12Y to C, exposure devices 13Y to C, developing devices 14Y to C, primary transfer rollers 15Y to C, and cleaning devices 16Y to C around the photosensitive drums 11Y to 11C. In this configuration, the photostatic devices 17Y to 17C are arranged in this order.

The photosensitive drums 11Y to 11C have a cylindrical shape with an outer diameter of 30 mm, a photosensitive layer (not shown) is formed on the surface, and are driven to rotate in the direction of arrow B.
The charging devices 12Y to 12C charge the surfaces of the photosensitive drums 11Y to 11C to a predetermined potential.
The exposure devices 13Y to 13C irradiate the surfaces of the photoconductive drums 11Y to 11C with light, thereby reducing the charge level in the irradiated area to form an electrostatic latent image.

The developing devices 14Y to 14C supply toner to the electrostatic latent images on the surfaces of the photosensitive drums 11Y to 11C to form toner images. The toner contains a material called a lubricant including zinc stearate. The content of zinc stearate is preferably about 0.1 to 0.5% / weight with respect to the toner.
The primary transfer rollers 15Y to 15C are arranged to face the photoconductive drums 11Y to 11C with the intermediate transfer belt 1a interposed therebetween, and toner is formed at a nip portion between the primary transfer rollers 15Y to 15C and the photoconductors 11Y to 11C. The image is transferred to the intermediate transfer belt 1a.

The cleaning devices 16Y to 16C clean the toner remaining on the peripheral surface of the photosensitive drum by scraping the cleaning blades 161Y to 161C having their tips in contact with the peripheral surfaces of the photosensitive members 11Y to 11C and the scraped toner. It consists of housings 164Y to 164C that contain particles.
FIG. 2B shows a mounting structure of a cleaning blade (hereinafter, referred to as “cleaning member”) 161C, which is attached to a support bar 165C that is installed and fixed in a housing 164C via a bracket 162C. It is worn. The other cleaning members 161Y and 161M are also attached with the same configuration.

The photostatic devices 17Y to 17C have a function of irradiating the surfaces of the photoconductive drums 11Y to 11C with light to remove charges on the surfaces and thereby stabilize the surface potential. In the present embodiment, a light emitting diode (LED) that performs red light output (wavelength: 500 to 800 nm) is used as a light source. However, other light neutralizing means may be applied as long as residual charges can be removed. it can.
<Monochrome image forming unit 10K>
The monochrome image forming unit 10K has a configuration in which a charging device 12K, an exposure device 13K, a developing device 14K, a primary transfer roller 15K, a light neutralizing device 17K, and a cleaning device 16K are arranged in this order around the photosensitive drum 11K.

The photosensitive drum 11K has a cylindrical shape with an outer diameter of 60 mm, and has a larger diameter than the photosensitive drums 11Y to 11C of the color image forming units 10Y to 10C. Since the diameter is larger than that of the color image forming units 10Y to 10C, even when the monochrome image forming unit 10K is used frequently, the number of rotations can be reduced and deterioration due to wear or the like at the cleaning position can be suppressed.
Except for the cleaning device 16K, the configuration of the charging device 12K, the exposure device 13K, the developing device 14K, the primary transfer roller 15K, and the light neutralizing device 17K is the same as that of the color image forming units 10Y to 10C, and thus the description thereof is omitted. To do. However, since the light neutralizing device 17K is different from the other image forming units 10Y to 10C in the arrangement position, this point will be described.

As shown in FIG. 2C, the cleaning device 16K is configured by attaching a cleaning member 161K to an L-shaped member 162K that is elastically biased in the direction of arrow A3 by a tension spring 163K. The L-shaped member 162K is rotatably supported around a shaft 166K supported by the housing 164K.
According to this configuration, even when the cleaning member 161K wears due to friction with the circumferential surface of the photosensitive drum as the usage time elapses, the cleaning member 161K is not separated from the surface of the photosensitive drum 11K, and is not affected by the elastic force of the tension spring 163K. The cleaning member 161K is always in elastic contact with the circumferential surface of the photosensitive drum 11K. Accordingly, if an elastic member having an appropriate elastic force is selected as the tension spring 163K, the cleaning member 161K can always be brought into contact with the circumferential surface of the photosensitive drum 11K with an appropriate contact force even if wear is slightly advanced. This means that the monochrome photosensitive drum 11K is used more frequently than the other photosensitive drums 11Y to 11C, and accordingly, the cleaning member 161K is expected to be more worn than the color cleaning members 161Y to 161C. However, the structure mainly composed of the tension spring 163K can ensure a long service life, and as a result, can match that of the color cleaning members 161Y to 161C.

Next, as shown in FIG. 2A, the monochromatic light neutralizing device 17K is arranged in a region from the transfer position to the cleaning position by the cleaning member 161K along the rotation direction of the photosensitive drum 11K. Yes. By arranging the optical static elimination device 17K in this way, the generation of noise described in the section “Problems to be solved by the invention”, specifically, the suppression of noise generation due to each factor shown in FIGS. That is, the surface of the photosensitive drum 11K is exposed in the exposure process to form a latent image (dotted line portion in FIG. 3A), and the latent image is developed with the toner T1 in the development process (FIG. 3). (B)) In the transfer step, the negative toner T1 is transferred onto the intermediate transfer belt 1a by an electrostatic force based on the application of a positive voltage (transfer voltage application) to the intermediate transfer belt 1a.

  Although it is desirable that all the toner on the photosensitive drum 11K is transferred to the intermediate transfer belt 1a, in practice, a part of the toner remains on the photosensitive drum 11K and remains as a residual toner P1 (FIG. 3C). It becomes. The inventors investigated the characteristics of the residual toner P1 and obtained the results shown in FIG. This figure is a graph showing the charge polarity ratio of the residual toner amount cleaned. From this graph, it can be seen that the residual toner for monochrome (“Black” graph in the figure) has a higher positive polarity ratio than the residual toner for color (“Color” graph in the figure). This is probably because the monochrome photosensitive drum 11K has a small curvature and the transfer region, so-called nip width, is larger than the color photosensitive drums 11Y to 11C.

  Next, the negative charge N1 before the primary transfer (FIG. 5A) may remain on the surface of the photosensitive drum 11K without being completely removed at the transfer position S1 (FIG. 5B). The residual toner P1 having a positive polarity is attracted to the photosensitive drum 11K at the cleaning position by the charge N1. Further, when executing a job to continuously print out a plurality of sheets S, the Nth sheet is formed on the surface of the photosensitive drum 11K if the charging device is kept charged from the start to the end of the job. The non-image forming area corresponding to the area between the trailing edge of the sheet S and the leading edge of the (N + 1) th sheet S is also charged, and the negative charge N1 charged in the non-image forming area is charged. May remain up to the cleaning position.

  When the adsorption by the remaining negative charge N1 and the stick-slip phenomenon occur, the residual toner P1 passes through the cleaning member 161K and causes noise. The stick-slip phenomenon is more likely to occur in the monochrome image forming unit 10K than in the color image forming units 10Y to 10C even when the lubricant according to Patent Document 2 is used. This can be understood from the results of FIG.

  FIG. 6 is a graph showing the change with time of the frictional force with the cleaning member on the photosensitive drum from when it was first used when the photosensitive drum was new. It can be seen that in the black color, the frictional resistance is increased from the start of use to the output of about 2000 sheets as compared to the color. Since the stick-slip phenomenon is likely to occur when the frictional force is large, it can be said that the stick-slip phenomenon is more likely to occur in black (monochrome) than in color. The reason why the frictional resistance is large is considered that the monochrome photosensitive drum 11K has a large diameter, so that it takes more time (number of output sheets) than the color for the lubricant to fit on the photosensitive drum 11K.

  As described above, the generation of noise is largely caused by the remaining negative charge. Therefore, in the present embodiment, as shown in the schematic diagram of FIG. 7, the monochrome image forming unit 10K is moved from the transfer position to the cleaning position. The negative charge on the photosensitive drum 11K is removed before the cleaning position is reached (corresponding to the dotted line portion in the figure) by disposing the photostatic discharger 17K until the cleaning position. As a result, it is possible to prevent the generation of electrostatic force that attracts the residual toner P1 to the photosensitive drum 11K, and noise due to the residual toner P1 is suppressed. Therefore, by increasing the diameter of the monochrome photosensitive drum 11K, it is possible to improve the cleaning performance of the monochrome image forming unit 10K while extending the life of the photosensitive drum 11K.

Further, as described above, the color image forming units 10Y to 10C are less likely to cause the stick-slip phenomenon than the monochrome image forming unit, and hardly cause noise until the user can visually recognize. Therefore, it can be said that there are fewer restrictions on the arrangement positions of the photostatic devices 17Y to 17C than the monochrome image forming unit 10K.
On the other hand, since the photosensitive drums 11Y to 11C have a smaller diameter than that for monochrome use, the area between the cleaning device and the intermediate transfer belt 1a is narrower than that for the monochrome image forming unit 10K (FIG. 2A). See). For this reason, if the color image forming units 10Y to 10C are disposed at the same positions as those for monochrome, the size of the color image forming units 10Y to 10C is increased. Further, there is a possibility that the light neutralization devices 17Y to 17C come into contact with the intermediate transfer belt 1a.

  In addition, the intermediate transfer belt 1a, with the backup roller 1d as a fulcrum, a first position (color image forming mode) where the intermediate transfer belt 1a contacts with all the photosensitive drums 10Y to 10K, the intermediate transfer belt 1a and the photosensitive member. In an apparatus configured to be movable between a second position (monochrome image forming mode) in which only the drum 10K is in contact and the other photosensitive drums 10Y to 10C are separated, the first position is changed from the second position. When returning to step S1, it is possible that the intermediate transfer belt 1a is bent or vibrated and contacts the photostatic devices 17Y to 17C.

Therefore, for the color use, the photostatic devices 17Y to 17C are arranged between the cleaning position and the charging device, thereby reducing the size of the color image forming units 10Y to 10C and the surface potential of the photosensitive drums 11Y to 11C. Both stabilization is realized.
[Modification of First Embodiment]
In the present embodiment, in addition to the above-described configuration, a modification in which a configuration described below is added may be employed. This modification is different only in the arrangement of the monochromatic light neutralizing device, and the difference will be described with reference to the schematic diagram of FIG.

  As shown in FIG. 8, two photostatic devices 171 </ b> K and 172 </ b> K are arranged in the monochrome image forming unit 101 </ b> K according to this modification. The first light static eliminator 171K is disposed at the same position as the above-described light static eliminator 17K, and the second light static eliminator 172K is arranged from the position where the cleaning device 16K is disposed in the rotation direction of the photosensitive drum to the charging device 12K. It is arranged in the area up to the arrangement position.

By the second light neutralizing device 172K, the negative charge removal performance on the surface of the photosensitive drum 11K is enhanced, and the cleaning performance can be further improved along with the potential stability of the photosensitive drum 11K.
[Second Embodiment]
Next, a configuration of the printer 100 different from that of the first embodiment will be described. Since this embodiment is different from the first embodiment only in the configuration of the cleaning device, the difference will be described with reference to the schematic diagram of FIG. In addition, the same component as 1st Embodiment is described with the same code | symbol.

  As shown in FIG. 9, the cleaning members 261 </ b> Y to 261 </ b> K are all supported at the base ends by the support members. The supporting state is the same for the color image forming units 102Y to 102C, but is different for the monochrome image forming unit 102K. Hereinafter, a cyan image forming unit 102C and a monochrome image forming unit 102K will be described with reference to FIGS. 9B and 9C as representative examples of the color image forming units 102Y to 102C. FIG. 9B is a schematic diagram of the main part of the cyan image forming unit 102C, and FIG. 9C is a schematic diagram of the main part of the monochrome image forming unit 102K.

As shown in both figures, the relationship between the free end length Lc of the cyan cleaning member 261C and the free end length Lk of the monochrome cleaning member 261K is Lc> Lk. As a preferable example of the free end lengths Lc and Lk, Lc can be about 10 to 12 mm, and Lk can be about 8 to 9 mm. The cleaning member 261C, 261K is an elastic body, and the length of the portion (free end) that is not supported by the support member is different for color and monochrome use, and the photosensitive drum 11C, Since it is arranged in the counter direction with respect to the rotation direction of 11K, it receives a frictional force with the photoconductive drums 11C and 11K, and the free end length portion is likely to be shaken during the rotation of the photoconductive drums 11C and 11K. When such vibrations occur, the free end lengths Lc and Lk perform minute periodic motions with the joints between the cleaning members 261C and 261K and the support members 162C and 162K as fulcrums (center points), and the tip portion 61Ca 61Ka moves slightly. The longer the free end length, the greater the swing width and the frictional force will fluctuate, leading to the stick-slip phenomenon. For this reason, the free end length Lk is set short for monochrome only, and the movement is reduced. This is intended to suppress the slip phenomenon. Note that if the free end length is shortened, the variation range of the abutting force with respect to the variation in the free end length may increase, and therefore the free end length Lc for the color photosensitive drum 11C having a small diameter is formed for monochrome. It is set longer than the free end length Lk of the unit 102K.
[Third embodiment]
This embodiment is different from the first embodiment only in the configuration of the cleaning device 36K. Hereinafter, the difference will be described with reference to FIG. FIG. 10 is a schematic diagram of the monochrome image forming unit 103K according to the present embodiment, and the same members as those in the first embodiment are denoted by the same reference numerals.

The cleaning member 161K is supported by a metal support member 362K, and the support member 362K is grounded by a ground circuit 361K. The reason for this grounding configuration is to prevent the cleaning member 161K from accumulating charges generated by friction with the rotating photosensitive drum 11K.
That is, as shown in the schematic diagram of the main part of FIG. 10B, positive charge is accumulated in the cleaning member 161K due to friction with the negative photosensitive drum 11K, and the accumulation proceeds as the accumulation proceeds. As described above, a discharge may occur between the negative charge on the surface of the photosensitive drum 11K and the positive charge accumulated in the cleaning member 161K (corresponding to a white arrow in the figure). When such a discharge occurs, the residual toner P12 that passes through the cleaning member 161K and adheres to the back surface portion 161Kb of the cleaning member 161K facing the photosensitive drum 11K is mechanically and electrically separated from the cleaning member 161K. There is a case where noise occurs due to adhesion to the surface of the photosensitive drum 11K.

In the present embodiment, by providing the ground circuit 361K, generated charges are discharged to the outside, and the occurrence of noise is suppressed by suppressing the occurrence of the discharge.
In addition, for example, when a monochrome image is formed by using only the monochrome image forming unit in the movable configuration described in the first embodiment, the driving of the color photosensitive drums 11Y to 11C is stopped. Similarly, it is desirable to provide the ground circuit 361K. In this configuration, as the monochrome usage frequency increases, the monochrome image forming unit 103K has a longer drive time than the color image forming units 10Y to 10C. Therefore, the monochrome cleaning member 161K is compared with the color cleaning unit 161K. This is because charges are easily accumulated. For color, considering that the amount of residual toner adhering to the back surface of the cleaning member is small and the amount of charge accumulation is small in terms of frequency of use, it should be grounded if there is no effect on image quality. The circuit may not be provided, and a grounding circuit may be provided to further improve the image quality.

Further, as shown in the schematic diagram of FIG. 11, if the circuit configuration 363K is such that the ground circuit 3632K of the cleaning member 161K is connected to the circuit 3631K for grounding the rotating shaft of the photosensitive drum 11K, the discharge is similarly suppressed. In addition, the grounding circuit can be simplified.
Further, as shown in the schematic diagram of FIG. 12, the support member 462K includes a circuit 461K provided with a voltage applying unit that applies a voltage having a polarity opposite to the charging polarity (here, negative polarity) of the photosensitive drum 11K. Even in the configuration, the same cleaning performance can be improved. In addition, since the voltage application means for applying a negative voltage to the support member 462K does not improve the cleaning performance, the positive voltage can be applied to the support member 462K as described above. .

Although the configuration is the same as that of the first embodiment except for the installation of the ground circuit and the voltage application unit, the configuration according to the second embodiment may be applied.
<Other matters>
(1) In each of the above embodiments, the support structure of the cleaning member is different for monochrome and color, but the present invention is not limited to this, and a structure suitable for each color is taken based on the frequency of use and the like. It is good.

(2) In addition, the light static eliminator according to the color image forming unit and the second light static eliminator according to the modification of the first embodiment are moved from the cleaning position to the transfer position along the rotation direction of each photosensitive drum. However, there is no limitation as long as there is no problem with the charging process, the exposure process, and the development process. For example, it can be arranged between the developing device and the transfer position. Let's go.
(3) In each embodiment, only the monochrome photosensitive drum 11K is configured to have a large diameter. However, the configuration is not limited to one, and a part of the entire image forming unit within a range in which the size can be reduced. The image forming unit may have a large photosensitive drum.

(4) Further, in this embodiment, an optical static eliminator using an LED as a light source is used as the static eliminator for removing the electric charge charged on the photosensitive drum. However, an optical static eliminator using tungsten or organic EL as a light source is used. It can also be used.
Further, in each of the embodiments described above, the description is limited to the photosensitive drum. However, the above-described content also exists in the belt-shaped photosensitive body, and these are problems common to the so-called image carrier. The same can be applied to a belt-shaped photoreceptor.

  The present invention is applicable to an image forming apparatus having an image forming unit having a configuration in which a cleaning member is in contact with an image carrier image.

1 is a schematic diagram illustrating an overall configuration of a printer according to a first embodiment. FIG. 3 is a schematic diagram showing each image forming unit according to the first embodiment. FIG. 3 is a schematic diagram of an image forming unit showing toner transfer. 6 is a graph showing the polarity of cleaned residual toner. It is a schematic diagram of an image forming unit showing a process in which residual toner is adsorbed. It is a graph which shows the time-dependent change of the friction coefficient in the photoreceptor drum surface from the printer use start. FIG. 3 is a schematic diagram of an image forming unit showing electric charges on the photosensitive drum according to the first embodiment. It is a schematic diagram which shows the monochrome image formation unit which concerns on the modification of 1st Embodiment. It is a schematic diagram which shows each image formation unit which concerns on 2nd Embodiment. It is a schematic diagram which shows the monochrome image formation unit which concerns on 3rd Embodiment. It is a schematic diagram of the monochrome image formation unit which concerns on the 1st modification of 3rd Embodiment. It is a schematic diagram of the monochrome image formation unit which concerns on the 2nd modification of 3rd Embodiment. It is a schematic diagram which shows each image forming unit which concerns on the conventional embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image process part 2 Feeding part 4 Fixing part 10Y, 10M, 10C, 10K Image forming unit 11Y, 11M, 11C, 11K Photosensitive drum 12Y, 12M, 12C, 12K Charging device 13Y, 13M, 13C, 13K Exposure device 14Y , 14M, 14C, 14K Developing device 15Y, 15M, 15C, 15K Primary transfer roller 16Y, 16M, 16C, 16K Cleaning device 17Y, 17M, 17C, 17K Photostatic device 100 Image forming device

Claims (7)

An image forming apparatus for forming a color image by multiply transferring toner images of respective colors formed by a plurality of image forming units onto a transfer target,
Each of the plurality of image forming units is
An image carrier, a charging unit for charging the surface of the image carrier, a transfer unit for transferring a toner image formed on the surface of the image carrier to be driven in rotation to the transfer target, and the image carrier. A cleaning member that cleans the residual toner after the transfer, and a light neutralizing means that removes the charge on the surface of the image carrier after the transfer,
Some image forming units include an image carrier having a larger diameter than the image carrier in the other image forming units,
In some of the image forming units, a light neutralizing unit is disposed between the transfer position on the rotation driving path on the surface of the image carrier and the position where the cleaning member is disposed.
In the another image forming unit, an optical charge eliminating unit is disposed between the position where the cleaning member is disposed on the rotation driving path on the surface of the image carrier and the charging unit . The cleaning member of the part of the image forming units is supported by an elastically biased and rotatable support member,
The image forming apparatus according to claim 1, wherein the cleaning member of the other image forming unit is supported by a fixed support member. In some of the image forming units, a light discharging unit different from the light discharging unit is further arranged between the position where the cleaning member is disposed on the rotation driving path on the surface of the image carrier and the charging unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. Each of the cleaning members is supported at the base end portion by the support member,
In the direction from the base end to the tip, the length of the cleaning member of the partial image forming unit that is not supported by the support member is longer than the length of the other image forming unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is short. The cleaning member in the partial image forming unit has a base end supported by a metal support member,
The image forming apparatus according to claim 1, wherein the support member is grounded. Between the connection paths until the support member is grounded, voltage application means for applying a voltage to the support member,
Each of the image forming units has charging means for charging the surface of the image carrier,
6. The image forming apparatus according to claim 5, wherein a voltage having a polarity opposite to a charging polarity of the surface of the image carrier in the partial image forming unit is applied to the support member by the voltage applying unit. apparatus. The part of the image forming unit is a monochrome image forming unit,
The image forming apparatus according to claim 1, wherein the other image forming unit is a color image forming unit.

Images