JP2003280320A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a temperature difference generated between photosensitive drums without using a heater nor a fan, etc., for what is called a tandem type image forming device. <P>SOLUTION: A temperature sensor 11 which detects respective surface temperatures is provided for four photosensitive drums 20. The maximum temperature difference among the respective photosensitive drums is found from the detection results of the temperature sensors and when the value exceeds a specified temperature difference, a control part 12 drives the photosensitive drums and an intermediate transfer belt 10 in contact with each other while inhibiting image forming operation from being carried out. Consequently, each photosensitive drum and the intermediate transfer belt exchange heat energy and the surface temperature of each photosensitive drum converges on the surface temperature of the intermediate transfer belt to reduce the temperature differences among the photosensitive drums. At this time, driving control is performed according to the detection results of the surface temperatures of the photosensitive drums, so neither the heater nor the fan need not be brought under ON/OFF control. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer and a facsimile, and more particularly to an image forming apparatus having an image carrier such as a plurality of photosensitive drums.

[0002]

2. Description of the Related Art Image forming apparatuses that form color images have been increasing in response to market demands.
The color image forming apparatus for forming a color image is roughly classified into the following two types. The first is to use a photoreceptor as a single image carrier and toner images of respective colors obtained by developing electrostatic latent images of respective colors sequentially formed on the photoreceptor, and transfer the toner images of respective colors to an intermediate transfer body or a recording material. A color image is obtained by sequentially superposing them on a transfer material. Hereinafter, this color image forming apparatus is referred to as a one-drum type image forming apparatus. The second is to obtain a color image by sequentially superposing a plurality of photoconductors corresponding to respective colors and toner images of respective colors obtained by developing electrostatic latent images formed on the photoconductors on a transfer material. It is a thing. Hereinafter, this color image forming apparatus is referred to as a tandem type image forming apparatus.

Since the one-drum type image forming apparatus has one photoconductor, it has advantages that the apparatus can be downsized and the cost can be reduced. However, since a single photoconductor is used, it is necessary to repeat a series of processes from latent image formation, development processing, and transfer to a transfer material for the number of colors (usually four times). Therefore, it is disadvantageous in terms of speeding up image formation. On the other hand, the tandem-type image forming apparatus has drawbacks that the apparatus is large and the cost is high.
Since the photoconductor is provided for each color, the series of processes described above can be performed only once. Therefore, it is advantageous in terms of speeding up image formation. In recent years, the tandem-type image forming apparatus is receiving attention because the market demands an image forming speed comparable to that of a monochrome image forming apparatus for a color image forming apparatus.

[0004]

However, in the image forming apparatus, there is a heat fixing device or the like which serves as a heat source to generate a temperature gradient inside the apparatus. When a temperature gradient occurs in the machine by such a heat source, a temperature difference occurs between the photoconductors in the tandem type image forming apparatus. Since the photoconductor generally has a higher light attenuation rate as the temperature rises, a difference in temperature between the photoconductors causes a difference in image density between the photoconductors. As a result, the density gradation of each color is deviated, and the temperature difference between the photoconductors causes deterioration of the quality of the color image.

In order to suppress such a temperature difference between the photoconductors, a method of controlling the temperature of each photoconductor by controlling ON / OFF of a heater or a fan is conventionally known. However, when using these methods, it is necessary to attach a heater and a fan to each photoconductor, which increases cost and
There is a problem that it is against the recent energy saving because the power consumption increases.

Further, Japanese Patent Laid-Open No. 2000-75681 discloses a tandem type image forming apparatus provided with a transfer drum which contacts a plurality of photoconductors corresponding to respective colors. This publication discloses a method of controlling the temperature of a transfer drum at a constant high temperature by controlling ON / OFF of a heater, and idling the transfer drum while contacting each of the photoconductors. In this method, the thermal energy of the transfer drum is propagated to each photoconductor to reduce the temperature difference between the photoconductors. According to this method, since only one heater needs to be provided in the transfer drum, the cost can be reduced as compared with the method in which a heater or the like needs to be attached to each photoconductor. However, even with this method, since it is still necessary to provide a heating means such as a heater in the transfer drum, there is a problem in that power consumption increases, which is against the recent energy saving.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an image carrier such as a photoconductor without using a heater or a fan in the tandem type image forming apparatus. An object of the present invention is to provide an image forming apparatus capable of suppressing a temperature difference that occurs between them.

[0008]

In order to achieve the above object, the invention of claim 1 contacts a plurality of image bearing members carrying toner images of different colors and the surfaces of the plurality of image bearing members. An image forming apparatus for forming a composite toner image on a recording material in which the toner images of respective colors formed on the plurality of image carriers are overlapped with each other. The surface temperature difference between the temperature detection means for detecting the surface temperature of at least two of the image bearing bodies and the image bearing body obtained based on the detection result of the temperature sensing means exceeds a predetermined temperature difference. At this time, drive control means for driving the plurality of image carriers and the endless moving member while contacting each other in a state where the image forming operation is prohibited are provided. According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, a heat fixing unit configured to heat and fix a synthetic toner image in which the toner images formed on the plurality of image carriers are superposed on the recording material. The image bearing member whose surface temperature is detected by the temperature sensing unit is disposed at a position closest to the heat fixing unit and at a position farthest from the heat fixing unit. The image carrier is an image carrier. According to a third aspect of the invention, in the image forming apparatus according to the first or second aspect, the endless moving member is an endless belt-shaped member. According to a fourth aspect of the invention, in the image forming apparatus according to the third aspect, the endless belt-shaped member carries an intermediate toner image on which the toner images formed on the plurality of image bearing members are superposed. The transfer belt is characterized in that at least one layer in the thickness direction is formed of an elastic material. According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the predetermined temperature difference is 10 ° C.
It is characterized by the following. According to a sixth aspect of the invention, in the image forming apparatus according to the fifth aspect, the predetermined temperature difference is 3 ° C. or more. The image forming apparatus of the first aspect is a so-called tandem type image forming apparatus that forms a composite toner image in which toner images of respective colors formed on a plurality of image carriers are superposed on a recording material. This image forming apparatus is equipped with an endless moving member whose surface moves endlessly so as to contact the surfaces of a plurality of image carriers. As the endless moving member, an existing intermediate transfer member or recording material conveying member can be used. In the image forming apparatus of the present invention, the temperature detecting means for detecting the surface temperature of at least two image bearing members of the plurality of image bearing members is provided. Then, when the surface temperature difference between the image carriers obtained based on the detection result of the temperature detection unit exceeds a predetermined temperature difference, the drive control unit prohibits the image forming operation, and a plurality of image carriers are held. The body and the endless moving member are driven while being in contact with each other.
When driven in this manner, the thermal energy of the image carrier propagates to the endless moving member or the thermal energy of the endless moving member propagates to the image carrier due to the difference between the surface temperature of the image carrier and the surface temperature of the endless moving member. To do Then, the surface temperature of each image carrier converges toward the surface temperature of the endless moving member. At this time, if there is a temperature difference between the plurality of image carriers, a difference occurs in the propagation speed of thermal energy between each image carrier and the endless moving member. That is, the speed of the surface temperature of the image carrier having a large temperature difference between the endless moving member and the surface temperature of the endless moving member is faster than that of the image carrier having a small temperature difference between the endless moving member. Therefore, as in the image forming apparatus of the present invention, if the plurality of image carriers and the endless moving member are driven while being in contact with each other in a state where the image forming operation is prohibited, the temperature difference between the image carriers can be reduced. can do. Here, in the image forming apparatus of the present claim, based on the detection result of the surface temperature of each image carrier,
The drive control is performed by the drive control unit to reduce the temperature difference between the image carriers. Therefore, unlike the conventional method described above, it is possible to reduce the temperature difference between the image bearing members without requiring ON / OFF control of the heater and the fan.
Moreover, in the image forming apparatus of the present invention, the temperature difference between the image carriers to be suppressed is fed back to the drive control described above, so that appropriate control according to the actual temperature difference between the image carriers can be performed. it can. Therefore, as compared with the case where the control for reducing the temperature difference between the image carriers is performed without detecting the surface temperature of the image carriers, the appropriate control can be performed. As a result, even if an unexpected situation occurs, such as when the surface temperature of each image carrier varies more than expected due to changes in the environment inside the machine, the image quality is affected by the temperature difference between the image carriers. It is possible to stably maintain the range that does not occur.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to an electrophotographic color copying machine (hereinafter simply referred to as "copying machine") as an image forming apparatus will be described below. The copying machine of this embodiment is the above-mentioned tandem type color image forming apparatus. FIG. 2 is a schematic configuration diagram of the entire copying machine according to the present embodiment. This copying machine includes a copying machine main body 100, a paper feed table 200 on which the copying machine main body is placed, and a scanner 3 mounted on the copying machine main body.
00 and an automatic document feeder (ADF) 400 attached to the upper part of the scanner.

FIG. 3 is an enlarged view showing the structure of the main body 100 of the copying machine. The copying machine main body 100 is provided with an intermediate transfer belt 10 which is an endless belt-shaped member as an endless moving member. The intermediate transfer belt 10 is rotatably driven in the clockwise direction in FIG. 3 while being stretched around the three support rollers 14, 15, and 16. Among the supporting rollers, a belt stretched portion between the first supporting roller 14 and the second supporting roller 15 has four image forming units 18Y, 18C, 18M, 1 for yellow, cyan, magenta, and black.
8BKs are arranged side by side. An exposure device 21 is provided above the image forming units 18Y, 18C, 18M and 18BK as shown in FIG. The exposure device 21 is based on image information of a document read by the scanner 300, and is a photosensitive drum 20Y, 20C, 20 as a latent image carrier provided in each image forming unit.
It is for forming an electrostatic latent image on M, 20BK. A secondary transfer device 22 is provided at a position facing the third support roller 16 among the support rollers.
The secondary transfer device 22 includes two rollers 23a and 23b.
An endless belt-shaped secondary transfer belt 24 is stretched between them. Then, when the toner image on the intermediate transfer belt 10 is secondarily transferred onto the transfer paper, the secondary transfer belt 24 is pressed against the portion of the intermediate transfer belt 10 wound around the third support roller 16 to perform the secondary transfer. I do. The secondary transfer device 2
The configuration 2 does not have to use the secondary transfer belt 24, but may have a configuration using, for example, a transfer roller or a non-contact transfer charger. Further, a fixing device 25 as a heat fixing device for fixing the toner image transferred onto the transfer paper is provided on the downstream side of the secondary transfer device 22 in the transfer paper conveyance direction by the secondary transfer belt 24. This fixing device 25
The pressure roller 27 is pressed against the heating roller 26.

A belt cleaning device 17 is provided at a position facing the second supporting roller 15 among the supporting rollers of the intermediate transfer belt 10. The belt cleaning device 17 is for removing the residual toner remaining on the intermediate transfer belt 10 after the toner image on the intermediate transfer belt 10 is transferred onto a transfer sheet as a recording material. The belt cleaning device 17 includes two fur brushes 90 and 91 as cleaning members. These fur brushes 90 and 91 are provided so as to rotate in contact with the metal rollers 92 and 93, respectively. In the present embodiment, a negative voltage is applied from the power source 94 to the metal roller 92 on the upstream side in the surface moving direction of the intermediate transfer belt 10, and the power source 95 is applied to the metal roller 93 on the downstream side.
A positive voltage is applied from. As a result, biases having different polarities are applied to the fur brushes 90 and 91. Blades 96 and 97 are in contact with the metal rollers 92 and 93, respectively.

The belt cleaning device 17 having the above-described structure first performs cleaning by applying a negative bias to the surface of the intermediate transfer belt 10 by the fur brush 90 on the upstream side. At this time, for example, the metal roller 92
If -700V is applied to the fur brush 90, the applied voltage of the fur brush 90 becomes about -400V. Therefore, the positive toner remaining on the intermediate transfer belt 10 is transferred to the fur brush 90 side. Then, the toner transferred to the fur brush 90 is further transferred from the fur brush 90 to the metal roller 92 due to the potential difference, and is scraped off by the blade 96. In this way, the toner scraped off by the blades 96 and 97 is collected in a tank (not shown).

In this way, the fur brush 90 on the upstream side
A large amount of toner still remains on the surface of the intermediate transfer belt 10 that has been cleaned by. Most of the remaining toner is a negative polarity toner or is a negative polarity toner that is negatively charged by charge injection or discharge by a negative polarity bias applied to the fur brush 90. Therefore, these toners are
Fur brush 9 on the downstream side to which a positive bias is applied
It is cleaned by 1. And fur brush 9
The toner transferred to 0 is further transferred from the fur brush 90 to the metal roller 92 due to the potential difference, scraped off by the blade 96, and collected in the tank.

In this way, the belt cleaning device 1
Most of the toner remaining on the intermediate transfer belt 10 is removed by the cleaning by 7, but a small amount of the toner remains on the intermediate transfer belt 10. But,
Since these toners are positively charged by the fur brush 91, they are transferred to the photosensitive drum 20 side by the primary transfer electric field in the next image forming process. Therefore, it is finally collected by the photoconductor cleaning device 63.

Next, the image forming units 18Y, 18C,
The configuration of 18M and 18BK will be described. In the following description, the image forming unit 18 that forms a black toner image
The image forming unit 1 will be described by taking BK as an example.
8Y, 18C, and 18M have the same structure. The image forming units 18Y, 18C, 18M and 18BK are
It can be configured as a process cartridge including at least the photoconductor drum 20 and all or a part of the components and components that configure the image forming unit. In this case, the image forming units 18Y, 18C, 18M, 18
Since the BK can be detachably attached to the copying machine main body 100, the maintainability is improved.

FIG. 4 is an enlarged view showing the configuration of two adjacent image forming units 18M and 18BK. In the reference numerals in the drawings, the symbols “M” and “BK” indicating the distinction of colors are omitted, and the symbols are appropriately omitted in the following description. In the image forming unit 18, a charging device 60, a developing device 61, a photoconductor cleaning device 63, and a charge eliminating device 64 are provided around the photoconductor drum 20. Also,
A primary transfer device 62 is provided at a position facing the photoconductor drum 20 via the intermediate transfer belt 10.

The charging device 60 is of a contact charging type that employs a charging roller, and contacts the photosensitive drum 20 to apply a voltage to uniformly charge the surface of the photosensitive drum 20. As the charging device 60, a non-contact charging type device such as a non-contact scorotron charger may be used.

The developing device 61 may use a one-component developer, but in this embodiment, a two-component developer composed of a magnetic carrier and a non-magnetic toner is used. The developing device 61 can be roughly divided into a stirring unit 66 and a developing unit 67. In the stirring section 66, the two-component developer (hereinafter, simply referred to as “developer”) is conveyed while being stirred and supplied onto the developing sleeve 65 as a developer carrier. The stirring unit 66 is provided with two parallel screws 68, and a partition plate for partitioning the two screws 68 so that they are communicated with each other at both ends. Further, a toner concentration sensor 71 for detecting the toner concentration of the developer in the developing device is attached to the developing case 70. On the other hand, in the developing section 67, the toner of the developer attached to the developing sleeve 65 is transferred to the photosensitive drum 20. The developing unit 67 has a developing sleeve 65 facing the photoconductor drum 20 through an opening of the developing case 70.
And a magnet (not shown) is fixedly arranged in the developing sleeve 65. Further, a doctor blade 73 is provided so that the tip of the developing sleeve 65 approaches the developing sleeve 65. In this embodiment, the diameter is 18 m.
The developing sleeve 65 of m is used. The surface of the developing sleeve 65 is sandblasted or 1 m.
A process for forming a plurality of grooves having a depth of m to several mm is performed, and the surface roughness is formed to be in the range of 10 to 30 μm in RZ.

In this developing device 61, the developer is conveyed and circulated while being agitated by the two screws 68, and the developing sleeve 6
Supply to 5. The developer supplied to the developing sleeve 65 is drawn and held by a magnet. The developer drawn into the developing sleeve 65 is
Is conveyed with the rotation of and is regulated to an appropriate amount by the doctor blade 73. The regulated developer is returned to the stirring section 66. The developer thus conveyed to the developing area facing the photoconductor drum 20 is in the state of a spike by the magnet to form a magnetic brush. In the developing area, the developing bias applied to the developing sleeve 65 forms a developing electric field that moves the toner in the developer to the electrostatic latent image portion on the photosensitive drum 20. As a result, the toner in the developer is transferred to the electrostatic latent image portion on the photoconductor drum 20, the electrostatic latent image on the photoconductor drum 20 is visualized, and a toner image is formed. The developer that has passed through the developing area is conveyed to a portion where the magnetic force of the magnet is weak, is separated from the developing sleeve 65, and is returned to the stirring section 66. When the toner concentration in the stirring unit 66 becomes low due to the repetition of such operations, the toner concentration sensor 7
1 and the toner is replenished to the stirring unit 66 based on the detection result.

Further, the primary transfer device 62 employs a primary transfer roller and is installed so as to be pressed against the photosensitive drum 20 with the intermediate transfer belt 10 sandwiched therebetween. The primary transfer device 62 does not have to have a roller shape, but may have a conductive brush shape or a non-contact corona charger. In addition, each primary transfer device 6
Between the two, a conductive roller 74 that is in contact with the back surface of the intermediate transfer belt 10, that is, the inner peripheral surface side is provided. This conductive roller 74 is used for each primary transfer device 62 during the primary transfer.
The bias applied by means of this prevents the bias from flowing into the adjacent image forming unit through the layer on the inner peripheral surface side of the intermediate transfer belt 10.

The photoconductor cleaning device 63 is also used.
Is provided with a cleaning blade 75 made of polyurethane rubber, for example, which is arranged so that its tip is pressed against the photosensitive drum 20. In addition, in the present embodiment, a conductive fur brush 76 that contacts the photoconductor drum 20 is also used in order to improve cleaning performance. A bias is applied to the fur brush 76 from a metal electric field roller 77, and the tip of a scraper 78 is pressed against the electric field roller 77. The toner removed from the photoconductor drum 20 by the cleaning blade 75 and the fur brush 76 is stored inside the photoconductor cleaning device 63. Then, the recovery screw 79
Is moved to one side of the photoconductor cleaning device 63 by
Through the toner recycling device 80 described later, the developing device 6
It is returned to 1 and reused.

The static eliminator 64 is composed of a static eliminator lamp and irradiates light to initialize the surface potential of the photosensitive drum 20.

In the image forming unit 18 having the above-described structure, the charging device 6 is rotated with the rotation of the photosensitive drum 20.
At 0, the surface of the photoconductor drum 20 is uniformly charged. Then, based on the image information read by the scanner 300, the exposure device 21 irradiates the writing light L from a laser, an LED or the like to form an electrostatic latent image on the photosensitive drum 20. Then, the developing device 61 visualizes the electrostatic latent image to form a toner image. This toner image is transferred to the primary transfer device 62.
Is primarily transferred onto the intermediate transfer belt 10. The transfer residual toner remaining on the surface of the photoconductor drum 20 after the primary transfer is removed by the photoconductor cleaning device 63, and then the surface of the photoconductor drum 20 is destaticized by the destaticizing device 64 to form the next image. Be served.

Next, the structure and operation of the toner recycling device 80 for reusing the transfer residual toner collected by the photoconductor cleaning device 63 in the developing device 61 will be described. FIG. 5 is an explanatory diagram showing a schematic configuration of the toner recycling device 80. FIG. 6 is an enlarged view of one end portion of the recovery screw 79 of the photoconductor cleaning device 63.
As shown in FIG. 6, the toner recycling device 80 includes a roller portion 82 provided at one end of the recovery screw 79 of the photoconductor cleaning device 63. This roller portion 82
A pin 81 is provided on the. This roller portion 82 is
A belt-shaped collected toner conveying member 83 is stretched around the roller portion 87 of the rotating shaft 86. At this time, the roller portion 8
The second pin 81 enters into the long hole 84 provided in the collected toner conveying member 83. Blades 85 are provided at regular intervals on the outer peripheral surface of the collected toner conveying member 83.

As shown in FIG. 5, the collected toner conveying member 83 is housed in the conveying path case 88 together with the rotating shaft 86. The transport path case 88 is integrally molded with a cartridge case 89 that integrally houses at least a part of the components of the image forming unit 18. Inside the transport path case 88, one of the two screws 68 is
The book projects from the inside of the developing device 61.

In such a structure, a driving force is transmitted from the outside to rotate the recovery screw 79 and rotationally drive the recovered toner conveying member 83. As a result, the toner collected by the photoconductor cleaning device 63 is conveyed toward the developing device 61 through the conveyance path case 88,
It is housed inside the developing device 61 by the screw 68.
After that, the collected toner is circulated by being agitated together with the developer in the developing device 61 by the two screws 68 as described above, and contributes to the development again.

Next, the operation of the copying machine in this embodiment will be described. When making a copy of a document using the copying machine having the above-described configuration, first, the document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened and the contact glass 3 of the scanner 300 is opened.
The original is set on the sheet 2, and the automatic document feeder 400 is closed and pressed by it. After that, when the user presses a start switch (not shown), when the document is set on the automatic document feeder 400, the document is conveyed onto the contact glass 32. Then, the scanner 300 is driven and the first
The traveling body 33 and the second traveling body 34 start traveling. As a result, the light from the first traveling body 33 is reflected by the document on the contact glass 32, the reflected light is reflected by the mirror of the second traveling body 34, and is guided to the reading sensor 36 through the imaging lens 35. . In this way, the image information of the original is read.

When the start switch is pressed by the user, a drive motor (not shown) is driven, and one of the support rollers 14, 15, 16 is rotationally driven, and the intermediate transfer belt 10 is rotationally driven. At the same time, the photosensitive drums 20Y, 20C, 20M and 20BK of the image forming units 18Y, 18C, 18M and 18BK are also rotationally driven. After that, based on the image information read by the reading sensor 36 of the scanner 300, the writing light L from the exposure device 21 onto the photoconductor drums 20Y, 20C, 20M, and 20BK of the image forming units 18Y, 18C, 18M, and 18BK. Are irradiated respectively. As a result, an electrostatic latent image is formed on each of the photoconductor drums 20Y, 20C, 20M, 20BK, and the developing devices 61Y, 61C, 61K are formed.
Visualized by M, 61BK. Then, yellow, cyan, magenta, and black toner images are formed on the photoconductor drums 20Y, 20C, 20M, and 20BK, respectively. The toner images of the respective colors thus formed are transferred to the primary transfer devices 62Y, 62C, 62M, 62B.
By K, primary transfer is sequentially performed so as to be sequentially overlapped on the intermediate transfer belt 10. As a result, a synthetic toner image in which the toner images of the respective colors are superposed is formed on the intermediate transfer belt 10. The intermediate transfer belt 1 after the secondary transfer
The transfer residual toner remaining on 0 is removed by the belt cleaning device 17.

When the user presses the start switch, the paper feed roller 42 of the paper feed table 200 corresponding to the transfer paper selected by the user is rotated, and the transfer paper is sent out from one of the paper feed cassettes 44. The transferred transfer paper is separated into one sheet by a separation roller 45, enters a paper feed path 46, and is conveyed by a conveyance roller 47 to a paper feed path 48 in the copying machine main body 100. The transfer sheet conveyed in this manner is stopped when it hits the registration roller 49. When using the transfer paper not set in the paper feed cassette 44, the transfer paper set in the manual feed tray 51 is sent out by the paper feed roller 50, separated by the separation roller 52 into one sheet, and then the manual paper feed path. It is transported through 53. Then, similarly, when it hits the registration roller 49, it is stopped.

The registration roller 49 transfers the synthetic toner image formed on the intermediate transfer belt 10 as described above.
The rotation is started at the timing of being conveyed to the secondary transfer portion of the secondary transfer device 22 facing the secondary transfer belt 24. Here, the registration roller 49 is generally grounded and used in many cases, but a bias may be applied to remove the paper dust of the transfer paper. A DC voltage is used as the applied bias, but an AC voltage having a DC offset component may be used to charge the transfer paper more uniformly. The surface of the transfer paper after passing through the resist roller 49 thus biased is
A little negatively charged. Therefore, in this case, at the time of the secondary transfer from the intermediate transfer body 10 to the transfer paper, the transfer condition is different from that of the transfer paper to which the bias is not applied to the registration roller 49, and it is necessary to change the transfer condition appropriately.

The transfer paper sent out by the registration rollers 49 is sent between the intermediate transfer belt 10 and the secondary transfer belt 24, and the secondary transfer device 22 transfers the synthetic toner image on the intermediate transfer belt 10 onto the transfer paper. Is secondarily transcribed. After that, the transfer paper is conveyed to the fixing device 25 in a state of being attracted to the secondary transfer belt 24, and the fixing device 25 applies heat and pressure to fix the toner image. The transfer sheets that have passed through the fixing device 25 are discharged onto a discharge tray 57 by a discharge roller 56 and stacked. If an image is to be formed on the back side of the surface on which the toner image is fixed,
A switching claw 55 for switching the transfer path of the transfer sheet that has passed through the fixing device 25.
To switch. Then, the transfer sheet is sent to the sheet reversing device 28 located below the secondary transfer device 22, is reversed there, and is guided to the secondary transfer portion again.

Next, the structure of the intermediate transfer belt 10 in this embodiment will be described. The intermediate transfer belt 10 is
Conventionally, a resin belt formed of a fluorine resin, a polycarbonate resin, a polyimide resin, or the like has been used, but in recent years, an elastic belt using an elastic material for all layers of the belt or a part of the belt is used. Often. An elastic belt is also used as the intermediate transfer belt 10 of this embodiment.
This is because the use of the resin belt has the following problems as compared with the case of using the elastic belt.

That is, a color image is usually formed by overlapping toner images of four colors. The composite toner image on the intermediate transfer belt 10 in which the toner images are overlapped is a primary transfer position between the photosensitive drums 20Y, 20C, 20M, and 20BK, and a secondary transfer between the secondary transfer belt 24. Subject to pressure as it passes through the location. When such a pressure is applied, the cohesive force between the toners in the synthetic toner image increases.
As a result, character dropouts, edge dropouts of solid image, and the like are likely to occur. At this time, if the intermediate transfer belt 10 is a resin belt, the hardness thereof is higher than that of an elastic belt, so that there is a problem that the toner is likely to aggregate when receiving pressure. Furthermore, in recent years, there is an increasing demand in the market for forming full-color images on various recording materials, such as Japanese paper and paper with intentionally unevenness. But,
When performing image formation on paper with poor surface smoothness,
At the time of the secondary transfer, a gap is likely to be generated between the toner and the sheet, and the transfer omission is likely to occur. If it is attempted to increase the adhesion between the toner and the paper in order to prevent this, there is a problem that the toner tends to aggregate due to the pressure in the resin belt having higher hardness than in the elastic belt.

The resin used in the intermediate transfer belt 10 in the present embodiment is polycarbonate, fluororesin (ET
FE, PVDF), polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-
Vinyl acetate copolymer, styrene-maleic acid copolymer,
Styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate Copolymer, etc.), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-
Chloromethyl acrylate copolymer, styrene-acrylonitrile-acrylic acid ester copolymer and other styrene resins (styrene or styrene-substituted homopolymer or copolymer), methyl methacrylate resin, butyl methacrylate resin, Ethyl acrylate resin, butyl acrylate resin, modified acrylic resin (silicone modified acrylic resin, vinyl chloride resin modified acrylic resin, acrylic urethane resin, etc.), vinyl chloride resin, styrene-vinyl acetate copolymer, vinyl chloride-vinyl acetate Copolymer, rosin-modified maleic acid resin, phenol resin, epoxy resin, polyester resin, polyester polyurethane resin, polyethylene, polypropylene, polybutadiene, polyvinylidene chloride, ionomer resin, polyurethane resin, silicone resin, ke Down resins, ethylene - can be used ethyl acrylate copolymer, xylene resin and polyvinyl butyral resin, polyamide resin, one kind or two kinds or more selected from the group consisting of modified polyphenylene oxide resin. However, the material is not limited to the above materials.

Further, as the elastic material rubber and the elastomer used in the intermediate transfer belt 10 in this embodiment, butyl rubber, fluorine rubber, acrylic rubber, EPDM, NB are used.
R, acrylonitrile-butadiene-styrene rubber natural rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, ethylene-propylene rubber, ethylene-
Propylene terpolymer, chloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, urethane rubber, syndiotactic 1,2-polybutadiene, epichlorohydrin rubber, recone rubber, fluororubber,
Polysulfide rubber, polynorbornene rubber, hydrogenated nitrile rubber, thermoplastic elastomer (for example, polystyrene type, polyolefin type, polyvinyl chloride type, polyurethane type,
One type or two or more types selected from the group consisting of polyamide type, polyurea, polyester type, fluororesin type) and the like can be used. However, the material is not limited to the above materials.

The conductive agent for adjusting the resistance value that can be used in the intermediate transfer belt 10 in this embodiment is not particularly limited, but examples thereof include carbon black, graphite, metal powder such as aluminum and nickel, and tin oxide. ,
Titanium oxide, antimony oxide, indium oxide, potassium titanate, antimony oxide-tin oxide composite oxide (AT
O), conductive metal oxides such as indium oxide-tin oxide composite oxide (ITO), and the like can be used. The conductive metal oxide may be coated with insulating fine particles such as barium sulfate, magnesium silicate and calcium carbonate.

The surface layer material that can be used in the intermediate transfer belt 10 in this embodiment is not limited,
The surface layer material of the intermediate transfer belt 10 is generally required to reduce the adhesive force of toner to improve the secondary transfer property. For example, one or more kinds of polyurethane, polyester, epoxy resin, etc. are used to reduce surface energy and improve lubricity, for example, fluororesin, fluorine compound, fluorocarbon, titanium dioxide, silicon car A powder such as a bite or the like, or one kind or two or more kinds of particles, or one in which particles having different particle diameters are dispersed can be used. Also, a fluorine-rich layer is formed on the surface by performing heat treatment like a fluorine-based rubber material,
It is also possible to use a material having a small surface energy.

The method of manufacturing the intermediate transfer belt 10 in this embodiment is not limited, and for example, a centrifugal molding method in which a material is poured into a rotating cylindrical mold to form a belt, or a thin film on the surface layer is formed. Spray coating method,
Use the dipping method of immersing the cylindrical mold in the solution of the material and pulling it up, the casting method of injecting into the inner mold, the outer mold, the method of winding the compound around the cylindrical mold and performing the vulcanization polishing. You can It is also possible to manufacture by combining a plurality of manufacturing methods.

Since the intermediate transfer belt 10 in this embodiment is an elastic belt, it is necessary to prevent the belt from expanding. As a method for preventing it, for example, a method of forming a rubber layer on a core resin layer having a small elongation,
Examples thereof include a method of adding a material for preventing elongation to the core layer. As a material forming the core layer for preventing elongation,
For example, natural fibers such as cotton and silk, polyester fibers,
Nylon fiber, acrylic fiber, polyolefin fiber, polyvinyl alcohol fiber, polyvinyl chloride fiber, polyvinylidene chloride fiber, polyurethane fiber, polyacetal fiber, polyfluoroethylene fiber, synthetic fiber such as phenol fiber, carbon fiber, glass fiber, boron fiber, etc. A woven fabric or thread can be used by using one kind or two or more kinds selected from the group consisting of inorganic fibers, metal fibers such as iron fibers and copper fibers. In addition, the thread-shaped
Twisted one or more filaments, single twist yarn,
Any twisting method such as plied yarn and twin yarn may be used. Further, for example, fibers of a material selected from the above material group may be mixed and spun. Moreover, it is also possible to use a thread-like material after subjecting it to an appropriate conductive treatment. On the other hand, as the woven fabric, any woven fabric such as a knitted fabric can be used. Of course, a woven fabric can also be used, and of course, a conductive treatment can be applied.

Further, the manufacturing method for providing the core layer on the intermediate transfer belt 10 in this embodiment is not particularly limited, and for example, a woven cloth woven into a cylinder is covered on a mold or the like, and is coated thereon. A method of providing a layer, a method of providing a coating layer on one or both surfaces of a core layer by immersing a tubular woven cloth in liquid rubber or the like, winding a thread around a mold or the like in a spiral shape at an arbitrary pitch, and It is possible to use a method of providing a coating layer on the above.

The thickness of the elastic layer of the intermediate transfer belt 10 in this embodiment depends on the hardness of the elastic layer, but if it is too thick, the expansion and contraction of the surface becomes large and cracks are likely to occur in the surface layer. In addition, it is not preferable that the thickness is too thick because the amount of expansion and contraction increases and the expansion and contraction of the image also increases.
Specifically, the thickness of the elastic layer is preferably about 1 mm or less. The proper range of hardness of the elastic layer is 10 ° ≦ H.
S ≦ 65 ° (JIS-A), but it is necessary to adjust the optimum hardness depending on the layer thickness of the belt. Hardness is 10 ° (JI
If it is smaller than S-A), it becomes very difficult to mold with high dimensional accuracy. This is because it tends to shrink and expand during molding. Further, in order to reduce the hardness, it is a general method to add an oil component to the base material. However, when such an intermediate transfer belt 10 is continuously operated in a pressurized state, the oil component is exposed on the surface. It begins to ooze. As a result, the photoconductor drum 20 that comes into contact with the surface of the intermediate transfer belt 10 is contaminated, and lateral stripe unevenness occurs.
Generally, a surface layer is provided to improve releasability, but in order to completely prevent the oil component from seeping out, quality requirements such as durability quality are high for the surface layer, and selection of materials and characteristics Will be difficult to secure. On the other hand, the hardness is 65 ° (JIS
If it exceeds -A), molding can be performed with high dimensional accuracy due to the increase in hardness, and the oil component is not contained or the content thereof can be suppressed to be small, so that contamination of the photosensitive drum 20 can be reduced. However, the hardness is 6
If the angle exceeds 5 ° (JIS-A), the transferability will be deteriorated, the character image will be hollowed out, and it will be difficult to stretch the roller.

Next, the photosensitive drum 2 in this embodiment
The configuration of 0 will be described. FIG. 7 is a sectional view schematically showing an example of the photosensitive drum 20 used in this embodiment. The photosensitive drum 20 has a function-separated photosensitive layer formed by laminating a charge generation layer 20b and a charge transport layer 20c on a conductive support 20a. FIG. 8 is a sectional view schematically showing another example of the photosensitive drum 20 used in this embodiment. This photoconductor drum 20
Is formed by laminating a charge generation layer 20b and a charge transport layer 20c on a conductive support 20a, and an undercoat layer 20d exists between the charge generation layer 20b and the charge transport layer 20c. To do. FIG. 9 is a sectional view schematically showing still another example of the photosensitive drum 20 used in this embodiment. The photoconductor drum 20 is formed by laminating a charge generation layer 20b and a charge transport layer 20c on a conductive support 20a, and a protective layer 20e is further laminated on the charge transport layer 20c. It is a thing.

As the conductive support 20a, one having conductivity with a volume resistance of 10 ¹⁰ Ω · cm or less, for example,
Aluminum, nickel, chrome, nichrome, copper, gold,
Metals such as silver and platinum, metal oxides such as tin oxide and indium oxide, coated on film or cylindrical plastic or paper by vapor deposition or sputtering, or aluminum, aluminum alloy, nickel, stainless steel, etc. Extruding boards and them,
It is possible to use a tube that has been surface-treated by cutting, superfinishing, polishing, etc., after forming a raw tube by a method such as drawing. Further, the endless nickel belt and the endless stainless belt disclosed in JP-A-52-36016 can also be used as the conductive support 20a.

In addition, the conductive support 20a has
It is also possible to use a conductive support in which conductive powder is dispersed in a suitable binder resin and coated. As the conductive powder, carbon black, acetylene black, aluminum, nickel, iron, nichrome, copper, zinc,
Examples thereof include metal powder such as silver, metal oxide powder such as conductive tin oxide and ITO. Further, the binder resin used at the same time, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer,
Styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral , Thermoplastic resins such as polyvinyl formal, polyvinyl toluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin and alkyd resin, thermosetting resin or photocurable resin. To be Such a conductive layer can be provided by dispersing and coating the conductive powder and the binder resin in a suitable solvent such as tetrahydrofuran, dichloromethane, methyl ethyl ketone or toluene. In addition, polyvinyl chloride, polypropylene, polyester,
The conductive support 20a may be formed by providing a conductive layer with a heat-shrinkable tube containing the above-mentioned conductive powder in a material such as polystyrene, polyvinylidene chloride, polyethylene, rubber chloride, or Teflon (registered trademark). Can be used favorably as

The charge generating layer 20b is a layer containing a charge generating substance as a main component, and a binder resin may be used if necessary. An inorganic material and an organic material can be used as the charge generating substance. Examples of the inorganic material include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compounds, and amorphous silicon. As the amorphous silicon, those in which dangling bonds are terminated with hydrogen atoms or halogen atoms, or those in which boron atoms, phosphorus atoms, etc. are doped are favorably used. On the other hand, as the organic material, a known material can be used. For example, phthalocyanine-based pigments such as metal phthalocyanine and metal-free phthalocyanine, azurenium salt pigment, squaric acid methine pigment, azo pigment having carbazole skeleton, azo pigment having triphenylamine skeleton, azo pigment having diphenylamine skeleton, dibenzothiophene skeleton Having azo pigment, azo pigment having fluorenone skeleton, azo pigment having oxadiazole skeleton, azo pigment having bisstilbene skeleton, azo pigment having distyryl oxadiazole skeleton, azo pigment having distyryl carbazole skeleton, perylene Pigments,
Examples thereof include anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, indigoid pigments, and bisbenzimidazole pigments. These charge generating substances can be used alone or as a mixture of two or more kinds.

As the binder resin used as necessary in the charge generation layer 20b, polyamide, polyurethane, epoxy resin, polyketone, polycarbonate,
Polyarylate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N-vinylcarbazole, polyacrylamide and the like are used. These binder resins can be used alone or as a mixture of two or more kinds. In addition, a low molecular weight charge transport material may be added if necessary.

In addition, the charge transport material that can be used in combination with the charge generation layer 20b includes an electron transport material and a hole transport material. Examples of the electron transport substance include chloranil, bromanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2, 4,5,7-Tetranitroxanthone, 2,
4,8-Trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophene-4
-One, 1,3,7-trinitrodibenzothiophene-
Examples include electron-accepting substances such as 5,5-dioxide. These electron transport materials can be used alone or as a mixture of two or more kinds. On the other hand, an electron-donating substance is preferably used as the hole-transporting substance. Examples of the electron-donating substance include oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl). Propane, styrylanthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives,
Examples thereof include phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives and thiophene derivatives. These hole transport materials can be used alone or as a mixture of two or more kinds. The charge generation layer 20b contains a charge generation material, a solvent, and a binder resin as main components, and contains additives such as a sensitizer, a dispersant, a surfactant, and silicone oil. May be.

As a method for forming the charge generation layer 20b, a vacuum thin film forming method and a casting method from a solution dispersion system can be largely cited. For the former method, vacuum vapor deposition method, glow discharge decomposition method, ion plating method, sputtering method, reactive sputtering method, CVD method, etc. are used, and they are well used for the above-mentioned inorganic materials and organic materials. it can. Further, in order to provide the charge generation layer 20b by a casting method, the above-mentioned inorganic or organic charge generation substance may be used together with a binder resin, if necessary.
Tetrahydrofuran, cyclohexanone, dioxane,
It can be formed by dispersing with a ball mill, an attritor, a sand mill or the like using a solvent such as dichloroethane or butanone, and appropriately diluting the dispersion. The coating can be performed by using a dip coating method, a spray coating method, a bead coating method, or the like. The thickness of the charge generation layer 20b provided as described above is appropriately about 0.01 to 5 μm, preferably 0.05 to 2 μm.

The charge-transporting layer 20c can be formed by dissolving or dispersing a mixture or copolymer containing a charge-transporting component and a binder component as main components in a suitable solvent, and applying and drying the mixture. The thickness of the charge transport layer is 10 to 100.
If about μm is appropriate and resolution is required, 10
Approximately 30 μm is suitable. Examples of the polymer compound that can be used as the binder component include polystyrene, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, styrene / maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride / acetic acid. Vinyl copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, acrylic resin, silicone resin, fluorine resin, epoxy resin, melamine resin, Examples thereof include thermoplastic or thermosetting resins such as urethane resin, phenol resin, and alkyd resin, but are not limited thereto. These polymer compounds can be used alone or as a mixture of two or more kinds, or can be used by copolymerizing with a charge transport material. Examples of the material that can be used as the charge transport material include the above-mentioned low-molecular-weight electron transport material and hole transport material. The amount of the charge transport material used is the amount of polymer compound 1
20 to 200 parts by weight, preferably 5 to 100 parts by weight
It is about 0 to 100 parts by weight.

Examples of the dispersion solvent that can be used when preparing the coating liquid for the charge transport layer include ketones such as methyl ethyl ketone, acetone, methyl isobutyl ketone and cyclohexanone, dioxane, tetrahydrofuran,
Examples thereof include ethers such as ethyl cellosolve, aromatics such as toluene and xylene, halogens such as chlorobenzene and dichloromethane, and esters such as ethyl acetate and butyl acetate. In addition, the charge transport layer 20c
When is the outermost surface layer of the photosensitive drum 20, a filler material may be contained in the surface portion of the charge transport layer 20c. The filler material includes an organic filler material and an inorganic filler material, and the organic filler material includes a fluororesin powder such as polytetrafluoroethylene, a silicone resin powder, and an a-carbon powder. As the conductive filler material, copper, tin, aluminum, metal powder such as indium, silica, tin oxide, zinc oxide, titanium oxide, alumina, indium oxide, antimony oxide, bismuth oxide, calcium oxide, tin oxide doped with antimony, Examples thereof include metal oxides such as indium oxide doped with tin, metal fluorides such as tin fluoride, calcium fluoride and aluminum fluoride, and inorganic materials such as potassium titanate and boron nitride. Among these fillers, it is advantageous to use an inorganic material from the viewpoint of the hardness of the filler to improve wear resistance. Especially silica,
Titanium oxide and alumina can be effectively used. These filler materials may be used alone or in combination of two or more. These filler materials can be dispersed together with the charge transport substance, the binder resin, the solvent and the like by using an appropriate disperser. The average primary particle size of the filler is
0.01-1.0 μm, preferably 0.05-0.5 μm
m is preferable from the viewpoint of the transmittance and wear resistance of the charge transport layer 20c. Further, although it is possible to include these fillers in the entire charge transport layer 20c, since the exposed portion potential may be high, the outermost surface side of the charge transport layer 20c has the highest filler content, and the conductive support is formed. Body side 2
A filler concentration gradient is provided so that the 0a side becomes low,
A plurality of charge transport layers 20c are provided to form a conductive support 20a.
It is preferable to have a structure in which layers having a high filler concentration are sequentially laminated from the side to the surface side.

As a method of reducing the unevenness of the charge transport layer 20c, for example, a method of adding a leveling agent is effective. As the leveling agent, a known material can be used, but a silicone oil-based leveling agent that can impart a high level of smoothness with a small amount and has a small influence on electrostatic characteristics is particularly preferable. Examples of silicone oil include dimethyl silicone oil,
Methyl phenyl silicone oil, methyl hydrogen polysiloxane, cyclic dimethyl polysiloxane, alkyl modified silicone oil, polyether modified silicone oil, alcohol modified silicone oil, fluorine modified silicone oil, amino modified silicone oil, mercapto modified silicone oil, epoxy modified silicone Examples thereof include oil, carboxyl-modified silicone oil, higher fatty acid-modified silicone oil, and higher fatty acid-containing silicone oil. In addition, it is possible to reduce unevenness depending on the conditions during coating. For example, in dip coating, the unevenness can be reduced by pulling up the photosensitive member and then covering it with a hood when the surface of the coating film is still wet so that the surface is not disturbed by the flow of wind or the like.

As shown in FIG. 8, an undercoat layer 20d may be provided between the conductive support 20a and the charge generation layer 20b. The undercoat layer 20d is provided for the purpose of improving the adhesiveness, preventing moire, improving the coatability of the upper layer, and reducing the residual potential. Subbing layer 20
d is generally a resin as a main component, but considering that the charge generation layer 20b is coated on the resin using a solvent, the resin is a resin having a high solubility resistance to a general organic solvent. Is desirable. Examples of such resins include polyvinyl alcohol, casein, water-soluble resins such as sodium polyacrylate, copolymerized nylon, alcohol-soluble resins such as methoxymethylated nylon, polyurethane, melamine resin, alkyd-melamine resin, and epoxy resin.
Examples thereof include curable resins that form a three-dimensional network structure. Further, a metal oxide such as titanium oxide, silica, alumina, zirconium oxide, tin oxide or indium oxide, or fine powder such as metal sulfide or metal nitride may be dispersed and contained. Such an undercoat layer 20d can be formed using an appropriate solvent and coating method.

Further, as the undercoat layer 20d, a metal oxide layer formed by using a silane coupling agent, a titanium coupling agent, a chromium coupling agent or the like, for example, by a sol-gel method is also useful. In addition to the above, the undercoat layer 20d has Al ₂ O ₃ provided by anodic oxidation, an organic substance such as polyparaxylylene (parylene), and S.
An inorganic substance such as nO ₂ , TiO ₂ , ITO or CeO ₂ provided by a vacuum thin film forming method can also be used favorably. The thickness of the undercoat layer 20d is suitably 0.1 to 20 μm, preferably 1 to 10 μm.

As shown in FIG. 9, a protective layer 20e may be provided on the charge transport layer 20c. Materials used for the protective layer 20e include ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, aryl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallyl sulfone, Polybutylene, polybutylene terephthalate, polycarbonate, polyether sulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, polymethylpentene, polypropylene, polyphenylene oxide, polysulfone, polystyrene,
Examples thereof include resins such as polyarylate, AS resin, butadiene-styrene copolymer, polyurethane, polyvinyl chloride, polyvinylidene chloride and epoxy resin.

When using the protective layer 20e, a filler material is added to the protective layer. The above-mentioned filler materials can be used as the filler material, and these filler materials can be used alone or in combination of two or more kinds. These filler materials can be dispersed together with the charge transport substance, the binder resin, the solvent and the like by using a known method such as a ball mill, an attritor, a sand mill and ultrasonic waves. The average primary particle size of the filler is 0.01 to
The thickness of 0.8 μm is preferable from the viewpoint of transmittance of the protective layer and the like and abrasion resistance. Further, the charge transport layer 20 is formed on the protective layer 20e.
Addition of the charge-transporting substance mentioned in c is an effective means for improving the image quality.

As the method for forming the protective layer 20e, known methods such as a dip coating method, a spray coating method, a beat coating method, a nozzle coating method, a spinner coating method and a ring coating method can be used. The protective layer 20e preferably has a thickness of about 0.1 to 10 μm. Here, when the protective layer 20e is formed on the charge transport layer 20c, it is considered that the surface charge at the time of charging exists on the protective layer 20e. Since it can be said that the difference in film thickness between the irregularities in the vicinity is the total thickness difference between the charge transport layer 20c and the protective layer 20e, the method of reducing the irregularities is applied when the protective layer is formed as in the case of the charge transport layer 20c. To be done. In addition, the protective layer 20e
Providing a layer with high abrasion resistance means that the history of the irregularities of the layer containing the charge transport substance during the formation of the photoreceptor is maintained for a long period of time. That is, in an electrophotographic photosensitive member having relatively low wear resistance, the surface is worn by outputting an image for a long period of time, but unevenness may occur due to a partial difference in the amount of wear. Therefore, as described above, it is necessary to reduce the unevenness of the film thickness of the unevenness before use and further increase the wear resistance by providing the protective layer 20e to suppress the occurrence of the unevenness due to the difference in the wear amount for a long time. It is a very effective means for obtaining a good image over the entire range. An electrophotographic photoreceptor having high abrasion resistance is an electrophotographic photoreceptor having high abrasion resistance such that the abrasion rate of the surface layer (abrasion amount of outermost layer / distance traveled by the photoreceptor) is 1.50 × 10 ⁻¹¹ or less. A photoreceptor, which has the protective layer 20e as described above,
Examples thereof include a polymer charge transporting substance contained in the outermost layer and a low molecular weight charge transporting substance contained therein.

Although not shown, it is also possible to provide an intermediate layer between the charge transport layer 20c and the protective layer 20e. This intermediate layer generally uses a binder resin as a main component. Examples of this resin include polyamide, alcohol-soluble nylon, water-soluble polyvinyl butyral, polyvinyl butyral, and polyvinyl alcohol. As a method for forming the intermediate layer, a generally used coating method as described above is adopted. The thickness of the intermediate layer is preferably about 0.05 to 2 μm.

Further, in order to improve the environment resistance, and particularly to prevent the sensitivity from lowering and the residual potential from rising, the charge generation layer 20b, the charge transport layer 20c, the undercoat layer 20d, the protective layer 2 are provided.
0e, each layer such as the intermediate layer, an antioxidant, a plasticizer, a lubricant,
An ultraviolet absorber and a low molecular weight charge transport material can be added. Among the typical materials of these compounds, examples of the antioxidant that can be added to each layer include phenol compounds. In particular, 2,6-di-t-butyl-p-
Cresol, butylated hydroxyanisole, 2,6-
Di-t-butyl-4-ethylphenol, n-octadecyl-3- (4'-hydroxy-3 ', 5'-di-t-
Butylphenol), 2,2'-methylene-bis- (4
-Methyl-6-t-butylphenol), 2,2'-methylene-bis- (4-ethyl-6-t-butylphenol), 4,4'-thiobis- (3-methyl-6-t-butylphenol), 4,4'-butylidene bis- (3-
Methyl-6-t-butylphenol), 1,1,3-tris- (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4.
6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3-
(3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, bis [3,3'-bis (4'-hydroxy-3'-t-butylphenyl) butyric assid] Clycol ester, tocopherols and the like are preferable.

Further, as the above-mentioned antioxidant, for example, para-phenylenediamines can be used. In particular,
N-phenyl-N'-isopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl-p-
Phenylenediamine, N, N'-di-isopropyl-p
-Phenylenediamine, N, N'-dimethyl-N, N '
-Di-t-butyl-p-phenylenediamine and the like are preferable. Moreover, as the above-mentioned antioxidant, for example, hydroquinones can be used. In particular, 2,5-di-t
-Octyl hydroquinone, 2,6-didodecyl hydroquinone, 2-dodecyl hydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-
Methyl hydroquinone, 2- (2-octadecenyl)-
5-methylhydroquinone and the like are preferable. Further, as the above-mentioned antioxidant, for example, organic sulfur compounds can be used. Particularly, dilauryl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, ditetradecyl-3,3'-thiodipropionate and the like are preferable. Further, as the antioxidant, for example, organic phosphorus compounds can be used. Especially triphenylphosphine, tri (nonylphenyl)
Phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine and the like are preferable.

As the plasticizer which can be added to each layer,
For example, a phosphoric acid ester plasticizer can be used. Particularly preferred are triphenyl phosphate, tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, trichloroethyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, tri-2-ethylhexyl phosphate, triphenyl phosphate and the like. . Further, as the plasticizer, for example, a phthalate ester plasticizer can be used. In particular, dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, dibutyl phthalate, diheptyl phthalate,
Di-2-ethylhexyl phthalate, diisooctyl phthalate, di-n-octyl phthalate, dinonyl phthalate,
Diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, butylbenzyl phthalate, butyllauryl phthalate, methyloleyl phthalate, octyldecyl phthalate, dibutyl fumarate, dioctyl fumarate, etc. are preferred. . Further, as the plasticizer, for example, an aromatic carboxylic acid ester plasticizer can be used. In particular, trioctyl trimellitate, tri-n-octyl trimellitate, octyl oxybenzoate and the like are preferable. As the plasticizer, for example, an aliphatic dibasic acid ester plasticizer can be used. In particular, dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, di-n-octyl adipate, -n-octyl-n-decyl adipate, diisodecyl adipate, dicapryl adipate, azelaine. Acid di-2-ethylhexyl, dimethyl sebacate, diethyl sebacate, dibutyl sebacate, di-n sebacate
-Octyl, di-2-ethylhexyl sebacate, di-2-ethoxyethyl sebacate, dioctyl succinate,
Diisodecyl succinate, dioctyl tetrahydrophthalate, di-n-octyl tetrahydrophthalate and the like are preferable. As the plasticizer, for example, a fatty acid ester derivative can be used. Particularly preferred are butyl oleate, glycerin monooleate, methyl acetylricinoleate, pentaerythritol ester, dipentaerythritol hexaester, triacetin, tributyrin and the like. As the plasticizer, for example, an oxyacid ester plasticizer can be used. Particularly, methyl acetylricinoleate, butyl acetylricinoleate, butylphthalylbutyl glycolate, tributyl acetylcitrate and the like are preferable. As the plasticizer, for example, an epoxy plasticizer can be used. In particular, epoxidized soybean oil, epoxidized linseed oil, butyl epoxystearate, decyl epoxystearate, octyl epoxystearate, benzyl epoxystearate, dioctyl epoxyhexahydrophthalate, didecyl epoxyhexahydrophthalate and the like are preferable. Further, as the plasticizer, for example, a dihydric alcohol ester plasticizer can be used. Particularly, diethylene glycol dibenzoate, triethylene glycol di-2-ethylbutyrate and the like are preferable. As the plasticizer, for example, a chlorine-containing plasticizer can be used. Particularly, chlorinated paraffin, chlorinated diphenyl, chlorinated fatty acid methyl, methoxychlorinated fatty acid methyl and the like are preferable. As the plasticizer, for example, a polyester plasticizer may be used. Particularly, polypropylene adipate, polypropylene sebacate, polyester, acetylated polyester and the like are preferable. In addition, as the plasticizer, for example, a sulfonic acid derivative can be used. In particular, p-toluenesulfonamide, o-toluenesulfonamide, p-
Toluene sulfone ethylamide, o-toluene sulfone ethylamide, toluene sulfone-N-ethylamide,
P-toluenesulfone-N-cyclohexylamide and the like are preferable. As the plasticizer, for example, a citric acid derivative can be used. Particularly, triethyl citrate, acetyl citrate triethyl, citrate tributyl, acetyl citrate tributyl, acetyl citrate tri-2-ethylhexyl, acetyl citrate -n-octyldecyl and the like are preferable. In addition to the above, terphenyl, partially hydrogenated terphenyl, camphor, 2-nitrodiphenyl, dinonylnaphthalene, methyl abietate, and the like can also be used as the plasticizer.

The lubricant that can be added to each layer is, for example, a hydrocarbon compound. Liquid paraffin, paraffin wax, microwax, low-polymerization polyethylene and the like are particularly preferable. Further, as the lubricant, for example, a fatty acid compound can be used. Particularly, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid and the like are preferable. As the lubricant, for example, a fatty acid amide compound can be used. Particularly, stearylamide, palmitylamide, oleinamide, methylenebisstearamide, ethylenebisstearamide and the like are preferable. Further, as the lubricant, for example, an ester compound can be used. In particular, lower alcohol ester of fatty acid, polyhydric alcohol ester of fatty acid, fatty acid polyglycol ester and the like can be mentioned. Moreover, as the lubricant, for example, an alcohol compound can be used. In particular, cetyl alcohol, stearyl alcohol,
Ethylene glycol, polyethylene glycol, polyglycerol and the like are preferable. Further, as the lubricant,
For example, metal soap can also be used. In particular, lead stearate, cadmium stearate, barium stearate, calcium stearate, zinc stearate, magnesium stearate and the like are preferable. Further, as the lubricant, for example, natural wax can be used. Particularly, carnauba wax, candelilla wax, beeswax, spermaceti wax, ivorot wax, montan wax and the like are preferable. In addition to the above, a silicone compound, a fluorine compound, or the like can be used as the lubricant.

Further, examples of the ultraviolet absorber that can be added to each layer include benzophenone type ones. In particular, 2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2 ', 4-trihydroxybenzophenone, 2,2', 4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, etc. Is preferred. Further, as the ultraviolet absorber, for example, salicylate-based one can be used. In particular, phenyl salsylate, 2,4 di-t
-Butylphenyl 3,5-di-t-butyl 4-hydroxybenzoate and the like are preferable. Further, as the ultraviolet absorber, for example, a benzotriazole-based one can be used. In particular, (2'-hydroxyphenyl) benzotriazole, (2'-hydroxy5'-methylphenyl) benzotriazole, (2'-hydroxy5 '
-Methylphenyl) benzotriazole, (2'-hydroxy 3'-tert-butyl 5'-methylphenyl)
5-chlorobenzotriazole and the like are preferable. Also,
As the ultraviolet absorber, for example, a cyanoacrylate-based one can also be used. In particular, ethyl-2-cyano-3,3-diphenyl acrylate, methyl 2-carbomethoxy 3 (paramethoxy) acrylate and the like are preferable. Further, as the ultraviolet absorber, for example, a quencher (metal complex salt type) can be used.
In particular, nickel (2,2 ′ thiobis (4-t-octyl) phenolate) normal butylamine, nickel dibutyldithiocarbamate, nickel dibutyldithiocarbamate, cobalt dicyclohexyldithiophosphate and the like are preferable. Moreover, as the ultraviolet absorber, for example, HALS (hindered amine) may be used. In particular, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,
2,6,6-Pentamethyl-4-piperidyl) sebacate, 1- [2- [3- (3,5-di-t-butyl-4-
Hydroxyphenyl) propionyloxy] ethyl]-
4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpyridine, 8-benzyl-7,7,9,9-
Tetramethyl-3-octyl-1,3,8-triazaspiro [4,5] undecane-2,4-dione, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine and the like are preferable.

Next, the operation control in consideration of the temperature difference among the four photoconductor drums 20Y, 20C, 20M and 20BK, which is a feature of the present invention, will be described. FIG. 1 is an explanatory diagram showing a schematic configuration for operation control in consideration of a temperature difference between photoconductor drums. In the present embodiment, the temperature sensors 11Y, 1 as temperature detecting means are provided on the four photoconductor drums 20Y, 20C, 20M, 20BK, respectively.
1C, 11M and 11BK are provided. These temperature sensors 11Y, 11C, 11M, and 11BK are provided for the photoconductor drum 20 during standby of each copying machine and during image formation.
The temperatures of Y, 20C, 20M, and 20BK are detected, and the detection result is output to the control unit 12. Temperature sensor 11Y, 1
As the 1C, 11M, and 11BK, known ones can be widely used, and the photoconductor drums 20Y, 20C, 20M, and 2 can be used.
A contact type that directly contacts 0BK to detect temperature or a non-contact type that does not contact to detect temperature may be used. Further, the temperature sensor is used for all the photosensitive drums 20.
It does not need to be provided for Y, 20C, 20M, and 20BK, and may be provided for at least two of the photoconductor drums arranged in the machine. In particular, since the temperature of the photoconductor drums is most affected by the fixing device 25, which is the maximum heat source in the machine, the four photoconductor drums 20Y, 20C,
Among 20M and 20BK, the photoconductor drum 20BK closest to the fixing device 25 shows the highest temperature. On the contrary, the photoconductor drum 20C farthest from the fixing device 25 shows the lowest temperature. Therefore, even if the temperature sensors are provided only on the photoconductor drum 20BK closest to the fixing device 25 and the photoconductor drum 20C farthest from the fixing device 25, the maximum temperature difference between the photoconductor drums in the normal time is not detected. You can figure it out. In this case, since the number of temperature sensors is reduced, the cost can be kept low.

Temperature sensors 11Y, 11C, 11M, 11
Upon receiving the detection result from BK, the control unit 12 controls the drive of the intermediate transfer belt 10 according to the detection result.
Specifically, the four photosensitive drums 20Y, 20C, 20
When the difference between the minimum temperature and the maximum temperature of M and 20BK (hereinafter, simply referred to as "temperature difference") exceeds a predetermined value, the image forming operation is temporarily stopped even during continuous printing. And
With the photoconductor drums 20Y, 20C, 20M, 20BK and the intermediate transfer belt 10 in contact with each other, the photoconductor drum and the intermediate transfer belt are idled. By idling in this way, the photosensitive drums 20Y, 20C, 20
Transfer of heat energy occurs between the M, 20BK and the intermediate transfer belt 10. At this time, the photosensitive drums 20Y,
The intermediate transfer belt 10 that exchanges heat energy with 20C, 20M, and 20BK is common to all the photoconductor drums. Therefore, the idle rotation of the intermediate transfer belt 10 causes the photosensitive drums 20Y, 20C, 20M, and 20BK.
Will change so as to approach the temperature of the intermediate transfer belt 10. As a result, the photosensitive drums 20Y, 20
The temperature difference between C, 20M and 20BK becomes smaller.

FIG. 10 is a flow chart showing an example of the flow of control by the control unit 12. Temperature sensor 11Y,
Upon receiving the detection results from 11C, 11M, and 11BK, the control unit 12 loads the temperature data into the memory for each temperature sensor at a predetermined timing (S1). Although this timing can be set arbitrarily, the photosensitive drums 20Y, 2
It is appropriately set according to the sensitivity to temperature rise of 0C, 20M, and 20BK. After taking the temperature data into the memory, the control unit 12 calculates the difference T between the maximum value and the minimum value of each temperature data (S2). The calculated value T indicates the temperature difference between the minimum temperature and the maximum temperature of the four photoconductor drums 20Y, 20C, 20M and 20BK. Then, the control unit 12 determines whether or not the calculated value T exceeds a predetermined value Ta (S3). The predetermined value Ta depends on structural conditions such as the arrangement of the fixing device 25 and the photosensitive drum 20.
It is appropriately set according to various conditions in which the temperature change affects the image quality, such as physical conditions such as temperature characteristics of Y, 20C, 20M, 20BK, the intermediate transfer belt 10 and the like.

When it is determined that the calculated value T exceeds the predetermined value Ta, the control section 12 first sets an image formation prohibition flag (S4). By thus setting the image formation prohibition flag, the image forming operation is not started even if the user presses the start switch to generate an image forming command. If an image forming command is issued while the image forming prohibition flag is set, the image forming command is stored in the memory. Then, when the image formation impossible flag is released and the image formation possible flag is set, the image forming instruction is read from the memory and the image forming operation is started.

When the image forming impossible flag is set, the control section 12 sets the photosensitive drums 20Y, 20C, 20M and 20BK.
A drive command is output to the drum drive motor 29 that drives the intermediate transfer belt 10 and the belt drive motor 13 that drives the intermediate transfer belt 10 (S5). As a result, the photosensitive drums 20Y, 20
C, 20M, 20BK and the intermediate transfer belt 10 are each 1
At the next transfer position, the surfaces move in the same direction at the same linear velocity. The linear velocity at this time may be the same linear velocity as during the image forming operation, but if the linear velocity is faster than that during the image forming operation, the calculated value T, that is, the temperature difference between the photoconductor drums, can be predetermined in a shorter time. It is possible to make the value Ta or less.

While the photosensitive drum and the intermediate transfer belt are being driven in this way, the control unit 12 again takes in temperature data based on the signals from the temperature sensors 11Y, 11C, 11M and 11BK into the memory (S6). ). Then, similarly to the above, the difference T between the maximum value and the minimum value of each temperature data is calculated (S7), and it is determined whether or not the calculated value T is equal to or less than the predetermined value Ta (S8). Then, the control unit 12
Is the calculated value T, which is the temperature difference between the photosensitive drums,
Steps S6 to S8 are repeated until it becomes a or less. Until the temperature difference T between the photosensitive drums becomes equal to or less than the predetermined value Ta,
Steps S6 to S8 are repeated.

When it is determined that the calculated value T has become equal to or less than the predetermined value Ta, the controller 12 outputs a drive stop command to the drum drive motor 29 and the belt drive motor 13 (S9).
Thereby, the photoconductor drums 20Y, 20C, 20M, 2
The drive of 0BK and the intermediate transfer belt 10 is stopped. After that, the control unit 12 cancels the image formation prohibition flag (S
10). As a result, the image forming operation can be started, and the image forming operation is performed according to the image forming instruction.

[Example 1] Next, an example using the copying machine of the above-described embodiment (hereinafter, this example is referred to as "Example 1") will be described. First, a method of manufacturing the photoconductor drums 20Y, 20C, 20M and 20BK used in this embodiment will be described. The photoconductor drum used in this embodiment has the structure shown in FIG. First, a method of forming the undercoat layer 20d will be described. 15 parts by weight of alkyd resin (Beckolite M6401-50 (manufactured by Dainippon Ink and Chemicals, Inc.)) and 10 parts by weight of melamine resin (Super Beckamine G-821-60 (manufactured by Dainippon Ink and Chemicals, Inc.)) Is dissolved in 150 parts by weight of methyl ethyl ketone. 80 parts by weight of rutile type titanium oxide powder (Taipaque CR-EL (manufactured by Ishihara Sangyo)) and 10 parts by weight of titanium oxide surface-treated with alumina (Taipaque CR-67 (manufactured by Ishihara Sangyo)). Was added and dispersed by a ball mill for 24 hours to prepare a coating liquid for the undercoat layer. This coating liquid was 30 mm in diameter and 0.
It was applied to an aluminum substrate which is the conductive support 20a having a thickness of 8 mm by a dip coating method and dried at 130 ° C. for 20 minutes to form an undercoat layer 20d having a thickness of 2 μm.

Next, a method of forming the charge generation layer 20b will be described. 150 parts of 4 parts by weight of polyvinyl butyral resin (S-REC HL-S (manufactured by Sekisui Chemical Co., Ltd.))
It was dissolved in parts by weight of cyclohexanone. Its structural formula is
This is as shown in Chemical Formula 1 below. To this solution, 10 parts by weight of bisazo pigment was added, dispersed with a ball mill for 48 hours, and then 210 parts by weight of cyclohexanone was added to obtain 3 parts.
Time dispersion was performed. This was taken out into a container and diluted with cyclohexanone to a solid content of 1.5% by weight. The coating liquid for the charge generation layer thus obtained,
Coating on the undercoat layer 20d by a dip coating method,
It was dried at 130 ° C. for 20 minutes. Thus, the charge generation layer 20b having a thickness of 0.2 μm was formed.

[0072]

[Chemical 1]

Next, a method of forming the charge transport layer 20c will be described. To 100 parts by weight of tetrahydrofuran, 1
0 parts by weight of bisphenol Z-type polycarbonate resin and 0.002 parts by weight of α- (3-methacryloxypropyl) polydimethylsiloxane (Silaplane FM0
725 (manufactured by Chisso Corp.)). To this, 8 parts by weight of a charge transporting material having the structural formula shown in Chemical Formula 2 below was added to prepare a coating solution for the charge transporting layer. The coating liquid thus obtained was applied onto the charge generation layer 20b by a dip coating method, and then dried at 110 ° C. for 20 minutes. Thus, the charge transport layer 20c having a thickness of 20 μm is formed.
Was formed.

[0074]

[Chemical 2]

In this embodiment, the photosensitive drums 20Y, 20C, 20M and 20BK manufactured as described above and the intermediate transfer belt 10 made of a resin belt made of PVDF (polyvinylidene fluoride) in which carbon is dispersed are mounted. Use a copier. Then, the control unit 1 of the above embodiment
While performing the operation control according to 2, first, a predetermined full-color image was output in a single shot on the entire surface of 200 sheets of A3 size paper. In this embodiment, the predetermined value Ta, which is the reference for the operation control, is set to 10 ° C. During the image forming operation of the 200 sheets, the operation of the photosensitive drums 20Y, 20C, 20M, 20BK and the intermediate transfer belt 10 performed when the calculated value T exceeds the predetermined value Ta (hereinafter referred to as "temperature difference reducing operation"). .) Was only done once. In addition, after the above-described image forming operation for 200 sheets, the copying machine is left with the power on for 1 second.
Five full color images were output after 3 hours and after 5 hours. During the leaving period of 3 hours, the temperature difference reducing operation was performed 7 times.

Example 2 Next, another example (hereinafter, this example is referred to as “Example 2”) using the copying machine of the above embodiment will be described. First, a method of manufacturing the photoconductor drums 20Y, 20C, 20M and 20BK used in this embodiment will be described. The photoconductor drum used in this embodiment has a structure including a protective layer 20e as shown in FIG. The layers other than the protective layer 20e are the same as those in the first embodiment. Hereinafter, the protective layer 20
A method of forming e will be described. 4 parts by weight of a bisphenol Z type polycarbonate resin and 3 parts by weight of a charge transport material having the structural formula shown in the above Chemical Formula 2 were dissolved in a mixed solvent consisting of 80 parts by weight of tetrahydrofuran and 280 parts by weight of cyclohexanone. . 0.7 parts by weight of α-alumina (Sumicorundum AA-03: manufactured by Sumitomo Chemical Co., Ltd.) and 0.002 parts by weight of dimethylpolysiloxane (SH200 (manufactured by Toray Dow Corning Silicone Co.)). In addition, it was dispersed by a ball mill for 2 hours to prepare a coating liquid for the protective layer. The coating liquid thus obtained was applied onto the charge transport layer 20c of the photoconductor drum of Example 1 by a spray coating method, and then at 110 ° C. for 2 hours.
It was dried for 0 minutes. Thus, the protective layer 20c having a thickness of 5 μm was formed.

In this example, the same operation as in Example 1 was performed and the same evaluation was performed, except that the predetermined value Ta serving as the reference for the operation control of the controller 12 was set to 5 ° C. In this embodiment, the temperature difference reducing operation was performed four times during the image forming operation of 200 sheets. In addition, after the above-described image forming operation of 200 sheets, the number of temperature difference reducing operations is 12 when the copying machine is left with the power on and five full color images are output after 1 hour and 3 hours, respectively. It was once.

[Comparative Example] The same operation as in Examples 1 and 2 was performed without performing the operation control by the controller 12 based on the temperature difference between the photosensitive drums, and the same evaluation was performed.
The photoconductor drums 20Y, 20C, 20M, 20 at this time
The same BK as in Example 2 was used. In this comparative example, the temperature difference reducing operation was not performed even during the image forming operation of 200 sheets or during the standing period after the image forming operation of 200 sheets.

Here, in the copying machines used in Examples 1 and 2 and Comparative Example, the photosensitive drums 20Y, 2
0C, 20M, 20BK temperature sensors 11Y, 11C,
The detection results of 11M and 11BK were monitored separately. The monitored temperatures are shown in Tables 1 and 2 below, respectively.

[0080]

[Table 1]

[0081]

[Table 2]

As shown in Tables 1 and 2, in the comparative example in which the temperature difference reducing operation is not performed, after the image forming operation and the standing period, the temperature between the photosensitive drums is about 14 ° C to 1 ° C.
There is a temperature difference of about 9 ° C. In addition, all the full-color images obtained by the image forming operation of 200 sheets and the image forming operation after left for 1 hour and 3 hours in the comparative example were evaluated. The color balance of the image after outputting 200 sheets was slightly darker in yellow. Further, a deviation was confirmed between the color density gradation and the black gradation. In the comparative example, the longer the standing time, the larger the temperature difference between the photosensitive drums. The larger the temperature difference, the larger the deviation between the color density gradation and the black density gradation.

On the other hand, according to the first embodiment, the temperature difference between the photosensitive drums 20Y, 20C, 20M and 20BK is
Almost suppressed within 10 ° C., and in Example 2,
It is kept within 6 ° C. Then, similarly to the comparative example, all full color images obtained by the image forming operation of 200 sheets and the image forming operation after being left for 1 hour and 3 hours were evaluated. The concentration balance of was good.

In the above-described embodiment and Examples 1 and 2, the plurality of photosensitive drums 20Y, 20C,
The so-called indirect transfer type copying machine has been described in which the toner images formed on 20M and 20BK are primarily transferred onto the intermediate transfer belt 10 so as to overlap each other, and then the synthetic toner images are secondarily transferred onto transfer paper. Other types of copying machines may be used. For example, a plurality of photoconductor drums 20Y, 2
Each toner image formed on 0C, 20M, 20BK is
The copying machine may be a direct transfer type copying machine which directly transfers so as to overlap on a transfer paper carried and carried by a transfer paper carrying belt as a recording material carrying member. In this case, instead of the intermediate transfer belt 10 described above, the recording material conveying member functions as an endless moving member.

However, in the direct transfer method, the photosensitive drums 20Y, 20C, 2 arranged side by side in the transfer paper conveying direction are arranged.
A paper feed mechanism such as a registration roller 49 must be arranged further upstream of 0M and 20BK. In addition, the fixing device 25 must be arranged further downstream of the photoconductor drums 20Y, 20C, 20M and 20BK. Therefore, there is a drawback in that the device becomes large in the transfer paper conveyance direction. On the other hand, in the indirect transfer method, the degree of freedom of the secondary transfer position for transferring the synthetic toner image on the transfer paper is relatively high.
Therefore, the sheet feeding mechanism such as the registration roller 49 and the fixing device 25 are provided, for example, in the photosensitive drums 20 arranged side by side.
It can be arranged on the opposite side of Y, 20C, 20M, and 20BK with the intermediate transfer member interposed therebetween. Therefore, there is an advantage that the apparatus can be downsized as compared with the direct transfer method. Further, in the direct transfer method, in order to make the size as small as possible in the transfer paper conveyance direction, it is necessary to bring the fixing device 25 close to the photoconductor drum 20BK located on the most downstream side in the transfer paper conveyance direction. In this case, the photosensitive drum 20
The fixing device 25 cannot be arranged with a sufficient margin that the transfer sheet that has passed the BK transfer position can be bent. Therefore, there is a drawback that the impact when the leading edge of the transfer paper enters the fixing device 25 and the speed difference between the transfer paper feed speed by the fixing device 25 and the transfer paper transport speed by the transfer paper transport belt are likely to affect the transfer. is there. On the other hand, in the indirect transfer method, since the degree of freedom in arranging the fixing device 25 is high as described above, there is no such drawback. From the above points, it is preferable to employ the indirect transfer type copying machine as in the above-described embodiment and Examples 1 and 2.

As described above, according to the present embodiment, the photosensitive drums 20Y, 20C, 20M and 20BK as a plurality of image bearing members that carry toner images of different colors are brought into contact with the surfaces of these photosensitive drums. An image forming apparatus that includes an intermediate transfer belt 10 as an endless moving member whose surface moves endlessly, and forms a composite toner image in which toner images of respective colors formed on a plurality of photoconductor drums are overlapped on a transfer sheet as a recording material. Multiple photoconductor drums 2
At least 2 of 0Y, 20C, 20M, 20BK
Temperature sensors 11Y, 11C, 11M, 11BK as temperature detecting means for detecting the surface temperature of one photoconductor drum.
And when the surface temperature difference T between the photoconductor drums obtained based on the detection results of these temperature sensors exceeds a predetermined temperature difference Ta, the plurality of photoconductor drums and the intermediate drum are held in a state where the image forming operation is prohibited. A control unit 12 is provided as drive control means for driving the transfer belt 10 while bringing them into contact with each other. This turns ON / OFF the heater and fan.
The photosensitive drums 20Y, 20C,
Since the temperature difference between 20M and 20BK can be reduced, it is possible to suppress the temperature difference between the image carriers such as the photoconductors without using a heater or a fan. Therefore, power consumption can be suppressed as compared with an apparatus using a heater, a fan, etc., and it is possible to cope with the recent trend of energy saving. Further, according to the present embodiment, the temperature difference T between the photoconductor drums 20Y, 20C, 20M, 20BK to be suppressed is fed back to the drive control, so that the surface temperature of each photoconductor drum varies due to, for example, an environmental change inside the machine. Even if an unexpected situation occurs such that the value exceeds the predicted value, the temperature difference between the photoconductor drums can be stably maintained within a range that does not affect the image quality. Therefore, it is possible to stably suppress the image quality deterioration such as the gradation deviation due to the temperature difference between the image carriers. Further, as described in the present embodiment, the plurality of photosensitive drums 20Y, 20C, 20
A fixing device 25 is provided as a heat fixing unit that heats and fixes a composite toner image, in which the toner images formed on M and 20BK overlap, on the transfer paper. The photoconductor drum whose surface temperature is detected by the temperature sensor is the photoconductor drum 20BK arranged at the position closest to the fixing device 25.
And the photoconductor drum 20C arranged at the position farthest from the fixing device 25. In this case, the maximum temperature difference T between the photoconductor drums in the normal state can be grasped as described above. And all the photoconductor drums 20
The number of temperature sensors can be reduced as compared with the case where the temperature sensors are installed for Y, 20C, 20M, and 20BK, and the cost can be kept low. Further, in this embodiment, each of the photoconductor drums 20Y, 20C, 2
The intermediate transfer belt 10 that exchanges heat energy between 0M and 20BK is an endless belt-shaped member. In addition to the endless belt-shaped member, a drum-shaped member can also be adopted as the endless moving member in the present invention. However, since the endless belt-shaped member is usually used in a state of being stretched over a plurality of rollers, the endless belt-shaped member is largely curved as compared with the drum-shaped member. Therefore, generally, the thickness of the endless belt-shaped member is thinner than the thickness of the drum-shaped member. Moreover, in general, a plurality of photosensitive drums 20Y, 20C, 20
In the endless moving member whose surface moves endlessly so as to come into contact with the surfaces of M and 20BK, the endless belt-like member has a longer circumference and a larger surface area than the drum-like member. For this reason, the heat dissipation effect of the endless belt-shaped member is generally higher than that of the drum-shaped member. Therefore, if it is an endless belt-shaped member, the photosensitive drums 20Y, 20C,
The thermal energy received from 20M and 20BK can be released efficiently. Therefore, if an endless belt-shaped member is used as the endless moving member, the surface temperature of the photoconductor drum 20BK having the highest surface temperature can be efficiently lowered to quickly approach the surface temperature of the photoconductor drum 20C having the lowest surface temperature. You can In particular, in this embodiment, the endless belt-shaped member is composed of a plurality of photosensitive drums 20Y, 20C,
The intermediate transfer belt 10 carries a composite toner image in which the toner images formed on the 20M and 20BK are superimposed. That is, this copying machine is a so-called indirect transfer type. Therefore, as described above, compared to the so-called direct transfer method, there is an advantage that the apparatus can be downsized and that the fixing device 25 can easily cope with the transfer paper so that the transfer paper is not affected. Moreover, the intermediate transfer belt 10 of the present embodiment is an elastic belt in which at least one layer in the thickness direction is formed of an elastic material. Therefore, as described above, compared to the case of the resin belt, it is possible to obtain an advantage that it is less likely that the hollow characters in the characters or the edge missing of the solid image due to the toner aggregation will occur. Further, in the present embodiment, the predetermined temperature difference Ta, which is a criterion for determining whether or not the drive control for reducing the temperature difference between the photoconductor drums is performed, is set to 10 ° C. or less. As a result, the temperature difference between the photoconductor drums can be maintained within a range in which the density gradation for each color does not deviate. In particular, in the present embodiment, since the predetermined temperature difference Ta is 3 ° C. or more, the frequency of drive control for reducing the temperature difference between the photoconductor drums can be suppressed to some extent to some extent. Therefore, the image forming operation is not frequently prohibited so as to prevent the smooth use of the copying machine by the user.

[0087]

According to the present invention, the temperature difference between the image bearing members can be reduced without requiring ON / OFF control of the heater and the fan, so that the photosensitive member can be exposed without using the heater or the fan. There is an excellent effect that it is possible to suppress the temperature difference generated between the image carriers such as the body. Further, according to the first to sixth aspects of the invention, even if an unexpected situation occurs, for example, when the variation in the surface temperature of each image carrier exceeds the prediction due to the environmental change in the machine, the image Since it becomes possible to stably maintain the temperature difference between the image bearing members within a range that does not affect the image quality, it is possible to stably suppress the image quality deterioration such as the gradation deviation due to the temperature difference between the image bearing members. It has an excellent effect that it can be done.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration for operation control in consideration of a temperature difference between photoconductor drums of a copying machine according to an embodiment.

FIG. 2 is a schematic configuration diagram of the entire copying machine.

FIG. 3 is an enlarged view showing a configuration of a copying machine main body portion of the copying machine.

FIG. 4 is an enlarged view showing a configuration of two adjacent image forming units provided in the copying machine.

FIG. 5 is an explanatory diagram showing a schematic configuration of a toner recycling device provided in the copying machine.

FIG. 6 is an enlarged view of one end portion of a recovery screw of the photoconductor cleaning device in the copying machine.

FIG. 7 is a sectional view schematically showing an example of a photoconductor drum provided in the copying machine.

FIG. 8 is a sectional view schematically showing another example of the photosensitive drum provided in the copying machine.

FIG. 9 is a sectional view schematically showing still another example of the photosensitive drum provided in the copying machine.

FIG. 10 is a flowchart showing an example of a control flow by a control unit of the copying machine.

[Explanation of symbols]

10 Intermediate transfer belt 11 Temperature sensor 12 Control unit 13 Belt drive motor 18 Image forming unit 20 photoconductor drum 24 Secondary transfer belt 25 Fixing device 29 Drum drive motor 61 Developing device 100 Copier body 200 paper feed table 300 scanner 400 Automatic document feeder

Continued front page    F term (reference) 2H027 DA13 DE07 DE10 EA13 EB04                       EC20 ED01 ED24 EE03 EE04                       EE07 EH10                 2H200 FA01 GA12 GA16 GA23 GA29                       GA30 GA33 GA34 GA44 GA47                       GB02 GB12 GB22 GB25 HA02                       HA12 HA28 HB03 HB12 HB22                       HB28 JA02 JB20 JC04 JC13                       JC15 JC17 JC19 MA03 MA04                       MA12 MA13 MA14 MA20 MC02                       PA11 PA15 PB07                 2H300 EA19 EB04 EB07 EB12 EB18                       EB19 EB26 EB27 EC02 EC05                       EC09 EC16 EF03 EF08 EG13                       EH16 EJ09 EJ51 GG01 GG02                       GG03 GG11 GG36 QQ12 QQ16                       QQ22 RR10 TT03 TT04

Claims (6)

[Claims] 1. A plurality of image carriers comprising: a plurality of image carriers for carrying toner images of different colors; and an endless moving member whose surface moves endlessly so as to contact the surfaces of the plurality of image carriers. In an image forming apparatus for forming a composite toner image on a recording material, in which toner images of respective colors formed on the body are overlapped, a temperature detection for detecting the surface temperature of at least two image carriers among the plurality of image carriers. Means and the image carrier obtained based on the detection result of the temperature detecting means exceeds a predetermined temperature difference, the plurality of image carriers and the image carrier with the image forming operation prohibited. An image forming apparatus, comprising: a drive control unit for driving the endless moving members while bringing them into contact with each other. 2. The image forming apparatus according to claim 1, further comprising a heat fixing unit for heating and fixing a composite toner image, in which the toner images formed on the plurality of image carriers are superposed, on the recording material. The image bearing member whose surface temperature is detected by the temperature sensing unit includes an image bearing member disposed closest to the heat fixing unit and an image bearing member disposed farthest from the heat fixing unit. And an image forming apparatus. 3. The image forming apparatus according to claim 1, wherein:
The image forming apparatus, wherein the endless moving member is an endless belt member. 4. The image forming apparatus according to claim 3, wherein the endless belt-shaped member is an intermediate transfer belt carrying a synthetic toner image in which the toner images formed on the plurality of image carriers are superposed. And at least one layer in the thickness direction is made of an elastic material. 5. The image forming apparatus according to claim 1, 2, 3 or 4, wherein the predetermined temperature difference is 10 ° C. or less. 6. The image forming apparatus according to claim 5, wherein the predetermined temperature difference is 3 ° C. or more.