JP2003295611A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To save energy during drive of an image forming apparatus, which conducts development by triboelectrification of one-component developer, and extend the life of the apparatus. <P>SOLUTION: The image forming apparatus has a triboelectrifying device 500, as an independent triboelectrifying means, which frictionally pre-electrifies toner in an upstream position before the toner reaches the surface of a developing roller 402. Specifically, a top of a casing 401 is open and a toner cartridge can be loaded on it. The triboelectrifying device, as the triboelectrifying means, is provided in a position where the inside of the toner cartridge and a toner storage part communicate when the toner cartridge is loaded. In a position apart from the surface of the developing roller, the triboelectrifying device triboelectrifies the toner. <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 facsimile, a printer, etc.
The present invention relates to an image forming apparatus which carries a triboelectrically charged one-component developer on a developer carrier and conveys it to a developing nip to develop a latent image.

[0002]

2. Description of the Related Art Conventionally, in this type of image forming apparatus,
As a structure for triboelectrifying toner as a one-component developer, there is known one in which toner is triboelectrified at a contact nip between a developing roller and a supply roller. FIG. 5 is a schematic configuration diagram of the printer showing this example. First, the configuration of this printer will be described.

In the printer shown in FIG. 5, a toner layer is formed on a developing roller 402 as a toner carrier, and the toner layer on the developing roller 402 is conveyed so as to be in contact with the photosensitive drum 1. The electrostatic latent image on the drum 1 is developed. In FIG. 5, the casing 40
Inside 1, there is provided an agitator 411 as a stirring means and a supply roller 412 as a toner supply member.
The supply roller 412 is in contact with the developing roller 402, which serves as a developer carrying member, provided in the opening of the casing 401 so as to bite into the developing roller 402 by a predetermined amount. Supply roller 412
Are rotationally driven in the same direction as the developing roller 402, that is, the surfaces of the rollers facing each other move in opposite directions. In the above structure, the toner T in the casing 401 is agitated by the rotation of the agitator 411 and mechanically supplied to the supply roller 412. Supply roller 412
The toner supplied to is charged by friction at the contact position between the supply roller 412 and the developing roller 402. The frictionally charged toner is carried on the surface of the developing roller 402, and excess toner is scraped off by a toner regulating member 420 provided on the downstream side in the surface moving direction of the developing roller 402.
As a result, a uniform amount of toner layer is always formed on the surface of the developing roller 402. After that, the uniform toner layer formed on the surface of the developing roller 402 is conveyed to a developing nip, which is a portion facing the photoconductor, and is used for development.

As described above, when friction charging is performed between the surface of the developing roller 402 and a contact member such as the supply roller 412, the contact pressure and the amount of biting of the supply roller 412 with respect to the developing roller 402 are set to a predetermined amount. The triboelectric charge amount of the toner was adjusted.

By the way, as measures against environmental problems, which are a big subject in recent years, there are energy saving at the time of driving the device and extension of the life of the device. Among them, as one method for saving energy when driving the printer, it is conceivable to enable low temperature fixing and reduce fixing energy. Then, in order to enable low-temperature fixing, it is considered that the melting point of the toner is lowered so that the image can be well fixed even if the heating energy is reduced, and it is under development.

[0006]

However, when a toner having a low melting point is used, the fixing energy can be reduced, but the toner easily melts at a low temperature. Therefore, it has been found that a new phenomenon occurs in a printer having a structure in which a one-component developer is triboelectrically charged and carried on a developer carrying member. This new phenomenon causes new problems. The new phenomena and the problems caused by them are as follows. In the developing device 4 used in the conventional printer shown in FIG. 5, the toner is frictionally charged at the contact portion between the developing roller 402 and the supply roller 412. Therefore, there has been a possibility that the toner generates microscopic heat at the contact portion, and the toner is melted and fused and fixed to the surface of the developing roller. However, when the melting point of the toner is lowered, the fusion of the toner on the surface of the developing roller is accelerated, and the phenomenon that the toner is firmly attached to the developing roller 402 occurs. Then, the phenomenon that the toner adheres to the surface of the developing roller causes various problems as follows. 1
One is that streaks and unevenness occur on the image. As the toner-fixed portion of the developing roller 402 rises, unevenness is generated on the surface of the developing roller 402. When the toner layer thickness on the surface of the developing roller 402 is made uniform by the toner regulating member, the toner carrying amount available for development in the convex portion becomes smaller than that in other portions. The image portion of the photosensitive drum facing the convex portion may not be developed or may be thinned, resulting in streaks or unevenness in the image.
The other is the occurrence of background stains. Originally, the material of the surface of the developing roller 402 affects the triboelectric charge amount of toner. This is because the difference in ionization potential between the surface material of the developing roller 402 and the toner material containing the polarity control agent determines the charge polarity and charge amount of the toner.
When the toner is fused and further fixed on the surface of the developing roller 402, the other party to which the toner rubs becomes the fixed toner, which causes friction between the toners, and thus the charge amount of the toner itself is easily reduced or the toner is easily reversely charged. Become. For example, since we want to negatively charge toner by frictional charging, we originally used toner that tends to be negatively charged.
Toner that is oppositely charged comes out. Then, when the charge amount of the toner is reduced or the toner is reversely charged, these toners adhere to the non-image portion on the photosensitive drum, causing a problem of background stain.

Further, regarding the life extension of the apparatus which is another measure against the environmental problem, in the printer having the structure in which the one-component developer is frictionally charged and carried on the developer carrying member, There is a problem to be solved. In FIG. 5, the surface of the developing roller 402 and the supply roller 412 had to be strongly pressed to satisfactorily triboelectrically charge the toner. Therefore, the surfaces of the developing roller 402 and the supply roller 412 are easily worn or damaged. Also,
Conventionally, a flexible roller such as a sponge roller is generally used as the supply roller 412. When the driving of the apparatus is stopped while the supply roller 412 is strongly pressed against the developing roller 402 and left for a long time, the part of the supply roller 412 pressed against the developing roller 402 is deformed. I will end up. Then, a phenomenon called so-called creep may occur in which the deformed portion does not return to the original shape due to the subsequent rotation. The creep generated on the supply roller 412 may cause unevenness in image density. For these reasons, it was difficult to use one developing roller 402 and one supply roller 412 for a long time, and it was difficult to realize a long life of the apparatus.

From the above, in order to achieve energy saving and long life of the apparatus in the image forming apparatus in which the one-component developer is triboelectrically charged for development,
Here are some things to look for: One of them is that even if a low-melting point toner is used for low-temperature fixing, streaks and unevenness are not generated in the image and scumming can be prevented. The other is to make it possible to maintain a member, which has been short-lived for the conventional triboelectrification, in a normal state for a long time.

The present invention has been made in view of the above background, and its purpose is as follows. That is, it is an object of the present invention to provide an image forming apparatus capable of achieving energy saving when the apparatus is driven and extending the life of the apparatus in an image forming apparatus which performs triboelectrification of a one-component developer for development.

[0010]

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention comprises a latent image bearing member carrying a latent image on its surface and a developer comprising a one-component developer on its surface. A developer carrier to be carried, and a frictional charging means for frictionally charging the developer, and the developer frictionally charged by the frictional charging means is carried on the developer carrier, and the latent image carrier is provided. In the image forming apparatus which conveys the latent image to the opposite portion of the developer, the frictional charging means is configured to perform the frictional charging of the developer at a position separated from the surface of the developer carrying member. It is what By the way, the developer after triboelectrification supplied onto the developer carrying member needs to be regulated to have a uniform layer thickness before being conveyed to a portion facing the latent image carrying member. In a conventional image forming apparatus, in order to scrape off a large amount of the developer supplied onto the developer carrier to form a uniform layer thickness, a toner regulating member such as a blade or a roller is strongly attached to the developer carrier surface. I was pushing. Therefore, when the melting point of the toner is lowered, the phenomenon of toner sticking to the toner regulating member is also accelerated. Further, when the toner regulating member is strongly pressed against the developer carrying member, the surface of the developer carrying member and the tip of the toner regulating member are easily worn or damaged. As a result, it is difficult to use one developer carrying member and one toner regulating member for a long time, and it is not preferable to realize a long life of the apparatus. In addition, the surface of the developer bearing member is damaged, and appears as streaks on the image. Therefore, an image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, wherein a developer supplying member for supplying the frictionally charged developer to the surface of the developer carrying member, and the developer supplying member. It is characterized in that it is provided with an electric field forming means for forming an electric field such that the developer moves from the side to the side of the developer carrying member. Claim 3
3. The image forming apparatus according to claim 1, wherein the image forming apparatus according to claim 1 or 2, comprises a first developer accommodating portion for accommodating the developer before being triboelectrically charged by the frictional charging means, and after being triboelectrically charged by the frictional charging means. A second developer accommodating portion for accommodating the developer and a developer conveying means for conveying the developer from the first image accommodating portion toward the second developer accommodating portion, and the friction charging means is provided. It is characterized in that it is provided in the developer conveying means. An image forming apparatus according to a fourth aspect is the image forming apparatus according to the third aspect, in which the developer can be passed between the rotor that rotates the developer transporting unit and the rotor in the entire rotation axis direction of the rotor. A stator, which has a passage and is in contact with and engaged with the rotor, is provided between the second image developer accommodating portion and the first developer accommodating portion, and the inside of the passage extends from the second image agent accommodating portion to the The present invention is characterized in that it is configured by providing a developer moving means for moving the developer toward the first developer accommodating portion. An image forming apparatus according to a fifth aspect is the image forming apparatus according to the fourth aspect, wherein at least one of the outer peripheral surface of the rotor and the inner peripheral surface of the stator is brought into contact with the developer, so that the developer is triboelectrically charged. The present invention is characterized in that a triboelectrification promoting member for promoting it is provided. An image forming apparatus according to a sixth aspect is the image forming apparatus according to the fourth or fifth aspect, wherein at least one of the rotor and the stator is made of a conductive material and is grounded via an electrode. It is a thing. In the image forming apparatus according to any one of claims 1 to 6, the triboelectrification of the one-component developer carried on the developer carrying body is carried out from the surface of the developer carrying body before reaching the surface of the developer carrying body by the frictional charging means. This is done in advance at the separated positions. By this, in order to frictionally charge the developer, the two members are relatively moved while the member such as the supply member is strongly pressed against the surface of the developer carrier,
By passing the developer through the pressure contact area, it is not necessary to frictionally charge the developer. In order to prevent the toner from sticking to the surface of the developer carrying member, it is desired to reduce the contact pressure with the supply member as much as possible, which is possible in the present invention. Therefore, even if a low-melting point toner is used for low-temperature fixing, streaks and unevenness are not generated in the image, and scumming can be prevented. Furthermore, since it is not necessary to strongly press a member such as the supply member against the developer carrying member, the surface of the developer carrying member or the supplying member is less likely to be worn or scratched. Further, conventionally, the supply member is used to obtain the frictional charging function of the developer together with the supply of the developer to the developer carrying member. However, since the frictional charging function of the developer is not necessary, the supply member is replaced with a sponge roller. Other members can also be used. In any case, the developer carrier is less likely to wear or damage the supply member or the like. Also,
The creep does not occur in the portion of the supply member that is in contact with the developer carrying member even if the apparatus is left for a long time with the drive stopped. Therefore, it is possible to use one developer carrier or supply member for a long time. Therefore, it is possible to maintain the developer carrier or the supply member, which has been shortened in the related art due to the frictional charging, for a long time in a normal state.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to an electrophotographic laser printer (hereinafter referred to as "printer") as an image forming apparatus will be described below. [First Embodiment] FIG. 1 is an explanatory diagram of a printer according to a first embodiment. The printer includes a casing 401 for containing toner as a one-component developer, and a casing 4
A developing roller 402 as a developer carrying member provided in the opening 01 is provided. And the casing 401
Inside, a supply roller 412 and a toner regulating member 420 are provided close to the surface of the developing roller 402. The supply roller 412 is a developer supply member for supplying toner to the developing roller 402, and the toner regulating member 4
Reference numeral 20 is a member that regulates the layer thickness of the toner carried on the surface of the developing roller 402. Further, the printer of the present embodiment has a frictional charging device 500 as an independent frictional charging means for performing triboelectrification of the toner in advance on the upstream side where the toner reaches the surface of the developing roller 402. Specifically, the upper part of the casing 401 is opened, and the toner cartridge 430 can be mounted.
Then, the frictional charging device 5 as a frictional charging unit is provided at a position where the inside of the toner cartridge 430 and the toner storage section are in communication with each other when the toner cartridge 430 is mounted.
00 is provided. The triboelectrification apparatus 500 performs triboelectrification of toner at a position separated from the surface of the developing roller 402.

The frictional charging device 500 comprises a sponge roller 501 as a first friction member and a flat plate 502 as a second friction member, which are pressed against each other. Figure 5 shows the sponge roller
, Similar to the supply roller 412 shown in the conventional printer, but does not directly contact the developing roller 402. Therefore, there is no regulation of hardness, bubble diameter, resistance value unevenness, appearance defect, etc., unlike the supply roller 412, and it is possible to freely select. As the material, sponge such as urethane rubber, silicon rubber, nitrile rubber can be used. On the other hand, although the second friction member is a flat plate made of metal, plastic or the like, a cylindrical member or the like may be used. Further, by forming a material having a triboelectrification property having a polarity opposite to that of the toner by painting or the like on the flat surface of the flat plate, the toner can be triboelectrically charged more efficiently. In this embodiment, a melamine resin, which is known to have an effect on negatively charged toner, is applied on an Al flat plate and baked to be used. Also, replace at least the second friction member,
Alternatively, if a mechanism for changing the contact position is provided, by performing this when replacing the toner cartridge 430, for example, it is possible to always perform stable toner charging. When the toner is frictionally charged by the friction charging device 500 having the above-described configuration, the sponge roller is rotationally driven so that the toner falls into the casing 401 while passing the contact position between the sponge roller and the flat plate.
The operation of the friction charging device 500, that is, the rotation of the sponge roller can be continuously performed, but the casing 401
If the amount of toner inside is detected and the drive is controlled to perform intermittent operation, only the required amount of toner can be supplied to the casing 401.

The toner charged by the friction charging device 500 as described above falls into the casing 401. Then, the toner in the casing 401 is then carried on the surface of the developing roller 402 and conveyed to the developing nip which is a nip with the photosensitive drum. Therefore, also in this embodiment, the supply roller 412 is provided so as to face the developing roller 402. However, in the present embodiment, the toner is already triboelectrically charged before it reaches the inside of the casing 401, so there is no need to press the supply roller 412 firmly against the developing roller 402 to triboelectrically charge the toner. In this embodiment, the bite amount of the supply roller 412 with respect to the developing roller 402 is set to 0 mm. As the developing roller 402, a roller made of metal or rubber and a functional film such as mold release formed on the roller are used. Conventionally, as with the flat plate as the second friction member, a material having a triboelectrification property having a polarity opposite to that of the toner is formed by painting or the like. However, since the toner is already charged in this embodiment, the degree of freedom in selecting materials is widened, and it is also possible to use a fluororesin or the like which cannot be used in the negatively charged toner. This time, an Al roller coated with the same melamine resin as the flat plate was used. Toner regulating member 420
As in the prior art, a metal blade, a metal roller, a rubber blade, a rubber roller or the like can be used. Finally, although the photoconductor is a drum-shaped photoconductor drum this time, a belt-shaped photoconductor belt may be used.

In order to compare the printer having the structure of the first embodiment as described above with the printer of FIG. 5 introduced in the prior art, the comparison was performed in which images were respectively formed. At the time of comparison, both supply rollers 412 were made of urethane sponge rollers which are exactly the same. In addition, the first of the first embodiment
The same urethane sponge was used for the sponge roller, which is a friction member. Then, the images after standing at 40 ° C. for 10 hours were compared. As a result of the comparison, there is no abnormality on the image in the printer of the first embodiment. However, in the conventional printer shown in FIG. 5, even if 20 or more sheets of band-shaped light and shade unevenness are passed, the unevenness does not disappear. It is considered that this is because the aforementioned creep phenomenon occurred in the conventional device. On the other hand, in the first embodiment,
The biting between the developing roller 402 and the supply roller 412 is 0 m
Since it is set to m, it cannot occur. Also in the first embodiment, it is predicted that the same phenomenon as in the conventional printer occurs in the frictional charging device 500. However, since the toner is triboelectrically charged at a position apart from the development area regardless of the development timing, it is considered that the toner is not recognizable. Further, the toner regulating member 420 was applied with the same thickness SUS blade under the same conditions in the first embodiment and the printer of FIG. As a result, the regulating member 4 of the first embodiment
It was found that the toner adhesion amount on the developing roller 402 after passing 20 was reduced by 10% as compared with the conventional configuration. It is considered that this is because in the first embodiment, the amount of toner supplied onto the developing roller 402 is only the required amount, which is significantly smaller than that of the conventional printer. Therefore, in the configuration of the first exemplary embodiment, the toner regulating member 42 is different from the conventional one.
It is also possible to reduce the contact pressure of 0 on the developing roller 402.

[Second Embodiment] Next, a printer according to a second embodiment will be described. FIG. 2 is an explanatory diagram of the printer according to the second embodiment. In this printer, the supply roller 412 in the printer of the first embodiment is replaced with a plate-shaped electrode member 413. Except for this, since it is the same as the first embodiment, the description of the same parts will be omitted. The electrode member 413 is provided with bias applying means (not shown) as electric field forming means. As a result, a bias is applied to the electrode member 413 and the developing roller 4
02 to assist the supply of toner to the upper part. if,
When the supply roller 412 is removed, the friction charging device 50
The toner charged with 0 is simply sprinkled on the developing roller 402. With this, reliable toner supply is difficult. Therefore, in the second embodiment, the developing roller 402 is utilized by utilizing the bias generated by the electrode member 413.
Toner is actively supplied. Electrode member 4
As shown in FIG. 3, 13 has a lower end facing the surface of the developing roller 402, and the electrode member 413 is inclined to form a V-groove-shaped region by the developing roller 402 and the electrode member 413. The area above the V groove is the frictional charging device 5.
It is located below 00. Thereby, the electrode member 4
13 dropped on the V groove formed by the surface of the developing roller 402 and the surface of the developing roller 402.
It is electrically supplied to the surface of the developing roller 402 by the bias of 2. Here, the charge amount due to the friction of the toner is -2.
An example of the bias applied to each member when 0 [μC / g] is shown. Toner regulating member -700V, electrode member -700V, developing roller 402-400V, image part of photosensitive drum is -100V, and non-image part is -800V.

By providing the electrode member 413 as in the second embodiment, the charged toner sent from the friction charging device 500 can be electrically supplied to the surface of the developing roller 402. As a result, the supply of the developer to the developing roller 402 is ensured, and the supply amount can be controlled by setting the internal astigmatism, so that an appropriate amount is substantially uniform as compared with the case where the supply roller 412 or the like mechanically supplies the developer. Can be supplied to.

[Third Embodiment] Next, a printer according to a third embodiment will be described. FIG. 3 is an explanatory diagram of a printer according to the third embodiment. In Embodiments 1 and 2 described above, it is necessary to newly install the frictional charging device 500 inside the apparatus, particularly inside the casing 401 of the developing apparatus. For this reason, there is a concern that the printer itself may become slightly larger. Therefore, in the third embodiment, the triboelectrification device 5 is provided at a position apart from the casing 401 of the developing device.
00 is provided.

In FIG. 3, a first toner containing portion 6 as a first developer containing portion located at a position separated from the developing device 4.
01 and a second toner accommodating portion 451 as a second developer accommodating portion that accommodates the toner after being triboelectrically charged. The second toner accommodating portion 451 is provided with the developing roller 402 so that a half of the surface of the second toner accommodating portion 451 is exposed to the outside. Further, a screw pump 701 is provided as a developer transporting unit that transports toner from the first toner storage unit 601 to the second toner storage unit 451. The first toner storage unit 601 is provided with the frictional charging device 500 having the same configuration as that shown in the first and second embodiments. Further, the second toner storage portion 451 has the same configuration as the portion of the casing 401 shown in the second embodiment below the frictional charging device 500.

The screw pump is a screw pump (USP2505136) known as a mono pump. This screw pump includes a rotor 702 and a stator 703 inside. The rotor is made of metal or resin and is fitted inside the stator.
On the other hand, the stator is made of metal or resin,
The oval cross section has a hole twisted in a spiral shape, and the rotor is fitted into this hole. Also, the rotor has its shaft 7
Reference numeral 02a is a drive motor (not shown) as developer moving means for rotating the rotor via the bearing 704.
It is connected to the. The rotor can be made by cutting a metal such as AI or SUS or molding a resin such as ABS or PC. The stator is ethylene propylene rubber,
It is possible to mold an elastic body such as silicone rubber, urethane rubber, nitrile rubber, or chloroprene rubber.
Further, the conductive bearing 704 of the rotor and the metal piece 703a provided at the stator end are grounded.

The first toner container 601 is provided at a position separated from the second toner container 451. Since the developing roller 402 is provided in the opening of the second toner container 451 and the developing roller 402 needs to be provided to face the photosensitive drum, it is necessary to provide the developing roller 402 adjacent to the photosensitive drum. On the other hand, the first toner container 60
1, the position to be provided is free.

In the above structure, when the image forming operation is performed, the internal toner is frictionally charged by the frictional charging device 500 provided in the first toner container 601. Then, the triboelectrically charged toner is conveyed from the first toner container 601 to the second toner container 451 by the screw pump. At this time, the toner passing through the inside of the screw pump comes into contact with each other while passing through the passage formed by the rotor and the stator, and the triboelectric charging proceeds further. Thus, the screw pump also has the function of performing triboelectric charging of the toner. The toner that has been sufficiently frictionally charged in the two stages of the frictional charging device 500 and the screw pump as described above reaches the second toner storage portion 451. The toner that has reached the second toner storage unit 451 is the same as that in the second embodiment.
Similarly, is supplied onto the developing roller 402 by the electrode member 413. Then, a toner layer is uniformly formed on the surface of the developing roller 402 by the toner regulating member 420, and the toner layer is conveyed to the nip portion with the photosensitive drum.

[Modification] Next, a modification of the third embodiment will be described. In the third embodiment, the triboelectrification of the toner is performed in two steps of the triboelectrification apparatus 500 and the screw pump. As a modified example, a configuration in which the screw pump has only one stage is introduced. This modified example is different from the configuration of the third embodiment shown in FIG.
00 shall be removed. Further, at least one surface of the rotor or the stator is coated with a material having a triboelectrification property opposite to that of the toner as a triboelectrification promoting member.
In this modification, since the toner is negatively charged, the triboelectrification promoting member is made of a material that is easily positively charged.

As described above, when at least one surface of the rotor or the stator is coated with a material having a triboelectrification property opposite to that of the toner, the triboelectrification efficiency of the toner passing therethrough can be improved. Therefore, the third embodiment
Even if the triboelectric charging device 500 is not provided as described above, the toner can be surely triboelectrically charged to a desired charge amount.

In the above-described third embodiment and its modification, the developing roller 402 which must be provided adjacent to the photosensitive drum.
It is possible to reduce the size of the second toner containing portion 451 including the above in comparison with the first and second embodiments. So, for example,
When used in a device such as a four-tandem tandem type color printer in which it is desired to downsize the members around the photosensitive drum,
The effect can be exerted more. Next, a quadruple tandem type color printer in which it is effective to adopt the third embodiment and its modification will be described.

FIG. 4 is a schematic configuration diagram of a four-tandem tandem type color printer. In the figure, reference numeral 100 is a copying apparatus main body,
Reference numeral 200 is a paper feed table on which it is placed, 300 is a scanner mounted on the copying apparatus main body 100, and 400 is an automatic document feeder (ADF) further mounted thereon.
An endless belt-shaped intermediate transfer member 10 is provided in the center of the copying apparatus main body 100. As shown in FIG. 2, the intermediate transfer member 10 comprises a base layer 11, a base layer made of a non-extensible material such as canvas with a fluororesin having a small elongation or a rubber material having a large elongation, and an elastic layer 12 formed thereon. To provide.
The elastic layer 12 is made of, for example, fluorine rubber or acrylonitrile-butadiene copolymer rubber. The elastic layer 12
The surface of is coated with, for example, a fluororesin and covered with a coat layer 13 having good smoothness.

As shown in FIG. 4, this intermediate transfer member is wound around three support rollers 14, 15, 16 so that it can be rotated and conveyed clockwise in the drawing. In this illustrated example, an intermediate transfer member cleaning device 17 that removes residual toner remaining on the intermediate transfer member 10 after image transfer is provided to the left of the second support roller 15 among the three. The first of the three
On the intermediate transfer body 10 stretched between the second support roller 14 and the second support roller 15, four image forming means 18 of cyan, magenta, yellow and black are arranged side by side along the conveying direction. is doing. Thereby, the tandem image forming section 20 is formed.

An exposure device 21 is further provided on the tandem image forming section 20 as shown in FIG. on the other hand,
A secondary transfer device 22 as a secondary transfer unit is provided on the side opposite to the tandem image forming section 20 with the intermediate transfer body 10 interposed therebetween. In the illustrated example, the secondary transfer device 22 is configured by spanning an endless secondary transfer belt 24 between two rollers 23, and presses the intermediate transfer member 10 against the third support roller 16. As a result, the image on the intermediate transfer member 10 is secondarily transferred to a sheet as an image holding member. Next to the secondary transfer device 22, a fixing device 25 that fixes the transferred image on the sheet is provided. The fixing device 25 is configured by pressing the pressure roller 27 against the fixing belt 26 which is an endless belt.

The above-mentioned secondary transfer device 22 is also provided with a sheet carrying function for carrying the sheet after the image transfer to the fixing device 25. Of course, a transfer roller or a non-contact charger may be arranged as the secondary transfer device 22, and in such a case, it is difficult to provide this sheet conveying function together. In the illustrated example, a sheet reversing device 28 that reverses the sheet to record images on both sides of the sheet in parallel with the above-described tandem image forming unit 20 under the secondary transfer device 22 and the fixing device 25. Equipped with.

Now, when making a copy using this color electrophotographic apparatus, a 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. Then, when a start switch (not shown) is pressed, the scanner 300 is driven and the first traveling body 33 and the second traveling body 34 travel. At this timing, when a document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 32, and then when the document is set on the other contact glass 32,
Immediately. Then, the first traveling body 33 emits light from the light source, and the light reflected from the document surface is further reflected and directed toward the second traveling body 34, reflected by the mirror of the second traveling body 34, and passed through the imaging lens 35. Put it in the reading sensor 36,
Read the contents of the original.

When a start switch (not shown) is pressed, the supporting rollers 14, 15, 16 are driven by a drive motor (not shown).
One of them is driven to rotate and the other two support rollers are driven to rotate, and the intermediate transfer member 10 is rotatably conveyed. At the same time, the photoconductor 40 is rotated by each of the image forming means 18 to rotate the photoconductor 40.
0, cyan, magenta, yellow, and black single-color images are formed on the screens 0, respectively. Then, as the intermediate transfer body 10 is conveyed, the single color images are sequentially transferred to form a composite color image on the intermediate transfer body 10.

On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, and the sheet is fed from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. Then, the sheets are separated one by one by the separating roller 45 and placed in the paper feed path 46, conveyed by the conveying roller 47 and guided to the paper feed path 48 in the copying machine main body 100, and abutted against the registration roller 49 to be stopped. Or
Sheets on the manual feed tray 51 are fed out by rotating the paper feed roller 50, separated by the separation roller 52 one by one, and inserted into the manual paper feed path 53, and similarly abutted against the registration rollers 49 and stopped.

Then, the registration roller 49 is rotated in synchronism with the composite color image on the intermediate transfer member 10, the sheet is fed between the intermediate transfer member 10 and the secondary transfer device 22, and the secondary transfer device 22 is operated. Transfer to record a color image on the sheet. The sheet after the image transfer is conveyed by the secondary transfer device 22 and sent to the fixing device 25. The fixing device 25 applies heat and pressure to fix the transferred image, and then the switching claw 55 switches the sheet to discharge the sheet. The sheet is discharged at 56 and is stacked on the sheet discharge tray 57. Alternatively, the sheet is switched by the switching claw 55 into the sheet reversing device 28, reversed there and guided to the transfer position again, and after recording an image on the back side, the sheet is discharged onto the sheet discharge tray 57 by the discharge roller 56. On the other hand, after the image transfer, the intermediate transfer body cleaning device 17 removes the residual toner remaining on the intermediate transfer body 10 by the intermediate transfer body cleaning device 17, and prepares for another image formation by the tandem image forming unit 20.

The structure shown in FIG. 3 is used as the photosensitive member 40 and the image forming means 18 around the photosensitive member of the above-mentioned four-series tandem type color printer. Since the position of the first toner storage portion 601 can be flexibly set, the second toner storage portion 451 provided around the photoconductor is provided.
Since it is not necessary to provide the frictional charging device 500, the space can be saved. Therefore, even when the four photoconductors are arranged in parallel, the entire width thereof can be relatively narrowed, and the first toner storage portion 601 can be provided by utilizing the gap in the apparatus. Become.

Embodiments 1, 2, 3 and Embodiment 3 described above
In the modified example described above, the triboelectrification of the toner is performed by the triboelectrification device 500 or the screw pump.
The position is separated from the surface. This makes it possible to reduce the contact pressure of the supply roller 412 or the electrode member 413 and the toner regulating member 420 on the developing roller 402. Therefore, even if a low-melting point toner is used for low-temperature fixing, streaks and unevenness are not generated in the image, and scumming can be prevented. Further, the developing roller 402, the supply member, the toner regulating member 420, etc. can be maintained in a normal state for a long time. Therefore, in a printer that develops by frictionally charging a one-component developer, it is possible to realize energy saving and long life when the device is driven. Further, in the second and third embodiments, toner is positively supplied to the developing roller 402 by utilizing the bias of the electrode member 413. Further, the toner is supplied to the V groove formed by the developing roller 402 and the electrode member 413 to promote the supply of the toner to the developing roller 402. As a result, the frictionally charged toner can be electrically supplied to the surface of the developing roller 402, and the toner can be supplied to the surface of the developing roller 402 in advance in an appropriate amount and substantially uniformly. Therefore, in addition to the conventional example, the toner scraping action of the toner regulating member 420 can be reduced compared to the first embodiment, and the contact pressure of the toner regulating member 420 on the developing roller 402 can be reduced. Become. As a result, the developing roller 40
2 It is possible to avoid wear and scratches on the surface and the tip of the toner regulating member 420, and these can be used for a long time. Further, it is possible to prevent the generation of streaks on the image due to the scratches on the developing roller 402. Therefore, it is more preferable to realize a long life of the device. Further, the developing roller 402
It is not necessary to deal with wear and scratches by selecting a material having a high strength or a material having a small friction coefficient as the surface material, and the selection range of the material is widened. In addition, in the third embodiment and the modified example thereof, the first toner storage unit 601.
A screw pump as a developer conveying means is provided between the second toner storage portion 451 and the second toner storage portion 451. As a result, the position of the first toner storage unit 601 can be flexibly set, so that it is not necessary to provide the frictional charging device 500 in the second toner storage unit 451 provided around the photoconductor, and the space can be saved. It will be possible. If this is used in an apparatus in which it is desired to reduce the size of the members around the photosensitive drum, such as a four-tandem tandem type color printer, the effect can be exhibited more effectively. Also, the toner can be triboelectrically charged as it passes through the screw pump. Therefore, the toner can be favorably charged even if the contact pressure between the sponge roller 501 and the flat plate 502 of the frictional charging device 500 according to the third embodiment is set to be low. Here, the time taken for the toner to pass through the passage surrounded by the rotor and the stator is considerably longer than the time taken for the toner to pass through the contact portion between the developing roller 402 and the supply roller 412. Therefore, the third embodiment
Further, in the modification, even if the contact pressure of the toner is small, it is possible to perform the triboelectric charging of the toner. Therefore, as compared with the conventional triboelectric charging that is performed only between the developing roller 402 and the supply roller 412, it is possible to favorably perform triboelectric charging while reducing the stress applied to the toner. Further, in the modified example of the third embodiment, a material having a triboelectrification property opposite to that of the toner is applied to at least one surface of the rotor or the stator as a triboelectrification promoting member,
The triboelectric charging efficiency of the toner passing therethrough is improved. Therefore, the triboelectrification of the toner can be sufficiently performed only by the screw pump, and the stress applied to the toner can be made smaller than that in the third embodiment. Also,
The screw pump itself can obtain a sufficient triboelectrification amount even if the length of the rotor, which is a control factor relating to the triboelectrification amount of toner, is shortened or the bite amount between the rotor and the stator is reduced. There are cases. In this case, the stress applied to the toner can be further reduced.
Further, in the third embodiment and its modified example, the conductive bearing 704 of the rotor and the metal piece 7 provided at the stator end portion.
And 03a are grounded. As a result, even if the rotor and the stator are used for a long period of time, the electric charge is not led to the ground and the rotor and the stator do not unexpectedly charge. Therefore, the triboelectric charging performance of the toner can be maintained in a stable state.

[0035]

According to the image forming apparatus of the first to sixth aspects, in the image forming apparatus for developing by frictionally charging the one-component developer, even if the low melting point toner is used for low temperature fixing, the image is formed. There are no streaks or unevenness, and it is possible to prevent scumming. Further, it is possible to maintain a member, which has been shortened in the related art due to frictional charging, for a long time in a normal state. Therefore, in the image forming apparatus that develops by frictionally charging the one-component developer, there is an excellent effect that energy saving when the apparatus is driven and the life of the apparatus can be extended.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a printer according to a first embodiment.

FIG. 2 is an explanatory diagram of a printer according to a second embodiment.

FIG. 3 is an explanatory diagram of a printer according to a third embodiment.

FIG. 4 is a schematic configuration diagram of a four-tandem tandem color printer.

FIG. 5 is a schematic configuration diagram of a conventional printer using a one-component developer.

[Explanation of symbols]

1 photoconductor drum 10 Intermediate transfer body 18 Image forming means 20 Tandem image forming unit 22 Secondary transfer device 25 Fixing device 26 fixing belt 40 photoconductor 60 charging device 61 Developing device 62 Primary transfer device 63 Photoconductor cleaning device 65 Development sleeve 66 Stirrer 67 Development Department 70 Development case 80 Toner recycling device 100 Copier body 200 paper feed table 300 scanner 401 casing 402 developing roller 412 Supply roller 413 electrode member 420 Toner regulating member 500 friction charging device 501 sponge roller 502 flat plate

Continued front page    (72) Inventor Takayuki Yoshii             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Taisuke Tokuwaki             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor ▲ Taka ▼ Yoshiyuki Nono             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F-term (reference) 2H077 AA02 AA15 AA25 AA35 AC04                       AD02 AD06 AD13 AD17 AE03                       AE08 BA08 EA11 FA25

Claims (6)

[Claims] 1. A latent image carrier for carrying a latent image on its surface, a developer carrier for carrying a developer consisting of a one-component developer on its surface, and a frictional charging means for frictionally charging the developer. In the image forming apparatus, the developer, which is frictionally charged by the frictional charging means, is carried on the developer carrier and is conveyed to a portion facing the latent image carrier to visualize the latent image. An image forming apparatus characterized in that the frictional charging means is configured so that the triboelectrification of the developer is performed at a position separated from the surface of the developer carrying member. 2. The image forming apparatus according to claim 1, wherein a developer supplying member for supplying the frictionally charged developer to the surface of the developer carrying member, and the developer carrying member from the side of the developer supplying member. An image forming apparatus comprising: an electric field forming unit that forms an electric field for moving the developer on the body side. 3. The image forming apparatus according to claim 1 or 2, wherein a first developer accommodating portion for accommodating a developer before being triboelectrically charged by the frictional charging means, and a first developer accommodating portion after being triboelectrically charged by the frictional charging means. A second developer accommodating section for accommodating the developer and a developer conveying means for conveying the developer from the first image accommodating section toward the second developer accommodating section are provided, and the friction charging means is provided. An image forming apparatus provided on a developer conveying means. 4. The image forming apparatus according to claim 3, wherein the developer transport means has a rotor that rotates and a passage through which the developer can pass between the rotor and the rotor in the entire rotation axis direction. At the same time, a stator which is in contact with and engaged with the rotor is provided between the second image developer accommodating portion and the first developer accommodating portion, and the inside of the passage is accommodated from the second image agent accommodating portion to the first developer accommodating portion. An image forming apparatus configured by providing a developer moving unit that moves a developer toward a portion. 5. The image forming apparatus according to claim 4, wherein at least one of the outer peripheral surface of the rotor and the inner peripheral surface of the stator is brought into contact with the developer to promote triboelectric charging of the developer. An image forming apparatus comprising an accelerating member. 6. The image forming apparatus according to claim 4, wherein at least one of the rotor and the stator is made of a conductive material and is grounded via an electrode.