JP3438057B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrostatic transfer process such as an electrostatic copying machine and a printer.

[0002]

2. Description of the Related Art In this type of image forming apparatus, there have been proposed a number of image forming apparatuses including a step of sequentially superposing toner images of a plurality of colors on the same transfer material.

FIG. 5 is a side view schematically showing an example of such an image forming apparatus, which will be briefly described below. An endless belt 8 that travels in the direction of the arrow X in the drawing is provided in the main body of the image forming apparatus. The belt 8 is made of a dielectric resin such as a polyethylene terephthalate resin film or a polyvinylidene fluoride resin film, and the transfer material 6 taken out from the cassette 60 is
It is supplied to the belt 8 via the registration rollers 13 and further conveyed to the left in the drawing.

On the upper surface of the endless belt 8, four image forming portions P having basically the same structure as shown in the figure are provided.
a, Pb, Pc, and Pd are arranged in series, and the internal configuration is shown only for the image forming portion Pa.
The other image forming units are omitted.

Since each of the image forming portions Pa to Pd has the same structure, the image forming portion Pa will be briefly described. The image forming portion Pa includes a rotating cylindrical image carrier 1a, and is provided with image forming members such as a primary charger 2a, a developing device 3a, and a cleaner 5a around the image carrier 1a. Image forming unit P
b and the like have the same structure as this, and only the image carriers 1b, 1c and 1d are shown in the drawing. A magenta toner, a cyan toner, a yellow toner, and a black toner are stored in the developing devices arranged in the respective image forming units.

An image signal based on the magenta component color of the original is projected onto the image carrier 1a via the polygon mirror 17 and the like to form an electrostatic latent image, on which magenta toner is supplied from the developing device 3a to form the latent image. The image becomes a magenta toner image. When this toner image arrives at the transfer site where the image carrier 1a and the endless belt 8 contact as the image carrier 1a rotates, the transfer material 6 taken out from the cassette 60 reaches the transfer site by this time. The magenta toner image is transferred to the transfer material by the transfer bias applied by the transfer means 4a. After that, the residual toner remaining on the image carrier is removed by the cleaner 5a, and the residual charges are removed by the pre-exposure means 21a, so that the image carrier is ready for the next image formation.

When the transfer material carrying the magenta toner image is conveyed to the image forming portion Pb by the transfer belt 8, the image forming portion Pb forms the image on the image bearing member 1b by the same time. The cyan toner image is transferred to the transfer material.

Similarly, as the transfer material advances to the image forming portions Pc and Pd, the yellow toner image and the black toner image are superposed and transferred on the toner image at the respective transfer portions, and then the toner images are carried. The transfer material is separated from the belt 8 and conveyed to the fixing device 7. The fixing device 7 includes a fixing roller 71 and a pressure roller 7 that is in pressure contact with the fixing roller 71.
2 is provided, and the transfer material is fed to the nip portion of these rollers, pressed and heated to fix and fix the color image, and then discharged outside the apparatus.

After that, a charge-eliminating charger 12 and a cleaning fur brush 16 are arranged at a portion corresponding to the return path of the conveyor belt 8 to remove the charge on the belt and the toner and the like adhering to the belt. To do.

FIG. 6 is a schematic side view showing a color image forming apparatus having another structure. In this apparatus, the transfer material 6 taken out from the cassette 60 is the registration roller 1
3 is supplied to a transfer drum 80 whose surface is made of a dielectric material. When the transfer material reaches the transfer drum 80, the transfer material is adsorbed and fixed on the transfer drum by the adsorbing means composed of the adsorbing charging member and the counter electrode, and rotates and runs together with the transfer material.

On the other hand, the image signal of the cyan component color obtained from the original is projected on the surface of the image carrier uniformly charged by the primary charger 2 to form an electrostatic latent image, and the latent image is formed as an image. When the carrier 1 and the developing device 3a accommodating the cyan toner reach a developing portion facing each other, the cyan toner is applied from the developing device 3a to form a cyan toner image.

When the cyan toner image reaches a transfer portion where the image carrier 1 and the transfer drum 80 face each other, the transfer material arrives at the transfer portion at the same timing and is disposed inside the transfer drum 80. The cyan toner image on the image carrier side is transferred to the transfer material by the action of the charged charging member 4.

After that, the transfer material is rotated while traveling on the transfer drum 80 and reaches the transfer portion again.
By this time, the developing device 3b containing magenta toner on the opposing image carrier 1 has rotated to the developing portion to form a magenta toner image, and when this toner image reaches the transfer portion, A magenta toner image is superposed on the transfer material on the transfer drum.

Thereafter, similarly, a yellow toner image is superposed on the transfer material by the developing device 3c and a black toner image is superposed on the transferring material by the developing device 3d.

The transfer material that has been transferred is the charge eliminator 1
The charge is removed by the toners 4, 15 and separated from the transfer drum 80, and reaches a fixing device 7 having a fixing roller 71 and a pressure roller 72, where each color toner image is fixed and a color image is formed and discharged to the outside of the apparatus. It

In such an image forming apparatus, in order to transfer the toner image on the image carrier to the transfer material in a good condition, it is important to regulate the transfer electric field so that the toner is not scattered. Is. In addition, as a transfer means, a non-contact type such as a corona discharger whose transfer current decreases when the impedance is high due to the thickness, material, water content, etc. of the transfer material, a contact for constant voltage control such as a transfer roller or a transfer brush. The mold transfer means requires a control means for measuring or estimating the resistance value during transfer in advance.

From this point of view, it is preferable to use a conductive plate as the transfer means because the transfer electric field is regulated within an appropriate range and constant current control is easy. That is, considering the plate-shaped member and the roller-shaped member as the transfer means, the former has a clearer boundary between the part in contact with the transfer material or the transfer material carrier and the part that does not. Therefore, it is easy to regulate the electric field. Further, conductive rubber, sponge, metal or the like is used for the transfer roller and the like. When pressing this toward the transfer material, the image carrier or the transfer material carrier, the toner is strongly pressed if the pressure is too strong. There is a risk that transfer failure will occur without transfer to the transfer material, but in the former case, such a problem is easily avoided. Also,
It can be said that the blade type is preferable in terms of easy production accuracy.

[0018]

However, such a blade type transfer means, which is usually made of conductive rubber, has a problem in that it is significantly worn because it contacts the transfer material or the transfer material carrier. When the abrasion of the blade increases, friction between the image carrier and the like increases, and in the case of the image forming apparatus as described above, the contact nip portion between the blade and the transfer material transport belt is located downstream in the traveling direction of the belt. When the blade is moved or the blade length is shortened and the nip moves to the upstream side, transfer at the predetermined position cannot be performed, abnormal discharge occurs between the image carrier and the transfer unit, and the electric field There is a possibility that shortage may occur and transfer failure may occur.

The present invention has been made to cope with such a situation, and reduces friction between the transfer means and the transfer material carrier as much as possible, and regulates the pressing action on the transfer material carrier. Therefore, it is an object of the present invention to provide an image forming apparatus capable of constantly performing stable transfer and charging by preventing improper bending and sticking.

[0020]

In order to achieve the above object, the present invention provides an image carrier for carrying an image, a movable transfer material carrier for carrying a transfer material, and a substrate made of conductive rubber. And a plate-shaped charging means for transferring the image on the image carrier to the transfer material carried on the transfer material carrier, wherein the charging means is on the downstream side in the moving direction of the transfer material carrier. In the image forming apparatus, which is provided so as to be inclined with respect to the transfer material carrier and is in contact with the opposite side of the transfer material carrying body from the side carrying the transfer material, the charging means transfers the transfer of the base made of the conductive rubber. A surface layer provided at an edge facing the material carrier and having a friction coefficient lower than that of the base body, which is in contact with the transfer material carrier body; and a surface layer of the base body arranged on the downstream side in the moving direction of the transfer material carrier body of the base body. And a pressing member that regulates bending, Image forming apparatus (1) or. In the above (1), the pressing member regulates the bending of the base body via a lubricating member, or the image forming apparatus (2), or any one of (1) or (2) above. Image forming apparatus (3), in which images of a plurality of colors are sequentially transferred to a transfer material carried by the transfer material carrying body, or in the above (3), the image carrying body Are provided to respectively carry images of a plurality of colors, and the plurality of charging means are provided to transfer images of a plurality of colors from the image carriers to the transfer material carried on the transfer material carrier. An image forming apparatus (4) characterized by the above.

With this configuration, the position of the transfer nip portion can be stabilized and the contact pressure can be reduced.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION "FIG. 1" is a side view of a transfer / charging means showing an embodiment of the present invention, and "FIG. 2" is a perspective view of an essential part. As shown in FIG. 2, the means includes a charging member in which a base 401 made of a conductive rubber in the shape of a rectangular plate and an electrode 402 made of a highly conductive material are joined in the longitudinal direction by a conductive adhesive 406. is doing. A surface layer 405 having a coefficient of friction lower than that of the substrate 401 is applied and formed on an end edge of the substrate 401 which is in contact with the transfer material carrier.

FIG. 1 is a sectional view showing a charging member provided with such a substrate, which is disposed at a transfer portion of the image forming apparatus as shown in FIG. A pressing member 404 is arranged close to the downstream side of the substrate 401 (as viewed in the transfer material conveying direction) so that a uniform pressing force can be obtained on the belt 8 over the entire length of the substrate 401.

The material of the base 401 is isoprene rubber, styrene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, butyl rubber, silicon rubber, chloroprene rubber, chlorosulfonated polyethylene, acrylic rubber, hydrin rubber, urethane rubber, fluororubber, etc. It is possible to use rubbers, which are prepared by dispersing tin oxide, carbon black or the like in these rubbers so as to have an appropriate volume resistivity. In this case, the volume resistivity of the conductive rubber substrate 401 is preferably about 10 ² to 10 ⁸ Ωcm.

By the way, when the charging means having such a structure is slid on the member to be charged, the occurrence of local uneven charging in the longitudinal direction becomes a problem. The cause is uneven contact of the charging means.This uneven contact is caused by the contact accuracy from the beginning and when foreign matter is stagnant at the contact site, and the contact is caused by longer-term use. It is possible that both or one of the parts is worn or damaged.

When transfer is performed using such a charging member, as shown in FIG. 5, the case where a dielectric layer is present between the charging member and the member to be charged, and the well-known monochrome type. As is seen in the image forming apparatus, the charging member may come into direct contact with the transfer material that is the member to be charged, and it has been found that the former case suppresses uneven charging.

However, even in the former case, charging unevenness occurs due to the hardness of the base member 401 of the charging member, which will be briefly described below.

Carbon black is mixed with epichlorohydrin rubber as the material of the substrate to adjust the surface resistance value to 10 ⁹ Ω, and hardness (JIS A) 50, 60, 7
Five kinds of bases of 0, 80, 90 degrees are formed, and a coating layer in which carbon fluoride powder is dispersed in nylon is provided on the surface,
A charging member as shown in "FIG. 3" was constructed, and this was mounted on the image forming apparatus as shown in "FIG. 5", and paper was passed.

In this case, in an environment of 23 ° C. and 5% RH, good transfer was performed without uneven charging at a hardness of 60 degrees, but streaky uneven charging was observed in the order of hardness of 70 degrees and 80 degrees. It was

Under the environment of 23 ° C. and 60% RH, good transfer images were obtained with all charging members, but the hardness was 9
With 0 degree, physical defects such as contact damage to the member to be charged appeared.

Further, if the pressing force of the above-mentioned charging member in contact with the transfer material carrier is too strong, the toner on the image carrier side does not transfer when transferring about 2 to 4 line images. An image is likely to be generated especially for a line drawing extending in the transfer material conveyance direction. On the contrary, when the pressure contact force is weakened, it is preferable to use a rubber having a low rubber hardness, but this type of conductive rubber tends to have an increased frictional resistance when the hardness becomes low. As a countermeasure against this, a pressing member 404 is provided on the downstream side of the base body 401 as indicated by reference numeral 404 in FIG.
The flexure of the substrate may be adjusted.

Further, in the image forming apparatus as shown in FIG. 5, in order to suppress the charging memory on the image carrier side,
An appropriate pattern is formed on the image carrier for controlling the toner density, surface potential of the image carrier, etc., and is read by an optical sensor (not shown) or the like for feedback control, or when the transfer material is not conveyed properly. In the case of processing or the like, the image carrier or the transfer material carrier may be separated from the charging member.

In such a case, the substrate 401 as described above is used.
If the pressing member 404 does not slide smoothly along the base body in the case of the flexure adjustment, the flexure may become improper thereafter, or the transfer nip position may change to cause a transfer failure.
In order to avoid such a problem, it is preferable to dispose a lubricant between the base body 401 and the pressing member 404, as indicated by reference numeral 407 in "FIG. 1" and "FIG. 4". As a material for the lubricant, an appropriate low-friction member such as Teflon, oil paper, release paper can be used, or silicone oil or the like may be applied.

The embodiment in which the present invention is applied to the image forming apparatus having a plurality of developing devices has been described above.
The present invention is not limited to this, and for example, a monochrome type image formation including a single image bearing member and a developing unit, and an endless belt transfer material conveying unit disposed in contact with the image bearing member. It can be easily understood that it can be applied to devices and the like.

[0035]

As described above, according to the present invention,
An image forming apparatus including an image carrier, a transfer material carrier that abuts on the image carrier, and a transfer blade-shaped charging unit located on the side opposite to the image carrier when viewed from the transfer material carrier. In the above, the charging means is formed of a base body made of conductive rubber, and a surface layer having a low friction is provided at the contact edge of the transfer material carrier, and the surface of the base body is provided on the opposite side of the surface layer of the conductive rubber base body. Since the pressing member for adjusting the position is provided, it is possible to effectively prevent abrasion of the conductive rubber substrate, a change in the transfer position due to improper bending or sticking, and the like, and to obtain a good transfer property for a long period of time. There is a stable effect.

[Brief description of drawings]

FIG. 1 is a side view of a charging member showing an embodiment of the present invention.

FIG. 2 is a perspective view of a base made of conductive rubber.

FIG. 3 is a side view showing another embodiment of the charging member.

FIG. 4 is a side view showing still another embodiment of the charging member.

FIG. 5 is a schematic side view of a color image forming apparatus suitable for applying the present invention.

FIG. 6 is a schematic side view of a color image forming apparatus having another configuration suitable for applying the present invention.

[Explanation of symbols]

401 Conductive rubber substrate 402 electrode 404 Pressing member 405 Low friction layer 406 adhesive

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References Japanese Patent Laid-Open No. 2-10391 (JP, A) Japanese Patent Laid-Open No. 5-134557 (JP, A) Japanese Patent Laid-Open No. 1-93762 (JP, A) Japanese Patent Laid-Open No. 4- 361283 (JP, A) Actual development 57-187457 (JP, U) Actual development 62-151566 (JP, U) Actual development 60-122969 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15 / 16,21 / 00

Claims (4)

(57) [Claims] 1. An image carrier for carrying an image, a movable transfer material carrier for carrying a transfer material, and a base made of conductive rubber, wherein the image on the image carrier is carried by the transfer material carrier. A plate-shaped charging unit that transfers to a transfer material carried by the transfer member, the charging unit being provided so as to incline toward the downstream side in the moving direction of the transfer material carrier, In the image forming apparatus, which is in contact with a side of the body opposite to the side carrying the transfer material, the charging unit is provided at an edge of the base made of the conductive rubber facing the transfer material carrying body. A surface layer that is in contact with the body and has a coefficient of friction lower than that of the base body; and a pressing member that is disposed close to the base body on the downstream side in the moving direction of the transfer material carrying body and restricts the deflection of the base body. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the pressing member regulates the bending of the base through a lubricating member. 3. The image forming apparatus according to claim 1, wherein images of a plurality of colors are sequentially transferred onto the transfer material carried by the transfer material carrier. 4. A plurality of the image bearing members are provided to carry images of a plurality of colors, respectively, and the charging unit transfers a plurality of color images from the image bearing members to the transfer material carried on the transfer material bearing member. The image forming apparatus according to claim 3, wherein a plurality of image forming apparatuses are provided for transferring the respective images.