JP3074069B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image for forming an image on a recording material by forming a toner image on an image carrier, transferring the toner image onto a recording material conveyed by a recording material conveying member. Regarding the forming apparatus, in particular, by bringing a contact type transfer means such as a conductive brush into contact with the back surface of the conveyance member, generating a transfer electric field by applying a voltage to the transfer member, and applying the transfer electric field to the recording material carried on the conveyance member. And an image forming apparatus for transferring a toner image onto a recording material.

[0002]

2. Description of the Related Art Conventionally, a plurality of image forming units are provided, and each image forming unit forms a toner image of a different color, and the toner images are sequentially superimposed on the same recording material and transferred to form a color image. A variety of so-called color image forming apparatuses have been proposed, and among them, a color copying apparatus based on a multicolor electrophotographic system is widely used.

An example of such a color electrophotographic copying apparatus will be described with reference to FIG. 13. First, second, third and fourth image forming sections (images) are provided in the apparatus main body of the color electrophotographic copying apparatus. (Forming stations) Pa, Pb, Pc, and Pd are arranged side by side, and toner images of different colors are formed through processes of latent image formation, development, and transfer.

The stations Pa, Pb, Pc, Pd
Are each provided with a dedicated image carrier, in this example, electrophotographic photosensitive drums 1a, 1b, 1c and 1d, and the toner images formed on the photosensitive drums 1a, 1b, 1c and 1d are
The recording material 6 on which the toner image is sequentially transferred onto the recording material 6 carried and conveyed on a transfer belt 8 moving adjacent to each image forming unit and transferred with a toner image is heated and pressed by a fixing device 7 to form a toner. After the image is fixed, the recording material 6 is discharged out of the image forming apparatus.

Around the photosensitive drums 1a, 1b, 1c and 1d, exposure lamps 21a, 21b, 21c, 21d,
Drum chargers 2a, 2b, 2c, 2d, developing units 3a, 3
b, 3c, 3d and cleaners 5a, 5b, 5c, 5d
Is arranged. Further, a common light source device (not shown) and a polygon mirror 17 are provided. Furthermore, each station P
The transfer belt 8 described above is provided below a, Pb, Pc, and Pd, and brush-like transfer charging means 4a, 4b, 4c, and 4d are arranged inside the transfer belt 8 as contact-type charging means.
A cleaning device 9 is arranged outside on the lower track of the transfer belt 8.

The laser light generated from the above light source device is scanned by rotating the polygon mirror 17, and the scanning light whose light beam direction is changed by the reflection mirror is passed through the fθ lens to the photosensitive drums 1a, 1b, 1c,. The photosensitive drums 1a, 1b, 1c, and 1d are condensed and exposed on the 1d bus.
A latent image of cyan, magenta, yellow, and black component colors corresponding to the image signal is formed thereon.

The developing devices 3a, 3b, 3c, and 3d are filled with predetermined amounts of cyan, magenta, yellow, and black developers by a supply device, and the photosensitive drums 1a, 1b, 1c, and 1d are filled with the developers. The latent image formed above is developed and visualized as a toner image.

[0008] The recording material 6 in the recording material cassette 60 is supplied to the transfer belt 8 via the registration roller 13 and is carried and conveyed by the transfer belt 8.

A transfer belt 8 which is a recording material carrying member of the recording material conveying member has a polyethylene terephthalate resin (P
ET), a sheet made of a dielectric resin such as polyvinylidene fluoride resin, polyurethane resin, etc. is used, and the both ends are overlapped and joined together to form an endless belt, or a seamless (seamless) endless belt. By doing so, it is used as the transfer belt 8. When the transfer belt 8 is a belt having a seam, a seam position detecting unit (not shown) may be provided so that transfer is not performed on the seam of the transfer belt 8.

When the transfer belt 8 starts rotating, the recording material 6 is sent out from the registration roller 13 onto the belt 8. At this time, the image writing signal is turned on, whereby image formation is started on the first photosensitive drum 1a at a certain timing, and a first color cyan toner image is formed on the photosensitive drum 1a. Then, when the recording material 6 comes below the photosensitive drum 1a, a first color cyan toner image is transferred onto the recording material 6 by applying a transfer electric field by the brush-like transfer charging means 4a. The recording material 6 is strongly electrostatically attracted and held on the transfer belt 8 by the charging at the time of the transfer, and is conveyed to the second station Pb and the subsequent stations in the held state, and is transferred onto the respective photosensitive drums 1b, 1c, and 1d. Is transferred.

The recording material 6 on which the transfer of the toner images at the first to fourth image forming stations Pa to Pd has been completed as described above is de-energized by the separation charger 14 and the peel-off charger 15 to have an electrostatic attraction force. Is attenuated from the transfer belt 8 and conveyed to the fixing device 7.

The fixing device 7 includes a fixing roller 71 and a pressure roller 72 each having a built-in heater 70, and a temperature control thermistor 79 provided on the surface of the pressure roller 72.
Is maintained at a constant temperature. The transfer material 6 sent to the fixing device 7 includes a rotating fixing roller 71 and a pressing roller 7.
The toner images of the four colors transferred onto the transfer material 6 in the process of being pinched and conveyed by the transfer roller 2 are fixed by heating, pressing, and fixing the toner image to the transfer material 6. It is. During this fixing operation, a releasing agent oil such as dimethyl silicone oil is applied to the fixing roller 71 by the application roller 77. Fixing roller 71, pressure roller 72
Are cleaned by the heat-resistant cleaning members 73 and 74.

On the other hand, the photosensitive drums 1a, 1b, 1c and 1d, to which the transfer of the toner image has been completed,
The cleaning by a, 5b, 5c, and 5d removes the developer remaining on the surface, and prepares for the subsequent formation of a latent image. The transfer belt 8 from which the transfer material 6 has been separated is neutralized by the belt neutralizer 12 to remove the electrostatic attraction force, and then the remaining developer is scraped off by the rotating fur brush 16 of the cleaning device 9. In addition to the fur brush 16, a blade, a nonwoven fabric, or a combination thereof is used as the cleaning member.

[0014]

The brushes of the brush-like transfer means 4a, 4b, 4c and 4d are made of conductive fibers or a mixture of conductive fibers and ordinary fibers for the purpose of adjusting the strength. . These brush fibers have a single fiber diameter of 30.
Under the conditions of ６ 6000 denier, 1 to 500 single filaments of yarn, and 200 to 1,000,000 yarns / inch ^{2 in} the density of yarns, it can be formed into an ordinary thick brush or a cylindrical fur brush. Thus, it is used as a brush for brush-like transfer means.

[0015] Brush-like transfer means 4a, 4b, 4c, 4d
Are used to apply a transfer electric field to the recording material 6 at the transfer positions where the photosensitive drums 1a, 1b, 1c, and 1d and the transfer belt 8 face each other. Partially protruding upstream of
A transfer electric field may be applied before the recording material and the photosensitive drum come into close contact with each other, and the obtained transferred image may be disturbed. In order to prevent this, conventionally, the charging means 4a, 4
The upstream end of each of the b, 4c and 4d brush fibers is regulated by an insulating regulating member (not shown) such as a dielectric film.

However, it is easy for the brush fiber regulating member such as a dielectric film to partially hit the brush fiber in its longitudinal direction (the same direction as the axial direction of the photosensitive drum). The portion in contact with the fiber has the same potential as the bias applied to the brush, but the portion not in contact with the brush fiber has a different potential due to the generation of triboelectric charge due to friction with the transfer belt 8 or the like.
As a result, the transfer electric field becomes non-uniform upstream of the brush fiber regulating member, and in some cases, the transfer electric field acts on the toner image before the recording material and the photosensitive drum are in contact with each other to transfer the toner image. That is, the transfer state changes between the portion of the regulating member where the brush fibers do not contact and the portion where the brush fibers contact, and image defects may occur.

The respective position settings of the brush-like transfer means 4a to 4d on the upstream side in the moving direction of the transfer belt 8 are as follows.
This is performed by using the tips of the brush fiber regulating members 4a to 4d upstream of the charging means. However, as described above, since the electric field state upstream of the brush fiber regulating members is different, the recording material and the photosensitive drum are different. In the so-called transfer area where the brush fiber regulating member is in contact with the brush fiber regulating member, the brush fiber regulating member and the brush-like transfer means must be moved downstream and set in an area that is not affected by the unevenness of the electric field state. No. This means that the transfer area is used narrowly, so that the entire toner image cannot be transferred in the transfer area, resulting in poor transfer or the portion where the toner image was not transferred passing through the transfer area and then downstream. Transfer failure due to the electric field from the brush fibers extending to the right side.

An object of the present invention is to provide a brush-type transfer means serving as a contact-type transfer means, wherein the brush fibers non-uniformly contact a brush fiber regulating member which regulates a brush fiber portion on an upstream side in a moving direction of a recording material conveying member. To prevent the potential of the brush fiber regulating member from becoming uneven, and to use the transfer area where the recording material and the image carrier are in contact with each other without narrowing the transfer area. An image forming apparatus capable of preventing and preventing toner scattering easily by transfer using a brush-like transfer means and obtaining a high-quality color image excellent in image uniformity, gradation, and graininess. It is to provide.

[0019]

[0020]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides an image carrier that carries a toner image, a recording material carrying member that carries and carries a recording material, and a toner image on the image carrier that comes into contact with the back surface of the recording material carrying member. A brush for electrostatically transferring the recording material to a recording material carried by the recording material conveying member, wherein the dielectric film regulates a position on the upstream side of the brush in a moving direction of the recording material conveying member. Wherein the dielectric film has an area that comes into contact with the brush via a conductive member.

According to one embodiment of the present invention, the volume efficiency of the conductive member is 10 ¹² Ω · cm or less. According to another embodiment, the conductive member is provided on a tip side of the dielectric film.

[0022]

[0023]

【Example】

Embodiment 1 FIG. 1 is a sectional view showing a transfer unit in an embodiment of the image forming apparatus of the present invention. This embodiment shows a case where the present invention is applied to the conventional image forming apparatus described with reference to FIG. As shown in FIG. 1, a brush-like transfer means 4 as a contact-type charging means and a brush fiber regulating member 101 thereof are installed in the transfer section. According to the present embodiment, the brush-like charging means 4 of the regulating member 101 is provided. The conductive member 102 is provided on the side surface. In the present embodiment, the brush regulating member 101 provided with such a conductive member 102 and the brush-like charging means 4
Are the image forming stations P of the image forming apparatus of FIG.
a-Pd are installed at transfer portions. The configuration and operation of the entire image forming apparatus are basically the same as those of the image forming apparatus shown in FIG. 13, and a description thereof will be omitted.

A negatively charged toner image is formed on the photosensitive drum 1 shown in FIG. 1, and the toner image is transferred onto a recording material carried and conveyed by a transfer belt 8 made of a dielectric sheet. The brush-like transfer means 4 described above as a transfer electric field applying means comprises a photosensitive drum 1 and a transfer belt 8.
Is provided on the back surface side of the transfer belt 8 at the abutting portion.
A power supply 105 for applying a bias for generating a transfer electric field (transfer charge) is connected to the brush-like transfer means 4.

In the present embodiment, the brush fiber constituting the brush 100 of the brush-like transfer means 4 is a fiber obtained by dyeing an acrylic fiber with copper sulfide and making it conductive.
About 8μm stainless steel fiber, resin fiber such as acrylic, nylon, polyester, rayon, etc. plated with metal, fiber in which conductive fine powder such as carbon and metal is dispersed in resin, and resin fiber etc. Conductive or semi-conductive fibers, such as carbon fibers, which are carbonized to impart conductivity, can be used.

The above-mentioned conductive or semiconductive fibers may be used alone or as a mixture. In addition, for the purpose of adjusting the strength of the brush or the resistance of the brush tip, acrylic, nylon, polyester, It may be used in combination with a fiber such as rayon.

In this embodiment, as the brush fiber, a fiber obtained by dyeing the above acrylic fiber with copper sulfide to make it conductive is used, and 100 single fibers having a fiber diameter of 600 deniers are converged into a yarn. 4100000 per inch ²
The brush 100 was formed in a thick plate shape by flocking the brush base 104 made of aluminum at a book density by tightening the base 104. Thickness of brush 100 (transfer belt 8
The width in the same direction as the traveling direction is 1 mm, but is not limited thereto. A polycarbonate resin was used as a dielectric sheet material for forming the transfer belt 8.

As shown in FIG. 1, the above-mentioned brush fiber regulating member 101 is disposed upstream of the brush-like transfer means 4 with respect to the moving direction of the transfer belt 8. A 75 μm thick polyester film was used as the brush fiber regulating member 101. The tip of this regulating member 101
The position was set at about 1 mm upstream from the center of the contact point between the photosensitive drum 1 and the transfer belt 8 in the moving direction of the transfer belt 8. The conductive member 102 is provided on the brush-like transfer means 4 side of the regulating member 101 as described above. In this embodiment, the conductive member 102 has a width 5mm the extending direction of the brush fibers, thickness 50 [mu] m, a volume resistivity of 10 ⁰ Ω · cm
The SUS plate member is provided at a distance of about 0.5 mm from the tip of the regulating member 101. A support member 103 is provided downstream of the brush-like transfer means 4 to elastically support and urge the brush 100 to abut the brush fibers on the back surface of the transfer belt 8.

A power supply 105 is connected to the aluminum base 104 of the brush-like transfer means 4, and a voltage is applied to the brush 100 by the power supply 105 using the base 104 as an electrode to generate a transfer electric field. The recording material that is carried and conveyed on the belt 8 is applied from the back surface of the transfer belt 8, and the toner image formed on the photosensitive drum 1 is transferred onto the recording material by the transfer electric field. According to the present invention, the toner image on the photosensitive drum 1 can be faithfully transferred and reproduced on a recording material. This will be described.

FIG. 2 is a diagram showing the state of contact between the brush 100 of the transfer means 4 and the brush fiber regulating member 101 when the brush-like transfer means 4 is urged toward the photosensitive drum 1 to transfer a toner image. The contact state was viewed from the direction of arrow X in FIG. As shown in FIG. 2, it was observed that the brush fibers of the transfer unit 4 and the regulating member 101 were partially in contact with each other. FIG. 3 is a diagram in which the surface potential of the regulating member 101 at that time is measured in the longitudinal direction (axial direction) of the photosensitive drum 1.

FIG. 4 shows a transfer section in each of the image forming stations Pa to Pd of the conventional image forming apparatus of FIG.
When the toner image is transferred using the brush-like transfer means 4 provided with the regulating member 101 'having the conventional configuration shown in FIG.
FIG. 5 shows the result of measuring the surface potential of the regulating member 101 '. In the case of the related art, the regulating member 101 ′ has no conductive member provided on the side of the brush-like transfer unit 4.

Comparing FIG. 3 and FIG. 5, the distribution of the surface potential during transfer has a greater variation in the case of the conventional regulating member 101 'than in the case of the regulating member 101 of the present invention.

In order to evaluate the variation of the potential distribution of the above-mentioned regulating members 101 and 101 ', these regulating members 10
An image was formed by using the brush-like transfer means 4 provided with each of the transfer rollers 1 and 101 'for the transfer. Photosensitive drum 1 used
Has a diameter of 80 mm, a process speed of 160 mm / sec, and uses a polyester resin-based negative toner.
By developing using the component developer, 1
A toner image of a line having a width of 20 μm was formed at an interval of 240 μm, and the toner image was transferred onto a recording material. Then, in the obtained line toner image on the recording material, the toner amount (scattered toner amount) of the portion protruding outside the 120 μm width due to the toner scattering is measured as the number of toners per unit area of 10 mm square, and the measurement point 10 is measured. The average value of the locations was calculated, and thereby the difference in transfer performance due to the difference in the potential distribution of the brush fiber regulating members 101 and 101 'was evaluated.

The results are as shown in Table 1. In the case of the present invention, the amount of scattered toner was extremely reduced to about 1/16 of the conventional case.

[0035]

[Table 1]

According to the brush fiber regulating member 101 according to the present invention, the reason why the amount of scattered toner is extremely reduced as compared with the prior art is considered as follows.

First, the state of contact between the conventional brush fiber regulating member 101 'and the brush fibers of the transfer means 4 shown in FIG. 4 is set, and the transfer is performed under the same conditions as in the present invention.
When the contact state during the transfer was observed in the same manner as described with reference to FIG. 2, no difference was found in the contact state between the regulating member 101 'and the brush fiber of the charging means 4 in the conventional case.

On the other hand, the potentials of the regulating member 101 of the present invention and the regulating member 101 'of the related art are shown in FIGS. 2 and 5 along the photosensitive drum longitudinal direction (the photosensitive drum thrust width direction).
Are substantially the same at the same position A. Position A above
Is a position near the front side in the longitudinal direction of the photosensitive drum, and in the present invention, the SUS provided on the brush-like transfer means 4
This is a portion where the conductive member 102 of the plate-shaped member and the brush fiber of the charging unit 4 are in contact with each other in a state where a transfer electric field is applied. At the position A, not only the present invention but also the conventional case is imagewise good. If only the position A is taken up in the related art as well, similar to the image quality of the present invention shown in Table 1,
Good image quality with extremely small amount of toner scattering was obtained.

A position B along the lengthwise direction of the photosensitive drum shown in FIGS. 2 and 5 is a position located farther than the above-mentioned position A. In the present invention, the conductive member 102 and the charging means 4 are provided.
This is a portion where the brush fiber of the charging means 4 is not in contact with the brush fiber regulating member 101 'in the related art. The image quality of the position B in the related art is worse than the image quality of the position B in the present invention, and is worse than the image quality of the conventional example shown in Table 1, and the scattered toner amount per unit area is shown in Table 1. More blurred line images were shown than shown.

This is because, in the conventional case, the polycarbonate resin constituting the transfer belt 8 and the brush fiber regulating member 10
1 ′ and the brush fibers of the conductive or semiconductive resin fibers forming the brush 100 of the brush-like transfer means 4 are frictionally charged with each other, and as a result, excessively more than in the case of the present invention. This is considered to be because the positively charged portion acts on the toner image on the photosensitive drum 1 before the recording material comes into contact with the photosensitive drum 1 to cause so-called pre-transfer.

In the triboelectric charging, the charging potential varies depending on the combination of the members in contact with each other and the frictional state (pressure, relative speed, atmosphere environment). Therefore, the above-mentioned excessively positively charged triboelectric potential largely depends on the actual state, for example, by changing the combination of members such as the transfer belt 8, the brush fiber regulating members 101 'and 101, and the brush-like transfer means 4.

In order to confirm the pre-transfer phenomenon in the conventional case, the transfer image at the position B in FIG.
When the brush fiber regulating member 101 'and the brush-like transfer means 4 in FIG. 4 were moved to the downstream side in the moving direction of the transfer belt 8, the brush fiber regulating member 101' was located at a position 1.0 mm downstream compared to the present invention. When the brush-like transfer means 4 is moved, a good transfer image can be obtained. Therefore, in the conventional case, it can be seen that pre-transfer has occurred at the original setting position.

The transfer area according to the present invention will be described.
When the recording material transporting member is a belt such as the transfer belt 8 or a sheet stretched on the surface of the transfer drum, the contact portion with the photosensitive drum is a line contact. Under the conditions that can be maintained stably, the nip width of the contact portion becomes about 3 to 4 mm. This means that the nip is a narrow nip extending only 1.5 to 2.0 mm upstream and downstream of the center point of the portion where the photosensitive drum 1 and the recording material conveying member are in line contact. As described above, in the transfer method using the recording material transporting member by the belt or the sheet, the nip cannot be sufficiently obtained in the transfer area, and this is disadvantageous in comparison with the transfer method in which the transfer electric field is directly applied to the back surface of the recording material. . However, at present, a transfer method using a recording material transporting member by a belt or a sheet is generally used in a multi-transfer type color copying machine or the like since a great effect is obtained in preventing color misregistration.

As described above, in the conventional case, it is preferable to move the brush transfer means 4 downstream in order to eliminate the pre-transfer. However, in this case, the transfer area where the nip width is originally narrow is further narrowed. In some cases, the transfer electric field and the transfer time required to transfer the solid toner image of the image in the remaining transfer area cannot be provided, and even if the image with a small amount of toner can be successfully transferred, Since the solid portion of the image cannot be sufficiently transferred, the obtained image is also an image with poor transfer.

In the present invention, since the conductive member 102 is provided on the brush fiber regulating member 101, the above-mentioned problem is eliminated. That is, as is apparent from the above description, a non-uniform electric potential is generated in the brush fiber regulating member 101 'in the longitudinal direction of the photosensitive drum 1 in the related art, which hinders the faithful transfer of the toner image. . The present invention aims at making the electric potential generated in the brush fiber regulating member 101 uniform, and the non-uniform electric potential which has conventionally occurred in the portion of the charging means 4 of the brush fiber regulating member 101 ′ which does not contact the brush fiber. According to the present invention, the conductive member 102 provided on the brush fiber regulating member 101 receives power from the brush fiber in contact therewith and makes the regulating member 101 uniform at the same potential in the longitudinal direction of the photosensitive drum. is there. Therefore, the toner image can be faithfully transferred.

As the conductive member 102, the metal represented by SUS used in the present embodiment or the dispersion ratio of the iron ferrite oxide to the polyester resin is changed, and the volume resistance of the conductive member 102 is changed. The upper limit of the rate is 10 ⁸ to 10 ¹² Ω
were tested approximately cm in prospect, the volume resistivity of 10 ^-5 to
At 10 ⁸ Ω · cm, the amount of toner scattered per unit volume did not change. Further, the toner scattered amount continued to increase gradually at 10 ⁹ Ω · cm or more, but even at 10 ¹² Ω · cm, the toner scattered amount was about half of the conventional amount.

From the above, to obtain the effect of the present invention,
It is understood that the volume resistivity of the conductive member 102 should be 10 ¹² Ω · cm or less. It is preferably 10 ⁸ Ω · cm or less, and the effect of the present invention is sufficiently exerted at 10 ⁸ Ω · cm or less.

The conductive member 102 according to the present invention has a width of 3.0 to 2.0 mm from the tip of the brush fiber regulating member 101 in the direction in which the brush of the transfer means 4 extends.
It suffices if the thickness is set to 8.0 mm, and the above-described effect is confirmed.

Further, the conductive member 102 may be provided by attaching the member under the above conditions to the brush fiber regulating member 101, or may be provided by a method such as vapor deposition or printing. Similarly, the effect of the present invention is achieved.

Embodiment 2 In the above embodiment, the brush 100 of the brush-like transfer means 4
Is formed in a thick plate shape in which brush fibers extending in the radial direction of the photosensitive drum 1 are arranged in the longitudinal direction (axial direction) of the photosensitive drum 1, but the present invention is not limited to this. The effect of the present invention can be sufficiently obtained even with the brush.
In this embodiment, an example will be described.

FIG. 6 is a cross-sectional view showing a transfer portion in this embodiment. In this embodiment, the brush 106 of the brush-like transfer means 4 is a cylindrical fur brush, and the fur brush 106 rotates in the direction of the arrow opposite to the direction of travel of the transfer belt 8 (recording material 6). It has become. A power supply 105 is connected to a shaft 107 of the fur brush 106.

A regulating member 101 for regulating the upstream side of the brush fiber is provided upstream of the fur brush 106.
Similarly, a plate-shaped conductive member 102 is provided on the surface of the regulating member 101 on the fur brush 106 side. The fur brush 106 rotates while brushing the brush fiber to which the voltage from the power supply 105 is applied by the regulating member 101, and the brush fiber contacts the conductive member 102 to supply power thereto. Therefore, also in this embodiment, the potential of the regulating member 101 can be made uniform in the longitudinal direction of the photosensitive drum, and the toner image can be faithfully transferred.

In this embodiment, the fur brush 106 is
In the first embodiment, the pressing force on the transfer belt 8 is maintained by the elastic force of the brush fibers and the inertial force due to the rotation of the brush 4.
There is an advantage that it is not necessary to provide the support member 103 on the downstream side of the brush 4 as in the case of (1).

Embodiment 3 FIG. 7 is a sectional view showing a transfer portion in still another embodiment of the image forming apparatus of the present invention. In the present embodiment, a thick plate-like brush 100 similar to that of the first embodiment in FIG.

Generally, the contact resistance of the brush 100 of the brush-like transfer means 4 to the transfer belt 8 is
And the pressed state is affected by the brush shape of the charging means 4, but the contact resistance generally differs between the side of the brush fiber and the end face of the tip of the brush fiber. Therefore, in order to bring the brush 100 of the charging means 4 into contact with the transfer belt 8, it is necessary to select a contacting method that reduces contact resistance.

Normally, the brush 100 of the charging means 4 often has a brush configuration in which the resistance of the outer portion is high and the resistance of the brush 100 is low. Therefore, the brush 100 of the charging means 4
In such a configuration, as shown in FIG. 7, the brush fiber abuts on the transfer belt 8 at the tip end face of the brush fiber, rather than abuts on the side portion (belly) of the brush fiber as shown in FIG. This is preferable because the contact resistance to the transfer belt 8 is reduced, and this embodiment shows this example.

It is desirable that the upstream end of the brush 100 of the charging means 4 is located on the center line of the photosensitive drum 1 and is in contact with the transfer belt 8, but more preferably within 0.5 mm from the center line. .

Embodiment 4 In each of the above-described embodiments, the image forming apparatus is configured as shown in FIG.
As shown in FIG. 8, the apparatus configuration uses a plurality of photosensitive drums 1a to 1d and a transfer belt 8 as a recording material conveying member. However, the present invention is not limited to this. As shown in the drawing, the recording material is supported on the surface of the transfer drum 18 and is rotated a plurality of times by holding only one photosensitive drum 1. An apparatus may be used in which a toner image of each color to be formed is multiplex-transferred to form a multi-color image on a transfer material.

As shown in FIG. 9, the transfer drum 18
Hollow frame 19 in which a pair of rings 19a are connected by a bone 19b
A dielectric sheet 81 is attached to the bone 19a, and the dielectric sheet 81 is stretched in the air space on the outer peripheral surface of the frame 19. The recording material 6 taken out of the cassette 60 is supplied to the transfer drum 18 via the registration roller 13,
It is held on the dielectric sheet 81 of the transfer drum 1 by electrostatic attraction or mechanically held by a gripper or the like, and is conveyed to a transfer unit facing the photosensitive drum 1.

A rotary developing device 3 provided with a primary charger 2, a cleaner 5, and four developing devices 3a, 3b, 3c, 3d is installed around the photosensitive drum 1. A latent image is formed by irradiating the light image E of each color component from the device 17 and is developed by a developing device corresponding to the color of the latent image.
A toner image of each color is sequentially formed on the photosensitive drum 1.

As shown in FIG. 10, a brush-like charging means 4 is provided at the transfer portion, and the brush 100 is brought into contact with the back surface of the dielectric sheet 81 of the transfer drum 18 at the time of transfer.
A voltage is applied from a power supply (not shown). Thereby, the recording material 6 carried on the transfer drum 18 and conveyed to the transfer position
Is applied, and the toner images of each color formed on the photosensitive drum 1 are sequentially superimposed and transferred onto the recording material 6.

Next, the recording material 6 to which the four color toner images have been transferred is neutralized by a separation charger 14 and a peeling charger 15,
Separated from the transfer drum 18 by the action of the separation claw 28,
The toner image is conveyed to the fixing device 7 where the toner image is mixed and fixed to form a full-color permanent image.

Also in this embodiment, the brush-like charging means 4
A brush fiber regulating member (not shown) provided on the upstream side in the rotation direction of the transfer drum 18 is provided with a conductive member (not shown) similar to the conductive member 102 in FIG. By making the potentials of the members uniformly the same in the longitudinal direction of the photosensitive drum, a faithful transfer image could be obtained on the recording material 6 by the transfer by the brush-like charging means 4.

As described above, in the first to fourth embodiments, the brush 100 or the fur 100 is moved by the brush fiber regulating member 101 provided at the upstream position in the moving direction of the transfer belt 8 or the transfer drum 18 of the brush-like transfer means 4. Since the conductive member 102 having a lower resistance than the brush 100 or the fur brush 106 is provided on the surface on the brush 106 side, it is possible to eliminate the non-uniformity of the electric potential between the portion of the regulating member 101 that contacts the brush fiber and the portion that does not contact the brush fiber. The transfer using the brush-like charging means 4 does not reduce the transfer area in the area where the recording material is in contact with the photosensitive drum 1 and does not cause post transfer downstream of the nip. , And an image with good gradation and graininess in which scattering is suppressed can be obtained.

Reference Example 1 FIG. 11 is a sectional view showing a transfer section as a reference example of the image forming apparatus of the present invention. The present embodiment is characterized in that an electric field regulating member of the charging unit 4 is provided at least on the downstream side with respect to the moving direction of the transfer belt 8 of the brush-shaped charging unit 4.
In this example, the electric field regulating members 1 are provided on the downstream side and the upstream side, respectively.
12 and 114 were provided. The brush fiber regulating member 101 and the support member 103 as in FIG. 1 are not provided on the upstream side and the downstream side of the brush-like charging unit 4. The image forming apparatus is similarly applied to the image forming apparatus shown in FIG.

In the image forming apparatus, when the high voltage means such as the transfer means and the static elimination means are arranged in close contact, electric field mutual interference occurs between these adjacent high voltage means when a high voltage is applied. There were drawbacks. In the case of the image forming apparatus shown in FIG. 13, since the four transfer means 4a to 4d are arranged, the structure of the apparatus becomes complicated and dense, and the mutual interference of electric fields between the adjacent high voltage means is particularly remarkable. When one transfer step is repeated a plurality of times, the transfer step is performed only once.

Therefore, in the present embodiment, as described above, the electric field regulating member of the charging means 4 is provided at least on the downstream side with respect to the moving direction of the transfer belt 8 of the brush-like charging means 4. Electric field regulating members 112 and 1
It was set to 14.

The electric field regulating members 112 and 114 need to have a higher resistance than the brush 100. In the present reference example, the volume resistivity of the brush fiber of the brush 100 of the charging means 4 is 10 ⁵ by dispersing carbon in rayon.
The conductive fiber controlled to Ω · cm is used, and the electric field regulating member 112 on the downstream side of the brush-like charging means 4 has a thickness of 130 μm.
m of polyethylene terephthalate (PET) and a 50 μm thick PET
Was used.

The transfer belt 8 has a volume resistivity of 10 ¹⁰ -1.
It is generally about 0 ¹⁸ Ω · cm, and a dielectric sheet such as a PET sheet, a polyvinylidene fluoride (PVdF) sheet, or a polyurethane sheet is used. In the present reference example, a polyvinylidene fluoride sheet was used for the transfer belt 8.

The brush base 104 made of aluminum of the brush-like charging means 4 holds the brush 1 by tightening the brush fibers.
The brush base 104 is also an electrode for connecting a power supply 105 and applying a voltage to the brush 100.

It is generally known that the contact-type charging means stabilizes an obtained image when a current contributing to transfer is set to a constant appropriate value. Therefore, even when the volume resistivity of the recording material or the transfer belt 8 changes due to the thickness of the recording material, the type of the material and the like, and the moisture absorption conditions, the transfer current is controlled so as to obtain a constant transfer current. That is common. The same applies to the present embodiment. For this purpose, the power supply 105 is controlled by a constant current, and in this embodiment, the constant current control is 18 μA.

In the transfer section of each of the stations Pa to Pd in the image forming apparatus shown in FIG.
When the transfer is performed using a to d, the transfer voltage at each transfer portion is 2 k in a temperature and humidity environment of approximately 23 ° C. and 55, although it depends on the resistance value of the toner image and the recording material and the toner charge amount.
V, 2.8 kV, 3.2 kV, and 3.5 kV.

When the humidity is low and the recording material is sufficiently dried, the voltage at the time of transfer increases and the potential of the surface of the recording material increases. For this reason, each photosensitive drum 1a, 1b, 1
c, the impedance in the direction of 1d also increases, so that high-voltage means such as the transfer means 4a, 4b, 4c, 4d and static elimination means 14, 15 cause mutual interference of electric fields between adjacent high-pressure means, causing toner scattering and concentration. Image defects such as thinness easily occur. Therefore, in miniaturizing the image forming apparatus and improving the quality of an image, it is an essential technology to prevent electric field interference between adjacent high voltage means.

In this embodiment, as described above, the electric field regulating members 112 and 114 are provided on the downstream side and the upstream side of the brush-like charging means 4, or the electric field regulating members 112 are provided at least on the downstream side of the brush-like charging means 4. Since the transfer means 4 is used as the transfer means 4a to 4d in FIG.
Between the transfer means 4a and 4b, 4b and 4c, 4c and 4d, and the transfer means 4d and the separation charger 14, the peeling charger 1
5 or belt static eliminator 12 can be suppressed or prevented from interfering with each other, and toner can be prevented from being scattered due to discharge near the upstream of the transfer nip. Also, the brush 100 of the brush-like charging means 4 is prevented from falling off or coming off due to abrasion, and
It is also possible to maintain a uniform pressure of 0 and stabilize the contact positions of the upstream electric field regulating member 114 and the brush 100 with the transfer belt 8.

Embodiment 2 FIG. 12 is a sectional view showing a transfer section as another embodiment of the image forming apparatus of the present invention. The electric field regulating member does not necessarily need to be disposed on the contact-type transfer unit in the upstream and downstream directions, and the transfer unit is not limited to a brush.

Therefore, in this embodiment, as shown in FIG. 12, a conductive sponge cylindrical body 1 is provided around a roller shaft 123.
24, a cylindrical electric field regulating member 126 made of a polycarbonate resin is provided on the outer surface of the sponge cylindrical body 124 at a little over half circumference so that a part of the sponge cylindrical body 124 is exposed. . Then, at the transfer position, at the time of transfer, the exposed portion of the sponge cylinder 124 without the electric field regulating member 126 is brought into contact with the back surface of the transfer belt 8 to generate a transfer electric field by applying a voltage from the power supply 105 connected to the shaft 123. Used for transfer.

Similarly, the electric field at the transfer position can be regulated by the electric field regulating member 126, the toner can be prevented from being scattered by the discharge near the upstream of the transfer nip, and the mutual interference with the adjacent high voltage means can be prevented. did it.

Reference Example 3 In this reference example, the present invention was applied to the image forming apparatus shown in FIGS. In the case of the present image forming apparatus, since the brush-like charging means 4 is adjacent to the inner and outer separating chargers 14 and 14 and the peeling charger 15, particularly when transferring the final color (the fourth color in this example). Although the concentration tends to be low due to the interference of the electric field between the chargers, the charging means 4 of Reference Example 1 in FIG.
The electric field restricting member 112 on the downstream side of the transfer belt 8 or the electric field restricting member similar to the electric field restricting member 114 on the upstream side of the transfer belt 8 is connected to the downstream side in the rotation direction of the transfer drum 18 of the charging unit 4 of the present embodiment or By providing it on the upstream side,
It was possible to prevent the transfer density of the final color from becoming low.

The effect of preventing the density from becoming low due to the interference of the electric field is more remarkably exhibited when the toner image is transferred four times than when the toner image is transferred once. Was. From this, it can be seen that the configuration of the present embodiment is particularly effective for a method of sequentially forming and transferring a plurality of color toner images as in the case of color image formation, but is not necessarily limited to this. Instead, the present invention can be applied to an image forming apparatus that forms and transfers only one color toner image and completes image formation.

As described above, in the first to third embodiments, the regulating member 112 for regulating the transfer electric field at least at the downstream position in the moving direction of the transfer belt 8 or the transfer drum 18 of the contact type charging means such as the brush-shaped transfer means 4. And so on, it is possible to prevent electric fields from interfering with each other between the contact-type charging means and another contact-type charging means adjacent to the contact-type charging means or between the contact-type charging means and the separation charging means. By regulating the electric field and stabilizing the position and the pressure at the time, a high-quality image can be easily and stably obtained by the transfer using the contact transfer means, and the apparatus can be downsized.

As described above, the present invention relates to an image carrier for carrying a toner image, a recording material carrying member for carrying and carrying a recording material, and And a brush for electrostatically transferring the toner image to the recording material carried on the recording material conveying member, wherein the dielectric member regulates a position on the upstream side of the brush in the moving direction of the recording material conveying member. Since the film has a structure in which the dielectric film has a region that comes into contact with the brush via the conductive member, the dielectric film makes uneven contact with the brush, so that the potential of the dielectric film becomes uneven. As a result, toner scattering can be prevented, and a high-quality image with excellent image uniformity, gradation, and graininess can be obtained.

[0082]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a transfer unit in an embodiment of an image forming apparatus according to the present invention.

FIG. 2 illustrates a state of contact between a brush of the transfer unit and a brush fiber regulating member when a toner image is transferred by urging a brush-like transfer unit provided in a transfer unit of FIG. 1 to a photosensitive drum side. It is the figure seen from the arrow X direction.

FIG. 3 is a diagram in which a surface potential of a regulating member at that time is measured in a longitudinal direction of a photosensitive drum.

FIG. 4 is a cross-sectional view illustrating a transfer unit in each image forming station of a conventional image forming apparatus.

FIG. 5 is a diagram illustrating a surface potential of a regulating member measured in a longitudinal direction of the photosensitive drum when a toner image is transferred by urging a brush-like transfer unit provided in the transfer unit of FIG. 4 toward the photosensitive drum; It is.

FIG. 6 is a cross-sectional view illustrating a transfer unit in another embodiment of the image forming apparatus of the present invention.

FIG. 7 is a cross-sectional view illustrating a transfer unit in still another embodiment of the image forming apparatus of the present invention.

FIG. 8 is a configuration diagram showing still another embodiment of the image forming apparatus of the present invention.

9 is a perspective view showing a transfer drum provided in the image forming apparatus of FIG.

FIG. 10 is a sectional view illustrating a transfer unit of the image forming apparatus of FIG. 8;

FIG. 11 is a sectional view showing a reference example of the image forming apparatus of the present invention.

FIG. 12 is a cross-sectional view illustrating another reference example of the image forming apparatus of the present invention.

FIG. 13 is a configuration diagram illustrating a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1a-1d Photosensitive drum 4, 4a-4d Brush-like transfer means 6 Recording material 8 Transfer belt 14 Separation charger 81 Dielectric sheet 100 Brush 101, 101 'Brush fiber regulating member 102 Conductive member 105 Power supply 106 Fur brush 112 , 114 Electric field regulating member 124 Sponge cylindrical body 126 Electric field regulating member

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-186387 (JP, A) JP-A-2-163779 (JP, A) JP-A-3-4272 (JP, A) JP-A-3-3 4270 (JP, A) JP-A-2-14875 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/16

Claims (3)

(57) [Claims] An image bearing member for carrying a toner image; a recording material carrying member for carrying and carrying a recording material; and a recording medium carrying the toner image on the image carrying member in contact with a back surface of the recording material carrying member. An image forming apparatus comprising: a brush that electrostatically transfers a recording material carried on a recording material conveying member; and a dielectric film that regulates a position on an upstream side of the brush in a moving direction of the recording material conveying member. The image forming apparatus is characterized in that the dielectric film has an area that comes into contact with the brush via a conductive member. 2. The volumetric efficiency of the conductive member is 10 ¹² Ω.
2. The image forming apparatus according to claim 1, wherein the size is not more than cm. 3. The image forming apparatus according to claim 1, wherein the conductive member is provided on a front end side of the dielectric film.